WorldWideScience

Sample records for monolayer formation characteristics

  1. Fracture Characteristics of Monolayer CVD-Graphene

    OpenAIRE

    Hwangbo, Yun; Lee, Choong-Kwang; Kim, Sang-Min; Kim, Jae-Hyun; Kim, Kwang-Seop; Jang, Bongkyun; Lee, Hak-Joo; Lee, Seoung-Ki; Kim, Seong-Su; Ahn, Jong-Hyun; Lee, Seung-Mo

    2014-01-01

    We have observed and analyzed the fracture characteristics of the monolayer CVD-graphene using pressure bulge testing setup. The monolayer CVD-graphene has appeared to undergo environmentally assisted subcritical crack growth in room condition, i.e. stress corrosion cracking arising from the adsorption of water vapor on the graphene and the subsequent chemical reactions. The crack propagation in graphene has appeared to be able to be reasonably tamed by adjusting applied humidity and stress. ...

  2. Fullerene monolayer formation by spray coating.

    Science.gov (United States)

    Cervenka, J; Flipse, C F J

    2010-02-10

    Many large molecular complexes are limited in thin film applications by their insufficient thermal stability, which excludes deposition via commonly used vapour phase deposition methods. Here we demonstrate an alternative way of monolayer formation of large molecules by a simple spray coating method under ambient conditions. This technique has been successfully applied on C(60) dissolved in toluene and carbon disulfide. Monolayer thick C(60) films have been formed on graphite and gold surfaces at particular deposition parameters, as confirmed by atomic force and scanning tunnelling microscopies. Structural and electronic properties of spray coated C(60) films on Au(111) have been found comparable to thermally evaporated C(60). We attribute the monolayer formation in spray coating to a crystallization process mediated by an ultrathin solution film on a sample surface.

  3. Fracture Characteristics of Monolayer CVD-Graphene

    Science.gov (United States)

    Hwangbo, Yun; Lee, Choong-Kwang; Kim, Sang-Min; Kim, Jae-Hyun; Kim, Kwang-Seop; Jang, Bongkyun; Lee, Hak-Joo; Lee, Seoung-Ki; Kim, Seong-Su; Ahn, Jong-Hyun; Lee, Seung-Mo

    2014-03-01

    We have observed and analyzed the fracture characteristics of the monolayer CVD-graphene using pressure bulge testing setup. The monolayer CVD-graphene has appeared to undergo environmentally assisted subcritical crack growth in room condition, i.e. stress corrosion cracking arising from the adsorption of water vapor on the graphene and the subsequent chemical reactions. The crack propagation in graphene has appeared to be able to be reasonably tamed by adjusting applied humidity and stress. The fracture toughness, describing the ability of a material containing inherent flaws to resist catastrophic failure, of the CVD-graphene has turned out to be exceptionally high, as compared to other carbon based 3D materials. These results imply that the CVD-graphene could be an ideal candidate as a structural material notwithstanding environmental susceptibility. In addition, the measurements reported here suggest that specific non-continuum fracture behaviors occurring in 2D monoatomic structures can be macroscopically well visualized and characterized.

  4. Nonlinear optical characteristics of monolayer MoSe{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Le, Chinh Tam; Ullah, Farman; Senthilkumar, Velusamy; Kim, Yong Soo [Department of Physics and Energy Harvest Storage Research Center, University of Ulsan (Korea, Republic of); Clark, Daniel J.; Jang, Joon I. [Department of Physics, Applied Physics and Astronomy, Binghamton University, Binghamton, NY (United States); Sim, Yumin; Seong, Maeng-Je [Department of Physics, Chung-Ang University, Seoul (Korea, Republic of); Chung, Koo-Hyun [School of Mechanical Engineering, University of Ulsan (Korea, Republic of); Park, Hyoyeol [Electronics, Communication and Semiconductor Applications Department, Ulsan College (Korea, Republic of)

    2016-08-15

    In this study, we utilized picosecond pulses from an Nd:YAG laser to investigate the nonlinear optical characteristics of monolayer MoSe{sub 2}. Two-step growth involving the selenization of pulsed-laser-deposited MoO{sub 3} film was employed to yield the MoSe{sub 2} monolayer on a SiO{sub 2}/Si substrate. Raman scattering, photoluminescence (PL) spectroscopy, and atomic force microscopy verified the high optical quality of the monolayer. The second-order susceptibility χ{sup (2)} was calculated to be ∝50 pm V{sup -1} at the second harmonic wavelength λ{sub SHG} ∝810 nm, which is near the optical gap of the monolayer. Interestingly, our wavelength-dependent second harmonic scan can identify the bound excitonic states including negatively charged excitons much more efficiently, compared with the PL method at room temperature. Additionally, the MoSe{sub 2} monolayer exhibits a strong laser-induced damage threshold ∝16 GW cm{sup -2} under picosecond-pulse excitation{sub .} Our findings suggest that monolayer MoSe{sub 2} can be considered as a promising candidate for high-power, thin-film-based nonlinear optical devices and applications. (copyright 2016 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Hexadecadienyl Monolayers on Hydrogen-Terminated Si(III): Faster Monolayer Formation and Improved Surface Coverage Using the Enyne Moiety

    NARCIS (Netherlands)

    Rijksen, B.M.G.; Pujari, S.P.; Scheres, L.M.W.; Rijn, van C.J.M.; Baio, J.E.; Weidner, T.; Zuilhof, H.

    2012-01-01

    To further improve the coverage of organic monolayers on hydrogen-terminated silicon (H–Si) surfaces with respect to the hitherto best agents (1-alkynes), it was hypothesized that enynes (H–C=C–HC-CH–R) would be even better reagents for dense monolayer formation. To investigate whether the increased

  6. Mechanic studies of monolayer formation on H-Si(111) surfaces

    NARCIS (Netherlands)

    Rijksen, B.M.G.

    2012-01-01

    Covalently attached organic monolayers on silicon surfaces form thermally and chemically stable platforms for (bio)functionalization of the surface. Recent advances in monolayer formation – yielding increases in monolayer quality and the complete exclusion of oxygen at modified surfaces &ndash

  7. Hexadecadienyl monolayers on hydrogen-terminated Si(111): faster monolayer formation and improved surface coverage using the enyne moiety.

    Science.gov (United States)

    Rijksen, Bart; Pujari, Sidharam P; Scheres, Luc; van Rijn, Cees J M; Baio, J E; Weidner, Tobias; Zuilhof, Han

    2012-04-24

    To further improve the coverage of organic monolayers on hydrogen-terminated silicon (H-Si) surfaces with respect to the hitherto best agents (1-alkynes), it was hypothesized that enynes (H-C≡C-HC═CH-R) would be even better reagents for dense monolayer formation. To investigate whether the increased delocalization of β-carbon radicals by the enyne functionality indeed lowers the activation barrier, the kinetics of monolayer formation by hexadec-3-en-1-yne and 1-hexadecyne on H-Si(111) were followed by studying partially incomplete monolayers. Ellipsometry and static contact angle measurements indeed showed a faster increase of layer thickness and hydrophobicity for the hexadec-3-en-1-yne-derived monolayers. This more rapid monolayer formation was supported by IRRAS and XPS measurements that for the enyne show a faster increase of the CH2 stretching bands and the amount of carbon at the surface (C/Si ratio), respectively. Monolayer formation at room temperature yielded plateau values for hexadec-3-en-1-yne and 1-hexadecyne after 8 and 16 h, respectively. Additional experiments were performed for 16 h at 80° to ensure full completion of the layers, which allows comparison of the quality of both layers. Ellipsometry thicknesses (2.0 nm) and contact angles (111-112°) indicated a high quality of both layers. XPS, in combination with DFT calculations, revealed terminal attachment of hexadec-3-en-1-yne to the H-Si surface, leading to dienyl monolayers. Moreover, analysis of the Si2p region showed no surface oxidation. Quantitative XPS measurements, obtained via rotating Si samples, showed a higher surface coverage for C16 dienyl layers than for C16 alkenyl layers (63% vs 59%). The dense packing of the layers was confirmed by IRRAS and NEXAFS results. Molecular mechanics simulations were undertaken to understand the differences in reactivity and surface coverage. Alkenyl layers show more favorable packing energies for surface coverages up to 50-55%. At higher

  8. Anti-tarnish Characteristics and Formation Mechanism of Self-Assembled Monolayers on Surface of Silver Coins%银币表面自组装膜抗变色性能及成膜机理

    Institute of Scientific and Technical Information of China (English)

    梁成浩; 杨长江; 黄乃宝; 金光明

    2013-01-01

    Octadecanethiol (C18SH) self-assembled monolayers (SAM) were prepared on the silver coin surface.The anti-tarnish characteristics of C18SH SAMs were investigated in 0.5 mol/L NaCl+0.01 mol/L Na2S solution by an electrochemical technique.The results indicate that silver's corrosion potential moves by 30 mV to positive direction after forming SAMs.C18SH SAMs could inhibit oxygen depolarization and silver sulfuration.The inhibition effect for cathode process is better than that for anode.After SAMs is formed on the surface of silver,the silver coin's charge-transfer resistance increases and double layer capacitance decreases.The formation of SAMs on silver is in accordance with a two-phase model.In the initial stage,the adsorption obeys two grade Langmuir equation,which is θ(t)=1.706ct/1+1.706ct.In the latter stage,the adsorption is the process of reforming and recrystallization,and is in accordance with onegrade Langmuir equation,which is θ (t) =1-e-0.547ct.The relationship between rate constant and temperature is ln(k)=5826/T+26.5 during absorption.The apparent activation energy of self-assembled process is 48.4 kJ/mol and the self-assembled process is controlled by chemical adsorption.%利用化学方法在银币表面制备了十八烷基硫醇组装膜(C18SH SAMs),并通过电化学技术研究了其在0.5 mol/LNaCl+0.01 mol/L Na2S溶液中的抗变色性能.结果表明:银表面形成SAMs后腐蚀电位正移30 mV;阴极氧去极化和阳极银的硫化过程均受到抑制,对阴极极化过程的阻滞作用较阳极极化过程明显;银表面成膜后,容抗弧、电荷传递系数Rt增大,双电层电容Cd降低.有效提高银币的抗变色性能.银表面C18SH SAMs的形成过程符合两阶段模型.膜初始吸附阶段(Ⅰ)为2级Langmuir吸附,重整结晶阶段(Ⅱ)为l级Langmuir吸附,动力学公式分别为,Ⅰ阶段:θ(t)=1.706ct/1+1.706ct,Ⅱ阶段:θ(t)=1-e-0.547ct.速率常数与温度的关系为ln(k)=-5826/T+26.5,自

  9. {alpha}-Man monolayer formation via Si-C bond formation and protein recognition

    Energy Technology Data Exchange (ETDEWEB)

    Funato, Koji [School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan); Shirahata, Naoto [National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Miura, Yoshiko, E-mail: miuray@jaist.ac.j [School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan)

    2009-11-30

    An acetylenyl-terminated saccharide was synthesized and the thin layer formation on the hydrogen-terminated silicon was investigated. The acetylenyl-terminated saccharide was synthesized by the condensation reaction of hexynoic acid and p-aminophenyl saccharide. This was reacted with hydrogen-terminated silicon (Si-H) by a photochemical reaction. The resulting saccharide modified substrate was analyzed by ellipsometry and X-ray photoelectron spectroscopy, which showed the formation of a uniform monolayer. The surface's ability to recognize proteins was analyzed by fluorescent microscopy, and showed specific interactions with sugar recognition proteins.

  10. Electronic characteristics of p-type transparent SnO monolayer with high carrier mobility

    Science.gov (United States)

    Du, Juan; Xia, Congxin; Liu, Yaming; Li, Xueping; Peng, Yuting; Wei, Shuyi

    2017-04-01

    More recently, two-dimensional (2D) SnO nanosheets are attaching great attention due to its excellent carrier mobility and transparent characteristics. Here, the stability, electronic structures and carrier mobility of SnO monolayer are investigated by using first-principles calculations. The calculations of the phonon dispersion spectra indicate that SnO monolayer is dynamically stable. Moreover, the band gap values are decreased from 3.93 eV to 2.75 eV when the tensile strain is applied from 0% to 12%. Interestingly, SnO monolayer is a p-type transparent semiconducting oxide with hole mobility of 641 cm2 V-1 s-1, which is much higher than that of MoS2 monolayer. These findings make SnO monolayer becomes a promising 2D material for applications in nanoelectronic devices.

  11. An Anomalous Formation Pathway for Dislocation-Sulfur Vacancy Complexes in Polycrystalline Monolayer MoS2.

    Science.gov (United States)

    Yu, Zhi Gen; Zhang, Yong-Wei; Yakobson, Boris I

    2015-10-14

    Two-dimensional (2D) molybdenum disulfide (MoS2) has attracted significant attention recently due to its direct bandgap semiconducting characteristics. Experimental studies on monolayer MoS2 show that S vacancy concentration varies greatly; while recent theoretical studies show that the formation energy of S vacancy is high and thus its concentration should be low. We perform density functional theory calculations to study the structures and energetics of vacancy and interstitial in both grain boundary (GB) and grain interior (GI) in monolayer MoS2 and uncover an anomalous formation pathway for dislocation-double S vacancy (V2S) complexes in MoS2. In this pathway, a (5|7) defect in an S-polar GB energetically favorably converts to a (4|6) defect, which possesses a duality: dislocation and double S vacancy. Its dislocation character allows it to glide into GI through thermal activation at high temperatures, bringing the double vacancy with it. Our findings here not only explain why VS is predominant in exfoliated 2D MoS2 and V2S is predominant in chemical vapor deposition (CVD)-grown 2D MoS2 but also reproduce GB patterns in CVD-grown MoS2. The new pathway for sulfur vacancy formation revealed here provides important insights and guidelines for controlling the quality of monolayer MoS2.

  12. Integrin alpha(3)-subunit expression modulates alveolar epithelial cell monolayer formation.

    Science.gov (United States)

    Lubman, R L; Zhang, X L; Zheng, J; Ocampo, L; Lopez, M Z; Veeraraghavan, S; Zabski, S M; Danto, S I; Borok, Z

    2000-07-01

    We investigated expression of the alpha(3)-integrin subunit by rat alveolar epithelial cells (AECs) grown in primary culture as well as the effects of monoclonal antibodies with blocking activity against the alpha(3)-integrin subunit on AEC monolayer formation. alpha(3)-Integrin subunit mRNA and protein were detectable in AECs on day 1 and increased with time in culture. alpha(3)- and beta(1)-integrin subunits coprecipitated in immunoprecipitation experiments with alpha(3)- and beta(1)-subunit-specific antibodies, consistent with their association as the alpha(3)beta(1)-integrin receptor at the cell membrane. Treatment with blocking anti-alpha(3) monoclonal antibody from day 0 delayed development of transepithelial resistance, reduced transepithelial resistance through day 5 compared with that in untreated AECs, and resulted in large subconfluent patches in monolayers viewed by scanning electron microscopy on day 3. These data indicate that alpha(3)- and beta(1)-integrin subunits are expressed in AEC monolayers where they form the heterodimeric alpha(3)beta(1)-integrin receptor at the cell membrane. Blockade of the alpha(3)-integrin subunit inhibits formation of confluent AEC monolayers. We conclude that the alpha(3)-integrin subunit modulates formation of AEC monolayers by virtue of the key role of the alpha(3)beta(1)-integrin receptor in AEC adhesion.

  13. Effects of irradiated biodegradable polymer in endothelial cell monolayer formation

    Energy Technology Data Exchange (ETDEWEB)

    Arbeitman, Claudia R.; Grosso, Mariela F. del [CONICET – Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina); Gerencia de Investigación y Aplicaciones, TANDAR-CNEA (Argentina); Behar, Moni [Instituto de Física, UFRGS, Porto Alegre, RS (Brazil); García Bermúdez, Gerardo, E-mail: ggb@tandar.cnea.gov.ar [CONICET – Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina); Gerencia de Investigación y Aplicaciones, TANDAR-CNEA (Argentina); Escuela de Ciencia y Tecnología, UNSAM (Argentina)

    2013-11-01

    In this work we study cell adhesion, proliferation and cell morphology of endothelial cell cultured on poly-L-lactide acid (PLLA) modified by heavy ion irradiation. Thin films of PLLA samples were irradiated with sulfur (S) at energies of 75 MeV and gold (Au) at 18 MeV ion-beams. Ion beams were provided by the Tandar (Buenos Aires, Argentina) and Tandetron (Porto Alegre, Brazil) accelerators, respectively. The growth of a monolayer of bovine aortic endothelial cells (BAEC) onto unirradiated and irradiated surfaces has been studied by in vitro techniques in static culture. Cell viability and proliferation increased on modified substrates. But the results on unirradiated samples, indicate cell death (necrosis/apoptosis) with the consequent decrease in proliferation. We analyzed the correlation between irradiation parameters and cell metabolism and morphology.

  14. Dipole Formation at Interfaces of Alkanethiolate Self-assembled Monolayers and Ag(111)

    NARCIS (Netherlands)

    Rusu, Paul C.; Giovannetti, Gianluca; Brocks, Geert

    2007-01-01

    The formation of interface dipoles in self-assembled monolayers (SAMs) of −CH3 and −CF3 terminated short-chain alkanethiolates on Ag(111) is studied by means of density functional theory calculations. The interface dipoles are characterized by monitoring the change in the surface work function upon

  15. Covalently bound fluorine-containing monolayers on silicon and oxides : formation, stability and tribology

    NARCIS (Netherlands)

    Pujari, S.P.

    2013-01-01

    The formation of fluorinated monolayers with a minimized surface energy and an improved chemical stability on specific substrates will enable outstanding tribological properties and is the main goal of the research described in this thesis. Inorganic substrates, such as Si(111), silicon carbide (SiC

  16. Determination of three characteristic regimes of weakly charged polyelectrolytes monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Farhan [Department of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Shin, Kwanwoo [Department of Chemistry and Interdisciplinary Program of Integrated Biotechnology, Sogang University, Seoul 121-742 (Korea, Republic of)], E-mail: kshin@sogang.ac.kr; Choi, Jae-Hak [Advanced Radiation Technology Institute, KAERI, Jeongeup 580-185 (Korea, Republic of); Satija, Sushil K. [National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Kim, Joon-Seop [Department of Polymer Science and Engineering, Chosun University (Korea, Republic of); Rafailovich, Miriam H.; Sokolov, Jon [Department of Materials Science and Engineering, Stony Brook University, Stony Brook, NY 11794 (United States)

    2008-09-15

    We have demonstrated that monolayer films of randomly charged polystyrene sulfonated acid (PSSA) can be produced by the Langmuir technique, and observed the micro-domain structures, produced by the phase separation of electrostatically charged moieties and the hydrophobic moieties. Using atomic force microscopy and Langmuir isotherm, we found three specific regimes for the polyelectrolytes with various degrees of sulfonation (4-35%); very low charged PSSA (4-5%) in the hydrophobic regime, moderately charged PSSA (6-16%) which possessed a well-balanced nature between electrostatic and the hydrophobic interactions, and strongly amphiphilic nature of PSSA (6-16%) in the ionomer regime. Finally, we could categorize PSSA 35% in the polyelectrolyte regime, due to the dominance of the electrostatic interactions over the hydrophobic interactions.

  17. Nanoparticle layer deposition for highly controlled multilayer formation based on high-coverage monolayers of nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yue; Williams, Mackenzie G.; Miller, Timothy J.; Teplyakov, Andrew V., E-mail: andrewt@udel.edu

    2016-01-01

    This paper establishes a strategy for chemical deposition of functionalized nanoparticles onto solid substrates in a layer-by-layer process based on self-limiting surface chemical reactions leading to complete monolayer formation within the multilayer system without any additional intermediate layers — nanoparticle layer deposition (NPLD). This approach is fundamentally different from previously established traditional layer-by-layer deposition techniques and is conceptually more similar to well-known atomic and molecular layer deposition processes. The NPLD approach uses efficient chemical functionalization of the solid substrate material and complementary functionalization of nanoparticles to produce a nearly 100% coverage of these nanoparticles with the use of “click chemistry”. Following this initial deposition, a second complete monolayer of nanoparticles is deposited using a copper-catalyzed “click reaction” with the azide-terminated silica nanoparticles of a different size. This layer-by-layer growth is demonstrated to produce stable covalently-bound multilayers of nearly perfect structure over macroscopic solid substrates. The formation of stable covalent bonds is confirmed spectroscopically and the stability of the multilayers produced is tested by sonication in a variety of common solvents. The 1-, 2- and 3-layer structures are interrogated by electron microscopy and atomic force microscopy and the thickness of the multilayers formed is fully consistent with that expected for highly efficient monolayer formation with each cycle of growth. This approach can be extended to include a variety of materials deposited in a predesigned sequence on different substrates with a highly conformal filling. - Highlights: • We investigate the formation of high-coverage monolayers of nanoparticles. • We use “click chemistry” to form these monolayers. • We form multiple layers based on the same strategy. • We confirm the formation of covalent bonds

  18. Pit Formation during the Self-Assembly of Dithiol Monolayers on Au(111)

    Science.gov (United States)

    Macdairmid, A. R.; Cappello, M. L.; Keeler, W. J.; Banks, J. T.; Gallagher, M. C.

    2000-03-01

    The formation of pits one gold atom deep during the growth of alkanethiol monolayers on Au(111), has been observed previously by others. Explanations for pit formation include etching of the substrate, or mass transport of gold atom + thiol molecule on the surface, due to changes in surface energy^1. We have investigated the structure of dithiothreitol (DTT) SAMs on Au(111). Ex situ STM measurements indicate similar pitting occurs during formation of the dithiol monolayer. The degree of pitting depends on exposure time, sample temperature during formation, and subsequent annealing of the sample. Pitting is enhanced considerasbly when DTT is coordinated with Ti, in fact DTT/Ti films exhibit considerable pit motion during STM imaging. ^1 F. Teran et al. Electrochimica Acta 44, 1053 (1998).

  19. Microwave-assisted formation of organic monolayers from 1-alkenes on silicon carbide.

    Science.gov (United States)

    van den Berg, Sebastiaan A; Alonso, Jose Maria; Wadhwa, Kuldeep; Franssen, Maurice C R; Wennekes, Tom; Zuilhof, Han

    2014-09-09

    The rate of formation of covalently linked organic monolayers on HF-etched silicon carbide (SiC) is greatly increased by microwave irradiation. Upon microwave treatment for 60 min at 100 °C (60 W), 1-alkenes yield densely packed, covalently attached monolayers on flat SiC surfaces, a process that typically takes 16 h at 130 °C under thermal conditions. This approach was extended to SiC microparticles. The monolayers were characterized by X-ray photoelectron spectroscopy and static water contact angle measurements. The microwave-assisted reaction is compatible with terminal functionalities such as alkenes that enable subsequent versatile "click" chemistry reactions, further broadening the range and applicability of chemically modified SiC surfaces.

  20. Poly(ethylene glycol) monolayer formation and stability on gold and silicon nitride substrates.

    Science.gov (United States)

    Cerruti, Marta; Fissolo, Stefano; Carraro, Carlo; Ricciardi, Carlo; Majumdar, Arun; Maboudian, Roya

    2008-10-07

    Poly(ethylene glycol) (PEG) self-assembled monolayers (SAMs) are extensively used to modify substrates to prevent nonspecific protein adsorption and to increase hydrophilicity. X-ray photoelectron spectroscopy analysis, complemented by water contact angle measurements, is employed to investigate the formation and stability upon aging and heating of PEG monolayers formed on gold and silicon nitride substrates. In particular, thiolated PEG monolayers on gold, with and without the addition of an undecylic spacer chain, and PEG monolayers formed with oxysilane precursors on silicon nitride have been probed. It is found that PEG-thiol SAMs are degraded after less than two weeks of exposure to air and when heated at temperatures as low as 120 degrees C. On the contrary, PEG-silane SAMs are stable for more than two weeks, and fewer molecules are desorbed even after two months of aging, compared to those desorbed in two weeks from the PEG-thiol SAMs. A strongly bound hydration layer is found on PEG-silane SAMs aged for two months. Heating PEG-silane SAMs to temperatures as high as 160 degrees C improves the quality of the monolayer, desorbing weakly bound contaminants. The differences in stability between PEG-thiol SAMs and PEG-silane SAMs are ascribed to the different types of bonding to the surface and to the fact that the thiol-Au bond can be easily oxidized, thus causing desorption of PEG molecules from the surface.

  1. Tunnelling characteristics of Stone-Wales defects in monolayers of Sn and group-V elements

    Science.gov (United States)

    Jamdagni, Pooja; Kumar, Ashok; Thakur, Anil; Pandey, Ravindra; Ahluwalia, P. K.

    2017-10-01

    Topological defects in ultrathin layers are often formed during synthesis and processing, thereby strongly influencing the electronic properties of layered systems. For the monolayers of Sn and group-V elements, we report the results based on density functional theory determining the role of Stone-Wales (SW) defects in modifying their electronic properties. The calculated results find the electronic properties of the Sn monolayer to be strongly dependent on the concentration of SW defects, e.g. defective stanene has nearly zero band gap (≈0.03 eV) for the defect concentration of 2.2  ×  1013 cm-2 which opens up to 0.2 eV for the defect concentration of 3.7  ×  1013 cm-2. In contrast, SW defects appear to induce conduction states in the semiconducting monolayers of group-V elements. These conduction states act as channels for electron tunnelling, and the calculated tunnelling characteristics show the highest differential conductance for the negative bias with the asymmetric current-voltage characteristics. On the other hand, the highest differential conductance was found for the positive bias in stanene. Simulated STM topographical images of stanene and group-V monolayers show distinctly different features in terms of their cross-sectional views and distance-height profiles. These distinctive features can serve as fingerprints to identify the topological defects in experiments for the monolayers of group-IV and group-V elements.

  2. Elasticity and tumorigenic characteristics of cells in a monolayer after nanosecond pulsed electric field exposure.

    Science.gov (United States)

    Steuer, A; Wende, K; Babica, P; Kolb, J F

    2017-09-01

    Nanosecond pulsed electric fields (nsPEFs) applied to cells can induce different biological effects depending on pulse duration and field strength. One known process is the induction of apoptosis whereby nsPEFs are currently investigated as a novel cancer therapy. Another and probably related change is the breakdown of the cytoskeleton. We investigated the elasticity of rat liver epithelial cells WB-F344 in a monolayer using atomic force microscopy (AFM) with respect to the potential of cells to undergo malignant transformation or to develop a potential to metastasize. We found that the elastic modulus of the cells decreased significantly within the first 8 min after treatment with 20 pulses of 100 ns and with a field strength of 20 kV/cm but was still higher than the elasticity of their tumorigenic counterpart WB-ras. AFM measurements and immunofluorescent staining showed that the cellular actin cytoskeleton became reorganized within 5 min. However, both a colony formation assay and a cell migration assay revealed no significant changes after nsPEF treatment, implying that cells seem not to adopt malignant characteristics associated with metastasis formation despite the induced transient changes to elasticity and cytoskeleton that can be observed for up to 1 h.

  3. Features in Formation and Properties of Langmuir-Blodgett Monolayers

    Directory of Open Access Journals (Sweden)

    A.P. Kuzmenko

    2013-12-01

    Full Text Available Features in formation of Langmuir-Blodgett films and possible control and study of their properties directly in deposing them onto sub-strates are studied. Linearity of the dependence of polarization on the slope angle of the static dipole moment for C18H36O2 and C18H34O2 has been checked.

  4. Formation of octadecyltrichlorosilane (OTS) self-assembled monolayers on amorphous alumina

    Science.gov (United States)

    Kelkar, Sanket S.; Chiavetta, David; Wolden, Colin A.

    2013-10-01

    The kinetics and thermodynamics of octadecyltrichlorosilane (OTS) self-assembled monolayers (SAMs) on vapor deposited alumina were quantified. Ozone cleaning serves to create well-defined hydrophilic surfaces for OTS attachment, and the use of heptane as a solvent enables the formation of high quality SAMs under ambient conditions. The kinetics was characterized as a function of OTS concentration using contact angle goniometry, ellipsometry and Fourier transform infrared (FTIR) spectroscopy. The kinetics of SAM formation and the saturation contact angle (∼100̊) on alumina are comparable to what has been observed for OTS on silicon. The free energy of adsorption with ΔGads values ranged from -7.5 to -5.4 kcal/mol, and the SAMs were stable up to 230 ̊C. The critical surface tension of the OTS monolayer was found to be 21.4 dyne/cm.

  5. Formation of octadecyltrichlorosilane (OTS) self-assembled monolayers on amorphous alumina

    Energy Technology Data Exchange (ETDEWEB)

    Kelkar, Sanket S.; Chiavetta, David; Wolden, Colin A., E-mail: cwolden@mines.edu

    2013-10-01

    The kinetics and thermodynamics of octadecyltrichlorosilane (OTS) self-assembled monolayers (SAMs) on vapor deposited alumina were quantified. Ozone cleaning serves to create well-defined hydrophilic surfaces for OTS attachment, and the use of heptane as a solvent enables the formation of high quality SAMs under ambient conditions. The kinetics was characterized as a function of OTS concentration using contact angle goniometry, ellipsometry and Fourier transform infrared (FTIR) spectroscopy. The kinetics of SAM formation and the saturation contact angle (∼100{sup o}) on alumina are comparable to what has been observed for OTS on silicon. The free energy of adsorption with ΔG{sub ads} values ranged from −7.5 to −5.4 kcal/mol, and the SAMs were stable up to 230 {sup o}C. The critical surface tension of the OTS monolayer was found to be 21.4 dyne/cm.

  6. Extended Moment Formation in Monolayer WS2Doped with 3d Transition-Metals

    KAUST Repository

    Singh, Nirpendra

    2016-08-30

    First-principles calculations with onsite Coulomb interaction and spin-orbit coupling are used to investigate the electronic structure of monolayer WS2 doped substitutionally with 3d transition-metals. While neither W vacancies nor strain induce spin polarization, we demonstrate an unprecedented tendency to extended moment formation under doping. The extended magnetic moments are characterized by dopant-specific spin density patterns with rich structural features involving the nearest neighbor W and S atoms.

  7. Implications of lipid monolayer charge characteristics on their selective interactions with a short antimicrobial peptide.

    Science.gov (United States)

    Ciumac, Daniela; Campbell, Richard A; Xu, Hai; Clifton, Luke A; Hughes, Arwel V; Webster, John R P; Lu, Jian R

    2017-02-01

    Many antimicrobial peptides (AMPs) target bacterial membranes and they kill bacteria by causing structural disruptions. One of the fundamental issues however lies in the selective responses of AMPs to different cell membranes as a lack of selectivity can elicit toxic side effects to mammalian host cells. A key difference between the outer surfaces of bacterial and mammalian cells is the charge characteristics. We report a careful study of the binding of one of the representative AMPs, with the general sequence G(IIKK)4I-NH2 (G4), to the spread lipid monolayers of DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) and DPPG (1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (sodium salt)) mimicking the charge difference between them, using the combined measurements from Langmuir trough, Brewster angle microscopy (BAM) and neutron reflection (NR). The difference in pressure rise upon peptide addition into the subphase clearly demonstrated the different interactions arising from different lipid charge features. Morphological changes from the BAM imaging confirmed the association of the peptide into the lipid monolayers, but there was little difference between them. However, NR studies revealed that the peptide bound 4 times more onto the DPPG monolayer than onto the DPPC monolayer. Importantly, whilst the peptide could only be associated with the head groups of DPPC it was well penetrated into the entire DPPG monolayer, showing that the electrostatic interaction strengthened the hydrophobic interaction and that the combined molecular interactive processes increased the power of G4 in disrupting the charged membranes. The results are discussed in the context of general antibacterial actions as observed from other AMPs and membrane lytic actions.

  8. Highly active engineered-enzyme oriented monolayers: formation, characterization and sensing applications

    Directory of Open Access Journals (Sweden)

    Patolsky Fernando

    2011-06-01

    Full Text Available Abstract Background The interest in introducing ecologically-clean, and efficient enzymes into modern industry has been growing steadily. However, difficulties associated with controlling their orientation, and maintaining their selectivity and reactivity is still a significant obstacle. We have developed precise immobilization of biomolecules, while retaining their native functionality, and report a new, fast, easy, and reliable procedure of protein immobilization, with the use of Adenylate kinase as a model system. Methods Self-assembled monolayers of hexane-1,6-dithiol were formed on gold surfaces. The monolayers were characterized by contact-angle measurements, Elman-reagent reaction, QCM, and XPS. A specifically designed, mutated Adenylate kinase, where cysteine was inserted at the 75 residue, and the cysteine at residue 77 was replaced by serine, was used for attachment to the SAM surface via spontaneously formed disulfide (S-S bonds. QCM, and XPS were used for characterization of the immobilized protein layer. Curve fitting in XPS measurements used a Gaussian-Lorentzian function. Results and Discussion Water contact angle (65-70°, as well as all characterization techniques used, confirmed the formation of self-assembled monolayer with surface SH groups. X-ray photoelectron spectroscopy showed clearly the two types of sulfur atom, one attached to the gold (triolate and the other (SH/S-S at the ω-position for the hexane-1,6-dithiol SAMs. The formation of a protein monolayer was confirmed using XPS, and QCM, where the QCM-determined amount of protein on the surface was in agreement with a model that considered the surface area of a single protein molecule. Enzymatic activity tests of the immobilized protein confirmed that there is no change in enzymatic functionality, and reveal activity ~100 times that expected for the same amount of protein in solution. Conclusions To the best of our knowledge, immobilization of a protein by the method

  9. Phases and phase transition in insoluble and adsorbed monolayers of amide amphiphiles: Specific characteristics of the condensed phases.

    Science.gov (United States)

    Vollhardt, D

    2015-08-01

    For understanding the role of amide containing amphiphiles in inherently complex biological processes, monolayers at the air-water interface are used as simple biomimetic model systems. The specific characteristics of the condensed phases and phase transition in insoluble and adsorbed monolayers of amide amphiphiles are surveyed to highlight the effect of the chemical structure of the amide amphiphiles on the interfacial interactions in model monolayers. The mesoscopic topography and/or two-dimensional lattice structures of selected amino acid amphiphiles, amphiphilic N-alkylaldonamide, amide amphiphiles with specific tailored headgroups, such as amide amphiphiles based on derivatized ethanolamine, e.g. acylethanolamines (NAEs) and N-,O-diacylethanolamines (DAEs) are presented. Special attention is devoted the dominance of N,O-diacylated ethanolamine in mixed amphiphilic acid amide monolayers. The evidence that a first order phase transition can occur in adsorption layers and that condensed phase domains of mesoscopic scale can be formed in adsorption layers was first obtained on the basis of the experimental characteristics of a tailored amide amphiphile. New thermodynamic and kinetic concepts for the theoretical description of the characteristics of amide amphiphile's monolayers were developed. In particular, the equation of state for Langmuir monolayers generalized for the case that one, two or more phase transitions occur, and the new theory for phase transition in adsorbed monolayers are experimentally confirmed at first by amide amphiphile monolayers. Despite the significant progress made towards the understanding the model systems, these model studies are still limited to transfer the gained knowledge to biological systems where the fundamental physical principles are operative in the same way. The study of biomimetic systems, as described in this review, is only a first step in this direction.

  10. Electrochemically driven organic monolayer formation on silicon surfaces using alkylammonium and alkylphosphonium reagents

    Science.gov (United States)

    Wang, Dong; Buriak, Jillian M.

    2005-10-01

    The functionalization of silicon surfaces with organic monolayers, bound through Si-C bonds, is an area of wide interest due to the technological promise of organosilicon hybrid devices, but also to investigate fundamental surface reactivity. In this paper, the use of alkylammonium and alkylphosphonium cations as sources of organic moieties to bind to hydrogen-terminated flat and porous silicon is demonstrated. Tetraalkylammonium, tetraalkyl/arylphosphonium reagents, and alkyl pyridinium salts can be utilized, but trialkylammonium salts cannot as they yield substantial surface oxidation. Under electrochemical conditions, either potentiostatic or galvanostatic modes, alkyl groups derived from the ammonium or phosphonium salts are grafted to the silicon surface and are bound through Si-C bonds. Covalent attachment of the organic monolayers to the surface was demonstrated by XPS, AFM scribing, and FTIR. The mechanism may proceed via reduction of the ammonium salt yielding alkyl radicals, R rad , which may be reduced to R - and attack surface Si-Si bonds, leading to Si-C bonds, or the formation of silyl anions (≡Si -) under the cathodic conditions followed by nucleophilic attack on the trialkylammonium cation.

  11. Formation, Energetics, and Electronic Properties of Graphene Monolayer and Bilayer Doped with Heteroatoms

    Directory of Open Access Journals (Sweden)

    Yoshitaka Fujimoto

    2015-01-01

    Full Text Available Doping with heteroatoms is one of the most effective methods to tailor the electronic properties of carbon nanomaterials such as graphene and carbon nanotubes, and such nanomaterials doped with heteroatom dopants might therefore provide not only new physical and chemical properties but also novel nanoelectronics/optoelectronics device applications. The boron and nitrogen are neighboring elements to carbon in the periodic table, and they are considered to be good dopants for carbon nanomaterials. We here review the recent work of boron and nitrogen doping effects into graphene monolayer as well as bilayer on the basis of the first-principles electronic structure calculations in the framework of the density-functional theory. We show the energetics and the electronic properties of boron and nitrogen defects in graphene monolayer and bilayer. As for the nitrogen doping, we further discuss the stabilities, the growth processes, and the electronic properties associated with the plausible nitrogen defect formation in graphene which is suggested by experimental observations.

  12. The Effects of Contact Interface on the Friction Characteristics of Self-assembly Monolayers

    Institute of Scientific and Technical Information of China (English)

    ZHANGHui-chen; GAOYu-zhou; YANLi

    2004-01-01

    The effects of different contact interfaces on the friction characteristics of OTS self-assembled monolayers were investigated by a universal micro-tribometer in different sliding velocities. The results indicate that there exist lower friction coefficients between OTS SAMs and Ti, Ni and Cu films deposited on GCrl5 steel balls than those between OTS SAMs and GCr15 steel ball. The friction coefftcient between OTS SAMs and Ti film is the largest, and the friction coefficient between OTS SAMs and Cu film is the least in these three films, which depends the iatrinsic characteristics of the materials. The friction coefficients between OTS SAMs and GCrI5 steel balland three nanometer films increase with the sliding velachy increasing, which can be explained by the relaxationcharacteristics of OTS molecules.

  13. Study on the formation of self-assembled monolayers on sol-gel processed hafnium oxide as dielectric layers.

    Science.gov (United States)

    Ting, Guy G; Acton, Orb; Ma, Hong; Ka, Jae Won; Jen, Alex K-Y

    2009-02-17

    High dielectric constant (k) metal oxides such as hafnium oxide (HfO2) have gained significant interest due to their applications in microelectronics. In order to study and control the surface properties of hafnium oxide, self-assembled monolayers (SAMs) of four different long aliphatic molecules with binding groups of phosphonic acid, carboxylic acid, and catechol were formed and characterized. Surface modification was performed to improve the interface between metal oxide and top deposited materials as well as to create suitable dielectric properties, that is, leakage current and capacitance densities, which are important in organic thin film transistors. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, contact angle goniometry, atomic force microscopy (AFM), and simple metal-HfO2-SAM-metal devices were used to characterize the surfaces before and after SAM modification on sol-gel processed hafnium oxide. The alkylphosphonic acid provided the best monolayer formation on sol-gel processed hafnium oxide to generate a well-packed, ultrathin dielectric exhibiting a low leakage current density of 2x10(-8) A/cm2 at an applied voltage of -2.0 V and high capacitance density of 0.55 microF/cm2 at 10 kHz. Dialkylcatechol showed similar characteristics and the potential for using the catechol SAMs to modify HfO2 surfaces. In addition, the integration of this alkylphosphonic acid SAM/hafnium oxide hybrid dielectric into pentacene-based thin film transistors yields low-voltage operation within 1.5 V and improved performance over bare hafnium oxide.

  14. Variation of Surface Adhesion Force During the Formation of OTS Self-assembled Monolayer Investigated by AFM

    Institute of Scientific and Technical Information of China (English)

    徐国华; HigashitaniKo

    1999-01-01

    Variation of the surface adhesion force during the formation of octadecyl trichlororilane (OTS) .self-assembled monolayer on a glass substrate surface was investigated hy atomic force microscope (AFM). The research shows that the hydrophobicity and the adbeslon force of the sample surface increases gradualy while the substrate surface is covered by OTS molecules as the reaction proceeds. After 15 min reaction, a cloee-pac.ked and smooth OTS self-assembled monolayer could from on the glass subetrate surface with an advancing contact angle of 105° and an interfaeial energy of 55.79 mJ.m-2.

  15. Formation and Characterization of Self-Assembled Phenylboronic Acid Derivative Monolayers toward Developing Monosaccaride Sensing-Interface

    Directory of Open Access Journals (Sweden)

    Kwangnak Koh

    2007-08-01

    Full Text Available We designed and synthesized phenylboronic acid as a molecular recognitionmodel system for saccharide detection. The phenylboronic acid derivatives that haveboronic acid moiety are well known to interact with saccharides in aqueous solution; thus,they can be applied to a functional interface of saccharide sensing through the formation ofself-assembled monolayer (SAM. In this study, self-assembled phenylboronic acidderivative monolayers were formed on Au surface and carefully characterized by atomicforce microscopy (AFM, Fourier transform infrared reflection absorption spectroscopy(FTIR-RAS, surface enhanced Raman spectroscopy (SERS, and surface electrochemicalmeasurements. The saccharide sensing application was investigated using surface plasmonresonance (SPR spectroscopy. The phenylboronic acid monolayers showed goodsensitivity of monosaccharide sensing even at the low concentration range (1.0 × 10-12 M.The SPR angle shift derived from interaction between phenylboronic acid andmonosaccharide was increased with increasing the alkyl spacer length of synthesizedphenylboronic acid derivatives.

  16. A note on the use of ellipsometry for studying the kinetics of formation of self-assembled monolayers

    Indian Academy of Sciences (India)

    Murali Sastry

    2000-06-01

    Ellipsometry is currently one of the most important techniques for characterization of the deposition and growth mode of ultra thin organic films. However, it is well known that for thicknesses normally encountered in organic monolayer films, as would occur for example in self-assembled monolayers, ellipsometry cannot be used to simultaneously determine the thickness and refractive index of the monolayer film. Current practice is to assume a reasonable value for the film refractive index and calculate an effective ‘ellipsometric thickness’. This communication seeks to show that the alternative approach of assuming a thickness for the monolayer (determined by the length of the molecule) and calculating the effective film refractive index lends itself to easier and more meaningful physical interpretation. The Lorentz–Lorenz formula is then used to transform the effective refractive index into a surface coverage and hence to an effective mass coverage. The methodology advanced is applied to the kinetics of formation of a self-assembled monolayer of a well-studied molecule, octadecanethiol on Au.

  17. Reducing Staphylococcus aureus biofilm formation on stainless steel 316L using functionalized self-assembled monolayers.

    Science.gov (United States)

    Kruszewski, Kristen M; Nistico, Laura; Longwell, Mark J; Hynes, Matthew J; Maurer, Joshua A; Hall-Stoodley, Luanne; Gawalt, Ellen S

    2013-05-01

    Stainless steel 316L (SS316L) is a common material used in orthopedic implants. Bacterial colonization of the surface and subsequent biofilm development can lead to refractory infection of the implant. Since the greatest risk of infection occurs perioperatively, strategies that reduce bacterial adhesion during this time are important. As a strategy to limit bacterial adhesion and biofilm formation on SS316L, self-assembled monolayers (SAMs) were used to modify the SS316L surface. SAMs with long alkyl chains terminated with hydrophobic (-CH3) or hydrophilic (oligoethylene glycol) tail groups were used to form coatings and in an orthogonal approach, SAMs were used to immobilize gentamicin or vancomycin on SS316L for the first time to form an "active" antimicrobial coating to inhibit early biofilm development. Modified SS316L surfaces were characterized using surface infrared spectroscopy, contact angles, MALDI-TOF mass spectrometry and atomic force microscopy. The ability of SAM-modified SS316L to retard biofilm development by Staphylococcus aureus was functionally tested using confocal scanning laser microscopy with COMSTAT image analysis, scanning electron microscopy and colony forming unit analysis. Neither hydrophobic nor hydrophilic SAMs reduced biofilm development. However, gentamicin-linked and vancomycin-linked SAMs significantly reduced S. aureus biofilm formation for up to 24 and 48 h, respectively.

  18. Water-repellent coating: formation of polymeric self-assembled monolayers on nanostructured surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Woo Kyung [Department of Chemistry and School of Molecular Science (BK21), Center for Molecular Design and Synthesis, KAIST, Daejeon 305-701 (Korea, Republic of); Park, Sangjin [Research Center for Biomolecular Nanotechnology, Department of Life Science, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Jon, Sangyong [Research Center for Biomolecular Nanotechnology, Department of Life Science, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Choi, Insung S [Department of Chemistry and School of Molecular Science (BK21), Center for Molecular Design and Synthesis, KAIST, Daejeon 305-701 (Korea, Republic of)

    2007-10-03

    In this paper, we suggest a facile and effective method for water-repellent coating of oxide surfaces. As a coating material, we synthesized a new random copolymer, referred to as poly(TMSMA-r-fluoroMA), by the radical polymerization of 3-(trimethoxysilyl)propyl methacrylate (TMSMA) and a fluoromonomer'' (registered) bearing methacrylate moiety (fluoroMA). The random copolymer was designed to consist of a 'surface-reactive part' (trimethoxysilyl group) for anchoring onto oxide-based surfaces and a 'functional part' (perfluoro group) for water repellency. The polymeric self-assembled monolayers (pSAMs) of poly(TMSMA-r-fluoroMA) were constructed on three different aluminum oxide substrates, such as flat, concave-textured, and nanoporous plates, and the static water contact angle of each surface before and after the formation of pSAMs was measured. The formation of pSAMs resulted in significantly enhanced hydrophobicity compared with the corresponding bare surfaces. In particular, among three poly(TMSMA-r-fluoroMA)-coated surfaces, the nanoporous plate showed the highest water-repellent property, with a static contact angle of {approx}163 deg., which is indicative of superhydrophobic surfaces.

  19. Formation of self-assembled monolayer of curcuminoid molecules on gold surfaces

    Science.gov (United States)

    Berlanga, Isadora; Etcheverry-Berríos, Álvaro; Mella, Andy; Jullian, Domingo; Gómez, Victoria Alejandra; Aliaga-Alcalde, Núria; Fuenzalida, Victor; Flores, Marcos; Soler, Monica

    2017-01-01

    We investigated the formation of self-assembled monolayers of two thiophene curcuminoid molecules, 2-thphCCM (1) and 3-thphCCM (2), on polycrystalline gold substrates prepared by immersion of the surfaces in a solution of the molecules during 24 h. The functionalized surfaces were studied by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). Despite the fact that both molecules have the same composition and almost the same structure, these molecules exhibit different behavior on the gold surface, which can be explained by the different positions of the sulfur atoms in the terminal aromatic rings. In the case of molecule 1, the complete formation of a SAM can be observed after 24 h of immersion. In the case of molecule 2, the transition from flat-lying to upright configuration on the surface is still in process after 24 h of immersion. This is attributed to the fact that molecule 2 have the sulfur atoms more exposed than molecule 1.

  20. Theoretical study of polyiodide formation and stability on monolayer and bilayer graphene.

    Science.gov (United States)

    Tristant, Damien; Puech, Pascal; Gerber, Iann C

    2015-11-28

    The presence of polyiodide complexes have been reported several times when carbon-based materials were doped by iodine molecules, but their formation mechanism remains unclear. By using first-principles calculations that include nonlocal correlation effects by means of a van der Waals density functional approach, we propose that the formation of triiodide (I3(-)) and pentaiodide (I5(-)) is due to a large density of iodine molecules (I2) in interaction with a carbonaceous substrate. As soon as the concentration of surface iodine reaches a threshold value of 12.5% for a graphene monolayer and 6.25% for a bilayer, these complexes spontaneously appear. The corresponding structural and energetic aspects, electronic structures and vibrational frequencies support this statement. An upshift of the Dirac point from the Fermi level with values of 0.45 and 0.52 eV is observed for adsorbed complexes on graphene and intercalated complexes between two layers, respectively. For doped-graphene, it corresponds to a graphene hole density of around 1.1 × 10(13) cm(-2), in quantitative agreement with experiments. Additionally, we have studied the thermal stability at room temperature of these adsorbed ions on graphene by means of ab initio molecular dynamics, which also shows successful p-doping with polyiodide complexes.

  1. Water-repellent coating: formation of polymeric self-assembled monolayers on nanostructured surfaces

    Science.gov (United States)

    Cho, Woo Kyung; Park, Sangjin; Jon, Sangyong; Choi, Insung S.

    2007-10-01

    In this paper, we suggest a facile and effective method for water-repellent coating of oxide surfaces. As a coating material, we synthesized a new random copolymer, referred to as poly(TMSMA-r-fluoroMA), by the radical polymerization of 3-(trimethoxysilyl)propyl methacrylate (TMSMA) and a fluoromonomer® bearing methacrylate moiety (fluoroMA). The random copolymer was designed to consist of a 'surface-reactive part' (trimethoxysilyl group) for anchoring onto oxide-based surfaces and a 'functional part' (perfluoro group) for water repellency. The polymeric self-assembled monolayers (pSAMs) of poly(TMSMA-r-fluoroMA) were constructed on three different aluminum oxide substrates, such as flat, concave-textured, and nanoporous plates, and the static water contact angle of each surface before and after the formation of pSAMs was measured. The formation of pSAMs resulted in significantly enhanced hydrophobicity compared with the corresponding bare surfaces. In particular, among three poly(TMSMA-r-fluoroMA)-coated surfaces, the nanoporous plate showed the highest water-repellent property, with a static contact angle of ~163°, which is indicative of superhydrophobic surfaces.

  2. Formation and stability of manganese-doped ZnS quantum dot monolayers determined by QCM-D and streaming potential measurements.

    Science.gov (United States)

    Oćwieja, Magdalena; Matras-Postołek, Katarzyna; Maciejewska-Prończuk, Julia; Morga, Maria; Adamczyk, Zbigniew; Sovinska, Svitlana; Żaba, Adam; Gajewska, Marta; Król, Tomasz; Cupiał, Klaudia; Bredol, Michael

    2017-10-01

    Manganese-doped ZnS quantum dots (QDs) stabilized by cysteamine hydrochloride were successfully synthesized. Their thorough physicochemical characteristics were acquired using UV-Vis absorption and photoluminescence spectroscopy, X-ray diffraction, dynamic light scattering (DLS), transmission electron microscopy (HR-TEM), energy dispersive spectroscopy (EDS) and Fourier transform infrared (FT-IR) spectroscopy. The average particle size, derived from HR-TEM, was 3.1nm, which agrees with the hydrodynamic diameter acquired by DLS, that was equal to 3-4nm, depending on ionic strength. The quantum dots also exhibited a large positive zeta potential varying between 75 and 36mV for ionic strength of 10(-4) and 10(-2)M, respectively (at pH 6.2) and an intense luminescent emission at 590nm. The quantum yield was equal to 31% and the optical band gap energy was equal to 4.26eV. The kinetics of QD monolayer formation on silica substrates (silica sensors and oxidized silicon wafers) under convection-controlled transport was quantitatively evaluated by the quartz crystal microbalance (QCM) and the streaming potential measurements. A high stability of the monolayer for ionic strength 10(-4) and 10(-2)M was confirmed in these measurements. The experimental data were adequately reflected by the extended random sequential adsorption model (eRSA). Additionally, thorough electrokinetic characteristics of the QD monolayers and their stability for various ionic strengths and pH were acquired by streaming potential measurements carried out under in situ conditions. These results were quantitatively interpreted in terms of the three-dimensional (3D) electrokinetic model that furnished bulk zeta potential of particles for high ionic strengths that is impractical by other experimental techniques. It is concluded that these results can be used for designing of biosensors of controlled monolayer structure capable to bind various ligands via covalent as well as electrostatic interactions

  3. Line-defect mediated formation of hole and Mo clusters in monolayer molybdenum disulfide

    Science.gov (United States)

    Ryu, Gyeong Hee; Lee, Jongyeong; Kim, Na Yeon; Lee, Yeongdong; Kim, Youngchan; Kim, Moon J.; Lee, Changgu; Lee, Zonghoon

    2016-03-01

    The production of hole and Mo cluster by electron beam irradiation in molybdenum disulfide (MoS2), which consists of S-Mo-S layers, is monitored over time using atomic resolution transmission electron microscopy. S vacancies are firstly formed due to knocking off of S atoms and then line defects are induced due to accumulation of S vacancies in MoS2 sheet instead of forming a hole. The line defects tend to be merged at a point and a hole is formed subsequently at the point. Mo atoms tend to be clustered discretely as a nano sheet along the edge of the hole due to difference in displacement threshold energy between Mo and S atoms under electron irradiation. After Mo clusters are nearly separated from MoS2 sheet, the clusters are transformed into body-centered cubic nanocrystal of Mo during prolonged electron beam irradiation. The line defect mediated formation of hole and Mo cluster only occurs within a single grain of monolayer MoS2 sheet.

  4. Covalently attached organic monolayers on SiC and SixN4 surfaces: Formation using UV light at room temperature

    NARCIS (Netherlands)

    Rosso, M.; Giesbers, M.; Arafat, A.; Schroën, C.G.P.H.; Zuilhof, H.

    2009-01-01

    We describe the formation of alkyl monolayers on silicon carbide (SiC) and silicon-rich silicon nitride (SixN4) surfaces, using UV irradiation in the presence of alkenes. Both the surface preparation and the monolayer attachment were carried out under ambient conditions. The stable coatings obtained

  5. Reducing Staphylococcus aureus biofilm formation on stainless steel 316L using functionalized self-assembled monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Kruszewski, Kristen M., E-mail: kruszewskik@duq.edu [Duquesne University, Department of Chemistry and Biochemistry, 600 Forbes Avenue, Pittsburgh, PA 15282 (United States); Nistico, Laura, E-mail: lnistico@wpahs.org [Allegheny General Hospital, Center for Genomic Sciences, Allegheny-Singer Research Institute, 320 East North Avenue, 11th floor, South Tower, Pittsburgh, PA 15212 (United States); Longwell, Mark J., E-mail: mlongwel@wpahs.org [Allegheny General Hospital, Center for Genomic Sciences, Allegheny-Singer Research Institute, 320 East North Avenue, 11th floor, South Tower, Pittsburgh, PA 15212 (United States); Hynes, Matthew J., E-mail: mjhynes@go.wustl.edu [Washington University in St. Louis, Department of Chemistry, One Brookings Drive, St. Louis, MO 63130 (United States); Maurer, Joshua A., E-mail: maurer@wustl.edu [Washington University in St. Louis, Department of Chemistry, One Brookings Drive, St. Louis, MO 63130 (United States); Hall-Stoodley, Luanne, E-mail: L.Hall-Stoodley@soton.ac.uk [Southampton Wellcome Trust Clinical Research Facility/NIHR Respiratory BRU, University of Southampton Faculty of Medicine, Southampton General Hospital, Tremona Road, Southampton, Hampshire SO16 6YD (United Kingdom); Gawalt, Ellen S., E-mail: gawalte@duq.edu [Duquesne University, Department of Chemistry and Biochemistry, McGowan Institute for Regenerative Medicine, 600 Forbes Avenue, Pittsburgh, PA 15282 (United States)

    2013-05-01

    Stainless steel 316L (SS316L) is a common material used in orthopedic implants. Bacterial colonization of the surface and subsequent biofilm development can lead to refractory infection of the implant. Since the greatest risk of infection occurs perioperatively, strategies that reduce bacterial adhesion during this time are important. As a strategy to limit bacterial adhesion and biofilm formation on SS316L, self-assembled monolayers (SAMs) were used to modify the SS316L surface. SAMs with long alkyl chains terminated with hydrophobic (− CH{sub 3}) or hydrophilic (oligoethylene glycol) tail groups were used to form coatings and in an orthogonal approach, SAMs were used to immobilize gentamicin or vancomycin on SS316L for the first time to form an “active” antimicrobial coating to inhibit early biofilm development. Modified SS316L surfaces were characterized using surface infrared spectroscopy, contact angles, MALDI-TOF mass spectrometry and atomic force microscopy. The ability of SAM-modified SS316L to retard biofilm development by Staphylococcus aureus was functionally tested using confocal scanning laser microscopy with COMSTAT image analysis, scanning electron microscopy and colony forming unit analysis. Neither hydrophobic nor hydrophilic SAMs reduced biofilm development. However, gentamicin-linked and vancomycin-linked SAMs significantly reduced S. aureus biofilm formation for up to 24 and 48 h, respectively. - Highlights: ► SS316L was modified with glycol terminated SAMs in order to reduce biofilm growth. ► Antibiotics gentamicin and vancomycin were immobilized on SS316L via SAMs. ► Only the antibiotic modifications reduced biofilm development on SS316L.

  6. Phosphatidylcholine Monolayer Formation at a Liquid:Liquid Interface as Monitored by the Dynamic Surface Tension

    Science.gov (United States)

    2007-11-02

    concentration, while liquid crystalline vesicles form tightly packed monolayers at bulk PC concentrations above 2 ^Molar. Resolving this paradigm ...regardless of lipid bilayer phase. Initially, vesicle rupture probably represents an entropically driven process. The system will become increasingly

  7. Atomic-level elucidation of the initial stages of self-assembled monolayer metallization and nanoparticle formation.

    Science.gov (United States)

    Keith, John A; Jacob, Timo

    2010-11-02

    The development of high-performance molecular electronics and nanotech applications requires deep understanding of atomic level structural, electronic, and magnetic properties of electrode/molecular interfaces. Recent electrochemical experiments on self-assembled monolayers (SAMs) have identified highly practical means to generate nanoparticles and metal monolayers suspended above substrate surfaces through SAM metallizations. A rational basis why this process is even possible is not yet well-understood. To clarify the initial stages of interface formation during SAM metallization, we used first-principles spin-polarized density functional theory (DFT) calculations to study Pd diffusion on top of 4-mercaptopyridine (4MP) SAMs on Au(111). After distinguishing potential-energy surfaces (PESs) for different spin configurations for transition metal atoms on the SAM, we find adatom diffusion is not possible over the clean 4MP-SAM surface. Pre-adsorption of transition-metal atoms, however, facilitates atomic diffusion that appears to explain multiple reports on experimentally observed island and monolayer formation on top of SAMs. Furthermore, these diffusions most likely occur by moving across low-lying and intersecting PESs of different spin states, opening the possibility of magnetic control over these systems. Vertical diffusion processes were also investigated, and the electrolyte was found to play a key role in preventing metal permeation through the SAM to the substrate.

  8. Characterization of Formation Kinetics of Self-Assembled Thiol Monolayers on Gold by Electrochemical Impedance Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Self-assembled monolayers of octadecanethiol (ODT) on gold have been studied by electrochemical impedance spectroscopy (EIS). The fractional coverage has been examined as a function of immersion time of Au in ODT deposition solution. The fractional coverage exhibits two distinct adsorption steps: an initial rapid step followed by a slow one. The fractional coverage of ODT monolayer increases sharply from zero to more than 99% of its maximum within the first minute. However, it takes a day for the fractional coverage to approach its final value.

  9. Possibility of a 2D SiC monolayer formation on Mg(0001) and MgO(111) substrates

    Science.gov (United States)

    Kuzubov, A. A.; Eliseeva, N. S.; Krasnov, P. O.; Tomilin, F. N.; Fedorov, A. S.; Tolstaya, A. V.

    2013-08-01

    The geometrical characteristics of a 2D SiC monolayer on Mg(0001) and MgO(111) plates regarded as potential materials for growing two-dimensional silicon carbide were studied. The most favorable positions of the atoms of 2D SiC on the substrates were determined. In the 2D SiC/Mg(0001) system, unlike in 2D SiC/MgO(111), the deviation of the carbon atom from the silicon carbide monolayer was insignificant (0.08 Å). Consequently, magnesium can be used as a substrate for growing two-dimensional silicon carbide. The use of MgO(111) is not recommended because of a significant distortion of the 2D SiC surface.

  10. A Trimeric Surfactant: Surface Micelles, Hydration-Lubrication, and Formation of a Stable, Charged Hydrophobic Monolayer.

    Science.gov (United States)

    Kampf, Nir; Wu, Chunxian; Wang, Yilin; Klein, Jacob

    2016-11-15

    The surface structure of the trimeric surfactant tri(dodecyldimethylammonioacetoxy)diethyltriamine trichloride (DTAD) on mica and the interactions between two such DTAD-coated surfaces were determined using atomic force microscopy and a surface force balance. In an aqueous solution of 3 mM, 5 times the critical aggregation concentration (CAC), the surfaces are coated with wormlike micelles or hemimicelles and larger (∼80 nm) bilayer vesicles. Repulsive normal interactions between the surfaces indicate a net surface charge and a solution concentration of ions close to that expected from the CAC. Moreover, this surface coating is strongly lubricating up to some tens of atmospheres, attributed to the hydration-lubrication mechanism acting at the exposed, highly hydrated surfactant headgroups. Upon replacement of the DTAD solution with surfactant-free water, the surface structures have changed on the DTAD monolayers, which then jump into adhesive contact on approach, both in water and following addition of 0.1 M NaNO3. This trimeric surfactant monolayer, which is highly hydrophobic, is found to be positively charged, which is evident from the attraction between the DTAD monolayer and negatively charged bare mica across water. These monolayers are stable over days even under a salt solution. The stability is attributed to the several stabilization pathways available to DTAD on the mica surface.

  11. Human disc cells in monolayer vs 3D culture: cell shape, division and matrix formation

    Directory of Open Access Journals (Sweden)

    Hanley Edward N

    2000-10-01

    Full Text Available Abstract Background The relationship between cell shape, proliferation, and extracellular matrix (ECM production, important aspects of cell behavior, is examined in a little-studied cell type, the human annulus cell from the intervertebral disc, during monolayer vs three-dimensional (3D culture. Results Three experimental studies showed that cells respond specifically to culture microenvironments by changes in cell shape, mitosis and ECM production: 1 Cell passages showed extensive immunohistochemical evidence of Type I and II collagens only in 3D culture. Chondroitin sulfate and keratan sulfate were abundant in both monolayer and 3D cultures. 2 Cells showed significantly greater proliferation in monolayer in the presence of platelet-derived growth factor compared to cells in 3D. 3 Cells on Matrigel™-coated monolayer substrates became rounded and formed nodular colonies, a finding absent during monolayer growth. Conclusions The cell's in vivo interactions with the ECM can regulate shape, gene expression and other cell functions. The shape of the annulus cell changes markedly during life: the young, healthy disc contains spindle shaped cells and abundant collagen. With aging and degeneration, many cells assume a strikingly different appearance, become rounded and are surrounded by unusual accumulations of ECM products. In vitro manipulation of disc cells provides an experimental window for testing how disc cells from given individuals respond when they are grown in environments which direct cells to have either spindle- or rounded-shapes. In vitro assessment of the response of such cells to platelet-derived growth factor and to Matrigel™ showed a continued influence of cell shape even in the presence of a growth factor stimulus. These findings contribute new information to the important issue of the influence of cell shape on cell behavior.

  12. Dynamics of cluster formation in driven magnetic colloids dispersed on a monolayer.

    Science.gov (United States)

    Jäger, Sebastian; Stark, Holger; Klapp, Sabine H L

    2013-05-15

    We report computer simulation results on the cluster formation of dipolar colloidal particles driven by a rotating external field in a quasi-two-dimensional setup. We focus on the interplay between permanent dipolar and hydrodynamic interactions and its influence on the dynamic behavior of the particles. This includes their individual as well as their collective motion. To investigate these characteristics, we employ Brownian dynamics simulations of a finite system with and without hydrodynamic interactions. Our results indicate that hydrodynamic interactions have a profound impact on the dynamic behavior of the clusters and the dynamics of the clustering process.

  13. Formation and Stability of Phenylphosphonic Acid Monolayers on ZnO: Comparison of In Situ and Ex Situ SAM Preparation.

    Science.gov (United States)

    Ostapenko, Alexandra; Klöffel, Tobias; Meyer, Bernd; Witte, Gregor

    2016-05-24

    Self-assembled monolayers (SAMs) enable an electronic interface tailoring of conductive metal oxides and offer an alternative to common transparent electrodes in optoelectronic devices. Here, the influence of surface orientation and pretreatment on the formation and stability of SAMs has been studied for the case of phenylphosphonic acid (PPA) on ZnO single crystals. Using thermal desorption spectroscopy (TDS), X-ray photoelectron spectroscopy (XPS), near-edge X-ray adsorption fine structure spectroscopy (NEXAFS) and density-functional theory (DFT) calculations, the thermal stability and orientational ordering of PPA-SAMs on the polar and mixed-terminated ZnO surfaces were analyzed. On all surfaces, PPA-SAMs remain stable up to 550 K, while at higher temperatures a C-P bond cleavage and dissociative desorption takes place yielding two distinct desorption peaks. Based on DFT calculations, these desorption channels are attributed to protonated and deprotonated chemisorbed PPA molecules, which can be related to tri- and bidentate species, hence allowing to determine their relative abundance from the intensity ratio. Beside immersion, an alternative monolayer preparation based on vacuum deposition in combination with controlled desorption of excess multilayers is demonstrated. This enables a SAM preparation on bare ZnO surfaces without any precoating due to exposure to ambient air, which is further compared with SAM formation on intentionally hydroxylated substrates. Corresponding TDS data indicate that initial hydroxylation favors the formation of tridentate and deprotonated bidentate, while the OMBD preparation on bare surfaces yields a larger fraction of protonated bidentate species. The orientation of PPA molecules adopted in the SAMs was determined from the dichroism of K-edge NEXAFS measurements and reveals an almost upright orientation for the deprotonated species, while a slight tilting is obtained for monolayer films with a large fraction of protonated

  14. “Lotus” Domain Formation by the Hydrolysis Reaction of Phospholipase D to Phospholipid Monolayer

    Institute of Scientific and Technical Information of China (English)

    Qiang HE; Jun Bai LI

    2003-01-01

    Hydrolysis reaction of L-α-dipalmitoylphosphatidylcholine (L-DPPC) monolayer with phospholipase D (PLD) has been investigated by Brewster angle microscopy (BAM) combined with the film balance. It has been found that the L-DPPC domains were changed into the "lotus" structure by PLD. It suggests that the hydrolysis reaction is incomplete and the products together with the nonreacted materials undergo a molecular rearrangement at the interface.

  15. Structure and homogeneity of pseudo-physiological phospholipid bilayers and their deposition characteristics on carboxylic acid terminated self-assembled monolayers.

    Science.gov (United States)

    Mechler, Adam; Praporski, Slavica; Piantavigna, Stefania; Heaton, Steven M; Hall, Kristopher N; Aguilar, Marie-Isabel; Martin, Lisandra L

    2009-02-01

    Supported phospholipid bilayers are frequently used to establish a pseudo-physiological environment required for the study of protein function or the design of enzyme-based biosensors and biocatalytic reactors. These membranes are deposited from bilayer vesicles (liposomes) that rupture and fuse into a planar membrane upon adhesion to a surface. However, the morphology and homogeneity of the resulting layer is affected by the characteristics of the precursor liposome suspension and the substrate. Here we show that two distinct liposome populations contribute to membrane formation--equilibrium liposomes and small unilamellar vesicles. Liposome deposition onto carboxylic acid terminated self-assembled monolayers resulted in planar mono- and multilayer, vesicular and composite membranes, as a function of liposome size and composition. Quartz crystal microbalance data provided estimates for layer thicknesses and sheer moduli and were used for classification of the final structure. Finally, atomic force microscopy data illustrated the inherently inhomogeneous and dynamic nature of these membranes.

  16. Effects of solvent on the formation of the MUA monolayer on Si and its diffusion barrier properties for Cu metallization

    Science.gov (United States)

    Rahman, Mohammad Arifur; Han, Jung Suk; Jeong, Kyunghoon; Nam, Ho-seok; Lee, Jaegab

    2014-05-01

    We investigated the effects of solvents, such as ethanol and isooctane, on self-assembly of the mercaptoundecanoic acid (MUA) monolayer on Si and its diffusion barrier properties for Cu metallization. The use of isooctane as a solvent produced MUA self-assembled monolayers (SAMs) (˜1.3 nm thick) on Si. These acted as an effective diffusion barrier against Cu diffusion up to 200°C. In contrast, the MUA SAMs produced by ethanol allowed the diffusion of Cu to a MUA-Si interface at 200°C, stimulating the out-diffusion of Si into Cu and thus resulting in the degraded diffusion barrier properties. This was possibly due to the partial formation of interplane hydrogen bonding between the terminal groups of the bound acid and free thiol groups. This provided less dense thiol surface groups, thus leading to poor adhesion of Cu to MUA SAMs. The fabricated Cu/isooctane-assisted MUA source/drain electrode a-Si:H thin film transistors with a channel length of 10 µm exhibited an excellent electron mobility of 0.74 cm2/V-s, threshold voltage of -0.51 V, I on / I off ratio of 3.25 × 106, specific contact resistance of 4.24 Ω-cm2 after annealing at 200°C.

  17. Characteristic parameters and dynamics of two-qubit system in self-assembled monolayers

    CERN Document Server

    Rinkevicius, Z; Tsifrinovich, V I; Tretiak, S; Rinkevicius, Zilvinas; Berman, Gennady P.; Tsifrinovich, Vladimir I.; Tretiak, Sergei

    2004-01-01

    We suggest the application of nitronylnitroxide substituted with methyl group and 2,2,6,6-tetramethylpiperidin organic radicals as 1/2-spin qubits for self-assembled monolayer quantum devices. We show that the oscillating cantilever driven adiabatic reversals technique can provide the read-out of the spin states. We compute components of the $g$-tensor and dipole-dipole interaction tensor for these radicals. We show that the delocalization of the spin in the radical may significantly influence the dipole-dipole interaction between the spins.

  18. Case studies on the formation of chalcogenide self-assembled monolayers on surfaces and dissociative processes

    Directory of Open Access Journals (Sweden)

    Yongfeng Tong

    2016-02-01

    Full Text Available This report examines the assembly of chalcogenide organic molecules on various surfaces, focusing on cases when chemisorption is accompanied by carbon–chalcogen atom-bond scission. In the case of alkane and benzyl chalcogenides, this induces formation of a chalcogenized interface layer. This process can occur during the initial stages of adsorption and then, after passivation of the surface, molecular adsorption can proceed. The characteristics of the chalcogenized interface layer can be significantly different from the metal layer and can affect various properties such as electron conduction. For chalcogenophenes, the carbon–chalcogen atom-bond breaking can lead to opening of the ring and adsorption of an alkene chalcogenide. Such a disruption of the π-electron system affects charge transport along the chains. Awareness about these effects is of importance from the point of view of molecular electronics. We discuss some recent studies based on X-ray photoelectron spectroscopy that shed light on these aspects for a series of such organic molecules.

  19. Characterization of monolayer formation on aluminum-doped zinc oxide thin films.

    Science.gov (United States)

    Rhodes, Crissy L; Lappi, Simon; Fischer, Daniel; Sambasivan, Sharadha; Genzer, Jan; Franzen, Stefan

    2008-01-15

    The optical and electronic properties of aluminum-doped zinc oxide (AZO) thin films on a glass substrate are investigated experimentally and theoretically. Optical studies with coupling in the Kretschmann configuration reveal an angle-dependent plasma frequency in the mid-IR for p-polarized radiation, suggestive of the detection of a Drude plasma frequency. These studies are complemented by oxygen depletion density functional theory studies for the calculation of the charge carrier concentration and plasma frequency for bulk AZO. In addition, we report on the optical and physical properties of thin film adlayers of n-hexadecanethiol (HDT) and n-octadecanethiol (ODT) self-assembled monolayers (SAMs) on AZO surfaces using reflectance FTIR spectroscopy, X-ray photoelectron spectroscopy (XPS), contact angle, and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Our characterization of the SAM deposition onto the AZO thin film reveals a range of possible applications for this conducting metal oxide.

  20. Inhibition of copper corrosion by the formation of Schiff base self-assembled monolayers

    Science.gov (United States)

    Zhang, Jing; Liu, Zheng; Han, Guo-Cheng; Chen, Shi-Liang; Chen, Zhencheng

    2016-12-01

    Self-assembled monolayers (SAMs) of 4-((2-thiophenecarboxylic acid hydrazide) methylene) benzoic acid (HD2) (denoted as HD2-SAMs) were formed on copper surface. The SAMs were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. Polarization curve and weight loss methods indicated that the highest inhibition efficiency was 93.9% for CO2-saturated simulative oilfield water at a self-assembled time of 3 h. Potential-time curve, electrochemical impedance tests showed that HD2-SAMs on copper surface exhibited excellent inhibition effect at 30 °C. The adsorption behavior of HD2-SAMs on the copper surface followed the Langmuir adsorption isotherm, which was indicative of typically chemical adsorption. Quantum chemistry calculation showed that O and N atoms can interact with Cu atoms by coordination bonds which were the mainly active area of the adsorption of HD2 molecules.

  1. Adsorption Characteristics of DNA Nucleobases, Aromatic Amino Acids and Heterocyclic Molecules on Silicene and Germanene Monolayers

    KAUST Repository

    Hussain, Tanveer

    2017-09-14

    Binding of DNA/RNA nucleobases, aromatic amino acids and heterocyclic molecules on two-dimensional silicene and germanene sheets have been investigated for the application of sensing of biomolecules using first principle density functional theory calculations. Binding energy range for nucleobases, amino acids and heterocyclic molecules with both the sheets have been found to be (0.43-1.16eV), (0.70-1.58eV) and (0.22-0.96eV) respectively, which along with the binding distances show that these molecules bind to both sheets by physisorption and chemisorption process. The exchange of electric charges between the monolayers and the incident molecules has been examined by means of Bader charge analysis. It has been observed that the introduction of DNA/RNA nucleobases, aromatic amino acids and heterocyclic molecules alters the electronic properties of both silicene and germanene nano sheets as studied by plotting the total (TDOS) and partial (PDOS) density of states. The DOS plots reveal the variation in the band gaps of both silicene and germanene caused by the introduction of studied molecules. Based on the obtained results we suggest that both silicene and germanene monolayers in their pristine form could be useful for sensing of biomolecules.

  2. Characteristics of localized surface plasmons excited on mixed monolayers composed of self-assembled Ag and Au nanoparticles.

    Science.gov (United States)

    Tanaka, Daisuke; Imazu, Keisuke; Sung, Jinwoo; Park, Cheolmin; Okamoto, Koichi; Tamada, Kaoru

    2015-10-07

    The fundamental characteristics of localized surface plasmon resonance (LSPR) excited on mixed monolayers composed of self-assembled Ag and Au nanoparticles (AgNPs and AuNPs, respectively) were investigated. Mixed monolayered films were fabricated at the air-water interface at different mixing ratios. The films retained their phase-segregated morphologies in which AuNPs formed several 10 to 100 nm island domains in a homogeneous AgNP matrix phase. The LSPR bands originating from the self-assembled domains shifted to longer wavelengths as the domain size increased, as predicted by a finite-difference time-domain (FDTD) simulation. The FDTD simulation also revealed that even an alternating-lattice-structured two-dimensional (2D) AgNP/AuNP film retained two isolated LSPR bands, revealing that the plasmon resonances excited on each particle did not couple even in a continuous 2D sheet, unlike in the homologous NP system. The fluorescence quenching test of Cy3 and Cy5 dyes confirmed that the independent functions of AuNPs and AgNPs remained in the mixed films, whereas the AuNPs exhibited significantly higher quenching efficiency for the Cy3 dye compared with AgNPs due to the overlap of the excitation/emission bands of the dyes with the AuNP LSPR band. Various applications can be considered using this nanoheterostructured plasmonic assembly to excite spatially designed, high-density LSPR on macroscopic surfaces.

  3. Formation of Self-Assembled Monolayer on Cerium Conversion Coated AZ31 Mg Alloy

    Science.gov (United States)

    Salman, S. A.; Akira, N.; Kuroda, K.; Okido, M.

    Magnesium alloys are recognized as alternatives to Al alloys and steel to reduce the weight of structural materials. However, a major obstacle to the widespread use of magnesium alloys is its poor corrosion resistance. Therefore, further surface treatment of magnesium and its alloy is important in meeting several industrial specifications. In a previous research, we investigated the surface treatment of AZ31 magnesium alloy using cerium conversion coating. The anticorrosion properties could be improved with the cerium treatment. In this present research, self-assembled monolayer (SAM) was adsorbed on the surface of cerium conversion coated AZ31 magnesium alloy. The SAM thin film was deposited using (Tridecafluoro-1, 1, 2, 2-tetrahydrooctyl) trimethoxysilane (FAS13) and Tetrakis(trimethylsiloxy)titanium (TTMS) as a catalyst. The corrosion resistance of cerium conversion coated AZ31 Mg alloy was improved with SAM post treatment. Furthermore, the contact angle increases from 13 deg. to 169 deg. indicating to production of super hydrophobic surface with SAM post treatment.

  4. Pattern formation in fatty acid-nanoparticle and lipid-nanoparticle mixed monolayers at water surface

    Science.gov (United States)

    Choudhuri, M.; Datta, A.; Iyengar, A. N. Sekar; Janaki, M. S.

    2015-06-01

    Dodecanethiol-capped gold nanoparticles (AuNPs) are self-organized in two different amphiphilic monolayers one of which is a single-tailed fatty acid Stearic acid (StA) and the other a double-tailed lipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). In the StA-AuNP film the AuNPs self-organize to form an interconnected network of nanoclusters on compression while in the DMPC-AuNP film the AuNPs aggregate to form random, isolated clusters in the film. The long time evolution of the films at constant surface pressure reveals ring structures in the former and diffusion limited aggregates in the latter that with time evolve into an irregular porous maze of AuNPs in the DMPC film. The difference in structure of the AuNP patterns in the two films can be attributed to a difference in the lipophilic interactions between the NPs and the amphiphilic molecules. The mean square intensity fluctuations f(ln) calculated along a typical line for the 2D structures in both the films at initial and final stages of long time evolution reflect the structural changes in the films over time.

  5. Processing follows function: pushing the formation of self-assembled monolayers to high-throughput compatible time scales.

    Science.gov (United States)

    Alt, Milan; Schinke, Janusz; Hillebrandt, Sabina; Hänsel, Marc; Hernandez-Sosa, Gerardo; Mechau, Norman; Glaser, Tobias; Mankel, Eric; Hamburger, Manuel; Deing, Kaja; Jaegermann, Wolfram; Pucci, Annemarie; Kowalsky, Wolfgang; Lemmer, Uli; Lovrincic, Robert

    2014-11-26

    Self-assembled monolayers (SAMs) of organic molecules can be used to tune interface energetics and thereby improve charge carrier injection at metal-semiconductor contacts. We investigate the compatibility of SAM formation with high-throughput processing techniques. Therefore, we examine the quality of SAMs, in terms of work function shift and chemical composition as measured with photoelectron and infrared spectroscopy and in dependency on molecular exposure during SAM formation. The functionality of the SAMs is determined by the performance increase of organic field-effect transistors upon SAM treatment of the source/drain contacts. This combined analytical and device-based approach enables us to minimize the necessary formation times via an optimization of the deposition conditions. Our findings demonstrate that SAMs composed of partially fluorinated alkanethiols can be prepared in ambient atmosphere from ethanol solution using immersion times as short as 5 s and still exhibit almost full charge injection functionality if process parameters are chosen carefully. This renders solution-processed SAMs compatible with high-throughput solution-based deposition techniques.

  6. A priori calculations of the free energy of formation from solution of polymorphic self-assembled monolayers.

    Science.gov (United States)

    Reimers, Jeffrey R; Panduwinata, Dwi; Visser, Johan; Chin, Yiing; Tang, Chunguang; Goerigk, Lars; Ford, Michael J; Sintic, Maxine; Sum, Tze-Jing; Coenen, Michiel J J; Hendriksen, Bas L M; Elemans, Johannes A A W; Hush, Noel S; Crossley, Maxwell J

    2015-11-10

    Modern quantum chemical electronic structure methods typically applied to localized chemical bonding are developed to predict atomic structures and free energies for meso-tetraalkylporphyrin self-assembled monolayer (SAM) polymorph formation from organic solution on highly ordered pyrolytic graphite surfaces. Large polymorph-dependent dispersion-induced substrate-molecule interactions (e.g., -100 kcal mol(-1) to -150 kcal mol(-1) for tetratrisdecylporphyrin) are found to drive SAM formation, opposed nearly completely by large polymorph-dependent dispersion-induced solvent interactions (70-110 kcal mol(-1)) and entropy effects (25-40 kcal mol(-1) at 298 K) favoring dissolution. Dielectric continuum models of the solvent are used, facilitating consideration of many possible SAM polymorphs, along with quantum mechanical/molecular mechanical and dispersion-corrected density functional theory calculations. These predict and interpret newly measured and existing high-resolution scanning tunnelling microscopy images of SAM structure, rationalizing polymorph formation conditions. A wide range of molecular condensed matter properties at room temperature now appear suitable for prediction and analysis using electronic structure calculations.

  7. Transport characteristics of isorhamnetin across intestinal Caco-2 cell monolayers and the effects of transporters on it.

    Science.gov (United States)

    Duan, Jingze; Xie, Yan; Luo, Huilin; Li, Guowen; Wu, Tao; Zhang, Tong

    2014-04-01

    Flavonoid isorhamnetin occurs in various plants and herbs, and demonstrates various biological effects in humans. This work will clarify the isorhamnetin absorption mechanism using the Caco-2 monolayer cell model. The isorhamnetin transport characteristics at different concentrations, pHs, temperatures, tight junctions and potential transporters were systemically investigated. Isorhamnetin was poorly absorbed by both passive diffusion and active transport mechanisms. Both trans- and paracellular pathways were involved during isorhamnetin transport. Active transport under an ATP-dependent transport mechanism was mediated by the organic anion transporting peptide (OATP); isorhamnetin's permeability from the apical to the basolateral side significantly decreased after estrone-3-sulfate was added (pisorhamnetin transport process. Among them, the MRPs (especially MRP2) were the main efflux transporters for isorhamnetin; transport from the apical to the basolateral side increased 10.8-fold after adding an MRP inhibitor (MK571). This study details isorhamnetin's cellular transport and elaborates isorhamnetin's absorption mechanisms to provide a foundation for further studies.

  8. Diffusion barrier characteristics of co monolayer prepared by Langmuir Blodgett technique

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Sumit, E-mail: sumitelsd2007@gmail.com [Electronic Science Department, Kurukshetra University, Kurukshetra, Haryana 136119 (India); Kumar, Mukesh, E-mail: kumarmukesh@gmail.com [Department of Electrical Engineering, College of Engineering at Wadi Aldawasir, Prince Sattam Bin Abdulaziz University, Wadi Aldawasir 11991 (Saudi Arabia); Rani, Sumita [Electronic Science Department, Kurukshetra University, Kurukshetra, Haryana 136119 (India); Kumar, Dinesh, E-mail: dineshelsd@gmail.com [Electronic Science Department, Kurukshetra University, Kurukshetra, Haryana 136119 (India)

    2016-04-30

    Graphical abstract: Thermal stability of structures (a) Cu/SiO{sub 2}/Si and (b) Cu/Co/SiO{sub 2}/Si, indicating that presence of thin cobalt layer improves the thermal stability of the structure up to 600 °C. - Highlights: • Monolayers of cobalt were deposited on SiO{sub 2}/Si substrates using LB technique. • Copper layers were deposited on this structures using thermal evaporation method. • Thermal stability was determined by annealing the structures at various temperatures. • The structure was found to be stable up to 650 °C. - Abstract: Monolayers of Co over SiO{sub 2}/Si substrate were deposited using Langmuir Blodgett (LB) technique. The diffusion barrier capability of Co layer was evaluated against copper diffusion. The structure of the deposited Co layer was analyzed using X-ray photoelectron spectroscopy (XPS), Energy Dispersive X-ray Spectroscopy (EDS) and Atomic force microscopy (AFM) techniques. Thermal stability of Cu/SiO{sub 2}/Si and Cu/Co/SiO{sub 2}/Si test structures was studied and compared using X-ray diffraction (XRD), scanning electron microscope (SEM) and four probe techniques. The samples were annealed at different temperatures starting from 200 °C up to 700 °C in vacuum for 30 min. XRD results indicated that combination of Co/SiO{sub 2} worked as diffusion barrier up to 550 °C whereas SiO{sub 2} alone could work as barrier only up to 300 °C. Sheet resistance of these samples was measured as a function of annealing temperature which also supports XRD results. C–V curves of these structures under the influence of Biased Thermal Stress (BTS) were analyzed. BTS was applied at 2.5 MV cm{sup −1} at 150 °C. Results showed that in the presence of Co barrier layer there was no shift in the C–V curve even after 90 min of BTS while in the absence of barrier there was a significant shift in the C–V curve even after 30 min of BTS. Further these test structures were examined for leakage current density (j{sub L}) at same BTS

  9. Dynamic pattern formation of liquid crystals using binary self-assembled monolayers on an ITO surface under DC voltage.

    Science.gov (United States)

    Ishida, Takao; Oyama, Makiko; Terada, Kei-ichi; Haga, Masa-aki

    2014-12-07

    There have been numerous studies of liquid crystal (LC) convection using sandwich-type LC cells under AC voltage. In contrast to previous LC convection studies under AC voltage, we propose the use of a binary self-assembled monolayer (SAM) with a redox-active Ru complex and insulating octadecyl phosphonic acid (C18) molecules on an indium tin oxide (ITO) surface as the electrode of sandwich-type LC cells under DC bias voltage. This is because the functionalized molecules immobilized on the ITO surface are expected to control the LC orientation and electrical conduction of LC cells, under an exact DC bias voltage. We successfully achieved LC pattern formation using ITO electrodes with binary SAMs in LC cells. Moreover, we confirmed that the LC pattern size was increased by increasing the coverage of the Ru complex in binary SAMs. We consider that a combination of three factors, electrical conduction change, controlling of LC orientation in the initial stage and redox-activity of the Ru-complex, is the reason for LC convection although we cannot fully explain the distribution of these three factors. We believe that our LC pattern formation is promising for new type devices e.g., artificial compound eyes using the LC device technology.

  10. Formation of a Pt-Decorated Au Nanoparticle Monolayer Floating on an Ionic Liquid by the Ionic Liquid/Metal Sputtering Method and Tunable Electrocatalytic Activities of the Resulting Monolayer.

    Science.gov (United States)

    Sugioka, Daisuke; Kameyama, Tatsuya; Kuwabata, Susumu; Yamamoto, Takahisa; Torimoto, Tsukasa

    2016-05-01

    A novel strategy to prepare a bimetallic Au-Pt particle film was developed through sequential sputter deposition of Au and Pt on a room temperature ionic liquid (RTIL). Au sputter deposition onto an RTIL containing hydroxyl-functionalized cations produced a monolayer of Au particles 4.2 nm in size on the liquid surface. Subsequent Pt sputtering onto the original Au particle monolayer floating on the RTIL enabled decoration of individual Au particles with Pt metals, resulting in the formation of a bimetallic Au-Pt particle monolayer with a Pt-enriched particle surface. The particle size slightly increased to 4.8 nm with Pt deposition for 120 min. The shell layer of a bimetallic particle was composed of Au-Pt alloy, the composition of which was tunable by controlling the Pt sputter deposition time. The electrochemical surface area (ECSA) was determined by cyclic voltammetry of bimetallic Au-Pt particle monolayers transferred onto HOPG electrodes by a horizontal liftoff method. The Pt surface coverage, determined by ECSAs of Au and Pt, increased from 0 to 56 mol % with elapse of the Pt sputter deposition time up to 120 min. Thus-obtained Au-Pt particle films exhibited electrocatalytic activity for methanol oxidation reaction (MOR) superior to the activities of pure Au or Pt particles. Volcano-type dependence was observed between the MOR activity and Pt surface coverage on the particles. Maximum activity was obtained for Au-Pt particles with a Pt coverage of 49 mol %, being ca. 120 times higher than that of pure Pt particles. This method enables direct decoration of metal particles with different noble metal atoms, providing a novel strategy to develop highly efficient multinary particle catalysts.

  11. Formation of Monolayers by the Coadsorption of Thiols on Gold: Variation in the Length of the Alkyl Chain

    Science.gov (United States)

    1989-05-01

    Methyl- terminated thiols generate surfaces that are composed of densely packed methyl groups and are both hydrophobic (Oa(H20) = 1120) and oleophobic ...together with monolayers of the two pure thiols. Both pure monolayers were autophobic and oleophobic : Oa(HD) = 470 for HS(CH2)2 1CH 3, 0a(HD) = 460 for...would be oleophobic , and we would expect Oa(HD) to be independent of the composition of the monolayer. The contact angles in Fig. 3 were measured

  12. Two step formation of metal aggregates by surface X-ray radiolysis under Langmuir monolayers: 2D followed by 3D growth

    Directory of Open Access Journals (Sweden)

    Smita Mukherjee

    2015-12-01

    Full Text Available In order to form a nanostructured metallic layer below a Langmuir monolayer, radiolysis synthesis was carried out in an adapted geometry that we call surface X-ray radiolysis. In this procedure, an X-ray beam produced by a synchrotron beamline intercepts the surface of an aqueous metal-ion solution covered by a Langmuir monolayer at an angle of incidence below the critical angle for total internal reflection. Underneath the organic layer, the X-ray beam induces the radiolytic synthesis of a nanostructured metal–organic layer whose ultrathin thickness is defined by the vertical X-ray penetration depth. We have shown that increasing the X-ray flux on the surface, which considerably enhances the kinetics of the silver layer formation, results in a second growth regime of silver nanocrystals. Here the formation of the oriented thin layer is followed by the appearance of a 3D powder of silver clusters.

  13. Characteristics of the influence of auxins on physicochemical properties of membrane phospholipids in monolayers at the air/aqueous solution interface.

    Science.gov (United States)

    Flasiński, Michał; Bartosik, Magdalena; Kowal, Sara; Broniatowski, Marcin; Wydro, Paweł

    2015-12-01

    Interactions between representatives of plant hormones and selected membrane lipids have been studied in monolayers at the air/aqueous solutions interface with π-A isotherm analysis, microscopic visualization and grazing incidence X-ray diffraction technique (GIXD). Four phytohormones: indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), 2-naphthoxyacetic acid (BNOA) and 2,4-dichlorophenoxyacetic acid (2,4-D), belonging to the class of auxins differ as regards the chemical structure of the aromatic molecular fragment. The studied phospholipids have been chosen since they are omnipresent in the biological membranes of plant and animal kingdom. Our results revealed that both natural (IAA and IBA) and synthetic (2,4-D and BNOA) phytohormones modify the physicochemical characteristics of the investigated lipid monolayers. Auxins caused strong diminishing of the monolayer condensation, especially for DPPC and SOPE, which may be attributed to the phase transition in these monolayers. In the performed experiments the key step of auxins action occurs when the molecules interact with monolayers in the expanded state-when the space in the lipid head-group region is large enough to accommodate the molecules of water soluble auxins. The application of GIXD technique confirmed that auxin molecules are also present at the interface at higher surface pressure (30 mN/m). The obtained results showed that among the investigated auxins, the largest influence on the lipid monolayers occurred in the case of BNOA, which molecule possesses the largest aromatic fragment. In contrast, 2,4-D, having the smallest aryl group affects the studied lipid systems to the smallest extent.

  14. Seamounts - characteristics, formation, mineral deposits and biodiversity

    Digital Repository Service at National Institute of Oceanography (India)

    Iyer, S.D.; Mehta, C.M.; Das, P.; Kalangutkar, N.G.

    affect the circulation patterns and currents, which in turn influence the surrounding biota. We review here the seamounts in terms of discovery, characteristics, distribution and their influence on the marine environment....

  15. Formation of Metal Nano- and Micropatterns on Self-Assembled Monolayers by Pulsed Laser Deposition Through Nanostencils and Electroless Deposition

    NARCIS (Netherlands)

    Speets, Emiel A.; Riele, te Paul; Boogaart, van den Marc A.F.; Doeswijk, Lianne M.; Ravoo, Bart Jan; Rijnders, Guus; Brugger, Jürgen; Reinhoudt, David N.; Blank, Dave H.A.

    2006-01-01

    Patterns of noble-metal structures on top of self-assembled monolayers (SAMs) on Au and SiO2 substrates have been prepared following two approaches. The first approach consists of pulsed laser deposition (PLD) of Pt, Pd, Au, or Cu through nano- and microstencils. In the second approach, noble-metal

  16. Synthesis of an Open-Cage Structure POSS Containing Various Functional Groups and Their Effect on the Formation and Properties of Langmuir Monolayers.

    Science.gov (United States)

    Dutkiewicz, Michał; Karasiewicz, Joanna; Rojewska, Monika; Skrzypiec, Marta; Dopierała, Katarzyna; Prochaska, Krystyna; Maciejewski, Hieronim

    2016-09-05

    Recently, silsesquioxanes have been recognized as a new group of film-forming materials. This study has been aimed at determining the effect of the kind of functional groups present in two different open-cage structure POSS molecules on the possibility of the formation of Langmuir monolayers and their properties. To achieve this goal, two new POSS derivatives (of open-cage structures) containing polyether and fluoroalkyl functional groups have been synthesized on the basis of a hydrosilylation process. An optimization of the process was performed, which makes it possible to obtain the above-mentioned derivatives with high yields. In the next step, the Langmuir technique was applied to measurements of the surface pressure (π) - the mean molecular area (A) isotherms during the compression of monolayers formed by molecules of the two POSS derivatives considered. Subsequently, the monolayers were transferred onto quartz plates according to the Langmuir-Blodgett technique. Both derivatives are able to form insoluble Langmuir films at the air-water interface, which can be transferred onto a solid substrate and effectively change its wetting properties.

  17. Thermal desorption characteristics of CO, O2 and CO2 on non-porous water, crystalline water and silicate surfaces at sub-monolayer and multilayer coverages

    CERN Document Server

    Noble, J A; Dulieu, F; Fraser, H J

    2011-01-01

    The desorption characteristics of molecules on interstellar dust grains are important for modelling the behaviour of molecules in icy mantles and, critically, in describing the solid-gas interface. In this study, a series of laboratory experiments exploring the desorption of three small molecules from three astrophysically relevant surfaces are presented. The desorption of CO, O2 and CO2 at both sub-monolayer and multilayer coverages was investigated from non-porous water, crystalline water and silicate surfaces. Experimental data was modelled using the Polanyi-Wigner equation to produce a mathematical description of the desorption of each molecular species from each type of surface, uniquely describing both the monolayer and multilayer desorption in a single combined model. The implications of desorption behaviour over astrophysically relevant timescales are discussed.

  18. Monolayer Formation Characteristics of Novel Organic Molecules with Nonlinear Optically Active Moieties

    Science.gov (United States)

    1989-05-31

    reviews and special issues5 .6 . We recently reported7 the design and synthesis of a class of organic compounds ( Schiff base ) possessing a large second...RESULTS AND DISCUSSION The molecular structures of the candidate materials are shown in Fig. lb. The molecular structures of the NLO active Schiff base compounds...numerals, l-VII!. Step I in Fig. la shows the synthetic route to the Schiff base compounds MI-M6. Steps 2 and 3 define the approach to the synthesis of

  19. The Electrochemical Characteristics of Multilayer Assembly of Hemoglobin and Polystyrene Sulfonate at Self-assembled Monolayer Surface

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A multilayer film of hemoglobin (Hb) molecules and polyelectrolyte sulfonate were fabricated on a thiol self-assembled monolayers (SAMs) by electrostatic force.The Hb maintains electroactive property in the multilayer film, methylene blue (MB) incorporated into the multilayer can enhance the electron transfer rate between the Hb and the electrode surface.

  20. Keyhole formation and its characteristics in laser welding mode transition

    Institute of Scientific and Technical Information of China (English)

    Qin Guoliang; Gao Jinqiang; Lin Shangyang

    2010-01-01

    Keyhole is the most important characteristic for laser deep penetration welding, and its formation indicates the beginning of laser deep penetration welding mode. The keyhole developing process was analyzed and the keyhole formation time was calculated according to welding speed and the length of weld bead formed in the keyhole formation process. The results showed that the keyhole forms in 40-70 ms at different rate of change of laser power. In laser deep penetration welding process, the variation of light intensity radiated by laser induced plasma can identify the keyhole formation, but it can not be used to estimate the keyhole formation time because of delay effect.

  1. Mechanical Model of Geometric Cell and Topological Algorithm for Cell Dynamics from Single-Cell to Formation of Monolayered Tissues with Pattern

    KAUST Repository

    Kachalo, Sëma

    2015-05-14

    Geometric and mechanical properties of individual cells and interactions among neighboring cells are the basis of formation of tissue patterns. Understanding the complex interplay of cells is essential for gaining insight into embryogenesis, tissue development, and other emerging behavior. Here we describe a cell model and an efficient geometric algorithm for studying the dynamic process of tissue formation in 2D (e.g. epithelial tissues). Our approach improves upon previous methods by incorporating properties of individual cells as well as detailed description of the dynamic growth process, with all topological changes accounted for. Cell size, shape, and division plane orientation are modeled realistically. In addition, cell birth, cell growth, cell shrinkage, cell death, cell division, cell collision, and cell rearrangements are now fully accounted for. Different models of cell-cell interactions, such as lateral inhibition during the process of growth, can be studied in detail. Cellular pattern formation for monolayered tissues from arbitrary initial conditions, including that of a single cell, can also be studied in detail. Computational efficiency is achieved through the employment of a special data structure that ensures access to neighboring cells in constant time, without additional space requirement. We have successfully generated tissues consisting of more than 20,000 cells starting from 2 cells within 1 hour. We show that our model can be used to study embryogenesis, tissue fusion, and cell apoptosis. We give detailed study of the classical developmental process of bristle formation on the epidermis of D. melanogaster and the fundamental problem of homeostatic size control in epithelial tissues. Simulation results reveal significant roles of solubility of secreted factors in both the bristle formation and the homeostatic control of tissue size. Our method can be used to study broad problems in monolayered tissue formation. Our software is publicly

  2. Formation of Monolayers by the Coadsorption of Thiols on Gold: Variation in the Length of the Head Group, Tail Group, and Solvent

    Science.gov (United States)

    1989-05-01

    oleophobic monolayer) and the other by a polar or polarizable group (yielding a hydrophilic or oleophilic monolayer). In these systems the contact...to comprise discrete islands, each of which were oleophobic , then the monolayer itself would not be wetted by hexadecane. We observed that hexadecane

  3. Formation of hard magnetic L1{sub 0}-FePt/FePd monolayers from elemental multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Goo, Nam Hoon

    2007-06-18

    In this thesis, ordered L1{sub 0}-FePt and FePd films of different nominal compositions are prepared from Fe/Pt and Fe/Pd multilayers by annealing. In case of the L1{sub 0}-FePt films the composition of the films is modified by changing the individual elemental layer thicknesses in the multilayer precursors. This simple variation of the composition is the great advantage of the multilayer approach compared to sputtering single alloy layer from an alloy target. The formation mechanism of the fct phase from the multilayers and the microstructural properties are investigated. The characteristics of the hysteresis loop (coercivity {mu}{sub 0}H{sub c}, remanence J{sub r}) and of the intrinsic magnetic properties (anisotropy constant K{sub l}, spontaneous polarization J{sub s}, exchange constant A) of the ordered L1{sub 0}-FePt and FePd films are studied. The effects of the composition of the L1{sub 0}-FePt films on the microstructural and magnetic properties are investigated. The microstructure of these ordered L1{sub 0}-FePt films are then correlated to the magnetic properties with microstructural parameters by investigating the temperature dependence of the coercivity. (orig.)

  4. Causes of formation and characteristics of water-fuel emulsions

    Directory of Open Access Journals (Sweden)

    П. Ф. Максютинський

    2000-09-01

    Full Text Available Considered are the causes of formation and characteristics of water-fuel emulsions in fuel tanks of aircrafts - dispersion and stability (time of water emulsion fallout Determined is distribution of emulsion water in fuel according to microdrops size caused by mechanical dispersion. It is shown that water-fuel emulsion formed by ultrasonic dispersion is similar to that formed by condensation

  5. Formation of a 1,8-octanedithiol self-assembled monolayer on Au(111) prepared in a lyotropic liquid-crystalline medium.

    Science.gov (United States)

    García Raya, Daniel; Madueño, Rafael; Blázquez, Manuel; Pineda, Teresa

    2010-07-20

    A characterization of the 1,8-octanedithiol (ODT) self-assembled monolayer (SAM) formed from a Triton X-100 lyotropic medium has been conducted by electrochemical techniques. It is found that an ODT layer of standing-up molecules is obtained at short modification time without removing oxygen from the medium. The electrochemical study shows that the ODT layer formed after 15 min of modification time has similar electron-transfer blocking properties to the layers formed from organic solvents at much longer modification times. On the basis of XPS data, it is demonstrated that the inability to bind gold nanoparticles (AuNPs) is due to the presence of extra ODT molecules either interdigited or on top of the layer. Treatment consisting of an acid washing step following the formation of the ODT-Au(111) SAM produces a layer that is able to attach AuNPs as demonstrated by electrochemical techniques and atomic force microscopy (AFM) images.

  6. Monolayer patterning using ketone dipoles.

    Science.gov (United States)

    Kim, Min Kyoung; Xue, Yi; Pašková, Tereza; Zimmt, Matthew B

    2013-08-14

    The self-assembly of multi-component monolayers with designed patterns requires molecular recognition among components. Dipolar interactions have been found to influence morphologies of self-assembled monolayers and can affect molecular recognition functions. Ketone groups have large dipole moments (2.6 D) and are easily incorporated into molecules. The potential of ketone groups for dipolar patterning has been evaluated through synthesis of two 1,5-disubstituted anthracenes bearing mono-ketone side chains, STM characterization of monolayers self-assembled from their single and two component solutions and molecular mechanics simulations to determine their self-assembly energetics. The results reveal that (i) anthracenes bearing self-repulsive mono-ketone side chains assemble in an atypical monolayer morphology that establishes dipolar attraction, instead of repulsion, between ketones in adjacent side chains; (ii) pairs of anthracene molecules whose self-repulsive ketone side chains are dipolar complementary spontaneously assemble compositionally patterned monolayers, in which the two components segregate into neighboring, single component columns, driven by side chain dipolar interactions; (iii) compositionally patterned monolayers also assemble from dipolar complementary anthracene pairs that employ different dipolar groups (ketones or CF2 groups) in their side chains; (iv) the ketone group, with its larger dipole moment and size, provides comparable driving force for patterned monolayer formation to that of the smaller dipole, and smaller size, CF2 group.

  7. On the formation of crystalline microstructures of monolayers seen in terms of qualitative diffusion-type models at mesoscale

    Science.gov (United States)

    Gadomski, A.

    2008-09-01

    It is well known (see, e.g., K. A. Beklemishev and D. B. Berg, Pis’ma Zh. Tekh. Fiz. 33 (19), 40 (2007) [Tech. Phys. Lett. 33, 825 (2007)]) that many diffusion-type growth models allow qualitative features of growing microstructures to be obtained without employing any special information on the molecules constituting the microstructural domains. It has also been noted that the time needed to obtain a polycrystalline structure must be carefully estimated by engaging statistical-mechanical ensemble-averaging methods. The latter seems to be, in general, a difficult task because the problem is left as non-ergodic. The former, in turn, is supposed to be remedied while realizing that the qualitative estimates can become quantitative when offered at the mesoscopic level and when appropriately supported by a suitable construction of the diffusion function. In addition to comprising the Gibbs (non-negative) entropy production framework as a firm basis deeply rooted in the first law of thermodynamics for open thermodynamic systems, this construction can be seen as good as the frequently used Avrami-Kolmogorov phenomenology. This type of proposal cannot be easily postponed in the modeling of phospholipid monolayers or other two-dimensional amphiphilic, soft-matter-type systems.

  8. Tuning the self-assembled monolayer formation on nanoparticle surfaces with different curvatures: investigations on spherical silica particles and plane-crystal-shaped zirconia particles.

    Science.gov (United States)

    Feichtenschlager, Bernhard; Lomoschitz, Christoph J; Kickelbick, Guido

    2011-08-01

    The ordering of dodecyl-chain self-assembled monolayers (SAM) on different nanoscopic surfaces was investigated by FT-IR studies. As model systems plane-crystal-shaped ZrO(2) nanoparticles and spherical SiO(2) nanoparticles were examined. The type of capping agent was chosen dependent on the substrate, therefore dodecylphosphonic acid and octadecylphosphonic acid were used for ZrO(2) and dodecyltrimethoxysilane for SiO(2) samples. The plane ZrO(2) nanocrystals yielded more ordered alkyl-chain structures whereas spherical SiO(2) nanoparticles showed significantly lower alkyl-chain ordering. Submicron-sized silica spheres revealed a significantly higher alkyl chain ordering, comparable to an analogously prepared SAM on a non-curved plane oxidized Si-wafer. In the case of ZrO(2) nanocrystals an intense alkyl-chain alignment could be disturbed by decreasing the grafting density from the maximum of 2.1 molecules/nm(2) through the variation of coupling agent concentration to lower values. Furthermore, the co-adsorption of a different coupling agent, such as phenylphosphonic acid for ZrO(2) and phenyltrimethoxysilane for SiO(2), resulted in a significantly lower alkyl-chain ordering for ZrO(2) plane crystals and for large SiO(2) spherical particles at high grafting density. An increasing amount of order-disturbing molecules leads to a gradual decrease in alkyl-chain alignment on the surface of the inorganic nanoparticles. In the case of the ZrO(2) nanoparticle system it is shown via dynamic light scattering (DLS) that the mixed monolayer formation on the particle surface impacts the dispersion quality in organic solvents such as n-hexane.

  9. Characteristics of collector formation during the rift developmental stage

    Energy Technology Data Exchange (ETDEWEB)

    Demidovich, L.A.

    1977-01-01

    An explanation is given for characteristics of the formation of collector properties in terrigenous and carbonate rock of the Devonian in the rift stage of the Pripyat downwarp development. An interconnection was noted between the paleostructural factor, lithogenesis, and the physical parameters of rocks. A forecast is made of collectors and for future oil and gas operations on the basis of an analysis of these data.

  10. Surface-water interface induces conformational changes critical for protein adsorption: Implications for monolayer formation of EAS hydrophobin

    Directory of Open Access Journals (Sweden)

    Kamron eLey

    2015-11-01

    Full Text Available The class I hydrophobin EAS is part of a family of small, amphiphilic fungal proteins best known for their ability to self-assemble into stable monolayers that modify the hydrophobicity of a surface to facilitate further microbial growth. These proteins have attracted increasing attention for industrial and biomedical applications, with the aim of designing surfaces that have the potential to maintain their clean state by resisting non-specific protein binding. To gain a better understanding of this process, we have employed all-atom molecular dynamics to study initial stages of the spontaneous adsorption of monomeric EAS hydrophobin on fully hydroxylated silica, a commonly used industrial and biomedical substrate. Particular interest has been paid to the Cys3-Cys4 loop, which has been shown to exhibit disruptive behavior in solution, and the Cys7-Cys8 loop, which is believed to be involved in the aggregation of EAS hydrophobin at interfaces. Specific and water mediated interactions with the surface were also analyzed. We have identified two possible binding motifs, one which allows unfolding of the Cys7-Cys8 loop due to the surfactant-like behavior of the Cys3-Cys4 loop, and another which has limited unfolding due to the Cys3-Cys4 loop remaining disordered in solution. We have also identified intermittent interactions with water which mediate the protein adsorption to the surface, as well as longer lasting interactions which control the diffusion of water around the adsorption site. These results have shown that EAS behaves in a similar way at the air-water and surface-water interfaces, and have also highlighted the need for hydrophilic ligand functionalization of the silica surface in order to prevent the adsorption of EAS hydrophobin.

  11. Nano-tribological characteristics of lanthanum-based thin films on sulfonated self-assembled monolayer of 3-mercaptopropyl trimethoxysilane

    Institute of Scientific and Technical Information of China (English)

    BAI Tao; CHENG Xianhua

    2008-01-01

    Silane coupling reagent (3-mercaptopropyl trimethoxysilane (MPTS)) was prepared on silicon substrate to form two-dimensional Self-Assembled Monolayer (SAM) and the terminal -SH group in the film was in situ oxidized to -SO3H group to endow the film with good chemisorption ability. Thus, lanthanum-based thin films were deposited on oxidized MPTS-SAM to form rare earth composite thin films (RE thin films), making use of the chemisorption ability of the --SO3H group. Atomic Force Microscope (AFM), X-ray Photoelectron Spectrometry (XPS), and contact angle measurements were used to characterize the RE thin films. Adhesive force and friction force of the RE thin films and silicon substrate were measured under various applied normal loads and scanning speed of AFM tip. The results showed that the friction force increased with applied normal loads and scanning speed of AFM tip. To study the effect of capillary force, tests were performed in various relative humidities. The results showed that the adhesive force of silicon substrate increased with relative humidity and the adhesive force of RE thin films only increased slightly with relative humidity. Research showed that surfaces with higher hydrophobic property reveal lowered adhesive and friction forces.

  12. Nano-tribological characteristics of TiO2 films on 3-mercaptopropyl trimethoxysilane sulfonated self-assembled monolayer

    Indian Academy of Sciences (India)

    J Li; X H Sheng

    2009-10-01

    Silane coupling reagent (3-mercaptopropyl trimethoxysilane (MPTS)) was used to prepare twodimensional self-assembled monolayer (SAM) on silicon substrate. The terminal –SH group was in situ oxidized to –SO3H group to endow the film with good chemisorption ability. Then TiO2 thin films were deposited on the oxidized MPTS–SAM to form composite thin films, making use of the chemisorption ability of the –SO3H group. Atomic force microscope (AFM) and contact angle measurements were used to characterize TiO2 films. Adhesive force and friction force of TiO2 thin films and silicon substrate were measured under various applied normal loads and scanning speed of AFM tip. Results showed that the friction force increased with applied normal loads and scanning speed of AFM tip. In order to study the effect of capillary force, tests were performed in various relative humidities. Results showed that the adhesive force of silicon substrate increases with relative humidities and the adhesive force of TiO2 thin films only increases slightly with relative humidity. Research showed that surfaces with more hydrophobic property revealed the lower adhesive and friction forces.

  13. Biofilm Formation Characteristics of Pseudomonas lundensis Isolated from Meat.

    Science.gov (United States)

    Liu, Yong-Ji; Xie, Jing; Zhao, Li-Jun; Qian, Yun-Fang; Zhao, Yong; Liu, Xiao

    2015-12-01

    Biofilms formations of spoilage and pathogenic bacteria on food or food contact surfaces have attracted increasing attention. These events may lead to a higher risk of food spoilage and foodborne disease transmission. While Pseudomonas lundensis is one of the most important bacteria that cause spoilage in chilled meat, its capability for biofilm formation has been seldom reported. Here, we investigated biofilm formation characteristics of P. lundensis mainly by using crystal violet staining, and confocal laser scanning microscopy (CLSM). The swarming and swimming motility, biofilm formation in different temperatures (30, 10, and 4 °C) and the protease activity of the target strain were also assessed. The results showed that P. lundensis showed a typical surface-associated motility and was quite capable of forming biofilms in different temperatures (30, 10, and 4 °C). The strain began to adhere to the contact surfaces and form biofilms early in the 4 to 6 h. The biofilms began to be formed in massive amounts after 12 h at 30 °C, and the extracellular polysaccharides increased as the biofilm structure developed. Compared with at 30 °C, more biofilms were formed at 4 and 10 °C even by a low bacterial density. The protease activity in the biofilm was significantly correlated with the biofilm formation. Moreover, the protease activity in biofilm was significantly higher than that of the corresponding planktonic cultures after cultured 12 h at 30 °C. © 2015 Institute of Food Technologists®

  14. Microlayer formation characteristics in pool isolated bubble boiling of water

    Science.gov (United States)

    Yabuki, Tomohide; Nakabeppu, Osamu

    2016-10-01

    Investigation of microlayer formation characteristics is important for developing a reliable nucleate boiling heat transfer model based on accurate physical mechanisms. Although formation mechanisms of the thin liquid film in two-phase flow of confined spaces, such as micro-tubes and closely positioned parallel plates, have been thoroughly studied, microlayer formation mechanisms of pool boiling have been sparsely studied. In a previous study (Yabuki and Nakabeppu in Int J Heat Mass Transf 76:286-297, 2014; Int J Heat Mass Transf 100:851-860, 2016), the spatial distribution of initial microlayer thickness under pool boiling bubbles was calculated by transient heat conduction analysis using the local wall temperature measured with a MEMS sensor. In this study, the hydrodynamic characteristics of microlayer formation in pool boiling were investigated using the relationship between derived initial microlayer thickness and microlayer formation velocity determined by transient local heat flux data. The trend of microlayer thickness was found to change depending on the thickness of the velocity boundary layer outside the bubble foot. When the boundary layer thickness was thin, the initial microlayer thickness was determined by the boundary layer thickness, and the initial microlayer thickness proportionally increased with increasing boundary layer thickness. On the other hand, when the boundary layer was thick, the initial microlayer thickness decreased with increasing boundary layer thickness. In this thick boundary layer region, the momentum balance in the dynamic meniscus region became important, in addition to the boundary layer thickness, and the microlayer thickness, made dimensionless using boundary layer thickness, correlated with the Bond number.

  15. Packing of ganglioside-phospholipid monolayers

    DEFF Research Database (Denmark)

    Majewski, J.; Kuhl, T.L.; Kjær, K.

    2001-01-01

    DPPE monolayer and does not distort the hexagonal in-plane unit cell or out-of-plane two-dimensional (2-D) packing compared with a pure DPPE monolayer. The oligosaccharide headgroups were found to extend normally from the monolayer surface, and the incorporation of these glycolipids into DPPE...... monolayers did not affect hydrocarbon tail packing (fluidization or condensation of the hydrocarbon region). This is in contrast to previous investigations of lipopolymer-lipid mixtures, where the packing structure of phospholipid monolayers was greatly altered by the inclusion of lipids bearing hydrophilic...... polymer groups. Indeed, the lack of packing disruptions by the oligosaccharide groups indicates that protein-GM, interactions, including binding, insertion, chain fluidization, and domain formation (lipid rafts), can be studied in 2-D monolayers using scattering techniques....

  16. Modeling Stimuli-Responsive Nanoparticle Monolayer

    Science.gov (United States)

    Yong, Xin

    2015-03-01

    Using dissipative particle dynamics (DPD), we model a monolayer formed at the water-oil interface, which comprises stimuli-responsive nanoparticles. The solid core of the nanoparticle encompasses beads arranged in an fcc lattice structure and its surface is uniformly grafted with stimuli-responsive polymer chains. The surface-active nanoparticles adsorb to the interface from the suspension to minimize total energy of the system and create a monolayer covering the interface. We investigate the monolayer formation by characterizing the detailed adsorption kinetics. We explore the microstructure of the monolayer at different surface coverage, including the particle crowding and ordering, and elucidate the response of monolayer to external stimuli. The collective behavior of the particles within the monolayer is demonstrated quantitatively by vector-vector autocorrelation functions. This study provides a fundamental understanding of the interfacial behavior of stimuli-responsive nanoparticles.

  17. Characteristics of soil radon transport in different geological formations

    Science.gov (United States)

    Ershaidat, N. M.; Al-Bataina, B. A.; Al-Shereideh, S. A.

    2008-07-01

    Soil radon concentration levels in Deir Abu-Said District, Irbid, Jordan were measured for several depths using CR-39 detectors, in the summer 2004 for six geological formations, namely, Wadi umm ghudran (WG), Wadi esSir “massive” limestone, Amman silicified limestone (ASL), Al-Hisa phosphatic limestone (AHP), Muwaqqar chalky-marl (MCM), and Basalt. Using a model (Yakovleva in Ann Geophys 48(1):195 198, 2005) based on the solution of the diffusion equation in the quasi-homogenous approximation, the characteristics of radon transport were calculated. Radon flux density from the Earth’s surface, the depth Z eq, at which the equilibrium value of soil radon concentration is reached and the convective radon flux velocity ( v) for the different soils are calculated and found to be consistent with similar values presented elsewhere. Calculations indicate that the soil covering WG has a low radon risk while, on the contrary, AHP has a higher radon risk as expected, since AHP has higher content of uranium. The other formations have intermediate values. The results of the present study confirm the statement by Yakovleva (Ann Geophys 48(1):195 198, 2005) that two measurements suffice in order to estimate the characteristics of soil radon transport.

  18. Simple direct formation of self-assembled N-heterocyclic carbene monolayers on gold and their application in biosensing

    Science.gov (United States)

    Crudden, Cathleen M.; Horton, J. Hugh; Narouz, Mina R.; Li, Zhijun; Smith, Christene A.; Munro, Kim; Baddeley, Christopher J.; Larrea, Christian R.; Drevniok, Benedict; Thanabalasingam, Bheeshmon; McLean, Alastair B.; Zenkina, Olena V.; Ebralidze, Iraklii I.; She, Zhe; Kraatz, Heinz-Bernhard; Mosey, Nicholas J.; Saunders, Lisa N.; Yagi, Akiko

    2016-09-01

    The formation of organic films on gold employing N-heterocyclic carbenes (NHCs) has been previously shown to be a useful strategy for generating stable organic films. However, NHCs or NHC precursors typically require inert atmosphere and harsh conditions for their generation and use. Herein we describe the use of benzimidazolium hydrogen carbonates as bench stable solid precursors for the preparation of NHC films in solution or by vapour-phase deposition from the solid state. The ability to prepare these films by vapour-phase deposition permitted the analysis of the films by a variety of surface science techniques, resulting in the first measurement of NHC desorption energy (158+/-10 kJ mol-1) and confirmation that the NHC sits upright on the surface. The use of these films in surface plasmon resonance-type biosensing is described, where they provide specific advantages versus traditional thiol-based films.

  19. Star Formation in Isolated Disk Galaxies. I. Models and Star Formation Characteristics

    CERN Document Server

    Li, Y; Klessen, R S; Li, Yuexing; Low, Mordecai-Mark Mac; Klessen, Ralf S.

    2005-01-01

    We model star formation in a wide range of isolated disk galaxies composed of a dark matter halo and a disk of stars and isothermal gas, using a three-dimensional smoothed particle hydrodynamics code. Absorbing sink particles are used to directly measure the mass of gravitationally collapsing gas. They reach masses characteristic of stellar clusters. In this paper, we describe our galaxy models and numerical methods, followed by an investigation of the gravitational instability in these galaxies. Gravitational collapse forms star clusters with correlated positions and ages, as observed in the Large Magellanic Cloud. Gravitational instability alone acting in unperturbed galaxies appears sufficient to produce flocculent spiral arms, though not more organized patterns. Unstable galaxies show collapse in thin layers in the galactic plane; associated dust will form thin dust lanes in those galaxies, in agreement with observations. We find an exponential relationship between the global star formation timescale and ...

  20. Polyspecies biofilm formation on implant surfaces with different surface characteristics

    Directory of Open Access Journals (Sweden)

    Patrick R. SCHMIDLIN

    2013-01-01

    Full Text Available Objective To investigate the microbial adherence and colonization of a polyspecies biofilm on 7 differently processed titanium surfaces. Material and Methods Six-species biofilms were formed anaerobically on 5-mm-diameter sterilized, saliva-preconditioned titanium discs. Material surfaces used were either machined, stained, acid-etched or sandblasted/acid-etched (SLA. Samples of the latter two materials were also provided in a chemically modified form, with increased wettability characteristics. Surface roughness and contact angles of all materials were determined. The discs were then incubated anaerobically for up to 16.5 h. Initial microbial adherence was evaluated after 20 min incubation and further colonization after 2, 4, 8, and 16.5 h using non-selective and selective culture techniques. Results at different time points were compared using ANOVA and Scheffé post hoc analysis. Results The mean differences in microorganisms colonizing after the first 20 min were in a very narrow range (4.5 to 4.8 log CFU. At up to 16.5 h, the modified SLA surface exhibited the highest values for colonization (6.9±0.2 log CFU, p<0.05 but increasing growth was observed on all test surfaces over time. Discrepancies among bacterial strains on the differently crafted titanium surfaces were very similar to those described for total log CFU. F. nucleatum was below the detection limit on all surfaces after 4 h. Conclusion Within the limitations of this in vitro study, surface roughness had a moderate influence on biofilm formation, while wettability did not seem to influence biofilm formation under the experimental conditions described. The modified SLA surface showed the highest trend for bacterial colonization.

  1. Formation of nanoscale tungsten oxide structures and colouration characteristics

    Indian Academy of Sciences (India)

    Vijay Bhooshan Kumar; Dambarudhar Mohanta

    2011-06-01

    In this work, pH dependent evolution of tungsten oxide (WO3) nanostructures is being reported along with physical characteristics. The synthesis was carried out via an inexpensive solvothermal cum chemical reduction route, with sodium tungstate (Na2WO4) and cetyl trimethyl ammonium bromide (C19H42NBr) as main reactants. The X-ray diffraction, together with transmission electron microscopic studies have revealed formation of regular polyhedral nanocrystalline structures and fractals as one goes from higher pH (= 5.5) to lower pH (= 2) values. The average crystallite size, as calculated throughWilliamson–Hall plots, was varied within 2.8–6.8 nm for different pH samples. Fourier transform infrared spectroscopy reveals in-plane bending vibration (W–OH), observable at ∼1630 cm-1 and strong stretching (W–O–W) located at ∼814 cm-1. Raman spectroscopy has divulged WO3 Raman active optical phonon modes positioned at ∼717 and 805 cm-1. The thermochromic and photochromic properties of the nanoscale WO3 sample prepared at pH = 5.5, are also highlighted.

  2. Simulation of the formation and characteristics of ultrasonic fountain.

    Science.gov (United States)

    Xu, Zheng; Yasuda, Keiji; Liu, Xiaojun

    2016-09-01

    In order to design an ultrasonic apparatus with a high throughput rate for generating atomization, the mechanism of fountain characteristics is important because the throughput rate of the ultrasonic atomization is decided by the area of the fountain surface. The formation of the fountain can be numerically studied by taking into account the effect of surface tension and radiation pressure. We have investigated the shape of the fountain with different ultrasound parameters or different kinds of solutions. When the amplitude of input sound pressure is higher than 1.3×10(5)Pa, the liquid separates from the ultrasonic fountain after irradiation for a very short period. It is further found that the area of the fountain surface increases with the concentration of the ethanol due to its low surface tension, density and sound speed. Finally, we discuss the difference between the ultrasonic fountain and the pump fountain, and find that the velocity field in the reactor induced by the pump is higher than that by the ultrasound.

  3. Formation of carboxy- and amide-terminated alkyl monolayers on silicon(111) investigated by ATR-FTIR, XPS, and X-ray scattering: Construction of photoswitchable surfaces

    DEFF Research Database (Denmark)

    Rück-Braun, Karola; Petersen, Michael Åxman; Michalik, Fabian

    2013-01-01

    We have prepared high-quality, densely packed, self-assembled monolayers (SAMs) of carboxy-terminated alkyl chains on Si(111). The samples were made by thermal grafting of methyl undec-10-enoate under an inert atmosphere and subsequent cleavage of the ester functionality to disclose the carboxyli...

  4. Electronic and magnetic properties of dopant atoms in SnSe monolayer: a first-principles study

    CERN Document Server

    Wang, Qingxia; Fu, Xiaonan; Qiao, Chong; Xia, Congxin; Jia, Yu

    2015-01-01

    SnSe monolayer with orthorhombic Pnma GeS structure is an important two-dimensional (2D) indirect band gap material at room temperature. Based on first-principles density functional theory calculations, we present systematic studies on the electronic and magnetic properties of X (X = Ga, In, As, Sb) atoms doped SnSe monolayer. The calculated electronic structures show that Ga-doped system maintains semiconducting property while In-doped SnSe monolayer is half-metal. The As- and Sb- doped SnSe systems present the characteristics of n-type semiconductor. Moreover, all considered substitutional doping cases induce magnetic ground states with the magnetic moment of 1{\\mu}B. In addition, the calculated formation energies also show that four types of doped systems are thermodynamic stable. These results provide a new route for the potential applications of doped SnSe monolayer in 2D photoelectronic and magnetic semiconductor devices.

  5. Investigating the pathway for the photochemical formation of VOCs in presence of an organic monolayer at the air/water interface.

    Science.gov (United States)

    Tinel, Liselotte; Rossignol, Stéphanie; Ciuraru, Raluca; George, Christian

    2015-04-01

    Investigating the pathway for the photochemical formation of VOCs in presence of an organic monolayer at the air/water interface. Liselotte Tinel, Stéphanie Rossignol, Raluca Ciuraru and Christian George Université de Lyon, Université Lyon 1, CNRS, UMR5256, IRCELYON, Institut de recherches sur la catalyse et l'environnement de Lyon, Villeurbanne, F-69626, France Recently the surface microlayer (SML) has received growing attention for its role in the deposition and emission of trace gases. This SML is presumably a highly efficient environment for photochemical reactions thanks to its physical and chemical properties, showing enrichment in chromophores [1]. Still, little is known about the possible photochemical processes that could influence the emission and deposition of volatile organic compounds (VOCs) in the SML. A recent study underlines the particularity of the presence of an organic microlayer, showing enhanced formation of peptide bonds at the air-water interface, although this reaction is thermodynamically disfavoured in bulk water [2]. Also, emissions of small gas phase carbonyl compounds formed photochemically by dissolved organic matter have been measured above natural water and glyoxal, for example, measured above the open ocean is thought to be photochemically produced [3, 4]. This study presents the results of a set of laboratory studies set up in order to better understand the role of the SML in the photochemical production of VOCs. Recently, our group has shown the formation of VOCs by light driven reactions in a small quartz reactor (14mL) containing aqueous solutions of humic acids (HA) in the presence of an organic (artificial or natural) microlayer [5]. The main VOCs produced were oxidized species, such as aldehydes, ketones and alcohols, as classically can be expected by the oxidation of the organics present at the interface initiated by triplet excited chromophores present in the HA. But also alkenes, dienes, including isoprene and

  6. Scanning tunneling microscopy study of the c(4x4) structure formation in the sub-monolayer Sb/Si(100) system

    Energy Technology Data Exchange (ETDEWEB)

    Saranin, A.A.; Zotov, A.V. [Osaka Univ., Suita (Japan). Faculty of Engineering; Kotlyar, V.G. [Institute of Automation and Control Processes, Vladivostok (RU)] (and others)

    2001-10-01

    Upon Sb desorption from a Sb-saturated Si(100) surface, the c(4x4) structure formed at about 0.25 monolayer Sb coverage. The c(4x4) reconstruction has been found to develop best when the surface is slightly contaminated, plausibly, by carbon. The Si(100)-c(4x4)-Sb surface shows up in the high-resolution filled state scanning tunneling microscopy images as being very similar to that of the recently reported c(4x4)-Si reconstruction. Here the main features of the Si(100)-c(4x4)-Sb structure are identified and the possible atomic arrangement is discussed. (author)

  7. The Formation and characteristics of Acrylonitrile/Urea Inclusion Compound

    CERN Document Server

    Zou, Jun-Ting; Pang, Wen-Min; Shi, Lei; Lu, Fei

    2012-01-01

    The formation process and composition of the acrylonitrile/urea inclusion compounds (AN/UIC) with different aging times and AN/urea molar feed ratios are studied by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). It is suggested that DSC could be one of the helpful methods to determine the guest/host ratio and the heat of decomposition. Meanwhile, the guest/host ratio and heat of deformation are obtained, which are 1.17 and 5361.53 J/mol, respectively. It is found that the formation of AN/UIC depends on the aging time. The formation process ends after enough aging time and the composition of AN/UIC becomes stable. It is suggested AN molecules included in urea canal lattice may be packed flat against each other. XRD results reveal that once AN molecules enter urea lattice, AN/UIC are formed, which possess the final structure. When AN molecules are sufficient, the content of AN/UIC increased as aging time prolonging until urea tunnels are saturated by AN.

  8. Characteristics of soot formation and burnout in turbulent recirculating flames

    Energy Technology Data Exchange (ETDEWEB)

    Touati, A.

    1987-01-01

    The present study represents an investigation of the effect of fuel type, fuel stream heat content, nitrogen dilution, and air jet velocity on soot formation rates and particle burnout in a highly recirculating, turbulent-type flame. Soot particle size and flux measurements have been made using an optical probe based on a large angle ratioing technique to measure the intensity of forward scattered light from individual particles at two off-axis angles. Chemical analyses of soot samples have been made using a gas chromatograph with a flame ionization detector (FID), and a morphological analysis of soot samples has been made using a scanning electron microscope (SEM). Physical probes have been used for temperature measurements and extraction of soot particles. Chemical analysis of the composition of the polycyclic aromatic hydrocarbons (PAHs) extracted from soot samples collected at the face of the burner and on a filter located downstream in the exhaust system suggests that multiple, convergent pathways, rather than one chemical mechanism, lead to the formation of high molecular weight PAHs and soot. Net soot production was found to be the result of the competition of soot particle formation and burnout. The fuel type and the fuel stream heat content appear the main parameters that determine the flame's propensity to soot. The addition of nitrogen to a fuel stream increases the difference in the net soot production among the fuel investigated. Dilution by nitrogen decreases more effectively the oxidation rate of soot particles in flames that use fuels of lower heat content.

  9. FLOW CHARACTERISTICS FORMATION OF POWER STEERING WITH ROTARY DISTRIBUTOR

    Directory of Open Access Journals (Sweden)

    V. Mikhailov

    2012-01-01

    Full Text Available In order to obtain an adequate mathematical model of vehicle hydro-mechanical steering which is  equipped with a steering mechanism combined with power steering and a rotary distributor  it is initially   necessary to get current consumption values in the units of hydraulic scheme which are determined by dynamic changes of flow passages of pressure and drain circuits according to turning angle of the distributor. Such characteristics are usually determined experimentally.The paper  proposes  a sequence which is recommended for determination of consumption characteristics which is formed with due account of multi-directional kinematic perturbations, mechanical clearance, possible emergence of hydraulic backlash and desired throttling law. The factors account makes it possible to obtain an acceptable mathematical analogue of a hydro-mechanical steering for execution of robust investigations. 

  10. Improved aging performance of vapor phase deposited hydrophobic self-assembled monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Gnanappa, Arun Kumar, E-mail: arun@imel.demokritos.gr [Tyndall National Institute, Lee Maltings, Prospect Row, Cork (Ireland); Institute of Microelectronics, NCSR Demokritos, Athens (Greece); O' Murchu, Cian; Slattery, Orla; Peters, Frank [Tyndall National Institute, Lee Maltings, Prospect Row, Cork (Ireland); O' Hara, Tony [Memsstar Technology (registered) , Starlaw Park, Starlaw Road, Livingston (United Kingdom); Aszalos-Kiss, Balazs; Tofail, Syed A.M. [Materials and Surface Science Institute, University of Limerick, Limerick (Ireland)

    2011-02-15

    A hydrophobic self-assembled monolayer (SAM) of fluoro-octyl-trichloro-silane (FOTS) was deposited on silicon using a vapor phase technique. The aging of the hydrophobic layer was examined using water contact angle measurements. It has been found that while such monolayer films suffer from a loss of hydrophobicity with time, pre-immersion nitrogen annealing can significantly improve the aging characteristics of these monolayers. The effect of nitrogen annealing on the improved aging properties of SAM coatings has been investigated by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The hydrolytic stability and the effect of nitrogen annealing were studied by morphological evolution during immersion. A spontaneous formation of silane mounds on the surface of the monolayers was found by AFM. These mounds have been irreversibly transformed from initially uniform hydrophobic surface layers. It is highly probable that the compliance of these mounds can reasonably allow hydrophilic sites to be located around the mounds. Interestingly, the density of these mounds formation is very less on the annealed samples. XPS reveals a higher level of coverage by the N{sub 2}-annealed film due to agglomeration. A relative abundance of CF{sub 3} and CF{sub 2} moieties in the annealed film may explain the enhancement of the hydrophobicity as revealed by higher level of water contact angle. This hydrophobicity was found to be significantly stable in water. This novel finding explains the improved hydrophobic stability of FOTS monolayers as primarily a morpho-chemical effect that originates from the densification of the monolayers upon annealing.

  11. Lupane-type pentacyclic triterpenes in Langmuir monolayers: a synchrotron radiation scattering study.

    Science.gov (United States)

    Broniatowski, Marcin; Flasiński, Michał; Wydro, Paweł

    2012-03-20

    Lupane-type pentacyclic triterpenes (lupeol, betulin, and betulinic acid) are natural products isolated from various plant sources. The terpenes exhibit a vast spectrum of biological activity and are applied in therapies for different diseases, among which the anticancer, anti-HIV, antihypercholesteremic, and antiinflammatory are the most promising. These chemicals possess amphiphilic structure and were proved to interact strongly with biomembranes, which can be the key stage in their mechanism of action. In our studies, we applied Langmuir monolayers as versatile models of biomembranes. It turned out that the three investigated terpenes are capable of stable monolayer formation; however, these monolayers differ profoundly regarding their physicochemical characteristics. In our research, we applied the Langmuir technique (surface pressure-mean molecular area (π-A) isotherm registration) coupled with Brewster angle microscopy (BAM), but the main focus was on the synchrotron radiation scattering method, grazing incidence X-ray diffraction (GIXD), which provides information on the amphiphilic molecule ordering in the angström scale. It was proved that all the investigated terpenes form crystalline phases in their monolayers. In the case of lupeol, only the closely packed upright phase was observed, whereas for betulin and betulinic acid, the phase situation was more complex. Betulinic acid molecules can be organized in an upright phase, which is crystalline, and in a tilted phase, which is amorphous. The betulin film is a conglomerate of an upright crystalline monolayer phase, tilted amorphous monolayer phase, and a crystalline tilted bilayer. In our paper, we discuss the factors leading to the formation of the observed phases and the implications of our results to the therapeutic applications of the native lupane-type triterpenes.

  12. Melting mechanism in monolayers of flexible rod-shaped molecules

    DEFF Research Database (Denmark)

    Hansen, Flemming Yssing; Taub, H.

    1992-01-01

    mechanism for melting in monolayers of flexible rod-shaped molecules. Melting requires the formation of vacancies in the monolayer by molecular motion perpendicular to the surface. This ‘‘footprint reduction’’ mechanism implies that strictly two-dimensional theories of melting are inapplicable...

  13. The characteristics of coignimbrite deposits and inferences for their formation

    Science.gov (United States)

    Engwell, S. L.; Eychenne, J.; Wulf, S.; De'Michieli Vitturi, M.

    2014-12-01

    Coignimbrite deposits form as fine-grained ash (traffic. To date, few coignimbrite deposits have been studied in detail, mainly due to their poor preservation potential, and difficulty distinguishing these deposits from Plinian deposits. As such, there is little in the published record regarding the physical characteristics of coignimbrite deposits. Deposits from Lago Grande di Monticchio, a maar lake 120 km east of the Campanian Volcanic Zone, Italy were analysed for this study. These lake sediments contain more than 340 distinct tephra layers, of which more than 300 are thought to have originated from the Campanian region. The physical characteristics of deposits from eruptions from within the past 50 kyrs are studied with particular emphasis placed on those with a known pyroclastic density current phase. Results show that in most cases, stratigraphy is comparable to proximal stratigraphy, and in the case of the Campanian Ignimbrite (Phlegrean Fields, 39.3 ka) and Monte Epomeo Green Tuff (Ischia, 55 ka) particularly, the coignimbrite contribution is easily identified. These coignimbrite deposits are composed of glass shards, with very small lithic and expanded pumice contents. Grainsize data from these coignimbrite events show remarkably similar characteristics, typically described by a very fine-grained mode (~50 microns), and poor sorting. This fine grain size implicates aggregation as the dominant process by which this ash is deposited. Similar trends are identified in the literature, for different types and scales of eruptions indicating the grainsize of these deposits is controlled by current dynamics rather than primary eruptive conditions at the vent. The results highlight the importance of lacustrine environments for deciphering eruption dynamics, specifically those from coignimbrite forming events. In addition, the distinct difference in grainsize trends between Plinian and coignimbrite events highlights the need to model coignimbrite events and ash

  14. IMPROVED VIBRATION CHARACTERISTICS OF FLEXIBLE POLYURETHANE FOAM VIA COMPOSITE FORMATION

    Directory of Open Access Journals (Sweden)

    Chan Wen Shan

    2013-06-01

    Full Text Available Flexible polyurethane (PU foam is used as cushioning material in automotive seating for load bearing. Owing to the demand for more comfortable compartments, seat cushions are now designed for better ride comfort, which is linked to the damping of seating foam. In this paper, PU polymer was mixed with short treated coir fibers (F and recycled tires (P to enhance damping and improve the vibrational characteristics of seating foam. Five samples with 2.5wt% filler loading were developed. The vibration characteristics of foam composites were examined by transmissibility tests generated at 1 and 1.5 mm peak amplitude in the frequency range of 2–20 Hz, using a shaker, shaking table, and a foam-block system. The foam-block system was fabricated by simulating the seat/occupant system in an automobile. The damping properties of foam composites were calculated from the transmissibility data obtained. The results showed that more vibration was dissipated by the developed foam composites after the fillers were added. System inserts with PU+2.5wt%P gave the lowest resonance peak: 2.460 and 2.695 at 1 and 1.5 mm base excitation, respectively, compared with 2.788 and 2.878 obtained from system inserts of pure PU foam. This is because a higher damping ratio (ξ foam was found in PU+2.5wt%P, which is 36.47% and 19.23% higher than pure PU foam. In addition, other composites, such as PU+2.5wt%F, PU+2.5wt% (50F50P, PU+2.5wt% (80P20F, and 2.5wt% (80F20P also showed favorable vibration and damping characteristics in the experiments. When compared with the conventional seat cushions used in the Proton car, foam composites could offer better vibration dampening at resonance.

  15. FLOW CHARACTERISTICS FORMATION OF POWER STEERING WITH ROTARY DISTRIBUTOR

    OpenAIRE

    Mikhailov, V; E. Strock

    2012-01-01

    In order to obtain an adequate mathematical model of vehicle hydro-mechanical steering which is  equipped with a steering mechanism combined with power steering and a rotary distributor  it is initially   necessary to get current consumption values in the units of hydraulic scheme which are determined by dynamic changes of flow passages of pressure and drain circuits according to turning angle of the distributor. Such characteristics are usually determined experimentally.The paper  proposes  ...

  16. Urban characteristics attributable to density-driven tie formation

    CERN Document Server

    Pan, Wei; Krumme, Coco; Cebrian, Manuel; Pentland, Alex

    2012-01-01

    Motivated by empirical evidence on the interplay between geography, population density and societal interaction, we propose a generative process for the evolution of social structure in cities. Our analytical and simulation results predict both super-linear scaling of social tie density and information flow as a function of the population. We demonstrate that our model provides a robust and accurate fit for the dependency of city characteristics with city size, ranging from individual-level dyadic interactions (number of acquaintances, volume of communication) to population-level variables (contagious disease rates, patenting activity, economic productivity and crime) without the need to appeal to modularity, specialization, or hierarchy.

  17. Micropatterned ferrocenyl monolayers covalently bound to hydrogen-terminated silicon surfaces: effects of pattern size on the cyclic voltammetry and capacitance characteristics.

    Science.gov (United States)

    Fabre, Bruno; Pujari, Sidharam P; Scheres, Luc; Zuilhof, Han

    2014-06-24

    The effect of the size of patterns of micropatterned ferrocene (Fc)-functionalized, oxide-free n-type Si(111) surfaces was systematically investigated by electrochemical methods. Microcontact printing with amine-functionalized Fc derivatives was performed on a homogeneous acid fluoride-terminated alkenyl monolayer covalently bound to n-type H-terminated Si surfaces to give Fc patterns of different sizes (5 × 5, 10 × 10, and 20 × 20 μm(2)), followed by backfilling with n-butylamine. These Fc-micropatterned surfaces were characterized by static water contact angle measurements, ellipsometry, X-ray photoelectron spectroscopy (XPS), infrared reflection-absorption spectroscopy (IRRAS), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The charge-transfer process between the Fc-micropatterned and underlying Si interface was subsequently studied by cyclic voltammetry and capacitance. By electrochemical studies, it is evident that the smallest electroactive ferrocenyl patterns (i.e., 5 × 5 μm(2) squares) show ideal surface electrochemistry, which is characterized by narrow, perfectly symmetric, and intense cyclic voltammetry and capacitance peaks. In this respect, strategies are briefly discussed to further improve the development of photoswitchable charge storage microcells using the produced redox-active monolayers.

  18. Flow Classification and Cave Discharge Characteristics in Unsaturated Karst Formation

    Science.gov (United States)

    Mariethoz, G.; Mahmud, K.; Baker, A.; Treble, P. C.

    2015-12-01

    In this study we utilize the spatial array of automated cave drip monitoring in two large chambers of the Golgotha Cave, SW Australia, developed in Quaternary aeolianite (dune limestone), with the aim of understanding infiltration water movement via the relationships between infiltration, stalactite morphology and groundwater recharge. Mahmud et al. (2015) used the Terrestrial LiDAR measurements to analyze stalactite morphology and to characterize possible flow locations in this cave. Here we identify the stalactites feeding the drip loggers and classify each as matrix (soda straw or icicle), fracture or combined-flow. These morphology-based classifications are compared with flow characteristics from the drip logger time series and the discharge from each stalactite is calculated. The total estimated discharge from each area is compared with infiltration estimates to better understand flow from the surface to the cave ceilings of the studied areas. The drip discharge data agrees with the morphology-based flow classification in terms of flow and geometrical characteristics of cave ceiling stalactites. No significant relationships were observed between the drip logger discharge, skewness and coefficient of variation with overburden thickness, due to the possibility of potential vadose-zone storage volume and increasing complexity of the karst architecture. However, these properties can be used to characterize different flow categories. A correlation matrix demonstrates that similar flow categories are positively correlated, implying significant influence of spatial distribution. The infiltration water comes from a larger surface area, suggesting that infiltration is being focused to the studied ceiling areas of each chamber. Most of the ceiling in the cave site is dry, suggesting the possibility of capillary effects with water moving around the cave rather than passing through it. Reference:Mahmud et al. (2015), Terrestrial Lidar Survey and Morphological Analysis to

  19. Laboratory and Numerical Modeling of Smoke Characteristics for Superfog Formation

    Science.gov (United States)

    Bartolome, C.; Lu, V.; Tsui, K.; Princevac, M.; Venkatram, A.; Mahalingam, S.; Achtemeier, G.; Weise, D.

    2011-12-01

    Land management techniques in wildland areas include prescribed fires to promote biodiversity and reduce risk of severe wildfires across the United States. Several fatal car pileups have been associated with smoke-related visibility reduction from prescribed burns. Such events have occurred in year 2000 on the interstate highways I-10 and I-95, 2001 on the I-4, 2006 on the I-95, and 2008 on the I-4 causing numerous fatalities, injuries, and damage to property. In some of the cases visibility reduction caused by smoke and fog combinations traveling over roadways have been reported to be less than 3 meters, defined as superfog. Our research focuses on delineating the conditions that lead to formation of the rare phenomena of superfog and creating a tool to enable land managers to effectively plan prescribed burns and prevent tragic events. It is hypothesized that the water vapor from combustion, live fuels, soil moisture, and ambient air condense onto the cloud condensation nuclei (CCN) particles emitted from low intensity smoldering fires. Physical and numerical modeling has been used to investigate these interactions. A physical model in the laboratory has been developed to characterize the properties of smoke resulting from smoldering pine needle litters at the PSW Forest Service in Riverside, CA. Temporal measurements of temperature, relative humidity, sensible heat flux, radiation heat flux, convective heat flux, particulate matter concentrations and visibilities have been measured for specific cases. The size distribution and number concentrations of the fog droplets formed inside the chamber by mixing cool dry and moist warm air masses to produce near superfog visibilities were measured by a Phase Doppler Particle Analyzer. Thermodynamic modeling of smoke and ambient air was conducted to estimate liquid water contents (LWC) available to condense into droplets and form significant reductions in visibility. The results show that LWC of less than 2 g m-3 can be

  20. Direct Patterning of Covalent Organic Monolayers on Silicon Using Nanoimprint Lithography

    NARCIS (Netherlands)

    Voorthuijzen, W. Pim; Yilmaz, M. Deniz; Gomez-Casado, Alberto; Jonkheijm, Pascal; Wiel, van der Wilfred G.; Huskens, Jurriaan

    2010-01-01

    Two fabrication schemes are reported for the direct patterning of organic monolayers on oxide-free silicon, combining top-down nanoimprint lithography and bottom-up monolayer formation. The first approach was designed to form monolayer patterns on the imprinted areas, while the second approach was d

  1. Influence of borehole and formation characteristics on elemental standard spectra in geochemical logging

    Science.gov (United States)

    Wu, Wensheng; Yue, Aizhong; Xiang, Wei; Wang, Shusheng; Fan, Dechang

    2017-10-01

    Accurate acquisition of elemental standard spectra is one of the key links in geochemical elemental logging. Because elemental standard spectra are affected by borehole and formation characteristics, it is necessary to study the borehole and formation conditions required for the acquisition of ideal spectra. For these, we constructed a model comprising instruments, borehole and formation; applied the Monte Carlo N-Particle Transport Code to simulate elemental standard spectral responses under different borehole and formation conditions; and performed a comparative analysis of these responses. The results demonstrate that, for the standard capture spectra of an element, a fresh water borehole yields spectra with good statistical properties and significant characteristic peaks. For elements with a high capture cross section and prominent characteristic peaks, a borehole of small diameter yields ideal spectra; conversely, a borehole of slightly larger diameter is suitable for elements with a low capture cross section and insignificant characteristic peaks. A formation containing a certain number of pores full of fresh water can yield better standard spectra except for elements that have a giant capture cross section such as Gd. A formation composed of various compounds of an element yields standard spectra with different effects, which means that an elemental compound has to be selected to get an ideal standard spectrum. For the standard inelastic spectrum of an element, the influence of the borehole fluid or pore fluid should be avoided as much as possible except for oxygen; formations composed of an elementary substance, or chlorides or hydrides of an element yields a better standard spectrum than one composed of its oxides, carbonates or other compounds containing elements with a large inelastic cross section. The compactness of the formation influences the characteristic peaks and statistical properties of the standard spectra. The simulation method takes fully

  2. A pentacene monolayer trapped between graphene and a substrate

    Science.gov (United States)

    Zhang, Qicheng; Peng, Boyu; Chan, Paddy Kwok Leung; Luo, Zhengtang

    2015-08-01

    A self-assembled pentacene monolayer can be fabricated between the solid-solid interface of few-layered graphene (FLG) and the mica substrate, through a diffusion-spreading method. By utilizing a transfer method that allows us to sandwich pentacene between graphene and mica, followed by controlled annealing, we enabled the diffused pentacene to be trapped in the interfaces and led to the formation of a stable monolayer. We found that the formation of a monolayer is kinetically favored by using a 2D Ising lattice gas model for pentacene trapped between the graphene-substrate interfaces. This kinetic Monte Carlo simulation results indicate that, due to the graphene substrate enclosure, the spreading of the first layer proceeds faster than the second layer, as the kinetics favors the filling of voids by molecules from the second layer. This graphene assisted monolayer assembly method provides a new avenue for the fabrication of two-dimensional monolayer structures.A self-assembled pentacene monolayer can be fabricated between the solid-solid interface of few-layered graphene (FLG) and the mica substrate, through a diffusion-spreading method. By utilizing a transfer method that allows us to sandwich pentacene between graphene and mica, followed by controlled annealing, we enabled the diffused pentacene to be trapped in the interfaces and led to the formation of a stable monolayer. We found that the formation of a monolayer is kinetically favored by using a 2D Ising lattice gas model for pentacene trapped between the graphene-substrate interfaces. This kinetic Monte Carlo simulation results indicate that, due to the graphene substrate enclosure, the spreading of the first layer proceeds faster than the second layer, as the kinetics favors the filling of voids by molecules from the second layer. This graphene assisted monolayer assembly method provides a new avenue for the fabrication of two-dimensional monolayer structures. Electronic supplementary information (ESI

  3. Formation of Self-assembled Monolayers of Silver Sulphide Nanoparticles%纳米半导体硫化银单层膜的自组装

    Institute of Scientific and Technical Information of China (English)

    郑昌戈; 邰子厚

    2002-01-01

    本文使用Triton X-100作为模板剂制备半导体硫化银纳米颗粒,并研究了其吸收光谱的兰移特性.在金属铝或金基底上自组装有机双功能分子单层膜后,将其浸入所制备的纳米硫化银颗粒的微乳液中,自组装得到硫化银纳米颗粒单层膜并研究了其表面形貌特征.%Nanosize silver sulphide semiconductor particles were synthesized using the nonionic surfactant,Triton X-1O0.A blue shift is obtained as compared with the optical band edge of bulk silver sulphide.Onto the glass or mica slides,self-assembled monolayers (SAMs) of bifunctional organic molecule were prepared on the gold or aluminum layers.By immersing them into the microemulsion of silver sulphide,the SAMs of nanosize silver sulphide particles were acquired.Further,The surface characterization about SAMs of nanoparticles was studied.

  4. Direct patterning of covalent organic monolayers on silicon using nanoimprint lithography.

    Science.gov (United States)

    Voorthuijzen, W Pim; Yilmaz, M Deniz; Gomez-Casado, Alberto; Jonkheijm, Pascal; van der Wiel, Wilfred G; Huskens, Jurriaan

    2010-09-07

    Two fabrication schemes are reported for the direct patterning of organic monolayers on oxide-free silicon, combining top-down nanoimprint lithography and bottom-up monolayer formation. The first approach was designed to form monolayer patterns on the imprinted areas, while the second approach was designed for monolayer formation outside of the imprinted features. By both approaches, covalently bonded Si-C monolayer patterns with feature sizes ranging from 100 nm to 100 microm were created via a hydrosilylation procedure using diluted reagents. Both unfunctionalized and omega-functionalized alkenes were patterned successfully.

  5. Effective p-type N-doped WS{sub 2} monolayer

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Xu, E-mail: zhaoxu@htu.cn; Xia, Congxin; Wang, Tianxing; Peng, Yuting; Dai, Xianqi

    2015-11-15

    Based on density functional theory, the characteristics of n- and p-type dopants are investigated by means of group V and VII atoms substituting sulfur in the WS{sub 2} monolayer. Numerical results show that for each doping case, the formation energy is lower under W-rich condition, which indicates that it is energy favorable to incorporate group V and VII atoms into WS{sub 2} under W-rich experimental conditions. Moreover, compared with other dopant cases, N-doped WS{sub 2} monolayer owns the lowest formation energy. In particular, the transition level of (−1/0) is only 75 meV in the N-doped case, which indicates that N impurities can offer effective p-type carriers in the WS{sub 2} monolayer. - Highlights: • The formation energy is lower under W-rich conditions. • N-doped system owns the lowest formation energy compared with other atoms. • The transition level of N-doping in WS{sub 2} is 75 meV. • N impurities can offer effective p-type carriers in the WS{sub 2}.

  6. Assembly of organic monolayers on polydicyclopentadiene.

    Science.gov (United States)

    Perring, Mathew; Bowden, Ned B

    2008-09-16

    The first well-defined organic monolayers assembled on polydicyclopentadiene is reported. Commercial grade dicyclopentadiene was polymerized with the Grubbs' second-generation catalyst in a fume hood under ambient conditions at very low monomer to catalyst loadings of 20 000 to 1. This simple method resulted in a polymer that was a hard solid and appeared slightly yellow. Brief exposures of a few seconds of this polymer to Br 2 lead to a surface with approximately half of the olefins brominated as shown by X-ray photoelectron spectroscopy (XPS) and attenuated total reflection-infrared (ATR-IR) spectroscopy. The ATR-IR spectroscopy was carried out with the polymer in contact with a Ge hemisphere housed in a GATR accessory from Harrick. This brominated polydicyclopentadiene was immersed in DMF with 4-(trifluoromethyl)benzylamine to assemble a monolayer. The amines displaced Br on the surface to form a monolayer that exposed a CF 3 group on the surface. The surface was extensively studied by XPS using the method described by Tougaard to find the distribution of F within the surface layer. The ratio for the peak area, Ap, to the background height, B, measured 30 eV below the peak maximum was 109.8 eV. This value clearly indicated that F was found only at the surface and was not found within the polymer. A surface coverage of 1.37 amines per nm (2) was estimated and indicated that the monolayer was 28% as dense as a similar monolayer assembled from thiols on gold. Finally, a simple method to pattern these monolayers using soft lithography is described. This work is critically important because it reports the first monolayers on a relatively new and emerging polymer that has many desirable physical characteristics such as high hardness, chemical stability, and ease of forming different shapes.

  7. Sub-THz Characterisation of Monolayer Graphene

    Directory of Open Access Journals (Sweden)

    Ehsan Dadrasnia

    2014-01-01

    Full Text Available We explore the optical and electrical characteristics of monolayer graphene by using pulsed optoelectronic terahertz time-domain spectroscopy in the frequency range of 325–500 GHz based on fast direct measurements of phase and amplitude. We also show that these parameters can, however, be measured with higher resolution using a free space continuous wave measurement technique associated with a vector network analyzer that offers a good dynamic range. All the scattering parameters (both magnitude and phase are measured simultaneously. The Nicholson-Ross-Weir method is implemented to extract the monolayer graphene parameters at the aforementioned frequency range.

  8. Star formation in the first galaxies - III. Formation, evolution, and characteristics of the first stellar cluster

    CERN Document Server

    Safranek-Shrader, Chalence; Milosavljevic, Milos; Bromm, Volker

    2015-01-01

    We simulate the formation of a low metallicity (0.01 Zsun) stellar cluster in a dwarf galaxy at redshift z~14. Beginning with cosmological initial conditions, the simulation utilizes adaptive mesh refinement and sink particles to follow the collapse and evolution of gas past the opacity limit for fragmentation, thus resolving the formation of individual protostellar cores. A time- and location-dependent protostellar radiation field, which heats the gas by absorption on dust, is computed by integration of protostellar evolutionary tracks with the MESA code. The simulation also includes a robust non-equilibrium chemical network that self-consistently treats gas thermodynamics and dust-gas coupling. The system is evolved for 18 kyr after the first protostellar source has formed. In this time span, 30 sink particles representing protostellar cores form with a total mass of 81 Msun. Their masses range from ~0.1 Msun to 14.4 Msun with a median mass ~0.5-1 Msun. Massive protostars grow by competitive accretion while...

  9. CHARACTERISTICS OF STRUCTURE FORMATION IN COOKED SAUSAGE PRODUCTS USING SONOCHEMICAL TECHNOLOGIES

    Directory of Open Access Journals (Sweden)

    A. M. Yevtushenko

    2016-01-01

    Full Text Available This paper studies the features of formation of sausage product structure in the process of cooking. It is shown that the viscosity of sausage meat varies in a complex manner and has three characteristic areas. The characteristic parameters that determine the formation of the structure of sausages for each area were found. It is established that the use of the cavitation brine gives the finished product a gentle consistence, elasticity and distinct taste that makes it more preferable for the consumer.

  10. Multivariate Analysis Of Ground Water Characteristics Of Geological Formations Of Enugu State Of Nigeria

    Directory of Open Access Journals (Sweden)

    Orakwe

    2015-08-01

    Full Text Available Abstract The chemometric data mining techniques using principal factor analysis PFA and hierarchical cluster analysis CA was employed to evaluate and to examine the borehole characteristics of geological formations of Enugu State of Nigeria to determine the latent structure of the borehole characteristics and to classify 9 borehole parameters from 49 locations into borehole groups of similar characteristics. PFA extracted three factors which accounted for a large proportion of the variation in the data 77.305 of the variance. Out of nine parameters examined the first PFA had the highest number of variables loading on a single factor where four borehole parameters borehole depth borehole casing static water level and dynamic water level loaded on it with positive coefficient as the most significant parameters responsible for variation in borehole characteristics in the study. The CA employed in this study to identified three clusters. The first cluster delineated stations that characterise Awgu sandstone geological formation while the second cluster delineated Agbani sandstone geological formation. The third cluster delineated Ajali sandstone formation. The CA grouping of the borehole parameters showed similar trend with PFA hence validating the efficiency of chemometric data mining techniques in grouping of variations in the borehole characteristics in the geological zone of the study area.

  11. Characteristics of hydrocarbon sources and controlling factors of their formation in Pingliang Formation, West Ordos Basin

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    According to organic geochemistry and organic petrology, the hydrocarbon sources in Pingliang Formation, W. Ordos basin, are systematically evaluated. The organic abundance of hydrocarbon source in this research is higher in the upper part of profiles than In the low, and more in mudstone than in carbonate. Most of organic matters become sapropelic, and few are humlc-aapropelic in the regions of Shibangou and Zhuzisan. According to stable isotopes of carbon and oxygen in carbonate rock, boron index and ratios of elements, palaeo-salinity and sedimentary velocity are calculated. The two factors of paleao-salinity and sediment velocity, which control the distribution of organic matters, are discussed.Good relationship is found between water salinity and abundance of organic matter; in contrast, poor correlation is observed between salinity and types of organic matters. The relative sediment velocity in the research regions is also related with organic abundance and types. A low sediment velocity would lead to high abundance and good type of organic matters, and vice versa.

  12. Thermodynamic characteristics of the formation of complexes of nickel(II) with L-homoserine

    Science.gov (United States)

    Gridchin, S. N.

    2016-12-01

    The formation of complexes of nickel(II) with L-homoserine at 298.15 K and ionic strengths I = 0.5, 1.0, and 1.5 (KNO3) are investigated by potentiometry and calorimetry. Standard characteristics of studied equilibria (log K°, Δr G°, Δr H°, and Δr S°) are determined.

  13. A Genetic Algorithm Approach for Group Formation in Collaborative Learning Considering Multiple Student Characteristics

    Science.gov (United States)

    Moreno, Julian; Ovalle, Demetrio A.; Vicari, Rosa M.

    2012-01-01

    Considering that group formation is one of the key processes in collaborative learning, the aim of this paper is to propose a method based on a genetic algorithm approach for achieving inter-homogeneous and intra-heterogeneous groups. The main feature of such a method is that it allows for the consideration of as many student characteristics as…

  14. A Genetic Algorithm Approach for Group Formation in Collaborative Learning Considering Multiple Student Characteristics

    Science.gov (United States)

    Moreno, Julian; Ovalle, Demetrio A.; Vicari, Rosa M.

    2012-01-01

    Considering that group formation is one of the key processes in collaborative learning, the aim of this paper is to propose a method based on a genetic algorithm approach for achieving inter-homogeneous and intra-heterogeneous groups. The main feature of such a method is that it allows for the consideration of as many student characteristics as…

  15. Characteristics of flora from the Datong Formation in Ningwu coalfield, Shanxi

    Energy Technology Data Exchange (ETDEWEB)

    Chang Jianglin; Gao Qiang [Shanxi Institute of Coal Geology (China)

    1996-12-31

    41 species assigned to 21 genus of plant remains from the Datong Formation in Ningwu Coalfield, Shanxi, are recognized by the authors. In this paper, the characteristics and geological age are discussed in detail. The flora is composed mainly of Filicinae and Ginkgophytes. Equistales and Coniferales are the second largest, and Cycadophyta is rarely found. It belong to Coniopteris-phoenicopsis flora is well-developed in North China and could be compared with the floras of the Datong Formation in Datong Coal-field, the Mentougou Group in West-Hills of Beijing, the Yanan Formation in Ordos Basin and the Dameigou Formation in Qinghai. The geological age of this flora may be assigned to the Middle Jurassic. 14 refs., 1 tab., 14 plates.

  16. Characteristics of Telemagmatic Metamorphism of the Ceshui Formation Coal in Lianyuan Coal Basin

    Institute of Scientific and Technical Information of China (English)

    毕华; 彭格林

    1998-01-01

    The Ceshui Formation coal is mostly anthracite and its metamorphism has been less documented.By analyzing systematically the reflectance of vitrinite and the results of X-ray diffraction of the Ceshui Formation cola in the Lianyuan coal basin,the spatial variation characteristics of coal ranks,coal metamorphic regions,the extension of coal metamorphic belts.coal metamorphic gradients,coal chemical structure and the effect on the degree of metamorphism of heat-production and -storge conditions,buried depth of the Indosinian-Yenshanian granites at the margins of the Lianyuan coal basin are discussed.The research results in conjunction of the features of regional hydrothermal alterations,endogenetic deposits with the Ceshui Formation coal measures,and the development of secondary vesicles indicate that the telemagmatic metamorphism is the main factor leading to the metamorphism of the Ceshui Formation coal in the region studied.

  17. Monolayer arrangement of fatty hydroxystearic acids on graphite: Influence of hydroxyl groups

    Energy Technology Data Exchange (ETDEWEB)

    Medina, S. [Laboratorio de Rayos-X, Centro de Investigación Tecnología e Innovación, de la Universidad de Sevilla (CITIUS), Universidad de Sevilla, Avenida Reina Mercedes, 4B. 41012, Sevilla (Spain); Benítez, J.J.; Castro, M.A. [Instituto de Ciencia de Materiales de Sevilla, Consejo Superior de Investigaciones Científicas-Universidad de Sevilla, Avenida Américo Vespucio, 49. 41092, Sevilla (Spain); Cerrillos, C. [Servicio de Microscopía, Centro de Investigación Tecnología e Innovación, de la Universidad de Sevilla (CITIUS), Universidad de Sevilla, Avenida Reina Mercedes, 4B. 41012, Sevilla (Spain); Millán, C. [Instituto de Ciencia de Materiales de Sevilla, Consejo Superior de Investigaciones Científicas-Universidad de Sevilla, Avenida Américo Vespucio, 49. 41092, Sevilla (Spain); Alba, M.D., E-mail: alba@icmse.csic.es [Instituto de Ciencia de Materiales de Sevilla, Consejo Superior de Investigaciones Científicas-Universidad de Sevilla, Avenida Américo Vespucio, 49. 41092, Sevilla (Spain)

    2013-07-31

    Previous studies have indicated that long-chain linear carboxylic acids form commensurate packed crystalline monolayers on graphite even at temperatures above their melting point. This study examines the effect on the monolayer formation and structure of adding one or more secondary hydroxyl, functional groups to the stearic acid skeleton (namely, 12-hydroxystearic and 9,10-dihydroxystearic acid). Moreover, a comparative study of the monolayer formation on recompressed and monocrystalline graphite has been performed through X-ray diffraction (XRD) and Scanning Tunneling Microscopy (STM), respectively. The Differential Scanning Calorimetry (DSC) and XRD data were used to confirm the formation of solid monolayers and XRD data have provided a detailed structural analysis of the monolayers in good correspondence with obtained STM images. DSC and XRD have demonstrated that, in stearic acid and 12-hydroxystearic acid adsorbed onto graphite, the monolayer melted at a higher temperature than the bulk form of the carboxylic acid. However, no difference was observed between the melting point of the monolayer and the bulk form for 9,10-dihydroxystearic acid adsorbed onto graphite. STM results indicated that all acids on the surface have a rectangular p2 monolayer structure, whose lattice parameters were uniaxially commensurate on the a-axis. This structure does not correlate with the initial structure of the pure compounds after dissolving, but it is conditioned to favor a) hydrogen bond formation between the carboxylic groups and b) formation of hydrogen bonds between secondary hydroxyl groups, if spatially permissible. Therefore, the presence of hydroxyl functional groups affects the secondary structure and behavior of stearic acid in the monolayer. - Highlights: • Hydroxyl functional groups affect structure and behavior of acids in the monolayer. • Acids on the surface have a rectangular p2 monolayer structure. • Lattice parameters of acids are uniaxially

  18. Experimental Study on the Characteristics of CO2 Hydrate Formation in Porous Media below Freezing Point

    Institute of Scientific and Technical Information of China (English)

    Zhang Xuemin; Li Jinping; Wu Qingbai; Wang Chunlong; Nan Junhu

    2015-01-01

    Porous medium has an obvious effect on the formation of carbon dioxide hydrate. In order to study the character-istics of CO2 hydrate formation in porous medium below the freezing point, the experiment of CO2 hydrate formation was conducted in a high-pressure 1.8-L cell in the presence of porous media with a particle size of 380μm, 500μm and 700μm, respectively. The test results showed that the porous medium had an important inlfuence on the process of CO2 hydrate for-mation below the freezing point. Compared with porous media with a particle size of 500μm and 700μm, respectively, the average hydrate formation rate and gas storage capacity of carbon dioxide hydrate in the porous medium with a particle size of 380μm attained 0.016 14 mol/h and 65.094 L/L, respectively. The results also indicated that, within a certain range of particle sizes, the smaller the particle size of porous medium was, the larger the average hydrate formation rate and the gas storage capacity of CO2 hydrate during the process of hydrate formation would be.

  19. Soot formation characteristics of gasoline surrogate fuels in counterflow diffusion flames

    KAUST Repository

    Choi, Byungchul

    2011-01-01

    The characteristics of polycyclic aromatic hydrocarbon (PAH) and soot for gasoline surrogate fuels have been investigated in counterflow diffusion flames by adopting laser-induced fluorescence (LIF) and laser-induced incandescence (LII) techniques for both soot formation and soot formation/oxidation flames. Tested fuels were three binary mixtures from the primary reference fuels of n-heptane, iso-octane, and toluene. The result showed that PAH and soot maintained near zero level for all mixtures of n-heptane/iso-octane case under present experimental conditions. For n-heptane/toluene and iso-octane/toluene mixtures, PAH initially increased and then decreased with the toluene ratio, exhibiting a synergistic effect. The soot formation increased monotonically with the toluene ratio, however the effect of toluene on soot formation was minimal for relatively small toluene ratios. These results implied that even though toluene had a dominant role in soot and PAH formations, small amount of toluene had a minimal effect on soot formation. Numerical simulations have also been conducted by adopting recently proposed two kinetic mechanisms. The synergistic behavior of aromatic rings was predicted similar to the experimental PAH measurement, however, the degree of the synergistic effect was over-predicted for the soot formation flame, indicating the need for refinements in the kinetic mechanisms. © 2010 Published by Elsevier Inc. on behalf of The Combustion Institute. All rights reserved.

  20. Star formation in the first galaxies - III. Formation, evolution, and characteristics of the first metal-enriched stellar cluster

    Science.gov (United States)

    Safranek-Shrader, Chalence; Montgomery, Michael H.; Milosavljević, Miloš; Bromm, Volker

    2016-01-01

    We simulate the formation of a low-metallicity (10-2 Z⊙) stellar cluster at redshift z ˜ 14. Beginning with cosmological initial conditions, the simulation utilizes adaptive mesh refinement and sink particles to follow the collapse and evolution of gas past the opacity limit for fragmentation, thus resolving the formation of individual protostellar cores. A time- and location-dependent protostellar radiation field, which heats the gas by absorption on dust, is computed by integration of protostellar evolutionary tracks. The simulation also includes a robust non-equilibrium chemical network that self-consistently treats gas thermodynamics and dust-gas coupling. The system is evolved for 18 kyr after the first protostellar source has formed. In this time span, 30 sink particles representing protostellar cores form with a total mass of 81 M⊙. Their masses range from ˜0.1 to 14.4 M⊙ with a median mass ˜0.5-1 M⊙. Massive protostars grow by competitive accretion while lower mass protostars are stunted in growth by close encounters and many-body ejections. In the regime explored here, the characteristic mass scale is determined by the cosmic microwave background temperature floor and the onset of efficient dust-gas coupling. It seems unlikely that host galaxies of the first bursts of metal-enriched star formation will be detectable with the James Webb Space Telescope or other next-generation infrared observatories. Instead, the most promising access route to the dawn of cosmic star formation may lie in the scrutiny of metal-poor, ancient stellar populations in the Galactic neighbourhood. The observable targets corresponding to the system simulated here are ultra-faint dwarf satellite galaxies such as Boötes II and Willman I.

  1. Anodic passivation of tin by alkanethiol self-assembled monolayers examined by cyclic voltammetry and coulometry.

    Science.gov (United States)

    Worley, Barrett C; Ricks, William A; Prendergast, Michael P; Gregory, Brian W; Collins, Ross; Cassimus, John J; Thompson, Raymond G

    2013-10-22

    The self-assembly of medium chain length alkanethiol monolayers on polycrystalline Sn electrodes has been investigated by cyclic voltammetry and coulometry. These studies have been performed in order to ascertain the conditions under which their oxidative deposition can be achieved directly on the oxide-free Sn surface, and the extent to which these electrochemically prepared self-assembled monolayers (SAMs) act as barriers to surface oxide growth. This work has shown that the potentials for their oxidative deposition are more cathodic (by 100-200 mV) than those for Sn surface oxidation and that the passivating abilities of these SAMs improve with increasing film thickness (or chain length). Oxidative desorption potentials for these films have been observed to shift more positively, and in a highly linear fashion, with increasing film thickness (~75 mV/CH2). Although reductive desorption potentials for the SAMs are in close proximity to those for reduction of the surface oxide (SnOx), little or no SnOx formation occurs unless the potential is made sufficiently anodic that the monolayers start to be removed oxidatively. Our coulometric data indicate that the charge involved with alkanethiol reductive desorption or oxidative deposition is consistent with the formation of a close-packed monolayer, given uncertainties attributable to surface roughness and heterogeneity phenomena. These experiments also reveal that the quantity of charge passed during oxidative desorption is significantly larger than what would be predicted for simple alkylsulfinate or alkylsulfonate formation, suggesting that oxidative removal involves a more complex oxidation mechanism. Analogous chronocoulometric experiments for short-chain alkanethiols on polycrystalline Au electrodes have evidenced similar oxidative charge densities. This implies that the mechanism for oxidative desorption on both surfaces may be very similar, despite the significant differences in the inherent dissolution

  2. Biofilm formation of Salmonella serotypes in simulated meat processing environments and its relationship to cell characteristics.

    Science.gov (United States)

    Wang, Huhu; Ding, Shijie; Dong, Yang; Ye, Keping; Xu, Xinglian; Zhou, Guanghong

    2013-10-01

    Salmonella attached to meat contact surfaces encountered in meat processing facilities may serve as a source of cross-contamination. In this study, the influence of serotypes and media on biofilm formation of Salmonella was investigated in a simulated meat processing environment, and the relationships between biofilm formation and cell characteristics were also determined. All six serotypes (Salmonella enterica serotype Heidelberg, Salmonella Derby, Salmonella Agona, Salmonella Indiana, Salmonella Infantis, and Salmonella Typhimurium) can readily form biofilms on stainless steel surfaces, and the amounts of biofilms were significantly influenced by the serotypes, incubation media, and incubation time used in this study. Significant differences in cell surface hydrophobicity, autoaggregation, motility, and growth kinetic parameters were observed between individual serotypes tested. Except for growth kinetic parameters, the cell characteristics were correlated with the ability of biofilm formation incubated in tryptic soy broth, whereas no correlation with biofilm formation incubated in meat thawing-loss broth (an actual meat substrate) was found. Salmonella grown in meat thawing-loss broth showed a "cloud-shaped" morphology in the mature biofilm, whereas when grown in tryptic soy broth it had a "reticulum-shaped" appearance. Our study provides some practical information to understand the process of biofilm formation on meat processing contact surfaces.

  3. Characteristics of Anabaena variabilis influencing plaque formation by cyanophage N-1

    Energy Technology Data Exchange (ETDEWEB)

    Currier, T.C.; Wolk, C.P.

    1979-07-01

    Phage N-1 grown in Anabaena strain 7120 (N-1 . 7120) forms plaques on A. variabilis about 10/sup -7/ to 10/sup -6/ as efficiently as on Anabaena 7120. By manipulating different characteristics of the interaction between phage and host, it was possible to increase the relative efficiency of plaque formation to 0.38. Growth of A. variabilis at 40/sup 0/C for at least three generations resulted in an increase in the rate of phage adsorption and a 10-fold increase in the efficiency of plaque formation. The efficiency of plaque formation was further increased about 42-fold, with little or no further increase in rate of adsorption, in a variant strain, A. variabilis strain FD, isolated from a culture of A. variabilis which had grown for more than 30 generations at 40/sup 0/C. The low relative efficiency of plaque formation by N-1 . 7120 on A. variabilis could be partially accounted for if A. variabilis contains a deoxyribonucleic acid restriction endonuclease which is absent from Anabaena 7120. Indirect evidence for such an endonuclease included the following: (i) phage N-1 grown in A. variabilis (N-1 . Av) had approximately a 7 x 10/sup 3/-fold higher relative efficiency of plaque formation on A. variabilis than had N-1 . 7120; and (ii) the efficiency of plaque formation by N-1 . 7120 on A. variabilis strain FD was increased by up to 146-fold after heating the latter organism at 51/sup 0/C.

  4. Statistical characteristics of formation and evolution of structure in the universe

    OpenAIRE

    Demianski, M.; Doroshkevich, A.

    1999-01-01

    An approximate statistical description of the formation and evolution of structure of the universe based on the Zel'dovich theory of gravitational instability is proposed. It is found that the evolution of DM structure shows features of self-similarity and the main structure characteristics can be expressed through the parameters of initial power spectrum and cosmological model. For the CDM-like power spectrum and suitable parameters of the cosmological model the effective matter compression ...

  5. Monolayer MoS2 heterojunction solar cells

    KAUST Repository

    Tsai, Menglin

    2014-08-26

    We realized photovoltaic operation in large-scale MoS2 monolayers by the formation of a type-II heterojunction with p-Si. The MoS 2 monolayer introduces a built-in electric field near the interface between MoS2 and p-Si to help photogenerated carrier separation. Such a heterojunction photovoltaic device achieves a power conversion efficiency of 5.23%, which is the highest efficiency among all monolayer transition-metal dichalcogenide-based solar cells. The demonstrated results of monolayer MoS 2/Si-based solar cells hold the promise for integration of 2D materials with commercially available Si-based electronics in highly efficient devices. © 2014 American Chemical Society.

  6. Unsupported single-atom-thick copper oxide monolayers

    Science.gov (United States)

    Yin, Kuibo; Zhang, Yu-Yang; Zhou, Yilong; Sun, Litao; Chisholm, Matthew F.; Pantelides, Sokrates T.; Zhou, Wu

    2017-03-01

    Oxide monolayers may present unique opportunities because of the great diversity of properties of these materials in bulk form. However, reports on oxide monolayers are still limited. Here we report the formation of single-atom-thick copper oxide layers with a square lattice both in graphene pores and on graphene substrates using aberration-corrected scanning transmission electron microscopy. First-principles calculations find that CuO is energetically stable and its calculated lattice spacing matches well with the measured value. Furthermore, free-standing copper oxide monolayers are predicted to be semiconductors with band gaps ∼3 eV. The new wide-bandgap single-atom-thick copper oxide monolayers usher a new frontier to study the highly diverse family of two-dimensional oxides and explore their properties and their potential for new applications.

  7. Predicting permeability from the characteristic relaxation time and intrinsic formation factor of complex conductivity spectra

    Science.gov (United States)

    Revil, A.; Binley, A.; Mejus, L.; Kessouri, P.

    2015-08-01

    Low-frequency quadrature conductivity spectra of siliclastic materials exhibit typically a characteristic relaxation time, which either corresponds to the peak frequency of the phase or the quadrature conductivity or a typical corner frequency, at which the quadrature conductivity starts to decrease rapidly toward lower frequencies. This characteristic relaxation time can be combined with the (intrinsic) formation factor and a diffusion coefficient to predict the permeability to flow of porous materials at saturation. The intrinsic formation factor can either be determined at several salinities using an electrical conductivity model or at a single salinity using a relationship between the surface and quadrature conductivities. The diffusion coefficient entering into the relationship between the permeability, the characteristic relaxation time, and the formation factor takes only two distinct values for isothermal conditions. For pure silica, the diffusion coefficient of cations, like sodium or potassium, in the Stern layer is equal to the diffusion coefficient of these ions in the bulk pore water, indicating weak sorption of these couterions. For clayey materials and clean sands and sandstones whose surface have been exposed to alumina (possibly iron), the diffusion coefficient of the cations in the Stern layer appears to be 350 times smaller than the diffusion coefficient of the same cations in the pore water. These values are consistent with the values of the ionic mobilities used to determine the amplitude of the low and high-frequency quadrature conductivities and surface conductivity. The database used to test the model comprises a total of 202 samples. Our analysis reveals that permeability prediction with the proposed model is usually within an order of magnitude from the measured value above 0.1 mD. We also discuss the relationship between the different time constants that have been considered in previous works as characteristic relaxation time, including

  8. Water exclusion at the nanometer scale provides long-term passivation of silicon (111) grafted with alkyl monolayers.

    Science.gov (United States)

    Gorostiza, P; Henry de Villeneuve, C; Sun, Q Y; Sanz, F; Wallart, X; Boukherroub, R; Allongue, P

    2006-03-23

    This work is a quantitative study of the conditions required for a long-term passivation of the interface silicon-alkyl monolayers prepared by thermal hydrosilyation of neat 1-alkenes on well-defined H-Si(111) surfaces. We present electrochemical capacitance measurements (C-U) in combination with ex situ atomic force microscopy (AFM) observations and X-ray photoelectron spectroscopy (XPS) measurements. Capacitance measurements as a function of the reaction time and XPS data reveal close correlations between the chemical composition at the interface and its electronic properties. A very low density of states is found if suboxide formation is carefully prevented. The monitoring of C-U plots and AFM imaging upon exposure of the sample in diverse conditions indicate that the initial electronic properties and structure of the interface are long-lasting only when the monolayer surface coverage is theta > 0.42. A model demonstrates that this threshold value corresponds to a monolayer with intermolecular channels narrower than approximately 2.82 A, which is equal to the diameter of a water molecule. Water exclusion from the monolayer promotes long-term passivation of the silicon surface against oxidation in air and water as well as perfect corrosion inhibition in 20% NH(4)F. We provide two criteria to assess when a sample is optimized: The first one is an effective dielectric constant <2.5, and the second one is a very characteristic energy diagram at open circuit potential.

  9. Collapse of Langmuir monolayer at lower surface pressure: Effect of hydrophobic chain length

    Energy Technology Data Exchange (ETDEWEB)

    Das, Kaushik, E-mail: kaushikdas2089@gmail.com; Kundu, Sarathi [Physical Sciences Division, Institute of Advanced Study in Science and Technology, Vigyan Path, Paschim Boragaon, Garchuk, Guwahati, Assam 781035 (India)

    2016-05-23

    Long chain fatty acid molecules (e.g., stearic and behenic acids) form a monolayer on water surface in the presence of Ba{sup 2+} ions at low subphase pH (≈ 5.5) and remain as a monolayer before collapse generally occurs at higher surface pressure (π{sub c} > 50 mN/m). Monolayer formation is verified from the surface pressure vs. area per molecule (π-A) isotherms and also from the atomic force microscopy (AFM) analysis of the films deposited by single upstroke of hydrophilic Si (001) substrate through the monolayer covered water surface. At high subphase pH (≈ 9.5), barium stearate molecules form multilayer structure at lower surface pressure which is verified from the π-A isotherms and AFM analysis of the film deposited at 25 mN/m. Such monolayer to multilayer structure formation or monolayer collapse at lower surface pressure is unusual as at this surface pressure generally fatty acid salt molecules form a monolayer on the water surface. Formation of bidentate chelate coordination in the metal containing headgroups is the reason for such monolayer to multilayer transition. However, for longer chain barium behenate molecules only monolayer structure is maintained at that high subphase pH (≈ 9.5) due to the presence of relatively more tail-tail hydrophobic interaction.

  10. Morphological characteristics, formation and glaciological significance of Rogen moraine in northern Scotland

    Science.gov (United States)

    Finlayson, Andrew G.; Bradwell, Tom

    2008-11-01

    Rogen moraine are enigmatic landforms whose exact origin is still debated. We use NEXTMap digital surface models and aerial photographs to map the distribution of previously unreported fields of Rogen moraine in the vicinity of Loch Shin, northern Scotland. Existing models of formation are tested against detailed morphological Rogen moraine characteristics obtained from the remote sensing data and field observations. Detailed morphometric analyses combined with their geographical setting lead us to postulate a likely mechanism of formation. Rogen moraine appear to have formed in areas where there were strong basal ice-flow velocity gradients. Thrusting by compression, or fracturing by extension of preexisting partially frozen sediment probably occurred in these areas, resulting in Rogen moraine formation. A general down-ice increase in ridge crest spacing suggests that the latter process may have been dominant, and is consistent with the location of Rogen moraine in the lee of topographic obstructions, in areas that experienced overall extensional ice flow. We also suggest that at least one field of Rogen moraine formed where lateral basal ice-flow velocity gradients were strongest — possibly in a subglacial shear margin setting. Given their location, the landforms may be consistent with formation during headward scavenging of the Moray Firth palaeo-ice stream into a shrinking core of cold-based ice.

  11. The Influence of topography on formation characteristics of hygroscopic and condensate water in Shapotou

    Science.gov (United States)

    Pan, Yanxia; Li, Xinrong; Hui, Rong; Zhao, Yang

    2016-04-01

    The formation characteristics of hygroscopic and condensate water for different topographic positions were observed using the PVC pipes manual weighing and CPM method in the typical mobile dunes fixed by straw checkerboard barriers in Shapotou. The results indicated that the formation amounts and duration of hygroscopic and condensate water show moderate spatial heterogeneity at the influence of topography. The formation amounts of hygroscopic and condensate water at different aspects conform to the classical convection model, in which the hygroscopic and condensate water amounts are highest at hollow, and windward aspect gets more water than leeward aspect, the hygroscopic and condensate water amounts at different aspects are expressed as: hollow>Western-faced aspect>Northern-faced aspect>hilltop>Southern-faced aspect>Eastern-faced aspect. The hygroscopic and condensate water amounts at different slope positions for every aspect are as follows: the foot of slope>middle slope>hilltop. A negatively linear correlation is got between slope angles and hygroscopic and condensate water amounts, hygroscopic and condensate water amounts decrease gradually along with the increase of slope angles, the amounts of hygroscopic and condensate water at the vertical aspect are only half of horizontal aspect, which indicated topography were important influence factors for the formation of the hygroscopic and condensate water in arid area.

  12. Radiation Hydrodynamics using Characteristics on Adaptive Decomposed Domains for Massively Parallel Star Formation Simulations

    CERN Document Server

    Buntemeyer, Lars; Peters, Thomas; Klassen, Mikhail; Pudritz, Ralph E

    2015-01-01

    We present an algorithm for solving the radiative transfer problem on massively parallel computers using adaptive mesh refinement and domain decomposition. The solver is based on the method of characteristics which requires an adaptive raytracer that integrates the equation of radiative transfer. The radiation field is split into local and global components which are handled separately to overcome the non-locality problem. The solver is implemented in the framework of the magneto-hydrodynamics code FLASH and is coupled by an operator splitting step. The goal is the study of radiation in the context of star formation simulations with a focus on early disc formation and evolution. This requires a proper treatment of radiation physics that covers both the optically thin as well as the optically thick regimes and the transition region in particular. We successfully show the accuracy and feasibility of our method in a series of standard radiative transfer problems and two 3D collapse simulations resembling the ear...

  13. Integral characteristics: a key to understanding structure formation in stochastic dynamic systems

    Energy Technology Data Exchange (ETDEWEB)

    Klyatskin, Valery I, E-mail: klyatskin@yandex.ru

    2011-05-31

    Some general problems concerning the stochastic approach are discussed in relation to parametrically excited stochastic dynamic systems described by partial differential equations. Such problems arise in hydrodynamics, magnetohydrodynamics, and astro, plasma, and radio physics and share the feature that the statistical characteristics of their solutions (moments, correlation and spectral functions, and so on) increasing exponentially with time, whereas some solution implementations lead to the formation of random structures with probability one as a result of clustering. The goal of this paper is to use the ideas of stochastic topography to find conditions under which such structures arise. (reviews of topical problems)

  14. Changes in electrical device characteristics during the formation of dislocations in situ in the TEM

    Energy Technology Data Exchange (ETDEWEB)

    Ross, F.M. (Lawrence Berkeley Lab., CA (United States)); Hull, R.; Bahnck, D.; Bean, J.C.; Peticolas, L.J.; King, C.A.; Kola, R.R. (AT and T Bell Labs., Murray Hill, NJ (United States))

    1993-03-01

    By adding electrical connections to a specimen heating holder for a transmission electron microscope, we have measured the characteristics of electronic devices such as diodes while they remain under observation in the microscope. We have made electron-transparent specimens from metastable GeSi/Si p-n junction diodes and introduced dislocations by heating in situ. The combination of electrical measurement and real-time observation of dislocation formation allows us to examine the electrical properties of dislocations in individual devices and the influence of defects on device performance.

  15. GEOLOGICAL AND GEOCHEMICAL CHARACTERISTICS AND RELATED MINERALIZATION OF CHERT FORMATIONS IN SOUTH TIBET

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    There occur abundant cherts in the Mesozoic and Cenozoic strata in southern Tibet. Some of them possess characteristic hydrothermal structures such as layered, laminated, massive and breccia structures.Ratios of Al/(Al+Fe+Mn), Co/Ni, Fe/Ti and TiO2-Al2O3 demonstrate that their origin is related to hydrothermal sedimentation. The chert formations have close relationship with Sb, Au and poly-metallic mineralization, and the ore-forming fluid show strong correlation with fossil hydrothermal water.

  16. Leachate formation and characteristics from gasification and grate incineration bottom ash under landfill conditions.

    Science.gov (United States)

    Sivula, Leena; Sormunen, Kai; Rintala, Jukka

    2012-04-01

    Characteristics and formation of leachates from waste gasification and grate firing bottom ash were studied using continuous field measurements from 112 m(3) lysimeters embedded into landfill body for three years. In addition, the total element concentrations of the fresh ash were analysed and laboratory batch tests were performed to study leachate composition. The three-year continuous flow measurement showed that about one fifth of the leachates were formed, when the flow rate was >200 l/d, covering 13) major part of the study. In the grate ash leachate pH was lower (landfill conditions. Copyright © 2011 Elsevier Ltd. All rights reserved.

  17. Tsunami characteristics and formation potential of sandy tsunami deposit in Sanriku Coast: implications from numerical modeling

    Science.gov (United States)

    Sugawara, D.; Haraguchi, T.; Takahashi, T.

    2013-12-01

    Geological investigation of paleotsunami deposit is crucial for knowing the history and magnitude of tsunami events in the past. Among various kinds of grain sizes, sandy tsunami deposit has been best investigated by previous studies, because of its potential for identification in the sedimentary column. Many sandy tsunami deposits have been found from coastal plains, which have sandy beach and low-lying wetlands. However, sandy tsunami deposits in narrow valleys at rocky ria coast have rarely been found. It may be presumed that formation potential of sandy tsunami layer in the rocky coasts is generally lower than coastal plains, because of the absence of sandy beach, tsunami run-up on steeper slope and stronger return flow. In this presentation, characteristics of the 2011 Tohoku-oki earthquake tsunami in Sanriku Coast, a continuous rocky ria coast located in the northeast Japan, is investigated based on numerical modeling. In addition, the formation potential of sandy tsunami deposit is also investigated based on numerical modeling of sediment transport. Preliminary result of tsunami hydrodynamics showed that the waveform and amplification of the tsunami are clearly affected by the local bathymetry, which is associated with submerged topography formed during the last glacial stage. Although the tsunami height in the offshore of each bay is around 8.0 m, the tsunami height at the bay head was increased in different way. The amplification factor at the bay head was typically 2.0 among most of V-shaped narrow embayments; meanwhile the amplification factor is much lower than 1.0 at some cases. The preliminary result of the modeling of sediment transport predicted huge amount of sediments may be suspended into the water column, given that sandy deposit is available there. Massive erosion and deposition of sea bottom sediments may commonly take place in the bays. However, formation of onshore tsunami deposit differs from each other. Whether the suspended sediments

  18. Bromate Formation Characteristics of UV Irradiation, Hydrogen Peroxide Addition, Ozonation, and Their Combination Processes

    Directory of Open Access Journals (Sweden)

    Naoyuki Kishimoto

    2012-01-01

    Full Text Available Bromate formation characteristics of six-physicochemical oxidation processes, UV irradiation, single addition of hydrogen peroxide, ozonation, UV irradiation with hydrogen peroxide addition (UV/H2O2, ozonation with hydrogen peroxide addition (O3/H2O2, and ozonation with UV irradiation (O3/UV were investigated using 1.88 μM of potassium bromide solution with or without 6.4 μM of 4-chlorobenzoic acid. Bromate was not detected during UV irradiation, single addition of H2O2, and UV/H2O2, whereas ozone-based treatments produced . Hydroxyl radicals played more important role in bromate formation than molecular ozone. Acidification and addition of radical scavengers such as 4-chlorobenzoic acid were effective in inhibiting bromate formation during the ozone-based treatments because of inhibition of hydroxyl radical generation and consumption of hydroxyl radicals, respectively. The H2O2 addition was unable to decompose 4-chlorobenzoic acid, though O3/UV and O3/H2O2 showed the rapid degradation, and UV irradiation and UV/H2O2 showed the slow degradation. Consequently, if the concentration of organic contaminants is low, the UV irradiation and/or UV/H2O2 are applicable to organic contaminants removal without bromate formation. However, if the concentration of organic contaminants is high, O3/H2O2 and O3/UV should be discussed as advanced oxidation processes because of their high organic removal efficiency and low bromate formation potential at the optimum condition.

  19. Physiological hydrostatic pressure protects endothelial monolayer integrity.

    Science.gov (United States)

    Müller-Marschhausen, K; Waschke, J; Drenckhahn, D

    2008-01-01

    Endothelial monolayer integrity is required to maintain endothelial barrier functions and has found to be impaired in several disorders like inflammatory edema, allergic shock, or artherosclerosis. Under physiologic conditions in vivo, endothelial cells are exposed to mechanical forces such as hydrostatic pressure, shear stress, and cyclic stretch. However, insight into the effects of hydrostatic pressure on endothelial cell biology is very limited at present. Therefore, in this study, we tested the hypothesis that physiological hydrostatic pressure protects endothelial monolayer integrity in vitro. We investigated the protective efficacy of hydrostatic pressure in microvascular myocardial endothelial (MyEnd) cells and macrovascular pulmonary artery endothelial cells (PAECs) by the application of selected pharmacological agents known to alter monolayer integrity in the absence or presence of hydrostatic pressure. In both endothelial cell lines, extracellular Ca(2+) depletion by EGTA was followed by a loss of vascular-endothelial cadherin (VE-caherin) immunostaining at cell junctions. However, hydrostatic pressure (15 cmH(2)O) blocked this effect of EGTA. Similarly, cytochalasin D-induced actin depolymerization and intercellular gap formation and cell detachment in response to the Ca(2+)/calmodulin antagonist trifluperazine (TFP) as well as thrombin-induced cell dissociation were also reduced by hydrostatic pressure. Moreover, hydrostatic pressure significantly reduced the loss of VE-cadherin-mediated adhesion in response to EGTA, cytochalasin D, and TFP in MyEnd cells as determined by laser tweezer trapping using VE-cadherin-coated microbeads. In caveolin-1-deficient MyEnd cells, which lack caveolae, hydrostatic pressure did not protect monolayer integrity compromised by EGTA, indicating that caveolae-dependent mechanisms are involved in hydrostatic pressure sensing and signaling.

  20. First principle identification of SiC monolayer as an efficient catalyst for CO oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Sinthika, S., E-mail: ranjit.t@res.srmuniv.ac.in, E-mail: sinthika90@gmail.com; Thapa, Ranjit, E-mail: ranjit.t@res.srmuniv.ac.in, E-mail: sinthika90@gmail.com [SRM Research Institute, SRM University, Kattankulathur 603203, Tamil Nadu (India); Reddy, C. Prakash [Department of Physics and Nanotechnology, SRM University, Kattankulathur 603203, Tamil Nadu (India)

    2015-06-24

    Using density functional theory, we investigated the electronic properties of SiC monolayer and tested its catalytic activity toward CO oxidation. The planar nature of a SiC monolayer is found to stable and is a high band gap semiconductor. CO interacts physically with SiC surface, whereas O{sub 2} is adsorbed with moderate binding. CO oxidation on SiC monolayer prefers the Eley Rideal mechanism over the Langmuir Hinshelwood mechanism, with an easily surmountable activation barrier during CO{sub 2} formation. Overall metal free SiC monolayer can be used as efficient catalyst for CO oxidation.

  1. Fluorinated alkyne-derived monolayers on oxide-free silicon nanowires via one-step hydrosilylation

    NARCIS (Netherlands)

    Nguyen, Quyen; Pujari, Sidharam P.; Wang, Bin; Wang, Zhanhua; Haick, Hossam; Zuilhof, Han; Rijn, van Cees J.M.

    2016-01-01

    Passivation of oxide-free silicon nanowires (Si NWs) by the formation of high-quality fluorinated 1-hexadecyne-derived monolayers with varying fluorine content has been investigated. Alkyl chain monolayers (C16H30−xFx) with a varying number of fluorine substituents (x = 0, 1, 3, 9, 17) were attached

  2. A Route to Permanent Valley Polarization in Monolayer MoS2

    KAUST Repository

    Singh, Nirpendra

    2016-10-24

    Realization of permanent valley polarization in Cr-doped monolayer MoS2 is found to be unfeasible because of extended moment formation. Introduction of an additional hole is suggested as a viable solution. V-doped monolayer MoS2 is demonstrated to sustain permanent valley polarization and therefore can serve as a prototype material for valleytronics.

  3. Effects of gaseous sulphuric acid on diesel exhaust nanoparticle formation and characteristics.

    Science.gov (United States)

    Rönkkö, Topi; Lähde, Tero; Heikkilä, Juha; Pirjola, Liisa; Bauschke, Ulrike; Arnold, Frank; Schlager, Hans; Rothe, Dieter; Yli-Ojanperä, Jaakko; Keskinen, Jorma

    2013-10-15

    Diesel exhaust gaseous sulphuric acid (GSA) concentrations and particle size distributions, concentrations, and volatility were studied at four driving conditions with a heavy duty diesel engine equipped with oxidative exhaust after-treatment. Low sulfur fuel and lubricant oil were used in the study. The concentration of the exhaust GSA was observed to vary depending on the engine driving history and load. The GSA affected the volatile particle fraction at high engine loads; higher GSA mole fraction was followed by an increase in volatile nucleation particle concentration and size as well as increase of size of particles possessing nonvolatile core. The GSA did not affect the number of nonvolatile particles. At low and medium loads, the exhaust GSA concentration was low and any GSA driven changes in particle population were not observed. Results show that during the exhaust cooling and dilution processes, besides critical in volatile nucleation particle formation, GSA can change the characteristics of all nucleation mode particles. Results show the dual nature of the nucleation mode particles so that the nucleation mode can include simultaneously volatile and nonvolatile particles, and fulfill the previous results for the nucleation mode formation, especially related to the role of GSA in formation processes.

  4. Sedimentary characteristics of tide-dominated estuary in Donghetang Formation(Upper Devonian), central Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The Donghetang Formation (Upper Devonian) in central Tarim Basin has been thought an important oil and gas reservoir since the abundant oil and gas resources were found in the wells W16, W20, W34, and other fields. However, the sedimentary environment of the Donghetang Formation has been disputed because it suffered from both tidal and fluvial actions and there were not rich fossils in the sandstone. After the authors analyzed sedimentary features by means of drill cores, well logging data, paleosols, and with SEM obseruations, three kinds of sedimentary environments were distinguished: alluvial fan, tide-dominated estuary, and shelf. Particularly, the sedimentary features of tide-dominated estuary were studied in detail. Besides, the authors discussed sedimentary characteristics of the Donghetang Formation which was divided into two fourth-order sequences and five system tracts. At the same time, according to the forming process of five system tracts, the whole vertical evolution and lateral transition of tide-dominated estuary were illustrated clearly. Finally, the reservoir quality was evaluated based on porosity and permeability.

  5. Radiation hydrodynamics using characteristics on adaptive decomposed domains for massively parallel star formation simulations

    Science.gov (United States)

    Buntemeyer, Lars; Banerjee, Robi; Peters, Thomas; Klassen, Mikhail; Pudritz, Ralph E.

    2016-02-01

    We present an algorithm for solving the radiative transfer problem on massively parallel computers using adaptive mesh refinement and domain decomposition. The solver is based on the method of characteristics which requires an adaptive raytracer that integrates the equation of radiative transfer. The radiation field is split into local and global components which are handled separately to overcome the non-locality problem. The solver is implemented in the framework of the magneto-hydrodynamics code FLASH and is coupled by an operator splitting step. The goal is the study of radiation in the context of star formation simulations with a focus on early disc formation and evolution. This requires a proper treatment of radiation physics that covers both the optically thin as well as the optically thick regimes and the transition region in particular. We successfully show the accuracy and feasibility of our method in a series of standard radiative transfer problems and two 3D collapse simulations resembling the early stages of protostar and disc formation.

  6. Strain Release Induced Novel Fluorescence Variation in CVD-Grown Monolayer WS2 Crystals.

    Science.gov (United States)

    Feng, Shanghuai; Yang, Ruilong; Jia, Zhiyan; Xiang, Jianyong; Wen, Fusheng; Mu, Congpu; Nie, Anmin; Zhao, Zhisheng; Xu, Bo; Tao, Chenggang; Tian, Yongjun; Liu, Zhongyuan

    2017-10-04

    Tensile strain is intrinsic to monolayer crystals of transition metal disulfides such as Mo(W)S2 grown on oxidized silicon substrates by chemical vapor deposition (CVD) owing to the much larger thermal expansion coefficient of Mo(W)S2 than that of silica. Here we report fascinating fluorescent variation in intensity with aging time in CVD-grown triangular monolayer WS2 crystals on SiO2 (300 nm)/Si substrates and formation of interesting concentric triangular fluorescence patterns in monolayer crystals of large size. The novel fluorescence aging behavior is recognized to be induced by the partial release of intrinsic tensile strain after CVD growth and the induced localized variations or gradients of strain in the monolayer crystals. The results demonstrate that strain has a dramatic impact on the fluorescence and photoluminescence of monolayer WS2 crystals and thus could potentially be utilized to tune electronic and optoelectronic properties of monolayer transition metal disulfides.

  7. Spontaneous Imbibition Dynamics of an n-Alkane in Nanopores: Evidence of Meniscus Freezing and Monolayer Sticking

    CERN Document Server

    Gruener, Simon; 10.1103/PhysRevLett.103.174501

    2009-01-01

    Capillary filling dynamics of liquid n-tetracosane (n-C24H50) in a network of cylindrical pores with 7 and 10 nm mean diameter in monolithic silica glass (Vycor) exhibit an abrupt temperature-slope change at Ts=54 deg C, ~4 deg C above bulk and ~16 deg C, 8 deg C, respectively, above pore freezing. It can be traced to a sudden inversion of the surface tension's T slope, and thus to a decrease in surface entropy at the advancing pore menisci, characteristic of the formation of a single solid monolayer of rectified molecules, known as surface freezing from macroscopic, quiescent tetracosane melts. The imbibition speeds, that are the squared prefactors of the observed square-root-of-time Lucas-Washburn invasion kinetics, indicate a conserved bulk fluidity and capillarity of the nanopore-confined liquid, if we assume a flat lying, sticky hydrocarbon backbone monolayer at the silica walls.

  8. Time-Varying Multifractal Characteristics and Formation Mechanism of Loaded Coal Electromagnetic Radiation

    Science.gov (United States)

    Hu, Shaobin; Wang, Enyuan; Li, Zhonghui; Shen, Rongxi; Liu, Jie

    2014-09-01

    Dynamic collapses of deeply mined coal rocks are severe threats to miners. To predict the collapses more accurately using electromagnetic radiation (EMR), we investigate the time-varying multifractal characteristics and formation mechanism of EMR induced by underground coal mining. A series of uniaxial compression and multi-stage loading experiments with coal samples of different mechanical properties were carried out. The EMR signals during their damage evolution were monitored in real-time; the inherent law of EMR time series was analyzed by fractal theory. The results show that the time-varying multifractal characteristics of EMR are determined by damage evolutions process, the dissipated energy caused by damage evolutions such as crack propagation, fractal sliding and shearing can be regard as the fingerprint of various EMR micro-mechanics. Based on the Irreversible thermodynamics and damage mechanics, we introduced the damage internal variable, constructed the dissipative potential function and established the coupled model of the EMR and the dissipative energy, which revealed the nature of dynamic nonlinear characteristics of EMR. Dynamic multifractal spectrum is the objective response of EMR signals, thus it can be used to evaluate the coal deformation and fracture process.

  9. Shale gas reservoir characteristics of Ordovician-Silurian formations in the central Yangtze area, China

    Science.gov (United States)

    Shan, Chang'an; Zhang, Tingshan; Wei, Yong; Zhang, Zhao

    2016-07-01

    The characteristics of a shale gas reservoir and the potential of a shale gas resource of Ordovician-Silurian age in the north of the central Yangtze area were determined. Core samples from three wells in the study area were subjected to thin-section examination, scanning electron microscopy, nuclear magnetic resonance testing, X-ray diffraction mineral analysis, total organic carbon (TOC) testing, maturity testing, gas-bearing analysis, and gas component and isothermal adsorption experiments. A favorable segment of the gas shale reservoir was found in both the Wufeng Formation and the lower part of the Longmaxi Formation; these formations were formed from the late Katian to early Rhuddanian. The high-quality shale layers in wells J1, J2, and J3 featured thicknesses of 54.88 m, 48.49 m, and 52.00 m, respectively, and mainly comprised carbonaceous and siliceous shales. Clay and brittle minerals showed average contents of 37.5% and 62.5% (48.9% quartz), respectively. The shale exhibited type II1 kerogens with a vitrinite reflectance ranging from 1.94% to 3.51%. TOC contents of 0.22%-6.05% (average, 2.39%) were also observed. The reservoir spaces mainly included micropores and microfractures and were characterized by low porosity and permeability. Well J3 showed generally high gas contents, i.e., 1.12-3.16 m3/t (average 2.15 m3/t), and its gas was primarily methane. The relatively thick black shale reservoir featured high TOC content, high organic material maturity, high brittle mineral content, high gas content, low porosity, and low permeability. Shale gas adsorption was positively correlated with TOC content and organic maturity, weakly positive correlated with quartz content, and weakly negatively correlated with clay content. Therefore, the Wufeng and Longmaxi formations in the north of the central Yangtze area have a good potential for shale gas exploration.

  10. Shale gas reservoir characteristics of Ordovician-Silurian formations in the central Yangtze area, China

    Science.gov (United States)

    Shan, Chang'an; Zhang, Tingshan; Wei, Yong; Zhang, Zhao

    2017-03-01

    The characteristics of a shale gas reservoir and the potential of a shale gas resource of Ordovician-Silurian age in the north of the central Yangtze area were determined. Core samples from three wells in the study area were subjected to thin-section examination, scanning electron microscopy, nuclear magnetic resonance testing, X-ray diffraction mineral analysis, total organic carbon (TOC) testing, maturity testing, gas-bearing analysis, and gas component and isothermal adsorption experiments. A favorable segment of the gas shale reservoir was found in both the Wufeng Formation and the lower part of the Longmaxi Formation; these formations were formed from the late Katian to early Rhuddanian. The high-quality shale layers in wells J1, J2, and J3 featured thicknesses of 54.88 m, 48.49 m, and 52.00 m, respectively, and mainly comprised carbonaceous and siliceous shales. Clay and brittle minerals showed average contents of 37.5% and 62.5% (48.9% quartz), respectively. The shale exhibited type II1 kerogens with a vitrinite reflectance ranging from 1.94% to 3.51%. TOC contents of 0.22%-6.05% (average, 2.39%) were also observed. The reservoir spaces mainly included micropores and microfractures and were characterized by low porosity and permeability. Well J3 showed generally high gas contents, i.e., 1.12-3.16 m3/t (average 2.15 m3/t), and its gas was primarily methane. The relatively thick black shale reservoir featured high TOC content, high organic material maturity, high brittle mineral content, high gas content, low porosity, and low permeability. Shale gas adsorption was positively correlated with TOC content and organic maturity, weakly positive correlated with quartz content, and weakly negatively correlated with clay content. Therefore, the Wufeng and Longmaxi formations in the north of the central Yangtze area have a good potential for shale gas exploration.

  11. Temporal patterns and behavioral characteristics of aggregation formation and spawning in the Bermuda chub ( Kyphosus sectatrix)

    Science.gov (United States)

    Nemeth, Richard S.; Kadison, Elizabeth

    2013-12-01

    Reef fish spawning aggregations are important life history events that occur at specific times and locations and represent the primary mode of reproduction for many species. This paper provides detailed descriptions of aggregation formation and mass spawning of the Bermuda chub ( Kyphosus sectatrix). Spawning coloration and gamete release of K. sectatrix were observed and filmed at the Grammanik Bank, a deep spawning aggregation site used by many different species located on the southern edge of the Puerto Rican shelf 10 km south of St. Thomas, US Virgin Islands. Underwater visual surveys using technical Nitrox and closed circuit re-breathers were conducted from December 2002 to March 2013 and documented spatial and temporal patterns of movement and aggregation formation along 1.5 km of mesophotic reef. The largest aggregations of K. sectatrix (>200 fish) were observed on the Grammanik Bank January to March from 0 to 11 d after the full moon with peak abundance from 60 to 80 d after the winter solstice across all survey years. Aggregation formation of K. sectatrix coincided with the spawning season of Nassau ( Epinephelus striatus) and yellowfin ( Mycteroperca venenosa) groupers. These spatial and temporal patterns of aggregation formation and spawning suggest that K. sectatrix, an herbivore, may also be a transient aggregating species. On several occasions, chubs were observed both pair spawning and mass spawning. Color patterns and behaviors associated with aggregation and spawning are described and compared to spawning characteristics observed in other species, many of which are similar but others that appear unique to K. sectatrix. This represents the first report of a kyphosid species aggregating to spawn and illuminates a portion of the poorly understood life history of the Bermuda chub.

  12. Phenomenological Modeling for Langmuir Monolayers

    Science.gov (United States)

    Baptiste, Dimitri; Kelly, David; Safford, Twymun; Prayaga, Chandra; Varney, Christopher N.; Wade, Aaron

    Experimentally, Langmuir monolayers have applications in molecular optical, electronic, and sensor devices. Traditionally, Langmuir monolayers are described by a rigid rod model where the rods interact via a Leonard-Jones potential. Here, we propose effective phenomenological models and utilize Monte Carlo simulations to analyze the phase behavior and compare with experimental isotherms. Research reported in this abstract was supported by UWF NIH MARC U-STAR 1T34GM110517-01.

  13. Processing of monolayer materials via interfacial reactions

    Energy Technology Data Exchange (ETDEWEB)

    Sutter, Peter Werner; Sutter, Eli Anguelova

    2014-05-20

    A method of forming and processing of graphene is disclosed based on exposure and selective intercalation of the partially graphene-covered metal substrate with atomic or molecular intercalation species such as oxygen (O.sub.2) and nitrogen oxide (NO.sub.2). The process of intercalation lifts the strong metal-carbon coupling and restores the characteristic Dirac behavior of isolated monolayer graphene. The interface of graphene with metals or metal-decorated substrates also provides for controlled chemical reactions based on novel functionality of the confined space between a metal surface and a graphene sheet.

  14. Slope streaks in the Antarctic Dry Valleys: Characteristics, candidate formation mechanisms, and implications for slope streak formation on Mars

    Science.gov (United States)

    Head, J. W.

    2007-12-01

    Slope streaks on Mars are typically dark, extend downslope for up to ~2 km, are relief, and have been observed to form and change over less than decadal time periods. Mars slope streaks occur exclusively in regions of low thermal inertia, steep slopes, and only where peak temperatures exceed 275 K; changes are observed only if the interval includes the warm season. Mechanisms proposed for Mars slope streaks include dry dust avalanches, dust avalanches controlled by wind, wet debris flows, both wet and dry debris flows, and erosive fluvial processes from spring discharge, where melting is aided by hydrothermal activity or hypersaline aquifers. Although the ADV represent one of the most Mars-like terrestrial environments, there are also substantial differences (e.g., atmospheric pressure and composition; abundance of water, etc.) and thus analogs must be assessed cautiously. We investigated very similar slope streaks in upper Wright Valley of the Antarctic Dry Valleys and interpret their formation to be due to snowpack and near-surface melting-derived saline water traveling downslope along the top of the ice table, wicking upward, and dampening the surface to cause the streak. Among the observations of Mars streaks that suggest that this mechanism should be seriously considered are: 1) similarities in characteristics, brightness, scales, slopes, aspect ratio, temporal behavior, and modes of occurrence; 2) distribution and geometry of occurrence suggesting a relation to solar insolation (low latitudes and northernmost streaks occur preferentially on warmer south-facing slopes); 3) the observation that they occur only where peak temperatures exceed 275 K, and that changes occur only where there has been an intervening warm season, suggesting a potential role for the melting of surface snow and ice. We thus conclude that the saline-assisted surface-near surface melting and water migration origin of slope streaks interpreted from the ADV should be further assessed as a

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

    NARCIS (Netherlands)

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

    2004-01-01

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

  16. Formation and nonvolatile memory characteristics of W nanocrystals by in-situ steam generation oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Shih-Cheng [Department of Electrical Engineering and Institute of Electronic Engineering, National Tsing Hua University, Taiwan (China); Chang, Ting-Chang, E-mail: tcchang@mail.phys.nsysu.edu.t [Department of Physics and Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University Taiwan (China); Hsieh, Chieh-Ming [Institute of Electronics, National Chiao Tung University, Taiwan, HsinChu, 300 Taiwan (China); Li, Hung-Wei [Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu, Taiwan (China); Sze, S.M. [Institute of Electronics, National Chiao Tung University, Taiwan, HsinChu, 300 Taiwan (China); Nien, Wen-Ping; Chan, Chia-Wei [ProMOS Technologies, No. 19 Li Hsin Rd., Science-Based Industrial Park, Hsinchu, 300 Taiwan (China); Yeh, Fon-Shan [Department of Electrical Engineering and Institute of Electronic Engineering, National Tsing Hua University, Taiwan (China); Tai, Ya-Hsiang [Department of Photonics and Display Institute, National Chiao Tung University, Hsinchu, Taiwan (China)

    2010-12-30

    The authors provide the formation and memory effects of W nanocrystals nonvolatile memory in this study. The charge trapping layer of stacked a-Si and WSi{sub 2} was deposited by low pressure chemical vapor deposition (LPCVD) and was oxidized by in-situ steam generation system to form uniform W nanocrystals embedded in SiO{sub 2}. Transmission electron microscopy analyses revealed the microstructure in the thin film and X-ray photon-emission spectra indicated the variation of chemical composition under different oxidizing conditions. Electrical measurement analyses showed the different charge storage effects because the different oxidizing conditions influence composition of trapping layer and surrounding oxide quality. Moreover, the data retention and endurance characteristics of the formed W nanocrystal memory devices were compared and studied. The results show that the reliability of the structure with 2% hydrogen and 98% oxygen at 950 {sup o}C oxidizing condition has the best performance among the samples.

  17. Microstructure characteristic and formation mechanism of crackfree TaC coating on C/C composite

    Institute of Scientific and Technical Information of China (English)

    LI Guo-dong; XIONG Xiang; HUANG Bai-yun

    2005-01-01

    The microstructure characteristic and formation mechanism of the crackfree and ablation-resistant TaC coating deposited on the C/C composite by Chemical Vapour Deposition(CVD) were investigated, using the reaction system of TaCl5-C3H6-H2-Ar. The results show that the nanosized pore structure formed in the TaC coating interior during CVD process is the main factor to reduce the hardness, elastic modulus, linear expansibility and inner thermal stress. Then crackfree coatings can be prepared and their thermal shock resistance can be enhanced. To obtain the dense and homogeneous matrix surface is necessary for the crackfree and low stress coating. The TaC coating structure that distributes from the dense matrix towards loose coating surface will result in the thick crackfree coating with good thermal shock resistance.

  18. Nonequilibrium microstructures in reactive monolayers as soft matter systems.

    Science.gov (United States)

    Mikhailov, Alexander S; Ertl, Gerhard

    2009-01-12

    Chemical systems provide classical examples of nonequilibrium pattern formation. Reactions in weak aqueous solutions, such as the extensively investigated Belousov-Zhabotinsky reaction, demonstrate a rich variety of patterns, ranging from travelling fronts to rotating spiral waves and chemical turbulence. Pattern formation in such systems is based on interplay between the reactions and diffusion. Intrinsically, this puts a restriction on the minimum length scale of the developing structures, which cannot be shorter than the diffusion length of the reactants. However, much smaller nonequilibrium structures, with characteristic lengths reaching down to nanoscales, are also possible. They are found in reactive soft matter, where energetic interactions between molecules are present as well. In these systems, chemical reactions and diffusion interfere with phase transitions, yielding active, stationary or dynamic microstructures. Nonequilibrium soft-matter microstructures are of fundamental importance for biological cells and may have interesting engineering applications. In this Minireview, we focus on the microstructures found in reactive soft-matter monolayers at solid surfaces or liquid-air interfaces.

  19. Biofilm Formation Derived from Ambient Air and the Characteristics of Apparatus

    Science.gov (United States)

    Kanematsu, H.; Kougo, H.; Kuroda, D.; Itho, H.; Ogino, Y.; Yamamoto, Y.

    2013-04-01

    Biofilm is a kind of thin film on solidified matters, being derived from bacteria. Generally, planktonic bacteria float in aqueous environments, soil or air, most of which can be regarded as oligotrophic environments. Since they have to survive by instinct, they seek for nutrients that would exist on materials surfaces as organic matters. Therefore, bacteria attach materials surfaces reversibly. The attachment and detachment repeat for a while and finally, they attach on them irreversibly and the number of bacteria on them increases. At a threshold number, bacteria produce polymeric matters at the same time by quorum sensing mechanism and the biofilm produces on material surfaces. The biofilm produced in that way generally contains water (more than 80%), EPS (Exopolymeric Substance) and bacteria themselves. And they might bring about many industrial problems, fouling, corrosion etc. Therefore, it is very important for us to control and prevent the biofilm formation properly. However, it is generally very hard to produce biofilm experimentally and constantly in ambient atmosphere on labo scale. The authors invented an apparatus where biofilm could form on specimen's surfaces from house germs in the ambient air. In this experiment, we investigated the basic characteristics of the apparatus, reproducibility, the change of biofilm with experimental time, the quality change of water for biofilm formation and their significance for biofilm research.

  20. Surface Modification through Chemically Adsorbed Monolayer of Thiophene Molecules

    Science.gov (United States)

    Yamamoto, Shin-ichi; Ogawa, Kazufumi

    2008-07-01

    Using a time-averaged dielectrophoretic force from an applied electric field, we have observed the assembly of a chemically adsorbed monomolecular layer (CAM) on microwires and connections and the formation of an electric path between a lithographically patterned array of two platinum (Pt) electrodes. A Pt electrode/monolayer/Pt electrode junction was fabricated by the self-assembly of a rigid monomolecular layer, namely 3-{6-[11-(trichlorosilyl)undecanoyl]hexyl} thiophene (TEN) with thiophene groups in the lateral direction between the Pt electrodes. Conductive probe AFM (CP-AFM) was used to investigate the forward bias conduction properties of a TEN film grown by a wet deposition process on a glass substrate. The self-assembly depends on the ideal rigidity of the CAM and the strong affinity of the thiophene end groups of the CAM for the Pt electrode. The current-voltage (I-V) characteristics of the conjugated thiophene junction exhibited stepwise features at room temperature. The I-V characteristics can be explained by electron transport through the junction. From the results of experiments carried out under ambient conditions, the conductivity of the laterally conjugated polythiophene groups was calculated to be 5.0 ×104 S/cm. Understanding and using these effects will allow the controlled fabrication and positioning of microwires or connections at densities much greater than those now achievable.

  1. Platinum monolayer electrocatalysts for oxygen reduction in fuel cells

    Science.gov (United States)

    Zhang, Junliang

    Fuel cells are expected to be one of the major clean energy sources in the near future. However, the slow kinetics of electrocatalytic oxygen reduction reaction (ORR) and the high loading of Pt for the cathode material are the urgent issues to be addressed since they determine the efficiency and the cost of this energy source. In this study, a new approach was developed for designing electrocatalysts for the ORR in fuel cells. These electrocatalysts consist of only one Pt monolayer, or mixed transition metal-Pt monolayer, on suitable carbon-supported metal, or alloy nanoparticles. The synthesis involved depositing a monolayer of Cu on a suitable transition metal or metal alloy surface at underpotentials, followed by galvanic displacement of the Cu monolayer with Pt or mixed metal-Pt. It was found that the electronic properties of Pt monolayer could be fine-tuned by the electronic and geometric effects introduced by the substrate metal (or alloy) and the lateral effects of the neighboring metal atoms. The role of substrates was found reflected in a "volcano" plot of the monolayer activity for the ORR as a function of their calculated d-band centers. The Pt mass-specific activity of the new Pt monolayer electrocatalysts was up to twenty times higher than the state-of-the-art commercial Pt/C catalysts. The enhancement of the activity is caused mainly by decreased formation of PtOH (the blocking species for ORR), and to a lesser degree by the electronic effects. Fuel cell tests showed a very good long term stability of the new electrocatalysts. Our results demonstrated a viable way to designing the electrocatalysts which could successfully alleviate two issues facing the commercialization of fuel cells---the costs of electrocatalysts and their efficiency.

  2. Characteristics and formation mechanism of a winter haze-fog episode in Tianjin, China

    Science.gov (United States)

    Han, Su-qin; Wu, Jian-hui; Zhang, Yu-fen; Cai, Zi-ying; Feng, Yin-chang; Yao, Qing; Li, Xiang-jin; Liu, Yi-wei; Zhang, Min

    2014-12-01

    Several heavy haze and fog episodes occurred in northern China in January of 2013. Data were collected and used to analyze the characteristics and mechanisms of formation of the haze-fog (HF) episode that occurred from January 10 to 12. The minimum hourly visibility was 112 m, as recorded on 12 January. The concentrations of particulate and gaseous pollutants increased continuously during this HF period. The concentration of PM2.5 increased faster than that of SO2 and NOx, and the rate of accumulation was greater at the beginning of the HF process than at other times. The average concentration of PM2.5, PM10, NOx, and SO2 on the HF days was 3.9, 3.6, 2.5, and 2.1 times higher than the values in the non-haze days. The scattering and absorption coefficients σsp and σap on the HF days were 4.0 and 4.3 times higher than the values in the non-HF days. The highest black carbon (BC) concentration was about 10 times higher than on the non-HF days. The concentrations of total carbon (TC), organic carbon (OC), and elemental carbon (EC) all increased, and the speed of the increase in OC was quicker than that of the EC. An increase in secondary inorganic pollutants (SO42-, NO3-) in PM2.5 was also observed. The concentrations of SO42- and NO3- on the HF days were 4 and 2 times those of the non-HF days. The increase in relative humidity on the HF days favored the formation of sulfate and nitrate during HF episode. Unfavorable meteorological conditions were the external cause of this HF episode. The southwest wind transported the pollutants from areas to the south of the study regions at the beginning of the HF episode. After the HF took shape, a strong descending air mass located in the high layer severely limited pollutant diffusion in the vertical direction. The strong temperature inversion and the weak horizontal wind limited the horizontal and vertical dispersion of pollutants. The high layer transport of the pollutants during the early period and the late accumulation of

  3. VOC characteristics, emissions and contributions to SOA formation during hazy episodes

    Science.gov (United States)

    Sun, Jie; Wu, Fangkun; Hu, Bo; Tang, Guiqian; Zhang, Junke; Wang, Yuesi

    2016-09-01

    Volatile organic compounds (VOC) are important precursors of secondary organic aerosols (SOA). The pollution processes in Beijing were investigated from 18th October to 6th November 2013 to study the characteristics, SOA formation potential and contributing factors of VOC during hazy episodes. The mean concentrations of VOC were 67.4 ± 33.3 μg m-3 on clear days and have 5-7-fold increase in polluted periods. VOC concentrations rapidly increased at a visibility range of 4-5 km with the rate of 25%/km in alkanes, alkenes and halocarbons and the rate of 45%/km in aromatics. Analysis of the mixing layer height (MLH); wind speed and ratios of benzene/toluene (B/T), ethylbenzene/m,p-xylene (E/X), and isopentane/n-pentane (i/n) under different visibility conditions revealed that the MLH and wind speed were the 2 major factors affecting the variability of VOC during clear days and that local emissions and photochemical reactions were main causes of VOC variation on polluted days. Combined with the fractional aerosol coefficient (FAC) method, the SOA formation potentials of alkanes, alkenes and aromatics were 0.3 ± 0.2 μg m-3, 1.1 ± 1.0 μg m-3 and 6.5 ± 6.4 μg m-3, respectively. As the visibility deteriorated, the SOA formation potential increased from 2.1 μg m-3 to 13.2 μg m-3, and the fraction of SOA-forming aromatics rapidly increased from 56.3% to 90.1%. Initial sources were resolved by a positive matrix factorization (PMF) model. Vehicle-related emissions were an important source of VOC at all visibility ranges, accounting for 23%-32%. As visibility declined, emissions from solvents and the chemical industry increased from 13.2% and 6.3% to 34.2% and 23.0%, respectively. Solvents had the greatest SOA formation ability, accounting for 52.5% on average on hazy days, followed by vehicle-related emissions (20.7%).

  4. Characteristics and formation of heavy winter haze pollution during 2014-2015 in Tianjin, China

    Science.gov (United States)

    Sun, Zhenli; Ma, Tao; Zhu, Lidan; Duan, Fengkui; He, Kebin

    2017-04-01

    With the rapid increase in the amount of vehicles and energy consumption during the past two decades, China faces a serious air pollution in urban areas, which has produced negative impact on the society development and human health. Tianjin, locating on the southeast of Beijing-Tianjin-Hebei region in north China, has been one of the heavy polluted cities during 2013-2016 of which the haze occurred frequently in particular in winter while the knowledge on its sources and formation mechanism are limited. For better understanding of the characteristics and the formation mechanisms of PM2.5 (particulate matter with an aerodynamic diameter ≤2.5 μm), especially secondary water-soluble inorganic species in these haze events, continuous and online hourly field observations in Tianjin urban area were carried out during 2014-2015 winter, that were, hourly concentrations of PM2.5, sulfate, nitrate, and ammonium (SNA) as well as the concentrations of gaseous pollutants and meteorological parameters. PM2.5 concentrations ranged from 5.6 μgṡm-3 to 495.5 μgṡm-3, with an average of 112.1 (±96.1) μgṡm-3. In general, SNA (sulfate, nitrate and ammonium) was the most abundant secondary water-soluble inorganic species and contributed to 35% of PM2.5 mass concentration. The most severe PM2.5 pollution was observed in January 2015 with four haze episodes observed. The chemical composition of four episodes was characterized by high level of SO42- (22%˜38%), together with high concentration of NO3- (22%˜34%), suggesting the contribution of secondary conversion. NOR and SOR increased with elevated PM2.5levels and heterogeneous processes seemed to be the most plausible explanation of this increase. Nitrogen oxidation ratio (NOR) was much higher than sulfur oxidation ratio (SOR), indicating the NO2 was easily oxidized in low temperature condition than that of SO2. Relative humidity (RH) played a considerable role in the formation of secondary inorganic aerosols, accelerated

  5. Self assembled monolayers of octadecyltrichlorosilane for dielectric materials

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Vijay, E-mail: cirivijaypilani@gmail.com [Centre for Nanoscience and Engineering, Indian Institute of Science-Bangalore (India); Mechanical Engineering Department, Birla Institute of Technology and Science-Pilani (India); Puri, Paridhi; Nain, Shivani [Mechanical Engineering Department, Birla Institute of Technology and Science-Pilani (India); Bhat, K. N. [Centre for Nanoscience and Engineering, Indian Institute of Science-Bangalore (India); Sharma, N. N. [Mechanical Engineering Department, Birla Institute of Technology and Science-Pilani (India); School of Automobile, Mechanical & Mechatronics, Manipal University-Jaipur (India)

    2016-04-13

    Treatment of surfaces to change the interaction of fluids with them is a critical step in constructing useful microfluidics devices, especially those used in biological applications. Selective modification of inorganic materials such as Si, SiO{sub 2} and Si{sub 3}N{sub 4} is of great interest in research and technology. We evaluated the chemical formation of OTS self-assembled monolayers on silicon substrates with different dielectric materials. Our investigations were focused on surface modification of formerly used common dielectric materials SiO{sub 2}, Si{sub 3}N{sub 4} and a-poly. The improvement of wetting behaviour and quality of monolayer films were characterized using Atomic force microscope, Scanning electron microscope, Contact angle goniometer, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) monolayer deposited oxide surface.

  6. Rolling Up a Monolayer MoS2 Sheet.

    Science.gov (United States)

    Meng, Jianling; Wang, Guole; Li, Xiaomin; Lu, Xiaobo; Zhang, Jing; Yu, Hua; Chen, Wei; Du, Luojun; Liao, Mengzhou; Zhao, Jing; Chen, Peng; Zhu, Jianqi; Bai, Xuedong; Shi, Dongxia; Zhang, Guangyu

    2016-07-01

    MoS2 nanoscrolls are formed by argon plasma treatment on monolayer MoS2 sheet. The nanoscale scroll formation is attributed to the partial removal of top sulfur layer in MoS2 during the argon plasma treatment process. This convenient, solvent-free, and high-yielding nanoscroll formation technique is also feasible for other 2D transition metal dichalcogenides.

  7. The crystalline structures of carboxylic acid monolayers adsorbed on graphite.

    Science.gov (United States)

    Bickerstaffe, A K; Cheah, N P; Clarke, S M; Parker, J E; Perdigon, A; Messe, L; Inaba, A

    2006-03-23

    X-ray and neutron diffraction have been used to investigate the formation of solid crystalline monolayers of all of the linear carboxylic acids from C(6) to C(14) at submonolayer coverage and from C(8) to C(14) at multilayer coverages, and to characterize their structures. X-rays and neutrons highlight different aspects of the monolayer structures, and their combination is therefore important in structural determination. For all of the acids with an odd number of carbon atoms, the unit cell is rectangular of plane group pgg containing four molecules. The members of the homologous series with an even number of carbon atoms have an oblique unit cell with two molecules per unit cell and plane group p2. This odd-even variation in crystal structure provides an explanation for the odd-even variation observed in monolayer melting points and mixing behavior. In all cases, the molecules are arranged in strongly hydrogen-bonded dimers with their extended axes parallel to the surface and the plane of the carbon skeleton essentially parallel to the graphite surface. The monolayer crystal structures have unit cell dimensions similar to certain close-packed planes of the bulk crystals, but the molecular arrangements are different. There is a 1-3% compression on increasing the coverage over a monolayer.

  8. Diacetylene mixed Langmuir monolayers for interfacial polymerization.

    Science.gov (United States)

    Ariza-Carmona, Luisa; Rubia-Payá, Carlos; García-Espejo, G; Martín-Romero, María T; Giner-Casares, Juan J; Camacho, Luis

    2015-05-19

    Polydiacetylene (PDA) and its derivatives are promising materials for applications in a vast number of fields, from organic electronics to biosensing. PDA is obtained through polymerization of diacetylene (DA) monomers, typically using UV irradiation. DA polymerization is a 1-4 addition reaction with both initiation and growth steps with topochemical control, leading to the "blue" polymer form as primary reaction product in bulk and at interfaces. Herein, the diacetylene monomer 10,12-pentacosadiynoic acid (DA) and the amphiphilic cationic N,N'-dioctadecylthiapentacarbocyanine (OTCC) have been used to build a mixed Langmuir monolayer. The presence of OTCC imposes a monolayer supramolecular structure instead of the typical trilayer of pure DA. Surface pressure, Brewster angle microscopy, and UV-vis reflection spectroscopy measurements, as well as computer simulations, have been used to assess in detail the supramolecular structure of the DA:OTCC Langmuir monolayer. Our experimental results indicate that the DA and OTCC molecules are sequentially arranged, with the two OTCC alkyl chains acting as spacing diacetylene units. Despite this configuration is expected to prevent photopolymerization of DA, the polymerization takes place without phase segregation, thus exclusively leading to the red polydiacetylene form. We propose a simple model for the initial formation of the "blue" or "red" PDA forms as a function of the relative orientation of the DA units. The structural insights and the proposed model concerning the supramolecular structure of the "blue" and "red" forms of the PDA are aimed at the understanding of the relation between the molecular and macroscopical features of PDAs.

  9. Formation and properties of surface-anchored polymer assemblies with tunable physico-chemical characteristics

    Science.gov (United States)

    Wu, Tao

    We describe two new methodologies leading to the formation of novel surface-anchored polymer assemblies on solid substrates. While the main goal is to understand the fundamentals pertaining to the preparation and properties of the surface-bound polymer assemblies (including neutral and chargeable polymers), several examples also are mentioned throughout the Thesis that point out to practical applications of such structures. The first method is based on generating assemblies comprising anchored polymers with a gradual variation of grafting densities on solid substrates. These structures are prepared by first covering the substrate with a molecular gradient of the polymerization initiator, followed by polymerization from these substrate-bound initiator centers ("grafting from"). We apply this technique to prepare grafting density gradients of poly(acryl amide) (PAAm) and poly(acrylic acid) (PAA) on silica-covered substrates. We show that using the grafting density gradient geometry, the characteristics of surface-anchored polymers in both the low grafting density ("mushroom") regime as well as the high grafting density ("brush") regime can be accessed conveniently on a single sample. We use a battery of experimental methods, including Fourier transform infrared spectroscopy (FTIR), Near-edge absorption fine structure spectroscopy (NEXAFS), contact angle, ellipsometry, to study the characteristics of the surface-bound polymer layers. We also probe the scaling laws of neutral polymer as a function of grafting density, and for weak polyelectrolyte, in addition to the grafting density, we study the affect of solution ionic strength and pH values. In the second novel method, which we coined as "mechanically assisted polymer assembly" (MAPA), we form surface anchored polymers by "grafting from" polymerization initiators deposited on elastic surfaces that have been previously extended uniaxially by a certain length increment, Deltax. Upon releasing the strain in the

  10. Microtextural Characteristics and Origin of Dolomites in the Tepearasi Formation, SW of Beysehir-Konya, Turkey

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The Tepearasi Formation of the autochthonous Geyikdagi Group in the Central Tauride Belt, SE of Beysehir, is Dogger in age and consists dominantly of massive limestones and greyish dolomites occurring within the middle to upper sections. The total thickness of the dolomitic levels ranges from 100–300 m and laterally extends 500–700 m. Three types of dolomite were distinguished through petrographic analyses: homogeneous, mottled (saddle-crystalline) and joint-filling dolomite, which were interpreted to have formed in two different stages, early diagenetic and late diagenetic. The homogeneous dolomite of the early diagenetic stage is light-coloured and monotonous-textured and shows the form of a dolosparite mosaic. The mottled dolomite formed in the late diagenetic stage is light- to dark-coloured and coarsely granular idiomorphic. The other type of late diagenetic dolomite, described as the joint-filling type, presents a crystal growth pattern from the joint walls towards the centre of the joint space. It is associated with coarse calcite crystals as well as primary dolomite crystal clasts which were formed in the early diagenetic stage. In addition to these characteristics, cataclastic texture indicating the influence of tectonism is also observed. Microtexture-oriented scanning electron microscopy (SEM) studies indicate that mottled dolomites show zonal structures and contain secondary dissolution vugs. SEM studies also revealed the existence of some remains (calcite, clay etc.) in joint-filling dolomites. Analyses by energy dispersive spectrometry (EDS) indicate the existence of clay minerals (likely to be illite) in the pores of dolomite. Isotope studies conducted to shed light onto the origin of the dolomites of the Tepearasi Formation yielded the results of ?18O= –2.48 to – 3.87‰ and ?13C=0.93 to 1.12‰ for the early diagenetic homogeneous dolomites. Mottled and joint-filling type dolomites of the late diagenetic stage, on the other hand, gave the

  11. Positional order in Langmuir monolayers

    DEFF Research Database (Denmark)

    Kaganer, V.M.; Brezesinski, G.; Möhwald, H.;

    1998-01-01

    We find that a structural solid-solid phase transition in a two-dimensional Langmuir film is accompanied by strong positional disorder. Specifically, we find by a grazing-incidence x-ray diffraction experiment that in monolayers of octadecanol both the hexagonal phase LS and the centered rectangu......We find that a structural solid-solid phase transition in a two-dimensional Langmuir film is accompanied by strong positional disorder. Specifically, we find by a grazing-incidence x-ray diffraction experiment that in monolayers of octadecanol both the hexagonal phase LS and the centered...

  12. Electromelting of Confined Monolayer Ice

    CERN Document Server

    Qiu, Hu

    2013-01-01

    In sharp contrast to the prevailing view that electric fields promote water freezing, here we show by molecular dynamics simulations that monolayer ice confined between two parallel plates can melt into liquid water under perpendicularly applied electric field. The melting temperature of the monolayer ice decreases with the increasing strength of the external field due to field-induced disruption of the water-wall interaction induced well-ordered network of hydrogen bond. This electromelting process should add an important new ingredient to the physics of water.

  13. Irregular Characteristics of Bond Interface Formation in Ultrasonic Wire Wedge Bonding

    Institute of Scientific and Technical Information of China (English)

    Mingyu LI; Hongjun JI; Chunqing WANG; Au Tai KUNG; Han Sur BANG; Hee Seon BANG

    2006-01-01

    The mechanism of ultrasonic wire wedge bonding, one of the die/chip interconnection methods, was investigated based on the characteristics of the ultrasonic wire bonding joints. The Al-1%Si wire of 25 μm in diameter was bonded on Au/Ni/Cu pad and the joint cross-section was analyzed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The results indicated that it is irregular for the ultrasonic bond formation, non-welded at the centre but joining well at the periphery, especially at the heel and toe of the joint. Furthermore, the diffusion and/or reaction at the cross-section interface are not clear at C-zone, while there exists a strip layer microstructure at P-zone, and the composition is 78.96 at. pct Al and 14.88 at. pct Ni, close to the Al3Ni intermetallic compound. All these observations are tentatively ascribed to the plastic flow enhanced by ultrasonic vibration and repeated cold deformation driving interdiffusion between Al and Ni at bond interface.

  14. Inhomogeneous Oxygen Vacancy Distribution in Semiconductor Gas Sensors: Formation, Migration and Determination on Gas Sensing Characteristics.

    Science.gov (United States)

    Liu, Jianqiao; Gao, Yinglin; Wu, Xu; Jin, Guohua; Zhai, Zhaoxia; Liu, Huan

    2017-08-10

    The density of oxygen vacancies in semiconductor gas sensors was often assumed to be identical throughout the grain in the numerical discussion of the gas-sensing mechanism of the devices. In contrast, the actual devices had grains with inhomogeneous distribution of oxygen vacancy under non-ideal conditions. This conflict between reality and discussion drove us to study the formation and migration of the oxygen defects in semiconductor grains. A model of the gradient-distributed oxygen vacancy was proposed based on the effects of cooling rate and re-annealing on semiconductive thin films. The model established the diffusion equations of oxygen vacancy according to the defect kinetics of diffusion and exclusion. We described that the steady-state and transient-state oxygen vacancy distributions, which were used to calculate the gas-sensing characteristics of the sensor resistance and response to reducing gases under two different conditions. The gradient-distributed oxygen vacancy model had the applications in simulating the sensor performances, such as the power law, the grain size effect and the effect of depletion layer width.

  15. Inhomogeneous Oxygen Vacancy Distribution in Semiconductor Gas Sensors: Formation, Migration and Determination on Gas Sensing Characteristics

    Directory of Open Access Journals (Sweden)

    Jianqiao Liu

    2017-08-01

    Full Text Available The density of oxygen vacancies in semiconductor gas sensors was often assumed to be identical throughout the grain in the numerical discussion of the gas-sensing mechanism of the devices. In contrast, the actual devices had grains with inhomogeneous distribution of oxygen vacancy under non-ideal conditions. This conflict between reality and discussion drove us to study the formation and migration of the oxygen defects in semiconductor grains. A model of the gradient-distributed oxygen vacancy was proposed based on the effects of cooling rate and re-annealing on semiconductive thin films. The model established the diffusion equations of oxygen vacancy according to the defect kinetics of diffusion and exclusion. We described that the steady-state and transient-state oxygen vacancy distributions, which were used to calculate the gas-sensing characteristics of the sensor resistance and response to reducing gases under two different conditions. The gradient-distributed oxygen vacancy model had the applications in simulating the sensor performances, such as the power law, the grain size effect and the effect of depletion layer width.

  16. The formation process and cloud physical characteristics for a typical downburst-producing thunderstorm in Beijing

    Institute of Scientific and Technical Information of China (English)

    GUO Xueliang; FU Danhong

    2003-01-01

    The formation process and characteristics of cloud physical structure of a severe thunderstorm accompanied with strong wind on 23 August, 2001 in Beijing was studied using PSU/NCAR mesoscale model (MM5)coupling with a severe storm model with hail-bin microphysics. The results show that the specific topography and distribution features of cold/warm current in the Beijing region played prominent roles in forming, developing and maintaining the severe storm. Due to solar radiation heating and topographic lifting, the convective cells were easily formed when the westerly airflow passed over high mountainous regions in Beijing. The warm and wet air entered the cloud from its frontage and enhanced the convection, and formed a large amount of graupel/hail particles at the middle and upper portion of the clouds. The precipitation was primarily formed due to melting of graupel/hail particles. The strong downdraft was mainly produced by negative buoyancy due to loading,melting of graupel/hail particles as well as evaporative cooling of rain water. The divergent airflow induced by the strong downdraft led to the disastrous burst winds at the surface and also forced lifting of warm and wet airflow in the moving direction of the storm and formed new clouds that further promoted and maintained the storm development.

  17. Statistical characteristics of formation and evolution of structure in the universe

    CERN Document Server

    Demianski, M

    1999-01-01

    An approximate statistical description of the formation and evolution of structure of the universe based on the Zel'dovich theory of gravitational instability is proposed. It is found that the evolution of DM structure shows features of self-similarity and the main structure characteristics can be expressed through the parameters of initial power spectrum and cosmological model. For the CDM-like power spectrum and suitable parameters of the cosmological model the effective matter compression reaches the observed scales $R_{wall}\\sim $20 -- 25$h^{-1}$Mpc with the typical mean separation of wall-like elements $D_{SLSS}\\sim $50 -- 70$h^{-1}$Mpc. This description can be directly applied to the deep pencil beam galactic surveys and absorption spectra of quasars. For larger 3D catalogs and simulations it can be applied to results obtained with the core-sampling analysis. It is shown that the interaction of large and small scale perturbations modulates the creation rate of early Zel'dovich pancakes and generates bia...

  18. Effect of formation characteristics on hydraulic conductivity in unconfined bed in Etchie, rivers state of Nigeria

    Directory of Open Access Journals (Sweden)

    Solomon Ndubuisi Eluozo

    2013-01-01

    Full Text Available Formation characteristics determine the hydraulic conductivity of the soil, the major parameter that determine the rate of hydraulic conductivity of the soil in study location are void ratio and permeability of the soil, degree of void ratio and permeability where determine to evaluate the rate of hydraulic conductivity and storage coefficient,the results from these two parameters  shows the variation deposition of void ratio and permeability in the study location. Ground water hydrogeological data where found to be unavailable in the study area this condition has resulted to a lots of abortive well, this has also cause a lot of abandoned ground water project done by government, this type of economic waste is a serious concern and need to be addressed., the study is imperative because it will improve the result of ground water exploration in the study area, the result from this study will definitely serve as baseline for professional to apply in   the development of ground water system in the study area .

  19. Formation and characteristics of biomimetic mineralo-organic particles in natural surface water

    Science.gov (United States)

    Wu, Cheng-Yeu; Martel, Jan; Wong, Tsui-Yin; Young, David; Liu, Chien-Chun; Lin, Cheng-Wei; Young, John D.

    2016-06-01

    Recent studies have shown that nanoparticles exist in environmental water but the formation, characteristics and fate of such particles remain incompletely understood. We show here that surface water obtained from various sources (ocean, hot springs, and soil) produces mineralo-organic particles that gradually increase in size and number during incubation. Seawater produces mineralo-organic particles following several cycles of filtration and incubation, indicating that this water possesses high particle-seeding potential. Electron microscopy observations reveal round, bacteria-like mineral particles with diameters of 20 to 800 nm, which may coalesce and aggregate to form mineralized biofilm-like structures. Chemical analysis of the particles shows the presence of a wide range of chemical elements that form mixed mineral phases dominated by calcium and iron sulfates, silicon and aluminum oxides, sodium carbonate, and iron sulfide. Proteomic analysis indicates that the particles bind to proteins of bacterial, plant and animal origins. When observed under dark-field microscopy, mineral particles derived from soil-water show biomimetic morphologies, including large, round structures similar to cells undergoing division. These findings have important implications not only for the recognition of biosignatures and fossils of small microorganisms in the environment but also for the geochemical cycling of elements, ions and organic matter in surface water.

  20. Ambient STM study of sequentially adsorbed octanethiol and biphenylthiol monolayers on Au(111)

    Science.gov (United States)

    Fitzgerald, Danielle M.; Krisanda, Emily K.; Szypko, Colleen G.; Gaby Avila-Bront, L.

    2017-08-01

    The mixed monolayers of biphenyl-4-thiol (BPT) and octanethiol (OT) are studied at the molecular level using scanning tunneling microscopy (STM) in ambient conditions and X-ray photoelectron spectroscopy (XPS) on Au(111). The effect of both the sequence of deposition, and the concentration of the BPT solution used is investigated. We observe signs of coexisting domains in the form of disordered patches surrounding flat patches when a 100 μM solution of BPT is used. This observation holds for both OT being deposited first, and BPT being deposited first. The most clear formation of coexisting domains occurs when an OT monolayer is immersed in a 100 μM solution of BPT. The XP spectra reveal a shift in the C 1s signal of the monolayers that is unique to what films are deposited on the surface. These data demonstrate the importance characterizing mixed self-assembled monolayers that form final monolayer structures unique to each mixture.

  1. Ablation behavior of monolayer and multilayer Ir coatings under carburizing and oxidizing oxyacetylene flames

    Science.gov (United States)

    Wu, Wangping; Jiang, Jinjin; Chen, Zhaofeng

    2016-06-01

    Iridium is one of the most promising candidates for protective barrier of refractory materials to endure high service temperature. The multilayer iridium coating was produced by a double glow plasma process on the polished tungsten carbide substrates, compared with monolayer. The ablation behaviors of the monolayer on the unpolished and polished substrates were investigated under carburizing and oxidizing oxyacetylene flames, respectively, at the same time the multilayer coating ablated under oxidizing flames. Multilayer coating was a polycrystalline phase with the preferential (220) orientation. Monolayer on the unpolished substrate had fine coarse grains and some small microcracks were present. Multilayer consisted of columnar grains with some voids between the grains boundaries. The formation of a WIr phase in the as-deposited multilayer was attributed to high deposition temperature. The monolayer could endure high temperature up to 1800 °C in carburizing flame. The substrates could be protected more effectively by multilayer than monolayer at 2000- 2200 °C in oxidizing flame.

  2. Decoupling of crystalline and conformational degrees of freedom in lipid monolayers

    DEFF Research Database (Denmark)

    Ipsen, John Hjorth; Mouritsen, Ole G.; Zuckermann, Martin J.

    1989-01-01

    by a liquid-conformationally ordered phase. This prediction is consistent with synchrotron x-ray experiments which show that the chain-ordering transition and the crystallization process need not take place at the same lateral pressure. A characterization is provided of the nonequilibrium effects and pattern-formation...... of the experimentally observed isotherms of lipid monolayer phase behavior. It is pointed out that cholesterol, which promotes lipid-chain conformational order, has a unique capacity of acting as a `crystal breaker' in the solid monolayer phases and therefore provides a molecular mechanism for decoupling crystalline...... and conformational order in lipid monolayers containing cholesterol. The phase diagram of mixed cholesterol–lipid monolayers is derived and discussed in relation to monolayer experiments. The Journal of Chemical Physics is copyrighted by The American Institute of Physics....

  3. Formation of atomically ordered and chemically selective Si—O—Ti monolayer on Si0.5Ge0.5(110) for a MIS structure via H2O2(g) functionalization

    Science.gov (United States)

    Park, Sang Wook; Choi, Jong Youn; Siddiqui, Shariq; Sahu, Bhagawan; Galatage, Rohit; Yoshida, Naomi; Kachian, Jessica; Kummel, Andrew C.

    2017-02-01

    Si0.5Ge0.5(110) surfaces were passivated and functionalized using atomic H, hydrogen peroxide (H2O2), and either tetrakis(dimethylamino)titanium (TDMAT) or titanium tetrachloride (TiCl4) and studied in situ with multiple spectroscopic techniques. To passivate the dangling bonds, atomic H and H2O2(g) were utilized and scanning tunneling spectroscopy (STS) demonstrated unpinning of the surface Fermi level. The H2O2(g) could also be used to functionalize the surface for metal atomic layer deposition. After subsequent TDMAT or TiCl4 dosing followed by a post-deposition annealing, scanning tunneling microscopy demonstrated that a thermally stable and well-ordered monolayer of TiOx was deposited on Si0.5Ge0.5(110), and X-ray photoelectron spectroscopy verified that the interfaces only contained Si—O—Ti bonds and a complete absence of GeOx. STS measurements confirmed a TiOx monolayer without mid-gap and conduction band edge states, which should be an ideal ultrathin insulating layer in a metal-insulator-semiconductor structure. Regardless of the Ti precursors, the final Ti density and electronic structure were identical since the Ti bonding is limited by the high coordination of Ti to O.

  4. Formation of atomically ordered and chemically selective Si-O-Ti monolayer on Si0.5Ge0.5(110) for a MIS structure via H2O2(g) functionalization.

    Science.gov (United States)

    Park, Sang Wook; Choi, Jong Youn; Siddiqui, Shariq; Sahu, Bhagawan; Galatage, Rohit; Yoshida, Naomi; Kachian, Jessica; Kummel, Andrew C

    2017-02-07

    Si0.5Ge0.5(110) surfaces were passivated and functionalized using atomic H, hydrogen peroxide (H2O2), and either tetrakis(dimethylamino)titanium (TDMAT) or titanium tetrachloride (TiCl4) and studied in situ with multiple spectroscopic techniques. To passivate the dangling bonds, atomic H and H2O2(g) were utilized and scanning tunneling spectroscopy (STS) demonstrated unpinning of the surface Fermi level. The H2O2(g) could also be used to functionalize the surface for metal atomic layer deposition. After subsequent TDMAT or TiCl4 dosing followed by a post-deposition annealing, scanning tunneling microscopy demonstrated that a thermally stable and well-ordered monolayer of TiOx was deposited on Si0.5Ge0.5(110), and X-ray photoelectron spectroscopy verified that the interfaces only contained Si-O-Ti bonds and a complete absence of GeOx. STS measurements confirmed a TiOx monolayer without mid-gap and conduction band edge states, which should be an ideal ultrathin insulating layer in a metal-insulator-semiconductor structure. Regardless of the Ti precursors, the final Ti density and electronic structure were identical since the Ti bonding is limited by the high coordination of Ti to O.

  5. Organic facies characteristics of the Carboniferous Pamucakyayla Formation, western Taurus, Antalya Nappes, Kemer (Antalya/Turkey)

    Science.gov (United States)

    Bertan Gulludag, Cevdet; Altunsoy, Mehmet; Ozcelik, Orhan

    2015-04-01

    The study area is located in the western part of the Taurus Belt (SW Turkey). This region exhibits a complex structure involving two autochthonous units surrounded and imbricated with three allochthonous complexes. Antalya Nappes is a complex tectonic imbricate structure including sedimantary and ultrabasic rocks. In this study, organic facies characteristics of Carboniferous coaly units in the Pamucakyayla region (Kemer, Antalya-Turkey) were examined. The Carboniferous Pamucakyayla Formation, which is characterized by sandstone, claystone, marl and coaly units. This units includes different levels of coal seams in different thicknesses. Organic matter is composed predominantly of woody and amorphous material, with a minor contribution of planty and coaly material. Kerogen in the deposits is type II/III, as indicated by organic petrographic observations and Rock-Eval data. Total organic carbon (TOC) values are generally between 0.01 and 1.44 %, but reach 5.81 % in the formation. Tmax values vary between 446 and 451 °C and indicate mature zone (Based on the value of 0.25 % TOC). Organic facies type BC, C and CD were identified in the investigated units. Organic facies BC is related sandstoneand marl lithofacies. This facis is deposited under an anoxic water column in a fine grained clastics, where rapid deposition creates anoxia in the sediments after deposition. This facies is characterized by average values of HI around 317 (equivalent to type II kerogene), TOC around 0.02 %, and an average of S2 of 0.04 mg HC/g of rock. Organic facies C is related to sandstone, marl and coal lithofacies. This facies is characterized by average values of HI around 176 (equivalent to type III kerogene), TOC around 0.19 %, and an average of S2 of 0.03 mg HC/g of rock. The organic matter is partly oxidized, and terrestrial. Organic facies C is the "gas-prone" facies. Organic facies CD is related to limestone, marl and coal lithofacies. This facies is characterized by average values

  6. Characteristics and formation mechanism of composite flower structures in the Shuntuo area, Tarim Basin, Northwest China

    Science.gov (United States)

    Han, X.; Tang, L.; Cao, Z.

    2016-12-01

    The Shuntuo area, located in the north part of the northern slope of Tazhong Uplift, is one of the key areas of Tarim Basin with great exploration potentials. Based on detailed 3D seismic interpretations of the Shuntuo area, the characteristics and formation mechanisms of the strike-slip faults were investigated. The research results show that a series of sinistral strike-slip faults, which cut through the basement strata and straight up to the Middle Devonian strata, developed in the study area. On the 3D seismic profiles, the strike-slip fault shows complex geometric features that consists of a lower convex strata deformation (positive flower structure) and an upper concave-shaped strata deformation (negative flower structure) that bounded by the Late Ordovician strata. Systematic research on the distribution, geometry and kinematics of the composite flower structures suggests that they are completely different fault systems formed in different time and controlled by different factors. According to fault open horizon and fault throw changes, the development history of the strike-slip faults may be divided into two stages including the Middle Caledonian and the Early Hercynian. On the seismic coherency maps, the lower strike-slip faults show NE linear extension. In the Middle Caledonian, the Tazhong Uplift experienced a strong compression from Ancient Kunlun ocean subducting in NE direction and Arkin ocean subducting in NW direction, which resulted in the formation of NE-trending strike-slip faults. The upper strike-slip faults are NW trending and present right-order en-echelon arrangements. During Early Hercynian, with the termination of the Kunlun Caledonian collision orogeny, the Tazhong Uplift was in the stress relaxation stage. The stress condition of the Shuntuo area transformed from compression to extension. Based on the lower strike-slip faults, the upper strike-slip faults were developed under the control of previous basement weak zones. Since the strike

  7. Tuning Oleophobicity of Silicon Oxide Surfaces with Mixed Monolayers of Aliphatic and Fluorinated Alcohols.

    Science.gov (United States)

    Lee, Austin W H; Gates, Byron D

    2016-12-13

    We demonstrate the formation of mixed monolayers derived from a microwave-assisted reaction of alcohols with silicon oxide surfaces in order to tune their surface oleophobicity. This simple, rapid method provides an opportunity to precisely tune the constituents of the monolayers. As a demonstration, we sought fluorinated alcohols and aliphatic alcohols as reagents to form monolayers from two distinct constituents for tuning the surface oleophobicity. The first aspect of this study sought to identify a fluorinated alcohol that formed monolayers with a relatively high surface coverage. It was determined that 1H,1H,2H,2H-perfluoro-1-octanol yielded high quality monolayers with a water contact angle (WCA) value of ∼110° and contact angle values of ∼80° with toluene and hexadecane exhibiting both an excellent hydrophobicity and oleophobicity. Tuning of the oleophobicity of the modified silicon oxide surfaces was achieved by controlling the molar ratio of 1H,1H,2H,2H-perfluoro-1-octanol within the reaction mixtures. Surface oleophobicity progressively decreased with a decrease in the fluorinated alcohol content while the monolayers maintained their hydrophobicity with WCA values of ∼110°. The simple and reliable approach to preparing monolayers of a tuned composition that is described in this article can be utilized to control the fluorocarbon content of the hydrophobic monolayers on silicon oxide surfaces.

  8. Aerobic granules formation and nutrients removal characteristics in sequencing batch airlift reactor (SBAR) at low temperature.

    Science.gov (United States)

    Bao, Ruiling; Yu, Shuili; Shi, Wenxin; Zhang, Xuedong; Wang, Yulan

    2009-09-15

    To understand the effect of low temperature on the formation of aerobic granules and their nutrient removal characteristics, an aerobic granular sequencing batch airlift reactor (SBAR) has been operated at 10 degrees C using a mixed carbon source of glucose and sodium acetate. The results showed that aerobic granules were obtained and that the reactor performed in stable manner under the applied conditions. The granules had a compact structure and a clear out-surface. The average parameters of the granules were: diameter 3.4mm, wet density 1.036 g mL(-1), sludge volume index 37 mL g(-1), and settling velocity 18.6-65.1 cm min(-1). Nitrite accumulation was observed, with a nitrite accumulation rate (NO(2)(-)-N/NO(x)(-)-N) between 35% and 43% at the beginning of the start-up stage. During the stable stage, NO(x) was present at a level below the detection limit. However, when the influent COD concentration was halved (resulting in COD/N a reduction of the COD/N from 20:1 to 10:1) nitrite accumulation was observed once more with an effluent nitrite accumulation rate of 94.8%. Phosphorus release was observed in the static feeding phase and also during the initial 20-30 min of the aerobic phase. Neither the low temperature nor adjustment of the COD/P ratio from 100:1 to 25:1 had any influence on the phosphorus removal efficiency under the operating conditions. In the granular reactor with the influent load rates for COD, NH(4)(+)-N, and PO(4)(3-)-P of 1.2-2.4, 0.112 and 0.012-0.024 kg m(-3)d(-1), the respective removal efficiencies at low temperature were 90.6-95.4%, 72.8-82.1% and 95.8-97.9%.

  9. An Improved Method for the Preparation of Organic Monolayers of 1-Alkenes on Hydrogen-Terminated Silicon Surfaces

    NARCIS (Netherlands)

    Sieval, A.B.; Vleeming, V.; Zuilhof, H.; Sudhölter, E.J.R.

    1999-01-01

    The possibility to use dilute alkene solutions for the formation of alkene monolayers with 1-hexadecene on a hydrogen-terminated silicon(100) surface has been investigated for a variety of solvents. The resulting monolayers were analyzed by water contact angles. Anisole, n-butylbenzene, and n-decane

  10. Controlled Oxidation, Biofunctionalization, and Patterning of Alkyl Monolayers on Silicon and Silicon Nitride Surfaces using Plasma Treatment

    NARCIS (Netherlands)

    Rosso, M.; Giesbers, M.; Schroën, C.G.P.H.; Zuilhof, H.

    2010-01-01

    A new method is presented for the fast and reproducible functionalization of silicon and silicon nitride surfaces coated with covalently attached alkyl monolayers. After formation of a methyl-terminated 1-hexadecyl monolayer on H-terminated Si(100) and Si(111) surfaces, short plasma treatments (1-3

  11. Formats

    Directory of Open Access Journals (Sweden)

    Gehmann, Ulrich

    2012-03-01

    Full Text Available In the following, a new conceptual framework for investigating nowadays’ “technical” phenomena shall be introduced, that of formats. The thesis is that processes of formatting account for our recent conditions of life, and will do so in the very next future. It are processes whose foundations have been laid in modernity and which will further unfold for the time being. These processes are embedded in the format of the value chain, a circumstance making them resilient to change. In addition, they are resilient in themselves since forming interconnected systems of reciprocal causal circuits.Which leads to an overall situation that our entire “Lebenswelt” became formatted to an extent we don’t fully realize, even influencing our very percep-tion of it.

  12. FORMATION OF SINGULARITIES FOR QUASILINEAR HYPERBOLIC SYSTEMS WITH CHARACTERISTICS WITH CONSTANT MULTIPLICITY

    Institute of Scientific and Technical Information of China (English)

    Xu Yumei

    2005-01-01

    In this paper we consider the Cauchy problem for quasilinear hyperbolic systems with characteristics with constant multiplicity. Without restriction on characteristics with constant multiplicity (> 1), a blow-up result is obtained for the C1 solution to the Cauchy problem under the assumptions where there is a simple genuinely nonlinear characteristic and the initial data possess certain weaker decaying properties.

  13. FORMATION OF SINGULARITIES FOR QUASILINEAR HYPERBOLIC SYSTEMS WITH CHARACTERISTICS WITH CONSTANT MULTIPLICITY

    Institute of Scientific and Technical Information of China (English)

    王利彬

    2003-01-01

    In this paper we consider the Cauchy problem for quasilinear hyperbolic systems with characteristics with constant multiplicity. Without restriction on characteristics with constant multiplicity(> 1), under the assumptions that there is a genuinely nonlinear simple characteristic and the initial data possess certain decaying properties, the blow-up result is obtained for the C,1 solution to the Cauchy problem.

  14. Sequestration and Distribution Characteristics of Cd(II by Microcystis aeruginosa and Its Role in Colony Formation

    Directory of Open Access Journals (Sweden)

    Xiangdong Bi

    2016-01-01

    Full Text Available To investigate the sequestration and distribution characteristics of Cd(II by Microcystis aeruginosa and its role in Microcystis colony formation, M. aeruginosa was exposed to six different Cd(II concentrations for 10 days. Cd(II exposure caused hormesis in the growth of M. aeruginosa. Low concentrations of Cd(II significantly induced formation of small Microcystis colonies (P93% of Cd(II was sequestrated in the groups with lower added concentrations of Cd(II. More than 80% of the sequestrated Cd(II was bioadsorbed by bEPS. The Pearson correlation coefficients of exterior and interior factors related to colony formation of M. aeruginosa revealed that Cd(II could stimulate the production of IPS and bEPS via increasing Cd(II bioaccumulation and bioadsorption. Increased levels of cross-linking between Cd(II and bEPS stimulated algal cell aggregation, which eventually promoted the formation of Microcystis colonies.

  15. Anti-fouling chemistry of chiral monolayers: enhancing biofilm resistance on racemic surface.

    Science.gov (United States)

    Bandyopadhyay, Debjyoti; Prashar, Deepali; Luk, Yan-Yeung

    2011-05-17

    This work reports the resistance to protein adsorption and bacterial biofilm formation by chiral monolayers of polyol-terminated alkanethiols surrounding micrometer-sized patterns of methyl-terminated alkanethiols on gold films. We discover that patterned surfaces surrounded by chiral polyol monolayers can distinguish different stages of biofilm formation. After inoculation on the surfaces, bacteria first reversibly attached on the chiral polyol monolayers. Over time, the bacteria detached from the polyol surfaces, and attached on the hydrophobic micropatterns to form biofilms. Interestingly, while both enantiomers of gulitol- and mannonamide-terminated monolayer resisted adsorption of proteins (bovine serum albumin, lysozyme, and fibrinogen) and confined biofilms formed on the micropatterns, the monolayers formed by the racemic mixture of either pair of enantiomers exhibited stronger antifouling chemistry against both protein adsorption and biofilm formation than monolayers formed by one enantiomer alone. These results reveal the different chemistries that separate the different stages of biofilm formation, and the stereochemical influence on resisting biofoulings at a molecular-level.

  16. Features of the complexation of octadecane-2,4-dione and lanthanide ions in Langmuir monolayers

    Science.gov (United States)

    Sokolov, M. E.; Repina, I. N.; Raitman, O. A.; Kolokolov, F. A.; Panyushkin, V. T.

    2016-05-01

    Monolayers of octadecane-2,4-dione on the surfaces of EuCl3 and TbCl3 solutions in the concentration range of 1 × 10-4 to 5 × 10-3 M at pH 5.8 are studied. It is found that the limiting area of octadecane-2,4-dione molecule in a monolayer dependence on Eu3+ and Tb3+ concentration is of extreme nature. The formation of complex compounds in the ligand monolayer is postulated, and structures are proposed for these compounds at different concentrations of metal ions.

  17. Graphene-like Boron-Carbon-Nitrogen Monolayers.

    Science.gov (United States)

    Beniwal, Sumit; Hooper, James; Miller, Daniel P; Costa, Paulo S; Chen, Gang; Liu, Shih-Yuan; Dowben, Peter A; Sykes, E Charles H; Zurek, Eva; Enders, Axel

    2017-03-28

    A strategy to synthesize a 2D graphenic but ternary monolayer containing atoms of carbon, nitrogen, and boron, h-BCN, is presented. The synthesis utilizes bis-BN cyclohexane, B2N2C2H12, as a precursor molecule and relies on thermally induced dehydrogenation of the precursor molecules and the formation of an epitaxial monolayer on Ir(111) through covalent bond formation. The lattice mismatch between the film and substrate causes a strain-driven periodic buckling of the film. The structure of the film and its corrugated morphology is discussed based on comprehensive data from molecular-resolved scanning tunneling microscopy imaging, X-ray photoelectron spectroscopy, low-energy electron diffraction, and density functional theory. First-principles calculations further predict a direct electronic band gap that is intermediate between gapless graphene and insulating h-BN.

  18. Formation Conditions and Sedimentary Characteristics of a Triassic Shallow Water Braided Delta in the Yanchang Formation, Southwest Ordos Basin, China.

    Directory of Open Access Journals (Sweden)

    Ziliang Liu

    Full Text Available A large, shallow braided river delta sedimentary system developed in the Yanchang Formation during the Triassic in the southwest of the Ordos basin. In this braided delta system, abundant oil and gas resources have been observed, and the area is a hotspot for oil and gas resource exploration. Through extensive field work on outcrops and cores and analyses of geophysical data, it was determined that developments in the Late Triassic produced favorable geological conditions for the development of shallow water braided river deltas. Such conditions included a large basin, flat terrain, and wide and shallow water areas; wet and dry cyclical climate changes; ancient water turbulence; dramatic depth cycle changes; ancient uplift development; strong weathering of parent rock; and abundant supply. The shallow water braided river delta showed grain sediment granularity, plastic debris, and sediment with mature composition and structure that reflected the strong hydrodynamic environment of large tabular cross-bedding, wedge cross-bedding, and multiple positive rhythms superimposed to form a thick sand body layer. The branch river bifurcation developed underwater, and the thickness of the sand body increased further, indicating that the slope was slow and located in shallow water. The seismic responses of the braided river delta reflected strong shallow water performance, indicated by a progradation seismic reflection phase axis that was relatively flat; in addition, the seismic reflection amplitude was strong and continuous with a low angle and extended over considerable distances (up to 50 km. The sedimentary center was close to the provenance, the width of the river was large, and a shallow sedimentary structure and a sedimentary rhythm were developed. The development of the delta was primarily controlled by tectonic activity and changes in the lake level; as a result, the river delta sedimentary system eventually presented a "small plain, big front

  19. Origin of the Silurian Crude Oils and Reservoir Formation Characteristics in the Tazhong Uplift

    Institute of Scientific and Technical Information of China (English)

    YANG Haijun; LI Sumei; PANG Xiongqi; XIAO Zhongyao; GU Qiaoyuan; ZHANG Baoshou

    2010-01-01

    The Silurian stratum in the Tazhong uplift is an important horizon for exploration because it preserves some features of the hydrocarbons produced from multi-stage tectonic evolution.For this reason,the study of the origin of the Silurian oils and their formation characteristics constitutes a major part in revealing the mechanisms for the composite hydrocarbon accumulation zone in the Tazhong area.Geochemical investigations indicate that the physical properties of the Silurian oils in Tazhong vary with belts and blocks,i.e.,heavy oils are distributed in the TZ47-15 well-block in the North Slope while normal and light oils in the No.I fault belt and the TZ16 well-block,which means that the oil properties are controlled by structural patterns.Most biomarkers in the Silurian oils are similar to that of the Mid-Upper Ordovician source rocks,suggesting a good genetic relationship.However,the compound specific isotope of n-alkanes in the oils and the chemical components of the hydrocarbons in fluid inclusions indicate that these oils are mixed oils derived from both the MidUpper Ordovician and the Cambrian-Lower Ordovician source rocks.Most Silurian oils have a record of secondary alterations like earlier biodegradation,including the occurrence of "UCM" humps in the total ion current (TIC) chromatogram of saturated and aromatic hydrocarbons and 25-norhopane in saturated hydrocarbons of the crude oils,and regular changes in the abundances of light and heavy components from the structural low to the structural high.The fact that the Silurian oils are enriched in chain alkanes,e.g.,n.alkanes and 25-norhopane,suggests that they were mixed oils of the earlier degraded oils with the later normal oils.It is suggested that the Silurian oils experienced at least three episodes of petroleum charging according to the composition and distribution as well as the maturity of reservoir crude oils and the oils in fluid inclusions.The migration and accumulation models of these oils in

  20. Paleosols, types and their characteristics in the Shurijeh Formation, Kopet- Dagh basin, NE Iran

    Directory of Open Access Journals (Sweden)

    Asadolah Mahbobi

    2012-01-01

    Full Text Available The Shurijeh Formation (Late Jurassic- Early Cretaceous consists of siliciclastic facies in the southeastern and eastern parts of the Kopet- Dagh basin, whereas evaporate and carbonate strata are present in its facies succession toward central and western parts of the basin. In addition, various paleosols are identified in this formation that based on relative preference of pedogenic procecces, are classified into three classes including histosols, oxisols and calcisols. The Shurijeh Formation calcisols, based on mineralogical composition, are divided into calcretes and dolocretes and contain special macromorphology and micromorphology features. Based on macroscopic- microscopic properties (alpha and beta microfabrics, the Shurijeh calcretes are divided into pedogenic and non- pedogenic (ground water types that are formed under different conditions. The Shurijeh Formation dolocretes, only found in one section (Esfidan section, and the mudstone host rocks, are probably non- pedogenic (ground water. Water table fluctuations with arid to semiarid climatic conditions are caused calsisols creation in the Shurijeh Formation.

  1. Room temperature Tamm-Plasmon Exciton-Polaritons with a WSe2 monolayer

    CERN Document Server

    Lundt, Nils; Cherotchenko, Evgeniia; Iff, Oliver; Nalitov, Anton V; Klaas, Martin; Betzold, Simon; Dietrich, Christof P; Kavokin, Alexey V; Höfling, Sven; Schneider, Christian

    2016-01-01

    Solid state cavity quantum electrodynamics is a rapidly advancing field which explores the frontiers of light-matter coupling. Plasmonic approaches are of particular interest in this field, since they carry the potential to squeeze optical modes to spaces significantly below the diffraction limit1,2, enhancing light-matter coupling. They further serve as an architecture to design ultra-fast, non-linear integrated circuits with smallest footprints3. Transition metal dichalcogenides are ideally suited as the active material in such circuits as they interact strongly with light at the ultimate monolayer limit4. Here, we implement a Tamm-plasmon-polariton structure, and study the coupling to a monolayer of WSe2, hosting highly stable excitons5. Exciton-Polariton formation at room temperature is manifested in the characteristic energy-momentum dispersion relation studied in photoluminescence, featuring an anti-crossing between the exciton and photon modes with a Rabi-splitting of 23.5 meV. Creating polaritonic qua...

  2. Optimal control of electrostatic self-assembly of binary monolayers

    Science.gov (United States)

    Shestopalov, N. V.; Henkelman, G.; Powell, C. T.; Rodin, G. J.

    2009-05-01

    A simple macroscopic model is used to determine an optimal annealing schedule for self-assembly of binary monolayers of spherical particles. The model assumes that a single rate-controlling mechanism is responsible for the formation of spatially ordered structures and that its rate follows an Arrhenius form. The optimal schedule is derived in an analytical form using classical optimization methods. Molecular dynamics simulations of the self-assembly demonstrate that the proposed schedule outperforms other schedules commonly used for simulated annealing.

  3. Anisotropic mechanical properties and Stone-Wales defects in graphene monolayer: A theoretical study

    Energy Technology Data Exchange (ETDEWEB)

    Fan, B.B. [School of Materials Science and Engineering, Zhengzhou University, Henan 450001 (China); Yang, X.B. [Department of Physics, South China University of Technology, Guangzhou 510640 (China); Zhang, R., E-mail: zhangray@zzu.edu.c [School of Materials Science and Engineering, Zhengzhou University, Henan 450001 (China); Zhengzhou Institute of Aeronautical Industry Management, Henan 450046 (China)

    2010-06-14

    We investigate the mechanical properties of graphene monolayer via the density functional theoretical (DFT) method. We find that the strain energies are anisotropic for the graphene under large strain. We attribute the anisotropic feature to the anisotropic sp{sup 2} hybridization in the hexagonal lattice. We further identify that the formation energies of Stone-Wales (SW) defects in the graphene monolayer are determined by the defect concentration and also the direction of applied tensile strain, correlating with the anisotropic feature.

  4. Patterned Array of Poly(ethylene glycol) Silane Monolayer for Label-Free Detection of Dengue

    OpenAIRE

    Nor Zida Rosly; Shahrul Ainliah Alang Ahmad; Jaafar Abdullah; Nor Azah Yusof

    2016-01-01

    In the present study, the construction of arrays on silicon for naked-eye detection of DNA dengue was demonstrated. The array was created by exposing a polyethylene glycol (PEG) silane monolayer to 254 nm ultraviolet (UV) light through a photomask. Formation of the PEG silane monolayer and photomodifed surface properties was thoroughly characterized by using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and contact angle measurements. The results of XPS confirmed that...

  5. Triazolobithiophene Light Absorbing Self-Assembled Monolayers: Synthesis and Mass Spectrometry Applications

    Directory of Open Access Journals (Sweden)

    Denis Séraphin

    2011-10-01

    Full Text Available The synthesis of five light absorbing triazolobithiophenic thiols, which were utilized for producing self-assembled monolayers (SAMs on gold surfaces, is presented. The monolayer formation was monitored by cyclic voltammetry, indicating excellent surface coverage. The new triazolobithiophenic compounds exhibited an absorption maximum around 340 nm, which is close to the emission wavelength of a standard nitrogen laser. Consequently these compounds could be used to aid ionization in laser desorption mass spectrometry (MS.

  6. Hydrophobic monolayered nanoflakes of tungsten oxide: coupled exfoliation and fracture in a nonpolar organic medium.

    Science.gov (United States)

    Honda, Masashi; Oaki, Yuya; Imai, Hiroaki

    2015-06-21

    Coupled exfoliation and fracture induced formation of hydrophobic monolayered nanoflakes in a nonpolar organic medium. The hydrophobic monolayered nanoflakes 5-20 nm in lateral size consisted of a tungstate layer with surface modification by stearylammonium ions (C18H37NH3)0.397 H0.603Cs3W11O35·xH2O (x < 0.625).

  7. Structural characteristics of green tea catechins for formation of protein carbonyl in human serum albumin.

    Science.gov (United States)

    Ishii, Takeshi; Mori, Taiki; Ichikawa, Tatsuya; Kaku, Maiko; Kusaka, Koji; Uekusa, Yoshinori; Akagawa, Mitsugu; Aihara, Yoshiyuki; Furuta, Takumi; Wakimoto, Toshiyuki; Kan, Toshiyuki; Nakayama, Tsutomu

    2010-07-15

    Catechins are polyphenolic antioxidants found in green tea leaves. Recent studies have reported that various polyphenolic compounds, including catechins, cause protein carbonyl formation in proteins via their pro-oxidant actions. In this study, we evaluate the formation of protein carbonyl in human serum albumin (HSA) by tea catechins and investigate the relationship between catechin chemical structure and its pro-oxidant property. To assess the formation of protein carbonyl in HSA, HSA was incubated with four individual catechins under physiological conditions to generate biotin-LC-hydrazide labeled protein carbonyls. Comparison of catechins using Western blotting revealed that the formation of protein carbonyl in HSA was higher for pyrogallol-type catechins than the corresponding catechol-type catechins. In addition, the formation of protein carbonyl was also found to be higher for the catechins having a galloyl group than the corresponding catechins lacking a galloyl group. The importance of the pyrogallol structural motif in the B-ring and the galloyl group was confirmed using methylated catechins and phenolic acids. These results indicate that the most important structural element contributing to the formation of protein carbonyl in HSA by tea catechins is the pyrogallol structural motif in the B-ring, followed by the galloyl group. The oxidation stability and binding affinity of tea catechins with proteins are responsible for the formation of protein carbonyl, and consequently the difference in these properties of each catechin may contribute to the magnitude of their biological activities.

  8. Sedimentological and petrophysical characteristics of Raha Formation at Wadi Tubia, Northern Gulf of Aqaba, Sinai, Egypt

    Directory of Open Access Journals (Sweden)

    Ahmed S. Mousa

    2011-06-01

    Statistical analysis of the measured petrophysical data shows that, the dolomitic lithic arenite and fossiliferous bioclastic grainstone microfacies have a good storage capacity in the Raha Formation of Wadi Tubia, Northern Gulf of Aqaba, Sinai, Egypt.

  9. Dynamics of the current filament formation and its steady-state characteristics in chalcogenide based PCM

    Science.gov (United States)

    Bogoslovskiy, Nikita; Tsendin, Konstantin

    2017-03-01

    In the phase-change memory (PCM) crystallization occurs in the high-current filament which forms during switching to the conductive state. In the present paper we conduct a numerical modeling of the current filament formation dynamics in thin chalcogenide films using an electronic-thermal model based on negative-U centers tunnel ionization and Joule heating. The key role of inhomogeneities in the filament formation process is shown. Steady-state filament parameters were obtained from the analysis of the stationary heat conduction equation. The filament formation dynamics and the steady-state filament radius and temperature could be controlled by material parameters and contact resistance. Consequently it is possible to control the size of the region wherein crystallization occurs. A good agreement with numerous experimental data leads to the conclusion that thermal effects play a significant role in CGS conduction and high-current filament formation while switching.

  10. Geochemical Characteristics and Origins of the Crude Oil of Triassic Yanchang Formation in Southwestern Yishan Slope, Ordos Basin

    Directory of Open Access Journals (Sweden)

    Xiaoli Zhang

    2017-01-01

    Full Text Available Biomarker compounds that derived from early living organisms play an important role in oil and gas geochemistry and exploration since they can record the diagenetic evolution of the parent materials of crude oil and reflect the organic geochemical characteristics of crude oil and source rocks. To offer scientific basis for oil exploration and exploitation for study area, gas chromatography-mass spectrometry method is applied to study the biomarker compounds of crude oil in Southwestern Yishan Slope of Ordos Basin, through qualitatively and quantitatively analyzing separated materials. The crude oil of Yanchang Formation and the source rocks of Yan’an and Yanchang Formation were collected in order to systematically analyze the characteristics of the biomarker compounds in saturated hydrocarbon fractions and clarify the organic geochemical characteristics of crude oil. The distribution and composition of various types of hydrocarbon biomarker compounds in crude oil suggest that the parent materials of crude oil are composed of hydrobiont and terrigenous plants, and the crude oil is mature oil which is formed in the weak reducing fresh water environment. Oil source correlation results show that the crude oil of Yanchang Formation in Yishan Slope is sourced from the source rocks of Chang 7 subformation.

  11. Member 1 of Yongji Formation (Ey1) sedimentary characteristics and its origin analysis in Yitong Graben

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Ey1 has the unique desultory-weak or gap seismic reflection structure as its one of the most important characteristics. It is very important to clarify sedimentary characteristics and its origin for Yitong Graben and its sedimentary facies and tectonic evolution. On the basis of the research of core analyses, well logging data analyses, sedimentary facies analyses and seismic reflection structure analyses, the authors have concluded the sedimentary characteristics of Ey1, and have carried out Ey1 sedimentary environments and its origin. The result shows that Ey1 desultory-weak or gap seismic reflection may be a series of small scale secondary sediment fans superimposition.

  12. Improving the dielectric properties of ethylene-glycol alkanethiol self-assembled monolayers.

    Science.gov (United States)

    Zaccari, Irene; Catchpole, Benjamin G; Laurenson, Sophie X; Davies, A Giles; Wälti, Christoph

    2014-02-11

    Self-assembled monolayers (SAMs) can be formed at the interface between solids and fluids, and are often used to modify the surface properties of the solid. One of the most widely employed SAM systems is exploiting thiol-gold chemistry, which, together with alkane-chain-based molecules, provides a reliable way of SAM formation to modify the surface properties of electrodes. Oligo ethylene-glycol (OEG) terminated alkanethiol monolayers have shown excellent antifouling properties and have been used extensively for the coating of biosensor electrodes to minimize nonspecific binding. Here, we report the investigation of the dielectric properties of COOH-capped OEG monolayers and demonstrate a strategy to improve the dielectric properties significantly by mixing the OEG SAM with small concentrations of 11-mercaptoundecanol (MUD). The monolayer properties and composition were characterized by means of impedance spectroscopy, water contact angle, ellipsometry and X-ray photoelectron spectroscopy. An equivalent circuit model is proposed to interpret the EIS data and to determine the conductivity of the monolayer. We find that for increasing MUD concentrations up to about 5% the resistivity of the SAM steadily increases, which together with a considerable decrease of the phase of the impedance, demonstrates significantly improved dielectric properties of the monolayer. Such monolayers will find widespread use in applications which depend critically on good dielectric properties such as capacitive biosensor.

  13. Surface viscoelastic properties of spread ferroelectric liquid crystal monolayer on air-water interface

    Science.gov (United States)

    Kaur, Ramneek; Bhullar, Gurpreet Kaur; Raina, K. K.

    2013-06-01

    Ferroelectric Liquid crystal having Smectic C* phase at room temperature was capable of forming Langmuir monolayer due to presence of both hydrophilic and hydrophobic groups in it. Surface viscoelasticity properties of FLC monolayer spread on water surface had been determined by dynamic oscillation method and discussed as a function of surface pressure. Dynamic viscoelastic properties such as G (Elastic modulus), G' (storage (elastic) modulus), G' (Loss (viscous) modulus) and phase change with sinusoidal oscillation had been measured at phase changing surface pressure values. As monolayer was becoming condensed, increasing trend was observed in G' values while G' was decreasing. At higher frequencies, viscous modulus G' had negative values. This relaxation phenomenon was probably caused by conformational rearrangements that acted to fluidize monolayer. Phase change tan θ was positive, response in surface pressure was ahead of the de-formation in area and the monolayer had positive dilatational viscosity. Phase change tan θ was negative, response in surface pressure was hysteretic to the deformation in area, and negative dilatational viscosity had been observed. Studies of monolayer in barrier oscillating mode provided us the surface pressure which was most suitable for Langmuir Blodgett monolayer deposition.

  14. Characteristics of Reactive Ni3Sn4 Formation and Growth in Ni-Sn Interlayer Systems

    Science.gov (United States)

    Lis, Adrian; Kenel, Christoph; Leinenbach, Christian

    2016-06-01

    The near-isothermal growth and formation of Ni3Sn4 intermetallic compounds (IMC) in Ni-Sn interlayer systems was studied in the solid state at 473 K (200 °C) and under solid-liquid conditions at 523 and 573 K (250 °C and 300 °C) from an initial state of a few seconds. Scalloped solid-state IMC formation was mainly driven by grain boundary diffusion of Ni through the IMC layer combined with the grain coarsening of the IMC layer. Under solid-liquid conditions, the formation of faceted and needle-shaped Ni3Sn4 grains as well as an atypical IMC growth behavior with similar parabolic growth constants for 523 K and 573 K (250 °C and 300 °C) was observed within the first 180 seconds of the holding time, and IMC growth occurred as an isothermal solidification from the Ni-saturated Sn melt. Due to the progressive densification of the IMC layer and the diffusion-controlled growth, the kinetics slowed down by approximately one order of magnitude after 180 seconds of annealing. The final stage was characterized by the formation of IMC islands ahead of the interfacial Ni3Sn4 layer. Needle-like IMC growth was effectively suppressed under combined solid-state and solid-liquid conditions. Textured Ni3Sn4 IMC formation at the Ni-Sn interface was approved with pole figure measurements. The activation energy Q for solid-liquid IMC formation was calculated as 43.3 kJ/mol, and processing maps for IMC growth and Sn consumption were derived as functions of temperature and time, respectively.

  15. Inventory of Shale Formations in the US, Including Geologic, Hydrological, and Mechanical Characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Dobson, Patrick; Houseworth, James

    2013-11-22

    The objective of this report is to build upon previous compilations of shale formations within many of the major sedimentary basins in the US by developing GIS data delineating isopach and structural depth maps for many of these units. These data are being incorporated into the LANL digital GIS database being developed for determining host rock distribution and depth/thickness parameters consistent with repository design. Methods were developed to assess hydrological and geomechanical properties and conditions for shale formations based on sonic velocity measurements.

  16. Free exciton emission and vibrations in pentacene monolayers

    Science.gov (United States)

    He, Rui

    2011-03-01

    Pentacene is a benchmark organic semiconductor material because of its potential applications in electronic and optoelectronic devices. Recently we demonstrated that optical and vibrational characterizations of pentacene films can be carried out down to the sub-monolayer limit. These milestones were achieved in highly uniform pentacene films that were grown on a compliant polymeric substrate. Films with thickness ranging from sub- monolayer to tens of monolayers were studied at low temperatures. The intensity of the free exciton (FE) luminescence band increases quadratically with the number of layers N when N is small. This quadratic dependence is explained as arising from the linear dependence of the intensity of absorption and the probability of emission on the number of layers N. Large enhancements of Raman scattering intensities at the FE resonance enable the first observations of low-lying lattice modes in the monolayers. The measured low- lying modes (in the 20 to 100 cm-1 range) display characteristic changes when going from a single monolayer to two layers. The Raman intensities by high frequency intra-molecular vibrations display resonance enhancement double-peaks when incident or scattered photon energies overlap the FE optical emission. The double resonances are about the same strength which suggests that Franck-Condon overlap integrals for the respective vibronic transitions have the same magnitude. The interference between scattering amplitudes in the Raman resonance reveals quantum coherence of the symmetry-split states (Davydov doublet) of the lowest intrinsic singlet exciton. These results demonstrate novel venues for ultra-thin film characterization and studies of fundamental physics in organic semiconductor structures. In collaboration with Nancy G. Tassi (Dupont), Graciela B. Blanchet (Nanoterra, Cambridge, MA), and Aron Pinczuk (Columbia University).

  17. Most Common Teacher Characteristics Related to Intentionality in Student Spiritual Formation

    Science.gov (United States)

    Moore, Deborah

    2014-01-01

    Teachers have the important commission of guiding students in their spiritual formation, which is the process through which an individual accepts Jesus Christ as Savior and continually becomes more like Him. Given this task, Christian teachers are able to be intentional within classroom management, through instruction, and by modeling. Teachers…

  18. Immobilization of Colloidal Monolayers at Fluid–Fluid Interfaces

    Directory of Open Access Journals (Sweden)

    Peter T. Bähler

    2016-07-01

    Full Text Available Monolayers of colloidal particles trapped at an interface between two immiscible fluids play a pivotal role in many applications and act as essential models in fundamental studies. One of the main advantages of these systems is that non-close packed monolayers with tunable inter-particle spacing can be formed, as required, for instance, in surface patterning and sensing applications. At the same time, the immobilization of particles locked into desired structures to be transferred to solid substrates remains challenging. Here, we describe three different strategies to immobilize monolayers of polystyrene microparticles at water–decane interfaces. The first route is based on the leaking of polystyrene oligomers from the particles themselves, which leads to the formation of a rigid interfacial film. The other two rely on in situ interfacial polymerization routes that embed the particles into a polymer membrane. By tracking the motion of the colloids at the interface, we can follow in real-time the formation of the polymer membranes and we interestingly find that the onset of the polymerization reaction is accompanied by an increase in particle mobility determined by Marangoni flows at the interface. These results pave the way for future developments in the realization of thin tailored composite polymer-particle membranes.

  19. Co-nucleus 1D/2D Heterostructures with Bi2S3 Nanowire and MoS2 Monolayer: One-Step Growth and Defect-Induced Formation Mechanism.

    Science.gov (United States)

    Li, Yongtao; Huang, Le; Li, Bo; Wang, Xiaoting; Zhou, Ziqi; Li, Jingbo; Wei, Zhongming

    2016-09-27

    Heterostructures constructed by low-dimensional (such as 0D, 1D, and 2D) materials have opened up opportunities for exploring interesting physical properties and versatile (opto)electronics. Recently, 2D/2D heterostructures, in particular, atomically thin graphene and transition-metal dichalcogenides, including graphene/MoS2, WSe2/MoS2, and WS2/WSe2, were efficiently prepared (by transfer techniques, chemical vapor deposition (CVD) growth, etc.) and systematically studied. In contrast, investigation of 1D/2D heterostructures was still very challenging and rarely reported, and the understanding of such heterostructures was also not well established. Herein, we demonstrate the one-step growth of a heterostructure on the basis of a 1D-Bi2S3 nanowire and a 2D-MoS2 monolayer through the CVD method. Multimeans were employed, and the results proved the separated growth of a Bi2S3 nanowire and a MoS2 sheet in the heterostructure rather than forming a BixMo1-xSy alloy due to their large lattice mismatch. Defect-induced co-nucleus growth, which was an important growth mode in 1D/2D heterostructures, was also experimentally confirmed and systematically investigated in our research. Such 1D/2D heterostructures were further fabricated and utilized in (opto)electronic devices, such as field-effect transistors and photodetectors, and revealed their potential for multifunctional design in electrical properties. The direct growth of such nanostructures will help us to gain a better comprehension of these specific configurations and allow device functionalities in potential applications.

  20. Systematic study of quasifission characteristics and timescales in heavy element formation reactions

    Directory of Open Access Journals (Sweden)

    Hinde D.J.

    2016-01-01

    Full Text Available Superheavy elements can only be created in the laboratory by the fusion of two massive nuclei. Mass-angle distributions give the most direct information on the characteristics and time scales of quasifission, the major competitor to fusion in these reactions. The systematics of 42 mass-angle distributions provide information on the global characteristics of quasifission. Deviations from the systematics reveal the major role played by the nuclear structure of the two colliding nuclei in determining the reaction outcome, and in hindering or favouring heavy element production.

  1. Phase separated anionic domains in ternary mixed lipid monolayers at the air-water interface.

    Science.gov (United States)

    Maloney, K M; Grainger, D W

    1993-04-01

    A series of ternary mixed monolayers containing varying amounts of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and equimolar additions of 1-palmitoyl-2-hydroxy-sn-glycero-3-phosphocholine (LYSO-PC) and palmitic acid (PA) were studied at the air-water interface. These mixed monolayers were used to model phospholipid biomembrane interfaces resulting from phospholipase A2 (PLA2) hydrolysis. Recent work [D.W. Grainger A. Reichert, H. Ringsdorf and C. Salesse (1989) Biochim. Biophys. Acta. 1023, 365-379] has shown that PLA2 hydrolysis of pure phospholipid monolayers results in formation of large PLA2 domains at the air-water interface. These domains are proposed to result from PLA2 adsorption to phase separated regions in the hydrolyzed monolayer. To elucidate the phase behaviour in these monolayer systems, surface pressure-area isotherms were measured for the ternary mixtures on pure water and buffered subphases. Fluorescence microscopy at the air-water interface was used to image fluorescent probe-doped monolayer mixtures during isothermal compressions. A water-soluble cationic carbocyanine dye was used to probe the interfacial properties of the mixed monolayers. Isotherm data do not provide unambiguous evidence for either phase separation or ideal mixing of monolayer components. Fluorescence microscopy is more revealing, showing that lateral phase separation of microstructures containing palmitic acid occurred only when monolayer subphases contained Ca2+ ions at alkaline pH. At either low pH or on Ca(2+)-free subphases, phase separation was not observed.

  2. Patterning monolayer graphene with zigzag edges on hexagonal boron nitride by anisotropic etching

    Science.gov (United States)

    Wang, Guole; Wu, Shuang; Zhang, Tingting; Chen, Peng; Lu, Xiaobo; Wang, Shuopei; Wang, Duoming; Watanabe, Kenji; Taniguchi, Takashi; Shi, Dongxia; Yang, Rong; Zhang, Guangyu

    2016-08-01

    Graphene nanostructures are potential building blocks for nanoelectronic and spintronic devices. However, the production of monolayer graphene nanostructures with well-defined zigzag edges remains a challenge. In this paper, we report the patterning of monolayer graphene nanostructures with zigzag edges on hexagonal boron nitride (h-BN) substrates by an anisotropic etching technique. We found that hydrogen plasma etching of monolayer graphene on h-BN is highly anisotropic due to the inert and ultra-flat nature of the h-BN surface, resulting in zigzag edge formation. The as-fabricated zigzag-edged monolayer graphene nanoribbons (Z-GNRs) with widths below 30 nm show high carrier mobility and width-dependent energy gaps at liquid helium temperature. These high quality Z-GNRs are thus ideal structures for exploring their valleytronic or spintronic properties.

  3. Patterning monolayer graphene with zigzag edges on hexagonal boron nitride by anisotropic etching

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Guole; Wu, Shuang; Zhang, Tingting; Chen, Peng; Lu, Xiaobo; Wang, Shuopei; Wang, Duoming; Shi, Dongxia; Yang, Rong, E-mail: ryang@iphy.ac.cn, E-mail: gyzhang@iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Watanabe, Kenji; Taniguchi, Takashi [National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044 (Japan); Zhang, Guangyu, E-mail: ryang@iphy.ac.cn, E-mail: gyzhang@iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Collaborative Innovation Center of Quantum Matter, Beijing 100190 (China); Beijing Key Laboratory for Nanomaterials and Nanodevices, Beijing 100190 (China)

    2016-08-01

    Graphene nanostructures are potential building blocks for nanoelectronic and spintronic devices. However, the production of monolayer graphene nanostructures with well-defined zigzag edges remains a challenge. In this paper, we report the patterning of monolayer graphene nanostructures with zigzag edges on hexagonal boron nitride (h-BN) substrates by an anisotropic etching technique. We found that hydrogen plasma etching of monolayer graphene on h-BN is highly anisotropic due to the inert and ultra-flat nature of the h-BN surface, resulting in zigzag edge formation. The as-fabricated zigzag-edged monolayer graphene nanoribbons (Z-GNRs) with widths below 30 nm show high carrier mobility and width-dependent energy gaps at liquid helium temperature. These high quality Z-GNRs are thus ideal structures for exploring their valleytronic or spintronic properties.

  4. Platinum monolayer electrocatalysts for oxygen reduction: effect of substrates, and long-term stability

    Directory of Open Access Journals (Sweden)

    J. ZHANG

    2005-03-01

    Full Text Available We describe a novel concept for a Ptmonolayer electrocatalyst and present the results of our electrochemical, X-ray absorption spectroscopy, and scanning tunneling microscopy studies. The electrocatalysts were prepared by a new method for depositing Pt monolayers involving the galvanic displacement by Pt of an underpotentially deposited Cu monolayer on substrates of Au (111, Ir(111, Pd(111, Rh(111 and Ru(0001 single crylstals, and Pd nanoparticles. The kinetics of O2 reduction showed significant enhancement with Pt monolayers on Pd(111 and Pd nanoparticle surfaces in comparisonwith the reaction on Pt(111 and Pt nanoparticles, respectively. This increase in catalytic activity is attributed partly to the decreased formation of PtOH, as shown by in situ X-ray absorption spectroscopy. The results illustrate that placing a Pt monolayer on a suitable substrate of metal nanoparticles is an attractive way of designing better O2 reduction electrocatalysts with very low Pt contents.

  5. First-principles study of the magnetism of Ni-doped MoS2 monolayer

    Science.gov (United States)

    Luo, Min; Hao Shen, Yu; Hao Chu, Jun

    2016-09-01

    The magnetic properties of Ni-doped monolayer MoS2 are investigated using the density function theory. The results show that two Ni-doped systems of the nearest-neighbor configuration are ferromagnetic. The p-d hybridization between the Ni dopant and its neighboring S atoms results in the splitting of energy levels near the Fermi energy. These results suggest the p-d hybridization mechanism for the magnetism of the Ni-doped MoS2 monolayer. The magnetic moment disappears with increasing Ni-Ni distance. Our studies predict the nearest two-Ni-doped MoS2 monolayers to be candidates for thin dilute magnetic semiconductors. Moreover, the formation energy calculations indicate that it would be easier to incorporate Ni atoms into a S-rich MoS2 monolayer in the experiment.

  6. Fluorinated alkyne-derived monolayers on oxide-free silicon nanowires via one-step hydrosilylation

    Science.gov (United States)

    Nguyen Minh, Quyen; Pujari, Sidharam P.; Wang, Bin; Wang, Zhanhua; Haick, Hossam; Zuilhof, Han; van Rijn, Cees J. M.

    2016-11-01

    Passivation of oxide-free silicon nanowires (Si NWs) by the formation of high-quality fluorinated 1-hexadecyne-derived monolayers with varying fluorine content has been investigated. Alkyl chain monolayers (C16H30-xFx) with a varying number of fluorine substituents (x = 0, 1, 3, 9, 17) were attached onto hydrogen-terminated silicon (Sisbnd H) surfaces with an effective one-step hydrosilylation. This surface chemistry gives well-defined monolayers on nanowires that have a cylindrical core-shell structure, as characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and static contact angle (SCA) analysis. The monolayers were stable under acidic and basic conditions, as well as under extreme conditions (such as UV exposure), and provide excellent surface passivation, which opens up applications in the fields of field effect transistors, optoelectronics and especially for disease diagnosis.

  7. Role of alkali metal promoter in enhancing lateral growth of monolayer transition metal dichalcogenides

    Science.gov (United States)

    Kim, Hyun; Han, Gang Hee; Yun, Seok Joon; Zhao, Jiong; Keum, Dong Hoon; Jeong, Hye Yun; Hue Ly, Thuc; Jin, Youngjo; Park, Ji-Hoon; Moon, Byoung Hee; Kim, Sung-Wng; Lee, Young Hee

    2017-09-01

    Synthesis of monolayer transition metal dichalcogenides (TMDs) via chemical vapor deposition relies on several factors such as precursor, promoter, substrate, and surface treatment of substrate. Among them, the use of promoter is crucial for obtaining uniform and large-area monolayer TMDs. Although promoters have been speculated to enhance adhesion of precursors to the substrate, their precise role in the growth mechanism has rarely been discussed. Here, we report the role of alkali metal promoter in growing monolayer TMDs. The growth occurred via the formation of sodium metal oxides which prevent the evaporation of metal precursor. Furthermore, the silicon oxide substrate helped to decrease the Gibbs free energy by forming sodium silicon oxide compounds. The resulting sodium metal oxide was anchored within such concavities created by corrosion of silicon oxide. Consequently, the wettability of the precursors to silicon oxide was improved, leading to enhance lateral growth of monolayer TMDs.

  8. Pulsed laser deposition for the synthesis of monolayer WSe2

    Science.gov (United States)

    Mohammed, A.; Nakamura, H.; Wochner, P.; Ibrahimkutty, S.; Schulz, A.; Müller, K.; Starke, U.; Stuhlhofer, B.; Cristiani, G.; Logvenov, G.; Takagi, H.

    2017-08-01

    Atomically thin films of WSe2 from one monolayer up to 8 layers were deposited on an Al2O3 r-cut ( 1 1 ¯ 02 ) substrate using a hybrid-Pulsed Laser Deposition (PLD) system where a laser ablation of pure W is combined with a flux of Se. Specular X-ray reflectivities of films were analysed and were consistent with the expected thickness. Raman measurement and atomic force microscopy confirmed the formation of a WSe2 monolayer and its spatial homogeneity over the substrate. Grazing-incidence X-ray diffraction uncovered an in-plane texture in which WSe2 [ 10 1 ¯ 0 ] preferentially aligned with Al2O3 [ 11 2 ¯ 0 ]. These results present a potential to create 2D transition metal dichalcogenides by PLD, where the growth kinetics can be steered in contrast to common growth techniques like chemical vapor deposition and molecular beam epitaxy.

  9. Atomic Defects and Doping of Monolayer NbSe2.

    Science.gov (United States)

    Nguyen, Lan; Komsa, Hannu-Pekka; Khestanova, Ekaterina; Kashtiban, Reza J; Peters, Jonathan J P; Lawlor, Sean; Sanchez, Ana M; Sloan, Jeremy; Gorbachev, Roman V; Grigorieva, Irina V; Krasheninnikov, Arkady V; Haigh, Sarah J

    2017-02-24

    We have investigated the structure of atomic defects within monolayer NbSe2 encapsulated in graphene by combining atomic resolution transmission electron microscope imaging, density functional theory (DFT) calculations, and strain mapping using geometric phase analysis. We demonstrate the presence of stable Nb and Se monovacancies in monolayer material and reveal that Se monovacancies are the most frequently observed defects, consistent with DFT calculations of their formation energy. We reveal that adventitious impurities of C, N, and O can substitute into the NbSe2 lattice stabilizing Se divacancies. We further observe evidence of Pt substitution into both Se and Nb vacancy sites. This knowledge of the character and relative frequency of different atomic defects provides the potential to better understand and control the unusual electronic and magnetic properties of this exciting two-dimensional material.

  10. Geologic framework, age, and lithologic characteristics of the North Park Formation in North Park, north-central Colorado

    Science.gov (United States)

    Shroba, Ralph R.

    2016-10-18

    , million years ago) ash-flow tuff near its base at Owl Ridge and is interbedded with 29-Ma rhyodacite lava flows and volcanic breccia at Owl Mountain. The formation locally contains vertebrate fossils at least as young as Barstovian age (about 15.9–12.6 Ma) and overlies rocks as young as the White River Formation, which contains vertebrate fossils of Chadronian age (about 37–33.8 Ma) in North Park and a bed of 36.0-Ma volcanic ash in the upper part of the Laramie River valley about 30 km northeast of Walden, Colorado. Based on the ages of the vertebrate fossils, folding of the rocks and sediments in the North Park syncline may be much younger than about 16 Ma.Bedding characteristics of the North Park Formation suggest that (1) some or much of the sand, sandstone, and pebbly sandstone may have been deposited as sheetwash alluvium; (2) much of the siltstone may have been deposited as sheetwash alluvium or ephemeral pond or marsh deposits; (3) beds of sandy limestone probably were deposited as ephemeral pond or marsh deposits; and (4) altered tuff probably was deposited in ephemeral ponds or marshes. Most of the conglomerate and gravel in the North Park Formation are stream-channel deposits that were deposited by high-energy ephemeral or intermittent streams that issued from volcanic terrain rather than debris-flow deposits in relatively near-source fan deposits dominated by sediment gravity flow. Laccolithic doming, uplift, and tilting in the Never Summer Mountains near the Mount Richthofen stock, as well as the formation of volcanic edifices in the Never Summer Mountains and the Rabbit Ears Range during the late Oligocene and Miocene, significantly steepened stream gradients and greatly increased the erosive power and transport capacity of streams that transported large rock fragments and finer sediment eroded from volcanic and sedimentary sources and deposited them in the North Park Formation.Much of the material that makes up the rocks and sediments of the North Park

  11. Application of the characteristics-based sectional method to spatially varying aerosol formation and transport

    NARCIS (Netherlands)

    Frederix, E.M.A.; Kuczaj, A.K.; Nordlund, M.; Veldman, A.E.P.; Geurts, B.J.

    2017-01-01

    The characteristics-based ssolution. It is easy to verify thatectional method (CBSM) offers an Eulerian description of an internally mixed aerosol. It was shown to be robust and capable of exact preservation of lower order moments, allowing for highly skewed sectional droplet size distributions. In

  12. Application of the characteristics-based sectional method to spatially varying aerosol formation and transport

    NARCIS (Netherlands)

    Frederix, E.M.A.; Kuczaj, Arkadiusz K.; Nordlund, M.; Veldman, A.E.P.; Geurts, Bernardus J.

    The characteristics-based ssolution. It is easy to verify thatectional method (CBSM) offers an Eulerian description of an internally mixed aerosol. It was shown to be robust and capable of exact preservation of lower order moments, allowing for highly skewed sectional droplet size distributions. In

  13. Social Interaction and the Formation of Entrepreneurial Characteristics: A Case Study in Authentic Enterprise Activity

    Science.gov (United States)

    Yu, Christina W. M.; Man, Thomas W. Y.

    2009-01-01

    Purpose: This paper is an empirical study which aims to investigate the development of social interaction and their impacts on developing learners' entrepreneurial characteristics throughout their participation in an authentic enterprise activity. Design/methodology/approach: The sample of this study was drawn from the participants of an…

  14. A comparison of different Gracilariopsis lemaneiformis (Rhodophyta) parts in biochemical characteristics, protoplast formation and regeneration

    Science.gov (United States)

    Wang, Zhongxia; Sui, Zhenghong; Hu, Yiyi; Zhang, Si; Pan, Yulong; Ju, Hongri

    2014-08-01

    Gracilariopsis lemaneiformis is a commercially exploited alga. Its filaceous thallus can be divided into three parts, holdfast, middle segment and tip. The growth and branch forming trend and agar content of these three parts were analyzed, respectively, in this study. The results showed that the tip had the highest growth rate and branched most, although it was the last part with branch forming ability. The holdfast formed branches earliest but slowly. Holdfast had the highest agar content. We also assessed the difference in protoplast formation and regeneration among three parts. The middle segment displayed the shortest enzymolysis time and the highest protoplast yield; whereas the tip had the strongest vitality of protoplasts formation. Juvenile plants were only obtained from the protoplasts generated from the tip. These results suggested that the differentiation and function of G. lemaneiformis was different.

  15. X—Ray Diffraction Characteristics of Ceshui Formation Coal in Lianyuan Coal Basin

    Institute of Scientific and Technical Information of China (English)

    毕华

    1998-01-01

    On the basis of X-ray diffraction analysis of Ceshui Furmation coal and its roof mudstone in the Lianyuan coal basin,it is concluded that telemagmatic metamorphism is the main factor leading to the metamorphism of the Ceshui Formation coal in the study region,which has a great impact on the chemical structure of the Ceshui coal series,and the dynamometamorphism is of local and secondary importance.

  16. Fluid Characteristics in Abdominal Aortic Aneurysms (AAAs) and Its Correlation to Thrombus Formation

    Science.gov (United States)

    Tang, Rubing; Bar-Yoseph, Pinhas Z.; Lasheras, Juan

    2008-11-01

    It has been observed that most large Abdominal Aortic Aneurysms (AAAs) develop an intraluminal thrombus as they progressively enlarge. Previous studies have suggested that the build up of the thrombus may be associated with the altered hemodynamic patterns that arise inside the AAA. We have performed a parametrical computational study of the flow patterns inside enlarging AAA to investigate the possible mechanism controlling the thrombus formation. Pulsatile blood flows were simulated in idealized models of fusiform aneurysms with different dilatation ratios and the effects of shear-activated platelet accumulation and platelet/wall interaction were evaluated based on the calculated flow fields. The platelet activation level (PAL) was determined by computing the integral over time of flow shear stresses exerted over the platelets as they are transported throughout the aneurysm. Our results have shown that the values of PAL in AAAs are in fact smaller than the maximum value obtained in a healthy abdominal aorta. However, we show that the transportation of blood cells towards the wall and the formation of stagnation points on the aneurysm's wall play more significant roles in thrombus formation than PAL.

  17. Sequestration and Distribution Characteristics of Cd(II) by Microcystis aeruginosa and Its Role in Colony Formation.

    Science.gov (United States)

    Bi, Xiangdong; Yan, Ran; Li, Fenxiang; Dai, Wei; Jiao, Kewei; Zhou, Qixing; Liu, Qi

    2016-01-01

    To investigate the sequestration and distribution characteristics of Cd(II) by Microcystis aeruginosa and its role in Microcystis colony formation, M. aeruginosa was exposed to six different Cd(II) concentrations for 10 days. Cd(II) exposure caused hormesis in the growth of M. aeruginosa. Low concentrations of Cd(II) significantly induced formation of small Microcystis colonies (P bEPS) contents of M. aeruginosa significantly (P 93% of Cd(II) was sequestrated in the groups with lower added concentrations of Cd(II). More than 80% of the sequestrated Cd(II) was bioadsorbed by bEPS. The Pearson correlation coefficients of exterior and interior factors related to colony formation of M. aeruginosa revealed that Cd(II) could stimulate the production of IPS and bEPS via increasing Cd(II) bioaccumulation and bioadsorption. Increased levels of cross-linking between Cd(II) and bEPS stimulated algal cell aggregation, which eventually promoted the formation of Microcystis colonies.

  18. Effect of keyhole characteristics on porosity formation during pulsed laser-GTA hybrid welding of AZ31B magnesium alloy

    Science.gov (United States)

    Chen, Minghua; Xu, Jiannan; Xin, Lijun; Zhao, Zuofu; Wu, Fufa; Ma, Shengnan; Zhang, Yue

    2017-06-01

    This paper experimentally investigates the relationship between laser keyhole characteristics on the porosity formation during pulsed laser-GTA welding of magnesium alloy. Based on direct observations during welding process, the influences of laser keyhole state on the porosity formation were studied. Results show that the porosities in the joint are always at the bottom of fusion zone of the joint, which is closely related to the keyhole behavior. A large depth to wide ratio always leads to the increase of porosity generation chance. Keeping the keyhole outlet open for a longer time benefits the porosity restriction. Overlap of adjacent laser keyhole can effectively decrease the porosity generation, due to the cutting effect between adjacent laser keyholes. There are threshold overlap rate values for laser keyholes in different state.

  19. Formation Characteristic of CO2 Corrosion Product Layer of P110 Steel Investigated by SEM and Electrochemical Techniques

    Institute of Scientific and Technical Information of China (English)

    ZHAO Guo-xian; LU Xiang-hong; XIANG Jian-min; HAN Yong

    2009-01-01

    Formation characteristic of CO2 corrosion product layer on the surface of P110 steel was investigated in simulated oilfield environment using mass-loss experiment, potentiodynamic polarization curve, impedance spectroscopy, and SEM micrograph analysis. Samples of different times up to 240 h were tested during exposure. Corrosion product was primarily composed of Fe(Ca, Mg)(CO3)2, which was distinguished by two layers. With an increase in the exposure time, the charge transfer resistance and polarization resistance increased progressively, the uniform corrosion rate decreased, and the corrosion reaction was controlled by the diffusion process instead of the activation process. All phenomena were attributed to the formation of the protective corrosion product layer. More compact and lower porosity of the layer made it more difficult to transfer and diffuse through the corrosion product layer for the charges and ions. Similar results were obtained by electrochemical test and mass-loss experiment.

  20. Lateral pressure profiles in lipid monolayers

    NARCIS (Netherlands)

    Baoukina, Svetlana; Marrink, Siewert J.; Tieleman, D. Peter

    2010-01-01

    We have used molecular dynamics simulations with coarse-grained and atomistic models to study the lateral pressure profiles in lipid monolayers. We first consider simple oil/air and oil/water interfaces, and then proceed to lipid monolayers at air/water and oil/water interfaces. The results are qual

  1. Monolayers at air-water interfaces: from origins-of-life to nanotechnology.

    Science.gov (United States)

    Ariga, Katsuhiko; Hill, Jonathan P

    2011-08-01

    The air-water interface presents several interesting features, namely a) a molecularly flat environment, b) a boundary region between two phases with different dielectric constants, c) permits or promotes dynamic interactions within the interface region, and d) a point of interaction between hydrophobic compounds and aqueous molecules. Accordingly, Langmuir monolayers at the air-water interface have several unique characteristics and properties, which require investigation. In this review-type personal account, typical examples of molecular recognition and molecular patterning at air-water interfaces are first introduced, followed by descriptions of specific and unusual properties of monolayers on water. In addition, two examples of our own results concerning Langmuir monolayers are explained. We have selected examples from two apparently unrelated research areas, these being the origin of life and future nanotechnology, in order to emphasize the diverse scientific contribution of research on monolayers at the air-water interface. Copyright © 2011 The Japan Chemical Journal Forum and Wiley Periodicals, Inc.

  2. CoCl2, a mimic of hypoxia, induces formation of polyploid giant cells with stem characteristics in colon cancer.

    Directory of Open Access Journals (Sweden)

    Laura M Lopez-Sánchez

    Full Text Available The induction of polyploidy is considered the reproductive end of cells, but there is evidence that polyploid giant cancer cells (PGCCs contribute to cell repopulation during tumor relapse. However, the role of these cells in the development, progression and response to therapy in colon cancer remains undefined. Therefore, the main objective of this study was to investigate the generation of PGCCs in colon cancer cells and identify mechanisms of formation. Treatment of HCT-116 and Caco-2 colon cancer cells with the hypoxia mimic CoCl2 induced the formation of cells with larger cell and nuclear size (PGCCs, while the cells with normal morphology were selectively eliminated. Cytometric analysis showed that CoCl2 treatment induced G2 cell cycle arrest and the generation of a polyploid cell subpopulation with increased cellular DNA content. Polyploidy of hypoxia-induced PGCCs was confirmed by FISH analysis. Furthermore, CoCl2 treatment effectively induced the stabilization of HIF-1α, the differential expression of a truncated form of p53 (p47 and decreased levels of cyclin D1, indicating molecular mechanisms associated with cell cycle arrest at G2. Generation of PGCCs also contributed to expansion of a cell subpopulation with cancer stem cells (CSCs characteristics, as indicated by colonosphere formation assays, and enhanced chemoresistance to 5-fluorouracil and oxaliplatin. In conclusion, the pharmacological induction of hypoxia in colon cancer cells causes the formation of PGCCs, the expansion of a cell subpopulation with CSC characteristics and chemoresistance. The molecular mechanisms involved, including the stabilization of HIF-1 α, the involvement of p53/p47 isoform and cell cycle arrest at G2, suggest novel targets to prevent tumor relapse and treatment failure in colon cancer.

  3. Characteristic Features of the Formation of a Combined Magnetron-Laser Plasma in the Processes of Deposition of Film Coatings

    Science.gov (United States)

    Burmakov, A. P.; Kuleshov, V. N.; Prokopchik, K. Yu.

    2016-09-01

    A block diagram of a facility for combined magnetron-laser deposition of coatings and of the systems of controlling and managing this process is considered. The results of analysis of the influence of the gas medium and of laser radiation parameters on the emission-optical properties of laser plasma are considered. The influence of the laser plasma on the electric characteristics of a magnetron discharge is analyzed. The formation of the laser plasma-initiated pulse arc discharge has been established and the influence of the laser radiation parameters on the electric characteristics of this discharge has been determined. The emission optical spectra of the magnetron discharge plasma and of erosion laser plasma are compared separately and in combination.

  4. Dew formation characteristics in a revegetation-stabilized desert ecosystem in Shapotou area, Northern China

    Science.gov (United States)

    Pan, Yan-xia; Wang, Xin-ping; Zhang, Ya-feng

    2010-06-01

    SummarySoil moisture in the upper layer plays an important role in arid desert ecosystems. Dew as an additional source of fresh water, may have a positive impact upon the ecosystems in arid and semi-arid zones. Measurements on dew formation amount and duration were carried out in the whole October of 2008 at different condensing surface types (bare dune sands, physical soil crusts and biological soil crusts) associated with different inter-space positions between plants, and at the area under plant canopy in a revegetation-stabilized arid desert ecosystem in Shapotou area, China. The results indicated that there was a positive linear correlation between dew amounts and relative humidity, while mean temperature was negatively linearly related to dew amounts and no significant relationship was found between dew amounts and wind speed. Clear and foggy mornings were characterized by higher dew amounts and longer dew duration, whereas less dew was recorded during cloudy and especially windy mornings. Crusts, especially the biological soil crusts, obtained significantly higher amounts of dew than that of bare moving sand dunes. It was more difficult for dew to condense under the canopy of the plants than on the bare sand dunes. At the first stage of ecological engineering projects, dew can renew the moisture losing through the evaporation of soil and transpiration of leaves, and thus can supply important source of water for xerophytic shrubs. The higher dew amount at the inter-space of re-vegetated plants is an important driving factor for the growth of microorganisms and spore plants, which further accelerate the formation of biological soil crusts and stabilization of moving sand dunes. The presence of biological soil crusts, in turn, helps to facilitate the formation of dew. Therefore, a mutual enhanced effect exists between dew and artificially revegetation ecosystems.

  5. Characteristics and Formation Mechanism of Polygonal Faults in Qiongdongnan Basin,Northern South China Sea

    Institute of Scientific and Technical Information of China (English)

    Sun Qiliang; Wu Shiguo; Yao Genshun; LI Fuliang

    2009-01-01

    Based on high-resolution 3D seismic data,we document the polygonal faults within the Miocene Meishan (梅山) Formation and Huangliu (黄流) Formation of the Qiongdongnan (琼东南)basin,northern South China Sea.Within the seismic section and time coherent slice,densely distributed extensional faults with small throw and polygonal shape were identified in map view.The orientation of the polygonal faults is almost isotropic,indicating a non-tectonic origin.The deformation is clearly layer-bounded,with horizontal extension of 11.2% to 16%,and 13.2% on average.The distribution of polygonal faults shows a negative correlation with that of gas chimneys.The development of polygonal faults may be triggered by over-pressure pore fluid which is restricted in the fine-grained sediments of bathyal facies when the sediments is compacted by the burden above.The polygonal faults developed to balance the volumetric contraction and restricted extension.The product of hydrocarbon in the Meishan Formation may have contributed to the development of the polygonal faults.In the study area,it was thought that the petroleum system of the Neogene post-rift sequence is disadvantageous because of poor migration pathway.However,the discovery of polygonal faults In the Miocene strata,which may play an important role on the fluid migra-tion,may change this view.A new model of the petroleum system for the study area is proposed.

  6. Characteristics and formation mechanism for stainless steel fiber with periodic micro-fins

    Science.gov (United States)

    Tang, Tao; Wan, Zhenping; Lu, Longsheng; Tang, Yong

    2016-05-01

    Metal fibers have been widely used in many industrial applications due to their unique advantages. In certain applications, such as catalyst supports or orthopedic implants, a rough surface or tiny outshoots on the surface of metal fibers to increase surface area are needed. However, it has not been concerned about the surface morphologies of metal fiber in the current research of metal fiber manufacturing. In this paper, a special multi-tooth tool composed of a row of triangular tiny teeth is designed. The entire cutting layer of multi-tooth tool bifurcates into several thin cutting layers due to tiny teeth involved in cutting. As a result, several stainless steel fibers with periodic micro-fins are produced simultaneously. Morphology of periodic micro-fins is found to be diverse and can be classified into three categories: unilateral plane, unilateral tapering and bilateral. There are two forming mechanisms for the micro-fins. One is that periodic burrs remained on the free side of cutting layer of a tiny tooth create micro-fins of stainless steel fiber produced by the next neighboring tiny tooth; the other is that the connections between two fibers stuck together come to be micro-fins if the two fibers are finally detached. Influence of cutting conditions on formation of micro-fins is investigated. Experimental results show that cutting depth has no significant effect on micro-fin formation, high cutting speed is conducive to micro-fin formation, and feed should be between 0.12 mm/r and 0.2 mm/r to reliably obtain stainless steel fiber with micro-fins. This research presents a new pattern of stainless steel fiber characterized by periodic micro-fins formed on the edge of fiber and its manufacturing method.

  7. Formation of nanostructure on hair surface: its characteristic optical properties and application to hair care products.

    Science.gov (United States)

    Watanabe, Shunsuke; Sato, Hirayuki; Shibuichi, Satoshi; Okamoto, Masayuki; Inoue, Shigeto; Satoh, Naoki

    2007-01-01

    Uneven structures on hair fiber surface, such as lift up of cuticle or build up of hair spray ingredients, generally cause a diffuse reflection which results in a dull and unhealthy appearance. However, in the case of finer structure than wavelength of visible light, the optical properties change significantly. An application of the phenomenon to hair care products is reported in this paper. Formation of the fine structure on hair surface was achieved by only a shampoo and rinse-off conditioner system including amino-silicone. Chroma enhancement of hair and light introduction into hair fibers were observed simultaneously with formation of the fine structure on the hair surface. The light introduction phenomenon is understood in terms of "Effective Medium Approximation" (EMA). The simulation study based on EMA indicates that a very low refractive index surface is expected to be realized, which well explains the optical experimental results. When the shampoo and conditioner system developed to form the structure on fiber surface was applied to dyed hair, enhancement and long-lasting of vivid appearance was confirmed in spite of dye elution.

  8. Age-related characteristics of risky decision-making and progressive expectation formation.

    Science.gov (United States)

    Kardos, Zsófia; Kóbor, Andrea; Takács, Ádám; Tóth, Brigitta; Boha, Roland; File, Bálint; Molnár, Márk

    2016-10-01

    During daily encounters, it is inevitable that people take risks. Investigating the sequential processing of risk hazards involve expectation formation about outcome contingencies. The present study aimed to explore risk behavior and its neural correlates in sequences of decision making, particularly in old age, which represents a critical period regarding risk-taking propensity. The Balloon Analogue Risk Task was used in an electrophysiological setting with young and elderly age groups. During the task each additional pump on a virtual balloon increased the likelihood of a balloon burst but also increased the chance to collect more reward. Event-related potentials associated with rewarding feedback were analyzed based on the forthcoming decisions (whether to continue or to stop) in order to differentiate between states of expectation towards gain or loss. In the young, the reward positivity ERP component increased as a function of reward contingencies with the largest amplitude for rewarding feedback followed by the decision to stop. In the elderly, however, reward positivity did not reflect the effect of reward structure. Behavioral indices of risk-taking propensity suggest that the performance of the young and the elderly were dissociable only with respect to response times: The elderly was characterized by hesitation and more deliberative decision making throughout the experiment. These findings signify that sequential tracking of outcome contingencies has a key role in cost-efficient action planning and progressive expectation formation.

  9. Characteristics of Growth and Yield Formation of Rice in Rice-Fish Farming System

    Institute of Scientific and Technical Information of China (English)

    YANG Yong; ZHANG Hong-cheng; HU Xiao-jun; DAI Qi-gen; ZHANG Yong-jiang

    2006-01-01

    By using single rice cultivation as a control, the effect of rice-fish culture on growth dynamic, plant type and yield formation of rice was studied. The results showed as follows: rice-fish culture improved the physical-chemical properties of arable layer soil of paddy field, extended growth period of rice, increased dry matter and LAI of different growth stages,improved three top leaves area, deterred the degeneration of leaves function, increased the diameter of stem, promoted the growth of roots and the formation of roots in the extended stem. At the same time, rice-fish culture extended the length of basal internodes, increased the number of internodes, uplifted the gravity of plant, and depressed the root vigor. For the grain yield and yield structure of rice, rice-fish culture decreased ear/tillering ratio, spikelet/panicle and seed set percentage,increased grain weight. If variety choice and cultivation technology were controlled appropriately, rice-fish culture could increase the effective panicles and improve grain yield of rice.

  10. Pulse formation and characteristics of the cw mode-locked titanium-doped sapphire laser

    Science.gov (United States)

    Zschocke, Wolfgang; Stamm, Uwe; Heumann, Ernst; Ledig, Mario; Guenzel, Uwe; Kvapil, Jiri; Koselja, Michael P.; Kubelka, Jiri

    1991-10-01

    We report on measurements of transient and steady-state pulse characteristics of an acousto- optically mode-locked titanium-doped sapphire laser. During the pulse evolution, oscillations in the pulse width and pulse energy are found. A steady state is reached after about 40 to 60 microsecond(s) . The steady-state pulse width is strongly influenced by the mode-locking loss as well as the intracavity bandwidth. Shortest pulses of typically 15 ps are obtained. The experiment is compared with results of a simple computer simulation.

  11. The Characteristics,Cause of Formation and Countermeasures of Migrant Workers’ Poverty

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The migrant worker is the special group in the process of Chinese economic and social transition.The migrant workers’ poverty has the characteristics as follows:transferability,marginality,intervention,aggregation,development,circulatory cumulativeness and intergenerational transmission of poverty.The migrant workers’ poverty includes capital poverty,right poverty and sustainability poverty.The capital poverty and right poverty hamper migrant workers’ survival,development and farmer’s citizenship,while the sustainability poverty is the root cause of poverty.Only by system reconstruction,endowment of capital and restoration of ability can the migrant workers get rid of the mire of poverty.

  12. Pseudomonas aeruginosa Aggregate Formation in an Alginate Bead Model System Exhibits In Vivo-Like Characteristics.

    Science.gov (United States)

    Sønderholm, Majken; Kragh, Kasper Nørskov; Koren, Klaus; Jakobsen, Tim Holm; Darch, Sophie E; Alhede, Maria; Jensen, Peter Østrup; Whiteley, Marvin; Kühl, Michael; Bjarnsholt, Thomas

    2017-05-01

    Alginate beads represent a simple and highly reproducible in vitro model system for diffusion-limited bacterial growth. In this study, alginate beads were inoculated with Pseudomonas aeruginosa and followed for up to 72 h. Confocal microscopy revealed that P. aeruginosa formed dense clusters similar in size to in vivo aggregates observed ex vivo in cystic fibrosis lungs and chronic wounds. Bacterial aggregates primarily grew in the bead periphery and decreased in size and abundance toward the center of the bead. Microsensor measurements showed that the O2 concentration decreased rapidly and reached anoxia ∼100 μm below the alginate bead surface. This gradient was relieved in beads supplemented with NO3(-) as an alternative electron acceptor allowing for deeper growth into the beads. A comparison of gene expression profiles between planktonic and alginate-encapsulated P. aeruginosa confirmed that the bacteria experienced hypoxic and anoxic growth conditions. Furthermore, alginate-encapsulated P. aeruginosa exhibited a lower respiration rate than the planktonic counterpart and showed a high tolerance toward antibiotics. The inoculation and growth of P. aeruginosa in alginate beads represent a simple and flexible in vivo-like biofilm model system, wherein bacterial growth exhibits central features of in vivo biofilms. This was observed by the formation of small cell aggregates in a secondary matrix with O2-limited growth, which was alleviated by the addition of NO3(-) as an alternative electron acceptor, and by reduced respiration rates, as well as an enhanced tolerance to antibiotic treatment.IMPORTANCEPseudomonas aeruginosa has been studied intensively for decades due to its involvement in chronic infections, such as cystic fibrosis and chronic wounds, where it forms biofilms. Much research has been dedicated to biofilm formation on surfaces; however, in chronic infections, most biofilms form small aggregates of cells not attached to a surface, but embedded in

  13. Junction formation and characteristics of CdS/CuInSe[sub 2]/metal interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Ashour, S. (Girls Coll., Science Branch, Riyadh (Saudi Arabia)); Alkuhaimi, S. (Girls Coll., Science Branch, Riyadh (Saudi Arabia)); Moutinho, H. (National Renewable Energy Lab., Golden, CO (United States)); Matson, R. (National Renewable Energy Lab., Golden, CO (United States)); Abou-Elfotouh, F. (National Renewable Energy Lab., Golden, CO (United States))

    1993-04-15

    Polycrystalline thin films of CuInSe[sub 2] (CIS) were prepared by galvanic electrochemical (EC) and physical vapor deposition (PVD) methods and were characterized using high resolution photoluminescence at low temperatures to study defect states, scanning electron microscopy to study surface morphology, and transmission electron microscopy to determine the grain size and individual crystallographic orientation of the grains for possible correlation between the properties of the two films. Metal contacts, Schottky devices in the form of Al/p-CIS, and CdS/p-CIS heterostructures were also prepared. The electrical properties of the resulting interfaces were investigated using current-voltage (I-V) and capacitance-voltage (C-V) characteristics, and by electron-beam-induced current measurements. Devices prepared from PVD films exhibited a higher generation factor G, sharp interfaces and the lowest density of interface states. On the contrary, devices of low G values (made from EC films) showed a much higher density of interface states with a high density of both shallow and deep traps, as detected by deep level transient spectroscopy. The results were used to correlate the resulting variation in the heterojunction characteristics and back contact behavior with the corresponding defect states dominating the CIS. (orig.)

  14. Coulomb excitations of monolayer germanene

    Science.gov (United States)

    Shih, Po-Hsin; Chiu, Yu-Huang; Wu, Jhao-Ying; Shyu, Feng-Lin; Lin, Ming-Fa

    2017-01-01

    The feature-rich electronic excitations of monolayer germanene lie in the significant spin-orbit coupling and the buckled structure. The collective and single-particle excitations are diversified by the magnitude and direction of transferred momentum, the Fermi energy and the gate voltage. There are four kinds of plasmon modes, according to the unique frequency- and momentum-dependent phase diagrams. They behave as two-dimensional acoustic modes at long wavelength. However, for the larger momenta, they might change into another kind of undamped plasmons, become the seriously suppressed modes in the heavy intraband e–h excitations, keep the same undamped plasmons, or decline and then vanish in the strong interband e–h excitations. Germanene, silicene and graphene are quite different from one another in the main features of the diverse plasmon modes. PMID:28091555

  15. Gas geochemistry characteristic of shale gas in Longmaxi Formation, SE Sichuan Basin, China

    Science.gov (United States)

    Cao, Chunhui; Du, Li; Li, Liwu; He, Jian; Li, Zhongping

    2017-01-01

    Shale gas samples collected from Lower Silurian Longmaxi Formation of Southern Sichuan Basin in Weiyuan were analysed for stable isotope composition of noble gases and molecular composition, stable carbon isotope composition of hydrocarbons. Results show these shale gases are of organic origin gas, and produced at high-over maturity stage. All the analysed hydrocarbon gases reveal complete inversed isotopic trends from methane to propane, and δ13C1, δ13C2 have obviously different between Weiyuan and Changning areas. CO2 was mainly generated during thermogenic processes of transformation of organic matter, although some gases can contain components from endogenic processes and from thermal destruction of carbonates. He and Ar are mainly product of α-decay of U and Th enriched in crustal materials. A small contribution of mantle origin He was found in the gas reservoirs. Continuous monitoring data indicate 3He/4He ratio didn’t change with the mining time.

  16. Spectral characteristics of banded iron formations in Singhbhum craton, eastern India: Implications for hematite deposits on Mars

    Directory of Open Access Journals (Sweden)

    Mahima Singh

    2016-11-01

    Full Text Available Banded iron formations (BIFs are major rock units having hematite layers intermittent with silica rich layers and formed by sedimentary processes during late Archean to mid Proterozoic time. In terrestrial environment, hematite deposits are mainly found associated with banded iron formations. The BIFs in Lake Superior (Canada and Carajas (Brazil have been studied by planetary scientists to trace the evolution of hematite deposits on Mars. Hematite deposits are extensively identified in Meridiani region on Mars. Many hypotheses have been proposed to decipher the mechanism for the formation of these deposits. On the basis of geomorphological and mineralogical studies, aqueous environment of deposition is found to be the most supportive mechanism for its secondary iron rich deposits. In the present study, we examined the spectral characteristics of banded iron formations of Joda and Daitari located in Singhbhum craton in eastern India to check its potentiality as an analog to the aqueous/marine environment on Mars. The prominent banding feature of banded iron formations is in the range of few millimeters to few centimeters in thickness. Fe rich bands are darker (gray in color compared to the light reddish jaspilitic chert bands. Thin quartz veins (<4 mm are occasionally observed in the hand-specimens of banded iron formations. Spectral investigations have been conducted in VIS/NIR region of electromagnetic spectrum in the laboratory conditions. Optimum absorption bands identified include 0.65, 0.86, 1.4 and 1.9 μm, in which 0.56 and 0.86 μm absorption bands are due to ferric iron and 1.4 and 1.9 μm bands are due to OH/H2O. To validate the mineralogical results obtained from VIS/NIR spectral radiometry, laser Raman and Fourier transform infrared spectroscopic techniques were utilized and the results were found to be similar. Goethite-hematite association in banded iron formation in Singhbhum craton suggests dehydration activity, which has

  17. Spectral characteristics of banded iron formations in Singhbhum craton, eastern India:Implications for hematite deposits on Mars

    Institute of Scientific and Technical Information of China (English)

    Mahima Singh; Jayant Singhal; K. Arun Prasad; V.J. Rajesh; Dwijesh Ray; Priyadarshi Sahoo

    2016-01-01

    Banded iron formations (BIFs) are major rock units having hematite layers intermittent with silica rich layers and formed by sedimentary processes during late Archean to mid Proterozoic time. In terrestrial environment, hematite deposits are mainly found associated with banded iron formations. The BIFs in Lake Superior (Canada) and Carajas (Brazil) have been studied by planetary scientists to trace the evo-lution of hematite deposits on Mars. Hematite deposits are extensively identified in Meridiani region on Mars. Many hypotheses have been proposed to decipher the mechanism for the formation of these deposits. On the basis of geomorphological and mineralogical studies, aqueous environment of deposi-tion is found to be the most supportive mechanism for its secondary iron rich deposits. In the present study, we examined the spectral characteristics of banded iron formations of Joda and Daitari located in Singhbhum craton in eastern India to check its potentiality as an analog to the aqueous/marine envi-ronment on Mars. The prominent banding feature of banded iron formations is in the range of few millimeters to few centimeters in thickness. Fe rich bands are darker (gray) in color compared to the light reddish jaspilitic chert bands. Thin quartz veins (<4 mm) are occasionally observed in the hand-specimens of banded iron formations. Spectral investigations have been conducted in VIS/NIR region of electromagnetic spectrum in the laboratory conditions. Optimum absorption bands identified include 0.65, 0.86, 1.4 and 1.9 mm, in which 0.56 and 0.86 mm absorption bands are due to ferric iron and 1.4 and 1.9 mm bands are due to OH/H2O. To validate the mineralogical results obtained from VIS/NIR spectral radiometry, laser Raman and Fourier transform infrared spectroscopic techniques were utilized and the results were found to be similar. Goethite-hematite association in banded iron formation in Singhbhum craton suggests dehydration activity, which has altered the primary

  18. Buckling in polymer monolayers: Molecular-weight dependence

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, S.; Basu, J.K.; (IIS)

    2010-11-12

    We present systematic investigations of buckling in Langmuir monolayers of polyvinyl acetate formed at the air-water interface. On compression the polymer monolayers are converted to a continuous membrane with a thickness of {approx}2-3 nm of well-defined periodicity, {lambda}{sub b}. Above a certain surface concentration the membrane undergoes a morphological transition buckling, leading to the formation of striped patterns. The periodicity seems to depend on molecular weight as per the predictions of the gravity-bending buckling formalism of Milner et al. for fluidlike films on water. However anomalously low values of bending rigidity and Young's modulus are obtained using this formalism. Hence we have considered an alternative model of buckling-based solidlike films on viscoelastic substrates. The values of bending rigidity and Young's modulus obtained by this method, although lower than expected, are closer to the bulk values. Remarkably, no buckling is found to occur above a certain molecular weight. We have tried to explain the observed molecular-weight dependence in terms of the variation in isothermal compressive modulus of the monolayers with surface concentration as well as provided possible explanations for the obtained low values of mechanical properties similar to that observed for ultrathin polymer films.

  19. Fluorescence detection and imaging of amino-functionalized organic monolayer

    Energy Technology Data Exchange (ETDEWEB)

    Shirahata, Naoto [National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)], E-mail: SHIRAHATA.naoto@nims.go.jp; Furumi, Seiichi [National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Masuda, Yoshitake; Hozumi, Atsushi [National Institute of Advanced Industrial Science and Technology (AIST), 2266-98 Anagahora, Shimo-shidami, Moriyama, Nagoya 463-8560 (Japan); Sakka, Yoshio [National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)

    2008-03-03

    Amino-terminated organic monolayer formed on silicon covered with native oxide (SiO{sub 2}/Si) was directly visualized under observation with fluorescent microscopy. This successful fluorescence visualization was achieved by a combination of fluorescamine method and photopatterning of the amino-terminated surface. As a typical example, an amino-terminated self-assembled monolayer (SAM) was formed on SiO{sub 2}/Si substrate in a vapor of 12.5 vol.% solution of N-(6-aminohexyl)-3-aminopropyltrimethoxysilane [H{sub 2}N(CH{sub 2}){sub 6}NH(CH{sub 2}){sub 3}Si(OCH{sub 3}){sub 3}, AHAPS] diluted with absolute toluene. A micropattern of AHAPS-SAM was photolithographycally prepared using 172 nm vacuum ultraviolet (VUV) light under a reduced pressure of 10 Pa for 30 min through a photomask. The resultant micropattern composed of AHAPS- and SiOH-covered regions was provided to fluorescamine method. Due to a nonluminescence of fluorescamine itself under UV/visible irradiation, a fluorescent emission could not be observed on SiOH regions of the micropattern. In contrast, fluorescamine reacted with the outermost amino group of the AHAPS-SAM to give a fluorescent emission. A comprehensible fluorescence method for verifying formation of an amino-terminated organic monolayer has been developed.

  20. The research of propagation characteristic and formation of double half-Gaussian hollow beams

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    A new kind of hollow beams, double half-Gaussian hollow beams,was put forward. With the help of the Collins formula, the analytical equation of propagation and transformation of the hollow laser beams in free space was deduced. The simulation shows that the intensity exhibits the three-dimensional trap distribution in the near-field, while the double half-Gaussian hollow beams turn into solid laser beams when propagating a certain distance, which shows the characteristics of self-focus. The double half-Gaussian hollow beams were obtained by means of the dual-reflecting splitting optical system. The intensity of the vertical loop in different distances was tested, which shows that the analytical equation of propagation and transformation is in agreement with the result.

  1. The research of propagation characteristic and formation of double half-Gaussian hollow beams

    Institute of Scientific and Technical Information of China (English)

    DONG Yuan; ZHANG XiHe; NING GuoBin; JIN GuangYong; LIANG Wei; L(U) YanFei; ZHANG Kai

    2009-01-01

    A new kind of hollow beams, double half-Gaussian hollow beams, was put forward. With the help of the Collins formula, the analytical equation of propagation and transformation of the hollow laser beams in free space was deduced. The simulation shows that the intensity exhibits the three-dimensional trap distribution in the near-field, while the double half-Gaussian hollow beams turn into solid laser beams when propagating a certain distance, which shows the characteristics of self-focus. The double half-Gaussian hollow beams were obtained by means of the dual-reflecting splitting optical system. The intensity of the vertical loop in different distances was tested, which shows that the analytical equation of propagation and transformation is in agreement with the result.

  2. Flow characteristics and micro-scale metallic particle formation in the laser supersonic heating technique

    Science.gov (United States)

    Lin, Shih-Lung; Lin, Jehnming

    2007-02-01

    The characteristics of the supersonic flow of the laser heating technique for producing micro-scale metallic particles were investigated in this study. A numerical model was established to predict the flow fields and particle trajectories leaving a spray nozzle with shock wave effects. The compressible flow of the shock waves and the trajectories of particles in diameters of 1-20 μm were simulated and compared with the flow visualization. In the experiment, a pulsed Nd-YAG laser was used as heat source on a carbon steel target within the nozzle, and the carbon steel particles were ejected by high-pressure air. The result shows that the shock wave structures were generated at various entrance pressures, and there is a significant increase in the amount of carbon steel particles and the spraying angles by increasing the entrance air pressure.

  3. Chemical characteristics of waters in Karst Formations at the Oak Ridge Y-12 Plant

    Energy Technology Data Exchange (ETDEWEB)

    Shevenell, L.A. [Univ. of Nevada, Reno, NV (United States). Nevada Bureau of Mines and Geology

    1994-11-01

    Several waste disposal sites are located adjacent to or on a karst aquifer composed of the Cambrian Maynardville Limestone (Cmn) and the Cambrian Copper Ridge Dolomite (Ccr) at the U.S. Department of Energy Oak Ridge Y-12 Plant in Oak Ridge, TN. Highly variable chemical characteristics (i.e., hardness) can indicate that the portion of the aquifer tapped by a particular well is subject to a significant quick-flow component where recharge to the system is rapid and water levels and water quality change rapidly in response to precipitation events. Water zones in wells at the Y-12 Plant that exhibit quick-flow behavior (i.e., high hydraulic conductivity) are identified based on their geochemical characteristics and variability in geochemical parameters, and observations made during drilling of the wells. The chemical data used in this study consist of between one and 20 chemical analyses for each of 102 wells and multipart monitoring zones. Of these 102 water zones, 10 were consistently undersaturated with respect to calcite suggesting active dissolution. Repeat sampling of water zones shows that both supersaturation and undersaturation with respect to dolomite occurs in 46 water zones. Twelve of the zones had partial pressure of CO{sub 2} near atmospheric values suggesting limited interaction between recharge waters and the gases and solids in the vadose zone and aquifer, and hence, relatively short residence times. The preliminary data suggest that the Cmn is composed of a complicated network of interconnected, perhaps anastomosing, cavities. The degree of interconnection between the identified cavities is yet to be determined, although it is expected that there is a significant vertical and lateral interconnection between the cavities located at shallow depths in the Cnm throughout Bear Creek Valley and the Y-12 Plant area.

  4. Effect of Doping on Hydrogen Evolution Reaction of Vanadium Disulfide Monolayer

    Science.gov (United States)

    Qu, Yuanju; Pan, Hui; Kwok, Chi Tat; Wang, Zisheng

    2015-12-01

    As cheap and abundant materials, transitional metal dichalcogenide monolayers have attracted increasing interests for their application as catalysts in hydrogen production. In this work, the hydrogen evolution reduction of doped vanadium disulfide monolayers is investigated based on first-principles calculations. We find that the doping elements and concentration affect strongly the catalytic ability of the monolayer. We show that Ti-doping can efficiently reduce the Gibbs free energy of hydrogen adsorption in a wide range of hydrogen coverage. The catalytic ability of the monolayer at high hydrogen coverage can be improved by low Ti-density doping, while that at low hydrogen coverage is enhanced by moderate Ti-density doping. We further show that it is much easier to substitute the Ti atom to the V atom in the vanadium disulfide (VS2) monolayer than other transitional metal atoms considered here due to its lowest and negative formation energy. It is expected that the Ti-doped VS2 monolayer may be applicable in water electrolysis with improved efficiency.

  5. Methymercury Formation in Marine and Freshwater Systems: Sediment Characteristics, Microbial Activity and SRB Phylogeny Control Formation Rates and Food-Chain Exposure

    Science.gov (United States)

    King, J. K.; Saunders, F. M.

    2004-05-01

    Mercury research in freshwater and marine systems suggests that sediment characteristics such as organic substrate, mercury speciation, and sulfate/sulfide concentrations influence availability of inorganic mercury for methylation. Similarly, sediment characteristics also influence sulfate-reducing bacterial (SRB) respiration as well as the presence/distribution of phylogenetic groups responsible for mercury methylation. Our work illustrates that the process of methylmercury formation in freshwater and marine systems are not dissimilar. Rather, the same geochemical parameters and SRB phylogenetic groups determine the propensity for methylmercury formation and are applicable in both fresh- and marine-water systems. The presentation will include our integration of sediment geochemical and microbial parameters affecting mercury methylation in specific freshwater and marine systems. Constructed wetlands planted with Schoenoplectus californicus and amended with gypsum (CaSO4) have demonstrated a capacity to remove inorganic mercury from industrial outfalls. However, bioaccumulation studies of periphyton, eastern mosquitofish (Gambusia holbrooki) and lake chubsucker (Erimyzon sucetta) were conducted in order to ascertain the availability of wetland-generated methylmercury to biota. Total mercury concentrations in mosquitofish from non-sulfate treated controls and the reference location were significantly lower than those from the low and high sulfate treatments while mean total mercury concentrations in lake chubsuckers were also significantly elevated in the high sulfate treatment compared to the low sulfate, control and reference populations. Methylmercury concentrations in periphyton also corresponded with mercury levels found in the tissue of the lake chubsuckers, and these findings fit well given the trophic levels identified for both species of fish. Overall, data from this study suggest that the initial use of gypsum to accelerate the maturity of a constructed

  6. Microstructure characteristics of illite from Chuanlinggou Formation of Changcheng System in Jixian County, Tianjin City

    Institute of Scientific and Technical Information of China (English)

    CHEN; Tao; WANG; HeJing

    2007-01-01

    The microstructure charateristics of illite from the Chuanlinggou Formation of Changcheng System (Chch) in Jixian County, Tianjin City has been studied by means of high-resolution transmission electron microscopy (HRTEM), selected-area electron diffraction (SAED), X-ray energy dispersive spectrum (EDS) and X-ray powder diffraction (XRD). The Kübler index of "illite crystallinity" is 0.505°△2θ, which indicates that the host rock is in a middle diagenetic stage. The chemical analyses of EDS for illite studied indicate a heavily absent in interlayer cation and an average chemical formula of K0.57(Al1.80Mg0.42Fe2+0.12)∑=2.34 (Si2.92Al1.08)∑=4O10(OH)2. It is found, from one-dimensional lattice images, that the layers of illite not only stack in a flat way but also in a curving way. A "matting fabric" illite structure results from stacking faults. Combined with SAED analysis the illite studied can be affirmed as 1M illite. The two-dimensional lattice images are obtained from [100] and [110] incidences, whose lattice images have the same d-values but different intersecting angles. The two-dimensional lattice image with [100] incidence is orthogonal to each other, whilst that with [110] incidence is oblique. This paper provides some important structure information of authigenic clay minerals for the well-known mesoproterozoic section of Jixian County.

  7. Formation and characteristics of patterns in atmospheric-pressure radio-frequency dielectric barrier discharge plasma

    Science.gov (United States)

    Yang, Lizhen; Liu, Zhongwei; Mao, Zhiguo; Li, Sen; Chen, Qiang

    2017-01-01

    The patterns in radio-frequency dielectric barrier discharge (RF DBD) are studied at atmospheric pressure of argon (Ar) or helium (He) mixed with nitrogen (N2) gas. When a small amount of N2 is mixed with He or Ar gas, discharge patterns are formed. In a N2/He gas mixture, besides the filament discharge that forms patterns, a glow background discharge is also observed, whereas only the filament discharge forms patterns in a N2/Ar gas mixture. The resolution of the hexagonal pattern as a function of applied power and gas flow rate is then explored. On the basis of spatial-temporal images taken using an intensified charge-coupled device (ICCD), we find that there is no interleaving of two transient hexagon sublattices in N2/Ar or N2/He plasma in RF DBD patterns, which are totally different from those in which surface charges dominated in the mid-frequency DBD plasma. This supports our hypothesis that the bulk charges dominate the pattern formation in RF DBD.

  8. Geochemical Characteristics and its Geological Significance of Oil Shale from the Youganwo Formation, Maoming Basin, China

    Science.gov (United States)

    Zhou, Yuanyuan; Qiu, Nansheng

    2016-04-01

    Geochemical elements of oil shale in the Maoming Basin were analyzed to discuss provenance attribute and depositional environment of the Youganwo formation. Experimental date of the major elements, trace elements and rare earth elements of 24 samples from the Maoye 1 well were examined.The analyzed oil shale samples were characterized by enrichment of Th, U, Pb and LREE, depleted of Zr, Cr and Hf,negative Eu and Ce anomalies, indicating that these samples were originated from continental crust. The chemical index of alteration (CIA) values and the Zr/Sc-Th/Sc diagrams indicate that source rocks had undergone intense chemical weathering and deposition recirculation. Based on the La/Th-Hf and La/Yb-∑REE diagrams and the negative anomaly of Eu element, the oil shale in the Maoming Basin has diverse sources, which mainly came from felsic source region of the upper crust or the mixture of felsic volcanic rocks, granite and sedimentary rocks. Ratios of the Sr/Cu, MgO/CaO suggest that oil shale was formed in fresh water under warm and humid climate, shallow water column became deeper during the middle and late sedimentary period. The depositional environment is interpreted to be limnetic with weak reduction at the early stage and gradually turned into semi-deep to deep lacustrine.

  9. Geochemical Characteristics of REE in Jurassic Coal of Yan'an Formation from Dongsheng Coalfield

    Institute of Scientific and Technical Information of China (English)

    赵峰华; 丛志远; 彭苏萍; 唐跃刚; 任德贻

    2002-01-01

    Concentrations of rare earth elements (REE) in Jurassic coal of YanAn Formation from Dongsheng coalfield located in the northeast of Ordos basin were determined by instrumental neutron activation analysis (INAA). Curves of distrib ution pattern of REE were drawn, and many geochemical parameters were calculated . The result shows that 1) The contents of REE in Jurassic coal with low ash an d sulfur are lower than those of Carboniferous and Permian coal from the Basin of North China; 2) Inside the Dongsheng coalfield, coal from the north has high er contents of REE than that form the south because the north is near the area of source rock which is the main supplier of REE, while the south is far away from the area of source rocks; 3) Although Jurassic coal in Dongsheng is the low-ash coal with less than 10%, the contents of REE are still proportional to ash yie ld of ash and SiO2 contents. 4) Although the Jurassic coal in Dongsheng were deposited in oxidative continental environment of river-lake, Eu depletion of RE E I n coal commonly exists, and positive abnormity of Ce dose not exist. This reflec ts the REE distribution pattern of REE in source rock of continental area; and 5) Compared with other rocks, coal shows extremely complexity of distribution pa ttern of REE, which is the result of continuous alteration and redistribution of matter in coal occurred in open basin system.

  10. Characteristics of the Triassic Source Rocks of the Aitutu Formation in the (West Timor Basin

    Directory of Open Access Journals (Sweden)

    Asep Kurnia Permana

    2014-12-01

    Full Text Available DOI:10.17014/ijog.v1i3.192The Triassic rocks of the (West Timor Basin have been identified that was mainly deposited in the  marine environment. The fine grained clastics and carbonate  rocks of this Triassic marine  facies are considered to be the most promising source rocks potential in this basin. In this paper we present geochemical and petrographic data from outcrop samples of the Triassic carbonate Aitutu Formation, due to emphasized the organic maturation, kerogen type of the organic matter and the origin of the organic matter.  A representative of selected sample were subjected to the Rock-Eval Pyrolisis, vitrinite reflectance and thermal alteration index, bitumen extraction, were analyzed on the GC-MS. The samples were collected from marine deposit of the Triassic Sequence. The TOC values of the analyzed sample range between rich and rich organic richness (0.51% - 9.16%, wt.%, TOC, which consists mainly of type II and III kerogen and the organic matter consider to be predominantly oil/gas prone and gas prone potential. The thermal maturity assessed from Tmax, TAI, and vitrinite reflectance shows an immature to early peak mature stage of the organic matter. The GC-MS analyses of the biomarkers indicate mainly the organic matter derived from mixed source rocks facies containing alga debris and higher plant terrestrial origin.

  11. Dense Gas and Star Formation Characteristics of Cloud Cores Associated with Water Masers

    CERN Document Server

    Plume, R; Evans, N J; Martín-Pintado, J; Gómez-González, J; Plume, Rene; II, Neal J. Evans

    1996-01-01

    We have observed 150 regions of massive star formation, selected originally by the presence of a water maser, in the J = 5-4, 3-2, and 2-1 transitions of CS, and 49 regions in the same transitions of C$^{34}$S. Over 90% of the 150 regions were detected in the J = 2-1 and 3-2 transitions of CS and 75% were detected in the J=5-4 transition. We have combined the data with the J = 7-6 data from our original survey (Plume et al. 1992) to determine the density by analyzing the excitation of the rotational levels. Using Large Velocity Gradient (LVG) models, we have determined densities and column densities for 71 of these regions. The gas densities are very high (the mean log of the density is 5.9), but much less than the critical density of the J=7-6 line. Small maps of 25 of the sources in the J = 5-4 line yield a mean diameter of 1.0 pc. The mean virial mass is 3800 solar masses. The mean ratio of bolometric luminosity to virial mass (L/M) is 190, about 50 times higher than estimates using CO emission, suggesting...

  12. Surface characteristics of HA coated Ti-Hf binary alloysafter nanotube formation

    Institute of Scientific and Technical Information of China (English)

    Yong-Hoon JEONG; Won-Gi KIM; Geun-Hyeong PARK; Han-Cheol CHOE; Yeong-Mu KO

    2009-01-01

    Ti-Hf binary alloys contained 10%, 20%, 30% and 40% (mass fraction)Hf were manufactured in the vacuum furnace system. And then, specimens were homogenized for 24 h at 1 000 ℃ in argon atmosphere. The formation of oxide nanotubes was conducted by anodic oxidation on the Ti-Hf alloy in 1 mol/L H3PO4 electrolytes containing small amounts of NaF at room temperature. The hydroxyapatite (HA) coating made of tooth ash prepared by electron-beam physical vapor deposition (EB-PVD) method. The corrosion behaviors of the specimens were examined through potentiodynamic test in 0.9% NaCl solution by potentiostat. The microstructures of the alloys were examined by field emission scanning electron microscopy (FE-SEM) and x-ray diffractometer (XRD). It was observed that the lamellar structure translated to needle-like structure with Hf contents. Nanotube formed and HA coated Ti-xHf alloys had a good corrosion resistance.

  13. Geochemical characteristics and petrogenesis of volcanic rocks from Baiyingaolao Formation in northeastern Hailar Basin

    Institute of Scientific and Technical Information of China (English)

    LI Xu; SUN Deyou; GOU Jun

    2016-01-01

    The volcanic rocks from Baiyingaolao Formation in the northeastern Hailar Basin are mainly com-posed of rhyolite and trachydacite.U-Pb dating of zircon shows these volcanic rocks formed in Early Cretaceous (128-124 Ma).Geochemical data indicate that they are sub-alkaline series in composition and rich in alkali and potassium.All samples have similar rare earth element patterns characterized by high total rare earth ele-ments contents (∑REE=113.96 ×10 -6-204.33 ×10 -6),significant fractionation of heavy and light rare earth elements (∑LREE/∑HREE =3.10-4.52)with middle negative Eu anomalies (δEu=0.46-0.76). The trace elements are characterized by enrichment in large-ion lithophile elements such as K,Rb,LREE and depletion in high field strength elements e.g.Nb,Ta,HREE,P and Ti,while enriched in Th and U.Rhyolite and trachydacite contain low initial 87Sr/86Sr ratios (0.704 9-0.7 053)and positive εNd(t)values (ca.4. 15).These data suggest that the magma of rhyolite and trachydacite were derived from mafic lower crust newly accreted from mantle,with the evolutional trend of comagmatic fractional crystallization.

  14. [Hydrochemical characteristics and formation mechanism of shallow groundwater in the Yellow River Delta].

    Science.gov (United States)

    An, Le-Sheng; Zhao, Quan-Sheng; Ye, Si-Yuan; Liu, Guan-Qun; Ding, Xi-Gui

    2012-02-01

    Understanding the chemical characteristics of groundwater in the Yellow River Delta is very important. It can provide a useful reference for the development and construction of the Yellow River Delta High-efficiency Ecological Economic Zone and ecological regulation in the lower Yellow River. Based on partitioning the sediment environment and the recharge-runoff-discharge system, we studied the hydrochemical features and causes of shallow groundwater in the Yellow River Delta by mathematical statistics and geostatistics, Piper diagram, ion ratios and so on. Following results are obtained: 1) Major cations and anions such as Na+, Mg2+, Ca2+, Cl(-), SO4(2-), HCO3(-) and TDS concentrations range from 0.1-25.0 g x L(-1), 3.6-3 815.0 mg x L(-1), 5.6-3 377.0 mg x L(-1), 0.1-45.1 g x L(-1), 24.2-4 947.0 mg x L(-1), 62.6-850.0 mg x L(-1) and 0.4-80.7 g x L(-1). Average ion concentrations further indicate that Cl(-), Na+ and TDS concentrations are high while HCO3(-), CO3(2-) and K+ concentrations are very low in the study area. 2) The Cl(-) and TDS concentrations of shallow groundwater possess conspicuous directional spatial variability and gradually increase along the groundwater flow direction, showing that Cl(-) is the most critical ion of shallow groundwater. 3) From the recharge area to the discharge area, shallow groundwater changes from the Na+ -Mg2+ -Ca2+ -Cl(-) -SO4(2-) facies to the Na -Mg2 + -Ca2+ -Cl(-), Mg2+ -Na+ -Ca2+ -Cl(-) and Na+ -Mg2+ -Cl(-) facies, finally evolves into Na+ -Cl(-) facies in the coast. 4) Ion ratios indicate that the following main hydrochemical processes are inferred to control the shallow groundwater chemical composition: mixing, evaporation concentrating, mineral dissolution, cation exchange and adsorption and human activities. These findings strongly suggest that changes of the Yellow River water course and seawater intrusion are key drivers to form the chemical characteristics of shallow groundwater in the region.

  15. Monolayer MoS2 self-switching diodes

    Science.gov (United States)

    Al-Dirini, Feras; Hossain, Faruque M.; Mohammed, Mahmood A.; Hossain, Md Sharafat; Nirmalathas, Ampalavanapillai; Skafidas, Efstratios

    2016-01-01

    This paper presents a new molybdenum disulphide (MoS2) nanodevice that acts as a two-terminal field-effect rectifier. The device is an atomically-thin two-dimensional self-switching diode (SSD) that can be realized within a single MoS2 monolayer with very minimal process steps. Quantum simulation results are presented confirming the device's operation as a diode and showing strong non-linear I-V characteristics. Interestingly, the device shows p-type behavior, in which conduction is dominated by holes as majority charge carriers and the flow of reverse current is enhanced, while the flow of forward current is suppressed, in contrast to monolayer graphene SSDs, which behave as n-type devices. The presence of a large bandgap in monolayer MoS2 results in strong control over the channel, showing complete channel pinch-off in forward conduction, which was confirmed with transmission pathways plots. The device exhibited large leakage tunnelling current through the insulating trenches, which may have been due to the lack of passivation; nevertheless, reverse current remained to be 6 times higher than forward current, showing strong rectification. The effect of p-type substitutional channel doping of sulphur with phosphorus was investigated and showed that it greatly enhances the performance of the device, increasing the reverse-to-forward current rectification ratio more than an order of magnitude, up to a value of 70.

  16. Monolayer MoS{sub 2} self-switching diodes

    Energy Technology Data Exchange (ETDEWEB)

    Al-Dirini, Feras, E-mail: alf@unimelb.edu.au; Hossain, Md Sharafat [Department of Electrical and Electronic Engineering, University of Melbourne, Victoria (Australia); Centre for Neural Engineering, University of Melbourne, Victoria (Australia); Victorian Research Laboratory, National ICT Australia, West Melbourne, Victoria (Australia); Hossain, Faruque M.; Skafidas, Efstratios [Department of Electrical and Electronic Engineering, University of Melbourne, Victoria (Australia); Centre for Neural Engineering, University of Melbourne, Victoria (Australia); Mohammed, Mahmood A. [Princess Sumaya University for Technology, Amman (Jordan); Nirmalathas, Ampalavanapillai [Department of Electrical and Electronic Engineering, University of Melbourne, Victoria (Australia); Melbourne Networked Society Institute (MNSI), University of Melbourne, Victoria (Australia)

    2016-01-28

    This paper presents a new molybdenum disulphide (MoS{sub 2}) nanodevice that acts as a two-terminal field-effect rectifier. The device is an atomically-thin two-dimensional self-switching diode (SSD) that can be realized within a single MoS{sub 2} monolayer with very minimal process steps. Quantum simulation results are presented confirming the device's operation as a diode and showing strong non-linear I-V characteristics. Interestingly, the device shows p-type behavior, in which conduction is dominated by holes as majority charge carriers and the flow of reverse current is enhanced, while the flow of forward current is suppressed, in contrast to monolayer graphene SSDs, which behave as n-type devices. The presence of a large bandgap in monolayer MoS{sub 2} results in strong control over the channel, showing complete channel pinch-off in forward conduction, which was confirmed with transmission pathways plots. The device exhibited large leakage tunnelling current through the insulating trenches, which may have been due to the lack of passivation; nevertheless, reverse current remained to be 6 times higher than forward current, showing strong rectification. The effect of p-type substitutional channel doping of sulphur with phosphorus was investigated and showed that it greatly enhances the performance of the device, increasing the reverse-to-forward current rectification ratio more than an order of magnitude, up to a value of 70.

  17. Drug induced `softening' in phospholipid monolayers

    Science.gov (United States)

    Basak, Uttam Kumar; Datta, Alokmay; Bhattacharya, Dhananjay

    2015-06-01

    Compressibility measurements on Langmuir monolayers of the phospholipid Dimystoryl Phospatidylcholine (DMPC) in pristine form and in the presence of the Non-steroidal Anti-inflammatory Drug (NSAID) Piroxicam at 0.025 drug/lipid (D/L) molecular ratio at different temperatures, show that the monolayer exhibits large increase (and subsequent decrease) in compressibility due to the drug in the vicinity of the Liquid Expanded - Liquid Condensed (LE-LC) phase transition. Molecular dynamics simulations of the lipid monolayer in presence of drug molecules show a disordering of the tail tilt, which is consistent with the above result.

  18. Electrochemical Deposition Of Thiolate Monolayers On Metals

    Science.gov (United States)

    Porter, Marc D.; Weissharr, Duane E.

    1995-01-01

    Electrochemical method devised for coating metal (usually, gold) surfaces with adherent thiolate monolayers. Affords greater control over location and amount of material deposited and makes it easier to control chemical composition of deposits. One important potential use for this method lies in fabrication of chemically selective thin-film resonators for microwave oscillators used to detect pollutants: monolayer formulated to bind selectively pollutant chemical species of interest, causing increase in mass of monolayer and corresponding decrease in frequency of resonance. Another important potential use lies in selective chemical derivatization for purposes of improving adhesion, lubrication, protection against corrosion, electrocatalysis, and electroanalysis.

  19. Particle number size distribution and new particle formation:New characteristics during the special pollution control period in Beijing

    Institute of Scientific and Technical Information of China (English)

    Jian Gao; Fahe Chai; Tao Wang; Shulan Wang; Wenxing Wang

    2012-01-01

    New particle formation is a key process in shaping the size distribution of aerosols in the atmosphere.We present here the measurement results of number and size distribution of aerosol particles (10-10000 nm in diameter) obtained in the summer of 2008,at a suburban site in Beijing,China.We firstly reported the pollution level,particle number size distribution,diurnal variation of the particle number size distribution and then introduced the characteristics of the particle formation processes.The results showed that the number concentration of ultrafine particles was much lower than the values measured in other urban or suburban areas in previous studies.Sharp increases of ultrafine particle count were frequently observed at noon.An examination of the diurnal pattern suggested that the burst of ultrafine particles was mainly due to new particle formation promoted by photochemical processes.In addition,high relative humidity was a key factor driving the growth of the particles in the afternoon.During the 2-month observations,new particle formation from homogeneous nucleation was observed for 42.7% of the study period.The average growth rate of newly formed particles was 3.2 nm/hr,and varied from 1.2 to 8.0 nm/hr.The required concentration of condensable vapor was 4.4 × 107 cm-3,and its source rate was 1.2 × 106 cm-3sec-1.Further calculation on the source rate of sulphuric acid vapor indicated that the average participation of sulphuric acid to particle growth rates was 28.7%.

  20. Influence of lattice vibrations on luminescence and transfer of excitons in WS2 monolayer semiconductors

    Science.gov (United States)

    Wang, X. H.; Su, Z. C.; Ning, J. Q.; Wang, M. Z.; Xu, S. J.; Han, S.; Jia, F.; Zhu, D. L.; Lu, Y. M.

    2016-11-01

    Monolayers of transition metal dichalcogenides (TMDs) have been recently demonstrated to be a new family of direct bandgap semiconductors exhibiting extraordinary excitonic effects and high-efficiency luminescence. Here we present a micro-photoluminescence (PL) study on temperature dependent luminescence of excitons from an exfoliated WS2 monolayer. It is found that lattice vibrations (i.e. phonons) have a profound influence on the excitonic luminescence of the WS2 monolayer in several aspects including the spectral peak shift, lineshape broadening, transfer, and even formation entropy of excitons. Our study not only leads to the determination of the fundamental excitonic bandgap: {{E}\\text{g}}=2.061~ eV at T=0 \\text{K} , but also reveals that 120 K is a ‘turning’ temperature for the competition and formation entropy of free excitons and defect-bound excitons in the studied 2D WS2 crystals.

  1. The Sedimentary Characteristics and Formation Mechanism of Shell Ridges Along the Southwest Coast of Bohai Bay

    Institute of Scientific and Technical Information of China (English)

    LIU Zhijie; ZHUANG Zhenye; HAN Deliang; QI Xingfen

    2005-01-01

    The present paper studies the sedimentary characteristics and mechanism of the shell ridges on the southwestern coast of Bohai Bay, which are the largest and have the highest shell (or shell fragment) content in the world. These shell ridges are composed of two sedimentary subfacies: the ridge subfacies and the ridge infill subfacies with different inner textures and sedimentary structures. The ridge subfacies primarily consists of fresh shells and/or shell fragments with parallel beddings and high-angle oblique beddings. The ridge infill subfacies consists of finer shell fragments and silty sand with parallel beddings oblique to land. The evolution of the shell ridge is controlled by the accumulation of substantial shell material,the relative slow erosion of shoreline, storm waves, winds and the shift of river routes. Wind tunnel tests indicate that the critical movement velocity of shell is lower than that of quartz sand of the same grain size. Deltaic progradation alternates with shell ridge growth. While the Yellow River empties into the sea through this area, accompanied by deltaic progradating, the shell material is scarce, which is unfavorable to the growth of the shell ridge. Conversely, erosion occurs along an abandoned delta coast where a shell ridge may develop, e.g. the shell ridge on the southwest of Bohai Bay.

  2. Formation Mechanism and Characteristics Research of Ball Lightning Based on Vortex Model

    Institute of Scientific and Technical Information of China (English)

    LI Zi-Cheng; YANG Guo-Hua

    2011-01-01

    The strange characteristics of ball lightning are considered as a question hard to explain. In order to solve the problem, in this paper a complete model of plasma vortex is presented for the ball lightning. By ideal MHD equations,through imposing disturbance to plasma column, the possibility of sausage and kink instability of the lightning channel is analyzed from the perspective the minimum potential energy. The conclusion is that the kink instability (m = 1) is most prone to occur. And when instability occurs, because of the difference of the magnetic field in the twisted area,the magnetic pressure makes the trend further and therefore forming the plasma vortex that may eventually turn into ball lightning if the energy of the vortex is large enough. The existence of the vortex makes ball lightning have a short period of time stability. By the proposed model, the ball lightning features that are hard to understand in the past are explained. In this paper, the reason for bead lightning is also explained from the perspective of the sausage instability.

  3. Thermal behavior, structure formation and optical characteristics of nanostructured basic fuchsine thin films

    Energy Technology Data Exchange (ETDEWEB)

    Zeyada, H.M. [Department of Physics, Faculty of Science at New Damietta, Damietta University, 34517, New Damietta (Egypt); Makhlouf, M.M., E-mail: m_makhlof@hotmail.com [Department of Physics, Faculty of Science at New Damietta, Damietta University, 34517, New Damietta (Egypt); Department of Physics, Faculty of Applied Medical Sciences at Turabah Branch, Taif University, 21995 (Saudi Arabia); Department of Physics, Damietta Cancer Institute, Damietta (Egypt); Ismail, M.I.M.; Salama, A.A. [Department of Physics, Faculty of Science, Port Said University, Port Said (Egypt)

    2015-08-01

    Thin films of basic fuchsine, BF, are prepared by thermal evaporation technique. The data of thermal gravimetric analysis, TGA, showed that BF has a thermal stability up to the temperature of 265 °C. The structural characteristics of BF thin films are investigated by using X-ray diffraction, and atomic force microscope techniques. BF is polycrystalline in powder form; it becomes nanocrystallites in thin film condition. Annealing temperatures decreased crystallites size and influenced optical constants of BF films. Optical constants of BF films were estimated by using spectrophotometer measurements of transmittance and reflectance in the spectral range from 190 to 2500 nm. The dependence of absorption coefficient on the photon energy and annealing temperatures was determined and the analysis of the results showed that the optical transition in BF films is indirect allowed one. The onset and fundamental energy gap of BF thin films are 1.91 and 3.72 eV, respectively and they decrease by annealing temperatures. The optical dielectric constants and dispersion parameters of BF thin film are calculated and showed remarkable dependence on photon energy and annealing temperatures. - Graphical abstract: Display Omitted - Highlights: • Polycrystalline BF powder becomes nanocrystallites film upon thermal deposition. • BF has thermal stability up to 265 °C. • BF can be applied as optical filter material. • The type of electron transition is indirect allowed with E{sub g} of 1.91 eV. • Annealing temperatures influenced absorption and dispersion parameters of BF films.

  4. Membrane fouling in a membrane bioreactor (MBR): sludge cake formation and fouling characteristics.

    Science.gov (United States)

    Ping Chu, Hiu; Li, Xiao-Yan

    2005-05-05

    A submerged membrane bioreactor (MBR) with a working volume of 1.4 L and a hollow fiber microfiltration membrane was used to treat a contaminated raw water supply at a short hydraulic retention time (HRT) of approximately 1 h. Filtration flux tests were conducted regularly on the membrane to determine various fouling resistances, and confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) were employed to characterize the biofouling development and sludge cake formation on the membrane. The experimental results demonstrate that the MBR is highly effective in drinking water treatment for the removal of organic pollutants, ammonia, and UV absorbance. During the MBR operation, the fouling materials were not uniformly distributed on the entire surface of all of the membrane fibers. The membrane was covered partially by a static sludge cake that could not be removed by the shear force of aeration, and partially by a thin sludge film that was frequently washed away by aeration turbulence. The filtration resistance coefficients were 308.4 x 10(11) m(-1) on average for the sludge cake, 32.5 x 10(11) m(-1) on average for the dynamic sludge film, and increased from 10.5 x 10(11) to 59.7 x 10(11) m(-1) for the membrane pore fouling after 10 weeks of MBR operation at a filtration flux of 0.5 m3/m2 x d. Polysaccharides and other biopolymers were found to accumulate on the membrane, and hence decreased membrane permeability. More important, the adsorption of biopolymers on the membrane modified its surface property and led to easier biomass attachment and tighter sludge cake deposition, which resulted in a progressive sludge cake growth and serious membrane fouling. The sludge cake coverage on the membrane can be minimized by the separation, with adequate space, of the membrane filters, to which sufficient aeration turbulence can then be applied.

  5. The boundary layer characteristics in the heavy fog formation process over Beijing and its adjacent areas

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Guangzhi; BIAN; Lingeng; WANG; Jizhi; YANG; Yuanqi

    2005-01-01

    By utilizing the Atmospheric Boundary Layer (ABL) observational data made available from the project "973" under the auspices of the Ministry of Science and Technology of the People's Republic of China - entitled the Beijing City Air Pollution Observation Field Experiment (BECAPEX), including the measurements by a wind profiler, captive airships, tower-based boundary layer wind and temperature gradient observational instruments (ultrasonic anemometers and electronic thermometers), air composition samplers, conventional upper-air, surface and Automatic Weather Stations (AWS) observations, this paper herewith analyzes, in a comprehensive manner, the occurrence of a heavy fog event over Beijing in February 2001, including its formation, development, persistence, dynamic and thermodynamic features as well as evolving stratification structures within the boundary layer at different stages. The results suggested: (i) as a typical case of urban heavy fog, before the fog onset over Beijing, a temperature inversion existed in the lower atmosphere, the smokes and the pollutants like SO2 and NO2 had been accumulated at a lower level. Proceeding the fog event, with the increase of SO2 and NO2 concentrations, condensability increased sharply. On the contrary, during the fog process, with increasing condensability, SO2 and NO2 concentrations decreased. This indicated that, acting as condensation nucleus, these accumulated pollutants were playing a key role in catalyzing the fog condensation. (ii) By analyzing mean gradient-, pulsation- and turbulence-distribution patterns derived from the wind measurements taken by the aforementioned tower-based instruments, they all indicated that about 10 hours before the fog onset, a signal foretelling potential strong disturbances in the lower boundary layer was detected, and a significant rise of both mean and disturbance kinetic energies was observed, revealing that the low-level wind shear was strengthened before the fog onset

  6. Structural Characteristics and Formation Mechanism in the Micangshan Foreland,South China

    Institute of Scientific and Technical Information of China (English)

    XU Huaming; LIU Shu; QU Guosheng; LI Yanfeng; SUN Gang; LIU Kang

    2009-01-01

    Lying at the junction of the Dabashan,Longmenshan and Qinling mountains,the Micangshan Orogenic Belt coupled with a basin is a duplex structure and back-thrust triangular belt with little horizontal displacement,small thrust faults and continuous sedimentary cover.On the basis of 3D seismic data,and through sedimentary and structural research,the Micangshan foreland can be divided into five subbelts.which from north to south are:basement thrust,frontal thrust,foreland Along the direction of strike from west to east, the arcuate structural belt of Micangshan can be divided into west,middle and east segments.During the collision between the Qinling and Yangtze plates,the Micangshan Orogenic Belt was subjected to the interaction of three rigid terranes:Bikou, Foping,and Fenghuangshan(a.k.a.Ziyang)terranes.The collision processes of rigid terranes controlled the structural development of the Micangshan foreland,which are:(a)the former collision between the Micangshan.Hannan and Bikou terranes forming the earlier rudiments of the structure; and(b)the later collision forming the main body of the structural belt.The formation processes of the Micangshan Orogenic Belt call be divided into four stages:(1)in the early stage of the Indosinian movement,the Micangshan.Hannan Rigid Terrane was jointed to the Qinling Plate by the clockwise subduction of the Yangtze Plate toward the Qinling Plate;(2)since the late Triassic,the earlier rudiments of the Tongnanba and Jiulongshan anticlines and corresponding syncline were formed by compression from different directions of the Bikou.Foping and Micangshan-Hannan terranes;(3)in the early stage of the Himalayan movement,the Micangshan-Hannan Terrane formed the Micangshan Nappe torwards the foreland basin and the compression stresses were mainly concentrated along both its flanks,whereas the Micangshan-Hannan Terrane wedged into the Qinling Orogenic Belt with force;(4)in the late stage of the Himalayan movement,the main collision of the

  7. [Effects of straw incorporation on rice carbon sequestration characteristics and grain yield formation].

    Science.gov (United States)

    Pei, Peng-Gang; Zhang, Jun-Hua; Zhu, Lian-Feng; Yu, Sheng-Miao; Hu, Zhi-Hua

    2014-10-01

    A field experiment was conducted to study the effects of straw incorporation on rice dry matter accumulation and transportation, rice carbon sequestration and grain yield formation. The experiment included four levels of straw incorporation: 0 (control), 4000, 6000 and 8000 kg · hm(-2). Hybrid rice cultivar Zhongzheyou 1 was used in this experiment. The results showed that the average rice dry matter accumulation amount of the three straw incorporation treatments was increased by 63.03 g · m(-2) compared with the control, and that of straw incorporation of 6000 kg · hm(-2) showed the most favorable result, which was 154.40 g · m(-2) higher than the control. Effects of straw incorporation on rice dry matter accumulation showed the best performance from the maximum tillering stage to the full heading stage, and the dry matter accumulation at this stage was 71.25 g · m(-2) higher than the control. Compared with the control, the average dry matter exportation rate and apparent transformation rate from rice stem and leaf in the straw incorporation treatments were increased by 4.2% and 3.7%, respectively. The highest dry matter exportation rate and apparent transformation rate from rice stem and leaf were observed in the straw incorporation treatment of 6000 kg · hm(-2), which were increased by 12.8% and 11.1% compared to the control, respectively. The average rice carbon sequestration from the straw incorporation treatments was increased by 55.38 g · m(-2) compared with the control, and straw incorporation of 6000 kg · hm(-2) performed best with an increase of 17.8% compared with the control. Straw incorporation played a positive role in regulating the carbon sequestration of stem and leaf at the early growth stage and carbon sequestration of spike at the late growth stage. The average grain yield from the straw incorporation treatments was increased by 794.59 kg · hm(-2) (9.5% higher) compared with the control. Rice grain yields from the straw incorporation

  8. Method to synthesize metal chalcogenide monolayer nanomaterials

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez-Sanchez, Bernadette A.; Boyle, Timothy J.

    2016-12-13

    Metal chalcogenide monolayer nanomaterials can be synthesized from metal alkoxide precursors by solution precipitation or solvothermal processing. The synthesis routes are more scalable, less complex and easier to implement than other synthesis routes.

  9. Model for large-area monolayer coverage of polystyrene nanospheres by spin coating

    Science.gov (United States)

    Chandramohan, Abhishek; Sibirev, Nikolai V.; Dubrovskii, Vladimir G.; Petty, Michael C.; Gallant, Andrew J.; Zeze, Dagou A.

    2017-01-01

    Nanosphere lithography, an inexpensive and high throughput technique capable of producing nanostructure (below 100 nm feature size) arrays, relies on the formation of a monolayer of self-assembled nanospheres, followed by custom-etching to produce nanometre size features on large-area substrates. A theoretical model underpinning the self-ordering process by centrifugation is proposed to describe the interplay between the spin speed and solution concentration. The model describes the deposition of a dense and uniform monolayer by the implicit contribution of gravity, centrifugal force and surface tension, which can be accounted for using only the spin speed and the solid/liquid volume ratio. We demonstrate that the spin recipe for the monolayer formation can be represented as a pathway on a 2D phase plane. The model accounts for the ratio of polystyrene nanospheres (300 nm), water, methanol and surfactant in the solution, crucial for large area uniform and periodic monolayer deposition. The monolayer is exploited to create arrays of nanoscale features using ‘short’ or ‘extended’ reactive ion etching to produce 30–60 nm (diameter) nanodots or 100–200 nm (diameter) nanoholes over the entire substrate, respectively. The nanostructures were subsequently utilized to create master stamps for nanoimprint lithography.

  10. Model for large-area monolayer coverage of polystyrene nanospheres by spin coating

    Science.gov (United States)

    Chandramohan, Abhishek; Sibirev, Nikolai V.; Dubrovskii, Vladimir G.; Petty, Michael C.; Gallant, Andrew J.; Zeze, Dagou A.

    2017-01-01

    Nanosphere lithography, an inexpensive and high throughput technique capable of producing nanostructure (below 100 nm feature size) arrays, relies on the formation of a monolayer of self-assembled nanospheres, followed by custom-etching to produce nanometre size features on large-area substrates. A theoretical model underpinning the self-ordering process by centrifugation is proposed to describe the interplay between the spin speed and solution concentration. The model describes the deposition of a dense and uniform monolayer by the implicit contribution of gravity, centrifugal force and surface tension, which can be accounted for using only the spin speed and the solid/liquid volume ratio. We demonstrate that the spin recipe for the monolayer formation can be represented as a pathway on a 2D phase plane. The model accounts for the ratio of polystyrene nanospheres (300 nm), water, methanol and surfactant in the solution, crucial for large area uniform and periodic monolayer deposition. The monolayer is exploited to create arrays of nanoscale features using ‘short’ or ‘extended’ reactive ion etching to produce 30–60 nm (diameter) nanodots or 100–200 nm (diameter) nanoholes over the entire substrate, respectively. The nanostructures were subsequently utilized to create master stamps for nanoimprint lithography. PMID:28102358

  11. Tip-enhanced Raman spectroscopic imaging shows segregation within binary self-assembled thiol monolayers at ambient conditions.

    Science.gov (United States)

    Lin, Wan-Ing; Shao, Feng; Stephanidis, Bruno; Zenobi, Renato

    2015-11-01

    Phase segregation of coadsorbed thiol molecules on a gold surface was investigated with nanoscale chemical imaging using tip-enhanced Raman spectroscopy (TERS). Samples were prepared using mixed solutions containing thiophenol (PhS) and an oligomeric phenylene-ethynylene (OPE) thiol, with 10:1, 2:1, and 1:1 molar ratios. Phase segregation into domains with sizes from ≈30 to 240 nm is observed with these molar ratios. A comparison of TERS images with different pixel sizes indicates that a pixel size bigger than 15 nm is not reliable in defining nanodomains, because of undersampling. In this study, the formation of nanodomains was clearly evident based on the molecular fingerprints provided by TERS, while ambient scanning tunneling microscopy (STM) was not capable of discerning individual domains via their apparent height difference. TERS therefore allows to image nanodomains in binary self-assembled monolayers, which are invisible to methods solely relying on topographic or electron density characteristics of self-assembled monolayers. Moreover, TERS mapping provides statistical data to describe the distribution of molecules on the sample surface in a well-defined manner. Peak ratio histograms of selected TERS signals from samples prepared with different mixing ratios give a better understanding of the adsorption preference of the thiols studied, and the relationship of their mixing ratio in solution and adsorbed on the surface.

  12. Evaluation of shale gas potential based on organic matter characteristics and gas concentration in the Devonian Horn River Formation, Canada

    Science.gov (United States)

    Choi, Jiyoung; Hong, Sung Kyung; Lee, Hyun Suk

    2017-04-01

    In this study, we investigate organic matter characteristics from the analysis of Rock-Eval6 and biomarker, and estimate methane concentration from headspace method in the Devonian Horn River Formation, which is one of the largest shale reservoir in western Canada. The Horn River Formation consists of the Evie, Otterpark and Muskwa members in ascending stratigraphic order. Total Organic Carbon (TOC) ranges from 0.34 to 7.57 wt%, with an average of 2.78 wt%. The Evie, middle Otterpark and Muskwa members have an average TOC of more than 3%, whereas those of the lower and upper Otterpark Member are less than 2%. Based on Pristane/n-C17 (0.2 0.6) and Phytane/n-C18 (0.3 0.9) ratios, the organic matter in the Evie, middle Otterpark and Muskwa members mainly consists of type II kerogen which are formed in reducing marine environment. Thermal maturity were examined through the use of the distributions of Phenanthrene (P) and Methylphenantrenes (MP) based on m/z 178 and 192 mass chromatograms, respectively (Radke et al., 1982). The methylphenanthrene index (MPI-1) are calculated as follows : MPI-1 = 1.5 × (2MP+3MP)/(P+1MP+9MP), and Ro are calculated as follows : Ro = -0.6 × MPI-1 + 2.3. Estimated Ro ranges between 1.88 and 1.93%, which indicates the last stage of wet gas generation. The methane concentrations in headspace range from 15 to 914 ppmv, with an average of 73.5 ppmv. The methane concentrations in the Evie, middle Otterpark and Muskwa members (up to 914 ppmv) are higher than those of the lower and upper Otterpark Member (up to 75 ppmv). Considering the organic geochemical characteristics and gas concentrations, the shale gas potentials of the Evie, middle Otterpark and Muskwa members are higher than those of other members.

  13. Structural and electronic properties of germanene/MoS2 monolayer and silicene/MoS2 monolayer superlattices

    OpenAIRE

    Li, Xiaodan; Wu, Shunqing; Zhou, Sen; Zhu, Zizhong

    2014-01-01

    Superlattice provides a new approach to enrich the class of materials with novel properties. Here, we report the structural and electronic properties of superlattices made with alternate stacking of two-dimensional hexagonal germanene (or silicene) and a MoS2 monolayer using the first principles approach. The results are compared with those of graphene/MoS2 superlattice. The distortions of the geometry of germanene, silicene, and MoS2 layers due to the formation of the superlattices are all r...

  14. Mass spectrometric analysis of monolayer protected nanoparticles

    Science.gov (United States)

    Zhu, Zhengjiang

    Monolayer protected nanoparticles (NPs) include an inorganic core and a monolayer of organic ligands. The wide variety of core materials and the tunable surface monolayers make NPs promising materials for numerous applications. Concerns related to unforeseen human health and environmental impacts of NPs have also been raised. In this thesis, new analytical methods based on mass spectrometry are developed to understand the fate, transport, and biodistributions of NPs in the complex biological systems. A laser desorption/ionization mass spectrometry (LDI-MS) method has been developed to characterize the monolayers on NP surface. LDI-MS allows multiple NPs taken up by cells to be measured and quantified in a multiplexed fashion. The correlations between surface properties of NPs and cellular uptake have also been explored. LDI-MS is further coupled with inductively coupled plasma mass spectrometry (ICP-MS) to quantitatively measure monolayer stability of gold NPs (AuNPs) and quantum dots (QDs), respectively, in live cells. This label-free approach allows correlating monolayer structure and particle size with NP stability in various cellular environments. Finally, uptake, distribution, accumulation, and excretion of NPs in higher order organisms, such as fish and plants, have been investigated to understand the environmental impact of nanomaterials. The results indicate that surface chemistry is a primary determinant. NPs with hydrophilic surfaces are substantially less toxic and present a lower degree of bioaccumulation, making these nanomaterials attractive for sustainable nanotechnology.

  15. Combustion characteristics and air pollutant formation during oxy-fuel co-combustion of microalgae and lignite.

    Science.gov (United States)

    Gao, Yuan; Tahmasebi, Arash; Dou, Jinxiao; Yu, Jianglong

    2016-05-01

    Oxy-fuel combustion of solid fuels is seen as one of the key technologies for carbon capture to reduce greenhouse gas emissions. The combustion characteristics of lignite coal, Chlorella vulgaris microalgae, and their blends under O2/N2 and O2/CO2 conditions were studied using a Thermogravimetric Analyzer-Mass Spectroscopy (TG-MS). During co-combustion of blends, three distinct peaks were observed and were attributed to C. vulgaris volatiles combustion, combustion of lignite, and combustion of microalgae char. Activation energy during combustion was calculated using iso-conventional method. Increasing the microalgae content in the blend resulted in an increase in activation energy for the blends combustion. The emissions of S- and N-species during blend fuel combustion were also investigated. The addition of microalgae to lignite during air combustion resulted in lower CO2, CO, and NO2 yields but enhanced NO, COS, and SO2 formation. During oxy-fuel co-combustion, the addition of microalgae to lignite enhanced the formation of gaseous species.

  16. Chiral Cyclobutane β-Amino Acid-Based Amphiphiles: Influence of Cis/Trans Stereochemistry on Condensed Phase and Monolayer Structure.

    Science.gov (United States)

    Sorrenti, Alessandro; Illa, Ona; Ortuño, Rosa M; Pons, Ramon

    2016-07-12

    New diastereomeric nonionic amphiphiles, cis- and trans-1, based on an optically pure cyclobutane β-amino ester moiety have been investigated to gain insight into the influence exerted by cis/trans stereochemistry and stereochemical constraints on the physicochemical behavior, molecular organization, and morphology of their Langmuir monolayers and dry solid states. All these features are relevant to the rational design of functional materials. trans-1 showed a higher thermal stability than cis-1. For the latter, a higher fluidity of its monolayers was observed when compared with the films formed by trans-1 whose BAM images revealed the formation of condensed phase domains with a dendritic shape, which are chiral, and all of them feature the same chiral sign. Although the formation of LC phase domains was not observed by BAM for cis-1, compact dendritic crystals floating on a fluid subphase were observed beyond the collapse, which are attributable to multilayered 3D structures. These differences can be explained by the formation of hydrogen bonds between the amide groups of consecutive molecules allowing the formation of extended chains for trans-1 giving ordered arrangements. However, for cis-1, this alignment coexists with another one that allows the simultaneous formation of two hydrogen bonds between the amide and the ester groups of adjacent molecules. In addition, the propensity to form intramolecular hydrogen bonds must be considered to justify the formation of different patterns of hydrogen bonding and, consequently, the formation of less ordered phases. Those characteristics are congruent also with the results obtained from SAXS-WAXS experiments which suggest a more bent configuration for cis-1 than for trans-1.

  17. Comparison of primary and secondary particle formation from natural gas engine exhaust and of their volatility characteristics

    Directory of Open Access Journals (Sweden)

    J. Alanen

    2017-07-01

    Full Text Available Natural gas usage in the traffic and energy production sectors is a growing trend worldwide; thus, an assessment of its effects on air quality, human health and climate is required. Engine exhaust is a source of primary particulate emissions and secondary aerosol precursors, which both contribute to air quality and can cause adverse health effects. Technologies, such as cleaner engines or fuels, that produce less primary and secondary aerosols could potentially significantly decrease atmospheric particle concentrations and their adverse effects. In this study, we used a potential aerosol mass (PAM chamber to investigate the secondary aerosol formation potential of natural gas engine exhaust. The PAM chamber was used with a constant UV-light voltage, which resulted in relatively long equivalent atmospheric ages of 11 days at most. The studied retro-fitted natural gas engine exhaust was observed to form secondary aerosol. The mass of the total aged particles, i.e., particle mass measured downstream of the PAM chamber, was 6–268 times as high as the mass of the emitted primary exhaust particles. The secondary organic aerosol (SOA formation potential was measured to be 9–20 mg kgfuel−1. The total aged particles mainly consisted of organic matter, nitrate, sulfate and ammonium, with the fractions depending on exhaust after-treatment and the engine parameters used. Also, the volatility, composition and concentration of the total aged particles were found to depend on the engine operating mode, catalyst temperature and catalyst type. For example, a high catalyst temperature promoted the formation of sulfate particles, whereas a low catalyst temperature promoted nitrate formation. However, in particular, the concentration of nitrate needed a long time to stabilize – more than half an hour – which complicated the conclusions but also indicates the sensitivity of nitrate measurements on experimental parameters such as emission

  18. Formation of thin luminescent Eu{sup 3+}-LB films by in situ coordination with 2,3,5,6-tetra(2 Prime -pyridyl)pyrazine and 1-octadecanol in pure and mixed Langmuir monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Fugisawa, Fernanda P. [Departamento de Quimica, Faculdade de Filosofia, Ciencias e Letras de Ribeirao Preto, Universidade de Sao Paulo, 14040-901 Ribeirao Preto, SP (Brazil); Ramos, Ana P., E-mail: anapr@ffclrp.usp.br [Departamento de Quimica, Faculdade de Filosofia, Ciencias e Letras de Ribeirao Preto, Universidade de Sao Paulo, 14040-901 Ribeirao Preto, SP (Brazil); Sousa Filho, Paulo C. de; Serra, Osvaldo A.; Zaniquelli, Maria E.D. [Departamento de Quimica, Faculdade de Filosofia, Ciencias e Letras de Ribeirao Preto, Universidade de Sao Paulo, 14040-901 Ribeirao Preto, SP (Brazil)

    2012-05-15

    The in situ complexation between 2,3,5,6-tetra(2-pyridyl)pyrazine (tppz) molecules and europium ions at the air-liquid interface by means of mixed 1-octadecanol Langmuir films is reported. These films were transferred to solid supports by means of the Langmuir-Blodgett (LB) technique. The EDS maps attested the homogeneity of the LB films as well as the presence of the europium ions. The mixed alcohol/tppz LB film contained a larger amount of europium ions as compared to the pure octadecanol LB film. This work reports the production of a thin luminescent Eu{sup 3+} film containing europium ions using only alcohol molecules as ligands-an unexpected result, since it is well known that there is an occurrence of non-radiative deactivation of excited europium by hydroxyl groups. Europium ion multiple binding sites were detected from lifetime decay measurements of these films in the presence of tppz molecules. - Highlights: Black-Right-Pointing-Pointer In situ complexation of Eu (III) ions with 1-octadecanol and tppz. Black-Right-Pointing-Pointer Formation of thin luminescent Eu(III)-LB films. Black-Right-Pointing-Pointer EDS and luminescence studies attest to the presence of Eu(III) in the films. Black-Right-Pointing-Pointer Eu(III) coordinates with both tppz and alcohol molecules at air/liquid interface. Black-Right-Pointing-Pointer Relatively strong luminescence is observed in LB-films containing only Eu(III) and O-H oscillators.

  19. Molecular detection on a defective MoS2 monolayer by simultaneous conductance and force simulations

    Science.gov (United States)

    González, C.; Dappe, Y. J.

    2017-06-01

    Based on simultaneous force and conductance simulations, a proof of concept for a potential method of molecular detection is presented. Using density functional theory calculations, a metallic tip has been approached to different small inorganic molecules such as CO, CO2, H2O , NO, N2, or O2. The molecules have been previously chemisorbed on a defect formed by two Mo atoms occupying a S divacancy on a MoS2 monolayer where they are strongly bonded to the topmost substitutional molybdenum. At that site, the fixed molecules can be imaged by a conductive atomic-force-microscopy tip. Due to the differences in atomic composition and electronic configurations, each molecule yields specific conductance/force curves during the tip approach. A molecule-tip contact is established at the force minimum, followed by the formation of a characteristic plateau in the conductance in most of the cases. Focusing our attention on the position and values of such force minimum and conductance maximum, we can conclude that both characteristic properties can give a clear signature of each molecule, proposing a different method of detecting molecules adsorbed on highly reactive sites.

  20. Structure of self-assembled monolayer of NPAN on Au(111) electrode

    Institute of Scientific and Technical Information of China (English)

    YANG Guangzheng; ZENG Qingdao; WAN Lijun; BAI Chunli

    2003-01-01

    Adsorption of 4-(4-nitrophenylazo)-1-naphthol (NPAN), an azobenzene derivative, on Au(111) has been investigated in aqueous HClO4 solution by using the cyclic voltammetry and scanning tunneling microscopy (STM). The molecule is found to form a stable monolayer on the electrode with a (6×4) structure relative to the underlying Au(111) lattice. Cyclic voltammograms show that the redox reactions occurring on the electrode are retarded by the formation of the monolayer. A structural model is proposed for the two-dimensional adlayer.

  1. Photolysis of incorporated benzophenone derivatives inside compressed lipid monolayers

    Directory of Open Access Journals (Sweden)

    DEJAN Z. MARKOVIC

    2001-05-01

    Full Text Available The goal of this work was to study the possibility of the occurrence of radical-type lipid peroxidation of the lipid constituents on biomembranes, in compressed monolayers, having lipoidal benzophenone photosensitizers incorporated. The triplets of the photosensitizer abstract allylic and doubly-allylic hydrogen atoms from anticonjugated moities of the lipid molecules. The results simultaneously confirmed the occurrence of H-abstraction (and so the initiation of the peroxidizing chain mechanism, and the absence of the formation of lipid peroxides. The reason lies in "cage effect": the highly restricted spacial area of compressed lipid monolayers limits the mobility of the created radicals (lipid radicals and ketyl radicals and leads to their recombination, thus preventing the propagation step of the chain mechanism. With certain reservations it may be concluded that these results have a clear implication on real biomembranes: the structure of which is one of themain factors preventing the spread of the chain reaction, and the formation of lipid peroxides.

  2. Adsorption of tannic acid on polyelectrolyte monolayers determined in situ by streaming potential measurements.

    Science.gov (United States)

    Oćwieja, M; Adamczyk, Z; Morga, M

    2015-01-15

    Physicochemical characteristics of tannic acid (tannin) suspensions comprising its stability for a wide range of ionic strength and pH were thoroughly investigated using UV-vis spectrophotometry, dynamic light scattering and microelectrophoretic measurements. These studies allowed to determine the hydrodynamic diameter of the tannic acid that was 1.63 nm for the pH range 3.5-5.5. For pH above 6.0 the hydrodynamic diameter significantly decreased as a result of the tannin hydrolysis. The electrophoretic mobility measurements confirmed that tannic acid is negatively charged for these values of pH and ionic strength 10(-4)-10(-2) M. Therefore, in order to promote adsorption of tannin molecules on negatively charged mica, the poly(allylamine hydrochloride) (PAH) supporting monolayers were first adsorbed under diffusion transport conditions. The coverage of polyelectrolyte monolayers was regulated by changing bulk concentration of PAH and the adsorption time. The electrokinetic characteristics of bare and PAH-covered mica were determined using the streaming potential measurements. The zeta potential of these PAH monolayers was highly positive, equal to 46 mV for ionic strength of 10(-2) M. The kinetics of tannin adsorption on these PAH supporting monolayers was evaluated by the in situ the streaming potential measurements. The zeta potential of PAH monolayers abruptly decreases with the adsorption of tannin molecules that was quantitatively interpreted in terms of the three-dimensional electrokinetic model. The acid-base characteristics of tannin monolayers were acquired via the streaming potential measurements for a broad range of pH. The obtained results indicate that it is possible to control adsorption of tannin on positively charged surfaces in order to designed new multilayer structures of desirable electrokinetic properties and stability.

  3. Comparative genomic and transcriptomic analysis revealed genetic characteristics related to solvent formation and xylose utilization in Clostridium acetobutylicum EA 2018

    Directory of Open Access Journals (Sweden)

    Wang Shengyue

    2011-02-01

    Full Text Available Abstract Background Clostridium acetobutylicum, a gram-positive and spore-forming anaerobe, is a major strain for the fermentative production of acetone, butanol and ethanol. But a previously isolated hyper-butanol producing strain C. acetobutylicum EA 2018 does not produce spores and has greater capability of solvent production, especially for butanol, than the type strain C. acetobutylicum ATCC 824. Results Complete genome of C. acetobutylicum EA 2018 was sequenced using Roche 454 pyrosequencing. Genomic comparison with ATCC 824 identified many variations which may contribute to the hyper-butanol producing characteristics in the EA 2018 strain, including a total of 46 deletion sites and 26 insertion sites. In addition, transcriptomic profiling of gene expression in EA 2018 relative to that of ATCC824 revealed expression-level changes of several key genes related to solvent formation. For example, spo0A and adhEII have higher expression level, and most of the acid formation related genes have lower expression level in EA 2018. Interestingly, the results also showed that the variation in CEA_G2622 (CAC2613 in ATCC 824, a putative transcriptional regulator involved in xylose utilization, might accelerate utilization of substrate xylose. Conclusions Comparative analysis of C. acetobutylicum hyper-butanol producing strain EA 2018 and type strain ATCC 824 at both genomic and transcriptomic levels, for the first time, provides molecular-level understanding of non-sporulation, higher solvent production and enhanced xylose utilization in the mutant EA 2018. The information could be valuable for further genetic modification of C. acetobutylicum for more effective butanol production.

  4. Comparative genomic and transcriptomic analysis revealed genetic characteristics related to solvent formation and xylose utilization in Clostridium acetobutylicum EA 2018

    Science.gov (United States)

    2011-01-01

    Background Clostridium acetobutylicum, a gram-positive and spore-forming anaerobe, is a major strain for the fermentative production of acetone, butanol and ethanol. But a previously isolated hyper-butanol producing strain C. acetobutylicum EA 2018 does not produce spores and has greater capability of solvent production, especially for butanol, than the type strain C. acetobutylicum ATCC 824. Results Complete genome of C. acetobutylicum EA 2018 was sequenced using Roche 454 pyrosequencing. Genomic comparison with ATCC 824 identified many variations which may contribute to the hyper-butanol producing characteristics in the EA 2018 strain, including a total of 46 deletion sites and 26 insertion sites. In addition, transcriptomic profiling of gene expression in EA 2018 relative to that of ATCC824 revealed expression-level changes of several key genes related to solvent formation. For example, spo0A and adhEII have higher expression level, and most of the acid formation related genes have lower expression level in EA 2018. Interestingly, the results also showed that the variation in CEA_G2622 (CAC2613 in ATCC 824), a putative transcriptional regulator involved in xylose utilization, might accelerate utilization of substrate xylose. Conclusions Comparative analysis of C. acetobutylicum hyper-butanol producing strain EA 2018 and type strain ATCC 824 at both genomic and transcriptomic levels, for the first time, provides molecular-level understanding of non-sporulation, higher solvent production and enhanced xylose utilization in the mutant EA 2018. The information could be valuable for further genetic modification of C. acetobutylicum for more effective butanol production. PMID:21284892

  5. Variations in spectroscopic characteristics and disinfection byproduct formation potentials of dissolved organic matter for two contrasting storm events

    Science.gov (United States)

    Nguyen, Hang Vo-Minh; Lee, Mi-Hee; Hur, Jin; Schlautman, Mark A.

    2013-02-01

    SummaryChanges in disinfection byproduct (DBP) precursors during storm events have not been intensively studied to date despite their dramatic impact on downstream drinking water supplies. For this study, variations in dissolved organic matter (DOM) spectroscopic properties and DBP formation potentials (DBPFPs), and the correlations among these various parameters, were investigated in river water samples collected under two contrasting storm event conditions (a strong summer storm versus a weak fall event). Fluorescence excitation-emission matrices (EEMs) combined with parallel factor analysis revealed that a combination of two humic-like components (C1 and C2) dominated the EEM data of the storm samples. Measured DOM characteristics and DBPFPs varied over a wider range during the more intense summer storm, exhibiting higher values of specific ultraviolet absorbance and C1/C2 ratio at high flow conditions. Variations in the fluorescence index were less pronounced during the two storm events. The spectroscopic changes were well explained by the input of terrestrial DOM sources from the surrounding catchments during the storms. Different trends of the formation potentials for trihalomethanes and haloacetic acids on the recession limb of the hydrographs suggest that the structures responsible for DBP precursors during storm events may not be the same for the two classes of DBPs. The ultraviolet light-absorbing moieties in DOM appear to play major roles in generating DBPs, as evidenced by their strong positive correlations with DBPFPs. Higher correlations with DBPFP for C1 versus C2 suggest that humic-like substances associated with more aromatic and condensed structures have a greater proclivity to generate DBP upon chlorination.

  6. Nanopatterning of mobile lipid monolayers on electron-beam-sculpted Teflon AF surfaces.

    Science.gov (United States)

    Shaali, Mehrnaz; Lara-Avila, Samuel; Dommersnes, Paul; Ainla, Alar; Kubatkin, Sergey; Jesorka, Aldo

    2015-02-24

    Direct electron-beam lithography is used to fabricate nanostructured Teflon AF surfaces, which are utilized to pattern surface-supported monolayer phospholipid films with 50 nm lateral feature size. In comparison with unexposed Teflon AF coatings, e-beam-irradiated areas show reduced surface tension and surface potential. For phospholipid monolayer spreading experiments, these areas can be designed to function as barriers that enclose unexposed areas of nanometer dimensions and confine the lipid film within. We show that the effectiveness of the barrier is defined by pattern geometry and radiation dose. This surface preparation technique represents an efficient, yet simple, nanopatterning strategy supporting studies of lipid monolayer behavior in ultraconfined spaces. The generated structures are useful for imaging studies of biomimetic membranes and other specialized surface applications requiring spatially controlled formation of self-assembled, molecularly thin films on optically transparent patterned polymer surfaces with very low autofluorescence.

  7. Self-assembled monolayer facilitates epithelial-mesenchymal interactions mimicking odontogenesis.

    Science.gov (United States)

    Muni, Tanvi; Mrksich, Milan; George, Anne

    2014-01-01

    Cell-cell interactions are vital for embryonic organ development and normal function of differentiated cells and tissues. In this study we have developed a self-assembled monolayer-based co-culture system to study tooth morphogenesis. Specifically, we designed a 2-D microenvironment present in the dental tissue by creating a well-structured, laterally organized epithelial and mesenchymal cell co-culture system by patterning the cell-attachment substrate. Chemical modifications were used to develop tunable surface patterns to facilitate epithelial-mesenchymal interactions mimicking the developing tooth. Such a design promoted interactions between monolayer's of the 2 cell types and provided signaling cues that resulted in cellular differentiation and mineralized matrix formation. Gene expression analysis showed that these co-cultures mimicked in-vivo conditions than monolayer cultures of a single cell type.

  8. Functionalizable self-assembled trichlorosilyl-based monolayer for application in biosensor technology

    Science.gov (United States)

    De La Franier, Brian; Jankowski, Alexander; Thompson, Michael

    2017-08-01

    This paper describes the design and synthesis of 3-(3-(trichlorosilyl)propoxy)propanoyl chloride (MEG-Cl), a compound capable of forming functionalizable monolayers on hydroxylated surfaces. The compound was synthesized in high purity, as suggested by nuclear magnetic resonance analysis, and in moderate overall yield. Contact angle measurement and X-ray photoelectron spectroscopy confirm the binding of MEG-Cl to an amorphous glass substrate and the further modification of the monolayer with a nickel (II)-binding ligand for the purpose of binding polyhistidine-tagged proteins. The compound will be useful in biosensing applications due to its ability to be easily modified with any number of nucleophilic functional groups subsequent to substrate monolayer formation.

  9. Growing extremely thin bulklike metal film on a semiconductor surface: Monolayer Al(111) on Si(111)

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Ying; Kim, Yong-Hyun; Zhang, S. B.; Ebert, Philipp; Yang, Shenyuan; Tang, Zhe; Wu, Kehui; Wang, E. G.

    2007-10-29

    We report combined scanning tunneling microscopy, x-ray photoelectron emission spectroscopy, electron energy loss spectroscopy, and theoretical study of the growth of ultrathin Al film on the Si(111) substrate. We show that by (i) a modification of the substrate reconstruction with a √3×√3 surface and (ii) a choice of materials with commensurate lattices, atomically flat film can be obtained even at the ultimate one monolayer limit, while maintaining a bulklike atomic structure. Detailed analysis shows that this monolayer Al(111)-1×1Al(111)-1×1 film is electronically decoupled from the Si substrate, and it shows metallic characteristics.

  10. Stiffness of polyelectrolyte multilayer film influences endothelial function of endothelial cell monolayer.

    Science.gov (United States)

    Chang, Hao; Zhang, He; Hu, Mi; Chen, Jia-Yan; Li, Bo-Chao; Ren, Ke-Feng; Martins, M Cristina L; Barbosa, Mário A; Ji, Jian

    2017-01-01

    Endothelialization has proved to be critical for maintaining long-term success of implantable vascular devices. The formation of monolayer of endothelial cells (ECs) on the implant surfaces is one of the most important factors for the endothelialization. However, endothelial function of regenerated EC monolayer, which plays a much more important role in preventing the complications of post-implantation, has not received enough attention. Here, a vascular endothelial growth factor (VEGF)-incorporated poly(l-lysine)/hyaluronan (PLL/HA) polyelectrolyte multilayer film was fabricated. Through varying the crosslinking degree, stiffness of the film was manipulated, offering either soft or stiff film. We demonstrated that ECs were able to adhere and proliferate on both soft and stiff films, subsequently forming an integrated EC monolayer. Furthermore, endothelial functions were evaluated by characterizing EC monolayer integrity, expression of genes correlated with the endothelial functions, and nitric oxide production. It demonstrated that EC monolayer on the soft film displayed higher endothelial function compared to that on the stiff film. Our study highlights the influence of substrate stiffness on endothelial function, which offers a new criterion for surface design of vascular implants. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Multicellular automaticity of cardiac cell monolayers: effects of density and spatial distribution of pacemaker cells

    Science.gov (United States)

    Elber Duverger, James; Boudreau-Béland, Jonathan; Le, Minh Duc; Comtois, Philippe

    2014-11-01

    Self-organization of pacemaker (PM) activity of interconnected elements is important to the general theory of reaction-diffusion systems as well as for applications such as PM activity in cardiac tissue to initiate beating of the heart. Monolayer cultures of neonatal rat ventricular myocytes (NRVMs) are often used as experimental models in studies on cardiac electrophysiology. These monolayers exhibit automaticity (spontaneous activation) of their electrical activity. At low plated density, cells usually show a heterogeneous population consisting of PM and quiescent excitable cells (QECs). It is therefore highly probable that monolayers of NRVMs consist of a heterogeneous network of the two cell types. However, the effects of density and spatial distribution of the PM cells on spontaneous activity of monolayers remain unknown. Thus, a simple stochastic pattern formation algorithm was implemented to distribute PM and QECs in a binary-like 2D network. A FitzHugh-Nagumo excitable medium was used to simulate electrical spontaneous and propagating activity. Simulations showed a clear nonlinear dependency of spontaneous activity (occurrence and amplitude of spontaneous period) on the spatial patterns of PM cells. In most simulations, the first initiation sites were found to be located near the substrate boundaries. Comparison with experimental data obtained from cardiomyocyte monolayers shows important similarities in the position of initiation site activity. However, limitations in the model that do not reflect the complex beat-to-beat variation found in experiments indicate the need for a more realistic cardiomyocyte representation.

  12. Photolysis and thermolysis of pyridyl carbonyl azide monolayers on single-crystal platinum.

    Science.gov (United States)

    Adkinson, Dana K; Magri, David C; Pitters, Jason L; Griffiths, Keith; Norton, Peter R; Workentin, Mark S

    2013-01-01

    The photochemical and thermal reactivity of a number of acyl azide-substituted pyridine compounds, namely nicotinyl azide, isonicotinyl azide, picolinyl azide and dinicotinyl azide with investigated as saturated monolayers on a single-crystal Pt(111) surface in an ultrahigh vacuum chamber. Multilayers of the substrates exhibited a maximum rate of desorption at 270 K, above which, stable saturated monolayers formed as characterized by reflection-absorption infrared spectroscopy by observation of C=O and N3 bands at 1700 cm(-1), and 2100 and 1300 cm(-1) respectively. The monolayers were stable up to 400 K. Photolysis of the monolayer (or heating above 400 K) results in the formation of the respective isocyanate intermediate after loss of nitrogen as evidenced by the appearance of a new infrared band at 2260 cm(-1) with concomitant loss of the azide bands. The resulting isocyanate saturated monolayer is stable in absence of nucleophiles, but can be quenched with appropriate nucleophiles. © 2013 The American Society of Photobiology.

  13. Electrochemical and scanning probe microscopic characterization of spontaneously adsorbed organothiolate monolayers at gold

    Energy Technology Data Exchange (ETDEWEB)

    Wong, Sze-Shun Season [Iowa State Univ., Ames, IA (United States)

    1999-12-10

    This dissertation presented several results which add to the general knowledge base regarding organothiolates monolayer spontaneously adsorbed at gold films. Common to the body of this work is the use of voltammetric reductive resorption and variants of scanning probe microscopy to gain insight into the nature of the monolayer formation process as well as the resulting interface. The most significant result from this work is the success of using friction force microscopy to discriminate the end group orientation of monolayer chemisorbed at smooth gold surfaces with micrometer resolution (Chapter 4). The ability to detect the differences in the orientational disposition is demonstrated by the use PDMS polymer stamp to microcontact print an adlayer of n-alkanethiolate of length n in a predefine pattern onto a gold surface, followed by the solution deposition of a n-alkanethiol of n ± 1 to fill in the areas on the gold surface intentionally not coated by the stamping process. These two-component monolayers can be discriminated by using friction force microscopy which detects differences in friction contributed by the differences in the orientation of the terminal groups at surfaces. This success has recently led to the detection of the orientation differences at nanometer scale. Although the substrates examined in this work consisted entirely of smooth gold films, the same test can be performed on other smooth substrates and monolayer materials.

  14. Characterization and reactivity of organic monolayers on gold and platinum surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Chien-Ching [Iowa State Univ., Ames, IA (United States)

    1995-12-06

    Purpose is to understand how the mobilization, dielectric, orientation, composition, coverage, and structure of self-assembled organic monolayers on metal surfaces affects the surface reactivities and properties of these films in order to facilitate the construction of desired films. Two model systems were used: tiols at Au and aromatic acids at Pt. Surface analysis methods, including contact angle, electrochemistry, ellipsometry, infrared reflection absorption spectroscopy (IRRAS), and x-ray photospectroscopy, were used to study the self-assembled organic monolayers on Au and Pt. IRRAS, contact angle, and electrochemistry were used to determine the surface pKa of phenylcarboxylic acids and pyridylcarboxylic acids monolayers on Pt. These techniques were also used to determine the orientation of polymethylene chain axis and the carboxylic follow the structural evolution of the chains and end group of the thiolate monolayers during formation. IRRAS was also used to assess the carboxylic acid group in terms of its possible existence as the non-hydrogen-bonded species, the hydrogen-bonded dimeric group, and the hydrogen-bonded polymeric group. These different forms of the end group were also followed vs coverage, as well as the reactivity vs solution pH. IRRAS and contact angle were used to calculate the rate constant of the esterification of carboxylic acid-terminated monolayers on Au.

  15. The thermodynamic characteristics of complex formation of Cd2+ with N,N-Bis(carboxymethyl)aspartic acid in aqueous solutions at 298.15 K

    Science.gov (United States)

    Lytkin, A. I.; Chernyavskaya, N. V.; Litvinenko, V. E.

    2011-01-01

    The equilibrium constants and heats of formation of complexes of N,N-bis(carboxymethyl)aspartic acid (H4Y) with Cd2+ ions at 298.15 K and ionic strengths of 0.2, 0.5, and 1.0 (KNO3) were determined by potentiometric titration and calorimetrically. The thermodynamic characteristics of formation of the CdY2- complex at fixed and zero ionic strength values were calculated. The values obtained were interpreted.

  16. Formation Mechanism of alpha-Fe2O3 Nanotubes via Electrospinning and Their Adsorption Characteristics of BSA and DNA.

    Science.gov (United States)

    Liu, Ruijiang; Wang, Peng; Tao, Yuting; Liu, Yifan; Shen, Xiangqian

    2016-02-01

    The alpha-Fe2O3 nanotubes with diameters of 400-700 nm have been prepared via the sol-gel assisted electrospinning and subsequent one-step heat treatment with ferric nitrate, ethanol and poly(vinyl pyrrolidone) as starting regents. The resultant alpha-Fe2O3 nanotubes were characterized by XRD, SEM, TEM, and VSM techniques. The hollow structure is mainly influenced by the water content in the gel precursor and the heating rate, and the hollow formation mechanism of alpha-Fe2O9 nanotubes is discussed. Adsorption of BSA onto the as-prepared alpha-Fe2O3 nanotubes exhibits a good capacity of 56.5 mg/g with the initial BSA concentration of 1.0 mg/mL, which demonstrates their feasibility in delivery of biomacromolecules. Subsequently, the adsorption characteristics of DNA onto the alpha-Fe2O3 nanotubes were investigated, and the adsorbance of DNA can achieve a maximum value of 4.19 microg/g when the initial DNA concentration is 50 microg/mL. The adsorption process of DNA onto alpha-Fe2O3 nanotubes can be described well by the pseudo-first-order kinetic model at room temperature according to the correlation coefficient R2 = 0.9978.

  17. Thermal ripples in model molybdenum disulfide monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Remsing, Richard C.; Klein, Michael L. [Institute for Computational Molecular Science, Center for the Computational, Design of Functional Layered Materials, and Department of Chemistry, Temple University, 1925 N. 12th St., 19122, Philadelphia, PA (United States); Waghmare, Umesh V. [Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, 560 064, Jakkur, Bangalore (India)

    2017-01-15

    Molybdenum disulfide (MoS{sub 2}) monolayers have the potential to revolutionize nanotechnology. To reach this potential, it will be necessary to understand the behavior of this two-dimensional (2D) material on large length scales and under thermal conditions. Herein, we use molecular dynamics (MD) simulations to investigate the nature of the rippling induced by thermal fluctuations in monolayers of the 2H and 1T phases of MoS{sub 2}. The 1T phase is found to be more rigid than the 2H phase. Both monolayer phases are predicted to follow long wavelength scaling behavior typical of systems with anharmonic coupling between vibrational modes as predicted by classic theories of membrane-like systems. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. Thermal transport in monolayer InSe

    Science.gov (United States)

    Nissimagoudar, Arun S.; Ma, Jinlong; Chen, Yani; Li, Wu

    2017-08-01

    Two-dimensional InSe, a recently synthesized semiconductor having a moderate band gap, has gained attention due to its ultra high mobility and high photo-responsivity. In this work, we calculate the lattice thermal conductivity (κ) of monolayer InSe by solving the phonon Boltzmann transport equation (BTE) with first-principles calculated inter atomic force constants. κ of monolayer InSe is isotropic and found to be around 27.6 W m K-1 at room temperature along the in-plane direction. The size dependence of κ shows the size effect can persist up to 20 μm. Further, κ can be reduced to half by tuning the sample size to 300 nm. This low value suggests that κ might be a limiting factor for emerging nanoelectronic applications of monolayer InSe.

  19. Elastic bending modulus of monolayer graphene

    Energy Technology Data Exchange (ETDEWEB)

    Lu Qiang; Huang Rui [Department of Aerospace Engineering and Engineering Mechanics, University of Texas, Austin, TX 78712 (United States); Arroyo, Marino [Department of Applied Mathematics 3, LaCaN, Universitat Politecnica de Catalunya (UPC), Barcelona 08034 (Spain)

    2009-05-21

    An analytic formula is derived for the elastic bending modulus of monolayer graphene based on an empirical potential for solid-state carbon atoms. Two physical origins are identified for the non-vanishing bending stiffness of the atomically thin graphene sheet, one due to the bond-angle effect and the other resulting from the bond-order term associated with the dihedral angles. The analytical prediction compares closely with ab initio energy calculations. Pure bending of graphene monolayers into cylindrical tubes is simulated by a molecular mechanics approach, showing slight nonlinearity and anisotropy in the tangent bending modulus as the bending curvature increases. An intrinsic coupling between bending and in-plane strain is noted for graphene monolayers rolled into carbon nanotubes. (fast track communication)

  20. Magneto photoluminescence measurements of tungsten disulphide monolayers

    Science.gov (United States)

    Kuhnert, Jan; Rahimi-Iman, Arash; Heimbrodt, Wolfram

    2017-03-01

    Layered transition-metal dichalcogenides have attracted great interest in the last few years. Thinned down to the monolayer limit they change from an indirect band structure to a direct band gap in the visible region. Due to the monolayer thickness the inversion symmetry of the crystal is broken and spin and valley are coupled to each other. The degeneracy between the two equivalent valleys, K and K‧, respectively, can be lifted by applying an external magnetic field. Here, we present photoluminescence measurements of CVD-grown tungsten disulphide (WS2) monolayers at temperatures of 2 K. By applying magnetic fields up to 7 T in Faraday geometry, a splitting of the photoluminescence peaks can be observed. The magnetic field dependence of the A-exciton, the trion and three bound exciton states is discussed and the corresponding g-factors are determined.

  1. Effect of Si doping on the electronic properties of BN monolayer.

    Science.gov (United States)

    Gupta, Sanjeev K; He, Haiying; Banyai, Douglas; Si, Mingsu; Pandey, Ravindra; Karna, Shashi P

    2014-05-21

    The effect of Si doping on the stability, electronic structure, and electron transport properties of boron nitride (BN) monolayer has been investigated by density functional theory method. Unique features in the electron transport characteristics consisting of a significant enhancement of current at the Si site, diode-like asymmetric current-voltage response, and negative differential resistance are noted for the doped BN monolayer. These features are found to result from new "tunnel" channels induced by the substitutional Si atom near Fermi level in the band gap. The calculated position-projected tunneling currents providing scanning tunneling micrograph clearly discern the site-dependence of the Si atom and can be used to distinguish substitutional sites of atomic dopants in the monolayer.

  2. Monolayers of MoS{sub 2} as an oxidation protective nanocoating material

    Energy Technology Data Exchange (ETDEWEB)

    Sen, H. Sener [UNAM-National Nanotechnology Research Center, Bilkent University, Ankara 06800 (Turkey); Sahin, H.; Peeters, F. M. [Department of Physics, University of Antwerp, 2610 Antwerp (Belgium); Durgun, E., E-mail: durgun@unam.bilkent.edu.tr [UNAM-National Nanotechnology Research Center, Bilkent University, Ankara 06800 (Turkey); Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800 (Turkey)

    2014-08-28

    First-principle calculations are employed to investigate the interaction of oxygen with ideal and defective MoS{sub 2} monolayers. Our calculations show that while oxygen atoms are strongly bound on top of sulfur atoms, the oxygen molecule only weakly interacts with the surface. The penetration of oxygen atoms and molecules through a defect-free MoS{sub 2} monolayer is prevented by a very high diffusion barrier indicating that MoS{sub 2} can serve as a protective layer for oxidation. The analysis is extended to WS{sub 2} and similar coating characteristics are obtained. Our calculations indicate that ideal and continuous MoS{sub 2} and WS{sub 2} monolayers can improve the oxidation and corrosion-resistance of the covered surface and can be considered as an efficient nanocoating material.

  3. Stability of two-dimensional PN monolayer sheets and their electronic properties.

    Science.gov (United States)

    Ma, ShuangYing; He, Chaoyu; Sun, L Z; Lin, Haiping; Li, Youyong; Zhang, K W

    2015-12-21

    Three two-dimensional phosphorus nitride (PN) monolayer sheets (named as α-, β-, and γ-PN, respectively) with fantastic structures and properties are predicted based on first-principles calculations. The α-PN and γ-PN have a buckled structure, whereas β-PN shows puckered characteristics. Their unique structures endow these atomic PN sheets with high dynamic stabilities and anisotropic mechanical properties. They are all indirect semiconductors and their band gap sensitively depends on the in-plane strain. Moreover, the nanoribbons patterned from these three PN monolayers demonstrate a remarkable quantum size effect. In particular, the zigzag α-PN nanoribbon shows size-dependent ferromagnetism. Their significant properties show potential in nano-electronics. The synthesis of the three phases of the PN monolayer sheet is proposed theoretically, which is deserving of further study in experiments.

  4. Pentagonal monolayer crystals of carbon, boron nitride, and silver azide

    Energy Technology Data Exchange (ETDEWEB)

    Yagmurcukardes, M., E-mail: mehmetyagmurcukardes@iyte.edu.tr; Senger, R. T., E-mail: tugrulsenger@iyte.edu.tr [Department of Physics, Izmir Institute of Technology, 35430 Urla, Izmir (Turkey); Sahin, H.; Kang, J.; Torun, E.; Peeters, F. M. [Department of Physics, University of Antwerp, Campus Groenenborgerlaan, 2020, Antwerp (Belgium)

    2015-09-14

    In this study, we present a theoretical investigation of structural, electronic, and mechanical properties of pentagonal monolayers of carbon (p-graphene), boron nitride (p-B{sub 2}N{sub 4} and p-B{sub 4}N{sub 2}), and silver azide (p-AgN{sub 3}) by performing state-of-the-art first principles calculations. Our total energy calculations suggest feasible formation of monolayer crystal structures composed entirely of pentagons. In addition, electronic band dispersion calculations indicate that while p-graphene and p-AgN{sub 3} are semiconductors with indirect bandgaps, p-BN structures display metallic behavior. We also investigate the mechanical properties (in-plane stiffness and the Poisson's ratio) of four different pentagonal structures under uniaxial strain. p-graphene is found to have the highest stiffness value and the corresponding Poisson's ratio is found to be negative. Similarly, p-B{sub 2}N{sub 4} and p-B{sub 4}N{sub 2} have negative Poisson's ratio values. On the other hand, the p-AgN{sub 3} has a large and positive Poisson's ratio. In dynamical stability tests based on calculated phonon spectra of these pentagonal monolayers, we find that only p-graphene and p-B{sub 2}N{sub 4} are stable, but p-AgN{sub 3} and p-B{sub 4}N{sub 2} are vulnerable against vibrational excitations.

  5. Monolayer optical memory cells based on artificial trap-mediated charge storage and release

    Science.gov (United States)

    Lee, Juwon; Pak, Sangyeon; Lee, Young-Woo; Cho, Yuljae; Hong, John; Giraud, Paul; Shin, Hyeon Suk; Morris, Stephen M.; Sohn, Jung Inn; Cha, Seungnam; Kim, Jong Min

    2017-03-01

    Monolayer transition metal dichalcogenides are considered to be promising candidates for flexible and transparent optoelectronics applications due to their direct bandgap and strong light-matter interactions. Although several monolayer-based photodetectors have been demonstrated, single-layered optical memory devices suitable for high-quality image sensing have received little attention. Here we report a concept for monolayer MoS2 optoelectronic memory devices using artificially-structured charge trap layers through the functionalization of the monolayer/dielectric interfaces, leading to localized electronic states that serve as a basis for electrically-induced charge trapping and optically-mediated charge release. Our devices exhibit excellent photo-responsive memory characteristics with a large linear dynamic range of ~4,700 (73.4 dB) coupled with a low OFF-state current (<4 pA), and a long storage lifetime of over 104 s. In addition, the multi-level detection of up to 8 optical states is successfully demonstrated. These results represent a significant step toward the development of future monolayer optoelectronic memory devices.

  6. Transepithelial transport of putrescine across monolayers of the human intestinal epithelial cell line, Caco-2

    Institute of Scientific and Technical Information of China (English)

    Vladan Milovic; Lyudmila Turchanowa; Jurgen Stein; Wolfgang F. Caspary

    2001-01-01

    AIM To study the transepithelial transport characteristics of the polyamine putrescine in human intestinal Caco-2 cell monolayers to elucidate the mechanisms of the putrescine intestinal absorption.METHODS The transepithelial transport and the cellular accumulation of putrescine was measured using Caco 2 cell monolayers grown on permeable filters.RESULTS Transepithelial transport of putrescine in physiological concentrations (>0.5 mM)from the apical to basolateral side was linear. Intracellular accumulation of putrescine was higher in confluent than in fully differentiated Caco-2 cells, but still negligible (less than 0.5%) of the overall transport across the monolayers in apical-to-basolateral direction. EGF enhanced putrescine accumulation in Caco-2 cells by four-fold, as well as putrescine conversion to spermidine and spermine by enhancing the activity of Sadenosylmethionine decarboxylase. However,EGF did not have any significant influence on putrescine flux across the Caco-2 cell monolayers. Excretion of putrescine from Caco-2cells into the basolateral medium did not exceed 50 picomoles, while putrescine passive flux from the apical to the basolateral chamber,contributed hundreds of micromoles polyamines to the basolateral chamber.CONCLUSION Transepithelial transport of putrescine across Caco-2 cell monolayers occurs in passive diffusion, and is not influenced when epithelial cells are stimulated to proliferate by a potent mitogen such as EGF.

  7. Stiffness of lipid monolayers with phase coexistence.

    Science.gov (United States)

    Caruso, Benjamín; Mangiarotti, Agustín; Wilke, Natalia

    2013-08-27

    The surface dilational modulus--or compressibility modulus--has been previously studied for monolayers composed of pure materials, where a jump in this modulus was related with the onset of percolation as a result of the establishment of a connected structure at the molecular level. In this work, we focused on monolayers composed of two components of low lateral miscibility. Our aim was to investigate the compressibility of mixed monolayers at pressures and compositions in the two-phase region of the phase diagram, in order to analyze the effect of the mechanical properties of each phase on the stiffness of the composite. In nine different systems with distinct molecular dipoles and charges, the stiffness of each phase and the texture at the plane of the monolayer were studied. In this way, we were able to analyze the general compressibility of two-phase lipid monolayers, regardless of the properties of their constituent parts. The results are discussed in the light of the following two hypotheses: first, the stiffness of the composite could be dominated by the stiffness of each phase as a weighted sum according to the percentage of each phase area, regardless of the distribution of the phases in the plane of the monolayer. Alternatively, the stiffness of the composite could be dominated by the mechanical properties of the continuous phase. Our results were better explained by this latter proposal, as in all the analyzed mixtures it was found that the mechanical properties of the percolating phase were the determining factors. The value of the compression modulus was closer to the value of the connected phase than to that of the dispersed phase, indicating that the bidimensional composites displayed mechanical properties that were related to the properties of each phases in a rather complex manner.

  8. Differential Sarcomere and Electrophysiological Maturation of Human iPSC-Derived Cardiac Myocytes in Monolayer vs. Aggregation-Based Differentiation Protocols

    Directory of Open Access Journals (Sweden)

    Dorota Jeziorowska

    2017-06-01

    Full Text Available Human induced pluripotent stem cells (iPSCs represent a powerful human model to study cardiac disease in vitro, notably channelopathies and sarcomeric cardiomyopathies. Different protocols for cardiac differentiation of iPSCs have been proposed either based on embroid body formation (3D or, more recently, on monolayer culture (2D. We performed a direct comparison of the characteristics of the derived cardiomyocytes (iPSC-CMs on day 27 ± 2 of differentiation between 3D and 2D differentiation protocols with two different Wnt-inhibitors were compared: IWR1 (inhibitor of Wnt response or IWP2 (inhibitor of Wnt production. We firstly found that the level of Troponin T (TNNT2 expression measured by FACS was significantly higher for both 2D protocols as compared to the 3D protocol. In the three methods, iPSC-CM show sarcomeric structures. However, iPSC-CM generated in 2D protocols constantly displayed larger sarcomere lengths as compared to the 3D protocol. In addition, mRNA and protein analyses reveal higher cTNi to ssTNi ratios in the 2D protocol using IWP2 as compared to both other protocols, indicating a higher sarcomeric maturation. Differentiation of cardiac myocytes with 2D monolayer-based protocols and the use of IWP2 allows the production of higher yield of cardiac myocytes that have more suitable characteristics to study sarcomeric cardiomyopathies.

  9. Low temperature photoresponse of monolayer tungsten disulphide

    Directory of Open Access Journals (Sweden)

    Bingchen Cao

    2014-11-01

    Full Text Available High photoresponse can be achieved in monolayers of transition metal dichalcogenides. However, the response times are inconveniently limited by defects. Here, we report low temperature photoresponse of monolayer tungsten disulphide prepared by exfoliation and chemical vapour deposition (CVD method. The exfoliated device exhibits n-type behaviour; while the CVD device exhibits intrinsic behaviour. In off state, the CVD device has four times larger ratio of photoresponse for laser on/off and photoresponse decay–rise times are 0.1 s (limited by our setup, while the exfoliated device has few seconds. These findings are discussed in terms of charge trapping and localization.

  10. Nonlinear optical studies of organic monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Y.R.

    1988-02-01

    Second-order nonlinear optical effects are forbidden in a medium with inversion symmetry, but are necessarily allowed at a surface where the inversion summary is broken. They are often sufficiently strong so that a submonolayer perturbation of the surface can be readily detected. They can therefore be used as effective tools to study monolayers adsorbed at various interfaces. We discuss here a number of recent experiments in which optical second harmonic generation (SHG) and sum-frequency generation (SFG) are employed to probe and characterize organic monolayers. 15 refs., 5 figs.

  11. Controlled synthesis of high-quality crystals of monolayer MoS2 for nanoelectronic device application

    DEFF Research Database (Denmark)

    Yang, Xiaonian; Li, Qiang; Hu, Guofeng

    2016-01-01

    Two-dimensional layered materials have attracted significant interest for their potential applications in electronic and optoelectronics devices. Among them, transition metal dichalcogenides (TMDs), especially molybdenum disulfide (MoS2), is extensively studied because of its unique properties....... Monolayer MoS2 so far can be obtained by mechanical exfoliation or chemical vapor deposition (CVD). However, controllable synthesis of large area monolayer MoS2 with high quality needs to be improved and their growth mechanism requires more studies. Here we report a systematical study on controlled...... synthesis of high-quality monolayer MoS2 single crystals using low pressure CVD. Large-size monolayer MoS2 triangles with an edge length up to 405 mu m were successfully synthesized. The Raman and photoluminescence spectroscopy studies indicate high homogenous optical characteristic of the synthesized...

  12. High-Quality Alkyl Monolayers on Silicon Surfaces

    NARCIS (Netherlands)

    Sieval, A.B.; Linke, R.; Zuilhof, H.; Sudh"lter, E.J.R.

    2000-01-01

    Covalent attachment of functionalized monolayers onto silicon surfaces (see Figure for examples) is presented here as a strategy for surface modification. The preparation and structure of both unfunctionalized and functionalized alkyl-based monolayers are described, as are potential applications,

  13. Magnetic moment formation in metal-organic monolayers

    Science.gov (United States)

    Mabrouk, Manel; Hayn, Roland

    2015-11-01

    We investigate the electronic and magnetic properties of a two-dimensional polymeric manganese phthalocyanine (Mn-Pc) network and its derivative, the metal-ligand network Mn-TCNB formed by the transition-metal atom Mn and the organic ligand TCNB (1,2,4,5-tetracyanobenzene), using first-principles calculations on the basis of density functional theory (DFT) with the Hubbard-like Coulomb term. Our calculations show that Mn-Pc and Mn-TCNB are metallic. It is found that the Mn-Pc network is more stable than the Mn-TCNB one, and both have a total magnetic moment of about 3 μB . In the case of Mn-Pc, also the local Mn moment is close to 3 μB . But in Mn-TCNB, we find a high spin state S =5 /2 at Mn that is partially screened by unpaired electrons at the ligands. That screening is static in the DFT + U results, but we argue in favor of a dynamical screening in reality. Using our proper model calculation on the basis of a suitable model Hamiltonian, we explain the ab initio calculations, analyze the partial screening effect that exists in the two-dimensional Mn-TCNB network, and compare both systems.

  14. Characteristics of rare earth elements of lacustrine exhalative rock in the Xiagou Formation of Lower Cretaceous in Qingxi sag, Jiuxi basin

    Institute of Scientific and Technical Information of China (English)

    WEN Huaguo; ZHENG Rongcai; GENG Wei; FAN Mingtao; WANG Manfu

    2007-01-01

    The exhalative rock occurring in the Xiagou Formation of Lower Cretaceous in Qingxi sag, Jiuxi basin is a sort of a rare lacustrine white smoke type, rich in ferrodolo-mites and albites. This paper introduces the geological back-ground, mineral association, and lithology of the exhalative rock, and discusses its REE geochemical characteristics and connection with hydrothermal environment. It is shown that the exhalative rock has basal characteristics of hydrothermal depositional formation of LREE>HREE, with positive δCe and negative δEu, which is different from the character-istics of marine exhalative rock. Since the REE pattern and exceptional distribution of δEu and δCe are highly similar to the characteristics of alkalescent tholeiitic basalt in the same layer, the exhalative rock of Xiagou Formation isconsidered to be closely related to the origin of basalt in the same horizon. The fact that the amount of REE of exhala-tive rock decreases outwards indicates that exhalative rock in the Xiagou Formation may be connected with lacustrine hydrothermal convection circulation.

  15. Adsorption of anionic polyelectrolytes to dioctadecyldimethylammonium bromide monolayers

    Science.gov (United States)

    Engelking, J.; Menzel, H.

    Monolayers of dioctadecyldimethylammonium bromide (DODA) at the air/water interface were used as model for charged surfaces to study the adsorption of anionic polyelectrolytes. After spreading on a pure water surface the monolayers were compressed and subsequently transferred onto a polyelectrolyte solution employing the Fromherz technique. The polyelectrolyte adsorption was monitored by recording the changes in surface pressure at constant area. For poly(styrene sulfonate) and carboxymethylcellulose the plot of the surface pressure as function of time gave curves which indicate a direct correlation between the adsorbed amount and surface pressure as well as a solely diffusion controlled process. In the case of rigid rod-like poly(p-phenylene sulfonate)s the situation is more complicated. Plotting the surface pressure as function of time results in a curve with sigmoidal shape, characterized by an induction period. The induction period can be explained by a domain formation, which can be treated like a crystallization process. Employing the Avrami expression developed for polymer crystallization, the change in the surface pressure upon adsorption of rigid rod-like poly(p-phenylene sulfonate)s can be described.

  16. EXPERIMENTAL STUDY ON THE VORTEX FORMATION AND ENTRA-INMENT CHARACTERISTICS FOR A ROUND TRANSVERSE JET IN SHALLOW WATER

    Institute of Scientific and Technical Information of China (English)

    FAN Jing-yu; ZHANG Yan; WANG Dao-zeng

    2009-01-01

    The vortex formation and entrainment characteristics for a round transverse jet in shallow water were experimentally investigated by means of a combination of LIF flow visualization and PIV measurement. A scarf vortex wrapped around the main body of the jet is formed in the near-wall region due to the interaction between the resulting wall jet and sufficiently shallow crossflow, with some more or less unsteady flow properties and with spreading ranges as functions of both the velocity ratio and the water depth within the near field. The entrainment of the ambient crossflow fluid into the jet main body is closely associated with the time-evolving features of the shear layer between the jet and surrounding fluid as well as the induced vortical structures near the wall. In the case of slight impingement upon the wall, the interaction between the jet shear layer and the weak, unstable scarf vortex gives rise to an appreciable local entrainment enhancement, confined in the near-wall region in the vicinity of the stagnation point. While in the case of intense impingement upon the wall, the well-organized and stable scarf vortex gives rise to a greatly enhanced entrainment and a greatly increased lateral spreading rate nearly throughout the overall near field as compared to the conventional wall jet. In addition, the entrainment of the ambient crossflow fluid by the scarf vortex in this case occurs largely on the surface of the unique spiral roller structure by itself due to the presence of smaller and unorganized eddies, and accordingly the scarf vortex is likely to keep its spiral roller structure steadily to a relatively great downstream distance within the near field.

  17. Stratigraphy, correlation, depositional setting, and geophysical characteristics of the Oligocene Snowshoe Mountain Tuff and Creede Formation in two cored boreholes

    Science.gov (United States)

    Larsen, Daniel; Nelson, Philip H.

    2000-01-01

    Core descriptions and geophysical logs from two boreholes (CCM-1 and CCM-2) in the Oligocene Snowshoe Mountain Tuff and Creede Formation, south-central Colorado, are used to interpret sedimentary and volcanic facies associations and their physical properties. The seven facies association include a mixed sequence of intracaldera ash-flow tuffs and breccias, alluvial and lake margin deposits, and tuffaceous lake beds. These deposits represent volcanic units related to caldera collapse and emplacement of the Snowshoe Mountain Tuff, and sediments and pyroclastic material deposited in the newly formed caldera basin, Early sedimentation is interpreted to have been rapid, and to have occurred in volcaniclastic fan environments at CCM-1 and in a variery of volcaniclastic fan, braided stream shallow lacustrine, and mudflat environments at CCM-2. After an initial period of lake-level rise, suspension settling, turbidite, and debris-flow sedimentation occurred in lacustrine slope and basin environments below wave base. Carbonate sedimentation was initially sporadic, but more continuous in the latter part of the recorded lake history (after the H fallout tuff). Sublacustrine-fan deposition occurred at CCM-1 after a pronounced lake-level fall and subsequent rise that preceded the H tuff. Variations in density, neutron, gamma-ray, sonic, and electrical properties of deposits penetrated oin the two holes reflect variations in lithology, porosity, and alteration. Trends in the geophysical properties of the lacustrine strata are linked to downhole changes in authigenic mineralology and a decrease in porosity interpreted to have resulted primarily from diagenesis. Lithological and geophysical characteristics provide a basis for correlation of the cores; however, mineralogical methods of correlation are hampered by the degree of diagenesis and alteration.

  18. Formation of microemulsions for using as cosmeceutical delivery systems: effects of various components and characteristics of some formulations.

    Science.gov (United States)

    Wuttikul, Krisada; Boonme, Prapaporn

    2016-06-01

    Microemulsions are interesting formulations for cosmeceutical applications due to their good appearance, high solubilization power, thermodynamic stability, and enhancement of skin penetration. In addition, they can spontaneously form when suitable types and amounts of components are simply mixed. In this study, the phase behavior of the nonionic systems with various parameters was studied by construction of phase diagrams using titration method. Natural oils, i.e., coconut oil (CO), rice bran oil (RBO), and palm oil (PO), were analyzed for their fatty acid compositions and then mixed with blends of nonionic surfactants (Tween80: Span80) and water or mixtures of water and a cosolvent, propylene glycol (PG), to find the microemulsion regions. Subsequently, some microemulsions were selected for physical characterization. The largest microemulsion regions which were obtained from CO, RBO, and PO covered the sizes of 11.65, 9.84, and 9.24 %, respectively. The surfactant mixture at weight ratio of 1:1 was the most suitable for CO and PO, but for RBO, it was 2:1. PG could increase the microemulsion regions of PO from 9.24 to 15.33 %, depending on PG concentrations. Hence, the sizes of the microemulsion regions were related to oil types, surfactant mixtures, and ratios between water and PG. The studied microemulsions were water-in-oil (w/o) type, and their internal droplets were in the nanosize range. They exhibited Newtonian flow behavior and their mean viscosity values were from 247.53 to 690.35 cP which were correlated with the types and concentrations of the components in the formulations. In conclusion, natural oils could form w/o microemulsions with nonionic surfactants. The microemulsion formation and characteristics were related to many parameters of the components.

  19. Glitter in a 2D monolayer.

    Science.gov (United States)

    Yang, Li-Ming; Dornfeld, Matthew; Frauenheim, Thomas; Ganz, Eric

    2015-10-21

    We predict a highly stable and robust atomically thin gold monolayer with a hexagonal close packed lattice stabilized by metallic bonding with contributions from strong relativistic effects and aurophilic interactions. We have shown that the framework of the Au monolayer can survive 10 ps MD annealing simulations up to 1400 K. The framework is also able to survive large motions out of the plane. Due to the smaller number of bonds per atom in the 2D layer compared to the 3D bulk we observe significantly enhanced energy per bond (0.94 vs. 0.52 eV per bond). This is similar to the increase in bond strength going from 3D diamond to 2D graphene. It is a non-magnetic metal, and was found to be the global minima in the 2D space. Phonon dispersion calculations demonstrate high kinetic stability with no negative modes. This 2D gold monolayer corresponds to the top monolayer of the bulk Au(111) face-centered cubic lattice. The close-packed lattice maximizes the aurophilic interactions. We find that the electrons are completely delocalized in the plane and behave as 2D nearly free electron gas. We hope that the present work can inspire the experimental fabrication of novel free standing 2D metal systems.

  20. Nanotubes based on monolayer blue phosphorus

    KAUST Repository

    Montes Muñoz, Enrique

    2016-07-08

    We demonstrate structural stability of monolayer zigzag and armchair blue phosphorus nanotubes by means of molecular dynamics simulations. The vibrational spectrum and electronic band structure are determined and analyzed as functions of the tube diameter and axial strain. The nanotubes are found to be semiconductors with a sensitive indirect band gap that allows flexible tuning.

  1. Non-rotator phases in phospholipid monolayers?

    DEFF Research Database (Denmark)

    Kenn, R.M.; Kjær, K.; Möhwald, H.

    1996-01-01

    Monolayers of diacylphosphatidylethanolamines at the air/water interface are studied by grazing incidence X-ray diffraction. The results prove the existence of phases which show analogies with the rotator phases of single-chain surfactants: hexagonal tail lattice with no tilt; rectangular lattice...

  2. Statistical mechanics of a lipid monolayer

    NARCIS (Netherlands)

    Kox, A.J.; Wiegel, F.W.

    1978-01-01

    We calculate from first principles the equation of state of a simple type of membrane: a monolayer consisting of lipid chain molecules with short-range repulsive and long-range attractive forces. An approximate solution to the packing problem of the hydrocarbon chains is obtained by using a mathemat

  3. Semiconductor monolayer assemblies with oriented crystal faces

    KAUST Repository

    Ma, Guijun

    2012-01-01

    Fabrication of two-dimensional monolayers of crystalline oxide and oxynitride particles was attempted on glass plate substrates. X-Ray diffraction patterns of the assemblies show only specific crystal facets, indicative of the uniform orientation of the particles on the substrate. The selectivity afforded by this immobilization technique enables the organization of randomly distributed polycrystalline powders in a controlled manner.

  4. Structure of cholesterol/ceramide monolayer mixtures

    DEFF Research Database (Denmark)

    Scheffer, L.; Solomonov, I.; Weygand, M.J.

    2005-01-01

    The structure of monolayers of cholesterol/ ceramide mixtures was investigated using grazing incidence x-ray diffraction, immunofluorescence, and atomic force microscopy techniques. Grazing incidence x-ray diffraction measurements showed the existence of a crystalline mixed phase of the two...

  5. Edge conduction in monolayer WTe2

    Science.gov (United States)

    Fei, Zaiyao; Palomaki, Tauno; Wu, Sanfeng; Zhao, Wenjin; Cai, Xinghan; Sun, Bosong; Nguyen, Paul; Finney, Joseph; Xu, Xiaodong; Cobden, David H.

    2017-07-01

    A two-dimensional topological insulator (2DTI) is guaranteed to have a helical one-dimensional edge mode in which spin is locked to momentum, producing the quantum spin Hall effect and prohibiting elastic backscattering at zero magnetic field. No monolayer material has yet been shown to be a 2DTI, but recently the Weyl semimetal WTe2 was predicted to become a 2DTI in monolayer form if a bulk gap opens. Here, we report that, at temperatures below about 100 K, monolayer WTe2 does become insulating in its interior, while the edges still conduct. The edge conduction is strongly suppressed by an in-plane magnetic field and is independent of gate voltage, save for mesoscopic fluctuations that grow on cooling due to a zero-bias anomaly, which reduces the linear-response conductance. Bilayer WTe2 also becomes insulating at low temperatures but does not show edge conduction. Many of these observations are consistent with monolayer WTe2 being a 2DTI. However, the low-temperature edge conductance, for contacts spacings down to 150 nm, never reaches values higher than ~20 μS, about half the predicted value of e2/h, suggesting significant elastic scattering in the edge.

  6. Adsorption of Ions at Uncharged Insoluble Monolayers

    Science.gov (United States)

    Peshkova, T. V.; Minkov, I. L.; Tsekov, R.; Slavchov, R. I.

    2016-08-01

    A method is proposed for the experimental determination of the adsorption of inorganic electrolytes at a surface covered with insoluble surfactant monolayer. This task is complicated by the fact that the change of the salt concentration alters both chemical potentials of the electrolyte and the surfactant. Our method resolves the question by combining data for the surface pressure versus area of the monolayer at several salt concentrations with data for the equilibrium spreading pressure of crystals of the surfactant (used to fix a standard state). We applied the method to alcohols spread at the surface of concentrated halide solutions. The measured salt adsorption is positive and has nonmonotonic dependence on the area per surfactant molecule. For the liquid expanded film, depending on the concentration, there is one couple of ions adsorbed per each 3–30 surfactant molecules. We analyzed which ion, the positive or the negative, stands closer to the surface, by measuring the effect of NaCl on the Volta potential of the monolayer. The potentiometric data suggest that Na+ is specifically adsorbed, while Cl– remains in the diffuse layer, i.e., the surface is positively charged. The observed reverse Hofmeister series of the adsorptions of NaF, NaCl, and NaBr suggests the same conclusion holds for all these salts. The force that causes the adsorption of Na+ seems to be the interaction of the ion with the dipole moment of the monolayer.

  7. Penetration of lipid monolayers by psychoactive drugs

    NARCIS (Netherlands)

    Demel, R.A.; Deenen, L.L.M. van

    1966-01-01

    The ability of a number of psychoactive drugs to penetrate lipid monolayers of varying composition was examined, and the following observation were made: (1) The increase in surface pressure of a monomolecular film appeared to depend on the chemical nature of the lipid as well as on the initial film

  8. Molecular diffusion in monolayer and submonolayer nitrogen

    DEFF Research Database (Denmark)

    Hansen, Flemming Yssing; Bruch, Ludwig Walter

    2001-01-01

    The orientational and translational motions in a monolayer fluid of physisorbed molecular nitrogen are treated using molecular dynamics simulations. Dynamical response functions and several approximations to the coefficient of translational diffusion are determined for adsorption on the basal pla...... where the ballistic approximation to the translational molecular self-correlation function is accurate....

  9. Semifluorinated Alkylphosphonic Acids Form High-Quality Self-Assembled Monolayers on Ag-Coated Yttrium Barium Copper Oxide Tapes and Enable Filamentization of the Tapes by Microcontact Printing.

    Science.gov (United States)

    Park, Chul Soon; Lee, Han Ju; Lee, Dahye; Jamison, Andrew C; Galstyan, Eduard; Zagozdzon-Wosik, Wanda; Freyhardt, Herbert C; Jacobson, Allan J; Lee, T Randall

    2016-08-30

    A custom-designed semifluorinated phosphonic acid, (9,9,10,10,11,11,12,12,13,13,14,14,15,15,16,16,16-heptadecafluorohexadecyl)phosphonic acid (F8H8PA), and a normal hexadecylphosphonic acid (H16PA) were synthesized and used to generate self-assembled monolayers (SAMs) on commercially available yttrium barium copper oxide (YBCO) tapes. In this study, we wished to evaluate the effectiveness of these monolayer films as coatings for selectively etching YBCO. Initial films formed by solution deposition and manual stamping using a non-patterned polydimethylsiloxane stamp allowed for a comparison of the film-formation characteristics. The resulting monolayers were characterized by X-ray photoelectron spectroscopy (XPS), contact angle goniometry, and polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS). To prepare line-patterned (filamentized) YBCO tapes, standard microcontact printing (μ-CP) procedures were used. The stamped patterns on the YBCO tapes were characterized by scanning electron microscopy (SEM) before and after etching to confirm the effectiveness of the patterning process on the YBCO surface and energy-dispersive X-ray spectroscopy (EDX) to obtain the atomic composition of the exposed interface.

  10. Interaction of methionine-enkephalins with raft-forming lipids: monolayers and BAM experiments.

    Science.gov (United States)

    Tsanova, A; Jordanova, A; Dzimbova, T; Pajpanova, T; Golovinsky, E; Lalchev, Z

    2014-05-01

    Enkephalins (Tyr-Gly-Gly-Phe-Met/Leu) are opioid peptides with proven antinociceptive action in organism. They interact with opioid receptors belonging to G-protein coupled receptor superfamily. It is known that these receptors are located preferably in membrane rafts composed mainly of sphingomyelin (Sm), cholesterol (Cho), and phosphatidylcholine. In the present work, using Langmuir's monolayer technique in combination with Wilhelmy's method for measuring the surface pressure, the interaction of synthetic methionine-enkephalin and its amidated derivative with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), Sm, and Cho, as well as with their double and triple mixtures, was studied. From the pressure/area isotherms measured, the compressional moduli of the lipids and lipid-peptide monolayers were determined. Our results showed that the addition of the synthetic enkephalins to the monolayers studied led to change in the lipid monolayers characteristics, which was more evident in enkephalinamide case. In addition, using Brewster angle microscopy (BAM), the surface morphology of the lipid monolayers, before and after the injection of both enkephalins, was determined. The BAM images showed an increase in surface density of the mixed surface lipids/enkephalins films, especially with double and triple component lipid mixtures. This effect was more pronounced for the enkephalinamide as well. These observations showed that there was an interaction between the peptides and the raft-forming lipids, which was stronger for the amidated peptide, suggesting a difference in folding of both enkephalins. Our research demonstrates the potential of lipid monolayers for elegant and simple membrane models to study lipid-peptide interactions at the plane of biomembranes.

  11. Fluctuations in a ferrofluid monolayer: an integral equation study.

    Science.gov (United States)

    Luo, Liang; Klapp, Sabine H L

    2009-07-21

    Using integral equation theory in the reference hypernetted chain (RHNC) approximation we investigate the structure and phase behavior of a monolayer of dipolar spheres. The dipole orientations of the particles fluctuate within the plane. The resulting angle dependence of the correlation functions is treated via an expansion in two-dimensional rotational invariants. For homogeneous, isotropic states the RHNC correlation functions turn out to be in good agreement with Monte Carlo simulation data. We then use the RHNC theory combined with a stability (fluctuation) analysis to identify precursors of the low-temperature behavior. As expected, the fluctuations point to pair and cluster formation in the range of low and moderate densities. At high densities, there is no clear indication for a ferroelectric transition, contrary to what is found in three-dimensional dipolar fluids. The stability analysis rather indicates an alignment of chains supplemented by local crystal-like order.

  12. Synthesis of a Two-Dimensional Covalent Organic Monolayer through Dynamic Imine Chemistry at the Air/Water Interface.

    Science.gov (United States)

    Dai, Wenyang; Shao, Feng; Szczerbiński, Jacek; McCaffrey, Ryan; Zenobi, Renato; Jin, Yinghua; Schlüter, A Dieter; Zhang, Wei

    2016-01-01

    A two-dimensional covalent organic monolayer was synthesized from simple aromatic triamine and dialdehyde building blocks by dynamic imine chemistry at the air/water interface (Langmuir-Blodgett method). The obtained monolayer was characterized by optical microscopy, scanning electron microscopy, and atomic force microscopy, which unambiguously confirmed the formation of a large (millimeter range), unimolecularly thin aromatic polyimine sheet. The imine-linked chemical structure of the obtained monolayer was characterized by tip-enhanced Raman spectroscopy, and the peak assignment was supported by spectra simulated by density functional theory. Given the modular nature and broad substrate scope of imine formation, the work reported herein opens up many new possibilities for the synthesis of customizable 2D polymers and systematic studies of their structure-property relationships.

  13. Characteristics and formation mechanism of a heavy air pollution episode caused by biomass burning in Chengdu, Southwest China.

    Science.gov (United States)

    Chen, Yuan; Xie, Shao-Dong

    2014-03-01

    To track the chemical characteristics and formation mechanism of biomass burning pollution, the hourly variations of meteorological factors and pollutant concentrations during a heavy pollution on 18-21 May, 2012 in Chengdu are presented in this study. The episode was the heaviest and most long-lasting pollution event in the historical record of Chengdu caused by a combination of stagnant dispersion conditions and enhanced PM2.5 emission from intensive biomass burning, with peak values surpassing 500 μg m(-3). The event was characterized by three nighttime peaks, relating to the burning practice and decreased boundary layer height at night. The prevailing northeasterly wind during nighttime preferentially brought more pollutants to the urban regions from northern suburbs of Chengdu, where dense fire spots were observed. Due to the obstruction of hilly topography and weak wind speed, minor regional features were reflected from the PM10 variations in nearby cities, whereas the long-distance transport of the plume impacted extensive regions in northern and eastern China. Carbon monoxide (CO) concentrations increased by more than 200%, while exceptionally high PM2.5 levels of 190.1 and 268.4 μg m(-3) on 17 May and 18 May, were observed and showed high correlation with CO (r=0.75). The relative contribution of biomass burning smoke to organic carbon was estimated from OC/EC ratios (organic carbon/elemental carbon) and elevated to 81.3% during the episode, indicating a significant impact on urban aerosol levels. The occurrence of high PM2.5/PM10 ratios (>0.80) and K(+)/EC ratios (>1.0), along with the increased carbonaceous concentrations and their fraction in PM2.5 (>40%) and high OC/EC ratios (about 8), could be used as immediate indicators for biomass burning pollution in cities. In addition, the heavy pollution involved a mixture of anthropogenic sources, reflected from the high SOR and NOR values and increases in the EFs (enrichment factors) of Mo, Zn, Cd, and Pb.

  14. Investigation on the permeability characteristics of bedded salt rocks and the tightness of natural gas caverns in such formations

    NARCIS (Netherlands)

    Liu, Wei; Muhammad, N.; Chen, Jie; Spiers, C.J.; Peach, C.J.; Deyi, Jiang; Li, Yinping

    In China, the salt formations close to the lower reaches of the large natural gas routes and the main gas consuming regions are all bedded structures. The presences of non-halite or low-halite mudstone interlayers and interfaces (salt-interlayer) in these bedded salt formations increase the concern

  15. [Comparative characteristic of the formation of stereotype of aging in participants of current war conflicts and World War II].

    Science.gov (United States)

    Iakymets', V M

    2006-01-01

    The study was carried out to examine participants of current war conflicts and World War II in order to compare the development of the formation of stereotype of old age. It was established that participants of World War II have higher level of the formation of pessimistic stereotype of old age than participants of current war conflicts have.

  16. Multivariate analysis of ground water characteristics of Ajali sandstone formation: A case study of Udi and Nsukka LGAs of Enugu State of Nigeria

    Science.gov (United States)

    Orakwe, L. C.; Chukwuma, E. C.

    2017-05-01

    Multivariate statistical techniques were applied for the evaluation and interpretation of borehole characteristics of the Ajali sandstone geological formation of Enugu state of Nigeria to determine the latent structure of the borehole characteristics and to classify 9 borehole parameters from 33 locations into borehole groups of similar characteristics. Two chemometric data mining techniques used were, Cluster Analysis (CA) and Principal Component Analysis (PCA). PCA identified the borehole parameters responsible for variation in the borehole characteristic of the study area. Out of the nine parameters examined, the PCA identified borehole depth, borehole casing, static water level and dynamic water level as the most significant parameters responsible for variation in borehole characteristics. Hierarchical Cluster Analysis also grouped the 33 borehole locations into three clusters. The CA grouping of the borehole parameters showed similar trend with PCA hence validating the grouping of variations in the borehole characteristics in the geological zone. The results of the study indicate that PCA and CA are useful in offering reliable classification of the borehole characteristic of the study area.

  17. Epitaxial growth by monolayer restricted galvanic displacement

    Directory of Open Access Journals (Sweden)

    Vasilić Rastko

    2012-01-01

    Full Text Available The development of a new method for epitaxial growth of metals in solution by galvanic displacement of layers pre-deposited by underpotential deposition (UPD was discussed and experimentally illustrated throughout the lecture. Cyclic voltammetry (CV and scanning tunneling microscopy (STM are employed to carry out and monitor a “quasi-perfect”, two-dimensional growth of Ag on Au(111, Cu on Ag(111, and Cu on Au(111 by repetitive galvanic displacement of underpotentially deposited monolayers. A comparative study emphasizes the displacement stoichiometry as an efficient tool for thickness control during the deposition process and as a key parameter that affects the deposit morphology. The excellent quality of layers deposited by monolayer-restricted galvanic displacement is manifested by a steady UPD voltammetry and ascertained by a flat and uniform surface morphology maintained during the entire growth process.

  18. Transport measurement of Li doped monolayer graphene

    Science.gov (United States)

    Khademi, Ali; Sajadi, Ebrahim; Dosanjh, Pinder; Folk, Joshua; Stöhr, Alexander; Forti, Stiven; Starke, Ulrich

    Lithium adatoms on monolayer graphene have been predicted to induce superconductivity with a critical temperature near 8 K, and recent experimental evidence by ARPES indicates a critical temperature nearly that high. Encouraged by these results, we investigated the effects of lithium deposited at cryogenic temperatures on the electronic transport properties of epitaxial and CVD monolayer graphene down to 3 K. The change of charge carrier density due to Li deposition was monitored both by the gate voltage shift of the Dirac point and by Hall measurements, in low and high doping regimes. In the high doping regime, a saturation density of 2×1013 cm-2 was observed independent of sample type, initial carrier density and deposition conditions. No signatures of superconductivity were observed down to 3 K.

  19. Molecular tilt on monolayer-protected nanoparticles

    KAUST Repository

    Giomi, L.

    2012-02-01

    The structure of the tilted phase of monolayer-protected nanoparticles is investigated by means of a simple Ginzburg-Landau model. The theory contains two dimensionless parameters representing the preferential tilt angle and the ratio ε between the energy cost due to spatial variations in the tilt of the coating molecules and that of the van der Waals interactions which favors the preferential tilt. We analyze the model for both spherical and octahedral particles. On spherical particles, we find a transition from a tilted phase, at small ε, to a phase where the molecules spontaneously align along the surface normal and tilt disappears. Octahedral particles have an additional phase at small ε characterized by the presence of six topological defects. These defective configurations provide preferred sites for the chemical functionalization of monolayer-protected nanoparticles via place-exchange reactions and their consequent linking to form molecules and bulk materials. Copyright © EPLA, 2012.

  20. Supramolecular Langmuir monolayers and multilayered vesicles of self-assembling DNA–lipid surface structures and their further implications in polyelectrolyte-based cell transfections

    Energy Technology Data Exchange (ETDEWEB)

    Demirsoy, Fatma Funda Kaya [Ankara University, The Central Laboratory of The Institute of Biotechnology (Turkey); Eruygur, Nuraniye [Gazi University, Department of Pharmacognosy, Faculty of Pharmacy (Turkey); Süleymanoğlu, Erhan, E-mail: erhans@mail.ru [Gazi University, Department of Pharmaceutical Chemistry, Faculty of Pharmacy (Turkey)

    2015-01-15

    The basic interfacial characteristics of DNA–lipid recognitions have been studied. The complex structures of individual unbound DNA molecules and their binary and ternary complexes with zwitterionic lipids and divalent cations were followed by employing lipid monolayers at the air–liquid interfaces, as well as by performing various microscopic, spectroscopic, and thermodynamic measurements with multilayered vesicles. The pressure-area isotherms depicted that Mg{sup 2+}-ions increase the surface pressure of lipid films and thus give rise to electrostatic and hydrophobic lipid–DNA interactions in terms of DNA adsorption, adhesion, and compaction. These features were further approached by using multilamellar vesicles with a mean diameter of 850 nm, where a metal ion-directed nucleic acid compaction and condensation effects were shown. The data obtained show the effectiveness of Langmuir monolayers and lipid multilayers in studying nucleic acid–lipid recognitions. The data provide with further details and support previous reports on mainly structural features of these recognitions. Biomolecular surface recognition events were presented in direct link with spectral and thermodynamic features of lipid vesicle–polynucleotide complex formations. The results serve to build a theoretical model considering the use of neutral lipids in lipoplex designs as a polyelectrolyte alternatives to the currently employed cytotoxic cationic liposomes. The supramolecular structures formed and their possible roles in interfacial electrostatic and hydrophobic mechanisms of endosomal escape in relevant cell transfection assays are particularly emphasized.

  1. Monolayer solid of N-2/Ag(111)

    DEFF Research Database (Denmark)

    Bruch, L.W.; Hansen, Flemming Yssing

    1998-01-01

    An incommensurate monolayer solid of N-2/Ag(111) is modeled using extensive molecular-dynamics simulations. The conditions treated range from the low-temperature orientationally ordered solid to the melting of the solid. The properties are evaluated as a function of spreading pressure. Comparison...... is made to recent experimental data for N-2/Ag(111) and to results for N-2 adsorbed on graphite. Cu(110), and MgO(001). [S0163-1829(98)02715-5]....

  2. Elasticity of a quantum monolayer solid

    DEFF Research Database (Denmark)

    Bruch, Ludwig Walter

    1992-01-01

    A perturbation-theory formulation of the zero-temperature elastic constants is used to verify symmetry relations for a (monolayer) triangluar lattice. A generalization of the Cauchy relation between the two elastic constants of the triangular lattice with central-pair-potential interactions is gi...... is given for the quantum solid. The first-order quantum corrections are rederived in this formalism, and previous calculations are reanalyzed....

  3. Fluidization of a dipalmitoyl phosphatidylcholine monolayer by fluorocarbon gases: potential use in lung surfactant therapy.

    Science.gov (United States)

    Gerber, Frédéric; Krafft, Marie Pierre; Vandamme, Thierry F; Goldmann, Michel; Fontaine, Philippe

    2006-05-01

    Fluorocarbon gases (gFCs) were found to inhibit the liquid-expanded (LE)/liquid-condensed (LC) phase transition of dipalmitoyl phosphatidylcholine (DPPC) Langmuir monolayers. The formation of domains of an LC phase, which typically occurs in the LE/LC coexistence region upon compression of DPPC, is prevented when the atmosphere above the DPPC monolayer is saturated with a gFC. When contacted with gFC, the DPPC monolayer remains in the LE phase for surface pressures lower than 38 mN m(-1), as assessed by compression isotherms and fluorescence microscopy (FM). Moreover, gFCs can induce the dissolution of preexisting LC phase domains and facilitate the respreading of the DPPC molecules on the water surface, as shown by FM and grazing incidence x-ray diffraction. gFCs have thus a highly effective fluidizing effect on the DPPC monolayer. This gFC-induced fluidizing effect was compared with the fluidizing effect brought about by a mixture of unsaturated lipids and proteins, namely the two commercially available lung surfactant substitutes, Curosurf and Survanta, which are derived from porcine and bovine lung extracts, respectively. The candidate FCs were chosen among those already investigated for biomedical applications, and in particular for intravascular oxygen transport, i.e., perfluorooctyl bromide, perfluorooctylethane, bis(perfluorobutyl)ethene, perfluorodecalin, and perfluorooctane. The fluidizing effect is most effective with the linear FCs. This study suggests that FCs, whose biocompatibility is well documented, may be useful in lung surfactant substitute compositions.

  4. Fluorinated alkyne-derived monolayers on oxide-free silicon nanowires via one-step hydrosilylation

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen Minh, Quyen [Laboratory of Organic Chemistry, Wageningen University, Stippeneng 4, 6708 WE Wageningen (Netherlands); Nanosens, IJsselkade 7, 7201 HB Zutphen (Netherlands); Pujari, Sidharam P. [Laboratory of Organic Chemistry, Wageningen University, Stippeneng 4, 6708 WE Wageningen (Netherlands); Wang, Bin [The Department of Chemical Engineering and Russell Berrie Nanotechnology Institute, Technion – Israel Institute of Technology, Haifa 3200003 (Israel); Wang, Zhanhua [Laboratory of Organic Chemistry, Wageningen University, Stippeneng 4, 6708 WE Wageningen (Netherlands); Haick, Hossam [The Department of Chemical Engineering and Russell Berrie Nanotechnology Institute, Technion – Israel Institute of Technology, Haifa 3200003 (Israel); Zuilhof, Han [Laboratory of Organic Chemistry, Wageningen University, Stippeneng 4, 6708 WE Wageningen (Netherlands); Rijn, Cees J.M. van, E-mail: cees.vanrijn@wur.nl [Laboratory of Organic Chemistry, Wageningen University, Stippeneng 4, 6708 WE Wageningen (Netherlands)

    2016-11-30

    Highlights: • Oxide-free H-terminated silicon nanowires undergo efficient surface modification by reaction with fluorinated 1-alkynes (HC≡C−(CH{sub 2}){sub 6}C{sub 8}H{sub 17−x}F{sub x}; x = 0–17). • These surface-modified Si NWs are chemically stable under range of conditions (including acid, base). • The surface coating yields efficient electrical passivation as demonstrated by a near-zero electrochemical activity of the surface. - Abstract: Passivation of oxide-free silicon nanowires (Si NWs) by the formation of high-quality fluorinated 1-hexadecyne-derived monolayers with varying fluorine content has been investigated. Alkyl chain monolayers (C{sub 16}H{sub 30−x}F{sub x}) with a varying number of fluorine substituents (x = 0, 1, 3, 9, 17) were attached onto hydrogen-terminated silicon (Si−H) surfaces with an effective one-step hydrosilylation. This surface chemistry gives well-defined monolayers on nanowires that have a cylindrical core–shell structure, as characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and static contact angle (SCA) analysis. The monolayers were stable under acidic and basic conditions, as well as under extreme conditions (such as UV exposure), and provide excellent surface passivation, which opens up applications in the fields of field effect transistors, optoelectronics and especially for disease diagnosis.

  5. Interfacial binding of divalent cations to calixarene-based Langmuir monolayers.

    Science.gov (United States)

    Tulli, Ludovico G; Wang, Wenjie; Lindemann, William R; Kuzmenko, Ivan; Meier, Wolfgang; Vaknin, David; Shahgaldian, Patrick

    2015-03-03

    The interactions of Langmuir monolayers produced through the self-assembly of an amphiphilic p-carboxycalix[4]arene (1) with a series of divalent, fourth-period transition metals, at the air-water interface, were investigated. Changes in the interfacial behavior of 1 in response to the presence of CuCl2, CoCl2, MnCl2, and NiCl2 were studied by means of Langmuir compression isotherms and Brewster angle microscopy (BAM). The measurements revealed that the self-assembly properties of 1 are significantly affected by Cu(2+) ions. The interactions of 1-based monolayers with Co(2+) and Cu(2+) ions were further investigated by means of synchrotron radiation-based X-ray reflectivity (XRR), X-ray near-total-reflection fluorescence (XNTRF), and grazing incidence X-ray diffraction (GIXD). XNTRF and XRR analyses revealed that the monolayer of 1 binds more strongly to Cu(2+) than Co(2+) ions. In the presence of relatively high concentrations of Cu(2+) ions in the subphase (1.4 × 10(-3) M), XNTRF exhibited anomalous depth profile behavior and GIXD measurements showed considerably strong diffuse scattering. Both measurements suggest the formation of Cu(2+) clusters contiguous to the monolayer of 1.

  6. Exciton center-of-mass localization and dielectric environment effect in monolayer WS2

    Science.gov (United States)

    Hichri, Aïda; Ben Amara, Imen; Ayari, Sabrine; Jaziri, Sihem

    2017-06-01

    The ultrathin transition metal dichalcogenides (TMDs) have emerged as promising materials for various applications using two dimensional semiconductors. They have attracted increasing attention due to their unique optical properties originate from neutral and charged excitons. In this paper, we study the strong localization of exciton center-of-mass motion within random potential fluctuations caused by the monolayer defects. Here, we report negatively charged exciton formation in monolayer TMDs, notably tungsten disulfide WS2. Our theory is based on an effective mass model of neutral and charged excitons, parameterized by ab-initio calculations. Taking into the account the strong correlation between the monolayer WS2 and the surrounding dielectric environment, our theoretical results are in good agreement with one-photon photoluminescence (PL) and reflectivity measurements. We also show that the exciton state with p-symmetry, experimentally observed by two-photon PL emission, is energetically below the 2s-state. We use the equilibrium mass action law, to quantify the relative weight of exciton and trion PL. We show that exciton and trion emission can be tuned and controlled by external parameters like temperature, pumping, and injection electrons. Finally, in comparison with experimental measurements, we show that exciton emission in monolayer tungsten dichalcogenides is substantially reduced. This feature suggests that free exciton can be trapped in disordered potential wells to form a localized exciton and therefore offers a route toward novel optical properties.

  7. The Tunable Hybrid Surface Phonon and Plasmon Polariton Modes in Boron Nitride Nanotube and Graphene Monolayer Heterostructures

    CERN Document Server

    Sun, Yu; Cheng, Jiangtao; Liu, Jiansheng

    2014-01-01

    The hybrid modes incorporating surface phonon polariton (SPhP) modes in boron nitride nanotubes (BNNTs) and surface plasmon polariton (SPP) modes in graphene monolayers are theoretically studied. The combination of the 1D BNNTs and 2D graphene monolayer further improves the modal characteristics with electrical tunability. Superior to the graphene monolayers, the proposed heterostructures supports single mode transmission with lateral optical confinement. The modal characteristics can be shifted from SPP-like toward SPhP-like. Both the figure of merit and field enhancement of hybrid modes are improved over 3 times than those of BNNT SPhP modes, which may further enable sub-wavelength mid-infrared applications.

  8. Comparative Study of Monolayer and Bilayer Epitaxial Graphene Field-Effect Transistors on SiC Substrates

    Institute of Scientific and Technical Information of China (English)

    Ze-Zhao He; Ke-Wu Yang; Cui Yu; Qing-Bin Liu; Jing-Jing Wang; Xu-Bo Song; Ting-Ting Han

    2016-01-01

    Monolayer and bilayer graphenes have generated tremendous excitement as the potentially useful electronic materials due to their unique features.We report on monolayer and bilayer epitaxial graphene field-effect transistors (GFETs) fabricated on SiC substrates.Compared with monolayer GFETs,the bilayer GFETs exhibit a significant improvement in dc characteristics,including increasing current density IDS,improved transconductance gm,reduced sheet resistance Ron,and current saturation.The improved electrical properties and tunable bandgap in the bilayer graphene lead to the excellent dc performance of the bilayer GFETs.Furthermore,the improved dc characteristics enhance a better rf performance for bilayer graphene devices,demonstrating that the quasifree-standing bilayer graphene on SiC substrates has a great application potential for the future graphene-based electronics.

  9. Strain mapping in a graphene monolayer nanocomposite.

    Science.gov (United States)

    Young, Robert J; Gong, Lei; Kinloch, Ian A; Riaz, Ibtsam; Jalil, Rashed; Novoselov, Kostya S

    2011-04-26

    Model composite specimens have been prepared consisting of a graphene monolayer sandwiched between two thin layers of polymer on the surface of a poly(methyl methacrylate) beam. It has been found that well-defined Raman spectra can be obtained from the single graphene atomic layer and that stress-induced Raman band shifts enable the strain distribution in the monolayer to be mapped with a high degree of precision. It has been demonstrated that the distribution of strain across the graphene monolayer is relatively uniform at levels of applied strain up to 0.6% but that it becomes highly nonuniform above this strain. The change in the strain distributions has been shown to be due to a fragmentation process due to the development of cracks, most likely in the polymer coating layers, with the graphene remaining intact. The strain distributions in the graphene between the cracks are approximately triangular in shape, and the interfacial shear stress in the fragments is only about 0.25 MPa, which is an order of magnitude lower than the interfacial shear stress before fragmentation. This relatively poor level of adhesion between the graphene and polymer layers has important implications for the use of graphene in nanocomposites, and methods of strengthening the graphene-polymer interface are discussed.

  10. Grafted silane monolayers: reconsideration of growth mechanisms

    Science.gov (United States)

    Ivanov, D. A.; Nysten, B.; Jonas, A. M.; Legras, R.

    1998-03-01

    Chemical force microscopy is a new technique devised to image chemical heterogeneities on surfaces. It requires the chemical modification of Atomic Force Microscopy (AFM) tips in order to create chemical probes. In this respect, self-assembled monolayers (SAM) of alkylchlorosilanes are particularly interesting as modifying agents for AFM tips. We report here our results on the kinetics of silanization and on the structure of such SAM's grafted on model surfaces (hydroxylated Si(100) wafers). AFM, contact angle measurements, X-ray reflectivity and X-ray photoelectron spectroscopy were used to characterize SAM's of octadecyltrichlorosilane (OTS) and octadecyldimethylchlorosilane (ODMS) grown from hexadecane and toluene solutions. The mechanism of grafting of OTS follows two stages. The first rapid stage corresponds to the nucleation and growth of island-like monolayer domains. The second slower stage is related to the densification of the monolayer. SAM's of ODMS were found to form thinner layers as compared to OTS, due to their lower grafting density probably resulting in a more disordered state of grafted alkyl chains. We also address the problems concerning the relationships between the quality of final SAM structures and the water content as well as the nature of the solvent used for silanization.

  11. Janus monolayers of transition metal dichalcogenides

    KAUST Repository

    Lu, Ang-Yu

    2017-05-15

    Structural symmetry-breaking plays a crucial role in determining the electronic band structures of two-dimensional materials. Tremendous efforts have been devoted to breaking the in-plane symmetry of graphene with electric fields on AB-stacked bilayers or stacked van der Waals heterostructures. In contrast, transition metal dichalcogenide monolayers are semiconductors with intrinsic in-plane asymmetry, leading to direct electronic bandgaps, distinctive optical properties and great potential in optoelectronics. Apart from their in-plane inversion asymmetry, an additional degree of freedom allowing spin manipulation can be induced by breaking the out-of-plane mirror symmetry with external electric fields or, as theoretically proposed, with an asymmetric out-of-plane structural configuration. Here, we report a synthetic strategy to grow Janus monolayers of transition metal dichalcogenides breaking the out-of-plane structural symmetry. In particular, based on a MoS2 monolayer, we fully replace the top-layer S with Se atoms. We confirm the Janus structure of MoSSe directly by means of scanning transmission electron microscopy and energy-dependent X-ray photoelectron spectroscopy, and prove the existence of vertical dipoles by second harmonic generation and piezoresponse force microscopy measurements.

  12. Investigation on gallium ions impacting monolayer graphene

    Directory of Open Access Journals (Sweden)

    Xin Wu

    2015-06-01

    Full Text Available In this paper, the physical phenomena of gallium (Ga+ ion impacting monolayer graphene in the nanosculpting process are investigated experimentally, and the mechanisms are explained by using Monte Carlo (MC and molecular dynamics (MD simulations. Firstly, the MC method is employed to clarify the phenomena happened to the monolayer graphene target under Ga+ ion irradiation. It is found that substrate has strong influence on the damage mode of graphene. The mean sputtering yield of graphene under 30 keV Ga+ ion irradiation is 1.77 and the least ion dose to completely remove carbon atoms in graphene is 21.6 ion/nm2. Afterwards, the focused ion beam over 21.6 ion/nm2 is used for the irradiation on a monolayer graphene supported by SiO2 experimentally, resulting in the nanostructures, i.e., nanodot and nanowire array on the graphene. The performances of the nanostructures are characterized by atomic force microscopy and Raman spectrum. A plasma plume shielding model is put forward to explain the nanosculpting results of graphene under different irradiation parameters. In addition, two damage mechanisms are found existing in the fabrication process of the nanostructures by using empirical MD simulations. The results can help us open the possibilities for better control of nanocarbon devices.

  13. Investigation on gallium ions impacting monolayer graphene

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Xin; Zhao, Haiyan, E-mail: hyzhao@tsinghua.edu.cn; Yan, Dong; Pei, Jiayun [State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, P. R. Chinaand Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China)

    2015-06-15

    In this paper, the physical phenomena of gallium (Ga{sup +}) ion impacting monolayer graphene in the nanosculpting process are investigated experimentally, and the mechanisms are explained by using Monte Carlo (MC) and molecular dynamics (MD) simulations. Firstly, the MC method is employed to clarify the phenomena happened to the monolayer graphene target under Ga{sup +} ion irradiation. It is found that substrate has strong influence on the damage mode of graphene. The mean sputtering yield of graphene under 30 keV Ga{sup +} ion irradiation is 1.77 and the least ion dose to completely remove carbon atoms in graphene is 21.6 ion/nm{sup 2}. Afterwards, the focused ion beam over 21.6 ion/nm{sup 2} is used for the irradiation on a monolayer graphene supported by SiO2 experimentally, resulting in the nanostructures, i.e., nanodot and nanowire array on the graphene. The performances of the nanostructures are characterized by atomic force microscopy and Raman spectrum. A plasma plume shielding model is put forward to explain the nanosculpting results of graphene under different irradiation parameters. In addition, two damage mechanisms are found existing in the fabrication process of the nanostructures by using empirical MD simulations. The results can help us open the possibilities for better control of nanocarbon devices.

  14. Exploring atomic defects in molybdenum disulphide monolayers

    KAUST Repository

    Hong, Jinhua

    2015-02-19

    Defects usually play an important role in tailoring various properties of two-dimensional materials. Defects in two-dimensional monolayer molybdenum disulphide may be responsible for large variation of electric and optical properties. Here we present a comprehensive joint experiment-theory investigation of point defects in monolayer molybdenum disulphide prepared by mechanical exfoliation, physical and chemical vapour deposition. Defect species are systematically identified and their concentrations determined by aberration-corrected scanning transmission electron microscopy, and also studied by ab-initio calculation. Defect density up to 3.5 × 10 13 cm \\'2 is found and the dominant category of defects changes from sulphur vacancy in mechanical exfoliation and chemical vapour deposition samples to molybdenum antisite in physical vapour deposition samples. Influence of defects on electronic structure and charge-carrier mobility are predicted by calculation and observed by electric transport measurement. In light of these results, the growth of ultra-high-quality monolayer molybdenum disulphide appears a primary task for the community pursuing high-performance electronic devices.

  15. Spectral characteristics of banded iron formations in Singhbhum craton, eastern India: Implications for hematite deposits on Mars

    OpenAIRE

    Singh, Mahima; Singhal, Jayant; K.arun Prasad; Rajesh, V.J.; Ray, Dwijesh; Sahoo, Priyadarshi

    2016-01-01

    Banded iron formations (BIFs) are major rock units having hematite layers intermittent with silica rich layers and formed by sedimentary processes during late Archean to mid Proterozoic time. In terrestrial environment, hematite deposits are mainly found associated with banded iron formations. The BIFs in Lake Superior (Canada) and Carajas (Brazil) have been studied by planetary scientists to trace the evolution of hematite deposits on Mars. Hematite deposits are extensively identified in Mer...

  16. Formation, structure, and properties of "welded" h-BN/graphene compounds

    Science.gov (United States)

    Chernozatonskii, L. A.; Demin, V. A.; Artyukh, A. A.

    2016-07-01

    Structures of h-BN/graphene with holes where atoms at the edges are bonded to each other by sp 2 hybridized C-B and C-N bonds and form continuous junctions from layer to layer with topological defects inside holes have been considered. Their formation, as well as the moiré-type stable atomic structure of such compounds (with different rotation angles of graphene with respect to the hexagonal boron nitride monolayer) with closed hexagonal holes in the AA centers of packing of the moiré superlattice, has been studied. The stability, as well as the electronic and mechanical properties, of such bilayer BN/graphene nanomeshes has been analyzed within electron density functional theory. It has been shown that they have semiconducting properties. Their electronic band structures and mechanical characteristics differ from the respective properties of separate monolayer nanomeshes with the same geometry and arrangement of holes.

  17. 《中国手语》中手语构词特点分析%Analysis on the Word Formation Characteristics of Entries in Chinese Sign Language

    Institute of Scientific and Technical Information of China (English)

    毛赛群; 兰继军

    2014-01-01

    The word formation characteristics of Chinese sign language means that there are some characteris-tics and relations between the entries of Chinese sign language.The word formation characteristics of entries in Chi-nese Sign Language are mainly embodied in five aspects:generation phenomenon,basic word phenomenon,reduc-tion phenomenon,facial expressions and posture as the component of sign language and the connection between sign position and word formation.%手语构词特点,指手语词汇之间共有的某些特点与联系,是从所有手语词汇中总结得出的规律与特征。《中国手语》中手语的构词特点主要表现在五个方面:兼代现象,基本词现象,简缩现象,面部表情与体态成为构词成分,手语位置与构词存在关联。

  18. A comparative study for Hydrogen storage in metal decorated graphyne nanotubes and graphyne monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Jinlian [Department of Physics, Xiangtan University, Xiangtan, Hunan 411105 (China); Guo, Yanhua [College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009 (China); Zhang, Yun; Tang, Yingru [Department of Physics, Xiangtan University, Xiangtan, Hunan 411105 (China); Cao, Juexian, E-mail: jxcao@xtu.edu.cn [Department of Physics, Xiangtan University, Xiangtan, Hunan 411105 (China); Beijing Computational Science Research Center, Beijing 100084 (China)

    2015-11-15

    A comparative study for hydrogen storage in metal decorated graphyne nanotubes and graphyne monolayers has been investigated within the framework of first-principle calculations. Our results show that the binding energies of Li, Ca, Sc, Ti on graphyne nanotubes are stronger than that on graphyne monolayers. Such strong binding would prevent the formation of metal clusters on graphyne nanotubes. From the charge transfer and partial density of states, it is found that the curvature effect of nanotubes plays an important role for the strong binding strength of metal on graphyne nanotubes. And the hydrogen storage capacity is 4.82 wt%, 5.08 wt%, 4.88 wt%, 4.76 wt% for Li, Ca, Sc, Ti decorated graphyne nanotubes that promise a potential material for storing hydrogen. - Graphical abstract: Metal atoms (Li, Ca, Sc and Ti) can strongly bind to graphyne nanotubes to avoid the formation of metal clusters, and a capacity of Ca@graphyne nanotube is 5.08 wt% which is close to the requirement of DOE in 2015. Twenty-four hydrogen molecules absorb to Ti-decorated graphyne nanotube. - Highlights: • The binding strength for metal on graphyne nanotubes is much stronger than that on γ-graphyne monolayer. • Metal atoms can strongly bind to the curving triangle acetylenes rings to avoid the formation of metal clusters. • A capacity of Ca@graphyne nanotube is 5.08 wt% which is close to the requirement of DOE in 2015.

  19. HAMLET forms annular oligomers when deposited with phospholipid monolayers.

    Science.gov (United States)

    Baumann, Anne; Gjerde, Anja Underhaug; Ying, Ming; Svanborg, Catharina; Holmsen, Holm; Glomm, Wilhelm R; Martinez, Aurora; Halskau, Oyvind

    2012-04-20

    Recently, the anticancer activity of human α-lactalbumin made lethal to tumor cells (HAMLET) has been linked to its increased membrane affinity in vitro, at neutral pH, and ability to cause leakage relative to the inactive native bovine α-lactalbumin (BLA) protein. In this study, atomic force microscopy resolved membrane distortions and annular oligomers (AOs) produced by HAMLET when deposited at neutral pH on mica together with a negatively charged lipid monolayer. BLA, BAMLET (HAMLET's bovine counterpart) and membrane-binding Peptide C, corresponding to BLA residues 75-100, also form AO-like structures under these conditions but at higher subphase concentrations than HAMLET. The N-terminal Peptide A, which binds to membranes at acidic but not at neutral pH, did not form AOs. This suggests a correlation between the capacity of the proteins/peptides to integrate into the membrane at neutral pH-as observed by liposome content leakage and circular dichroism experiments-and the formation of AOs, albeit at higher concentrations. Formation of AOs, which might be important to HAMLET's tumor toxic action, appears related to the increased tendency of the protein to populate intermediately folded states compared to the native protein, the formation of which is promoted by, but not uniquely dependent on, the oleic acid molecules associated with HAMLET. Copyright © 2012 Elsevier Ltd. All rights reserved.

  20. Electronic and magnetic properties of X-doped (X=Ni, Pd, Pt) WS{sub 2} monolayer

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Xu, E-mail: zhaoxu@htu.cn [College of Physics and Electronic Engineering, Henan Normal University, Xinxiang, Henan 453007 (China); Xia, Congxin [College of Physics and Electronic Engineering, Henan Normal University, Xinxiang, Henan 453007 (China); Dai, Xianqi [College of Physics and Electronic Engineering, Henan Normal University, Xinxiang, Henan 453007 (China); Department of Physics, Zhengzhou Normal University, Zhengzhou, Henan 450044 (China); Wang, Tianxing; Chen, Peng; Tian, Liang [College of Physics and Electronic Engineering, Henan Normal University, Xinxiang, Henan 453007 (China)

    2016-09-15

    We investigate the electronic and magnetic properties of X-doped (X=Ni, Pd, Pt) WS{sub 2} monolayer using the first-principles methods based on density functional theory. The results show that WS{sub 2} monolayer doped by Ni, Pd and Pt is ferromagnetic. The impurity states near the Fermi level depend highly on the atomic size and electronegativity. For different X-doped WS{sub 2}, the formation energy is lower under S-rich conditions, which indicates that it is energy favorable and relatively easier to incorporate X atom into WS{sub 2} under S-rich experimental conditions. Moreover, Ni-doped system owns the lowest formation energy compared with other atoms under S-rich experimental condition. Our studies predict X-doped (X=Ni, Pd, Pt) WS{sub 2} monolayers to be candidates for thin dilute magnetic semiconductors. Ni-doped WS{sub 2} has relatively wide half-metallic gap. So Ni-doped WS{sub 2} is the most ideal for spin injection among Ni, Pd, and Pt, which is important for application in semiconductor spintronics. - Highlights: • WS{sub 2} monolayer doped by Ni, Pd and Pt is ferromagnetic. • The formation energy is lower under S-rich conditions. • Ni-doped system owns wide half-metallic gap and the lowest formation energy. • Ni-doped WS{sub 2} is the most ideal for spin injection among Ni, Pd, and Pt.

  1. Development of a living membrane comprising a functional human renal proximal tubule cell monolayer on polyethersulfone polymeric membrane

    NARCIS (Netherlands)

    Schophuizen, Carolien M S; De Napoli, Ilaria E; Jansen, Jitske; Teixeira, Sandra; Wilmer, Martijn J; Hoenderop, Joost G J; Van den Heuvel, Lambert P W; Masereeuw, R.; Stamatialis, Dimitrios

    2015-01-01

    The need for improved renal replacement therapies has stimulated innovative research for the development of a cell-based renal assist device. A key requirement for such a device is the formation of a "living membrane", consisting of a tight kidney cell monolayer with preserved functional organic ion

  2. Interfacial Interactions and Nanostructure Changes in DPPG/HD Monolayer at the Air/Water Interface

    Directory of Open Access Journals (Sweden)

    Huaze Zhu

    2015-01-01

    Full Text Available Lung surfactant (LS plays a crucial role in regulating surface tension during normal respiration cycles by decreasing the work associated with lung expansion and therefore decreases the metabolic energy consumed. Monolayer surfactant films composed of a mixture of phospholipids and spreading additives are of optional utility for applications in lung surfactant-based therapies. A simple, minimal model of such a lung surfactant system, composed of 1,2-dipalmitoyl-sn-glycero-3-[phosphor-rac-(1-gylcerol] (DPPG and hexadecanol (HD, was prepared, and the surface pressure-area (π-A isotherms and nanostructure characteristics of the binary mixture were investigated at the air/water interface using a combination of Langmuir-Blodgett (LB and atomic force microscopy (AFM techniques. Based on the regular solution theory, the miscibility and stability of the two components in the monolayer were analyzed in terms of compression modulus (Cs-1 , excess Gibbs free energy (ΔGexcπ , activity coefficients (γ, and interaction parameter (ξ. The results of this paper provide valuable insight into basic thermodynamics and nanostructure of mixed DPPG/HD monolayers; it is helpful to understand the thermodynamic behavior of HD as spreading additive in LS monolayer with a view toward characterizing potential improvements to LS performance brought about by addition of HD to lung phospholipids.

  3. Functional monolayers for direct electrical biosensing

    Science.gov (United States)

    Clare, Tami Lasseter

    Frequency-dependent electrochemical impedance spectroscopy has been used to characterize changes in electrical response that accompany specific binding of a protein to its substrate, using the biotin-avidin system as a model. This thesis work shows that avidin, at concentrations in the nanomolar range, can be detected electrically in a completely label-free manner under conditions of zero average current flow and without the use of any auxiliary redox agents. Electrical circuit modeling of the interface was used to relate the frequency-dependent electrical response to the physical picture of the interface before and after avidin binding. The interaction of proteins with semiconductors such as silicon and diamond is of great interest for applications such as electronic biosensing. Investigations into the use of covalently bound oligo(ethylene glycol), EG, monolayers on diamond and silicon to minimize nonspecific protein adsorption were conducted. Protein adsorption was monitored by fluorescence scanning as a function the length of the ethylene glycol chain (EG3 through EG6) and the terminal functional group (methyl- versus hydroxyl-terminated EG3 monolayer). More quantitative measurements were made by eluting adsorbed avidin from the surface and measuring the intensity of fluorescence in the solution. This thesis work shows that high quality EG monolayers are formed on silicon and diamond and that these EG3 monolayers are as effective as EG3 self-assembled monolayers on gold at resisting nonspecific avidin adsorption. These results show promise for use of silicon and diamond materials in many potential applications such as biosensing and medical implants. Substrate roughness is shown to play a role in nonspecific protein adsorption, where carbon-based surfaces having features less than approximately 5 nm, are highly resistant to protein adsorption. Functionalization of the surfaces with hexaethylene glycol confers additional resistance to protein adsorption. These

  4. Ferroelectric Switching of Vinylidene and Trifluoroethylene Copolymer Thin Films on Au Electrodes Modified with Self-Assembled Monolayers

    Directory of Open Access Journals (Sweden)

    Naoto Tsutsumi

    2014-09-01

    Full Text Available The ferroelectric switching characteristics of a vinylidene fluoride and trifluoroethylene copolymer were significantly changed via the chemical modification of a gold electrode with an alkanethiol self-assembled monolayer (SAM. The alkanethiol SAM-Au electrode successfully suppressed the leakage current (dark current from the electrode to the bulk ferroelectric. Smaller leakage currents led to the formation of an effective electric field in the bulk ferroelectric. At switching cycles ranging from 10 to 100 kHz, significant changes in the ferroelectric properties were observed. At 100 kHz, a remanent polarization (Pr of 68 mC·m−2 was measured, whereas a very small Pr value of 2.4 mC·m−2 was measured for the sample without a SAM. The switching speed of the SAM-Au electrode is as twice as fast as that of the unmodified electrode. A large potential barrier was formed via the insertion of a SAM between the Au electrode and the ferroelectric, effectively changing the ferroelectric switching characteristics.

  5. ENVIRONMENTALLY FRIENDLY COMPLEXONES. THE THERMODYNAMIC CHARACTERISTICS OF THE FORMATION OF AL3+ ION COMPLEXES WITH ETHYLENEDIAMINEDISUCCINIC ACID IN AQUEOUS SOLUTIONS

    Directory of Open Access Journals (Sweden)

    L.N. Tolkacheva

    2012-06-01

    Full Text Available Complex formation between Al3+ and ethylenediamine - N,N`-disuccinic acid (H4L was studied at 25°C against the background of 0.1, 0.5, 1.0 N solutions of KNO3 by potentiometry and mathematical modeling. The extrapolation of concentration constants to zero ionic strength was used to calculate the thermodynamic constants of the formation of the AlL–, AlHL complexes using an equation with one individual parameter (logβ0 = 16.27 ± 0.07, 9.19 ± 0.2 respectively.

  6. Comparison of the water change characteristics between the formation and dissociation of methane hydrate and the freezing and thawing of ice in sand

    Institute of Scientific and Technical Information of China (English)

    Peng Zhang; Qingbai Wu; Yingmei Wang

    2009-01-01

    Hydrate formation and dissociation processes are always accompanied by water migration in porous media, which is similar to the ice. In our study, a novel pF-meter sensor which could detect the changes of water content inside sand was first applied to hydrate formation and dissociation processes. It also can study the water change characteristics in the core scale of a partially saturated silica sand sample and compare the differences of water changes between the processes of formation and dissociation of methane hydrate and freezing and thawing of ice. The experimental results showed that the water changes in the processes of formation and dissociation of methane hydrate were basically similar to that of the freezing and thawing of ice in sand. When methane hydrate or ice was formed, water changes showed the decrease in water content on the whole and the pF values rose following the formation processes. However, there were very obvious differences between the ice thawing and hydrate dissociation.

  7. Electrochemical metallization of self-assembled porphyrin monolayers.

    Science.gov (United States)

    Nann, Thomas; Kielmann, Udo; Dietrich, Christoph

    2002-04-01

    Multifunctional sensor systems are becoming increasingly important in electroanalytical chemistry. Together with ongoing miniaturization there is a need for micro- and nanopatterning tools for thin electroactive layers (e.g. self-assembling monolayers). This paper documents a method for production of a micro-array of different metal-porphyrin monolayers with different sensor properties. A new method has been developed for the selective and local metallization of bare porphyrin monolayers by cathodic pulsing and sweeping. The metal-porphyrin monolayers obtained were characterized by cyclic voltammetry. It was shown that porphyrin monolayers can be metallized with manganese, iron, cobalt, and nickel by use of the new method. It is expected that all types of metal-porphyrin monolayers can be produced in the same manner.

  8. Controlled crystallization of hydroxyapatite under hexadecylamine self-assembled monolayer

    Institute of Scientific and Technical Information of China (English)

    黄苏萍; 周科朝; 刘咏; 黄伯云

    2003-01-01

    The role of self-assembled monolayer in inducing the crystal growth was investigated by X-ray diffractions (XRD), and scanning electron microscopy (SEM). Results show that crystallization in the absence of monolayer results in a mixture of poorly crystallized calcium phosphates, including hydroxyapatite (HAP) and octacalcium phosphate (OCP), while the presence of self-assembled monolayer gives rise to oriented and well crystallized HAP crystals. Moreover, the HAP crystal grows very quickly under the self-assembled monolayer, whereas very little calcium phosphate crystals grow without the monolayer. It is rationalized that the hexadecylamine monolayer with high polarity and charged density leads to increase supersaturation and lower the interfacial energy, which attributes to the HAP crystals nucleation. On the other hand, the positive headgroups construct the ordered "recognized site" with distinct size and topology, which results in the oriented HAP crystals deposit.

  9. ELASTICITY OF MONOLAYER OF LINOLEIC ACID AND ITS POLYMER

    Institute of Scientific and Technical Information of China (English)

    1998-01-01

    The dynamic elasticity of linoleic acid monolayer on a subphase of 10-4mol/L TbCla at various surface pressure has been measured by means of dynamic oscillation method in measuring the change of surface pressure caused by periodic compressionexpansion cycles of the barrier. The elasticity of monolayer increases with increasing of surface pressure linegrly. The linoleic acid polymer monolayer has been obtained under UV-irradiation in situ when keeping a constant surface pressure. But the elasticity of the resulting polymerized monolayer is even smaller than that of its corresponding monomer monolayer. The elasticity of the polymerized linoleic acid monolayer decreases with increasing polymerization time. The explanation based on entropy has been presented.

  10. Electrical and optical characterization of thrombin-induced permeability of cultured endothelial cell monolayers on semiconductor electrode arrays

    Science.gov (United States)

    Hillebrandt, H.; Abdelghani, A.; Abdelghani-Jacquin, C.; Aepfelbacher, M.; Sackmann, E.

    Impedance spectroscopy and phase-contrast microscopy are combined to monitor the electrical and morphological properties of human umbilical vein endothelial cell monolayers. The cells were cultured on optically transparent indium-tin-oxide (ITO) semiconductor electrode arrays coated with collagen IV, and the effect of the inflammatory mediator thrombin on monolayer permeability was monitored in real time. ITO electrodes provide several advantages for these kinds of experiments, because they are optically transparent, polarizable and highly sensitive due to the absence of insulating oxide layers. A qualitative correlation between the thrombin-induced gap formation and the electrical parameters of the cell layer is established.

  11. Electron transport across the alkanethiol self-assembled monolayer/Au(111) interface: role of the chemical anchor.

    Science.gov (United States)

    Lindstrom, C D; Muntwiler, M; Zhu, X-Y

    2005-11-24

    Alkanethiol self-assembled monolayers (SAMs) on Au(111) are model systems for molecular electronics. We probe the role of the chemisorption bond on electron dynamics at the SAM/Au interface using time-resolved two-photon photoemission. Formation of the Au-S bond is evidenced by a localized sigma resonance, which broadens and shifts upward in energy when the lying-down chemisorbed molecules stand up. The localized chemisorption bond does not affect the electronic coupling between delocalized image resonances and the metal substrate. Instead, lifetimes of image resonances are decreased due to scattering with S atoms within the thiol or thiolate monolayer.

  12. Comparison of permanganate preoxidation and preozonation on algae containing water: cell integrity, characteristics, and chlorinated disinfection byproduct formation.

    Science.gov (United States)

    Xie, Pengchao; Ma, Jun; Fang, Jingyun; Guan, Yinghong; Yue, Siyang; Li, Xuchun; Chen, Liwei

    2013-12-17

    Aqueous suspensions of Microcystis aeruginosa were preoxidized with either ozone or permanganate and then subjected to chlorination under conditions simulating drinking water purification. The impacts of the two oxidants on the algal cells and on the subsequent production of dissolved organic matter and disinfection byproducts were investigated. Preozonation dramatically increased disinfection byproduct formation during chlorination, especially the formation of haloaldehydes, haloacetonitriles, and halonitromethanes. Preoxidation with permanganate had much less effect on disinfection byproduct formation. Preozonation destroyed algal cell walls and cell membranes to release intracellular organic matter (IOM), and less than 2.0% integrated cells were left after preozonation with the dosage as low as 0.4 mg/L. Preoxidation with permanganate mainly released organic matter adsorbed on the cells' surface without causing any damage to the cells' integrity, so the increase in byproduct formation was much less. More organic nitrogen and lower molecular weight precursors were produced in a dissolved phase after preozonation than permanganate preoxidation, which contributes to the significant increase of disinfection byproducts after preozonation. The results suggest that permanganate is a better choice than ozone for controlling algae derived pollutants and disinfection byproducts.

  13. Characteristic of skin formation using zircon- and graphite-coated mold in thin wall ductile iron fabrication

    Science.gov (United States)

    Dhaneswara, Donanta; Suharno, Bambang; Nugroho, Janu Ageng; Ariobimo, Rianti Dewi S.; Sofyan, Nofrijon

    2017-03-01

    One of the problems in thin wall ductile iron (TWDI) fabrication is skin formation during the casting. The presence of this skin will decrease strength and strain of the TWDI. One of the ways to control this skin formation is to change the cooling rate during the process through a mold coating. In testing the effectiveness of skin prevention, the following variables were used for the mold coating i.e. (i) graphite: (ii) zirconium; and (iii) double layer of graphite-zirconium. After the process, the plates were characterized by non-etching, etching, tensile test, and SEM observation. The results showed that the average skin formation using graphite: 65 µm; zirconium: 13.04 µm; and double layer of graphite-zirconium: 33.25 µm. It seems that zirconium has the most effect on the skin prevention due to sulfur binding and magnesium locked, which then prevented rapid cooling resulting in less skin formation. The results also showed the number of nodules obtained in specimen with graphite: 703 nodules/mm2 with average diameter of 12.57 µm, zirconium: 798 nodules/mm2 with average diameter of 12.15 µm, and double layer of graphite-zirconium: 697 nodules/mm2 with average diameter of 11.9 µm and nodularity percentage of 82.58%, 84.53%, and 84.22%, respectively. Tensile test showed that the strength of the specimen with graphite is 301.1 MPa, with zirconium is 388.8 MPa, and with double layer of graphite-zirconium is 304 MPa. In overall, zirconium give the best performance on the skin formation prevention in TWDI fabrication.

  14. Zitterbewegung in monolayer silicene in a magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Romera, E. [Departamento de Física Atómica, Molecular y Nuclear and Instituto Carlos I de Física Teórica y Computacional, Universidad de Granada, Fuentenueva s/n, 18071 Granada (Spain); Roldán, J.B. [Departamento de Electrónica y Tecnología de Computadores and CITIC, Universidad de Granada, Fuentenueva s/n, 18071 Granada (Spain); Santos, F. de los [Departamento de Electromagnetismo y Física de la Materia, and Instituto Carlos I de Física Teórica y Computacional, Universidad de Granada, Fuentenueva s/n, 18071 Granada (Spain)

    2014-07-04

    We study the Zitterbewegung in monolayer silicene under a perpendicular magnetic field. Using an effective Hamiltonian, we have investigated the autocorrelation function and the density currents in this material. Moreover, we have analyzed other types of periodicities of the system (classical and revival times). Finally, the above results are compared with their counterparts in two other monolayer materials subject to a magnetic field: graphene and MoS{sub 2}. - Highlights: • We study Zitterbewegung in monolayer silicene in a magnetic field. • We have analyzed other types of periodicities in silicene. • The above results are compared with other monolayer materials (graphene and MoS{sub 2})

  15. Carbon phosphide monolayers with superior carrier mobility

    Science.gov (United States)

    Wang, Gaoxue; Pandey, Ravindra; Karna, Shashi P.

    2016-04-01

    Two dimensional (2D) materials with a finite band gap and high carrier mobility are sought after materials from both fundamental and technological perspectives. In this paper, we present the results based on the particle swarm optimization method and density functional theory which predict three geometrically different phases of the carbon phosphide (CP) monolayer consisting of sp2 hybridized C atoms and sp3 hybridized P atoms in hexagonal networks. Two of the phases, referred to as α-CP and β-CP with puckered or buckled surfaces are semiconducting with highly anisotropic electronic and mechanical properties. More remarkably, they have the lightest electrons and holes among the known 2D semiconductors, yielding superior carrier mobility. The γ-CP has a distorted hexagonal network and exhibits a semi-metallic behavior with Dirac cones. These theoretical findings suggest that the binary CP monolayer is a yet unexplored 2D material holding great promise for applications in high-performance electronics and optoelectronics.Two dimensional (2D) materials with a finite band gap and high carrier mobility are sought after materials from both fundamental and technological perspectives. In this paper, we present the results based on the particle swarm optimization method and density functional theory which predict three geometrically different phases of the carbon phosphide (CP) monolayer consisting of sp2 hybridized C atoms and sp3 hybridized P atoms in hexagonal networks. Two of the phases, referred to as α-CP and β-CP with puckered or buckled surfaces are semiconducting with highly anisotropic electronic and mechanical properties. More remarkably, they have the lightest electrons and holes among the known 2D semiconductors, yielding superior carrier mobility. The γ-CP has a distorted hexagonal network and exhibits a semi-metallic behavior with Dirac cones. These theoretical findings suggest that the binary CP monolayer is a yet unexplored 2D material holding great

  16. 欠平衡钻井条件下地层造斜特性研究%Research on deflecting characteristic of formation while underbalanced drilling

    Institute of Scientific and Technical Information of China (English)

    张辉; 高德利; 段明星; 杨建旭

    2012-01-01

    钻井实践中发现,由于对欠平衡钻井条件下的地层造斜特性不够了解,不能有的放矢地采取措施有效控制井斜.因此,欠平衡钻井条件下地层造斜特性的研究,是一项迫切需要开展的工作,对于欠平衡钻井技术的发展具有重要意义.应用有限元方法分析了不同井底压差下倾斜地层近井底岩石应力的分布状态,得出了井底压差和地层倾角对井底应力分布的影响规律;同时分析并确定了井斜趋势的判定依据,进而研究了欠平衡钻井条件对地层造斜作用的影响.结果表明,欠平衡钻井中井底保持负压差,放大了井底上倾和下倾两侧岩石应力的不对称性,增强了地层的造斜作用;地层倾角越大,这种增强作用越显著.%In drilling practice, Because of the lack of understanding of deflecting characteristic of anisotropy formation while un-derbalanced drilling, a appropriate measure can not be taken accordingly. So research on deflecting characteristic of anisotropy formation while underbalance drilling will play an important role in underbalace drill technology and should be carried out immediately. In this thesis, the stress distribution of bottomhole rock in various pressure difference and formations with various angle of bedding is analyzed by means of finite element method, the influence of pressure difference and formation angle on the stress distribution of bottom hole is founded, the discrimination criteria of inclination trend is established, the effect of underbalance drilling condition on the deflecting characteristic of anisotropy formation is further discussed. The result shows that the negative pressure differences while underbalanced drilling amplify the asymmetry of stress distribution and strengthen the deflecting tendency of formation. This will be more remarkable with the increase of angle of bedding.

  17. Fabrication of a Mono-Domain Alignment Ferroelectric Liquid Crystal Device Using a Polar Self-Assembled Monolayer

    Institute of Scientific and Technical Information of China (English)

    ZOU Zhong-Fei; YAO Li-Shuang; TANG Xian-Zhu; JI Xin-Jian; XUAN Li

    2008-01-01

    A mono-domain ferroelectric liquid crystal device (FLCD) is fabricated using a novel method. The cell used in this method is an asymmetric cell, typically the combination of a polar self-assembled monolayer (SAM) for one substrate and a rubbed polyimide for the other substrate. A defect-free alignment of ferroelectric liquid crystal is fabricated without applying a dc voltage to remove degeneracy in the layer structure. The contact angles of self-assembled monolayer and PI-2942 are measured and the polarity of SAM is higher than the PI alignment. It is found that the polarity of self-assembled monolayer is a key factor in the formation of mono-domain alignment of FLC.

  18. A theoretical investigation on anomalous switching of single-stranded deoxyribonucleic acid (ssDNA) monolayers by water vapor

    Institute of Scientific and Technical Information of China (English)

    赵新军; 高志福; 蒋中英

    2015-01-01

    In this paper, we use a molecular theory to study the anomalous switching of ssDNA monolayers. Here, both ssDNA–water and water–water hydrogen bonds and their explicit coupling to the ssDNA conformations are considered. We find that hydrogen bonding becomes a key element in inducing the anomalous switching of ssDNA monolayers. This finding accords well with the experimental observations. Based on our theoretical model, we predict that the anomalous switching induced by water vapor will be applicable to a wide range of hydrogen bonds polymers, and ssDNA–water hydrogen bonds and water–water hydrogen bonds hybridization will lead to the hydrogen-bond network formation of 3D ssDNA monolayers.

  19. Modeling of anisotropic two-dimensional materials monolayer HfS{sub 2} and phosphorene metal-oxide semiconductor field effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Jiwon [SEMATECH, 257 Fuller Rd #2200, Albany, New York 12203 (United States)

    2015-06-07

    Ballistic transport characteristics of metal-oxide semiconductor field effect transistors (MOSFETs) based on anisotropic two-dimensional materials monolayer HfS{sub 2} and phosphorene are explored through quantum transport simulations. We focus on the effects of the channel crystal orientation and the channel length scaling on device performances. Especially, the role of degenerate conduction band (CB) valleys in monolayer HfS{sub 2} is comprehensively analyzed. Benchmarking monolayer HfS{sub 2} with phosphorene MOSFETs, we predict that the effect of channel orientation on device performances is much weaker in monolayer HfS{sub 2} than in phosphorene due to the degenerate CB valleys of monolayer HfS{sub 2}. Our simulations also reveal that at 10 nm channel length scale, phosphorene MOSFETs outperform monolayer HfS{sub 2} MOSFETs in terms of the on-state current. However, it is observed that monolayer HfS{sub 2} MOSFETs may offer comparable, but a little bit degraded, device performances as compared with phosphorene MOSFETs at 5 nm channel length.

  20. Fluidization of a horizontally driven granular monolayer.

    Science.gov (United States)

    Heckel, Michael; Sack, Achim; Kollmer, Jonathan E; Pöschel, Thorsten

    2015-06-01

    We consider the transition of a horizontally vibrated monodisperse granular monolayer between its condensed state and its three-dimensional gaseous state as a function of the vibration parameters, amplitude, and frequency as well as particle number density. The transition is characterized by an abrupt change of the dynamical state which leaves its fingerprints in several measurable quantities including dissipation rate, sound emission, and a gap size which characterizes the sloshing motion of the material. The transition and its pronounced hysteresis is explained through the energy due to the collective motion of the particles relative to the container.

  1. Template-Directed Self-Assembly of Alkanethiol Monolayers: Selective Growth on Preexisting Monolayer Edges

    NARCIS (Netherlands)

    Sharpe, Ruben B.A.; Burdinski, Dirk; Huskens, Jurriaan; Zandvliet, Harold J.W.; Reinhoudt, David N.; Poelsema, Bene

    2007-01-01

    Self-assembled monolayers were investigated for their suitability as two-dimensional scaffolds for the selective growth of alkanethiol edge structures. Heterostructures with chemical contrast could be grown, whose dimensions were governed by both the initial pattern sizes and the process time. n-Oct

  2. Catalystlike behavior of Si adatoms in the growth of monolayer Al film on Si(111).

    Science.gov (United States)

    Teng, Jing; Zhang, Lixin; Jiang, Ying; Guo, Jiandong; Guo, Qinlin; Wang, Enge; Ebert, Philipp; Sakurai, T; Wu, Kehui

    2010-07-07

    The formation mechanism of monolayer Al(111)1x1 film on the Si(111) radical3x radical3-Al substrate was studied by scanning tunneling microscopy and first-principles calculations. We found that the Si adatoms on the radical3x radical3-Al substrate play important roles in the growth process. The growth of Al-1x1 islands is mediated by the formation and decomposition of SiAl(2) clusters. Based on experiments and theoretical simulations we propose a model where free Si atoms exhibit a catalystlike behavior by capturing and releasing Al atoms during the Al film growth.

  3. Rare Earths, Trace Element Characteristics of High-Mg Volcanic Rocks of Yixian Formation in Sihetun West Liaoning Province and Its Apocalypse

    Institute of Scientific and Technical Information of China (English)

    Zhang Hong; Zhang Qi

    2005-01-01

    The high-Mg volcanic rocks of the Yixian Formation in the Sihetun area have the obvious characteristics of mantle-derived lava in rare earth, trace element characteristics with high Mg# (62~70) and high content of compatible elements. In the meantime, the volcanic rocks also have the obvious characteristics of Crust-source material in rare earth, trace element characteristics with high ∑REE (158.78×10-6~359.66×10-6), high (La/Yb)N (14.61~29.60), high La/Nb(2.37~7.52) and high Ba/Nb(67.58~205.96), obvious positive anomaly of Pb and negative anomaly of Nb, Ta in trace element spider-gram. In Sr-Nd-Pb isotope the (87Sr/86Sr)i ratio is higher than 0.706 and the εNd(t) ratio is from -3.4 to -13, both reflect enriched Mantle characteristics. The characteristics above of the volcanic rocks combined with the content of Sr, Ba, Y, Yb and the ratio of Sr/Y show that the volcanic rocks have the property of the Sanukite rocks in Setouchi Japan beside subduction zone, and illuminate that the Sanukite rocks can be formed not only in island-arc near subduction zone but also in intro-plate. The analysis indicates that the high-Mg volcanic rocks in the Sihetun area result from the collective function of mantle-derived lava and crust-source materials. The result illuminates that the West Liaoning region is very special in tectonic geochemical background in Cretaceous in East China, and is an ideal region for us to further study the characteristics of magmatic activity as well as the process of Crust-Mantle interaction in Eastern China.

  4. Mechanism of the Formation of Singularities to the Goursat Problem for Diagonal Systems with Linearly Degenerate Characteristic Fields

    Institute of Scientific and Technical Information of China (English)

    Yong Fu YANG

    2011-01-01

    For an inhomogeneous quasilinear hyperbolic system of diagonal form, under the assumptions that the system is linearly degenerate and the C1 norm of the boundary data is bounded, we show that the mechanism of the formation of singularities of C1 classical solution to the Goursat problem with C1 compatibility conditions at the origin must be an ODE type. The similar result is also obtained for the weakly discontinuous solution with C0 compatibility conditions at the origin.

  5. Islands and holes on the free surface of thin diblock copolymer films. I. Characteristics of formation and growth

    OpenAIRE

    Coulon, G.; Collin, B.; Ausserre, D.; Chatenay, D.; Russell, T.P.

    1990-01-01

    When deposited on a silicon substrate, symmetric polystyrene/polymethylmethacrylate P(S-b-MMA) diblock copolymers form, at equilibrium, a multilayer structure parallel to the substrate. If the top layer is incomplete, islands or holes are formed in this layer. The kinetics of formation and growth of islands or holes is investigated, here, by in situ interference microscopy. The present study is focused on dense systems (≃ 30 % of islands (or holes) in area coverage). In the early stage, the w...

  6. Influence of amine structural characteristics on N-nitrosamine formation potential relevant to postcombustion CO2 capture systems.

    Science.gov (United States)

    Dai, Ning; Mitch, William A

    2013-11-19

    Concerns have arisen for the possible contamination of air or drinking water supplies downwind of amine-based CO2 capture facilities by potentially carcinogenic N-nitrosamines formed from reactions between flue gas NOx and amine solvents. This study evaluated the influence of amine structure on the potential to form total N-nitrosamines within the absorber and washwater units of a laboratory-scale CO2 capture reactor, and in the solvent after a pressure-cooker treatment as a mimic of desorber conditions. Among 16 amines representing 3 amine classes (alkanolamines, straight-chain and cyclic diamines, and amino acids), the order of the amine was the primary determinant of total N-nitrosamine formation in the absorber unit, with total N-nitrosamine formation in the order: secondary amines ≈ tertiary amines ≫ primary amines. Similar results were observed upon pressure-cooker treatment, due to reactions between nitrite and amines at high temperature. For secondary and tertiary amines, total N-nitrosamine formation under these desorber-like conditions appeared to be more important than in the absorber, but for primary amines, significant formation of total N-nitrosamines was only observed in the absorber. For diamines and amino acids, total N-nitrosamine accumulation rates in washwaters were lowest for primary amines. For alkanolamines, however, total N-nitrosamine accumulation in the washwater was similar regardless of alkanolamine order, due to the combined effects of amine reactivity toward nitrosation and amine volatility. While total N-nitrosamine accumulation rates in washwaters were generally 1-2 orders of magnitude lower than in the absorber, they were comparable to absorber rates for several primary amines. Decarboxylation of the amino acid sarcosine resulted in the accumulation of significant concentrations of N-nitrosodimethylamine and N-nitrodimethylamine in the washwater.

  7. Source and formation characteristics of water-soluble organic carbon in the anthropogenic-influenced Yellow River Delta, North China

    Science.gov (United States)

    Zong, Zheng; Wang, Xiaoping; Tian, Chongguo; Chen, Yingjun; Han, Guangxuan; Li, Jun; Zhang, Gan

    2016-11-01

    High intensity measurement of water-soluble organic carbon (WSOC) in PM2.5 was conducted at Yellow River Delta (YRD), North China, from 29 May to 1 July 2013. On average, concentration of WSOC was 3.09 ± 2.45 μg m-3 with a relative high WSOC/OC mass ratio (56.39%), implying organic aerosol in YRD was aged. WSOC concentration in day time was obviously higher than night time, which was mainly attributed to the decrease of source emission. While secondary formation of WSOC was strengthen in night time under stable atmospheric condition. The significant relationship between WSOC and SOC indicated WSOC was mostly secondary formation product. Furthermore, WSOC formation was enhanced at high level of acidity, providing direct evidence for the great impact of aerosol acidity on WSOC formation. WSOC correlated well with nss-K+, nss-SO42-, NO3-, Zn and Cu, suggesting a major part of observed WSOC and/or its precursors was of biomass burning and fossil fuel combustion origin. Moreover, vehicle emission may make great proportion in the fossil fuel combustion. Conditional probability function (CPF) analysis showed significant contribution of WSOC occurred when wind came from southerly (135-195°) and northwesterly (285, 345°) directions. In order to further confirm the source of WSOC, two merged samples representing the two directions were selected for radiocarbon (14C) measurement. 14C results demonstrated the average value of ƒc(WSOC) was 0.57 ± 0.01, implying biogenic and biomass burning (B&B) was the major source of WSOC. However, fossil fuel contribution could not be ignored in North China in summer.

  8. Thermodynamic and elastic fluctuation analysis of Langmuir mixed monolayers composed by dehydrocholic acid (HDHC) and didodecyldimethylammonium bromide (DDAB).

    Science.gov (United States)

    Messina, Paula V; Prieto, Gerardo; Ruso, Juan Manuel; Fernández-Leyes, Marcos D; Schulz, Pablo C; Sarmiento, Félix

    2010-01-01

    The physicochemical and elastic properties of Langmuir mixed monolayers composed by dehydrocholic acid (HDHC) and didodecyldimethylammonium bromide (DDAB) were evaluated. The experiments were performed with a constant surface pressure penetration Langmuir balance based on Axisymmetric Drop Shape Analysis (ADSA). The behavior of such amphiphiles in monolayer was clearly non-ideal and would be seriously influenced by the amount of HDHC molecules present. The presence of bile acid type molecules caused the monolayer be more condensed (A(c) diminution) and the intermolecular attractive interactions be stronger (high epsilon(0) values). This fact would be related to H-bond formation between water and carboxilate and carbonile groups in the cholesteric ring and agreed with the existence of laterally structured microdomains at the monolayer (determined by the analysis of the first virial coefficient, b(0)35 mJ m(-2)) just with the obtained negative values of the free energy of mixing Delta G(mix), and the excess second virial coefficient (b(1))(E) obtained allows us to infer that net attractive interaction existed between HDHC and DDAB molecules at the monolayer and that mixed systems would be able to be used in the formulation of supramolecular assemblies.

  9. Modification of degenerative photoluminescence in aged monolayer WSsub>2sub> by PCsub>61sub>BM surface processing.

    Science.gov (United States)

    Liu, Yu; Zheng, Xin; Li, Han; Xu, Zhongjie; Jiang, Tian

    2017-02-01

    Owing to their unique physical properties, monolayer transition metal dichalcogenides (TMDCs) have been widely used in applications of light-emitting diodes (LEDs). However, monolayers of TMDCs undergo dramatic aging effects, including intense degradation in optical behavior, extensive cracking, and severe quenching of the direct gap photoluminescence (PL), seriously limiting the device performance. In this work, we show that monolayer WSsub>2sub> stored for three months even in the glovebox exhibits obvious degenerative PL with changed peak position that can be attributed to the presence of a large number of trions induced by the aging effect. PCsub>61sub>BM surface processing was used to modify the surface of the aged monolayer WSsub>2sub>. As expected, higher uniformity in the PL spectrum was obtained. Besides, the PL peak wavelength was modified to be the same as that of the nonaged one and did not change even at higher excitation power. This strategy is shown to successfully suppress the formation of the trion by transferring the excess electrons from WSsub>2sub> to PCsub>61sub>BM. The results demonstrate the feasibility of applying PCsub>61sub>BM surface modification to improve the performance of the LED based on monolayer WSsub>2sub>.

  10. Two-component Langmuir monolayers and LB films of DPPC with partially fluorinated alcohol (F8H9OH).

    Science.gov (United States)

    Nakahara, Hiromichi; Hirano, Chikayo; Shibata, Osamu

    2013-01-01

    The interaction of (perfluorooctyl)nonanol (F8H9OH) with dipalmitoylphosphatidylcholine (DPPC) was systematically studied in two-component monolayers at air-water interface. The thermodynamic property and phase morphology of the monolayers were investigated by isotherm measurements and several microscopic methods such as Brewster angle microscopy, fluorescence microscopy, and atomic force microscopy (AFM). The AFM topographies for Langmuir-Blodgett films of F8H9OH exhibit the formation of monodispersed surface micelles. In the two-component system, the incorporation of F8H9OH induces condensation (or solidification) of DPPC monolayers. The excess Gibbs free energy and interaction parameter (or energy) of the two components were calculated from the isotherm data. Both the phase transition pressure for the coexistence of ordered and disordered phases and collapse pressure of monolayers vary with the mole fraction of F8H9OH, indicating binary miscibility between F8H9OH and DPPC within a monolayer state. The miscibility is also confirmed visually by in situ and ex situ microscopy at micro- and nanometer scales.

  11. Interfacial properties in Langmuir monolayers and LB films of DPPC with partially fluorinated alcohol (F8H7OH).

    Science.gov (United States)

    Nakahara, Hiromichi; Hirano, Chikayo; Fujita, Ichiro; Shibata, Osamu

    2013-01-01

    Two-component interactions between (perfluorooctyl) heptanol (F8H7OH) and dipalmitoylphosphatidylcholine (DPPC), which is a major component of pulmonary surfactants in mammals, were systematically elucidated using Langmuir monolayers and Langmuir-Blodgett (LB) films of the compounds. The interactions such as the miscibility of the compounds and their phase behavior were examined from thermodynamic and morphological perspectives. The surface pressure (π)-molecular area (A) and surface potential (ΔV)-A isotherms of the binary monolayers containing F8H7OH in different mole fractions (XF8H7OH) were measured simultaneously. The excess Gibbs free energy of mixing of the two components was calculated from the π-A isotherms. The resulting isotherm data were employed to construct a two-dimensional (2D) phase diagram of the system. The phase diagram revealed that the transition pressure as well as the monolayer collapse pressure change with changes in XF8H7OH. These thermodynamic analyses suggested that the miscibility of the two components and the solidification of DPPC monolayers can be induced by the addition of F8H7OH. The phase behavior upon monolayer compression was observed morphologically in situ using Brewster angle microscopy (BAM) and fluorescence microscopy (FM), as well as ex situ using atomic force microscopy (AFM). Interestingly, the AFM-based analysis revealed the formation of monodispersed 2D micelles consisting of F8H7OH at low surface pressures.

  12. Isostructural solid-solid phase transition in monolayers of soft core-shell particles at fluid interfaces: structure and mechanics.

    Science.gov (United States)

    Rey, Marcel; Fernández-Rodríguez, Miguel Ángel; Steinacher, Mathias; Scheidegger, Laura; Geisel, Karen; Richtering, Walter; Squires, Todd M; Isa, Lucio

    2016-04-21

    We have studied the complete two-dimensional phase diagram of a core-shell microgel-laden fluid interface by synchronizing its compression with the deposition of the interfacial monolayer. Applying a new protocol, different positions on the substrate correspond to different values of the monolayer surface pressure and specific area. Analyzing the microstructure of the deposited monolayers, we discovered an isostructural solid-solid phase transition between two crystalline phases with the same hexagonal symmetry, but with two different lattice constants. The two phases corresponded to shell-shell and core-core inter-particle contacts, respectively; with increasing surface pressure the former mechanically failed enabling the particle cores to come into contact. In the phase-transition region, clusters of particles in core-core contacts nucleate, melting the surrounding shell-shell crystal, until the whole monolayer moves into the second phase. We furthermore measured the interfacial rheology of the monolayers as a function of the surface pressure using an interfacial microdisk rheometer. The interfaces always showed a strong elastic response, with a dip in the shear elastic modulus in correspondence with the melting of the shell-shell phase, followed by a steep increase upon the formation of a percolating network of the core-core contacts. These results demonstrate that the core-shell nature of the particles leads to a rich mechanical and structural behavior that can be externally tuned by compressing the interface, indicating new routes for applications, e.g. in surface patterning or emulsion stabilization.

  13. Diagenesis characteristics and their influence on Porosity and Permeability of sandstone from Yingcheng Formation in Jinshan field

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ruiyao,GAO Fuhong; ZHANG Zhongyue

    2014-01-01

    In order to understand the diagenesis and its influence on Porosity and Permeability of sandstones from Yingcheng Formation in Jinshan field,aPPlying thin sections,casting and scanning electron microscoPe, the authors studied PetrograPhy,diagenesis,Porosity and Permeability of Yingcheng Formation sandstone reser-voir. The results show that the reservoir of Yingcheng Formation is mainly comPosed of lithic arkoses. Sand-stones exPerienced comPaction,Pressolution,cementation,metasomatism and dissolution. The Primary Pores of the sandstones are undeveloPed;most of Pores are the secondary Pores,which are mainly intragranular dissolu-tion Pores in feldsPar and debris. The comPaction and cementation reduced the Primary Pores in sandstones,the Porosity and Permeability decreased;while the dissolution formed the secondary Pores,resulting in the Porosity and Permeability increase. Due to comPaction and cementation,the Porosity and Permeability are reduced with increasing of dePth. There exists an abnormal enlargement of Porosity and Permeability within a dePth range 2 310-2 450 m. In combination with analysis of Petrology,the dissolution of feldsPar and debris is most deve-loPed in the dePth range. Therefore,comPaction,cementation and dissolution are the imPortant factors which affect the Porosity and Permeability of sandstones.

  14. FLUIDITY SPEECH FORMATION AS A QUALITATIVE CHARACTERISTIC OF THE ORAL STATEMENT OF PRESCHOOL AGE CHILDREN WITH STUTTER

    Directory of Open Access Journals (Sweden)

    E. A. Borisova

    2014-01-01

    Full Text Available The research objective is to disclose the subject matter of speech therapy work focused on fluidity speech formation of preschool age children, suffering stutter. Stutter is a difficult disorder of articulation organs suchthat the tempo-rhythmical organisation of statements is distressed that leads to defects and failures of dialogue system, negatively influences on individual development of the child; more specifically it generates the mental stratifications, specific features of emotional-volitional sphere, and causes undesirable qualities ofcharacter such as shyness, indecision, isolation, negativism. The author notes that the problem of early stutter correction among junior preschool-aged children considered as topical and immediate issue. Methods. Concerning the clinical, physiological, psychological and psychologic-pedagogical positions, the author summarizes theoretical framework; an experimentally-practical approbation of an author's method of speech fluidity and stutter abolition of preschool children is described. Stage-by-stage process of correction,spontaneous and non-convulsive speech formation: 1. restraint mode application in order to decrease incorrect verbal output; 2. training exercises to long phonatory and speech expiration; 3. development of coordination and movements rhythm helping to pronounce words and phrases; 4. formation of situational speech, at first consisted of short sentences, then passing to long ones; 5. training to coherent text statements. The research demonstrates data analyses of postexperimental diagnostic examination of stuttering preschool children, proving the efficiency of the author’s applied method. Scientific novelty. The research findings demonstrate a specific approach to correction and stutter abolition of preschool children. Proposed author’s approach consists of complementary to each other directions of speech therapy work which are combines in the following way: coherent speech

  15. Anomalous spreading behaviour of polyethyleneglycoldistearate monolayers at air/water interface

    Indian Academy of Sciences (India)

    S John Collins; Aruna Dhathathreyan; T Ramasami

    2001-04-01

    Spreading behaviour of the dimeric surfactant polyethyleneglycoldistearate (PEGDS) monolayer at air/water interface has been studied using surface pressure-area ( -) isotherms as a function of temperature. The isotherms show a plateau suggesting a transition between a liquid expanded (LE) and a condensed state. The condensed state possibly arises due to nucleation and growth of multilayers from the monolayer. Isobaric measurements of both - and - at constant area show transitions at = 295 K. These plots suggest a melting followed by formation of condensed microcrystallites. Structure optimization carried out using various angles of orientation of the alkyl tails with respect to the backbone in PEGDS reveals tilt transitions of the tails in different states which can be related to the packing behaviour seen in the isotherms. Optical microscopy has been used to confirm the structures in these states.

  16. Influence of head group methylation on the phase behavior of lipid monolayers

    DEFF Research Database (Denmark)

    Brezesinski, G.; Bringezu, F.; Weidemann, G.

    1998-01-01

    per three tails exceeds that per head, an influence of the head group methylation on the monolayer structure is observed. The tilt angles at lower lateral pressures and the transition pressure to a hexagonal packing of upright oriented chains increase with increasing methylation degree. The transition...... from the NN tilted rectangular to this hexagonal phase is connected with a pressure region where the in-plane components Q(xy) of the two peaks coincide while the out-of-plane components Q(z) differ. This indicates an undistorted hexagonal in-plane lattice even for tilted chains. The area-pressure...... and X-ray measurements below 10 mN/m, can be explained by the formation of holes in the monolayer. Possibly the tilting of the triple-chain molecules leads to an orientational ordering of the head group dipoles and therefore to an electrostatic repulsion between condensed phase domains. (C) 1998...

  17. Self-assembled host monolayer based chemical microsensors for volatile organic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Jing-Xuan; Moore, L.W.; Springer, K.N. [Los Alamos National Lab., NM (United States)] [and others

    1995-12-01

    The interaction of organic vapors with self-assembled host monolayers on the surface of 200 MHz surface acoustic wave (SAW) resonators is studied as a method of tracking toxins in the gas phase. Molecular self-assembly techniques were employed to achieve covalent surface-attachment of two families of {open_quotes}bucket{close_quotes} molecules - cyclodextrins and calix[n]arenes - to native oxides on Si<100> and single-crystal ST-cut quartz. The formation of the covalently-bound functionalized bucket monolayers on oxide surfaces was characterized by polarized, variable-angle, internal attenuated total reflection infrared spectroscopy and surface acoustic mass transduction. SAW based sensors were capable of detecting volatile organic compounds (VOCs) down to ppb levels. Pattern recognition with an array of complementary microsensors appears to be a viable approach for identifying and quantifying a particular VOC.

  18. Monolayer to Bilayer Structural Transition in Confined Pyrrolidinium-Based Ionic Liquids.

    Science.gov (United States)

    Smith, Alexander M; Lovelock, Kevin R J; Gosvami, Nitya Nand; Licence, Peter; Dolan, Andrew; Welton, Tom; Perkin, Susan

    2013-02-07

    Ionic liquids can be intricately nanostructured in the bulk and at interfaces resulting from a delicate interplay between interionic and surface forces. Here we report the structuring of a series of dialkylpyrrolidinium-based ionic liquids induced by confinement. The ionic liquids containing cations with shorter alkyl chain substituents form alternating cation-anion monolayer structures on confinement to a thin film, whereas a cation with a longer alkyl chain substituent leads to bilayer formation. The crossover from monolayer to bilayer structure occurs between chain lengths of n = 8 and 10 for these pyrrolidinium-based ionic liquids. The bilayer structure for n = 10 involves full interdigitation of the alkyl chains; this is in contrast with previous observations for imidazolium-based ionic liquids. The results are pertinent to these liquids' application as electrolytes, where the electrolyte is confined inside the pores of a nanoporous electrode, for example, in devices such as supercapacitors or batteries.

  19. The Formation of the “Sichuan Model” with Regard to Legislation in Ethnic Autonomous Regions and Its Basic Characteristics

    Institute of Scientific and Technical Information of China (English)

    Chen Enmei

    2015-01-01

    Ethnic regional autonomy with Chi ̄nese characteristics is a proper way to handle eth ̄nic issues, and is a fundamental national political system established in the Constitution. The legisla ̄tion in ethnic autonomous regions is important,and creates the basic laws for realizing autonomous rights. The legislation in ethnic autonomous re ̄gions is a generic term which refers to the activities that the people’s congresses of the ethnic autono ̄mous regions undertake,to formulate,amend and a ̄bolish autonomous regulations and specific regula ̄tions in accordance with relevant provisions found in the Constitution, the Law of Ethnic Regional Au ̄tonomy and the Law of Legislation, and which are based on local ethnic political, economic and cul ̄tural characteristics.

  20. Examination of fluorination effect on physical properties of saturated long-chain alcohols by DSC and Langmuir monolayer.

    Science.gov (United States)

    Nakahara, Hiromichi; Nakamura, Shohei; Okahashi, Yoshinori; Kitaguchi, Daisuke; Kawabata, Noritake; Sakamoto, Seiichi; Shibata, Osamu

    2013-02-01

    Partially fluorinated long-chain alcohols have been newly synthesized from a radical reaction, which is followed by a reductive reaction. The fluorinated alcohols have been investigated by differential scanning calorimetry (DSC) and compression isotherms in a Langmuir monolayer state. Their melting points increase with an increase in chain length due to elongation of methylene groups. However, the melting points for the alcohols containing shorter fluorinated moieties are lower than those for the typical hydrogenated fatty alcohols. Using the Langmuir monolayer technique, surface pressure (π)-molecular area (A) and surface potential (ΔV)-A isotherms of monolayers of the fluorinated alcohols have been measured in the temperature range from 281.2 to 303.2K. In addition, a compressibility modulus (Cs(-1)) is calculated from the π-A isotherms. Four kinds of the alcohol monolayers show a phase transition (π(eq)) from a disordered to an ordered state upon lateral compression. The π(eq) values increase linearly with increasing temperatures. A slope of π(eq) against temperature for the alcohols with shorter fluorocarbons is unexpectedly larger than that for the corresponding fatty alcohols. Generally, fluorinated amphiphiles have a greater thermal stability (or resistance), which is a characteristic of highly fluorinated or perfluorinated compounds. Herein, however, the alcohols containing perfluorobutylated and perfluorohexylated chains show the irregular thermal behavior in both the solid and monolayer states.

  1. Trion valley coherence in monolayer semiconductors

    Science.gov (United States)

    Hao, Kai; Xu, Lixiang; Wu, Fengcheng; Nagler, Philipp; Tran, Kha; Ma, Xin; Schüller, Christian; Korn, Tobias; MacDonald, Allan H.; Moody, Galan; Li, Xiaoqin

    2017-06-01

    The emerging field of valleytronics aims to exploit the valley pseudospin of electrons residing near Bloch band extrema as an information carrier. Recent experiments demonstrating optical generation and manipulation of exciton valley coherence (the superposition of electron-hole pairs at opposite valleys) in monolayer transition metal dichalcogenides (TMDs) provide a critical step towards control of this quantum degree of freedom. The charged exciton (trion) in TMDs is an intriguing alternative to the neutral exciton for control of valley pseudospin because of its long spontaneous recombination lifetime, its robust valley polarization, and its coupling to residual electronic spin. Trion valley coherence has however been unexplored due to experimental challenges in accessing it spectroscopically. In this work, we employ ultrafast 2D coherent spectroscopy to resonantly generate and detect trion valley coherence in monolayer MoSe2 demonstrating that it persists for a few-hundred femtoseconds. We conclude that the underlying mechanisms limiting trion valley coherence are fundamentally different from those applicable to exciton valley coherence.

  2. Mediated Electron Transfer at Redox Active Monolayers

    Directory of Open Access Journals (Sweden)

    Michael E.G. Lyons

    2001-12-01

    Full Text Available A theoretical model describing the transport and kinetic processes involved in heterogeneous redox catalysis of solution phase reactants at electrode surfaces coated with redox active monolayers is presented. Although the analysis presented has quite general applicability, a specific focus of the paper is concerned with the idea that redox active monolayers can be used to model an ensemble of individual molecular nanoelectrodes. Three possible rate determining steps are considered: heterogeneous electron transfer between immobilized mediator and support electrode ; bimolecular chemical reaction between redox mediator and reactant species in the solution phase, and diffusional mass transport of reactant in solution. A general expression for the steady state reaction flux is derived which is valid for any degree of reversibility of both the heterogeneous electron transfer reaction involving immobilized mediator species and of the bimolecular cross exchange reaction between immobilized mediator and solution phase reactant. The influence of reactant transport in solution is also specifically considered. Simplified analytical expressions for the net reaction flux are derived for experimentally reasonable situations and a kinetic case diagram is constructed outlining the relationships between the various approximate solutions. The theory enables simple diagnostic plots to be constructed which can be used to analyse experimental data.

  3. Predicting Two-Dimensional Silicon Carbide Monolayers.

    Science.gov (United States)

    Shi, Zhiming; Zhang, Zhuhua; Kutana, Alex; Yakobson, Boris I

    2015-10-27

    Intrinsic semimetallicity of graphene and silicene largely limits their applications in functional devices. Mixing carbon and silicon atoms to form two-dimensional (2D) silicon carbide (SixC1-x) sheets is promising to overcome this issue. Using first-principles calculations combined with the cluster expansion method, we perform a comprehensive study on the thermodynamic stability and electronic properties of 2D SixC1-x monolayers with 0 ≤ x ≤ 1. Upon varying the silicon concentration, the 2D SixC1-x presents two distinct structural phases, a homogeneous phase with well dispersed Si (or C) atoms and an in-plane hybrid phase rich in SiC domains. While the in-plane hybrid structure shows uniform semiconducting properties with widely tunable band gap from 0 to 2.87 eV due to quantum confinement effect imposed by the SiC domains, the homogeneous structures can be semiconducting or remain semimetallic depending on a superlattice vector which dictates whether the sublattice symmetry is topologically broken. Moreover, we reveal a universal rule for describing the electronic properties of the homogeneous SixC1-x structures. These findings suggest that the 2D SixC1-x monolayers may present a new "family" of 2D materials, with a rich variety of properties for applications in electronics and optoelectronics.

  4. Characteristics of carbonate gas pool and multistage gas pool formation history of Hetianhe gas field, Tarim Basin, Northwest China

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Hetianhe is a big carbonate gas field which is found and demonstrated in the period of "Chinese National Ninth 5-Year Plan". The proved reserve of Hetianhe gas field is over 600×108 m3. Its main producing layers are Carboniferous bioclastic limestone and Ordovician carbonate composed of buried hill. The former is stratified gas pool with water around its side, and the latter is massive gas pool with water in its bottom. The gases in the gas pools belong to dry gases with normal temperature and pressure systems. Based on the correlation of gas and source rock, the gases are mainly generated from Cambrian source rocks. According to the researches on source rock and structure evolution, and the observations on the thin section to reservoir bitumen and the studies on homogenization temperature of fluid inclusions, the gas pool has been identified and divided into three formation periods. The first is Late Caledonian when the oil generated from the Cambrian source rocks and migrated along faults, as a form of liquid facies into Ordovician carbonate reservoir and accumulated there. After that, the crust uplifted, the oil reservoir had been destroyed. The second is Late Hercynian when condensate gases generated from the Cambrian source rocks and migrated into Ordovician reservoir, as a form of liquid facies. Since the fractures had reached P strata, so the trap might have a real poor preservation condition, and the large-scale gas pool formation had not happened. The third gas reservoir formation period occurred in Himalaya. The fractures on both sides of Hetianhe gas field developed violently under the forces of compression, and thus the present fault horst formed. The dry gases generated from Cambrian source rocks and migrated upwards as the form of gas facies into Ordovician and Carboniferous reservoirs, and the large gas pool as discovered at present was formed finally.

  5. Characteristics of hydrothermal sedimentation process in the Yanchang Formation, south Ordos Basin, China: Evidence from element geochemistry

    Science.gov (United States)

    He, Cong; Ji, Liming; Wu, Yuandong; Su, Ao; Zhang, Mingzhen

    2016-11-01

    Hydrothermal sedimentation occurred in the Triassic Yanchang Formation, Ordos Basin, China. However, their macroscopic features at the scale of the stratum and hydrothermal sources still lack correlational research. This paper performed element geochemical study on a large number of core samples collected from the Yanchang Formation of a new drilling well located in the south Ordos Basin. The SiO2/(K2O + Na2O) vs. MnO/TiO2 crossplot and Fe vs. Mn vs. (Cu + Co + Ni) × 10 ternary diagram demonstrate that the Yanchang stratum in the study area has, in general, hydrothermal components. The Al/(Al + Fe + Mn) and (Fe + Mn)/Ti ratios of the core samples range from 0.34 to 0.84 and 4.81 to 50.54, averaging 0.66 and 10.67, respectively, indicating that the stratum is a set of atypical hydrothermal sedimentation with much terrigenous input. Data analysis shows that the hydrothermal source in the study area was from the deep North Qinling Orogen around the south margin of the basin, where some active tectonic and volcanic activities took place, rather than from the relatively stable internal basin. Early Indosinian movement and volcanic activities activated basement faults around the southern margin of the basin, providing vents for the deep hydrothermal fluid upwelling. The hydrothermal indicators suggest that the study area experienced 4 episodes of relatively stronger hydrothermal activity, namely during the Chang 10, Chang 9-1, Chang 7-3 and Chang 6-2 periods. We also propose a new hydrothermal sedimentation model of hydrothermal fluids overflowing from basin margin faults, for the Yanchang Formation, which is reported here for the first time.

  6. Intrinsic Electronic Transport through Alkanedithiol Self-Assembled Monolayer

    Science.gov (United States)

    Lee, Takhee; Wang, Wenyong; Reed, Mark A.

    2005-01-01

    Electronic transport through an alkanedithiol self-assembled monolayer (SAM) is investigated using a nanometer scale device. Temperature-independent current-voltage characteristics are observed, indicating tunneling is the main conduction mechanism. The measured current-voltage characteristics are analyzed with a metal-insulator-metal tunneling model. The inelastic electron tunneling spectroscopy (IETS) study on the octanedithiol device clearly shows the vibrational signatures of molecules. The pronounced IETS peaks correspond to vibrational modes perpendicular to the junction interface, which include the stretching modes of Au-S (at 33 mV) and C-C (at 133 mV), and wagging mode of CH2 (at 158 mV). Intrinsic linewidths are determined as 1.69 (upper limit), 3.73± 0.98, and 13.5± 2.4 meV for Au-S, C-C streching modes, and CH2 wagging mode, respectively. The observed peak intensities and peak widths are in good agreement with theoretical predictions.

  7. Formation and characteristics of aqueous two-phase systems formed by a cationic surfactant and a series of ionic liquids.

    Science.gov (United States)

    Wei, Xi-Lian; Wang, Xiu-Hong; Ping, A-Li; Du, Pan-Pan; Sun, De-Zhi; Zhang, Qing-Fu; Liu, Jie

    2013-11-15

    Aqueous two-phase systems (ATPS) were obtained in the aqueous mixtures of a cationic surfactant and a series of ionic liquids (ILs). The effects of IL structure, temperature and additives on the phase separation were systematically investigated. The microstructures of some ATPS were observed by freeze-fracture replication technique. Lyotropic liquid crystal was found in the bottom phase besides micelles under different conditions. Remarkably, both IL structure and additives profoundly affected the formation and properties of the ATPSs. The phase separation can be attributed to the existence of different aggregates and the cation-π interactions of the cationic surfactant with the ILs, which has a significant role in the formation of ATPS. The extraction capacity of the studied ATPS was also evaluated through their application in the extraction of two biosubstances. The results indicate that the ILs with BF4(-) as anion show much better extraction efficiencies than the corresponding ILs with Br(-) as anion do under the same conditions. l-Tryptophan was mainly distributed into the NPTAB-rich phase, while methylene blue and capsochrome were mainly in the IL-rich phase.

  8. Modelling Organic Surfaces with Self-Assembled Monolayers

    Science.gov (United States)

    1989-05-01

    reactive organic liquids. Fluorinated thiols form monolayers that are more water and oil-repellent than Teflon. The hydrophobicity and oleophobicity of...and are both hydrophobic and oleophobic . The surface of a monolayer containing an approximately equal mixture of the two components 13 resembles a

  9. A MOLECULAR-DYNAMICS STUDY OF LECITHIN MONOLAYERS

    NARCIS (Netherlands)

    AHLSTROM, P; BERENDSEN, HJC

    1993-01-01

    Two monolayers of didecanoyllecithin at the air-water interface have been studied using molecular dynamics simulations. The model system consisted of two monolayers of 42 lecithin molecules each separated by a roughly 4 nm thick slab of SPC water. The area per lecithin molecule was 0.78 nm(2)

  10. A dielectric model of self-assembled monolayer interfaces by capacitive spectroscopy.

    Science.gov (United States)

    Góes, Márcio S; Rahman, Habibur; Ryall, Joshua; Davis, Jason J; Bueno, Paulo R

    2012-06-26

    The presence of self-assembled monolayers at an electrode introduces capacitance and resistance contributions that can profoundly affect subsequently observed electronic characteristics. Despite the impact of this on any voltammetry, these contributions are not directly resolvable with any clarity by standard electrochemical means. A capacitive analysis of such interfaces (by capacitance spectroscopy), introduced here, enables a clean mapping of these features and additionally presents a means of studying layer polarizability and Cole-Cole relaxation effects. The resolved resistive term contributes directly to an intrinsic monolayer uncompensated resistance that has a linear dependence on the layer thickness. The dielectric model proposed is fully aligned with the classic Helmholtz plate capacitor model and additionally explains the inherently associated resistive features of molecular films.

  11. [Differences in the expression of prekeratin and vimentin in organ and monolayer cultures of rat hepatocytes].

    Science.gov (United States)

    Karavanova, I D; Bannikov, G A; Troianovskiĭ, S M

    1985-09-01

    Results obtained by the indirect immunofluorescence method employing specific monoclonal antibodies show that during the first 24 hours of cultivation in a monolayer there appears another protein of intermediate filaments--vimentin, which is a characteristic of most mesenchymal cells. At the same time, in the organ liver culture maintained in the same culture medium, no expression of vimentin was observed up to 5-7 days of cultivation. Vimentin was revealed only in cells that migrated from a tissuepiece to collagen. Besides the vimentin expression in these migrating cells and monolayer cultures of hepatocytes, a redistribution of prekeratin filaments took place: the cytoplasmic network appeared instead of thick fibers underlying membranes. The results of the present work suggest that the vimentin expression and the prekeratin filament redistribution in epithelial liver cells in vitro do not depend on the changes of natural humoral factors for the components of culture medium but are due to damages of the intact liver tissue structure.

  12. Scanning conductive probe microscopy of thiophen molecules incorporated into chemically adsorbed monolayer

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, S-I [Department of Electrical Engineering, Kobe City College of Technology, 8-3, Gakuenhigashi-machi, Nishi-ku, Kobe 651-2194 (Japan); Ogawa, K [Department of Advanced Materials Science, Faculty of Engineering, Kagawa University, 2217-20, Hayashi-cho, Takamatsu 761-0396 (Japan)], E-mail: shin1@kobe-kosen.ac.jp

    2008-03-15

    We will describe a technique for acquiring the current-voltage characteristics of a metal-molecule-metal probe junction in the lateral direction using a conducting probe atomic force microscopy (CP-AFM) technique. To conduct a repetitive experiment efficiently, we have utilized the current imaging mode of the CP-AFM system. We have prepared a chemically adsorbed monolayer (CAM) of 3-{l_brace}6-{l_brace}11-(Trichlorosilyl)undecanoyl{r_brace}hexyl{r_brace} thiophene (TEN) on a glass substrate. The samples with the electric path were prepared by a chemical adsorption technique with TEN on a glass substrate, followed by an electro-oxidative polymerization with pure water. The conductivity of a polythiophene derivative monolayer was investigated for its application as a wire. The corresponding I-V curves have exhibited stability and are steep in current.

  13. Scanning conductive probe microscopy of thiophen molecules incorporated into chemically adsorbed monolayer

    Science.gov (United States)

    Yamamoto, S.-I.; Ogawa, K.

    2008-03-01

    We will describe a technique for acquiring the current-voltage characteristics of a metal-molecule-metal probe junction in the lateral direction using a conducting probe atomic force microscopy (CP-AFM) technique. To conduct a repetitive experiment efficiently, we have utilized the current imaging mode of the CP-AFM system. We have prepared a chemically adsorbed monolayer (CAM) of 3-{6-{11-(Trichlorosilyl)undecanoyl}hexyl} thiophene (TEN) on a glass substrate. The samples with the electric path were prepared by a chemical adsorption technique with TEN on a glass substrate, followed by an electro-oxidative polymerization with pure water. The conductivity of a polythiophene derivative monolayer was investigated for its application as a wire. The corresponding I-V curves have exhibited stability and are steep in current.

  14. The role of current characteristics of the arc evaporator in formation of the surface metal-coating composite

    Science.gov (United States)

    Plikhunov, V. V.; Petrov, L. M.; Grigorovich, K. V.

    2016-07-01

    The influence of current characteristics of the vacuum arc evaporator on the interaction process of plasma streams with the surface under treatment during generation of the physicochemical properties of the formed metal-coating composite is considered. It is shown that the interaction of plasma streams with the processed surface provides surface heating, defects elimination, change in energy properties, and mass transfer of plasma stream elements activating surface diffusion processes whose intensity is evaluated by the arc current magnitude and location of the processed surface relative to the cathode axis.

  15. Formation of merchandizing characteristics and extension of the commercial range of products from wild-growing berries

    Directory of Open Access Journals (Sweden)

    Дмитро Миколайович Одарченко

    2015-11-01

    Full Text Available The methods and main parameters for the receipt of reversible phases of wild-growing berries are substantiated and its merchandizing characteristics are studied. Cryoscopic and optical properties of solid phase are studied. Based on the determination of the consumer properties of liquid and solid phases from berries the possible ways for their application in food technologies are suggested. It is also determined that electrophysical method can work as the method of express-analysis during the expertise of fresh wild-growing berries and products after their processing

  16. Plaque morphology of Teschen disease viruses and certain pig enteroviruses in primary pig kidney monolayer cultures.

    Science.gov (United States)

    Dardiri, A H

    1968-04-01

    Plaque patterns and diameters of four virulent strains and one tissue culture mutant of Teschen disease virus were compared with six pig enteroviruses isolated in the United States. They are described as they were produced in primary pig kidney monolayer cultures. Reproducible plaques, with similar characteristics and class-types of each of the viruses tested were obtained with the application of a 45-minute virus adsorption time. Their morphologic characteristics and the proportion in which the plaque types appeared may assist in the differentiation of these virus strains.

  17. Monolayer-by-monolayer stacked pyramid-like MoS2 nanodots on monolayered MoS2 flakes with enhanced photoluminescence.

    Science.gov (United States)

    Yuan, Cailei; Cao, Yingjie; Luo, Xingfang; Yu, Ting; Huang, Zhenping; Xu, Bo; Yang, Yong; Li, Qinliang; Gu, Gang; Lei, Wen

    2015-11-07

    The precise control of the morphology and crystal shape of MoS2 nanostructures is of particular importance for their application in nanoelectronic and optoelectronic devices. Here, we describe a single step route for the synthesis of monolayer-by-monolayer stacked pyramid-like MoS2 nanodots on monolayered MoS2 flakes using a chemical vapor deposition method. First-principles calculations demonstrated that the bandgap of the pyramid-like MoS2 nanodot is a direct bandgap. Enhanced local photoluminescence emission was observed in the pyramid-like MoS2 nanodot, in comparison with monolayered MoS2 flakes. The findings presented here provide new opportunities to tailor the physical properties of MoS2via morphology-controlled synthesis.

  18. Influence of Powder Characteristics on Formation of Porosity in Additive Manufacturing of Ti-6Al-4V Components

    Science.gov (United States)

    Iebba, Maurizio; Astarita, Antonello; Mistretta, Daniela; Colonna, Ivano; Liberini, Mariacira; Scherillo, Fabio; Pirozzi, Carmine; Borrelli, Rosario; Franchitti, Stefania; Squillace, Antonino

    2017-06-01

    This paper aims to study the genesis of defects in titanium components made through two different additive manufacturing technologies: selective laser melting and electron beam melting. In particular, we focussed on the influence of the powders used on the formation of porosities and cavities in the manufactured components. A detailed experimental campaign was carried out to characterize the components made through the two additive manufacturing techniques aforementioned and the powders used in the process. It was found that some defects of the final components can be attributed to internal porosities of the powders used in the manufacturing process. These internal porosities are a consequence of the gas atomization process used for the production of the powders themselves. Therefore, the importance of using tailored powders, free from porosities, in order to manufacture components with high mechanical properties is highlighted.

  19. Critical solvent properties affecting the particle formation process and characteristics of celecoxib-loaded PLGA microparticles via spray-drying

    DEFF Research Database (Denmark)

    Wan, Feng; Bohr, Adam; Maltesen, Morten Jonas;

    2013-01-01

    ) microparticles prepared by spray-drying. METHODS: Binary mixtures of acetone and methanol at different molar ratios were applied to dissolve celecoxib and PLGA prior to spray-drying. The resulting microparticles were characterized with respect to morphology, texture, surface chemistry, solid state properties...... by the PLGA precipitation rate, which is solvent-dependent, and the migration rate of celecoxib molecules during drying. The texture and surface chemistry of the spray-dried PLGA microparticles can therefore be tailored by adjusting the solvent composition....... power of the feed solution. An obvious burst release was observed for the microparticles prepared by the feed solutions with the highest amount of poor solvent for PLGA. TGA analysis revealed distinct drying kinetics for the binary mixtures. CONCLUSIONS: The particle formation process is mainly governed...

  20. Influence of Powder Characteristics on Formation of Porosity in Additive Manufacturing of Ti-6Al-4V Components

    Science.gov (United States)

    Iebba, Maurizio; Astarita, Antonello; Mistretta, Daniela; Colonna, Ivano; Liberini, Mariacira; Scherillo, Fabio; Pirozzi, Carmine; Borrelli, Rosario; Franchitti, Stefania; Squillace, Antonino

    2017-08-01

    This paper aims to study the genesis of defects in titanium components made through two different additive manufacturing technologies: selective laser melting and electron beam melting. In particular, we focussed on the influence of the powders used on the formation of porosities and cavities in the manufactured components. A detailed experimental campaign was carried out to characterize the components made through the two additive manufacturing techniques aforementioned and the powders used in the process. It was found that some defects of the final components can be attributed to internal porosities of the powders used in the manufacturing process. These internal porosities are a consequence of the gas atomization process used for the production of the powders themselves. Therefore, the importance of using tailored powders, free from porosities, in order to manufacture components with high mechanical properties is highlighted.

  1. Hydromechanics for the formation and development of radial sandbanks (Ⅰ)——Plane characteristics of tidal flow

    Institute of Scientific and Technical Information of China (English)

    严以新; 诸裕良; 薛鸿超

    1999-01-01

    Based upon the long-term observation of field data, a two-dimensional numerical model is applied to simulating the tidal flow covering from the neap tide to spring tide in the radial sandbank area in the southern Yellow Sea. From the development of tidal current ridges under the hydrodynamic action, multi-purpose analysis and study are carried out, which include the propagation process of tidal wave, the distributions of tidal wave energy rate and tidal range, the tidal ellipses and traces. It is shown that the tidal current is the major dynamic factor for the formation and development of the radial sandbanks, and the differences of tidal wave energy rate and current strength determine the distinct plane shapes of ridges and troughs in this region.

  2. Quaternary fans and terraces in the Khumbu Himal south of Mount Everest: their characteristics, age and formation

    Science.gov (United States)

    Barnard, P.L.; Owen, L.A.; Finkel, R.C.

    2006-01-01

    Large fans and terraces are frequent in the Khumbu Himal within the high Himalayan valleys south of Mt. Everest. These features are composed of massive matrix- and clast-supported diamicts that were formed from both hyperconcentrated flows and coarse-grained debris flows. Cosmogenic radionuclide (CRN) exposure ages for boulders on fans and terraces indicate that periods of fan and terrace formation occurred at c. 16, c. 12, c. 8, c. 4 and c. 1.5 ka, and are broadly coincident with the timing of glaciation in the region. The dating precision is insufficient to resolve whether the surfaces formed before, during or after the correlated glacial advance. However, the sedimentology, and morphostratigraphic and geomorphological relationships suggest that fan and terrace sedimentation in this part of the Himalaya primarily occurs during glacier retreat and is thus paraglacial in origin. Furthermore, modern glacial-lake outburst floods and their associated deposits are common in the Khumbu Himal as the result of glacial retreat during historical times. We therefore suggest that Late Quaternary and Holocene fan and terrace formation and sediment transfer are probably linked to temporal changes in discharge and sediment load caused by glacier oscillations responding to climate change. The timing of major sedimentation events in this region can be correlated with fans and terraces in other parts of the Himalaya, suggesting that major sedimentation throughout the Himalaya is synchronous and tied to regional climatic oscillations. Bedrock incision rates calculated from strath terrace ages average c. 3.9 mm a−1, suggesting that the overall rate of incision is set by regional uplift.

  3. Kinetics of inclusion body formation and its correlation with the characteristics of protein aggregates in Escherichia coli.

    Science.gov (United States)

    Upadhyay, Arun K; Murmu, Aruna; Singh, Anupam; Panda, Amulya K

    2012-01-01

    The objective of the research was to understand the structural determinants governing protein aggregation into inclusion bodies during expression of recombinant proteins in Escherichia coli. Recombinant human growth hormone (hGH) and asparaginase were expressed as inclusion bodies in E.coli and the kinetics of aggregate formation was analyzed in details. Asparaginase inclusion bodies were of smaller size (200 nm) and the size of the aggregates did not increase with induction time. In contrast, the seeding and growth behavior of hGH inclusion bodies were found to be sequential, kinetically stable and the aggregate size increased from 200 to 800 nm with induction time. Human growth hormone inclusion bodies showed higher resistance to denaturants and proteinase K degradation in comparison to those of asparaginase inclusion bodies. Asparaginase inclusion bodies were completely solubilized at 2-3 M urea concentration and could be refolded into active protein, whereas 7 M urea was required for complete solubilization of hGH inclusion bodies. Both hGH and asparaginase inclusion bodies showed binding with amyloid specific dyes. In spite of its low β-sheet content, binding with dyes was more prominent in case of hGH inclusion bodies than that of asparaginase. Arrangements of protein molecules present in the surface as well as in the core of inclusion bodies were similar. Hydrophobic interactions between partially folded amphiphillic and hydrophobic alpha-helices were found to be one of the main determinants of hGH inclusion body formation. Aggregation behavior of the protein molecules decides the nature and properties of inclusion bodies.

  4. Kinetics of inclusion body formation and its correlation with the characteristics of protein aggregates in Escherichia coli.

    Directory of Open Access Journals (Sweden)

    Arun K Upadhyay

    Full Text Available The objective of the research was to understand the structural determinants governing protein aggregation into inclusion bodies during expression of recombinant proteins in Escherichia coli. Recombinant human growth hormone (hGH and asparaginase were expressed as inclusion bodies in E.coli and the kinetics of aggregate formation was analyzed in details. Asparaginase inclusion bodies were of smaller size (200 nm and the size of the aggregates did not increase with induction time. In contrast, the seeding and growth behavior of hGH inclusion bodies were found to be sequential, kinetically stable and the aggregate size increased from 200 to 800 nm with induction time. Human growth hormone inclusion bodies showed higher resistance to denaturants and proteinase K degradation in comparison to those of asparaginase inclusion bodies. Asparaginase inclusion bodies were completely solubilized at 2-3 M urea concentration and could be refolded into active protein, whereas 7 M urea was required for complete solubilization of hGH inclusion bodies. Both hGH and asparaginase inclusion bodies showed binding with amyloid specific dyes. In spite of its low β-sheet content, binding with dyes was more prominent in case of hGH inclusion bodies than that of asparaginase. Arrangements of protein molecules present in the surface as well as in the core of inclusion bodies were similar. Hydrophobic interactions between partially folded amphiphillic and hydrophobic alpha-helices were found to be one of the main determinants of hGH inclusion body formation. Aggregation behavior of the protein molecules decides the nature and properties of inclusion bodies.

  5. Kinetics of Inclusion Body Formation and Its Correlation with the Characteristics of Protein Aggregates in Escherichia coli

    Science.gov (United States)

    Upadhyay, Arun K.; Murmu, Aruna; Singh, Anupam; Panda, Amulya K.

    2012-01-01

    The objective of the research was to understand the structural determinants governing protein aggregation into inclusion bodies during expression of recombinant proteins in Escherichia coli. Recombinant human growth hormone (hGH) and asparaginase were expressed as inclusion bodies in E.coli and the kinetics of aggregate formation was analyzed in details. Asparaginase inclusion bodies were of smaller size (200 nm) and the size of the aggregates did not increase with induction time. In contrast, the seeding and growth behavior of hGH inclusion bodies were found to be sequential, kinetically stable and the aggregate size increased from 200 to 800 nm with induction time. Human growth hormone inclusion bodies showed higher resistance to denaturants and proteinase K degradation in comparison to those of asparaginase inclusion bodies. Asparaginase inclusion bodies were completely solubilized at 2–3 M urea concentration and could be refolded into active protein, whereas 7 M urea was required for complete solubilization of hGH inclusion bodies. Both hGH and asparaginase inclusion bodies showed binding with amyloid specific dyes. In spite of its low β-sheet content, binding with dyes was more prominent in case of hGH inclusion bodies than that of asparaginase. Arrangements of protein molecules present in the surface as well as in the core of inclusion bodies were similar. Hydrophobic interactions between partially folded amphiphillic and hydrophobic alpha-helices were found to be one of the main determinants of hGH inclusion body formation. Aggregation behavior of the protein molecules decides the nature and properties of inclusion bodies. PMID:22479486

  6. Effects of Ceramic Fibre Insulation Thickness on Skin Formation and Nodule Characteristics of Thin Wall Ductile Iron Casting

    Science.gov (United States)

    Dhaneswara, D.; Suharno, B.; Nugraha, N. D.; Ariobimo, R. D. S.; Sofyan, N.

    2017-02-01

    Skin formation has become one of the problems in the thin wall ductile iron casting because it will reduce the mechanical properties of the materials. One of the solutions to reduce this skin formation is by using heat insulator to control the cooling rate. One of the insulators used for this purpose is ceramic fibre. In this research, the thickness of the ceramic fibre heat insulator used in the mould was varied, i.e. 50 mm on one side and 37.5 mm on the other side (A), no heat insulator (B), and 37.5 mm on both sides (C). After the casting process, the results were characterized in terms of metallography by using scanning electron microscope (SEM) and tensile test for mechanical properties. The results showed that the skin thickness formed in A is 34.21 μm, 23.38 μm in B, and 27.78 μm in C. The nodule count in A is 541.98 nodule/mm2 (84.7%) with an average diameter of 15.14 μm, 590 nodule/mm2 (86.7%) with an average diameter of 13.18 μm in B, and 549.73 nodule/mm2 (87.2%) with an average diameter of 13.95 μm in C. The average ultimate tensile strength for A was 399 MPa, B was 314 MPa, and C was 415 MPa. Microstructural examination under SEM showed that the materials have a ductile fracture with matrix full of ferrite.

  7. Determination of The Effects of Different Amino Acids, Sodium Formate and Their Combinations on Some Growth Characteristics of Mixed and Single Cell Cultures of Yoghurt Bacteria

    Directory of Open Access Journals (Sweden)

    B. Kaptan

    2005-05-01

    Full Text Available In this research, different amino acids, sodium formate and their combinations were added into the milk for determining their stimulatory or inhibitory effects on some growth characteristics of mixed and single cell cultures of yoghurt bacteria. Among the added individual amino acids (each of them 100 ppm, cystein was the most stimulant agent for mixed and single cell cultures of the S. salivarius subsp. thermophilus for their acetaldehyde and volatile fatty acid contents. Histidine and glutamic acid were also stimulatory for mentioned parameters. But for the samples, inoculated with single cell culture of L. delbrueckii subsp. bulgaricus, glutamic acid, cysteine and methionine were to be the most stimulatory for volatile fatty acid contents. Sodium formate added into the milk (500 ppm, as a growth factor aspecially for L. delbrueckii subsp. bulgaricus, showed more stimulant effect on the growth characteristics of this single culture of this bacteria. According to different compounds and culture groups added into the milk, statistically important (p<0.01 differences were determined among the investigated parameters.

  8. Potential energies of characteristic atoms on basis of experimental heats of formation of AuCu and AuCu_3 compounds (Ⅰ)

    Institute of Scientific and Technical Information of China (English)

    XIE You-qing; LIU Xin-bi; LI Xiao-bo; PENG Hong-jian; NIE Yao-zhuang

    2009-01-01

    The systematic science of alloys(SSA) is a framework of the total energy and total volume able to be separated. The potential energy sequences of characteristic atoms at the central sites of the basic clusters in the fcc-based lattice Au-Cu system are separated out from smaller experimental heats of formation of L10-AuCu and L1_2-AuCu_3 compounds only, by nine potential energy E-functions and through the use of structural unit inversion method. From these potential energy sequences, the potential energies and heats of formation of the disordered Au1-xCux alloys at 0 K are calculated. The potential energies, heats of formation and Tc-temperatures of order-disorder transitions of the L1_0-AuCu, L1_2-Au_3Cu and L1_2-AuCu_3 compounds, as well as the Au_3Cu-, AuCu- and AuCu_3~- type ordered alloys with maximal ordering degrees are calculated too. The results show that the 5th E-function may be chosen for developing it into the free energy-, enthalpy-, vibrational energy- and vibrational entropy-functions for describing thermodynamic properties of the compounds, ordered and disordered phases and for establishing the phase diagram of the Au-Cu system in the future.

  9. The impact of combustion characteristics and flame structure on soot formation in oxy-enhanced and oxy-fuel diffusion flames

    Institute of Scientific and Technical Information of China (English)

    GUO; Zhe; LOU; Chun; LIU; ZhengDong; ZHOU; HuaiChun

    2013-01-01

    Based on a detailed chemical mechanism, impacts of combustion characteristics and flame structure on soot formation in opposed-flow diffusion ethylene flames was studied with different stoichiometric mixture fractions in O2/N2and O2/CO2atmospheres. The results showed the followings. 1) In both atmospheres, with the increase of stoichiometric mixture fraction, the flame structure changed significantly. The stagnation plane shifted toward the oxidizer side. Furthermore, there were less C2H2 but more O and OH to occur in the soot inception zone, therefore the amount of soot in the flame decreased. 2) Compared withN2, CO2had a suppression effect on soot formation, which was mainly due to thermal and direct chemical interaction effects of CO2. This is because the specific heat capacity of CO2is higher than that of N2, which will cause the flame temperature to drop,and mole fractions of C2H2, H, O, OH and main PAHs to decrease. Soot oxidation played a dominant role, while soot surface growth was attributed to the secondary position. Meanwhile, when CO2 abounded in the flame, OH concentration was increased through the backward reaction of CO+OH=CO2+H, and this would be conducive to the oxidation of soot precursor and incipient soot particles. In addition, the results of maximum particle density indicated the thermal effect of CO2on soot for-mation is more important than the direct chemical interaction effect.

  10. Characteristic differences in the formation of complex coacervate core micelles from neodymium and zinc-based coordination polymers.

    Science.gov (United States)

    Yan, Yun; Besseling, Nicolaas A M; de Keizer, Arie; Stuart, Martien A Cohen

    2007-05-31

    In this paper we compare the formation of complex coacervate core micelles (C3Ms) from two different tricompontent mixtures, namely neodymium, the bisligand L2EO4 and the poly(cation)-block-poly(neutral) diblock copolymer P2MVP41-b-PEO205, and zinc, L2EO4 and P2MVP41-b-PEO205 mixed systems. Three sets of titration experiments were carried out for each system: (i) titration of diblock copolymer P2MVP41-b-PEO205 with the stoichiometric mixture of metal ions and bisligands, (ii) titration of a mixture of diblock copolymer and bisligand with metal ions, and (iii) titration of a mixture of diblock copolymer and metal ions with bisligands. In all the above three cases, micelles are found to form either in a broad range of charge ratios or in a broad range of metal/bisligand ratios. Upon addition of Nd2-(L2EO4)3 coordination polymer to P2MVP41-b-PEO205 solution, and upon addition of Nd3+ to a mixture of L2EO4 and P2MVP41-b-PEO205, micelles are found to form immediately after the first addition, whereas micelles show up in the similar zinc system only after a certain threshold Zn-(L2EO4) or Zn2+ concentration. This difference can be traced to the different structures of the Nd2-(L2EO4)3 and Zn-(L2EO4) coordination compounds. At very low concentrations, Zn-(L2EO4) are ring-like oligomers, but Nd2-(L2EO4)3 are larger networks. The network structure favors the formation of coacervate micellar core with P2MVP41-b-PEO205. Moreover, excess of Nd3+ ions will break up the C3Ms, while the same amount of Zn2+ has hardly any effect on the C3Ms. The breakdown of C3Ms by Nd3+ is due to the charge inversion of the coordination complex with increasing [Nd3+]/[L2EO4] ratio, which results in repulsive interaction between the coordination complex and the diblock copolymer, whereas no such interaction can occur in the zinc system.

  11. Defect-Tolerant Monolayer Transition Metal Dichalcogenides

    DEFF Research Database (Denmark)

    Pandey, Mohnish; Rasmussen, Filip Anselm; Kuhar, Korina;

    2016-01-01

    -principles investigation of defect tolerance in 29 monolayer transition metal dichalcogenides (TMDs) of interest for nanoscale optoelectronics. We find that the TMDs based on group VI and X metals form deep gap states upon creation of a chalcogen (S, Se, Te) vacancy, while the TMDs based on group IV metals form only...... shallow defect levels and are thus predicted to be defect-tolerant. Interestingly, all the defect sensitive TMDs have valence and conduction bands with a very similar orbital composition. This indicates a bonding/antibonding nature of the gap, which in turn suggests that dangling bonds will fall inside...... the gap. These ideas are made quantitative by introducing a descriptor that measures the degree of similarity of the conduction and valence band manifolds. Finally, the study is generalized to nonpolar nanoribbons of the TMDs where we find that only the defect sensitive materials form edge states within...

  12. Vector assembly of colloids on monolayer substrates

    Science.gov (United States)

    Jiang, Lingxiang; Yang, Shenyu; Tsang, Boyce; Tu, Mei; Granick, Steve

    2017-06-01

    The key to spontaneous and directed assembly is to encode the desired assembly information to building blocks in a programmable and efficient way. In computer graphics, raster graphics encodes images on a single-pixel level, conferring fine details at the expense of large file sizes, whereas vector graphics encrypts shape information into vectors that allow small file sizes and operational transformations. Here, we adapt this raster/vector concept to a 2D colloidal system and realize `vector assembly' by manipulating particles on a colloidal monolayer substrate with optical tweezers. In contrast to raster assembly that assigns optical tweezers to each particle, vector assembly requires a minimal number of optical tweezers that allow operations like chain elongation and shortening. This vector approach enables simple uniform particles to form a vast collection of colloidal arenes and colloidenes, the spontaneous dissociation of which is achieved with precision and stage-by-stage complexity by simply removing the optical tweezers.

  13. Interface chemistry and molecular bonding of functional ethoxysilane-based self-assembled monolayers on magnesium surfaces.

    Science.gov (United States)

    Killian, Manuela S; Seiler, Steffen; Wagener, Victoria; Hahn, Robert; Ebensperger, Christina; Meyer, Bernd; Schmuki, Patrik

    2015-05-06

    The modification of magnesium implants with functional organic molecules is important for increasing the biological acceptance and for reducing the corrosion rate of the implant. In this work, we evaluated by a combined experimental and theoretical approach the adsorption strength and geometry of a functional self-assembled monolayer (SAM) of hydrolyzed (3-aminopropyl)triethoxysilane (APTES) molecules on a model magnesium implant surface. In time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS), only a minor amount of reverse attachment was observed. Substrate-O-Si signals could be detected, as well as other characteristic APTES fragments. The stability of the SAM upon heating in UHV was investigated additionally. Density-functional theory (DFT) calculations were used to explore the preferred binding mode and the most favorable binding configuration of the hydrolyzed APTES molecules on the hydroxylated magnesium substrate. Attachment of the molecules via hydrogen bonding or covalent bond formation via single or multiple condensation reactions were considered. The impact of the experimental conditions and the water concentration in the solvent on the thermodynamic stability of possible APTES binding modes is analyzed as a function of the water chemical potential of the environment. Finally, the influence of van der Waals contributions to the adsorption energy will be discussed.

  14. Synthesis, Characteristics and Standard Molar Enthalpies of Formation of MZn2HPO4PO4 (M=Na+, K+)

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    MZn2HPO4PO4(M=Na+,K+) double salts were synthesized by a solid-state reaction at low temperature and a hydrothermal method, respectively, and characterized by XRD, FT-IR, TG and SEM. Thermochemical study was performed by an isoperibol solution calorimeter. According to Hess's law, a new thermochemical cycle was de-signed. The results show that the obtained products are layered compounds with an isostructure of triclinic system.The decomposition temperatures are 415 and 430℃ by TG, respectively. With the dissolution enthalpies and other standard chemical data, the standard molar formation enthalpies of the MZn2HPO4PO4(M=Na+,K+) were worked out as follows: △fH(○)m[NaZn2HPO4PO4,s]=(-3042.38±0.31) kJ·mol-1 and △fH(○)m[KZn2HPO4PO4,s] = (-3093.46±0.27) kJ·mol-1.

  15. Biofilm Formation and Adherence Characteristics of Listeria ivanovii Strains Isolated from Ready-to-Eat Foods in Alice, South Africa

    Directory of Open Access Journals (Sweden)

    Mirriam E. Nyenje

    2012-01-01

    Full Text Available The present study was carried out to investigate the potential of Listeria ivanovii isolates to exist as biofilm structures. The ability of Listeria ivanovii isolates to adhere to a surface was determined using a microtiter plate adherence assay whereas the role of cell surface properties in biofilm formation was assessed using the coaggregation and autoaggregation assays. Seven reference bacterial strains were used for the coaggregation assay. The degree of coaggregation and autoaggregation was determined. The architecture of the biofilms was examined under SEM. A total of 44 (88% strains adhered to the wells of the microtiter plate while 6 (12% did not adhere. The coaggregation index ranged from 12 to 77% while the autoaggregation index varied from 11 to 55%. The partner strains of S. aureus, S. pyogenes, P. shigelloides, and S. sonnei displayed coaggregation indices of 75% each, while S. Typhimurium, A. hydrophila, and P. aeruginosa registered coaggregation indices of 67%, 58%, and 50%, respectively. The ability of L. ivanovii isolates to form single and multispecies biofilms at 25°C is of great concern to the food industry where these organisms may adhere to kitchen utensils and other environments leading to cross-contamination of food processed in these areas.

  16. Facies characteristics of the basal part of the Talchir Formation, Talchir Basin, India – depositional history revisited

    Indian Academy of Sciences (India)

    Prabir Dasgupta; Rishiraj Sahoo

    2007-02-01

    The lowest unit of the Talchir Formation of Talchir Basin, Orissa, was described by pioneer workers as the 'basal oulder bed'. In an attempt to explain the co-existence of gravel and clay, materials of contrasting hydraulic properties, a probable situation resembling the effects of the action of ground-ice enabled boulders to be carried down by sluggish currents resulting in an intermixture of large boulders and fine mud was conceived. Misinterpretation of this conclusion led to a general tendency to describe the 'basal boulder bed' as 'glacial tillite'. However, the unit described as 'basal boulder bed is actually represented by a matrix rich conglomerate with pockets of normally graded silty clay. The present study reveals that the depositional imprints preserved in this part of the sedimentary succession indicate emplacement of successive debris flows generated through remobilization of pre-existing unconsolidated sediments. Small pockets of fine-grained turbidites presumably deposited from the entrained turbidity currents associated with the debris flows suggest the composite character of the debris flow deposit.

  17. Monolayer semiconductor nanocavity lasers with ultralow thresholds

    Science.gov (United States)

    Wu, Sanfeng; Buckley, Sonia; Schaibley, John R.; Feng, Liefeng; Yan, Jiaqiang; Mandrus, David G.; Hatami, Fariba; Yao, Wang; Vučković, Jelena; Majumdar, Arka; Xu, Xiaodong

    2015-04-01

    Engineering the electromagnetic environment of a nanometre-scale light emitter by use of a photonic cavity can significantly enhance its spontaneous emission rate, through cavity quantum electrodynamics in the Purcell regime. This effect can greatly reduce the lasing threshold of the emitter, providing a low-threshold laser system with small footprint, low power consumption and ultrafast modulation. An ultralow-threshold nanoscale laser has been successfully developed by embedding quantum dots into a photonic crystal cavity (PCC). However, several challenges impede the practical application of this architecture, including the random positions and compositional fluctuations of the dots, extreme difficulty in current injection, and lack of compatibility with electronic circuits. Here we report a new lasing strategy: an atomically thin crystalline semiconductor--that is, a tungsten diselenide monolayer--is non-destructively and deterministically introduced as a gain medium at the surface of a pre-fabricated PCC. A continuous-wave nanolaser operating in the visible regime is thereby achieved with an optical pumping threshold as low as 27 nanowatts at 130 kelvin, similar to the value achieved in quantum-dot PCC lasers. The key to the lasing action lies in the monolayer nature of the gain medium, which confines direct-gap excitons to within one nanometre of the PCC surface. The surface-gain geometry gives unprecedented accessibility and hence the ability to tailor gain properties via external controls such as electrostatic gating and current injection, enabling electrically pumped operation. Our scheme is scalable and compatible with integrated photonics for on-chip optical communication technologies.

  18. Acid monolayer functionalized iron oxide nanoparticle catalysts

    Science.gov (United States)

    Ikenberry, Myles

    Superparamagnetic iron oxide nanoparticle functionalization is an area of intensely active research, with applications across disciplines such as biomedical science and heterogeneous catalysis. This work demonstrates the functionalization of iron oxide nanoparticles with a quasi-monolayer of 11-sulfoundecanoic acid, 10-phosphono-1-decanesulfonic acid, and 11-aminoundecanoic acid. The carboxylic and phosphonic moieties form bonds to the iron oxide particle core, while the sulfonic acid groups face outward where they are available for catalysis. The particles were characterized by thermogravimetric analysis (TGA), transmission electron microscopy (TEM), potentiometric titration, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray photoelectron spectrometry (XPS), and dynamic light scattering (DLS). The sulfonic acid functionalized particles were used to catalyze the hydrolysis of sucrose at 80° and starch at 130°, showing a higher activity per acid site than the traditional solid acid catalyst Amberlyst-15, and comparing well against results reported in the literature for sulfonic acid functionalized mesoporous silicas. In sucrose catalysis reactions, the phosphonic-sulfonic nanoparticles (PSNPs) were seen to be incompletely recovered by an external magnetic field, while the carboxylic-sulfonic nanoparticles (CSNPs) showed a trend of increasing activity over the first four recycle runs. Between the two sulfonic ligands, the phosphonates produced a more tightly packed monolayer, which corresponded to a higher sulfonic acid loading, lower agglomeration, lower recoverability through application of an external magnetic field, and higher activity per acid site for the hydrolysis of starch. Functionalizations with 11-aminoundecanoic acid resulted in some amine groups binding to the surfaces of iron oxide nanoparticles. This amine binding is commonly ignored in iron oxide

  19. Emission characteristics of volatile organic compounds and their secondary organic aerosol formation potentials from a petroleum refinery in Pearl River Delta, China.

    Science.gov (United States)

    Zhang, Zhijuan; Wang, Hao; Chen, Dan; Li, Qinqin; Thai, Phong; Gong, Daocheng; Li, Yang; Zhang, Chunlin; Gu, Yinggang; Zhou, Lei; Morawska, Lidia; Wang, Boguang

    2017-02-08

    A campaign was carried out to measure the emission characteristics of volatile organic compounds (VOCs) in different areas of a petroleum refinery in the Pearl River Delta (PRD) region in China. In the refining area, 2-methylpentane, 2,3-dimethylbutane, methylcyclopentane, 3-methylhexane, and butane accounted for >50% of the total VOCs; in the chemical industry area, 2-methylpentane, p-diethylbenzene, 2,3-dimethylbutane, m-diethylbenzene and 1,2,4-trimethylbenzene were the top five VOCs detected; and in the wastewater treatment area, the five most abundant species were 2-methylpentane, 2,3-dimethylbutane, methylcyclopentane, 3-methylpentane and p-diethylbenzene. The secondary organic aerosol (SOA) formation potential was estimated using the fractional aerosol coefficients (FAC), secondary organic aerosol potential (SOAP), and SOA yield methods. The FAC method suggests that toluene, p-diethylbenzene, and p-diethylbenzene are the largest contributors to the SOA formation in the refining, chemical industry, and wastewater treatment areas, respectively. With the SOAP method, it is estimated that toluene is the largest contributor to the SOA formation in the refining area, but o-ethyltoluene contributes the most both in the chemical industry and wastewater treatment areas. For the SOA yield method, aromatics dominate the yields and account for nearly 100% of the total in the three areas. The SOA concentrations estimated of the refining, chemical industry and wastewater treatment areas are 30, 3835 and 137μgm(-3), respectively. Despite the uncertainties and limitations associated with the three methods, the SOA yield method is suggested to be used for the estimation of SOA formation from the petroleum refinery. The results of this study have demonstrated that the control of VOCs, especially aromatics such as toluene, ethyltoluene, benzene and diethylbenzene, should be a focus of future regulatory measures in order to reduce PM pollution in the PRD region.

  20. Engineering geological characteristics and the hydraulic fracture propagation mechanism of the sand-shale interbedded formation in the Xu5 reservoir

    Science.gov (United States)

    Lu, Cong; Li, Mei; Guo, Jian-Chun; Tang, Xu-Hai; Zhu, Hai-Yan; Yong-Hui, Wang; Liang, Hao

    2015-06-01

    In the Xu5 formation the sandstone reservoir and the shale reservoir are interbedded with each other. The average thickness of each formation is about 8 m, which increases the difficulty of the hydraulic fracturing treatment. The shale thickness ratio (the ratio of shale thickness to formation thickness) is 55-62.5%. The reservoir is characterized by ultra-low porosity and permeability. The brittleness index of sandstone is 0.5-0.8, and the brittleness index of shale is 0.3-0.8. Natural fractures are poorly developed and are mainly horizontal and at a low angle. The formation strength is medium and the reservoir is of the hybrid strike-slip fault and reverse fault stress regime. The difference between the minimum principal stress and the vertical stress is small, and the maximum horizontal principal stress is 20 MPa higher than the minimum horizontal principal stress and vertical stress. A mechanical model of a hydraulic fracture encountering natural fractures is built according to geological characteristics. Fracture mechanics theory is then used to establish a hydraulic fracturing model coupling the seepage-stress-damage model to simulate the initiation and propagation of a fracture. The hydraulic fracture geometry is mainly I-shaped and T-shaped, horizontal propagation dominates the extension, and vertical propagation is limited. There is a two to three meter stress diversion area around a single hydraulic fracture. The stress diversion between a hydraulic fracture and a natural fracture is advantageous in forming a complex fracture. The research results can provide theoretical guidance for tight reservoir fracturing design.

  1. Strain-tunable half-metallicity in hybrid graphene-hBN monolayer superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Fanchao, E-mail: fanchao.meng@mail.mcgill.ca [Department of Mining and Materials Engineering, McGill University, Montréal, QC H3A 0C5 (Canada); Zhang, Shiqi [School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, AZ 85281 (United States); Lee, In-Ho [Korea Research Institute of Standards and Science, 1 Doryong-Dong, Yuseong-Gu, Daejeon 305-600 (Korea, Republic of); Jun, Sukky [Department of Mechanical Engineering, University of Wyoming, Laramie, WY 82071 (United States); Ciobanu, Cristian V., E-mail: cciobanu@mines.edu [Department of Mechanical Engineering, Colorado School of Mines, Golden, CO 80401 (United States)

    2016-07-01

    Highlights: • Armchair superlattices have a bandgap modulated by the deformed domain widths. • Strain and domain width lead to novel spin-dependent behavior for zigzag boundaries. • Limits for spin-dependent bandgap and half-metallic behavior have been charted. - Abstract: As research in 2-D materials evolves toward combinations of different materials, interesting electronic and spintronic properties are revealed and may be exploited in future devices. A way to combine materials is the formation of spatially periodic domain boundaries in an atom-thick monolayer: as shown in recent reports, when these domains are made of graphene and hexagonal boron nitride, the resulting superlattice has half-metallic properties in which one spin component is (semi)metallic and the other is semiconductor. We explore here the range of spin-dependent electronic properties that such superlattices can develop for different type of domain boundaries, domain widths, and values of tensile strain applied to the monolayer. We show evidence of an interplay between strain and domain width in determining the electronic properties: while for armchair boundaries the bandgap is the same for both spin components, superlattices with zigzag boundaries exhibit rich spin-dependent behavior, including different bandgaps for each spin component, half-metallicity, and reversal of half-metallicity. These findings can lead to new ways of controlling the spintronic properties in hybrid-domain monolayers, which may be exploited in devices based on 2-D materials.

  2. Gold Nanoparticle Monolayers from Sequential Interfacial Ligand Exchange and Migration in a Three-Phase System

    Science.gov (United States)

    Yang, Guang; Hallinan, Daniel T.

    2016-10-01

    Using a three-phase system, centimeter-scale monolayer gold nanoparticle (Au NP) films have been prepared that have long-range order and hydrophobic ligands. The system contains an interface between an aqueous phase containing Au NPs and an oil phase containing one of various types of amine ligands, and a water/air interface. As the Au NPs diffuse to the water/oil interface, ligand exchange takes place which temporarily traps them at the water/oil interface. The ligand-exchanged particles then spontaneously migrate to the air/water interface, where they self-assemble, forming a monolayer under certain conditions. The spontaneous formation of the NP film at the air/water interface was due to the minimization of the system Helmholtz free energy. However, the extent of surface functionalization was dictated by kinetics. This decouples interfacial ligand exchange from interfacial self-assembly, while maintaining the simplicity of a single system. The interparticle center-to-center distance was dictated by the amine ligand length. The Au NP monolayers exhibit tunable surface plasma resonance and excellent spatial homogeneity, which is useful for surface-enhanced Raman scattering. The “air/water/oil” self-assembly method developed here not only benefits the fundamental understanding of NP ligand conformations, but is also applicable to the manufacture of plasmonic nanoparticle devices with precisely designed optical properties.

  3. Gold Nanoparticle Monolayers from Sequential Interfacial Ligand Exchange and Migration in a Three-Phase System

    Science.gov (United States)

    Yang, Guang; Hallinan, Daniel T.

    2016-01-01

    Using a three-phase system, centimeter-scale monolayer gold nanoparticle (Au NP) films have been prepared that have long-range order and hydrophobic ligands. The system contains an interface between an aqueous phase containing Au NPs and an oil phase containing one of various types of amine ligands, and a water/air interface. As the Au NPs diffuse to the water/oil interface, ligand exchange takes place which temporarily traps them at the water/oil interface. The ligand-exchanged particles then spontaneously migrate to the air/water interface, where they self-assemble, forming a monolayer under certain conditions. The spontaneous formation of the NP film at the air/water interface was due to the minimization of the system Helmholtz free energy. However, the extent of surface functionalization was dictated by kinetics. This decouples interfacial ligand exchange from interfacial self-assembly, while maintaining the simplicity of a single system. The interparticle center-to-center distance was dictated by the amine ligand length. The Au NP monolayers exhibit tunable surface plasma resonance and excellent spatial homogeneity, which is useful for surface-enhanced Raman scattering. The “air/water/oil” self-assembly method developed here not only benefits the fundamental understanding of NP ligand conformations, but is also applicable to the manufacture of plasmonic nanoparticle devices with precisely designed optical properties. PMID:27762394

  4. Cholesterol-Induced Buckling in Physisorbed Polymer-Tethered Lipid Monolayers

    Directory of Open Access Journals (Sweden)

    Christoph A. Naumann

    2013-04-01

    Full Text Available The influence of cholesterol concentration on the formation of buckling structures is studied in a physisorbed polymer-tethered lipid monolayer system using epifluorescence microscopy (EPI and atomic force microscopy (AFM. The monolayer system, built using the Langmuir-Blodgett (LB technique, consists of 3 mol % poly(ethylene glycol (PEG lipopolymers and various concentrations of the phospholipid, 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine (SOPC, and cholesterol (CHOL. In the absence of CHOL, AFM micrographs show only occasional buckling structures, which is caused by the presence of the lipopolymers in the monolayer. In contrast, a gradual increase of CHOL concentration in the range of 0–40 mol % leads to fascinating film stress relaxation phenomena in the form of enhanced membrane buckling. Buckling structures are moderately deficient in CHOL, but do not cause any notable phospholipid-lipopolymer phase separation. Our experiments demonstrate that membrane buckling in physisorbed polymer-tethered membranes can be controlled through CHOL-mediated adjustment of membrane elastic properties. They further show that CHOL may have a notable impact on molecular confinement in the presence of crowding agents, such as lipopolymers. Our results are significant, because they offer an intriguing prospective on the role of CHOL on the material properties in complex membrane architecture.

  5. Synthesis of one-dimensional silver oxide nanoparticle arrays and silver nanorods templated by Langmuir monolayers.

    Science.gov (United States)

    Liu, Hong-Guo; Xiao, Fei; Wang, Chang-Wei; Xue, Qingbin; Chen, Xiao; Lee, Yong-Ill; Hao, Jingcheng; Jiang, Jianzhuang

    2007-10-01

    One-dimensional (1D) silver oxide nanoparticle arrays were synthesized by illuminating the composite Langmuir-Blodgett monolayers of porphyrin derivatives/Ag(+) and n-hexadecyl dihydrogen phosphate (n-HDP)/Ag(+) deposited on carbon-coated copper grids with daylight and then exposing them to air. Transmission electron microscopy (TEM) observation shows that the nanoparticle size is around 3 nm, with the separation of about 2-3 nm. High-resolution TEM (HRTEM) investigation indicates that the particles are made up of Ag(2)O. Ag nanorods with the width of 15-35 nm and the length of several hundreds of nanometers were synthesized by irradiating the composite Langmuir monolayers of porphyrin derivatives/Ag(+) and n-HDP/Ag(+) by UV-light directly at the air/water interface at room temperature. HRTEM image and selected-area electron diffraction (SAED) pattern indicate that the nanorods are single crystals with the (110) face of the face-centered cubic (fcc) silver parallel to the air/water interface. The formation of the 1D arrays and the nanorods should be attributed to the templating effect of the linear supramolecules formed by porphyrin derivative or n-HDP molecules in Langmuir monolayers through non-covalent interactions.

  6. N-Hydroxysuccinimide-terminated self-assembled monolayers on gold for biomolecules immobilisation

    Energy Technology Data Exchange (ETDEWEB)

    Cabrita, J.F. [Laboratorio de SPM, Faculdade de Ciencias da Universidade de Lisboa, Ed. ICAT, Campo Grande, 1749-016 Lisbon (Portugal); CQB, Departamento de Quimica e Bioquimica da Faculdade de Ciencias da Universidade de Lisboa, Campo Grande, 1749-016 Lisbon (Portugal); Abrantes, L.M. [Laboratorio de SPM, Faculdade de Ciencias da Universidade de Lisboa, Ed. ICAT, Campo Grande, 1749-016 Lisbon (Portugal); CQB, Departamento de Quimica e Bioquimica da Faculdade de Ciencias da Universidade de Lisboa, Campo Grande, 1749-016 Lisbon (Portugal); Viana, A.S. [Laboratorio de SPM, Faculdade de Ciencias da Universidade de Lisboa, Ed. ICAT, Campo Grande, 1749-016 Lisbon (Portugal)]. E-mail: anaviana@icat.fc.ul.pt

    2005-03-15

    Pure and mixed N-hydroxysuccinimide-terminated and butanethiol monolayers were prepared on flat gold (1 1 1) surfaces with the intent of developing suitable platforms for the direct biomolecules immobilisation. The self-assembled monolayers (SAMs) were characterised by electrochemical reductive desorption of the thiolate from the gold surface. The data have shown that certain solution proportions of the two compounds yield modified electrodes exhibiting intermediate electrochemical behaviour of the corresponding pure SAMs. The reactivity of the terminal N-hydroxysuccinimide (NHS) towards amine functionalities has been tested for the covalent attachment of Dopamine. The cyclic voltammetric responses of the investigated monolayers, after contacting with a Dopamine solution, have confirmed the chemical coupling of the amine as well as the formation of mixed SAMs. The Dopamine surface coverage increased with the amount of surface NHS. Laccase was also successfully immobilised onto this modified electrodes. The electrochemical behaviour of the modified SAMs with Laccase indicates direct electron transfer between the immobilised enzyme and the gold surface. Evidence for Laccase immobilisation was also provided by atomic force microscopic measurements.

  7. Behavior of lysozyme adsorbed onto biological liquid crystal lipid monolayer at the air/water interface

    Science.gov (United States)

    Lu, Xiaolong; Shi, Ruixin; Hao, Changchun; Chen, Huan; Zhang, Lei; Li, Junhua; Xu, Guoqing; Sun, Runguang

    2016-09-01

    The interaction between proteins and lipids is one of the basic problems of modern biochemistry and biophysics. The purpose of this study is to compare the penetration degree of lysozyme into 1,2-diapalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphoethano-lamine (DPPE) by analyzing the data of surface pressure-area (π-A) isotherms and surface pressure-time (π-T) curves. Lysozyme can penetrate into both DPPC and DPPE monolayers because of the increase of surface pressure at an initial pressure of 15 mN/m. However, the changes of DPPE are larger than DPPC, indicating stronger interaction of lysozyme with DPPE than DPPC. The reason may be due to the different head groups and phase state of DPPC and DPPE monolayers at the surface pressure of 15 mN/m. Atomic force microscopy reveals that lysozyme was absorbed by DPPC and DPPE monolayers, which leads to self-aggregation and self-assembly, forming irregular multimers and conical multimeric. Through analysis, we think that the process of polymer formation is similar to the aggregation mechanism of amyloid fibers. Project supported by the National Natural Science Foundation of China (Grant Nos. 21402114 and 11544009), the Natural Science Basic Research Plan in Shaanxi Province of China (Grant No. 2016JM2010), the Fundamental Research Funds for the Central Universities of China (Grant No. GK201603026), and the National University Science and Technology Innovation Project of China (Grant No. 201610718013).

  8. Biomimetic nanoparticles with polynucleotide and PEG mixed-monolayers enhance calcium phosphate mineralization

    Energy Technology Data Exchange (ETDEWEB)

    Vasconcellos, Kayla B.; McHugh, Sean M.; Dapsis, Katherine J.; Petty, Alexander R.; Gerdon, Aren E., E-mail: gerdoar@emmanuel.edu [Emmanuel College (United States)

    2013-09-15

    Biomineralization of hydroxyapatite (Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2}) is of significant importance in biomedical applications such as bone and dental repair, and biomimetic control of mineral formation may lead to more effective restorative procedures. Gold nanoparticles are functional scaffolds on which to assemble multi-component monolayers capable of mimicking protein activity in the templated synthesis of calcium phosphate. The goal of this research was to explore nanoparticle templates with mixed-monolayers of uncharged polar polyethylene glycol (PEG) molecules and highly charged polynucleotide and amino acid molecules in their ability to influence mineralization rates and mineral particle size and morphology. This research demonstrates through time-resolved optical density and dynamic light scattering measurements that the combination of tiopronin, PEG, and DNA presented on a nanoparticle surface decreases nanoparticle aggregation from 59 to 21 nm solvated radius, increases mineralization kinetics from 1.5 Multiplication-Sign 10{sup -3} to 3.1 Multiplication-Sign 10{sup -3} OD/min, and decreases mineral particle size from 685 to 442 nm average radius. FT-IR and TEM data demonstrate that mineralized material, while initially amorphous, transforms to a semi-crystalline material when guided by template interactions. This demonstrates that surface-tailored monolayer protected cluster scaffolds are successful and controllable mineralization templates with further potential for biomedical applications involving calcium phosphate and other biomaterials.

  9. Biomimetic nanoparticles with polynucleotide and PEG mixed-monolayers enhance calcium phosphate mineralization

    Science.gov (United States)

    Vasconcellos, Kayla B.; McHugh, Sean M.; Dapsis, Katherine J.; Petty, Alexander R.; Gerdon, Aren E.

    2013-09-01

    Biomineralization of hydroxyapatite (Ca10(PO4)6(OH)2) is of significant importance in biomedical applications such as bone and dental repair, and biomimetic control of mineral formation may lead to more effective restorative procedures. Gold nanoparticles are functional scaffolds on which to assemble multi-component monolayers capable of mimicking protein activity in the templated synthesis of calcium phosphate. The goal of this research was to explore nanoparticle templates with mixed-monolayers of uncharged polar polyethylene glycol (PEG) molecules and highly charged polynucleotide and amino acid molecules in their ability to influence mineralization rates and mineral particle size and morphology. This research demonstrates through time-resolved optical density and dynamic light scattering measurements that the combination of tiopronin, PEG, and DNA presented on a nanoparticle surface decreases nanoparticle aggregation from 59 to 21 nm solvated radius, increases mineralization kinetics from 1.5 × 10-3 to 3.1 × 10-3 OD/min, and decreases mineral particle size from 685 to 442 nm average radius. FT-IR and TEM data demonstrate that mineralized material, while initially amorphous, transforms to a semi-crystalline material when guided by template interactions. This demonstrates that surface-tailored monolayer protected cluster scaffolds are successful and controllable mineralization templates with further potential for biomedical applications involving calcium phosphate and other biomaterials.

  10. Influences of the Driver and Ambient Medium Characteristics on the Formation of Shocks in the Solar Atmosphere

    Science.gov (United States)

    Nat, Gopalswamy; Hong, Xie; Seiji, Yashiro; Pertti, Makela; Sachiko, Akiyama

    2010-01-01

    Traveling interplanetary (IP) shocks were discovered in the early 1960s, but their solar origin has been controversial. Early research focused on solar flares as the source of the shocks, but when coronal mass ejections (CMEs) were discovered, it became clear that fast CMEs clearly can drive the shocks. Type II radio bursts are excellent signatures of shocks near the Sun. The close correspondence between type II radio bursts and solar energetic particles (SEPs) makes it clear that the same shock accelerates ions and electrons. A recent investigation involving a large number of IP shocks revealed that about 35% of IP shocks do not produce type II bursts or SEPs. Comparing these radio quiet (RQ) shocks with the radio loud (RL) ones revealed some interesting results: (1) there is no evidence for blast waves, in that all IP shocks can be attributed to CMEs, (2) a small fraction (20%) of RQ shocks is associated with ion enhancements at the shocks when they move past the observing spacecraft, (3) the primary difference between the RQ and RL shocks can be traced to the different kinematic properties of the associated CMEs and the variation of the characteristic speeds of the ambient medium, and (4) the shock properties measured at 1 AU are not too different for the RQ and RL cases due to the interaction of the shock driver with the IP medium that seems to erase the difference.

  11. Influence of Coal nature and Structure on Ash Size Formation Characteristic and Related pollutant Emissions During CFB Combustion

    Institute of Scientific and Technical Information of China (English)

    MinQIAN; YongjieNA; 等

    2000-01-01

    The size distribution of coal particles in a Circulating Fluidized Bed(CFB) boiler plays a crucial role in the complicated combustion,heat exchange and pollutant emissions in such a plant.Therefore,it is fundamental to study the different factors having influence on the size distribution of coal particles.Above all,the coal itself and in particular,the coal comminution phenomenon is a very influent factor.In the frame of this work,the coal nature (eleentary compostion) and coal internal structure (mineral componeents) are studied in detail.At this intermediary stage,experients on three typical Chinese coals on a 1.5 MWt CFBC pilot plant have been made.Some primary fragmentation test hae also been made in a small lab scale fluidized bed reactor.The resutls from the hot pilot test show i)the variation of coal ash distributions and other CFB performance data due to the cyclone and the coal characteristics and ii) the variation of desulfurization efficiency with limestone.Whereas the bench scale primary fragmentation test,likely linked to the caking propriety of a coal,does not seem to change considerable the char size distribution.

  12. Biofilm Formation and Its Relationship with the Molecular Characteristics of Food-Related Methicillin-Resistant Staphylococcus aureus (MRSA).

    Science.gov (United States)

    Vergara, Alberto; Normanno, Giovanni; Di Ciccio, Pierluigi; Pedonese, Francesca; Nuvoloni, Roberta; Parisi, Antonio; Santagada, Gianfranco; Colagiorgi, Angelo; Zanardi, Emanuela; Ghidini, Sergio; Ianieri, Adriana

    2017-09-11

    The capability to produce biofilm is an important persistence and dissemination mechanism of some foodborne bacteria. This paper investigates the relationship between some molecular characteristics (SCCmec, ST, spa-type, agr-type, cna, sarA, icaA, icaD, clfA, fnbA, fnbB, hla, hlb) of 22 food-related methicillin-resistant Staphylococcus aureus (MRSA) strains and their ability to form biofilm on stainless steel and polystyrene. Five (22.7%, 5/22) strains were able to synthesize biofilm on polystyrene, and one of these (4.5%, 1/22) strains was also able to synthesize biofilm on stainless steel. The largest amount of biofilm was formed on polystyrene by 2 MRSA strains isolated from cows' milk, thus raising concern about the dairy industry. The majority of MRSA biofilm producers carried SCCmec type IVa, suggesting that the presence of SCCmecIVa and/or agr type III could be related to the ability to form biofilm. In conclusion, in order to achieve an acceptable level of food safety, Good Hygiene Practices should be strictly implemented along the food chain to reduce the risk of colonization and dissemination of MRSA biofilm-producing strains in the food industry. © 2017 Institute of Food Technologists®.

  13. Bovine and human insulin adsorption at lipid monolayers: a comparison

    Directory of Open Access Journals (Sweden)

    Sergio eMauri

    2015-07-01

    Full Text Available Insulin is a widely used peptide in protein research and it is utilised as a model peptide to understand the mechanics of fibril formation, which is believed to be the cause of diseases such as Alzheimer and Creutzfeld-Jakob syndrome. Insulin has been used as a model system due to its biomedical relevance, small size and relatively simple tertiary structure. The adsorption of insu lin on a variety of surfaces has become the focus of numerous studies lately. These works have helped in elucidating the consequence of surface/protein hydrophilic/hydrophobic interaction in terms of protein refolding and aggregation. Unfortunately, such model surfaces differ significantly from physiological surfaces. Here we spectroscopically investigate the adsorption of insulin at lipid monolayers, to further our understanding of the interaction of insulin with biological surfaces.In particular we study the effect of minor mutations of insulin’s primary amino acid sequence on its interaction with 1,2-Dipalmitoyl-sn-glycero-3-phosphoglycerol (DPPG model lipid layers. We probe the structure of bovine and human insulin at the lipid/water interface using sum frequency generation spectroscopy (SFG. The SFG experiments are complemented with XPS analysis of Langmuir-Schaefer deposited lipid/insulin films. We find that bovine and human insulin, even though very similar in sequence, show a substantially different behavior when interacting with lipid films.

  14. Identifying multiexcitons in Mo S2 monolayers at room temperature

    Science.gov (United States)

    Lee, Hyun Seok; Kim, Min Su; Kim, Hyun; Lee, Young Hee

    2016-04-01

    One of the unique features of atomically thin two-dimensional materials is strong Coulomb interactions due to the reduced dielectric screening effect; this feature enables the study of many-body phenomena such as excitons, trions, and biexcitons. However, identification of biexcitons remains unresolved owing to their broad peak feature at room temperature. Here, we investigate multiexcitons in monolayer Mo S2 using both electrical and optical doping and identify the transition energies for each exciton. The binding energy of the assigned biexciton is twice that of the trion, in quantitative agreement with theoretical predictions. The biexciton population is predominant under optical doping but negligible under electrical doping. The biexciton population is quadratically proportional to the exciton population, obeying the mass-action theory. Our results illustrate the stable formation of not only trions but also biexcitons due to strong Coulomb interaction even at room temperature; therefore, these results provide a deeper understanding of the complex excitonic behaviors in two-dimensional semiconductors.

  15. Size effects in tin-based lead-free solder joints: Kinetics of bond formation and mechanical characteristics

    Science.gov (United States)

    Abdelhadi, Ousama Mohamed Omer

    Continuous miniaturization of microelectronic interconnects demands smaller joints with comparable microstructural and structural sizes. As the size of joints become smaller, the volume of intermetallics (IMCs) becomes comparable with the joint size. As a result, the kinetics of bond formation changes and the types and thicknesses of IMC phases that form within the constrained region of the bond varies. This dissertation focuses on investigating combination effects of process parameters and size on kinetics of bond formation, resulting microstructure and the mechanical properties of joints that are formed under structurally constrained conditions. An experiment is designed where several process parameters such as time of bonding, temperature, and pressure, and bond thickness as structural chracteristic, are varied at multiple levels. The experiment is then implemented on the process. Scanning electron microscope (SEM) is then utilized to determine the bond thickness, IMC phases and their thicknesses, and morphology of the bonds. Electron backscatter diffraction (EBSD) is used to determine the grain size in different regions, including the bulk solder, and different IMC phases. Physics-based analytical models have been developed for growth kinetics of IMC compounds and are verified using the experimental results. Nanoindentation is used to determine the mechanical behavior of IMC phases in joints in different scales. Four-point bending notched multilayer specimen and four-point bending technique were used to determine fracture toughness of the bonds containing IMCs. Analytical modeling of peeling and shear stresses and fracture toughness in tri-layer four-point bend specimen containing intermetallic layer was developed and was verified and validated using finite element simulation and experimental results. The experiment is used in conjunction with the model to calculate and verify the fracture toughness of Cu6Sn5 IMC materials. As expected two different IMC phases

  16. Formation and characteristics of AlGaN-based three-dimensional hexagonal nanopyramid semi-polar multiple quantum wells

    Science.gov (United States)

    Tian, Yingdong; Yan, Jianchang; Zhang, Yun; Zhang, Yonghui; Chen, Xiang; Guo, Yanan; Wang, Junxi; Li, Jinmin

    2016-05-01

    We demonstrated for the first time the formation and study of semi-polar AlGaN multiple-quantum-wells (MQWs) grown on highly regular hexagonal AlN nanopyramids. The AlN nanopyramids were obtained by a metal-organic chemical vapor phase deposition regrowth method on a well-ordered AlN nanorod array prepared by a top-down etching process. The growth mechanism of the AlN nanopyramids was ascribed to the slow growth of the (101&cmb.macr;1) semi-polar plane, which resulted from hydrogen passivation. Beneath the semi-polar facets, air voids were formed. This was attributed to the insufficient delivery of gas reactants to the bottom of the nanorods during the growth process. The polarization effect in semi-polar AlGaN MQWs was numerically calculated. The results showed that the internal electric field (IEF) in the semi-polar MQWs was remarkably reduced by 80% in comparison with c-plane MQWs. Power dependent photoluminescence indicated that the semi-polar AlGaN MQWs had negligible wavelength shifts that resulted from the reduced IEF, which was in accordance with theoretical predictions. In addition, epitaxial strain was greatly relieved in the AlN regrowth layer, which was revealed from the peak shift of the E2(high) phonon using micro-Raman spectroscopy. The advantages of AlGaN-based hexagonal nanopyramid semi-polar three dimensional nanostructures would lead to a large improvement of output power in UV-LEDs.

  17. Adhesive and conformational behaviour of mycolic acid monolayers.

    Science.gov (United States)

    Zhang, Zhenyu; Pen, Yu; Edyvean, Robert G; Banwart, Steven A; Dalgliesh, Robert M; Geoghegan, Mark

    2010-09-01

    We have studied the pH-dependent interaction between mycolic acid (MA) monolayers and hydrophobic and hydrophilic surfaces using molecular (colloidal probe) force spectroscopy. In both cases, hydrophobic and hydrophilic monolayers (prepared by Langmuir-Blodgett and Langmuir-Schaefer deposition on silicon or hydrophobized silicon substrates, respectively) were studied. The force spectroscopy data, fitted with classical DLVO (Derjaguin, Landau, Verwey, and Overbeek) theory to examine the contribution of electrostatic and van der Waals forces, revealed that electrostatic forces are the dominant contribution to the repulsive force between the approaching colloidal probe and MA monolayers. The good agreement between data and the DLVO model suggest that beyond a few nm away from the surface, hydrophobic, hydration, and specific chemical bonding are unlikely to contribute to any significant extent to the interaction energy between the probe and the surface. The pH-dependent conformation of MA molecules in the monolayer at the solid-liquid interface was studied by ellipsometry, neutron reflectometry, and with a quartz crystal microbalance. Monolayers prepared by the Langmuir-Blodgett method demonstrated a distinct pH-responsive behaviour, while monolayers prepared by the Langmuir-Schaefer method were less sensitive to pH variation. It was found that the attachment of water molecules plays a vital role in determining the conformation of the MA monolayers.

  18. The Modeling of Pulmonary Particulate Matter Transport Using Langmuir Monolayers

    Science.gov (United States)

    Eaton, Jeremy M.

    The effects of a barrier in proximity to the air-water interface on the dynamics of a Langmuir monolayer system are observed. A monolayer of Survanta, bovine lung surfactant, is deposited onto the interface of an aqueous buffer solution. Polystyrene particles one micron in diameter and tagged with fluorescent carboxylate groups are distributed evenly throughout the monolayer surface. The bead-monolayer system is compressed and expanded to induce folding. A polydimethylsiloxane (PDMS) substrate is placed below the monolayer in the buffer solution to study interactions between the folding monolayer and a barrier. The presence of the substrate is shown to shift surface pressure-area isotherms toward regions of lower area by an average of 8.9 mN/m. The surface of the PDMS substrate can be imaged using fluorescence microscopy to detect the presence of particles or surfactant that may have been transported there from the air-water interface during folding. Images show the transferral of particles and monolayer together suggesting the pinch-off of a fold or the direct interaction of a fold with the barrier.

  19. Electrochemical characterization of a 1,8-octanedithiol self-assembled monolayer (ODT-SAM) on a Au(111) single crystal electrode

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Raya, Daniel; Madueno, Rafael; Sevilla, Jose Manuel; Blazquez, Manuel; Pineda, Teresa [Departamento de Quimica Fisica y Termodinamica Aplicada, Universidad de Cordoba, Campus de Rabanales, Cordoba (Spain)

    2008-11-15

    Recently, it has becoming increasingly important to control the organization of self-assembled monolayers (SAMs) of {omega}-functionalized thiols for its potential applications in the construction of more complex molecular architectures. In this paper, we report on the spontaneous formation of a SAM of octanedithiol (ODT) as a function of the modification time. Electrochemical techniques such as cyclic voltammetry, double layer capacitance and electrochemical impedance spectroscopy are used for the characterization of this monolayer. The increase in modification time brings about changes in the octanedithiol self-assembled monolayer (ODT-SAM) reductive desorption voltammograms that indicate an evolution toward a more ordered and compact monolayer. This trend has also been found by following the changes in the electron transfer processes of the redox probe K{sub 3}Fe(CN){sub 6}. In fact, the ODT-SAM formed at low-modification time does not significantly perturb the electrochemical response as it is typical of either a low coverage or of the presence of large defects in the layer. Upon increasing the modification time, the voltammograms of the redox probe adopt a sigmoidal shape indicating the existence of pinholes in the monolayer distributed as an array of microelectrodes. The surface coverage as well as the size and distribution of these pinholes have been determined by the impedance technique that gives a more reliable evaluation of these monolayer structural parameters. (author)

  20. Electrochemical characterization of a 1,8-octanedithiol self-assembled monolayer (ODT-SAM) on a Au(1 1 1) single crystal electrode

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Raya, Daniel; Madueno, Rafael; Sevilla, Jose Manuel; Blazquez, Manuel [Departamento de Quimica Fisica y Termodinamica Aplicada, Universidad de Cordoba, Campus de Rabanales, Ed. Marie Curie, E-14071 Cordoba (Spain); Pineda, Teresa [Departamento de Quimica Fisica y Termodinamica Aplicada, Universidad de Cordoba, Campus de Rabanales, Ed. Marie Curie, E-14071 Cordoba (Spain)], E-mail: tpineda@uco.es

    2008-11-15

    Recently, it has becoming increasingly important to control the organization of self-assembled monolayers (SAMs) of {omega}-functionalized thiols for its potential applications in the construction of more complex molecular architectures. In this paper, we report on the spontaneous formation of a SAM of octanedithiol (ODT) as a function of the modification time. Electrochemical techniques such as cyclic voltammetry, double layer capacitance and electrochemical impedance spectroscopy are used for the characterization of this monolayer. The increase in modification time brings about changes in the octanedithiol self-assembled monolayer (ODT-SAM) reductive desorption voltammograms that indicate an evolution toward a more ordered and compact monolayer. This trend has also been found by following the changes in the electron transfer processes of the redox probe K{sub 3}Fe(CN){sub 6}. In fact, the ODT-SAM formed at low-modification time does not significantly perturb the electrochemical response as it is typical of either a low coverage or of the presence of large defects in the layer. Upon increasing the modification time, the voltammograms of the redox probe adopt a sigmoidal shape indicating the existence of pinholes in the monolayer distributed as an array of microelectrodes. The surface coverage as well as the size and distribution of these pinholes have been determined by the impedance technique that gives a more reliable evaluation of these monolayer structural parameters.