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Sample records for nonlinear langmuir blodgett

  1. Langmuir-Blodgett films of amylose-esters and chiral azo-dyes : structure and second order nonlinear optical behaviour

    NARCIS (Netherlands)

    Schoondorp, Monique Annette

    1992-01-01

    This thesis describes the structure and second order nonlinear optical behaviour of several Langmuir-Blodgett films. Langmuir-Blodgett (LB) films are ultra thin films produced by the Langmuir-Blodgett technique, named after their inventors (Irving Langmuir and Katharina Blodgett).

  2. Langmuir-Blodgett films of amylose-esters and chiral azo-dyes: structure and second order nonlinear optical behaviour

    OpenAIRE

    Schoondorp, Monique Annette

    1992-01-01

    This thesis describes the structure and second order nonlinear optical behaviour of several Langmuir-Blodgett films. Langmuir-Blodgett (LB) films are ultra thin films produced by the Langmuir-Blodgett technique, named after their inventors (Irving Langmuir and Katharina Blodgett).

  3. Near-field nonlinear optical spectroscopy of Langmuir-Blodgett films

    DEFF Research Database (Denmark)

    Bozhevolnyi, Sergey I.; Geisler, T.

    1998-01-01

    Using an uncoated fiber tip as a light source and a multilayer Langmuir-Blodgett film of 2-docosylamino-5-nitropyridine as a sample, we obtain near-field images at the fundamental-harmonic (FH) and second-harmonic (SH) wavelengths for different polarizations and wavelengths of the pump light...

  4. Langmuir-Blodgett Films of Graphene Derivatives

    DEFF Research Database (Denmark)

    Petersen, Søren Vermehren

    The work presented in this PhD thesis can be divided into two main categories: 1) Syn-thesis and Langmuir-Blodgett assembly of graphene derivatives and 2) Application and characterization of graphene derivatives as an interface material in molecular electron-ics. While the first category could...... be divided further, the synthesis and Langmuir-Blodgett results are intertwined in such a way that it would be more confusing to pre-sent them separately. The Langmuir-Blodgett deposition also played a crucial, but more isolated, part in the investigation of graphene derivatives as interface material....... Solution processable graphene in the form of chemically derived graphene has been synthesized through the modified Hummers method with subsequent reduction into reduced graphene oxide with hydrazine. The completeness of oxidation, the effect of the refinement steps and the reduction of the graphene oxide...

  5. Langmuir Blodgett multilayers and related nanostructures

    Indian Academy of Sciences (India)

    Langmuir Blodgett (LB) process is an important route to the development of organized molecular layered structures of a variety of organic molecules with suitably designed architecture and functionality. LB multilayers have also been used as templates and precursors to develop nano-structured thin films. In this article ...

  6. Langmuir Blodgett multilayers and related nanostructures

    Indian Academy of Sciences (India)

    Abstract. Langmuir Blodgett (LB) process is an important route to the development of organized molecular layered structures of a variety of organic molecules with suitably designed architecture and functionality. LB multilayers have also been used as templates and precursors to develop nano-structured thin films.

  7. Langmuir-Blodgett Films of Graphene Derivatives

    DEFF Research Database (Denmark)

    Petersen, Søren Vermehren

    The work presented in this PhD thesis can be divided into two main categories: 1) Syn-thesis and Langmuir-Blodgett assembly of graphene derivatives and 2) Application and characterization of graphene derivatives as an interface material in molecular electron-ics. While the first category could....... Solution processable graphene in the form of chemically derived graphene has been synthesized through the modified Hummers method with subsequent reduction into reduced graphene oxide with hydrazine. The completeness of oxidation, the effect of the refinement steps and the reduction of the graphene oxide...... immobilization of the monolayered graphene oxide via the Langmuir-Blodgett deposition technique prior to a three step reduction scheme involving hydrazine reduc-tion, sulfuric acid de-oxygenation, and thermal annealing. This method resulted in wrin-kle-free reduced graphene oxide with a negligible oxygen content...

  8. Simulation of Langmuir-Blodgett film surface STM images

    International Nuclear Information System (INIS)

    Agabekov, V.E.; Zhavnerko, G.K.; Bar, G.; Cantov, H.J.

    1998-01-01

    The simulation of the STM image of a hydrocarbon tail of the fatty acid was carried out and compared to the experimental results. The simulation procedure includes calculations of the distribution of an isolated molecule electronic density by the extended Huckel-Hoffman method. An agreement between the calculated and experimental STM images of closely packed Langmuir-Blodgett film of cobalt behenate on the graphite surface and the adsorbed molecules constituting bi- and multilayer Langmuir-Blodgett films can be neglected in simulations of STM images. (author)

  9. Preparation of supramolecular networks using Langmuir-Blodgett techniques

    Czech Academy of Sciences Publication Activity Database

    Dudič, Miroslav; Perman, Jason; Cipolloni, Marco; Michl, Josef

    2012-01-01

    Roč. 106, - (2012), s1218-s1218 ISSN 0009-2770. [EuCheMS Chemistry Congress /4./. 26.08.2012-30.08.2012, Prague] EU Projects: European Commission(XE) 227756 - DIPOLAR ROTOR ARRAY Institutional support: RVO:61388963 Keywords : supramolecular * monolayer * Langmuir - Blodgett Subject RIV: CC - Organic Chemistry

  10. Langmuir and Langmuir-Blodgett films of capsules of haemoglobin ...

    Indian Academy of Sciences (India)

    Organized assemblies of capsules of haemoglobin (Hb), in the size range of 0.1 to 0.3 in Langmuir films have been studied at air/water interface below and above the isoelectric point. Spread films of these organizates suggest that there is no expulsion of individual particles or particle assemblies at the interface and the ...

  11. Evidence for magnetic ordering in ultrathin gadolinium Langmuir-Blodgett films

    DEFF Research Database (Denmark)

    Tishin, A.M.; Koksharov, Yu.A.; Bohr, Jakob

    1997-01-01

    Magnetic ultrathin Langmuir-Blodgett films containing rare earths are investigated. Electron paramagnetic resonance measurements suggest the possible existence of a transition from a paramagnetic to a magnetically ordered state. In Langmuir-Blodgett films with one hundred layers of Gd, a transition...

  12. Bulk organisation and alignment in Langmuir and Langmuir-Blodgett films of tetrachloroperylene tetracarboxylic acid esters

    Science.gov (United States)

    Modlińska, Anna; Filipowicz, Marek; Martyński, Tomasz

    2016-12-01

    Perylene derivatives with chlorine atoms attached at the bay position to the dye core are expected to affect organisation and tendency to aggregation in Langmuir and Langmuir-Blodgett (LB) films. Therefore, newly synthesized core-twisted homologous series of tetrachloroperylene tetracarboxylic acid esters with n = 1,4,5,6,9 carbon atoms in terminal alkyl chains were studied. Phase transitions and crystalline structures were specified by differential scanning calorimetry (DSC) and single crystal X-ray diffraction (XRD), respectively. Intermolecular interactions and organisation of the dyes in monomolecular films were investigated by means of Brewster angle microscope (BAM), UV-Vis absorption and emission spectroscopy, fluorescence microscopy and atomic force microscopy (AFM). The dyes investigated do not form thermotropic mesogenic phases in bulk. The crystalline triclinic elementary cell with P-1 symmetry is revealed from X-ray experiments. In Langmuir and Langmuir-Blodgett films molecular tilted head-on alignment is postulated. Spectroscopic research confirmed by AFM texture images of the LB films show that in the Langmuir and LB films the dyes, depending on length of terminal chains, have a tendency to create H or I molecular aggregates. The impact of the twisted core on the molecular behavior in a bulk and thin films is discussed.

  13. Second harmonic generation in anisotropic Langmuir-Blodgett films of N-docosyl-4-nitroaniline

    DEFF Research Database (Denmark)

    Geisler, T.; Rosenkilde, S.; Ramanujam, P.S.

    1992-01-01

    Langmuir-Blodgett (LB) films of N-docosyl-4-nitroaniline have been made and their nonlinear optical properties studied by second harmonic generation (SHG) measurements. A significant enhancement of the intensity of the second harmonic of the 1.064-mu-m YAG was observed when a two layer Y-type film...... structure. Both of these observations are not common for Y-type LB films and the usual assumption of C(infinity nu) symmetry is therefore not valid. The results make us suggest that these LB films possess C(s) and C2-nu symmetry for mono- and multilayers, respectively. Theoretical expressions...

  14. Density determination of langmuir-blodgett monolayer films using x-ray reflectivity technique

    International Nuclear Information System (INIS)

    Damar Yoga Kusuma

    2015-01-01

    Monolayer deposition by Langmuir-Blodgett technique produces monolayer films that are uniform with controllable thickness down to nanometer scale. To evaluate the quality of the monolayer deposition, X-ray reflectivity technique are employed to monitor the monolayers density. Langmuir-Blodgett monolayer with good coverage and uniformity results in film density close to its macroscopic film counterpart whereas films with presence of air gaps shows lower density compared to its macroscopic film counterpart. (author)

  15. Photopatterning of heterostructured polymer Langmuir-Blodgett films

    International Nuclear Information System (INIS)

    Li Tiesheng; Mitsuishi, Masaya; Miyashita, Tokuji

    2008-01-01

    Heterostructured polymer Langmuir-Blodgett (LB) film prepared by using poly(N-dodecylacrylamide-co-t-butyl 4-vinylphenyl carbonate) (p(DDA-tBVPC53)) and poly(N-neopentyl methacrylamide-co-9-anthrylmethyl methacrylate) (p(nPMA-AMMA10)) polymer LB films which can act as photogenerator layers were investigated. Patterns with a resolution of 0.75 μm were obtained on heterostructured polymer LB films composed of 4 layers of p(nPMA-AMMA10) LB film (top layers) and 40 layers of p(DDA-tBVPC53) LB film (under layers) on a silicon wafer by deep UV irradiation followed by development with 1% tetramethylammonium hydroxide aqueous solution. The sensitivity of the heterostructured polymer LB films was improved without loss of the resolution compared with p(DDA-tBVPC53) LB film. The etch resistance of the heterostructured polymer LB films was sufficiently good to allow patterning of a copper film suitable for photomask fabrication

  16. Metallic Langmuir and Langmuir-Blodgett films based on TTF derivatives and fatty acid

    International Nuclear Information System (INIS)

    Ohnuki, H.; Ishizaki, Y.; Suzuki, M.; Desbat, B.; Delhaes, P.; Giffard, M.; Imakubo, T.; Mabon, G.; Izumi, M.

    2002-01-01

    Recent progress in the metallic conducting Langmuir-Blodgett (LB) films built from TTF derivative and fatty acids is reported. A simple LB method of transferring the mixed Langmuir (L) film of BEDO-TTF (BO) and stearic acid (SA) onto substrates provided metallic conducting LB films. A homogeneous L film formation on the water surface observed by Brewster angle microscope (BAM) is an essential factor for the well-ordered LB films. In the L film, the carboxylate group of fatty acid forms anion layer bringing about a spontaneous formation of mixed valence state (MVS) of BO layer. Similar spontaneous formation was also found in the molecular combination of nonoxygen-substituted donor of EDT-TTF and octadecanesulfonic acid (OS). This type of reaction would be useful for obtaining conducting LB films. For the LB films of BEDO-TTF and stearic acid, we found a negative transverse magnetoresistance at low temperature that was interpreted in the weak localization of a two-dimensional (2D) electronic system based on the well-defined conducting layer

  17. Thermal and electrothermal sensitivity of polyglutamic acid with incorporated carbocyanine dyes in Langmuir-Blodgett films

    Energy Technology Data Exchange (ETDEWEB)

    Popova, G. [Mendeleyev University of Chemical Technology of Russia, Miusskaya sq., 9, Moscow 125047 (Russian Federation)], E-mail: galina@muctr.edu.ru; Spitsyn, A.; Vantsyan, M. [Mendeleyev University of Chemical Technology of Russia, Miusskaya sq., 9, Moscow 125047 (Russian Federation); Matveeva, N. [Lukin Institute Phys. Problems, Zelenograd (Russian Federation); Yudin, S.; Palto, S. [Crystallography Institute Rus., Leninsky prosp., 57, 117336 Moscow (Russian Federation)

    2008-03-31

    Light-and electrosensitive carbocyanine dyes were incorporated into polyglutamic acid via covalent and non-covalent bonding. The reversible colour change on heating the Langmuir-Blodgett films of polyaminoacid has been studied by absorption spectroscopy and electroconductivity techniques. Characteristic shifts of the absorption spectrum are explained by formation of aggregates and hydrogen bonds. It was shown that H-aggregates and dimers are formed in Langmuir-Blodgett films; each type of assemblies contributes to the absorption spectrum. At elevated temperatures the ratio between concentrations of monomers, dimers and H-aggregates varies due to a breakdown of a part of aggregates into monomers. The change in molecular polarizability was also noticed. Electroconductivity of Langmuir-Blodgett films is observed in longitudinal and transverse directions. Electrochromic effect is noticed under weak electric current by change from red to colourless with iodine doping.

  18. Optimized Deposition of Graphene Oxide Langmuir-Blodgett Thin Films

    Directory of Open Access Journals (Sweden)

    Dravniece A.

    2014-08-01

    Full Text Available Vienslāņa grafēns ir inovatīvs gaismas caurlaidīgs materiāls, kam piemīt augsta elektrības un siltumvadītspēja, līdz ar to, tradicionālos elektrodus aizstājot ar grafēna monoslāni, tiktu paaugstināta optoelektrisko ierīču efektivitāte. Pētījumā grafēna oksīda (GO iegūšanai izmantota modificēta Hammera (Hummer metode un parauga liofilizācija, lai atbrīvotos no ūdens. Grafēna oksīda plānās kārtiņas uzklāšanai izvēlēta Lengmīra - Blodžetas (Langmuir - Blodgett metode, kurai piedāvāts jauns paņēmiens GO monoslāņa iegūšanai uz gaisa/ūdens robežvirsmas. Pretēji iepriekš LB tehnoloģijā izmantotām GO suspensijām ūdenī parādīts, ka kā suspensijas un uznešanas šķīdinātājs var tikt izmantots benzols vai benzola/metanola maisījums. Lai samazinātu GO lokšņu skaitu Lengmīra kārtiņā, veikta GO slāņu papildus eksfoliēšana uznešanas šķīdinātājā, paraugu sonējot un centrifugējot. Novērota substrāta virsmas apstrādes ietekme - stikla substrāta hidrofilizēšana un ozonēšana uzlabo plānās kārtiņas uznešanas iznākumu, savukārt ar ITO (indium tin oxide pārklāta stikla substrāta ozonēšana ir nepieciešama, lai varētu veikt uznešanu. Iegūtās GO suspensijas un plānās kārtiņas raksturotas ar skenējošo elektronu mikroskopiju

  19. Structure and Electrical Conductivity of Hybrid Langmuir-Blodgett Films from BEDO-TTF and Fatty Acid

    NARCIS (Netherlands)

    Akhtar, Naureen; Gengler, Regis Y. N.; Palstra, Thomas T. M.; Rudolf, Petra

    2012-01-01

    Conducting Langmuir-Blodgett films are one of the candidates for molecular electronics. We investigated the structural and electrical properties of Langmuir-Blodgett films built up as a mixed molecular system of bis(ethylenedioxy)tetrathiafulvalene, in short BEDO-TTF, and fatty acid, as a function

  20. Magnetic volcanos in gadolinium Langmuir-Blodgett films

    DEFF Research Database (Denmark)

    Tishin, A.M.; Snigirev, O.V.; Khomutov, G.B.

    2001-01-01

    Magnetic, structural and electronic properties of Langmuir–Blodgett films with incorporated Gd3+ ions has been detected using a scanning DC SQUID microscope, scanning electron microscope and X-ray diffraction. The magnetic images of 28 and 50 layer thick films at 77 K have been obtained after in...

  1. Langmuir and Langmuir–Blodgett films of capsules of haemoglobin ...

    Indian Academy of Sciences (India)

    Haemoglobin; capsules; Langmuir–Blodgett films; pH; multi-walled capsules; isoelectric point. 1. Introduction. Drug delivery and storage of formulations in pharma- ceutical applications require microencapsulation tech- niques. Many different methods have been used to develop encapsulation techniques for the purpose of.

  2. Functionalized surfaces of polylactide modified by Langmuir-Blodgett films of amphiphilic block copolymers

    Czech Academy of Sciences Publication Activity Database

    Kubies, Dana; Machová, Luďka; Brynda, Eduard; Lukáš, Jaromír; Rypáček, František

    2003-01-01

    Roč. 14, č. 2 (2003), s. 143-149 ISSN 0957-4530 R&D Projects: GA ČR GA203/99/0576 Institutional research plan: CEZ:AV0Z4050913 Keywords : polylactide * Langmuir - Blodgett films * amphiphilic block copolymers Subject RIV: CD - Macromolecular Chemistry Impact factor: 0.930, year: 2003

  3. Radicals as EPR probes of magnetization of gadolinium stearate Langmuir-Blodgett film

    DEFF Research Database (Denmark)

    Koksharov, Y.A.; Bykov, I.V.; Malakho, A.P.

    2002-01-01

    In the present work we have applied the method of the EPR spin probes which allows performing simultaneously EPR and magnetization measurements to the investigation of magnetism of the Cid stearate Langmuir-Blodgett (LB) films. For this purpose we have prepared and studied by the EPR technique...

  4. Langmuir- Blodgett layers of amphiphilic molecules investigated by Atomic Force Microscopy

    NARCIS (Netherlands)

    Zdravkova, Aneliya Nikolova

    2007-01-01

    Langmuir - Blodgett technique and Atomic Force Microscopy were used to study the phase behaviour of organic molecules (fatty alcohols and monoacid saturated triglycerides) at air-water and air-solid interfaces. The structure of binary mixed LB monolayers of fatty alcohols was reported. The

  5. Structural studies of Langmuir-Blodgett films containing rare-earth metal cations

    DEFF Research Database (Denmark)

    Khomutov, G.B.; Antipina, M.N.; Bykov, I.V.

    2002-01-01

    Comparative structural study of gadolinium stearate Langmuir-Blodgett (LB) films formed by monolayer deposition from either aqueous gadolinium acetate or gadolinium chloride solutions have been carried out. Structure of the films was characterized by X-ray diffraction, Fourier transform infrared ...

  6. Properties of excited singular states of the anthraquinone dye in the Langmuir-Blodgett films

    International Nuclear Information System (INIS)

    Baratova, A.A.; Ibraev, N.Kh.

    2004-01-01

    The spectral luminescence properties of the anthraquinone dye solution and the Langmuir-Blodgett films have been investigated. The nature of the absorption centers is determined from the spectral characteristics. The conclusion about probable spatial configuration of the dye molecule in the dye molecule in monolayer on water surface is made. (author)

  7. Molecular structure of dipalmitoylphospatidylcholine Langmuir-Blodgett monolayers studied by atomic force microscopy.

    NARCIS (Netherlands)

    Zhai, X.; Kleijn, J.M.

    1997-01-01

    Monolayers of dipalmitoylphosphatidylcholine (DPPC) on the air-water interface have been transferred at various surface pressures onto quartz substrates using the Langmuir-Blodgett (LB) technique. The topography of these layers, on a molecular scale, has been examined by atomic force microscopy

  8. Investigation on single walled carbon nanotube thin films deposited by Langmuir Blodgett method

    Energy Technology Data Exchange (ETDEWEB)

    Vishalli,, E-mail: vishalli-2008@yahoo.com; Dharamvir, Keya [Department of Physics, Panjab University, Chandigarh (India); Kaur, Ramneek; Raina, K. K. [Materials Research Laboratory, School of Physics and Materials Science, Thapar University, Patiala (India)

    2015-05-15

    Langmuir Blodgett is a technique to deposit a homogeneous film with a fine control over thickness and molecular organization. Thin films of functionalized SWCNTs have been prepared by Langmuir Blodgett method. The good surface spreading properties of SWCNTs at air/water interface are indicated by surface pressure-area isotherm and the monolayer formed on water surface is transferred onto the quartz substrate by vertical dipping. A multilayer film is thus obtained in a layer by layer manner. The film is characterized by Atomic Force Microscope (AFM), UV-Vis-NIR spectroscopy and FTIR.AFM shows the surface morphology of the deposited film. UV-Vis-NIR spectroscopy shows the characteristic peaks of semiconducting SWCNTs. The uniformity of LB film can be used further in understanding the optical and electrical behavior of these materials.

  9. Macroscopic alignment of graphene stacks by Langmuir-Blodgett deposition of amphiphilic hexabenzocoronenes

    DEFF Research Database (Denmark)

    Laursen, B.W.; Nørgaard, K.; Reitzel, N.

    2004-01-01

    e present structural studies of Langmuir V and Langmuir-Blodgett (LB) films of new amphiphilic hexa-peri-hexabenzocoronene (HBC) discotics, carrying five branched alkyl side chains and one polar group. The polar group is either a carboxylic acid moiety or an electron acceptor moiety (anthraquinone...... and tilted relative to the water surface. The intercolumnar distance is 20 A. The HBCs are confined to a layer lying on top of the layer of polar groups that are in contact with the water subphase. Efficient transfer of the monolayer of the anthraquinone-substituted HBC derivative to hydrophobic quartz...

  10. Synthesis and photoreaction of Schiff bases derived from p-nitro cinnamaldehyde and diamines in Langmuir and Langmuir Blodgett films

    Science.gov (United States)

    Kanthimathi, Mookandi; Dhathathreyan, Aruna

    2003-01-01

    Monolayers of Schiff bases derived from ethylene diamine and o-phenylene diamine with p-nitro cinnamaldehyde, (compounds 1 and 2) at air/water interface have been studied. Photolysis of 1 in chloroform solution undergoes cis- trans isomerization on irradiation of white light while compound 2 does not undergo isomerization under photolytic conditions. The photolysis of 1 and 2 in Langmuir-Blodgett films (LB films) transferred to quartz plates form dimers. The change in product distribution is attributed to the influence of bridging group of the cinnamaldehyde moieties, molecular configuration and mobility of the compounds in solution, solid state and the aggregation of molecules in monolayer assemblies.

  11. Aggregation properties of tetrachloroperylene-tetracarboxylic acid in binary Langmuir and Langmuir–Blodgett films

    Energy Technology Data Exchange (ETDEWEB)

    Modlińska, Anna; Piosik, Emilia [Faculty of Technical Physics, Poznan University of Technology, Poznan (Poland); Paluszkiewicz, Joanna [Institute of Polymers and Dyes Technology, Lodz University of Technology, Lodz (Poland); Martyński, Tomasz, E-mail: tomasz.martynski@put.poznan.pl [Faculty of Technical Physics, Poznan University of Technology, Poznan (Poland)

    2014-04-15

    The Langmuir and Langmuir–Blodgett films formed of tetra-n-butyl-1,6,7,12-tetrachloroperylene-3,4,9,10-tetracarboxylate and its binary mixtures with 4-octyl-4′-cyanobiphenyl and arachidic acid have been studied. The Langmuir films were characterized by surface pressure versus mean molecular area isotherms and the films morphology observations were made by means of a Brewster angle microscope. The miscibility of the compounds was determined. Subsequently, the Langmuir films were transferred onto hydrophilic quartz substrates forming the monolayer Langmuir–Blodgett films. The electronic absorption and fluorescence spectra reveal aggregation of the chromophores in ground state driven by π–π molecular orbitals interactions. Perylene-like dye aggregation depends upon the dye concentration in the dye/liquid crystal mixed films and is concentration-independent in dye/arachidic acid one. -- Highlights: • A new perylene derivative with four chlorine atoms in the core was synthetized. • Langmuir films of pure dye and its binary mixtures were studied thermodynamically. • The miscibility of the components in the films changes the π–π stacking of the dye. • We describe the dye aggregation in the pure and mixed films deposited onto quartz.

  12. Chain length dependence of the helix orientation in Langmuir-Blodgett monolayers of alpha-helical diblock copolypeptides

    NARCIS (Netherlands)

    Nguyen, Le-Thu T.; Ardana, Aditya; Vorenkamp, Eltjo J.; ten Brinke, Gerrit; Schouten, Arend J.

    2010-01-01

    The effect of chain length on the helix orientation of alpha-helical diblock copolypeptides in Langmuir and Langmuir-Blodgett monolayers is reported for the first time. Amphiphilic diblock copolypeptides (PLGA-b-PMLGSLGs) of poly(alpha-L-glutamic acid) (PLGA) and

  13. Molecular positional order in Langmuir-Blodgett films by atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Bourdieu, L.; Ronsin, O.; Chatenay, D. (Inst. Curie, Paris (France))

    1993-02-05

    Langmuir-Blodgett films of barium arachidate have been studied on both macroscopic and microscopic scales by atomic force microscopy. As prepared, the films exhibit a disordered hexagonal structure; molecularly resolved images in direct space establish a connection between the extent of the positional order and the presence of defects such as dislocations. Upon heating, the films reorganize into a more condensed state with a centered rectangular crystallographic arrangement; in this new state the films exhibit long-range positional order and unusual structural features, such as a height modulation of the arachidic acid molecules. 22 refs., 4 figs.

  14. An introduction to ultrathin organic films from Langmuir-Blodgett to self-assembly

    CERN Document Server

    Ulman, Abraham

    1991-01-01

    The development of oriented organic monomolecular layers by the Langmuir-Blodgett (LB) and self-assembly (SA) techniques has led researchers toward their goal of assembling individual molecules into highly ordered architectures. Thus the continually growing contribution of LB and SA systems to the chemistry and physics of thin organic films is widely recognized. Equally well-known is the difficulty in keeping up to date with the burgeoning multidisciplinary research in this area. Dr. Ulman provides a massive survey of the available literature. The book begins with a section on analytical tools

  15. Enzymes immobilized in Langmuir-Blodgett films: Why determining the surface properties in Langmuir monolayer is important?

    Directory of Open Access Journals (Sweden)

    LUCIANO CASELI

    2018-01-01

    Full Text Available ABSTRACT In this review we discuss about the immobilization of enzymes in Langmuir-Blodgett films in order to determine the catalytic properties of these biomacromolecules when adsorbed on solid supports. Usually, the conformation of enzymes depends on the environmental conditions imposed to them, including the chemical composition of the matrix, and the morphology and thickness of the film. In this review, we show an outline of manuscripts that report the immobilization of enzymes as LB films since the 1980’s, and also some examples of how the surface properties of the floating monolayer prepared previously to the transfer to the solid support are important to determine the efficiency of the resulting device.

  16. The Langmuir-Blodgett Technique as a Tool for Homeotropic Alignment of Fluorinated Liquid Crystals Mixed with Arachidic Acid

    Directory of Open Access Journals (Sweden)

    Anna Modlińska

    2011-08-01

    Full Text Available Some fluoro-substituted liquid crystals mixed with arachidic acid in monolayers formed at air-liquid (Langmuir films and air-solid substrate (Langmuir-Blodgett films interfaces were investigated. Molecular organization in Langmuir films was determined on the basis of the analysis of the shape of the surface pressure-mean molecular area isotherm and observations made by means of a Brewster angle microscope. It was found that in the compression process the liquid crystal molecules are pushed out towards the top of the first monolayer being in direct contact with the subphase. Langmuir films were transferred onto the quartz substrates at various surface pressures and mono- and multilayered Langmuir-Blodgett films were obtained. The films were characterized using electronic absorption measurements. The conditions for obtaining the homeotropic orientation of the liquid crystal molecules were determined.

  17. Supramolecular structure formation of Langmuir-Blodgett films of comblike precursor and polyimide

    Energy Technology Data Exchange (ETDEWEB)

    Goloudina, S. I., E-mail: goloudina@mail.ru; Luchinin, V. V. [St. Petersburg Electrotechnical University (Russian Federation); Rozanov, V. V. [Russian Academy of Sciences, Institute for Analytical Instrumentation (Russian Federation); Pasyuta, V. M. [St. Petersburg Electrotechnical University (Russian Federation); Gofman, I. V.; Sklizkova, V. P.; Kudryavtsev, V. V. [Russian Academy of Sciences, Institute of Macromolecular Compounds (Russian Federation)

    2013-03-15

    The surface structure of Langmuir-Blodgett films of a comblike polyimide precursor-a rigid-chain polyamic acid alkylamine salt bearing multichains of tertiary amine-and films of the corresponding polyimide were studied by atomic force microscopy (AFM). An analysis of the images of the surface of three-layer films revealed a domain structure. It was found that the Langmuir-Blodgett film formation of the precursor occurs as a result of the layer-by-layer deposition of two-dimensional domains (composed of polyamic acid salt molecules on the water surface) onto a substrate. The formation of domains in a monolayer is associated with the chemical structure of the precursor, to be more precise, with the rigidity of the main chain and the presence of closely spaced aliphatic side chains in the polymer chain, whose total cross-section area is close to the surface area of the projection onto the plane of the repeating unit of the main chain. Polyimide films inherit the domain structure of the precursor films; the inhomogeneity of the film thickness substantially decreases, whereas the domain size and character of their distribution in the film remain unchanged.

  18. Luminescent Langmuir-Blodgett film of a new amphiphilic Eu3+ β-diketonate

    International Nuclear Information System (INIS)

    Gomes, Luciano F.; Oliveira, Kleber T. de; Neri, Claudio R.; Sousa Filho, Paulo C. de; Bianco, Marcos J. dal; Ramos, Ana P.; Zaniquelli, Maria E.D.; Serra, Osvaldo A.

    2008-01-01

    This work reports on the synthesis and characterization of the ligand 3-hexadecylpentane-2,4-dione (Hhdacac) and its Eu 3+ complexes Eu(hdacac) 6 .2H 2 O, Eu(hdacac) 6 .phen and Eu(hdacac) 6 .tta, where phen and tta denote 1,10-phenanthroline and thenoyltrifluoroacetone, respectively. These new compounds present long carbon chains and their expected miscibility into non-polar ambients is confirmed by the emission spectra of Eu(hdacac) 6 .tta in hexane. Moreover, the amphiphilic properties of Eu(hdacac) 6 complexes allow the obtainment of thin luminescent films by the Langmuir-Blodgett technique. In both cases (solids and films), the typical antenna effect of β-diketonates is observed. The alluring characteristics of these compounds raise great interest in many fields of Materials Science, like photo- and electro-luminescent materials (mainly thin 'organic' films), metal catalysts or probes in non-polar solutions, and Langmuir-Blodgett films of several compositions. For the characterization of these products, nuclear magnetic resonance spectroscopy ( 1 H NMR), thermogravimetric analysis, elementary analyses (C, H), scanning electron microscopy (energy dispersive X-ray spectroscopy), absorption (UV-vis/FT-IR) and photoluminescence spectroscopies were used

  19. Photo-switching of a non-ionic azobenzene amphiphile in Langmuir and Langmuir-Blodgett films.

    Science.gov (United States)

    Piosik, Emilia; Kotkowiak, Michał; Korbecka, Izabela; Galewski, Zbigniew; Martyński, Tomasz

    2017-08-30

    The concept of programmable and reconfigurable soft matter has emerged in science in the last few decades and can be realized by photoisomerization of azobenzene derivatives. This possibility results in great application potential of these compounds in optical storage devices, molecular junctions of electronic devices, command layers of liquid crystal displays or holographic gratings. In this paper, we present the results of a study on the organization and isomerization of the non-ionic and amphiphilic methyl 4-[(E)-2-[4-(nonyloxy)phenyl]diazen-1-yl]benzoate (LCA) in a 2D layer architecture of Langmuir and Langmuir-Blodgett (LB) films supported by spectroscopic studies on LCA chloroform solutions. Our investigation has shown a significantly different molecular organization of LCA depending on the ratio of trans and cis isomers in the monolayers. Taking advantage of a relatively low packing density and aggregation strength in the cis-LCA monolayer, we demonstrated the reversible isomerization in the LB film initially formed of LCA molecules in the cis form, while in the trans-LCA monolayer this effect was not observed. Our approach allows the formation of a switchable monolayer made of the amphiphilic LCA showing liquid crystalline properties without introducing an ionic group into the molecule structure, mixing with another compound or changing the subphase pH to provide free space for the molecules' isomerization.

  20. Annealing-Induced Changes in Double-Brush Langmuir-Blodgett Films of alpha-Helical Diblock Copolypeptides

    NARCIS (Netherlands)

    Nguyen, Le-Thu T.; Musser, Andrew J.; Vorenkamp, Eltjo J.; Polushkin, Evgeny; ten Brinke, Gerrit; Schouten, Arend J.

    2010-01-01

    The effect of annealing on the structure and the helix orientation in Langmuir-Blodgett (LB) monolayers of diblock copolymers (PLGA-b-PMLGSLGs) of poly(alpha-L-glutamic acid) (PLGA) and poly(gamma-methyl-L-glutamate-ran-gamma-stearyl-L-glutamate) with 30 mol % of stearyl substituents (PMLGSLG) with

  1. Structural and optical properties of langmuir-blodgett films of the electron acceptor 2-octadecylthio-1,4-benzoquinone

    DEFF Research Database (Denmark)

    Bjørnholm, T.; Larsen, N. B.; Christensen, Finn Erland

    1993-01-01

    The electron acceptor 2-octadecylthio-1,4-benzoquinone forms stable monolayers at air/water interfaces. Transfer to hydrophobic substrates yields Y-type Langmuir-Blodgett films. By studies of multilayers using X-ray diffraction and spectroscopy with polarized light a structure model is obtained...

  2. Langmuir-Blodgett films of a functionalized molecule with cross-sectional mismatch between head and tail

    DEFF Research Database (Denmark)

    Garnaes, J.; Larsen, N.B.; Bjørnholm, T.

    1994-01-01

    A functionalized surfactant has been investigated as floating monolayers by synchrotron x-ray diffraction and as bilayers transferred to solid supports by the Langmuir-Blodgett technique through atomic force microscopy. The transfer process is accompanied by an increase of the unit cell area (about...

  3. Comment on 'extrinsic versus intrinsic ferroelectric switching : experimental investigations using ultra-thin PVDF Langmuir-Blodgett films'

    NARCIS (Netherlands)

    Naber, R.C.G.; Blom, P.W.M.; de Leeuw, DM

    2006-01-01

    Previous work on ultra-thin P(VDF-TrFE) Langmuir-Blodgett films has indicated a transition from extrinsic to intrinsic ferroelectric switching. The lack of several key features of intrinsic switching in the experimental work reported by Kliem et al argues against intrinsic switching. In this Comment

  4. Antibacterial and Antibiofouling Properties of Light Triggered Fluorescent Hydrophobic Carbon Quantum Dots Langmuir-Blodgett Thin Films

    Czech Academy of Sciences Publication Activity Database

    Stanković, N. K.; Bodik, M.; Šiffalovič, P.; Kotlár, M.; Mičušik, M.; Špitalsky, Z.; Danko, M.; Milivojević, D. D.; Kleinová, A.; Kubát, Pavel; Capáková, Z.; Humpolíček, P.; Lehocký, M.; Todorović Marković, B. M.; Marković, Z. M.

    2018-01-01

    Roč. 6, č. 3 (2018), s. 4154-4163 ISSN 2168-0485 R&D Projects: GA ČR(CZ) GA17-05095S Institutional support: RVO:61388955 Keywords : Hydrophobic carbon quantum dots * Langmuir-Blodgett thin films * Photodynamic therapy * Singlet oxygen Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 5.951, year: 2016

  5. Photoluminescence kinetics in CdS nanoclusters formed by the Langmuir-Blodgett technique

    Energy Technology Data Exchange (ETDEWEB)

    Zarubanov, A. A., E-mail: alexsundr@mail.ru; Zhuravlev, K. S. [Russian Academy of Sciences, Institute of Semiconductor Physics, Siberian Branch (Russian Federation)

    2015-03-15

    The photoluminescence kinetics in CdS nanocrystals produced by the Langmuir-Blodgett technique is studied at a temperature of 5 K. The photoluminescence kinetics is described by the sum of two exponential functions, with characteristic times of about 30 and 160 ns. It is found that the fast and slow decay times become longer, as the nanocrystal size increases. Analysis of the data shows that the fast decay time is controlled by trion recombination in nanocrystals with defects, whereas the slow decay time is controlled by the annihilation of optically inactive excitons in nanocrystals without defects. It is established that, as the nanocrystal size is decreased, the fraction of imperfect nanocrystals is reduced because of an increase in the energy of defect formation.

  6. Inorganic insertion compounds under the form of Langmuir-Blodgett films

    International Nuclear Information System (INIS)

    Zylberajch, Claire

    1989-01-01

    As the study of organic or mineral compounds under the form of thin layers showed that they are displaying very original properties with respect to massive compounds, this research thesis reports a work which aimed at obtaining mineral conductive materials under the form of extremely thin layers, notably metallic sulfides of mercury and cadmium. Synthesis is performed in soft conditions within an organic matrix produced by using the Langmuir-Blodgett technique with successive diffusions of mineral reactants. Salt formation is monitored by infrared spectroscopy. Physical properties of these compounds have been studied by various techniques (UV, visible, and IR spectroscopy, linear dichroism, X ray diffraction, X ray photoelectron spectrometry, conduction, and so on). Structural and electronic properties of these extremely thin films confirm that metallic sulfides adopt a lamellar geometry with molecular thickness. Conductivity and photo-conductivity are interpreted by means of a conventional band diagram [fr

  7. Determination of the structure of Langmuir-Blodgett monolayers by infrared dichroism

    International Nuclear Information System (INIS)

    Chollet, Pierre-Alain

    1982-01-01

    We show that the study of absorption and reflexion infrared dichroism is a suitable tool for the determination of the crystallographic structure and of the molecules orientation in Langmuir-Blodgett multilayers. Their thickness range is comprised between 30 and 2000 angstroms. We have worked up a theoretical model which allows a quantitative interpretation of the absorption of thin anisotropic crystals. Two kind of multilayers are studied: one built of a saturated aliphatic acid and the other one with an ethylenic acid. These layers are composed of adjoining crystallites which are oriented on the substrate during the transfer process. The crystallisation propagates in a direction perpendicular to the layers in the case of the saturated acid, while ethylenic acid monolayers are constituted of a superimposition of two-dimensional smectic structures. Using reflexion experiments on metallic substrates we show that the molecules in the very first layers are oriented in a direction perpendicular to the substrate. (author) [fr

  8. Structure and frictional properties of Langmuir-Blodgett films of Cu nanoparticles modified by dialkyldithiophosphate

    International Nuclear Information System (INIS)

    Xu Jun; Dai Shuxi; Cheng Gang; Jiang Xiaohong; Tao Xiaojun; Zhang Pingyu; Du Zuliang

    2006-01-01

    Langmuir-Blodgett (LB) films of dialkyldithiophosphate (DDP) modified Cu nanoparticles were prepared. The structure, microfrictional behaviors and adhesion of the LB films were investigated by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and atomic/friction force microscopy (AFM/FFM). Our results showed that the modified Cu nanoparticles have a typical core-shell structure and fine film-forming ability. The images of AFM/FFM showed that LB films of modified Cu nanoparticles were composed of many nanoparticles arranged closely and orderly and the nanoparticles had favorable behaviors of lower friction. The friction loop of the films indicated that the friction force was affected prominently by the surface slope of the Cu nanoparticles and the microfrictional behaviors showed obvious 'ratchet effect'. The adhesion experiment showed that the modified Cu nanoparticle had a very small adhesive force

  9. Large-sized and highly radioactive 3H and 109Cd Langmuir-Blodgett films

    International Nuclear Information System (INIS)

    Shibata, S.; Kawakami, H.; Kato, S.

    1994-02-01

    A device for the deposition of a radioactive Langmuir-Blodgett (LB) film was developed with the use of: (1) a modified horizontal lifting method, (2) an extremely shallow trough, and (3) a surface pressure-generating system without piston oil. It made a precious radioactive subphase solution repeatedly usable while keeping its radioactivity concentration as high as possible. Any large-size thin films can be prepared by just changing the trough size. Two monomolecular-layers of Y-type films of cadmium [ 3 H] icosanoate and 109 Cd icosanoate were built up as 3 H and 109 Cd β-sources for electron spectroscopy with intensities of 1.5 GBq (40 mCi) and 7.4 MBq (200 μCi), respectively, and a size of 65x200 mm 2 . Excellent uniformity of the distribution of deposited radioactivity was confirmed by autoradiography and photometry. (author)

  10. Circular patterns of calcium oxalate monohydrate induced by defective Langmuir-Blodgett film on quartz substrates

    Energy Technology Data Exchange (ETDEWEB)

    He Jieyu [Institute of Biomineralization and Lithiasis Research, Jinan University, Guangzhou 510632 (China); Institute of Biomineralization and Lithiasis Research, Jinan University, Guangzhou 510632 (China); Ouyang Jianming [Institute of Biomineralization and Lithiasis Research, Jinan University, Guangzhou 510632 (China); Institute of Biomineralization and Lithiasis Research, Jinan University, Guangzhou 510632 (China)], E-mail: toyjm@jnu.edu.cn

    2009-01-01

    The defective Langmuir-Blodgett (LB) film of dipalmitoylphosphatidylcholine (DPPC) on quartz injured by potassium oxalate (K{sub 2}C{sub 2}O{sub 4}) was used as a model system to induce growth of calcium oxalate crystals. Atomic force microscopy (AFM) indicated that circular defective domains with a diameter of 1-200 {mu}m existed in the LB film. Scanning electron microscopy (SEM) showed circular patterns of aggregated calcium oxalate monohydrate (COM) crystallites were induced by these defective domains. It was ascribed to that the interaction between the negatively-charged oxalate ions and the phosphatidyl groups in DPPC headgroups makes the phospholipid molecules rearranged and exist in an out-of-order state in the LB film, especially at the boundaries of liquid-condensed (LC)/liquid-expanded (LE) phases, which provide much more nucleating sites for COM crystals.

  11. Thin nanocomposite films of polyaniline/Au nanoparticles by the Langmuir-Blodgett technique.

    Science.gov (United States)

    Tanami, Golan; Gutkin, Vitaly; Mandler, Daniel

    2010-03-16

    The Langmuir-Blodgett (LB) method was used to deposit multilayers of polyaniline (PANI)- and mercaptoethanesulfonate (MES)-stabilized Au nanoparticles. The electrostatic interaction between the negatively charged nanoparticles in the subphase and the positively charged PANI at the air-water interface assisted the deposition of the nanocomposite film onto a solid support. These PANI/Au-NPs films were characterized using cyclic voltammetry, copper under potential deposition, scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. We found that the nanocomposite layers were uniform and reproducible. The density of Au-NPs in the monolayer depended on the acidity of the subphase as well as on the nanoparticles concentration. Moreover, the Au-NPs extrude above the PANI and therefore could be used as nanoelectrodes for the underpotential deposition (UPD) of copper.

  12. Langmuir-Blodgett (LB)-based nanobiocrystallography at the frontiers of cancer proteomics.

    Science.gov (United States)

    Pechkova, Eugenia; Bragazzi, Nicola Luigi; Fiordoro, Stefano; Nicolini, Claudio

    2015-02-01

    Langmuir-Blodgett (LB) films used as templates for crystallization lead to marked changes in protein stability and water dehydration, despite slight changes in protein atomic structure. Herein, we discuss the importance of LB-based nanocrystallography at the frontiers of cancer proteomics focusing on two model proteins with important biological roles in cancer, namely CK2alpha and RNase A. Computational mutagenesis using the KINARI Mutagen webserver exhibits different behaviors in terms of stability and robustness, as well as in terms of water dynamics. Introduction of LB film leads to the appearance of water molecules close to the protein surface with larger volume, causing changes in crystal stability against radiation and appearing replicated in mutant proteins. Implications for drug design, drug delivery and cancer-causing protein variants are herein presented, along with a review of the most recent findings in LB-based nanobiocrystallography. Copyright© 2015 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.

  13. A theoretical model for the pyroelectric response in Langmuir-Blodgett films

    International Nuclear Information System (INIS)

    Capan, R.; Basaran, I.; Richardson, T.H.; Lacey, D.

    2002-01-01

    Understanding the structure of pyroelectric materials is important to elucidate the nature of the temperature-dependent microscopic and macroscopic electric polarisation. Pyroelectric materials must have a non-centrosymmetric structure. Previously, researchers [C.A. Jones, PhD thesis, University of Durham, (1987); J. Mater. Chem. 1 (1991) 819; Langmuir 11 (1995) 4623] have reported the pyroelectric effect of non-centrosymmetric ultrathin LB films prepared using the alternate layer Langmuir-Blodgett (LB) deposition technique. They have proposed three main mechanisms to explain the origin of the pyroelectric activity, namely, tilting, proton transfer, and ionic processes. Linear and cyclic polysiloxane materials with aliphatic and aromatic side groups have been studied in this work. These materials have been alternately deposited with eicosylamine to form the active pyroelectric material in metal-LB film-metal (MIM) devices, whose pyroelectric coefficients have been measured using a quasi-static measurement technique [W.H. Majid, Abd., PhD thesis, Univ. of Sheffield (1994); Mater. Sci. Eng., C, Biomim. Mater., Sens. Syst. 3 (1995) 197; Thin Solid Films 327-329 (1998) 369]. The relation between pyroelectric mechanism(s) and microscopic and macroscopic pyroelectric response for polysiloxane/eicosylamine alternate layer LB films will be explained in this work. Results indicate that the physical mechanism by which the pyroelectric activity arises in the LB films is critically dependent upon their structural quality, the ions within the multilayer arrangement and the molecular dipole moments of the molecules

  14. Photoisomerization of amphiphilic azobenzene derivatives in Langmuir Blodgett films prepared as polyion complexes, using ionic polymers

    Energy Technology Data Exchange (ETDEWEB)

    Shembekar, Vishakha R. [Department of Chemistry, Indian Institute of Technology, Bombay, Mumbai-400 076 (India); Contractor, A.Q. [Department of Chemistry, Indian Institute of Technology, Bombay, Mumbai-400 076 (India); Major, S.S. [Department of Physics, Indian Institute of Technology, Bombay, Mumbai-400 076 (India); Talwar, S.S. [Department of Physics, Indian Institute of Technology, Bombay, Mumbai-400 076 (India)]. E-mail: chsstia@phy.iitb.ac.in.z

    2006-07-03

    Polyion complexation in mixed Langmuir and Langmuir Blodgett (LB) films of photochromic amphiphilic azobenzene carboxylic acids, 11-[4-(4-hexylphenyl)azo] phenoxyundecanoic acid, 11-(4-phenylazo)phenoxyundecanoic acid, and diamine grafted poly(methylmethaacrylate) polymers has been studied. Monolayer behaviour of the pure components and mixed films was studied through pressure-area isotherms and LB films were characterized by spectroscopic, X-ray diffraction and Atomic force microscopy techniques. Aggregation (H-type), often observed in LB films of pure amphiphilic azo acids, was partly avoided in the mixed LB films as indicated by absorption spectral studies. Photoisomerization of the polyion complexed LB films was also studied. The results altogether demonstrate that amine grafted polymer enter into a polyion complexation with azo acid carboxylate group. LB films could be obtained by transfer of the composite monolayers and these LB films exhibited different levels of aggregation of the azo acids. Reversible photoisomerization was observed in LB films with unaggregated azo acid.

  15. Supramolecular architectures of iron phthalocyanine Langmuir-Blodgett films: The role played by the solution solvents

    Science.gov (United States)

    Rubira, Rafael Jesus Gonçalves; Aoki, Pedro Henrique Benites; Constantino, Carlos José Leopoldo; Alessio, Priscila

    2017-09-01

    The developing of organic-based devices has been widely explored using ultrathin films as the transducer element, whose supramolecular architecture plays a central role in the device performance. Here, Langmuir and Langmuir-Blodgett (LB) ultrathin films were fabricated from iron phthalocyanine (FePc) solutions in chloroform (CHCl3), dichloromethane (CH2Cl2), dimethylformamide (DMF), and tetrahydrofuran (THF) to determine the influence of different solvents on the supramolecular architecture of the ultrathin films. The UV-vis absorption spectroscopy shows a strong dependence of the FePc aggregation on these solvents. As a consequence, the surface pressure vs. mean molecular area (π-A) isotherms and Brewster angle microscopy (BAM) reveal a more homogeneous (surface morphology) Langmuir film at the air/water interface for FePc in DMF. The same morphological pattern observed for the Langmuir films is preserved upon LB deposition onto solid substrates. The Raman and FTIR analyses indicate the DMF-FePc interaction relies on coordination bonds between N atom (from DMF) and Fe atom (from FePc). Besides, the FePc molecular organization was also found to be affected by the DMF-FePc chemical interaction. It is interesting to note that, if the DMF-FePc leads to less aggregated FePc either in solution or ultrathin films (Langmuir and LB), with time (one week) the opposite trend is found. Taking into account the N-Fe interaction, the performance of the FePc ultrathin films with distinct supramolecular architectures composing sensing units was explored as proof-of-principle in the detection of trace amounts of atrazine herbicide in water using impedance spectroscopy. Further statistical and computational analysis reveal not only the role played by FePc supramolecular architecture but also the sensitivity of the system to detect atrazine solutions down to 10-10 mol/L, which is sufficient to monitor the quality of drinking water even according to the most stringent international

  16. Electrical conductivity in Langmuir-Blodgett films of n-alkyl cyanobiphenyls using current sensing atomic force microscope

    Energy Technology Data Exchange (ETDEWEB)

    Gayathri, H. N.; Suresh, K. A., E-mail: suresh@cnsms.res.in [Centre for Nano and Soft Matter Sciences, P. B. No. 1329, Jalahalli, Bangalore 560013 (India)

    2015-06-28

    We report our studies on the nanoscale electrical conductivity in monolayers of n-alkyl cyanobiphenyl materials deposited on solid surface. Initially, the 8CB, 9CB, and 10CB monolayer films were prepared by the Langmuir technique at air-water interface and characterized by surface manometry and Brewster angle microscopy. The monolayer films were transferred on to solid substrates by the Langmuir-Blodgett (L-B) technique. The 8CB, 9CB, and 10CB monolayer L-B films were deposited on freshly cleaved mica and studied by atomic force microscope (AFM), thereby measuring the film thickness as ∼1.5 nm. The electrical conductivity measurements were carried out on 9CB and 10CB monolayer L-B films deposited onto highly ordered pyrolytic graphite using current sensing AFM. The nanoscale current-voltage (I-V) measurements show a non-linear variation. The nature of the curve indicates electron tunneling to be the mechanism for electrical conduction. Furthermore, analysis of the I-V curve reveals a transition in the electron conduction mechanism from direct tunneling to injection tunneling. From the transition voltage, we have estimated the values of barrier height for 9CB and 10CB to be 0.71 eV and 0.37 eV, respectively. For both 9CB and 10CB, the effective mass of electron was calculated to be 0.021 m{sub e} and 0.065 m{sub e}, respectively. These parameters are important in the design of molecular electronic devices.

  17. Infrared photoluminescence spectra of PbS nanoparticles prepared by Langmuir-Blodgett and laser ablation methods

    Czech Academy of Sciences Publication Activity Database

    Remeš, Zdeněk; Novák, T.; Stuchlík, Jiří; Stuchlíková, The-Ha; Dřínek, Vladislav; Fajgar, Radek; Zhuravlev, K.

    2014-01-01

    Roč. 54, č. 6 (2014), s. 426-429 ISSN 1210-2709 R&D Projects: GA ČR(CZ) GA14-05053S; GA MŠk(CZ) LD14011; GA MŠk LH12236 Institutional support: RVO:68378271 ; RVO:67985858 Keywords : infrared photoluminescence * PbS * LangmuirBlodgett * laser ablation Subject RIV: BM - Solid Matter Physics ; Magnetism

  18. Fluorescence Resonance Energy Transfer between organic dyes adsorbed onto nano-clay and Langmuir-Blodgett (LB) films.

    Science.gov (United States)

    Hussain, Syed Arshad; Chakraborty, S; Bhattacharjee, D; Schoonheydt, R A

    2010-02-01

    In this communication we investigate two dyes N,N'-dioctadecyl thiacyanine perchlorate (NK) and octadecyl rhodamine B chloride (RhB) in Langmuir and Langmuir-Blodgett (LB) films with or with out a synthetic clay laponite. Observed changes in isotherms of RhB in absence and presence of nano-clay platelets indicate the incorporation of clay platelets onto RhB-clay hybrid films. AFM images confirm the incorporation of clay into hybrid films. FRET is observed in clay dispersion and LB films with and without clay. Efficiency of energy transfer is maximum in LB films with clay. Copyright (c) 2009 Elsevier B.V. All rights reserved.

  19. Técnicas de caracterização para investigar interações no nível molecular em filmes de Langmuir e Langmuir-Blodgett (LB Characterization techniques to investigate molecular-level interactions in Langmuir and Langmuir-Blodgett (LB films

    Directory of Open Access Journals (Sweden)

    Marystela Ferreira

    2005-06-01

    Full Text Available This paper discusses fundamental concepts for the characterization of Langmuir monolayers and Langmuir-Blodgett (LB films, with emphasis on investigations of material properties at the molecular level. By way of illustration, results for phospholipid monolayers interacting with the drug dipyridamole are highlighted. These results were obtained with several techniques, including in situ grazing incidence X-ray diffraction, Fourier transform infrared (FTIR spectroscopy, fluorescence microscopy, in addition to surface pressure and surface potential isotherms. Also mentioned are the difficulties in producing Langmuir and LB films from macromolecules, and how molecular-level interactions in mixed polymer LB films can be exploited in sensors.

  20. Large Area Fabrication of Semiconducting Phosphorene by Langmuir-Blodgett Assembly

    Science.gov (United States)

    Kaur, Harneet; Yadav, Sandeep; Srivastava, Avanish. K.; Singh, Nidhi; Schneider, Jörg J.; Sinha, Om. P.; Agrawal, Ved V.; Srivastava, Ritu

    2016-01-01

    Phosphorene is a recently new member of the family of two dimensional (2D) inorganic materials. Besides its synthesis it is of utmost importance to deposit this material as thin film in a way that represents a general applicability for 2D materials. Although a considerable number of solvent based methodologies have been developed for exfoliating black phosphorus, so far there are no reports on controlled organization of these exfoliated nanosheets on substrates. Here, for the first time to the best of our knowledge, a mixture of N-methyl-2-pyrrolidone and deoxygenated water is employed as a subphase in Langmuir-Blodgett trough for assembling the nanosheets followed by their deposition on substrates and studied its field-effect transistor characteristics. Electron microscopy reveals the presence of densely aligned, crystalline, ultra-thin sheets of pristine phosphorene having lateral dimensions larger than hundred of microns. Furthermore, these assembled nanosheets retain their electronic properties and show a high current modulation of 104 at room temperature in field-effect transistor devices. The proposed technique provides semiconducting phosphorene thin films that are amenable for large area applications. PMID:27671093

  1. Fast optical NO sub 2 gas sensing of porphyrin Langmuir-Blodgett films

    CERN Document Server

    Dooling, C M

    2002-01-01

    A porphyrin sensor for the detection of NO sub 2 gas in the 0.1-5.0 ppm range has been developed. The sensing characteristics of 5,10,15,20-tetrakis(3,4,-bis[-ethylhexyloxy]phenyl)-21H,23H-porphine (EHO) Langmuir-Blodgett (LB) films are shown to be dependent on a range of parameters including surface pressure, film thickness and deposition speed. This research has led to exceptionally fast response times with the best t sub 5 sub 0 values of approx 15s achieved with relatively large absorbance changes of typically 60%. The kinetics of the sensing response have been simulated using the Elovichian model and shown to exhibit Langmuirian and Arrhenius behaviour. Ultra-fast LB deposition (500-1000 mm min sup - sup 1) has been developed as a means of both decreasing sample production time and increasing the surface area - volume ratio for enhanced gas response. This technique maintains orientational symmetry and high transfer ratio, yet displays a highly disordered porous structure. The 'bed of nails' texture is pr...

  2. Critical reflection of neutrons from Langmuir-Blodgett films on glass

    International Nuclear Information System (INIS)

    Highfield, R.R.; Thomas, R.K.; Hayter, J.B.; Schaerpf, O.

    1983-01-01

    Results of critical reflection of neutrons from Langmuir-Blodgett multilayers of cadmium arachidate-d 39 on glass are presented. For the first time with neutrons, interference fringes from an organic multilayer were observed. Reflectivity profiles are presented of samples 2, 4, 6, 8, 10, 20, 25 and 59 molecular layers thick and the evolution of the reflectivity profile with increasing thickness is analysed. The spacing of the interference fringes gives a measure of the overall thickness of the film and hence the average thickness of a molecular layer. Using a model which treats the film as a uniform slab, the average thickness per layer (24.6 +- 0.2 A) are found to be less than the observed neutron Bragg spacing (26.7 +- 0.1 A) as well as the length of the arachidate molecule. An alternative model incorporating (1) a zone of slightly reduced scattering density in the glass surface and (2) a reduction in the thickness of the first few layers gives a good fit to all the interference and Bragg diffraction data obtained on multilayer samples prepared on hydrophobic plates. In contrast, multilayers prepared on untreated glass conform to the uniform slab model with an average thickness per layer of 24.75 +- 0.1 A. (Auth.)

  3. Synthesis of Triptycene-Based Molecular Rotors for Langmuir-Blodgett Monolayers.

    Science.gov (United States)

    Kaleta, Jiří; Kaletová, Eva; Císařová, Ivana; Teat, Simon J; Michl, Josef

    2015-10-16

    We describe syntheses of six triptycene-containing molecular rotors with several single-crystal X-ray diffraction analyses. These rod-shaped molecules carrying an axial rotator are designed to interleave on an aqueous surface into Langmuir-Blodgett (LB) monolayers containing a two-dimensional trigonal array of dipoles rotatable about an axis normal to the surface. Monolayer formation was verified with the simplest of the rotor structures. On an aqueous subphase containing divalent cations (Mg(2+), Ca(2+), Zn(2+), Sr(2+), or Cd(2+)), the LB isotherm yielded an area of 53 ± 3 Å(2)/molecule (monolayer of type A), compatible with the anticipated triangular packing of axes normal to the surface. On pure water, the area is 30 ± 3 Å(2)/molecule, and it is proposed that in this monolayer (type B), the molecular axes are tilted by 40-45° to a structure similar to those observed in single crystals of related triptycenes. After transfer to a gold surface, ellipsometry and PM IRRAS yield tilt angles of 29 ± 4° (monolayers of type A) and 38 ± 4° (type B). A full-scale examination of monolayers from all the rotors on a subphase and after transfer is underway and will be reported separately.

  4. Plasma-treated Langmuir-Blodgett reduced graphene oxide thin film for applications in biophotovoltaics

    Science.gov (United States)

    Ibrahim, Siti Aisyah; Jaafar, Muhammad Musoddiq; Ng, Fong-Lee; Phang, Siew-Moi; Kumar, G. Ghana; Majid, Wan Haliza Abd; Periasamy, Vengadesh

    2018-01-01

    The surface optimization and structural characteristics of Langmuir-Blodgett (LB) reduced graphene oxide thin (rGO) film treated by argon plasma treatment were studied. In this work, six times deposition of rGO was deposited on a clean glass substrate using the LB method. Plasma technique involving a variation of plasma power, i.e., 20, 60, 100 and 140 W was exposed to the LB-rGO thin films under argon ambience. The plasma treatment generally improves the wettability or hydrophilicity of the film surface compared to without treatment. Maximum wettability was observed at a plasma power of 20 W, while also increasing the adhesion of the rGO film with the glass substrate. The multilayer films fabricated were characterized by means of spectroscopic, structural and electrical studies. The treatment of rGO with argon plasma was found to have improved its biocompatibility, and thus its performance as an electrode for biophotovoltaic devices has been shown to be enhanced considerably.

  5. Behaviour of columnar salts at the interface air-water isotropic Langmuir-Blodgett films

    International Nuclear Information System (INIS)

    Perez, Javier

    1993-01-01

    In this research thesis, the author highlights the ability of a columnar discotic salt, in this case the 2,4,6-tri-aryl-pyrylium tetrafluoroborate, to form a steady single layer at the air-water interface without requiring a modification of its chemical structure. The author also shows the possibility to sequentially transfer the single layer to a solid substrate. The so-obtained Langmuir-Blodgett film has a structure with two centrosymmetric layers. This structure is typical of that of conventional amphiphilic films, but thermally metastable. A high anisotropy of orientation of molecular plans is noticed with respect to transfer direction. The author highlights a relationship between this anisotropy and the dynamics imposed to the single layer by the transfer process. A second molecular type is the introduced (TCNQC 18 ), hoping it would have a knock-on effect on the orientation. This results in the production of ultra-thin materials displaying an intrinsic conductivity highly oriented in the plane [fr

  6. Preparation and properties of multilayer poly(3,4-ethylenedioxythiophene) Langmuir-Blodgett film

    International Nuclear Information System (INIS)

    Yang Yajie; Jiang Yadong; Xu Jianhua; Yu Junsheng

    2008-01-01

    Multilayer ultrathin film of poly(3,4-ethylene dioxythiophene) (PEDOT) was fabricated using a modified Langmuir-Blodgett (LB) method. The chemical polymerization of PEDOT occurred in the multilayer nanometer space of an as-prepared LB film by exposing the film to 3,4-ethylene dioxythiophene vapor. UV-Vis-near infrared absorption spectrum and Fourier-transform infrared spectrum techniques were applied to confirm the formation of the PEDOT ultrathin film. The results of atomic force microscopy investigation for the PEDOT LB film showed that the film surface consisted of small clusters having diameters ranging from 50 to 200 nm. X-ray photoelectron spectroscopy and secondary-ion mass spectrometry were employed to analyze the atomic composition of the PEDOT LB film and the location of the formed PEDOT. It was found that the atomic composition of the composite film was almost consistent with the theoretical value, and the PEDOT clusters were well located in different planes of the multilayer structure. The PEDOT LB film exhibited higher conductivity than conventional films and better doping/dedoping characteristics of conductivity. The sensitivity of the PEDOT LB film to NH 3 and HCl gases was also discussed

  7. Closed-Form Solutions of the Thomas-Fermi in Heavy Atoms and the Langmuir-Blodgett in Current Flow ODEs in Mathematical Physics

    Directory of Open Access Journals (Sweden)

    Efstathios E. Theotokoglou

    2015-01-01

    Full Text Available Two kinds of second-order nonlinear, ordinary differential equations (ODEs appearing in mathematical physics are analyzed in this paper. The first one concerns the Thomas-Fermi (TF equation, while the second concerns the Langmuir-Blodgett (LB equation in current flow. According to a mathematical methodology recently developed, the exact analytic solutions of both TF and LB ODEs are proposed. Both of these are nonlinear of the second order and by a series of admissible functional transformations are reduced to Abel’s equations of the second kind of the normal form. The closed form solutions of the TF and LB equations in the phase and physical plane are given. Finally a new interesting result has been obtained related to the derivative of the TF function at the limit.

  8. Characterization of Langmuir and Langmuir–Blodgett films of an octasubstituted zinc phthalocyanine

    Energy Technology Data Exchange (ETDEWEB)

    Torrent-Burgués, J. [Department of Chemical Engineering, Universitat Politècnica de Catalunya (UPC), C/Colom 1, 08222 Terrassa, Barcelona (Spain); Institut de Bioenginyeria de Catalunya (IBEC), 08028 Barcelona (Spain); Cea, P. [Departamento de Química Orgánica y Química Física, Facultad de Ciencias, Universidad de Zaragoza, 50009 Zaragoza (Spain); Instituto de Nanociencia de Aragón (INA) y Laboratorio de Microscopias Avanzadas (LMA), Edificio i+d, Campus Rio Ebro, Universidad de Zaragoza, C/Mariano Esquillor, s/n, 50017 Zaragoza (Spain); Giner, I. [Departamento de Química Orgánica y Química Física, Facultad de Ciencias, Universidad de Zaragoza, 50009 Zaragoza (Spain); Guaus, E. [Department of Chemical Engineering, Universitat Politècnica de Catalunya (UPC), C/Colom 1, 08222 Terrassa, Barcelona (Spain)

    2014-04-01

    In this work we report the fabrication of Langmuir and Langmuir–Blodgett (LB) films of a substituted ZnPc (octakis(oxyoctyl)phthalocyanine of zinc), and their characterization by means of several techniques. These characterization techniques include surface pressure (π-A) and surface potential (ΔV-A) isotherms as well as UV–vis Reflection spectroscopy and Brewster Angle Microscopy (BAM) for the films at the air–water interface together with UV–vis absorption and IR spectroscopies and Atomic Force Microscopy (AFM) for the LB films. The π-A and ΔV-A isotherms and BAM images indicate a phase transition at a surface pressure of ca. 9 mN/m and a multilayer formation at surface pressures around 19–20 mN/m; at a surface pressure around 27 mN/m a disordered collapse of the film occurs. In addition, AFM images of LB films at π = 10 mN/m and π = 20 mN/m show a monomolecular and a multilayered film, respectively. The comparison of the UV–vis spectrum of ZnPc in solution, the reflection spectra of the Langmuir films and UV–vis spectra of LB films reveals a significant reduction in the Q band intensity for the films, indicative of an organization of ZnPc in the Langmuir and LB films versus the random distribution in solution. The UV–vis Reflection spectra are also consistent with multilayer formation at surface pressures around 19–20 mN/m. The relative intensities of the IR spectrum bands change from the KBr pellet to the LB film which is also attributable to orientation effects in the film. Cyclic voltammetric experiments of LB films incorporating the ZnPc derivative show peaks that can be correlated with redox processes occurring in the phthalocyanine ring. A small but significant influence of the surface pressure and the number of deposited layers in the electrochemical behaviour is observed. The electrochemical response of cast films exhibits some differences with respect to that of LB films which have been attributed to their different molecular

  9. A multiscale structural study of nanoparticle films prepared by the Langmuir-Blodgett technique

    Science.gov (United States)

    Dochter, Alexandre; Pichon, Benoit P.; Fleutot, Solenne; Medard, Nicolas; Begin-Colin, Sylvie

    2013-02-01

    Arrays of magnetic nanoparticles (NPs) represent a very interesting challenge toward the development of new devices for magnetic applications such as data storage and spintronic. The final properties of such assemblies depending essentially on the spatial arrangement of NPs, it is of first importance to investigate precisely their structure. Here, the structure of monolayer and multilayer films of magnetic iron oxide NPs assembled by the Langmuir-Blodgett (LB) technique has been studied by usual techniques such as SEM, AFM and ellipsometry and by a new and an easy to process enhanced optical technique: the Surface Enhancement Ellipsometry Contrast (SEEC) microscopy. This technique is based on the use of a new generation of microscope slides used as substrates which allow the strong enhancement of the sample contrast to a point where it becomes possible to visualize the structure of monolayer and multilayer films at the nanoscale with a conventional optical microscope. The SEEC microscopy is demonstrated to be complementary to usual characterization techniques to study the structure of NPs films, especially for films containing very small nanosized NPs which are more difficult to analyze by usual techniques. While the film structure is investigated with lateral resolution of microns, the layer thickness is analyzed at the nanoscale (with a precision of 0.3 nm) with a close fit to the experimental measurements on local (AFM) and on larger (ellipsometry) areas. This technique presents the advantage to visualize directly the topography of NPs assemblies on very large areas by extracting information such as the height profile, the film roughness and generating 3D images.

  10. Immbolization of uricase enzyme in Langmuir and Langmuir-Blodgett films of fatty acids: possible use as a uric acid sensor.

    Science.gov (United States)

    Zanon, Nathaly C M; Oliveira, Osvaldo N; Caseli, Luciano

    2012-05-01

    Preserving the enzyme structure in solid films is key for producing various bioelectronic devices, including biosensors, which has normally been performed with nanostructured films that allow for control of molecular architectures. In this paper, we investigate the adsorption of uricase onto Langmuir monolayers of stearic acid (SA), and their transfer to solid supports as Langmuir-Blodgett (LB) films. Structuring of the enzyme in β-sheets was preserved in the form of 1-layer LB film, which was corroborated with a higher catalytic activity than for other uricase-containing LB film architectures where the β-sheets structuring was not preserved. The optimized architecture was also used to detect uric acid within a range covering typical concentrations in the human blood. The approach presented here not only allows for an optimized catalytic activity toward uric acid but also permits one to explain why some film architectures exhibit a superior performance. Copyright © 2011 Elsevier Inc. All rights reserved.

  11. Photophysical properties of 4-methyl 3-phenyl coumarin organized in Langmuir-Blodgett films: Formation of aggregates

    Energy Technology Data Exchange (ETDEWEB)

    Acharya, Somobrata [Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 84105 (Israel)], E-mail: acharya@bgumail.bgu.ac.il; Kamilya, Tapanendu [Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Calcutta 700032 (India); Sarkar, Jyotirmoy [Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Calcutta 700032 (India); Parichha, Tapan Kr. [Department of Chemistry, Suri Vidyasagar College, Suri, Birbhum (India); Pal, Prabir [Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Calcutta 700032 (India); Talapatra, G.B. [Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Calcutta 700032 (India)], E-mail: spgbt@iacs.res.in

    2007-07-15

    Langmuir-Blodgett (LB) films of 4-methyl 3-phenyl coumarin (MPC), a non-amphiphilic derivative of coumarin mixed with stearic acid (SA) are studied. The surface pressure-area ({pi}-A) isotherm study at air-water interface reveals a repulsive type of interaction between the MPC and SA molecules resulting in the formation of aggregates of MPC molecules. Absorption, fluorescence and phosphorescence studies indicate the formation of J-type aggregate in LB film. Low temperature (77 K) phosphorescence lifetime is found to be decreased due to aggregate formation. Micro structured aggregates are observed after examining the surface morphology of LB film by scanning electron microscopy (SEM)

  12. Surface-based molecular self-assembly: Langmuir-Blodgett films of amphiphilic Ln(III) complexes.

    Science.gov (United States)

    Wales, Dominic J; Kitchen, Jonathan A

    2016-01-01

    The unique photophysical properties of the Ln(III) series has led to significant research efforts being directed towards their application in sensors. However, for "real-life" applications, these sensors should ideally be immobilised onto surfaces without loss of function. The Langmuir-Blodgett (LB) technique offers a promising method in which to achieve such immobilisation. This mini-review focuses on synthetic strategies for film formation, the effect that film formation has on the physical properties of the Ln(III) amphiphile, and concludes with examples of Ln(III) LB films being used as sensors.

  13. 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

  14. Langmuir and Langmuir-Blodgett films of amphiphilic hexa-peri-hexabenzocoronene: New phase transitions and electronic properties controlled by pressure

    DEFF Research Database (Denmark)

    Reitzel, N.; Hassenkam, T.; Balashev, K.

    2001-01-01

    -400 Angstrom) pi -stacked lamellae of HBC molecules tilted approximate to 45 degrees relative to the surface normal is observed in the low-pressure phase. In this phase. the HBC molecules pack in a rectangular two-dimensional unit cell with a = 22.95 Angstrom and b = 4.94 Angstrom. In the high-pressure phase...... x 23.9 Angstrom (2). Thin monolayer films can be transferred to solid supports by the Langmuir-Blodgett (LB) technique. Atomic force microscopy (AFM) with atomic resolution reveals the crystalline packing of alkyl chains in the high-pressure phase. Kelvin force microscopy (KFM) shows a clear...... potential difference between the high- and low-pressure phases. This is discussed in terms of orbital delocalization (band formation) in the highly coherent low-pressure phase, which is in contrast to the localized molecular orbitals present in the high-pressure phase. The highly coherent pi stack...

  15. Salt dependent stability of stearic acid Langmuir-Blodgett films exposed to aqueous electrolytes

    NARCIS (Netherlands)

    Kumar, Naveen; Wang, Lei; Sîretanu, Igor; Duits, Michael H.G.; Mugele, Friedrich Gunther

    2013-01-01

    We use contact angle goniometry, imaging ellipsometry, and atomic force microscopy to study the stability and wettability of Langmuir–Blodgett (LB) monolayers of stearic acid on silica substrates, upon drying and exposure to aqueous solutions of varying salinity. The influences of Ca2+ and Na+ ions

  16. Characterization of interfacial effects in organic macrocycles Langmuir and Langmuir-Blodgett layers studied by surface potential and FT-IR spectroscopy examination

    Energy Technology Data Exchange (ETDEWEB)

    Boguta, Andrzej [Faculty of Technical Physics, Institute of Physics, Poznan University of Technology, Nieszawska 13a, 60 - 965 Poznan (Poland); Wrobel, Danuta [Faculty of Technical Physics, Institute of Physics, Poznan University of Technology, Nieszawska 13a, 60 - 965 Poznan (Poland)]. E-mail: wrobel@phys.put.poznan.pl; Bartczak, Adam [Faculty of Technical Physics, Institute of Physics, Poznan University of Technology, Nieszawska 13a, 60 - 965 Poznan (Poland); Swietlik, Roman [Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60 - 197 Poznan (Poland); Stachowiak, Zdzislaw [Central Laboratory of Accumulators and Cells, Forteczna 12, 61 - 362 Poznan (Poland); Ion, Rodica M. [Department of Chemical Analysis, Institute for Chemical Research ICECHIM, Splaiul Independentei 202, Bucharest 79611 (Romania)

    2004-10-15

    Surface potential (SP) examination and FT-IR (infrared) reflection-absorption spectra were used for the characterization of interfacial effects in organic dye thin layer on solid substrates. Surface potentials of magnesium tetranaphtylporphyrin (MgTNP), magnesium or lead phthalocyanine monolayer on the water subphase were measured and the dipole moments of the investigated dyes were evaluated (1.07 D, 0.52 D and 0.31 D for MgTNP, MgPc and PbPc, respectively). The differences between the dipolar moment values were attributed to the differences between porphyrin and phthalocyanines molecular structures and to the differences in metal electronegativity and metal ion distortion in the molecular frame. Also asymmetry in the covalent linkage and coordination bonding in the center of the molecular skeleton and the differences in polarisablility of the dye molecules as sources of the difference in the dipolar moment values were taken into consideration. The FT-IR reflection-absorption spectra were used for the characterization of the magnesium phthalocyanines Langmuir-Blodgett (LB) layer formed on semiconducting (In{sub 2}O{sub 3}) or Au substrates. The modification of the IR spectra upon Langmuir-Blodgett dye layer deposition was attributed to the redistribution of electrons at the semiconducting (metallic)/dye layer interface and to different substrate morphology. The difference in the band splitting for dye on Au and In{sub 2}O{sub 3} was related to the smaller amount of charge transferred to the dye film from In{sub 2}O{sub 3} than from Au substrate and to the changes in the topology of the different substrates after coating with the dye layer.

  17. Thin-Film Behavior of Poly(methyl methacrylates). 2. An FT-IR Study of Langmuir-Blodgett Films of Isotactic PMMA

    NARCIS (Netherlands)

    Brinkhuis, R.H.G.; Schouten, A.J.

    1991-01-01

    The structure of Langmuir-Blodgett films of isotactic PMMA transferred to substrates was investigated with FT-infrared techniques. From the results it is argued that at high surface pressures, the isotactic PMMA is transferred in a crystalline-like conformation, presumably as double helices. The

  18. Porous hydroxyapatite template grown on self-assembly of lysozyme and saccharose and langmuir-blodgett thin films

    Energy Technology Data Exchange (ETDEWEB)

    Cavinattot, D.; Zavaglia, C.A.C. [Federal School of Itajuba, MG (Brazil). Inst. of Mechanical Engineering; Costa, N. [State Univ. of Campinas (Brazil). Faculty of Mechanical Engineering

    2001-07-01

    The methodology adopted on this work consists on producing an organic template with functional group and intermolecular distance defined by the Langmuir-Blodgett (LB) techniques. The functionalized substrates work orientating crystal growth of hydroxyapatite after being immersed in a solution simulating the body fluid at the body usual temperature. Electrons beams used in electronic microscopy can destroy the organic thin film. Based on that, the technique adopted on the characterization of the organic template and the hydroxyapatite film is the Atomic Force Microscopy. Porous and adhesive hydroxyapatite layers have been obtained, creating a good interface between the implanted material and the cellular tissue and also improving its bioactive and mechanical performance. It will certainly improve the performance of the prosthetic material when implanted. (orig.)

  19. A low-symmetrical zinc phthalocyanine-based Langmuir-Blodgett thin films forNO2 gas sensor applications

    Science.gov (United States)

    Krichevsky, D. M.; Zasedatelev, A. V.; Tolbin, A. Yu; Zelenskiy, Yu M.; Krasovskii, V. I.; Karpo, A. B.; Tomilova, L. G.

    2016-08-01

    For many years effective detection of hazardous substances such as nitrogen oxides has remained a crucial task for environmental safety. In this article, we demonstrate high promising NO2-sensitive Langmuir-Blodgett monolayer structures based on 2-((2'- hydroxymethyl)-benzyloxy)-9(10),16(17),23(24)-tri-/re/-butyl- substituted low symmetrical zinc phthalocyanine complex bearing hydroxyl group on the periphery (compound 1). Amphiphilic arrangement of macrocycles was demonstrated to eliminate disordered molecular aggregation, resulting in a marked NO2 gas sensing effect under real atmospheric conditions. The optical response of monolayers was at room temperature, with the significant spectral changes being caused by the specific charge transfer process in phthalocyanine n-conjugated electronic system.

  20. New effects in Langmuir and Langmuir-Blodgett monolayers from fluorescently labelled phospholipids and their possible use for water quality control

    Science.gov (United States)

    Ivanov, G. R.; Geshev, N. I.

    2016-02-01

    Secondary water contamination poses significant challenges to the sensitivity and selectivity of sensors used for its detection and monitoring. Currently only lab tests can detect these contaminants and by the time this happens the contaminated water has entered the city water supply system. Fluorescent chromophore NitroBenzoxaDiazole (NBD) is very suitable and had been successfully used in biosensor applications due to its high sensitivity to close proximity polarity of the medium. Over the years we have discovered 3 new effects in NBD- labelled phospholipids which can significantly improve the performance of biosensors. The phospholipid matrix provides flexible biocompatible environment for immobilization of selectively reacting enzymes, microorganisms, DNA, immunoagents, whole cells. Use of single layer (3.1 nm thickness) films at the air-water interface (Langmuir films) or deposited on solid support as Langmuir-Blodgett (LB) film gives fast response times for real time monitoring (no slow diffusion processes) and precise molecule ordering and orientation. The first new effect was fluorescence self-quenching in Langmuir and LB films. In the liquid phase films exhibit normal fluorescence. Upon transition to solid phase fluorescence intensity is almost completely self-quenched and fluorescence lifetimes in the nanosecond region decrease 2 times. This is easily measured. Usually large heavy metal atoms quench fluorescence. We observed the opposite new effect when LB film is deposited in the solid phase from a subphase containing heavy metals. The third new effect is the obtaining of nanosized cylinders with bilayer thickness, which remain stable at least for months, when LB monolayer is deposited in the phase coexistence region at thermodynamic equilibrium. This greatly increases reacting surface and sensitivity of possible sensors. Almost all possible optical experimental methods were used for this research. This includes polarized ATR FTIR and polarized UV

  1. Effect of subphase temperature on the phase-separated structures of mixed Langmuir and Langmuir-Blodgett films of fatty acids and hybrid carboxylic acids.

    Science.gov (United States)

    Watanabe, Satoshi; Okuda, Ryo; Azumi, Reiko; Sakai, Hideki; Abe, Masahiko; Matsumoto, Mutsuyoshi

    2011-11-01

    We examined the phase-separated structures of the mixed Langmuir-Blodgett (LB) films of C(k)H(2k+1)COOH (HkA: k=17, 21) and C(m)F(2m+1)C(10)H(20)COOH (FmH10A: m=6, 8) fabricated isothermally or after isobaric thermal treatments. Under isothermal fabrication conditions, disks and wire-type domains formed in the H17A/F6H10A LB films at high and low fabrication temperatures, respectively, because the line tension and dipole-dipole interaction were comparable with each other. The thermodynamically stable phases of H21A/F6H10A LB films at high and low fabrication temperatures were disks and polygonal domains, respectively. Isobaric thermal treatments of the Langmuir films affected the domain size and not the domain shape when the transfer temperature was the same. Isobaric thermal treatments were effective in controlling the domain size. The thermodynamically stable phases of both H17A/F8H10A LB films and H21A/F8H10A LB films were nanowires in the range of the fabrication temperatures studied. Isobaric thermal treatments of the Langmuir films did not affect the domain shape significantly and affected the domain size in both the LB films studied. The change in the value m of FmH10A was more effective in controlling the phase-separated structures of the mixed LB films than the value of k of HkA. Copyright © 2011 Elsevier Inc. All rights reserved.

  2. Langmuir-Blodgett films of alkane chalcogenice (S, Se, Te) stabilized gold nanoparticles

    DEFF Research Database (Denmark)

    Brust, M.; Stuhr-Hansen, N.; Norgaard, K.

    2001-01-01

    Gold nanoparticles stabilized by alkanethiolates, alkaneselenides, and alkanetellurides have been prepared by analogous methods. Chloroform solutions of thiolate and selenide stabilized particles were spread and evaporated on the water/air interface where the particles formed well-defined Langmuir...

  3. Easily processable highly ordered Langmuir-Blodgett films of quaterthiophene disiloxane dimer for monolayer organic field-effect transistors.

    Science.gov (United States)

    Sizov, Alexey S; Anisimov, Daniil S; Agina, Elena V; Borshchev, Oleg V; Bakirov, Artem V; Shcherbina, Maxim A; Grigorian, Souren; Bruevich, Vladimir V; Chvalun, Sergei N; Paraschuk, Dmitry Yu; Ponomarenko, Sergei A

    2014-12-23

    Self-assembly of highly soluble water-stable tetramethyldisiloxane-based dimer of α,α'-dialkylquaterthiophene on the water-air interface was investigated by Langmuir, grazing incidence X-ray diffraction, and X-ray reflectivity techniques. The conditions for formation of very homogeneous crystalline monolayer Langmuir-Blodgett (LB) films of the oligomer were found. Monolayer organic field-effect transistors (OFETs) based on these LB films as a semiconducting layer showed hole mobilities up to 3 × 10(-3) cm(2)/(V s), on-off ratio of 10(5), small hysteresis, and high long-term stability. The electrical performance of the LB films studied is close to that for the same material in the bulk or in the monolayer OFETs prepared from water vapor sensitive chlorosilyl derivatives of quaterthiophene by self-assembling from solution. These findings show high potential of disiloxane-based LB films in monolayer OFETs for large-area organic electronics.

  4. Physicochemical and structural characterization of a two-dimensional polymer performed by using the Langmuir-Blodgett technique

    International Nuclear Information System (INIS)

    Lefevre, Didier

    1995-01-01

    This research thesis addresses the physicochemical and structural characterization of two-dimensional polymer made of polymerizable macro-cycles pre-organised in-plane by using the Langmuir-Blodgett technique. Macro-cycles are porphyrins with four acetylenic functions which bind in both plane directions by formation of diacetylenic covalent bonds. These porphyrins are adsorbed under a single layer of dihexadecyl-phosphoric acid to build up a monomer amphiphilic film. The author reports the characterization of the Langmuir film by the study of compression isotherms and by Brewster angle microscopy. Other techniques are used (UV, visible and infrared spectroscopy, Raman spectroscopy) to highlight the polymerization in LB film. X photo-electronic spectroscopy and secondary ion mass spectroscopy are also used. The author reports the study of the orientation of macro-cycles before and after polymerization by using linear dichroism, electronic paramagnetic resonance and X ray diffraction. The in-plane LB film structure is studied by transmission X ray diffraction, atomic force microscopy in correlation with molecular simulation. The two-dimensional feature of the polymer formed at the water surface is highlighted. The membrane is visualized by electronic and optic microscopy, and characterized by EDXS and electronic diffraction [fr

  5. Electroactivity of a starburst hole-transport material in Langmuir-Blodgett films. Solid state effects and intervalence charge transfer.

    Science.gov (United States)

    Parra, Vicente; Del Caño, Teodosio; Rodríguez-Méndez, María L; De Saja, José A; Bouvet, Marcel; Shirota, Yasuhiko

    2007-06-14

    Here we report on the electroactivity properties of Langmuir-Blodgett (LB) films of the hole-transport molecule 4,4',4''-tris[3-methylphenyl(phenyl)amino] triphenylamine (m-MTDATA). Fairly stable Langmuir films at the air-water interface are accomplished, despite the non-amphiphilic character of the molecule. The reflection-absorption infrared spectroscopy (RAIRS) and Fourier transform infrared (FT-IR) analysis revealed that the molecules arrange with no neat preferential orientation, in agreement with the amorphous glassy nature of this starburst molecule. However, there is a tendency of the molecules to organize in a more planar conformation due to the intermolecular stacking induced by the LB technique. On the other hand, the fundamental electrochemistry (by cyclic voltammetry, CV) of the films is also analyzed. The CV studies of both solution and films reveal that both the solid state and the electrolyte's anions clearly affect the m-MTDATA's electroactivity, exhibiting a unique and broad redox process instead of the two reversible oxidations observed in solution. The oxidization mechanism is discussed. Finally, the spectroelectrochemistry studies evidence that the oxidization of the films leads to new absorption bands, among which the emerging bands in the NIR region ascribed to intervalence charge transfer (IVCT) between the generated aminyl radical cations should be pointed out.

  6. Cellulase and alcohol dehydrogenase immobilized in Langmuir and Langmuir-Blodgett films and their molecular-level effects upon contact with cellulose and ethanol.

    Science.gov (United States)

    Rodrigues, Dilmer; Camilo, Fernanda Ferraz; Caseli, Luciano

    2014-02-25

    The key challenges for producing devices based on nanostructured films with control over the molecular architecture are to preserve the catalytic activity of the immobilized biomolecules and to provide a reliable method for determining the intermolecular interactions and the accommodation of molecules at very small scales. In this work, the enzymes cellulase and alcohol dehydrogenase (ADH) were coimmobilized with dipalmitoylphosphatidylcholine (DPPC) as Langmuir-Blodgett (LB) films, and their biological activities were assayed by accommodating the structure formed in contact with cellulose. For this purpose, the polysaccharide was dissolved in an ionic liquid, 1-buthyl-3-methylimidazolium chloride (BMImCl), and dropped on the top of the hybrid cellulase-ADH-DPPC LB film. The interactions between cellulose and ethanol, which are the catalytic substrates of the enzymes as well as important elements in the production of second-generation fuels, were then investigated using polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS). Investigation of the secondary structures of the enzymes was performed using PM-IRRAS, through which the presence of ethanol and cellulose was observed to highly affect the structures of ADH and cellulase, respectively. The detection of products formed from the catalyzed reactions as well as the changes of secondary structure of the enzymes immobilization could be carried out, which opens the possibility to produce a means for producing second-generation ethanol using nanoscale arrangements.

  7. Atomic composition and stability of Langmuir-Blodgett monolayers based on siloxane dimer of quaterthiophene on the surface of polycrystalline gold

    Science.gov (United States)

    Komolov, A. S.; Lazneva, E. F.; Zhukov, Yu. M.; Pshenichnyuk, S. A.; Agina, E. V.; Dominskii, D. I.; Anisimov, D. S.; Parashchuk, D. Yu.

    2017-12-01

    Atomic composition of monolayers based on siloxane dimer of quaterthiophene deposited by Langmuir-Blodgett technique on a silicon dioxide surface partially covered by gold film and the stability of these monolayers upon surface treatment by Ar+ ions bombardment have been studied. Experimental results for the chemical composition of a series of studied surfaces have been obtained by X-ray photoelectron spectroscopy (XPS) by recording XPS spectra of C 1s, O 1s, S 2 p, and Au 4 f core levels. The relative concentration of Au and Si substrate atoms and the composition of ex situ prepared surface under study were determined within 10-15%, which indicates that Langmuir-Blodgett monolayers based on siloxane dimer of quaterthiophene form continuous coating in a considerable extent. Prior to the treatment of the studied surface by Ar+ ions bombardment, carbon- and oxygen-containing surface adsorbates provided a considerable contribution to the results of XPS measurements. The surface cleaning by Ar+ ions with energy 3 keV at electric current through sample of 1 μA in several 30-s steps has led to the etching of surface adsorbates and next Langmuir-Blodgett films of the siloxane dimer of quaterthiophene.

  8. Relation between anchorings of liquid crystals and conformation changes in aligning agents by the Langmuir-Blodgett film technique investigation

    International Nuclear Information System (INIS)

    Zhu, Y.; Lu, Z.; Wei, Y.

    1995-01-01

    The anchoring direction of liquid crystals on a solid substrate surface depends upon many parameters characterizing the liquid-crystal--substrate interface, a variation of which may change this anchoring direction leading to the so-called anchoring transition. Here, based on the Langmuir-Blodgett film technique, we present two model systems to study the relation between anchoring directions and the conformation changes in aligning agents. A double-armed crown ether liquid crystal and a side chain polymer liquid crystal at an air-water interface both show phase transitions, accompanied by conformation changes. However, when the monolayers in different phases were transferred onto solid substrates to orient liquid crystals, we found that for the crown ether material the conformation change can alter the anchoring of liquid crystals between homeotropic and homogeneous alignments, while for the polymer liquid crystal, despite the conformation changes, the liquid crystals can only be aligned homeotropically. The involved mechanisms were briefly discussed in terms of the Landau-type phenomenological theory

  9. Langmuir-Blodgett assembly of visible light responsive TiO{sub 2} nanotube arrays/graphene oxide heterostructure

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Ying; Gao, Hongyan; Wei, Danming; Dong, Xinju; Cao, Yan, E-mail: yan.cao@wku.edu

    2017-01-15

    Highlights: • First to report a heterostructure of TNA with GO prepared by LB assembly. • Much better photocurrent (32 μAcm{sup −2}) of TNA-GO, contrasting to TNA (12 μAcm{sup −2}). • Schottky junction formed between TNA and GO enhanced the photocurrent. • GO on TNA improved the hydrophilicity of TNA-GO. - Abstract: The hybrid nanocomposites of titanium dioxide (TiO{sub 2}) with graphene oxide (GO) have recently garnered much attention as electronic devices, energy conversion devices, photocatalysts and other applications. In this study, Langmuir-Blodgett (LB) assembly method was firstly reported to prepare a TiO{sub 2} nanotube arrays (TNA)-GO heterostructure. The as-prepared TNA-GO sample was characterized by X-ray diffraction, Raman spectra, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The promising characteristics of this TNA-GO material, the inexpensive, nontoxic and highly visible-light responsiveness, may raise the potential uses in many, various photocatalytic applications.

  10. Heteroepitaxial growth of SiC films by carbonization of polyimide Langmuir-Blodgett films on Si

    Directory of Open Access Journals (Sweden)

    Goloudina S.I.

    2017-01-01

    Full Text Available High quality single crystal SiC films were prepared by carbonization of polyimide Langmuir-Blodgett films on Si substrate. The films formed after annealing of the polyimide films at 1000°C, 1100°C, 1200°C were studied by Fourier transform-infrared (FTIR spectroscopy, X-ray diffraction (XRD, Raman spectroscopy, transmission electon microscopy (TEM, transmission electron diffraction (TED, and scanning electron microscopy (SEM. XRD study and HRTEM cross-section revealed that the crystalline SiC film begins to grow on Si (111 substrate at 1000°C. According to the HRTEM cross-section image five planes in 3C-SiC (111 film are aligned with four Si(111 planes at the SiC/Si interface. It was shown the SiC films (35 nm grown on Si(111 at 1200°C have mainly cubic 3C-SiC structure with a little presence of hexagonal polytypes. Only 3C-SiC films (30 nm were formed on Si (100 substrate at the same temperature. It was shown the SiC films (30-35 nm are able to cover the voids in Si substrate with size up to 10 μm.

  11. Synthesis of amphiphilic macrocyclic molecules from family of aza-porphyrins and study in Langmuir-Blodgett films

    International Nuclear Information System (INIS)

    Palacin, Serge

    1988-01-01

    The cellular automata, also called formal neurons, directly inspired by the knowledge concerning the nervous system, are able to mimic some basic processes of brain, as shape recognition, connecting memory, information sorting... This work aims to build a molecular structure able to fit the working rules of a bidimensional cellular automata. So, amphiphilic molecules belonging to the aza-porphyrin family are synthesized and organized into a planar paving by the Langmuir-Blodgett technique. The regular structure of the outcoming ultra-thin films is studied by linear dichroism and anisotropic electron spin resonance. The physico-chemical behaviour of the amphiphilic molecules is studied and brings about an explanation of the redox phenomena which are observed on the monomolecular film on the water surface. So are we able to outline the future chemical addressing ways of the bidimensional cellular automata. In the end of this dissertation, different ways likely to insure covalent bindings between the active sites and allow the transfer of information within the cellular network are discussed. (author) [fr

  12. Micron and submicron patterning of dicyanopyrazine-linked porphyrin molecules using micro-contact printing and Langmuir-Blodgett assembly.

    Science.gov (United States)

    Cho, Jaepil; Ahn, Heejoon

    2010-11-01

    We describe a method to conveniently fabricate micron- and submicron-sized patterns of well-ordered and densely-packed dicyanopyrazine-linked porphyrin (4-TDCPP) molecules by using micro-contact printing (micro-CP) in conjunction with Langmuir-Blodgett (LB) deposition. SEM and AFM images reveal that the sizes and shapes of the 4-TDCPP patterns are well-matched with the geometric features of the polydimethylsiloxane (PDMS) stamps used for micro-CP. Fluorescence images show strong, red emission from the 4-TDCPP patterns. However, the thicknesses of the 4-TDCPP patterns transferred onto a silicon substrate by micro-CP are not the same, even though the same amount of 4-TDCPP layers are deposited on the surface of PDMS stamps in the LB process. The thicknesses of the 10 microm line, 2 microm dot and 300 nm line patterns of 10-layered 4-TDCPP molecules are 34.6, 26.7 and 5.9 nm, respectively. These differences may be due to variations in adhesion forces between the silicon substrate and 4-TDCPP on PDMS stamps having different size patterns. Larger patterns have greater contact areas compared to smaller patterns. This phenomenon can cause stronger adhesion forces, resulting in greater pattern thickness.

  13. Hierarchically structured superhydrophobic coatings fabricated by successive Langmuir-Blodgett deposition of micro-/nano-sized particles and surface silanization.

    Science.gov (United States)

    Tsai, Ping-Szu; Yang, Yu-Min; Lee, Yuh-Lang

    2007-11-21

    The present study demonstrates the creation of a stable, superhydrophobic surface by coupling of successive Langmuir-Blodgett (LB) depositions of micro- and nano-sized (1.5 µm/50 nm, 1.0 µm/50 nm, and 0.5 µm/50 nm) silica particles on a glass substrate with the formation of a self-assembled monolayer of dodecyltrichlorosilane on the surface of the particulate film. Particulate films, in which one layer of 50 nm particles was deposited over one to five sublayers of larger micro-sized particles, with hierarchical surface roughness and superhydrophobicity, were successfully fabricated. Furthermore, the present 'two-scale' (micro- and nano-sized particles) approach is superior to the previous 'one-scale' (micro-sized particles) approach in that both higher advancing contact angle and lower contact angle hysteresis can be realized. Experimental results revealed that the superhydrophobicity exhibited by as-fabricated particulate films with different sublayer particle diameters increases in the order of 0.5 µm>1.0 µm>1.5 µm. However, no clear trend between sublayer number and surface superhydrophobicity could be discerned. An explanation of superhydrophobicity based on the surface roughness introduced by two-scale particles is also proposed.

  14. Design and Synthesis of Aviram-Ratner-Type Dyads and Rectification Studies in Langmuir-Blodgett (LB) Films.

    Science.gov (United States)

    Jayamurugan, Govindasamy; Gowri, Vijayendran; Hernández, David; Martin, Santiago; González-Orive, Alejandro; Dengiz, Cagatay; Dumele, Oliver; Pérez-Murano, Francesc; Gisselbrecht, Jean-Paul; Boudon, Corinne; Schweizer, W Bernd; Breiten, Benjamin; Finke, Aaron D; Jeschke, Gunnar; Bernet, Bruno; Ruhlmann, Laurent; Cea, Pilar; Diederich, François

    2016-07-18

    The design and synthesis of Aviram-Ratner-type molecular rectifiers, featuring an anilino-substituted extended tetracyanoquinodimethane (exTCNQ) acceptor, covalently linked by the σ-spacer bicyclo[2.2.2]octane (BCO) to a tetrathiafulvalene (TTF) donor moiety, are described. The rigid BCO spacer keeps the TTF donor and exTCNQ acceptor moieties apart, as demonstrated by X-ray analysis. The photophysical properties of the TTF-BCO-exTCNQ dyads were investigated by UV/Vis and EPR spectroscopy, electrochemical studies, and theoretical calculations. Langmuir-Blodgett films were prepared and used in the fabrication and electrical studies of junction devices. One dyad showed the asymmetric current-voltage (I-V) curve characteristic for rectification, unlike control compounds containing the TTF unit but not the exTCNQ moiety or comprising the exTCNQ acceptor moiety but lacking the donor TTF part, which both gave symmetric I-V curves. The direction of the observed rectification indicated that the preferred electron current flows from the exTCNQ acceptor to the TTF donor. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. ATR-IR spectroscopy for the detection of induced-phase transition in Langmuir-Blodgett monolayer film

    International Nuclear Information System (INIS)

    Widayati, Suci

    1996-01-01

    The rate at which a solid substrate is transferred through the Air/Water interface in the Langmuir-Blodgett process of preparing monomolecular films influences the final structure of the transferred film. This phenomenon has been observed from the attenuated total reflectance infra-red (ATR-IR) spectra of fatty acid monolayer transferred onto germanium substrate. This transfer-induced effect is most evidence when the monolayer is transferred from an expanded region of the surface-pressure-molecular area isotherm, but has limited influence on the hydrocarbon chain conformation of film molecules transferred in the condensed phases at high surface pressure. Such a conformational ordering may due to a kinetically limited phase transition taking place in the meniscus formed between the solid substrate and aqueous sub phase. In addition, these results suggest that the structure of the amphiphilic molecules may modulate the extent and nature of the dipping-speed-induced structural changes taking place in the monomolecular L-B film. In order to use monomolecular L-B films to accurately characterize the structure, orientation and phase properties of monolayers at the Air/Water interface, the L-B transfer must be performed at transfer speeds that minimize this structural phase transition

  16. Langmuir-Blodgett films of alkane chalcogenice (S, Se, Te) stabilized gold nanoparticles

    DEFF Research Database (Denmark)

    Brust, M.; Stuhr-Hansen, N.; Norgaard, K.

    2001-01-01

    Gold nanoparticles stabilized by alkanethiolates, alkaneselenides, and alkanetellurides have been prepared by analogous methods. Chloroform solutions of thiolate and selenide stabilized particles were spread and evaporated on the water/air interface where the particles formed well-defined Langmuir...... films. The films were transferred to solid supports of freshly cleaved mica and were studied by atomic force microscopy (AFM). The particles were found to have an average core diameter of 2 nm. The stability of the particles under ambient conditions increased in the order Te

  17. Spectroscopic characterizations of non-amphiphilic 2-(4-biphenylyl)-6-phenyl benzoxazole molecules at the air-water interface and in Langmuir-Blodgett films

    Energy Technology Data Exchange (ETDEWEB)

    Hussain, S.A. [Department of Physics, Tripura University, Suryamaninagar, Agartala: 799130 Tripura (India); Deb, S. [Department of Physics, Tripura University, Suryamaninagar, Agartala: 799130 Tripura (India); Bhattacharjee, D. [Department of Physics, Tripura University, Suryamaninagar, Agartala: 799130 Tripura (India)]. E-mail: tuphysic@sancharnet.in

    2005-09-15

    This communication reports about the successful incorporation of a well-known non-amphiphilic derivative of oxazole chromophore 2-(4-biphenylyl)-6-phenyl benzoxazole abbreviated as PBBO, in Langmuir-Blodgett films when mixed with stearic acid (SA) as well as also an inert polymer matrix polymethylmethacrylate (PMMA). The surface pressure versus area per molecule isotherms of the Langmuir films of PBBO mixed with PMMA or SA at different mole fractions reveal that the area per molecule decreases consistently with increasing mole fractions of PBBO. Area per molecule versus mole fraction curve shows that the experimental data points coincide with the ideality curve predicted by the additivity rule, which leads to the conclusion of either ideal mixing or complete demixing of the binary components. The UV-vis absorption and fluorescence spectroscopic studies of mixed LB films of PBBO reveal the nature of complete demixing of the binary components of the sample molecules (PBBO) and PMMA or SA molecules. This complete demixing leads to the formation of clusters and aggregates of PBBO molecules in Langmuir and Langmuir-Blodgett films. J-type aggregates of PBBO molecules in LB films have been confirmed by UV-vis absorption spectroscopic study. Aggregation of PBBO molecules in LB films giving rise to excimeric emission has been demonstrated by fluorescence spectroscopic study. Excitation spectroscopic study clearly confirmed the presence of excimeric sites.

  18. Control of indium tin oxide anode work function modified using Langmuir-Blodgett monolayer for high-efficiency organic photovoltaics

    Directory of Open Access Journals (Sweden)

    Yuya Yokokura

    2017-08-01

    Full Text Available The use of Langmuir-Blodgett (LB monolayers to modify the indium tin oxide (ITO work function and thus improve the performance of zinc phthalocyanine (ZnPc/fullerene (C60-based and boron subphthalocyanine chloride (SubPc/C60-based small molecule organic photovoltaic devices (OPVs was examined. In general, LB precursor compounds contain one or more long alkyl chain substituents that can act as spacers to prevent electrical contact with adjoining electrode surfaces. As one example of such a compound, arachidic acid (CH3(CH218COOH was inserted in the forms of one-layer, three-layer or five-layer LB films between the anode ITO layer and the p-type layer in ZnPc-C60-based OPVs to investigate the effects of the long alkyl chain group when it acts as an electrically insulating spacer. The short-circuit current density (Jsc values of the OPVs with the three- and five-layer inserts (1.78 mA·cm−2 and 0.61 mA·cm−2, respectively were reduced dramatically, whereas the Jsc value for the OPV with the single-layer insertion (2.88 mA·cm−2 was comparable to that of the OPV without any insert (3.14 mA·cm-2. The ITO work function was shifted positively by LB deposition of a surfactant compound, C9F19C2H4-O-C2H4-COOH (PFECA, which contained a fluorinated head group. This positive effect was maintained even after formation of an upper p-type organic layer. The Jsc and open-circuit voltage (Voc of the SubPc-C60-based OPV with the LB-modified ITO layers were effectively enhanced. As a result, a 42% increase in device efficiency was achieved.

  19. Atomic force microscopy and Langmuir-Blodgett monolayer technique to assess contact lens deposits and human meibum extracts.

    Science.gov (United States)

    Hagedorn, Sarah; Drolle, Elizabeth; Lorentz, Holly; Srinivasan, Sruthi; Leonenko, Zoya; Jones, Lyndon

    2015-01-01

    The purpose of this exploratory study was to investigate the differences in meibomian gland secretions, contact lens (CL) lipid extracts, and CL surface topography between participants with and without meibomian gland dysfunction (MGD). Meibum study: Meibum was collected from all participants and studied via Langmuir-Blodgett (LB) deposition with subsequent Atomic Force Microscopy (AFM) visualization and surface roughness analysis. CL Study: Participants with and without MGD wore both etafilcon A and balafilcon A CLs in two different phases. CL lipid deposits were extracted and analyzed using pressure-area isotherms with the LB trough and CL surface topographies and roughness values were visualized using AFM. Meibum study: Non-MGD participant meibum samples showed larger, circular aggregates with lower surface roughness, whereas meibum samples from participants with MGD showed more lipid aggregates, greater size variability and higher surface roughness. CL Study: Worn CLs from participants with MGD had a few large tear film deposits with lower surface roughness, whereas non-MGD participant-worn lenses had many small lens deposits with higher surface roughness. Balafilcon A pore depths were shallower in MGD participant worn lenses when compared to non-MGD participant lenses. Isotherms of CL lipid extracts from MGD and non-MGD participants showed a seamless rise in surface pressure as area decreased; however, extracts from the two different lens materials produced different isotherms. MGD and non-MGD participant-worn CL deposition were found to differ in type, amount, and pattern of lens deposits. Lipids from MGD participants deposited irregularly whereas lipids from non-MGD participants showed more uniformity. Copyright © 2014 Spanish General Council of Optometry. Published by Elsevier Espana. All rights reserved.

  20. A raft-associated species of phosphatidylethanolamine interacts with cholesterol comparably to sphingomyelin. A Langmuir-Blodgett monolayer study.

    Directory of Open Access Journals (Sweden)

    Michal Grzybek

    Full Text Available BACKGROUND: Specific interactions between sphingomyelin (SM and cholesterol (Ch are commonly believed to play a key role in the formation of rafts in the biological membranes. A weakness of this model is the implication that these microdomains are confined to the outer bilayer leaflet. The cytoplasmic leaflet, which contains the bulk of phosphatidylethanolamine (PE, phosphatidylserine (PS and phosphatidylinositol (PI, is thought also to harbour half of the membrane cholesterol. Moreover, SLPE (1-stearoyl-2-linoleoyl-sn-glycero-3-phosphatidyl-ethanolamine has recently been shown to be enriched in isolated detergent-resistant membranes (DRM, and this enrichment was independent of the method of isolation of DRM. METHODOLOGY/PRINCIPAL FINDINGS: Here we present quantitative evidence coming from Langmuir-Blodgett monolayer experiments that SLPE forms complex with Ch similar to that between SM and Ch. The energies of these interactions as calculated form the monolayer studies are highly negative. FRAP analysis showed that NBD-Ch recovery was similar in liposomes composed of DOPC/Ch SM or SLPE but not DPPE, providing further evidence that SLPE may form an l(o phase in the presence of high Ch concentration. Experiments on the solubility of DOPC liposomes containing DPPE/Ch (1ratio1, SM/Ch (1ratio1 or SLPE/Ch (1ratio1 showed the presence of Triton X-100 insoluble floating fraction (TIFF in the case of SM/Ch or SLPE/Ch but not in DPPE/Ch containing liposomes. Quantitative determination of particular lipid species in the TIFF fraction confirms the conclusion that SLPE (or similar PE species could be an important constituent of the inner leaflet raft. CONCLUSION: Such interactions suggest a possible existence of inner-leaflet nanoscale assemblies composed of cholesterol complexes with SLPE or similar unsaturated PE species.

  1. Phase-separated structures of mixed Langmuir-Blodgett films of fatty acid and hybrid carboxylic acid.

    Science.gov (United States)

    Kimura, Hideto; Watanabe, Satoshi; Shibata, Hirobumi; Azumi, Reiko; Sakai, Hideki; Abe, Masahiko; Matsumoto, Mutsuyoshi

    2008-12-04

    Phase separation often occurs in mixed Langmuir-Blodgett (LB) films. Usually circular domains at the micrometer length scale form in the LB films. The size and shape of the domains are governed by a compromise between two competing interactions of line tension and dipole-dipole interaction. An attempt was made to control the line tension by varying systematically the hydrophobic moieties of the film-forming molecules. Phase-separated structures of two-component mixed LB films of fatty acid [C(k)H(2k+1)COOH (HkA)] and hybrid carboxylic acid [C(m)F(2m+1)C(n)H(2n)COOH (FmHnA)] were investigated. IR spectra of the mixed LB films of H17A and F8H10A revealed that the alkyl chains were in an all-trans conformation and that the molecular orientation remained unchanged when the two components were mixed. Nanowires formed in the mixed LB films of HkA and F8H10A. The width of the nanowires increased with an increase in k. Domain size and shape in the mixed LB films of H17A and FmHnA depended strongly on the values of m and n. Circular domains at the micrometer length scale formed in the region m + n or = 16 except for F6H10A. These results were explained by using a lattice model that considers the effect of the hydrophobic moieties of fatty acid and hybrid carboxylic acid on the line tension.

  2. Crossover from layering to island formation in Langmuir-Blodgett growth: role of long-range intermolecular forces.

    Science.gov (United States)

    Mukherjee, Smita; Datta, Alokmay

    2011-04-01

    Combined studies by atomic force microscopy, x-ray reflectivity, and Fourier transform infrared spectroscopy on transition-metal stearate (M-St, M = Mn, Co, Zn, and Cd) Langmuir-Blodgett films clearly indicate association of bidentate coordination of the metal-carboxylate head group to layer-by-layer growth as observed in MnSt and CoSt and partially in ZnSt. Crossover to islandlike growth, as observed in CdSt and ZnSt, is associated with the presence of unidentate coordination in the head group. Morphological evolutions as obtained from one, three, and nine monolayers (MLs) of M-St films are consistent with Frank van der Merwe, Stranski-Krastanov, and Volmer Weber growth modes for M=Mn/Co, Zn, and Cd, respectively, as previously assigned, and are found to vary with number (n) of metal atoms per head group, viz. n=1 (Mn/Co), n=0.75 (Zn), and n=0.5 (Cd). The parameter n is found to decide head-group coordination such that n=1.0 corresponds to bidentate and n=0.5 corresponds to unidentate coordination; the intermediate value in Zn corresponds to a mixture of both. The dependence of the growth mode on head-group structure is explained by the fact that in bidentate head groups, with the in-plane dipole moment being zero, intermolecular forces between adjacent molecules are absent and hence growth proceeds via layering. On the other hand, in unidentate head groups, the existence of a nonzero in-plane dipole moment results in the development of weak in-plane intermolecular forces between adjacent molecules causing in-plane clustering leading to islandlike growth. ©2011 American Physical Society

  3. Control of indium tin oxide anode work function modified using Langmuir-Blodgett monolayer for high-efficiency organic photovoltaics

    Science.gov (United States)

    Yokokura, Yuya; Dogase, Tomomichi; Shinbo, Tatsuki; Nakayashiki, Yuya; Takagi, Yusuke; Ueda, Kazuyoshi; Sarangerel, Khayankhyarvaa; Delgertsetseg, Byambasuren; Ganzorig, Chimed; Sakomura, Masaru

    2017-08-01

    The use of Langmuir-Blodgett (LB) monolayers to modify the indium tin oxide (ITO) work function and thus improve the performance of zinc phthalocyanine (ZnPc)/fullerene (C60)-based and boron subphthalocyanine chloride (SubPc)/C60-based small molecule organic photovoltaic devices (OPVs) was examined. In general, LB precursor compounds contain one or more long alkyl chain substituents that can act as spacers to prevent electrical contact with adjoining electrode surfaces. As one example of such a compound, arachidic acid (CH3(CH2)18COOH) was inserted in the forms of one-layer, three-layer or five-layer LB films between the anode ITO layer and the p-type layer in ZnPc-C60-based OPVs to investigate the effects of the long alkyl chain group when it acts as an electrically insulating spacer. The short-circuit current density (Jsc) values of the OPVs with the three- and five-layer inserts (1.78 mA.cm-2 and 0.61 mA.cm-2, respectively) were reduced dramatically, whereas the Jsc value for the OPV with the single-layer insertion (2.88 mA.cm-2) was comparable to that of the OPV without any insert (3.14 mA.cm-2). The ITO work function was shifted positively by LB deposition of a surfactant compound, C9F19C2H4-O-C2H4-COOH (PFECA), which contained a fluorinated head group. This positive effect was maintained even after formation of an upper p-type organic layer. The Jsc and open-circuit voltage (Voc) of the SubPc-C60-based OPV with the LB-modified ITO layers were effectively enhanced. As a result, a 42% increase in device efficiency was achieved.

  4. Fabrication and characterization of NiO based metal−insulator−metal diode using Langmuir-Blodgett method for high frequency rectification

    Directory of Open Access Journals (Sweden)

    Ibrahim Azad

    2018-04-01

    Full Text Available Thin film metal–insulator–metal (MIM diodes have attracted significant attention for use in infrared energy harvesting and detection applications. As demonstrated over the past decades, MIM or metal-insulator-insulator-metal (MIIM diodes can operate at the THz frequencies range by quantum tunneling of electrons. The aim of this work is to synthesize required ultra-thin insulating layers and fabricate MIM diodes using the Langmuir-Blodgett (LB technique. The nickel stearate (NiSt LB precursor film was deposited on glass, silicon (Si, ITO glass and gold coated silicon substrates. The photodesorption (UV exposure and the thermodesorption (annealing at 100 °C and 350 °C methods were used to remove organic components from the NiSt LB film and to achieve a uniform homogenous nickel oxide (NiO film. These ultrathin NiO films were characterized by EDS, AFM, FTIR and cyclic voltammetry methods, respectively. The MIM diode was fabricated by depositing nickel (Ni on the NiO film, all on a gold (Au plated silicon (Si substrate. The current (I-voltage (V characteristics of the fabricated diode were studied to understand the conduction mechanism assumed to be tunneling of electron through the ultra-thin insulating layer. The sensitivity of the diode was measured to be as high as 35 V-1. The diode resistance was ∼100 ohms (at a bias voltage of 0.60 V, and the rectification ratio was about 22 (for a signal voltage of ±200 mV. At the bias point, the diode response demonstrated significant non-linearity and high asymmetry, which are very desirable characteristics for applications in infrared detection and harvesting.

  5. Fabrication and characterization of NiO based metal-insulator-metal diode using Langmuir-Blodgett method for high frequency rectification

    Science.gov (United States)

    Azad, Ibrahim; Ram, Manoj K.; Goswami, D. Yogi; Stefanakos, Elias

    2018-04-01

    Thin film metal-insulator-metal (MIM) diodes have attracted significant attention for use in infrared energy harvesting and detection applications. As demonstrated over the past decades, MIM or metal-insulator-insulator-metal (MIIM) diodes can operate at the THz frequencies range by quantum tunneling of electrons. The aim of this work is to synthesize required ultra-thin insulating layers and fabricate MIM diodes using the Langmuir-Blodgett (LB) technique. The nickel stearate (NiSt) LB precursor film was deposited on glass, silicon (Si), ITO glass and gold coated silicon substrates. The photodesorption (UV exposure) and the thermodesorption (annealing at 100 °C and 350 °C) methods were used to remove organic components from the NiSt LB film and to achieve a uniform homogenous nickel oxide (NiO) film. These ultrathin NiO films were characterized by EDS, AFM, FTIR and cyclic voltammetry methods, respectively. The MIM diode was fabricated by depositing nickel (Ni) on the NiO film, all on a gold (Au) plated silicon (Si) substrate. The current (I)-voltage (V) characteristics of the fabricated diode were studied to understand the conduction mechanism assumed to be tunneling of electron through the ultra-thin insulating layer. The sensitivity of the diode was measured to be as high as 35 V-1. The diode resistance was ˜100 ohms (at a bias voltage of 0.60 V), and the rectification ratio was about 22 (for a signal voltage of ±200 mV). At the bias point, the diode response demonstrated significant non-linearity and high asymmetry, which are very desirable characteristics for applications in infrared detection and harvesting.

  6. Studies on morphology of Langmuir-Blodgett films of stearic acid deposited with different orientation of substrates with respect to compression

    Energy Technology Data Exchange (ETDEWEB)

    Choudhary, Keerti; Manjuladevi, V.; Gupta, R. K., E-mail: raj@pilani.bits-pilani.ac.in [Department of physics, Birla Institute of Technology & Science, Pilani-333031, Rajasthan (India)

    2016-05-06

    The Langmuir monolayer at an air-water interface shows remarkably different surface pressure – area isotherm, when measured with the surface normal of a Wilhemly plate parallel or perpendicular to the direction of compression of the monolayer. Such difference arises due to difference in stress exerted by the monolayer on the plate in different direction. In this article, we report the effect of changing the direction of substrate normal with respect to the compression of the monolayer during Langmuir-Blodgett (LB) film deposition on the morphology of the films. The morphology of the LB film of stearic acid was studied using an atomic force microscope (AFM). The morphology of the LB films was found to be different due to difference in the stress in different directions.

  7. Effect of clay in controlling the non-fluorescence H-dimeric states of a cationic dye Nile Blue Chloride (NBC) in hybrid Langmuir-Blodgett (LB) film

    Science.gov (United States)

    Debnath, Chandan; Shil, Ashis; Hussain, S. A.; Bhattacharjee, D.

    2018-01-01

    Present communication reports the effect of amphiphilic matrices and nano-clay platelets on the aggregation properties of a water soluble cationic fluorescent dye Nile Blue Chloride (NBC) in Langmuir-Blodgett (LB) films. In-situ Brewster Angle Microscopic (BAM) studies showed distinct domain structures of complex and hybrid Langmuir monolayer at the air-water interface. UV-vis absorption spectra showed non-fluorescent H-dimeric band in concentrated aqueous solution of NBC and in complex LB film of NBC with stearic acid. By changing various parameters, a great control over H-dimeric states has been achieved in clay incorporated hybrid LB films. These films can act as efficient fluorescence probe.

  8. Incorporation in Langmuir-Blodgett films of an amphiphilic derivative of fullerene C{sub 60} and oligo-para-phenylenevinylene

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez-Venicio, V. [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico (UNAM), Circuito Exterior, CU, C.P. 04510, D.F. (Mexico); Gutierrez-Nava, M. [CIATEQ, A.C., Centro de Tecnologia Avanzada, Circuito de la Industria Poniente Lote: 11, Mza. 3, No. 11, Colonia Parque Industrial Ex Hacienda Dona Rosa, Lerma C.P. 52004, Estado de Mexico (Mexico); Amelines-Sarria, O. [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico (UNAM), Circuito Exterior, CU, C.P. 04510, D.F. (Mexico); Alvarez-Zauco, E. [Facultad de Ciencias, UNAM, Circuito Exterior, C.U., C.P. 04510, D.F. (Mexico); Basiuk, V.A. [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico (UNAM), Circuito Exterior, CU, C.P. 04510, D.F. (Mexico); Carreon-Castro, M.P., E-mail: pilar@nucleares.unam.mx [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico (UNAM), Circuito Exterior, CU, C.P. 04510, D.F. (Mexico)

    2012-12-30

    Langmuir (L) and Langmuir-Blodgett (LB) films of fullerene C{sub 60}-oligo-para-phenylenevinylene (OPV) derivative with six C{sub 12}H{sub 25} aliphatic chains were characterized. For the Langmuir films, isotherms of surface pressure versus molecular area, compression/expansion cycles (hysteresis curves) and Brewster angle microscopic images were obtained. We performed molecular mechanics and density functional theory calculations to determine the molecular and electronic structure of our compound at a water-air interface. We found agreement between experimental and theoretical values for the molecular surface area. LB films of up to ten layers were obtained on glass substrates, and were characterized by ultraviolet-visible spectroscopy. We observed that the absorbance at a wavelength of 326 nm grows almost linearly as a function of the number of layers. Films on glass-indium tin oxide were characterized by atomic force microscopy. We also observed a uniform deposition over the whole area of the scanned substrate. We demonstrated that the fullerene C{sub 60}-OPV derivative is able to form both L and LB films preventing fullerene aggregation with its aliphatic chains. We suggest that, due to its electron-acceptor properties, the C{sub 60}-OPV derivative could be used for organic-photovoltaic and organic-electronic applications. - Highlights: Black-Right-Pointing-Pointer We performed isotherm and hysteresis studies of fullerene derivative compound. Black-Right-Pointing-Pointer We found that the theoretical and experimental molecular areas agree. Black-Right-Pointing-Pointer We deposited Langmuir-Blodgett (LB) films on glass-indium tin oxide. Black-Right-Pointing-Pointer LB films were characterized using UV-visible spectroscopy. Black-Right-Pointing-Pointer We observed the morphology of the LB films through atomic force microscopy.

  9. Spectroscopic and structural characteristics of Langmuir-Blodgett films of bis[2,3,9,10,16,17,24,25-octakis(octyloxy)phthalocyaninato] rare earth complexes

    International Nuclear Information System (INIS)

    Wang Xueying; Chen Yanli; Liu Hongguo; Jiang Jianzhuang

    2006-01-01

    The monolayer behavior of bis[2,3,9,10,16,17,24,25-octakis(octyloxy)phthalocyaninato] rare earth complexes M[Pc(OC 8 H 17 ) 8 ] 2 (M = Eu, Dy, Er) at the air-water interface and their ordered molecular assemblies fabricated by Langmuir-Blodgett technique have been investigated by a series of techniques including surface pressure-area isotherms, electronic absorption spectra, polarized absorption spectra, low-angle X-ray diffraction patterns, and transmission electron microscope (TEM). The results indicated that bis(phthalocyaninato) rare earth molecules form well-ordered stable monolayers with a face-to-face configuration and edge-on arrangement to the water surface at the air-water interface and lamellar multilayers on solid substrates. The orientation angle of phthalocyanine rings with respect to the quartz plate surface in the Langmuir-Blodgett films has been determined to be 64.6 o , 63.5 o , and 63.3 o for the Eu, Dy, and Er double-decker complexes, respectively, by the polarized absorption spectroscopy. High-resolution TEM reveals that a series of well-ordered rodlike aggregates of bis(phthalocyaninato) rare earth complexes, which can be considered as molecular cable arrays, were formed by self-organization in the monolayers

  10. Extensibility effect of poly(3-hexylthiophene) on the glucose sensing performance of mixed poly(3-hexylthiophene)/octadecylamine/glucose oxidase Langmuir-Blodgett films.

    Science.gov (United States)

    Wang, Ke-Hsuan; Hsu, Wen-Ping; Chen, Liang-Huei; Lin, Wei-Don; Lee, Yuh-Lang

    2017-07-01

    Poly(3-hexylthiophene) (P3HT) is utilized as a material to enhance the glucose sensing performance of glucose oxidase (GOx) Langmuir-Blodgett (LB) films. To enhance the extensibility and homogeneity of the P3HT in the LB films, octadecylamine (ODA) is introduced. The characteristics of the mixed P3HT/ODA Langmuir monolayers are investigated first and then, utilized as template layers to adsorb GOx from the subphase, preparing P3HT/ODA/GOx Langmuir-Blodgett films for glucose sensing. The results show that P3HT molecules tend to aggregate at the air/liquid interface and, furthermore, the P3HT monolayer has a weak ability to adsorb GOx from the subphase. By using mixed P3HT/ODA monolayer, the presence of ODA not only inhibits the aggregation of P3HT, but also increases the adsorption ability of the monolayer to GOx. The extensibility of P3HT and the homogeneity of the P3HT/ODA monolayers are closely related to the concentration of P3HT/ODA stock solutions. On the glucose sensing experiments, the performance of the P3HT/ODA/GOx LB film is greatly improved due to the presence of P3HT and, furthermore, the sensibility increases with increasing extensibility of P3HT molecules. The best sensitivity achieved for the P3HT/ODA/GOx film is 5.4μAmM -1 cm -2 which is over two times the value obtained by the ODA/GOx film (2.3μAmM -1 cm -2 ). Copyright © 2017 Elsevier B.V. All rights reserved.

  11. Morphological characterization of Langmuir-Blodgett films from polyaniline and a ruthenium complex (Rupy): influence of the relative concentration of Rupy

    International Nuclear Information System (INIS)

    Souza, Nara C de; Ferreira, Marystela; Wohnrath, Karen; Silva, Josmary R; Oliveira Osvaldo, N Jr; Giacometti, Jose A

    2007-01-01

    We report on the use of dynamic scale theory and fractal analyses in a study of the growth stages of Langmuir-Blodgett (LB) films of polyaniline and a neutral biphosphinic ruthenium complex, namely mer-[RuCl 3 (dppb)(py)] (dppb = 1,4-bis(diphenylphosphine)buthane, py = pyridine), Rupy. The LB films were deposited onto indium-tin-oxide substrates and characterized with atomic force microscopy. From the granular morphology exhibited by the films one could infer growth processes inside and outside the grains. Growth outside was found to follow the Kardar-Parisi-Zhang model, with fractal dimensions of about 2.7. As one would expect, inside the grains the morphology is close to a Euclidian surface with fractal dimension of about 2

  12. Energy transfer and electron transfer in dimers and polymers of porphyrin and phthalocyanines: from the liquid phase to Langmuir-Blodgett films

    International Nuclear Information System (INIS)

    Lipskier, Jean-Francois

    1991-01-01

    The understanding of phenomena of photo-induced transfer of energy and of electron between chromophores belonging to a same supra-molecular entity is necessary for the design and fabrication of molecule devices performing the conversion of a light signal into electric signal or chemical potential. As porphyrin oligomers and phthalocyanine oligomers are examples of interest for the systematic study of parameters governing these processes, the first part of this research thesis addresses the study of dimers and trimers bound by covalent bridges. The second part addresses the study of physical-chemical properties of complexes bound by the Van der Waals interaction as well as by the Coulomb attraction. An extension to Langmuir-Blodgett films is proposed, and the properties of complexes organised in thin films according to this methodology are compared with those of their homologues in solution [fr

  13. Langmuir-Blodgett Films of the Metal-Organic Framework MIL-101(Cr): Preparation, Characterization, and CO2 Adsorption Study Using a QCM-Based Setup.

    Science.gov (United States)

    Benito, Javier; Sorribas, Sara; Lucas, Irene; Coronas, Joaquin; Gascon, Ignacio

    2016-06-29

    This work reports the fabrication and characterization of Langmuir-Blodgett films of nanoparticles (size 51 ± 10 nm) of the metal organic framework MIL-101(Cr). LB film characterization by SEM, UV-vis, GIXRD, and QCM has shown that the addition of 1 wt % of behenic acid to MOF dispersion allows obtaining dense monolayers at the air-water interface that can be deposited onto solid substrates of different nature with transfer ratios close to 1. Moreover, a QCM-based setup has been built and used for the first time to measure CO2 adsorption isotherms at 303 K on MOF LB films, proving that LB films with MOF masses between 1.2 (1 layer) and 2.3 (2 layers) μg can be used to obtain accurate adsorption values at 100 kPa, similar to those obtained by conventional adsorption methods that require much larger MOF quantities (tens of milligrams).

  14. Magnetic properties of Langmuir-Blodgett (LB) films: a theoretical study. III. LB films consisting of different types of stable π-monoradicals.

    Science.gov (United States)

    Drebov, Nedko; Tyutyulkov, Nikolai; Dietz, Fritz

    2013-01-22

    We present theoretical results for the magnetic properties of modeled two-dimensional (2-D) Langmuir-Blodgett films consisting of different types of stable organic π-monoradicals. Their energy spectra and magnetic characteristics are investigated using the many-body band theory of magnetism in π-electron approximation. The main factors which determine the magnitude and character of the magnetic interaction in the 2-D molecular arrangements are thoroughly studied. Semiempirical electronic structure calculations have been also carried out for molecular clusters to gain further insight into their magnetic properties. The proposed models for LB films are potential candidates for new 2-D ferromagnetic materials which are characterized by a substantial increase of the critical temperatures up to 250 K in comparison to only about 5 K for the now existing magnetic LB films based on organometallic systems.

  15. Preparation of pillar[5]arene-quinoline Langmuir-Blodgett thin films for detection of volatile organic compounds with host-guest principles.

    Science.gov (United States)

    Kursunlu, Ahmed Nuri; Acikbas, Yaser; Ozmen, Mustafa; Erdogan, Matem; Capan, Rifat

    2017-10-07

    In this study, a novel pillar[5]arene-quinoline (P5-Q) as an organic material is used to fabricate Langmuir-Blodgett (LB) thin films and its organic vapor sensing properties have been investigated. The LB deposition process is characterized by UV-visible spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM) and quartz crystal microbalance (QCM) techniques. The typical frequency shift per layer is obtained as 31.75 Hz per layer and the deposited mass onto a quartz crystal is calculated to be 539.69 ng per layer (2.03 ng mm -2 ). The fitted surface plasmon resonance (SPR) data were utilized to calculate the film thickness of this material. The thickness of a single layer is calculated to be 1.26 ± 0.09 nm. QCM and SPR systems are used to investigate gas sensing performance of macrocyclic LB films during exposure to Volatile Organic Compounds (VOCs). The macrocyclic LB thin films are more sensitive to dichloromethane than that of other vapors used in this study. The sensitivity and detection limit performance of the P5-Q QCM sensor to dichloromethane vapor were calculated to be 14.751 Hz ppm -1 and 0.203 ppm, respectively. These results demonstrated that the P5-Q material is promising as an organic vapor sensing device at room temperature. Despite Langmuir-Blodgett being a traditional technique in colloid and interface science, this study presents the first gas sensor application for pillararene LB films. Because of the unique symmetric pillar architecture of P5-Q, self-assembly of pillar[5]arene molecules should afford various characteristic nanometer-scale architectures such as micelles, vesicles, and tubes.

  16. Structural characterization and plasmonic properties of two-dimensional arrays of hydrophobic large gold nanoparticles fabricated by Langmuir-Blodgett technique

    Energy Technology Data Exchange (ETDEWEB)

    Ishida, Takuya; Tachikiri, Yuki; Sako, Takayuki [Department of Materials Physics and Chemistry, Graduate School of Engineering, Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan); Takahashi, Yukina, E-mail: yukina@mail.cstm.kyushu-u.ac.jp [Department of Applied Chemistry, Faculty of Engineering, Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan); Yamada, Sunao, E-mail: yamada@mail.cstm.kyushu-u.ac.jp [Department of Applied Chemistry, Faculty of Engineering, Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan); Center for Future Chemistry, Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan)

    2017-05-15

    Highlights: • Hydrophobic gold nanoparticles (AuNPs) by our method were large and stable enough. • Two-dimensional (2D) arrays of the AuNPs were obtained by Langmuir-Blodgett method with polyethylene glycol. • The plasmon resonant wavelength of the 2D arrays can be controlled by the diameter. - Abstract: We have succeeded in fabricating two-dimensional (2D) arrays of larger gold nanoparticles (AuNPs) (diameters 17, 28, and 48 nm) by Langmuir-Blodgett (LB) method. Although the particle size of AuNPs is one of the most important factors in order to control the optical properties of 2D arrays, there have been reported only the size of less than ∼20 nm. This is a first report on the bottom-up fabrication of 2D arrays consisting of hydrophobic AuNP with the diameter of ∼50 nm, of which the size is expected to obtain maximum near-field effects. Octadecylthiolate-capped AuNPs (ODT-AuNPs) which were prepared by our method could be re-dispersed in chloroform even after drying completely, realizing the spreading of the colloidal chloroform solution onto the water surface. Accordingly, densely-packed 2D LB films of ODT-AuNPs could be fabricated on an indium-tin-oxide substrate, when water as the subphase and polyethylene glycol (PEG) as an amphiphilic agent were used. PEG played an important role to form densely-packed film uniformly due to increasing affinity between hydrophobic AuNP and water. Absorption spectra of the films revealed that the resonance wavelengths of plasmon oscillation through interparticle plasmon coupling were clearly correlated with the particle sizes rather than deposition densities.

  17. Co-Deposition of Gold Nanoparticles and Metalloporphyrin Using the Langmuir-Blodgett (LB) Technique for Surface-Enhanced Raman Scattering (SERS).

    Science.gov (United States)

    Camacho, Sabrina A; Aoki, Pedro H B; de Assis, Francisco F; Pires, Ana M; de Oliveira, Kleber T; Aroca, Ricardo F; Constantino, Carlos J L

    2015-04-01

    The synergistic effect produced by metallic nanoparticles when incorporated into different systems empowers a research field that is growing rapidly. In addition, organometallic materials are at the center of intensive research with diverse applications such as light-emitting devices, transistors, solar cells, and sensors. The Langmuir-Blodgett (LB) technique has proven to be suitable to address challenges inherent to organic devices, since the film properties can be tuned at the molecular level. Here we report a strategy to incorporate gold nanoparticles (AuNPs) into the LB film by co-deposition in order to achieve surface-enhanced Raman scattering (SERS) of the zinc(II)-protoporphyrin (IX) dimethyl ester (ZnPPIX-DME). Prior to the LB co-deposition, the properties of the Langmuir monolayer of ZnPPIX-DME at the air-water interface, containing AuNPs in the subphase, are studied through the surface-pressure versus mean molecular area (π-A) isotherms. The ZnPPIX-DME+AuNPs π-A isotherm presented a significant shift to higher molecular area, suggesting an interaction between both ZnPPIX-DME molecules and AuNPs. Those interactions are a key factor allowing the co-deposition of both AuNPs and ZnPPIX-DME molecules onto a solid substrate, thus forming the LB film. SERS of ZnPPIX-DME was successfully attained, ensuring the spatial distribution of the AuNPs. Higher enhancement factors were found at AuNP aggregates, as a result of the intense local electromagnetic field found in the metal nanoparticle aggregates. The main vibrational bands observed in the SERS spectra suggest a physical adsorption of the ZnPPIX-DME onto the surface of AuNPs. The latter is not only in agreement with the interactions pointed out by the π-A isotherms but also suggests that this interaction is kept upon LB film co-deposition.

  18. Large Area 2D and 3D Colloidal Photonic Crystals Fabricated by a Roll-to-Roll Langmuir-Blodgett Method.

    Science.gov (United States)

    Parchine, Mikhail; McGrath, Joe; Bardosova, Maria; Pemble, Martyn E

    2016-06-14

    We present our results on the fabrication of large area colloidal photonic crystals on flexible poly(ethylene terephthalate) (PET) film using a roll-to-roll Langmuir-Blodgett technique. Two-dimensional (2D) and three-dimensional (3D) colloidal photonic crystals from silica nanospheres (250 and 550 nm diameter) with a total area of up to 340 cm(2) have been fabricated in a continuous manner compatible with high volume manufacturing. In addition, the antireflective properties and structural integrity of the films have been enhanced via the use of a second roll-to-roll process, employing a slot-die coating of an optical adhesive over the photonic crystal films. Scanning electron microscopy images, atomic force microscopy images, and UV-vis optical transmission and reflection spectra of the fabricated photonic crystals are analyzed. This analysis confirms the high quality of the 2D and 3D photonic crystals fabricated by the roll-to-roll LB technique. Potential device applications of the large area 2D and 3D colloidal photonic crystals on flexible PET film are briefly reviewed.

  19. In situ and real-time atomic force microscopy studies of the stability of oligothiophene langmuir-blodgett monolayers in liquid

    KAUST Repository

    Yin, Naining

    2014-03-20

    Oligothiophene thin films have been considered as promising material for molecular electronics due to their desirable electronic properties and high structural stability under ambient conditions. To ensure performance in devices the functional structures, such as individual ordered domains, must be stable under practical and operational conditions or environments including exposure to various media. This work investigates the structure of oligothiophene Langmuir-Blodgett (LB) films upon exposure to liquid media such as water, ethanol (EtOH), and mixed tetrahydrofuran (THF)/EtOH solutions. The LB films form islands ranging from 500 nm up to 1 μm consisting of densely packed oligothiophene molecules. These islands are surrounded by bare substrate and loosely packed adsorbates. In situ and time-dependent AFM images were acquired to reveal the structural evolution, from which degradation pathways and kinetics are extracted. Degradation of these LB films initiates and propagates from intraisland defect sites, such as cracks and pin holes, whereas the edges of islands remain intact on the surface. The observations appear to be in contrast to the known degradation mechanism among self-assembled monolayers, such as alkanethiols on gold, which initiates and progresses at domain boundaries. Rationale for the observed degradation processes will also be discussed. © 2014 American Chemical Society.

  20. Oxygen Sensing by the Hybrid Langmuir-Blodgett Films of Iridium(III Complexes and Synthetic Saponite on the Basis of Energy Transfer

    Directory of Open Access Journals (Sweden)

    Hisako Sato

    2017-09-01

    Full Text Available An ultra-thin hybrid film of amphiphilic iridium(III complexes and synthetic saponite was manipulated by means of the modified Langmuir-Blodgett method. In the film deposited onto a quartz substrate, the external mixed molecular layer of amphiphilic iridium(III complexes was reinforced by the inner layer of exfoliated synthetic saponite. As components of the molecular layer, two iridium(III complexes were used: [Ir(dfppy2(dc9bpy]+ (dfppyH = 2-(4′,6′-difluorophenyl pyridine; dc9bpy = 4,4′-dinonyl-2,2′-bipyridine (denoted as DFPPY and [Ir(piq2(dc9bpy]+ (piqH = 1-phenyisoquinoline denoted as PIQ. The emission spectra from the films changed from blue to red maxima with the decrease of a ratio of DFPPY/PIQ due to the energy transfer from excited DFPPY to PIQ. The intensity of red decreased with the increase of oxygen pressure through the quenching of excited iridium(III complexes, promising a possibility as an oxygen-sensing film.

  1. Langmuir-Blodgett monolayers of cationic dyes in the presence and absence of clay mineral layers: N,N'-dioctadecyl thiacyanine, octadecyl rhodamine B and laponite.

    Science.gov (United States)

    Hussain, Syed Arshad; Schoonheydt, Robert A

    2010-07-20

    Langmuir-Blodgett (LB) films of N,N'-dioctadecyl thiacyanine perchlorate (TC18) and octadecyl rhodamine B chloride (RhB18) and their mixtures in the presence and absence of clay mineral layers were investigated by recording surface pressure-area (pi-A) isotherms and by UV-vis and fluorescence spectroscopies. The pi-A isotherms of TC18, RhB18, and their mixtures are characteristic of liquid expanded state behavior with repulsive interactions between the two cationic dyes. In the presence of laponite, the pi-A isotherms show liquid expanded and condensed-state behavior. In laponite dispersions and in monolayers, TC18 has a strong tendency to aggregate with formation of H- and J- aggregates. The absorption and fluorescence maxima of the monomers in the films are at 435 nm and at 480 nm; H-dimers have an absorption maximum around 410 nm and do not fluoresce. J-dimers are present in all the films with absorption maximum at 461 nm and fluorescence at 463 nm. RhB18 is mainly present as monomers in the LB films with an absorption maximum at 576 nm and fluorescence at 595 nm. Fluorescence resonance energy transfer from TC18 to RhB18 has been observed in clay dispersions and in films with and without laponite. The optimum condition for TC18 --> RhB18 fluorescence energy transfer in the films is 90 mol % TC18 + 10 mol % RhB18.

  2. Non-Linear Langmuir Wave Modulation in Collisionless Plasmas

    DEFF Research Database (Denmark)

    Dysthe, K. B.; Pécseli, Hans

    1977-01-01

    in the expressions concerning the modulation instability of a plane Langmuir wave. When the Vlasov equation for the ions is applied, a Langmuir wave is modulationally unstable for arbitrary perturbations independent of the unperturbed wave amplitude, in contrast to what is found for fluid ions. A simple analogy...

  3. Thermal behavior of J-aggregates in a Langmuir-Blodgett film of pure merocyanine dye investigated by UV-visible and IR absorption spectroscopy.

    Science.gov (United States)

    Hirano, Yoshiaki; Tateno, Shinsuke; Maio, Ari; Ozaki, Yukihiro

    2009-03-05

    We have characterized the structure of J-aggregate in a Langmuir-Blodgett film of pure merocyanine dye (MS18) fabricated under an aqueous subphase containing a cadmium ion (Cd2+) and have investigated its thermal behavior by UV-visible and IR absorption spectroscopy in the range from 25 to 250 degrees C with a continuous scan. The results of both UV-visible and IR absorption spectra indicate that temperature-dependent changes in the MS18 aggregation state in the pure MS18 system are closely and mildly linked with the MS18 intramolecular charge transfer and the behavior of the packing, orientation, conformation, and thermal mobility of MS18 hydrocarbon chain, respectively. The J-aggregate in the pure MS18 system dissociates from 25 to 150 degrees C, and the dissociation temperature at 150 degrees C is higher by 50 degrees C than that in the previous MS18- arachidic acid (C20) binary system. The lower dissociation temperature in the binary system originates from the fact that temperature-dependent structural disorder of cadmium arachidate (CdC20), being phase-separated from MS18, has an influence on the dissociation of J-aggregate. From 160 to 180 degrees C, thermally induced blue-shifted bands, caused by the oligomeric MS18 aggregation, appear at around 520 nm in the pure MS18 system by contraries, regardless of the lack of driving force by the melting phenomenon of CdC20. The temperature at which the 520 nm bands occur is in good agreement with the melting point (160 degrees C) of hydrocarbon chain in MS18 with Cd2+, whereas its chromophore part is clearly observed to melt near 205 degrees C by UV-visible spectra. Therefore, it is suggested that the driving force that induces the 520 nm band in the pure MS18 system arises from the partial melting of hydrocarbon chain in MS18 with Cd2+.

  4. Influence of chlorine atoms in bay positions of perylene-tetracarboxylic acids on their spectral properties in Langmuir-Blodgett films

    Science.gov (United States)

    Piosik, Emilia; Synak, Anna; Martyński, Tomasz

    2018-01-01

    The influence of chlorine atoms in the bay positions of the perylene-3,4,9,10-tetracarboxylic acids with the different alkyl chains length on their spectral properties in monomolecular films has been studied. The chlorinated (PCln) and for comparison non-chlorinated (Pn) perylene derivatives were deposited onto quartz plates using a Langmuir-Blodgett (LB) technique. The absorption spectra showed that the PCln and Pn dyes form in monolayers the I- and J-type aggregates, respectively. In turn, their steady-state and time-resolved emission spectra revealed presence of two emitter types, which we assigned to monomers and excimers. The luminescence lifetimes of the PCln monomers and excimers determined with a time-correlated single photon counting method (TCSPC) are significantly shorter than these obtained for the same emitter types in the Pn monolayers. In the case of the chlorinated dyes, the contribution of the monomer emission dominates over the excimer emission and is almost independent from the alkyl chain length. By contrast, the share of the Pn monomer emission increases strongly with a number of carbon atoms in their hydrocarbon chains. The luminescence quantum yields (LQY) of the Pn and PCln monolayers measured in an integrating sphere are in the range of 0.06-0.11. The presented results reveal that the PCln dyes exhibit lower tendency for aggregation than the non-chlorinated derivatives. It can be explained by limited intermolecular interaction between neighbouring PCln molecules caused by deformation of the perylene core as a result of strongly electronegative chlorine atoms in the bay positions of these dyes. Moreover, the strong influence of the alkyl chain length on the Pn aggregation contrary to the case of the PCln derivatives was observed.

  5. Construction of highly ordered lamellar nanostructures through Langmuir-Blodgett deposition of molecularly thin titania nanosheets tens of micrometers wide and their excellent dielectric properties.

    Science.gov (United States)

    Akatsuka, Kosho; Haga, Masa-aki; Ebina, Yasuo; Osada, Minoru; Fukuda, Katsutoshi; Sasaki, Takayoshi

    2009-05-26

    Exfoliated unilamellar titania nanosheets of Ti(0.87)O(2) with a lateral size of 10-30 microm were deposited layer-by-layer onto various substrates by Langmuir-Blodgett procedure to produce a highly ordered lamellar nanofilms. The nanosheets dispersed in an aqueous suspension containing quaternary ammonium ions as a supporting electrolyte floated spontaneously at the air/liquid interface, and they were successfully transferred onto the substrate after surface compression. Neat tiling of the nanosheets could be realized at an optimized surface pressure. The film thus obtained was exposed to UV light to turn the substrate surface hydrophilic, which was helpful for stable repetition of monolayer deposition. Layer-by-layer growth was confirmed by UV-visible absorption spectra, which showed progressive enhancement of an absorption band due to the nanosheet. Cross-sectional transmission electron microscopy images visualized the ultrathin film homogeneously deposited on the substrate surface and a lamellar fringe of the layer-by-layer assembled nanosheets was clearly resolved at a higher magnification. X-ray diffraction data on the films showed sharp basal reflections up to the seventh order, and Williamson-Hall analysis of the pattern indicated that the film was coherent across the total thickness with respect to X-ray and that the lattice strain was extremely small. In addition, the first basal reflection was accompanied by small satellite peaks, which are accounted for by the Laue interference function. All these features clearly indicate the formation of a highly ordered lamellar nanostructure of the titania nanosheets comparable to artificial lattice films produced via modern vapor-phase deposition processes. The obtained films showed superior dielectric and insulating properties as a reflection of the highly organized film nanoarchitecture.

  6. Nonlinear Langmuir Wave Modulation in Weakly Magnetized Plasmas

    DEFF Research Database (Denmark)

    Dysthe, K. B.; Pécseli, Hans

    1978-01-01

    influence on the modulation stability of plane Langmuir waves. As in the unmagnetized case, kinetic results were found to deviate considerably from those obtained by using a fluid description for the ion dynamics. With particular attention to ionospheric phenomena, the effect is included of the spatially...

  7. Synthesis and Characterization of Novel Dendrons Bearing Amino-Nitro-Substituted Azobenzene Units and Oligo(ethylene glycol Spacers: Thermal, Optical Properties, Langmuir Blodgett Films and Liquid-Crystalline Behaviour

    Directory of Open Access Journals (Sweden)

    Ernesto Rivera

    2013-01-01

    Full Text Available In this work, we report the synthesis and characterization of a novel series of first and second generation Fréchet type dendrons bearing amino-nitro substituted azobenzene units and tetra(ethylene glycol spacers. These compounds were fully characterized by FTIR, 1H and 13C-NMR spectroscopies, and their molecular weights were determined by MALDI-TOF-MS. The thermal properties of the obtained dendrons were studied by TGA and DSC and their optical properties by absorption spectroscopy in solution and cast film. Molecular calculations were performed in order to determine the optimized geometries of these molecules in different environments. Besides, Langmuir and Langmuir Blodgett films were prepared with the first generation dendrons that were shown to be amphiphilic. Finally, some of the dendrons showed a liquid crystalline behaviour, which was studied by light polarized microscopy as a function of the temperature in order to determine the transition temperatures and the structure of the mesophase.

  8. Synthesis and study of lamellar inorganic materials inserted in Langmuir-Blodgett matrix: metallic hexa-thio-hypo-diphosphates (M2P2S6 with M = Cd,Ni,Mn)

    International Nuclear Information System (INIS)

    Perez, Henri

    1991-01-01

    This research thesis reports the study of the fabrication of bi-dimensional inorganic materials with mono-molecular thickness which can be produced by insertion by using the Langmuir-Blodgett (LB) technique. The author more particularly addressed the synthesis of lamellar M 2 P 2 S 6 materials. After a presentation of the main physical and chemical characteristics of these compounds, a presentation of the LB technique used to produce such a compound, the author presents the two possible synthesis methods, and the chemical and structural characterisation methods used for the study of the LB films (spectroscopy, XPS, X ray diffraction). The next parts reports the study and assessment of both synthesis methods: one of them gives positive results, whereas the second one raised some problems [fr

  9. Statistical analysis of nonlinear wave interactions in simulated Langmuir turbulence data

    Directory of Open Access Journals (Sweden)

    J. Soucek

    2003-03-01

    Full Text Available We present a statistical analysis of strong turbulence of Langmuir and ion-sound waves resulting from beam-plasma interaction. The analysis is carried out on data sets produced by a numerical simulation of one-dimensional Zakharov’s equations. The nonlinear wave interactions are studied using two different approaches: high-order spectra and Volterra models. These methods were applied to identify two and three wave processes in the data, and the Volterra model was furthermore employed to evaluate the direction and magnitude of energy transfer between the wave modes in the case of Langmuir wave decay. We demonstrate that these methods allow one to determine the relative importance of strongly and weakly turbulent processes. The statistical validity of the results was thoroughly tested using surrogated data set analysis.Key words. Space plasma physics (wave-wave interactions; experimental and mathematical techniques; nonlinear phenomena

  10. Stimulated Raman scattering and ion dynamics: the role of Langmuir wave non-linearities

    International Nuclear Information System (INIS)

    Bonnaud, G.; Pesme, D.

    1988-02-01

    The non-linear evolution of stimulated Raman scattering by coupling of the SRS-driven Langmuir waves to ion acoustic waves is studied numerically, in a homogeneous density laser-irradiated plasma. The coupled wave amplitude behaviour is represented either by envelope equations or by complete wave-like equations. The various physical phenomena which are involved are described. This preliminary work has been presented at the 17th Anomalous Absorption Conference, held in last May, in Lake Tahoe City (USA) [fr

  11. Effects of a central metal on the organization of 5,10,15,20-tetra-(p-chlorophenyl)-rare earth porphyrin hydroxyl compound at the air/water interface and in Langmuir-Blodgett films.

    Science.gov (United States)

    Li, Xiaoling; Xu, Weiqing; Itoh, Tamitake; Ikehata, Akifumi; Zhao, Bing; Li, Bofu; Ozaki, Yukihiro

    2005-04-15

    Langmuir monolayers and Langmuir-Blodgett (LB) films of 5,10,15,20-tetra-(p-chlorophenyl) terbium/gadolinium porphyrin hydroxyl compound (TbOH and GdOH) and their mixtures with stearic acid (SA) in a molar ratio of 1:1 were investigated by Brewster angle microscopy (BAM), ultraviolet-visible (UV-vis), and infrared (IR) spectroscopy and atomic force microscopy (AFM). pi-A isotherms showed that well-defined Langmuir monolayers were formed at an air/water interface for the porphyrins and their mixture with SA. The BAM observations suggest that the pi-pi interaction between the GdOH molecules is stronger than that between the TbOH molecules. This result can be further confirmed by the AFM measurements. After the introduction of SA, the pi-pi interaction between the TbOH molecules is broken and thus two phases formed in the mixed LB film. However, it cannot break the stronger pi-pi interaction between the GdOH molecules. Therefore, no phase separation is observed in the GdOH/SA LB film. IR reflection-absorption (RA) spectra showed that the COOH groups of SA are partly converted to COO(-) groups, suggesting that there is an interaction between MOH and SA in the films. This interaction leads the benzene rings of TbOH to rotate toward parallel to the substrate and those of GdOH to rotate toward perpendicular to the substrate. All these results have demonstrated that the central metal ions have great effects on the organization and formation of the films.

  12. Analytical Solitons for Langmuir Waves in Plasma Physics with Cubic Nonlinearity and Perturbations

    Science.gov (United States)

    Zhou, Qin; Mirzazadeh, M.

    2016-09-01

    We presented an analytical study on dynamics of solitons for Langmuir waves in plasma physics. The mathematical model is given by the perturbed nonlinear Schrödinger equation with full nonlinearity and Kerr law nonlinearity. There are three techniques of integrability were employed to extract exact solutions along with the integrability conditions. The topological 1-soliton solutions, singular 1-soliton solutions, and plane wave solution were reported by Ricatti equation expansion approach and then the bright 1-soliton solution, singular 1-soliton solution, periodic singular solutions, and plane wave solution were derived with the help of trial solution method. Finally, based on the G'/G-expansion scheme, we obtained the hyperbolic function travelling wave solution, trigonometric function travelling wave solution, and plane wave solution.

  13. Langmuir-Blodgett mono- and multilayers of (di)alkoxy-substituted poly(p-phenylenevinylene) precursor polymers. 1. Langmuir monolayers of homo- and copolymers of (di)alkoxy-substituted precursor PPVs

    NARCIS (Netherlands)

    Hagting, J.G.; Vos, R.E.T.P. de; Sinkovics, K.; Vorenkamp, E.J.; Schouten, A.J.

    1999-01-01

    The Langmuir monolayer behavior of (di)alkoxy-substituted precursor poly(p-phenylenevinylenes) (PPVs) with a methoxy-leaving group was studied. The average orientation of the aromatic ring and the ether groups at the air-water interface was elucidated by external F-T-infrared reflection spectroscopy

  14. LANGMUIR-BLODGETT-FILMS OF AMYLOSE ACETATE/DYE MIXTURES .1. MONOLAYER BEHAVIOR OF MIXTURES OF AMYLOSE ACETATE AND A CHIRAL PARA-NITROAZOBIS[BENZENE] DYE

    NARCIS (Netherlands)

    SCHOONDORP, MA; SCHOUTEN, AJ; HULSHOF, JBE; FERINGA, BL; OOSTERGETEL, GT

    The monolayer behavior at the air-water interface of a chiral nonlinear optical dye was evaluated. The dye alone, an ester of palmitic acid and 4-nitro-4'-[(3R)-hydroxypyrrolidino]-1,1'-azobis[benzene], did not form a stable monolayer at 23-degrees-C at the air-water interface. However, mixtures of

  15. Langmuir-Blodgett Films of Amylose Acetate/Dye Mixtures. 1. Monolayer Behavior of Mixtures of Amylose Acetate and a Chiral p-Nitroazobis[benzene] Dye

    NARCIS (Netherlands)

    Schoondorp, Monique A.; Schouten, Arend Jan; Hulshof, Johannes; Feringa, Ben L.; Oostergetel, Gerrit T.

    1992-01-01

    The monolayer behavior at the air-water interface of a chiral nonlinear optical dye was evaluated. The dye alone, an ester of palmitic acid and 4-nitro-4'-[(3R)-hydroxypyrrolidino]-1,1'-azobis[benzene], did not form a stable monolayer at 23 °C at the air-water interface. However, mixtures of the dye

  16. Self-Assembly, Interfacial Nanostructure, and Supramolecular Chirality of the Langmuir-Blodgett Films of Some Schiff Base Derivatives without Alkyl Chain

    Directory of Open Access Journals (Sweden)

    Tifeng Jiao

    2013-01-01

    Full Text Available A special naphthyl-containing Schiff base derivative, N,N′-bis(2-hydroxy-1-naphthylidene-1,2-phenylenediamine, was synthesized, and its coordination with various metal ions in situ at the air/water interface has been investigated. Although the ligand contains no alkyl chain, it can be spread on water surface. When metal ions existed in the subphase, an interfacial coordination between the ligand and different metal ions occurred in the spreading film, while different Nanostructures were fabricated in the monolayers. Interestingly to note that among various metal ions, only the in situ coordination-induced Cu(II-complex film showed supramolecular chirality, although the multilayer films from the ligand or preformed complex are achiral. The chirality of the in situ Cu(II-coordinated Langmuir film was developed due to the special distorted coordination reaction and the spatial limitation at the air/water interface. A possible organization mechanism at the air/water interface was suggested.

  17. Thermal behavior of H-aggregate in a mixed Langmuir-Blodgett film of merocyanine dye, arachidic acid, and n-octadecane ternary system investigated by UV-visible and IR absorption spectroscopy.

    Science.gov (United States)

    Hirano, Yoshiaki; Tateno, Shinsuke; Yamashita, Yoshihide; Ozaki, Yukihiro

    2008-11-13

    We have investigated the thermal behavior of H-aggregate in a mixed Langmuir-Blodgett (LB) film of the merocyanine dye (MS18)-arachidic acid (C20)- n-octadecane (AL18) ternary system by means of UV-visible and IR absorption spectroscopy in the range from 25 to 250 degrees C with a continuous scan. The results of both UV-visible and IR spectra indicate that the temperature-dependent variation in MS 18 aggregation state is linked not only with the degree of intramolecular charge transfer and the behavior of packing, orientation, conformation, and thermal mobility of the MS18 hydrocarbon chain but also with the presence and absence of AL18. The H-aggregate dissociates from 25 up to 50 degrees C, which is caused by the AL18 evaporation from the mixed LB film and the increment of thermal mobility of the MS18 hydrocarbon chain. From 110 to 160 degrees C, blue-shifted bands, attributed to the oligomeric MS18 aggregation, appear near 515 nm in the MS18-C 20-AL18 ternary system as well. The temperature at which the 515 nm band occurs is identical for both present ternary system and previously investigated MS18-deuterated arachidic acid (C20- d) binary system, and it is in good agreement with the melting point (110 degrees C) of cadmium arachidate (CdC20). Therefore, it is indicated that the driving force which induces the 515 nm band comes from the melting phenomenon of CdC20 molecules which are phase-separated from MS 18 molecules in as-deposited LB films.

  18. Thermal behavior of J-aggregates in mixed Langmuir-Blodgett films composed of merocyanine dye and deuterated arachidic acid investigated by UV-visible and infrared absorption spectroscopy.

    Science.gov (United States)

    Hirano, Yoshiaki; Tateno, Shinsuke; Ozaki, Yukihiro

    2007-06-19

    We have investigated the thermal behavior of J-aggregates in the mixed Langmuir-Blodgett (LB) films composed of the merocyanine dye (MS18)-deuterated arachidic acid (C20-d) binary system in the temperature range from 25 to 250 degrees C by means of UV-visible and IR transmission absorption spectroscopy. The temperature-dependent variations in both UV-visible and IR absorption spectra indicate that the MS18 aggregation states are linked with the MS18 intramolecular charge transfer and the behavior of the packing, orientation, conformation, and thermal mobility of the MS18 hydrocarbon chain. The J-aggregate formed at 25 degrees C in the mixed LB films dissociates in the temperature range from 25 to 110 degrees C, which is mainly ascribed to the increase in the thermal mobility of MS18 hydrocarbon chain and the dissociation of the chelation by a cadmium ion to the MS18 keto group. A thermally induced blue-shifted band appears at around 515 nm from 110 to 160 degrees C. This band is attributed to oligomeric aggregation with side-by-side alignment of the MS18 transition dipole moments on the basis of the shift to a higher-energy side, broadening, and temporary increment of the MS18 intramolecular charge transfer of the band. Consequently, the appearance of the thermally induced blue-shifted band indicates the possibility that the MS18 aggregation states can be controlled from the red shift to the blue shift by the annealing method adopted in the present study.

  19. Langmuir Blodgett multilayers and related nanostructures

    Indian Academy of Sciences (India)

    S S Major, S S Talwar and R S Srinivasa for 50 mol% CdA or more (not shown here) the scissoring band doublet dominates and resembles the features associated with pure CdA multilayer. Figure 5 shows the corresponding X-ray reflectivity scans of these multilayers showing third and higher order Bragg reflections.

  20. Statistical analysis of nonlinear wave interaction in simulated Langmuir turbulence data

    Czech Academy of Sciences Publication Activity Database

    Souček, Jan; Dudok de Wit, T.; Krasnoselskikh, V.; Volokitin, A.

    2003-01-01

    Roč. 21, - (2003), s. 681-692 ISSN 0992-7689 R&D Projects: GA ČR GA205/01/1064 Grant - others:CNRS(FR) PICS 1175 Institutional research plan: CEZ:AV0Z3042911 Keywords : space plasma physics * wave-wave interactions * experimental and matehmatical techniques * nonlinear phenomena Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.031, year: 2003

  1. Functional 2D nanomaterials for optoelectronics based on langmuir bacteriorhodopsin films

    Directory of Open Access Journals (Sweden)

    Sergei I. Valyansky

    2016-09-01

    Full Text Available We have tested the possibility of using monomolecular layers of bacteriorhodopsin (BR for the synthesis of highly sensitive and highly selective sensors based on second harmonic generation and surface plasma waves. We have used various methods to study the optical and nonlinear optical properties of Langmuir-Blodgett films of BR in order to clarify the extent to which specific properties of BR molecules are retained during their transfer from the surface of water to a solid substrate. We show that the second harmonic generation method is efficient for analyzing the molecular orientation and quality of Langmuir-Blodgett films. The experimental nonlinear optical susceptibility of second order BR molecules is 3.4·10−11 m/V. The relative change in the resonant wave vector is (3.6±0.1·10−2 at an excitation light wavelength of 630 nm. We have obtained a BR spectrum with the effective excitation by incident radiation of surface plasma waves. On the basis of these studies, we have proposed new schemes of biosensors operating on the basis of second harmonic generation and surface plasma resonance caused by fundamental frequency reflection from BR monomolecular layers. This scheme was tested for a model device and demonstrated the possibility of obtaining sensitivities of the order of 1011 molecules/cm3.

  2. Cathode liminescence properties of organic lengmuir-blodgett films

    CERN Document Server

    Voronkina, N I; L'vov, A N; Skibin, V I

    2001-01-01

    Some investigation results of the beta-sensitivity of organic Langmuir-Blodgett (LB) films irradiated with an electron beam are described. The dependences of the integral luminescence (DELTA lambda=380-450nm) on the electron energy (0.2...6kV) with a constant density (0.05...4.0 mu A/cm sup 2) are represented. The possible spheres of LB films application as scintillator detectors of ionizing radiation are discussed.

  3. A Langmuir study of novel Schiff Base ligand for ion sensor application

    African Journals Online (AJOL)

    Two novel Schiff Base ligands are used in this work. These amphiphilic ligands were being chosen because of the suitability in forming Langmuir film by using Langmuir-Blodgett (LB) technique. Characterizations of these ligands were carried out through LB technique to obtain the surface pressure-mean molecular area ...

  4. Structural characterization of a mixed Langmuir-Blodgett film of a merocyanine dye derivative-deuterated arachidic acid binary system and the influence of successive hydrothermal treatment in the liquid phase on the film as investigated by polarized UV-visible and IR absorption spectroscopy.

    Science.gov (United States)

    Hirano, Yoshiaki; Yamazaki, Asuka; Maio, Ari; Kitahama, Yasutaka; Ozaki, Yukihiro

    2010-08-26

    We have investigated the structure of the mixed Langmuir-Blodgett (LB) film of a merocyanine dye derivative (MO(18))-deuterated arachidic acid (C(20)-d) binary system and the influence of successive hydrothermal treatment in the liquid phase (HTTL) on the mixed LB film by means of polarized UV-visible and IR absorption spectroscopy. The visible absorption band with in-plane anisotropy at 503 nm before HTTL transforms into an absorption band with in-plane isotropy at 557 nm after HTTL for 16-18 min through a peak maximum near 520 nm after HTTL for 2-12 min. The degree of total MO(18) intramolecular charge transfer for the 503 nm band is the largest among those for all of the bands. Therefore, the 503 nm band is ascribed to the MO(18) H-like aggregation, based on its shape, peak height, and in-plane anisotropy, the subsequent change to two kinds of visible peaks by successive HTTL, and the most degree of MO(18) intramolecular charge transfer among all of the aggregation states. While the MO(18) hydrocarbon chain takes the all-trans conformation before HTTL, its conformation and orientation are most disarranged after HTTL for 2 min. Subsequently, the original conformation and orientation are recovered by degrees with successive HTTL, except after final HTTL for 18 min, when the orientation is again changed. On the other hand, the C(20)-d hydrocarbon chain maintains the all-trans conformation before and after HTTL. The orientation of the C(20)-d hydrocarbon chain after HTTL for 2 min is more ordered than that before HTTL, with the nature of the C(20)-d subcell packing changing from hexagonal to orthorhombic. During successive HTTL from 2 to 18 min, the C(20)-d orientation is gradually disorganized but with the orthorhombic nature remaining constant. Thus, the variations in the conformation and orientation of the MS(18) hydrocarbon chain and in the orientation of the C(20)-d hydrocarbon chain tend to change from ordered and disordered structures and turn to more

  5. Hot-electron generation by “cavitating” Langmuir turbulence in the nonlinear stage of the two-plasmon–decay instability

    International Nuclear Information System (INIS)

    Vu, H. X.; DuBois, D. F.; Russell, D. A.; Myatt, J. F.

    2012-01-01

    The kinetic reduced-description particle-in-cell simulation technique has been applied to study the nonlinear stage of two-plasmon–decay (TPD) instability in an inhomogeneous plasma driven by crossed laser beams. The TPD instability is found to be a prolific generator of “cavitating” Langmuir turbulence. Langmuir “cavitons”—localized longitudinal electric fields, oscillating near the local electron plasma frequency, trapped in ponderomotive density depressions—collapse to dimensions of a few electron Debye lengths, where the electric field energy is collisionlessly transferred to electron kinetic energy. The resulting hot electrons can attain instantaneous temperatures up to 100 keV with net suprathermal heat flux out of the system of up to a few percent of the input laser energy. Scaling laws for this hot-electron generation by TPD, in regimes motivated by recent experiments on the Omega laser, were presented recently by Vu et al. (H. X. Vu, D. F. DuBois, D. A. Russell, and J. F. Myatt, Phys. Plasmas 19, 102703 (2012)). This paper concentrates on the microscopic mechanisms for hot-electron generation. The spatial distribution of the maxima of the electric field envelope modulus is found to be very spiky, with the distribution of electric field envelope maxima obeying Gaussian statistics. The cavitons are produced in density-depletion trenches produced by the combined ponderomotive interference of the crossed laser beams and the ponderomotive beats of the primary backward-going TPD Langmuir waves (LWs) resulting from the crossed beams. The Langmuir turbulence is strongest in the electron-density region near 0.241× the laser's critical density, where the forward LWs from the crossed-beam TPD are degenerate. Nucleation of cavitons is assisted by the modulation of the electron density in the trenches, which in turn is caused by the beating of the common forward-going LW and the pair of backward-going LWs. The autocorrelation function of the LW envelope

  6. Irving Langmuir

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 13; Issue 7. Irving Langmuir - A Pioneering Industrial Physical Chemist. Anil K Rajvanshi. General Article Volume 13 Issue 7 July 2008 pp 619-626. Fulltext. Click here to view fulltext PDF. Permanent link:

  7. Langmuir and Langmuir–Blodgett films of capsules of haemoglobin ...

    Indian Academy of Sciences (India)

    Abstract. Organized assemblies of capsules of haemoglobin (Hb), in the size range of 0.1 to 0.3 μ in Lang- muir films have been studied at air/water interface below and above the isoelectric point. Spread films of these organizates suggest that there is no expulsion of individual particles or particle assemblies at the interface ...

  8. Topics in strong Langmuir turbulence

    International Nuclear Information System (INIS)

    Skoric, M.M.

    1981-01-01

    This thesis discusses certain aspects of the turbulence of a fully ionised non-isothermal plasma dominated by the Langmuir mode. Some of the basic properties of strongly turbulent plasmas are reviewed. In particular, interest is focused on the state of Langmuir turbulence, that is the turbulence of a simple externally unmagnetized plasma. The problem of the existence and dynamics of Langmuir collapse is discussed, often met as a non-linear stage of the modulational instability in the framework of the Zakharov equations (i.e. simple time-averaged dynamical equations). Possible macroscopic consequences of such dynamical turbulent models are investigated. In order to study highly non-linear collapse dynamics in its advanced stage, a set of generalized Zakharov equations are derived. Going beyond the original approximation, the author includes the effects of higher electron non-linearities and a breakdown of slow-timescale quasi-neutrality. He investigates how these corrections may influence the collapse stabilisation. Recently, it has been realised that the modulational instability in a Langmuir plasma will be accompanied by the collisionless-generation of a slow-timescale magnetic field. Accordingly, a novel physical situation has emerged which is investigated in detail. The stability of monochromatic Langmuir waves in a self-magnetized Langmuir plasma, is discussed, and the existence of a novel magneto-modulational instability shown. The wave collapse dynamics is investigated and a physical interpretation of the basic results is given. A problem of the transient analysis of an interaction of time-dependent electromagnetic pulses with linear cold plasma media is investigated. (Auth.)

  9. Eigenmode Structure in Solar Wind Langmuir Waves

    Science.gov (United States)

    Malaspina, D. M.; Ergun, R.; Bougeret, J.; Kaiser, M. L.; Bale, S.; Cairns, I. H.; Cattell, C. A.; Kellogg, P. J.; Newman, D. L.

    2007-12-01

    Bursty Langmuir waves associated with space plasma phenomena including type II and type III solar radio bursts, auroral field-aligned electrons, and radiation from shocks often exhibit localized beat-type waveforms. A consensus view on the modulation mechanism remains elusive. Current theories include multi-wave interactions, turbulence, or non-linear growth such as kinetic localization. Most of these theories start with the assumption that the density of the background plasma is near-uniform, in spite of numerous observations to the contrary. An alternative approach is to start with the assumption that density perturbations pre-exist. We construct an analytical electric field solution, describing Langmuir waves as a combination of trapped eigenmodes within a parabolic density well. This hypothesis is supported by discreet frequency structure in auroral Langmuir wave observations observed to be associated with density fluctuations, and by the high degree of localization observed in solar wind borne Langmuir waves. This simple, one-dimensional model can reproduce waveform and frequency structure of localized Langmuir waves observed by STEREO/SWAVES. The waveforms can be reasonably reproduced using linear combinations of only a few low-mode eigenmode solutions. The eigenmode solutions are sensitive to plasma environmental parameters such as the electron temperature and solar wind velocity. The trapped-eigenmode solutions can form a theoretical basis to explore the non-linear behavior of Langmuir waves which may allow for efficient conversion and escape of electromagnetic emissions and second harmonic production.

  10. Thiophene-based monolayer OFETs prepared by Langmuir techniques

    Science.gov (United States)

    Agina, Elena V.; Sizov, Alexey S.; Anisimov, Daniil S.; Trul, Askold A.; Borshchev, Oleg V.; Paraschuk, Dmitry Y.; Shcherbina, Maxim A.; Chvalun, Sergey N.; Ponomarenko, Sergey A.

    2015-08-01

    A novel fast, easily processible and highly reproducible approach to thiophene-based monolayer OFETs fabrication by Langmuir-Blodgett or Langmuir-Schaefer techniques was developed and successfully applied. It is based on selfassembly of organosilicon derivatives of oligothiophenes or benzothienobenzothiophene on the water-air interface. Influence of the conjugation length and the anchor group chemistry of the self-assembling molecules on the monolayer structure and electric performance of monolayer OFETs was systematically investigated. The efficient monolayer OFETs with the charge carrier mobilities up to 0.01 cm2/Vs and on/off ratio up to 106 were fabricated, and their functionality in integrated circuits under normal air conditions was demonstrated.

  11. Formation and control of excimer of a coumarin derivative in Langmuir–Blodgett films

    International Nuclear Information System (INIS)

    Chakraborty, Santanu; Bhattacharjee, D.; Hussain, Syed Arshad

    2014-01-01

    In this communication we report the formation and control of excimer of a coumerin derivative 7-Hydroxy-N-Octadecyl Coumarin-3-Carboxamide (7HNO3C) assembled onto Langmuir–Blodgett (LB) films. Surface pressure–area per molecule isotherm revealed that 7HNO3C formed stable Langmuir monolayer at the air–water interface. Spectroscoipic characterizations confirmed the formation of excimer of 7HNO3C in the LB film prepared at 20 mN/m surface pressure. The excimer band remains present even when 7HNO3C molecules are diluted with a long chain fatty acid stearic acid in LB films. The excimer formation of 7HNO3C can be controlled by incorporating clay particle laponite in the LB film. The excimer band is totally absent in the hybrid 7HNO3C–laponite LB films. In-situ fluorescence imaging microscopy and atomic force microscopy confirmed the incorporation of clay laponite onto LB films. -- Highlights: • Formation of Langmuir monolayer and Langmuir–Blodgett (LB) film of a coumarin derivative. • Presence of excimeric species in the LB film lifted at 20 mN/m surface pressure is confirmed from the spectroscopic studies. • Control of excimer formation by incorporating clay particle laponite on to the LB film. • In-situ fluorescence imaging microscopy and atomic force microscopy confirmed the incorporation of clay laponite onto LB films

  12. Formation and control of excimer of a coumarin derivative in Langmuir–Blodgett films

    Energy Technology Data Exchange (ETDEWEB)

    Chakraborty, Santanu; Bhattacharjee, D.; Hussain, Syed Arshad, E-mail: sa_h153@hotmail.com

    2014-01-15

    In this communication we report the formation and control of excimer of a coumerin derivative 7-Hydroxy-N-Octadecyl Coumarin-3-Carboxamide (7HNO3C) assembled onto Langmuir–Blodgett (LB) films. Surface pressure–area per molecule isotherm revealed that 7HNO3C formed stable Langmuir monolayer at the air–water interface. Spectroscoipic characterizations confirmed the formation of excimer of 7HNO3C in the LB film prepared at 20 mN/m surface pressure. The excimer band remains present even when 7HNO3C molecules are diluted with a long chain fatty acid stearic acid in LB films. The excimer formation of 7HNO3C can be controlled by incorporating clay particle laponite in the LB film. The excimer band is totally absent in the hybrid 7HNO3C–laponite LB films. In-situ fluorescence imaging microscopy and atomic force microscopy confirmed the incorporation of clay laponite onto LB films. -- Highlights: • Formation of Langmuir monolayer and Langmuir–Blodgett (LB) film of a coumarin derivative. • Presence of excimeric species in the LB film lifted at 20 mN/m surface pressure is confirmed from the spectroscopic studies. • Control of excimer formation by incorporating clay particle laponite on to the LB film. • In-situ fluorescence imaging microscopy and atomic force microscopy confirmed the incorporation of clay laponite onto LB films.

  13. Statistical theory of Langmuir turbulence

    International Nuclear Information System (INIS)

    DuBois, D.F.; Rose, H.A.; Goldman, M.V.

    1979-01-01

    A statistical theory of Langmuir turbulence is developed by applying a generalization of the direction interaction approximation (DIA) of Kraichnan to the Zakharov equations describing Langmuir turbulence. 7 references

  14. Nanoparticle assembly following Langmuir-Hinshelwood kinetics on a Langmuir film and chain networks captured in LB films.

    Science.gov (United States)

    Maganti, Lasya; Jash, Madhuri; Nair, Anju; Radhakrishnan, T P

    2015-03-21

    The Langmuir-Blodgett (LB) technique is an elegant protocol for the steered assembly of metal nanoparticles, the deposition pressure serving as a convenient parameter to tune the assembly. Adsorption of nanoparticles from the subphase to the air-water interface can provide further control of the process. Citrate-stabilized gold nanoparticles in the aqueous subphase are shown to assemble into extended 2-dimensional chain networks following adsorption on a cationic amphiphile Langmuir film at the air-water interface. Kinetic investigations show that the process can be visualized as a surface-catalyzed reaction and explained in terms of the Langmuir-Hinshelwood mechanism. The LB deposition proves to be a unique route to capture the reaction product together with the amphiphile film. The deposition pressure is used to tune the density of nanoparticle chain networks in the LB film, and their optical extinction spectrum. The unusual blue shift of the extinction observed with increasing deposition pressure is attributed to the impact of the amphiphile monolayer environment. The extent of formation of the chain network is analyzed in terms of the pathways in the corresponding graph representation, and shown to scale with the deposition pressure. The current investigation highlights the use of a charged monolayer as a heterogeneous catalyst surface, provides fundamental insight into the kinetics of nanoparticle assembly at interfaces, and demonstrates the utility of the LB technique in tuning the formation of 2-dimensional nanoparticle chain networks.

  15. Organization of copper nanoclusters in Langmuir–Blodgett films

    Indian Academy of Sciences (India)

    Stable nanoclusters of Cu were synthesized using Langmuir–Blodgett films of octadecylsuccinic acid (ODSA) as template. The Langmuir–Blodgett films of ODSA formed from subphase containing copper ions were first subjected to sulphidation (S) using sodium sulphide and then hydrogenated (H) using hydrogen gas.

  16. Block copolymer assisted self-assembly of nanoparticles into Langmuir–Blodgett films: Effect of polymer concentration

    Energy Technology Data Exchange (ETDEWEB)

    Martín-García, Beatriz; Velázquez, M. Mercedes, E-mail: mvsal@usal.es

    2013-08-15

    We propose to use the self-assembly ability of a block copolymer to obtain CdSe quantum dots (QDs) structures of different morphology. The methodology proposed consist in transferring mixed Langmuir monolayers of QDs and the polymer poly (styrene-co-maleic anhydride) partial 2 buthoxy ethyl ester cumene terminated, PS-MA-BEE onto mica by the Langmuir–Blodgett (LB) methodology. The morphology of the LB films was analyzed by AFM and TEM measurements. Our results show that it is possible to modulate the self-assembly process by modifying the composition of the mixed Langmuir monolayer precursor of the LB film. The different morphologies are interpreted according to two different dewetting mechanisms, growth of holes and spinodal-like dewetting. The growth of holes dewetting process is driven by gravitatory effects and was observed for LB films obtained by transferring Langmuir monolayer of the smallest elasticity values in which the polymer is in brush conformation. The spinodal dewetting mechanism prevailed when the Langmuir monolayer presents the highest elasticity values. - Graphical abstract: Display Omitted - Highlights: • Effect of the surface composition on the LB films architecture. • QDs/polymer LB films morphology interpreted in terms of dewetting mechanism. • The dewetting mechanism depends on the Langmuir monolayer state.

  17. Synthesis of Triptycene-Based Molecular Rotors for Langmuir-Blodgett Monolayers

    Czech Academy of Sciences Publication Activity Database

    Kaleta, Jiří; Kaletová, Eva; Císařová, I.; Teat, S. J.; Michl, Josef

    2015-01-01

    Roč. 80, č. 20 (2015), s. 10134-10150 ISSN 0022-3263 EU Projects: European Commission(XE) 227756 - DIPOLAR ROTOR ARRAY Institutional support: RVO:61388963 Keywords : surface inclusion * films * arrays Subject RIV: CC - Organic Chemistry Impact factor: 4.785, year: 2015

  18. Langmuir-Blodgett film formation and second-harmonic generation of poly(isocyanide)s

    NARCIS (Netherlands)

    Teerenstra, Marcel Nicolaas

    1995-01-01

    Het doel van het beschreven onderzoek is het maken en bestuderen van dunne polymere films die een stabiele en hoge tweede-orde niet-lineair optische (NLO) activiteit bezitten. Deze films kunnen toegepast worden in bijvoorbeeld optische schakelaars die nodig zijn voor optische signaalverwerking. In

  19. Average Orientation of a Molecular Rotor Embedded in a Langmuir-Blodgett Monolayer

    Czech Academy of Sciences Publication Activity Database

    Casher, D. L.; Kobr, L.; Michl, Josef

    2012-01-01

    Roč. 28, č. 2 (2012), s. 1625-1637 ISSN 0743-7463 Institutional research plan: CEZ:AV0Z40550506 Keywords : infrared reflection spectroscopy * self-assembled monolayers * electric-field * linear dichroism * fatty-acids Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.187, year: 2012

  20. QDs Supported on Langmuir-Blodgett Films of Polymers and Gemini Surfactant

    Directory of Open Access Journals (Sweden)

    T. Alejo

    2013-01-01

    Full Text Available Different LB films of poly(octadecene-co-maleic anhydride, PMAO, poly(styrene-co-maleic anhydride partial 2 butoxy ethyl ester cumene terminated, PS-MA-BEE, and Gemini surfactant ethyl-bis(dimethyl octadecylammonium bromide, 18-2-18, have been used to study the effect of the substrate coating on the surface self-assembly of CdSe quantum dots (QDs. Results show that all the “coating molecules” avoid the 3D aggregation of QDs observed when these nanoparticles are directly deposited on mica. Different morphologies were observed depending on the molecules used as coatings, and this was related to the surface properties, such as wetting ability, and the morphology of the coating LB films.

  1. Structural studies of Langmuir-Blodgett films containing rare-earth metal cations

    DEFF Research Database (Denmark)

    Khomutov, G.B.; Antipina, M.N.; Bykov, I.V.

    2002-01-01

    chloride subphases had substantially different structure. The gadolinium stearate LB films formed with gadolinium acetate subphase were highly ordered and consisted of hexagonal layers with unit cell parameter a approximate to 4.8 Angstrom and interlayer spacing d approximate to 49 Angstrom. LB films...

  2. Dispersions of Electroabsorption Susceptibilities: Application to a Polymeric Langmuir-Blodgett Film

    National Research Council Canada - National Science Library

    Yang, K

    1997-01-01

    ...,... are derivatives of their next lower order polarizabilities, with respect to the effective internal field F across the polarizable p-conjugated systems, and that these derivative relationships...

  3. Polysarcosine-Based Lipids: From Lipopolypeptoid Micelles to Stealth-Like Lipids in Langmuir Blodgett Monolayers

    Directory of Open Access Journals (Sweden)

    Benjamin Weber

    2016-12-01

    Full Text Available Amphiphiles and, in particular, PEGylated lipids or alkyl ethers represent an important class of non-ionic surfactants and have become key ingredients for long-circulating (“stealth” liposomes. While poly-(ethylene glycol (PEG can be considered the gold standard for stealth-like materials, it is known to be neither a bio-based nor biodegradable material. In contrast to PEG, polysarcosine (PSar is based on the endogenous amino acid sarcosine (N-methylated glycine, but has also demonstrated stealth-like properties in vitro, as well as in vivo. In this respect, we report on the synthesis and characterization of polysarcosine based lipids with C14 and C18 hydrocarbon chains and their end group functionalization. Size exclusion chromatography (SEC and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS analysis reveals that lipopeptoids with a degree of polymerization between 10 and 100, dispersity indices around 1.1, and the absence of detectable side products are directly accessible by nucleophilic ring opening polymerization (ROP. The values for the critical micelle concentration for these lipopolymers are between 27 and 1181 mg/L for the ones with C18 hydrocarbon chain or even higher for the C14 counterparts. The lipopolypeptoid based micelles have hydrodynamic diameters between 10 and 25 nm, in which the size scales with the length of the PSar block. In addition, C18PSar50 can be incorporated in 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC monolayers up to a polymer content of 3%. Cyclic compression and expansion of the monolayer showed no significant loss of polymer, indicating a stable monolayer. Therefore, lipopolypeptoids can not only be synthesized under living conditions, but my also provide a platform to substitute PEG-based lipopolymers as excipients and/or in lipid formulations.

  4. Structural Study of Langmuir-Blodgett Mono- and Multilayers of Poly(β-hydroxybutyrate)

    NARCIS (Netherlands)

    Lambeek, G.; Vorenkamp, E.J.; Schouten, A.J.

    1995-01-01

    In this study poly(β-hydroxybutyrate) (PHB) was used as a spreading material to form LB monolayers at the air-water interface. Isotherms were found to show a transition at about 14 mN/m that is argued to be associated with a phase transition in the monolayer. Stable monolayers could be obtained at

  5. Finite-size scaling of flexoelectricity in Langmuir-Blodgett polymer thin films

    Science.gov (United States)

    Poddar, Shashi; Foreman, Keith; Adenwalla, Shireen; Ducharme, Stephen

    2016-01-01

    The flexoelectric effect, which is a linear coupling between a strain gradient and electrical polarization, is a fundamental electromechanical property of all materials with potential for use in nanoscale devices, where strain gradients can be quite large. We report a study of the dependence of the flexoelectric response on thickness in ultrathin films of polar and non-polar polymers. The measurements of the flexoelectric response in non-polar polyethylene and the polar relaxor polymer polyvinylidene-co-trifluoroethylene-co-chlorofluoroethylene were made using a bent cantilever method and corrected for the contribution from the electrode oxide. The results show that the value of the flexoelectric coefficient increases with decreasing thickness, by up to a factor of 70 compared to the bulk value, reaching such enhanced values in films of only 10 nm thickness. These results are consistent with a model accounting for interfacial contributions, and underline how large electromechanical coupling can be produced at the nanoscale. The results also distinguish the surface flexoelectric response from that coming from the volume.

  6. Resonance effects in Raman scattering of quantum dots formed by the Langmuir-Blodgett method

    Energy Technology Data Exchange (ETDEWEB)

    Milekhin, A G; Sveshnikova, L L; Duda, T A [Institute of Semiconductor Physics, Lavrentjev av.13, 630090, Novosibirsk (Russian Federation); Surovtsev, N V; Adichtchev, S V [Institute of Automation and Electrometry, Koptyug av.1, 630090, Novosibirsk (Russian Federation); Azhniuk, Yu M [Institute of Electron Physics, Universytetska Str. 21, 88017, Uzhhorod (Ukraine); Himcinschi, C [Institut fuer Theoretische Physik, TU Bergakademie Freiberg, Leipziger Str. 23, 09596, Freiberg (Germany); Kehr, M; Zahn, D R T, E-mail: milekhin@thermo.isp.nsc.r [Semiconductor Physics, Chemnitz University of Technology, Chemnitz (Germany)

    2010-09-01

    The enhancement of Raman scattering by optical phonon modes in quantum dots was achieved in resonant and surface-enhanced Raman scattering experiments by approaching the laser energy to the energy of either the interband transitions or the localized surface plasmons in silver nanoclusters deposited onto the nanostructures. Resonant Raman scattering by TO, LO, and SO phonons as well as their overtones was observed for PbS, ZnS, and ZnO quantum dots while enhancement for LO and SO modes in CdS quantum dots with a factor of about 700 was measured in surface enhanced Raman scattering experiments. Multiple phonon Raman scattering observed up to 5th and 7th order for CdS and ZnO, respectively, confirms the high crystalline quality of the grown QDs.

  7. Distance-dependent energy transfer between indole and anthracene moieties in Langmuir Blodgett films

    Science.gov (United States)

    Saha, D. C.; Bhattacharjee, D.; Misra, T. N.

    1998-09-01

    1,2-Diphenyl indole (DPI) and 9,10-diphenyl anthracene (DPA) are non-amphiphilic molecules but form excellent LB films when mixed with stearic acid (SA). Spectroscopic investigations of these films indicate formation of aggregates of DPI and DPA in the mixed LB films. DPA has been used as the quencher of the fluorescence of the DPI donor. Distance-dependent energy transfer between donor and acceptor monolayers in the LB film, where they can be precisely separated by inert spacers of stearic acid layers of varied thickness, is shown to satisfy Khun's quadratic equation. This suggests that the donor excitations are delocalized. The large critical transfer distance estimated from the experimental results has been attributed to the formation of aggregates of the molecules in a LB monolayer.

  8. Nonlinear optical polymers for electro-optic signal processing

    Science.gov (United States)

    Lindsay, Geoffrey A.

    1991-01-01

    Photonics is an emerging technology, slated for rapid growth in communications systems, sensors, imagers, and computers. Its growth is driven by the need for speed, reliability, and low cost. New nonlinear polymeric materials will be a key technology in the new wave of photonics devices. Electron-conjubated polymeric materials offer large electro-optic figures of merit, ease of processing into films and fibers, ruggedness, low cost, and a plethora of design options. Several new broad classes of second-order nonlinear optical polymers were developed at the Navy's Michelson Laboratory at China Lake, California. Polar alignment in thin film waveguides was achieved by electric-field poling and Langmuir-Blodgett processing. Our polymers have high softening temperatures and good aging properties. While most of the films can be photobleached with ultraviolet (UV) light, some have excellent stability in the 500-1600 nm range, and UV stability in the 290-310 nm range. The optical nonlinear response of these polymers is subpicosecond. Electro-optic switches, frequency doublers, light modulators, and optical data storage media are some of the device applications anticipated for these polymers.

  9. Local Environment and Interactions of Liquid and Solid Interfaces Revealed by Spectral Line Shape of Surface Selective Nonlinear Vibrational Probe

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Shun-Li; Fu, Li; Chase, Zizwe A.; Gan, Wei; Wang, Hong-Fei

    2016-11-10

    Vibrational spectral lineshape contains important detailed information of molecular vibration and reports its specific interactions and couplings to its local environment. In this work, recently developed sub-1 cm-1 high-resolution broadband sum frequency generation vibrational spectroscopy (HR-BB-SFG-VS) was used to measure the -C≡N stretch vibration in the 4-n-octyl-4’-cyanobiphenyl (8CB) Langmuir or Langmuir-Blodgett (LB) monolayer as a unique vibrational probe, and the spectral lineshape analysis revealed the local environment and interactions at the air/water, air/glass, air/calcium fluoride and air/-quartz interfaces for the first time. The 8CB Langmuir or LB film is uniform and the vibrational spectral lineshape of its -C≡N group has been well characterized, making it a good choice as the surface vibrational probe. Lineshape analysis of the 8CB -C≡N stretch SFG vibrational spectra suggests the coherent vibrational dynamics and the structural and dynamic inhomogeneity of the -C≡N group at each interface are uniquely different. In addition, it is also found that there are significantly different roles for water molecules in the LB films on different substrate surfaces. These results demonstrated the novel capabilities of the surface nonlinear spectroscopy in characterization and in understanding the specific structures and chemical interactions at the liquid and solid interfaces in general.

  10. LANGMUIR WAVE DECAY IN INHOMOGENEOUS SOLAR WIND PLASMAS: SIMULATION RESULTS

    Energy Technology Data Exchange (ETDEWEB)

    Krafft, C. [Laboratoire de Physique des Plasmas, Ecole Polytechnique, F-91128 Palaiseau Cedex (France); Volokitin, A. S. [IZMIRAN, Troitsk, 142190, Moscow (Russian Federation); Krasnoselskikh, V. V., E-mail: catherine.krafft@u-psud.fr [Laboratoire de Physique et Chimie de l’Environnement et de l’Espace, 3A Av. de la Recherche Scientifique, F-45071 Orléans Cedex 2 (France)

    2015-08-20

    Langmuir turbulence excited by electron flows in solar wind plasmas is studied on the basis of numerical simulations. In particular, nonlinear wave decay processes involving ion-sound (IS) waves are considered in order to understand their dependence on external long-wavelength plasma density fluctuations. In the presence of inhomogeneities, it is shown that the decay processes are localized in space and, due to the differences between the group velocities of Langmuir and IS waves, their duration is limited so that a full nonlinear saturation cannot be achieved. The reflection and the scattering of Langmuir wave packets on the ambient and randomly varying density fluctuations lead to crucial effects impacting the development of the IS wave spectrum. Notably, beatings between forward propagating Langmuir waves and reflected ones result in the parametric generation of waves of noticeable amplitudes and in the amplification of IS waves. These processes, repeated at different space locations, form a series of cascades of wave energy transfer, similar to those studied in the frame of weak turbulence theory. The dynamics of such a cascading mechanism and its influence on the acceleration of the most energetic part of the electron beam are studied. Finally, the role of the decay processes in the shaping of the profiles of the Langmuir wave packets is discussed, and the waveforms calculated are compared with those observed recently on board the spacecraft Solar TErrestrial RElations Observatory and WIND.

  11. Self-consistent Langmuir waves in resonantly driven thermal plasmas

    International Nuclear Information System (INIS)

    Lindberg, R. R.; Charman, A. E.; Wurtele, J. S.

    2007-01-01

    The longitudinal dynamics of a resonantly driven Langmuir wave are analyzed in the limit that the growth of the electrostatic wave is slow compared to the bounce frequency. Using simple physical arguments, the nonlinear distribution function is shown to be nearly invariant in the canonical particle action, provided both a spatially uniform term and higher-order spatial harmonics are included along with the fundamental in the longitudinal electric field. Requirements of self-consistency with the electrostatic potential yield the basic properties of the nonlinear distribution function, including a frequency shift that agrees closely with driven, electrostatic particle simulations over a range of temperatures. This extends earlier work on nonlinear Langmuir waves by Morales and O'Neil [G. J. Morales and T. M. O'Neil, Phys. Rev. Lett. 28, 417 (1972)] and Dewar [R. L. Dewar, Phys. Plasmas 15, 712 (1972)], and could form the basis of a reduced kinetic treatment of plasma dynamics for accelerator applications or Raman backscatter

  12. Ammonia at Blodgett Forest, Sierra Nevada, USA

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, Marc L.; Littlejohn, David

    2007-11-06

    Ammonia is a reactive trace gas that is emitted in large quantities by animal agriculture and other sources in California, which subsequently forms aerosol particulate matter, potentially affecting visibility, climate, and human health. We performed initial measurements of NH{sub 3} at the Blodgett Forest Research Station (BFRS) during a two week study in June, 2006. The site is used for ongoing air quality research and is a relatively low-background site in the foothills of the Sierra Nevada. Measured NH{sub 3} mixing ratios were quite low (< 1 to {approx} 2 ppb), contrasting with typical conditions in many parts of the Central Valley. Eddy covariance measurements showed NH{sub 3} fluxes that scaled with measured NH{sub 3} mixing ratio and calculated aerodynamic deposition velocity, suggesting dry deposition is a significant loss mechanism for atmospheric NH{sub 3} at BFRS. A simple model of NH{sub 3} transport to the site supports the hypothesis that NH{sub 3} is transported from the Valley to BFRS, but deposits on vegetation during the summer. Further work is necessary to determine whether the results obtained in this study can be generalized to other seasons.

  13. Measurements of Ammonia at Blodgett Forest

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, Marc L.; Littlejohn, David

    2007-04-01

    Ammonia is a reactive trace gas that is emitted in large quantities by animal agriculture and other sources in California, which subsequently forms aerosol particulate matter, potentially affecting visibility, climate, and human health. We performed initial measurements of NH{sub 3} at the Blodgett Forest Research Station (BFRS) during a 3 week study in June, 2006. The site is used for ongoing air quality research and is a relatively low-background site in the foothills of the Sierra Nevada. Measured NH{sub 3} mixing ratios were quite low (< 1 to {approx}2 ppb), contrasting with typical conditions in many parts of the Central Valley. Eddy covariance measurements showed NH{sub 3} fluxes that scaled with measured NH{sub 3} mixing ratio and calculated aerodynamic deposition velocity, suggesting dry deposition is a significant loss mechanism for atmospheric NH{sub 3} at BFRS. A simple model of NH{sub 3} transport to the site supports the hypothesis that NH{sub 3} is transported from the Valley to BFRS, but deposits on vegetation during the summer. Further work is necessary to determine whether the results obtained in this study can be generalized to other seasons.

  14. Chorus Wave Modulation of Langmuir Waves in the Radiation Belts

    Science.gov (United States)

    Li, Jinxing; Bortnik, Jacob; An, Xin; Li, Wen; Thorne, Richard M.; Zhou, Meng; Kurth, William S.; Hospodarsky, George B.; Funsten, Herbert O.; Spence, Harlan E.

    2017-12-01

    Using high-resolution waveforms measured by the Van Allen Probes, we report a novel observation in the radiation belts. Namely, we show that multiband, discrete, rising-tone whistler mode chorus emissions exhibit a one-to-one correlation with Langmuir wave bursts. Moreover, the periodic Langmuir wave bursts are generally observed at the phase location where the chorus wave E|| component is oriented opposite to its propagation direction. The electron measurements show a beam in phase space density at the particle velocity that matches the parallel phase velocity of the chorus waves. Based on this evidence, we conclude that the chorus waves accelerate the suprathermal electrons via Landau resonance and generate a localized electron beam in phase space density. Consequently, the Langmuir waves are excited locally and are modulated by the chorus wave phase. This microscale interaction between chorus waves and high-frequency electrostatic waves provides a new insight into the nonlinear wave-particle interaction process.

  15. Dynamics of Langmuir and ion-sound waves in type III solar radio sources

    Science.gov (United States)

    Robinson, P. A.; Willes, A. J.; Cairns, I. H.

    1993-01-01

    The study traces the evolution of Langmuir and ion-sound waves in type III sources, incorporating linear growth, linear damping, and nonlinear electrostatic decay. Improved estimates are obtained for the wavenumber range of growing waves and the nonlinear coupling coefficient for the decay process. It is shown that the conditions in the solar wind do not allow a steady state to be attained; instead, bursty linear and nonlinear interactions take place, consistent with the highly inhomogeneous and impulsive waves actually observed. Nonlinear growth is found to be rapid enough to saturate the growth of the parent Langmuir waves in the available interaction time. The competing processes of nonlinear wave collapse and quasi-linear relaxation are discussed, and it is concluded that neither is responsible for the saturation of Langmuir growth.

  16. Langmuir wave turbulence generated by electromagnetic waves in the laboratory and the ionosphere

    International Nuclear Information System (INIS)

    Lee, M.C.; Riddolls, R.J.; Moriarty, D.T.; Dalrymple, N.E.; Rowlands, M.J.

    1996-01-01

    The authors will present some recent results of the laboratory experiments at MIT, using a large plasma device known as the Versatile Toroidal Facility (VTF). These experiments are aimed at cross-checking the ionospheric plasma heating experiments at Arecibo, Puerto Rico using an HF heating facility (heater). The plasma phenomenon under investigation is the spectral characteristic of Langmuir wave turbulence produced by ordinary (o-mode) electromagnetic pump waves. The Langmuir waves excited by o-mode heaters waves at Arecibo have both a frequency-upshifted spectrum and a frequency-downshifted (viz., cascading) spectrum. While the cascading spectrum can be well explained in terms of the parametric decay instability (PDI), the authors have interpreted the frequency-upshifted Langmuir waves to be anti-Stokes Langmuir waves produced by a nonlinear scattering process as follows. Lower hybrid waves creates presumably by lightning-induced whistler waves can scatter nonlinearly the PDI-excited mother langmuir waves, yielding obliquely propagating langmuir waves with frequencies as the summation of the mother Langmuir wave frequencies and the lower hybrid wave frequencies. This suggested process has been confirmed in the laboratory experiments, that can reproduce the characteristic spectra of Langmuir wave turbulence observed in the Arecibo experiments

  17. Management of Giant Sequoia at Blodgett Forest Research Station

    Science.gov (United States)

    Robert C. Heald

    1986-01-01

    Researchers at Blodgett Forest Research Station, University of California, are studying giant sequoia (Sequoiadendron giganteum [Lindl.] Buchholz) growth under both even-age and selection management in relationship to the presence of several shrub species and five native conifers. The sequoias are also being studied under several types of site...

  18. Organization of copper nanoclusters in Langmuir–Blodgett films

    Indian Academy of Sciences (India)

    Unknown

    Organization of copper nanoclusters in Langmuir–Blodgett films ... A number of methods have been employed for preparing metallic nano- .... Work is pre- sently underway to investigate such films. Acknowledgement. The authors would like to thank the Department of. Science and Technology, New Delhi, for a project grant.

  19. Organization of copper nanoclusters in Langmuir–Blodgett films

    Indian Academy of Sciences (India)

    The Langmuir–Blodgett films of ODSA formed from subphase containing copper ions were first subjected to sulphidation (S) using sodium sulphide and then hydrogenated (H) using hydrogen gas. Diffuse reflectance UV-visible spectroscopy (DIR-UV-vis), X-ray photoelectron spectroscopy (XPS) and transmission electron ...

  20. Emergence of the bifurcation structure of a Langmuir–Blodgett transfer model

    KAUST Repository

    Köpf, Michael H

    2014-10-07

    © 2014 IOP Publishing Ltd & London Mathematical Society. We explore the bifurcation structure of a modified Cahn-Hilliard equation that describes a system that may undergo a first-order phase transition and is kept permanently out of equilibrium by a lateral driving. This forms a simple model, e.g., for the deposition of stripe patterns of different phases of surfactant molecules through Langmuir-Blodgett transfer. Employing continuation techniques the bifurcation structure is numerically investigated using the non-dimensional transfer velocity as the main control parameter. It is found that the snaking structure of steady front states is intertwined with a large number of branches of time-periodic solutions that emerge from Hopf or period-doubling bifurcations and end in global bifurcations (sniper and homoclinic). Overall the bifurcation diagram has a harp-like appearance. This is complemented by a two-parameter study in non-dimensional transfer velocity and domain size (as a measure of the distance to the phase transition threshold) that elucidates through which local and global codimension 2 bifurcations the entire harp-like structure emerges.

  1. Langmuir–Blodgett films of cholesterol oxidase and S-layer proteins onto screen-printed electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Guimarães, Juliana Aguilar, E-mail: helen@peq.coppe.ufrj.br; Ferraz, Helen Conceição; Alves, Tito Lívio Moitinho

    2014-04-01

    Graphical abstract: - Highlights: • Langmuir and LB monolayers of ChOx and S-layer proteins were obtained. • Mixed ChOx/S-layer proteins films presented an ideal-like behavior. • Modified sensor showed stable peaks with moderate intensity. • The type of LB deposition affects the sensor ability of detecting cholesterol. • Mixed ChOx/S-layer proteins LB films improve sensor properties. - Abstract: Stable Langmuir monolayers of cholesterol oxidase (ChOx) and S-layer proteins were produced at the water–air interface and subsequently transferred onto the surface of screen-printed carbon electrodes by the Langmuir–Blodgett (LB) technique. The modified electrode surface was characterized by atomic force microscopy (AFM) and cyclic voltammetry (CV). AFM indicated the presence of deposited layers, showing reduction of surface roughness (RMS and Rt parameters). Significant changes in the shape of CVs were observed in modified electrodes compared to bare electrodes. The anodic peaks could be observed in cyclic voltammograms (CV), at a scan rate equal to 25 mV s{sup −1}, using electrodes with Z-type LB deposition. The presence of S-layer proteins in the ChOx LB film increases the oxidation peak intensity and reduces the oxidation potential. Altogether, these results demonstrate the feasibility of producing a cholesterol biosensor based on the immobilization of ChOx and S-layer proteins by LB technique.

  2. Preparation of large-area molecular junctions with metallic conducting Langmuir–Blodgett films

    Energy Technology Data Exchange (ETDEWEB)

    Mochizuki, Kengo [Division of Marine Technology, Tokyo University of Marine Science and Technology, 2-1-6 Etchujima Koto-ku, Tokyo 135-8533 (Japan); Ohnuki, Hitoshi, E-mail: ohnuki@kaiyodai.ac.jp [Division of Marine Technology, Tokyo University of Marine Science and Technology, 2-1-6 Etchujima Koto-ku, Tokyo 135-8533 (Japan); Shimizu, Daisuke [Division of Marine Technology, Tokyo University of Marine Science and Technology, 2-1-6 Etchujima Koto-ku, Tokyo 135-8533 (Japan); Imakubo, Tatsuro [Department of Materials and Technology, Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka, Niigata 940-2188 (Japan); Tsuya, Daiju [National Institute for Materials Science,1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Izumi, Mitsuru [Division of Marine Technology, Tokyo University of Marine Science and Technology, 2-1-6 Etchujima Koto-ku, Tokyo 135-8533 (Japan)

    2014-03-03

    Metallic conducting Langmuir–Blodgett (LB) films were used as soft electrodes to fabricate molecular junctions with self-assembled monolayers (SAMs) of alkanethiols (CH{sub 3}(CH{sub 2}){sub n−1}SH) on an Au surface. Alkanethiols can form highly ordered, stable dielectric SAMs on metal surfaces over large areas. However, it is difficult to establish electrical contacts on such SAMs, which has limited their application. In this work, we used metallic conducting LB films composed of bis(ethylenedioxy)tetrathiafulvalene and stearic acid as a soft electrode onto alkanethiol SAMs (C{sub n}-SAM, n = 12, 14, 16, 18) to prepare Au/SAM/metal junctions of relatively large size (∼ 15.6 × 10{sup 3} μm{sup 2}). The current density–voltage (J–V) characteristics across the junctions exhibited rectifying behavior with a ratio R of ∼ 5 (R = |J(V)|/|J(− V)| at ± 1 V). The lower transfer rate corresponding to the electron transport from Au to the LB films exhibited nonlinear J–V characteristics, while the higher transfer rate of electrons from the LB film to Au showed linear J–V characteristics. Kelvin probe force microscopy revealed that the work function of the metallic LB films was smaller than that of Au. The observed rectification behavior is probably caused by different electron transport mechanisms between the two current directions. - Highlights: • Metallic Langmuir–Blodgett (LB) films were used as soft electrodes. • Molecular junctions of metal–alkanethiol–LB films were fabricated. • The current–voltage curve across the junctions exhibited rectifying behavior. • This is the first observation for alkanethiol monolayer junctions. • The work function difference between the electrodes induces the rectification.

  3. Luminescent Organic Semiconducting Langmuir Monolayers.

    Science.gov (United States)

    Agina, Elena V; Mannanov, Artur A; Sizov, Alexey S; Vechter, Olga; Borshchev, Oleg V; Bakirov, Artem V; Shcherbina, Maxim A; Chvalun, Sergei N; Konstantinov, Vladislav G; Bruevich, Vladimir V; Kozlov, Oleg V; Pshenichnikov, Maxim S; Paraschuk, Dmitry Yu; Ponomarenko, Sergei A

    2017-05-31

    In recent years, monolayer organic field-effect devices such as transistors and sensors have demonstrated their high potential. In contrast, monolayer electroluminescent organic field-effect devices are still in their infancy. One of the key challenges here is to create an organic material that self-organizes in a monolayer and combines efficient charge transport with luminescence. Herein, we report a novel organosilicon derivative of oligothiophene-phenylene dimer D2-Und-PTTP-TMS (D2, tetramethyldisiloxane; Und, undecylenic spacer; P, 1,4-phenylene; T, 2,5-thiophene; TMS, trimethylsilyl) that meets these requirements. The self-assembled Langmuir monolayers of the dimer were investigated by steady-state and time-resolved photoluminescence spectroscopy, atomic force microscopy, X-ray reflectometry, and grazing-incidence X-ray diffraction, and their semiconducting properties were evaluated in organic field-effect transistors. We found that the best uniform, fully covered, highly ordered monolayers were semiconducting. Thus, the ordered two-dimensional (2D) packing of conjugated organic molecules in the semiconducting Langmuir monolayer is compatible with its high-yield luminescence, so that 2D molecular aggregation per se does not preclude highly luminescent properties. Our findings pave the way to the rational design of functional materials for monolayer organic light-emitting transistors and other optoelectronic devices.

  4. A computerized Langmuir probe system

    Science.gov (United States)

    Pilling, L. S.; Bydder, E. L.; Carnegie, D. A.

    2003-07-01

    For low pressure plasmas it is important to record entire single or double Langmuir probe characteristics accurately. For plasmas with a depleted high energy tail, the accuracy of the recorded ion current plays a critical role in determining the electron temperature. Even for high density Maxwellian distributions, it is necessary to accurately model the ion current to obtain the correct electron density. Since the electron and ion current saturation values are, at best, orders of magnitude apart, a single current sensing resistor cannot provide the required resolution to accurately record these values. We present an automated, personal computer based data acquisition system for the determination of fundamental plasma properties in low pressure plasmas. The system is designed for single and double Langmuir probes, whose characteristics can be recorded over a bias voltage range of ±70 V with 12 bit resolution. The current flowing through the probes can be recorded within the range of 5 nA-100 mA. The use of a transimpedance amplifier for current sensing eliminates the requirement for traditional current sensing resistors and hence the need to correct the raw data. The large current recording range is realized through the use of a real time gain switching system in the negative feedback loop of the transimpedance amplifier.

  5. Development of new type of nonlinear optical materials with a function of ultrafast optical modulation; Chokosoku hikari reiki hencho kino wo motsu atarashii hisenkei kogaku zairyo no kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    Sakaguchi, H. [Shizuoka University, Shizuoka (Japan). Research Institute of Electronics

    1995-12-15

    Ultrafast modulation of second harmonies from a Langmuir-Blodgett film consisting of a ruthenium complex was demonstrated for the first time. The mechanism of the modulator of SHG intensity on laser irradiation was ascribed to the change of molecular hyperpolarizability of the ruthenium complex on going from the ground state to the excited state. 9 refs., 12 figs.

  6. Supramolecular Structure, Physical Properties, and Langmuir-Blodgett Film Formation of an Optically Active Liquid-Crystalline Phthalocyanine

    NARCIS (Netherlands)

    Nostrum, Cornelus F. van; Bosman, Anton W.; Gelinck, Gerwin H.; Schouten, Pieter G.; Warman, John M.; Devillers, Marinus A.C.; Meijerink, Andries; Picken, Stephen J.; Sohling, Ulrich; Schouten, Arend-Jan; Nolte, Roeland J.M.

    The structure and physical properties of optically active, metal-free 2,3,9,10,16,17,23,24-octa(S-3,7-dimethyloctoxy)phthalocyanine ((S)-Pc(8,2)) are reported and compared with those of the phthalocyanine with (R,S) side chains (mixture of 43 stereoisomers). Unlike the latter compound, (S)-Pc(8,2)

  7. TWO-DIMENSIONAL MAGNETISM IN LANGMUIR-BLODGETT FILMS OF MANGANESE STEARATE MEASURED IN A He3-SQUID MAGNETOMETER

    OpenAIRE

    Head, D.; Blott, B.; Melville, D.

    1988-01-01

    The magnetisation of manganese stearate layers on aluminium foil has been measured between 20 K and 0.4 K. With the applied magnetic field parallel to the film we deduced an equivalent susceptibility of 6.4 x 10-3 4.2 K. This is close to our paramagnetic calculation based on the measured manganese spacing. Our results would be consistent with a transition to antiferromagnetism below 0.4 K.

  8. Collisionless dissipation of Langmuir turbulence

    International Nuclear Information System (INIS)

    Erofeev, V.I.

    2002-01-01

    An analysis of two experimental observations of Langmuir wave collapse is performed. The corresponding experimental data are shown to give evidence against the collapse. The physical reason for preventing the collapses is found to be the nonresonant electron diffusion in momentums. In this process, plasma thermal electrons are efficiently heated at the expense of wave energy, and intense collisionless wave dissipation takes place. The basic reason of underestimation of this phenomenon in traditional theory is shown to be the substitution of real plasma by a plasma probabilistic ensemble. A theory of nonresonant electron diffusion in a single collisionless plasma is developed. It is shown that corresponding collisionless wave dissipation may arrest spectral energy transfer towards small wave numbers

  9. High frequency ion sound waves associated with Langmuir waves in type III radio burst source regions

    Directory of Open Access Journals (Sweden)

    G. Thejappa

    2004-01-01

    Full Text Available Short wavelength ion sound waves (2-4kHz are detected in association with the Langmuir waves (~15-30kHz in the source regions of several local type III radio bursts. They are most probably not due to any resonant wave-wave interactions such as the electrostatic decay instability because their wavelengths are much shorter than those of Langmuir waves. The Langmuir waves occur as coherent field structures with peak intensities exceeding the Langmuir collapse thresholds. Their scale sizes are of the order of the wavelength of an ion sound wave. These Langmuir wave field characteristics indicate that the observed short wavelength ion sound waves are most probably generated during the thermalization of the burnt-out cavitons left behind by the Langmuir collapse. Moreover, the peak intensities of the observed short wavelength ion sound waves are comparable to the expected intensities of those ion sound waves radiated by the burnt-out cavitons. However, the speeds of the electron beams derived from the frequency drift of type III radio bursts are too slow to satisfy the needed adiabatic ion approximation. Therefore, some non-linear process such as the induced scattering on thermal ions most probably pumps the beam excited Langmuir waves towards the lower wavenumbers, where the adiabatic ion approximation is justified.

  10. Characterization of 10,12-pentacosadiynoic acid Langmuir–Blodgett monolayers and their use in metal–insulator–metal tunnel devices

    Directory of Open Access Journals (Sweden)

    Saumya Sharma

    2014-11-01

    Full Text Available The characterization of Langmuir–Blodgett thin films of 10,12-pentacosadiynoic acid (PDA and their use in metal–insulator–metal (MIM devices were studied. The Langmuir monolayer behavior of the PDA film was studied at the air/water interface using surface tension–area isotherms of polymeric and monomeric PDA. Langmuir–Blodgett (LB, vertical deposition and Langmuir–Schaefer (LS, horizontal deposition techniques were used to deposit the PDA film on various substrates (glass, quartz, silicon, and nickel-coated film on glass. The electrochemical, electrical and optical properties of the LB and LS PDA films were studied using cyclic voltammetry, current–voltage characteristics (I–V, and UV–vis and FTIR spectroscopies. Atomic force microscopy measurements were performed in order to analyze the surface morphology and roughness of the films. A MIM tunnel diode was fabricated using a PDA monolayer assembly as the insulating barrier, which was sandwiched between two nickel layers. The precise control of the thickness of the insulating monolayers proved critical for electron tunneling to take place in the MIM structure. The current–voltage characteristics of the MIM diode revealed tunneling behavior in the fabricated Ni–PDA LB film–Ni structures.

  11. High performance dye-sensitized solar cells using graphene modified fluorine-doped tin oxide glass by Langmuir–Blodgett technique

    Energy Technology Data Exchange (ETDEWEB)

    Roh, Ki-Min [Rare Metals Research Center, Korea Institute of Geoscience and Mineral Resources, Daejeon 305-350 (Korea, Republic of); Jo, Eun-Hee; Chang, Hankwon [Rare Metals Research Center, Korea Institute of Geoscience and Mineral Resources, Daejeon 305-350 (Korea, Republic of); Nanomaterials Science and Engineering Major, University of Science and Technology, Daejeon 305-350 (Korea, Republic of); Han, Tae Hee [Department of Organic and Nano Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Jang, Hee Dong, E-mail: hdjang@kigam.re.kr [Rare Metals Research Center, Korea Institute of Geoscience and Mineral Resources, Daejeon 305-350 (Korea, Republic of); Nanomaterials Science and Engineering Major, University of Science and Technology, Daejeon 305-350 (Korea, Republic of)

    2015-04-15

    Since the introduction of dye-sensitized solar cells (DSSCs) with low fabrication cost and high power conversion efficiency, extensive studies have been carried out to improve the charge transfer rate and performance of DSSCs. In this paper, we present DSSCs that use surface modified fluorine-doped tin oxide (FTO) substrates with reduced graphene oxide (r-GO) sheets prepared using the Langmuir–Blodgett (LB) technique to decrease the charge recombination at the TiO{sub 2}/FTO interface. R-GO sheets were excellently attached on FTO surface without physical deformations such as wrinkles; effects of the surface coverage of r-GO on the DSSC performance were also investigated. By using graphene modified FTO substrates, the resistance at the interface of TiO{sub 2}/FTO was reduced and the power conversion efficiency was increased to 8.44%. - Graphical abstract: DSSCs with graphene modified FTO glass were fabricated with the Langmuir Blodgett technique. GO sheets were transferred to FTO at various surface pressures in order to change the surface density of graphene and the highest power conversion efficiency of the DSSC was 8.44%. - Highlights: • By LB technique, r-GO sheets were coated on FTO without physical deformation. • DSSCs were fabricated with, r-GO modified FTO substrates. • With surface modification by r-GO, the interface resistance of DSSC decreased. • Maximum PCE of the DSSC was increased up to 8.44%.

  12. Non linear dynamic of Langmuir and electromagnetic waves in space plasmas

    International Nuclear Information System (INIS)

    Guede, Jose Ricardo Abalde

    1995-11-01

    The aim of this work is to study the nonlinear dynamics of Langmuir and electromagnetic waves in space plasmas. Firstly, the generalized Zakharov equations are derived which are used to study the hybrid parametric instability involving the generation of daughter Langmuir, electromagnetic and ion-acoustic waves induced by two counter-propagating Langmuir pump waves with different amplitudes based on a coupled dispersion relation. Secondly, starting from the generalized Zakharov equations the linear and nonlinear coupled mode theories of three-wave and four-wave parametric interactions are developed, respectively. In three-waves processes, a Langmuir wave decays into another Langmuir wave and an ion-acoustic wave (electrostatic parametric decay) or into an electromagnetic wave and an ion-acoustic wave (electromagnetic parametric decay). In four-wave (modulational) processes, the interaction involves two wave triplets: in the decay triplet a pump wave couples with a low-frequency wave to generate a Stokes wave, and in the fusion triplets: in the decay triplet a pump wave couples with a low-frequency wave to generate a Stokes wave, and in the fusion triplet the coupling of a pump wave with a low-frequency wave generate an anti-Stokes wave. These modulational processes are convective and resonant processes wherein the low-frequency modes are Eigenmodes of plasma and are known as the stimulated modulational processes. Four such processes are investigated in this thesis: two with Langmuir pump waves (electrostatic and hybrid stimulated modulation processes) and the other two with electromagnetic pump waves (stimulated modulation Brillouin scattering and electromagnetic stimulated modulation process). Applications of the theoretical results in space plasmas are discussed. In particular, it is shown that the electrostatic and electromagnetic parametric decay processes of Langmuir waves can model the generation and modulation of radio emissions and Langmuir waves in the

  13. Solitary Langmuir waves in two-electron temperature plasma

    Science.gov (United States)

    Prudkikh, V. V.; Prudkikh

    2014-06-01

    Nonlinear interaction of Langmuir and ion-acoustic waves in two-electron temperature plasma is investigated. New integrable wave interaction regime was discovered, this regime corresponds to the Langmuir soliton with three-hump amplitude, propagating with a speed close to the ion-sound speed in the conditions of strong non-isothermality of electronic components. It was discovered that besides the known analytical solution in the form of one- and two-hump waves, there exists a range of solutions in the form of solitary waves, which in the form of envelope has multi-peak structure and differs from the standard profiles described by hyperbolic functions. In case of fixed plasma parameters, different group velocities correspond to the waves with different number of peaks. It is found that the Langmuir wave package contains both even and uneven numbers of oscillations. Low-frequency potential here has uneven number of peaks. Interrelation of obtained and known earlier results are also discussed.

  14. Characterisation of the membrane affinity of an isoniazide peptide conjugate by tensiometry, atomic force microscopy and sum-frequency vibrational spectroscopy, using a phospholipid Langmuir monolayer model.

    Science.gov (United States)

    Hill, Katalin; Pénzes, Csanád Botond; Schnöller, Donát; Horváti, Kata; Bosze, Szilvia; Hudecz, Ferenc; Keszthelyi, Tamás; Kiss, Eva

    2010-10-07

    Tensiometry, sum-frequency vibrational spectroscopy, and atomic force microscopy were employed to assess the cell penetration ability of a peptide conjugate of the antituberculotic agent isoniazide. Isoniazide was conjugated to peptide (91)SEFAYGSFVRTVSLPV(106), a functional T-cell epitope of the immunodominant 16 kDa protein of Mycobacterium tuberculosis. As a simple but versatile model of the cell membrane a phospholipid Langmuir monolayer at the liquid/air interface was used. Changes induced in the structure of the phospholipid monolayer by injection of the peptide conjugate into the subphase were followed by tensiometry and sum-frequency vibrational spectroscopy. The drug penetrated lipid films were transferred to a solid support by the Langmuir-Blodgett technique, and their structures were characterized by atomic force microscopy. Peptide conjugation was found to strongly enhance the cell penetration ability of isoniazide.

  15. Dynamic of Langmuir and Ion-Sound Waves in Type 3 Solar Radio Sources

    Science.gov (United States)

    Robinson, P. A.; Willes, A. J.; Cairns, I. H.

    1993-01-01

    The evolution of Langmuir and ion-sound waves in type 3 sources is investigated, incorporating linear growth, linear damping, and nonlinear electrostatic decay. Improved estimates are obtained for the wavenumber range of growing waves and the nonlinear coupling coefficient for the decay process. The resulting prediction for the electrostatic decay threshold is consistent with the observed high-field cutoff in the Langmuir field distribution. It is shown that the conditions in the solar wind do not allow a steady state to be attained; rather, bursty linear and nonlinear interactions take place, consistent with the highly inhomogeneous and impulsive waves actually observed. Nonlinear growth is found to be fast enough to saturate the growth of the parent Langmuir waves in the available interaction time. The resulting levels of product Langmuir and ion-sound waves are estimated theoretically and shown to be consistent with in situ ISEE 3 observations of type 3 events at 1 AU. Nonlinear interactions slave the growth and decay of product sound waves to that of the product Langmuir waves. The resulting probability distribution of ion-sound field strengths is predicted to have a flat tail extending to a high-field cutoff. This prediction is consistent with statistics derived here from ISEE 3 observations. Agreement is also found between the frequencies of the observed waves and predictions for the product S waves. The competing processes of nonlinear wave collapse and quasilinear relaxation are discussed, and it is concluded that neither is responsible for the saturation of Langmuir growth. When wave and beam inhomogeneities are accounted for, arguments from quasi-linear relaxation yield an upper bound on the Langmuir fields that is too high to be relevant. Nor are the criteria for direct wave collapse of the beam-driven waves met, consistent with earlier simulation results that imply that this process is not responsible for saturation of the beam instability. Indeed, even

  16. Estimation of Specific Surface Area using Langmuir Isotherm ...

    African Journals Online (AJOL)

    Michael Horsfall

    fitting isotherm, However, the Langmuir isotherm can be linearized as four different types. (Table 1), and simple linear regression will result in different parameter estimates The more popular linear forms used are Langmuir-1 and Langmuir- 2,.

  17. Non linear dynamic of Langmuir and electromagnetic waves in space plasmas; Dinamica nao linear de ondas de Langmuir e eletromagneticas em plasmas espaciais

    Energy Technology Data Exchange (ETDEWEB)

    Guede, Jose Ricardo Abalde

    1995-11-01

    The aim of this work is to study the nonlinear dynamics of Langmuir and electromagnetic waves in space plasmas. Firstly, the generalized Zakharov equations are derived which are used to study the hybrid parametric instability involving the generation of daughter Langmuir, electromagnetic and ion-acoustic waves induced by two counter-propagating Langmuir pump waves with different amplitudes based on a coupled dispersion relation. Secondly, starting from the generalized Zakharov equations the linear and nonlinear coupled mode theories of three-wave and four-wave parametric interactions are developed, respectively. In three-waves processes, a Langmuir wave decays into another Langmuir wave and an ion-acoustic wave (electrostatic parametric decay) or into an electromagnetic wave and an ion-acoustic wave (electromagnetic parametric decay). In four-wave (modulational) processes, the interaction involves two wave triplets: in the decay triplet a pump wave couples with a low-frequency wave to generate a Stokes wave, and in the fusion triplets: in the decay triplet a pump wave couples with a low-frequency wave to generate a Stokes wave, and in the fusion triplet the coupling of a pump wave with a low-frequency wave generate an anti-Stokes wave. These modulational processes are convective and resonant processes wherein the low-frequency modes are Eigenmodes of plasma and are known as the stimulated modulational processes. Four such processes are investigated in this thesis: two with Langmuir pump waves (electrostatic and hybrid stimulated modulation processes) and the other two with electromagnetic pump waves (stimulated modulation Brillouin scattering and electromagnetic stimulated modulation process). Applications of the theoretical results in space plasmas are discussed. In particular, it is shown that the electrostatic and electromagnetic parametric decay processes of Langmuir waves can model the generation and modulation of radio emissions and Langmuir waves in the

  18. Synthesis and characterization of a J-aggregating TDBC derivative in solution and in Langmuir–Blodgett films

    Energy Technology Data Exchange (ETDEWEB)

    Aviv, Hagit [Department of Chemistry, Bar-Ilan University (Israel); Institute for Nanotechnology and Advanced Materials, Bar-Ilan University (Israel); Tischler, Yaakov R., E-mail: yrt@biu.ac.il [Department of Chemistry, Bar-Ilan University (Israel); Institute for Nanotechnology and Advanced Materials, Bar-Ilan University (Israel)

    2015-02-15

    Here we present the synthesis and optical characterization of a new amphiphilic cyanine dye, 1,1′-dioctadecane-3,3′-di(4-sulfobutyl)-5,5′,6,6′-tetrachloro -benzimidazolocarbo-cyanine (C18S4). C18S4 is a derivative of the heavily studied J-aggregating cyanine dye TDBC that was designed specifically for creating stable amphiphilic monolayers when spread at an air–water interface. Unlike TDBC, which readily J-aggregates in water, we show that C18S4 introduced into water tends to produce micelles with monomeric spectral properties and only exhibits strong J-aggregation after an emulsification procedure and a week of dye reorganization. When deposited on a Langmuir Blodgett (LB) trough, C18S4 forms a stable monolayer with a repeatable isotherm. Layers transferred via LB deposition to a functionalized glass substrate show pronounced J-aggregation, depending on the surface transfer pressure. Layers transferred at 35 mN/m present an intense narrow absorption spectrum peaked at λ=589 nm with FWHM=523 cm{sup −1} (18 nm). The accompanying fluorescence shows a narrow spectrum with FWHM=332 cm{sup −1} (11.5 nm) and a Stokes shift less than 1 nm. The ability to create J-aggregates of C18S4 via LB deposition provides control over the J-aggregation process of TDBC-like molecules and can ultimately lead to tuning the J-aggregate coupling for specific experiments and applications. - Highlights: • C18S4 is an amphiphilic J-aggregating cyanine dye. • C18S4 J-aggregates in aqueous solution. • C18S4 forms a stable isotherm when spread at the air–water interface. • C18S4 J-aggregates at an air–water interface upon compression. • Langmuir–Blodgett J-aggregated films have narrow absorption and emission spectra.

  19. Stable Langmuir solitons in plasma with diatomic ions

    Directory of Open Access Journals (Sweden)

    M. Dvornikov

    2013-08-01

    Full Text Available We study stable axially and spherically symmetric spatial solitons in plasma with diatomic ions. The stability of a soliton against collapse is provided by the interaction of induced electric dipole moments of ions with the rapidly oscillating electric field of a plasmoid. We derive the new cubic-quintic nonlinear Schrödinger equation, which governs the soliton dynamics and numerically solve it. Then we discuss the possibility of implementation of such plasmoids in realistic atmospheric plasma. In particular, we suggest that spherically symmetric Langmuir solitons, described in the present work, can be excited at the formation stage of long-lived atmospheric plasma structures. The implication of our model for the interpretation of the results of experiments for the plasmoids generation is discussed.

  20. First observation of 3D aggregates in a single-component Langmuir film below the equilibrium spreading pressure

    Directory of Open Access Journals (Sweden)

    Ivanov George R.

    2017-01-01

    Full Text Available Single component monolayers from Dipalamitoyl Phosphatidyl Ethanolamine head labelled with the fluorescent chromophore NitroBenzoxaDiazole (DP-NBD-PE were investigated at the air-water interface as Langmuir films and deposited on silicon wafers or glass plates as Langmuir-Blodgett (LB films. A step compression and monitoring of the pressure relaxation together with domain formation as observed with Brewster angle microscopy suggests that main transition from liquid expanded to liquid compressed state start at around 6.9 mN/m though on the isotherm it starts around 9 mN/m at 25° C. Brewster angle microscopy also reveals a nonuniform structure in the monolayer. 3D aggregates - cylinders with 50 – 150 nm diameter and bilayer height were observed with Atomic Force Microscopy when deposition was carried at 7 mN/m, above the main phase transition but considerably lower than the equilibrium spreading pressure of 19.6 mN/m for this molecule. When LB film deposition is carried just below the main phase transition a uniform height layer of film in a liquid phase is observed with AFM with no structures. Both compression and deposition were carried at very low speeds with large time to relax in ordered to avoid kinetic effects. These 3D aggregates are not due to the transfer process or interaction with the substrate. These aggregates provide a highly developed area combined with monolayer thick structure which can produce very fast and highly sensitive biosensors.

  1. 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.

  2. Structure of binary mixed polymer Langmuir layers

    NARCIS (Netherlands)

    Bernardini, C.

    2012-01-01

    The possibility of preparing 2D stable emulsions through mixing of homopolymers in a Langmuir monolayer is the core topic of this thesis. While colloid science has achieved well established results in the study of bulk dispersed systems, accounts on properties of mixed monomolecular films are fewer,

  3. Scattering of waves by Langmuir solitons

    Energy Technology Data Exchange (ETDEWEB)

    Mendonca, J.T. (Instituto Superior Tecnico, Lisbon (Portugal). Centro de Electrodinamica)

    1983-08-01

    Scattering of electromagnetic and electrostatic waves by one-dimensional Langmuir solitons in a uniform and isotropic plasma is studied analytically using a perturbation method. Mode conversion via scattering by solitons is also considered. The results are also relevant for the case of ion-acoustic solitons.

  4. Structure of binary mixed polymer Langmuir layers

    NARCIS (Netherlands)

    Bernardini, C.

    2012-01-01

    The possibility of preparing 2D stable emulsions through mixing of homopolymers in a Langmuir monolayer is the core topic of this thesis. While colloid science has achieved well established results in the study of bulk dispersed systems, accounts on properties of mixed monomolecular films are

  5. Langmuir Wave Instability And Photoelectron Emission In Irradiated ...

    African Journals Online (AJOL)

    We have investigated dust charged fluctuation due to the combined effect of Langmuir Wave and Photoelectron Emission in Irradiated Dusty Plasma. The dispersion relation and growth of the Langmuir wave instability is also presented. The applicability of the developed dispersion relation and growth rate of the Langmuir ...

  6. Structure of binary mixed polymer Langmuir layers

    OpenAIRE

    Bernardini, C.

    2012-01-01

    The possibility of preparing 2D stable emulsions through mixing of homopolymers in a Langmuir monolayer is the core topic of this thesis. While colloid science has achieved well established results in the study of bulk dispersed systems, accounts on properties of mixed monomolecular films are fewer, and seldom systematic. The aim of this investigation is to contribute to a deeper understanding of the subject, in order to explore opportunities to apply the acquired knowledge to the fabrication...

  7. An indigenously developed electronic control system for Langmuir ...

    Indian Academy of Sciences (India)

    Unknown

    systems of co-operating molecules, i.e. systems of molecules that interlock and interact like parts of a machine (Peterson 1992). Many efforts are being made to assemble the molecules in a well-ordered way, using a variety of different deposition techniques. (Kuhn et al 1972; Tredgold 1994). The Langmuir–Blodgett (LB) ...

  8. Synthesis of cadmium sulphide in pure and mixed Langmuir ...

    Indian Academy of Sciences (India)

    sodium sulphide (Na2S) with Langmuir–Blodgett (LB) films of cadmium salts of n- octadecylsuccinic acid (ODSU) and with LB films of ODSU in mixtures of octadecylamine and octadecyl alcohol. The results indicate that heterogeneous nucleation and aggregation in the pure ODSU LB films due to processes like Ostwald.

  9. Effect of the conditions of transfer on the structure and optical properties of Langmuir graphene oxide films during deposition on a substrate

    Science.gov (United States)

    Seliverstova, E. V.; Ibrayev, N. Kh.; Dzhanabekova, R. Kh.

    2017-09-01

    The effect the solvent and transfer pressure of graphene oxide (SLGO) Langmuir-Blodgett films on the physicochemical properties of monolayers, and on their structural and optical properties, is studied. Examination of the physicochemical properties of SLGO monolayers on subphase surfaces that are formed from SLGO dispersions in different organic solvents reveals that monolayer behavior is virtually independent of the solvent. Electron microscope and optical studies show that the monolayers formed from SLGO dispersions in DMF and acetone have the highest transfer coefficients. It is concluded that the structural heterogeneity of the surfaces of graphene oxide films results from simultaneous effect of electrostatic interactions between graphene oxide particles and Van der Waals interactions with the solvation shell of the particles. Studies focusing on the effect the pressure of transferring a graphene oxide monolayer onto the surface of a solid substrate has on structural features of LB films show that films produced at low surface pressures have more homogeneous structures.

  10. Extracting surface diffusion coefficients from batch adsorption measurement data: application of the classic Langmuir kinetics model.

    Science.gov (United States)

    Chu, Khim Hoong

    2017-11-09

    Surface diffusion coefficients may be estimated by fitting solutions of a diffusion model to batch kinetic data. For non-linear systems, a numerical solution of the diffusion model's governing equations is generally required. We report here the application of the classic Langmuir kinetics model to extract surface diffusion coefficients from batch kinetic data. The use of the Langmuir kinetics model in lieu of the conventional surface diffusion model allows derivation of an analytical expression. The parameter estimation procedure requires determining the Langmuir rate coefficient from which the pertinent surface diffusion coefficient is calculated. Surface diffusion coefficients within the 10 -9 to 10 -6  cm 2 /s range obtained by fitting the Langmuir kinetics model to experimental kinetic data taken from the literature are found to be consistent with the corresponding values obtained from the traditional surface diffusion model. The virtue of this simplified parameter estimation method is that it reduces the computational complexity as the analytical expression involves only an algebraic equation in closed form which is easily evaluated by spreadsheet computation.

  11. Algal polysaccharides on lipid Langmuir–Blodgett films and molecular effects upon metal ion contact

    Energy Technology Data Exchange (ETDEWEB)

    Kalinouski de Brito, Audrey; Caseli, Luciano, E-mail: lcaseli@unifesp.br; Nordi, Cristina S.F.

    2013-05-01

    The capability of extracellular polysaccharides released from microorganisms to bind to metal ions is a potential molecular biotechnological tool to produce biosorbents as an alternative for the removal of heavy metals from aquatic environments. In this paper, we exploit the ability of polysaccharides from extracellular polymeric substances produced by phytoplankton adsorbed on lipid monolayers as Langmuir–Blodgett films to interact with silver ions in aqueous environments. The properties of the biomacromolecules after the interaction were investigated with polarisation modulation infrared reflection-absorption spectroscopy and atomic force microscopy. The vibrational spectroscopy technique applied to the Langmuir–Blodgett films before and after contact with silver ions indicated significant changes for the bands related to the chemical groups present in polypeptides and polysaccharides. These changes point to the influence of the metal interaction on the molecular organisation and on the structure of the Langmuir–Blodgett film. Therefore, the behaviour of these biomacromolecules adsorbed at bioinspired interfaces is better understood in terms of properties at the molecular level. This understanding leads to a model in which metal incorporation affects the molecular structure of the ultrathin film. - Highlights: ► Extracellular material released from algae was adsorbed at a lipid monolayer. ► Monolayer changes its rheological properties with material incorporation. ► Changes in proteins and polysaccharides are identified with PM-IRRAS. ► Langmuir–Blodgett films of this composite are sensitive to metal ions in water.

  12. On the theory of Langmuir solitons

    International Nuclear Information System (INIS)

    Gibbons, J.; Thornhill, S.G.; Wardrop, M.J.; Ter Haar, D.

    1977-01-01

    A Lagrangian density is found from which the equations of motion for the Langmuir solitons follow in the usual way. It is shown how this Lagrangian leads to the usual conservation laws. For the one-dimensional case a consideration of these conservation laws can help in understanding some of the results obtained in numerical experiments on the behaviour of a strongly turbulent plasma. It is shown that the situation in the three-dimensional case may be fundamentally different, and the near-sonic perturbations and Karpman's treatment of these is discussed. (U.K.)

  13. Wavenumber-in-cell simulation of weak Langmuir turbulence

    International Nuclear Information System (INIS)

    Pecseli, H.L.; Trulsen, J.

    1990-01-01

    A wave-number-in-cell code was developed for simulation of a model proposed by Vendenov, Gordeev, and Rudakov for studying weak Langmuir turbulence. The model uses a WKB approach for describing the Langmuir wave field. Theoretical results for damping of ion acoustic waves caused by resonant interaction of Langmuir waves with group velocity around the sound speed were confirmed. Simulations corresponding to an initial condition with an intense wave burst demonstrate a formation of almost stationary localized cavities of intense wideband self-trapped Langmuir wave fields. These cavities have features in common with phase-space vortices

  14. Langmuir condensation by spontaneous scattering off electrons in two dimensions

    International Nuclear Information System (INIS)

    Ziebell, L F; Yoon, P H; Gaelzer, R; Pavan, J

    2012-01-01

    In a pair of recent papers (Ziebell et al 2008 Phys. Plasmas 15 032303, 2008 Plasma Phys. Control. Fusion 50 085011) it was shown, within the context of weak turbulence theory, that the Langmuir turbulence generated by the bump-in-tail instability does not lead to Langmuir condensation (or accumulation of wave energy and momentum in the long-wavelength regime) in two dimensions. The present analysis finds that it is important to include the spontaneous scattering off Langmuir turbulence of the electrons, which is ignored in the customary literature when compared with a similar process involving ions, in order to recover the condensation of Langmuir waves in two dimensions. (paper)

  15. Electronic system for Langmuir probe measurements

    Science.gov (United States)

    Mitov, M.; Bankova, A.; Dimitrova, M.; Ivanova, P.; Tutulkov, K.; Djermanova, N.; Dejarnac, R.; Stöckel, J.; Popov, Tsv K.

    2012-03-01

    A newly developed Langmuir probe system for measurements of current-voltage (IV) characteristics in the tokamak divertor area is presented and discussed. The system is partially controlled by a computer allowing simultaneous and independent feeding and registration of signals. The system is mounted in the COMPASS tokamak, Institute of Plasma Physics, Academy of Sciences of the Czech Republic. The new electronic circuit boards include also active low-pass filters which smooth the signal before recording by the data acquisition system (DAQ). The signal is thus less noisy and the data processing is much easier. We also designed and built a microcontroller-driven waveform generator with resolution of 1 Ms/s. The power supply is linear and uses a transformer. We avoided the use of a switching power supply because of the noise that it could generate. Examples of measurements of the IV characteristics by divertor probes in the COMPASS tokamak and evaluation of the EEDF are presented.

  16. On the role of sound in the strong Langmuir turbulence

    International Nuclear Information System (INIS)

    Malkin, V.M.

    1989-01-01

    The main directions in the precision of the theory of strong Langmuir turbulence caused by the necessity of account of sound waves in plasma are preseted. In particular the effect of conversion of short-wave modulations in Langmuir waves induced by sound waves, are briefly described. 8 refs

  17. An Observation of Diamond-Shaped Particle Structure in a Soya Phosphatidylcohline and Bacteriorhodopsin Composite Langmuir Blodgett Film Fabricated by Multilayer Molecular Thin Film Method

    Science.gov (United States)

    Tsujiuchi, Y.; Makino, Y.

    A composite film of soya phosphatidylcohline (soya PC) and bacteriorhodopsin (BR) was fabricated by the multilayer molecular thin film method using fatty acid and lipid on a quartz substrate. Direct Force Microscopy (DFM), UV absorption spectra and IR absorption spectra of the film were characterized on the detail of surface structure of the film. The DFM data revealed that many rhombus (diamond-shaped) particles were observed in the film. The spectroscopic data exhibited the yield of M-intermediate of BR in the film. On our modelling of molecular configuration indicate that the coexistence of the strong inter-molecular interaction and the strong inter-molecular interaction between BR trimmers attributed to form the particles.

  18. Layer by layer assembly of gold nanoparticles and graphene via Langmuir Blodgett method for efficient light-harvesting in photocatalytic applications

    Energy Technology Data Exchange (ETDEWEB)

    Shakir, Imran, E-mail: shakir@skku.edu [Deanship of scientific research, College of Engineering, King Saud University, PO-BOX 800, Riyadh 11421 (Saudi Arabia); Ali, Zahid [BK 21 Physics Research Division, Department of Energy Science, Institute of Basic Sciences, SKKU Advanced Institute of Nanotechnology, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); National Institute of Lasers and Optronics, Islamabad (Pakistan); Kang, Dae Joon [BK 21 Physics Research Division, Department of Energy Science, Institute of Basic Sciences, SKKU Advanced Institute of Nanotechnology, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2014-12-25

    Highlights: • Layer by layer assembly of gold nanoparticles and graphene. • Efficient visible light photocatalysis. • Plasmonic resonances by nanoparticles are utilized for visible light scattering. • Electron scavenging reaction. • Easy handling and recycling. - Abstract: The synthesis of a photocatalyst that is highly active under visible light is one of the most challenging tasks for solar-energy utilization. Here we report a multilayer assembly of gold nanoparticles and graphene that offers dual functionality to efficiently harness visible photons. Firstly, plasmonic resonances by gold nanoparticles are utilized for visible light scattering; secondly the electron scavenging reaction is enhanced by the gold nanoparticles trapping the electrons that are injected from the dye into the graphene. Moreover, the structure is in the form of a thin film, which demonstrates the potential for easy handling and recycling. Precise control over light harvesting and the photocatalytic response is achieved by controlling the number of layers.

  19. Funkcionalizace povrchu polylaktidu absorpcí Langmuir-Blodgett filmů amfifilních blokových kopolymerů

    Czech Academy of Sciences Publication Activity Database

    Kubies, Dana; Machová, Luďka; Brynda, Eduard; Lukáš, Jaromír; Rypáček, František

    2002-01-01

    Roč. 96, č. 4 (2002), s. 224 ISSN 0009-2770. [Sigma - Aldrich Conference of Young Chemists and Biologists /2./. 22.05.2002-25.05.2002, Velké Meziříčí] R&D Projects: GA AV ČR KSK4055109 Keywords : polylactide * polycaprolactone Subject RIV: CC - Organic Chemistry

  20. Layer by layer assembly of gold nanoparticles and graphene via Langmuir Blodgett method for efficient light-harvesting in photocatalytic applications

    International Nuclear Information System (INIS)

    Shakir, Imran; Ali, Zahid; Kang, Dae Joon

    2014-01-01

    Highlights: • Layer by layer assembly of gold nanoparticles and graphene. • Efficient visible light photocatalysis. • Plasmonic resonances by nanoparticles are utilized for visible light scattering. • Electron scavenging reaction. • Easy handling and recycling. - Abstract: The synthesis of a photocatalyst that is highly active under visible light is one of the most challenging tasks for solar-energy utilization. Here we report a multilayer assembly of gold nanoparticles and graphene that offers dual functionality to efficiently harness visible photons. Firstly, plasmonic resonances by gold nanoparticles are utilized for visible light scattering; secondly the electron scavenging reaction is enhanced by the gold nanoparticles trapping the electrons that are injected from the dye into the graphene. Moreover, the structure is in the form of a thin film, which demonstrates the potential for easy handling and recycling. Precise control over light harvesting and the photocatalytic response is achieved by controlling the number of layers

  1. International Conference on Langmuir-Blodgett Films (5th) Held in Paris, France on 26-30 August 1991, Abstracts Booklet

    Science.gov (United States)

    1991-08-01

    glyceryl monooleate ( GMO ) and bovine-brain pbhophazidylsflne (PS) bilayer lipid membranes (BLMs) were investigated by simultaneous optical and electrical...interfacial tensions (,y) of GMO and PS BLMs were calculated to be 0.22:0.02 mN/m and 0.29_+0.03 mN/m, respectively. Support of this work by a grant...Halobacterium holobium has been introduced into LB film of soybean phospholipid and the orientation of bacteriorhodopsin in multilayer LB films has been measured

  2. ON QUIET-TIME SOLAR WIND ELECTRON DISTRIBUTIONS IN DYNAMICAL EQUILIBRIUM WITH LANGMUIR TURBULENCE

    International Nuclear Information System (INIS)

    Zaheer, S.; Yoon, P. H.

    2013-01-01

    A recent series of papers put forth a self-consistent theory of an asymptotically steady-state electron distribution function and Langmuir turbulence intensity. The theory was developed in terms of the κ distribution which features Maxwellian low-energy electrons and a non-Maxwellian energetic power-law tail component. The present paper discusses a generalized κ distribution that features a Davydov-Druyvesteyn type of core component and an energetic power-law tail component. The physical motivation for such a generalization is so that the model may reflect the influence of low-energy electrons interacting with low-frequency kinetic Alfvénic turbulence as well as with high-frequency Langmuir turbulence. It is shown that such a solution and the accompanying Langmuir wave spectrum rigorously satisfy the balance requirement between the spontaneous and induced emission processes in both the particle and wave kinetic equations, and approximately satisfy the similar balance requirement between the spontaneous and induced scattering processes, which are nonlinear. In spite of the low velocity modification of the electron distribution function, it is shown that the resulting asymptotic velocity power-law index α, where f e ∼ v –α is close to the average index observed during the quiet-time solar wind condition, i.e., α ∼ O(6.5) whereas α average ∼ 6.69, according to observation

  3. Equilibrium spreading pressure and Langmuir–Blodgett film formation of omega-substituted palmitic acids

    Energy Technology Data Exchange (ETDEWEB)

    Snow, Arthur W., E-mail: arthur.snow@nrl.navy.mil; Jernigan, Glenn G.; Ancona, Mario G.

    2014-04-01

    Langmuir–Blodgett isotherms and equilibrium spreading pressures were measured for compounds of the series X–(CH{sub 2}){sub 15}COOH, X = CH{sub 3}, SH, OH, F, Cl, Br. Only the CH{sub 3} and F terminated compounds formed monolayers with sufficient stability for accurate isotherm measurement, film transfer and X-ray photoelectron spectroscopic analysis. The presence of the terminal heteroatom substituents significantly diminished the stability of the L–B film and depressed the equilibrium spreading pressures (20 °C) from 15.4 mN/m for the CH{sub 3} terminated compound to a range of 0.95 to 0.08 mN/m for the other members of the series. These characteristics are attributed to the monolayer film being in a metastable state and the dipole moment of the heteroatom terminal group increasing the monolayer film kinetic instability by facilitating the formation of three-dimensional structures. - Highlights: • Compound series X–(CH{sub 2}){sub 15}COOH, X = CH{sub 3}, SH, OH, F, Cl, Br was analyzed. • Only-CH{sub 3} and-F terminated compounds form stable Langmuir–Blodgett films. • Heteroatom terminal groups promote kinetic instability in Langmuir–Blodgett films. • X-ray photoelectron spectra analyzed for molecular orientation and packing density.

  4. Ar{sup +} ion irradiation-induced reorganization of colloidal silica nanoparticles in Langmuir–Blodgett monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Lugomer, S., E-mail: lugomer@irb.hr [Rudjer Boskovic» Institute, Bijenicka c. 54, 10001 Zagreb (Croatia); Zolnai, Z.; Tóth, A.L.; Deák, A.; Nagy, N. [Research Centre for Natural Sciences, Institute of Technical Physics and Materials Science, Hungarian Academy of Sciences, 1121 Budapest, Konkoly Thege M. út 29-33 (Hungary)

    2015-01-01

    The Ar{sup +} ion irradiation-induced reorganization of Langmuir–Blodgett monolayers of colloidal silica nanoparticles with a diameter of 220 nm and 450 nm deposited on silicon substrate is investigated in a wide range of ion fluences. The cluster formation, average cluster size, ion beam-induced charging and discharging of particles, heating effects, the ion beam-induced viscous flow as well as the swelling of the Si substrate as a function of the ion fluence are discussed. Inhomogeneous particle distribution causes strong nonlinear Si swelling inside wide defect-channels between the clusters and linear Si swelling inside narrow channels between the particles. At low ion fluences particle charging and Coulomb repulsion forces govern the particle reorganization process, while at high ion fluences ion beam-induced viscous flow and hydrodynamic forces between the particles and the underlying substrate play major role. Two different types of patterns: smaller compact clusters of few particles and longer chain-like clusters of dozens of particles are observed. The dynamics of the reorganization process in both cases is treated analogous to the dynamics of colloidal suspensions based on the Tanaka–Araki model. The results of the model are comparable to the experimentally observed cluster characteristics. - Highlights: • Reorganization of LB layers under low energy Ar{sup +} ion irradiation • Low fluence: the particles move as solid particles on solid substrate. • High fluence: the solid particles move on the soft fluid-like substrate. • Very high fluence: the soft particles move on the soft fluid-like substrate. • Reorganization is modeled by dynamics of colloidal suspensions.

  5. Synthesis and spectral properties of preorganized BODIPYs in solutions and Langmuir-Schaefer films

    Science.gov (United States)

    Marfin, Yuriy S.; Usoltsev, Sergey D.; Kazak, Alexandr V.; Smirnova, Antonina I.; Rumyantsev, Evgeniy V.; Molchanov, Evgeniy E.; Kuznetsov, Vladimir V.; Chumakov, Alexey S.; Glukhovskoy, Evgeny G.

    2017-12-01

    In order to investigate the influence of molecular structure peculiarities of boron-dipyrrine dyes (BODIPYs) on their properties in solutions and supramolecular organization in Langmuir-Schaefer (LS) films, four new BODIPY dyes with various aliphatic, aromatic or mixed nature meso-subtituents were synthesized and investigated. Spectral characteristics (electronic absorption and fluorescence) of the synthesized compounds in organic solvents and LS-films were studied. Floating monolayers of the BODIPYs were formed from chloroform solutions placed onto water subphase in Langmuir-Blodgett through. Thin films were prepared using the Langmuir-Schaefer technique by the transfer of floating monolayers onto standard polished glass, ITO covered glass or pure silicon substrate. The variation of the dye structure we consider as a preorganization aiming to influence the structure of LS-films. The morphology and structure of the LS-films was examined by fluorescent microscopy, scanning electron microscopy, atomic force microscopy and small angle X-ray diffraction analysis. It was found that the introduced substituents have no substantial influence on the position of the absorption and fluorescence bands in dilute solutions. In contrast, the fluorescent characteristics of the LS-films significantly depend on the substituent nature. Therefore, this strategy could be used for the direct tuning of compounds fluorescent properties in LS-films. Concerning the LS-film surface characteristics it was proved that the films are homogeneous, without disruptions and only some widely-spaced microcrystals could be observed. With respect to the LS-film structure, the change of the substituents introduced to the BODIPY molecule did not influence the average given periodicity of layers (d = 0.3-0.4 nm). This value corresponds to a single-layer arrangement of BODIPY molecules located parallel to the substrate surface. Nevertheless, the diffraction peak intensities depended on the molecular

  6. Experimental signatures of localization in Langmuir wave turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Rose, H.A.; DuBois, D.F.; Russell, D.; Bezzerides, B.

    1988-01-01

    Features in certain laser-plasma and ionospheric experiments are identified with the basic properties of Langmuir wave turbulence. Also, a model of caviton nucleation is presented which leads to certain novel scaling predictions. 12 refs., 19 figs.

  7. An Adaptive Langmuir Probe for CubeSats and Explorers

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to build an Adaptive Langmuir Probe (ALP) for CubeSats designed to mitigate spacecraft charging unique to small platforms. This project builds a new...

  8. Electrical characterization of single molecule and Langmuir–Blodgett monomolecular films of a pyridine-terminated oligo(phenylene-ethynylene derivative

    Directory of Open Access Journals (Sweden)

    Henrry M. Osorio

    2015-05-01

    Full Text Available Monolayer Langmuir–Blodgett (LB films of 1,4-bis(pyridin-4-ylethynylbenzene (1 together with the “STM touch-to-contact” method have been used to study the nature of metal–monolayer–metal junctions in which the pyridyl group provides the contact at both molecule–surface interfaces. Surface pressure vs area per molecule isotherms and Brewster angle microscopy images indicate that 1 forms true monolayers at the air–water interface. LB films of 1 were fabricated by deposition of the Langmuir films onto solid supports resulting in monolayers with surface coverage of 0.98 × 10−9 mol·cm−2. The morphology of the LB films that incorporate compound 1 was studied using atomic force microscopy (AFM. AFM images indicate the formation of homogeneous, monomolecular films at a surface pressure of transference of 16 mN·m−1. The UV–vis spectra of the Langmuir and LB films reveal that 1 forms two dimensional J-aggregates. Scanning tunneling microscopy (STM, in particular the “STM touch-to-contact” method, was used to determine the electrical properties of LB films of 1. From these STM studies symmetrical I–V curves were obtained. A junction conductance of 5.17 × 10−5 G0 results from the analysis of the pseudolinear (ohmic region of the I–V curves. This value is higher than that of the conductance values of LB films of phenylene-ethynylene derivatives contacted by amines, thiols, carboxylate, trimethylsilylethynyl or acetylide groups. In addition, the single molecule I–V curve of 1 determined using the I(s method is in good agreement with the I–V curve obtained for the LB film, and both curves fit well with the Simmons model. Together, these results not only indicate that the mechanism of transport through these metal–molecule–metal junctions is non-resonant tunneling, but that lateral interactions between molecules within the LB film do not strongly influence the molecule conductance. The results presented here

  9. Oscillatory barrier-assisted Langmuir–Blodgett deposition of large-scale quantum dot monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Shicheng, E-mail: johnxu@stanford.edu [Department of Mechanical Engineering, Stanford University, Stanford, CA 94305 (United States); Dadlani, Anup L. [Department of Chemistry, Stanford University, Stanford, CA 94305 (United States); Acharya, Shinjita; Schindler, Peter [Department of Mechanical Engineering, Stanford University, Stanford, CA 94305 (United States); Prinz, Fritz B. [Department of Mechanical Engineering, Stanford University, Stanford, CA 94305 (United States); Department of Material Science and Engineering, Stanford University, Stanford, CA 94305 (United States)

    2016-03-30

    Graphical abstract: - Highlights: • Large-scale monolayers of quantum dots with full coverage up to several millimeters have been achieved by incorporating oscillatory barriers in the commonly used Langmuir–Blodgett method. • By examining dilatational moduli as a function of average particle density, one can obtain an appropriate density and proper timing for depositing desired films. • Time evolution of dilatational moduli gives a clear indication of the film morphology and its stability. - Abstract: Depositing continuous, large-scale quantum dot films with low pinhole density is an inevitable but nontrivial step for studying their properties for applications in catalysis, electronic devices, and optoelectronics. This rising interest in high-quality quantum dot films has provided research impetus to improve the deposition technique. We show that by incorporating oscillatory barriers in the commonly used Langmuir–Blodgett method, large-scale monolayers of quantum dots with full coverage up to several millimeters have been achieved. With assistance of perturbation provided by the oscillatory barriers, the film has been shown to relax towards thermal equilibrium, and this physical process has been supported by molecular dynamics simulation. In addition, time evolution of dilatational moduli has been shown to give a clear indication of the film morphology and its stability.

  10. Ethical and Friendly Researchers, but not Insiders: A Response to Blodgett, Boyer, and Turk

    Directory of Open Access Journals (Sweden)

    Michelle K. McGinn

    2005-09-01

    Full Text Available This commentary is a response to the article by Lisa J. BLODGETT, Wanda BOYER, and Emily TURK (2005 in this issue of FQS. The original article describes ethical challenges and relational issues within a large, ongoing, qualitative study about the development of self-regulation in early childhood. Those authors focus in particular upon: (a obtaining free and informed consent, (b working with vulnerable populations, and (c bal­ancing insider and outsider roles. I identify some key strengths of the research that may provide use­ful models for other researchers, while cautioning against the evident overgeneralization of the term "insider." BLODGETT et al. clearly demonstrate that they are ethical and friendly researchers, but they are not insiders in the daycare settings where their research takes place. I conclude with a call for researchers to seriously consider and empirically document what it might mean to adopt a subject-centered perspective on research ethics. URN: urn:nbn:de:0114-fqs0503375

  11. Spatiotemporal temperature fluctuation measurements by means of a fast swept Langmuir probe array.

    Science.gov (United States)

    Schubert, M; Endler, M; Thomsen, H

    2007-05-01

    Stationary Langmuir probe measurements of ion saturation current and floating potential in a plasma cannot give direct information on density and plasma potential fluctuations in the presence of temperature fluctuations. This problem can be avoided if the probe bias voltage is continuously swept faster than the fluctuation time scale, recording the current-voltage characteristic. This article reports the development of a spatiotemporal highly resolving Langmuir probe array with 15 fast swept tips, operating in the strongly magnetized, collisionless edge plasma of the Wendelstein 7-AS stellarator [Plasma Phys. Controlled Fusion 31, 1579 (1989)]. The probe tips are aligned in the poloidal direction, the tip spacing is 2 mm, and the sweeping frequency is 1.4 MHz. Current and voltage data are sampled with 50 MHz. The high bandwidth of the measurement is achieved by placing miniaturized differential amplifiers close to the probe tips in order to do an impedance transform. The surface-mounting technology and an additional inverse feedback module are utilized, allowing for an input voltage range of +/-100 V, and a common mode rejection rate of 55 dB at 4 MHz, which is sufficient to resolve the nonlinear probe characteristic. For the evaluation of the data, a fit model for stationary probes is employed and found adequate. Changes of the plasma parameters during one voltage sweep are taken into account by a linear interpolation of the fit parameters. Spatio-temporal fluctuation data gained by a fast swept Langmuir probe array, which can be relevant for the turbulent radial transport of particles and energy, are presented.

  12. Spatiotemporal temperature fluctuation measurements by means of a fast swept Langmuir probe array

    Science.gov (United States)

    Schubert, M.; Endler, M.; Thomsen, H.

    2007-05-01

    Stationary Langmuir probe measurements of ion saturation current and floating potential in a plasma cannot give direct information on density and plasma potential fluctuations in the presence of temperature fluctuations. This problem can be avoided if the probe bias voltage is continuously swept faster than the fluctuation time scale, recording the current-voltage characteristic. This article reports the development of a spatiotemporal highly resolving Langmuir probe array with 15 fast swept tips, operating in the strongly magnetized, collisionless edge plasma of the Wendelstein 7-AS stellarator [Plasma Phys. Controlled Fusion 31, 1579 (1989)]. The probe tips are aligned in the poloidal direction, the tip spacing is 2mm, and the sweeping frequency is 1.4MHz. Current and voltage data are sampled with 50MHz. The high bandwidth of the measurement is achieved by placing miniaturized differential amplifiers close to the probe tips in order to do an impedance transform. The surface-mounting technology and an additional inverse feedback module are utilized, allowing for an input voltage range of ±100V, and a common mode rejection rate of 55dB at 4MHz, which is sufficient to resolve the nonlinear probe characteristic. For the evaluation of the data, a fit model for stationary probes is employed and found adequate. Changes of the plasma parameters during one voltage sweep are taken into account by a linear interpolation of the fit parameters. Spatio-temporal fluctuation data gained by a fast swept Langmuir probe array, which can be relevant for the turbulent radial transport of particles and energy, are presented.

  13. Study of a Laser-Produced Plasma by Langmuir Probes

    DEFF Research Database (Denmark)

    Chang, C. T.; Hasimi, M.; Pant, H. C.

    1977-01-01

    The structure, the parameters and the expansion of the plasma produced by focusing a 7 J, 20 ns Nd-glass laser on stainless-steel and glass targets suspended in a high-vacuum chamber were investigated by Langmuir probes. It was observed that the probe signals consisted of a photoelectric-emission......The structure, the parameters and the expansion of the plasma produced by focusing a 7 J, 20 ns Nd-glass laser on stainless-steel and glass targets suspended in a high-vacuum chamber were investigated by Langmuir probes. It was observed that the probe signals consisted of a photoelectric...

  14. Irving langmuir: o milagre da ciência

    Directory of Open Access Journals (Sweden)

    Gugliotti Marcos

    2001-01-01

    Full Text Available Irving Langmuir received the Nobel Prize in Chemistry in 1932 "...for his outstanding discoveries and investigations within the field of surface chemistry", according to the Swedish Academy. However, few people know that his work comprises other very important contributions, and not only for chemistry, such as the discovery of plasma, the atomic hydrogen, the pure thermoionic phenomenon, the development of the cloud seeding technique for weather modification, among many others. This paper summarizes Langmuir's most important discoveries and theories, with an especial mention for his practical inventions and his work on the atomic theory.

  15. An investigation of dust particles orbiting a Langmuir probe

    Energy Technology Data Exchange (ETDEWEB)

    Ramazanov, T S; Kodanova, S K; Dzhumagulova, K N; Dosbolayev, M K; Jumabekov, A N [IETP, Al Farabi Kazakh National University, Tole Bi 96a, 050012 Almaty (Kazakhstan); Petrov, O F; Antipov, S N [Joint Institute for High Temperatures of RAS, 13-2, Izhorskaya St, Moscow 125412 (Russian Federation)

    2009-05-29

    In the present work, the behavior of dust particles near an attracting Langmuir cylindrical probe in glow discharge plasma was investigated experimentally. Trajectories of dust particles for different initial kinetic energies and impact parameters were analyzed numerically. The comparision between experimental and simulation results are made. The results obtained can be used for the development of new dusty plasma diagnostic techniques.

  16. SYNTHESIS, PHYSICAL CHARACTERIZATIONS, AND LANGMUIR FILMS OF NEW METHANOFULLERENES

    NARCIS (Netherlands)

    RAVAINE, S; LEPECQ, F; MINGOTAUD, C; DELHAES, P; HUMMELEN, JC; WUDL, F; PATTERSON, LK

    1995-01-01

    Various methanofullerenes functionalized with either hydrophobic or polar groups have been synthesized. Studies of such compounds by surface pressure measurements and in situ UV-visible spectroscopy in Langmuir films show that these two types of functionalizations do not prevent the formation of

  17. Langmuir probe study of plasma expansion in pulsed laser ablation

    DEFF Research Database (Denmark)

    Hansen, T.N.; Schou, Jørgen; Lunney, J.G.

    1999-01-01

    Langmuir probes were used to monitor the asymptotic expansion of the plasma produced by the laser ablation of a silver target in a vacuum. The measured angular and temporal distributions of the ion flux and electron temperature were found to be in good agreement with the self-similar isentropic...

  18. Langmuir probe study in the nonresonant current drive regime of ...

    Indian Academy of Sciences (India)

    Abstract. Characterization of the current drive regime is done for helicon wave- generated plasma in a torus, at a very high operating frequency. A radiofrequency- compensated Langmuir probe is designed and used for the measurement of plasma parameters along with the electron energy distributions in radial scans of the ...

  19. Terahertz generation by beating two Langmuir waves in a warm and collisional plasma

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiao-Bo; Qiao, Xin; Cheng, Li-Hong; Tang, Rong-An; Zhang, Ai-Xia; Xue, Ju-Kui, E-mail: xuejk@nwnu.edu.cn [Key Laboratory of Atomic & Molecular Physics and Functional Materials of Gansu Province, College of Physics and Electronics Engineering, Northwest Normal University, Lanzhou 730070 (China)

    2015-09-15

    Terahertz (THz) radiation generated by beating of two Langmuir waves in a warm and collisional plasma is discussed theoretically. The critical angle between the two Langmuir waves and the critical wave-length (wave vector) of Langmuir waves for generating THz radiation are obtained analytically. Furthermore, the maximum radiation energy is obtained. We find that the critical angle, the critical wave-length, and the generated radiation energy strongly depend on plasma temperature and wave-length of the Langmuir waves. That is, the THz radiation generated by beating of two Langmuir waves in a warm and collisional plasma can be controlled by adjusting the plasma temperature and the Langmuir wave-length.

  20. INFRARED PHOTOLUMINESCENCE SPECTRA OF PBS NANOPARTICLES PREPARED BY LANGMUIR–BLODGETT AND LASER ABLATION METHODS

    Directory of Open Access Journals (Sweden)

    Zdeněk Remes

    2014-12-01

    Full Text Available We optimized the optical setup originally designed for the photoluminescence measurements in the spectral range 400‒1100 nm. New design extends the spectral range into the near infrared region 900‒1700 nm and allows the colloidal solutions measurements in cuvettes as well as the measurements of nanoparticles deposited in the form of thin films on glass substrates. The infrared photoluminescence spectra of the PbS nanoparticles prepared by the Langmuir–Blodgett technique show the higher photoluminescence intensity and the shift to the shorter wavelengths compared to the infrared photoluminescence spectra of the PbS nanoparticles prepared by the laser ablation from PbS target. We aslo proved the high stability of PbS nanoparticles prepared in the form of thin layers.

  1. Annealing assisted structural and surface morphological changes in Langmuir–Blodgett films of nickel octabutoxy phthalocyanine

    Energy Technology Data Exchange (ETDEWEB)

    Shilpa Harish, T.; Viswanath, P., E-mail: viswanath@cnsms.res.in

    2016-01-01

    We report our studies on thin films of metallo-phthalocyanine (MPc), Nickel(II)1,4,8,11,15,18,22,25-octabutoxy-29H,31H-phthalocyanine (NiPc(OBu){sub 8}) transferred in a well defined thermodynamic state over a self assembled monolayer (octadecyl trichlorosilane)/SiO{sub 2}/Si substrate using the Langmuir–Blodgett (LB) method. The films are characterized using differential scanning calorimetry (DSC), grazing incidence X-ray diffraction (GIXD) and atomic force microscopy (AFM) techniques. DSC studies on powdered samples in the bulk indicate enantiotropic solid–solid phase transition. GIXD studies on the as-deposited LB film show a Bragg peak indicating crystallinity of the thin film. Annealing (373 K) results in reduction of lattice spacing (1.21 Å) signifying changes in molecular packing within the unit cell. At this stage, an additional Bragg peak is observed which grows at the expense of the former one and they coexist between 373 K and 423 K. A discontinuity in lattice spacing from 20.73 to 15.12 Å with annealing indicates clearly a structural change of the underlying crystalline lattice. Correspondingly, the surface morphology images obtained using AFM show, with annealing, a transformation from spherical granular morphology to elongated, flat crystallites suggesting asymmetric growth process. Statistical parameters of the grain extracted from the AFM images show that the size, fractal dimension and circularity are affected by annealing. Based on these studies, we infer the structural and surface morphological changes of the meta-stable phase (Form I) to the stable phase (Form II) in annealed LB films of phthalocyanine. - Highlights: • Langmuir–Blodgett (LB) films of phthalocyanine subjected to thermal annealing. • Structural transformation and coexistence of polymorphs in LB films • Surface morphology changes from nanoscale grains to elongated crystallites. • Reduction of fractal dimension and circularity index reveals asymmetric growth.

  2. CASSINI SS/S RPWS DERIVED LANGMUIR PROBE SWEEP V1.0

    Data.gov (United States)

    National Aeronautics and Space Administration — The Cassini Radio and Plasma Wave Science (RPWS) Langmuir Probe Sweep data set includes all thermal plasma information derived from Langmuir Probe voltage sweeps...

  3. Evaluating polymeric biomaterial-environment interfaces by Langmuir monolayer techniques.

    Science.gov (United States)

    Schöne, Anne-Christin; Roch, Toralf; Schulz, Burkhard; Lendlein, Andreas

    2017-05-01

    Polymeric biomaterials are of specific relevance in medical and pharmaceutical applications due to their wide range of tailorable properties and functionalities. The knowledge about interactions of biomaterials with their biological environment is of crucial importance for developing highly sophisticated medical devices. To achieve optimal in vivo performance, a description at the molecular level is required to gain better understanding about the surface of synthetic materials for tailoring their properties. This is still challenging and requires the comprehensive characterization of morphological structures, polymer chain arrangements and degradation behaviour. The review discusses selected aspects for evaluating polymeric biomaterial-environment interfaces by Langmuir monolayer methods as powerful techniques for studying interfacial properties, such as morphological and degradation processes. The combination of spectroscopic, microscopic and scattering methods with the Langmuir techniques adapted to polymers can substantially improve the understanding of their in vivo behaviour. © 2017 The Author(s).

  4. TRANSPOSICION DIDACTICA DEL MODELO CIENTIFICO DE LEWIS-LANGMUIR

    Directory of Open Access Journals (Sweden)

    Janneth Isabel Herreño Chaves

    2010-04-01

    Full Text Available Este artículo presenta las conclusiones obtenidas en un proyecto de investigación, en el que se auscultó la transposición didáctica que hacen del modelo de Lewis-Langmuir, diez de los textos para la enseñanza de la química más empleados por algunos profesores universitarios y de educación secundaria. Para el análisis se tuvo en cuenta lo histórico, lo epistemológico y lo didáctico. Los resultados muestran que en estos textos no hay referencia a la historia de la construcción del modelo y solo se reducen a la utilización didáctica de las fórmulas de Lewis. Tampoco aluden al papel cumplido por I. Langmuir en la divulgación de dicho modelo.

  5. Photo-induced travelling waves in condensed Langmuir monolayers

    CERN Document Server

    Tabe, Y; Yokoyama, H

    2003-01-01

    We report the detailed properties of photo-induced travelling waves in liquid crystalline Langmuir monolayers composed of azobenzene derivatives. When the monolayer, in which the constituent rodlike molecules are coherently tilted from the layer normal, is weakly illuminated to undergo the trans-cis photo-isomerization, spatio-temporal periodic oscillations of the molecular azimuth begin over the entire excited area and propagate as a two-dimensional orientational wave. The wave formation takes place only when the film is formed at an asymmetric interface with broken up-down symmetry and when the chromophores are continuously excited near the long-wavelength edge of absorption to induce repeated photo-isomerizations between the trans and cis forms. Under proper illumination conditions, Langmuir monolayers composed of a wide variety of azobenzene derivatives have been confirmed to exhibit similar travelling waves with velocity proportional to the excitation power irrespective of the degree of amphiphilicity. T...

  6. Characteristics of langmuir probe in low temperature, weakly magnetized plasmas

    International Nuclear Information System (INIS)

    Wu Liqi; Liu Wandong; Xie Jinlin; Yu Zhi; Lan Tao; Ouyang Liang; Wang Yi; Zhao Kai

    2003-01-01

    The systematic Langmuir probe measurements for a weakly magnetized plasma have been carried out in the Linear Magnetized Plasma Device for different magnetic fields. By comparing the ion current density of probes with different sizes, the sheath thickness can be evaluated. It is found that while the ratio of cylindrical probe's dimension to ion Larmor radius is not more than 2, the model of probe for non-magnetized plasma is still applicable

  7. Epidemic Intelligence. Langmuir and the Birth of Disease Surveillance

    OpenAIRE

    Lyle Fearnley

    2010-01-01

    In the wake of the SARS and influenza epidemics of the past decade, one public health solution has become a refrain: surveillance systems for detection of disease outbreaks. This paper is an effort to understand how disease surveillance for outbreak detection gained such paramount rationality in contemporary public health. The epidemiologist Alexander Langmuir is well known as the creator of modern disease surveillance. But less well known is how he imagined disease surveillance as one part o...

  8. Epidemic Intelligence. Langmuir and the Birth of Disease Surveillance

    Directory of Open Access Journals (Sweden)

    Lyle Fearnley

    2010-12-01

    Full Text Available In the wake of the SARS and influenza epidemics of the past decade, one public health solution has become a refrain: surveillance systems for detection of disease outbreaks. This paper is an effort to understand how disease surveillance for outbreak detection gained such paramount rationality in contemporary public health. The epidemiologist Alexander Langmuir is well known as the creator of modern disease surveillance. But less well known is how he imagined disease surveillance as one part of what he called “epidemic intelligence.” Langmuir developed the practice of disease surveillance during an unprecedented moment in which the threat of biological warfare brought civil defense experts and epidemiologists together around a common problem. In this paper, I describe how Langmuir navigated this world, experimenting with new techniques and rationales of epidemic control. Ultimately, I argue, Langmuir′s experiments resulted in a set of techniques and infrastructures – a system of epidemic intelligence – that transformed the epidemic as an object of human art.

  9. Effects of group velocity and multiplasmon resonances on the modulation of Langmuir waves in a degenerate plasma.

    Science.gov (United States)

    Misra, Amar P; Chatterjee, Debjani; Brodin, Gert

    2017-11-01

    We study the nonlinear wave modulation of Langmuir waves (LWs) in a fully degenerate plasma. Using the Wigner-Moyal equation coupled to the Poisson equation and the multiple scale expansion technique, a modified nonlocal nonlinear Schrödinger (NLS) equation is derived which governs the evolution of LW envelopes in degenerate plasmas. The nonlocal nonlinearity in the NLS equation appears due to the group velocity and multiplasmon resonances, i.e., resonances induced by the simultaneous particle absorption of multiple wave quanta. We focus on the regime where the resonant velocity of electrons is larger than the Fermi velocity and thereby the linear Landau damping is forbidden. As a result, the nonlinear wave-particle resonances due to the group velocity and multiplasmon processes are the dominant mechanisms for wave-particle interaction. It is found that in contrast to classical or semiclassical plasmas, the group velocity resonance does not necessarily give rise the wave damping in the strong quantum regime where ℏk∼mv_{F} with ℏ denoting the reduced Planck's constant, m the electron mass, and v_{F} the Fermi velocity; however, the three-plasmon process plays a dominant role in the nonlinear Landau damping of wave envelopes. In this regime, the decay rate of the wave amplitude is also found to be higher compared to that in the modest quantum regime where the multiplasmon effects are forbidden.

  10. Nonlinear generation of the fundamental radiation in plasmas

    International Nuclear Information System (INIS)

    Chian, A.C.L.; Rizzato, F.B.

    1993-01-01

    Nonlinear generation of coherent electromagnetic radiation by intense Langmuir waves in the vicinity of the fundamental plasma frequency f p is of current interest in space and laboratory plasmas. In a pioneer work, Lashmore-Davies demonstrated that an efficient process for converting intense Langmuir waves into f p electromagnetic radiation can be achieved by two counterstreaming Langmuir pump waves through an electromagnetic oscillating two-stream instability. Recently Chian and Alves, Akimoto and Rizzato and Chian extended the formalism of Lashmore-Davies in order to include mixed processes with induced modes which are purely electrostatic or electromagnetic. In this paper we extend our previous analysis, in order to study the nonlinear interaction involving travelling electromagnetic pumps, low-frequency density fluctuations and high-frequency f p modes which can be electrostatic-electromagnetic hybrids. (author) 5 refs., 2 figs

  11. Nonlinear decay of foreshock Langmuir waves in the presence of plasma inhomogeneities: Theory and Cluster observations

    Czech Academy of Sciences Publication Activity Database

    Souček, Jan; Krasnoselskikh, V.; Dudok de Wit, T.; Pickett, J.; Kletzing, C.

    2005-01-01

    Roč. 110, A8 (2005), A08102/1-A08102/10 ISSN 0148-0227 R&D Projects: GA MŠk ME 650; GA ČR GA202/03/0832 Grant - others:CNRS(FR) PICS 1175; ESA PRODEX(XE) 14529; NSF(US) 0307319; NASA (US) NAG5-9974; NASA (US) NNG04GB98G; European Comunity(XE) HPRN-CT-2001-00314 Institutional research plan: CEZ:AV0Z30420517 Keywords : plasma waves * kinetic waves and instabilities * foreshock * solar wind Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.784, year: 2005

  12. Langmuir monolayers composed of single and double tail sulfobetaine lipids.

    Science.gov (United States)

    Hazell, Gavin; Gee, Anthony P; Arnold, Thomas; Edler, Karen J; Lewis, Simon E

    2016-07-15

    Owing to structural similarities between sulfobetaine lipids and phospholipids it should be possible to form stable Langmuir monolayers from long tail sulfobetaines. By modification of the density of lipid tail group (number of carbon chains) it should also be possible to modulate the two-dimensional phase behaviour of these lipids and thereby compare with that of equivalent phospholipids. Potentially this could enable the use of such lipids for the wide array of applications that currently use phospholipids. The benefit of using sulfobetaine lipids is that they can be synthesised by a one-step reaction from cheap and readily available starting materials and will degrade via different pathways than natural lipids. The molecular architecture of the lipid can be easily modified allowing the design of lipids for specific purposes. In addition the reversal of the charge within the sulfobetaine head group relative to the charge orientation in phospholipids may modify behaviour and thereby allow for novel uses of these surfactants. Stable Langmuir monolayers were formed composed of single and double tailed sulfobetaine lipids. Surface pressure-area isotherm, Brewster Angle Microscopy and X-ray and neutron reflectometry measurements were conducted to measure the two-dimensional phase behaviour and out-of-plane structure of the monolayers as a function of molecular area. Sulfobetaine lipids are able to form stable Langmuir monolayers with two dimensional phase behaviour analogous to that seen for the well-studied phospholipids. Changing the number of carbon tail groups on the lipid from one to two promotes the existence of a liquid condensed phase due to increased Van der Waals interactions between the tail groups. Thus the structure of the monolayers appears to be defined by the relative sizes of the head and tail groups in a predictable way. However, the presence of sub-phase ions has little effect on the monolayer structure, behaviour that is surprisingly different to

  13. The charge transfer characteristic of tetraphenylporphyrin iron chloride Langmuir–Blodgett films

    Energy Technology Data Exchange (ETDEWEB)

    Du, Y.; Li, Z.H., E-mail: liziheng@jlu.edu.cn; Qi, P.; Wang, F.; Liu, D.

    2013-11-01

    The charge transfer characteristic of tetraphenylporphyrin iron (III) chloride (FeP) Langmuir–Blodgett (LB) films on the surface of the ITO glass electrode was reported. When the cyclic voltammetry (CV) scanning was running, the charge transfer characteristic was controlled by the oxidation–reduction process of Fe(III)/Fe(II). The charge transfer characteristic was related to the following factors: the cross-sectional area, relative to the electrode, of FeP as the electron donor (or acceptor). The greater the cross-sectional area of the aggregation of FeP as the electron donor (or acceptor) was, the larger the number of the donated (or accepted) electrons was. The projected area of the cross-section on the ITO electrode. The greater the projected area was, the larger the number of the donated (or accepted) electrons was. The distance between the center of the electron donor (or acceptor) of FeP and the surface of ITO electrode. The smaller the distance was, the greater the rate of donating (or accepting) electrons was. The monolayer coverage, which formed because of the FeP lying on the ITO surface in the form of the monomer and aggregate, was more sensitive to detect oxygen.

  14. The charge transfer characteristic of tetraphenylporphyrin iron chloride Langmuir–Blodgett films

    International Nuclear Information System (INIS)

    Du, Y.; Li, Z.H.; Qi, P.; Wang, F.; Liu, D.

    2013-01-01

    The charge transfer characteristic of tetraphenylporphyrin iron (III) chloride (FeP) Langmuir–Blodgett (LB) films on the surface of the ITO glass electrode was reported. When the cyclic voltammetry (CV) scanning was running, the charge transfer characteristic was controlled by the oxidation–reduction process of Fe(III)/Fe(II). The charge transfer characteristic was related to the following factors: the cross-sectional area, relative to the electrode, of FeP as the electron donor (or acceptor). The greater the cross-sectional area of the aggregation of FeP as the electron donor (or acceptor) was, the larger the number of the donated (or accepted) electrons was. The projected area of the cross-section on the ITO electrode. The greater the projected area was, the larger the number of the donated (or accepted) electrons was. The distance between the center of the electron donor (or acceptor) of FeP and the surface of ITO electrode. The smaller the distance was, the greater the rate of donating (or accepting) electrons was. The monolayer coverage, which formed because of the FeP lying on the ITO surface in the form of the monomer and aggregate, was more sensitive to detect oxygen

  15. Thermionic phenomena the collected works of Irving Langmuir

    CERN Document Server

    Suits, C Guy

    1961-01-01

    Thermionic Phenomena is the third volume of the series entitled The Collected Works of Irving Langmuir. This volume compiles articles written during the 1920's and early 1930's, the period when the science of thermionics is beginning to be of importance. This text is divided into two parts. The first part discusses vacuum pumps, specifically examining the effect of space charge and residual gases on thermionic currents in high vacuum. This part also explains fundamental phenomena in electron tubes having tungsten cathodes and the use of high-power vacuum tubes. The second part of this text loo

  16. Close Columnar Packing of Triangulenium Ions in Langmuir Films

    DEFF Research Database (Denmark)

    Simonsen, Jens B.; Kjær, Kristian; Howes, Paul

    2009-01-01

    Three new tris(dialkylamino)trioxatriangulenium (ATOTA(+)) salts rendered amphiphilic by attachment of two (5a center dot PF6 and 5b center dot PF6) or four (5c center dot PF6) n-decyl chains have been synthesized, and their Langmuir films have been studied by grazing incidence X-ray diffraction...... moiety itself (similar to 17 angstrom), while the repeat distance along the columnar aggregates is only 3.45 angstrom, implicating a near cofacial columnar structure with only a small tilt of the planar carbenium ions relative to the columnar axis. A detailed Bragg rod analysis confirmed an 8-9 degrees...

  17. LINDA – the Astrid-2 Langmuir probe instrument

    Directory of Open Access Journals (Sweden)

    B. Holback

    2001-06-01

    Full Text Available The Swedish micro-satellite Astrid-2, designed for studies in magnetosperic physics, was launched into orbit on 10 December 1998 from the Russian cosmodrome Plesetsk. It was injected into a circular orbit at 1000 km and at 83 degrees inclination. The satellite carried, among other instruments, a double Langmuir Probe instrument called LINDA (Langmuir INterferometer and Density instrument for Astrid-2. The scientific goals of this instrument, as well as the technical design and possible modes of operation, are described. LINDA consists of two lightweight deployable boom systems, each carrying a small spherical probe. With these probes, separated by 2.9 meters, and in combination with a high sampling rate, it was possible to discriminate temporal structures (waves from spatial structures. An on-board memory made it possible to collect data also at times when there was no ground contact. Plasma density and electron temperature data from all magnetic latitudes and for all seasons have been collected.Key words. Ionosphere (plasma temperature and density; plasma waves and instabilities; instruments and techniques

  18. Designs of Langmuir probes for W7-X

    International Nuclear Information System (INIS)

    Laube, Ralph; Laux, Michael; Ye, Min You; Greuner, Henri; Lindig, Stefan

    2011-01-01

    Several designs of Langmuir probes for the stellarator Wendelstein 7-X (W7-X) are described. Different types of probes are proposed for the different divertors to be used during different operational phases of W7-X. Comb-like arrays of stiff probes, arrays of flexible probes, and fixed inlay probes are reviewed. For the initial phase of W7-X it was decided to install arrays of fixed inlay probes. Two mockups were manufactured and one of them was tested with success in the high heat flux test facility GLADIS. For long-pulse operation of W7-X different conceptual designs are proposed and are still developed further. This paper summarizes the different design constrains for the Langmuir probes in the different divertor surroundings, describes the design of the array of inlay probes for the initial phase and the result of the GLADIS test, and gives a preview of the conceptual designs of probes for the long-pulse operational phase of W7-X.

  19. Designs of Langmuir probes for W7-X

    Energy Technology Data Exchange (ETDEWEB)

    Laube, Ralph, E-mail: ralph.laube@ipp.mpg.de [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Teilinstitut Greifswald, Wendelsteinstr. 1, D-17491 Greifswald (Germany); Laux, Michael; Ye, Min You [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Teilinstitut Greifswald, Wendelsteinstr. 1, D-17491 Greifswald (Germany); Greuner, Henri; Lindig, Stefan [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Boltzmannstr. 2, D-85748 Garching (Germany)

    2011-10-15

    Several designs of Langmuir probes for the stellarator Wendelstein 7-X (W7-X) are described. Different types of probes are proposed for the different divertors to be used during different operational phases of W7-X. Comb-like arrays of stiff probes, arrays of flexible probes, and fixed inlay probes are reviewed. For the initial phase of W7-X it was decided to install arrays of fixed inlay probes. Two mockups were manufactured and one of them was tested with success in the high heat flux test facility GLADIS. For long-pulse operation of W7-X different conceptual designs are proposed and are still developed further. This paper summarizes the different design constrains for the Langmuir probes in the different divertor surroundings, describes the design of the array of inlay probes for the initial phase and the result of the GLADIS test, and gives a preview of the conceptual designs of probes for the long-pulse operational phase of W7-X.

  20. Photo-induced travelling waves in condensed Langmuir monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Tabe, Y [Yokoyama Nano-Structured Liquid Crystal Project, ERATO, Japan Science and Technology Corporation, 5-9-9 Tokodai, Tsukuba, Ibaraki 300-2635, Japan (Japan); Yamamoto, T [Yokoyama Nano-Structured Liquid Crystal Project, ERATO, Japan Science and Technology Corporation, 5-9-9 Tokodai, Tsukuba, Ibaraki 300-2635, Japan (Japan); Yokoyama, H [Yokoyama Nano-Structured Liquid Crystal Project, ERATO, Japan Science and Technology Corporation, 5-9-9 Tokodai, Tsukuba, Ibaraki 300-2635, Japan (Japan)

    2003-06-01

    We report the detailed properties of photo-induced travelling waves in liquid crystalline Langmuir monolayers composed of azobenzene derivatives. When the monolayer, in which the constituent rodlike molecules are coherently tilted from the layer normal, is weakly illuminated to undergo the trans-cis photo-isomerization, spatio-temporal periodic oscillations of the molecular azimuth begin over the entire excited area and propagate as a two-dimensional orientational wave. The wave formation takes place only when the film is formed at an asymmetric interface with broken up-down symmetry and when the chromophores are continuously excited near the long-wavelength edge of absorption to induce repeated photo-isomerizations between the trans and cis forms. Under proper illumination conditions, Langmuir monolayers composed of a wide variety of azobenzene derivatives have been confirmed to exhibit similar travelling waves with velocity proportional to the excitation power irrespective of the degree of amphiphilicity. The dynamics can be qualitatively explained by the modified reaction-diffusion model proposed by Reigada, Sagues and Mikhailov.

  1. Behavior of Triple Langmuir Probes in Non-Equilibrium Plasmas

    Science.gov (United States)

    Polzin, Kurt A.; Ratcliffe, Alicia C.

    2018-01-01

    The triple Langmuir probe is an electrostatic probe in which three probe tips collect current when inserted into a plasma. The triple probe differs from a simple single Langmuir probe in the nature of the voltage applied to the probe tips. In the single probe, a swept voltage is applied to the probe tip to acquire a waveform showing the collected current as a function of applied voltage (I-V curve). In a triple probe three probe tips are electrically coupled to each other with constant voltages applied between each of the tips. The voltages are selected such that they would represent three points on the single Langmuir probe I-V curve. Elimination of the voltage sweep makes it possible to measure time-varying plasma properties in transient plasmas. Under the assumption of a Maxwellian plasma, one can determine the time-varying plasma temperature T(sub e)(t) and number density n(sub e)(t) from the applied voltage levels and the time-histories of the collected currents. In the present paper we examine the theory of triple probe operation, specifically focusing on the assumption of a Maxwellian plasma. Triple probe measurements have been widely employed for a number of pulsed and timevarying plasmas, including pulsed plasma thrusters (PPTs), dense plasma focus devices, plasma flows, and fusion experiments. While the equilibrium assumption may be justified for some applications, it is unlikely that it is fully justifiable for all pulsed and time-varying plasmas or for all times during the pulse of a plasma device. To examine a simple non-equilibrium plasma case, we return to basic governing equations of probe current collection and compute the current to the probes for a distribution function consisting of two Maxwellian distributions with different temperatures (the two-temperature Maxwellian). A variation of this method is also employed, where one of the Maxwellians is offset from zero (in velocity space) to add a suprathermal beam of electrons to the tail of the

  2. The Effect of Large Scale Salinity Gradient on Langmuir Turbulence

    Science.gov (United States)

    Fan, Y.; Jarosz, E.; Yu, Z.; Jensen, T.; Sullivan, P. P.; Liang, J.

    2017-12-01

    Langmuir circulation (LC) is believed to be one of the leading order causes of turbulent mixing in the upper ocean. It is important for momentum and heat exchange across the mixed layer (ML) and directly impact the dynamics and thermodynamics in the upper ocean and lower atmosphere including the vertical distributions of chemical, biological, optical, and acoustic properties. Based on Craik and Leibovich (1976) theory, large eddy simulation (LES) models have been developed to simulate LC in the upper ocean, yielding new insights that could not be obtained from field observations and turbulent closure models. Due its high computational cost, LES models are usually limited to small domain sizes and cannot resolve large-scale flows. Furthermore, most LES models used in the LC simulations use periodic boundary conditions in the horizontal direction, which assumes the physical properties (i.e. temperature and salinity) and expected flow patterns in the area of interest are of a periodically repeating nature so that the limited small LES domain is representative for the larger area. Using periodic boundary condition can significantly reduce computational effort in problems, and it is a good assumption for isotropic shear turbulence. However, LC is anisotropic (McWilliams et al 1997) and was observed to be modulated by crosswind tidal currents (Kukulka et al 2011). Using symmetrical domains, idealized LES studies also indicate LC could interact with oceanic fronts (Hamlington et al 2014) and standing internal waves (Chini and Leibovich, 2005). The present study expands our previous LES modeling investigations of Langmuir turbulence to the real ocean conditions with large scale environmental motion that features fresh water inflow into the study region. Large scale gradient forcing is introduced to the NCAR LES model through scale separation analysis. The model is applied to a field observation in the Gulf of Mexico in July, 2016 when the measurement site was impacted by

  3. Microscopic and spectroscopic properties of Langmuir–Blodgett films composed of flavins and their aggregation structures

    International Nuclear Information System (INIS)

    Lim, Jong Kuk; Jo, Jihee; Jang, Dasol; Jang, Hyeong Ju

    2015-01-01

    Isoalloxazine derivatives (flavins) are commonly found in natural systems that are involved in an electron transfer process, such as photosynthetic or metabolic systems, and are also frequently used as electron donors in organic-based electronic devices. As an example, molecular photodiodes composed of 7,8-dimethyl-10-dodecyl isoalloxazine (DDI) have been fabricated by the Langmuir–Blodgett (LB) technique, and such devices showed characteristic properties of photodiodes. The efficiency of molecular photodiodes is dependent on the assembled structure of the LB films, which is related to the morphology of the LB films. For that reason, Lim has investigated the morphology of LB films, and found that rod-shaped domains are formed when a DDI monolayer is transferred to a solid substrate above a specific surface pressure (Thin Solid Films, 531 (2013) 499). In that paper, rod-shaped domains were revealed to be collapsed triple layers, i.e., double layers collapsed on the monolayer; however, the detailed aggregation structure of the constituent molecules (DDI) has not been studied. Herein, we investigate the microscopic and spectroscopic properties of LB films composed of DDI. We apply the extended dipole model to explain spectral changes in the absorption spectra and propose an aggregation structure for DDI in the LB films. - Highlights: • Aggregation structure of DDI in LB films was experimentally investigated. • Theoretical estimation is in good agreement with experimental result. • Molecular aggregation structure for DDI in LB films was proposed. • Molecular configuration in LB films is changed from side-by-side to face-to-face.

  4. Dip-coating with prestructured substrates: transfer of simple liquids and Langmuir–Blodgett monolayers

    International Nuclear Information System (INIS)

    Wilczek, Markus; Thiele, Uwe; Gurevich, Svetlana V; Zhu, Juan; Chi, Lifeng

    2017-01-01

    When a plate is withdrawn from a liquid bath, either a static meniscus forms in the transition region between the bath and the substrate or a liquid film of finite thickness (a Landau–Levich film) is transferred onto the moving substrate. If the substrate is inhomogeneous, e.g. has a prestructure consisting of stripes of different wettabilities, the meniscus can be deformed or show a complex dynamic behavior. Here we study the free surface shape and dynamics of a dragged meniscus occurring for striped prestructures with two orientations, parallel and perpendicular to the transfer direction. A thin film model is employed that accounts for capillarity through a Laplace pressure and for the spatially varying wettability through a Derjaguin (or disjoining) pressure. Numerical continuation is used to obtain steady free surface profiles and corresponding bifurcation diagrams in the case of substrates with different homogeneous wettabilities. Direct numerical simulations are employed in the case of the various striped prestructures. The final part illustrates the importance of our findings for particular applications that involve complex liquids by modeling a Langmuir–Blodgett transfer experiment. There, one transfers a monolayer of an insoluble surfactant that covers the surface of the bath onto the moving substrate. The resulting pattern formation phenomena can be crucially influenced by the hydrodynamics of the liquid meniscus that itself depends on the prestructure on the substrate. In particular, we show how prestructure stripes parallel to the transfer direction lead to the formation of bent stripes in the surfactant coverage after transfer and present similar experimental results. (paper)

  5. Nonlinear optics

    CERN Document Server

    Bloembergen, Nicolaas

    1996-01-01

    Nicolaas Bloembergen, recipient of the Nobel Prize for Physics (1981), wrote Nonlinear Optics in 1964, when the field of nonlinear optics was only three years old. The available literature has since grown by at least three orders of magnitude.The vitality of Nonlinear Optics is evident from the still-growing number of scientists and engineers engaged in the study of new nonlinear phenomena and in the development of new nonlinear devices in the field of opto-electronics. This monograph should be helpful in providing a historical introduction and a general background of basic ideas both for expe

  6. Soliton and strong Langmuir turbulence in solar flare processes

    Science.gov (United States)

    Song, M. T.; Wu, S. T.; Dryer, M.

    1989-01-01

    The occurrence of modulational instability in the current sheet of a solar flare is investigated. Special attention is given to the plasma microinstability in this sheet and its relation to the flare process. It is found that solitons or strong Langmuir turbulence are likely to occur in the diffusion region under solar flare conditions in which the electric resistivity could be enhanced by several orders of magnitude in the region, resulting in significant heating and stochastic acceleration of particles. A numerical example is used to demonstrate the transition of the magnetic field velocity and plasma density from the outer MHD region into the diffusive region and then back out again with the completion of the energy conversion process. This is all made possible by an increase in resistivity of four to five orders of magnitude over the classical value.

  7. 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.

  8. Formation of thin luminescent Eu3+-LB films by in situ coordination with 2,3,5,6-tetra(2′-pyridyl)pyrazine and 1-octadecanol in pure and mixed Langmuir monolayers

    International Nuclear Information System (INIS)

    Fugisawa, Fernanda P.; Ramos, Ana P.; Sousa Filho, Paulo C. de; Serra, Osvaldo A.; Zaniquelli, Maria E.D.

    2012-01-01

    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 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: ► In situ complexation of Eu (III) ions with 1-octadecanol and tppz. ► Formation of thin luminescent Eu(III)-LB films. ► EDS and luminescence studies attest to the presence of Eu(III) in the films. ► Eu(III) coordinates with both tppz and alcohol molecules at air/liquid interface. ► Relatively strong luminescence is observed in LB-films containing only Eu(III) and O–H oscillators.

  9. Langmuir, Freundlich and Temkin Adsorption Isotherms of Propranolol on Multi-Wall Carbon Nanotube

    OpenAIRE

    Mehdi Vadi

    2017-01-01

    We have studied the adsorption of the isotherm of Propranolol, on multi carbon nanotube. The adsorption equilibrium isotherms were fitted by Freundlich, Langmuir, and Temkin models. It was found that the Langmuir model described the adsorption process better than other two isotherm models. The amount of NSAIDs (Propranolol) adsorbed on carbon nanotube surface increased with the increase of the initial NSAIDs concentration.

  10. Nonlinear Science

    CERN Document Server

    Yoshida, Zensho

    2010-01-01

    This book gives a general, basic understanding of the mathematical structure "nonlinearity" that lies in the depths of complex systems. Analyzing the heterogeneity that the prefix "non" represents with respect to notions such as the linear space, integrability and scale hierarchy, "nonlinear science" is explained as a challenge of deconstruction of the modern sciences. This book is not a technical guide to teach mathematical tools of nonlinear analysis, nor a zoology of so-called nonlinear phenomena. By critically analyzing the structure of linear theories, and cl

  11. Nonlinear oscillations

    CERN Document Server

    Nayfeh, Ali Hasan

    1995-01-01

    Nonlinear Oscillations is a self-contained and thorough treatment of the vigorous research that has occurred in nonlinear mechanics since 1970. The book begins with fundamental concepts and techniques of analysis and progresses through recent developments and provides an overview that abstracts and introduces main nonlinear phenomena. It treats systems having a single degree of freedom, introducing basic concepts and analytical methods, and extends concepts and methods to systems having degrees of freedom. Most of this material cannot be found in any other text. Nonlinear Oscillations uses sim

  12. Three-dimensional Langmuir wave instabilities in type III solar radio bursts

    International Nuclear Information System (INIS)

    Bardwell, S.; Goldman, M.V.

    1976-01-01

    Assuming that type III solar radio bursts are associated with electron streams moving at about c/3, Langmuir waves should be strongly excited. We have studied all of the Langmuir-wave linear parametric instabilities excited in cylindrical symmetry by an electron-stream--driven Langmuir wave-pump propagating along the stream axis. Included in this unified homogeneous treatment are induced backscattering off ions, the oscillating two-stream instability, and a new ''stimulated modulational instability,'' previously unconsidered in this context. Near a few solar radii, the latter two deposit Langmuir wave energy into a forward-scattering cone about the stream axis. It is concluded that the linear stage of the forward-scattering instabilities involves transfer of energy to Langmuir waves which remain in resonance with the stream, and therefore probably do not prevent rapid depletion of the electron stream due to quasilinear plateau formation at these distances from the Sun

  13. Concerning the electromagnetic radiation spectrum of a hot plasma with Langmuir turbulence in a magnetic field

    International Nuclear Information System (INIS)

    Tirsky, V.V.; Ledenev, V.G.; Tomozov, V.M.

    2001-01-01

    We consider the process of generation of electromagnetic waves as a consequence of the merging of two Langmuir plasmons. The case of a hot plasma in a magnetic field is investigated. It is shown that under such conditions the frequency of Langmuir plasmons can vary over the range from 0.8 to 1.1 of the Langmuir frequency of electrons. The spectrum and polarization of electromagnetic radiation are analyzed. It is shown that allowance for the thermal motion of plasma particles under the conditions involved permits electromagnetic waves in the range from 1.6 to 2.2 of the Langmuir frequency of electrons to be generated. The degree of circular polarization of the radiation can reach 50% even in the case of an isotropic spectrum of Langmuir turbulence. (orig.)

  14. Nonlinear analysis

    National Research Council Canada - National Science Library

    Rassias, Themistocles M

    1987-01-01

    ... known that nonlinear partial differential equations can not be treated in the same systematic way as linear ones and this volume provides, among other things, proofs of existence and uniqueness theorems for nonlinear differential equations of a global nature. However, the basic techniques which have proven to be efficient in dealing with li...

  15. Nonlinear systems

    CERN Document Server

    Palmero, Faustino; Lemos, M; Sánchez-Rey, Bernardo; Casado-Pascual, Jesús

    2018-01-01

    This book presents an overview of the most recent advances in nonlinear science. It provides a unified view of nonlinear properties in many different systems and highlights many  new developments. While volume 1 concentrates on mathematical theory and computational techniques and challenges, which are essential for the study of nonlinear science, this second volume deals with nonlinear excitations in several fields. These excitations can be localized and transport energy and matter in the form of breathers, solitons, kinks or quodons with very different characteristics, which are discussed in the book. They can also transport electric charge, in which case they are known as polarobreathers or solectrons. Nonlinear excitations can influence function and structure in biology, as for example, protein folding. In crystals and other condensed matter, they can modify transport properties, reaction kinetics and interact with defects. There are also engineering applications in electric lattices, Josephson junction a...

  16. Statistical analysis of C/NOFS planar Langmuir probe data

    Directory of Open Access Journals (Sweden)

    E. Costa

    2014-07-01

    Full Text Available The planar Langmuir probe (PLP onboard the Communication/Navigation Outage Forecasting System (C/NOFS satellite has been monitoring ionospheric plasma densities and their irregularities with high resolution almost seamlessly since May 2008. Considering the recent changes in status of the C/NOFS mission, it may be interesting to summarize some statistical results from these measurements. PLP data from 2 different years (1 October 2008–30 September 2009 and 1 January 2012–31 December 2012 were selected for analysis. The first data set corresponds to solar minimum conditions and the second one is as close to solar maximum conditions of solar cycle 24 as possible at the time of the analysis. The results from the analysis show how the values of the standard deviation of the ion density which are greater than specified thresholds are statistically distributed as functions of several combinations of the following geophysical parameters: (i solar activity, (ii altitude range, (iii longitude sector, (iv local time interval, (v geomagnetic latitude interval, and (vi season.

  17. Isotherm investigation for the sorption of fluoride onto Bio-F: comparison of linear and non-linear regression method

    Science.gov (United States)

    Yadav, Manish; Singh, Nitin Kumar

    2017-12-01

    A comparison of the linear and non-linear regression method in selecting the optimum isotherm among three most commonly used adsorption isotherms (Langmuir, Freundlich, and Redlich-Peterson) was made to the experimental data of fluoride (F) sorption onto Bio-F at a solution temperature of 30 ± 1 °C. The coefficient of correlation (r2) was used to select the best theoretical isotherm among the investigated ones. A total of four Langmuir linear equations were discussed and out of which linear form of most popular Langmuir-1 and Langmuir-2 showed the higher coefficient of determination (0.976 and 0.989) as compared to other Langmuir linear equations. Freundlich and Redlich-Peterson isotherms showed a better fit to the experimental data in linear least-square method, while in non-linear method Redlich-Peterson isotherm equations showed the best fit to the tested data set. The present study showed that the non-linear method could be a better way to obtain the isotherm parameters and represent the most suitable isotherm. Redlich-Peterson isotherm was found to be the best representative (r2 = 0.999) for this sorption system. It is also observed that the values of β are not close to unity, which means the isotherms are approaching the Freundlich but not the Langmuir isotherm.

  18. Comparison of linear and non-linear models for the adsorption of fluoride onto geo-material: limonite.

    Science.gov (United States)

    Sahin, Rubina; Tapadia, Kavita

    2015-01-01

    The three widely used isotherms Langmuir, Freundlich and Temkin were examined in an experiment using fluoride (F⁻) ion adsorption on a geo-material (limonite) at four different temperatures by linear and non-linear models. Comparison of linear and non-linear regression models were given in selecting the optimum isotherm for the experimental results. The coefficient of determination, r², was used to select the best theoretical isotherm. The four Langmuir linear equations (1, 2, 3, and 4) are discussed. Langmuir isotherm parameters obtained from the four Langmuir linear equations using the linear model differed but they were the same when using the nonlinear model. Langmuir-2 isotherm is one of the linear forms, and it had the highest coefficient of determination (r² = 0.99) compared to the other Langmuir linear equations (1, 3 and 4) in linear form, whereas, for non-linear, Langmuir-4 fitted best among all the isotherms because it had the highest coefficient of determination (r² = 0.99). The results showed that the non-linear model may be a better way to obtain the parameters. In the present work, the thermodynamic parameters show that the absorption of fluoride onto limonite is both spontaneous (ΔG 0). Scanning electron microscope and X-ray diffraction images also confirm the adsorption of F⁻ ion onto limonite. The isotherm and kinetic study reveals that limonite can be used as an adsorbent for fluoride removal. In future we can develop new technology for fluoride removal in large scale by using limonite which is cost-effective, eco-friendly and is easily available in the study area.

  19. Nonlinear optics

    CERN Document Server

    Boyd, Robert W

    2013-01-01

    Nonlinear Optics is an advanced textbook for courses dealing with nonlinear optics, quantum electronics, laser physics, contemporary and quantum optics, and electrooptics. Its pedagogical emphasis is on fundamentals rather than particular, transitory applications. As a result, this textbook will have lasting appeal to a wide audience of electrical engineering, physics, and optics students, as well as those in related fields such as materials science and chemistry.Key Features* The origin of optical nonlinearities, including dependence on the polarization of light* A detailed treatment of the q

  20. Effect of radiation damping on the Child-Langmuir law in open diodes

    Science.gov (United States)

    González, Gabriel

    2017-11-01

    We present a microscopic derivation of the space charge limited current for the motion of non-relativistic charged particles inside a parallel vacuum tube diode taking into account the radiation reaction force. We study the space charged limited current for two different limiting cases. Our results reveal that in the high field regime, the space charge current does not follow the Child-Langmuir law, while in the low field regime, the space charge current follows the Child-Langmuir law with an effective electrostatic field, i.e., the so-called modified Child-Langmuir law.

  1. Nonlinear reconstruction

    Science.gov (United States)

    Zhu, Hong-Ming; Yu, Yu; Pen, Ue-Li; Chen, Xuelei; Yu, Hao-Ran

    2017-12-01

    We present a direct approach to nonparametrically reconstruct the linear density field from an observed nonlinear map. We solve for the unique displacement potential consistent with the nonlinear density and positive definite coordinate transformation using a multigrid algorithm. We show that we recover the linear initial conditions up to the nonlinear scale (rδrδL>0.5 for k ≲1 h /Mpc ) with minimal computational cost. This reconstruction approach generalizes the linear displacement theory to fully nonlinear fields, potentially substantially expanding the baryon acoustic oscillations and redshift space distortions information content of dense large scale structure surveys, including for example SDSS main sample and 21 cm intensity mapping initiatives.

  2. Nonlinear analysis

    CERN Document Server

    Gasinski, Leszek

    2005-01-01

    Hausdorff Measures and Capacity. Lebesgue-Bochner and Sobolev Spaces. Nonlinear Operators and Young Measures. Smooth and Nonsmooth Analysis and Variational Principles. Critical Point Theory. Eigenvalue Problems and Maximum Principles. Fixed Point Theory.

  3. Practical Nonlinearities

    Science.gov (United States)

    2016-07-01

    architectures , practical nonlinearities, nonlinear dynamics 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT: SAR 8. NUMBER OF PAGES...performers from Mesodynamic Architectures (MESO) and uPNT all to include devices in these runs. This cost-sharing was planned, and is necessary for...contributions to the performance of MEMS gyroscopes. In particular, we have demonstrated for the first time that Parametric Amplification can improve the

  4. Dynamic Raman Spectroelectrochemistry of Single Walled Carbon Nanotubes modified electrodes using a Langmuir-Schaefer method

    OpenAIRE

    Ibáñez, David; Romero, Edna Cecilia; Colina, Álvaro; Heras, Aránzazu

    2014-01-01

    Raman spectroelectrochemistry is a fundamental technique to characterize single walled carbon nanotube (SWCNT) films. In this work, we have performed the study of SWCNT films transferred to a glassy carbon electrode using a Langmuir-Schaefer method. Langmuir balance has allowed us to control the characteristics of the film that can be easily transferred to the electrode support. Time-resolved Raman spectroelectrochemistry experiments at scan rates between 20 and 400 mV s−1 were done in two di...

  5. Validation of double Langmuir probe in-orbit performance onboard a nano-satellite

    Science.gov (United States)

    Tejumola, Taiwo Raphael; Zarate Segura, Guillermo Wenceslao; Kim, Sangkyun; Khan, Arifur; Cho, Mengu

    2018-03-01

    Many plasma measurement systems have been proposed and used onboard different satellites to characterize space plasma. Most of these systems employed the technique of Langmuir probes either using the single or double probes methods. Recent growth of lean satellites has positioned it on advantage to be used for space science missions using Langmuir probes because of its simplicity and convenience. However, single Langmuir probes are not appropriate to be used on lean satellites because of their limited conducting area which leads to spacecraft charging and drift of the instrument's electrical ground during measurement. Double Langmuir probes technique can overcome this limitation, as a measurement reference in relation to the spacecraft is not required. A double Langmuir probe measurement system was designed and developed at Kyushu Institute of Technology for HORYU-IV satellite, which is a 10 kg, 30 cm cubic class lean satellite launched into Low Earth Orbit on 17th February 2016. This paper presents the on-orbit performance and validation of the double Langmuir probe measurement using actual on-orbit measured data and computer simulations.

  6. Nonlinear optimization

    CERN Document Server

    Ruszczynski, Andrzej

    2011-01-01

    Optimization is one of the most important areas of modern applied mathematics, with applications in fields from engineering and economics to finance, statistics, management science, and medicine. While many books have addressed its various aspects, Nonlinear Optimization is the first comprehensive treatment that will allow graduate students and researchers to understand its modern ideas, principles, and methods within a reasonable time, but without sacrificing mathematical precision. Andrzej Ruszczynski, a leading expert in the optimization of nonlinear stochastic systems, integrates the theory and the methods of nonlinear optimization in a unified, clear, and mathematically rigorous fashion, with detailed and easy-to-follow proofs illustrated by numerous examples and figures. The book covers convex analysis, the theory of optimality conditions, duality theory, and numerical methods for solving unconstrained and constrained optimization problems. It addresses not only classical material but also modern top...

  7. Propagation of nonlinear reactive contaminants in porous media

    Science.gov (United States)

    Serrano, Sergio E.

    2003-08-01

    A study on the effect of nonlinear reactions on the space and time distribution of contaminant plumes governed by the advective-dispersive equation in porous media was conducted. Several models of nonlinear reactions were considered: the irreversible nonlinear first-order kinetic sorption model, the nonlinear Freundlich sorption isotherm model, the nonlinear Langmuir sorption isotherm model, and the reversible nonlinear kinetic sorption model. Each of these models was coupled with the advective-dispersive equation with dimensionless concentration and an approximate analytical series solutions was obtained. Comparison between linear and nonlinear plumes indicated that nonlinear reactions may have a significant effect on the shape and spatial distribution of a contaminant at a given time and in certain cases may explain quantitatively the occurrence of scaled (e.g., concentration change while preserving shape), retarded, and nonsymmetric plumes as well as the presence of back tails and sharp front ends usually observed in the field. By adopting a nonlinear model of contaminant migration a more realistic representation of contaminant propagation is possible than that obtained with a linear model.

  8. A study on near-UV blue photoluminescence in graphene oxide prepared by Langmuir–Blodgett method

    Energy Technology Data Exchange (ETDEWEB)

    Han, Feng; Yang, Shuming, E-mail: shuming.yang@mail.xjtu.edu.cn; Jing, Weixuan; Jiang, Zhuangde; Liu, Huan; Li, Lei

    2015-08-01

    Highlights: • GO films were deposited on substrates using LB method and reduced into rGO at 800 °C. • The PL of GO and rGO showed the near-UV blue emission. • This blue shift and decrease in PL was due to the newly formed sp{sup 2} clusters in rGO. - Abstract: The paper reports a study on a near-UV blue photoluminescence (PL) in graphene oxide (GO) films prepared by Langmuir–Blodgett (LB)-based method. GO films was reduced into reduced-graphene oxide (rGO) through thermal process at 800 °C. The surface morphology of both GO and rGO is characterized by atomic force microscope (AFM) and scanning electron microscope (SEM). X-ray photoelectron spectroscopy (XPS) analysis shows the largely restoration of graphitic domains in GO after reduction. The photoluminescence (PL) of rGO shows the near-UV blue emission, which is blueshifted along with luminescent decreased as compared to GO. This blueshift and decrease in PL is mainly due to the newly formed sp{sup 2} clusters in rGO, which established percolation pathways between the sp{sup 2} clusters already present.

  9. Surface-enhanced Raman scattering by colloidal CdSe nanocrystal submonolayers fabricated by the Langmuir–Blodgett technique

    Directory of Open Access Journals (Sweden)

    Alexander G. Milekhin

    2015-12-01

    Full Text Available We present the results of an investigation of surface-enhanced Raman scattering (SERS by optical phonons in colloidal CdSe nanocrystals (NCs homogeneously deposited on both arrays of Au nanoclusters and Au dimers using the Langmuir–Blodgett technique. The coverage of the deposited NCs was less than one monolayer, as determined by transmission and scanning electron microscopy. SERS by optical phonons in CdSe nanocrystals showed a significant enhancement that depends resonantly on the Au nanocluster and dimer size, and thus on the localized surface plasmon resonance (LSPR energy. The deposition of CdSe nanocrystals on the Au dimer nanocluster arrays enabled us to study the polarization dependence of SERS. The maximal SERS signal was observed for light polarization parallel to the dimer axis. The polarization ratio of the SERS signal parallel and perpendicular to the dimer axis was 20. The SERS signal intensity was also investigated as a function of the distance between nanoclusters in a dimer. Here the maximal SERS enhancement was observed for the minimal distance studied (about 10 nm, confirming the formation of SERS “hot spots”.

  10. Diameter control of vertically aligned carbon nanotubes using CoFe2O4 nanoparticle Langmuir–Blodgett films

    Science.gov (United States)

    Tamiya, Shuhei; Sato, Taiga; Kushida, Masahito

    2018-03-01

    Vertically aligned carbon nanotubes (VA-CNTs) are suggested for utilization as a new catalyst support of polymer electrolyte fuel cells (PEFCs). The independent control of the diameter and number density of VA-CNTs is essential for application in PEFCs. As the catalyst for VA-CNT growth, we fabricated CoFe2O4 nanoparticle (NP) films using the Langmuir–Blodgett (LB) technique. Using the LB technique, we were able to separately control the diameter and number density of VA-CNTs. The number density of VA-CNTs was changed by mixing with the filler moleculer, palmitic acid (C16). The VA-CNT diameter was changed by the adjusting the CoFe2O4 NP diameter. However, the heat-induced aggregation of CoFe2O4 NPs occurred in thermal chemical vapor deposition to synthesize VA-CNTs. Therefore, we examined how to minimize the effect of heat-induced aggregation of CoFe2O4 NPs. As a result, selection of the appropriate number density and diameter of CoFe2O4 NPs was found to be important for the control of VA-CNT diameter.

  11. Surface Chemistry and Spectroscopic Study of a Cholera Toxin B Langmuir Monolayer.

    Science.gov (United States)

    Sharma, Shiv K; Seven, Elif S; Micic, Miodrag; Li, Shanghao; Leblanc, Roger M

    2018-02-20

    In this article, we explored the surface chemistry properties of a cholera toxin B (CTB) monolayer at the air-subphase interface and investigated the change in interfacial properties through in situ spectroscopy. The study showed that the impact of the blue shift was negligible, suggesting that the CTB molecules were minimally affected by the subphase molecules. The stability of the CTB monolayer was studied by maintaining the constant surface pressure for a long time and also by using the compression-decompression cycle experiments. The high stability of the Langmuir monolayer of CTB clearly showed that the driving force of CTB going to the amphiphilic membrane was its amphiphilic nature. In addition, no major change was detected in the various in situ spectroscopy results (such as UV-vis, fluorescence, and IR ER) of the CTB Langmuir monolayer with the increase in surface pressure. This indicates that no aggregation occurs in the Langmuir monolayer of CTB.

  12. Understanding Solvent Spreading for Langmuir Deposition of Nanomaterial Films: A Hansen Solubility Parameter Approach.

    Science.gov (United States)

    Large, Matthew J; Ogilvie, Sean P; King, Alice A K; Dalton, Alan B

    2017-12-26

    To prepare high-quality Langmuir films of 2D materials it is important to select a solvent optimized for both exfoliation and spreading at the air-water interface. Whereas it is generally accepted that exfoliation and stabilization of 2D materials is well-described using the Hansen solubility parameter theory, a complementary description of solvent spreading behavior is lacking. To this end we develop an understanding of solvent spreading using a Hansen solubility parameter framework. Our model accurately predicts the behavior of both water-immiscible and water-miscible solvents in Langmuir film formation experiments. We demonstrate that spreading behavior can be modified by controlling the surface pressure of the subphase using an amphiphilic species and accordingly utilize this approach to determine the maximum spreading pressure for a selection of solvents. Ultimately, by building on this understanding we open up additional routes to optimize the preparation of Langmuir films of 2D materials and other nanoparticles.

  13. First simultaneous measurements of Reynolds stress with ball-pen and Langmuir probes

    Science.gov (United States)

    Grover, Ondrej; Adamek, Jiri; Seidl, Jakub; Devitre, Alexis; Sos, Miroslav; Vondracek, Petr; Bilkova, Petra; Hron, Martin

    2017-06-01

    A new multi-pin probe head was installed and tested at the COMPASS tokamak. The probe head consists of several ball-pen and Langmuir probes in similar geometric configurations, which enables fast, simultaneous measurements of the radial and poloidal electric field components from differences of plasma or floating potentials using appropriately positioned ball-pen or Langmuir probes, respectively. The fast measurements of the radial electric field are compared with other methods of measuring selected frequency components of the radial electric field. The radial profiles of the Reynolds stress calculated from correlations of electric field fluctuations obtained by either probe type are compared along with their spectral composition. Lower Reynolds stress values are found for Langmuir probes in comparison to ball-pen probes due to negative contributions from higher frequency fluctuations possibly associated with electron temperature fluctuations.

  14. First simultaneous measurements of Reynolds stress with ball-pen and Langmuir probes.

    Science.gov (United States)

    Grover, Ondrej; Adamek, Jiri; Seidl, Jakub; Devitre, Alexis; Sos, Miroslav; Vondracek, Petr; Bilkova, Petra; Hron, Martin

    2017-06-01

    A new multi-pin probe head was installed and tested at the COMPASS tokamak. The probe head consists of several ball-pen and Langmuir probes in similar geometric configurations, which enables fast, simultaneous measurements of the radial and poloidal electric field components from differences of plasma or floating potentials using appropriately positioned ball-pen or Langmuir probes, respectively. The fast measurements of the radial electric field are compared with other methods of measuring selected frequency components of the radial electric field. The radial profiles of the Reynolds stress calculated from correlations of electric field fluctuations obtained by either probe type are compared along with their spectral composition. Lower Reynolds stress values are found for Langmuir probes in comparison to ball-pen probes due to negative contributions from higher frequency fluctuations possibly associated with electron temperature fluctuations.

  15. Ion-sound emission by Langmuir soliton reflected at density barrier

    International Nuclear Information System (INIS)

    El-Ashry, M.Y.

    1989-07-01

    The emission of ion-sound waves by an accelerated Langmuir soliton is studied. The acceleration of the soliton is due to an inhomogeneous density barrier. On the assumption that the kinetic energy of the Langmuir soliton is smaller than the potential energy created by the barrier. The basic equations describing the dynamic behaviour of the soliton and the emission of the ion-sound waves are formulated. The qualitative spatial distributions of the perturbed concentration in the ion-sound waves are analyzed at different characteristic points of the soliton. The energy lost by the soliton, as a result of the emission, is estimated. (author). 6 refs, 4 figs

  16. New soliton solutions of the system of equations for the ion sound and Langmuir waves

    Directory of Open Access Journals (Sweden)

    Seyma Tuluce Demiray

    2016-11-01

    Full Text Available This study is based on new soliton solutions of the system of equations for the ion sound wave under the action of the ponderomotive force due to high-frequency field and for the Langmuir wave. The generalized Kudryashov method (GKM, which is one of the analytical methods, has been tackled for finding exact solutions of the system of equations for the ion sound wave and the Langmuir wave. By using this method, dark soliton solutions of this system of equations have been obtained. Also, by using Mathematica Release 9, some graphical simulations were designed to see the behavior of these solutions.

  17. The Langmuir isotherm and the standard model of ion-assisted etching

    International Nuclear Information System (INIS)

    Lieberman, M A

    2009-01-01

    Langmuir is lured to the General Electric Research Laboratory, where he creates a new science-surface chemistry-and christens another-plasma. His atomistic views of gas-surface interactions are extended 65 years later to describe ion-assisted plasma etching, an indispensable process in modern semiconductor device manufacturing.

  18. Modification of the Langmuir-Schaefer method for fabrication of ordered protein films

    Science.gov (United States)

    Kovalchuk, M. V.; Boikova, A. S.; Dyakova, Yu. A.; Marchenkova, M. A.; Opolchentsev, A. M.; Pisarevsky, Yu. V.; Prosekov, P. A.; Seregin, A. Yu.

    2017-07-01

    A modification of the Langmuir-Schaefer method for the fabrication of high-quality protein films on a solid substrate was proposed and applied to lysozyme. The procedure relies on the use of a pre-prepared protein solution, the parameters of which correspond to crystallization conditions. A lysozyme Langmuir monolayer was shown to be formed with the involvement of complexes, namely, dimers and octamers of protein molecules that are present in such protein solutions. These complexes apparently retain the structure after spreading a protein solution onto an aqueous subphase in a Langmuir trough. The thickness of the film after the transfer of the monolayer, which was formed by the proposed procedure, onto a solid substrate corresponds to the diameter of the octamer and this film is dense, continuous, and uniform, as was demonstrated by several methods: X-ray reflectivity, total external reflection X-ray standing wave, and atomic force microscopy. A layer of chloride ions that formed under the Langmuir monolayer was found at the air-protein film interface. This fact confirms an important role of the precipitating agent (chloride ions) in all steps of the formation of lysozyme films.

  19. Langmuir probe measurement of the bismuth plasma plume formed by an extreme-ultraviolet pulsed laser

    Czech Academy of Sciences Publication Activity Database

    Pira, P.; Burian, T.; Kolpaková, A.; Tichý, M.; Kudrna, P.; Daniš, S.; Juha, Libor; Lančok, Ján; Vyšín, Luděk; Civiš, Svatopluk; Zelinger, Zdeněk; Kubát, Pavel; Wild, J.

    2014-01-01

    Roč. 47, č. 40 (2014), 1-6 ISSN 0022-3727 R&D Projects: GA ČR(CZ) GAP108/11/1312 Institutional support: RVO:68378271 ; RVO:61388955 Keywords : XUV laser * pulsed laser deposition * Langmuir probe * plasma plume Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.721, year: 2014

  20. Accounting for Debye sheath expansion for proud Langmuir probes in magnetic confinement fusion plasmas

    Science.gov (United States)

    Tsui, C. K.; Boedo, J. A.; Stangeby, P. C.; TCV Team

    2018-01-01

    A Child-Langmuir law-based method for accounting for Debye sheath expansion while fitting the current-voltage I-V characteristic of proud Langmuir probes (electrodes that extend into the volume of the plasma) is described. For Langmuir probes of a typical size used in tokamak plasmas, these new estimates of electron temperature and ion saturation current density values decreased by up to 60% compared to methods that did not account for sheath expansion. Changes to the collection area are modeled using the Child-Langmuir law and effective expansion perimeter lp, and the model is thus referred to as the "perimeter sheath expansion method." lp is determined solely from electrode geometry, so the method may be employed without prior measurement of the magnitude of the sheath expansion effects for a given Langmuir probe and can be used for electrodes of different geometries. This method correctly predicts the non-saturating ΔI/ΔV slope for cold, low-density plasmas where sheath-expansion effects are strong, as well as for hot plasmas where ΔI/ΔV ˜ 0, though it is shown that the sheath can still significantly affect the collection area in these hot conditions. The perimeter sheath expansion method has several advantages compared to methods where the non-saturating current is fitted: (1) It is more resilient to scatter in the I-V characteristics observed in turbulent plasmas. (2) It is able to separate the contributions to the ΔI/ΔV slope from sheath expansion to that of the high energy electron tail in high Te conditions. (3) It calculates the change in the collection area due to the Debye sheath for conditions where ΔI/ΔV ˜ 0 and for V = Vf.

  1. Accounting for Debye sheath expansion for proud Langmuir probes in magnetic confinement fusion plasmas.

    Science.gov (United States)

    Tsui, C K; Boedo, J A; Stangeby, P C

    2018-01-01

    A Child-Langmuir law-based method for accounting for Debye sheath expansion while fitting the current-voltage I-V characteristic of proud Langmuir probes (electrodes that extend into the volume of the plasma) is described. For Langmuir probes of a typical size used in tokamak plasmas, these new estimates of electron temperature and ion saturation current density values decreased by up to 60% compared to methods that did not account for sheath expansion. Changes to the collection area are modeled using the Child-Langmuir law and effective expansion perimeter l p , and the model is thus referred to as the "perimeter sheath expansion method." l p is determined solely from electrode geometry, so the method may be employed without prior measurement of the magnitude of the sheath expansion effects for a given Langmuir probe and can be used for electrodes of different geometries. This method correctly predicts the non-saturating ΔI/ΔV slope for cold, low-density plasmas where sheath-expansion effects are strong, as well as for hot plasmas where ΔI/ΔV ∼ 0, though it is shown that the sheath can still significantly affect the collection area in these hot conditions. The perimeter sheath expansion method has several advantages compared to methods where the non-saturating current is fitted: (1) It is more resilient to scatter in the I-V characteristics observed in turbulent plasmas. (2) It is able to separate the contributions to the ΔI/ΔV slope from sheath expansion to that of the high energy electron tail in high Te conditions. (3) It calculates the change in the collection area due to the Debye sheath for conditions where ΔI/ΔV ∼ 0 and for V = V f .

  2. Nonlinear resonances

    CERN Document Server

    Rajasekar, Shanmuganathan

    2016-01-01

    This introductory text presents the basic aspects and most important features of various types of resonances and anti-resonances in dynamical systems. In particular, for each resonance, it covers the theoretical concepts, illustrates them with case studies, and reviews the available information on mechanisms, characterization, numerical simulations, experimental realizations, possible quantum analogues, applications and significant advances made over the years. Resonances are one of the most fundamental phenomena exhibited by nonlinear systems and refer to specific realizations of maximum response of a system due to the ability of that system to store and transfer energy received from an external forcing source. Resonances are of particular importance in physical, engineering and biological systems - they can prove to be advantageous in many applications, while leading to instability and even disasters in others. The book is self-contained, providing the details of mathematical derivations and techniques invo...

  3. PLASMA EMISSION BY NONLINEAR ELECTROMAGNETIC PROCESSES

    Energy Technology Data Exchange (ETDEWEB)

    Ziebell, L. F.; Petruzzellis, L. T.; Gaelzer, R. [Instituto de Física, UFRGS, Porto Alegre, RS (Brazil); Yoon, P. H. [Institute for Physical Science and Technology, University of Maryland, College Park (United States); Pavan, J., E-mail: luiz.ziebell@ufrgs.br, E-mail: laripetruzzellis@yahoo.com.br, E-mail: rudi.gaelzer@ufrgs.br, E-mail: yoonp@umd.edu, E-mail: joel.pavan@ufpel.edu.br [Instituto de Física e Matemática, UFPel, Pelotas, RS (Brazil)

    2015-06-20

    The plasma emission, or electromagnetic (EM) radiation at the plasma frequency and/or its harmonic(s), is generally accepted as the radiation mechanism responsible for solar type II and III radio bursts. Identification and characterization of these solar radio burst phenomena were done in the 1950s. Despite many decades of theoretical research since then, a rigorous demonstration of the plasma emission process based upon first principles was not available until recently, when, in a recent Letter, Ziebell et al. reported the first complete numerical solution of EM weak turbulence equations; thus, quantitatively analyzing the plasma emission process starting from the initial electron beam and the associated beam-plasma (or Langmuir wave) instability, as well as the subsequent nonlinear conversion of electrostatic Langmuir turbulence into EM radiation. In the present paper, the same problem is revisited in order to elucidate the detailed physical mechanisms that could not be reported in the brief Letter format. Findings from the present paper may be useful for interpreting observations and full-particle numerical simulations.

  4. Preparation of Langmuir–Blodgett thin films of calix[6]arenes and p-tert butyl group effect on their gas sensing properties

    Energy Technology Data Exchange (ETDEWEB)

    Ozmen, Mustafa, E-mail: musozmen@gmail.com [Department of Chemistry, University of Selcuk, 42075 Konya (Turkey); Ozbek, Zikriye, E-mail: zikriye@comu.edu.tr [Department of Bioengineering, University of Canakkale Onsekiz Mart, 17100 Canakkale (Turkey); Bayrakci, Mevlut [Department of Bioengineering, University of Karamanoglu Mehmetbey, 70200 Karaman (Turkey); Ertul, Seref; Ersoz, Mustafa [Department of Chemistry, University of Selcuk, 42075 Konya (Turkey); Capan, Rifat [Department of Physics, University of Balikesir, 10145 Balikesir (Turkey)

    2015-12-30

    Graphical abstract: - Highlights: • In this work, we prepared Langmuir–Blodgett films of calix[6]arene derivatives. • Then LB films of calixarene compounds were characterized. • Organic vapor sensing properties of prepared LB films were investigated. - Abstract: Organic vapor sensing properties of Langmuir–Blodgett (LB) thin films of p-tert-butyl calix[6]arene and calix[6]arene, and their certain characterization are reported in this work. LB films of these calixarenes have been characterized by contact angle measurement, quartz crystal microbalance (QCM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). QCM system was used for the measurement of sensor response against chloroform, benzene, toluene and ethanol vapors. Forming of stable monolayers was observed at the water surface using surface pressure–area isotherm graph. The results indicate that good quality, uniform LB films can be prepared with a transfer ratio of over 0.95. Due to the adsorption of vapors into the LB film structures; they yield a response to all vapors as of large, fast, and reproducible.

  5. [Nonlinear magnetohydrodynamics

    International Nuclear Information System (INIS)

    1994-01-01

    Resistive MHD equilibrium, even for small resistivity, differs greatly from ideal equilibrium, as do the dynamical consequences of its instabilities. The requirement, imposed by Faraday's law, that time independent magnetic fields imply curl-free electric fields, greatly restricts the electric fields allowed inside a finite-resistivity plasma. If there is no flow and the implications of the Ohm's law are taken into account (and they need not be, for ideal equilibria), the electric field must equal the resistivity times the current density. The vanishing of the divergence of the current density then provides a partial differential equation which, together with boundary conditions, uniquely determines the scalar potential, the electric field, and the current density, for any given resistivity profile. The situation parallels closely that of driven shear flows in hydrodynamics, in that while dissipative steady states are somewhat more complex than ideal ones, there are vastly fewer of them to consider. Seen in this light, the vast majority of ideal MHD equilibria are just irrelevant, incapable of being set up in the first place. The steady state whose stability thresholds and nonlinear behavior needs to be investigated ceases to be an arbitrary ad hoc exercise dependent upon the whim of the investigator, but is determined by boundary conditions and choice of resistivity profile

  6. Experimental investigation of the creation of a fire-rod by Langmuir and emissive probes

    International Nuclear Information System (INIS)

    Gyergyek, T.; Cercek, M.

    2000-01-01

    Positive voltage steps are applied to a plane electrode immersed in a weakly magnetized discharge plasma column with its surface perpendicular to the magnetic field lines. Steps of different amplitude are applied at various neutral gas pressures. If the amplitude of the voltage step and the gas pressure are high enough, additional discharge occurs in front of the anode and a fire-rod is created. In this work time development of the electron distribution function is measured using Langmuir and emissive probes. The formation of the anode plasma electron population is followed on the derivatives of the probe characteristics. Results obtained by Langmuir and emissive probes are compared and are found to be in good agreement. (author)

  7. Biasing, Acquisition and Interpretation of a Dense Langmuir Probe Array in NSTX

    International Nuclear Information System (INIS)

    Jaworski, M.A.; Kallman, J.; Kaita, R.; Kugel, H.; LeBlanc, B.; Marsala, R.; Ruzic, D.

    2010-01-01

    A dense array of 99 Langmuir probes has been installed in the lower divertor region of the National Spherical Torus Experiments (NSTX). This array is instrumented with a system of elec- tronics that allows flexibility in the choice of probes to bias as well as the type of measurement (including standard swept, single probe, triple probe and operation as passive floating potential and scrape-off-layer (SOL) current monitors). The use of flush-mounted probes requires careful inter- pretation. The time dependent nature of the SOL makes swept-probe traces difficult to interpret. To overcome these challenges, the single- and triple-Langmuir probe signals are used in comple- mentary fashion to determine the temperature and density at the probe location. A comparison to mid-plane measurements is made.

  8. Pulsed floating-type Langmuir probe for measurements of electron energy distribution function in plasmas

    Science.gov (United States)

    Choi, Ikjin; Kim, Aram; Lee, Hyo-Chang; Kim, Dong-Hwan; Chung, Chin-Wook

    2017-01-01

    A floating type Langmuir probe was studied to measure the electron energy distribution function (EEDF) in plasmas. This method measures the current (I)-voltage (V) curve with rising and falling variations based on a floating potential by using charge-discharge characteristics of the series capacitor when a square-pulse voltage is applied. In addition, this method measures the EEDF by using the alternating current (ac) superposition method. The measured EEDFs were in good agreement with results from a conventional single Langmuir probe. This technique could be applied as a plasma diagnostic method in the capacitively coupled plasma where the plasma potential is extremely high or the processing plasma where the deposition gas is used.

  9. Child-Langmuir law for cathode sheath of glow discharge in CO2

    International Nuclear Information System (INIS)

    Lisovskiy, V.A.; Krol, H.H.; Osmayev, R.O.; Yegorenkov, V.D.

    2016-01-01

    This work is devoted to the determination of the law that may be applicable to the description of the cathode sheath in CO 2 . To this end three versions of the Child-Langmuir law have been considered - a collision free one (for the ions moving through a cathode sheath without collisions with gas molecules) as well as two collision- related versions - one for a constant mean free path of positive ions and one for a constant mobility of positive ions. The current-voltage characteristics and the cathode sheath thickness of the glow discharge in CO 2 have been simultaneously measured in the pressure range from 0.05 to 1 Torr and with the discharge current values up to 80 mA. In the whole range of the discharge conditions we have studied the cathode sheath characteristics are found to obey correctly only to the Child-Langmuir law version with a constant ion mobility.

  10. Multiple Raman up-conversion of radiation from pre-existing Langmuir turbulence

    Science.gov (United States)

    Russell, D.; Goldman, M.; Newman, D.

    1985-07-01

    Little is known regarding the mechanisms involved in the production of radiation at frequencies which are much higher than the maximum plasma frequency in nonmagnetic plasmas. It is pointed out that radiation at high multiples of the plasma frequency has been observed in laser-pellet experiments, in relativistic beam-plasma interactions, and in low-energy beam-plasma interactions. Radiation at twice the plasma frequency can be produced by coalescence of two Langmuir waves. Another approach is based on radiation near the plasma frequency or its second harmonic, produced by instability or by external sources. Raman scatter from preexisting Langmuir turbulence is permitted repeatedly. At each step such scattering will produce frequency upshifts (anti-Stokes process) and downshifts (Stokes process). The present paper is concerned with this process. Attention is given to equilibrium spectra, analytic approximations, laser-plasma interaction and coherent radiation from relativistic electron beams.

  11. A compact, smart Langmuir Probe control module for MAST-Upgrade

    Science.gov (United States)

    Lovell, J.; Stephen, R.; Bray, S.; Naylor, G.; Elmore, S.; Willett, H.; Peterka, M.; Dimitrova, M.; Havranek, A.; Hron, M.; Sharples, R.

    2017-11-01

    A new control module for the MAST-Upgrade Langmuir Probe system has been developed. It is based on a Xilinx Zynq FPGA, which allows for excellent configurability and ease of retrieving data. The module is capable of arbitrary bias voltage waveform generation, and digitises current and voltage readings from 16 probes. The probes are biased and measured one at a time in a time multiplexed fashion, with the multiplexing sequence completely configurable. In addition, simultaneous digitisation of the floating potential of all unbiased probes is possible. A suite of these modules, each coupled with a high voltage amplifier, enables biasing and digitisation of 640 Langmuir Probes in the MAST-Upgrade Super-X divertor. The system has been successfully tested on the York Linear Plasma Device and on the COMPASS tokamak. It will be installed on MAST-Upgrade ready for operations in 2018.

  12. Chiral hierarchical self-assembly in Langmuir monolayers of diacetylenic lipids

    KAUST Repository

    Basnet, Prem B.

    2013-01-01

    When compressed in the intermediate temperature range below the chain-melting transition yet in the low-pressure liquid phase, Langmuir monolayers made of chiral lipid molecules form hierarchical structures. Using Brewster angle microscopy to reveal this structure, we found that as the liquid monolayer is compressed, an optically anisotropic condensed phase nucleates in the form of long, thin claws. These claws pack closely to form stripes. This appears to be a new mechanism for forming stripes in Langmuir monolayers. In the lower temperature range, these stripes arrange into spirals within overall circular domains, while near the chain-melting transition, the stripes arrange into target patterns. We attributed this transition to a change in boundary conditions at the core of the largest-scale circular domains. © 2013 The Royal Society of Chemistry.

  13. Statistics of Langmuir wave amplitudes observed inside Saturn's foreshock by the Cassini spacecraft

    Czech Academy of Sciences Publication Activity Database

    Píša, David; Hospodarsky, G. B.; Kurth, W. S.; Santolík, Ondřej; Souček, Jan; Gurnett, D. A.; Masters, A.; Hill, M. E.

    2015-01-01

    Roč. 120, č. 4 (2015), s. 2531-2542 ISSN 2169-9380 R&D Projects: GA ČR GAP205/10/2279; GA ČR(CZ) GAP209/12/2394 Institutional support: RVO:68378289 Keywords : Langmuir waves * foreshock * Saturn * Cassini Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.318, year: 2015 http://onlinelibrary.wiley.com/doi/10.1002/2014JA020560/abstract

  14. Second derivative Langmuir probe diagnostics of gas discharge plasma at intermediate pressures (review article)

    International Nuclear Information System (INIS)

    Popov, Tsv K; Dimitrova, M; Dias, F M; Tsaneva, V N; Stelmashenko, N A; Blamire, M G; Barber, Z H

    2006-01-01

    The second-derivative Langmuir probe method for precise determination of the plasma potential, the electron energy distribution function (respectively the electron temperature,) and the electron density of gas discharge plasma at intermediate pressures (100-1000 Pa) is reviewed. Results of applying the procedure proposed to different kinds of gas discharges are presented. Factors affecting the accuracy of the plasma characteristics evaluated are discussed

  15. Spatial distribution of Langmuir waves observed upstream of Saturn's bow shock by Cassini

    Czech Academy of Sciences Publication Activity Database

    Píša, David; Santolík, Ondřej; Hospodarsky, G. B.; Kurth, W. S.; Gurnett, D. A.; Souček, Jan

    2016-01-01

    Roč. 121, č. 8 (2016), s. 7771-7784 ISSN 2169-9380 R&D Projects: GA ČR GJ16-16050Y; GA ČR(CZ) GAP209/12/2394 Institutional support: RVO:68378289 Keywords : Langmuir waves * Cassini * foreshock * Saturn Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.733, year: 2016 http://onlinelibrary.wiley.com/doi/10.1002/2016JA022912/abstract

  16. Investigation of Langmuir-probe-characteristic behavior at high bias frequency

    Science.gov (United States)

    Newbury, Sarah; Cohen, Samuel; Matteucci, Jack

    2015-11-01

    Langmuir probe characteristics recorded for magnetized DC hollow-cathode neon plasmas yield increasing values for electron temperature, plasma potential, and ion saturation current with increasing frequency of the applied probe bias voltage. The extent to which stray capacitance to the probe plays a role was investigated. Langmuir probe characteristics were recorded at frequencies ranging from 10 Hz to 8 kHz while the applied voltage to the probe was sawtooth modulated - thus the rate of change of the bias voltage is constant. From these characteristics, the plasma temperature and density, as well as estimates for the capacitance in the wires, were calculated. The consistency and accuracy of these calculations were analyzed and found to indicate that the stray capacitance is the major factor contributing to the effects observed at higher bias frequencies. Similar experiments were performed with the PFRC-2 Langmuir probe apparatus, and the results of these experiments confirm the significant role of the stray capacitance. Contributions from electron thermalization, ion transit time, Debye length/probe radius, gyroradius, and displacement current at high bias frequencies have also been considered, but were found to be unlikely to produce the observed effects. This work supported by DOE contract DE-AC02-09CH11466.

  17. Langmuir and Freundlich Isotherm Adsorption Equations for Chromium (VI) Waste Adsorption by Zeolite

    International Nuclear Information System (INIS)

    Murni Handayani; Eko Sulistiyono

    2009-01-01

    The research of chromium (VI) waste adsorption by zeolite has done. Wastes which are produced by Industries, both radioactive waste and heavy metal waste need done more processing so that they are not endanger environment and human health. Zeolite has very well-ordered crystal form with cavity each other to way entirely so that cause surface wide of zeolite become very big and very good as adsorbents. This research intends to know appropriate isotherm adsorption method to determine maximum capacity of zeolite to chromium (VI) waste. The equations which used in adsorption process are Langmuir and Freundlich isotherm Adsorption equations. The instrument was used in adsorption process by using Atomic Adsorption Spectroscopy (AAS). The experiment result showed that the biggest mass of chromium (VI) metal ion which was absorb by zeolite in 20 ppm concentration was 7.71 mg/gram zeolite. Adsorption process of Chromium (VI) waste by zeolite followed Langmuir and Freundlich isotherm equations with R 2 >0,9 . Appropriate equation to determine maximum adsorption capacity of zeolite for chromium (VI) waste adsorption is Langmuir equation. The maximum adsorption capacity of zeolite is 52.25 mg/gram. (author)

  18. Height dependence of the observed spectrum of radar backscatter from HF-induced ionospheric Langmuir turbulence

    Science.gov (United States)

    Fejer, J. A.; Sulzer, M. P.; Djuth, F. T.

    1991-09-01

    Results are presented of observations of the spectrum of the 430-MHz radar backscatter from HF-induced Langmuir turbulence with height discrimination. During very stable ionospheric conditions under which the height of the below-threshold backscatter spectrum changed by less than 300 m during a 7-min period, a 20-s-long temporary increase in the HF power from 3 MW ERP to 38-MW-equivalent-radiated HF power is found to result in subsequent strong above-threshold spectra extending to heights up to 1200 m greater than the height of the below-threshold spectrum for more than a minute. The generation of irregularities in the plasma density during the 20 s of enhanced HF power is suggested as a possible cause of this persistence of strong above-threshold spectra at greater heights. The initial temporal evolution of the backscatter spectrum from Langmuir turbulence after the start of HF transmissions is observed for different heights. The observational results are compared with the predictions of existing theories of Langmuir turbulence.

  19. Impact of Langmuir Turbulence on Upper Ocean Response to Hurricane Edouard: Model and Observations

    Science.gov (United States)

    Blair, A.; Ginis, I.; Hara, T.; Ulhorn, E.

    2017-12-01

    Tropical cyclone intensity is strongly affected by the air-sea heat flux beneath the storm. When strong storm winds enhance upper ocean turbulent mixing and entrainment of colder water from below the thermocline, the resulting sea surface temperature cooling may reduce the heat flux to the storm and weaken the storm. Recent studies suggest that this upper ocean turbulence is strongly affected by different sea states (Langmuir turbulence), which are highly complex and variable in tropical cyclone conditions. In this study, the upper ocean response under Hurricane Edouard (2014) is investigated using a coupled ocean-wave model with and without an explicit sea state dependent Langmuir turbulence parameterization. The results are compared with in situ observations of sea surface temperature and mixed layer depth from AXBTs, as well as satellite sea surface temperature observations. Overall, the model results of mixed layer deepening and sea surface temperature cooling under and behind the storm are consistent with observations. The model results show that the effects of sea state dependent Langmuir turbulence can be significant, particularly on the mixed layer depth evolution. Although available observations are not sufficient to confirm such effects, some observed trends suggest that the sea state dependent parameterization might be more accurate than the traditional (sea state independent) parameterization.

  20. Nonlinear beam mechanics

    NARCIS (Netherlands)

    Westra, H.J.R.

    2012-01-01

    In this Thesis, nonlinear dynamics and nonlinear interactions are studied from a micromechanical point of view. Single and doubly clamped beams are used as model systems where nonlinearity plays an important role. The nonlinearity also gives rise to rich dynamic behavior with phenomena like

  1. MODEL ADSORPSI LANGMUIR GAS DINITROGEN MONOKSIDA DALAM SISTEM BIOFILTER DENGAN MEDIUM PUPUK KOMPOS

    Directory of Open Access Journals (Sweden)

    Tania Surya Utami

    2012-04-01

    Full Text Available  LANGMUIR ADSORPTION MODEL FOR DINITROGEN MONOXIDE IN BIOFILTER SYSTEM USING COMPOST FERTILIZER MEDIUM. Nitrous oxide (N2O is mostly emitted from various industrial processes and agricultural activities. This gas causes serious environmental problems and is considered as a dangerous pollutant. In the past, traditional control technologies, such as Selective Catalytic Reduction (SCR and Selective Non-Catalytic Reduction (SNCR, were applied to control N2O emissions in some industries. However, these two processes required high temperatures and the use of catalysts. Economic and technical constraints in SCR and SNCR methods motivated researchers to develop new, cost-effective processes to remove N2O. Biofiltration is an emerging technology that offers a number of advantages over traditional methods of air pollution control. The purpose of this research is to modelise the biofiltration experimental results into the Langmuir adsorption model. This research is conducted in laboratory scale biofilter column, with parameters studied are effect of biofilter length and N2O gas flowrate. The result of the model is simulated into sensitivity analysis. The average Langmuir constant obtained in the model of the research is 16.006 liter/mol. Dinitrogen Monoksida (N2O merupakan emisi dari proses industri dan kegiatan pertanian. Gas tersebut merupakan gas polutan berbahaya dan menyebabkan masalah lingkungan yang serius. Sebelumnya, teknologi kontrol tradisional seperti Selective Catalytic Reduction (SCR dan Selective Non-Catalytic Reduction (SNCR digunakan untuk mengontrol emisi N2O pada kegiatan-kegiatan industri. Akan tetapi, kedua proses ini membutuhkan suhu yang tinggi dan penggunaan katalis. Adanya masalah dari segi ekonomi dan teknis memotivasi peneliti untuk mengembangkan teknologi baru yang lebih murah dan efisien untuk menghilangkan N2O dari gas buangan. Pengolahan N2O secara biologis dalam proses biofiltrasi adalah salah satu alternatif ramah

  2. Effect of Climate Variability and Management Practices on Carbon, Water and Energy Fluxes of a Young Ponderosa Pine Plantation at the Blodgett Forest Ameriflux Site

    Science.gov (United States)

    Misson, L.; McKay, M.; Goldstein, A. H.

    2003-12-01

    Our research at Blodgett Forest in the Sierra Nevada mountains of California seeks to better understand how fluxes of CO2, H2O, and energy in a mid-elevation, young pine plantation change interannually in response to climate variability, and how they are impacted by management practices such as shrub removal and thinning. Ecosystem scale fluxes have been measured by the eddy covariance method since 1997, along with meteorological parameters. During winter, the young Ponderosa pine plantation at Blodgett acted mainly as a sink of carbon. Strong variations in winter carbon sequestration occurred due to changes in leaf area index and frequency of freezing temperatures. Interannual variations in springtime carbon flux occurred mainly due to differences in the timing of seasonally increasing temperatures. Drought is a regular feature of the California climate, making water availability the major controller of gas exchange in summer and fall. In late summer 2001, drought stress reduced ecosystem carbon uptake by 1/5, while the Bowen ratio increased by 1/3. Thinning is a widespread procedure in plantation management carried out to reduce stand density, improve forest health, and optimize tree growth. In spring 2000, 2/3 of the trees were removed by mastication, the process of mechanically chewing up unwanted trees, which is becoming a widespread method for pre-commercial thinning in the U.S. During and after thinning, the plantation remained a sink of carbon. Thinning at the Blodgett site reduced the leaf area index from ~3 to ~1.5 m2 m-2, and created branch and stem debris of 400-500 g m-2. During summer 2000, mastication decreased ecosystem carbon uptake by 1/3. Ecosystem water use efficiency decreased by 1/5 and the Bowen ratio increased by 1/3. This indicates the increasing heat lost as sensible versus latent heat as the water flux decreased due to the reduction in leaf area index. After thinning, leaf area index rapidly increased to ~2.5 m2 m-2 by the end of 2000

  3. Lead bromide-based layered perovskite Langmuir–Blodgett films having π-conjugated molecules as organic layer prepared by using squeezed out technique

    Science.gov (United States)

    Era, Masanao; Shironita, Yu; Soda, Koichi

    2018-03-01

    Using the squeezed out technique, we successfully prepared PbBr-based layered perovskite Langmuir–Blodgett (LB) films, which have π-conjugated materials as an organic layer (i.e., a phenylenevinylene oligomer, a dithienylethene derivative, and a π-conjugated polyfluorene derivative). The mixed monolayers of π-conjugated materials and octadecylammonium bromide were spread on an aqueous subphase containing saturated PbBr2. During pressing, octadecylammonium molecules were squeezed from the mixed monolayer, and the squeezed ammonium molecules formed the PbBr-based layered perovskite structure at the air-aqueous subphase interface. The monolayers with the PbBr-based layered perovskite structure could be deposited on fused quartz substrates by the LB technique. In addition to the preparation procedure, the structural and optical properties of the layered perovskite LB films and their formation mechanism are reported in this paper.

  4. A heterostructured SnO{sub 2}–TiO{sub 2} thin film prepared by Langmuir–Blodgett technique

    Energy Technology Data Exchange (ETDEWEB)

    Choudhury, Sipra, E-mail: sipra@barc.gov.in; Betty, C.A.

    2013-08-15

    SnO{sub 2}–TiO{sub 2} heterostructure films were prepared through Langmuir–Blodgett (LB) route. LB films of octadecyl amine (ODA)–titanyl oxalate multilayer deposited on Si (100) and decomposed at 600 °C showed rutile and anatase phases of ultrathin TiO{sub 2} film. Subsequently, multilayer LB film of ODA–stannate deposited on the pre deposited TiO{sub 2} film after decomposition at 600 °C resulted in thin SnO{sub 2} films on the TiO{sub 2} thin film. The phase analysis of the SnO{sub 2}–TiO{sub 2} film showed cassiterite phase of SnO{sub 2} as well as the rutile/anatase mixture of TiO{sub 2} indicating a SnO{sub 2}–TiO{sub 2} heterostructured film. Surface morphology of the pure TiO{sub 2} film and SnO{sub 2}–TiO{sub 2} film were analyzed by using AFM. Electrical characterization by AC impedance analysis suggested SnO{sub 2}–TiO{sub 2} heterostructure formation. DC current voltage measurement showed increase in photocurrent indicating visible light absorption and efficient charge separation under the sunlight type radiation. - Highlights: • Thin film of SnO{sub 2}–TiO{sub 2} heterostructure was prepared by Langmuir–Blodgett technique. • The decomposition temperature of LB film was 600 °C to form oxide thin films. • Structural and electrical properties were studied by XRD, DC and AC impedance studies. • Increase in photocurrent was observed in heterostructure film in presence of visible light.

  5. Non-parametric correlative uncertainty quantification and sensitivity analysis: Application to a Langmuir bimolecular adsorption model

    Directory of Open Access Journals (Sweden)

    Jinchao Feng

    2018-03-01

    Full Text Available We propose non-parametric methods for both local and global sensitivity analysis of chemical reaction models with correlated parameter dependencies. The developed mathematical and statistical tools are applied to a benchmark Langmuir competitive adsorption model on a close packed platinum surface, whose parameters, estimated from quantum-scale computations, are correlated and are limited in size (small data. The proposed mathematical methodology employs gradient-based methods to compute sensitivity indices. We observe that ranking influential parameters depends critically on whether or not correlations between parameters are taken into account. The impact of uncertainty in the correlation and the necessity of the proposed non-parametric perspective are demonstrated.

  6. Langmuir Probe Evaluation of the Plasma Potential in Tokamak Edge Plasma for Non-Maxwellian EEDF

    Czech Academy of Sciences Publication Activity Database

    Popov, Tsv.K.; Dimitrova, Miglena; Ivanova, P.; Hasan, E.; Horáček, Jan; Dejarnac, Renaud; Stöckel, Jan; Weinzettl, Vladimír; Kovačič, J.

    2014-01-01

    Roč. 54, č. 3 (2014), s. 267-272 ISSN 0863-1042. [International Workshop on Electric Probes in Magnetized Plasmas/10./. Madrid, 09.07.2013-12.07.2013] R&D Projects: GA MŠk(CZ) LM2011021; GA ČR(CZ) GAP205/12/2327 Institutional support: RVO:61389021 Keywords : Langmuir probe * Plasma potential * First derivative probe technique * Scrape-off-layer * COMPASS tokamak Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 0.838, year: 2014 http://onlinelibrary.wiley.com/doi/10.1002/ctpp.201410076/abstract

  7. Spectroscopic measurements of turbulent Langmuir fields at the relativistic electron beam experiment REBEX

    International Nuclear Information System (INIS)

    Ullschmied, J.; Simek, M.; Kolacek, K.; Ripa, M.

    1996-01-01

    Theoretical and experimental parameters characterizing the Langmuir turbulence in the REBEX machine are summarized. The experimental data collected up to now support the idea that at the end of the beam injection the beam-heated plasma in the REBEX machine reaches a strongly turbulent state. Nevertheless the attempts to determine the turbulence level on the base of spectroscopic measurements were unsuccessful up to now. From this point of view, the advantages and disadvantages of three different spectroscopic apparatuses used for detailed measurements of the profiles of hydrogen emission lines are discussed. (J.U.). 2 tabs., 5 figs., 13 refs

  8. First simultaneous measurements of Reynolds stress with ball-pen and Langmuir probes

    Czech Academy of Sciences Publication Activity Database

    Grover, Ondřej; Adámek, Jiří; Seidl, Jakub; Devitre, A.; Šos, Miroslav; Vondráček, Petr; Bílková, Petra; Hron, Martin

    2017-01-01

    Roč. 88, č. 6 (2017), č. článku 063501. ISSN 0034-6748 R&D Projects: GA ČR(CZ) GA15-10723S; GA ČR(CZ) GA16-25074S; GA MŠk(CZ) LM2015045 Institutional support: RVO:61389021 Keywords : COMPASS tokamak * Electric field effects * Electric fields * Langmuir probes * Magnetoplasma * Ball-pen probes Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: 2.11 Other engineering and technologies Impact factor: 1.515, year: 2016 http://aip.scitation.org/doi/full/10.1063/1.4984240

  9. Effects of Langmuir Turbulence on Reactive Tracers in the Upper Ocean

    Science.gov (United States)

    Smith, K.; Hamlington, P.; Niemeyer, K.; Fox-Kemper, B.; Lovenduski, N. S.

    2017-12-01

    Reactive tracers such as carbonate chemical species play important roles in the oceanic carbon cycle, allowing the ocean to hold 60 times more carbon than the atmosphere. However, uncertainties in regional ocean sinks for anthropogenic CO2 are still relatively high. Many carbonate species are non-conserved, flux across the air-sea interface, and react on time scales similar to those of ocean turbulent processes, such as small-scale wave-driven Langmuir turbulence. All of this complexity gives rise to heterogeneous tracer distributions that are not fully understood and can greatly affect the rate at which CO2 fluxes across the air-sea interface. In order to more accurately model the biogeochemistry of the ocean in Earth system models (ESMs), a better understanding of the fundamental interactions between these reactive tracers and relevant turbulent processes is required. Research on reacting flows in other contexts has shown that the most significant tracer-flow couplings occur when coherent structures in the flow have timescales that rival reaction time scales. Langmuir turbulence, a 3D, small-scale, wave-driven process, has length and time scales on the order of O(1-100m) and O(1-10min), respectively. Once CO2 transfers across the air-sea interface, it reacts with seawater in a series of reactions whose rate limiting steps have time scales of 10-25s. This similarity in scales warrants further examination into interactions between these small-scale physical and chemical processes. In this presentation, large eddy simulations are used to examine the evolution of reactive tracers in the presence of realistic upper ocean wave- and shear-driven turbulence. The reactive tracers examined are those specifically involved in non-biological carbonate chemistry. The strength of Langmuir turbulence is varied in order to determine a relationship between the degree of enhancement (or reduction) of carbon that is fluxed across the air-sea interface due to the presence of Langmuir

  10. RF plasma parameter determination by a Langmuir multipoint double probe array

    International Nuclear Information System (INIS)

    Rojas-Olmedo, I A; López-Callejas, R; De la Piedad-Beneitez, A; Valencia-Alvarado, R; Peña-Eguiluz, R; Mercado-Cabrera, A; Barocio, S R; Muñoz-Castro, A E; Rodríguez-Méndez, B G

    2012-01-01

    A multipoint double Langmuir (MDL) probe system, which is exempt from interference, has been designed and assembled to be applied to an RF plasma. The system provides the measurement of fundamental plasma parameters such as density, temperature, plasma potential, etc. on the basis of the Bohm Approximation Theory and the Orbital Movement Limit. Thus, one pair of the MDL system is selected so as to consider the right plasma parameters within the prevailing pressure-power intervals. Both the hardware and software of the system have been applied to the modification of material properties by means of the PIII process.

  11. Non-parametric correlative uncertainty quantification and sensitivity analysis: Application to a Langmuir bimolecular adsorption model

    Science.gov (United States)

    Feng, Jinchao; Lansford, Joshua; Mironenko, Alexander; Pourkargar, Davood Babaei; Vlachos, Dionisios G.; Katsoulakis, Markos A.

    2018-03-01

    We propose non-parametric methods for both local and global sensitivity analysis of chemical reaction models with correlated parameter dependencies. The developed mathematical and statistical tools are applied to a benchmark Langmuir competitive adsorption model on a close packed platinum surface, whose parameters, estimated from quantum-scale computations, are correlated and are limited in size (small data). The proposed mathematical methodology employs gradient-based methods to compute sensitivity indices. We observe that ranking influential parameters depends critically on whether or not correlations between parameters are taken into account. The impact of uncertainty in the correlation and the necessity of the proposed non-parametric perspective are demonstrated.

  12. Quantitative study of the trapped particle bunching instability in Langmuir waves

    International Nuclear Information System (INIS)

    Hara, Kentaro; Boyd, Iain D.; Chapman, Thomas; Joseph, Ilon; Berger, Richard L.; Banks, Jeffrey W.; Brunner, Stephan

    2015-01-01

    The bunching instability of particles trapped in Langmuir waves is studied using Vlasov simulations. A measure of particle bunching is defined and used to extract the growth rate from numerical simulations, which are compared with theory [Dodin et al., Phys. Rev. Lett. 110, 215006 (2013)]. In addition, the general theory of trapped particle instability in 1D is revisited and a more accurate description of the dispersion relation is obtained. Excellent agreement between numerical and theoretical predictions of growth rates of the bunching instability is shown over a range of parameters

  13. Quantitative study of the trapped particle bunching instability in Langmuir waves

    Energy Technology Data Exchange (ETDEWEB)

    Hara, Kentaro, E-mail: kenhara@umich.edu; Boyd, Iain D. [Department of Aerospace Engineering, University of Michigan, Ann Arbor, Michigan 48109 (United States); Chapman, Thomas; Joseph, Ilon; Berger, Richard L. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Banks, Jeffrey W. [Department of Mathematical Sciences, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Brunner, Stephan [Centre de Recherches en Physique des Plasmas, Association Euratom-Confederation Suisse, Ecole Polytechnique Fédérale de Lausanne, CRPP-PPB, CH-1015 Lausanne (Switzerland)

    2015-02-15

    The bunching instability of particles trapped in Langmuir waves is studied using Vlasov simulations. A measure of particle bunching is defined and used to extract the growth rate from numerical simulations, which are compared with theory [Dodin et al., Phys. Rev. Lett. 110, 215006 (2013)]. In addition, the general theory of trapped particle instability in 1D is revisited and a more accurate description of the dispersion relation is obtained. Excellent agreement between numerical and theoretical predictions of growth rates of the bunching instability is shown over a range of parameters.

  14. Synthesis of Novel Amphiphilic Azobenzenes and X-ray Scattering Studies of Their Langmuir Monolayers

    DEFF Research Database (Denmark)

    Sørensen, Thomas Just; Kjær, Kristian; Breiby, Dag Werner

    2008-01-01

    . At the air-water interface, the amphiphilic azobenzenes form noncrystalline but stable Langmuir films that display an unusual reversible monolayer collapse close to 35 mN/m. The structures and phase transitions were studied by X-ray reflectivity (XR) and grazing-incidence X-ray diffraction, both utilizing...... synchrotron radiation. Compression beyond the collapse point does not change the XR data, showing that the film is unchanged at the molecular level, even at areas less than half of that of the collapse. This leads to the conclusion that few macroscopic collapse sites are responsible for reversibly removing...

  15. Modification of ion-acoustic solitons on interaction with Langmuir waves

    International Nuclear Information System (INIS)

    Basovich, A.Ya.; Gromov, E.M.; Karpman, V.I.

    1981-01-01

    Variation of an ion-accoustic soliton under the effect of the Langmuir quasimonochromatic wave has been considered. Parameters of the soliton tail and variation of soliton velocity have been determined. It is shown that the soliton tail consists of two parts: averaged and oscillating. Density oscillations have a forced nature and are related to the modulation of striction force appearing during interference of waves incident and reflected from a soliton. Oscillations appear behind soliton when the wave runs after soliton and in front of soliton when soliton runs after wave [ru

  16. Conceptual design of a Langmuir probe system for the tokamak ASDEX-UPGRADE

    International Nuclear Information System (INIS)

    Anastassiadis, A.; Tsingas, A.C.; Tsois, N.N.; Zoumbos, G.A.

    1985-05-01

    The conceptual design of a Langmuir probe system for the tokamak ASDEX-UPG is presented. This system is intended to carry out electrostatic measurements, in space and time, on the boundary layer plasma over the largest possible volume of the divertor plasma during discharges. Conducted by preset design requirements a fast probe system is proposed. During discharges signal measurements will be performed by means of a data-acquisition system and the motion will be controlled by a real-time computer. The desired information concerning plasma parameters and the motion of the probe system will be available to the diagnostician via a video display unit. (author)

  17. On modified finite difference method to obtain the electron energy distribution functions in Langmuir probes

    Science.gov (United States)

    Kang, Hyun-Ju; Choi, Hyeok; Kim, Jae-Hyun; Lee, Se-Hun; Yoo, Tae-Ho; Chung, Chin-Wook

    2016-06-01

    A modified central difference method (MCDM) is proposed to obtain the electron energy distribution functions (EEDFs) in single Langmuir probes. Numerical calculation of the EEDF with MCDM is simple and has less noise. This method provides the second derivatives at a given point as the weighted average of second order central difference derivatives calculated at different voltage intervals, weighting each by the square of the interval. In this paper, the EEDFs obtained from MCDM are compared to those calculated via the averaged central difference method. It is found that MCDM effectively suppresses the noises in the EEDF, while the same number of points are used to calculate of the second derivative.

  18. On modified finite difference method to obtain the electron energy distribution functions in Langmuir probes

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Hyun-Ju; Chung, Chin-Wook, E-mail: joykang@hanyang.ac.kr [Department of Electrical Engineering, Hanyang University, 222, Wangsimni-ro, Seongdong-gu, Seoul 133-791 (Korea, Republic of); Choi, Hyeok; Kim, Jae-Hyun; Lee, Se-Hun; Yoo, Tae-Ho [Seoul Science High School, 63, Hyehwa-ro, Jongno-gu, Seoul 110-530 (Korea, Republic of)

    2016-06-15

    A modified central difference method (MCDM) is proposed to obtain the electron energy distribution functions (EEDFs) in single Langmuir probes. Numerical calculation of the EEDF with MCDM is simple and has less noise. This method provides the second derivatives at a given point as the weighted average of second order central difference derivatives calculated at different voltage intervals, weighting each by the square of the interval. In this paper, the EEDFs obtained from MCDM are compared to those calculated via the averaged central difference method. It is found that MCDM effectively suppresses the noises in the EEDF, while the same number of points are used to calculate of the second derivative.

  19. Nonlinear elliptic differential equations with multivalued nonlinearities

    Indian Academy of Sciences (India)

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

    Nonlinear elliptic differential equations with multivalued ... has a solution. Finally in the last part we consider an eigenvalue problem with a nonmonotone multivalued nonlinearity. Using the critical point theory for nonsmooth .... A is upper semicontinuous (as a set-valued map) from every finite dimensional subspace of X into ...

  20. THE EFFECTS OF ELECTRON-BEAM-INDUCED ELECTRIC FIELD ON THE GENERATION OF LANGMUIR TURBULENCE IN FLARING ATMOSPHERES

    International Nuclear Information System (INIS)

    Zharkova, Valentina V.; Siversky, Taras V.

    2011-01-01

    The precipitation of an electron beam injected into the solar atmosphere is studied for the generation of Langmuir wave turbulence in the presence of collisional and Ohmic losses. The system of quasi-linear time-dependent kinetic equations describing the evolution of beams and Langmuir waves is solved by using the summary approximation method. It is found that at upper atmospheric levels the self-induced electric field suppresses the generation of Langmuir turbulence to very small regions below injection. With further precipitation into deeper atmosphere the initial single power-law distributions of beam electrons are transformed into energy distributions with maxima at lower energies formed by collisional and Ohmic energy depletion. The electrons with lower energies (<20 keV) generate on large spatial scales intense low-hybrid and high-hybrid Langmuir waves with well-defined patterns in the corona while higher energy electrons generate moderate low-hybrid waves in the chromosphere. The maximum wave density appears at the maximum of the ambient density. The self-induced electric field reduces the level and makes the regions with low-hybrid Langmuir turbulence narrower in the corona and upper chromosphere. The higher the beam energy flux or its self-induced electric field, the narrower the regions with Langmuir turbulence. High-hybrid Langmuir waves in the form of multiple patterns in space (in the corona) and energy (below 20 keV) are found to be generated only by a very intense electron beam. The number of patterns in both dimensions is also shown to be significantly reduced by the self-induced electric field.

  1. On Poisson Nonlinear Transformations

    Directory of Open Access Journals (Sweden)

    Nasir Ganikhodjaev

    2014-01-01

    Full Text Available We construct the family of Poisson nonlinear transformations defined on the countable sample space of nonnegative integers and investigate their trajectory behavior. We have proved that these nonlinear transformations are regular.

  2. Terahertz semiconductor nonlinear optics

    DEFF Research Database (Denmark)

    Turchinovich, Dmitry; Hvam, Jørn Märcher; Hoffmann, Matthias

    2013-01-01

    In this proceedings we describe our recent results on semiconductor nonlinear optics, investigated using single-cycle THz pulses. We demonstrate the nonlinear absorption and self-phase modulation of strong-field THz pulses in doped semiconductors, using n-GaAs as a model system. The THz nonlinear...

  3. Nonlinear Microwave Optomechanics

    NARCIS (Netherlands)

    Shevchuk, O.

    2017-01-01

    The nonlinearity is essential for creation of non-classical states of the cavity or mechanical resonator such as squeezed or cat states. A microwave cavity can be made nonlinear by, for instance, adding Josephson junctions. The mechanical resonator is inherently nonlinear. The radiation pressure

  4. Advances in nonlinear optics

    CERN Document Server

    Chen, Xianfeng; Zeng, Heping; Guo, Qi; She, Weilong

    2015-01-01

    This book presents an overview of the state of the art of nonlinear optics from weak light nonlinear optics, ultrafast nonlinear optics to electro-optical theory and applications. Topics range from the fundamental studies of the interaction between matter and radiation to the development of devices, components, and systems of tremendous commercial interest for widespread applications in optical telecommunications, medicine, and biotechnology.

  5. Enthalpies of sublimation of ferrocene and nickelocene measured by calorimetry and the method of Langmuir

    Energy Technology Data Exchange (ETDEWEB)

    Rojas, Aaron, E-mail: arojas@cinvestav.mx [Departamento de Quimica del Centro de Investigacion y de Estudios Avanzados del IPN, Av. Instituto Politecnico Nacional 2508, C.P. 07360, Mexico D.F. (Mexico); Vieyra-Eusebio, Maria Teresa [Departamento de Quimica del Centro de Investigacion y de Estudios Avanzados del IPN, Av. Instituto Politecnico Nacional 2508, C.P. 07360, Mexico D.F. (Mexico)

    2011-11-15

    Highlights: > Calorimetric enthalpies of sublimation of ferrocene and nickelocene are supplied. > Sublimation enthalpies of both metallocenes were also obtained by indirect Langmuir's method. > Calorimetric and indirect enthalpies of sublimation are comparable in accuracy and dispersion. > Sublimation enthalpies are congruent with both compounds being monoclinic and isostructural. - Abstract: A quick and accurate methodology that is based on Langmuir's equation and that is developed by utilising a DSC7 device is proposed for the measurement of the enthalpies of sublimation of substances characterised by vapour pressures of approximately 1.0 Pa at room temperature. The procedure was applied to ferrocene and nickelocene; the accuracy and uncertainty associated with the experimental results show that the reliability of the developed indirect method is comparable to the direct calorimetric measurements also performed in this work. Furthermore, the melting data and crystal-phase heat capacities for both metallocenes were calorimetrically measured, whereas the gas-phase heat capacity for each metallic bis(cyclopentadienyl) was theoretically estimated by DFT calculations.

  6. Fluctuations measured by flush mounted versus proud divertor Langmuir probes - why are they different?

    Science.gov (United States)

    Garcia, O. E.; Kuang, A. Q.; Brunner, D.; Labombard, B.; Kube, R.

    2017-10-01

    A flush-mounted, toroidally-elongated, and field-aligned divertor `rail' Langmuir probe array was installed in Alcator C-Mod in 2015. This geometry is heat flux tolerant and effectively mitigates sheath expansion effects down to incident field line angles of 0.5 degree. Further complications have arisen that cannot be explained by sheath-expansion. In particular, the `rail' probe geometry measures significantly higher plasma fluctuation levels in the common flux region compared to traditional proud probes, whereas they are similar in the private flux zone. In some instances, the amplitudes of ion saturation current fluctuations normalized to the mean are a factor of 2 higher; probability distribution functions correspondingly record large amplitude events that are not seen by the proud probes. This discrepancy also appears to depend on divertor plasma regime. For example, fluctuations become similar near the strikepoint when the electron temperature is low. To ensure that these discrepancies were not due to perturbations caused by the voltage bias or currents collected by the probes, the two Langmuir probe systems were left to `float' and the fluctuation statistics analyzed. Yet, even in this non-perturbative situation, there exist clear differences in the fluctuation characteristics. The raises two questions: how does the probe geometry affect plasma fluctuations measurements and what are the true plasma fluctuations experienced by the divertor surface? Supported by USDoE awards DE-FC02-99ER54512.

  7. Description of two-metal biosorption equilibria by Langmuir-type models.

    Science.gov (United States)

    Chong, K H; Volesky, B

    1995-08-20

    A biosorbent prepared from Ascophyllum nodosum seaweed biomass, FCAN2, was examined for its sorption capacity. Equilibrium batch sorption studies were performed using two-matal systems containing either (Cu + Zn), (Cu + Cd), or (Zn + Cd). In the evaluation of the two-metal sorption system performance, simple isotherm curves had to be replaced by three-dimensional sorption isotherm surfaces. In order to describe the isotherm surfaces mathematically, three Langmuir-type models were evaluated. The apparent one-parameter Langmuir constant (b) was used to quantify FCAN2 "affinity" for one metal in the presence of another one. The uptake of Zn decreased drastically when Cu or Cd were present. The uptake of Cd wasmuch more sensitive to the presence of Cu than to that of Zn. The presence of Cd and Zn alter the "affinity" of FCAN2 for Cu the least at high Cu equilibrium concentrations. The mathematical model of the two-metal sorption system enabled quantitative estimation of one-metal (bio)sorption inhibition due to the influence of a second metal. (c) 1995 John Wiley & Sons Inc.

  8. Enthalpies of sublimation of ferrocene and nickelocene measured by calorimetry and the method of Langmuir

    International Nuclear Information System (INIS)

    Rojas, Aaron; Vieyra-Eusebio, Maria Teresa

    2011-01-01

    Highlights: → Calorimetric enthalpies of sublimation of ferrocene and nickelocene are supplied. → Sublimation enthalpies of both metallocenes were also obtained by indirect Langmuir's method. → Calorimetric and indirect enthalpies of sublimation are comparable in accuracy and dispersion. → Sublimation enthalpies are congruent with both compounds being monoclinic and isostructural. - Abstract: A quick and accurate methodology that is based on Langmuir's equation and that is developed by utilising a DSC7 device is proposed for the measurement of the enthalpies of sublimation of substances characterised by vapour pressures of approximately 1.0 Pa at room temperature. The procedure was applied to ferrocene and nickelocene; the accuracy and uncertainty associated with the experimental results show that the reliability of the developed indirect method is comparable to the direct calorimetric measurements also performed in this work. Furthermore, the melting data and crystal-phase heat capacities for both metallocenes were calorimetrically measured, whereas the gas-phase heat capacity for each metallic bis(cyclopentadienyl) was theoretically estimated by DFT calculations.

  9. An ellipsometric approach towards the description of inhomogeneous polymer-based Langmuir layers

    Directory of Open Access Journals (Sweden)

    Falko O. Rottke

    2016-08-01

    Full Text Available The applicability of nulling-based ellipsometric mapping as a complementary method next to Brewster angle microscopy (BAM and imaging ellipsometry (IE is presented for the characterization of ultrathin films at the air–water interface. First, the methodology is demonstrated for a vertically nonmoving Langmuir layer of star-shaped, 4-arm poly(ω-pentadecalactone (PPDL-D4. Using nulling-based ellipsometric mapping, PPDL-D4-based inhomogeneously structured morphologies with a vertical dimension in the lower nm range could be mapped. In addition to the identification of these structures, the differentiation between a monolayer and bare water was possible. Second, the potential and limitations of this method were verified by applying it to more versatile Langmuir layers of telechelic poly[(rac-lactide-co-glycolide]-diol (PLGA. All ellipsometric maps were converted into thickness maps by introduction of the refractive index that was derived from independent ellipsometric experiments, and the result was additionally evaluated in terms of the root mean square roughness, Rq. Thereby, a three-dimensional view into the layers was enabled and morphological inhomogeneity could be quantified.

  10. A generalization of the child-langmuir relation for one-dimensional time-dependent diodes

    International Nuclear Information System (INIS)

    Kadish, A.; Jones, M.E.; Peter, W.

    1985-01-01

    The steady-state Child-Langmuir relation between current and applied voltage has been a basic principle upon which all modern diode physics has been based. With advances in pulsed power technology and diode design, new devices which operate in vastly different parameter regimes have recently become of interest. Many of these devices cannot be said to satisfy the strict requirements necessary for Child-Langmuir flow. For instance, in a recent pulsed electron device for use in high-current accelerators, the applied voltage is sinusoidal in time. In another case, development of sources for heavy ion fusion necessitates understanding of transient current oscillations when the voltage is applied abruptly. We derive the time-dependent relationship between the emitted current and time-dependent applied voltage in a nonrelativistic planar diode. The relationship is valid for arbitrary voltage shapes V(t) applied to the diode for times less than the beam-front transit time across the gap. Using this relationship, transient and time-dependent effects in the start-up phase of any nonrelativistic diode can be analyzed

  11. Study of plasma-material surface interaction using Langmuir probe technique during plasma treatment

    International Nuclear Information System (INIS)

    Saloum, S.; Akel, M.

    2009-06-01

    In this study, we tried to understand the plasma-surface interactions by using Langmuir probes. Two different types of plasmas were studied, the first is the electropositive plasma in Argon and the second is the electronegative plasma in Sulfur Hexafluoride. In the first type, the effects of Argon gas pressure, the injection of Helium in the remote zone and the substrate bias on the measurements of the Electron Energy Probability Function (EEPF) and on the plasma parameters (electron density (n e ), effective electron temperature (T e ff), plasma potential (V p ) and floating potential (V f )) have been investigated. The obtained EEPFs and plasma parameters have been used to control two remote plasma processes. The first is the remote Plasma Enhanced Chemical Vapor Deposition (PE-CVD) of thin films, on silicon wafers, from Hexamethyldisoloxane (HMDSO) precursor diluted in the remote Ar-He plasma. The second is the pure Argon remote plasma treatment of polymethylmethacrylate (PMMA) polymer surface. In the second type, the plasma diagnostics were performed in the remote zone as a function of SF 6 flow rate, where relative concentrations of fluorine atoms were measured using actinometry optical emission spectroscopy; electron density, electron temperature and plasma potential were determined using single cylindrical Langmuir probe, positive ion flux and negative ion fraction were determined using an planar probe. The silicon etching process in SF 6 plasma was studied. (author)

  12. Experimental evaluation of Langmuir probe sheath potential coefficient on the HL-2A tokamak

    Science.gov (United States)

    Nie, L.; Xu, M.; Ke, R.; Yuan, B. D.; Wu, Y. F.; Cheng, J.; Lan, T.; Yu, Y.; Hong, R. J.; Guo, D.; Ting, L.; Dong, Y. B.; Zhang, Y. P.; Song, X. M.; Zhong, W. L.; Wang, Z. H.; Sun, A. P.; Xu, J. Q.; Chen, W.; Yan, L. W.; Zou, X. L.; Duan, X. R.; HL-2A team

    2018-03-01

    Systematic calibration experiment of Langmuir probe sheath potential coefficient Λ, which is a critical coefficient for estimating plasma sheath potential, has been carried out in the HL-2A tokamak deuterium plasmas. The electron energy probability function (EEPF) shows that electron outside last-closed-flux-surface (LCFS) is Maxwell distribution, but inside LCFS it changes to bi-Maxwell. Two kinds of plasma potential measuring method and three kinds Λ estmating method were compared. It is found that the estimated Λ coefficient is in the region of 2–3 outside LCFS and then increases to ~5 inside LCFS due to the high temperature electron effect. Fortunately, the results show that the commonly used value Λ  =  2.8 is still available to calculate plasma potential when we use the overestimated electron temperature measured by three-tip probe in bi-Maxwell case. Further analysis indicated this value should be corrected. Or it may lead to a error when we calculate the the electric field {{E}r} and its shear d{{E}r}/dr . The corrected value monotonically increased from ~2.2 to ~2.9 while Langmuir probe moved from 40 mm outside LCFS to 20 mm inside LCFS.

  13. Presenting a new kinetic model for methanol to light olefins reactions over a hierarchical SAPO-34 catalyst using the Langmuir-Hinshelwood-Hougen-Watson mechanism

    Science.gov (United States)

    Javad Azarhoosh, Mohammad; Halladj, Rouein; Askari, Sima

    2017-10-01

    In this study, a new kinetic model for methanol to light olefins (MTO) reactions over a hierarchical SAPO-34 catalyst using the Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanism was presented and the kinetic parameters was obtained using a genetic algorithm (GA) and genetic programming (GP). Several kinetic models for the MTO reactions have been presented. However, due to the complexity of the reactions, most reactions are considered lumped and elementary, which cannot be deemed a completely accurate kinetic model of the process. Therefore, in this study, the LHHW mechanism is presented as kinetic models of MTO reactions. Because of the non-linearity of the kinetic models and existence of many local optimal points, evolutionary algorithms (GA and GP) are used in this study to estimate the kinetic parameters in the rate equations. Via the simultaneous connection of the code related to modelling the reactor and the GA and GP codes in the MATLAB R2013a software, optimization of the kinetic models parameters was performed such that the least difference between the results from the kinetic models and experiential results was obtained and the best kinetic parameters of MTO process reactions were achieved. A comparison of the results from the model with experiential results showed that the present model possesses good accuracy.

  14. Scales of Langmuir circulation generated using a large-eddy simulation model

    International Nuclear Information System (INIS)

    Skyllingstad, Eric D.

    2001-01-01

    Sensitivity experiments were performed using a large-eddy simulation (LES) turbulence model of the ocean surface boundary layer. Parameters defining wind and wave forcing were varied to help understand how different forcing affects the formation and dispersive qualities of Langmuir circulation (LC). Comparison of the model with observed surface velocity variance shows a consistent linear increase in velocity scale with increasing wave Stokes drift, however, the model systematically under predicts the velocity scale for large Stokes drift. Results using particle trajectories show that in open-ocean conditions, wave forcing dominates the structure of near surface turbulence causing organized LC cells that actively collect surface material. With weak waves, surface particles display a more random pattern in comparison to strong wave cases. Analysis of the turbulence kinetic energy budget shows that the reduction in wave forcing is offset by shear production, which produces less organized patterns in surface material in comparison to LC. (Author)

  15. Selective Mechanical Transfer Deposition of Langmuir Graphene Films for High-Performance Silver Nanowire Hybrid Electrodes.

    Science.gov (United States)

    Large, Matthew J; Ogilvie, Sean P; Alomairy, Sultan; Vöckerodt, Terence; Myles, David; Cann, Maria; Chan, Helios; Jurewicz, Izabela; King, Alice A K; Dalton, Alan B

    2017-10-31

    In this work, we present silver nanowire hybrid electrodes prepared through the addition of small quantities of pristine graphene by mechanical transfer deposition from surface-assembled Langmuir films. This technique is a fast, efficient, and facile method for modifying the optoelectronic performance of AgNW films. We demonstrate that it is possible to use this technique to perform two-step device production by selective patterning of the stamp used, leading to controlled variation in the local sheet resistance across a device. This is particularly attractive for producing extremely low cost sensors on arbitrarily large scales. Our aim is to address some of the concerns surrounding the use of AgNW films as replacements for indium tin oxide (ITO), namely, the use of scarce materials and poor stability of AgNWs against flexural and environmental degradation.

  16. Langmuir hydrogen dissociation approach in radiolabeling carbon nanotubes and graphene oxide

    International Nuclear Information System (INIS)

    Badun, Gennadii A.; Chernysheva, Maria G.; Eremina, Elena A.; Egorov, Alexander V.; Grigorieva, Anastasia V.

    2016-01-01

    Carbon-based nanomaterials have piqued the interest of several researchers. At the same time, radioactive labeling is a powerful tool for studying processes in different systems, including biological and organic; however, the introduction of radioactive isotopes into carbon-based nanomaterial remains a great challenge. We have used the Langmuir hydrogen dissociation method to introduce tritium in single-walled carbon nanotubes and graphene oxide. The technique allows us to achieve a specific radioactivity of 107 and 27 Ci/g for single-layer graphene oxide and single-walled carbon nanotubes, respectively. Based on the analysis of characteristic Raman modes at 1350 and 1580 cm -1 , a minimal amount of structural changes to the nanomaterials due to radiolabeling was observed. The availability of a simple, nondestructive, and economic technique for the introduction of radiolabels to single-walled carbon nanotubes and graphene oxide will ultimately expand the applicability of these materials.

  17. Fractional-dimensional Child-Langmuir law for a rough cathode

    International Nuclear Information System (INIS)

    Zubair, M.; Ang, L. K.

    2016-01-01

    This work presents a self-consistent model of space charge limited current transport in a gap combined of free-space and fractional-dimensional space (F α ), where α is the fractional dimension in the range 0 < α ≤ 1. In this approach, a closed-form fractional-dimensional generalization of Child-Langmuir (CL) law is derived in classical regime which is then used to model the effect of cathode surface roughness in a vacuum diode by replacing the rough cathode with a smooth cathode placed in a layer of effective fractional-dimensional space. Smooth transition of CL law from the fractional-dimensional to integer-dimensional space is also demonstrated. The model has been validated by comparing results with an experiment.

  18. Damping kinetics of annihilation slowed fluorescence of aromatic molecules in Langmuir films

    International Nuclear Information System (INIS)

    Ibraev, N.Kh.; Latonin, V.A.; Satybaldina, D.Zh.

    1996-01-01

    The paper is devoted to study of decay mechanism of phosphors molecules triplet states in the Langmuir-Blogett (L-B) films. The L-B-films have being prepared on the base of anthracene, pyrene, 3,4-benzopyrene and 1,2-benzanthracene molecules. Spectral and kinetic investigations were carried out in photons counting regime. Long-lived luminescence was observed under excitation of the LB-film by nitrogen laser radiation (λ=337 nm) .Spectrum of the long-lived luminescence coincides with spectrum of fast fluorescence of same film. Received spectral data indicate on similarity of LB-films structure of aromatic molecules and its crystals. It was defined, that deactivation of triplet states of aromatic molecules in LB-films has being carried out mainly in the result of annihilation of triplet excitation. 14 refs., 2 tabs., 5 figs

  19. Design and fabrication of an actively cooled Langmuir probe for long pulse applications

    International Nuclear Information System (INIS)

    Paterson, J.A.; Biagi, L.A.; Ehlers, K.W.; Koehler, G.W.

    1985-11-01

    The details of the mechanical design and fabrication for a Langmuir Probe for the continuous monitoring of plasma density are given. The probe was designed for use as a diagnostic tool in the development of long pulse positive ion plasma sources for use on neutral beam systems. The essential design feature of this probe is the incorporation of two electrically isolated cooling water circuits which actively cool the probe tip and probe jacket. The electrical isolation is required to prevent drain currents from the probe body disturbing the measurement of the probe tip current and thereby the plasma density measurement. The successful realization of the design requires precision components and vacuum tight ceramic to refractory metal brazes. To date this design has successfully operated in steady-state in plasma densities up to 250 mA/cm 2 and surface heat fluxes of 25 W/cm 2

  20. Stirring competes with chemical induction in chiral selection of Langmuir monolayer domains

    Directory of Open Access Journals (Sweden)

    Petit-Garrido Nuria

    2013-08-01

    Full Text Available Chirality, the absence of mirror symmetry, can be equally invoked in relation to physical forces and chemical induction processes, yet a competition between these two types of influences is rarely reported. Here, we employ Langmuir monolayers of azobenzene surfactants as a prototypical self-assembled two-dimensional system in which chiral selection is controlled by the combined independent action of a chiral dopant and vortical stirring. The two effects can be arbitrarily coupled, either constructively or destructively, leading to a situation of perfect compensation. The induced enantiomorphic excess is measured in terms of the statistical imbalance of an ensemble of sub-millimeter monolayer domains, where achiral molecules self-assemble with a well-defined orientational chirality, which is unambiguously resolved using Brewster angle microscopy.

  1. Langmuir hydrogen dissociation approach in radiolabeling carbon nanotubes and graphene oxide

    Energy Technology Data Exchange (ETDEWEB)

    Badun, Gennadii A.; Chernysheva, Maria G.; Eremina, Elena A.; Egorov, Alexander V. [Lomonosov Moscow State Univ. (Russian Federation). Dept. of Chemistry; Grigorieva, Anastasia V. [Lomonosov Moscow State Univ., Moscow (Russian Federation). Dept. of Materials Science

    2016-11-01

    Carbon-based nanomaterials have piqued the interest of several researchers. At the same time, radioactive labeling is a powerful tool for studying processes in different systems, including biological and organic; however, the introduction of radioactive isotopes into carbon-based nanomaterial remains a great challenge. We have used the Langmuir hydrogen dissociation method to introduce tritium in single-walled carbon nanotubes and graphene oxide. The technique allows us to achieve a specific radioactivity of 107 and 27 Ci/g for single-layer graphene oxide and single-walled carbon nanotubes, respectively. Based on the analysis of characteristic Raman modes at 1350 and 1580 cm{sup -1}, a minimal amount of structural changes to the nanomaterials due to radiolabeling was observed. The availability of a simple, nondestructive, and economic technique for the introduction of radiolabels to single-walled carbon nanotubes and graphene oxide will ultimately expand the applicability of these materials.

  2. Stochastic Growth Theory of Spatially-Averaged Distributions of Langmuir Fields in Earth's Foreshock

    Science.gov (United States)

    Boshuizen, Christopher R.; Cairns, Iver H.; Robinson, P. A.

    2001-01-01

    Langmuir-like waves in the foreshock of Earth are characteristically bursty and irregular, and are the subject of a number of recent studies. Averaged over the foreshock, it is observed that the probability distribution is power-law P(bar)(log E) in the wave field E with the bar denoting this averaging over position, In this paper it is shown that stochastic growth theory (SGT) can explain a power-law spatially-averaged distributions P(bar)(log E), when the observed power-law variations of the mean and standard deviation of log E with position are combined with the log normal statistics predicted by SGT at each location.

  3. String defects connecting pairs of half-integer disclinations and tilting transition of a langmuir monolayer.

    Science.gov (United States)

    Hatta, E; Fischer, Th M

    2005-02-24

    The static and dynamic string defect textures connecting pairs of half-integer disclinations have been observed by Brewster angle microscopy in the solid phase of pentacosadiynoic acid Langmuir monolayers. The static string defect structures have appeared coexisting with two kinds of point disclinations that have four and two black brushes. The use of local laser heating has allowed one to observe kinetics of creation and annihilation of string defects connecting the two-half-integer disclinations in the splitting process of an s = 1 point disclination into fractional disclinations. These kinetics have been analyzed by studying the competition between the orientational elasticity of the molecules and the line tension of the string and the drag force of the disclinations.

  4. Incorporation of nano-clay saponite layers in the organo-clay hybrid films using anionic amphiphile stearic acid by Langmuir–Blodgett technique

    International Nuclear Information System (INIS)

    Hussain, Syed Arshad; Chakraborty, S.; Bhattacharjee, D.; Schoonheydt, R.A.

    2013-01-01

    In general cationic amphiphiles are used to prepare organo-clay hybrid film in Langmuir–Blodgett (LB) technique. In this present communication we demonstrated a unique technique to prepare the organo–clay hybrid films using an anionic amphiphile. The T–O–T type clay saponite was incorporated onto a floating stearic acid monolayer via a divalent cation Mg 2+ . Salt MgCl 2 was mixed along with the clay dispersion in the LB trough and amphiphile solution was spread onto the subphase in order to make the organo-clay hybrid films. It was observed that salt (MgCl 2 ) concentration on the subphase affects the organization of nano-dimensional clay platelet (saponite) in organo-clay hybrid films at air–water interface as well as in LB films. Noticeable changes in area per molecule and shape of the isotherms were observed and measured at subphases with different salt concentrations. Infrared reflection absorption spectroscopy studies reveal that only an in-plane (996 cm −1 ) vibration of ν (Si-O) band occurred when the salt concentration was 10 mM. However, both in-plane (996 cm −1 ) and out-of-plane (1063 cm −1 ) vibrations of the ν (Si-O) band of saponite occurred when the subphase salt concentration was 100 mM. Also the out-of-plane vibration of ν (OH) of saponite was prominent at higher salt concentration. This is because at lower salt concentration clay sheets remain flat on the surface whereas; at higher MgCl 2 concentration they aggregated and form stacks of saponite layers. Also they may be slightly tilted with a very small tilt angle at higher salt concentration making a favorable condition for both in-plane and out-of-plane vibrations of ν (Si-O) in the hybrid films. Observed decrease in starting area per molecule in the pressure area isotherm measured at higher salt concentration also supports the tilting of clay layers at air–clay dispersion interface. Attentuated total reflectance Fourier transform infrared spectroscopy and Atomic Force

  5. Flame exposure time on Langmuir probe degradation, ion density, and thermionic emission for flame temperature

    Science.gov (United States)

    Doyle, S. J.; Salvador, P. R.; Xu, K. G.

    2017-11-01

    The paper examines the effect of exposure time of Langmuir probes in an atmospheric premixed methane-air flame. The effects of probe size and material composition on current measurements were investigated, with molybdenum and tungsten probe tips ranging in diameter from 0.0508 to 0.1651 mm. Repeated prolonged exposures to the flame, with five runs of 60 s, resulted in gradual probe degradations (-6% to -62% area loss) which affected the measurements. Due to long flame exposures, two ion saturation currents were observed, resulting in significantly different ion densities ranging from 1.16 × 1016 to 2.71 × 1019 m-3. The difference between the saturation currents is caused by thermionic emissions from the probe tip. As thermionic emission is temperature dependent, the flame temperature could thus be estimated from the change in current. The flame temperatures calculated from the difference in saturation currents (1734-1887 K) were compared to those from a conventional thermocouple (1580-1908 K). Temperature measurements obtained from tungsten probes placed in rich flames yielded the highest percent error (9.66%-18.70%) due to smaller emission current densities at lower temperatures. The molybdenum probe yielded an accurate temperature value with only 1.29% error. Molybdenum also demonstrated very low probe degradation in comparison to the tungsten probe tips (area reductions of 6% vs. 58%, respectively). The results also show that very little exposure time (<5 s) is needed to obtain a valid ion density measurement and that prolonged flame exposures can yield the flame temperature but also risks damage to the Langmuir probe tip.

  6. Nonlinear graphene plasmonics

    Science.gov (United States)

    Ooi, Kelvin J. A.; Tan, Dawn T. H.

    2017-10-01

    The rapid development of graphene has opened up exciting new fields in graphene plasmonics and nonlinear optics. Graphene's unique two-dimensional band structure provides extraordinary linear and nonlinear optical properties, which have led to extreme optical confinement in graphene plasmonics and ultrahigh nonlinear optical coefficients, respectively. The synergy between graphene's linear and nonlinear optical properties gave rise to nonlinear graphene plasmonics, which greatly augments graphene-based nonlinear device performance beyond a billion-fold. This nascent field of research will eventually find far-reaching revolutionary technological applications that require device miniaturization, low power consumption and a broad range of operating wavelengths approaching the far-infrared, such as optical computing, medical instrumentation and security applications.

  7. Nonlinear Dirac Equations

    Directory of Open Access Journals (Sweden)

    Wei Khim Ng

    2009-02-01

    Full Text Available We construct nonlinear extensions of Dirac's relativistic electron equation that preserve its other desirable properties such as locality, separability, conservation of probability and Poincaré invariance. We determine the constraints that the nonlinear term must obey and classify the resultant non-polynomial nonlinearities in a double expansion in the degree of nonlinearity and number of derivatives. We give explicit examples of such nonlinear equations, studying their discrete symmetries and other properties. Motivated by some previously suggested applications we then consider nonlinear terms that simultaneously violate Lorentz covariance and again study various explicit examples. We contrast our equations and construction procedure with others in the literature and also show that our equations are not gauge equivalent to the linear Dirac equation. Finally we outline various physical applications for these equations.

  8. Stationary nonlinear Airy beams

    International Nuclear Information System (INIS)

    Lotti, A.; Faccio, D.; Couairon, A.; Papazoglou, D. G.; Panagiotopoulos, P.; Tzortzakis, S.; Abdollahpour, D.

    2011-01-01

    We demonstrate the existence of an additional class of stationary accelerating Airy wave forms that exist in the presence of third-order (Kerr) nonlinearity and nonlinear losses. Numerical simulations and experiments, in agreement with the analytical model, highlight how these stationary solutions sustain the nonlinear evolution of Airy beams. The generic nature of the Airy solution allows extension of these results to other settings, and a variety of applications are suggested.

  9. Nonlinear evolution equations

    CERN Document Server

    Uraltseva, N N

    1995-01-01

    This collection focuses on nonlinear problems in partial differential equations. Most of the papers are based on lectures presented at the seminar on partial differential equations and mathematical physics at St. Petersburg University. Among the topics explored are the existence and properties of solutions of various classes of nonlinear evolution equations, nonlinear imbedding theorems, bifurcations of solutions, and equations of mathematical physics (Navier-Stokes type equations and the nonlinear Schrödinger equation). The book will be useful to researchers and graduate students working in p

  10. Nonlinear Physics of Plasmas

    CERN Document Server

    Kono, Mitsuo

    2010-01-01

    A nonlinearity is one of the most important notions in modern physics. A plasma is rich in nonlinearities and provides a variety of behaviors inherent to instabilities, coherent wave structures and turbulence. The book covers the basic concepts and mathematical methods, necessary to comprehend nonlinear problems widely encountered in contemporary plasmas, but also in other fields of physics and current research on self-organized structures and magnetized plasma turbulence. The analyses make use of strongly nonlinear models solved by analytical techniques backed by extensive simulations and available experiments. The text is written for senior undergraduates, graduate students, lecturers and researchers in laboratory, space and fusion plasmas.

  11. Nonlinear optics at interfaces

    International Nuclear Information System (INIS)

    Chen, C.K.

    1980-12-01

    Two aspects of surface nonlinear optics are explored in this thesis. The first part is a theoretical and experimental study of nonlinear intraction of surface plasmons and bulk photons at metal-dielectric interfaces. The second part is a demonstration and study of surface enhanced second harmonic generation at rough metal surfaces. A general formulation for nonlinear interaction of surface plasmons at metal-dielectric interfaces is presented and applied to both second and third order nonlinear processes. Experimental results for coherent second and third harmonic generation by surface plasmons and surface coherent antiStokes Raman spectroscopy (CARS) are shown to be in good agreement with the theory

  12. Nonlinear drift tearing mode

    International Nuclear Information System (INIS)

    Zelenyj, L.M.; Kuznetsova, M.M.

    1989-01-01

    Nonlinear study of magnetic perturbation development under single-mode conditions in collision-free plasma in configurations with the magnetic field shear is investigated. Results are obtained with regard of transverse component of electrical field and its effect on ion dynamics within wide range of ion Larmor radius value and values of magnetic field shear. Increments of nonlinear drift tearing mode are obtained and it is shown that excitation drastic conditions of even linearly stable modes are possible. Mechanism of instability nonlinear stabilization is considered and the value of magnetic island at the saturation threshold is estimeted. Energy of nonlinear drift tearing mode is discussed

  13. Comparison of fluctuations properties measured by Langmuir and ball-pen probes in the ISTTOK boundary plasma

    International Nuclear Information System (INIS)

    Silva, C; Fernandes, H; Figueiredo, H; Adamek, J

    2015-01-01

    In this work, the fluctuations properties measured by Langmuir and ball-pen probes are compared, aiming at investigating the influence of temperature fluctuations on Langmuir probe measurements, including the cross-field turbulent particle flux. With this aim, a 5-pin probe was designed to estimate the radial particle transport due to fluctuations simultaneously using Langmuir and ball-pen probes. A considerable difference is observed in the amplitude of the floating potential fluctuations measured by the two types of probes, but not in statistical properties such as skewness. The turbulent particle flux was found to be roughly four times larger when measured with Langmuir probes. However, quantities such as the phase velocity of the fluctuations or the poloidal correlation lengths are not significantly different, as floating potential fluctuations measured by both types of probes are highly correlated and roughly in phase. Finally, it is suggested that ball-pen and emissive probes may underestimate the amplitude of the plasma potential fluctuations and therefore probe measurements must be carefully validated. (paper)

  14. Comparison of fluctuations properties measured by Langmuir and ball-pen probes in the ISTTOK boundary plasma

    Science.gov (United States)

    Silva, C.; Adamek, J.; Fernandes, H.; Figueiredo, H.

    2015-02-01

    In this work, the fluctuations properties measured by Langmuir and ball-pen probes are compared, aiming at investigating the influence of temperature fluctuations on Langmuir probe measurements, including the cross-field turbulent particle flux. With this aim, a 5-pin probe was designed to estimate the radial particle transport due to fluctuations simultaneously using Langmuir and ball-pen probes. A considerable difference is observed in the amplitude of the floating potential fluctuations measured by the two types of probes, but not in statistical properties such as skewness. The turbulent particle flux was found to be roughly four times larger when measured with Langmuir probes. However, quantities such as the phase velocity of the fluctuations or the poloidal correlation lengths are not significantly different, as floating potential fluctuations measured by both types of probes are highly correlated and roughly in phase. Finally, it is suggested that ball-pen and emissive probes may underestimate the amplitude of the plasma potential fluctuations and therefore probe measurements must be carefully validated.

  15. Spacecraft nonlinear control

    Science.gov (United States)

    Sheen, Jyh-Jong; Bishop, Robert H.

    1992-01-01

    The feedback linearization technique is applied to the problem of spacecraft attitude control and momentum management with control moment gyros (CMGs). The feedback linearization consists of a coordinate transformation, which transforms the system to a companion form, and a nonlinear feedback control law to cancel the nonlinear dynamics resulting in a linear equivalent model. Pole placement techniques are then used to place the closed-loop poles. The coordinate transformation proposed here evolves from three output functions of relative degree four, three, and two, respectively. The nonlinear feedback control law is presented. Stability in a neighborhood of a controllable torque equilibrium attitude (TEA) is guaranteed and this fact is demonstrated by the simulation results. An investigation of the nonlinear control law shows that singularities exist in the state space outside the neighborhood of the controllable TEA. The nonlinear control law is simplified by a standard linearization technique and it is shown that the linearized nonlinear controller provides a natural way to select control gains for the multiple-input, multiple-output system. Simulation results using the linearized nonlinear controller show good performance relative to the nonlinear controller in the neighborhood of the TEA.

  16. Nonlinear Optics and Applications

    Science.gov (United States)

    Abdeldayem, Hossin A. (Editor); Frazier, Donald O. (Editor)

    2007-01-01

    Nonlinear optics is the result of laser beam interaction with materials and started with the advent of lasers in the early 1960s. The field is growing daily and plays a major role in emerging photonic technology. Nonlinear optics play a major role in many of the optical applications such as optical signal processing, optical computers, ultrafast switches, ultra-short pulsed lasers, sensors, laser amplifiers, and many others. This special review volume on Nonlinear Optics and Applications is intended for those who want to be aware of the most recent technology. This book presents a survey of the recent advances of nonlinear optical applications. Emphasis will be on novel devices and materials, switching technology, optical computing, and important experimental results. Recent developments in topics which are of historical interest to researchers, and in the same time of potential use in the fields of all-optical communication and computing technologies, are also included. Additionally, a few new related topics which might provoke discussion are presented. The book includes chapters on nonlinear optics and applications; the nonlinear Schrodinger and associated equations that model spatio-temporal propagation; the supercontinuum light source; wideband ultrashort pulse fiber laser sources; lattice fabrication as well as their linear and nonlinear light guiding properties; the second-order EO effect (Pockels), the third-order (Kerr) and thermo-optical effects in optical waveguides and their applications in optical communication; and, the effect of magnetic field and its role in nonlinear optics, among other chapters.

  17. Lasers for nonlinear microscopy.

    Science.gov (United States)

    Wise, Frank

    2013-03-01

    Various versions of nonlinear microscopy are revolutionizing the life sciences, almost all of which are made possible because of the development of ultrafast lasers. In this article, the main properties and technical features of short-pulse lasers used in nonlinear microscopy are summarized. Recent research results on fiber lasers that will impact future instruments are also discussed.

  18. Nonlinear optical systems

    CERN Document Server

    Lugiato, Luigi; Brambilla, Massimo

    2015-01-01

    Guiding graduate students and researchers through the complex world of laser physics and nonlinear optics, this book provides an in-depth exploration of the dynamics of lasers and other relevant optical systems, under the umbrella of a unitary spatio-temporal vision. Adopting a balanced approach, the book covers traditional as well as special topics in laser physics, quantum electronics and nonlinear optics, treating them from the viewpoint of nonlinear dynamical systems. These include laser emission, frequency generation, solitons, optically bistable systems, pulsations and chaos and optical pattern formation. It also provides a coherent and up-to-date treatment of the hierarchy of nonlinear optical models and of the rich variety of phenomena they describe, helping readers to understand the limits of validity of each model and the connections among the phenomena. It is ideal for graduate students and researchers in nonlinear optics, quantum electronics, laser physics and photonics.

  19. Nonlinear optics and photonics

    CERN Document Server

    He, Guang S

    2015-01-01

    This book provides a comprehensive presentation on most of the major topics in nonlinear optics and photonics, with equal emphasis on principles, experiments, techniques, and applications. It covers many major new topics including optical solitons, multi-photon effects, nonlinear photoelectric effects, fast and slow light , and Terahertz photonics. Chapters 1-10 present the fundamentals of modern nonlinear optics, and could be used as a textbook with problems provided at the end of each chapter. Chapters 11-17 cover the more advanced topics of techniques and applications of nonlinear optics and photonics, serving as a highly informative reference for researchers and experts working in related areas. There are also 16 pages of color photographs to illustrate the visual appearances of some typical nonlinear optical effects and phenomena. The book could be adopted as a textbook for both undergraduates and graduate students, and serve as a useful reference work for researchers and experts in the fields of physics...

  20. Download this PDF file

    African Journals Online (AJOL)

    pc

    35900 Tanjong Malim, Perak, Malaysia. Published online: 10 November 2017 ase ligands are used in this work. These amphiphilic ligands were being e suitability in forming Langmuir film by using Langmuir-Blodgett (LB izations of these ...

  1. A hybrid SAM phospholipid approach to fabricating a 'free' supported lipid bilayer

    DEFF Research Database (Denmark)

    Hughes, A.V.; Goldar, A.; Gerstenberg, M.C.

    2002-01-01

    Using a combination of self assembly, Langmuir-Blodgett and Langmuir-Schaeffer techniques, we have produced a multilayered film of dimyristoylphosphatidylcholine ( DMPC) intended for use as a biomembrane mimic. Neutron reflectivity measurements have revealed that the upper two layers...

  2. Nonlinear crack mechanics

    International Nuclear Information System (INIS)

    Khoroshun, L.P.

    1995-01-01

    The characteristic features of the deformation and failure of actual materials in the vicinity of a crack tip are due to their physical nonlinearity in the stress-concentration zone, which is a result of plasticity, microfailure, or a nonlinear dependence of the interatomic forces on the distance. Therefore, adequate models of the failure mechanics must be nonlinear, in principle, although linear failure mechanics is applicable if the zone of nonlinear deformation is small in comparison with the crack length. Models of crack mechanics are based on analytical solutions of the problem of the stress-strain state in the vicinity of the crack. On account of the complexity of the problem, nonlinear models are bason on approximate schematic solutions. In the Leonov-Panasyuk-Dugdale nonlinear model, one of the best known, the actual two-dimensional plastic zone (the nonlinearity zone) is replaced by a narrow one-dimensional zone, which is then modeled by extending the crack with a specified normal load equal to the yield point. The condition of finite stress is applied here, and hence the length of the plastic zone is determined. As a result of this approximation, the displacement in the plastic zone at the abscissa is nonzero

  3. Distinctive interactions of oleic acid covered magnetic nanoparticles with saturated and unsaturated phospholipids in Langmuir monolayers.

    Science.gov (United States)

    Matshaya, Thabo J; Lanterna, Anabel E; Granados, Alejandro M; Krause, Rui W M; Maggio, Bruno; Vico, Raquel V

    2014-05-27

    The growing number of innovations in nanomedicine and nanobiotechnology are posing new challenges in understanding the full spectrum of interactions between nanomateriales and biomolecules at nano-biointerfaces. Although considerable achievements have been accomplished by in vivo applications, many issues regarding the molecular nature of these interactions are far from being well-understood. In this work, we evaluate the interaction of hydrophobic magnetic nanoparticles (MNP) covered with a single layer of oleic acid with saturated and unsaturated phospholipids found in biomembranes through the use of Langmuir monolayers. We find distinctive interactions among the MNP with saturated and unsaturated phospholipids that are reflected by both, the compression isotherms and the surface topography of the films. The interaction between MNP and saturated lipids causes a noticeable reduction of the mean molecular area in the interfacial plane, while the interaction with unsaturated lipids promotes area expansion compared to the ideally mixed films. Moreover, when liquid expanded and liquid condensed phases of the phospholipid(s) coexist, the MNP preferably partition to the liquid-expanded phase, thus hindering the coalescence of the condensed domains with increasing surface pressure. In consequence organizational information on long-range order is attained. These results evidence the existence of a sensitive composition-dependent surface regulation given by phospholipid-nanoparticle interactions which enhance the biophysical relevance of understanding nanoparticle surface functionalization in relation to its interactions in biointerfaces constituted by defined types of biomolecules.

  4. Characteristics of the Plasma Source for Ground Ionosphere Simulation Surveyed by Disk-Type Langmuir Probe

    Science.gov (United States)

    Ryu, Kwangsun; Lee, Junchan; Kim, Songoo; Chung, Taejin; Shin, Goo-Hwan; Cha, Wonho; Min, Kyoungwook; Kim, Vitaly P.

    2017-12-01

    A space plasma facility has been operated with a back-diffusion-type plasma source installed in a mid-sized vacuum chamber with a diameter of 1.5 m located in Satellite Technology Research Center (SaTReC), Korea Advanced Institute of Science and Technology (KAIST). To generate plasma with a temperature and density similar to the ionospheric plasma, nickel wires coated with carbonate solution were used as filaments that emit thermal electrons, and the accelerated thermal electrons emitted from the heated wires collide with the neutral gas to form plasma inside the chamber. By using a disk-type Langmuir probe installed inside the vacuum chamber, the generation of plasma similar to the space environment was validated. The characteristics of the plasma according to the grid and plate anode voltages were investigated. The grid voltage of the plasma source is realized as a suitable parameter for manipulating the electron density, while the plate voltage is suitable for adjusting the electron temperature. A simple physical model based on the collision cross-section of electron impact on nitrogen molecule was established to explain the plasma generation mechanism.

  5. Characterisation of target plasma required for REB-plasma interaction studies using cylindrical Langmuir probes

    International Nuclear Information System (INIS)

    Roychowdhury, P.; Paithankar, A.S.; Iyyengar, S.K.; Rohatgi, V.K.

    1987-01-01

    The target plasma required for relativistic electron beam (REB)-plasma interaction studies has been generated by coaxial plasma gun. The measurement of electron density and temperature has been carried out using cylindrical Langmuir probes. Probes both oriented parallel and transverse to the flow have been used. The spatial as well as temporal variation of electron density and temperature have been studied. The typical electron density and temperature measured by probe were in the range of 9.0-3.5 x 10 13 cm -3 and 5-7 eV respectively. The typical e-folding decay time of density was 6.2 μs, while no appreciable change in electron temperature was observed until 10 μs after the peak density. The density decays by about 50% at distance of 30 cm from the gun. The plasma flow velocity has been measured by the time of flight technique and was found to be 2.5 x 10 6 cm s -1 . The plasma radius measured by dosimeter film, at distance of 30 cm from the gun was 3 cm. (author)

  6. Interaction of DNA with Cationic Lipid Mixtures-Investigation at Langmuir Lipid Monolayers.

    Science.gov (United States)

    Janich, Christopher; Hädicke, André; Bakowsky, Udo; Brezesinski, Gerald; Wölk, Christian

    2017-10-03

    Four different binary lipid mixtures composed of a cationic lipid and the zwitterionic colipids DOPE or DPPC, which show different DNA transfer activities in cell culture models, were investigated at the soft air/water interface to identify transfection efficiency determining characteristics. Langmuir films are useful models to investigate the interaction between DNA and lipid mixtures in a two-dimensional model system by using different surface sensitive techniques, namely, epifluorescence microscopy and infrared reflection-absorption spectroscopy. Especially, the effect of adsorbed DNA on the properties of the lipid mixtures has been examined. Distinct differences between the lipid composites were found which are caused by the different colipids of the mixtures. DOPE containing lipid mixtures form fluid monolayers with a uniform distribution of the fluorescent probe in the presence and absence of DNA at physiologically relevant surface pressures. Only at high nonphysiological pressures, the lipid monolayer collapses and phase separation was observed if DNA was present in the subphase. In contrast, DPPC containing lipid mixtures show domains in the liquid condensed phase state in the presence and absence of DNA in the subphase. The adsorption of DNA at the positively charged mixed lipid monolayer induces phase separation which is expressed in the morphology and the point of appearance of these domains.

  7. High heat flux Langmuir probe array for the DIII-D divertor platesa)

    Science.gov (United States)

    Watkins, J. G.; Taussig, D.; Boivin, R. L.; Mahdavi, M. A.; Nygren, R. E.

    2008-10-01

    Two modular arrays of Langmuir probes designed to handle a heat flux of up to 25 MW/m2 for 10 s exposures have been installed in the lower divertor target plates of the DIII-D tokamak. The 20 pyrolytic graphite probe tips have more than three times higher thermal conductivity and 16 times larger mass than the original DIII-D isotropic graphite probes. The probe tips have a fixed 12.5° surface angle to distribute the heat flux more uniformly than the previous 6 mm diameter domed collectors and a symmetric "rooftop" design to allow operation with reversed toroidal magnetic field. A large spring-loaded contact area improves heat conduction from each probe tip through a ceramic insulator into a cooled graphite divertor floor tile. The probe tips, brazed to molybdenum foil to ensure good electrical contact, are mounted in a ceramic tray for electrical isolation and reliable cable connections. The new probes are located 1.5 cm radially apart in a staggered arrangement near the entrance to the lower divertor pumping baffle and are linearly spaced 3 cm apart on the shelf above the in-vessel cryopump. Typical target plate profiles of Jsat, Te, and Vf with 4 mm spatial resolution are shown.

  8. High heat flux Langmuir probe array for the DIII-D divertor plates.

    Science.gov (United States)

    Watkins, J G; Taussig, D; Boivin, R L; Mahdavi, M A; Nygren, R E

    2008-10-01

    Two modular arrays of Langmuir probes designed to handle a heat flux of up to 25 MW/m(2) for 10 s exposures have been installed in the lower divertor target plates of the DIII-D tokamak. The 20 pyrolytic graphite probe tips have more than three times higher thermal conductivity and 16 times larger mass than the original DIII-D isotropic graphite probes. The probe tips have a fixed 12.5 degree surface angle to distribute the heat flux more uniformly than the previous 6 mm diameter domed collectors and a symmetric "rooftop" design to allow operation with reversed toroidal magnetic field. A large spring-loaded contact area improves heat conduction from each probe tip through a ceramic insulator into a cooled graphite divertor floor tile. The probe tips, brazed to molybdenum foil to ensure good electrical contact, are mounted in a ceramic tray for electrical isolation and reliable cable connections. The new probes are located 1.5 cm radially apart in a staggered arrangement near the entrance to the lower divertor pumping baffle and are linearly spaced 3 cm apart on the shelf above the in-vessel cryopump. Typical target plate profiles of J(sat), T(e), and V(f) with 4 mm spatial resolution are shown.

  9. A Langmuir probe system for high power RF-driven negative ion sources on high potential

    International Nuclear Information System (INIS)

    McNeely, P; Christ-Koch, S; Fantz, U; Dudin, S V

    2009-01-01

    A fully automated Langmuir probe system capable of operating simultaneously with beam extraction has been developed and commissioned for the negative hydrogen ion source testbeds at IPP Garching. It allows the measurement of temporal and spatial distributions of the plasma parameters within a single plasma pulse ( 10 18 m -3 ) and hot (T e > 10 eV) plasma with bi-Maxwellian electron energy distribution at low pressures. The plasma found near the plasma grid is very different being of low density (≤10 17 m -3 ) and very cold (T e < 2 eV). This plasma is also strongly influenced by the presence of caesium, the potential of the plasma grid, and if an ion beam is extracted from the source. Caesium strongly reduces the plasma potential of the source and enhances the negative ion density near the plasma grid. Extracting an ion beam is observed to reduce the electron density and increase the potential near the plasma grid. Applying a potential greater than the plasma potential to the plasma grid is found to significantly decrease the electron density near the plasma grid.

  10. Solving the Capacitive Effect in the High-Frequency sweep for Langmuir Probe in SYMPLE

    International Nuclear Information System (INIS)

    Pramila; Patel, J J; Rajpal, R; Hansalia, C J; Anitha, V P; Sathyanarayana, K

    2017-01-01

    Langmuir Probe based measurements need to be routinely carried out to measure various plasma parameters such as the electron density (n e ), the electron temperature (T e ), the floating potential (V f ), and the plasma potential (V p ). For this, the diagnostic electronics along with the biasing power supplies is installed in standard industrial racks with a 2KV isolation transformer. The Signal Conditioning Electronics (SCE) system is populated inside the 4U-chassis based system with the front-end electronics, designed using high common mode differential amplifiers which can measure small differential signal in presence of high common mode dc- bias or ac ramp voltage used for biasing the probes. DC-biasing of the probe is most common method for getting its I-V characteristic but method of biasing the probe with a sweep at high frequency encounters the problem of corruption of signal due to capacitive effect specially when the sweep period and the discharge time is very fast and die down in the order of μs or lesser. This paper presents and summarises the method of removing such effects encountered while measuring the probe current. (paper)

  11. Gas transfer through the air-water interface in LES of Langmuir circulation in shallow water

    Science.gov (United States)

    Akan, Cigdem; Tejada-Martínez, Andrés E.

    2008-11-01

    Over the past century the study of gas exchange rates between the atmosphere and the ocean has received increased attention because of concern about the fate of slightly soluble, greenhouse gases such as CO2 released into the atmosphere. Of recent interest is the oceanic uptake of CO2 along US shallow water coastal regions (e.g. see http://www.nacarbon.org). We present surface gas transfer results from large-eddy simulation (LES) of wind-driven shallow water flow with and without wave effects. Wave effects, parameterized by the well-known Craik-Leibovich vortex force, lead to the generation of Langmuir circulation (LC), serving as a mechanism for surface renewal of low concentration fluid. Our computations are motivated by the infrared imagery of Marmorino et al. (2004) suggesting that LC can affect gas transfer across the surface through straining and stretching of the gas concentration boundary layer. Preliminary LES shows that shallow water LC can increase the surface gas transfer rate by about 30 percent. Here we will focus on the accuracy of surface renewal models in predicting gas transfer velocity, a measure of gas transfer efficiency, in the presence of LC. Gas transfer velocity predicted by the surface renewal models will be compared to the prediction obtained directly from the LES.

  12. Theory of cylindrical Langmuir probes in weakly ionized, non-thermal, stationary and moderately collisional plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Bryant, P M [University of Liverpool, Department of Electrical Engineering and Electronics, Brownlow Hill, Liverpool L69 3GJ (United Kingdom)], E-mail: p.m.bryant@liv.ac.uk

    2009-02-01

    A finite length cylindrical Langmuir probe is modelled as an ellipsoid of revolution with spheroidal equipotential surfaces and confocal orthogonal hyperboloidal electric field lines. The theory is applicable in the transition regime of probe operation between the collisionless and fully collisional limits. The plasma is assumed to be weakly ionized, non-thermal and stationary, being characterized by frozen reactions and constant temperatures. It is further assumed that in an isotropic plasma the cold ions follow the field lines, as a result of ion-neutral collisions, in the presheath and sheath regions with collisionless Maxwellian electrons. The governing system of equations is derived and solved numerically with the results presented of the presheath and sheath solutions in collisionless and collisional regimes. These show convergence to the respective collisionless and collisional radial motion limits for spherical and cylindrical probes. Analytical approximations are also obtained for the sheath width (defined as the point where the ions reach the Bohm speed) and the Bohm potential over a wide range of collisionality. The collisional presheath drop according to the perturbation theory of Shih and Levi, as applied to cylindrical probes, is shown to significantly underestimate the numerical results. These are in better agreement with the collisional presheath drop for spheres even for long probes. Application of the theory to experimentally derived probe characteristics is also discussed.

  13. Solving the Capacitive Effect in the High-Frequency sweep for Langmuir Probe in SYMPLE

    Science.gov (United States)

    Pramila; Patel, J. J.; Rajpal, R.; Hansalia, C. J.; Anitha, V. P.; Sathyanarayana, K.

    2017-04-01

    Langmuir Probe based measurements need to be routinely carried out to measure various plasma parameters such as the electron density (ne), the electron temperature (Te), the floating potential (Vf), and the plasma potential (Vp). For this, the diagnostic electronics along with the biasing power supplies is installed in standard industrial racks with a 2KV isolation transformer. The Signal Conditioning Electronics (SCE) system is populated inside the 4U-chassis based system with the front-end electronics, designed using high common mode differential amplifiers which can measure small differential signal in presence of high common mode dc- bias or ac ramp voltage used for biasing the probes. DC-biasing of the probe is most common method for getting its I-V characteristic but method of biasing the probe with a sweep at high frequency encounters the problem of corruption of signal due to capacitive effect specially when the sweep period and the discharge time is very fast and die down in the order of μs or lesser. This paper presents and summarises the method of removing such effects encountered while measuring the probe current.

  14. Solvent-extraction and Langmuir-adsorption-based transport in chemically functionalized nanopore membranes.

    Science.gov (United States)

    Odom, Damian J; Baker, Lane A; Martin, Charles R

    2005-11-10

    We have investigated the transport properties of nanopore alumina membranes that were rendered hydrophobic by functionalization with octadecyltrimethoxysilane (ODS). The pores in these ODS-modified membranes are so hydrophobic that they are not wetted by water. Nevertheless, nonionic molecules can be transported from an aqueous feed solution on one side of the membrane, through the dry nanopores, and into an aqueous receiver solution on the other side. The transport mechanism involves Langmuir-type adsorption of the permeating molecule onto the ODS layers lining the pore walls, followed by solid-state diffusion along these ODS layers; we have measured the diffusion coefficients associated with this transport process. We have also investigated the transport properties of membranes prepared by filling the ODS-modified pores with the water-immiscible (hydrophobic) liquid mineral oil. In this case the transport mechanism involves solvent extraction of the permeating molecule into the mineral oil subphase confined with the pores, followed by solution-based diffusion through this liquid subphase. Because of this different transport mechanism, the supported-liquid membranes show substantially better transport selectivity than the ODS-modified membranes that contain no liquid subphase.

  15. High-resolution disruption halo current measurements using Langmuir probes in Alcator C-Mod

    Science.gov (United States)

    Tinguely, R. A.; Granetz, R. S.; Berg, A.; Kuang, A. Q.; Brunner, D.; LaBombard, B.

    2018-01-01

    Halo currents generated during disruptions on Alcator C-Mod have been measured with Langmuir ‘rail’ probes. These rail probes are embedded in a lower outboard divertor module in a closely-spaced vertical (poloidal) array. The dense array provides detailed resolution of the spatial dependence (~1 cm spacing) of the halo current distribution in the plasma scrape-off region with high time resolution (400 kHz digitization rate). As the plasma limits on the outboard divertor plate, the contact point is clearly discernible in the halo current data (as an inversion of current) and moves vertically down the divertor plate on many disruptions. These data are consistent with filament reconstructions of the plasma boundary, from which the edge safety factor of the disrupting plasma can be calculated. Additionally, the halo current ‘footprint’ on the divertor plate is obtained and related to the halo flux width. The voltage driving halo current and the effective resistance of the plasma region through which the halo current flows to reach the probes are also investigated. Estimations of the sheath resistance and halo region resistivity and temperature are given. This information could prove useful for modeling halo current dynamics.

  16. Estimation of plasma ion saturation current and reduced tip arcing using Langmuir probe harmonics.

    Science.gov (United States)

    Boedo, J A; Rudakov, D L

    2017-03-01

    We present a method to calculate the ion saturation current, I sat , for Langmuir probes at high frequency (>100 kHz) using the harmonics technique and we compare that to a direct measurement of I sat . It is noted that the I sat estimation can be made directly by the ratio of harmonic amplitudes, without explicitly calculating T e . We also demonstrate that since the probe tips using the harmonic method are oscillating near the floating potential, drawing little power, this method reduces tip heating and arcing and allows plasma density measurements at a plasma power flux that would cause continuously biased tips to arc. A multi-probe array is used, with two spatially separated tips employing the harmonics technique and measuring the amplitude of at least two harmonics per tip. A third tip, located between the other two, measures the ion saturation current directly. We compare the measured and calculated ion saturation currents for a variety of plasma conditions and demonstrate the validity of the technique and its use in reducing arcs.

  17. Saponin Interactions with Model Membrane Systems - Langmuir Monolayer Studies, Hemolysis and Formation of ISCOMs.

    Science.gov (United States)

    de Groot, Carolin; Müller-Goymann, Christel C

    2016-12-01

    Saponins are used in medicine due to their pharmacological and immunological effects. To better understand interactions of saponins with model membranes and natural membranes of, for example, erythrocytes, Langmuir film balance experiments are well established. For most saponins, a strong interaction with cholesterol was demonstrated in dependence of both the aglycone part and the sugar moieties and is suggested to be correlated with a strong hemolytic activity, high toxicity, and high surface activity, as was demonstrated for the steroid saponin digitonin. In general, changes in the sugar chain or in substituents of the aglycone result in a modification of the saponin properties. A promising saponin with regard to fairly low hemolytic activity and high adjuvant effect is α -tomatine, which still shows a high affinity for cholesterol. An interaction with cholesterol and lipids has also been proven for the Quillaja saponin from the bark of Quillaja saponaria Molina. This triterpene saponin was approved in marketed vaccines as an adjuvant due to the formation of immunostimulating complexes. Immunostimulating complexes consist of a Quillaja saponin, cholesterol, phospholipids, and a corresponding antigen. Recently, another saponin from Quillaja brasiliensis was successfully tested in immunostimulating complexes, too. Based on the results of interaction studies, the formation of drug delivery systems such as immunostimulating complexes or similar self-assembled colloids is postulated for a variety of saponins. Georg Thieme Verlag KG Stuttgart · New York.

  18. Totally asymmetric simple exclusion process with langmuir kinetics depending on the occupancy of the neighboring sites

    International Nuclear Information System (INIS)

    Ichiki, Shingo; Sato, Jun; Nishinari, Katsuhiro

    2016-01-01

    We generalize the totally asymmetric simple exclusion process with Langmuir kinetics (TASEP-LK). In the original TASEP-LK, when a site on the lattice is empty, a particle is attached at a certain rate, whereas the particle is detached at a certain rate when the site is occupied. In the extended TASEP-LK, the rates of attachment and detachment depend on the occupancy of the neighboring sites. In particular, we consider the case where the attachment rate and detachment rate are equal in each state of the neighboring sites. We analytically study a density profile using a mean-field approximation. Then, the results are compared with Monte Carlo simulations. We find in detail that the characteristic of the density profile is changed by manipulating each attachment and detachment parameter. It is showed that the position of a domain wall, which is fixed in the original model, changes depending on the inflow and outflow rates when the rates at the right and left boundaries are the same. (author)

  19. Improvement of density control by feedback on Langmuir probe signals in Tore Supra

    International Nuclear Information System (INIS)

    Gunn, J.; Bucalossi, J.; Costanzo, L.; Grisolia, C.; Ghendrih, Ph.; Grosman, A.; Loarer, T.; Martin, G.; Monier-Garbet, P.; Moulin, D.; Pascal, J.Y.; Saint-Laurent, F.

    1999-12-01

    Real time control of deuterium or helium gas injection by feedback on Langmuir probe signals is implemented in Tore Supra ergodic divertor discharges. The feedback schemes are based on the robust experimental observation that the density limit coincides with edge temperature T e ∼ 10 eV. Three control algorithms are used: (1) proportional feedback on the central line-averaged density with real-time attenuation of the system gain and security cut-off of the gas injection if the edge temperature becomes too low; (2) proportional feedback on the central line-averaged density with security cut-off controlled by the degree of detachment (DoD); (3) proportional feedback on edge temperature with security cut-off on the DoD. The DoD is defined for deuterium discharges, but not for helium since those do not detach. All three feedback modes permit operation close to the density limit and have been successfully applied for plasma currents 0.4 p p =1.4 MA with up to 4 MW of ICRH power. (author)

  20. Molecular-Scale Investigation of Heavy Metal Ions at a Charged Langmuir Monolayer

    Science.gov (United States)

    Rock, William; Qiao, Baofu; Uysal, Ahmet; Bu, Wei; Lin, Binhua

    Solvent extraction - the surfactant-aided preferential transfer of a species from an aqueous to an organic phase - is an important technique used in heavy and precious metal refining and reprocessing. Solvent extraction requires transfer through an oil/water interface, and interfacial interactions are expected to control transfer kinetics and phase stability, yet these key interactions are poorly understood. Langmuir monolayers with charged headgroups atop concentrated salt solutions containing heavy metal ions act as a model of solvent extraction interfaces; studies of ions at a charged surface are also fundamentally important to many other phenomena including protein solvation, mineral surface chemistry, and electrochemistry. We probe these charged interfaces using a variety of surface-sensitive techniques - vibrational sum frequency generation (VSFG) spectroscopy, x-ray reflectivity (XRR), x-ray fluorescence near total reflection (XFNTR), and grazing incidence diffraction (GID). We integrate experiments with Molecular Dynamics (MD) simulations to uncover the molecular-level interfacial structure. This work is supported by the U.S. DOE, BES, Contract DE-AC02-06CH11357. ChemMatCARS is supported by NSF/CHE-1346572.

  1. Thermodynamics and mesoscopic organisation in Langmuir monolayers of an azobenzene derivative.

    Science.gov (United States)

    Ignés-Mullol, J

    2010-12-15

    We have carried out the analysis of liquid crystalline Langmuir monolayers at the air-water interface composed of the amphiphilic azobenzene derivative 8Az5COOH. By varying the temperature and the isomeric (trans-cis) composition, the monolayer behaviour has been studied in comparison with a shorter homologue, 8Az3COOH, by measuring the surface pressure-area isotherms along with Brewster angle microscopy (BAM). Our data with the pure trans isomer enable a posterior thermodynamic analysis, which was not feasible with the shorter homologue. For the mixed trans-cis monolayers, BAM observations reveal a phase segregation with trans enriched domains surrounded by a cis enriched matrix. Line tension between the two phases is lower than in the shorter homologue. The organisation of the rodlike molecules inside the trans domains results in highly symmetric textures that make the quantitative analysis of the BAM images possible, and a better understanding of the microscopic structure of the monolayer can be achieved. Copyright © 2010 Elsevier Inc. All rights reserved.

  2. Non-linear oscillations

    CERN Document Server

    Hagedorn, Peter

    1982-01-01

    Thoroughly revised and updated, the second edition of this concise text provides an engineer's view of non-linear oscillations, explaining the most important phenomena and solution methods. Non-linear descriptions are important because under certain conditions there occur large deviations from the behaviors predicted by linear differential equations. In some cases, completely new phenomena arise that are not possible in purely linear systems. The theory of non-linear oscillations thus has important applications in classical mechanics, electronics, communications, biology, and many other branches of science. In addition to many other changes, this edition has a new section on bifurcation theory, including Hopf's theorem.

  3. Nonlinear wave equations

    CERN Document Server

    Li, Tatsien

    2017-01-01

    This book focuses on nonlinear wave equations, which are of considerable significance from both physical and theoretical perspectives. It also presents complete results on the lower bound estimates of lifespan (including the global existence), which are established for classical solutions to the Cauchy problem of nonlinear wave equations with small initial data in all possible space dimensions and with all possible integer powers of nonlinear terms. Further, the book proposes the global iteration method, which offers a unified and straightforward approach for treating these kinds of problems. Purely based on the properties of solut ions to the corresponding linear problems, the method simply applies the contraction mapping principle.

  4. An Experimental Concept for Probing Nonlinear Physics in Radiation Belts

    Science.gov (United States)

    Crabtree, C. E.; Ganguli, G.; Tejero, E. M.; Amatucci, B.; Siefring, C. L.

    2017-12-01

    A sounding rocket experiment, Space Measurement of Rocket-Released Turbulence (SMART), can be used to probe the nonlinear response to a known stimulus injected into the radiation belt. Release of high-speed neutral barium atoms (8- 10 km/s) generated by a shaped charge explosion in the ionosphere can be used as the source of free energy to seed weak turbulence in the ionosphere. The Ba atoms are photo-ionized forming a ring velocity distribution of heavy Ba+ that is known to generate lower hybrid waves. Induced nonlinear scattering will convert the lower hybrid waves into EM whistler/magnetosonic waves. The escape of the whistlers from the ionospheric region into the radiation belts has been studied and their observable signatures quantified. The novelty of the SMART experiment is to make coordinated measurement of the cause and effect of the turbulence in space plasmas and from that to deduce the role of nonlinear scattering in the radiation belts. Sounding rocket will carry a Ba release module and an instrumented daughter section that includes vector wave magnetic and electric field sensors, Langmuir probes and energetic particle detectors. The goal of these measurements is to determine the whistler and lower hybrid wave amplitudes and spectrum in the ionospheric source region and look for precipitated particles. The Ba release may occur at 600-700 km near apogee. Ground based cameras and radio diagnostics can be used to characterize the Ba and Ba+ release. The Van Allen Probes can be used to detect the propagation of the scattering-generated whistler waves and their effects in the radiation belts. By detecting whistlers and measuring their energy density in the radiation belts the SMART mission will confirm the nonlinear generation of whistlers through scattering of lower hybrid along with other nonlinear responses of the radiation belts and their connection to weak turbulence.

  5. parametric nonlinear quasivariational inequalities

    Directory of Open Access Journals (Sweden)

    Zeqing Liu

    2005-01-01

    uniqueness results and sensitivity analysis of solutions are also established for the system of generalized nonlinear parametric quasivariational inequalities and some convergence results of iterative sequence generated by the algorithm with errors are proved.

  6. Nonlinear Source Emulator

    DEFF Research Database (Denmark)

    Nguyen-Duy, Khiem

    and remains the prime source of energy in non-terrestrial applications such as those in sky-explorers. However, a renewable energy source is expensive, bulky, and its performance is weather dependent, which make testing of downstream converters very difficult. As a result, a nonlinear source emulator (NSE...... of a proposed NSE system with high dynamic performance. The goal of the work is to achieve a state-of-the art transient time of 10 µs. In order to produce the arbitrary nonlinear curve, the exponential function of a typical diode is used, but the diode can be replaced by other nonlinear curve reference...... simulation of nonlinear source systems with higher output power. In this work, a module will consist of two fundamental units: an isolated power supply and an NSE. The isolated power supply has to possess a very low circuit input-to-output capacitance (very low Cio) in order to reduce the effect...

  7. Cognitive Nonlinear Radar

    Science.gov (United States)

    2013-01-01

    filter, Bayesian decision theory, Generalized Likelihood Ratio Test (GLRT), and constant false alarm rate ( CFAR ) processing (31). Once the...Abbreviations, and Acronyms CFAR constant false alarm rate CNR cognitive nonlinear radar EM electromagnetic FCC Federal Communications Comission

  8. Nonlinear Optical Terahertz Technology

    Data.gov (United States)

    National Aeronautics and Space Administration — We develop a new approach to generation of THz radiation. Our method relies on mixing two optical frequency beams in a nonlinear crystalline Whispering Gallery Mode...

  9. Nonlinear differential equations

    CERN Document Server

    Struble, Raimond A

    2017-01-01

    Detailed treatment covers existence and uniqueness of a solution of the initial value problem, properties of solutions, properties of linear systems, stability of nonlinear systems, and two-dimensional systems. 1962 edition.

  10. Nonlinear ambipolar diffusion waves

    Energy Technology Data Exchange (ETDEWEB)

    Mendonca, J.T.; Rowlands, G.

    1985-07-01

    The evolution of a plasma perturbation in a neutral gas is considered using the ambipolar diffusion approximation. A nonlinear diffusion equation is derived and, in the one-dimensional case, exact solutions of shock type are obtained.

  11. Degenerate nonlinear diffusion equations

    CERN Document Server

    Favini, Angelo

    2012-01-01

    The aim of these notes is to include in a uniform presentation style several topics related to the theory of degenerate nonlinear diffusion equations, treated in the mathematical framework of evolution equations with multivalued m-accretive operators in Hilbert spaces. The problems concern nonlinear parabolic equations involving two cases of degeneracy. More precisely, one case is due to the vanishing of the time derivative coefficient and the other is provided by the vanishing of the diffusion coefficient on subsets of positive measure of the domain. From the mathematical point of view the results presented in these notes can be considered as general results in the theory of degenerate nonlinear diffusion equations. However, this work does not seek to present an exhaustive study of degenerate diffusion equations, but rather to emphasize some rigorous and efficient techniques for approaching various problems involving degenerate nonlinear diffusion equations, such as well-posedness, periodic solutions, asympt...

  12. Crossing a Nonlinear Resonance

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 19; Issue 9. Crossing a Nonlinear Resonance: Adiabatic Invariants and the Melnikov-Arnold Integral. Sudhir R Jain. General Article Volume 19 Issue 9 September 2014 pp 797-813 ...

  13. Introduction to nonlinear science

    CERN Document Server

    Nicolis, G

    1995-01-01

    One of the most unexpected results in science in recent years is that quite ordinary systems obeying simple laws can give rise to complex, nonlinear or chaotic, behavior. In this book, the author presents a unified treatment of the concepts and tools needed to analyze nonlinear phenomena and to outline some representative applications drawn from the physical, engineering, and biological sciences. Some of the interesting topics covered include: dynamical systems with a finite number of degrees of freedom, linear stability analysis of fixed points, nonlinear behavior of fixed points, bifurcation analysis, spatially distributed systems, broken symmetries, pattern formation, and chaotic dynamics. The author makes a special effort to provide a logical connection between ordinary dynamical systems and spatially extended systems, and to balance the emphasis on chaotic behavior and more classical nonlinear behavior. He also develops a statistical approach to complex systems and compares it to traditional deterministi...

  14. Large scale solvothermal synthesis and a strategy to obtain stable Langmuir–Blodgett film of CoFe2O4 nanoparticles

    International Nuclear Information System (INIS)

    Thampi, Arya; Babu, Keerthi; Verma, Seema

    2013-01-01

    Highlights: • Large scale, monodisperse CoFe 2 O 4 nanoparticles by solvothermal route. • LB technique to obtain stable film of CoFe 2 O 4 nanoparticles over a large area. • Hydrophobicity of substrate was enhanced utilizing LB films of cadmium arachidate. • P–A isotherm and AFM cross sectional height profile analysis confirms stability. • Large scale organization of nanoparticles for surface pressure higher than 15 mN/m. -- Abstract: Nearly monodisperse oleic acid coated cobalt ferrite nanoparticles were synthesized in large scale by a simple solvothermal method utilizing N-methyl 2-Pyrrolidone (NMP) as a high boiling solvent. The magnetic oxide was further investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and vibrating sample magnetometer (VSM). Langmuir–Blodgett (LB) technique is discussed to obtain a 2D assembly of oleic acid coated CoFe 2 O 4 nanoparticles over a large area. We describe a method to obtain stable, condensed three layers of cadmium arachidate on a piranha treated glass substrate. The hydrophobic surface thus obtained was subsequently used for forming a stable monolayer of oleic acid stabilized cobalt ferrite nanoparticles at the air–water interface. The stability of the LB films at the air–water interface was studied by pressure–area isotherm curves and atomic force microscopy (AFM) cross sectional height profile analysis. 2D organization of the magnetic nanoparticles at different surface pressures was studied by TEM. Preparation of large area LB films of CoFe 2 O 4 nanoparticles is reported for a surface pressure more than 15 mN/m

  15. Nonlinear Multiantenna Detection Methods

    Directory of Open Access Journals (Sweden)

    Chen Sheng

    2004-01-01

    Full Text Available A nonlinear detection technique designed for multiple-antenna assisted receivers employed in space-division multiple-access systems is investigated. We derive the optimal solution of the nonlinear spatial-processing assisted receiver for binary phase shift keying signalling, which we refer to as the Bayesian detector. It is shown that this optimal Bayesian receiver significantly outperforms the standard linear beamforming assisted receiver in terms of a reduced bit error rate, at the expense of an increased complexity, while the achievable system capacity is substantially enhanced with the advent of employing nonlinear detection. Specifically, when the spatial separation expressed in terms of the angle of arrival between the desired and interfering signals is below a certain threshold, a linear beamformer would fail to separate them, while a nonlinear detection assisted receiver is still capable of performing adequately. The adaptive implementation of the optimal Bayesian detector can be realized using a radial basis function network. Two techniques are presented for constructing block-data-based adaptive nonlinear multiple-antenna assisted receivers. One of them is based on the relevance vector machine invoked for classification, while the other on the orthogonal forward selection procedure combined with the Fisher ratio class-separability measure. A recursive sample-by-sample adaptation procedure is also proposed for training nonlinear detectors based on an amalgam of enhanced -means clustering techniques and the recursive least squares algorithm.

  16. Comparison of fluctuations properties measured by Langmuir and ball-pen probes in the ISTTOK boundary plasma

    Czech Academy of Sciences Publication Activity Database

    Silva, C.; Adámek, Jiří; Fernandes, H.; Figueiredo, H.

    2015-01-01

    Roč. 57, č. 2 (2015), č. článku 025003. ISSN 0741-3335 R&D Projects: GA ČR(CZ) GAP205/12/2327; GA MŠk(CZ) LM2011021 Institutional support: RVO:61389021 Keywords : langmuir probes * turbulence * tokamak Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 2.404, year: 2015 http://iopscience.iop.org/0741-3335/57/2/025003

  17. Numerical evaluation of Cs adsorption in PB column by extended Langmuir formula and one-dimensional adsorption model

    International Nuclear Information System (INIS)

    Hiroshi Ogawa; Akiko Kitajima; Hisashi Tanaka; Tohru Kawamoto

    2015-01-01

    Adsorption property of granulated Prussian blue adsorbent on radioactive cesium was evaluated for efficient decontamination in Fukushima area. The adsorbent was found to show an inflective adsorption isotherm, which was expressed by extended Langmuir formula with three adsorption sites. Adsorption speeds of each site were evaluated by time-dependent batch experiment. The simulation using derived parameters and one-dimensional adsorption model successfully reproduced the experimental data of cesium decontamination by small and large columns. (author)

  18. Fundamentals of nonlinear optical materials

    Indian Academy of Sciences (India)

    Nonlinear optics; nonlinear polarization; optical fiber communication; optical switch- ing. PACS Nos 42.65Tg; ... The importance of nonlinear optics is to understand the nonlinear behavior in the induced polarization and to ..... but much work in material development and characterization remains to be done. 16. Conclusion.

  19. High-spatial-resolution electron density measurement by Langmuir probe for multi-point observations using tiny spacecraft

    Science.gov (United States)

    Hoang, H.; Røed, K.; Bekkeng, T. A.; Trondsen, E.; Clausen, L. B. N.; Miloch, W. J.; Moen, J. I.

    2017-11-01

    A method for evaluating electron density using a single fixed-bias Langmuir probe is presented. The technique allows for high-spatio-temporal resolution electron density measurements, which can be effectively carried out by tiny spacecraft for multi-point observations in the ionosphere. The results are compared with the multi-needle Langmuir probe system, which is a scientific instrument developed at the University of Oslo comprising four fixed-bias cylindrical probes that allow small-scale plasma density structures to be characterized in the ionosphere. The technique proposed in this paper can comply with the requirements of future small-sized spacecraft, where the cost-effectiveness, limited space available on the craft, low power consumption and capacity for data-links need to be addressed. The first experimental results in both the plasma laboratory and space confirm the efficiency of the new approach. Moreover, detailed analyses on two challenging issues when deploying the DC Langmuir probe on a tiny spacecraft, which are the limited conductive area of the spacecraft and probe surface contamination, are presented in the paper. It is demonstrated that the limited conductive area, depending on applications, can either be of no concern for the experiment or can be resolved by mitigation methods. Surface contamination has a small impact on the performance of the developed probe.

  20. Langmuir probe diagnostics of an atmospheric pressure, vortex-stabilized nitrogen plasma jet

    Energy Technology Data Exchange (ETDEWEB)

    Prevosto, L.; Mancinelli, B. R. [Grupo de Descargas Electricas, Departamento Ingenieria Electromecanica, Facultad Regional Venado Tuerto (UTN), Laprida 651, (2600) Venado Tuerto, Santa Fe (Argentina); Kelly, H. [Grupo de Descargas Electricas, Departamento Ingenieria Electromecanica, Facultad Regional Venado Tuerto (UTN), Laprida 651, (2600) Venado Tuerto, Santa Fe (Argentina) and Instituto de Fisica del Plasma (CONICET), Departamento de Fisica, Facultad de Ciencias Exactas y Naturales UBA Ciudad Universitaria Pab. I, (1428) Buenos Aires (Argentina)

    2012-09-15

    Langmuir probe measurements in an atmospheric pressure direct current (dc) plasma jet are reported. Sweeping probes were used. The experiment was carried out using a dc non-transferred arc torch with a rod-type cathode and an anode of 5 mm diameter. The torch was operated at a nominal power level of 15 kW with a nitrogen flow rate of 25 Nl min{sup -1}. A flat ion saturation region was found in the current-voltage curve of the probe. The ion saturation current to a cylindrical probe in a high-pressure non local thermal equilibrium (LTE) plasma was modeled. Thermal effects and ionization/recombination processes inside the probe perturbed region were taken into account. Averaged radial profiles of the electron and heavy particle temperatures as well as the electron density were obtained. An electron temperature around 11 000 K, a heavy particle temperature around 9500 K and an electron density of about 4 Multiplication-Sign 10{sup 22} m{sup -3}, were found at the jet centre at 3.5 mm downstream from the torch exit. Large deviations from kinetic equilibrium were found throughout the plasma jet. The electron and heavy particle temperature profiles showed good agreement with those reported in the literature by using spectroscopic techniques. It was also found that the temperature radial profile based on LTE was very close to that of the electrons. The calculations have shown that this method is particularly useful for studying spraying-type plasma jets characterized by electron temperatures in the range 9000-14 000 K.

  1. Interactions between an anticancer drug - edelfosine - and cholesterol in Langmuir monolayers

    International Nuclear Information System (INIS)

    Wiecek, Agata; Dynarowicz-Latka, Patrycja; Minones, J.; Conde, Olga; Casas, Matilde

    2008-01-01

    Edelfosine (1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine, abbr. Et-18-OCH 3 ) is a new generation anticancer drug based on a phospholipids-like structure. Since its mechanism of action is believed to be related to the lipids of cellular membrane, we have investigated the interactions between edelfosine and main mammalian sterol: cholesterol, using the Langmuir monolayer technique. The interactions have been analyzed by comparing the experimental curves with theoretical ones, obtained basing on the additivity rule. The observed contraction together with negative deviations from ideality observed on the mean molecular area (A 12 ) vs film composition plots proves the existence of strong attractive forces between edelfosine and cholesterol, which have been quantified with the excess free energy of mixing (ΔG exc ) values, calculated from the surface pressure-area isotherms datapoints. The most negative values of ΔG exc have been found for the mixture of equimolar composition, proving its highest thermodynamic stability and the existence of the strongest interactions between film components. Thus, it has been postulated that at the surface edelfosine and cholesterol form stable complexes of 1:1 stoichiometry. The analysis of the collapse pressure values for the investigated mixed monolayers proves that films of edelfosine mole fraction ≤ 0.5 are miscible within the whole range of surface pressures, while monolayers richer in edelfosine mix in the pressure region below ca. 37.6 mN/m, which corresponds to the collapse of pure edelfosine monolayer. At this very surface pressure, edelfosine is expelled from the mixed monolayer and the remaining film is composed by surface complexes of high stability. The hypothesis of complex formation explains the results performed in vitro on cell cultures, indicating that the increase of cholesterol content significantly reduces the uptake of edelfosine

  2. A Quantitative Study of Tethered Chains in Various Solution Conditions Using Langmuir Diblock Copolymer Monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Kent, Michael S.

    1999-08-13

    This article summarizes our investigations of tethered chain systems using Langmuir monolayer of polydimethysiloxane-poly styrene (PDMS-PS) diblock copolymers on organic liquids. In this system, the PDMS block adsorbs to the air surface while the PS block dangles into the subphase liquid. The air surface can be made either repulsive or attractive for the tethered PS chain segments by choosing a subphase liquid which has a surface tension lower or greater than that of PS, respectively. The segment profile of the PS block is determined by neutron reflection as a function of the surface density, the molecular weights of the PS and PDMS blocks, and the solution conditions. We cover the range of reduced surface density (SIGMA) characteristic of the large body of data in the literature for systems of chains tethered onto solid surfaces from dilute solution in good or theta solvent conditions (SIGMA < 12). We emphasize quantitative comparisons with analytical profile forms and scaling predictions. We find that the strong-stretching limit invoked in analytical SCF and scaling theories is not valid over this Z range. On the other hand, over a large portion of this range (SIGMA < 5) tethered layers are well described by a renormalization group theory addressing weakly interacting or noninteracting chains. Simultaneous with the study of the profile form, the free energy of the chains is examined through the surface tension. A strong increase in the surface pressure is observed with increasing surface density which determines the maximum surface density which can be achieved. This apparently nonequilibrium effect is attributed to steric interactions and limited lateral interpenetration. This effect may explain several outstanding discrepancies regarding the adsorption of end-functionalized chains and diblock copolymers onto solid surfaces.

  3. Novel amphiphiles with preorganized functionalities-formation of Langmuir-films and efficiency in mineral flotation.

    Science.gov (United States)

    Müller, P U; Akpo, C C; Stöckelhuber, K W; Weber, E

    2005-06-30

    Based on the principle of supramolecular preorganization, three different types of new oligofunctional surfactants have been designed and prepared differing in both the degree of conformational flexibility and the hydrophilic-lipophilic balance of their structures due to the chosen building blocks including rather rigid and shape-persistent backbones or a dendritic subunit. Surface-active properties of the oligofunctional surfactants involving critical micellization concentration, surface tension at cmc, effectiveness of surface tension reduction, and the efficiency of adsorption were determined by use of the surface tension isotherms, respectively. In particular the amino-acid-based amphiphiles show remarkable surface-active properties with the adsorption at the air/water interface and also the aggregation to micelles starting at very low concentration. By analysis of the surface pressure-surface area isotherms interesting information on the packing behavior and orientation of the amphiphilic molecules in relation to the molecular structure could be obtained. Moreover, limiting area and collapse pressure of the Langmuir-films were determined. Morphological observation of the dynamic process of monolayer compression at the air/water interface was carried out by Brewster angle microscopy illustrating several phase states visualized as snap shots. Furthermore, the effectiveness of the new surfactants acting as collecting agents in the process of flotation using the model mineral fluorite was studied. A surprisingly high recovery of the mineral was obtained for the surfactants with constricted flexibility. The flotation plots clearly manifest that bundling of surfactant subunits by tethering to an aromatic core or by dendritic branching is profitable, indicating that effects of preorganization of the oligofunctional surfactant molecules are important.

  4. Thermal ion imagers and Langmuir probes in the Swarm electric field instruments

    Science.gov (United States)

    Knudsen, D. J.; Burchill, J. K.; Buchert, S. C.; Eriksson, A. I.; Gill, R.; Wahlund, J.-E.; Öhlen, L.; Smith, M.; Moffat, B.

    2017-02-01

    The European Space Agency's three Swarm satellites were launched on 22 November 2013 into nearly polar, circular orbits, eventually reaching altitudes of 460 km (Swarm A and C) and 510 km (Swarm B). Swarm's multiyear mission is to make precision, multipoint measurements of low-frequency magnetic and electric fields in Earth's ionosphere for the purpose of characterizing magnetic fields generated both inside and external to the Earth, along with the electric fields and other plasma parameters associated with electric current systems in the ionosphere and magnetosphere. Electric fields perpendicular to the magnetic field B→ are determined through ion drift velocity v→i and magnetic field measurements via the relation E→⊥=-v→i×B→. Ion drift is derived from two-dimensional images of low-energy ion distribution functions provided by two Thermal Ion Imager (TII) sensors viewing in the horizontal and vertical planes; v→i is corrected for spacecraft potential as determined by two Langmuir probes (LPs) which also measure plasma density ne and electron temperature Te. The TII sensors use a microchannel-plate-intensified phosphor screen imaged by a charge-coupled device to generate high-resolution distribution images (66 × 40 pixels) at a rate of 16 s-1. Images are partially processed on board and further on the ground to generate calibrated data products at a rate of 2 s-1; these include v→i, E→⊥, and ion temperature Ti in addition to electron temperature Te and plasma density ne from the LPs.

  5. Nonlinear Approaches in Engineering Applications

    CERN Document Server

    Jazar, Reza

    2012-01-01

    Nonlinear Approaches in Engineering Applications focuses on nonlinear phenomena that are common in the engineering field. The nonlinear approaches described in this book provide a sound theoretical base and practical tools to design and analyze engineering systems with high efficiency and accuracy and with less energy and downtime. Presented here are nonlinear approaches in areas such as dynamic systems, optimal control and approaches in nonlinear dynamics and acoustics. Coverage encompasses a wide range of applications and fields including mathematical modeling and nonlinear behavior as applied to microresonators, nanotechnologies, nonlinear behavior in soil erosion,nonlinear population dynamics, and optimization in reducing vibration and noise as well as vibration in triple-walled carbon nanotubes. This book also: Provides a complete introduction to nonlinear behavior of systems and the advantages of nonlinearity as a tool for solving engineering problems Includes applications and examples drawn from the el...

  6. 50 years of nonlinear optics

    International Nuclear Information System (INIS)

    Shen Yuanrang

    2011-01-01

    This article presents a brief introduction to the birth and early investigations of nonlinear optics, such as second harmonic generation,sum and difference frequency generation, stimulated Raman scattering,and self-action of light etc. Several important research achievements and applications of nonlinear optics are presented as well, including nonlinear optical spectroscopy, phase conjugation and adaptive optics, coherent nonlinear optics, and high-order harmonic generation. In the end, current and future research topics in nonlinear optics are summarized. (authors)

  7. The Adsorption Equilibrium Isotherms Freundlich, Langmuir, and Temkin Models for Two Steroidal anti-Inflammatory Drugs (NSAIDs) Betamethasone and Clobetasol on Multi-Walled Carbon Nanotube

    OpenAIRE

    MEHDI VADI; NAJAF HOSSINIE; ZAHRA SHEKARI

    2013-01-01

    We have studied the interaction of Betamethasone and Clobetasol solutions on multi carbon nanotube. After investigated comparative study and assigned to either Betamethasone or Clobetasolon adsorption isotherms. The adsorption equilibrium isotherms were fitted by Freundlich, Langmuir, and Temkin models. It was found that the Langmuir model described the adsorption process better than other two isotherm models. The amount of SAIDs (Betamethasone, Clobetasol) adsorbed on carbon nanotube surface...

  8. Multidimensional nonlinear descriptive analysis

    CERN Document Server

    Nishisato, Shizuhiko

    2006-01-01

    Quantification of categorical, or non-numerical, data is a problem that scientists face across a wide range of disciplines. Exploring data analysis in various areas of research, such as the social sciences and biology, Multidimensional Nonlinear Descriptive Analysis presents methods for analyzing categorical data that are not necessarily sampled randomly from a normal population and often involve nonlinear relations. This reference not only provides an overview of multidimensional nonlinear descriptive analysis (MUNDA) of discrete data, it also offers new results in a variety of fields. The first part of the book covers conceptual and technical preliminaries needed to understand the data analysis in subsequent chapters. The next two parts contain applications of MUNDA to diverse data types, with each chapter devoted to one type of categorical data, a brief historical comment, and basic skills peculiar to the data types. The final part examines several problems and then concludes with suggestions for futu...

  9. Nonlinear dynamics of structures

    CERN Document Server

    Oller, Sergio

    2014-01-01

    This book lays the foundation of knowledge that will allow a better understanding of nonlinear phenomena that occur in structural dynamics.   This work is intended for graduate engineering students who want to expand their knowledge on the dynamic behavior of structures, specifically in the nonlinear field, by presenting the basis of dynamic balance in non‐linear behavior structures due to the material and kinematics mechanical effects.   Particularly, this publication shows the solution of the equation of dynamic equilibrium for structure with nonlinear time‐independent materials (plasticity, damage and frequencies evolution), as well as those time dependent non‐linear behavior materials (viscoelasticity and viscoplasticity). The convergence conditions for the non‐linear dynamic structure solution  are studied, and the theoretical concepts and its programming algorithms are presented.  

  10. Nonlinear elastic waves in materials

    CERN Document Server

    Rushchitsky, Jeremiah J

    2014-01-01

    The main goal of the book is a coherent treatment of the theory of propagation in materials of nonlinearly elastic waves of displacements, which corresponds to one modern line of development of the nonlinear theory of elastic waves. The book is divided on five basic parts: the necessary information on waves and materials; the necessary information on nonlinear theory of elasticity and elastic materials; analysis of one-dimensional nonlinear elastic waves of displacement – longitudinal, vertically and horizontally polarized transverse plane nonlinear elastic waves of displacement; analysis of one-dimensional nonlinear elastic waves of displacement – cylindrical and torsional nonlinear elastic waves of displacement; analysis of two-dimensional nonlinear elastic waves of displacement – Rayleigh and Love nonlinear elastic surface waves. The book is addressed first of all to people working in solid mechanics – from the students at an advanced undergraduate and graduate level to the scientists, professional...

  11. Fundamentals of nonlinear optics

    CERN Document Server

    Powers, Peter E

    2011-01-01

    Peter Powers's rigorous but simple description of a difficult field keeps the reader's attention throughout. … All chapters contain a list of references and large numbers of practice examples to be worked through. … By carefully working through the proposed problems, students will develop a sound understanding of the fundamental principles and applications. … the book serves perfectly for an introductory-level course for second- and third-order nonlinear optical phenomena. The author's writing style is refreshing and original. I expect that Fundamentals of Nonlinear Optics will fast become pop

  12. Nonlinear fiber optics

    CERN Document Server

    Agrawal, Govind

    2012-01-01

    Since the 4e appeared, a fast evolution of the field has occurred. The 5e of this classic work provides an up-to-date account of the nonlinear phenomena occurring inside optical fibers, the basis of all our telecommunications infastructure as well as being used in the medical field. Reflecting the big developments in research, this new edition includes major new content: slow light effects, which offers a reduction in noise and power consumption and more ordered network traffic-stimulated Brillouin scattering; vectorial treatment of highly nonlinear fibers; and a brand new chapter o

  13. Fully nonlinear elliptic equations

    CERN Document Server

    Caffarelli, Luis A

    1995-01-01

    The goal of the book is to extend classical regularity theorems for solutions of linear elliptic partial differential equations to the context of fully nonlinear elliptic equations. This class of equations often arises in control theory, optimization, and other applications. The authors give a detailed presentation of all the necessary techniques. Instead of treating these techniques in their greatest generality, they outline the key ideas and prove the results needed for developing the subsequent theory. Topics discussed in the book include the theory of viscosity solutions for nonlinear equa

  14. Engineered nonlinear lattices

    DEFF Research Database (Denmark)

    Clausen, Carl A. Balslev; Christiansen, Peter Leth; Torner, L.

    1999-01-01

    We show that with the quasi-phase-matching technique it is possible to fabricate stripes of nonlinearity that trap and guide light like waveguides. We investigate an array of such stripes and find that when the stripes are sufficiently narrow, the beam dynamics is governed by a quadratic nonlinear...... discrete equation. The proposed structure therefore provides an experimental setting for exploring discrete effects in a controlled manner. In particular, we show propagation of breathers that are eventually trapped by discreteness. When the stripes are wide the beams evolve in a structure we term...

  15. Nonlinearity in nanomechanical cantilevers

    DEFF Research Database (Denmark)

    Villanueva Torrijo, Luis Guillermo; Karabalin, R. B.; Matheny, M. H.

    2013-01-01

    predictions deviate strongly from our measurements for the nonlinearity of the fundamental flexural mode, which show a systematic dependence on aspect ratio (length/width) together with random scatter. This contrasts with the second mode, which is always found to be in good agreement with theory....... These findings underscore the delicate balance between inertial and geometric nonlinear effects in the fundamental mode, and strongly motivate further work to develop theories beyond the Euler-Bernoulli approximation. DOI: 10.1103/PhysRevB.87.024304...

  16. Nonlinearities and transit times in soil organic matter models: new developments in the SoilR package

    Science.gov (United States)

    Sierra, Carlos; Müller, Markus

    2016-04-01

    SoilR is an R package for implementing diverse models representing soil organic matter dynamics. In previous releases of this package, we presented the implementation of linear first-order models with any number of pools as well as radiocarbon dynamics. We present here new improvements of the package regarding the possibility to implement models with nonlinear interactions among state variables and the possibility to calculate ages and transit times for nonlinear models with time dependencies. We show here examples on how to implement model structures with Michaelis-Menten terms for explicit microbial growth and resource use efficiency, and Langmuir isotherms for representing adsorption of organic matter to mineral surfaces. These nonlinear terms can be implemented for any number of organic matter pools, microbial functional groups, or mineralogy, depending on user's requirements. Through a simple example, we also show how transit times of organic matter in soils are controlled by the time-dependencies of the input terms.

  17. Properties of the Langmuir films made by petroleum asphaltenes. Model systems of crude oil-water emulsions; Proprietes des films de Langmuir formes par des asphaltenes du petrole. Systemes modeles des emulsions eau - petrole brut

    Energy Technology Data Exchange (ETDEWEB)

    Deghais, S.; Solimando, R. [Institut National Polytechnique de Lorraine, Ecole Nationale Superieure des Industries Chimiques, Lab. de Thermodynamique des Separations, 54 - Nancy (France); Zywocinski, A.; Rogalska, E. [Universite Henri Poincare, Lab. de Physco-Chimie des Colloides, UMR CNRS 7565, 54 - Vandoeuvre les Nancy (France); Rogalski, M.; Rogalska, E. [Metz Univ., Lab. de Thermodynamique et d' Analyse Chimique, 57 (France)

    2001-07-01

    This work deals with the analysis of the properties of the water-petroleum fluid interfaces using the Langmuir films technique. The stability of the water-petroleum emulsions is ensured by complex interactions which exist at the interface between paraffins and heavy petroleum compounds like asphaltenes and resins. The experiments performed have shown that the stabilizing properties of the asphaltene films depend on the dielectric constant of the fluid, on the presence or not of resins, and on the presence of possible paraffinic depositions. (J.S.)

  18. Analysis of organic acids and phenols of interest in the wine industry using Langmuir–Blodgett films based on functionalized nanoparticles

    International Nuclear Information System (INIS)

    Medina-Plaza, C.; García-Cabezón, C.; García-Hernández, C.; Bramorski, C.; Blanco-Val, Y.; Martín-Pedrosa, F.; Kawai, T.; Saja, J.A. de; Rodríguez-Méndez, M.L.

    2015-01-01

    Highlights: • For the first time functionalized NPs immobilized in LB films have been used as voltammetric sensors. • Films showed excellent electrocatalytic properties toward phenols and acids found in wines. • Improved performance is due to combination of electrocatalytic NPs with the high surface/volume of LB films. • The potential applications in the wine industry have been evidenced. - Abstract: A chemically modified electrode consisting of Langmuir–Blodgett (LB) films of n-dodecanethiol functionalized gold nanoparticles (S DOD AuNP-LB), was investigated as a voltammetric sensor of organic and phenolic acids of interest in the wine industry. The nanostructured films demonstrated interfacial properties being able to detect the main organic acids present in grapes and wines (tartaric, malic, lactic and citric). Compared to a bare ITO electrode, the modified electrodes exhibited a shift of the reduction potential in the less positive direction and a marked enhancement in the current response. Moreover, the increased electrocatalytic properties made it possible to distinguish between the different dissociable protons of polyprotic acids. The S DOD AuNP-LB sensor was also able to provide enhanced responses toward aqueous solutions of phenolic acids commonly found in wines (caffeic and gallic acids). The presence of nanoparticles increased drastically the sensitivity toward organic acids and phenolic compounds. Limits of detection as low as 10 −6 mol L −1 were achieved. Efficient catalytic activity was also observed in mixtures of phenolic acid/tartaric in the range of pHs typically found in wines. In such mixtures, the electrode was able to provide simultaneous information about the acid and the phenol concentrations with a complete absence of interferences. The excellent sensing properties shown by these sensors could be attributed to the electrocatalytic properties of the nanoparticles combined with the high surface to volume ratio and homogeneity

  19. Analysis of organic acids and phenols of interest in the wine industry using Langmuir–Blodgett films based on functionalized nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Medina-Plaza, C. [Department of Inorganic Chemistry, Engineers School, Universidad de Valladolid (Spain); García-Cabezón, C. [Department of Materials Science, Engineers School, Universidad de Valladolid (Spain); García-Hernández, C.; Bramorski, C. [Department of Inorganic Chemistry, Engineers School, Universidad de Valladolid (Spain); Blanco-Val, Y.; Martín-Pedrosa, F. [Department of Materials Science, Engineers School, Universidad de Valladolid (Spain); Kawai, T. [Department of Industrial Chemistry, Tokyo University of Science (Japan); Saja, J.A. de [Department of Condensed Matter Physics, Universidad de Valladolid (Spain); Rodríguez-Méndez, M.L., E-mail: mluz@eii.uva.es [Department of Inorganic Chemistry, Engineers School, Universidad de Valladolid (Spain)

    2015-01-01

    Highlights: • For the first time functionalized NPs immobilized in LB films have been used as voltammetric sensors. • Films showed excellent electrocatalytic properties toward phenols and acids found in wines. • Improved performance is due to combination of electrocatalytic NPs with the high surface/volume of LB films. • The potential applications in the wine industry have been evidenced. - Abstract: A chemically modified electrode consisting of Langmuir–Blodgett (LB) films of n-dodecanethiol functionalized gold nanoparticles (S{sub DOD}AuNP-LB), was investigated as a voltammetric sensor of organic and phenolic acids of interest in the wine industry. The nanostructured films demonstrated interfacial properties being able to detect the main organic acids present in grapes and wines (tartaric, malic, lactic and citric). Compared to a bare ITO electrode, the modified electrodes exhibited a shift of the reduction potential in the less positive direction and a marked enhancement in the current response. Moreover, the increased electrocatalytic properties made it possible to distinguish between the different dissociable protons of polyprotic acids. The S{sub DOD}AuNP-LB sensor was also able to provide enhanced responses toward aqueous solutions of phenolic acids commonly found in wines (caffeic and gallic acids). The presence of nanoparticles increased drastically the sensitivity toward organic acids and phenolic compounds. Limits of detection as low as 10{sup −6} mol L{sup −1} were achieved. Efficient catalytic activity was also observed in mixtures of phenolic acid/tartaric in the range of pHs typically found in wines. In such mixtures, the electrode was able to provide simultaneous information about the acid and the phenol concentrations with a complete absence of interferences. The excellent sensing properties shown by these sensors could be attributed to the electrocatalytic properties of the nanoparticles combined with the high surface to volume ratio

  20. Methods of nonlinear kinetics

    OpenAIRE

    Gorban, A. N.; Karlin, I. V.

    2003-01-01

    Nonlinear kinetic equations are reviewed for a wide audience of specialists and postgraduate students in physics, mathematical physics, material science, chemical engineering and interdisciplinary research. Contents: The Boltzmann equation, Phenomenology and Quasi-chemical representation of the Boltzmann equation, Kinetic models, Discrete velocity models, Direct simulation, Lattice Gas and Lattice Boltzmann models, Minimal Boltzmann models for flows at low Knudsen number, Other kinetic equati...

  1. Nonlinear fractional relaxation

    Indian Academy of Sciences (India)

    Abstract. We define a nonlinear model for fractional relaxation phenomena. We use ε-expansion method to analyse this model. By studying the fundamental solutions of this model we find that when t → 0 the model exhibits a fast decay rate and when t → ∞ the model exhibits a power-law decay. By analysing the frequency ...

  2. Nonlinear silicon photonics

    Science.gov (United States)

    Borghi, M.; Castellan, C.; Signorini, S.; Trenti, A.; Pavesi, L.

    2017-09-01

    Silicon photonics is a technology based on fabricating integrated optical circuits by using the same paradigms as the dominant electronics industry. After twenty years of fervid development, silicon photonics is entering the market with low cost, high performance and mass-manufacturable optical devices. Until now, most silicon photonic devices have been based on linear optical effects, despite the many phenomenologies associated with nonlinear optics in both bulk materials and integrated waveguides. Silicon and silicon-based materials have strong optical nonlinearities which are enhanced in integrated devices by the small cross-section of the high-index contrast silicon waveguides or photonic crystals. Here the photons are made to strongly interact with the medium where they propagate. This is the central argument of nonlinear silicon photonics. It is the aim of this review to describe the state-of-the-art in the field. Starting from the basic nonlinearities in a silicon waveguide or in optical resonator geometries, many phenomena and applications are described—including frequency generation, frequency conversion, frequency-comb generation, supercontinuum generation, soliton formation, temporal imaging and time lensing, Raman lasing, and comb spectroscopy. Emerging quantum photonics applications, such as entangled photon sources, heralded single-photon sources and integrated quantum photonic circuits are also addressed at the end of this review.

  3. Nonlinear Control System

    Directory of Open Access Journals (Sweden)

    Jaydeep Jesur

    2000-01-01

    and features are added such a way that it can be also used for design of nonlinear control systems to achieve desired performance. It is very simple to learn this tool. One can easily use it with preliminary knowledge of DF and PPT methods.

  4. Nonlinear collisionless magnetic reconnection

    Science.gov (United States)

    Ottaviani, M.; Porcelli, F.

    1993-12-01

    Collisionless magnetic reconnection in regimes where the mode structure is characterized by global convection cells is found to exhibit a quasiexplosive time behavior in the early nonlinear stage where the fluid displacement is smaller than the equilibrium scale length. This process is accompanied by the formation of a current density sublayer narrower than the skin depth. This sublayer keeps shrinking with time.

  5. Intramolecular and nonlinear dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Davis, M.J. [Argonne National Laboratory, IL (United States)

    1993-12-01

    Research in this program focuses on three interconnected areas. The first involves the study of intramolecular dynamics, particularly of highly excited systems. The second area involves the use of nonlinear dynamics as a tool for the study of molecular dynamics and complex kinetics. The third area is the study of the classical/quantum correspondence for highly excited systems, particularly systems exhibiting classical chaos.

  6. Nonlinearity and disorder: Classification and stability of nonlinear impurity modes

    DEFF Research Database (Denmark)

    Sukhorukov, Andrey A.; Kivshar, Yuri S.; Bang, Ole

    2001-01-01

    We study the effects produced by competition of two physical mechanisms of energy localization in inhomogeneous nonlinear systems. As an example, we analyze spatially localized modes supported by a nonlinear impurity in the generalized nonlinear Schrödinger equation and describe three types of no...

  7. Plasma potential and electron temperature evaluated by ball-pen and Langmuir probes in the COMPASS tokamak

    Science.gov (United States)

    Dimitrova, M.; Popov, Tsv K.; Adamek, J.; Kovačič, J.; Ivanova, P.; Hasan, E.; López-Bruna, D.; Seidl, J.; Vondráček, P.; Dejarnac, R.; Stöckel, J.; Imríšek, M.; Panek, R.; the COMPASS Team

    2017-12-01

    The radial distributions of the main plasma parameters in the scrape-off-layer of the COMPASS tokamak are measured during L-mode and H-mode regimes by using both Langmuir and ball-pen probes mounted on a horizontal reciprocating manipulator. The radial profile of the plasma potential derived previously from Langmuir probes data by using the first derivative probe technique is compared with data derived using ball-pen probes. A good agreement can be seen between the data acquired by the two techniques during the L-mode discharge and during the H-mode regime within the inter-ELM periods. In contrast with the first derivative probe technique, the ball-pen probe technique does not require a swept voltage and, therefore, the temporal resolution is only limited by the data acquisition system. In the electron temperature evaluation, in the far scrape-off layer and in the limiter shadow, where the electron energy distribution is Maxwellian, the results from both techniques match well. In the vicinity of the last closed flux surface, where the electron energy distribution function is bi-Maxwellian, the ball-pen probe technique results are in agreement with the high-temperature components of the electron distribution only. We also discuss the application of relatively large Langmuir probes placed in parallel and perpendicularly to the magnetic field lines to studying the main plasma parameters. The results obtained by the two types of the large probes agree well. They are compared with Thomson scattering data for electron temperatures and densities. The results for the electron densities are compared also with the results from ASTRA code calculation of the electron source due to the ionization of the neutrals by fast electrons and the origin of the bi-Maxwellian electron energy distribution function is briefly discussed.

  8. Mode Conversion of Langmuir to Electromagnetic Waves with Parallel Inhomogeneity in the Solar Wind and the Corona

    International Nuclear Information System (INIS)

    Kim, Eun-Hwa; Cairns, Iver H.; Robinson, Peter A.

    2008-01-01

    Linear mode conversion of Langmuir waves to radiation near the plasma frequency at density gradients is potentially relevant to multiple solar radio emissions, ionospheric radar experiments, laboratory plasma devices, and pulsars. Here we study mode conversion in warm magnetized plasmas using a numerical electron fluid simulation code with the density gradient parallel to the ambient magnetic field B0 for a range of incident Langmuir wavevectors. Our results include: (1) Both o- and x-mode waves are produced for (Omega) ∝ (ωL) 1/3 (ω c /ω) ∼ 1.5. Here ω c is the (angular) electron cyclotron frequency, ω the angular wave frequency, and L the length scale of the (linear) density gradient. (2) In the unmagnetized limit, equal amounts of o- and x-mode radiation are produced. (3) The mode conversion window narrows as (Omega) increases. (4) As (Omega) increases the total electromagnetic field changes from linear to circular polarization, with the o- and x- mode signals remaining circularly polarized. (5) The conversion efficiency to the x mode decreases monotonically as (Omega) increases while the o-mode conversion efficiency oscillates due to an interference phenomenon between incoming and reflected Langmuir/z modes. (6) The total conversion efficiency for wave energy from the Langmuir/z mode to radiation is typically less than 10%, but the corresponding power efficiencies differ by the ratio of the group speeds for each mode and are of order 50-70%. (7) The interference effect and the disappearance of the x mode at (Omega) ∼> 1 can be accounted for semiquantitatively using a WKB-like analysis. (8) Constraints on density turbulence are developed for the x mode to be generated and be able to propagate from the source. (9) Standard parameters for the corona and the solar wind near 1 AU suggest that linear mode conversion should produce both o- and x- mode radiation for solar and interplanetary radio bursts. It is therefore possible that linear mode conversion

  9. Plasma potential and electron temperature evaluated by ball-pen and Langmuir probes in the COMPASS tokamak.

    Czech Academy of Sciences Publication Activity Database

    Dimitrova, Miglena; Popov, Tsv.K.; Adámek, Jiří; Kovačič, J.; Ivanova, P.; Hasan, E.; López-Bruna, D.; Seidl, Jakub; Vondráček, Petr; Dejarnac, Renaud; Stöckel, Jan; Imríšek, Martin; Pánek, Radomír

    2017-01-01

    Roč. 59, č. 12 (2017), č. článku 125001. ISSN 0741-3335 R&D Projects: GA ČR(CZ) GA15-10723S; GA MŠk(CZ) LM2015045 Institutional support: RVO:61389021 Keywords : Plasma potential * electron temperature * bi-Maxwellian EEDF * ball-pen probe * Langmuir probe * COMPASS tokamak * last closed flux surface Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 2.392, year: 2016

  10. Towards Fast Measurement of the Electron Temperature in the SOL of ASDEX Upgrade Using Swept Langmuir Probes

    Czech Academy of Sciences Publication Activity Database

    Müller, H. W.; Adámek, Jiří; Horáček, Jan; Ionita, C.; Mehlmann, F.; Rohde, V.; Schrittwieser, R.

    2010-01-01

    Roč. 50, č. 9 (2010), s. 847-853 ISSN 0863-1042. [International Workshop on Electric Probes in Magnetized Plasmas/8th./. Innsbruck, 21.09.2009-24.09.2009] R&D Projects: GA AV ČR KJB100430901; GA ČR GA202/09/1467 Institutional research plan: CEZ:AV0Z20430508 Keywords : Tokamak * Langmuir probe * swept probe * ball-pen probe * fast temperature measurement * ELM Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.006, year: 2010 http://onlinelibrary.wiley.com/doi/10.1002/ctpp.201010144/pdf

  11. Advances in Langmuir probe diagnostics of the plasma potential and electron-energy distribution function in magnetized plasma

    Czech Academy of Sciences Publication Activity Database

    Popov, Tsv.K.; Dimitrova, Miglena; Ivanova, P.; Kovačič, J.; Gyergyek, T.; Dejarnac, Renaud; Stöckel, Jan; Pedrosa, M.A.; López-Bruna, D.; Hidalgo, C.

    2016-01-01

    Roč. 25, č. 3 (2016), č. článku 033001. ISSN 0963-0252 R&D Projects: GA ČR(CZ) GAP205/12/2327; GA MŠk(CZ) LM2011021 EU Projects: European Commission(XE) 633053 - EUROfusion Institutional support: RVO:61389021 Keywords : COMPASS tokamak * Langmuir probes * magnetized plasma * second-derivative probe techniques * first-derivative probe techniques * plasma potential * EEDF Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.302, year: 2016 http://iopscience.iop.org/article/10.1088/0963-0252/25/3/033001/meta

  12. Validating the collision-dominated Child-Langmuir law for a dc discharge cathode sheath in an undergraduate laboratory

    International Nuclear Information System (INIS)

    Lisovskiy, V; Yegorenkov, V

    2009-01-01

    In this paper, we propose a simple method of observing the collision-dominated Child-Langmuir law in the course of an undergraduate laboratory work devoted to studying the properties of gas discharges. To this end we employ the dc gas discharge whose properties are studied in sufficient detail. The undergraduate laboratory work itself is reduced to registering the voltage drop across the electrodes, the discharge current as well as the cathode sheath thickness. We can easily perform the measurements of all three quantities with sufficient accuracy in a laboratory equipped with vacuum pumps.

  13. Assessment of the effect of parallel temperature gradients in the JET SOL on Te measured by divertor target Langmuir probes

    Czech Academy of Sciences Publication Activity Database

    Ďuran, Ivan; Ješko, Karol; Fuchs, Vladimír; Groth, M.; Guillemaut, C.; Gunn, J. P.; Horáček, Jan; Pitts, R.A.; Tskhakaya, D.

    2015-01-01

    Roč. 463, August (2015), s. 432-435 ISSN 0022-3115. [PLASMA-SURFACE INTERACTIONS 21: International Conference on Plasma-Surface Interactions in Controlled Fusion Devices. Kanazawa, 26.05.2014-30.05.2014] R&D Projects: GA ČR GAP205/10/2055 Institutional support: RVO:61389021 Keywords : Langmuir probes * SOL Subject RIV: JF - Nuclear Energetics OBOR OECD: Nuclear related engineering Impact factor: 2.199, year: 2015 http://www.sciencedirect.com/science/article/pii/S0022311515000665

  14. A new compact and low cost Langmuir Probe and associated onboard data handling system for CubeSat

    Science.gov (United States)

    Muralikrishna, Polinaya; Domingos, Sinval; Paredes, Andres; Abrahão Dos Santos, Walter

    2016-07-01

    A new compact and low cost Langmuir Probe and associated onboard data handling system are being developed at Instituto Nacional de Pesquisas Espaciais for launching on board one of the future 2U CubeSat missions. The system is a simplified and compacted version of the Langmuir Probe payloads launched on board several Brazilian SONDA III rockets and also developed for the Brazilian scientific satellites SACI-1 and SACI-2. The onboard data handling system will have the dual functions of preprocessing the data collected by the Langmuir Probe and acting as the interface between the experiment and the on board computer. The Langmuir Probe sensor in the form of two rectangular stainless steel strips of total surface area of approximately 80cm2 will be deployed soon after the injection of the CubeSat into orbit. A sweep voltage varying linearly from 0V to 3.0V in about 1.5 seconds and then remaining fixed at 3.0V for 1 second will be applied to the LP sensor to obtain both the electron density and electron temperature. A high sensitivity preamplifier will be used to convert the sensor current expected to be in the range of a few nano amperes to a few micro amperes into a varying potential. In order to cover the large dynamic range of the expected sensor current the preamplifier output will be further amplified by a logarithmic amplifier before being sampled and sent to the data handling system. The data handling system is projected to handle 8 analog channels and 4 digital words of 8 bits each. The incoming data will be stored in a RAM and later sent to the on board computer using a serial RS422 communication protocol. The interface unit will process the telecommands received from the on board computer. The interface is also projected to do FFT analysis of the LP sensor data and send the averaged FFT spectral amplitudes in place of the original unprocessed data. The system details are presented here.

  15. Pattern Formation in Langmuir Monolayers Due to Long-Range Electrostatic Interactions

    Science.gov (United States)

    Fischer, Thomas M.; Lösche, Mathias

    A distinctive characteristic of Langmuir monolayers that bears important consequences for the physics of structure formation within membranes is the uniaxial orientation of the constituent dipolar molecules, brought about by the symmetry break which is induced by the surface of the aqueous substrate. The association of oriented molecular dipoles with the interface leads to the formation of image dipoles within the polarizeable medium - the subphase - such that the effective dipole orientation of every of the individual molecules is strictly normal to the surface, even within molecularly disordered phases. As a result, dipole-dipole repulsions play an eminently important role for the molecular interactions within the system - independent of the state of phase (while the dipole area density does of course depend on the state of phase) - and control the morphogenesis of the phase boundaries in their interplay with the one-dimensional (1D) line tension between coexisting phases. The physics of these phenomena is only now being explored and is particularly exciting for systems within a three-phase coexistence region where complete or partial wetting, as well as dewetting between the coexisting phases may be experimentally observed by applying fluorescence microscopy to the monolayer films. It is revealed that the wetting behavior depends sensitively on the details of the electrostatic interactions, in that the apparent contact angles observed at three-phase contact points depends on the sizes of the coexisting phases. This is in sharp contrast to the physics of wetting in conventional 3D systems where the contact angle is a materials property, independent of the local details. In 3D systems, this leads to Youngs equation - which has been established more than two centuries ago. We report recent progress in the understanding of this unusual and rather unexpected behavior of a quasi-2D system by reviewing recent experimental results from optical microscopy on equilibrium

  16. On nonlinear Fourier transform: towards the nonlinear superposition

    Science.gov (United States)

    Saksida, Pavle

    2017-01-01

    In the paper we consider the nonlinear Fourier transform associated to the AKNSZS systems. In particular, we discuss the construction of the nonlinear Fourier modes of this transform by means of a perturbation scheme. The linearization of the AKNS-ZS nonlinear Fourier transform is the usual, linear Fourier transform and the linearization of a nonlinear Fourier mode of frequency d is the linear Fourier mode of the same frequency. We show that the first non-trivial term in the perturbation expression of any nonlinear Fourier mode is given by the dilogarithm function.

  17. Nonlinearity, Conservation Law and Shocks

    Indian Academy of Sciences (India)

    Nonlinearity, Conservation Law and Shocks. Part I : Genuine Nonlinearity and Discontinuous Solutions. Phoolan Prasad is with the. Department of. Mathematics, Indian. Institute of Science and has been working in the area of nonlinear waves and hyperbolic partial differential equations. He is deeply interested in.

  18. Terahertz Nonlinear Optics in Semiconductors

    DEFF Research Database (Denmark)

    Turchinovich, Dmitry; Hvam, Jørn Märcher; Hoffmann, Matthias C.

    2013-01-01

    We demonstrate the nonlinear optical effects – selfphase modulation and saturable absorption of a single-cycle THz pulse in a semiconductor. Resulting from THz-induced modulation of Drude plasma, these nonlinear optical effects, in particular, lead to self-shortening and nonlinear spectral...... breathing of a single-cycle THz pulse in a semiconductor....

  19. FRF decoupling of nonlinear systems

    Science.gov (United States)

    Kalaycıoğlu, Taner; Özgüven, H. Nevzat

    2018-03-01

    Structural decoupling problem, i.e. predicting dynamic behavior of a particular substructure from the knowledge of the dynamics of the coupled structure and the other substructure, has been well investigated for three decades and led to several decoupling methods. In spite of the inherent nonlinearities in a structural system in various forms such as clearances, friction and nonlinear stiffness, all decoupling studies are for linear systems. In this study, decoupling problem for nonlinear systems is addressed for the first time. A method, named as FRF Decoupling Method for Nonlinear Systems (FDM-NS), is proposed for calculating FRFs of a substructure decoupled from a coupled nonlinear structure where nonlinearity can be modeled as a single nonlinear element. Depending on where nonlinear element is, i.e., either in the known or unknown subsystem, or at the connection point, the formulation differs. The method requires relative displacement information between two end points of the nonlinear element, in addition to point and transfer FRFs at some points of the known subsystem. However, it is not necessary to excite the system from the unknown subsystem even when the nonlinear element is in that subsystem. The validation of FDM-NS is demonstrated with two different case studies using nonlinear lumped parameter systems. Finally, a nonlinear experimental test structure is used in order to show the real-life application and accuracy of FDM-NS.

  20. Fault Detection for Nonlinear Systems

    DEFF Research Database (Denmark)

    Stoustrup, Jakob; Niemann, H.H.

    1998-01-01

    The paper describes a general method for designing fault detection and isolation (FDI) systems for nonlinear processes. For a rich class of nonlinear systems, a nonlinear FDI system can be designed using convex optimization procedures. The proposed method is a natural extension of methods based o...

  1. Nonlinear differential equations

    Energy Technology Data Exchange (ETDEWEB)

    Dresner, L.

    1988-01-01

    This report is the text of a graduate course on nonlinear differential equations given by the author at the University of Wisconsin-Madison during the summer of 1987. The topics covered are: direction fields of first-order differential equations; the Lie (group) theory of ordinary differential equations; similarity solutions of second-order partial differential equations; maximum principles and differential inequalities; monotone operators and iteration; complementary variational principles; and stability of numerical methods. The report should be of interest to graduate students, faculty, and practicing scientists and engineers. No prior knowledge is required beyond a good working knowledge of the calculus. The emphasis is on practical results. Most of the illustrative examples are taken from the fields of nonlinear diffusion, heat and mass transfer, applied superconductivity, and helium cryogenics.

  2. Nonlinear terahertz superconducting plasmonics

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Jingbo; Liang, Lanju; Jin, Biaobing, E-mail: bbjin@nju.edu.cn, E-mail: tonouchi@ile.osaka-u.ac.jp, E-mail: phwu@nju.edu.cn; Kang, Lin; Xu, Weiwei; Chen, Jian; Wu, Peiheng, E-mail: bbjin@nju.edu.cn, E-mail: tonouchi@ile.osaka-u.ac.jp, E-mail: phwu@nju.edu.cn [Research Institute of Superconductor Electronics (RISE), School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Zhang, Caihong; Kawayama, Iwao; Murakami, Hironaru; Tonouchi, Masayoshi, E-mail: bbjin@nju.edu.cn, E-mail: tonouchi@ile.osaka-u.ac.jp, E-mail: phwu@nju.edu.cn [Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871 (Japan); Wang, Huabing [Research Institute of Superconductor Electronics (RISE), School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); National Institute for Materials Science, Tsukuba 305-0047 (Japan)

    2014-10-20

    Nonlinear terahertz (THz) transmission through subwavelength hole array in superconducting niobium nitride (NbN) film is experimentally investigated using intense THz pulses. The good agreement between the measurement and numerical simulations indicates that the field strength dependent transmission mainly arises from the nonlinear properties of the superconducting film. Under weak THz pulses, the transmission peak can be tuned over a frequency range of 145 GHz which is attributed to the high kinetic inductance of 50 nm-thick NbN film. Utilizing the THz pump-THz probe spectroscopy, we study the dynamic process of transmission spectra and demonstrate that the transition time of such superconducting plasmonic device is within 5 ps.

  3. Essentials of nonlinear optics

    CERN Document Server

    Murti, Y V G S

    2014-01-01

    Current literature on Nonlinear Optics varies widely in terms of content, style, and coverage of specific topics, relative emphasis of areas and the depth of treatment. While most of these books are excellent resources for the researchers, there is a strong need for books appropriate for presenting the subject at the undergraduate or postgraduate levels in Universities. The need for such a book to serve as a textbook at the level of the bachelors and masters courses was felt by the authors while teaching courses on nonlinear optics to students of both science and engineering during the past two decades. This book has emerged from an attempt to address the requirement of presenting the subject at college level. A one-semester course covering the essentials can effectively be designed based on this.

  4. Nonlinear data assimilation

    CERN Document Server

    Van Leeuwen, Peter Jan; Reich, Sebastian

    2015-01-01

    This book contains two review articles on nonlinear data assimilation that deal with closely related topics but were written and can be read independently. Both contributions focus on so-called particle filters. The first contribution by Jan van Leeuwen focuses on the potential of proposal densities. It discusses the issues with present-day particle filters and explorers new ideas for proposal densities to solve them, converging to particle filters that work well in systems of any dimension, closing the contribution with a high-dimensional example. The second contribution by Cheng and Reich discusses a unified framework for ensemble-transform particle filters. This allows one to bridge successful ensemble Kalman filters with fully nonlinear particle filters, and allows a proper introduction of localization in particle filters, which has been lacking up to now.

  5. Nonlinear Photonics 2014: introduction.

    Science.gov (United States)

    Akhmediev, N; Kartashov, Yaroslav

    2015-01-12

    International Conference "Nonlinear Photonics-2014" took place in Barcelona, Spain on July 27-31, 2014. It was a part of the "Advanced Photonics Congress" which is becoming a traditional notable event in the world of photonics. The current focus issue of Optics Express contains contributions from the participants of the Conference and the Congress. The articles in this focus issue by no means represent the total number of the congress contributions (around 400). However, it demonstrates wide range of topics covered at the event. The next conference of this series is to be held in 2016 in Australia, which is the home of many researchers working in the field of photonics in general and nonlinear photonics in particular.

  6. Nonlinear (Anharmonic Casimir Oscillator

    Directory of Open Access Journals (Sweden)

    Habibollah Razmi

    2011-01-01

    Full Text Available We want to study the dynamics of a simple linear harmonic micro spring which is under the influence of the quantum Casimir force/pressure and thus behaves as a (an nonlinear (anharmonic Casimir oscillator. Generally, the equation of motion of this nonlinear micromechanical Casimir oscillator has no exact solvable (analytical solution and the turning point(s of the system has (have no fixed position(s; however, for particular values of the stiffness of the micro spring and at appropriately well-chosen distance scales and conditions, there is (are approximately sinusoidal solution(s for the problem (the variable turning points are collected in a very small interval of positions. This, as a simple and elementary plan, may be useful in controlling the Casimir stiction problem in micromechanical devices.

  7. Nonlinear chiral transport phenomena

    Science.gov (United States)

    Chen, Jiunn-Wei; Ishii, Takeaki; Pu, Shi; Yamamoto, Naoki

    2016-06-01

    We study the nonlinear responses of relativistic chiral matter to the external fields such as the electric field E , gradients of temperature and chemical potential, ∇T and ∇μ . Using the kinetic theory with Berry curvature corrections under the relaxation time approximation, we compute the transport coefficients of possible new electric currents that are forbidden in usual chirally symmetric matter but are allowed in chirally asymmetric matter by parity. In particular, we find a new type of electric current proportional to ∇μ ×E due to the interplay between the effects of the Berry curvature and collisions. We also derive an analog of the "Wiedemann-Franz" law specific for anomalous nonlinear transport in relativistic chiral matter.

  8. Phase Coupling in Langmuir Wave Packets: Evidence for Four Wave Interactions in Solar Type III Radio Bursts

    Science.gov (United States)

    Thejappa, G.; MacDowall, R. J.; Bergamo, M.

    2012-01-01

    The four wave interaction process, known as the oscillating two stream instability (OTSI) is considered as one of the mechanisms responsible for stabilizing the electron beams associated with solar type III radio bursts. It has been reported that (1) an intense localized Langmuir wave packet associated with a type III burst contains the spectral characteristics of the OTSI: (a) a resonant peak at the local electron plasma frequency, f(sub pe), (b) a Stokes peak at a frequency slightly lower than f(sub pe), (c) anti-Stokes peak at a frequency slightly higher than f(sub pe), and (d) a low frequency enhancement below a few hundred Hz, (2) the frequencies and wave numbers of these spectral components satisfy the resonance conditions of the OTSI, and (3) the peak intensity of the wave packet is well above the thresholds for the OTSI as well as spatial collapse of envelope solitons. Here, for the first time, applying the trispectral analysis on this wave packet, we show that the tricoherence, which measures the degree of coherent four-wave coupling amongst the observed spectral components exhibits a peak. This provides an additional evidence for the OTSI and related spatial collapse of Langmuir envelope solitons in type III burst sources.

  9. Aqueous-phase aerosols on the air-water interface: Response of fatty acid Langmuir monolayers to atmospheric inorganic ions.

    Science.gov (United States)

    Li, Siyang; Du, Lin; Wei, Zhongming; Wang, Wenxing

    2017-02-15

    Atmospheric aerosol particles composed of a mixture of organic and inorganic compounds are common and constitute an important fraction of air pollutants. In this study, the activities of common atmospheric inorganic ions (Ag + , Zn 2+ , Fe 3+ , Fe 2+ , Ca 2+ and Al 3+ ) and fatty acid molecules (stearic acid and arachidic acid) at air-aqueous interface were investigated by Langmuir methods and infrared reflection-absorption spectroscopy (IRRAS). In the presence of different inorganic ions, surface pressure-area isotherms of the Langmuir films showed compressed or expanded characteristics. IRRAS spectra confirmed that the existence of inorganic ions in the fatty acid monolayer changes the surface properties of aqueous-phase aerosols. Formation of different coordination types of carboxylates at the air-water interface alters the dissolution and partitioning behavior, which has significant influence of Raoult effect on nucleating cloud droplets. Our work displays the relationship between structure and surface properties for aqueous-phase aerosols and implies an efficient method for further understanding of their formation mechanism and potential atmospheric implications. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. The forced nonlinear Schroedinger equation

    International Nuclear Information System (INIS)

    Kaup, D.J.; Hansen, P.J.

    1985-01-01

    The nonlinear Schroedinger equation describes the behaviour of a radio frequency wave in the ionosphere near the reflexion point where nonlinear processes are important. A simple model of this phenomenon leads to the forced nonlinear Schroedinger equation in terms of a nonlinear boundary value problem. A WKB analysis of the time evolution equations for the nonlinear Schroedinger equation in the inverse scattering transform formalism gives a crude order of magnitude estimation of the qualitative behaviour of the solutions. This estimation is compared with the numerical solutions. (D.Gy.)

  11. Nonlinear gyrokinetic tokamak physics

    International Nuclear Information System (INIS)

    Brizard, A.J.

    1990-01-01

    The gyrokinetic reduced description of low-frequency and small-perpendicular-wavelength nonlinear tokamak dynamics is presented in three different versions: the reduced dynamical description of test particles moving in electromagnetic fields; the reduced gyrokinetic description of the self-consistent interaction of particles and fields through the Maxwell-Vlasov equations; and the reduced description of nonlinear fluid motion. The unperturbed tokamak plasma is described in terms of a noncanonical Hamiltonian guiding-center theory. The unperturbed guiding-center tokamak plasma is then perturbed by gyrokinetic electromagnetic fields and consequently the perturbed guiding-center dynamical system acquires new gyrophase dependence. The perturbation analysis that follows makes extensive use of Lie-transform perturbation techniques. Because the electromagnetic perturbations affect both the Hamiltonian and the Poisson-bracket structure, the Phase-space Lagrangian Lie perturbation method is used. The description of the reduced test-particle dynamics is given in terms of a non-canonical Hamiltonian gyrocenter theory. The description of the reduced kinetic dynamics is concerned with the self consistent response of the guiding-center plasma and is described in terms of the nonlinear gyrokinetic Maxwell-Vlasov equations. It is also shown that the gyrokinetic Maxwell-Vlasov system possesses a gyrokinetic energy adiabatic invariant and that, in both the linear and nonlinear (quadratic) approximations, the corresponding energy invariants are exact. The description of the reduced fluid dynamics is concerned with the derivation of a closed set of reduced fluid equations. Three generations of reduced fluid models are presented: the reduced MHD equations; the reduced FLR-MHD equations; and the gyrofluid equations

  12. Damped nonlinear Schrodinger equation

    International Nuclear Information System (INIS)

    Nicholson, D.R.; Goldman, M.V.

    1976-01-01

    High frequency electrostatic plasma oscillations described by the nonlinear Schrodinger equation in the presence of damping, collisional or Landau, are considered. At early times, Landau damping of an initial soliton profile results in a broader, but smaller amplitude soliton, while collisional damping reduces the soliton size everywhere; soliton speeds at early times are unchanged by either kind of damping. For collisional damping, soliton speeds are unchanged for all time

  13. Strongly nonlinear oscillators analytical solutions

    CERN Document Server

    Cveticanin, Livija

    2014-01-01

    This book provides the presentation of the motion of pure nonlinear oscillatory systems and various solution procedures which give the approximate solutions of the strong nonlinear oscillator equations. The book presents the original author’s method for the analytical solution procedure of the pure nonlinear oscillator system. After an introduction, the physical explanation of the pure nonlinearity and of the pure nonlinear oscillator is given. The analytical solution for free and forced vibrations of the one-degree-of-freedom strong nonlinear system with constant and time variable parameter is considered. Special attention is given to the one and two mass oscillatory systems with two-degrees-of-freedom. The criteria for the deterministic chaos in ideal and non-ideal pure nonlinear oscillators are derived analytically. The method for suppressing chaos is developed. Important problems are discussed in didactic exercises. The book is self-consistent and suitable as a textbook for students and also for profess...

  14. Improvement of signal-to-noise ratio in oxygen sensitive emission from hybrid Langmuir–Blodgett films of amphiphilic iridium complexes with the exfoliated nanosheets using a metal layer

    Science.gov (United States)

    Ozaki, Ryotaro; Yamada, Tetsuya; Yudate, Shinji; Kadowaki, Kazunori; Sato, Hisako

    2018-03-01

    Cyclometalated Ir(III) complexes are attracting extensive attention due to their high emission properties in the visible region. Oxygen sensitive photoluminescence (PL) emissions from single- and multi-layered Ir(III) Langmuir–Blodgett (LB) films are measured. The single-layered LB film on a non-aluminum coated glass substrate shows oxygen sensitive PL emission but its intensity is very weak. In contrast, the multi-layered LB film shows higher intensity but their oxygen sensitivity is lower than that of the single-layered sample. To break the trade-off between intensity and sensitivity, PL characteristics from the LB film on an aluminum-coated glass substrate are investigated. The PL emission from the LB film on the metal layer show higher intensity and good oxygen sensitivity. The mechanism of the emission enhancement is also discussed in this paper.

  15. Nonlinear robust hierarchical control for nonlinear uncertain systems

    Directory of Open Access Journals (Sweden)

    Leonessa Alexander

    1999-01-01

    Full Text Available A nonlinear robust control-system design framework predicated on a hierarchical switching controller architecture parameterized over a set of moving nominal system equilibria is developed. Specifically, using equilibria-dependent Lyapunov functions, a hierarchical nonlinear robust control strategy is developed that robustly stabilizes a given nonlinear system over a prescribed range of system uncertainty by robustly stabilizing a collection of nonlinear controlled uncertain subsystems. The robust switching nonlinear controller architecture is designed based on a generalized (lower semicontinuous Lyapunov function obtained by minimizing a potential function over a given switching set induced by the parameterized nominal system equilibria. The proposed framework robustly stabilizes a compact positively invariant set of a given nonlinear uncertain dynamical system with structured parametric uncertainty. Finally, the efficacy of the proposed approach is demonstrated on a jet engine propulsion control problem with uncertain pressure-flow map data.

  16. Suppression of parasitic noise by strong Langmuir wave damping in quasitransient regimes of backward Raman amplification of intense laser pulses in plasmas.

    Science.gov (United States)

    Malkin, Vladimir; Fisch, Nathaniel

    2009-11-01

    Currently built powerful soft x-ray sources may be able to access intensities needed for backward Raman amplification (BRA) of x-ray pulses in plasmas. However, high plasma densities, needed to provide enough coupling between the pump and seed x-ray pulsed, cause strong damping of the Langmuir wave that mediates energy transfer from the pump to the seed pulse. Such damping could reduce the coupling, thus making efficient BRA impossible. This work shows that efficient BRA can survive despite the Langmuir wave damping significantly exceeding the linear BRA growth rate. Moreover, the strong Langmuir wave damping can suppress deleterious instabilities of BRA seeded by the thermal noise. This shows that it may be feasible to observe x-ray BRA for the first time soon.

  17. Discrete nonlinear Schrodinger equations with arbitrarily high-order nonlinearities

    DEFF Research Database (Denmark)

    Khare, A.; Rasmussen, Kim Ø; Salerno, M.

    2006-01-01

    A class of discrete nonlinear Schrodinger equations with arbitrarily high-order nonlinearities is introduced. These equations are derived from the same Hamiltonian using different Poisson brackets and include as particular cases the saturable discrete nonlinear Schrodinger equation and the Ablowitz......-Ladik equation. As a common property, these equations possess three kinds of exact analytical stationary solutions for which the Peierls-Nabarro barrier is zero. Several properties of these solutions, including stability, discrete breathers, and moving solutions, are investigated....

  18. Comparative characteristics of membrane-active single-chained ether phospholipids: PAF and lyso-PAF in Langmuir monolayers.

    Science.gov (United States)

    Flasiński, Michał; Broniatowski, Marcin; Wydro, Paweł; Dynarowicz-Łątka, Patrycja

    2012-03-15

    1-O-Octadecyl-2-acetyl-sn-glycero-3-phosphocholine (PAF) and its deacetylated precursor (lyso-PAF) are membrane-active single-chained ether phospholipids, which play an important signaling role in different physiological processes. There is strong evidence that one of the possible mechanisms of PAF and lyso-PAF activity is connected with their direct influence on biomembranes. Although both lipids have very similar structure, their biological activity is very different and in some cases even antagonistic. Unfortunately, there is a lack of the studies correlating these observations with the molecular structure of both compounds. Therefore, we decided to apply model systems and advanced physicochemical methods to explore this subject and look for the reasons of the observed discrepancies. As a model system, we prepared Langmuir monolayers of PAF and lyso-PAF at the air/water interface. The physicochemical characteristic of the model membranes under different experimental conditions was performed with the application of the Langmuir monolayer technique, Brewster angle microscopy, and the methods based on synchrotron radiation scattering (XR and GIXD). Both compounds form stable Langmuir monolayers, in which the lipid molecules are strongly immersed into the water subphase. The monolayers have expanded character, meaning that the hydrophobic tails are considerably tilted and disordered. Similarly to biochemical studies, also in our model systems, profound differences in the properties of PAF and lyso-PAF were observed. Contrary to PAF, the lyso-PAF molecules express the propensity to form organized, periodical structures in the model membranes. It is manifested in the phase transition observed in the course of the lyso-PAF π-A isotherm which was correlated with the diffraction signal registered with the application of the GIXD method. The formation of 2D domains of hexagonal ordering of the film forming molecules was observed only for the lyso precursor. The observed

  19. A physically based framework for modeling the organic fractionation of sea spray aerosol from bubble film Langmuir equilibria

    Directory of Open Access Journals (Sweden)

    S. M. Burrows

    2014-12-01

    Full Text Available The presence of a large fraction of organic matter in primary sea spray aerosol (SSA can strongly affect its cloud condensation nuclei activity and interactions with marine clouds. Global climate models require new parameterizations of the SSA composition in order to improve the representation of these processes. Existing proposals for such a parameterization use remotely sensed chlorophyll a concentrations as a proxy for the biogenic contribution to the aerosol. However, both observations and theoretical considerations suggest that existing relationships with chlorophyll a, derived from observations at only a few locations, may not be representative for all ocean regions. We introduce a novel framework for parameterizing the fractionation of marine organic matter into SSA based on a competitive Langmuir adsorption equilibrium at bubble surfaces. Marine organic matter is partitioned into classes with differing molecular weights, surface excesses, and Langmuir adsorption parameters. The classes include a lipid-like mixture associated with labile dissolved organic carbon (DOC, a polysaccharide-like mixture associated primarily with semilabile DOC, a protein-like mixture with concentrations intermediate between lipids and polysaccharides, a processed mixture associated with recalcitrant surface DOC, and a deep abyssal humic-like mixture. Box model calculations have been performed for several cases of organic adsorption to illustrate the underlying concepts. We then apply the framework to output from a global marine biogeochemistry model, by partitioning total dissolved organic carbon into several classes of macromolecules. Each class is represented by model compounds with physical and chemical properties based on existing laboratory data. This allows us to globally map the predicted organic mass fraction of the nascent submicron sea spray aerosol. Predicted relationships between chlorophyll a and organic fraction are similar to existing empirical

  20. Organic materials for second harmonic generation. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Twieg, R.J. (comp.)

    1985-03-31

    Materials were chosen by screening the Cambridge Crystallographic Index for new noncentrosymmetric crystalline compounds, by screening commercially available materials or by synthesis of unique new substances. Measurements were then made on the powder form of these materials. Langmuir-Blodgett films were deposited and studied. In addition to the above studies, a computer program was developed to calculate (hyper) polarizabilities of organic molecules and thus aid in the selection of materials for testing. The nonlinear molecules have been divided into three classes according to absorption cutoff: 400 to 500 nm, 300 to 400 nm, and 200 to 300 nm. 108 refs., 7 tabs. (WRF)

  1. Organic materials for second harmonic generation. Final report

    International Nuclear Information System (INIS)

    Twieg, R.J.

    1985-01-01

    Materials were chosen by screening the Cambridge Crystallographic Index for new noncentrosymmetric crystalline compounds, by screening commercially available materials or by synthesis of unique new substances. Measurements were then made on the powder form of these materials. Langmuir-Blodgett films were deposited and studied. In addition to the above studies, a computer program was developed to calculate (hyper) polarizabilities of organic molecules and thus aid in the selection of materials for testing. The nonlinear molecules have been divided into three classes according to absorption cutoff: 400 to 500 nm, 300 to 400 nm, and 200 to 300 nm. 108 refs., 7 tabs

  2. Non-linear osmosis

    Science.gov (United States)

    Diamond, Jared M.

    1966-01-01

    1. The relation between osmotic gradient and rate of osmotic water flow has been measured in rabbit gall-bladder by a gravimetric procedure and by a rapid method based on streaming potentials. Streaming potentials were directly proportional to gravimetrically measured water fluxes. 2. As in many other tissues, water flow was found to vary with gradient in a markedly non-linear fashion. There was no consistent relation between the water permeability and either the direction or the rate of water flow. 3. Water flow in response to a given gradient decreased at higher osmolarities. The resistance to water flow increased linearly with osmolarity over the range 186-825 m-osM. 4. The resistance to water flow was the same when the gall-bladder separated any two bathing solutions with the same average osmolarity, regardless of the magnitude of the gradient. In other words, the rate of water flow is given by the expression (Om — Os)/[Ro′ + ½k′ (Om + Os)], where Ro′ and k′ are constants and Om and Os are the bathing solution osmolarities. 5. Of the theories advanced to explain non-linear osmosis in other tissues, flow-induced membrane deformations, unstirred layers, asymmetrical series-membrane effects, and non-osmotic effects of solutes could not explain the results. However, experimental measurements of water permeability as a function of osmolarity permitted quantitative reconstruction of the observed water flow—osmotic gradient curves. Hence non-linear osmosis in rabbit gall-bladder is due to a decrease in water permeability with increasing osmolarity. 6. The results suggest that aqueous channels in the cell membrane behave as osmometers, shrinking in concentrated solutions of impermeant molecules and thereby increasing membrane resistance to water flow. A mathematical formulation of such a membrane structure is offered. PMID:5945254

  3. Nonlinearity of bituminous mixtures

    Science.gov (United States)

    Mangiafico, S.; Babadopulos, L. F. A. L.; Sauzéat, C.; Di Benedetto, H.

    2018-02-01

    This paper presents an experimental characterization of the strain dependency of the complex modulus of bituminous mixtures for strain amplitude levels lower than about 110 μm/m. A series of strain amplitude sweep tests are performed at different temperatures (8, 10, 12 and 14°C) and frequencies (0.3, 1, 3 and 10 Hz), during which complex modulus is monitored. For each combination of temperature and frequency, four maximum strain amplitudes are targeted (50, 75, 100 and 110 μm/m). For each of them, two series of 50 loading cycles are applied, respectively at decreasing and increasing strain amplitudes. Before each decreasing strain sweep and after each increasing strain sweep, 5 cycles are performed at constant maximum targeted strain amplitude. Experimental results show that the behavior of the studied material is strain dependent. The norm of the complex modulus decreases and phase angle increases with strain amplitude. Results are presented in Black and Cole-Cole plots, where characteristic directions of nonlinearity can be identified. Both the effects of nonlinearity in terms of the complex modulus variation and of the direction of nonlinearity in Black space seem to validate the time-temperature superposition principle with the same shift factors as for linear viscoelasticity. The comparison between results obtained during increasing and decreasing strain sweeps suggests the existence of another phenomenon occurring during cyclic loading, which appears to systematically induce a decrease of the norm of the complex modulus and an increase of the phase angle, regardless of the type of the strain sweep (increasing or decreasing).

  4. Methods of nonlinear analysis

    CERN Document Server

    Bellman, Richard Ernest

    1970-01-01

    In this book, we study theoretical and practical aspects of computing methods for mathematical modelling of nonlinear systems. A number of computing techniques are considered, such as methods of operator approximation with any given accuracy; operator interpolation techniques including a non-Lagrange interpolation; methods of system representation subject to constraints associated with concepts of causality, memory and stationarity; methods of system representation with an accuracy that is the best within a given class of models; methods of covariance matrix estimation;methods for low-rank mat

  5. Topics in Nonlinear Dynamics

    DEFF Research Database (Denmark)

    Mosekilde, Erik

    Through a significant number of detailed and realistic examples this book illustrates how the insights gained over the past couple of decades in the fields of nonlinear dynamics and chaos theory can be applied in practice. Aomng the topics considered are microbiological reaction systems, ecological...... food-web systems, nephron pressure and flow regulation, pulsatile secretion of hormones, thermostatically controlled radiator systems, post-stall maneuvering of aircrafts, transfer electron devices for microwave generation, economic long waves, human decision making behavior, and pattern formation...... in chemical reaction-diffusion systems....

  6. Nonlinear diffusion equations

    CERN Document Server

    Wu Zhuo Qun; Li Hui Lai; Zhao Jun Ning

    2001-01-01

    Nonlinear diffusion equations, an important class of parabolic equations, come from a variety of diffusion phenomena which appear widely in nature. They are suggested as mathematical models of physical problems in many fields, such as filtration, phase transition, biochemistry and dynamics of biological groups. In many cases, the equations possess degeneracy or singularity. The appearance of degeneracy or singularity makes the study more involved and challenging. Many new ideas and methods have been developed to overcome the special difficulties caused by the degeneracy and singularity, which

  7. Limits to Nonlinear Inversion

    DEFF Research Database (Denmark)

    Mosegaard, Klaus

    2012-01-01

    For non-linear inverse problems, the mathematical structure of the mapping from model parameters to data is usually unknown or partly unknown. Absence of information about the mathematical structure of this function prevents us from presenting an analytical solution, so our solution depends on our...... ability to produce efficient search algorithms. Such algorithms may be completely problem-independent (which is the case for the so-called 'meta-heuristics' or 'blind-search' algorithms), or they may be designed with the structure of the concrete problem in mind. We show that pure meta...

  8. Nonlinear backreaction in cosmology

    Science.gov (United States)

    Green, Stephen Roland

    This thesis, based on two papers by Green and Wald, investigates the problem of nonlinear backreaction in cosmology. We first analyze the problem in a general context by developing a new, mathematically precise framework for treating the effects of nonlinear phenomena occurring on small scales in general relativity. Our framework requires the metric to be close to a background metric (not necessarily a cosmological metric), but allows arbitrarily large stress-energy fluctuations on small scales. We prove that, within our framework, if the matter stress-energy tensor satisfies the weak energy condition (i.e., positivity of energy density in all frames), then the only effect that small-scale inhomogeneities can have on the background metric is to provide an effective stress-energy tensor that is traceless and satisfies the weak energy condition itself—corresponding to the presence of gravitational radiation. In particular, nonlinear effects produced by small-scale inhomogeneities cannot mimic the effects of dark energy. We also develop perturbation theory off of the background metric. We derive an equation for the long-wavelength part of the leading order deviation of the metric from the background metric, which contains the usual terms occurring in linearized perturbation theory plus additional contributions from the small-scale inhomogeneities. Next, we apply our framework to the cosmological context, specializing our background metric to be of the Friedmann-Lemaitre-Robertson-Walker form. We demonstrate that, in the case of dust matter, a cosmological constant, and vanishing spatial curvature (i.e., our universe today), Newtonian gravity alone provides a good global description of an inhomogeneous general relativistic cosmology, even when there is significant nonlinear dynamical behavior at small scales. Namely, we find a relatively straightforward dictionary—which is exact at the linearized level—that maps Newtonian dust cosmologies into general

  9. Nonlinear surface electromagnetic phenomena

    CERN Document Server

    Ponath, H-E

    1991-01-01

    In recent years the physics of electromagnetic surface phenomena has developed rapidly, evolving into technologies for communications and industry, such as fiber and integrated optics. The variety of phenomena based on electromagnetism at surfaces is rich and this book was written with the aim of summarizing the available knowledge in selected areas of the field. The book contains reviews written by solid state and optical physicists on the nonlinear interaction of electromagnetic waves at and with surfaces and films. Both the physical phenomena and some potential applications are

  10. Oscillators from nonlinear realizations

    Science.gov (United States)

    Kozyrev, N.; Krivonos, S.

    2018-02-01

    We construct the systems of the harmonic and Pais-Uhlenbeck oscillators, which are invariant with respect to arbitrary noncompact Lie algebras. The equations of motion of these systems can be obtained with the help of the formalism of nonlinear realizations. We prove that it is always possible to choose time and the fields within this formalism in such a way that the equations of motion become linear and, therefore, reduce to ones of ordinary harmonic and Pais-Uhlenbeck oscillators. The first-order actions, that produce these equations, can also be provided. As particular examples of this construction, we discuss the so(2, 3) and G 2(2) algebras.

  11. Interaction of toremifene with dipalmitoyl-phosphatidyl-glycerol in monolayers at the air–water interface followed by fluorescence microscopy in Langmuir–Blodgett films

    International Nuclear Information System (INIS)

    Romão, Rute I.S.; Maçôas, Ermelinda; Martinho, José M.G.; Gonçalves da Silva, Amélia M.P.S.

    2013-01-01

    Langmuir monolayers of dipalmitoyl-phosphatidyl-glycerol (DPPG) containing toremifene (TOR), an antiestrogen drug derivative of tamoxifen, were prepared in order to study the interaction of the drug with the cell membrane. TOR is not surface active but it remains at the interface in DPPG rich monolayers anchored by electrostatic interaction with the anionic DPPG up to the equimolar composition. The fluidity of mixed monolayers increases up to the TOR mole fraction X TOR = 0.3, remaining practically invariant for higher compositions. Brewster angle microscopy shows that the TOR disturbs the DPPG organization and the liquid condensed (LC) domains of DPPG become undetectable for X TOR ≥ 0.4. Laser scanning confocal fluorescence microscopy images of the LB films doped with rhodamine B-piperazine amide dye confirm the progressive reduction in size of LC domains, from which TOR and rhodamine are excluded. The incorporation of TOR in DPPG monolayers up to the equimolar composition supports the formation of a TOR:DPPG complex (1:1) due to electrostatic interactions between the negatively charged polar groups of DPPG and protonated TOR. - Highlights: • Toremifene (TOR) in dipalmitoyl-phosphatidyl-glycerol (DPPG) monolayers • Electrostatic interactions between DPPG and TOR form a 1:1 complex. • TOR increases the fluidity of DPPG monolayers. • Incorporation of TOR in the fluid phase of DPPG followed by fluorescence imaging

  12. Nonlinearity management in higher dimensions

    International Nuclear Information System (INIS)

    Kevrekidis, P G; Pelinovsky, D E; Stefanov, A

    2006-01-01

    In the present paper, we revisit nonlinearity management of the time-periodic nonlinear Schroedinger equation and the related averaging procedure. By means of rigorous estimates, we show that the averaged nonlinear Schroedinger equation does not blow up in the higher dimensional case so long as the corresponding solution remains smooth. In particular, we show that the H 1 norm remains bounded, in contrast with the usual blow-up mechanism for the focusing Schroedinger equation. This conclusion agrees with earlier works in the case of strong nonlinearity management but contradicts those in the case of weak nonlinearity management. The apparent discrepancy is explained by the divergence of the averaging procedure in the limit of weak nonlinearity management

  13. Global Analysis of Nonlinear Dynamics

    CERN Document Server

    Luo, Albert

    2012-01-01

    Global Analysis of Nonlinear Dynamics collects chapters on recent developments in global analysis of non-linear dynamical systems with a particular emphasis on cell mapping methods developed by Professor C.S. Hsu of the University of California, Berkeley. This collection of contributions prepared by a diverse group of internationally recognized researchers is intended to stimulate interests in global analysis of complex and high-dimensional nonlinear dynamical systems, whose global properties are largely unexplored at this time. This book also: Presents recent developments in global analysis of non-linear dynamical systems Provides in-depth considerations and extensions of cell mapping methods Adopts an inclusive style accessible to non-specialists and graduate students Global Analysis of Nonlinear Dynamics is an ideal reference for the community of nonlinear dynamics in different disciplines including engineering, applied mathematics, meteorology, life science, computational science, and medicine.  

  14. Nonlinear evolution of drift instabilities

    International Nuclear Information System (INIS)

    Lee, W.W.; Krommes, J.A.; Oberman, C.R.; Smith, R.A.

    1984-01-01

    The nonlinear evolution of collisionless drift instabilities in a shear-free magnetic field has been studied by means of gyrokinetic particle simulation as well as numerical integration of model mode-coupling equations. The purpose of the investigation is to identify relevant nonlinear mechanisms responsible for the steady-state drift wave fluctuations. It is found that the saturation of the instability is mainly caused by the nonlinear E x B convection of the resonant electrons and their associated velocity space nonlinearity. The latter also induces energy exchange between the competing modes, which, in turn, gives rise to enhanced diffusion. The nonlinear E x B convection of the ions, which contributes to the nonlinear frequency shift, is also an important ingredient for the saturation

  15. Second derivative Langmuir probe diagnostics of Ar/O2 gas discharge for DC YBCO-124 sputtering

    International Nuclear Information System (INIS)

    Popov, Tsv K; Tsaneva, V N; Stelmashenko, N A; Dimitrova, M; Blamire, M G; Barber, Z H; Evetts, J E

    2005-01-01

    Second derivative Langmuir probe measurements of the electron energy distribution function (EEDF) in an argon-oxygen d.c. gas discharge in conditions close to the optimal for on-axis sputter deposition of YBa 2 Cu 4 O 8 films have been performed. Taking into account the effect of plasma depletion caused by the electron sink of the probe surface, an extension of Druyvesteyn's method for determination of the plasma potential and the EEDF (respectively, the electron temperature, T and the electron density, n) of the argon-oxygen plasma in the vicinity of the substrate was used. The film composition was monitored as a function of the deposition parameters and related to the relevant plasma characteristics

  16. A comparison of the packing behavior of egg phosphatidylcholine with cholesterol and biogenically related sterols in Langmuir monolayer films.

    Science.gov (United States)

    Lintker, Kimberly Borrenpohl; Kpere-Daibo, Peter; Fliesler, Steven J; Serfis, Alexa Barnoski

    2009-09-01

    Cholesterol and selected derivatives were studied as mixed Langmuir monolayers with egg phosphatidylcholine (PC). As an extension of our earlier work, which employed binary sterol/PC mixtures, here we examined ternary mixed monolayers containing cholesterol along with an alternate sterol and PC in different molar ratios, using pressure-area isotherms. The ternary systems behaved similarly to the binary sterol/PC systems reported previously, with similar condensation noted for the sterol/PC films. To better understand how variations in sterol structure affect sterol packing in such membrane monolayers, binary mixtures containing cholestenone, cholestanol, and lanosterol with PC were also studied. Cholestanol behaved similarly to cholesterol when incorporated with PC, while cholestenone and lanosterol did not cause as much film condensation. The observed differences in molecular packing, and attributed sterol structural differences, are considered within the context of sterol/phospholipid mixtures in biological membranes.

  17. Nonlinear Analysis and Variational Problems

    CERN Document Server

    Pardalos, Panos M

    2010-01-01

    The chapters in this volume, written by international experts from different fields of mathematics, are devoted to honoring George Isac, a renowned mathematician. These contributions focus on recent developments in complementarity theory, variational principles, stability theory of functional equations, nonsmooth optimization, and several other important topics at the forefront of nonlinear analysis and optimization. "Nonlinear Analysis and Variational Problems" is organized into two parts. Part I, Nonlinear Analysis, centers on stability issues for functional equations, fixed point

  18. Applications of nonlinear fiber optics

    CERN Document Server

    Agrawal, Govind

    2008-01-01

    * The only book describing applications of nonlinear fiber optics * Two new chapters on the latest developments: highly nonlinear fibers and quantum applications* Coverage of biomedical applications* Problems provided at the end of each chapterThe development of new highly nonlinear fibers - referred to as microstructured fibers, holey fibers and photonic crystal fibers - is the next generation technology for all-optical signal processing and biomedical applications. This new edition has been thoroughly updated to incorporate these key technology developments.The bo

  19. Interfacial and thermal energy driven growth and evolution of Langmuir-Schaefer monolayers of Au-nanoparticles.

    Science.gov (United States)

    Mukhopadhyay, Mala; Hazra, S

    2018-01-03

    Structures of Langmuir-Schaefer (LS) monolayers of thiol-coated Au-nanoparticles (DT-AuNPs) deposited on H-terminated and OTS self-assembled Si substrates (of different hydrophobic strength and stability) and their evolution with time under ambient conditions, which plays an important role for their practical use as 2D-nanostructures over large areas, were investigated using the X-ray reflectivity technique. The strong effect of substrate surface energy (γ) on the initial structures and the competitive role of room temperature thermal energy (kT) and the change in interfacial energy (Δγ) at ambient conditions on the evolution and final structures of the DT-AuNP LS monolayers are evident. The strong-hydrophobic OTS-Si substrate, during transfer, seems to induce strong attraction towards hydrophobic DT-AuNPs on hydrophilic (repulsive) water to form vertically compact partially covered (with voids) monolayer structures (of perfect monolayer thickness) at low pressure and nearly covered buckled monolayer structures (of enhanced monolayer thickness) at high pressure. After transfer, the small kT-energy (in absence of repulsive water) probably fluctuates the DT-AuNPs to form vertically expanded monolayer structures, through systematic exponential growth with time. The effect is prominent for the film deposited at low pressure, where the initial film-coverage and film-thickness are low. On the other hand, the weak-hydrophobic H-Si substrate, during transfer, appears to induce optimum attraction towards DT-AuNPs to better mimic the Langmuir monolayer structures on it. After transfer, the change in the substrate surface nature, from weak-hydrophobic to weak-hydrophilic with time (i.e. Δγ-energy, apart from the kT-energy), enhances the size of the voids and weakens the monolayer/bilayer structure to form a similar expanded monolayer structure, the thickness of which is probably optimized by the available thermal energy.

  20. Perspectives of nonlinear dynamics

    International Nuclear Information System (INIS)

    Jackson, E.A.

    1985-03-01

    Four lectures were given weekly in October and November, 1984, and some of the ideas presented here will be of use in the future. First, a brief survey of the historical development of nonlinear dynamics since about 1890 was given, and then, a few topics were discussed in detail. The objective was to introduce some of many concepts and methods which are presently used for describing nonlinear dynamics. The symbiotic relationship between sciences of all types and mathematics, two main categories of the models describing nature, the method for describing the dynamics of a system, the idea of control parameters and topological dimension, the asymptotic properties of dynamics, abstract dynamics, the concept of embedding, singular perturbation theory, strange attractor, Fermi-Pasta-Ulam phenomena, an example of computer heuristics, the idea of elementary catastrophe theory and so on were explained. The logistic map is the simplest introduction to complex dynamics. The complicated dynamics is referred to as strange attractors. Two-dimensional maps are the highest dimensional maps commonly studied. These were discussed in detail. (Kako, I.)