Neste trabalho são apresentados os estudos de formação de diversas especies de ions positivos e negativos de hidrogenio feitos a maquina de plasma quiescente (PQUI-I) do Laboratorio Associado de Plasma do INPE (LAP-INPE) utilizando-se dois metodos para medidas das concentracoes de ions nos plasmas. O metodo das pressões parciais utiliza uma sonda eletrostática de Langmuir e um medidor de pressão por ionização fornecendo resultados relativos dasconcentrações ionicas; o segundo destina-se as medidas de densidadee temperaturas de ions negativos utilizando-se uma sonda sensivel aions negativos construida no LAP-INPE. Também e apresentado o sistema de aquisição e analise de dados por computador instalado naPQUI-I como parte deste trabalho.

O ibuprofeno é um antiinflamatório não esteróide, com baixa solubilidade em água, que apresenta diversos efeitos colaterais, incluindo lesão gástrica e intestinal. Esses efeitos podem depender da interação com a membrana celular, o que nos motivou a investigar, na primeira parte deste trabalho, a incorporação do ibuprofeno em monocamadas de Langmuir como modelos de membrana celular. Monocamadas de dipalmitoil fosfatidil glicerol (DPPG) e dipalmitoil fosfatidil colina (DPPC) co-espalhadas com o ibuprofeno ou depositadas sobre subfases contendo o fármaco foram estudadas por meio das isotermas de pressão e potencial de superfície. Foram observados efeitos significativos para monocamadas de DPPC, particularmente na transição de fase líquido-expandida para líquido-condensada, com modificações relevantes na elasticidade da monocamada. Esses efeitos aumentaram com a concentração do ibuprofeno. Para os dois tipos de fosfolipídios, o ibuprofeno pôde penetrar na região hidrofóbica, o que foi confirmado por espectroscopia de reflexão e absorção no infravermelho com modulação da polarização (PM-IRRAS), indicando assim a presença de interações hidrofóbicas. A análise por microscopia no ângulo de Brewster (BAM) mostrou que o ibuprofeno impede a formação de grandes domínios de DPPC, enquanto que não foram observadas alterações significativas para o DPPG. A interação entre o ibuprofeno e o DPPG também foi confirmada após a imobilização da monocamada mista em filmes LB com alterações na absorção no UV-Vis da molécula de ibuprofeno. No que diz respeito às implicações biológicas, a ação farmacológica que depende diretamente da interação com a membrana deve ocorrer primeiramente em regiões neutras via penetração do ibuprofeno na região hidrofóbica da membrana celular. A segunda parte deste trabalho foi dedicada à interação de capsaicinóides extraídos da pimenta malagueta com monocamadas de Langmuir constituídas de DPPG e DPPC. A capsaicina é um potente analgésico de uso tópico, que pode causar dessensibilização no local de aplicação dependendo da dose e, portanto há interesse na sua incorporação em sistemas de liberação controlada, como os lipossomos. A técnica de Langmuir foi empregada para verificar essa possibilidade. Os capsaicinóides expandiram as monocamadas de DPPG e aumentaram sua elasticidade. As isotermas de potencial de superfície indicaram que os capsaicinóides provocam aumento de 10% no momento de dipolo numa concentração de 30% em mol. Para os filmes mistos de DPPC e capsaicinóides, a área mínima diminuiu e a elasticidade da monocamada aumentou. De acordo com as isotermas de potencial, os momentos de dipolo diminuíram para as monocamadas de DPPC independentemente da concentração de capsaicinóides. Esses resultados sugerem que as moléculas de DPPC são solubilizadas para a subfase na presença do fármaco. A partir destes resultados, conclui-se que os capsaicinóides podem ser incorporados em estruturas lipídicas, constituídas principalmente de DPPG, o que é relevante para uso em sistemas de liberação de fármacos. / Ibuprofen is a nonsteroidal anti-inflammatory drug, with low solubility in water, which exhibits side effects including gastric and intestinal injury, often irreversible. Some of these effects may depend on the interaction with the cell membrane, which motivated us to investigate the incorporation of ibuprofen in Langmuir monolayers as cell membrane models, in the first part of this thesis. Dipalmitoyl phosphatidyl choline (DPPC) or dipalmitoyl phosphatidyl glycerol (DPPG) monolayers co-spread with ibuprofen or deposited on ibuprofen-containing aqueous subphases were studied using surface pressure and surface potential isotherms. Significant effects were observed for DPPC monolayers, particularly at the liquid-expanded to liquid-condensed phase transition, with relevant changes in the elasticity of the monolayer. These effects increased with the ibuprofen concentration. For both types of phospholipids, ibuprofen could penetrate into the hydrophobic part of the monolayer, which was confirmed with polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS), thus indicating the presence of hydrophobic interactions. BAM images showed that ibuprofen prevents the formation of large domains of DPPC, while no significant changes were observed for DPPG. The interaction between DPPG-ibuprofen was also confirmed for deposited layers in the form of LB films, with changes in the ibuprofen UV-Vis absorption. As for the biological implications, the pharmacological action depending directly on the membrane interaction should occur primarily with zwitterionic regions of the membrane via penetration of ibuprofen in the hydrophobic part of the monolayer. The second part of this thesis is dedicated to the interaction of capsaicinoids, extracted from malagueta pepper, with Langmuir monolayers of DPPC and DPPG. Capsaicin is a powerful analgesic of topical use, which can cause desensitization in the application site depending on the dose, and therefore there is interest in its incorporation in drug delivery systems, such as liposomes. The Langmuir technique was employed to verify this possibility. The capsaicinoids expanded the DPPG monolayer and increased its elasticity. Surface potential isotherms indicated that the capsaicinoids increased the average dipole moment by 10 % for 30 mol % of capsaicinoids. For the mixed films of DPPC and capsaicinoids, the minimum area decreased and the elasticity increased. According to the surface potential isotherms, the dipole moments decreased for DPPC monolayers regardless of the capsaicinoid concentrations. These results suggest that the DPPC molecules are solubilized into the subphase in the presence of the drug. From these results, it is concluded that the capsaicinoids can be incorporated into structures as the liposomes constituted mainly of DPPG, which is relevant for use in drug delivery systems.

Neste trabalho foram estudadas equações de estado encontradas na literatura para a descrição das isotermas de pressão superficial versus área molecular média de monocamadas de Langmuir. As equações foram subdivididas em duas classes: equações para monocamadas de Langmuir de polímeros e macromoléculas, e equações para monocamadas de Langmuir de substâncias anfifilicas. As equações foram aplicadas a monocamadas de PMMA (um polímero), Ácido Araquídico (um ácido graxo, que é urna substância anlifilica que contém apenas uma cauda hidrofóbica) e DPPC (um fosfolipídio, que é uma substância antifilica que contém duas caudas hidrofóbicas). Também foi estabelecida, baseado no modelo de Shin et al., uma equação de estado específica para substâncias anfifilicas com duas caudas hidrofóbicas, o que não foi previamente observado na literatura. A maioria das equações forneceu urna boa concordância qualitativa com as isotermas experimentais, porém não foi possível uma concordância quantitativa na maioria dos casos. Os diferentes modelos e hipóteses empregados na derivação das equações permitiram uma melhor compreensão de algumas propriedades das monocamadas / A brief summary concerning equations of state describing isotherms exhibited by Langmuir monolayers is presented. The equations may be classified in two categories: the first applies to monolayers formed by polymers or macromolecules and the second to monolayers formed by amphiphilic substances. They were applied to monolayers of PMMA (a polymer), Arachidic Acid (a fatty acid) and DPPC (a phospholipid). The agreement with experimental results is qualitatively acceptable, however, it was not possible a quantitatively good result. A model for amphiphilic substances whose hydrophobic moiety consists of two tails was not found in the literature. Such equation is developed following Shin et al. method and the agreement shows to be satisfactory. With this work a better understanding of some properties of monolayers is achieved

Orientador: Priscila Alessio Constantino / Resumo: O presente trabalho descreve o estudo da interação entre o lipídio AA (ácido araquídico), os fosfolipídios DPPC (1,2-dipalmitoil-sn-glicero-3-fosfatidilcolina) e DPPG (1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol) com a enzima Ty (tirosinase). Através da interação monocamada lipídica/enzima foi desenvolvido um biossensor para a detecção de polifenóis. O estudo de interação foi realizado via filmes de Langmuir, ou seja, monocamadas lipídicas dispostas na interface ar/água que mimetizaram modelos de membranas biológicas, sendo estes analisados através de isotermas (π-A) e do módulo de compressibilidade. Além disso, foram realizadas medidas de PM-IRRAS (do inglês - Polarization Modulation - Infrared Reflection-Adsorption Spectroscopy) que auxiliaram no estudo da interação membrana/enzima em nível molecular. Por meio desses estudos foi possível observar uma maior interação e incorporação da enzima nas monocamadas de DPPC/Ty. Então, os filmes de Langmuir foram depositados em ITO (substrato eletrocondutor de vidro recoberto com óxido de estanho dopado com índio) utilizando a técnica de Langmuir-Blodgett (LB). Os filmes foram avaliados como biossensores para detecção de polifenóis em amostras padrões de catecol por voltametria cíclica. Nessa etapa, foram avaliados os efeitos das matrizes lipídicas, número de camadas e concentração do eletrólito de suporte no processo eletrocatalítico de redução do catecol. Além disso, foi avaliado o efeito da incorporação do mediador eletrônico LuPc... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work describes the study of interaction between lipid AA (arachidic acid), phospholipids DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine) and DPPG (1,2-dipalmitoyl-snglycero-3-phosphoglycerol) with the enzyme Ty (tyrosinase). A biosensor for the detection of polyphenols was developed through the interaction of lipid monolayer/enzyme. The study of interaction was performed in Langmuir films, in other words, lipids monolayer organized at the air/water interface simulated biological membrane models, using the isotherms (π-A) and the compressibility module. In addition, measurements of PM-IRRAS (Polarization Modulation - Infrared Reflection-adsorption Spectroscopy) were performed to study of membrane/enzyme interaction at the molecular level. In these studies, it was possible to observe a strong interaction and incorporation of the enzyme in DPPC monolayer. Thus, the films were grown on ITO (indium doped tin oxide glass substrate) using the Langmuir-Blodgett (LB) technique. The films were evaluated as biosensors for detection of polyphenols in standard catechol samples using cyclic voltammetry. At this stage, the effects of lipid matrices, number of layers and support electrolyte concentration on the electrocatalytic catechol reduction process were evaluated. After that, the effect of the incorporation of the electron mediator LuPc2 (Lutetium bisphthalocyanine) into the lipid matrix was evaluated. Electrochemical studies indicated that DPPC/Ty and DPPC:LuPc2/Ty films,... (Complete abstract click electronic access below) / Mestre

The history of public health has suggested that the progress of societies cannot be understood without understanding community health conditions. The federal government of the United States established the Communicable Disease Center (CDC) in 1946 to assist the states in controlling outbreaks of infectious disease. This coincided with the early days of the Cold War. The concern of some health officials of the time, most notable among them was the CDC’s Chief of Epidemiology, Alexander D. Langmuir, was to address the 1950s threat of “germ warfare,” or bio-terrorism. To do this effectively the CDC established the Epidemic Intelligence Service (EIS) to train field epidemiologists as the first line of defense against biological attack. The role of the Chief EIS Officer was vital to its success. An examination of the Chiefs’ performance from 1951 through 2006 supports this contention.

The Rosetta spacecraft is on route to rendezvous with the comet 67P/ Churyomov-Gerasimenko. One of the instruments onboard is the Langmuir probe instrument (LAP) developed by the Swedish Institute of Space Physics. The LAP includes two spherical probes used to measure a number of properties of the surrounding plasma. One measured property is the plasma density for which the spacecraft potential is a good proxy. By the determining the potential between spacecraft and Langmuir probe, the spacecraft potential can be measured. But such measurements are sometimes disturbed by the potential from the spacecraft itself, the influence from photoemitted electrons and the solar wind wake behind Rosetta. In order to correct for the errors caused by spacecraft-plasma interaction in the solar wind a model depending on the spacecraft (and Langmuir probe) orientation is developed. The data is obtained from three-dimensional simulations of Rosetta, with varying plasma parameters, using the software SPIS (Spacecraft Plasma Interaction System). Least squares fitting with a set of basis functions then provide the input for a parametric modelling. The developed model makes it possible to estimate the influence of each of the disturbing effects. The developed model gives good fits to data obtained in SPIS simulations. The two angular dependent factors, modelling perturbation on potential measurements caused by photoelectrons and wake effects, show errors below the 100 mV level in all cases. The model describing the influence from spacecraft potential is slightly less accurate, with errors at or below the 400 mV level in all relevant cases.

No description available.

By modelling and simulating the ESA spacecraft Rosetta in a plasma with solar wind parameters, and simultaneously simulating a particle detection experiment of Langmuir probe voltage sweep type using the ESA open source software SPIS Science, we investigate the features of Rosetta’s envi- ronment in the solar wind and the e↵ect of photoemission from the space- craft on the measurements made by the Langmuir Probe instrument on board Rosetta. For a 10 V positively charged spacecraft and Maxwellian distributed photoelectron emission with photoelectron temperature, Tf = 2 eV in a plasma of typical 1 AU solar wind parameters: ne = 5 ⇥ 106 m3, vSW = 4 ⇥ 105 m/s, Te = 12 eV, Tion = 5 eV, we detect a floating potential of 6.4 (± 0.2) V at Langmuir probe 1. Two models used in literature on photoemission was used and compared and we report a clear preference to the Maxwellian energy distribution of photoelectrons from a point source model with our simulation result.

The overall objective of this PhD thesis research is to characterize, understand and ultimately control phase-separated structures in mixed films consisting of a perfluorinated fatty acid and a photopolymerizable surfactant. In these systems, film morphology, mechanical properties and spectroscopic properties are inter-related and this thesis explores these relationships. In this context the interaction between perfluorotetradecanoic acid (C13F27COOH, referred to as PF in this dissertation), and 10,12-pentacosadynoic acid (CH3(CH2)11−C≡C−C≡C−(CH2)8COOH, referred to as PCDA in this dissertation) has been studied in monolayers using a combination of surface and spectroscopic characterization techniques. To investigate the inter-relationship of the properties described above, film behavior under a variety of conditions, including behavior at different interfaces (solid-liquid, air-liquid), different film compositions and under different conditions of photoillumination and mechanical stress were explored. Thermodynamic and morphological studies of mixed monolayer surfactant films of PF and the photo-polymerizable diacetylene molecule, PCDA, were carried out. The films were prepared at the air-water interface and transferred onto solid supports such as a glass slides via Langmuir-Blodgett (LB) deposition technique. The presence of the perfluoroacid helped to stabilize the diacetylene surfactant monolayer in comparison with the diacetylene alone, allowing film transfer onto solid substrates without needing to add cations to the sub-phase or photo-polymerize the components prior to deposition. Addition of the perfluorocarbon to PCDA resulted in films with the photopolymer strands oriented perpendicular to the direction of the film compression in a Langmuir trough. This is in contrast with film structures formed from pure PCDA. Formation of these features could be explained by a two-step process that happened sequentially: first, the compression of monolayer with trough barriers while trying to maintain the surface pressure constant induces stress on the film surface; second, additional film buckling which was enhanced by the strong cohesion between PF and PCDA. Film compression data, supported by in situ fluorescence spectrophotometry, Brewster angle microscope imaging and atomic force microscope images of deposited films, supported this mechanism. Factors that controlled the orientation of the photopolymer fibers were also investigated. Fibers were found to consist of multiple strands, with each strand having a different orientation. Our investigation also revealed there was a preferred orientation for fibers in the film as a whole. The angle of approximately 60o to the direction of film compression during deposition from a Langmuir trough has been calculated with the help of dual-view, polarized fluorescence microscopy. This orientation was attributed to the mechanical stress exerted by the trough compression barriers coupled with rotation of the polymer fibers during film draining. The combination of Atomic Force Microscope (AFM) and fluorescence microscopy (FM) provided a thorough and comprehensive mapping of fundamental properties of mixed monolayer system, and enabled a quantitative determination of the degree of selectivity of the polymerization process.

This thesis describes the design and construction of a Brewster Angle Microscope (BAM) to investigate monolayer films at the air/water interface. A Schiff base coordination polymer, Cu(ll) 5,5'-methylenebis(N-hexadecyl- sallcylideneamine (poly(CuMBSH)), was initially investigated using the BAM equipment. This material is being developed as the active material in vapour sensing devices produced by the Langmuir Blodgett (LB) method. Transfer of the monomer (MBSH) to the substrate was found to be poor but poly(CuMBSH) had a good deposition ratio (>0.95). The film was polymerised at the air/water interface by injecting a solution of Cu(ll) ions into the subphase. BAM was able to record the polymerisation of MBSH to poly(CuMBSH) in real time. Qualitative image analysis indicates a reordering of the material at the interface and a decrease in film thickness. The technique of BAM clearly displays the change in structure between the monomer film and the polymer film and that the poly(CuMBSH) film is homogenous at the micron level. Poly(para-phenylenevinylenes) PPV derivatives are presently being examined as potential LED devices. One method used to produce such devices is the LB method. BAM was used to investigate ordering of the monolayer prior to deposition. Results by the Physics and Engineering department indicated that if subphase contained water that had been left to stand for several days film transfer was improved. A range of BAM experiments were conducted with varying subphases to determine the cause of this effect. A new technique of determining the surface excess concentration was developed in this work which is known as Brewster Reflectivity (BAR). The reflectivity of simple surfactants; sodium dodecylbenzenesulfonate, Getyltrimethylammonium bromide, tetradecyltrimethylammonium bromide and dodecyltrimethyl-ammonium bromide at concentrations above and below the critical micelle concentration (CMC) were correlated to surface excess. This is a new, simple, non-invasive method for probing the surface excess using intrinsic properties of the system.