642 resultados para Angle de contact
Resumo:
Un cas exemplaire, un cas d'école, un beau cas, un cas de figure, un cas extrême, un cas particulier, un cas épineux, un cas limite ... Les modalités de l'étude de cas sont multiples et expriment le fait que tout raisonnement suivi, toute explication, toute théorie bute une fois ou l'autre sur la nécessité d'explorer et d'approfondir les propriétés d'une singularité accessible à l'observation. Publier un ouvrage sur la question du cas unique, c'est participer à ce moment de réflexion sur les méthodes scientifiques en psychologie. C'est aussi oeuvrer à un repositionnement constructif de cette modalité de faire science, en donnant la parole aux auteurs spécialistes de ces questions ou directement concernés par celles-ci à travers leurs recherches ou leurs pratiques.
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Le glaucome est la seconde cause de cécité dans le monde après la cataracte et est caractérisé par la perte progressive de cellules ganglionnaires de la rétine allant vers la dégénérescence du nerf optique. On distingue deux formes de glaucome; le glaucome à angle fermé et le glaucome à angle ouvert. L'hérédité du glaucome est souvent sporadique, parfois autosomique dominante. Une pression intraoculaire de plus de 21 mmHg représente un facteur de risque important pour son développement. Actuellement, la mutation la plus fréquente, observée dans 5% des cas de glaucome héréditaire, est retrouvée dans le gène MYOC (trabecular meshwork inducible glucocorticoide response). À ce jour, les causes et mécanismes moléculaires sous-jacent ne sont que partiellement compris. Récemment, il a été démontré qu'une souris transgénique exprimant le gène Notch2 dans luvée, développait un glaucome. Pour cette raison, nous avons analysé le gène NOTCH2 chez l'homme afin de déterminer s'il était impliqué. NOTCH2 est composé de 34 exons sur le chromosome 1 et code une protéine transmembranaire essentielle à la prolifération, l'apoptose, la différenciation cellulaire et le destin cellulaires. L'expression du gène est localisée dans le segment antérieur de l'oeil, le segment externe du corps ciliaire et le trabéculum. Les fonctions principales de ces deux tissus sont la production et le drainage de l'humeur aqueuse. Pour mémoire, une perturbation du flux peut générer une augmentation de la pression intraoculaire. Le but de cette étude était de rechercher d'éventuelles mutations du gène NOTCH2 chez des patients souffrant de glaucome. 130 patients ont été vu à l'hôpital ophtalmique Jules- Gonin et un échantillon d'ADN a été récolté afin d'identifier l'origine moléculaire de leur pathologie. L'analyse moléculaire s'est fait étape par étape. Premièrement, j'ai séquencé l'exon 3 du gène MYOC. Deuxièment, la Chromatographie en phase liquide à haute performance a été utilisée pour l'analyse des 34 exons du gène NOTCH2. Troisièment, tous les exons présentant une courbe suspecte au chromatogramme ont été séquencés selon la méthode de Sanger. Dans la première partie de l'étude, j'ai analysé l'exon 3 du gène MYOC afin de déterminer les éventuels porteurs d'une mutation dominante. Aucune mutation pathogénique n'a été mis en évidence mais 4 patients sur les 130 étaient porteurs d'un variant connu et fréquent. Dans la deuxième partie de mon étude, j'ai analysé les 34 exons du gène NOTCH2, qui n'ont révélé aucune mutation. Bien que les méthodes utilisées dans cette étude montrent quelques limitations, il est peu probable que des mutations dans les régions codantes de NOTCH2 soient un facteur de risque important dans le glaucome primaire à angle ouvert.
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The aim of this investigation was to analyze the dental occlusion in the deciduous dentition, and the effects of orthodontic treatment carried out in the early mixed dentition with the eruption guidance appliance. The deciduous occlusion and craniofacial morphology of 486 children (244 girls and 242 boys) were investigated at the onset of the mixed dentition period (mean age 5.1 years, range 4.0-7.8 years). Treatment in the treatment group and follow-up in the control group were started when the first deciduous incisor was exfoliated (T1) and ended when all permanent incisors and first molars were fully erupted (T2). The mean age of the children was 5.1 years (SD 0.5) at T1 and 8.4 years (SD 0.5) at T2. Treatment was carried out with the eruption guidance appliance. Occlusal changes that took place in 167 children were compared with those of 104 untreated control children. Pre- and post-treatment cephalometric radiographs were taken, and the craniofacial morphology of 115 consecutively treated children was compared with that of 104 control children. The prevalence of malocclusion in the deciduous dentition was 68% or 93% depending on how the cut-off value between the acceptable and non-acceptable occlusal characteristic was defined. The early dentofacial features of children with distal occlusion, large overjet and deepbite differed from those with normal occlusion. However, the skeletal pattern of these three malocclusions showed considerable similarity each being characterized by a retrusive mandible, small maxillo-mandibular difference, convex profile, retrusive lower incisors, and large interincisal angle. In the treatment group, overjet and overbite decreased significantly from T1 to T2. Following treatment, a tooth-to-tooth contact was found in 99% of the treated children but only in 24% of the controls. A Class I molar relationship was observed in 90% of the children in the treatment group, and in 48% in the control group. Good alignment of the incisors was observed in 98% of the treated children, whereas upper crowding was found in 32% and lower crowding in 47% of the controls. A significant difference between the groups was found in the mandibular length, midfacial length and maxillo-mandibular differential. The occlusal correction, brought about by the eruption guidance appliance, was achieved mainly through changes in the dentoalveolar region of the mandible. In addition, the appliance seemed to enhance the growth of the mandible. Treatment in the early mixed dentition using the eruption guidance appliance is an effective method to normalize occlusion and reduce further need of orthodontic treatment. Only few spontaneous corrective changes can be expected without active intervention.
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This paper presents a study of adsorption of xanthate with alkyl chain of two (C2XK), four (C4XK) and eight (C8XK) atoms of carbon, on pyrite from Santa Catarina, Brazil. The results showed that pyrite surface changes from hydrophilic to hydrophobic when xanthate is adsorbed increasing the contact angle to 35º for C2XK, and to 90º for C4XK and C8XK. The rate of flotation of pyrite particles after adsorption increases with the increase of the number of carbon atoms in the alkyl chain in agreement with the results of contact angle measurements.
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The singular properties of hydrogenated amorphous carbon (a-C:H) thin filmsdeposited by pulsed DC plasma enhanced chemical vapor deposition (PECVD), such as hardness and wear resistance, make it suitable as protective coating with low surface energy for self-assembly applications. In this paper, we designed fluorine-containing a-C:H (a-C:H:F) nanostructured surfaces and we characterized them for self-assembly applications. Sub-micron patterns were generated on silicon through laser lithography while contact angle measurements, nanotribometer, atomic force microscopy (AFM), and scanning electron microscopy (SEM) were used to characterize the surface. a-C:H:F properties on lithographied surfaces such as hydrophobicity and friction were improved with the proper relative quantity of CH4 and CHF3 during deposition, resulting in ultrahydrophobic samples and low friction coefficients. Furthermore, these properties were enhanced along the direction of the lithographypatterns (in-plane anisotropy). Finally, self-assembly properties were tested with silicananoparticles, which were successfully assembled in linear arrays following the generated patterns. Among the main applications, these surfaces could be suitable as particle filter selector and cell colony substrate.
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A theoretical model for the noise properties of Schottky barrier diodes in the framework of the thermionic-emission¿diffusion theory is presented. The theory incorporates both the noise inducedby the diffusion of carriers through the semiconductor and the noise induced by the thermionicemission of carriers across the metal¿semiconductor interface. Closed analytical formulas arederived for the junction resistance, series resistance, and contributions to the net noise localized indifferent space regions of the diode, all valid in the whole range of applied biases. An additionalcontribution to the voltage-noise spectral density is identified, whose origin may be traced back tothe cross correlation between the voltage-noise sources associated with the junction resistance andthose for the series resistance. It is argued that an inclusion of the cross-correlation term as a newelement in the existing equivalent circuit models of Schottky diodes could explain the discrepanciesbetween these models and experimental measurements or Monte Carlo simulations.
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A theoretical model for the noise properties of Schottky barrier diodes in the framework of the thermionic-emission¿diffusion theory is presented. The theory incorporates both the noise inducedby the diffusion of carriers through the semiconductor and the noise induced by the thermionicemission of carriers across the metal¿semiconductor interface. Closed analytical formulas arederived for the junction resistance, series resistance, and contributions to the net noise localized indifferent space regions of the diode, all valid in the whole range of applied biases. An additionalcontribution to the voltage-noise spectral density is identified, whose origin may be traced back tothe cross correlation between the voltage-noise sources associated with the junction resistance andthose for the series resistance. It is argued that an inclusion of the cross-correlation term as a newelement in the existing equivalent circuit models of Schottky diodes could explain the discrepanciesbetween these models and experimental measurements or Monte Carlo simulations.
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Työn tavoitteena oli selvittää pintaenergian vaikutus painovärin tarpeeseen IGT-laboratoriopainokoneella. Lisäksi selvitettiin onko karheudella vaikutusta kontaktikulmamittaukseen. Työ koostui kirjallisuusosasta ja kokeellisesta osasta. Kirjallisuusosassa tarkasteltiin aihepiiriä koskevia teorioita ja aiempia tutkimuksia. Kokeellisessa osassa valmistettiin laboratoriomittakaavassa pintaenergialtaan ja karheudeltaan erilaisia papereita. Pintaenergiaa muuteltiin kolmen erilaisen massaliiman ja kahden erilaisen pintaliiman avulla. Paperin karheutta säädettiin kalanteroinnilla. Papereista mitattiin pintaominaisuuksia, nesteen ja paperin välinen kontaktikulma, sekä suoritettiin painatuskokeita. Pintaenergia laskettiin kirjallisuudesta löytyneiden teorioiden perusteella ja näiden pintaenergian laskemismenetelmien käyttökelpoisuutta pintaenergian määrittämiseen selvitettiin. Lisäksi tutkittiin pintaenergian vaikutusta painovärin tarpeeseen. Tämä työ selvästi osoittaa, että yhden, kahden ja kolmen komponentin menetelmällä ja nesteitä vaihtelemalla saadaan erilaisia pintaenergian tuloksia. Pintaenergian määrittämiseen vaikuttaa myös kontaktikulmamittausten hankaluus ja kontaktikulman suuri vaihtelu, joka vaikuttaa koko mittaussarjan luotettavuustarkasteluun. Lisäksi paperin karheudella ja huokoisuudella oli merkitystä kontaktikulmamittaukseen.
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Ultrasuodatus on tehokas entsyymiliuosten konsentrointi- ja puhdistusmenetelmä. Prosessin ongelmana on kuitenkin kalvojen likaantumisesta johtuva suodatuksen aikainen vuon pienentyminen ja kalvojen hankala puhdistaminen. Oikeilla kalvovalinnoilla ja optimaalisilla pesustrategioilla voidaan suodatus- ja pesuaikoja lyhentää ja nain parantaa suodatusprosessin tehokkuutta ja tuotteen laatua. Työn kirjallisessa osassa on käsitelty entsyymiliuosten ja polymeerikalvojen suodatusprosessiin vaikuttavia ominaisuuksia. Työssä on esitelty myös pesuaineiden ja pesukemikaalien ominaisuuksia sekä pesuprosessiin vaikuttavia tekijöitä. Työn kokeellinen osa koostui kahdesta osasta. Työn ensimmäisessä osassa etsittiin entsyymiliuosten ultrasuodatusprosessiin sopivaa kalvoa vertailemalla kalvojen permeabiliteetteja, hydrofiilisyytta, varausta ja peseytyvyyttä. Suodatuksissa käytettiin kahta Roal Oy:n tuottamaa entsyymiliuosta ja suodatukset tehtiin DSS Labstak M20-laitteistolla. Työn toisen osan tarkoituksena oli etsiä entsyymiliuosten suodatuksessa käytettävien kalvojen likaantumisen syyt sekä tehokas puhdistusaine kalvojen pesuun. Tehokasta pesuainetta etsittiin liotuskokeilla ja laboratoriomittakaavan poikkivirtauslaitteistolla. Analysointeja tehtiin muun muassa FTIR- spektroskoopilla, vuomittauksilla, pyyhkäisyelektronimikroskoopilla ja kontaktikulmamittauksilla. Entsyymiliuosten suodatuksiin sopivan kalvon etsinnässä testattujen kalvojen välillä oli suuria eroja niin permeabiliteeteissa kuin likaantumisessa ja puhdistumisessa, mutta mikään kalvoista ei erottunut ylivoimaisesti parhaaksi. Pesuaineista kaupalliset membraanien puhdistukseen tarkoitetut emäksiset pesuaineet osoittautuivat tehokkaimmiksi lian poistajiksi.
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A thorough critical analysis of the theoretical relationships between the bond-angle dispersion in a-Si, Δθ, and the width of the transverse optical Raman peak, Γ, is presented. It is shown that the discrepancies between them are drastically reduced when unified definitions for Δθ and Γ are used. This reduced dispersion in the predicted values of Δθ together with the broad agreement with the scarce direct determinations of Δθ is then used to analyze the strain energy in partially relaxed pure a-Si. It is concluded that defect annihilation does not contribute appreciably to the reduction of the a-Si energy during structural relaxation. In contrast, it can account for half of the crystallization energy, which can be as low as 7 kJ/mol in defect-free a-Si
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Background: Intraocular pressure (IOP) is the pressure inside the eye that helps to maintain the integrity and the suitable form of the ocular globe. Precise and accurate measures of IOP are needed for the diagnosis as well as follow-up of glaucoma. In daily clinical practice, Goldmann applanation tonometer (GAT) and Non-contact tonometer (NCT) are the most common devices for measuring IOP. A close agreement between these methods has been showed, particularly in normotensive patients and a poor agreement, especially when IOP levels are above the normal range. Ophthalmologists have noticed a poor agreement between NCT and GAT, observing that by using NCT and after comparing with GAT, there is an overestimation of IOP readings, and particularly it occurs when the eyes are tearful. Previous studies investigate the effect of tears in Non-contact tonometer readings by the instillation of artificial tears, concluding in one of the studies that the variation was less than 1mmHg and not clinically significant, in contrast with another study which the increases were sadistically significant. Tear menisci are a thin strip of tear fluid located between the bulbar conjunctiva and the eyelid margins. We think that the overestimation of IOP readings using NCT could be due to the presence of a higher volume of tear in the lower tear meniscus which might cause an optical interference in the optoelectronic applanation monitoring system of this deviceObjectives: To research the influence of a certain volume of fluid in the lower tear meniscus on IOP measurements using the NCT in healthy eyes. Moreover, to investigate the agreement between IOP readings obtained by NCT and GAT in the presence and absence of this volume of fluidMethods: The study design will be transversal for diagnostic tests of repeated measures. We will study patients with no ocular pathology and IOP<21mmHg. It will consist in the measurement of IOP using NCT before and after the instillation of COLIRCUSÍ FLUOTEST, used as a volume of fluid in the lower tear meniscus, to observe if there will be differences using the paired t-test. Moreover, we will take IOP measures by GAT in order to know the agreement between these methods after and before the application of these eyedrops, using the ICC (intraclass correlation coefficient) and the Bland-Altmann method
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Alteration in hydrophilicity feature of chitosan films by hexamethyldisilazane (HMDS) cold-plasma treatment is evaluated. All treated films were colorless and transparent with no apparent textural changes. The effect on surfaces was characterized through contact angle measurements, degree of swelling and water vapor permeation. A significant reduction in all of the hydrophilicity parameters was observed. It is assumed that the HMDS treatment forms nonpolar silicone type structures. The goal is to investigate the formation of a stable hydrophobic barrier in order to increase the chitosan films usefulness in packaging applications.
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The application of one-dimensional proton high-resolution magic angle spinning (¹H HR-MAS) NMR combined with a typical advantages of solid and liquid-state NMR techniques was used as input variables for the multivariate statistical analysis. In this paper, different cultivars of beans (Phaseolus vulgaris) developed and in development by Embrapa - Arroz e Feijão were analyzed by ¹H HR-MAS, which have been demonstrated to be a valuable tool in its differentiation according chemical composition and avoid the manipulation of the samples as used in other techniques.
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An UV-Ozone reactor was developed with an ignition tube extracted into HID mercury lamp used to irradiation on zinc oxide (ZnO) and fluorinated tin oxide (FTO) films for PLEDs devices. Different exposures times were used. In contact angle measurements revealed better results for ZnO and FTO by 15 and 5 min, respectively. In Diffuse Reflectance Infra-red Fourier Transformed (DRIFT) spectroscopy allowed the observation of water, hydrocarbon and carbon dioxide adsorbed on the untreated TCO surfaces. After the UV-Ozone treatment the contaminants were significantly reduced or eliminated and the PLEDs devices decreased threshold voltages in comparison with respectively untreated TCOs.