Search results for "reflection"

Solid state electrochemical behavior of organosulfur compounds

2017

Abstract The solid-sate electrochemistry of organosulfur compounds existing in petroleum and its derived matrices is described using the voltammetry of immobilized microparticles methodology. Cyclic and square wave voltammogrammetric responses of sulfur compounds responsible of aging of asphalt pavements, namely, thiophenes, disulfides, sulfides, sulfoxides and sulfones were determined at compound-modified graphite electrodes in contact with 0.10 M H2SO4. The electrochemical oxidation/reduction products were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy with energy dispersion x-ray detection (SEM-EDX) couple…

Headspace-Liquid Phase Microextraction for Attenuated Total Reflection Infrared Determination of Volatile Organic Compounds at Trace Levels

2010

A combination of headspace (HS) sampling and liquid phase microextraction (LPME) has been successfully developed to solve sensitivity problems in attenuated total reflection (ATR) infrared determination of volatile organic compounds (VOCs). The HS sampling facilitates the selective extraction of the target volatile analytes from the sample matrix, while the liquid phase microextraction allows their preconcentration prior to infrared analysis. The direct determination of extracted analytes in the acceptor solvent provides high preconcentration factors of the order of 200 with a reduced consumption of organic solvents and a minimum generation of wastes, being thus the developed methodology a …

Non-porous polybutadiene-coated silicas as stationary phases in reversed-phase chromatography

1990

Abstract Non-porous silica of mean particle diameter 1.7 μm (Monospher) was coated with polybutadiene (PBD) following a published procedure. The silicas were prepared with graduated polymer loads up to 8% (w/w). Examination of the PBD-coated packings by means of electron spectroscopy for chemical analysis, scanning electron microscopy, diffuse reflection infrared fourier transform spectroscopy and differential thermal gravimetry indicated that the optimum polymer load was between 1 and 3% (w/w) with regard to a dense coverage corresponding to an average layer thickness of about 4 nm. No silanophilic interactions could be monitored using 1–3% (w/w) coated silicas under reversed-phase conditi…

Economical device for measuring thickness of a thin polymer film

1994

An inexpensive device (about $2K) for thickness measurements of thin (<1 μm) polymer films has been constructed. The homogeneous film is placed on a bulk substrate and three semiconductor lasers of different wavelengths are used to measure the reflectances at normal incidence. The thickness can be deduced with typically 4–8 nm uncertainty.

Evaluation of mucoadhesive properties of α,β-poly(N-hydroxyethyl)-dl-aspartamide and α,β-poly(aspartylhydrazide) using ATR–FTIR spectroscopy

2002

Abstract The mucoadhesive properties of α,β poly( N -hydroxyethyl)- dl -aspartamide (PHEA) and α,β-polyaspartylhydrazide (PAHy) have been investigated using attenuated total reflection infrared (ATR–FTIR) spectroscopy. In particular, films based on these polymers have been contacted with a mucin solution at pH 7 and, the interfacial interaction and interpenetration between the glycoprotein and PHEA or PAHy have been studied by analysing the ATR–FTIR spectra. A diffusion model using a solution of Ficks' second law has been employed to determine the diffusion coefficient of water into polymeric films as a consequence of interdiffusion which occurs at the polymer film/mucin solution interface.

Microstructure of a Discotic Polymer as Revealed by Electron Diffraction and High-Resolution Imaging

1989

Changes in collagen cross-linking of articular cartilage are revealed by spectral reflectance imaging

2012

Excessive cross-linking of collagen during aging may contribute to degeneration of articular cartilage. Traditionally, the amount of cross-links is derived by using destructive high-performance liquid chromatography (HPLC). However, a sensitive, non-destructive method could help to evaluate tissue integrity, including cross-links. We increased collagen cross-linking in bovine articular cartilage by controlled threose incubation. During the incubation, optical spectral reflectance images of the samples were captured and related to HPLC results using regression analysis. Significant correlations with reflectance and cross-links were observed. When further developed the optical method may enab…

Miradas urbanas del profesorado iberoamericano desde la cultura visual

2018

We are interested in knowing if there is a proper view of the teaching staff towards the urban reality. We start with verbal and visual descriptions, through images and texts. The research has been developed in Santiago de Chile, Valencia, Lima, Medellin, Montevideo and Buenos Aires, and combines direct participatory actions with personal interviews. The methodology follows a mixed method and is based on a case study that is complemented by research based on the arts. We concluded that there is a particular view of the teaching group towards their own city, which is full of critical reflection. This is a topic that has been little addressed and needs more attention.

Revista iberoamericana de educación

2012

Título, resumen y palabras clave en español, portugués e inglés Monográfico con el título: "Didáctica de la Lengua y la Literatura" Resumen tomado de la publicación Se propone el examen de las implicaciones del concepto de género discursivo, tomado de M. Bajtín, para la enseñanza de la composición escrita dentro del marco metodológico de las secuencias didácticas. Además de situar la enseñanza en un marco comunicativo, integra los aprendizajes específicos de habilidades lingüístico-comunicativas dentro de una tarea global que les da sentido. Se destaca de un modo especial la importancia de esta integración en cuanto a los conocimientos explícitos sobre la lengua y sus condiciones de uso. Se…

Gestión del cuerpo y planificación urbana: Desplazamiento de significado en la reivención de cuepos y ciudades

2020

Contemporary cities have administrations increasingly marked by urban planning guidelines that are guided by business and marketing and, to attract investments and tourists, implement strategies that aim to homogenize, spectacularize and control urban space. However, other experiences in the city potentially build new meaning to it, which would escape those strategically planned, creating alternative possibilities of uses, diverging from the way thar are predicted and proposed by the governmental power in their urban marketing strategies. The article discusses how the occupation of urban spaces by transvestites for prostitution may imply reflections on the role of norms of gender in the (re…