Search results for "elemental"
showing 10 items of 131 documents
Copolyamides from adipic and truxillic acids: Synthesis and characterization by direct pyrolysis in the mass spectrometer
1977
The synthesis of a series of polyamides and copolyamides containing α-truxillic and adipic units in the chain is reported. The thermal degradation of these polymers was investigated by direct pyrolysis in the ion source of a mass spectrometer. Thermal degradation reactions were followed directly by this method by detecting the thermal- and electron-impact-induced fragments. The results obtained show a good correlation between the intensity of mass peaks characteristic of truxillic and adipic moieties and the composition of the copolyamides, as ascertained by elemental analysis. This is an important result since it shows the potential of the direct pyrolysis method in the analysis of copolym…
Synthesis and Characterization of the Hybrid Clay-Based Material Montmorillonite-Melanoidin: A Potential Soil Model
2010
The study of the interactions among metals, minerals, and humic substances is essential in understanding the migration of inorganic pollutants in the geosphere. A considerable amount of organic matter in the environment is associated with clay minerals. To understand the role of organic matter in the environment and its association with clay minerals, a hybrid clay-based material (HCM), montmorillonite (STx-1)-melanoidin, was prepared from L-tyrosine and L-glutamic acid by the Maillard reaction. The HCM was characterized by elemental analysis, nuclear magnetic resonance, x-ray photoelectron spectroscopy (XPS), scanning transmission x-ray microscopy (STXM), and thermal analysis. The presence…
MODIFICATION OF HUMIC SUBSTANCES FOR DEVELOPMENT OF MATERIALS FOR ENVIRONMENTAL TECHNOLOGIES
2019
Humic substances are high molecular weight refractory polycationites formed during decay of living organic matter and through biosynthesis of low molecular weight organic substances (metabolites or decay products of living organisms). Presence of many functional groups in the structure of humic substances determines their ability to interact with metal ions forming stable complexes and influencing metal ion speciation in the environment and mobility, behaviour and speciation forms in the environment. Presently humic substances are a product of industrial scale and quantities in amounts of hundreds of tons are produced. The aim of this study is to analyse derivatization possibilities of humi…
Oxidative halogenation of substituted pyrroles with cu(II). Part I. Bromination of some 3-acetylpyrroles
1990
3-Acetylpyrroles are brominated with copper(II) bromide. The reaction afforded almost quantitatively only nuclear monobromination. Evidence for the structures of final compounds was by mass spectrometry, 1 H-nuclear magnetic resonance, ir, and elemental analysis
Discrimination of serial auditory patterns in rats : roles of configural and elemental associations
2011
In order to test whether rats could discriminate between tone sequences, food deprived rats were given appetitive discrimination conditioning with repeated ascending or descending series of musical notes serving as conditioned stimuli (CSs). The other type of tone sequence was reinforced as the other was followed by nothing. In Experiment 1, each series of 8 tones formed a 2 s cycle. The cycle was repeated six times so that the duration of the whole sequence was 12 s. In Experiment 2, the CSs were similar to those in Experiment 1 except that they started with a random note. As a result, rats could discriminate between the stimuli when the CS started systematically with the same note. When t…
Determinación multielemental de metales traza en agua de mar
2015
Los metales traza presentes en las aguas marinas, procedentes de actividades antropogénicas, constituyen un serio problema ambiental y de salud debido a su toxicidad y a las repercusiones que ocasionan sobre los seres vivos, al introducirse en la cadena trófica. La determinación de metales traza en agua de mar supone un problema analítico complejo derivado de la baja concentración a la que se encuentran los analitos y al elevado contenido salino que dificulta la cuantificación. Por ello, surge la necesidad de contar con técnicas de detección sensibles y con metodologías de separación / preconcentración de muestra que permitan aislar los analitos de la matriz y aumentar su concentración para…
Aplicacions de mètodes no pertorbatius a la dinàmica del sabor
2008
RESUMEN A día de hoy, el Modelo Estándar de las interacciones electrodébiles describe correctamente todos los fenómenos observados en la naturaleza. Sin embargo no proporciona ninguna explicación al hecho de que existan tres familias fermiónicas, incluyendo cada una quarks y leptones. Estas familias se distinguen por el grado de libertad sabor. Debido a la ruptura espontánea de la simetría local gauge, existe un patrón de sabor muy rico. En particular, las partículas tienen masas diferentes, y las diversas familias se mezclan (en el caso de los quarks) cuando interaccionan con los bosones mediadores. El conocimiento preciso de las masas y ángulos de mezcla de los quarks es fundamental para …
LHC phenomenology of two-Higgs-doublet models in the LHC era
2014
En esta tesis se analiza la posibilidad de que el bosón recién descubierto en el LHC pertenezca a un sector escalar extendido conocido como modelo de dos dobletes de Higgs, teniendo en cuenta experimentos en la frontera de intensidad y de energía. Hay varias razones para estudiar la fenomenología de sectores escalares extendidos. Por un lado, ningún principio fundamental de la teoria electrodébil explica la ruptura espontánea de la simetría de gauge electrodébil, uno más bien tiene que asumir que este fenómeno ocurre. Muchos modelos o teorías que tratan de explicar el rompimiento de la simetría electrodébil involucran sectores escalares más complejos que el del modelo estándar. Sectores esc…
Beyond Standard Model phenomenology with or without a light Higgs
2012
144 páginas. Tesis Doctoral del Departamento de Física Teórica, de la Universidad de Valencia, y del Instituto de Física Corpuscular (IFIC). Fecha de lectura: 11 diciembre 2012.
A new approach for the measurement of gaseous elemental mercury (GEM) and H2S in air from anthropogenic and natural sources: Examples from Mt. Amiata…
2017
Real-time measurements of GEM and H2S discharged from natural and anthropogenic sources are a valuable tool to investigate the dispersion dynamics of these contaminants in air. In this study, a new approach to measure GEM and H2S concentrations in air, carried out by coupling a portable Zeeman atomic absorption spectrometer with high frequency modulation of light polarization (Lumex RA-915M) and a pulsed fluorescence gas analyzer (Thermo Scientific Model 450i), was applied to two distinct areas: (i) in the surroundings of Piancastagnaio (Siena, Central Italy), located in the eastern flanks of Mt. Amiata (a 200,000Â years old volcano), where three geothermal plants are operating and whose ex…