Search results for "Diss"
showing 10 items of 2500 documents
Evaluation of molecular mass and tacticity of polyvinyl alcohol by non-equilibrium capillary electrophoresis of equilibrium mixtures of a polymer and…
2011
Non-equilibrium capillary electrophoresis of equilibrium mixtures (NECEEM) has been used to characterize polyvinyl alcohol (PVA). Commercial PVA samples with different molecular masses, from M(w)=15 up to 205 kDa, were used. According to the (13)C NMR spectra, the samples also differed in tacticity (stereoregularity). Mixtures of PVA and the anionic azo-dye Congo Red (CR) were injected in the presence of a borate buffer. The electropherograms gave a band and a peak due to the residual PVA-CR complex and the excess dye, respectively, plus a superimposed exponential decay due to the partial dissociation of the complex during migration. The stoichiometry of the PVA-CR complex, q=[monomer]/[dye…
Molecular heterogeneity of the hemocyanin isolated from the king crabParalithodes camtschaticae
2000
Native Paralithodes camtschaticae hemocyanin is found as a mixture of dodecamers (24S; 80%) and hexamers (16S; 20%). Removal of Ca2+ ions by dialysis against EDTA-containing buffer solution at neutral pH induces complete dissociation of the 24S form into the 16S form. Under these conditions, a further increase in pH to 9.2 produces complete dissociation of the hexamers into monomers (5S). In both cases, the dissociation process is reversible. The dodecamer (24S) is composed of two different hexamers which can be discriminated only by ion-exchange chromatography in the presence of Ca2+ ions. At alkaline pH and in the presence of EDTA, two major monomeric fractions can be separated by ion-exc…
Analytical methodologies for chromium speciation in solid matrices: a survey of literature
1998
The analytical literature about chromium speciation in solid samples has been surveyed. From 451 articles published on the speciation of chromium from 1983 to 1997, the methodologies to do speciation in solids after sample pretreatment are discussed, through consideration of the types of samples and their dissolution, the analytical techniques employed for chromium measurement, and the figures of merit of the 86 papers reported in the Analytical Abstracts data base.
Chromium liquid waste inertization in an inorganic alkali activated matrix: Leaching and NMR multinuclear approach
2015
A class of inorganic binders, also known as geopolymers, can be obtained by alkali activation of aluminosilicate powders at room temperature. The process is affected by many parameters (curing time, curing temperature, relative humidity etc.) and leads to a resistant matrix usable for inertization of hazardous waste. In this study an industrial liquid waste containing a high amount of chromium (≈ 2.3 wt%) in the form of metalorganic salts is inertized into a metakaolin based geopolymer matrix. One of the innovative aspects is the exploitation of the water contained in the waste for the geopolymerization process. This avoided any drying treatment, a common step in the management of liquid ha…
Electronic properties and corrosion resistance of passive films on austenitic and duplex stainless steels
2018
Abstract Passive films were grown at constant potential in acidic (pH∼2) and alkaline (pH∼13) solutions on chromium, AISI 304L, AISI 316L and Duplex stainless steels. Passive films on chromium grow following a high field mechanism considering the presence of dissolution phenomena. According to the photoelectrochemical characterization, passive films on Cr have a bandgap of 3.4 eV when formed in acidic solution, and of 2.4 eV when formed in alkaline solution due to the formation of Cr(OH)3. These films result to be poorly stable against anodic dissolution due to a very anodic flat band potential. Conversely, impedance and photoelectrochemical measurements proved that passive films on stainle…
Instantaneous frequency measurement of dissipative soliton resonant light pulses
2016
Fil: Cuadrado-Laborde, Christian. Universidad de Valencia. Departamento de Física Aplicada y Electromagnetismo. Instituto Universitario de Ciencia de los Materiales; España Fil: Cuadrado-Laborde, Christian. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Física Rosario; Argentina Fil: Cuadrado-Laborde, Christian. Pontificia Universidad Católica Argentina. Facultad de Química e Ingeniería del Rosario; Argentina Fil: Armas Rivera, I. Benemérita Universidad Autónoma de Puebla. Facultad de Ciencias Físico Matemáticas; Mexico Fil: Carrascosa, A. Universidad de Valencia. Departamento de Física Aplicada y Electromagnetismo. Instituto Universitario de Ciencia de los Materia…
Thermal stability of trimeric light-harvesting chlorophyll a/b complex (LHCIIb) in liposomes of thylakoid lipids.
2006
The major light-harvesting chlorophyll a/b complex (LHCIIb) of photosystem (PS) II functions by harvesting light energy and by limiting and balancing the energy flow directed towards the PSI and PSII reaction centers. The complex is predominantly trimeric; however, the monomeric form may play a role in one or several of the regulatory functions of LHCIIb. In this work the dissociation temperature was measured of trimeric LHCIIb isolated from Pisum thylakoids and inserted into liposomes made of various combinations of thylakoid lipids at various protein densities. Dissociation was measured by monitoring a trimer-specific circular dichroism signal in the visible range. The LHCIIb density in t…
Characterization of gramicidin A in an inverted micellar environment. A combined high-performance liquid chromatographic and spectroscopic study
1992
We have investigated the conformational adaptability of gramicidin A incorporated into reverse micelles of sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/isooctane/water, a so far unexplored "host" membrane-mimetic model system for this peptide. A high-performance liquid chromatographic strategy previously developed for the study of gramicidin in phospholipid vesicles and normal micelles [Bañó et al. (1989) FEBS Lett. 250, 67; Bañó et al. (1991) Biochemistry 30, 886] has been successfully extended to this system. The method has permitted the separation of peptide conformational species, namely, double-stranded dimers and monomers, and an accurate quantitation of their proportion in the invert…
A semi-empirical approach for the simulation of circular dichroism spectra of gramicidin A in a model membrane
1992
In an extension of our previous work (Bañó, M. C., Braco, L., and Abad, C. 1991. Biochemistry. 30:886-94), the kinetics of dissociation of gramicidin A double-stranded dimers into beta 6.3-helical monomers in small unilamellar vesicles prepared following different protocols, were investigated using in combination circular dichroism (CD) and high-performance liquid chromatography (HPLC). The analysis of the data from both techniques according to a two-component model strongly supports that any given CD pattern of gramicidin incorporated in the phospholipid bilayer can be deconvoluted essentially as a linear combination of the reference subspectra calculated for the double-stranded dimer and …
One-Sided Prototype Selection on Class Imbalanced Dissimilarity Matrices
2012
In the dissimilarity representation paradigm, several prototype selection methods have been used to cope with the topic of how to select a small representation set for generating a low-dimensional dissimilarity space. In addition, these methods have also been used to reduce the size of the dissimilarity matrix. However, these approaches assume a relatively balanced class distribution, which is grossly violated in many real-life problems. Often, the ratios of prior probabilities between classes are extremely skewed. In this paper, we study the use of renowned prototype selection methods adapted to the case of learning from an imbalanced dissimilarity matrix. More specifically, we propose the…