Search results for "Analytical"

Localized surface plasmon resonance sensor based on Ag-PVA nanocomposite thin films

2009

In this work we demonstrate the use of nanocomposite thin films of poly(vinyl alcohol) with embedded silver NPs for chemosensing purposes. Silver NPs are in situ synthesized inside polyvinyl alcohol during the bake step of the formation of a nanocomposite thin film. The polymer in the nanocomposite provides an appropriate chemical and electromagnetic environment for metal NPs in order to interact with and hence detect the chemical species. A limit of detection below 20 nM is found when detecting 2-mercaptoethanol as the analyte, when measuring spectral changes (peak wavelength, linewidth and intensity) in the Localized Surface Plasmon Resonance. Potential qualitative and semi-quantitative s…

Time-monitoring sensor based on oxygen diffusion in an indicator/polymer matrix

2013

Abstract A time-monitoring sensor based on the oxidation of leuco methylene blue (LMB) to methylene blue (MB) was developed. The sensor changes its color from yellow to green in the presence of oxygen and was integrated into a poly(vinyl alcohol) matrix. The diffusion of the oxygen in the polymer matrix as well as the oxygen uptake due to the oxidation reaction determines the time monitoring of the sensor. A physical model has been developed that accounts for both the diffusion as well as the oxidation reaction. For this purpose, the reaction kinetics was determined experimentally. Moreover, the diffusion coefficient of oxygen was determined and concentration profiles in the polymer matrix …

Phase separation of flowing polymer solutions studied by viscosity and by turbidity

1980

Kinetics in a Double Antibody Radioimmunoassay (RIA): Diffussion Control

2012

Competitive protein binding radioimmunoassay (CPB-RIA) is a principal method for quantifying serum C Peptide concentration. The accuracy of this method is critically dependent on factors that influence the reaction between anti-C Peptide antibody (P) with 125I-C Peptide (M). We studied the influence of initial concentration of M, ionic strength, and viscosity on the reaction between M and P. A kinetic model for the the reaction between. Such model adjusts satisfac- torily to the results. Bi-exponential and irreversible kinetics is determined. The results of the viscosity analysis show clear negative influence on the direct reaction rate. The ionic strength shows scarce influence on equilibr…

Yeast interaction on Chardonnay wine composition: Impact of strain and inoculation time.

2022

Abstract It is of great importance to understand the molecular characteristics and substantial chemical transformations due to yeast-yeast interaction. Non-targeted metabolomics was used to unravel must in fermentation composition, inoculated with non-Saccharomyces (NS) yeasts and Saccharomyces cerevisiae (S) for sequential fermentation. ultrahigh-resolution mass spectrometry was able to distinguish thousands of metabolites and provides deep insights into grape must composition allowing better understanding of the yeast-yeast interactome. The dominance of S, characterized by a metabolic richness not found with NS, is dependent on inoculation time and on the yeast species present. Co-inocula…

Monoterpenes in grape juice and wines.

2000

The importance of monoterpenes on varietal flavour of wines has been reviewed. These compounds were mainly found linked to sugar moieties in the grape juice and wines, showing no olfactive characteristics. In this way, mechanisms to liberate terpenes were studied, making a comparative study between acidic and enzymic hydrolysis of terpene glycosides. Finally, analytical techniques developed to study these compounds, in both free or glycosidically forms, and also to fractionate glycosidic precursors, have been discussed.

Influence of polysaccharides on wine protein aggregation.

2016

Abstract Polysaccharides are the major high-molecular weight components of wines. In contrast, proteins occur only in small amounts in wine, but contribute to haze formation. The detailed mechanism of aggregation of these proteins, especially in combination with other wine components, remains unclear. This study demonstrates the different aggregation behavior between a buffer and a model wine system by dynamic light scattering. Arabinogalactan-protein, for example, shows an increased aggregation in the model wine system, while in the buffer system a reducing effect is observed. Thus, we could show the importance to examine the behavior of wine additives under conditions close to reality, in…

LARGE DEFORMATION CREEP BEHAVIOR OF A SOLID POLYMER.

1981

Abstract The effect of loading rate and strain on the creep behavior after sample yielding has been studied in previous communications (14–15) for Mylar in tension and for Lexan in compression. In this work the creep behavior of Lexan samples previously elongated is considered both in tension and in compression. A procedure which collects all the data independently of both loading rate and initial creep strain is proposed.

New insights for materials science characterisation using different complementary techniques combined with X-ray absorption Spectroscopy

2005

The combination of x-ray absorption spectroscopy (XAS) with UV-Vis and Raman spectroscopies or with Differential Scanning Calorimetry (DSC) has been recently carried out on the D44 beamline of DCI-LURE. The different set-ups used to perform such combinations are described and examples of combined investigations belonging to different field of materials science (coordination chemistry, sol-gel and catalysis) are presented.

Über eine Beziehung zwischen Verdünnunasentropie und Verdünnungsenthalpie in Lösungen von Polystyrol und Polymethylmethacrylat

1973

Durch Lichtstreuungsmessungen wurde der Entropieanteil und der Enthalpieanteil des 2. osmotischen Virialkoeffizienten (A2) von athermischen und exothermischen Losungen von Polystyrol (PS) und Polymethylmethacrylat (PMMA) bei 25°C und Normaldruck bestimmt. Zur Auffindung von athermischen und exothermischen Losungsmitteln fur diese Polymeren wurde die Temperaturabhangigkeit des STAUDINGERindex verwendet. Die ermittelten thermodynamischen Grosen A2, A2,S und A2,H ergeben zusammen mit fruheren Messungen eine beziehung, die nahezu unabhangig vom speziellen System ist. The second osmotic virial coefficient A2 and its entropic and enthalpic parts of athermal and exothermal solutions of polystyrene…