Study of ceramic pigments based on Er2Ce2?x Mo x O7

This contribution is focused on the synthesis, characterization and optical properties of new inorganic pigments which are environment friendly and can substitute some toxic metals in interesting colour compounds. Pyrochlores belong to the group of high-temperature pigments, and are a variety of actual and potential applications for several materials. Examples include catalysts, thermal barrier coatings, solid electrolytes, nuclear waste forms and host materials for luminescence centers. The pigments were prepared by the solid state reaction and also by method of suspension mixing of materials in the series with increasing content of molybdenum. The pigments were applied into organic matrix and ceramic glaze. The colour properties of these applications were investigated depending on content of Mo, method of preparation and temperature of calcination (1350?C1550?°C after step 50?°C). The optimum conditions for their synthesis were determined. The pigments were evaluated from standpoint of their structure, colour and particle sizes. Characterization of Er₂Ce_2?x Mo _x O₇ pigments (x?=?0.1, 0.3, 0.5 and 0.7) suggests that they have a potential to be alternative yellow or orange colourants for paints, plastics, ceramics and building materials.     

Robustness in stochastic programs with risk constraints

This paper is a contribution to the robustness analysis for stochastic programs whose set of feasible solutions depends on the probability distribution?P. For various reasons, probability distribution P may not be precisely specified and we study robustness of results with respect to perturbations of?P. The main tool is the contamination technique. For the optimal value, local contamination bounds are derived and applied to robustness analysis of the optimal value of a portfolio performance under risk-shaping CVaR constraints. A?new robust portfolio efficiency test with respect to the second order stochastic dominance criterion is suggested and the contamination methodology is exploited to analyze its resistance with respect to additional scenarios.     

Approximation and contamination bounds for probabilistic programs

In many applications of manufacturing and service industries, the quality of a process is characterized by the functional relationship between a response variable and one or more explanatory variables. Profile monitoring is for checking the stability of this relationship over time. In some situations, multiple profiles are required in order to model the quality of a product or process effectively. General multivariate linear profile monitoring is particularly useful in practice due to its simplicity and flexibility. However, in such situations, the existing parametric profile monitoring methods suffer from a drawback in that when the profile parameter dimensionality is large, the detection ability of the procedures commonly used T ²-type charting statistics is likely to decline substantially. Moreover, it is also challenging to isolate the type of profile parameter change in such high-dimensional circumstances. These issues actually inherit from those of the conventional multivariate control charts. To resolve these issues, this paper develops a new methodology for monitoring general multivariate linear profiles, including the regression coefficients and profile variation. After examining the connection between the parametric profile monitoring and multivariate statistical process control, we propose to apply a variable-selection-based multivariate control scheme to the transformations of estimated profile parameters. Our proposed control chart is capable of determining the shift direction automatically based on observed profile data. Thus, it offers a balanced protection against various profile shifts. Moreover, the proposed control chart provides an easy but quite effective diagnostic aid. A real-data example from the logistics service shows that it performs quite well in the application.     

Effects of lactate and acetate on the determination of serum ethyl glucuronide by CZE

The analysis of ethyl glucuronide (EtG), a marker of recent alcohol consumption, in serum with an optimized CZE assay is reported. The method uses a 0.1-mm id fused-silica capillary of 50 cm effective length that is coated with linear polyacrylamide, a pH 4.4 nicotinic acid/epsilon-aminocaproic acid (EACA) BGE, reversed polarity and indirect analyte detection. The assay is based on a 1:1 dilution of serum with deionized water and has LODs for EtG, lactate and acetate of 3.8 x 10(-7) M, 2.60 x 10(-6 )M and 2.18 x 10(-6 )M, respectively. Separation of EtG from endogenous macro- and microcomponents (anionic serum components of high and low concentration, respectively) and its quantification are shown to be possible for a wide range of lactate (stacker) and acetate (destacker) concentrations, macrocomponents that have an impact on the CZE behavior of EtG and that change after intake of ethanol. The assay has been successfully applied to the analysis of EtG, lactate and acetate in (i) sera of volunteers that ingested known amounts of alcohol and (ii) samples of patients that were classified (teetotalers and social drinkers vs. alcohol abusers) via analysis of carbohydrate-deficient transferrin.     

ITP in dynamically double-coated fused-silica capillaries

Bidirectional ITP in fused-silica capillaries double-coated with Polybrene and poly-(vinylsulfonate) is a robust approach for analysis of low-molecular-mass compounds. EOF towards the cathode is strong (mobility >4.0 x 10(-8) m(2)/Vs) within the entire pH range investigated (2.40-8.08), dependent on ionic strength and buffer used and, at constant ionic strength, higher at alkaline pH. Electrokinetic separations and transport in such coated capillaries can be described with a dynamic computer model which permits the combined simulation of electrophoresis and electroosmosis in which the EOF is predicted either with a constant (i.e. pH- and ionic strength-independent) or a pH- and ionic strength-dependent electroosmotic mobility. Detector profiles predicted by computer simulation agree qualitatively well with bidirectional isotachopherograms that are monitored with a setup comprising two axial contactless conductivity detectors and a UV absorbance detector. The varying EOF predicted with a pH- and ionic strength-dependent electroosmotic mobility can be regarded as being realistic.     

Simultaneous determination of eight biologically active thiol compounds using gradient elution-liquid chromatography with Coul-Array detection

The most active form of sulfur in biomolecules is the thiol group, present in a number of biologically active compounds. Here we present a comprehensive study of thiol analysis using flow injection analysis/HPLC with electrochemical detection. The effect of different potentials of working electrodes, of organic solvent contents in the mobile phase, and of isocratic and gradient elution on simultaneous determination of thiol compounds (cysteine, cystine, N-acetylcysteine, homocysteine, reduced and oxidised glutathione, desglycinephytochelatin, and phytochelatins) are described and discussed. These thiol compounds were well separated and detected under optimised HPLC-electrochemical detection conditions (mobile phase: 80 mM trifluoroacetic acid and methanol with a gradient profile starting at 97:3 (TFA:methanol), kept constant for the first 8 min, then decreasing to 85:15 during one minute, kept constant for 8 min, and finally increasing linearly up to 97:3 from 17 to 18 min; the flow rate was 0.8 mL/min, column and detector temperature 25 degrees C, and the electrode potential 900 mV). We were able to determine tens of femtomoles (3 S/N) of the thiols per injection (5 microL), except for phytochelatin5 whose detection limit was 2.1 pmole. This technique was consequently used for simultaneous determination of compounds of interest in biological samples (maize tissue and human blood serum).     

A hydrophilic interaction chromatography coupled to a mass spectrometry for the determination of glutathione in plant somatic embryos

An electrospray ionization mass spectrometric (ESI-MS) determination of glutathione (GSH), a sulfur-containing tripeptide (gamma-Glu-Cys-Gly) with regulation and detoxication functions in metabolisms of most living organisms, from nanomolar to micromolar levels is described. A hydrophilic interaction chromatography (HILIC) with an isocratic elution using a mobile phase containing acetonitrile and an aqueous 0.00005% solution of trifluoroacetic acid (60/40%, v/v) was applied for the separation of GSH. The peptide detection was achieved in the presence of L-ascorbic acid which significantly enhanced the signal intensity of the molecular ion GSH [M+H]+ (m/z 308). The calibration curve was linear (R2=0.9995) in the concentration range from 2 nM to 10 microM with a detection limit (LOD, S/N=3) of 0.5 nM. The excellent detection limit, and the excellent selectivity and high reproducibility of this method enabled determination of GSH in a single plant somatic embryo of a Norway spruce (Picea abies). The average amount of GSH in the single somatic embryos (n=18) was 9 pmol per embryo. Owing to our results, it can be supposed that the proposed HILIC/ESI-MS analysis might be used for GSH determination in microscopic cell structures and in single cell analyses.     

Reactivity in radical polymerisation: An improved method for the prediction of monomer reactivity ratios and transfer constants

Half a century after the Q-e scheme was promulgated, a substantially improved method for predicting monomer reactivity ratios and transfer constants has been developed from the Patterns of Reactivity scheme. It is based on the same premise as its predecessors, that reactivity is controlled partly by thermodynamic and partly by polar factors, but the new treatment yields values much closer, on average, to the reported experimental data.