Sonic spray ionization technology: performance study and application to a LC/MS analysis on a monolithic silica column for heroin impurity profiling

Sonic spray (SS) ionization is a relatively novel atmospheric pressure ionization technique for LC/MS, based on the principle of "spray ionization", which only recently became commercially available. In this paper, we evaluate the performance of this ion source as an interface for LC/MS in comparison with the more traditional and better studied pneumatically assisted electrospray or ion spray (IS). The effect of organic modifiers, volatile acids, and buffer systems in the LC eluent on the ionization efficiency of both interfaces is described and some possible explanations for the observed phenomena are highlighted. We could conclude that the presence of organic solvents gradually increased the ionization efficiency for IS and SS, while volatile acids or buffers gave a significant signal suppression. Furthermore, we present the application of the sonic spray interface to a fast LC/MS analysis, for the simultaneous determination of the seven prime opium alkaloids in heroin impurity profiling. Chromatographic separation is performed in 5 min on a monolithic silica column (Chromolith Performance) with a gradient elution system and an optimized flow of 5 mL/min. By means of a postcolumn split of approximately 1/20, a coupling between the fast LC system and the mass spectrometer is made. The method is validated and successfully applied to the analysis of real-time seized heroin street samples.     

Less Is Sometimes More: Goal Content Matters.

According to expectancy-value theories, increasing the utility value of a learning activity should result in higher motivation and better learning. In contrast, self-determination theory posits that the content of the future goals (intrinsic vs. extrinsic) that enhance the utility value of the learning activity needs to be considered as well. Contrast-cell analyses of an experimental study showed that double goal framing (intrinsic plus extrinsic) facilitated a mastery orientation, performance, and persistence and decreased a performance-approach orientation compared with extrinsic goal framing. However, double goal framing resulted in a less optimal pattern of outcomes compared with intrinsic goal framing, suggesting that the content of the provided goals matters. Goal content effects on both performance and persistence were fully mediated by mastery orientation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On efficient simulation of non-Newtonian flow in saturated porous media with a multigrid adaptive refinement solver

Flow of non-Newtonian fluid in saturated porous media can be described by the continuity equation and the generalized Darcy law. Here we discuss the efficient solution of the resulting second order nonlinear elliptic equation. The equation is discretized by the finite volume method on a cell-centered grid. Local adaptive refinement of the grid is introduced in order to reduce the number of unknowns. We develop a special implementation, that allows us to perform unstructured local refinement in conjunction with the finite volume discretization. Two residual based error indicators are exploited in the adaptive refinement criterion. Second order accurate discretization of the fluxes on the interfaces between refined and non-refined subdomains, as well as on the boundaries with Dirichlet boundary condition, are presented here as an essential part of an accurate and efficient algorithm. A nonlinear full approximation storage multigrid algorithm is developed especially for the above described composite (coarse plus locally refined) grid approach. In particular, second order approximation of the fluxes around interfaces is a result of a quadratic approximation of slave nodes in the multigrid-adaptive refinement (MG-AR) algorithm. Results from numerical solution of various academic and practice-induced problems are presented and the performance of the solver is discussed.     

Multi-variable sensitivity and identifiability analysis for a complex environmental model in view of integrated water quantity and water quality modeling

Environmental models are often over-parameterized. A sensitivity analysis can identify influential model parameters for, e.g. the parameter estimation process, model development, research prioritization and so on. This paper presents the results of an extensive study of the Latin-Hypercube-One-factor-At-a-Time (LH-OAT) procedure applied to the Soil and Water Assessment Tool (SWAT). The LH-OAT is a sensitivity analysis method that can be categorized as a screening method. The results of the sensitivity analyses for all output variables indicate that the SWAT model of the river Kleine Nete is mainly sensitive to flow related parameters. Rarely, water quality parameters get a high priority ranking. It is observed that the number of intervals used for the Latin-Hypercube sampling should be sufficiently high to achieve converged parameter rankings. Additionally, it is noted that the LH-OAT method can enhance the understanding of the model, e.g. on the use of water quality input data.     

Glass formation for iron-based alloys by combining kinetic and thermodynamic parameters

The glass formation was intensively studied for Fe-based alloys. Parameters defining kinetics and thermodynamic behavior of crystallization were calculated using calorimetric measurements and physical properties of constituent elements. It is found that the critical cooling rate R c estimated by combining kinetic and thermodynamic parameters highly correlates with measured R c found in literatures with correlation coefficient R 2 =0.944, and alloy compositions with high melting enthalpy ΔH m can easily form glass even without high undercooling and high value of the β-parameter of Turnbull’s theory, revealing that the glass formation in this group of alloys is mostly controlled by growth limitation. This combination of kinetic and thermodynamic parameters can be used to determine alloy composition with good glass forming ability in Fe-based alloys just using physical properties of alloying elements and calorimetric measurements.     

A new pH‐based procedure to model toxic effects on nitrifiers in activated sludge

A combination of a titration experiment and a biokinetic parameter estimation procedure is proposed as an experimental tool to study the kinetics of NH₄⁺‐oxidizing bacteria in activated sludge. The method was used to quantify the effect of low concentrations of a toxic compound on the maximum substrate removal capacity and the substrate affinity constant (K_NH) of NH₄⁺‐oxidizing bacteria in activated sludge samples. Experiments in the presence of increasing concentrations of a toxic compound (CN⁻, 3,5‐DCP, Cu²⁺ and phenol) were performed with nitrifying activated sludge samples obtained from two full‐scale wastewater treatment plants. The repeatability of the proposed procedure was found to be sufficient to deduce trends in the behavior of the NH₄⁺‐N‐oxidizing bacteria based on one series of experiments with increasing toxicant concentrations. The experimental results showed that the two sludge samples reacted completely differently in the presence of a certain concentration of the same toxic compound. For phenol, the shape of the titration curves did not correspond any longer to a simple Monod model. In this case, titration curves could be described by a model including both nitrification inhibition by phenol and degradation of the phenol by heterotrophic bacteria. © 1999 Society of Chemical Industry     

The phenomenology and the mathematical modeling of the silicone‐supported chemical oxidation of aqueous sulfide to elemental sulfur by ferric sulphate

When pumping a sulfide solution through a silicone cylinder immersed in a solution of ferric sulfate, a cloud of elemental sulfur is formed in the ferric sulfate if the pH of the sulfide solution is below about 8.5. The elemental sulfur subsequently sediments as orthorhombic α‐sulfur particles. H₂S(aq) diffuses through the pores of the hydrophobic silicone membrane and simultaneously reacts to become sulfur. This was confirmed by a mass balance between the amount of sulfide removed from the sulfide solution and the amount of solid product formed in the ferric solution. During the experiment, the pH of the non‐buffered sulfide solution rises up to a maximum of 8.5; this is explained by the continuous protonation of HS caused by the removal of H₂S(aq). The pH of the strongly acidic (pH 1.5) ferric sulfate solution hardly decreased. A mathematical model has been developed to quantify the phenomena related to the removal of H₂S(aq). The model has been succesfully validated with the data of batch experiments. An Arrhenius‐like relationship was found between the process temperature and the overall mass transfer coefficient K. A sulfide oxidation rate of 2.5 g S dm⁻³ day⁻¹ was predicted for a plug flow reactor. The integration of the novel process with biological sulfate reduction was studied. © 1999 Society of Chemical Industry     

Review: Treatment and reuse of wastewater from the textile wet-processing industry: Review of emerging technologies

New ecolabels for textile products and tighter restrictions on wastewater discharges are forcing textile wet processors to reuse process water and chemicals. This challenge has prompted intensive research in new advanced treatment technologies, some of which currently making their way to full-scale installations. These comprise polishing treatments such as filtration, chemical oxidation and specialized flocculation techniques and pre-treatment steps including anaerobic digestion, fixed-film bioreactors, Fenton's reagent oxidation, electrolysis, or foam flotation. Though several of these new technologies are promising in terms of cost and performance, they all suffer limitations which require further research and/or need broader validation. A segment of the research deals with the separate handling of specific sub-streams such as dyebath effluents to which membrane filtration is sometimes applied. The main limitation of this approach is the treatment of the concentrate stream. The spectrum of available technologies may, in the future, be further broadened to include fungi/H₂O₂-driven oxidation, specialized bio-sorptive processes, solvent extraction, or photocatalysis. © 1998 SCI     

Evaluation of current wet sludge disintegration techniques

The handling and processing of excess biomass produced in wastewater treatment plants is an important aspect of wastewaster treatment. Current approaches to sludge treatment include the wet destruction of the biosolids. This approach does not require preceding dewatering operations and enhances biodegradability of the sludge particles. However, high costs, corrosion problems and restricted knowledge still prevent wet sludge disintegration from realising its understanding of potential as an industrial process. This paper reviews the current state of the art and compares several wet sludge disintegration techniques, including mechanical, chemical, thermochemical, biological and oxidative treatments. © 1998 Society of Chemical Industry     

Pollution of the Rhine River: An introduction to numerical modelling

This study describes the implementation and evaluation of an effective laboratory to learn the basics of numerical modelling. This laboratory is used as an introduction to an efficient use of Computational Fluid Dynamics (CFD) tools for third year undergraduate students. The laboratory is delivered at Chimie ParisTech. The subject has been chosen on motivational, technical and pedagogical criteria and is based on the pollution of the Rhine River that occurred in 1986 after a major blaze. The model is based on a simple 1D advection-diffusion equation. The laboratory is described using Lebrun's learning model: motivation, information, activities, interactions and productions. We present the evaluation of the laboratory based on a survey including the evolution of the perceived skill level by the students.