Convergence of the Finite Difference Scheme for a Fast Diffusion Equation in Porous Media

We are concerned with an implicit scheme for the finite difference solution to a nonlinear parabolic equation with a multivalued coefficient that describes the fast diffusion in a porous medium. The boundary conditions contain the multivalued function as well. We prove the stability and the convergence of the scheme, emphasizing the precise nature of convergence in this specific case, and compute the error level of the approximating solution. The method is aimed to simplify the numerical computations for the solutions to equations of this type, without performing an approximation of the multivalued function. The theory is illustrated by numerical results.     

Stroboscopic microscopy—direct imaging of structure development and phase separation during spin‐coating

Spin‐coated polymer blends possess a rich variety of accessible non‐equilibrium morphologies, formed through a process of phase separation and self‐assembly, the complexities of which remain incompletely understood. The technique of stroboscopic microscopy has now been developed to allow direct observations of microscopic and mesoscopic morphological development during spin‐coating and has afforded unequivocal information regarding morphological development. The technique so far has three modes of operation providing information on topographical, compositional, and crystal development. In this review, we look at the technique's development, its applications and comment on the future potential for this technique. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 17–25     

How do we know who to include in collaborative research? Toward a method for the identification of experts

Collaborative research, defined as research involving actors participating in the problem situation under study, has an important role in operational research, strategic management and systems thinking. In a recent study, we found that a strong organizational focus incorporated into many soft operational research (OR) approaches is inadequate for studying societal problem situations, which are fragmented and have no clear boundary. Specifically, we failed to find a process of identifying individuals that is capable of representing the perspectives of actors and sufficient for research into societal problem situations. We found no clear terminology accounting for ontological differences between actors, individuals representing them and conceptual representations of acting entities. In response to this gap in the literature, we propose terminology that differentiates among actors (individuals or collective entities in the real world), experts (individuals capable of representing the perspective of an actor) and agents (ideal-typical representations of actors). Based on this terminology, we propose an iterative method to guide the assembly of an expert group to undertake collaborative research into societal problem situations. To demonstrate the application of our method, we present selected insights from our study in an electronic supplement.     

Sources and Time-Variations of Reactive Hydrocarbon Immissions in the Atmosphere of Different Industrial and Rural Areas

Abstract

The problem of determining the concentration changes of reactive hydrocarbon immissions as a function of time was solved by means of an automatic gas chromatograph which, without enrichment, could record ethylene and acetylene in ppb concentrations. At the same time various other pollutants were covered, so that by a mutual allocation of the individual components it was possible to identify certain emitter groups. The results clearly show that ethylene and acetylene primarily originate from the combustion processes of the automobiles, while the handling and storage of petroleum products and their processing do not exert any influence on the immission of the two components. By way of time series measurements during a summer week in 1976 with very intensive solar radiation it was possible to show indirect secondary photochemical reactions.     

In vitro metabolism study of Strychnos alkaloids using high‐performance liquid chromatography combined with hybrid ion trap/time‐of‐flight mass spectrometry

In this report, the in vitro metabolism of Strychnos alkaloids was investigated using liquid chromatography/high‐resolution mass spectrometry for the first time. Strychnine and brucine were selected as model compounds to determine the universal biotransformations of the Strychnos alkaloids in rat liver microsomes. The incubation mixtures were separated by a bidentate‐C₁₈ column, and then analyzed by on‐line ion trap/time‐of‐flight mass spectrometry. With the assistance of mass defect filtering technique, full‐scan accurate mass datasets were processed for the discovery of the related metabolites. The structural elucidations of these metabolites were achieved by comparing the changes in accurate molecular masses, calculating chemical component using Formula Predictor software and defining sites of biotransformation based upon accurate MSⁿ spectral information. As a result, 31 metabolites were identified, of which 26 metabolites were reported for the first time. These biotransformations included hydroxylation, N‐oxidation, epoxidation, methylation, dehydrogenation, de‐methoxylation, O‐demethylation, as well as hydrolysis reactions. Copyright © 2013 John Wiley & Sons, Ltd.     

Robustness of Pathwise Stability of Semilinear Perturbed Stochastic Evolution Equations

Abstract

The purpose of this paper is to investigate pathwise stability for certain Hilbert space-valued stochastic evolution equations. We are especially interested in the robustness analysis of perturbed stochastic differential equations in infinite dimensions. Sufficient conditions are established to ensure the almost surely stable decay of the given stochastic systems. Lastly, a corollary and corresponding example are studied to illustrate our theory.     

In vivo metabolism study of bergenin in rats by HPLC‐QTOF mass spectrometry

Bergenin is the major component of Ardisia creanta sims and Rodgersia sambucifolia hemsl with many biological activities. Although bergenin has been used to treat human diseases in China for man years, there is no report regarding its metabolism. This is the first report to separate and identify the metabolites of bergenin in vivo. In the study, HPLC/Q‐TOF‐MS/MS was used to investigate the metabolites of bergenin in vivo by analyzing the rat body fluid and feces samples. Three metabolites of bergenin were finally identified by the TIC chromatograms, and the structures were also confirmed by their MS² spectra. Copyright © 2013 John Wiley & Sons, Ltd.     

Evaluation of calcipotriol transdermal permeation through pig,rat and mouse skin using liquid chromatography–tandem mass spectrometry

A rapid and sensitive liquid chromatography–tandem mass spectrometric method to evaluate the permeation and retention of calcipotriol in excised samples of pig, rat and mouse skin after application of a calcipotriol ointment has been developed and validated. After sample preparation of ointment, skin homogenate and receptor medium by liquid–liquid extraction, chromatography was performed on an Extend‐C₁₈ column using isocratic elution. Detection was by electrospray ionization in the negative ion mode using multiple‐reaction monitoring of the precursor to product ion transitions of calcipotriol at m/z 411.1 → 393.5, and of lovastatin (internal standard) at m/z 403.2 → 101.2. The assay was linear in all matrices with LLOQs of 1, 0.5 and 40 ng/mL for skin homogenate, receptor medium and ointment samples respectively. In terms of the permeation profiles, it was found that calcipotriol permeated through all skins to only a limited extent over 20 h after application but was efficiently retained in all skins at a level at 20 h of between 40% (pig) and 60% (rat and mouse) of the applied dose. This indicates that calcipotriol ointment has the potential to provide sustained therapeutic benefit in the treatment of psoriasis with minimal systemic side effects. Copyright © 2013 John Wiley & Sons, Ltd.     

LOW OXIDATION STATE GROUP 15 ELEMENTS AS PNICTA-WITTIG REAGENTS

We have synthesized a new As(I) salt and performed a Density Functional Theory investigation into the use of such compounds as pnicta-Wittig reagents.     

Erosion of Thin Foils by Sputtering in Hollow Cathodes

A thin copper foil placed diagonally in a cylindrical copper hollow cathode undergoes fast erosion caused by cathode sputtering. Changes in the foil shape are related to current distribution along the hollow cathode axis. The experimental results aid in understanding the increase in spectral lines intensities emitted from conical bottom hollow cathode lamps.