Interval methods as a simulation tool for the dynamics of biological wastewater treatment processes with parameter uncertainties

This paper presents sophisticated interval algorithms for the simulation of discrete-time dynamical systems with bounded uncertainties of both initial conditions and system parameters. Since naive implementations of interval algorithms might lead to guaranteed enclosures of all system states which are too conservative to be practically useful, we present algorithmic extensions of classical approaches which are applicable to the simulation of non-cooperative systems with time-varying uncertain parameters. Overestimation arising in the interval evaluation of dynamical system models due to the wrapping effect is reduced by an exact pseudo-linear transformation of nonlinear state equations and by new heuristics for the subdivision of interval enclosures which especially prefer splitting of unstable intervals. To highlight the typical procedure for parameterization of interval-based simulation routines and to demonstrate their efficiency, a nonlinear model of biological wastewater treatment processes is discussed. For this application, we consider the maximum specific growth rate of substrate consuming bacteria as a time-varying uncertain parameter. Only worst-case bounds are assumed to be available for the range of this parameter while no information is provided about its actual variation rate.     

Synthesis and Characterization of Benzonitrile-Substituted Silyl Ethers

The silyl ethers (siloxanes) Me_{4? x}Si(OC₆H₅CN)_x (x = 1–4) (1–4), O(Si(OC₆H₄CN) (Me)₂)₂ (5), and Me₃Si–O–C₆F₄CN (6) have been synthesized by the reaction of the respective p-hydroxybenzonitriles and chlorosilanes in the presence of N,N,N′,N′-tetramethylethylenediamine (TMEDA) as hydrogen chloride acceptor. All compounds have been fully characterized by CHN-analysis, melting point, IR, Raman, mass spectroscopy, and ¹H, ¹³C, ²⁹Si NMR spectroscopy. Furthermore, the crystal structures of these compounds—with the exception of Me₂Si(OC₆H₅CN)₂, which is a liquid—were determined by X-ray diffractometry.     

New Trioxane Copolymers

Abstract

A review is given on two types of trioxane copolymers: trioxane/dioxolane copolymers and copolymers of trioxane with polar monomers. It has been possible to find reaction conditions that influence the transacetalization reaction and, hence, the molecular weight distribution and the sequence length of trioxane/dioxolane copolymers. Trioxane copolymers with varying dioxolane content show an unusual behavior with respect to density, specific volume, and melting point as a function of composition. This is possibly caused by the formation of at least four different crystal structures in such copolymers. The synthesis of polyoxymethylenes carrying reactive groups is possible by copolymerizing trioxane with substituted phenylglycidyl ethers. These copolymers can be subjected to further chemical modification leading to poly-oxymethylenes with aldehyde, carboxy, and amino groups or derivatives thereof.     

Chlorine‐Enhanced Surface Mobility of Au(100)

Motivated by experimental studies of two‐dimensional Ostwald ripening on Au(100) electrodes in chlorine‐containing electrolytes, we have studied diffusion processes using density functional theory. We find that chlorine has a propensity to temporary form AuCl complexes, which diffuse significantly faster than gold adatoms. With and without chlorine, the lowest activation energy is found for the exchange mechanism. Chlorine furthermore reduces the activation energy for the detachment from kink sites. Kinetic Monte Carlo simulations were performed on the basis of extensive density functional theory calculations. The island‐decay rate obtained from these Monte Carlo simulations, as well as the decay rate obtained from the theoretical activation energies and frequency factors when inserted into analytical solutions for Ostwald ripening, are in agreement with experimental island‐decay rates in chlorine‐containing electrolytes.     

Improved chemical composition separation of ethylene–propylene random copolymers by high-temperature solvent gradient interaction chromatography

High-temperature solvent gradient interaction chromatography (HT-SGIC) is a fast and efficient fractionation technique for the chemical composition analysis of olefin copolymers. The separation of ethylene–propylene random copolymers (EPRs) was achieved on a graphitic stationary phase, Hypercarb, at 160 °C by using linear solvent gradient elution from 1-decanol to 1,2,4-trichlorobenzene (TCB). In the present work, the solvent gradient profile was modified to improve the chromatographic separation of EPRs. With the aim to obtain a better resolution in separation, a slow increase in the volume fraction of TCB was applied. This allowed for a relatively large retention region for linear polyethylene (PE) chains on the column; thereby, a broader elution volume zone between the start of the gradient and the PE elution was achieved. The efficiency of this new gradient profile was demonstrated by analysing two fully amorphous EPR samples. Clear differences in the chemical composition of these EPR samples with similar ethylene contents have been proven by using this modified solvent gradient. The comprehensive chemical composition and microstructure analysis of the SGIC-separated fractions by FTIR revealed that ethylene/propylene (EP) copolymer chains were eluted according to their ethylene/propylene contents and E or P sequence lengths, even though they are distributed in a random manner. These results showed that the solvent composition is an important factor to affect the interactive adsorption or desorption behaviour of EP chains on Hypercarb. In this way, for the first time, the determination of the complex composition and chain structure of EPR samples was achieved within short analysis time, which is not possible till now using other fractionation techniques reported.

An improved SPE method for fractionation and identification of phospholipids

This work reports an efficient and universal SPE method developed for separation and identification of phospholipids derived from complex biological samples. For the separation step, sequential combination of silica gel‐aminopropyl‐silica gel SPE cartridges is applied. This setup enables separation of phosphatidylcholine, lysophosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, phosphatidic acid, phosphatidylinositol, phosphatidylserine, cardiolipin, and sphingomyelin into four fractions according to the polarity of their headgroups. Sample acquisition of the SPE fractions is performed by a high‐resolution LC‐MS system consisting of a hybrid linear IT Fourier transform ion cyclotron resonance mass spectrometer coupled to RP‐HPLC. The unequivocal advantage of our SPE sample preparation setup is avoidance of analyte peak overlapping in the determination step done by RP‐HPLC. Overlapping phospholipid signals would otherwise exert adverse ion suppression effects. An additional benefit of this method is the elimination of polar and nonpolar (e.g. neutral lipids) contaminants from the phospholipid fractions, which highly reduces contamination of the LC‐MS system. The method was validated with fermentation samples of organic waste, where 78 distinct phospholipid and sphingomyelin species belonging to six lipid classes were successfully identified.     

Asymmetrical flow field-flow fractionation as a novel technique for the analysis of PS-b-PI copolymers

Asymmetrical flow field-flow fractionation (AF4) was used as a fractionation technique to investigate the molecular heterogeneity of poly(styrene-b-isoprene) diblock copolymers synthesized by either sequential living anionic polymerization or coupling of living precursor blocks. AF4 coupled to multi-angle laser light scattering (MALLS), refractive index (RI), and ultraviolet (UV) detectors was used to separate the diblock copolymers from the homopolymers and coupling products, and the molar masses of the different components were analyzed. In order to get more information about the separated block copolymers, homopolymers, and coupling products, fractions were collected directly after the AF4 channel. The collected fractions were analyzed offline by ¹H NMR to provide identification of the different species and additional information on the true chemical composition, and the microstructure of the diblock copolymer was obtained.

Synthesis of a Bicyclic Diamine Derived from Kemp's Acid

A bicyclic diamine with defined and stable conformation in solution was prepared from Kemp's triacid. The efficient four-step synthesis of the Boc-protected diamine requires only a single purification by column chromatography. X-ray analysis and NMR spectroscopy confirm the structure of the diamine in the solid state and in solution.     

Polyelectrolyte–protein interaction at low ionic strength: required chain flexibility depending on protein average charge

The effect of low ionic strength leading to reduced polyelectrolyte–protein interactions has been shown by in silico and in vitro experiments, suggesting polyelectrolyte rigidity increasing at low ionic strength, thus leading to reduced interactions with proteins. This contribution elucidates polyelectrolyte–protein precipitation in the 0–2.6-mS?cm^?1 ionic strength regime with polyelectrolyte rigidity determinations, using viscosimetry at these conditions, also considering protein charge distributions, using different proteins. Precipitation yields increased from 5 to 40 % at low ionic strength to up to 90 % at intermediate ionic strength, depending on protein and polyelectrolyte type, using lysozyme and three different monoclonal antibodies. Comparing precipitation behavior of the monoclonal antibodies, a qualitative correlation between required polyelectrolyte flexibility to enhance protein precipitation and protein average charge as well as hydrophobicity of the antibodies was discovered. Antibodies with lower average charge and less hydrophobicity required more flexible polyelectrolytes to enhance precipitation behavior by allowing interaction of the polyelectrolytes with proteins, attaching to positively charged protein patches while “circumnavigating” negatively charged protein areas. In contrast, antibodies with higher protein average charge showed increasing precipitation yields up to 90 % already at lower ionic strength, associated with then more rigid polyelectrolyte structures. Therefore, designing polyelectrolytes with specific chain flexibility could help to improve precipitation behavior toward specific target proteins in polyelectrolyte-driven purification techniques.