Vibrational analysis of H2 and D2 adsorption on Pt/SiO2

Vibrational properties of surface species formed upon H2 and D2 exposure of silica supported platinum particles have been investigated with in situ diffuse reflection infrared Fourier transform spectroscopy. Experiments have been performed at 50-250 degrees C, using different platinum loading of the samples in the absence and presence of oxygen. In addition, electronic structure calculations and vibrational analysis have been performed within the density functional theory for H adsorption on a silica cluster, (HO)3SiOSi(OH)3. The spectroscopy experiments showed reversible formation of isolated OH and OD groups on the silica surface when the samples were exposed to H2 and D2, respectively. In addition to the absorption peak corresponding to isolated OH and OD groups, an intense broad band was observed around 3270 cm(-1) (2500 cm(-1)) during H2 (D2) exposure. Supported by the calculations, this band was assigned to perturbed OH groups on the silica surface. The surface coverage of new OH groups was found to correlate to the platinum loading in the samples, indicating that the new silanol groups were formed in the vicinity of the Pt particles. In the investigated temperature interval, the formation rate of OH groups was not found to be temperature dependent.     

A Highly Asymmetric Gold(III) η3-Allyl Complex

A highly asymmetric Au^III η³-allyl complex has been generated by treating Au(η¹-allyl)Br(tpy) (tpy=2-(p-tolyl)pyridine) with AgNTf₂. The resulting η³-allyl complex has been characterized by NMR spectroscopy and X-ray crystallography. DFT calculations and variable temperature ¹H NMR suggest that the allyl ligand is highly fluxional.     

High stereoselectivity in chelation-controlled intermolecular Heck reactions with aryl chlorides, vinyl chlorides and vinyl triflates

Highly stereoselective chelation-controlled Pd(0)-catalyzed beta-arylations and beta-vinylations of a five-membered chiral, pyrrolidine-based vinyl ether were achieved using aryl- and vinyl chlorides as substrates, yielding quaternary 2-aryl/vinyl-2-methyl cyclopentanones in 89-96% ee under neutral reaction conditions.     

Convergence analysis of finite element approximations of the Joule heating problem in three spatial dimensions

In this paper we present a finite element discretization of the Joule-heating problem. We prove existence of solution to the discrete formulation and strong convergence of the finite element solution to the weak solution, up to a sub-sequence. We also present numerical examples in three spatial dimensions. The first example demonstrates the convergence of the method in the second example we consider an engineering application.     

An explicit Koppelman formula for dd c and Green currents on {mathbb {P}^n}

We compute a quite explicit Koppelman formula for dd ^c on projective space, and obtain Green currents for closed (p, p)-currents.     

Anaerobic treatment of animal byproducts from slaughterhouses at laboratory and pilot scale

Different mixtures of animal byproducts, other slaughterhouse waste (i.e., rumen, stomach and intestinal content), food waste, and liquid manure were codigested at mesophilic conditions (37°C) at laboratory and pilot scale. Animal byproducts, including blood, represent 70–80% of the total biogas potential from waste generated during slaughter of animals. The total biogas potential from waste generated during slaughter is about 1300 MJ/cattle and about 140 MI/pig. Fed-batch digestion of pasteurized (70°C, 1h) animal byproducts resulted in a fourfold increase in biogas yield (1.14L/g of volatile solids [VS]) compared with nonpasteurized animal bypproducts (0.31L/g of VS). Mixtures with animal byproducts representing 19–38% of the total dry matter were digested in continuous-flow stirred tank reactors at laboratory and pilot scale. Stable processes at organic loading rates (OLRs) exceeding 2.5g of VS/(L·d) and hydraulic retention times (HRTs) less than 40 d could be obtained with total ammonia nitrogen concentrations (NH₄−N+NH₃−N) in the range of 4.0–5.0 g/L. After operating one process for more than 1.5 yr at total ammonia nitrogen concentrations >4 g/L, an increase in OLR to 5 g of VS/(L·d) and a decrease in HRT to 22 d was possible without accumulation of volatile fatty acids.     

Influence of allyl ethers in coating resins

The effects of allyl ethers in coating resins have been studied in relations to different systems. The details that have been investigated are: the reactions between allyl ethers-styrene-cobalt salt in air, the influence of cobalt salt on oxidized allyl ethers, and the interaction between allyl ethers and maleic esters with respect to copolymerization. The curing rates of allyl functional oligomers as coatings have also been studied. The results are summarized together with the results from a previous article by the same authors to give an overall view of the curing mechanism in allyl ether functional unsaturated polyester resins dissolved in styrene.     

A self-polishing platinum ring voltammetric sensor and its application to complex media

A self-polishing voltammetric sensor was recently developed and has been applied to samples of urea, milk and sewage water. The polishing device continuously grinds a platinum ring electrode, offering a reproducible and clean electrode surface. Principal component analysis (PCA) and partial least squares (PLS) techniques were applied to interpret the data and to build prediction models. In an evaluation of samples with different urea concentrations, the grinding step allows for repeatable measurements, similar to those after electrochemical cleaning. Furthermore, for the determination of sewage water concentrations in drinking water and for the evaluation of different fat contents in milk samples, the polishing eliminates sensor drift produced by electrode fouling. The results show that the application of a self-polishing unit offers a promising tool for electrochemical studies of difficult analytes and complex media.     

Inhomogeneous biopolymer gels

The microstructure and rheological behaviour of inhomogeneous biopolymer gels was studied using a model system of β-lactoglobulin. It can form both fine-stranded and particulate gels which can be homogeneous or inhomogeneous depending on pH and heating rate. The dense and loose regions of the fine-stranded gels had different relaxation times which significantly influenced the mechanical spectrum. The particulate gels showed coarser inhomogeneities influencing the fracture properties of the gels.