Dislocation modeling of quasi-static crack propagation in an elasto-plastic medium

A dislocation model for simulating two-dimensional quasi-static crack propagation is presented. The crack and plastic flow along slip planes are described using dislocation dipoles. A stationary crack can be modeled as well as a propagating crack along a straight line inclined at an arbitrary angle to a free surface of a semi-infinite medium. Cracks are also allowed to kink. A superdipole algorithm is introduced to save simulation time without loosing important information and necessary geometric details. It reduces the number of dislocation dipoles on slip planes in the plastic wake. The paper gives results on crack shapes for stationary and advancing cracks as well as it describes how the size of the plastic zone depends on crack inclination angles. Results on stress intensity factors (SIF) are given using two different approaches as well as kinking cracks are introduced and SIF at kinked crack tips are calculated.     

A simplified linear iterative predictive functional control approach for chamber pressure of industrial coke furnace

This paper describes the application of a linear iterative design of nonlinear predictive functional control for chamber pressure of industrial coke furnace. The control target is to maintain the chamber pressure of a coke furnace within a set range while rejecting the effect of disturbances (mainly the coke removing process and the switch of coke towers).The proposed control is easy to implement, as it selects a simple structure and a linear iterative approach instead of nonlinear control schemes to improve control performance in such a way that results compared with traditional PID controllers are improved. Application of industrial plant demonstrates the efficiency of the method.     

Reduction of nitroaromatic compounds by Fe(II) species associated with iron-rich smectites

Reductive transformation reactions involving mineral-bound Fe2+ species are of great relevance for the fate of groundwater contaminants. For clay minerals, which are ubiquitously present in soils and sediments, the factors determining the reactivity of structural Fe2+ and surface-bound Fe2+ are not well understood. We investigated the reactivity and availability of Fe2+ species in suspensions of chemically reduced montmorillonite (SAz-1) as well as in suspensions of oxidized and reduced nontronite (SWa-1, ferruginous smectite) using two acetylnitrobenzene isomers as reactive probe compounds. The analyses of the reduction kinetics of the two nitroaromatic compounds (NACs) suggested that Fe2+ bound in the octahedral layer of reduced smectites is the predominant reductant and that electron transfer presumably occurs via basal siloxane planes. In contrast, reduction of NACs by Fe2+ associated with oxidized nontronite is orders of magnitude slower than reduction by octahedral Fe2+. Reductive transformation and reversible, nonreactive electron donor-acceptor (EDA) complexation of NACs at basal smectite surfaces occur simultaneously at reduced montmorillonite exhibiting low structural iron content. In contrast, EDA complexation was not observed in suspensions of reduced iron-rich nontronite. Due to the similar reduction rate constants measured for the two NACs, we propose that the (re)- generation of octahedral Fe2+ sites, e.g., by electron transfer and/or Fe rearrangement within the octahedral nontronite layers, partly limited the rate of contaminant transformation. Since iron in clay minerals is available for microbial reduction, our study suggests that octahedral Fe2+ can contribute to abiotic contaminant transformation in anoxic environments.     

Determination of fractional synthesis rates of mouse hepatic proteins via metabolic 13C-labeling, MALDI-TOF MS and analysis of relative isotopologue abundances using average masses

Proteins of a liver extract taken from a metabolically (13)C-labeled mouse were separated by 2D-PAGE and identified after tryptic digestion by MALDI-TOF MS peptide mass fingerprinting. (13)C-Labeling of proteins was achieved by an infusion of U-(13)C-glucose, which is metabolized to labeled nonessential amino acids. The labeling was analyzed using the relative isotopologue abundances of the measured isotope pattern of tryptic peptides and quantified by their increase in the average molecular mass (DeltaAVM). Fractional synthesis rates (FSR) of proteins were determined from corresponding peptides using measured DeltaAVM values as well as DeltaAVM values deduced from tRNA-precursor amino acid labeling, which in turn was derived from proteins showing high (13)C enrichments. The 8-h FSR values of 43 proteins were determined to range from 0 +/- 0.6 to 95 +/- 1%/8 h, with typical errors given as SEM values, which depend on the number of peptides of a specific protein usable for calculation. The method demonstrates that FSR values as an indicator for protein turnover in the liver proteome can be estimated within narrow error margins, providing baseline values from which treatment-dependent deviations could be detected with high statistical certainty.     

Cell function in the bovine mammary gland: a preliminary study on interdependence of healthy and infected udder quarters

Udder defence mechanisms are not completely explained by current mastitis research. The anatomical construction of the udder implies that infection of one udder quarter does not influence the immune status of neighbouring quarters. To test this hypothesis, we compared the immune reactions of individual udder quarters in response to microbial attacks. In the course of immune reactions, polymorphonuclear leucocytes (PMN) release oxygen radicals, which can be determined by chemiluminescence (CL). Milk from 140 udder quarters of 36 cows was analysed for somatic cell count (SCC), differential cell count, viability and CL activity. Quarters with an SCC < 100,000 cells/ml and free of pathogens were defined as uninfected, all other quarters were categorized as infected. Three groups of cows were classified cytologically: group A (healthy, 11 animals, SCC limit < 100,000 cells/ml); group B (moderate mastitis, 8 cows, SCC > or = 100,000 and < 400,000 cells/ml in at least one quarter); and group C (severe mastitis, 17 cows, SCC > or = 400,000 cells/ml in at least one quarter). Infected and uninfected quarters in groups B and C were analysed separately. Viability of PMN leucocytes was significantly (P=0.0012) lower in group A (72.6%) than in healthy quarters of group C (84.0%). Lowering the SCC limit of healthy quarters to <50,000 cells/ml (group A: all quarters within the udder) revealed striking differences between samples of groups B and C: in addition to varying differential cell counts and viabilities, CL activity of group B<50 (2929 CL units/million PMN) was markedly lower than that of the other groups (5616 in group A<50 and 6445 CL units/million PMN in group C<50). These results allow the conclusion that the infection of one udder quarter influences the cell activity of neighbouring quarters. When the SCC threshold for healthy quarters was reduced to 50,000 cells/ml, greater differences in cell activities were detected between healthy udders and healthy quarters of infected udders.     

Synthesis and X-ray Crystal Structures of New Tetrahedral Arylethynyl Substituted Silanes

The tetrakis(arylethynyl)silanes 1–4 of which 2–4 are new compounds have been synthesized and determined by single crystal structure analysis to show their tetrahedral molecular geometries reflected in slightly disturbed S₄ symmetry in the crystal lattices. The lattice structures are mainly determined by close packing effects while the interactions of π-stacking type or C–H···π contacts are rather secondary. A similar behaviour is found for the crystal structure of the comparative compound 5 with reference to 4 which lacks the ethynylene units. It is demonstrated that the given molecular constructions are distinguished by a high degree of tetrahedral persistency governing the packing structures.     

Partially decoupled approach of extended non-minimal state space predictive functional control for MIMO processes

This paper presents a partially decoupled design of the state space predictive functional control for MIMO processes. The multivariable process is first treated into MISO process by a simple Cramer's rule solution to linear equations which provides a balance between model complexity and control system design, and then the derived MISO process based extended state space predictive functional control is presented. The overall design of the controller enables the controller to consider both the process state dynamics and the output dynamics, thus improved control performance for tracking set-points and disturbance rejection is resulted. The proposed controller is tested on both model match and model mismatch cases to demonstrate its superiority. In addition, a closed-form of transfer function representation that facilitates frequency analysis of the control system is provided to give further insight into the proposed method.     

Diamond Nanoparticles: Jewels for Chemistry and Physics

Nanodiamond materials have become broadly available. Their synthesis is usually carried out by explosion or shock wave methods. They exhibit a unique surface structure and can be functionalized in various ways. This opens a broad range of applications in composites, biological systems, electronics, and surface technology.     

Zwitterion‐Functionalized Detonation Nanodiamond with Superior Protein Repulsion and Colloidal Stability in Physiological Media

Nanodiamond (ND) is a versatile and promising material for bioapplications. Despite many efforts, agglomeration of nanodiamond and the nonspecific adsorption of proteins on the ND surface when exposed to biofluids remains a major obstacle for biomedical applications. Here, the functionalization of detonation nanodiamond with zwitterionic moieties in combination with tetraethylene glycol (TEG) moieties immobilized by click chemistry to improve the colloidal dispersion in physiological media with strong ion background and for the simultaneous prevention of nonspecific interactions with proteins is reported. Based on five building blocks, a series of ND conjugates is synthesized and their performance is compared in biofluids, such as fetal bovine serum (FBS) and Dulbecco's modified Eagle medium (DMEM). The adsorption of proteins is investigated via dynamic light scattering (DLS) and thermogravimetric analysis. The colloidal stability is tested with DLS monitoring over prolonged periods of time in various ratios of water/FBS/DMEM and at different pH values. The results show that zwitterions efficiently promote the anti‐fouling properties, whereas the TEG linker is essential for the enhanced colloidal stability of the particles.