Preparation of Glycosyltriazenes

O‐Unprotected glycosyltriazenes are prepared for the first time by coupling of 1‐anthraquinone‐1‐diazonium hydrogensulfate with β‐glycopyranosylamines to afford 1‐ (anthraquinone‐1‐yl)‐3‐( β‐glycopyranosyl)triazenes 3a—h . Acetylation of compounds 3 furnished the O‐acetates 4a—g . The stability of triazenes 3 results from fixation of the NH proton in an intramolecular hydrogen bond to one of the anthraquinone carbonyl oxgen atoms. Treatment of triazenes 4 with tert‐butyl hypochlorite afforded acetoglycosyl chlorides 6 and 1‐azidoanthraquinone 7 . With acetic acid the triazene 4a formed tetra‐O‐acetyl‐D‐xylopyranose 9 together with 1‐ aminoanthraquinone 10 .     

Synthesis,Inhibition Potency,Binding Mode,and Antiprotozoal Activities of Fluorescent Inhibitors of Trypanothione Reductase Based on Mepacrine‐Conjugated Diaryl Sulfide Scaffolds

Trypanothione reductase (TR) is a flavoenzyme unique to trypanosomatid parasites and a target for lead discovery programs. Various inhibitor scaffolds have emerged in the past, exhibiting moderate affinity for the parasite enzyme. Herein we show that the combination of two structural motifs of known TR inhibitors — diaryl sulfides and mepacrine — enables the simultaneous addressing of two hydrophobic patches in the active site. The binding efficacy of these conjugates is enhanced over that of the respective parent inhibitors. They show K_ic values for the parasite enzyme down to 0.9±0.1 μm and exhibit high selectivity for TR over human glutathione reductase (GR). Despite their considerable molecular mass and in some cases permanent positive charges, in vitro studies revealed IC₅₀ values in the low micromolar to sub‐micromolar range against Trypanosoma brucei rhodesiense and Trypanosoma cruzi, as well as the malaria parasite Plasmodium falciparum, which lack trypanothione metabolism. The inhibitors exhibit strong fluorescence due to their aminoacridine moiety. This feature allows visualization of the drugs in the parasite where high accumulation was observed by fluorescence microscopy even after short exposure times.     

Decomposition of Bt and Non-Bt Corn Hybrid Residues in the Field

Results of a previous laboratory study indicated that six transgenic crops expressing the Cry1Ab insecticidal protein from Bacillus thuringiensis (Bt) decomposed at a slower rate than their respective non-Bt isolines. Consequently, litter decomposition rates, nitrogen cycling, and carbon pools may change in agricultural systems as the result of the widespread use of Bt crops. In this study, we assessed the decomposition rates and chemical composition of commonly grown hybrids of Bt and non-Bt isolines of corn (Zea mays L.) in the field. Leaves, stalks, and cobs from two Bt corn hybrids (Pioneer 34N44 Bt and NC+ 4990 Bt) and their non-Bt isolines (Pioneer 34N43 and NC+ 4880) were analyzed for biomass fractions (soluble, hemicellulose, cellulose, and lignin) and total C and N content. Litterbags containing these residues were buried at a depth of 10 cm in a Holdrege silt loam (fine-silty, mixed, mesic Typic Argiustolls) soil and recovered 5, 11, 17, and 23 months after placement in the field. There were no differences in the rates of decomposition and mass of C remaining over time between the Bt and non-Bt corn residues. Plant parts differed in decomposition rates where leaves > stalks > cobs. There were differences in total C, total N, biomass fractions, and C:N ratios between initial Bt and non-Bt corn residues, and between companies (NC+ and Pioneer), however, these differences did not result in differences in their rates of decomposition or mass of C remaining over time. For each plant part, there were no differences in lignin content between the Bt and non-Bt residues. These data suggest that the Bt and non-Bt corn hybrids used in this study should not cause differences in carbon sequestration when their residues decompose under similar environmental conditions.     

Efficient and damage-free ultrashort pulsed laser cutting of polymer intraocular lens implants

Ophthalmic intraocular lenses are conventionally machined by diamond tools. A promising alternative approach is contour cutting by ultrashort pulsed laser micromachining. To improve process knowledge, a parametric study of picosecond and femtosecond laser machining of medical grade hydrophilic copolymers and PMMA is carried out. Material removal rates and machining quality with respect to main process parameters are determined. Reasons for chipping and formation of heat affected zones are identified and an optimized process strategy is derived. By choosing a defined pulse overlap, heat accumulation is kept minimal while increasing absorptivity through incubation avoids chipping.     

Improving the thickness accuracy of cold rolled narrow strip by piezoelectric roll gap control at high rolling speed

Particularly in fast rolling mills, conventional actuators reach their dynamic limits, when longitudinal thickness variations of the incoming strip shall be reduced with high accuracy by model-predictive roll gap control. Accordingly, the applicability of highly dynamic piezoelectric actuators in combination with electromechanical spindles and a high frequency precision measurement of the thickness in front of the roll gap was examined. Rolling tests in a cold rolling mill for narrow slit strips show that this novel concept is suitable to provide the required dynamic actuation especially at high rolling speed.     

A cutting force model for finishing processes using helical end mills with significant runout

Analytical cutting force models play an important role in a wide array of simulation approaches of milling processes. The accuracy of the simulated processes directly depends on the predictive power of the applied cutting force model, which may vary under specific circumstances. End milling processes with small radial cutting depths, e.g. finishing processes, are particularly problematic. In this case, the tool runout, which is usually neglected in established cutting force models, can become quite significant. Within this article, well-known cutting force models are implemented for runout-prone finishing processes and modified by integrating additional parameters. A method is presented for how these additional runout parameters can be efficiently determined alongside commonly used cutting coefficients. For this purpose, a large number of milling experiments have been performed where the cutting forces were directly measured using a stationary dynamometer. The measured cutting forces were compared with the simulated cutting forces to verify and assess the modified model. By using the presented model and calibration method, cutting forces can be accurately predicted even for small radial cutting depths and significant tool runout.     

Solid-state reactions during high-energy milling of mixed powders

The phase formation of carbides and borides during high-energy ball milling has been investigated by measuring the gas temperature inside the vial and by X-ray diffraction studies of specimens taken at different stages of the milling process. The formation mechanism changes from a gradual process to an instantaneous, explosion-like reaction with increasing milling intensity and enthalpy of product formation. Finally, a model was developed to describe the milling process, and to determine the peak temperatures that are reached in the powder particles during ball collisions as well as the microstructure evolution. Using an effective coefficient of diffusion and calculating the evolution of the continuously growing diffusion layer, it was possible to determine whether and when rapid phase formation occurs. The model was tested by reproducing the milling times needed for rapid phase formation inside the mill.     

Model-based analysis of effects from large-scale wind power production

For an economically and ecologically optimised integration of fluctuating renewable power generation (especially wind power) into electricity generation, a detailed consideration of fluctuation-induced effects on the existing power system is essential. A model-based approach is introduced in this paper, which comprehensively analyses the impact of such effects on power plant scheduling and facilitates their integration into the development of strategies for an optimised evolution of the future power system structure. The newly developed Aeolius tool for the simulation of power plant scheduling is described. In a combined analysis of long- and short-term effects it is used together with the multi-periodic cost-optimising energy system model PERSEUS-CERT. Based on the Matlab/Simulink^® package, Aeolius considers the challenges for plant scheduling down to a time scale of 10 min. Special attention is paid to the provision of stand-by capacities and control power, as well as intermediate storage. Thus, a sophisticated quantification of the actual (net) benefits of wind power feed-in is achieved. Model results for Germany show that wind mainly substitutes power from intermediate-load and base-load plants (coal-, lignite-, and nuclear-fired). However, the required provision of stand-by capacities and control power does not only limit the substitution of conventional capacities, but also the achievable net savings of fuel and emissions in conventional power generation.