Dislocation creep controlled superplasticity in the high carbon steel 140NiCr16-6

Superplasticity in the alloyed high carbon-steel 140NiCr16-6 with phosphorus additions and a fine grained microdupiex structure – containing cementite in volume fractions of 22 % (Fe,Cr,Ni)₃C, particle size of about 1 μm and with a medium ferrite grain size of about 2 μm – has been investigated in the temperature regime of 550 to 675°C and in the strain rate range of 10^?5 to 5 · 10^?2 s^?1. Maximum strain rate exponents of m = 0,45 at 675°C with strain rates of the order of 10^?4 s^?1 have been determined. Maximum superplastic elongations of about 700 % were detected. At higher strain rates of 10^?3 s^?1 superplastic elongations of about 570 % were achieved. At relatively low test temperatures of 550°C elongations up to 230 % were recorded. The activation analysis in the temperature regime of 550 to 650°C show an activation energy for superplastic flow of 250 ± 20 kJ/mol. This is in agreement with the activation energy for lattice self diffusion of iron in α-iron. Above 650°C the activation energy decreases to 70 kJ/mol. This is due to a stress induced decrease in the eutectoid α-γ-transformation temperature from 685°C to somewhat lower temperatures during superplastic deformation. The superplastic deformability (m > 0.3) of this steel in a wide strain rate range at relatively low temperatures above 550°C allows near net shape forming of complex parts applying low flow stresses.     

Hydroxy Acid Activation in Fungal Non-Ribosomal Peptide Synthesis Assessed by Site-Directed Mutagenesis

The fungal cyclodepsipeptides (CDPs) enniatin, beauvericin, bassianolide, and PF1022 consist of alternating N-methylated l -amino and d -hydroxy acids. They are synthesized by non-ribosomal peptide synthetases (NRPS). The amino acid and hydroxy acid substrates are activated by adenylation (A) domains. Although various A domains have been characterized thus giving insights into the mechanism of substrate conversion, little is known about the utilization of hydroxy acids in NRPSs. Therefore, we used homology modelling and molecular docking of the A₁ domain of enniatin synthetase (EnSyn) to gain insights into the mechanism of hydroxy acid activation. We introduced point mutations into the active site and used a photometric assay to study the substrate activation. The results suggest that the hydroxy acid is selected by interaction with backbone carbonyls rather than by a specific side chain. These insights enhance the understanding of non-amino acid substrate activation and could contribute to the engineering of depsipeptide synthetases.     

Activation Profile of TAS2R2, the 26th Human Bitter Taste Receptor

Scope

To avoid ingestion of potentially harmful substances, humans are equipped with about 25 bitter taste receptor genes (TAS2R) expressed in oral taste cells. Humans exhibit considerable variance in their bitter tasting abilities, which are associated with genetic polymorphisms in bitter taste receptor genes. One of these variant receptor genes, TAS2R2, is initially believed to represent a pseudogene. However, TAS2R2 exists in a putative functional variant within some populations and can therefore be considered as an additional functional bitter taste receptor.

Methods and results

To learn more about the function of the experimentally neglected TAS2R2, a functional screening with 122 bitter compounds is performed. The study observes responses with eight of the 122 bitter substances and identifies the substance phenylbutazone as a unique activator of TAS2R2 among the family of TAS2Rs, thus filling one more gap in the array of cognate bitter substances.

Conclusions

The comprehensive characterization of the receptive range of TAS2R2 allows the classification into the group of TAS2Rs with a medium number of bitter agonists. The variability of bitter taste and its potential influences on food choice in some human populations may be even higher than assumed.     

Polymers containing formamidine groups

Summary Aromatic polyformamidines were synthesized by high temperature solution polycondensation of aromatic diamines with triethyl orthoformate. In order to obtain high molecular weight polymers, general investigations on the influence of reaction conditions such as reaction time, temperature and solvent were carried out on the basis of polyformamidine prepared from 4,4'-methylenedianiline. The proposed structures of aromatic polyformamidines were confirmed by elemental analysis, NMR-and IR-spectroscopy. Molecular weights were determined by ¹H NMR end group analysis. Polyformamidines having inherent viscosities of 0.25–0.36 dl/g show excellent solubility in polar solvents and in strong acids. Thermal analysis indicated that these polymers are stable up to 300°C, and a 10% weight loss were recorded on the TG curves in the temperature range of 350–366°C in nitrogen.     

Comparison of waste silica fillers modified with various proadhesive compounds

Results are presented on the improvement of the degree of surface hydrophobization of post-fluorine waste silicas. Two types of waste silica were used, representing by-products of aluminium fluoride and hydrofluoric acid production, respectively. The silicas were subjected to surface modification to obtain appropriately active fillers for the production of rubber vulcanizates and urethane elastomers. To this end, proadhesive compounds were used including surfactants, silane and titanate coupling agents, and organic compounds with oxyethylene chains. The effects of the type of proadhesive compound used and its amount on the mechanical properties of Ker 1500 butadiene-styrene rubber vulcanizates and of urethane elastomers were examined.     

Waste cement dusts as fillers for rubber compounds

The possibility of substitution of expensive active fillers, e.g. carbon black, for the waste products which can play the role of these fillers, e.g. the waste cement dusts or the waste post-HF silica, were investigated. The physico-chemical properties of the investigated waste cement dusts and the waste post-HF silica, as well as the strength properties of the rubber compounds containing these as fillers, were determined. To increase the activity and chemical affinity with the rubber, the waste cement dusts and the waste post-HF silica were modified by the use of adhesion promoters, that is alkoxysilanes. It was found that it would be possible to partly substitute carbon black for the waste cement dusts and the waste post-HF silica. The mixture ratio of a compound which had these wastes and showed the optimum strength properties was proposed.     

General modelling method of power losses in transmission with parameter identification

There is rarely a general or standard method to calculate the overall efficiency of a complete vehicle gearbox. This paper aims to develop such method which can possibly be applied to different types of transmissions in a flexible way and provide a platform to compare several different products from different OEMs or suppliers in parallel.A number of standards and publications concerning the calculation of power losses specifically for one transmission component such as gears, roller bearings or specific phenomenon like oil churning are available in the literature. Different models from these sources are compared, selected and combined to obtain the resulting efficiency map of a complete gearbox system.This paper presents the calculation of such a combined efficiency map of a transmission for an electric vehicle through either the standard models (ISO14179) for industry transmissions or this new joint overall model. The comparisons of available experimental data and calculations show that the result of the joint overall model has a better proximity to the test results. Nevertheless, the uncertainties in the input parameters of the model strongly affect the calculated power loss and the resulting efficiency of the gearbox. Parameter studies are conducted to determine the most influential parameters in the joint overall model. Several selected parameters are identified through experimental overall efficiency maps by classic parameter identification method and algorithm. On the one hand, a much better proximity is achieved. On the other hand, the identified parameters indicate the optimization potential of the component losses for benchmarking of transmissions.     

Partition-based workload scheduling in living data warehouse environments

The demand for so-called living or real-time data warehouses is increasing in many application areas such as manufacturing, event monitoring and telecommunications. In these fields, users normally expect short response times for their queries and high freshness for the requested data. However, meeting these fundamental requirements is challenging due to the high loads and the continuous flow of write-only updates and read-only queries that might be in conflict with each other. Therefore, we present the concept of workload balancing by election (WINE), which allows users to express their individual demands on the quality of service and the quality of data, respectively. WINE exploits these information to balance and prioritize both types of transactions—queries and updates—according to the varying user needs. A simulation study shows that our proposed algorithm outperforms competing baseline algorithms over the entire spectrum of workloads and user requirements.     

Fundamental experiments as benchmark problems for modeling ultrasonic micro-impact processes

Many ultrasonic processes are based on the mechanical contact of oscillating parts. Within ultrasonic machining (drilling, milling, grinding) micro impacts lead to abrasion at the processed workpiece and hopefully do not damage the tool. In ultrasonic motors ideally neither part gets worn. Thus the appropriate design of contact partners as well as their kinematics is a substantial task during the development of such devices. A first step to optimize contact mechanics is to understand their behavior and dependencies on parameter variations, such as vibration amplitude and pre-stress of the impacting parts. For a detailed understanding models validated with convincing experimental data from measurements are absolutely essential. This paper focuses on simple vibro-impact experiments which can be used as benchmark data for future models. The setup of the experiment and first experimental investigations are described in detail.