High-Precision Nucleation Rate Measurements for Higher Melting Metals

Nucleation of a crystal in undercooled melts of higher melting face-centered-cubic-metals has often been studied in the past. However, the data available were not of sufficient accuracy and only covered nucleation rates in too small of a range to allow precise conclusions concerning the nature of the underlying process as well as concerning important parameters such as the solid–liquid interface free energy that can in principle be deducted from such analyses. One way to circumvent ambiguities and analyze nucleation kinetics under well-defined conditions experimentally is given by performing statistically significant numbers of repeated single droplet experiments. Application of proper statistics analyses yields nucleation rates that are independent of a specific nucleation model. The first studies that were conducted in accordance with this approach on pure model materials revealed that the approach is valid. The results are comparable to those obtained by classic nucleation theory applied to experimental data, and it was shown that one might need to rethink the common assumption that heterogeneous nucleation is almost always responsible for solidification initiation. The current results also show that often-used models for the solid–liquid interface free energy might lead to overestimated values.     

Ultrafine Dust Filtration Using Precoat Materials Considering the Influence of Filter Media

Ultrafine dust separation from different sources like industry, traffic, or private households has become increasingly important in the last decade. A compact baghouse filter system has been developed which is suitable for pellet heaters. For filtration, a precoat material is required to prevent clogging of the filter media by the ultrafine dust particles. In order to ensure the best performance of this filter system, different combinations of filter media and precoat materials, e.g., grade efficiencies and the cake area load for the various filter media, were investigated in a special test rig. With this highly efficient technology, extremely high separation efficiencies of > 99 % and ultrafine dust concentrations of > 1 mg cm^?3 could be reached in a long‐term stable process.     

All in good time: knowledge introduction,restructuring, and development of shared opinions as different stages in collaborative writing

When learners collaborate with each other in order to elaborate on a particular subject, this collaboration may be influenced by the differing perspectives the learners have on the topic. There has been very little research to date on how differing perspectives have an impact in collaboration situations in which people are supposed to form a shared opinion on a particular topic. In this study, we analyzed which stages people’s activities pass through on their way to reaching shared opinions in a collaborative writing task. We examined how dyads of secondary school students, who in a previous instructional session had dealt with differing theoretical approaches to media effects, collaborated in writing a shared text about the topic of media violence. Quantitative analysis indicated that the participants engaged in different activities at different stages of the collaboration processes: In the early stages they were predominantly engaged in introducing the knowledge that they had acquired in the previous lesson. This activity was replaced in the middle stage of the collaboration by restructuring activities. Forming and phrasing shared opinions rarely occurred until very late in the collaboration, but played the leading role in the final stage. We applied a qualitative content analysis to illustrate these different activities by presenting examples of the collaboratively written texts. In doing so, we discuss the distinct activities as well as their character and functionalities for collaboration.     

Effects of calcium chloride and calcium lactate applications with osmotic pretreatment on physicochemical aspects and consumer acceptances of dried papaya

This study explored the effects of calcium chloride (CaCl₂) and calcium lactate (Ca‐L) pretreatments prior to osmotic dehydration on physicochemical characteristics and consumer acceptance of dried papaya. Three different calcium concentrations [0.5, 1.5 and 2.5% (w/v)] were applied to samples before they were soaked in a 30 °Brix sucrose solution and subsequently dried at 70 °C. The results showed that the dried samples treated with calcium exhibited significantly lower moisture content, water activity, apparent density and shrinkage, while volume was higher when compared to the control. Calcium applications did not obviously influence sugar content of samples and maintained the quality of dried papaya in terms of colour and textural characteristics. Calcium chloride at 2.5% (w/v) was found to particularly impart undesirable bitterness to the dried papaya. In contrast, using 2.5% (w/v) Ca‐L provided the best acceptance scores. Thus, the use of Ca‐L could be an alternative to CaCl₂ in the pretreatment of fruits prior to drying as it offers improved quality.     

Microalloy Precipitation at the Glass–Steel Interface Enabling Adherence of Porcelain Enamel

The adherence of vitreous enamels on steel plates is studied clarifying the mechanisms taking place at the interface during firing. Evidence is provided from electron microprobe analysis for an iron alloy precipitation at the interface, which results from oversaturation of ferrous iron in the enamel glass. Subsequent coalescence of the alloy particles is observed but only after their bonding to the base metal adherence after cupping is achieved. The formation of microalloys requires Co²⁺, Ni²⁺, and Cu²⁺ ions in the enamel glass. A selective dissolution of the base metal by the latter cations does not occur.     

Mechanical properties of silicone methacrylate microparticles determined by AFM Colloidal Probe Technique

The mechanical properties of seven types of silicone methacrylate microparticles prepared by solution polymerization with a Pickering emulsifier were investigated by Atomic Force Microscope force–displacement curves acquired in air with the Colloidal Probe Technique, i.e., with spherical SiO₂ particles of known radius glued on tipless cantilevers. The deformation curves derived from the force–displacement curves were fitted with Hertz equation for the contact between two spherical particles, which lead to the determination of the elastic modulus of the samples.     

Development of bottleneck detection methods allowing for an effective fault repair prioritization in machining lines of the automobile industry

Fault repair prioritization is an important topic for organizing operators in every plant where their numbers are restricted. Prioritization helps the operators to focus on critical machines to increase the machining line’s output. The goal of this paper is to define and test effective fault repair prioritization methods based on analytically identified bottlenecks. For that purpose, several bottleneck detection methods known from the literature were analyzed; however, none of them was able to be used for a fault repair prioritization in typical machining lines of the automobile industry. Hence, three new bottleneck detection methods are going to be introduced in this paper. The new methods focus on the detection of short-term and real-time bottlenecks, as well as on near future bottlenecks. At the end of the paper the effectiveness of the new methods is tested using a simulation model of a real machining line in the automobile industry.     

Three-dimensional structure of a mutant E.coli aspartate aminotransferase with increased enzymic activity

The aspartate and tyrosine aminotransferases from Escherichiacoli have 43% sequence identity and nearly identical activesites. Both are equally good enzymes for dicarboxylate substrates,but the latter transaminates aromatic amino acids 1000 timesfaster. In an attempt to discover the critical residues forthis differential substrate specificity, the aspartate aminotransferasemutant V39L has recently been prepared. It showed improved k_cal/K_mvalues for aspartate, glutamate and tyrosine and the correspondingoxo acids, mainly due to two to ten times lower K_m values. Forexample, the K_m values of V39L (wild type) for Asp and Glu are0.12 (1.0) and 0.85 (2.7) mM respectively. The mutant was co-crystallizedwith 30 mM maleate from both polyethylene glycol and ammoniumsulfate. Both structures were solved and refined to R-factorsof 0.22 and 0.20 at 2.85 and 2.5 Å resolution respectively.They bear strong resemblance to the closed structure of thewild type enzyme complexed with maleate. The unexpected featureis that, for the first time, the closed form was produced incrystals grown from ammonium sulfate. It is concluded that themutation has shifted the conformational equilibrium towardsthe closed form, which leads to generally reduced substrateK_mS