Activity-composition relations at 1100°C in the system calcium oxide-iron oxide-manganese oxide in contact with metallic iron

The extent of the solid miscibility gap in the system CaO−“FeO”−MnO at 1100°C has been determined termined by electron microprobe, point-counting, and X-ray diffraction analysis of coexisting phases within the miscibility gap. Activities of FeO in ternary solid solutions have been determined at 1100°C by equilibrating the solid solutions with metallic iron and a gas phase of known oxygen pressures. Activity-composition curves for CaO and MnO in the ternary system are calculated from a Gibbs-Duhem integration, and the data are extrapolated to the binary system CaO−MnO, which is shown to display a considerable positive deviation from ideality at 1100°C. NILS TIBERG, formerly Graduate Assistant, Department of metallurgy, The Pennsylvania State Univeristy, University Park, Pa.     

Office automation and users need' for support

We investigated a recently introduced office automation system at Swedish Telecom. In a first study, where 275 users answered an inventory, the users indicated that they found the system useful, but that they would like better user support. Paper and on-line support were most often used at the syntax level, but were not regarded to be very satisfactory. Human advisors were found to be consulted most often, as well as being reported the most satisfactory means of support at the task and conceptual levels. In an interview study concerning the electronic mail system, the results from 35 users showed that the users were satisfied with the system, but that they knew fairly little about it, particularly at the semantic level. A third study showed that the system support personnel knew their users rather well. When asked to describe the system, system support personnel mainly described the system in computer terms, whereas many other users described it non-informatively. It is concluded that knowledgeable human advisors are needed to support the efficient use of a system by illuminating task and semantic aspects. At the same time, easy-to-use manuals are needed to support the reminding about syntactic and interaction details.     

Thermal Shock Behavior of Duplex Ceramics

The thermal-stress fracture behavior of duplex ceramics is investigated by quenching in water and in oil. Comparison with the matrix materials shows that the critical quenching temperature difference, Δ T _c , is not or is only slightly reduced, even for duplex ceramics of significantly reduced strength. In sintered composites, thermal-stress-induced microcracking within pressure zones and crack initiation at pressure zone–matrix interfacial defects develop before Δ T _c is reached. The effects are accompanied by a gradual reduction in strength. At Δ T _c , critical crack propagation occurs. The retained strength after thermal shock of duplex ceramics is significantly improved compared with the respective matrix materials. This behavior can be related reasonably well with the K ^R -curve behavior.     

Synthesis and biological evaluation of novel EG5 inhibitors

Human Eg5 is a mitotic kinesin that is essential for bipolar spindle formation and maintenance during mitosis. Recently, the discovery of compounds that inhibit Eg5 and cause mitotic arrest has attracted great interest, due to their potential use as the next generation of antimitotics. Here, we present the synthesis and biological investigation of 3,4-dihydrophenylquinazoline-2(1H)-thiones as selective and potent Eg5 inhibitors.     

Solid-phase extraction NMR studies of chromatographic fractions of saponins from Quillaja saponaria

The saponin mixture QH-B from the tree Quillaja saponaria var. Molina was fractionated by RP-HPLC in several steps. The fractions were analyzed by solid-phase extraction NMR (SPE-NMR), a technique combining the workup by solid-phase extraction with on-line coupling to an NMR flow probe. Together with MALDI-TOF mass spectrometry and comparison with chemical shifts of similar saponins, the structures of both major and minor components in QH-B could be obtained. The procedure described is a simple method to determine the structure of components in a complex mixture. The two major fractions of the mixture were found to contain at least 28 saponins, differing in the carbohydrate substructures. Eight of these have not previously been determined. The 28 saponins formed 14 equilibrium pairs by the migration of an O-acyl group between two adjacent positions on a fucosyl residue.     

Dissolution and melting of secondary Al2Cu phase particles in an AlCu alloy

When up-quenching an Al-4.2 wt pct Cu alloy which has been equilibrated at 450 °C to a temperature at or above the eutectic temperature of 547 °C, liquid drops are found to form. Inside the matrix grains they have a globular shape, while they have a lenticular shape with a low dihedral angle when formed on grain boundaries. It is demonstrated metallographically that drops are formed by the melting of the Al₂Cu phase particles together with the surroundingα matrix to form a liquid of chemical composition around the eutectic composition. On prolonged annealing, the drops are dissolved in theα matrix. The kinetics of this dissolution reaction of the drops, as well as the dissolution of Al₂Cu phase particles at a temperature below 547 °C, is studied in some detail and compared with a simple mathematical model. Also, the thermodynamics of the melting and dissolution reactions are discussed by means of a free-energy diagram.     

Dissolution of particles in binary alloys: part II. experimental investigation on an Al-Si alloy

A detailed experimental study of the dissolution kinetics of Si particles in an Al-Si alloy has been carried out in order to test the validity of the two models presented in the accompanying article.[1] In these models, the dissolution kinetics are dependent on the particle size distribution of the alloy. An alloy with composition C_o = 0.77 at. pct Si was heat-treated in order to obtain rather coarse spherical particles (1 to 10 μn). The size distribution of the particles was found to be close to the log-normal distribution. At high temperatures, when the solvus concentration was well above C_o, the experimental values were very close to the values of the model which predicted the highest dissolution rates. At lower temperatures, when the solvus concentration was closer toC _o, the experimental values lay in between the values predicted by the two models. The results clearly demonstrate that a size distribution of particles must be included in the model if an accurate prediction of the dissolution kinetics is to be achieved.