Chemical colouration of sodium beta-aluminas

A variety of experiments was performed on Na -alumina single crystals and Na -alumina polycrystals of different microstructures, to clarify the nature of chemical colouration produced by contact with sodium. It was found that the colouration is due to a reduction of the electrolyte by sodium, introducing oxygen vacancies compensated by electrons. Colouration and bleaching kinetics have been determined. It was found that in polycrystals colouration proceeds along the grain boundaries. Water has no effect. The role of the colouration in electrolyte degradation is discussed.     

Abrasive Wear Behavior of Heat-Treated ABC-Silicon Carbide

Hot-pressed silicon carbide, containing aluminum, boron, and carbon additives (ABC-SiC), was subjected to three-body and two-body wear testing using diamond abrasives over a range of sizes. In general, the wear resistance of ABC-SiC, with suitable heat treatment, was superior to that of commercial SiC. When the fine-scale (3 μm) diamond abrasives were used, it was found that thermal annealing at 1300°C increased the resistance to three-body wear by a factor of almost three, and two-body wear by a factor of almost two, compared with as-hot-pressed samples. Higher annealing temperatures, however, led to a decline in wear resistance from its highest value. Similar behavior was seen for 1300°C-annealed samples subjected to 15 μm diamond abrasive, although higher-temperature annealing at 1500°–1600°C enhanced the wear resistance again. When coarse abrasives (72 μm) were used, the wear resistance progressively increased with increased annealing temperature from ∼1000° to 1600°C. Corresponding transmission and scanning electron microscopy studies indicated that, whereas transgranular, conchoidal cracking was dominant in the mild abrasive wear with fine-scale (3 μm) abrasives, intergranular cracking and subsequent grain pullout was far more predominant in the more severe abrasive wear with coarse abrasives. Because the hardness and indentation toughness were barely altered during thermal treatment, the observed wear behavior was attributed mainly to the thermally induced microstructural changes, including the crystallization of glassy grain-boundary films, the possible strengthening of the boundaries due to the enhancement of the aluminum, and the formation of aluminum-rich, coherent nanoscale precipitates in the matrix grains above 1300°C.     

Reaction Sintering of ZnO-AI2O3

The reaction sintering of equimolar mixtures of ZnO and A1₂O₃ powders was investigated as a function of primary processing parameters such as the temperature, heating rate, green density, and particle size. The powder mixtures were prepared by two different methods. In one method, the ZnO and A1₂O₃ powders were ball-milled. In the other method, the ZnO powder was chemically precipitated onto the A1₂O₃ particles dispersed in a solution of zinc chloride. The sintering characteristics of the compacted powders prepared by each method were compared with those for a prereacted, single-phase powder of zinc aluminate, ZnAl₂O₄. The chemical reaction between ZnO and A1₂O₃ occurred prior to densification of the powder compact and was accompanied by fairly large expansion. The mixing procedure had a significant effect on the densification rate during reaction sintering. The densification rate of the compact formed from the ball-milled powder was strongly inhibited compared to that for the single-phase ZnAl₂O₄ powder. However, the densification rate of the compact formed from the chemically precipitated mixture was almost identical to that for the ZnAl₂O₄ powder. The difference in sintering between the ball-milled mixture and the chemically precipitated mixture is interpreted in terms of differences in the microstructural uniformity of the initial powder compacts resulting from the different preparation procedures.     

Silicon Carbide Platelet/Silicon Carbide Composites

α-silicon carbide platelet/β-silicon carbide composites have been produced in which the individual platelets were coated with an aluminum oxide layer. Hot-pressed composites showed a fracture toughness as high as 7.2 MPa·m^1/2. The experiments indicated that the significant increase in fracture toughness is mainly the result of crack deflection and accompanying platelet pullout. The coating on the platelets also served to prevent the platelets from acting as nucleation sites for the α- to β-phase transformation, so that the advantageous microstructure remains preserved during high-temperature processing.     

Determining optimal electricity technology mix with high level of wind power penetration

Notwithstanding its variability and limited controllability, wind power is expected to contribute strongly to electricity generation from renewable energy sources in the coming decades. Treating wind power as non-dispatchable by subtracting its output from the original load profile, results in a net load profile, which must be covered by conventional power generation. The screening curve methodology is a first approximation to find the optimal generation technology mix, based on relative cost levels. However, increased variability of the net load profile, due to wind power generation, strongly influences system operation. Therefore a static linear programming investment model is developed to determine the optimal technology mix. This alternative methodology shows a reduced capacity of inflexible generation after including operational constraints to properly account for net load variability. In order to illustrate this methodology, an example is set up, showing the sensitivity with respect to ramp rates of conventional generation, transmission interconnection and energy storage. The comparison of those different sources of system flexibility suggests that energy storage facilities better facilitate the integration of wind power generation.     

An inter-laboratory ring trial for the detection and isolation of Mycobacterium avium subsp. paratuberculosis from raw milk artificially contaminated with naturally infected faeces

There is a need for standardised, robust, reproducible molecular and culture methods to achieve clarification of the inactivation of Mycobacterium avium subsp. paratuberculosis (Map), the causative microbial agent of Johne's disease, in (faecally) contaminated milk and other food products such as meat. This study assessed the performance of a commercially available Map DNA extraction kit for milk Adiapure and accompanying PCR detection kit Adiavet alongside 'in-house' molecular and culture methods in an inter-laboratory ring trial using raw milk spiked with Map-infected faeces. The combined Adiapure-Adiavet Map DNA extraction and detection kit consistently detected 30 copies of IS900 (equivalent to approximately 2 cells) ml(-1) raw milk, when used in four different laboratories. Improvements in sensitivity and ease of use for 'in-house' Map detection were observed when the Adiapure extraction kit was combined with 'in-house' detection assays. Detection by real-time PCR methods, using the commercial extraction and detection systems, resulted in an overall detection rate of 100%, 90%, 85% and 25% for respective Map concentrations of 300, 30, 3 and 0.3 copies of IS900ml(-1) raw milk. Map, at 300 copies of IS900 (equivalent to approximately 20 Map cells) ml(-1) raw milk, was recovered from all samples cultured in mycobacteria growth indicator tube (MGIT) medium, from 10 of 12 samples on Herrold's egg yolk medium (HEYM) and not recovered from any samples using BACTEC medium. In conclusion, the Adiapure DNA extraction kit allows for sensitive and easy detection of Map in raw milk. The extraction method can form a candidate part of essential methodology and real-time PCR can further increase the sensitivity of the detection method. Moreover, MGIT medium is promising for culture-dependent detection of Map from raw milk.     

Apoptosis Imaging in Oncology by Means of Positron Emission Tomography: A Review

To date, a wide variety of potential PET-apoptosis imaging radiopharmaceuticals targeting apoptosis-induced cell membrane asymmetry and acidification, as well as caspase 3 activation (substrates and inhibitors) have been developed with the purpose of rapidly assessing the response to treatment in cancer patients. Many of these probes were shown to specifically bind to their apoptotic target in vitro and their uptake to be enhanced in the in vivo-xenografted tumours in mice treated by means of chemotherapy, however, to a significantly variable degree. This may, in part, relate to the tumour model used given the fact that different tumour cell lines bear a different sensitivity to a similar chemotherapeutic agent, to differences in the chemotherapeutic concentration and exposure time, as well as to the different timing of imaging performed post-treatment. The best validated cell membrane acidification and caspase 3 targeting radioligands, respectively ¹⁸F-ML-10 from the Aposense family and the radiolabelled caspase 3 substrate ¹⁸F-CP18, have also been injected in healthy individuals and shown to bear favourable dosimetric and safety characteristics. However, in contrast to, for instance, the ^99mTc-HYNIC-Annexin V, neither of both tracers was taken up to a significant degree by the bone marrow in the healthy individuals under study. Removal of white and red blood cells from the bone marrow through apoptosis plays a major role in the maintenance of hematopoietic cell homeostasis. The major apoptotic population in normal bone marrow are immature erythroblasts. While an accurate estimate of the number of immature erythroblasts undergoing apoptosis is not feasible due to their unknown clearance rate, their number is likely substantial given the ineffective quote of the erythropoietic process described in healthy subjects. Thus, the clinical value of both ¹⁸F-ML-10 and ¹⁸F-CP18 for apoptosis imaging in cancer patients, as suggested by a small number of subsequent clinical phase I/II trials in patients suffering from primary or secondary brain malignancies using ¹⁸F-ML-10 and in an ongoing trial in patients suffering from cancer of the ovaries using ¹⁸F-CP18, remains to be proven and warrants further investigation.     

A Scaffold-Hopping Strategy toward the Identification of Inhibitors of Cyclin G Associated Kinase

We recently reported the discovery of isothiazolo[4,3-b]pyridine-based inhibitors of cyclin G associated kinase (GAK) displaying low nanomolar binding affinity for GAK and demonstrating broad-spectrum antiviral activity. To come up with novel core structures that act as GAK inhibitors, a scaffold-hopping approach was applied starting from two different isothiazolo[4,3-b]pyridines. In total, 13 novel 5,6- and 6,6-fused bicyclic heteroaromatic scaffolds were synthesized. Four of them displayed GAK affinity with K_d values in the low micromolar range that can serve as chemical starting points for the discovery of GAK inhibitors based on a different scaffold.     

Cu-YSZ cermet solid oxide fuel cell anode prepared by high-temperature sintering

Porous YSZ-Cu alloy cermet structures are prepared by sintering above the metal melting point in reducing atmosphere. Unexpectedly good wetting of the molten metal within the YSZ network is obtained, resulting in cermets with fine structure and excellent electronic conductivity. Anode-supported solid oxide fuel cells are prepared with YSZ-Cu alloy cermet as the anode. Addition of infiltrated ceria catalyst improved the initial performance. Maximum power density of about 275 mA cm⁻² and operation for about 110 h was achieved in the 700-800 °C range. After operation, AC impedance revealed that the high-frequency impedance was unchanged, whereas the low-frequency impedance increased. It was concluded that the Cu alloy network conductivity remains high, but catalyst stability needs improvement.     

Human atrial repolarization: effects of sinus rate, pacing and drugs on the surface electrocardiogram

OBJECTIVES: We studied the effects of rate and some cardioactive drugs on the atrial surface electrocardiogram (ECG). BACKGROUND: In atrioventricular block, atrial surface ECG is unmasked. The effect of rate alone permits detection of the effect of other exogenous stimulations such as drugs in the presence of rate alterations. METHODS: High fidelity, high gain ECG leads I, II and III were recorded from 51 patients with heart block. Durations of P and Ta waves and the total PTa interval were measured from nonconducted atrial events. RESULTS: No relationship was found between sinus cycle length and PTa, P or Ta in 31 patients. In 20 patients, progressively decreasing the atrial pacing cycle length from 853 ms to 381 ms resulted in a linear reduction of the PTa interval from 444 to 291 ms (rho = 0.76, slope = 0.24). This was largely due to shortening of Ta. A linear rate correction formula was derived: corrected PTa = PTa - 0.24 (PP - 1000). Atropine (0.02 mg/kg) shortened the PP interval (p < 0.001) and the PTa interval (p < 0.01). Propranolol (0.1 mg/kg) prolonged the PP interval (p < 0.001) but did not alter the PTa interval. Neither disopyramide (2.0 mg/kg) nor flecainide acetate (2.0 mg/kg) altered the PP interval, but both prolonged the PTa interval (p < 0.001). This was largely due to P wave lengthening after flecainide (p < 0.001) and to Ta prolongation after disopyramide (p < 0.001). CONCLUSIONS: In heart block, PTa, P and Ta waves can be measured reliably. The effects of pacing and some antiarrhythmic drugs on the atrial myocardium are similar to those known at the ventricular level.