Catalyst instabilities during the liquid phase partial oxidation of methane

A promising catalytic system for the low temperature oxidation of methane to a methanol derivative has been investigated under both batch and semi-continuous operation in two different reactor types. The system comprises of a bimetallic palladium and copper(II) chloride catalyst contained in a trifluoroacetic acid (TFA) and an aqueous phase. Methane, oxygen and a co-reductant carbon monoxide constitute the gas phase. Typical operating conditions were a temperature of 85 °C and a pressure of 83 bar.

The yields of the methyl trifluoroacetate product observed in this present work were less than those obtained in other batch autoclave works, which employed only 4 ml of liquid phase, compared with 50 ml in this study. Furthermore, an encouraging initial product formation rate of ca. 40 mol/m³ h, quickly decreased after the first hour, and came to an apparent end after only 2 h. This observation had not been reported previously.

Work performed in a semi-continuous porous tube reactor (300 ml of re-circulating liquid phase) also showed the same reaction characteristics as in the batch reactor. Thus, the deteriorating product formation rate cannot be attributed to gaseous reactant depletion (batch operation). The results suggest problems associated with catalyst instabilities, e.g. with the previously elucidated Wacker chemistry.     

Fundamental properties of radiation from a leaky mode excited on a planar transmission line

By using a specific normalization, it is shown that the TM/sub 0/ radiation field from a leaky mode that is excited by a source on any printed-circuit structure can be represented in a unified manner. The general properties of the normalized leaky-mode radiation field are examined in detail for a variety of phase and attenuation constants, as well as distances from the source, and for different types of source excitations. The normalized leaky-mode radiation field is compared to similarly normalized geometrical-optics and far-field radiation expressions to provide further insight into the nature of the radiation fields in the near- and far-field regions. The results provide a general view of leaky-mode radiation properties independent of the type of planar transmission line or background structure.     

CW high power single-lobed far-field operation of long-cavityAlGaAs-GaAs single-quantum-well laser diodes grown by MOCVD

Data on long-cavity 100-μm-wide broad-stripe laser diodes that lase with a barrow single-lobed far-field pattern in continuous room-temperature operation are presented. Diodes with a cavity length of 1250 μm emit a power of 200 mW per facet into a 2.5° lobe (full width at half maximum). Short-cavity devices (cavity length of 350 μm) lase with a continuously increasing number of lateral modes right from threshold, and exhibit a far-field divergence that is over three times greater than that of 1250-μm diodes. Explanations for the effect of increasing cavity length on the field patterns of these devices are proposed, based on the measured increase in injected carrier diffusion length in long-cavity diodes and the influence of thermal waveguiding and mirror losses on intermodel discrimination     

The effect of metal ions on neutrophil degranulation

This study examined neutrophil activation, after incubation of these cells with metal ions. Activation was examined using lysozyme and chemiluminescence assays. Cobalt ions (0.5–30 p.p.m.), chromium ions (0.5–20 p.p.m.), nickel ions (1–50 p.p.m.) and aluminium ions (0.05–7.5 p.p.m.) did not stimulate neutrophils to release lysozyme and did not stimulate a respiratory burst. Copper ions (0.25–7.5 p.p.m.) stimulated neutrophils to release lysozyme, a result which was significant at the 5% level. This was not as a result of copper ions causing neutrophils to lyse. Lysozyme secretion was inhibited when neutrophils were pre-incubated with cytochalasin B, although cytochalasin B had no effect on the enzyme secretion due to stimulation by opsonized zymosan and zymosan-activated serum. This suggests that the mechanism by which copper ions stimulate neutrophil degranulation is different from that of opsonized zymosan and zymosan-activated serum. Enzyme secretion was not accompanied by a respiratory burst.     

Flow equations of particle fluid mixtures

Summary A set of flow equations are derived for the velocity components of the solid and liquid phases of a particle fluid mixture. The equations have a limited validity to the case of uniaxial flow accompanied by radial expansion.The Terzaghi fluidization criterion is used to fix an internal parameter in the equations. Using a stability analysis it is demonstrated that the process of the onset of fluidization is accompanied by a smoothing out of internal heterogeneity in the system.The applications treated are the permeability of a densely packed material and the settlement of a geotechnical filter.     

Staphylococcus aureus mastitis: pathogenesis and treatment with bovine interleukin-1 beta and interleukin-2.

Polymorphonuclear leukocytes play a central role in the pathogenesis of bovine mastitis. Intramammary challenge with Staphylococcus aureus was shown to induce both quantitative and qualitative changes in mammary gland polymorphonuclear leukocytes. Intramammary infusion of recombinant bovine interleukin-1 beta and interleukin-2 elicited a similar cellular response. Staphylococcus aureus, interleukin-1 beta, and interleukin-2 all increased the number of somatic cells after intramammary infusion and activated the inducible superoxide production in milk polymorphonuclear leukocytes. Interleukin-2 also activated phagocytosis of these cells, and their activation was maintained for 3 to 5 d after intramammary administration. Interleukin-1 beta and interleukin-2 were moderately effective in the therapy of experimental S. aureus mastitis. Approximately 54% of the glands treated with interleukin-1 beta responded to therapy by transiently clearing the milk of S. aureus, 30% of which relapsed, and a total of 38% of the treated glands remained cured. In contrast, 83% of glands treated with interleukin-1 beta responded to therapy, but 50% of these quarters relapsed. A total of 42% of the quarters treated with interleukin-1 beta remained cured. Homologous recombinant cytokines are effective immunomodulators that augment natural defensive mechanisms similar to the normal response to pathogens and may prove to be suitable alternatives to, or may be used in combination with, antibiotics as effective mastitis therapeutic agents.     

Millimeter-wave components and subsystems built using microstriptechnology

The author describes the evaluation of microstrip as a transmission medium for components and subsystems operating in the millimeter wavebands. The manufacturing process for thin-film MICs on single-crystal quartz is described. The microwave integrated circuit (MIC) manufacturing process is suitable for high-value manufacturing of highly integrated subsystems since manufacturing costs for the circuits are almost independent of the number of circuit functions. Designs for various circuit elements are discussed, and an integrated subsystem is described in which MIC techniques are used to produce a miniature millimeter-wave distance-measuring sensor. Range measurement results for the miniature sensor are presented