Characterisation and mechanical testing of hydrothermally treated HA/ZrO2 composites.

Hydrothermal treatment is traditionally employed to improve the sinterability of powder compacts by reducing porosity and increasing apparent density. The effect of hydrothermal treatment on green powder compacts has been assessed in order to better understand how treatment may affect the sinterability of the bodies. Laboratory synthesised nano sized hydroxyapatite (HA) and a commercial zirconia (ZrO(2)) powder have been ball milled together to create composite mixtures containing 0-5 wt% ZrO(2) loadings. Disc shaped bodies have been formed using uniaxial and subsequent isostatic pressure. The resultant coherent samples were subjected to hydrothermal treatment at either 120 or 250 degrees C for 10 h in order to assess the effect of this processing technique on the physical, mechanical and microstructural properties of the green composites. ZrO(2) loadings up to 3 wt% increased apparent density from 90 to 92%, whereas increased loading to 5 wt% increased flexural strength, from 6 to 9 MPa. Increasing the hydrothermal treatment temperature increased open porosity, from ~44 to ~48% and reduced biaxial flexural strengths of the treated bodies compared to those of their room temperature isostatically pressed counterparts (~10 to ~6 MPa).

Cross-correlation in flow-injection analysis with parallel flow streams and amperometric detection.

Cross-correlation was implemented for flow-injection analysis by using two parallel flow lines, each with amperometric detectors, and driven by peristaltic pumps. One flow line was used to generate the reference signal for an analog correlator circuit and the other to generate the analyte signal. Cross-correlation was performed by multiplying these signals together at a time delay of zero, followed by low pass filtering. Using dopamine as a test system, improvements in signal-to-noise ratios of about two orders of magnitude were found for the correlation signal over the direct measurement of the electrode current.

Flow-injection analysis of catecholamine secretion from bovine adrenal medulla cells on microbeads.

Bovine adrenal medullary cells have been cultured on microbeads which are placed in a low-volume flow system for measurements of stimulation-response parameters. Electronically controlled stream switching allows stimulation of cells with pulse lengths from 1 s to many minutes; pulses may be repeated indefinitely. Catecholamines secreted are detected by an electrochemical detector downstream from the cells. This flow-injection analysis technique provides a new level of sensitivity and precision for measurement of kinetic parameters of secretion. A manual injection valve allows stimulation by higher levels of stimulant in the presence of constant low levels of stimulant. Such experiments show interesting differences between the effects of K+ and acetylcholine on cells partially desensitized to acetylcholine.

Symbolic solutions for deadly dilemmas: an analysis of federal coal mine health and safety legislation.

Numerous studies of coal mine laws have argued that the passage of all significant health and safety legislation can be attributed to a succession of catastrophic disasters which heightened awareness and propelled lawmakers into action. This paper takes issue with this "disaster-law" argument because it obscures the intricacies of law creation by focusing on a single factor. More accurately, mining disasters represent one dimension of a process aimed at resolving conflicts occurring within a specific social context. Historically, legislation has been utilized to avert economic crises by addressing the demands of protesting miners. Unfortunately, while the "written law" assured improvements, the "law in action" did not meet these guarantees and the deaths in the mines continued. A case study of the Coal Mine Health and Safety Act of 1969 demonstrates how a law with apparently progressive standards can fail to effect change because of its dualistic nature and incomplete implementation.

Pressurometric titrations with xenon trioxide as oxidant.

The reaction of XeO(3) with thirteen reducing agents was studied qualitatively. From these, Fe(II) and Ti(III) were chosen for direct titration with XeO(3) with pressurometric end-point detection. The precision was a few parts per thousand. Evidence was found for the production of oxygen during both titrations, and of hydrogen peroxide formation during the Ti(III) reaction. The Ti(III)/Xe reacting ratio was independent of the amount of Ti(III) from 35.5 to 87.7 micromole and was 5.93 +/- 0.03 instead of the expected 6.00. The ratio for the Fe(II) reaction varied from 5.85 to 5.95 over the Fe(II) range from 10.05 to 78.7 micromole. The stoichiometric ratio for the iodometric standardization of XeO(3) solutions was confirmed as 6.00.

Treatment of phenothiazine induced bulbar persistent dyskinesia with deanol acetamidobenzoate.

The late manifestation of neuroleptic-induced dyskinesia (persistent dyskinesia) is an irreversible complication of long-term treatment that is poorly understood and difficult to treat. Recently, a theory of dopamine receptor hypersensitivity in the dopaminergic-cholinergic system has suggested an explanation of choreiform movements and, thus, an implication for the management of persistent dyskinesia. The case presented is that of bulbar persistent dyskinesia in a patient who had been prescribed a phenothiazine derivative for eleven years; his symptoms improved with the use of deanol, which probably converts to acetylcholine after crossing the blood brain barrier. This improvement suggests that deanol may shift the neuroleptic-induced dopaminergic-cholinergic system unbalance toward equilibrium by matching predominant dopaminergic effect or by enhancing deficient cholinergic action in the dopaminergic-cholinergic system. This isolated finding needs to be confirmed by more research in neuropharmacology.