The time required to transcribe and analyse lengthy conversation puts conversational discourse analysis (CDA) out of reach for most practising clinicians. However, standards have not been established for appropriate conversation sample size. Data are presented supporting the use of conversation samples 5-10 minutes when studying conversation repair, speaking rate, and utterance length. Ten minute samples adequately represented 'parent' conversations from which they were derived when measuring conversation repair for six of eight cases. For measuring speaking efficiency (length of utterance and speaking rate) 5 minutes was adequate for all eight cases. For variables occurring once per minute, 10 minute samples were adequate, and for variables occurring three times per minute, 5 minute samples were adequate.

The long history of the synthesis of hydrogen peroxide via the cathodic reduction of oxygen in caustic soda catholyte is reviewed. Recent progress is analysed on the electrochemical syntheses of mixtures of caustic soda and hydrogen peroxide in various by-weight ratios from 2.3: 1 NaOH to H2O2 to about 1 : 1. The analysis presented focuses primarily on published work concerning planar fuel cell type electrodes in membrane-divided cells and particulate bed electrodes in cells employing microporous separators with well-defined anolyte-to-catholyte flows. Potential ancillary technology for changing the ratios of products is also discussed. One configuration of the processes described encompasses the simultaneous near 50/50 use of two variations of generation technology. A highly desired product, for instance 1.2: 1 NaOH to H2O2, may be formed using the catholyte product of a membrane or diaphragm cell with a caustic anolyte as the catholyte feed stream for a membrane cell with an acidic anolyte. Although the particulate bed cathode approach has reached commercial trials, the planar cathode membrane cell approach may prove a difficult process to develop as the performance of electrodes optimized for realistic hydraulic depths may prove very different to that of electrodes used in small scale laboratory development.

Removal of benthic barriers one to two years following installation allowed a systematic study of macrophyte recolonization. Within grids installed in the barren zone, species presence and relative abundance were recorded at 30-day intervals through two growing seasons. At each site, colonization of the 18 m(2) grid systems was observed, with typically 9 to 12 species found 30 days post benthic barrier removal. Sixty days post barrier removal (August), both the number of species (averaging 4.7 m(2)) and plant cover peaked (49% cover). A decline in species number and average percent cover observed after 120 days (October) was related to seasonal patterns of growth and die back of annual species. In the second growing season, the number of species stabilized while overall average percent cover (areal coverage) continued to increase. Eurasian watermilfoil colonized all sites, with 71% of all grid squares containing milfoil by the end of the second growing season, representing an average percent cover of 13.6% while total community percent cover averaged 74%. Removal of benthic barrier allowed for the rapid recolonization of both native species and Eurasian watermilfoil.

Seven sites on Lake George, New York, were selected for control of Eurasian watermilfoil by a diver-operated suction harvester. Prior to suction harvesting, ten 0.1-m(2) biomass samples were collected from each site. Samples were randomized within the area to be harvested, sorted by species, dried and weighed. A grid system of 36 contiguous 1-m(2) quadrats was also located within each of the treatment areas. The species present and their relative percent cover in each quadrat were recorded prior to harvest, shortly after and 1 year postharvest. A substantial reduction in the biomass of milfoil at all sites was noted as a result of suction harvesting. One year after harvest, the impact of harvesting on the native plant community included a greater number of species per unit area and reduced biomass and percent cover at a majority of the treated sites.

Full-scale (1.2 m2) immersed-tank hydrogen-diffusion anodes have been prepared by a newly patented lamination technique onto metallic sheet substrates. The use of such free-standing electrodes has been characterized in the electrowinning of zinc, but the electrodes are also suitable for use in the electrowinning of other metals and in electroplating. The electrodes may find application in processes where voltage savings of approximately 1.8–2.0 V versus oxygen evolution are of importance, or where parasitic anodic oxidations need to be eliminated. The hydrogen-diffusion anode structure developed incorporates a novel microporous polymeric coating designed to prevent both the percolation of feed hydrogen through the electrode to the electrolyte and the seepage of electrolyte into the gas plenum.