Diagnostic techniques for atmospheric streamer discharges

Fast electrical and optical diagnostics are required for the analysis of atmospheric streamer discharges. This is illustrated for the case of positive streamer corona produced along wire electrodes by high voltage pulses with rise times of tens of nanoseconds. Electrical measurements with a high time resolution reveal the energy input in two discharge phases (primary and secondary streamer). The discharge structure is visualised using a gated image intensifier. The number of streamers per unit length of anode wire and the streamer diameter are determined. The streamer velocity is measured with a time-of-flight method using two optical fibres. Time-resolved spectroscopic measurements of the intensity ratio of N2+ and N 2 emission lines reveal that the average electron energy in the primary streamer phase is significantly higher than in the subsequent secondary streamer. The neutral gas temperature in the discharge is determined from the rotational structure of an N2 emission line and is only slightly above the background gas temperature. Schlieren photographs visualise the heat dissipated in residual streamer channel

Gas phase hydrogen peroxide production in atmospheric pressure glow discharges operating in He - H2O

The gas phase production of hydrogen peroxide (H2O2) in a RF atmospheric pressure glow discharge with helium and water vapour has been investigated as a function of the gas flow. It is shown that the production of H2O2 is through the recombination of two OH radicals in a three body collision and the main destruction is through radical reactions involving OH or surface losses at the electrodes. Balancing these production and losses of H2O2 allows estimating OH densities which correspond with reported densities in literature for this type of discharge. 1. Introductio

Circular 117

The annual flower trials were planted from 30 May through 4 June, 1999 in the Perennial Landscape and All America Selections Display Garden of the Georgeson Botanical Garden (64°51N, 147°52W). Fairbanks silt loam soil was fertilized with 1 0 -2 0 -2 0 S (4 lbs per 100 sq feet, 195 g per sq meter) on 28 May. With the exception of dahlias, all flowers were grown as seedling transplants and were hardened off outdoors for one week prior to transplanting. Tuberous roots of dahlias were planted in containers five weeks prior to transplanting and were hardened off

Gas phase hydrogen peroxide production in atmospheric pressure glow discharges operating in He - H2O

The gas phase production of hydrogen peroxide (H2O2) in a RF atmospheric pressure glow discharge with helium and water vapour has been investigated as a function of the gas flow. It is shown that the production of H2O2 is through the recombination of two OH radicals in a three body collision and the main destruction is through radical reactions involving OH or surface losses at the electrodes. Balancing these production and losses of H2O2 allows estimating OH densities which correspond with reported densities in literature for this type of discharge. 1. Introductio

The relationship between ethnic composition of the residential environment and self-reported health among Turks and Moroccans in Amsterdam

Previous studies from the US and UK suggest that neighbourhood ethnic composition is associated with health, positive or negative, depending on the health outcome and ethnic group. We examined the association between neighbourhood ethnic composition and self-reported health in these groups in Amsterdam, and we aimed to explore whether there is spatial variation in this association. We used micro-scale data to describe the ethnic composition in buffers around the home location of 2701 Turks and 2661 Moroccans. Multilevel regression analysis was used to assess the association between three measures of ethnic composition (% co-ethnics, % other ethnic group, Herfindahl index) and three measures of self-reported health: self-rated health, Physical and Mental Component Score (PCS, MCS). We adjusted for socioeconomic position at individual and area level. We used geographically weighted regression and spatially stratified regression analyses to explore whether associations differed within Amsterdam. Ethnic heterogeneity and own ethnic density were not related to self-rated health for both ethnic groups. Higher density of Turks was associated with better self-rated health among Moroccans at all buffer sizes, with the most significant relations for small buffers. Higher heterogeneity was associated with lower scores on PCS and MCS among Turks (suggesting worse health). We found spatial variation in the association of the density of the other ethnic group with self-rated health of Moroccans and Turks. We found a positive association for both groups, spatially concentrated in the sub-district Geuzenveld. Our study showed that the association of ethnic composition with self-reported health among Turks and Moroccans in Amsterdam differed between the groups and reveals mainly at small spatial scales. Among both groups, an association of higher density of the other group with better self-rated health was found in a particular part of Amsterdam, which might be explained by the presence of a relatively strong sense of community between the two groups in that area. The study suggests that it is important to pay attention to other-group density, to use area measurements at small spatial scales and to examine the spatial variation in these associations. This may help to identify neighbourhood characteristics contributing to these type of area effects on urban minority healt