Photophysics of pristine and C60-doped disubstituted polyacetylene

Journal ArticleUsing a variety of steady-state spectroscopies we studied the long-lived photoexcitations and electronic excited states of poly disubstituted acetylene (PDPA-nBu), the backbone structure of which is a disubstituted trans-polyacetylene, as well as PDPA-nBu/C60 blends. The cw spectroscopies include absorption, photoluminescence (PL), photoinduced absorption (PA), and PA-detected magnetic resonance (PADMR). Although Using a variety of steady-state spectroscopies we studied the long-lived photoexcitations and electronic excited states of poly disubstituted acetylene (PDPA-nBu), the backbone structure of which is a disubstituted trans-polyacetylene, as well as PDPA-nBu/C60 blends. The cw spectroscopies include absorption, photoluminescence (PL), photoinduced absorption ~PA!, and PA-detected magnetic resonance (PADMR). Although PDPA-nBu is a degenerate ground-state polymer, nevertheless, and in contrast to trans-polyacetylene, we found that it has a strong PL band with quantum efficiency larger than 60%. From polarized PL studies on stretched oriented films we conclude that the PL emission originates from intrachain excitons rather than the polymer side groups. This shows that the lowest-lying exciton in PDPA-nBu is a Bu state rather than an Ag state, in contrast to the order of the lowest-lying excitonic states in trans-polyacetylene. The polarized absorption in PDPA-nBu contains three distinctly different bands with different polarization properties, which are interpreted according to the model of Shukla and Mazumdar

Excitation dynamics in disubstituted polyacetylene

Journal ArticleWe studied the excitation dynamics in films of disubstituted polyacetylene, a degenerate ground-state conjugated polymer, using psec transient and steady-state spectroscopies. The polymer is found to support charged and neutral topological soliton excitations concurrent with a strong intrinsic photoluminescence band with quantum efficiency, η ≈50%. This leads to stimulated emission in thin films and lasing in cylindrical µ cavities. The seeming contradiction of a degenerate ground-state polymer with high η is explained by the lowest excited-state ordering

Species Segregation and Functional Groups in the Hill Country of New Zealand

In the hill country of New Zealand, the soil-sward relationship on hill microrelief was studied. Three categories of slope or microsites were distinguished: low, medium and high. The hypothesis was that soil variables of neighbouring microsites differ, and because of this, there is a segregation of species or functional groups of species between the microsites. Soil features, botanical composition and total annual yield were measured in the slope categories in two similar paddocks; one of which had received long-term phosphorus fertilisation and a non-fertilised paddock. ANOVA, cluster analysis and canonical variate analysis were performed on the data. Unsaturated hydraulic conductivity, slope, bulk density, volumetric soil moisture, soil total nitrogen content, soil phosphorus content and soil compressibility explained most of the variation between microsites. All the measured variables showed that differences amongst microsites were larger than between paddocks. The soil of the low slopes was more developed and fertile than the soil of the other microsites. From the botanical composition, seven functional groups were determined. Low slope microsites yielded significantly greater dry matter than medium and high slopes and were dominated by high fertility grasses and Lolium perenne. Low fertility species and Agrostis capillaris dominated the high slope category. Dicotyledons that colonised high fertility and species with low presence were indifferent to changes in the soil variables. The group of medium fertility species was intermediate between the high and low fertility groups. In conclusion, environmental variables segregated species and functional groups. Species and functional groups differed in ecological strategy. High competitors dominated in environments with high availability of resource. Environments with low resources availability were dominated by stress tolerant species

Assessment of Advertising as a Social Marketing Tool for Managing HIV/AIDS Spread Amongst the Rural Populace in Nigeria

The study undertook a critical assessment of advertising as a social marketing tool for managing HIV/AIDS spread amongst the rural populace in Nigeria. It was motivated by the fact that over 70 percent of the populace dwell and earn their living in the rural areas, while over the years, health promoters and marketers in Africa have emphasized the use of above-the-line advertising media, which do not significantly permeate the rural populace. The objectives of the study included to: appraise the effect of above-the-line advertising and below-the-line advertising as social marketing tools for the prevention and management of HIV/AIDS amongst the rural populace in Nigeria. Survey research design was employed in the study. The area of study was three rural communities in Nigeria. The population of the study was 3,000, comprising of farmers, market women, artisans, teachers and students in the areas. A sample size of 240 was judgmentally determined. The main instrument for data collection was a structured questionnaire consisting of four-point Likert scale. Non-probability sampling technique of purposive sampling was used to distribute the questionnaire. Pearson Product Moment Correlation was employed for the data analysis. Results indicate that: above-the-line advertising media were not significantly effective as social marketing tools for the prevention and management of HIV/AIDS amongst the rural populace in Nigeria; while below-the-line advertising media were significantly effective as social marketing tools for the prevention and management of HIV/AIDS amongst the rural populace in Nigeria. It was then recommended among other things that health marketers and communicators should de-emphasize the use of mass media in their social marketing campaigns to the populace, especially the rural dwellers. Keywords: Advertising, Social Marketing, HIV/AIDS Prevention, Health-Marketing