SCHOOL OF PHYSICAL SCIENCE

White light photothermal lens spectrophotometer for the determination of absorption in scattering samples

Wed, 01 Jan 2014 00:00:00 GMT

White light photothermal lens spectrophotometer for the determination of absorption in scattering samples Marcano, Aristides; Alvarado, Salvador; Meng, Junwei; Caballero, Daniel; Moares, Ernesto Marin; Edziah, Raymond We developed a pump-probe photothermal lens spectrophotometer that uses a broadband arc-lamp and a set of interference filters toprovide tunable, nearly monochromatic radiation between 370 and 730 nm as the pump light source. This light is focused onto an absorbing sample, generating a photothermal lens of millimeter dimensions. A highly collimated monochromatic probe light from a low-power He–Ne laser interrogates the generated lens, yielding a photothermal signal proportional to the absorption of light. We measure the absorption spectra of scattering dye solutions using the device. We show that the spectra are not affected by the presence of scattering, confirming that the method only measures the absorption of light that results in generation of heat. By comparing the photothermal spectra with the usual absorption spectra determined using commercial transmission spectrophotometers, we estimate the quantum yield of scattering of the sample. We discuss applications of the device for spectroscopic characterization of samples such as blood and gold nanoparticles that exhibit a complex behavior upon interaction with light 6p:, ill.

Wettability property in natural systems: A case of flying insects

Mon, 01 Jan 2018 00:00:00 GMT

Wettability property in natural systems: A case of flying insects Sackey, J.; Sone, B.T.; Dompreh, K. A.; Maaza, M. Recently, scientists have demonstrated that material surfaces in nature that possess special wettability properties are composed of micro- and nanostructures. In this study, we focused on the importance of surface structures in determining the wettability of wings of the flying insect species: Idea malabarica, Lucilia sericata and Chrysomya marginalis. Scanning Electron Microscopy (SEM) analysis indicates the different nano-/micro- structures identified on the wings. Surface roughness which plays a role in influencing the wettability was theoretically estimated from the SEM images. While the spherical liquid water droplets used for testing wettability were observed to float on the surface of the Idea malabarica and Lucilia sericata wings, the surface of the Chrysomya marginalis wing was made completely wet. The super-hydrophobicity of the Idea malabarica wing as compared to the near hydrophobicity/mild hydrophilicity of the Lucilia sericata wing and the distinct hydrophilicity of the Chrysomya marginilis wing could be attributed to its complicated composition of nano- /microstructures and higher surface roughness value. 8p:, ill.

Violet diode laser-induced chlorophyll fluorescence: a tool for assessing mosaic disease severity in cassava (Manihot esculenta Crantz) cultivars

Sun, 01 Jan 2012 00:00:00 GMT

Violet diode laser-induced chlorophyll fluorescence: a tool for assessing mosaic disease severity in cassava (Manihot esculenta Crantz) cultivars Anderson, Benjamin; Eghan, Moses J; Asare-Bediako, Elvis; Bassuah, Paul K Buah Violet diode laser-induced chlorophyll fluorescence was used in agronomical assessment (disease severity and average yield per plant). Because cassava (Manihot esculenta Crantz) is of economic importance, improved cultivars with various levels of affinity for cassava mosaic disease were investigated. Fluorescence data correlated with cassava mosaic disease severity levels and with the average yield per plant 7p:, ill.

Variation in the susceptibility of okra (Abelmoschus esculentus L. Moench) genotypes to okra mosaic virus and Podagrica species under field conditions

Sun, 01 Jan 2017 00:00:00 GMT

Variation in the susceptibility of okra (Abelmoschus esculentus L. Moench) genotypes to okra mosaic virus and Podagrica species under field conditions Asare-Bediako, Elvis; Agyarko, Faustina; Verbeek, Martin; Taah, Kingsley J.; Asare, Aaron; Agyei, Frimpong K.; Sarfo, Justice; Eghan, Moses Jojo; Combey, Rofella A total of 21 okra (Abelmoschus escuentus L. Moench) genotypes were screened for their reactions against okra mosaic disease (OMD) and flea beetles (Podagrica species) infestations in field trials which were conducted from May to October, 2015 (wet season) and November 2015 to March 2016 (dry season), in order to identify sources of resistance and or tolerance. The trials were laid out in a randomised complete block design (RCBD) with four replications. Field resistance in the genotypes was assessed at 2, 6 and 10 weeks after planting using a 0 to 5 visual scale based on disease symptoms (where 1 denotes no symptom and 5, very severe symptom). Enzyme linked immunosorbent assay (ELISA) was performed to detect the presence of Okra mosaic virus (OkMV) in the okra genotypes. Populations of the flea beetle (Podagrica spp.), the vector of OkMV, and the associated leaf and fruit damage were also assessed. All the okra genotypes exhibited a varying range of disease symptoms and the flea beetle infestations, and lacked immunity. Genotypes GH2052, GH2063, GH2026, GH3760, GH5302, GH5332, GH5793, GH6105 and UCCC6 exhibited mild symptoms of OMD, and were less susceptible to flea beetle infestation and associated leaf damage during both seasons. Using ELISA, OkMV was detected in all the 21 genotypes. The mean number of fruits per plant and the mean fruit yield (t ha -1) differed significantly (P<0.05) among the okra genotypes. Genotype GH5332 had the highest fruit yield of 11.88 t ha -1 followed by genotype GH6105 (9.34 t ha-1 ). Percentage fruit damage due to the flea beetle infestation differed significantly among the okra genotypes, ranging between 43.7 and 91.2% and from 47 to 84% in both trials respectively 11p:, ill.