Monitoring spatial-temporal variability of aerosol over Kenya

This study sought to investigate the spatial and temporal variations of aerosols over Kenya based on Moderate Resolution Imaging  Spectroradiometer (MODIS) satellite sensor Aerosol Optical Depth (AOD) data for the period between 2001 and 2012. A Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model was used for trajectory analysis in order to reconstruct the origins of air masses and understand the Spatial and temporal variability of aerosol concentrations. Validation of MODIS AOD using Aerosol Robotic Network (AERONET) indicated that MODIS overestimated the aerosol loading over the study region. Space time variability of MODIS AOD measurements over Kenya showed a decreasing trend in aerosol loading with a long term mean of between 0.02 and 0.56. Mean monthly AOD values showed two peaks during the months of July and December while seasonal variations indicated high aerosol loading during the December – January –February (DJF) and June –July –August (JJA) season. Back trajectory analyses showed that aerosols mainly dust and sea salt reaching Kenya were transported from either Arabian or Indian sub continent or western parts of the Indian Ocean respectively. Therefore, long term and more comprehensive satellite AOD retrievals are necessary in order to achieve a better understanding of spatial and temporal  variations in aerosols over KenyaKey Words: Aerosol Optical Depth, MODIS, Keny

Sensitivity of Anopheles gambiae population dynamics to meteo-hydrological variability: a mechanistic approach

<p>Abstract</p> <p>Background</p> <p>Mechanistic models play an important role in many biological disciplines, and they can effectively contribute to evaluate the spatial-temporal evolution of mosquito populations, in the light of the increasing knowledge of the crucial driving role on vector dynamics played by meteo-climatic features as well as other physical-biological characteristics of the landscape.</p> <p>Methods</p> <p>In malaria eco-epidemiology landscape components (atmosphere, water bodies, land use) interact with the epidemiological system (interacting populations of vector, human, and parasite). In the background of the eco-epidemiological approach, a mosquito population model is here proposed to evaluate the sensitivity of <it>An. gambiae </it>s.s. population to some peculiar thermal-pluviometric scenarios. The scenarios are obtained perturbing meteorological time series data referred to four Kenyan sites (Nairobi, Nyabondo, Kibwesi, and Malindi) representing four different eco-epidemiological settings.</p> <p>Results</p> <p>Simulations highlight a strong dependence of mosquito population abundance on temperature variation with well-defined site-specific patterns. The upper extreme of thermal perturbation interval (+ 3°C) gives rise to an increase in adult population abundance at Nairobi (+111%) and Nyabondo (+61%), and a decrease at Kibwezi (-2%) and Malindi (-36%). At the lower extreme perturbation (-3°C) is observed a reduction in both immature and adult mosquito population in three sites (Nairobi -74%, Nyabondo -66%, Kibwezi -39%), and an increase in Malindi (+11%). A coherent non-linear pattern of population variation emerges. The maximum rate of variation is +30% population abundance for +1°C of temperature change, but also almost null and negative values are obtained. Mosquitoes are less sensitive to rainfall and both adults and immature populations display a positive quasi-linear response pattern to rainfall variation.</p> <p>Conclusions</p> <p>The non-linear temperature-dependent response is in agreement with the non-linear patterns of temperature-response of the basic bio-demographic processes. This non-linearity makes the hypothesized biological amplification of temperature effects valid only for a limited range of temperatures. As a consequence, no simple extrapolations can be done linking temperature rise with increase in mosquito distribution and abundance, and projections of <it>An. gambiae </it>s.s. populations should be produced only in the light of the local meteo-climatic features as well as other physical and biological characteristics of the landscape.</p

Plant regeneration from immature embryos of Kenyan maize inbred lines and their respective single cross hybrids through somatic embryogenesis

Field grown, self pollinated maize genotypes were planted in KARI (Kiboko and Kabete) research stations between January 2004 and May 2005. Immature maize embryos from twelve parental inbred lines andtheir respective single cross hybrids were evaluated for their ability form callus, somatic embryos and subsequent regeneration into plants. The embryos were excised from surface sterilized kernelsharvested at different physiological stages, namely 10 - 24 days after pollination (DAP). They were used as explants to initiate callus on solid N6 basal media with varying level of 2,4-D (0 - 20 mg L-1) andregenerated on hormone free MS media. Optimal induction of primary callus at 2 mg L-1 averaged 83% and 67 in hybrids and inbred lines respectively. Somatic embryo competence was demonstrated in 6inbreeds and 4 hybrids. However, plant regeneration was only achieved in 4 inbreeds and 3 hybrids. 90% percent of regenerants were normal and fertile. The successful regeneration of some of the inbredlines and/or hybrids provides a basis for development of genetic transformation using Agrobacterium tumefaciens to improve priority traits such as enhanced insects/pest and drought tolerance