Joint Spatial Modeling of Recurrent Infection and Growth with Processes Under Intermittent Observation

In this article we present new statistical methodology for longitudinal studies in forestry where trees are subject to recurrent infection and the hazard of infection depends on tree growth over time. Understanding the nature of this dependence has important implications for reforestation and breeding programs. Challenges arise for statistical analysis in this setting with sampling schemes leading to panel data, exhibiting dynamic spatial variability, and incomplete covariate histories for hazard regression. In addition, data are collected at a large number of locations which poses computational difficulties for spatiotemporal modeling. A joint model for infection and growth is developed; wherein, a mixed non-homogeneous Poisson process, governing recurring infection, is linked with a spatially dynamic nonlinear model representing the underlying height growth trajectories. These trajectories are based on the von Bertalanffy growth model and a spatially-varying parametrization is employed. Spatial variability in growth parameters is modeled through a multivariate spatial process derived through kernel convolution. Inference is conducted in a Bayesian framework with implementation based on hybrid Monte Carlo. Our methodology is applied for analysis in an eleven year study of recurrent weevil infestation of white spruce in British Columbia

A comprehensive mapping of malarial infections in children under 10 years in Kano Central Senatorial District, Kano State, northern Nigeria

This study is a baseline to assess and map out the distribution of malaria infection using the prevalence level within the central senatorial districts of Kano State, Northern Nigeria. Blood samples were collected from 50 individuals’ aged below 0 - 10 years from which each of the 15 LGA. Thick and thin blood films were prepared and stained with Giemsa following standard procedure and examined for malaria parasites species identification. The overall prevalence of malaria was 40% and was caused by Plasmodium falciparum. Mapping of malaria using prevalence data showed level of endemicity that ranged from meso to hyper endemicity with a larger proportion of the LGAs (40.6%) being meso-endemic. In conclusion, targeted mass treatments of infections including asymptomatic ones are recommended as promising measures to reduce malaria surge.Keywords: Mapping, malaria distribution in children under 10 years, P. falciparum, Kano Stat

Improving growth and yield of cowpea by foliar application of chitosan under water stress

Water stress impaired cowpea plant growth and decreased ion percentage and chlorophyll and carbohydrate concentration in the shoot as well as yield and its quality. Foliar-applied chitosan, in particular 250 mg/l, increased plant growth, yield and its quality as well as physiological constituents in plant shoot under stressed or nonstressed conditions as compared to untreated plants. Anatomically, water stress decreased thickness of leaf blade at midrib region, thickness of mesophyll tissue, thickness of midrib vascular bundle. Treatment with chitosan, in particular, 250 mg/l and their interactions with stress conditions increased all the above mentioned parameters in either non-stressed or stressed plants. It is suggested that the severity of cowpea plants damaged from water stress was reduced by 250 mg/l chitosan application.Keywords: water stress, chitosan, cowpea, anatomy, growth, yield

Alleviation of oxidative stress induced by spider mite invasion through application of elicitors in bean plants

Spider mite invasion induces oxidative stress on bean plants and increased soluble sugars, phenole, proline and peroxidase activity, but decreased catalase activity and ascorbic acid and carotenoid concentration. Application of elicitors significantly enhanced spider mite tolerance by decreasing hydrogen peroxide, malondialdehyde, electrolyte leakage, and increasing peroxidase activity and antioxidant compounds reported previously, leading to increasing ion percentage in plant shoot. This finding suggests that elicitors might be activating antioxygenic enzymes and elevating antioxidants there by controlling free radical generation, hence preventing membrane peroxidation and denaturation of biomolecules resulting into improving plant growth.Keywords: Tetranychus urticae, Phaseolus vulgaris, salicylate, methyl jasmonate, antioxidants