Optimal progressive taxation in a model with endogenous skill supply

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Some results on contractive mappings as related to pattern recognition

Several of the techniques used in pattern recognition are reformulated as the problem of determining fixed points of a function. If x sub 0 is a fixed point of f and if f is contractive at x sub 0, then, for any y belonging to a sufficiently small neighborhood of x sub 0 the orbit of y will converge to x sub 0. Several general results regarding contractive mappings are developed with emphasis on functions

Micro-geographic risk factors for malarial infection.

BACKGROUND: Knowledge of geography is integral to the study of insect-borne infectious disease such as malaria. This study was designed to evaluate whether geographic parameters are associated with malarial infection in the East Sepik province of Papua New Guinea (PNG), a remote area where malaria is a major cause of morbidity and mortality. METHODS: A global positioning system (GPS) unit was used at each village to collect elevation, latitude and longitude data. Concurrently, a sketch map of each village was generated and the villages were sub-divided into regions of roughly equal populations. Blood samples were taken from subjects in each region using filter paper collection. The samples were later processed using nested PCR for qualitative determination of malarial infection. The area was mapped using the GPS-information and overlaid with prevalence data. Data tables were examined using traditional chi square statistical techniques. A logistic regression analysis was then used to determine the significance of geographic risk factors including, elevation, distance from administrative centre and village of residence. RESULTS: Three hundred and thirty-two samples were included (24% of the total estimated population). Ninety-six were positive, yielding a prevalence of 29%. Chi square testing within each village found a non-random distribution of cases across sub-regions (p < 0.05). Multivariate logistic regression techniques suggested malarial infection changed with elevation (OR = 0.64 per 10 m, p < 0.05) and distance from administrative centre (OR = 1.3 per 100 m, p < 0.05). CONCLUSION: These results suggest that malarial infection is significantly and independently associated with lower elevation and greater distance from administrative centre in a rural area in PNG. This type of analysis can provide information that may be used to target specific areas in developing countries for malaria prevention and treatment

A Classical Molecular Dynamics Study on the Effect of Si/Al Ratio and Silanol Nest Defects on Water Diffusion in Zeolite HY

The diffusion of water confined in zeolite HY has been studied using classical molecular dynamics at 300 K to probe the effects of water loading, Si/Al ratio, and silanol nest defect presence on the behavior of water confined in Brønsted acidic faujasite (FAU) zeolites. Water loading, ranging from 5 to 33 wt %, is shown to have a significant effect on diffusivity, showing an increase by a factor of ∼7 over the loading range, toward a maximum diffusivity. Upon probing the effect of Si/Al ratio (in a range of Si/Al = 5 to fully siliceous), water diffusivity tends to decrease with the concentration of Brønsted acid sites which show strong interactions with the water molecules and thus hinder molecular mobility. The average residence time of water adsorbed to each Brønsted acid site also decreased with both water loading and Si/Al ratio. Water diffusivity shows the highest dependency on Si/Al ratio at 18 wt % loading, as a lack of total mobility in the systems at the lowest loadings is observed (due to significant populations of water molecules being immobilized via interaction with the framework and Brønsted acid sites), and less of a dependence is observed at the highest loadings due to the prevalence of sorbate-sorbate interactions. Notably, silanol nest presence (at a concentration of 1 per unit cell) had no significant effect on the diffusivity of water in HY at any water loading or Si/Al ratio. Reasons considered for this lack of influence include silanol geometry and flexibility at ambient temperature and potentially a lower effective charge density of the defect site.</p

A Classical Molecular Dynamics Study on the Effect of Si/Al Ratio and Silanol Nest Defects on Water Diffusion in Zeolite HY

The diffusion of water confined in zeolite HY has been studied using classical molecular dynamics at 300 K to probe the effects of water loading, Si/Al ratio, and silanol nest defect presence on the behavior of water confined in Brønsted acidic faujasite (FAU) zeolites. Water loading, ranging from 5 to 33 wt %, is shown to have a significant effect on diffusivity, showing an increase by a factor of ∼7 over the loading range, toward a maximum diffusivity. Upon probing the effect of Si/Al ratio (in a range of Si/Al = 5 to fully siliceous), water diffusivity tends to decrease with the concentration of Brønsted acid sites which show strong interactions with the water molecules and thus hinder molecular mobility. The average residence time of water adsorbed to each Brønsted acid site also decreased with both water loading and Si/Al ratio. Water diffusivity shows the highest dependency on Si/Al ratio at 18 wt % loading, as a lack of total mobility in the systems at the lowest loadings is observed (due to significant populations of water molecules being immobilized via interaction with the framework and Brønsted acid sites), and less of a dependence is observed at the highest loadings due to the prevalence of sorbate-sorbate interactions. Notably, silanol nest presence (at a concentration of 1 per unit cell) had no significant effect on the diffusivity of water in HY at any water loading or Si/Al ratio. Reasons considered for this lack of influence include silanol geometry and flexibility at ambient temperature and potentially a lower effective charge density of the defect site.</p