Comparative Evaluation Of Impact Research Articles

Prospective malaria control using entomopathogenic fungi: comparative evaluation of impact on transmission and selection for resistance

BackgroundChemical insecticides against adult mosquitoes are a key element in most malaria management programmes, but their efficacy is threatened by the evolution of insecticide-resistant mosquitoes. By killing only older mosquitoes, entomopathogenic fungi can in principle significantly impact parasite transmission while imposing much less selection for resistance. Here an assessment is made as to which of the wide range of possible virulence characteristics for fungal biopesticides best realise this potential.MethodsWith mathematical models that capture relevant timings and survival probabilities within successive feeding cycles, transmission and resistance-management metrics are used to compare susceptible and resistant mosquitoes exposed to no intervention, to conventional instant-kill interventions, and to delayed-action biopesticides with a wide range of virulence characteristics.ResultsFungal biopesticides that generate high rates of mortality at around the time mosquitoes first become able to transmit the malaria parasite offer potential for large reductions in transmission while imposing low fitness costs. The best combinations of control and resistance management are generally accessed at high levels of coverage. Strains which have high virulence in malaria-infected mosquitoes but lower virulence in malaria-free mosquitoes offer the ultimate benefit in terms of minimizing selection pressure whilst maximizing impact on transmission. Exploiting this phenotype should be a target for product development. For indoor residual spray programmes, biopesticides may offer substantial advantages over the widely used pyrethroid-based insecticides. Not only do fungal biopesticides provide substantial resistance management gains in the long term, they may also provide greater reductions in transmission before resistance has evolved. This is because fungal spores do not have contact irritancy, reducing the chances that a blood-fed mosquito can survive an encounter and thus live long enough to transmit malaria.ConclusionsDelayed-action products, such as fungal biopesticides, have the potential to achieve reductions in transmission comparable with those achieved with existing instant-kill insecticides, and to sustain this control for substantially longer once resistant alleles arise. Given the current insecticide resistance crisis, efforts should continue to fully explore the operational feasibility of this alternative approach.

Comparative Evaluation of Impact and Flexural Strength of Four Commercially Available Flexible Denture Base Materials: An In Vitro Study

Poly-methyl methacrylate is a rigid material. It is generally observed that the impact and flexural strength of this material is not satisfactory and that is reflected in the continuous efforts to improve these mechanical properties. Hence there was a serious need to make another material which could overcome the limitations of the existing materials and could have better properties, like thermoplastic materials. The study was aimed to evaluate and compare the impact strength and the flexural strength of four different flexible denture base materials (thermoplastic denture base resins) with the conventional denture base material (high impact polymethyl-methacrylate). Two, machine made master moulds of metal blocks according to the size of sample holder of the equipment were prepared to test the impact and flexural strength. Total 40 samples, 10 for each group of flexible denture base materials namely: De-flex (Deflex, United Kingdom), Lucitone FRS (Densply, Germany), Valplast (Novoblast, USA), and Bre-flex (Bredent, Germany) in specially designed flask by injection molded process. For different flexible materials, the time, temperature and pressure for injecting the materials were followed as per the manufacturer's instructions. Total 20 samples for control (Trevelon denture base materials) were prepared by compression moulded process, for each test. ANOVA test was applied to calculate p value. Unpaired t test was applied to calculate t-value. Tukey-Kramer multiple test was provided for comparison between the groups for flexural and impact strength. From the statistical analysis, it was found that, the impact strength of Group III (Valplast) was found to be the highest than all other groups and nearer to the control group. Whereas Group IV (Bre-flex) had the maximum flexural strength. The flexural strength of Group I (De-flex) was lowest than all other groups and nearer to control group. The values were found to be statistically significant but clinically non-significant with the control (p<0.001). The overall results of the study showed that, Group III (Valplast) had the maximum impact strength and Group I (De-flex) had the lowest flexural strength, whereas Group IV (Bre-flex) had the maximum flexural strength and lowest impact strength.