Toxicity of Vernonia anthelmintica Linn. (Asteracea) seeds against mosquitoes vectors

The Toxicological activity (larvicidal, adulticidal and repellent toxicity) of Vernonia anthelmintica seeds fraction was tested against different species of mosquito vectors viz, malaria (Anopheles culicifacies and Anopheles stephensi), filaria (Culex quinquefasciatus) and dengue (Aedes aegypti). The larvicidal toxicity of Vernonia anthelmintica seeds fraction was evaluated against the early 4th instars larvae of different mosquitoes species. Mean LC50 value of the column fraction KAL-4 from seeds of V. anthelmintica against the larvae of An. culicifacies, An. stephensi, Culex quinquifaciatus and Aedes aegpyti were found to be 64 ppm, 70 ppm, 143 ppm and 166 ppm respectively. The larvicidal toxicity was more against An. culicifacies, An. stephensi than Culex quinquifaciatus and Aedes aegypti. The seed extracts did not show any adulticidal toxicity and repellent toxicity even at 10% concentrated impregnated paper and 5% on human hand, respectively

Evaluation of Daphnia Magna as an Indicator of Toxicity and Treatment Efficacy of Municipal Sewage Treatment Plant

Performance evaluation of wastewater treatment plants (WWTPs) with special reference to toxicity reduction using Daphnia magna straus as test organism is very important to study the likely adverse effects of the treated wastewater on the aquatic ecosystem of receiving waters and to detect common environmentally realistic concentrations of pollutants at different concentration levels and toxicity discriminatory ability to distinguish different degree of toxicity and toxic specificity of the compounds on target organisms. This test can be considered as useful analytical tool for screening of chemical analysis and early warning system to monitor the different operational units of wastewater treatment plants. Interrelationship between COD, SS with respect to Daphnia toxicity (Gd) suggests that improvement of the toxicological quality of wastewater could be linked to the removal of both COD and suspended solids. Both the parameters (COD & SS) can serve as a regulatory tool in lieu of an explicit toxicological standard. An important feature of this work was to emphasize the significance of toxicity tests. It could help to reduce influent toxicity and thereby avoid impacting microorganisms\u2019 population in activated sludge systems. This study shows the difference between using physico-chemical and biological criteria to define the quality or toxicity of wastewater, making it clear that both methods are indispensable and complimentary and support the earlier view that Daphnia magna can serve as a valuable model for bio- monitoring of water pollution and for evaluation of the toxicity of an effluent and risk assessment in an aquatic body, as it is highly sensitive to pollutants

Reflection of electrons from a domain wall in magnetic nanojunctions

Electronic transport through thin and laterally constrained domain walls in ferromagnetic nanojunctions is analyzed theoretically. The description is formulated in the basis of scattering states. The resistance of the domain wall is calculated in the regime of strong electron reflection from the wall. It is shown that the corresponding magnetoresistance can be large, which is in a qualitative agreement with recent experimental observations. We also calculate the spin current flowing through the wall and the spin polarization of electron gas due to reflections from the domain wall.Comment: 7 pages, 4 figure

Nonlinear dynamic analysis of masonry buildings and definition of seismic damage states

A large part of the building stock in seismic-prone areas worldwide are masonry structures that have been designed without seismic design considerations. Proper seismic assessment of such structures is quite a challenge, particularly so if their response well into the inelastic range, up to local or global failure, has to be predicted, as typically required in fragility analysis. A critical issue in this respect is the absence of rigid diaphragm action (due to the presence of relatively flexible floors), which renders particularly cumbersome the application of popular and convenient nonlinear analysis methods like the static pushover analysis. These issues are addressed in this paper that focusses on a masonry building representative of Southern European practice, which is analysed in both its pristine condition and after applying retrofitting schemes typical of those implemented in pre-earthquake strengthening programmes. Nonlinear behaviour is evaluated using dynamic response-history analysis, which is found to be more effective and even easier to apply in this type of building wherein critical modes are of a local nature, due to the absence of diaphragm action. Fragility curves are then derived for both the initial and the strengthened building, exploring alternative definitions of seismic damage states, including some proposals originating from recent international research programmes