Pyrite-induced hydroxyl radical formation and its effect on nucleic acids

BACKGROUND: Pyrite, the most abundant metal sulphide on Earth, is known to spontaneously form hydrogen peroxide when exposed to water. In this study the hypothesis that pyrite-induced hydrogen peroxide is transformed to hydroxyl radicals is tested. RESULTS: Using a combination of electron spin resonance (ESR) spin-trapping techniques and scavenging reactions involving nucleic acids, the formation of hydroxyl radicals in pyrite/aqueous suspensions is demonstrated. The addition of EDTA to pyrite slurries inhibits the hydrogen peroxide-to-hydroxyl radical conversion, but does not inhibit the formation of hydrogen peroxide. Given the stability of EDTA chelation with both ferrous and ferric iron, this suggests that the addition of the EDTA prevents the transformation by chelation of dissolved iron species. CONCLUSION: While the exact mechanism or mechanisms of the hydrogen peroxide-to-hydroxyl radical conversion cannot be resolved on the basis of the experiments reported in this study, it is clear that the pyrite surface promotes the reaction. The formation of hydroxyl radicals is significant because they react nearly instantaneously with most organic molecules. This suggests that the presence of pyrite in natural, engineered, or physiological aqueous systems may induce the transformation of a wide range of organic molecules. This finding has implications for the role pyrite may play in aquatic environments and raises the question whether inhalation of pyrite dust contributes to the development of lung diseases

Understanding diagnosis and management of dementia and guideline implementation in general practice: a qualitative study using the theoretical domains framework

Dementia is a growing problem, causing substantial burden for patients, their families, and society. General practitioners (GPs) play an important role in diagnosing and managing dementia; however, there are gaps between recommended and current practice. The aim of this study was to explore GPs' reported practice in diagnosing and managing dementia and to describe, in theoretical terms, the proposed explanations for practice that was and was not consistent with evidence-based guidelines

High-gain output feedback for a miniature UAV

We consider the problem of output feedback robust stabilization of a ducted-fan aerial vehicle in which high-gain observers are used to overtake the knowledge of the linear and angular velocities of the vehicle in the control law. The proposed result is semiglobal in the attitude dynamics and in the estimation error, and global in the position variables. It is shown how the high-gain control structure is effective notwithstanding the nonminimum-phase behavior of the considered class of systems, provided that the airframe fulfills some geometric properties. The controller relies upon the use of nested saturations and high-gain control laws. Although the theory is specified for a force-torque generation mechanism of a ducted-fan aerial vehicle, the results can be simply extended to the output feedback of many other under-actuated rotorcrafts, such as helicopters. Experimental results are also proposed showing the effectiveness of the control law.We consider the problem of output feedback robust stabilization of a ducted-fan aerial vehicle in which high-gain observers are used to overtake the knowledge of the linear and angular velocities of the vehicle in the control law. The proposed result is semiglobal in the attitude dynamics and in the estimation error, and global in the position variables. It is shown how the high-gain control structure is effective notwithstanding the nonminimum-phase behavior of the considered class of systems, provided that the airframe fulfills some geometric properties. The controller relies upon the use of nested saturations and high-gain control laws. Although the theory is specified for a force-torque generation mechanism of a ducted-fan aerial vehicle, the results can be simply extended to the output feedback of many other under-actuated rotorcrafts, such as helicopters. Experimental results are also proposed showing the effectiveness of the control law