this paper considers the problem of stable limit cycles generating in a class of uncertain nonlinear systems which leads to stable oscillations in the system’s output.this is a wanted behavior in many practical engineering problems. for this purpose, first the equation of the desirable limit cycle is achieved according to shape, amplitude and frequency of the required output oscillations. then,...

a label-free electrochemical nucleic acid aptasensor for the detection of methamphetamine (ma) by the immobilization of thiolated self-assembled dna sequences on a gold nanoparticles-chitosan modified electrode is constructed. when ma was complexed specifically to the aptamer, the configuration of the nucleic acid aptamer switched to a locked structure and the interface of the biosensor changed...

in this research, air sampling of workplaces was carried out by two methods (long - time and short - time). the mean formaldehyde concentration with long - time method in pathology labs, surgery and endoscopy sections were 0.96 0.25 and 0.13 ppm and with short - time method, 8 hours, was 3, 0.3 and 0.2 ppm. the mean formaldehyde concentration in pathology labs was above the standard values (tlv...

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