Preparation and biodegradation of clay composites of PLA

PurposePerspective applications of nanocomposites in biomedical applications are investigated in this work by producing intercalated dispersions of clays into a biodegradable polymer matrix. Poly(lactic acid) (PLA) was selected being produced from renewable resources and approved by the Food and Drug Administration for medical use.In order to improve PLA mechanical properties and to accelerate its degradation, different layered silicate nanoclays are added: montmorillonites and fluorohectorites, without or with organic modifiers. Preparation, characterization, mechanical properties and biodegradation in blood plasma are evaluated.ResultsNew biodegradable materials were obtained, with improved mechanical properties (Young modulus, Peak stress and Strain at break) and with increased degradation rate (weight loss and lactic acid release).     

Stimulation artifact in surface EMG signal: effect of the stimulation waveform, detection system, and current amplitude using hybrid stimulation technique

The purpose of this study was to investigate the amplitude properties of the artifact generated on the recorded surface electromyography (EMG) signals during transcutaneous electrical muscle stimulation. The factors which were investigated are the shape of the stimulation waveform, the distance of the stimulating electrode from the recording system, the interelectrode distance of the detection system, the spatial filter used for signal detection, and the stimulation current amplitude. Surface EMG signals were recorded during electrical stimulation of the biceps brachii motor point with a linear adhesive array of eight electrodes. Electrical stimulation was applied with seven stimulation waveforms (mono- and biphasic triangular, sinusoidal, and rectangular), generated by a specifically designed neuromuscular stimulator with hybrid output stage. The stimulation peak current was linearly increased from 0 mA to the maximum tolerated by the subject. The detection systems investigated were single and double differential with interelectrode distances multiple of 5 mm. Two trials for each contraction were performed on three different days. The average rectified artifact values (both absolute and normalized with respect to the corresponding M-wave values) were computed to investigate the artifact amplitude properties. Results indicated that, while the artifact average rectified value, normalized with respect to the M-wave amplitude, depended on the distance of the detecting electrodes from the stimulation point, it did not depend on the stimulation waveform, on the current intensity, on the interelectrode distance, and on the spatial filter. It was concluded that, using hybrid stimulation techniques, the selection of particular stimulation waveforms, interelectrode distances, or spatial filters has a minor effect on the reduction of the artifact when recording M-waves.     

Chronotropic, inotropic and lusitropic effects of capsaicin on isolated rat atria

Family members, teachers, and colleagues are all influential in our socialization as professionals and nurse scientists. This article discusses lessons learned from mentors and facilitators during the various stages in my career, including clinical practice, graduate education, and academia. The value of postdoctoral experiences, whether formal or informal, in the pursuit of excellence is also discussed. Finally, the need to maintain a balanced quality of life is stressed in all phases of a career trajectory to facilitate attainment of our goals and the ability to maintain a standard of excellence.