Tribo-mechanical properties of thin boron coatings deposited on polished cobalt alloy surfaces for orthopedic applications.

This paper presents experimental evidence that thin (< approximately 200 nm) boron coatings, deposited with a (vacuum) cathodic arc technique on pre-polished Co-Cr-Mo surfaces, could potentially extend the life of metal-on-polymer orthopedic devices using cast Co-Cr-Mo alloy for the metal component. The primary tribological test used a linear, reciprocating pin-on-disc arrangement, with pins made of ultra-high molecular weight polyethylene. The disks were cast Co-Cr-Mo samples that were metallographically polished and then coated with boron at a substrate bias of 500 V and at about 100 degrees C.

Prefrontal cortex and striatal activation by feedback in Parkinson's disease.

Positive feedbacks reinforce goal-directed behavior and evoke pleasure. In Parkinson's disease (PD) the striatal dysfunction impairs motor performance, but also may lead to decreased positive feedback (reward) processing. This study investigates two types of positive feedback processing (monetary feedback and positive informative feedback), both compared to meaningless feedback, in PD patients and elderly healthy controls, using fMRI.

Reward processing in the brain: a prerequisite for movement preparation?

In the last decade, expanding animal studies on the cerebral organization of reward processing toward human in vivo situations has become possible. In this review, we define some of the concepts associated with reward, summarize the crucial importance of the dopaminergic system, and discuss the currently available neuroimaging studies in man. We will show that abstract concepts of human behavior like emotions, drive, arousal, and reinforcement are now open for further exploration in man at the level of neuronal circuit organization.