instruments have been traditionally used with a continuous rotary motion, but more recently, a new approach to the use of nickel-titanium instruments in a reciprocating movement has been introduced by Yared (2004). The clockwise (CW) and counter-clockwise (CCW) rotations used by Yared were four-tenths and two-tenths of a circle respectively, and the rotational speed utilized was 400 rpm. The co...

Reciprocity is an important motivator of human judgement and is frequently used to justify decisions. It is a common feature of social relationships wherein beneficial conduct is encouraged through rewards while deleterious behaviors are discouraged via punishment. However, despite its ubiquity and pervasiveness in intraand inter-organizational relationships, there are circumstances when recipr...

The following is a model of psychological contracting with unmonitorable performance, implicit o¤ers, and screening for non-performance by the announcement of the expectation of performance. It is motivated by the $250 billion prescription drug industry, which spends $19 billion per year on marketing to US doctors, mostly on ‘gifts’, and often, as at Yale, with no monitoring for reciprocation. ...

People often interact repeatedly: with relatives, through file sharing, in politics, etc. Many such interactions are reciprocal: reacting to the actions of the other. In order to facilitate decisions regarding reciprocal interactions, we analyze the development of reciprocation over time. To this end, we propose a model for such interactions that is simple enough to enable formal analysis, but ...

Cooperation violates the view of "nature red in tooth and claw" that prevails in our understanding of evolution, yet examples of cooperation abound. Most work has focused on maintenance of cooperation within a single species through mechanisms such as kin selection. The factors necessary for the evolutionary origin of aiding unrelated individuals such as members of another species have not been...

Cooperative behaviour through reciprocation or interchange of valuable services in primates has received considerable attention, especially regarding the timeframe of reciprocation and its ensuing cognitive implications. Much less, however, is known about reciprocity in other animals, particularly birds. We investigated patterns of agonistic support (defined as a third party intervening in an o...