Étude des variations des vitesses d’hydrolyse trypsique de quelques esters acylés

Lors de l’hydrolyse trypsique de quelques esters acylés de l’arginine on observe des variations de la vitesse de réaction en fonction du pH dont le caractère dépend du choix particulier du substrat. Les vitesse d'hydrolyse des deux isomères optiques du TAM (p-toluène-sulfonylarginine méthylester) par la trypsine, en fonction du pH, correspondent à deux courbes différentes quand les mesures sont effectuées avec des concentrations en substrat constantes. L’hydrolyse du L-BAE (benzoyl-L-arginine éthylester) en fonction du pH conduit à une courbe encore différente de celles qui se rapportent à l’hydrolyse des deux isomères optiques. La méthode potentiométrique à pH constant est susceptible d’introduire des erreurs si un groupement du substrat est ionisé d’une manière appréciable dans la zone des mesures du pH. Par conséquent, l’on ne peut attribuer aux groupements de l’enzyme, les pK évalués expérimentalement

Tutorial on operating characteristics of microprocessor-based multiterminal line current differential relays

Line current differential (87L) protection schemes face extra challenges compared with other forms of differential protection, in addition to the traditional requirements of sensitivity, speed, and immunity to current transformer saturation. Some of these challenges include data communication, alignment, and security; line charging current; and limited communications bandwidth. To address these challenges, microprocessor-based 87L relays apply elaborate operating characteristics, which are often different than a traditional percentage differential characteristic used for bus or transformer protection. These sophisticated elements may include adaptive restraining terms, apply an Alpha Plane, use external fault detection logic for extra security, and so on. While these operating characteristics provide for better performance, they create the following challenges for users: x Understanding how the 87L elements make the trip decision. x Understanding the impact of 87L settings on sensitivity and security, as well as grasping the relationship between the traditional percentage differential characteristic and the various 87L operating characteristics. x Having the ability to transfer settings between different 87L operating characteristics while keeping a similar balance between security and dependability. x Testing the 87L operating characteristics. These issues become particularly significant in applications involving more than two currents in the line protection zone (multiterminal lines) and lines terminated on dual-breaker buses. This paper is a tutorial on this relatively new protection topic and offers answers to the outlined challenges