A review of the tensile and fatigue responses of cellulosic fibre-reinforced polymer composites

ABSTRACT

The use of polymer-based composites has been gaining popularity in the industry over the last few decades. Their high strength to weight ratio and high fatigue resistance make these composites the preferred materials for a wide variety of applications. The current trend has inclined towards hybrid fibre reinforced composites owing to their outstanding characteristics compared to non-hybrid composites. Numerous research works have been conducted to study the fatigue life behaviour of such composite materials. This study addressed the monotonic and dynamic performance of non-hybrid and hybrid natural fibre based composite materials, and the factors that influence their fatigue performance, along with the stiffness decay of each composite material. Most studies have shown the superior potential of using natural fibres in place of synthetic fibres in those critical applications that involve tensile and cyclic loading.     

An essential protease involved in bacterial cell-cycle control

Proteolytic inactivation of key regulatory proteins is essential in eukaryotic cell-cycle control. We have identified a protease in the eubacterium Caulobacter crescentus that is indispensable for viability and cell-cycle progression, indicating that proteolysis is also involved in controlling the bacterial cell cycle. Mutants of Caulobacter that lack the ATP-dependent serine protease ClpXP are arrested in the cell cycle before the initiation of chromosome replication and are blocked in the cell division process. ClpXP is composed of two types of polypeptides, the ClpX ATPase and the ClpP peptidase. Site-directed mutagenesis of the catalytically active serine residue of ClpP confirmed that the proteolytic activity of ClpXP is essential. Analysis of mutants lacking ClpX or ClpP revealed that both proteins are required in vivo for the cell-cycle-dependent degradation of the regulatory protein CtrA. CtrA is a member of the response regulator family of two-component signal transduction systems and controls multiple cell-cycle processes in Caulobacter. In particular, CtrA negatively controls DNA replication and our findings suggest that specific degradation of the CtrA protein by the ClpXP protease contributes to G1-to-S transition in this organism.     

Interracial and intraracial quasi-counseling interactions when counselors avoid discussing race.

Dyadic interactions composed of Black clients and White or Black race-avoidant counselors in 1-time quasi-counseling sessions were influenced by myriad factors, including how these clients responded to influential purveyors of a race-neutralizing climate. Using C. E. Thompson, R. Worthington, and D. R. Atkinson's (see record 1994-30597-001) data set, 24 of these interactions were analyzed to identify significant patterns in the counseling process. The following core categories related to interactional quality were uncovered: smooth, exasperated, constricted, and disjunctive. The following factors explicated these interactional quality categories: (1) whether and how the client introduced race or race-related concerns, (2) client racial identity perspectives; and (3) client affiliation (or lack thereof) with the counselor based on race. The implications of these findings are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)