University of Memphis

About: University of Memphis is a education organization based out in Memphis, Tennessee, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 7710 authors who have published 20082 publications receiving 611618 citations. The organization is also known as: U of M.

Design and characterization of a novel chitosan/nanocrystalline calcium phosphate composite scaffold for bone regeneration

Abstract: To meet the challenge of regenerating bone lost to disease or trauma, biodegradable scaffolds are being investigated as a way to regenerate bone without the need for an auto- or allograft. Here, we have developed a novel microsphere-based chitosan/nanocrystalline calcium phosphate (CaP) composite scaffold and investigated its potential compared to plain chitosan scaffolds to be used as a bone graft substitute. Composite and chitosan scaffolds were prepared by fusing microspheres of 500-900 microm in diameter, and porosity, degradation, compressive strength, and cell growth were examined. Both scaffolds had porosities of 33-35% and pore sizes between 100 and 800 . However, composite scaffolds were much rougher and, as a result, had 20 times more surface area/unit mass than chitosan scaffolds. The compressive modulus of hydrated composite scaffolds was significantly higher than chitosan scaffolds (9.29 +/- 0.8 MPa vs. 3.26 +/- 2.5 MPa), and composite scaffolds were tougher and more flexible than what has been reported for other chitosan-CaP composites or CaP scaffolds alone. Using X-ray diffraction, scaffolds were shown to contain partially crystalline hydroxyapatite with a crystallinity of 16.7% +/- 6.8% and crystallite size of 128 +/- 55 nm. Fibronection adsorption was increased on composite scaffolds, and cell attachment was higher on composite scaffolds after 30 min, although attachment rates were similar after 1 h. Osteoblast proliferation (based on dsDNA measurements) was significantly increased after 1 week of culture. These studies have demonstrated that composite scaffolds have mechanical properties and porosity sufficient to support ingrowth of new bone tissue, and cell attachment and proliferation data indicate composite scaffolds are promising for bone regeneration.

Peer Groups, Popularity, and Social Preference Trajectories of Social Functioning Among Students With and Without Learning Disabilities

Abstract: The extant literature on the social functioning of students with learning disabilities (LD) has indicated that whereas a majority belong to peer groups, a higher proportion are isolated and most have lower social status among peers in general than their typically achieving classmates. Although some work has examined these issues over short-term longitudinal studies, none to date have examined them over extensive time periods. Toward this end, the current study examined a sample of 1,361 students (678 girls and 683 boys; 55 with LD) using multiple measures of peer social functioning assessed each semester from spring of third grade through fall of sixth grade. The results indicated that whereas students with LD were similar to their typically achieving peers in terms of group functioning and characteristics, they were viewed as lower in social standing among their classmates as a whole. These effects were maintained over time, indicating that long-term inclusion may not substantially affect peer social functioning among students with LD.

Relative Effects of Interventions Supporting the Social Competence of Young Children with Disabilities.

Abstract: This study compared the effects of different intervention approaches designed to promote peer-related social competence of young children with disabilities. Preschool-age children with disabilities who were enrolled in classes in Tennessee and Minnesota participated in four intervention conditions (environmental arrangements, child specific, peer mediated, and comprehensive) and a control (no intervention) condition. A performance-based assessment of social competence, which consisted of observational, teacher rating, and peer rating measures, was collected before and after the interventions and again the following school year. Analyses revealed that the peer-mediated condition had the greatest and most sustained effect on children's participation in social interaction and on the quality of interaction, with the child-specific condition also having a strong effect. The environmental arrangements condition had the strongest effect on peer ratings. These findings indicate that there are effective interventi...

Colonial Style and Post-Colonial Ethnic Conflict in Africa

Abstract: Though European colonialism had a profound and lasting impact on the development of contemporary Africa, there are few studies that assess these effects empirically. This study explores one facet of the colonial legacy: ethnic conflict. Despite the pervasiveness of ethnic strife across the continent, grievance-based approaches have had only limited success in modeling ethnic conflict in Africa. Using a structural approach, we argue that the distinctive colonial styles of the British and French created fundamentally different systems of ethnic stratification, which left contrasting legacies for post-colonial ethnic conflict. Specifically, the indirect, decentralized rule of the British fostered an unranked system of ethnic stratification, while the legacy of the centralized French style approximated a ranked system. Because unranked systems foster competition between ethnic groups - which can readily spiral into conflict - we posit that the British colonial legacy is positively related to both the frequenc...