Archive for August, 2007
A Path Analysis of the Relationships between Social Problem Solving and White Racial Identity
Diversity on U.S. college campuses is increasing, with the enrollment of students of color growing by over 48% in the last decade (McTighe, Garcia, Hudgins, Nettles, Sedlack, & Smith,, 1999). Consequently, White college students are increasingly interacting with individuals from different racial groups. In addition, identity development becomes particularly relevant during this period (Erikson, 1968). As such, White college students psychological orientation towards racial group membership (i.e., White racial identity) may become salient as students begin to explore their reactions to societal dynamics of racial oppression (Carter, 1997; Helms, 1996). › Continue reading
Influence of Dissolved Organic Carbon on the Viability and Infectivity of Cryptosporidium
Cryptosporidium is a group of waterborne protozoan parasites that cause significant gastrointestinal infection in humans. The challenges associated with pathogen removal from water supplies, combined with the lack of medical cure for this infection, makes environmental controls important to investigate. The infectivity of Cryptosporidium oocysts under different environmental conditions must be examined to determine the risk of human exposure and infection. The research goal is to understand the direct effect of dissolved organic carbon (DOC) on the viability and infectivity of Cryptosporidium, as well as its indirect effects through other related environmental factors, including pH and UV radiation (UVR). This project examines direct and indirect effects of DOC on the viability and infectivity of Cryptosporidium using DAPI/PI staining, an excystation assay, and an in-vitro cell culture infectivity assay. The results show that both pH and DOC have significant impacts on Cryptosporidium viability and infectivity. This negative effect of DOC appears to be greater than the protective effect DOC has on oocysts by blocking damaging UVR. By identifying the influence of DOC and its interactions with other ecological factors on Cryptosporidium, watersheds at risk for supporting infectious oocysts can be identified and targeted for enhanced protection and/or water treatment.
SHIM: A Scalable Hierarchical Inter-domain Multicast Approach for Disruption Tolerant Networks
Disruption Tolerant Network (DTN) technologies are emerging solutions to networks that experience frequent partitions. In this paper, we propose the scalable hierarchical inter-domain multicast (SHIM) approach for DTNs. SHIM has the following characteristics: i) it is capable of delivering multicast messages to receivers distributed in different domains; ii) the size of the membership information maintained by the source leader is determined by its out-degree in the leader layer, no matter how large the number of the real receivers is; and iii) it at least doubles the message delivery efficiency than that of directly extending the existing intra-domain DTN multicast methods to perform the inter-domain multicast operations. Our results also show that the message delivery ratio of SHIM can be improved to be almost 100% when the custodian transfer functionality is enabled in the overall networks.