Dynamic Social Impact and the Evolution of Social Representations: A Natural History of Stereotypes

It should be evident by now that, like cells and organisms, populations are kept together and integrated by systems of communication. ( MacArthur & Connell, 1766, p. 119 )     

Synthesis and Characterization of Monodisperse α,ω-Divinylpolydimethylsiloxane and ω-Vinylpolydimethylsiloxane

Abstract

ω-Vinylpolydimethylsiloxanes (ω-PDMS) and α,ω-divynilpolydimethylsiloxanes (α,ω-PDMS) have been synthesized by anionic polymerization of hexamethylcyclotrisiloxane (D3). The reactions were carried out in n-hexane and tetrahydrofuran (THF), respectively. The initiator was n-butyl-lithium (n-BuLi); tetrahydrofuran was used as an electron donor compound to promote the polymerization of D3. The synthesized polymers have been characterized by infrared (FTIR), proton nuclear magnetic resonance spectroscopy (NMR), light scattering (LALLS), and gel permeation chromatography (GPC). Molecular weights ranging from 20,000 to 100,000 were obtained with relatively narrow molecular weight distributions; Mw/Mn < 1.25.     

Analysis of the prodiginine biosynthesis gene cluster of Streptomyces coelicolor A3(2): new mechanisms for chain initiation and termination in modular multienzymes

BACKGROUND: Prodiginines are a large family of pigmented oligopyrrole antibiotics with medicinal potential as immunosuppressants and antitumour agents that are produced by several actinomycetes and other eubacteria. Recently, a gene cluster in Streptomyces coelicolor encoding the biosynthesis of undecylprodiginine and butyl-meta-cycloheptylprodiginine has been sequenced. RESULTS: Using sequence comparisons, functions have been assigned to the majority of the genes in the cluster, several of which encode homologues of enzymes involved in polyketide, non-ribosomal peptide, and fatty acid biosynthesis. Based on these assignments, a complete pathway for undecylprodiginine and butyl-meta-cycloheptylprodiginine biosynthesis in S. coelicolor has been deduced. Gene knockout experiments have confirmed the deduced roles of some of the genes in the cluster. CONCLUSIONS: The analysis presented provides a framework for a general understanding of the genetics and biochemistry of prodiginine biosynthesis, which should stimulate rational approaches to the engineered biosynthesis of novel prodiginines with improved immunosuppressant or antitumour activities. In addition, new mechanisms for chain initiation and termination catalysed by hitherto unobserved domains in modular multienzyme systems have been deduced.     

Dynamic Code Assignment Medium Access (DCAMA) Protocol for Wireless Integrated Services Networks

A medium access control (MAC) protocol for wireless mobile networks that supports integrated services and provides quality of service (QoS) support is presented and evaluated via simulation. A controlled random access protocol which allows all terminals to dynamically share a group of spread spectrum spreading codes is used. The protocol provides mobile terminals the access control required for efficient transfer of integrated traffic with QoS guarantees. Two service classes are provided; "best-effort" service, with priority queueing, and reserved bandwidth circuit service. The performance of the protocol is evaluated via simulation for traffic consisting of integrated voice, data and compressed video. The performance assessment measure is packet delay.