Review of "The Twelfth West Coast Retrovirus Meeting" and "The Twenty-third Annual Symposium on Nonhuman Primate Models for AIDS"

Two recent meetings held on the west coast of the USA highlighted current work being done in the field of retrovirology and AIDS. The meetings, "The Twelfth West Coast Retrovirus Meeting" (Palm Springs CA; October 6–8, 2005), and the "Twenty-third Annual Symposium on Nonhuman Primate Models for AIDS" (Portland OR; September 21–24) covered a broad range of topics. The highlights covered here are not meant to be inclusive but reflect presentations of interest in the identification and development of new HIV therapies and the role played by animal models in their development

Functionalised Nanopores: Chemical and Biological Modifications

Nanopore technology has established itself as a powerful tool for single-molecule studies. By analysing changes in the ion current flowing through a single transmembrane channel, a wealth of molecular information can be elucidated. Early studies utilised nanopore technology for sensing applications, and subsequent developments have diversified its remit. Nanopores can be synthetic, solid-state, or biological in origin, but recent work has seen these boundaries blurred as hybrid functionalised pores emerge. The modification of existing pores and the construction of novel synthetic pores has been an enticing goal for creating systems with tailored properties and functionality. Here, we explore chemically functionalised biological pores and the bio-inspired functionalisation of solid-state pores, highlighting how the convergence of these domains provides enhanced functionality

Biofilms: Biomaterials and chronic wounds

Healthcare associated infections (HCAIs) are a large and growing problem. Bacterial infections of patients and on the medical devices used to treat them represent a significant source of morbidity and mortality. There is also a significant economical impact to the healthcare system attributed to HCAIs. While bacterial infections per se are not a novel problem, the discovery of an adherent polymicrobial phenotype called a biofilm is. A biofilm is defined by its structure and the community of bacteria therein. This study investigated bacteria biofilms in a number of pertinent clinical scenarios. To achieve this, samples were taken from five different but related clinical areas where biofilms are known to infect or are suspected to, namely endotracheal tubes, tracheostomy tubes, burn wounds, chronic wounds and chronic wound dressings. Samples were analysed using microbiological and molecular analysis techniques, the latter included polymerase chain reactions, species-specific PCR and denaturing gradient gel electrophoresis to assess microbial diversity. Fluorescent in-situ hybridization was used subsequently to analyse species orientation and biofilm structure within the biofilm. This study showed a diverse bacterial population in all the samples, with the presence of oral biota in the ETT specimens, changing to commensal bacteria over time. Large threedimensional biofilm structures were present in the specimens confirming the presence of biofilms, and within one of the chronic wound dressings where a complex biofilm was visible within the matrix of the dressing itself. These findings have considerable significance clinically, not only in demonstrating the need for biofilm targeted diagnostic techniques, but also in highlighting the need for specific biofilm treatment modalities in critical care, burn services and chronic wound management

Evaluation of intake charge hydrogen enrichment in a heavy-duty diesel engine

Concerns over CO2 emissions and global warming continue to enforce the transport sector to reduce the fuel consumption of heavy duty diesel goods vehicles as one major contributor of CO2. Such powertrain platforms look set to remain the dominant source of heavy duty vehicle propulsion for decades to come. The currently reported work was concerned with experimental evaluation of the potential to partially displace diesel with hydrogen fuel, which continues to attract attention as a potential longer term alternative fuel solution whether produced on-board or remotely via sustainable methods. The single cylinder engine adopted was of 2.0 litre capacity, with common rail diesel fuel injection and EGR typical of current production technology. The work involved fumigation of H2 into the engine intake system at engine loads typically visited under real world driving conditions. Highest practical hydrogen substitution ratios increased indicated efficiency by up to 4.6% at 6bar IMEPn and 2.4% at 12bar IMEPn. In 6bar IMEPn, CO2, CO and soot all reduced by 58%, 83% and 58% respectively while the corresponding reduction of these emissions in 12bar IMEPn, were 27%, 45% and 71% respectively toward diesel-only baseline. Under such conditions the use of a pre-injection prior to the main diesel injection was essential to control the heat release and pressure rise rates

Synthetically Diversified Protein Nanopores: Resolving Click Reaction Mechanisms

Nanopores are emerging as a powerful tool for the investigation of nanoscale processes at the single-molecule level. Here, we demonstrate the methionine-selective synthetic diversification of α-hemolysin (α-HL) protein nanopores and their exploitation as a platform for investigating reaction mechanisms. A wide range of functionalities, including azides, alkynes, nucleotides, and single-stranded DNA, were incorporated into individual pores in a divergent fashion. The ion currents flowing through the modified pores were used to observe the trajectory of a range of azide–alkyne click reactions and revealed several short-lived intermediates in Cu­(I)-catalyzed azide–alkyne [3 + 2] cycloadditions (CuAAC) at the single-molecule level. Analysis of ion-current fluctuations enabled the populations of species involved in rapidly exchanging equilibria to be determined, facilitating the resolution of several transient intermediates in the CuAAC reaction mechanism. The versatile pore-modification chemistry offers a useful approach for enabling future physical organic investigations of reaction mechanisms at the single-molecule level

Generalized Sums over Histories for Quantum Gravity II. Simplicial Conifolds

This paper examines the issues involved with concretely implementing a sum over conifolds in the formulation of Euclidean sums over histories for gravity. The first step in precisely formulating any sum over topological spaces is that one must have an algorithmically implementable method of generating a list of all spaces in the set to be summed over. This requirement causes well known problems in the formulation of sums over manifolds in four or more dimensions; there is no algorithmic method of determining whether or not a topological space is an n-manifold in five or more dimensions and the issue of whether or not such an algorithm exists is open in four. However, as this paper shows, conifolds are algorithmically decidable in four dimensions. Thus the set of 4-conifolds provides a starting point for a concrete implementation of Euclidean sums over histories in four dimensions. Explicit algorithms for summing over various sets of 4-conifolds are presented in the context of Regge calculus. Postscript figures available via anonymous ftp at black-hole.physics.ubc.ca (137.82.43.40) in file gen2.ps.Comment: 82pp., plain TeX, To appear in Nucl. Phys. B,FF-92-