Costs of resistance: genetic correlations and potential trade-offs in an insect immune system

Theory predicts that natural selection will erode additive genetic variation in fitness-related traits. However, numerous studies have found considerable heritable variation in traits related to immune function, which should be closely linked to fitness. This could be due to trade-offs maintaining variation in these traits. We used the Egyptian cotton leafworm, Spodoptera littoralis, as a model system to examine the quantitative genetics of insect immune function. We estimated the heritabilities of several different measures of innate immunity and the genetic correlations between these immune traits and a number of life history traits. Our results provide the first evidence for a potential genetic trade-off within the insect immune system, with antibacterial activity (lysozyme-like) exhibiting a significant negative genetic correlation with haemocyte density, which itself is positively genetically correlated with both haemolymph phenoloxidase activity and cuticular melanization. We speculate on a potential trade-off between defence against parasites and predators, mediated by larval colour, and its role in maintaining genetic variation in traits under natural selection.

Advanced Ceramic Substrate with Ordered and Designed Micro-Structure for Applications in Automotive Catalysts

This study describes an innovative monolith structure designed for applications in automotive catalysis using an advanced manufacturing approach developed at Imperial College London. The production process combines extrusion with phase inversion of a ceramic-polymer-solvent mixture in order to design highly ordered substrate micro-structures that offer improvements in performance, including reduced PGM loading, reduced catalyst ageing and reduced backpressure.

This study compares the performance of the novel substrate for CO oxidation against commercially available 400 cpsi and 900 cpsi catalysts using gas concentrations and a flow rate equivalent to those experienced by a full catalyst brick when attached to a vehicle. Due to the novel micro-structure, no washcoat was required for the initial testing and 13 g/ft3 of Pd was deposited directly throughout the substrate structure in the absence of a washcoat.

Initial results for CO oxidation indicate that the advanced micro-structure leads to enhanced conversion efficiency. Despite an 79% reduction in metal loading and the absence of a washcoat, the novel substrate sample performs well, with a light-off temperature (LOT) only 15 °C higher than the commercial 400 cpsi sample.

To test the effects of catalyst ageing on light-off temperature, each sample was aged statically at a temperature of 1000 °C, based on the Bench Ageing Time (BAT) equation. The novel substrate performed impressively when compared to the commercial samples, with a variation in light-off temperature of only 3% after 80 equivalent hours of ageing, compared to 12% and 25% for the 400 cpsi and 900 cpsi monoliths, respectively.

Joining the `Crusade against the Giants': Keir Hardie's Fairy Tales and The Socialist Child Reader

This article focuses on Keir Hardie's forgotten fiction and journalism for children, published in his paper The Labour Leader during the 1890s. It argues that Hardie's dialogue with child correspondents was shaped by a socialist periodical culture that redefined reading as a communal, political activity. Relating Hardie's appropriation of fantasy to that of a fellow socialist editor, John Trevor, the article examines the fairy tale as a propaganda tool in the process of `making socialists', but also questions the model of child readers as passive consumers, arguing that young readers were both empowered and controlled by Hardie's journalistic strategies.

Development of a rapid colorimetric time-kill assay for determining the in vitro activity of ceftazidime and tobramycin in combination against Pseudomonas aeruginosa

It is standard clinical practice to use a combination of two or more antimicrobial agents to treat an infection caused by Pseudonionas aeruginosa. The antibiotic combinations are usually selected empirically with methods to determine the antimicrobial effect of the combination such as the time-kill assay rarely used as they are time-consuming and labour intensive to perforin. Here, we report a modified time-kill assay, based on the reduction of the tetrazolium salt, 2,3-bis[2-methyloxy-4-nitro-5-sulfopheny1]-2H-tetrazolium-5-carboxanilide (XTT), that allows simple, inexpensive and more rapid determination of the in vitro activity of antibiotic combinations against P aeruginosa. The assay was used to determine the in vitro activity of ceftazidime and tobramycin in combination against P. aertiginosa isolates from cystic fibrosis patients and the results obtained compared with those from conventional viable count time-kill assays. There was good agreement in interpretation of results obtained by the XTT and conventional viable count assays, with similar growth curves apparent and the most effective concentration combinations determined by both methods identical for all isolates tested. The XTT assay clearly indicated whether an antibiotic combination had a synergistic, indifferent or antagonistic effect and could, therefore, provide a useful method for rapidly determining the activity of a large number of antibiotic combinations against clinical isolates. (C) 2004 Elsevier B.V. All rights reserved.

Addressing Bed Costs for the Elderly: A New Methodology for Modelling Patient Outcomes and Length of Stay

The proportion of elderly in the population has dramatically increased and will continue to do so for at least the next 50 years. Medical resources throughout the world are feeling the added strain of the increasing proportion of elderly in the population. The effective care of elderly patients in hospitals may be enhanced by accurately modelling the length of stay of the patients in hospital and the associated costs involved. This paper examines previously developed models for patient length of stay in hospital and describes the recently developed conditional phase-type distribution (C-Ph) to model patient duration of stay in relation to explanatory patient variables. The Clinics data set was used to demonstrate the C-Ph methodology. The resulting model highlighted a strong relationship between Barthel grade, patient outcome and length of stay showing various groups of patient behaviour. The patients who stay in hospital for a very long time are usually those that consume the largest amount of hospital resources. These have been identified as the patients whose resulting outcome is transfer. Overall, the majority of transfer patients spend a considerably longer period of time in hospital compared to patients who die or are discharged home. The C-Ph model has the potential for considering costs where different costs are attached to the various phases or subgroups of patients and the anticipated cost of care estimated in advance. It is hoped that such a method will lead to the successful identification of the most cost effective case-mix management of the hospital ward.