Modal coupling in linear control systems using robust eigenstructure assignment

Eigenvalue assignment methods are used widely in the design of control and state-estimation systems. The corresponding eigenvectors can be selected to ensure robustness. For specific applications, eigenstructure assignment can also be applied to achieve more general performance criteria. In this paper a new output feedback design approach using robust eigenstructure assignment to achieve prescribed mode input and output coupling is described. A minimisation technique is developed to improve both the mode coupling and the robustness of the system, whilst allowing the precision of the eigenvalue placement to be relaxed. An application to the design of an automatic flight control system is demonstrated.

Lactobacilli antagonize the growth, motility, and adherence of brachyspira pilosicoli: a potential intervention against avian intestinal spirochetosis

Avian intestinal spirochetosis (AIS) results from the colonization of the ceca and colorectum of poultry by pathogenic Brachyspira species. The number of cases of AIS has increased since the 2006 European Union ban on the use of antibiotic growth promoters, which, together with emerging antimicrobial resistance in Brachyspira, has driven renewed interest in alternative intervention strategies. Probiotics have been reported as protecting livestock against infection with common enteric pathogens, and here we investigate which aspects of the biology of Brachyspira they antagonize in order to identify possible interventions against AIS. The cell-free supernatants (CFS) of two Lactobacillus strains, Lactobacillus reuteri LM1 and Lactobacillus salivarius LM2, suppressed the growth of Brachyspira pilosicoli B2904 in a pH-dependent manner. In in vitro adherence and invasion assays with HT29-16E three-dimensional (3D) cells and in a novel avian cecal in vitro organ culture (IVOC) model, the adherence and invasion of B. pilosicoli in epithelial cells were reduced significantly by the presence of lactobacilli (P < 0.001). In addition, live and heat-inactivated lactobacilli inhibited the motility of B. pilosicoli, and electron microscopic observations indicated that contact between the lactobacilli and Brachyspira was crucial in inhibiting both adherence and motility. These data suggest that motility is essential for B. pilosicoli to adhere to and invade the gut epithelium and that any interference of motility may be a useful tool for the development of control strategies.

Evaluating the legacies of state-building: success, failure, and the role of responsibility

What impact do international state-building missions have on the domestic politics of states they seek to build, and how can we measure this impact with confidence? This article seeks to address these questions and challenge some existing approaches that often appear to assume that state-builders leave lasting legacies rather than demonstrating such influence with the use of carefully chosen empirical evidence. Too often, domestic conditions that follow in the wake of international state-building are assumed to follow as a result of international intervention, usually due to insufficient attention to the causal processes that link international actions to domestic outcomes. The article calls for greater appreciation of the methodological challenges to establishing causal inferences regarding the legacies of state-building and identifies three qualitative methodological strategies—process tracing, counterfactual analysis, and the use of control cases—that can be used to improve confidence in causal claims about state-building legacies. The article concludes with a case study of international state-building in East Timor, highlighting several flaws of existing evaluations of the United Nations' role in East Timor and identifying the critical role that domestic actors play even in the context of authoritative international intervention

The multiple antibiotic resistance (mar) locus and its significance

Chromosomally encoded systems involved in low level resistance of bacteria to different classes of antibiotics (mainly beta-lactams, chloramphenicol, quinolones and tetracycline), disinfectants and in resistance to organic solvents have been the focus of considerable interest in recent years. The multiple antibiotic resistance (mar) locus of Escherichia coli and Salmonella is perhaps the best described system involved in this type of resistance which is induced by MarA, the activator protein encoded by the marRAB locus. The mar-locus is reported to mediate resistance primarily by up-regulating efflux of some antibiotics, disinfectants and organic solvents via the AcrAB-TolC efflux pump and down regulating influx through Outer Membrane Protein F (OmpF). Whilst the level of antibiotic resistance conferred by marRAB is only low level, there are increasing data to suggest that marRAB and related systems are important in clinical antibiotic resistance, possibly as a 'stepping stone' to higher levels of resistance. Other related systems include up-regulation of RobA, SoxS and AcrAB which give rise to a similar resistance phenotype to that conferred by up-regulation of MarA. The aim of this paper is to review the function and significance of the mar-locus and related systems with a particular focus on its implications in veterinary medicine. (C) 2002 Published by Elsevier Science Ltd.

EspJ is a prophage-carried type III effector protein of attaching and effacing pathogens that modulates infection dynamics

Enterohemorrhagic Escherichia coli, enteropathogenic E. coli, and Citrobacter rodentium are highly adapted enteropathogens that successfully colonize their host's gastrointestinal tract via the formation of attaching and effacing (A/E) lesions. These pathogens utilize a type III secretion system (TTSS) apparatus, encoded by the locus of enterocyte effacement, to translocate bacterial effector proteins into epithelial cells. Here, we report the identification of EspJ (E. coli-secreted protein J), a translocated TTSS effector that is carried on the 5' end of the cryptic prophage CP-933U. Infection of epithelial cells in culture revealed that EspJ is not required for A/E lesion activity in vivo and ex vivo. However, in vivo studies performed with mice demonstrated that EspJ possesses properties that influence the dynamics of clearance of the pathogen from the host's intestinal tract, suggesting a role in host survival and pathogen transmission.

The effects of retinoic acid on human corneal stromal keratocytes cultured in vitro under serum-free conditions

Purpose: Retinoic acid (RA) is a metabolite of vitamin A that plays a fundamental role in the development and function of the human eye. The purpose of this study was to investigate the effects of RA on the phenotype of corneal stromal keratocytes maintained in vitro for extended periods under serum-free conditions. Methods: Keratocytes isolated from human corneas were cultured up to 21 days in serum-free media supplemented with RA or DMSO vehicle. The effects of RA and of its removal after treatment on cell proliferation and morphology were evaluated. In addition, the expression of keratocyte markers was quantified at the transcriptional and protein levels by quantitative PCR and immunoblotting or ELISA, respectively. Furthermore, the effects of RA on keratocyte migration were tested using scratch assays. Results: Keratocytes cultured with RA up to 10×10-6 M showed enhanced proliferation and stratification, and reduced mobility. RA also promoted the expression of keratocyte-characteristic proteoglycans such as keratocan, lumican, and decorin, and increased the amounts of collagen type-I in culture while significantly reducing the expression of matrix metalloproteases 1, 3, and 9. RA effects were reversible, and cell phenotype reverted to that of control after removal of RA from media. Conclusions: RA was shown to control the phenotype of human corneal keratocytes cultured in vitro by regulating cell behaviour and extracellular matrix composition. These findings contribute to our understanding of corneal stromal biology in health and disease, and may prove useful in optimizing keratocyte cultures for applications in tissue engineering, cell biology, and medicine.

Structure and stress of Re(11%21); chiral terraces at a racemic surface

The surface structure and morphology of the clean Re(11%21) surface has been investigated through combined low energy electron diffraction intensity analysis of data taken at multiple angles of incidence, scanning tunneling microscopy, and first-principles density functional calculations. The results show how this globally racemic surface terminates in two chirally distinct terraces, which show largescale out-of-plane atomic relaxations and in-plane lateral movement of the uppermost atoms. We further identify and discuss the initial stages of step bunching upon adsorption of oxygen that leads ultimately to the large-scale faceting of the surface. Finally, we present calculations of surface stress and the response to applied surface strain, which suggest routes to the exertion of control over the expression of chirality at the surface.