The track nanotechnology

The discipline now called Solid State Nuclear Track Detection (SSNTD) dates back to 1958 and has its roots in the United Kingdom. Its strength stems chiefly from factors such as its simplicity, small geometry, permanent maintenance of the nuclear record and other diversified applications. A very important field with exciting applications reported recently in conjuction with the nuclear track technique is nanotechnology, which has applications in biology, chemistry, industry, medicare and health, information technology, biotechnology, and metallurgical and chemical technologies. Nanotechnology requires material design followed by the study of the quantum effects for final produced applications in sensors, medical diagnosis, information technology to name a few. We, in this article, present a review of past and present applications of SSNTD suggesting ways to apply the technique in nanotechnology, with special reference to development of nanostructure for applications utilising nanowires, nanofilters and sensors.

Delays versus performance of visually guided systems

The paper presents an overview of dynamic systems with inherent delays in both feedforward and feedback paths and how the performance of such systems can be affected by such delays. The authors concentrate on visually guided systems, where the behaviour of the system is largely dependent on the results of the vision sensors, with particular reference to active robot heads (real-time gaze control). We show how the performance of such systems can deteriorate substantially with the presence of unknown and/or variable delays. Considered choice of system architecture, however, allows the performance of active vision systems to be optimised with respect to the delays present in the system.

Random-walk-based characterisation of multiple access interference in a DS/SSMA system

The problem of calculating the probability of error in a DS/SSMA system has been extensively studied for more than two decades. When random sequences are employed some conditioning must be done before the application of the central limit theorem is attempted, leading to a Gaussian distribution. The authors seek to characterise the multiple access interference as a random-walk with a random number of steps, for random and deterministic sequences. Using results from random-walk theory, they model the interference as a K-distributed random variable and use it to calculate the probability of error in the form of a series, for a DS/SSMA system with a coherent correlation receiver and BPSK modulation under Gaussian noise. The asymptotic properties of the proposed distribution agree with other analyses. This is, to the best of the authors' knowledge, the first attempt to propose a non-Gaussian distribution for the interference. The modelling can be extended to consider multipath fading and general modulation

Identification of genetic and phenotypic differences associated with prevalent and non-prevalent Salmonella Enteritidis phage types: analysis of variation in amino acid transport

In this study, differences at the genetic level of 37 Salmonella Enteritidis strains from five phage types (PTs) were compared using comparative genomic hybridization (CGH) to assess differences between PTs. There were approximately 400 genes that differentiated prevalent (4, 6, 8 and 13a) and sporadic (11) PTs, of which 35 were unique to prevalent PTs, including six plasmid-borne genes, pefA, B, C, D, srgC and rck, and four chromosomal genes encoding putative amino acid transporters. Phenotype array studies also demonstrated that strains from prevalent PTs were less susceptible to urea stress and utilized L-histidine, L-glutamine, L-proline, L-aspartic acid, gly-asn and gly-gln more efficiently than PT11 strains. Complementation of a PT11 strain with the transporter genes from PT4 resulted in a significant increase in utilization of the amino acids and reduced susceptibility to urea stress. In epithelial cell association assays, PT11 strains were less invasive than other prevalent PTs. Most strains from prevalent PTs were better biofilm formers at 37 degrees C than at 28 degrees C, whilst the converse was true for PT11 strains. Collectively, the results indicate that genetic and corresponding phenotypic differences exist between strains of the prevalent PTs 4, 6, 8 and 13a and non-prevalent PT11 strains that are likely to provide a selective advantage for strains from the former PTs and could help them to enter the food chain and cause salmonellosis.

Fimbriae- and flagella-mediated association with and invasion of cultured epithelial cells by Salmonella enteritidis

Salmonella enteritidis expresses flagella and several finely regulated fimbriae, including SEF14, SEF17 and SEF21 (type 1). A panel of mutants was prepared in three strains of S. enteritidis to elucidate the role of these surface appendages in the association with and invasion of cultured epithelial cells. In all assays, the naturally occurring regulatory-defective strain 27655R associated with tissue culture cells significantly more than wild-type progenitor strains LA5 and S1400/94. Compared with wild-type strains, SEF14 mutants had no effect on association and invasion, whereas SEF17, SEF21 and aflagellate mutants showed significant reductions in both processes. Histological examination suggested a role for SEF17 in localized, aggregative adherence, which could be specifically blocked by anti-SEF17 sera and purified SEF17 fimbriae. SEF21-mediated association was neutralized by mannose and a specific monoclonal antibody, although to observe enhanced association it was necessary for the bacteria to be in fimbriate phase prior to infection. Additionally, aflagellate mutants associated and invaded less than motile bacteria. This study demonstrated the potential for multifactorial association and invasion of epithelial cells which involved SEF17 and SEF21 fimbriae, and flagella-mediated motility.

In situ preservation of wetland heritage: hydrological and chemical change in the burial environment of the Somerset Levels, UK.

In Situ preservation is a core strategy for the conservation and management of waterlogged remains at wetland sites. Inorganic and organic remains can, however, quickly become degraded, or lost entirely, as a result of chemical or hydrological changes. Monitoring is therefore crucial in identifying baseline data for a site, the extent of spatial and or temporal variability, and in evaluating the potential impacts of these variables on current and future In Situ preservation potential. Since August 2009, monthly monitoring has taken place at the internationally important Iron Age site of Glastonbury Lake Village in the Somerset Levels, UK. A spatial, stratigraphic, and analytical approach to the analysis of sediment horizons and monitoring of groundwater chemistry, redox potential, water table depth and soil moisture (using TDR) was used to characterize the site. Significant spatial and temporal variability has been identified, with results from water-table monitoring and some initial chemical analysis from Glastonbury presented here. It appears that during dry periods parts of this site are at risk from desiccation. Analysis of the chemical data, in addition to integrating the results from the other parameters, is ongoing, with the aim of clarifying the risk to the entire site.