Groundwater animals

Groundwater animals are adapted to live in environments with no light and limited nutrients, They can provide insights into fundamental questions of evolution, ecology and biodiversity. They also have an important role to play in informing the reconstruction of past changes in geomorphology and climate, and can be used for characterising aquifers. The BGS is undertaking a systematic survey of selected areas and lithologies in the UK where groundwater animals have not been investigated. This is important because little is known about groundwater ecosystems in the UK despite the unique contribution to biodiversity made by these animals. Groundwater organisms are also thought to provide ecosystem services by means of their role in nutrient cycling and natural remediation of pollutants in the subsurface. They may also be useful indicators of human impacts on groundwaters

Critically assessing digital documents: materiality and the interpretative role of software

As a contribution to the ongoing tradition of critically assessing documents for research, this paper aims to highlight materiality as a key factor in the co-shaping of knowledge derived from digital documents. The paper first builds upon prior debates in document studies with work from the fields of Science and Technology Studies, and Communication Studies, to establish the role of document materiality in the interpretative process. By first establishing digital documents’ material reality as electrical signal, the paper then discusses the interpretative role of software, in both the representation of that signal for human interpretation and the production of the document through software tools. Finally, the paper considers the implications for persistence and access to digital documents posed by their material reality and the private archival contexts in which they often reside

Investigating transport of dust particles in plasmas

An algorithm has been developped, which makes it possible to automatically extract trajectories of a large number of particles from fast imaging data, allowing a statistical analysis of particles trajectories under various plasma conditions, a better understanding of their influence on plasma properties, and a better characterization of the plasma itself. In this contribution, we focus on results obtained in a radiofrequency parallel plate reactor, where a large amount of micron-sized carbon dust is produced in situ. The use of the rescaled range analysis (R/S analysis) applied to dust particles displacements allows decomposing dust dynamic on different time scales. It is shown that dust displacement is dominated by collisions on short time scales whereas long term behaviour is strongly influenced by large scale plasma fluctuations.Comment: This version contains 8 pages and 5 figures. This work has been presented in the 1st Int. Conf. on Plasma Diagnostics, O8, April 12-16 2010, Pont-\`a-Mousson, France (2010). It has been submitted to Contribution to Plasma Physic

Matter-wave bistability in coupled atom-molecule quantum gases

We study the matter-wave bistability in coupled atom-molecule quantum gases, in which heteronuclear molecules are created via an interspecies Feshbach resonance involving either two-species Bose or two-species Fermi atoms at zero temperature. We show that the resonant two-channel Bose model is equivalent to the nondegenerate parametric down-conversion in quantum optics, while the corresponding Fermi model can be mapped to a quantum optics model that describes a single-mode laser field interacting with an ensemble of inhomogeneously broadened two-level atoms. Using these analogy and the fact that both models are subject to the Kerr nonlinearity due to the two-body s-wave collisions, we show that under proper conditions, the population in the molecular state in both models can be made to change with the Feshbach detuning in a bistable fashion.Comment: 6 pages, 5 figure

The cellular and molecular carcinogenic effects of radon exposure: a review.

Journal ArticleResearch Support, Non-U.S. Gov'tReviewOpen access articleRadon-222 is a naturally occurring radioactive gas that is responsible for approximately half of the human annual background radiation exposure globally. Chronic exposure to radon and its decay products is estimated to be the second leading cause of lung cancer behind smoking, and links to other forms of neoplasms have been postulated. Ionizing radiation emitted during the radioactive decay of radon and its progeny can induce a variety of cytogenetic effects that can be biologically damaging and result in an increased risk of carcinogenesis. Suggested effects produced as a result of alpha particle exposure from radon include mutations, chromosome aberrations, generation of reactive oxygen species, modification of the cell cycle, up or down regulation of cytokines and the increased production of proteins associated with cell-cycle regulation and carcinogenesis. A number of potential biomarkers of exposure, including translocations at codon 249 of TP53 in addition to HPRT mutations, have been suggested although, in conclusion, the evidence for such hotspots is insufficient. There is also substantial evidence of bystander effects, which may provide complications when calculating risk estimates as a result of exposure, particularly at low doses where cellular responses often appear to deviate from the linear, no-threshold hypothesis. At low doses, effects may also be dependent on cellular conditions as opposed to dose. The cellular and molecular carcinogenic effects of radon exposure have been observed to be both numerous and complex and the elevated chronic exposure of man may therefore pose a significant public health risk that may extend beyond the association with lung carcinogenesis

Galaxy Mass, Metallicity, Radius and Star Formation Rates

Working with 108,786 Sloan Digital Sky Survey low redshift galaxies we have examined the relation between galaxy mass, metallicity, radius, and star formation rates primarily in the central portions of galaxies. We subdivided the redshift range covered in our sample, 0.07<z<0.3, into three narrower redshift bins, and three sets of radial size. We show that for 72% of the galaxies the observed gas metallicities, Zx, are consistent with (i) a quantitative physical relation for star formation through episodic infall of gas of metallicity Zi = 0.125x10^-3 +/- 1.25x10^-3; (ii) thorough mixing of infalling and native gas before onset of star formation; (iii) a star formation rate (SFR) proportional to the 3/2 power of the infalling mass rate, Mi; and (iv) intermittent quiescent phases devoid of star formation during which the native gas in a galaxy exhibits a characteristic elevated gas metallicity, Z0, dependent on galaxy mass, M*, and a characteristic ratio of stellar mass to native mass of gas, Mg. Most if not all our star-forming galaxies with M* < 2.0x10^10 Msun, and many with M* > 2.0x10^10 Msun and large radii appear fed by infall. Smaller massive galaxies with high Zx and high star formation rates show more complex behavior. A mean-field-theory toy model for the physics of infall accounts for the (SFR) \propto Mi^(3/2) relation and permits us to estimate the mean densities and velocities of clumps of baryonic matter traversing the dark matter halos in which the SDSS galaxies may be embedded.Comment: 34 pages plus bibliography and supplementary figures, 3 main figures, 131 supplementary online figures, ascii data tables availabl

Candida albicans biofilm heterogeneity does not influence denture stomatitis but strongly influences denture cleansing capacity

Approximately 20  % of the UK population wear some form of denture prosthesis, resulting in denture stomatitis in half of these individuals. Candida albicans is primarily attributed as the causative agent, due to its biofilm -forming ability. Recently, there has been increasing evidence of C. albicans biofilm heterogeneity and the negative impact it can have clinically; however, this phenomenon has yet to be studied in relation to denture isolates. The aims of this study were to evaluate C. albicans biofilm formation of clinical denture isolates in a denture environment and to assess antimicrobial activity of common denture cleansers against these tenacious communities. C. albicans isolated from dentures of healthy and diseased individuals was quantified using real-time PCR and biofilm biomass assessed using crystal violet. Biofilm development on the denture substratum poly(methyl methacrylate), Molloplast B and Ufi-gel was determined. Biofilm formation was assessed using metabolic and biomass stains, following treatment with denture hygiene products. Although C. albicans was detected in greater quantities in diseased individuals, it was not associated with increased biofilm biomass. Denture substrata were shown to influence biofilm biomass, with poly(methyl methacrylate) providing the most suitable environment for C. albicans to reside. Of all denture hygiene products tested, Milton had the most effective antimicrobial activity, reducing biofilm biomass and viability the greatest. Overall, our results highlight the complex nature of denture- related disease, and disease development cannot always be attributed to a sole cause. It is the distinct combination of various factors that ultimately determines the pathogenic outcome

Mechanisms for Interteam Integration: Findings from Five Case Studies

Many product development programs consist of multiple integrated product teams (IPTs) and functional groups. Interteam information dependencies greatly affect program success. Program integration has thus become an issue of increasing interest. This paper summarizes findings from five case studies of integrative mechanisms (IMs) in complex system product development projects at Chrysler, General Electric Aircraft Engines, McDonnell Douglas, Sundstrand, and Texas Instruments. Two types of IMs are investigated in this paper: (1) Systems engineering and interface optimization and (2) Improved information and communication technologies. As the appropriateness of a given IM varies as a function of many parameters—such as program stage, size, complexity, risk, etc.—the goal of this research was not to formulate a universal template for IM application. Rather, it is hoped that the lessons learned by these five programs will help others determine the appropriateness of particular IMs in their situations. Also, the continued development of an IM categorization scheme will hopefully prove useful to those developing an integration “tool kit.

The Power of General Relativity

We study the cosmological and weak-field properties of theories of gravity derived by extending general relativity by means of a Lagrangian proportional to $R^{1+\delta}$. This scale-free extension reduces to general relativity when $\delta \to 0$. In order to constrain generalisations of general relativity of this power class we analyse the behaviour of the perfect-fluid Friedmann universes and isolate the physically relevant models of zero curvature. A stable matter-dominated period of evolution requires $\delta >0$ or $\delta <-1/4$. The stable attractors of the evolution are found. By considering the synthesis of light elements (helium-4, deuterium and lithium-7) we obtain the bound $-0.017<\delta <0.0012.$ We evaluate the effect on the power spectrum of clustering via the shift in the epoch of matter-radiation equality. The horizon size at matter--radiation equality will be shifted by $\sim 1$ for a value of $\delta \sim 0.0005.$ We study the stable extensions of the Schwarzschild solution in these theories and calculate the timelike and null geodesics. No significant bounds arise from null geodesic effects but the perihelion precession observations lead to the strong bound $\delta =2.7\pm 4.5\times 10^{-19}$ assuming that Mercury follows a timelike geodesic. The combination of these observational constraints leads to the overall bound $0\leq \delta <7.2\times 10^{-19}$ on theories of this type.Comment: 26 pages and 5 figures. Published versio