A Topological Characterization Of Knots and Links Arising From Site-Specific Recombination

We develop a topological model of knots and links arising from a single (or multiple processive) round(s) of recombination starting with an unknot, unlink, or (2,m)-torus knot or link substrate. We show that all knotted or linked products fall into a single family, and prove that the size of this family grows linearly with the cube of the minimum number of crossings. Additionally, we prove that the only possible products of an unknot substrate are either clasp knots and links or (2,m)-torus knots and links. Finally, in the (common) case of (2,m)-torus knot or link substrates whose products have minimal crossing number m+1, we prove that the types of products are tightly prescribed, and use this to examine previously uncharacterized experimental data.Comment: 18 pages, 3 tables, 18 figures. See also arXiv:0707.3775v1 for biological evidence for and applications of the model developed her

Metastable Flux Configurations and de Sitter Spaces

We derive stability conditions for the critical points of the no-scale scalar potential governing the dynamics of the complex structure moduli and the axio-dilaton in compactifications of type IIB string theory on Calabi-Yau three-folds. We discuss a concrete example of a T^6 orientifold. We then consider the four-dimensional theory obtained from compactifications of type IIB string theory on non-geometric backgrounds which are mirror to rigid Calabi-Yau manifolds and show that the complex structure moduli fields can be stabilized in terms of H_{RR} only, i.e. with no need of orientifold projection. The stabilization of all the fields at weak coupling, including the axio-dilaton, may require to break supersymmetry in the presence of H_{NS} flux or corrections to the scalar potential.Comment: 24 page

Health, Health Insurance and Retirement: A Survey

The degree to which retirement decisions are driven by health is a key concern for both academics and policymakers. In this paper we survey the economic literature on the health-retirement link in developed countries. We describe the mechanisms through which health affects labor supply, and discuss how they interact with public pensions and public health insurance. The historical evidence suggests that health is not the primary source of variation in retirement across countries and over time. Furthermore, declining health with age can only explain a small share of the decline in employment near retirement age. Health considerations nonetheless play an important role, especially in explaining cross-sectional variation in employment and other outcomes within countries. We review the mechanisms through which health affects retirement and discuss recent empirical analyses

Application of passive seismic to the detection of buried hollows

Pilot studies involving the use of passive seismic techniques in a range of geological settings and applications, e.g., mapping bedrock, studies of soil erosion and Quaternary mapping have shown that it is a versatile, non-invasive and economic technique. This paper presents the findings of three case studies that trialled the use of passive seismic techniques for the detection and characterisation of buried hollows in carbonate rocks, comprising: i) a buried hollow in the Cretaceous Chalk at Ashford Hill in the Kennet Valley, a tributary of the River Thames, UK; ii) buried karst in the foundation excavations for wind turbines in Carboniferous Limestone at Brassington, Wirksworth, Derbyshire, UK, and iii) defining the extent of solution hollows that host terrestrial Miocene deposits, near Friden, Newhaven, Derbyshire, UK. Whilst case studies ii) and iii) are focused on areas of buried dolines, the geological context of the Ashford Hill site is more complex; comprising a deformation hollow with an uplifted “pinnacle” of chalk bedrock at the centre. The data were collected using a (Tromino), a three-component, broadband seismometer to measure background ambient noise (microtremors induced by wind, ocean waves, industrial machinery, road and rail traffic, etc.). The Tromino is small, portable with an operating range of 0.1 Hz to 1,024 Hz and interpreted using proprietary software (Grilla), which subjects the data to Fourier transformation and smoothing. Where possible, estimated shear wave velocities used in the Grilla Software modelling, based on peaks identified on the H/V spectrum, have been calibrated using borehole data or parallel geophysical techniques. In each case, the karst features were defined by Nakamura’s horizontal to vertical (H/V) spectral ratio technique, where microtremors are converted to show impedance contrasts (velocity x density), or a pseudo layered seismic stratigraphy of the near surface along each profile. An additional benefit of the use of this technique is its depth of penetration and potential for defining the structural and lithological context of the hollows, thereby contributing to the process understanding associated with their formation. To this end the technique has helped define discontinuity (fault, joint or bedding) guidance of the hollows.S. Castellaro, Mrs J. Renwick, West Coast Energy Ltd (GDF Suez), Mr Roger Durrant (Raymond Brown Construction Ltd

An investigation into the mechanism underlying enhanced hydrolysis of complex carbon in a biosulphidogenic recycling sludge bed reactor (RSBR)

The potential for using readily available and cost-effective complex carbon sources such as primary sewage sludge for a range of biological processes, including the bioremediation of acid mine drainage, has been constrained by the slow rate of solubilisation and low yield of soluble products, which drive the above mentioned processes. Previous research into the hydrolysis of complex organic matter, such as primary sludge, under biosulphidogenic conditions within a novel Recycling Sludge Bed Reactor (RSBR) demonstrated solubilisation in excess of 50%. However, further investigation was required into the mechanism of this enhanced hydrolysis. The current study was aimed at confirming that hydrolysis is enhanced under biosulphidogenic conditions, and to obtain an estimate of the relative rates of hydrolysis using toluene as a specific metabolic inhibitor. The solubilisation of primary sewage sludge under sulphate reducing conditions was conducted in controlled flask studies and previously reported findings of enhanced hydrolysis were confirmed. The maximum percentage solubilisation obtained in this study over a 10-day period was 31% and 64% for the methanogenic and sulphidogenic systems respectively. By using toluene as an inhibitor of bacterial uptake of soluble carbohydrates, it was possible to determine the rate of production of various key products of the hydrolytic step. From the results of the current experiment, the rate of production of soluble carbohydrate, and therefore the rate of hydrolysis of complex carbohydrates, in terms of COD equivalents was estimated at 543 mgCOD·l-1·d-1 and 156 mgCOD·l- 1·d-1 under sulphidogenic and methanogenic conditions, respectively.. Water SA Vol. 30 (5) 2005: pp.150-15

Found: High Surface Brightness Compact Galaxies

We are using the 2dF spectrograph to make a survey of all objects (`stars' and `galaxies') in a 12 sq.deg region towards the Fornax cluster. We have discovered a population of compact emission-line galaxies unresolved on photographic sky survey plates and therefore missing in most galaxy surveys based on such material. These galaxies are as luminous as normal field galaxies. Using H-alpha to estimate star formation they contribute at least an additional 5 per cent to the local star formation rate.Comment: To appear in "The Low Surface Brightness Universe", IAU Coll 171, eds. J.I. Davies et al., A.S.P. Conference Series. 3 pages, LaTex, 1 encapsulated ps-figure, requires paspconf.st

Social and spatial heterogeneity in psychosis proneness in a multilevel case-prodrome-control study

To test whether spatial and social neighbourhood patterning of people at ultra-high risk (UHR) of psychosis differs from first-episode psychosis (FEP) participants or controls and to determine whether exposure to different social environments is evident before disorder onset

Predetermined time constant approximation method for optimising search space boundary by standard genetic algorithm

In this paper, a new predetermined time constant approximation (Tsp) method for optimising the search space boundaries to improve SGAs convergence is proposed. This method is demonstrated on parameter identification of higher order models. Using the dynamic response period and desired settling time of the transfer function coefficients offered a better suggestion for initial Tsp values. Furthermore, an extension on boundaries derived from the initial Tsp values and the consecutive execution, brought the elite groups within feasible boundary regions for better exploration. This enhanced the process of locating of the optimal values of coefficients for the transfer function. The Tsp method is investigated on two processes; excess oxygen and a third order continuous model with and without random disturbance. The simulation results assured the Tsp method's effectiveness and flexibility in assisting SGAs to locate optimal transfer function coefficients. Copyright © 2015 ACM

Decentralised Control Optimisation for a Glass Furnace by SGA’s

In this paper, the potential of standard genetic algorithms (SGAs) are presented to optimise the discrete PID parameters for multivariable glass furnace. Control oriented models of each multivariable glass furnace; glass temperature and excess oxygen are used to optimise the discrete controller with personalised cost function and adjusted boundaries by SGAs, individually. Well optimised discrete PID parameters by control oriented model are applied to realistic multivariable model by decentralised method