Possible attenuation of the G2 DNA damage cell cycle checkpoint in HeLa cells by extremely low frequency (ELF) electromagnetic fields

BACKGROUND: The issue remains unresolved as to whether low frequency magnetic fields can affect cell behaviour, with the possibility that they may be in part responsible for the increased incidence of leukaemia in parts of the population exposed to them. METHODS: Combined treatment of HeLa cells with gamma-irradiation (1, 3 and 5 Grays) and extra low frequency magnetic fields of ~50 Hz was carried out under rigorously controlled conditions. RESULTS: Synchronised cells progressing from S-phase arrived at mitosis on average marginally ahead of irradiation controls not exposed to ELF. In no instance out of a total of twenty separate experiments did this "double-insult" further delay entry of cells into mitosis, as had been anticipated. CONCLUSION: This apparently "non-genotoxic" agent (ELF) appears to be capable of affecting cells that would normally arrest for longer in G2, suggesting a weakening of the stringency of the late cycle (G2) checkpoint

The Force of a Tsunami on a Wave Energy Converter

With an increasing emphasis on renewable energy resources, wave power technology is fast becoming a realistic solution. However, the recent tsunami in Japan was a harsh reminder of the ferocity of the ocean. It is known that tsunamis are nearly undetectable in the open ocean but as the wave approaches the shore its energy is compressed creating large destructive waves. The question posed here is whether a nearshore wave energy converter (WEC) could withstand the force of an incoming tsunami. The analytical 3D model of Renzi & Dias (2012) developed within the framework of a linear theory and applied to an array of fixed plates is used. The time derivative of the velocity potential allows the hydrodynamic force to be calculated.Comment: 12 pages, 6 figures, 2 tables, 16 references. Paper presented at the ISOPE-2012 conference. Other author's papers can be downloaded at http://www.lama.univ-savoie.fr/~dutykh

On the use of finite fault solution for tsunami generation problems

The present study is devoted to the problem of tsunami wave generation. The main goal of this work is two-fold. First of all, we propose a simple and computationally inexpensive model for the description of the sea bed displacement during an underwater earthquake, based on the finite fault solution for the slip distribution under some assumptions on the dynamics of the rupturing process. Once the bottom motion is reconstructed, we study waves induced on the free surface of the ocean. For this purpose we consider three different models approximating the Euler equations of the water wave theory. Namely, we use the linearized Euler equations (we are in fact solving the Cauchy-Poisson problem), a Boussinesq system and a novel weakly nonlinear model. An intercomparison of these approaches is performed. The developments of the present study are illustrated on the 17 July 2006 Java event, where an underwater earthquake of magnitude 7.7 generated a tsunami that inundated the southern coast of Java.Comment: 31 pages, 10 figures, 3 tables. Other author's papers can be downloaded at http://www.lama.univ-savoie.fr/~dutykh

Metabolic scaling: consensus or controversy?

BACKGROUND: The relationship between body mass (M) and standard metabolic rate (B) among living organisms remains controversial, though it is widely accepted that in many cases B is approximately proportional to the three-quarters power of M. RESULTS: The biological significance of the straight-line plots obtained over wide ranges of species when B is plotted against log M remains a matter of debate. In this article we review the values ascribed to the gradients of such graphs (typically 0.75, according to the majority view), and we assess various attempts to explain the allometric power-law phenomenon, placing emphasis on the most recent publications. CONCLUSION: Although many of the models that have been advanced have significant attractions, none can be accepted without serious reservations, and the possibility that no one model can fit all cases has to be more seriously entertained

A Class of Random Field Memory Models for Mortality Forecasting

International audienceThis article proposes a parsimonious alternative approach for modeling the stochastic dynamics of mortality rates. Instead of the commonly used factor-based decomposition framework , we consider modeling mortality improvements using a random field specification with a given causal structure. Such a class of models introduces dependencies among adjacent cohorts aiming at capturing, among others, the cohort effects and cross generations correlations. It also describes the conditional heteroskedasticity of mortality. The proposed model is a generalization of the now widely used AR-ARCH models for random processes. For such class of models, we propose an estimation procedure for the parameters. Formally, we use the quasi-maximum likelihood estimator (QMLE) and show its statistical consistency and the asymptotic normality of the estimated parameters. The framework being general, we investigate and illustrate a simple variant, called the three-level memory model, in order to fully understand and assess the effectiveness of the approach for modeling mortality dynamics

Resterende sterkte van gecorrodeerde omtreklassen uit pijpleidingen

Laboratorium Soete heeft, op vraag van Fluxys NV, de aanvaardbaarheid van corrosie in omtreklassen van pijpleidingen onderzocht. Hiertoe werden 33 middenschalige trekproeven op lassen uitgevoerd, waarbij metaalverlies via frezen werd gesimuleerd. De resultaten hebben aanleiding gegeven tot een beoordelingscriterium en voorwaarden m.b.t. lassterkte en –taaiheid om dit criterium te kunnen toepassen

Improving the reliability of on-site concrete strength estimation with non-destructive techniques

The non-destructive assessment of concrete strength in existing structures is a complex issue. While many standards exist addressing the way non-destructive measurements must be carried out, few exist for the strength assessment itself. Many questions remain unanswered, like for instance the reliability of the strength estimation, the possibility of estimating the concrete variability, or the advantages of combining several non-destructive techniques. These problems have been tackled by a recent RILEM committee (TC ISC 249) whose Guidelines and Recommendations are to be released soon. This paper details their main innovations and how they are expected to improve the engineering practice and the reliability of strength estimation in existing structures

Modelling Time Dependent Transient Deformation in New Zealand

Most organisations who maintain regional terrestrial reference frames base their realisations on the global International Terrestrial Reference Frame (ITRS) that uses space based positioning techniques (e.g. GNSS, ITRF, SLR, DORIS) to realize the International Terrestrial Reference Frame (e.g. ITRF2005, ITRF2008). Where ITRF sites are located within stable plates, the coordinate motion is largely of a linear nature. However, sites that are located within plate boundary zones, can exhibit non linear motion that is the result of other geophysical processes such as earthquake events, volcanic activity, subduction, subsidence and up lift. In such zones, a precise coordinate frame transformation that provides the linkages between global and regional ITRF realisations are not valid. Many of these processes exhibit motion that is time dependent and hence more complex models are required in order to accurately model the deformation. This in turn has implications for national geodetic infrastructure and land surveying applications e.g. Network RTK (NRTK) and GIS. Although periodic earthquake events that cause co seismic displacement are a consequence of t he tectonic situation in New Zealand, a greater challenge is the time dependent transient deformation caused by post seismic relaxation and slow slip events (SSE). NRTK systems require accurate, current epoch (or instantaneous) site coordinates, which can be di fficult to determine when a site periodically (and unpredictably) undergoes slow slip deformation. In addition, most NRTK systems use simple predictive models (e.g. position and velocity only) and do not have any ability to account for non linear deformation. This paper describes some of the methods and results that are being developed to model these complex deformation events. In particular, examples from NRTK sites will be used to illustrate the transient nature of the deformation both in time and space.Non Peer Reviewe

Finite volume and pseudo-spectral schemes for the fully nonlinear 1D Serre equations

After we derive the Serre system of equations of water wave theory from a generalized variational principle, we present some of its structural properties. We also propose a robust and accurate finite volume scheme to solve these equations in one horizontal dimension. The numerical discretization is validated by comparisons with analytical, experimental data or other numerical solutions obtained by a highly accurate pseudo-spectral method.Comment: 28 pages, 16 figures, 75 references. Other author's papers can be downloaded at http://www.denys-dutykh.com