Fine‐scale measurement of diffusivity in a microbial mat with nuclear magnetic resonance imaging

Noninvasive 1H‐nuclear magnetic resonance (NMR) imaging was used to investigate the diffusive properties of microbial mats in two dimensions. Pulsed field gradient NMR was used to acquire images of the H2O diffusion coefficient, Ds, and multiecho imaging NMR was used to obtain images of the water density in two structurally different microbial mats sampled from Solar Lake (Egypt). We found a pronounced lateral and vertical variability of both water density and water diffusion coefficient, correlated with the laminated and heterogeneous distribution of microbial cells and exopolymers within the mats. The average water density varied from 0.5 to 0.9, whereas the average water diffusion coefficient ranged from 0.4 to 0.9 relative to the values obtained in the stagnant water above the mat samples. The apparent water diffusivities estimated from NMR imaging compared well to apparent O2 diffusivities measured with a diffusivity microsensor. Analysis of measured O2 concentration profiles with a diffusion‐reaction model showed that both the magnitude of calculated rates and the depth distribution of calculated O2 consumption/production zones changed when the observed variations of diffusivity were taken into account. With NMR imaging, diffusivity can be determined at high spatial resolution, which can resolve inherent lateral and vertical heterogeneities found in most natural benthic systems

MRI in soils: determination of water concent changes due to root water uptake by means of a multi-slice-multi-echo sequence (MSME)

Root water uptake by ricinus communis (castor bean) in fine sand was investigated using MRI with multiecho sampling. Before starting the experiments the plants germinated and grew for 3 weeks in a cylindrical container with a diameter of 9 cm. Immediately before the MRI experiments started, the containers were water-saturated and sealed, so water content changes were only caused by root water uptake. In continuation of a preceding work, where we applied SPRITE we tested a multi-echo multi-slice sequence (MSME). In this approach, the water content was imaged by setting TE = 6.76 ms and nE = 128 with an isotropic resolution of 3.1mm. We calculated the water content maps by biexponential fitting of the multi-slice echo train data and normalisation on reference cuvettes filled with glass beads and 1 mM NiCl2 solution. The water content determination was validated by comparing to mean gravimetric water content measurements. By coregistration with the root architecture, visualised by a 3D fast spin echo sequence (RARE), we conclude that the largest water content changes occurred in the neighbourhood of the roots and in the upper layers of the soil

Fluctuations of a Greenlandic tidewater glacier driven by changes in atmospheric forcing : observations and modelling of Kangiata Nunaata Sermia, 1859–present

Acknowledgements. The authors wish to thank Stephen Price, Mauri Pelto, and the anonymous reviewer for their reviews and comments that helped to improve the manuscript. RACMO2.1 data were provided by Jan van Angelen and Michiel van den Broeke, IMAU, Utrecht University. MAR v3.2 data used for runoff calculations were provided by Xavier Fettweis, Department of Geography, University of Liège. The photogrammetric DEM used in Figs. 1 and 3 was provided by Kurt H. Kjær, Centre for GeoGenetics, University of Copenhagen. This research was financially supported by J. M. Lea’s PhD funding, NERC grant number NE/I528742/1. Support for F. M. Nick was provided through the Conoco-Phillips/Lundin Northern Area Program CRIOS project (Calving Rates and Impact on Sea Level).Peer reviewedPublisher PD

Radiation protection at the National Nuclear Research Centre, Pelindaba

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Can fireworks-related injuries to children during festivities be prevented?

Objective. To determine the epidemiological features and outcome of fireworks-related injuries among children 0 - 13 years old.Design. A retrospective study from the trauma registry of a children’s hospital from 2001 - 2009.Results. Fifty-five children were treated for injuries from fireworks. The mean age was 8.8 years, 78% were boys, and the largest age group was 5 - 9 years old. Firecrackers accounted for 95% of the injuries; the most commonly injured body sites were hands (44%), eyes (42%) and face (31%); 47% of the patients had more than one injury. The most common injury type was burns (67%); 25 children were admitted, mostly to the burns and ophthalmology units. The mean length of hospital stay was 3.5 days. Surgical intervention was required in 38% of the patients. Most of the fireworks accidents occurred in or around the patients’ homes. There were more fireworks-related injuries around Guy Fawkes Day (85%) than New Year’s Eve (9%).Conclusion. Consumer fireworks cause serious but preventable injuries to children, either as users or bystanders. Children and their families should be encouraged to enjoy pyrotechnical displays conducted by professionals at designated areas. All fireworks for individual private use should either be supervised by an adult or banned. Current legislation should be more strictly enforced, especially the sale to under-age children

Dispersive wave runup on non-uniform shores

Historically the finite volume methods have been developed for the numerical integration of conservation laws. In this study we present some recent results on the application of such schemes to dispersive PDEs. Namely, we solve numerically a representative of Boussinesq type equations in view of important applications to the coastal hydrodynamics. Numerical results of the runup of a moderate wave onto a non-uniform beach are presented along with great lines of the employed numerical method (see D. Dutykh et al. (2011) for more details).Comment: 8 pages, 6 figures, 18 references. This preprint is submitted to FVCA6 conference proceedings. Other author papers can be downloaded at http://www.lama.univ-savoie.fr/~dutykh

Epidemic space

The aim of this article is to highlight the importance of 'spatiality' in understanding the materialization of risk society and cultivation of risk sensibilities. More specifically it provides a cultural analysis of pathogen virulence (as a social phenomenon) by means of tracing and mapping the spatial flows that operate in the uncharted zones between the microphysics of infection and the macrophysics of epidemics. It will be argued that epidemic space consists of three types of forces: the vector, the index and the vortex. It will draw on Latour's Actor Network Theory to argue that epidemic space is geared towards instability when the vortex (of expanding associations and concerns) displaces the index (of finding a single cause)

The abandoned ice sheet base at Camp Century, Greenland, in a warming climate

In 1959 the U.S. Army Corps of Engineers built Camp Century beneath the surface of the northwestern Greenland Ice Sheet. There they studied the feasibility of deploying ballistic missiles within the ice sheet. The base and its wastes were abandoned with minimal decommissioning in 1967, under the assumption they would be preserved for eternity by perpetually accumulating snowfall. Here we show that a transition in ice sheet surface mass balance at Camp Century from net accumulation to net ablation is plausible within the next 75 years, under a business-as-usual anthropogenic emissions scenario (Representative Concentration Pathway 8.5). Net ablation would guarantee the eventual remobilization of physical, chemical, biological, and radiological wastes abandoned at the site. While Camp Century and four other contemporaneous ice sheet bases were legally established under a Danish-U.S. treaty, the potential remobilization of their abandoned wastes, previously regarded as sequestered, represents an entirely new pathway of political dispute resulting from climate change

Large surface meltwater discharge from the Kangerlussuaq sector of the Greenland ice sheet during the record-warm year 2010 explained by detailed energy balance observations

This study uses data from six on-ice weather stations, calibrated MODIS-derived albedo and proglacial river gauging measurements to drive and validate an energy balance model. We aim to quantify the record-setting positive temperature anomaly in 2010 and its effect on mass balance and runoff from the Kangerlussuaq sector of the Greenland ice sheet. In 2010, the average temperature was 4.9 °C (2.7 standard deviations) above the 1974–2010 average in Kangerlussuaq. High temperatures were also observed over the ice sheet, with the magnitude of the positive anomaly increasing with altitude, particularly in August. Simultaneously, surface albedo was anomalously low in 2010, predominantly in the upper ablation zone. The low albedo was caused by high ablation, which in turn profited from high temperatures and low winter snowfall. Surface energy balance calculations show that the largest melt excess (∼170%) occurred in the upper ablation zone (above 1000 m), where higher temperatures and lower albedo contributed equally to the melt anomaly. At lower elevations the melt excess can be attributed to high atmospheric temperatures alone. In total, we calculate that 6.6 ± 1.0 km<sup>3</sup> of surface meltwater ran off the ice sheet in the Kangerlussuaq catchment in 2010, exceeding the reference year 2009 (based on atmospheric temperature measurements) by ∼150%. During future warm episodes we can expect a melt response of at least the same magnitude, unless a larger wintertime snow accumulation delays and moderates the melt-albedo feedback. Due to the hypsometry of the ice sheet, yielding an increasing surface area with elevation, meltwater runoff will be further amplified by increases in melt forcings such as atmospheric heat