Proton NMR relaxometry as a useful tool to evaluate swelling processes in peat soils

Dramatic physical and physico-chemical changes in soil properties may arise due to temperature and moisture variations as well as swelling of soil organic matter (SOM) under constant conditions. Soil property variations may influence sorption/desorption and transport processes of environmental contaminants and nutrients in natural-organic-matterrich soils. Notwithstanding the studies reported in literature, a mechanistic model for SOM swelling is unavailable yet. The objective of the present study was the evaluation of the swelling of peat soils, considered as SOM models, by 1H NMR relaxometry and differential scanning calorimetry (DSC). Namely, information on the processes governing physical and physicochemical changes of peat during re-hydration were collected. The basic hypothesis of the present study was that the changes are slow and may affect water state as well as amounts of different water types into the peats. For this reason, such changes can be evidenced through the variations of mobility and thermal behaviour of the involved H2O molecules by using 1H NMR relaxometry and DSC. According to the experimental results, a mechanistic model, describing the fundamental processes of peat swelling, was obtained. Two different peats re-wetted at three temperatures were used. The swelling process was monitored by measuring spin-spin relaxation time (T2) over a hydration time of several months. Moreover, DSC, T1 – T2 and T2 – D correlation measurements were done at the beginning and at the end of the hydration. Supplementary investigations were also done in order to discriminate between the swelling effects and the contributions from soil solution, internal magnetic field gradients and/or soil microorganisms to proton relaxation. All the results revealed peat swelling. It was evidenced by pore size distribution changes, volumetric expansion and redistribution of water, increasing amounts of nonfreezable and loosely bound water, as well as formation of gel phases and reduction of the translational and rotational mobility of H2O molecules. All the findings implied that changes of the physical and physicochemical properties of peats were obtained. In particular, three different processes having activation energies comprised in the interval 5 – 50 kJ mol-1 were revealed. The mechanistic model which was, then, developed included water reorientation in bound water phases, water diffusion into the peat matrix and reorientation of SOM chains as fundamental processes governing SOM swelling. This study is of environmental significance in terms of re-naturation and re-watering of commercially applied peatlands and of sorption/desorption and transport processes of pollutants and nutrients in natural organic matter rich soil

Functional imaging of plants: A nuclear magnetic resonance study of a cucumber plant

Functional magnetic resonance imaging was used to study transients of biophysical parameters in a cucumber plant in response to environmental changes. Detailed flow imaging experiments showed the location of xylem and phloem in the stem and the response of the following flow characteristics to the imposed environmental changes: the total amount of water, the amount of stationary and flowing water, the linear velocity of the flowing water, and the volume flow. The total measured volume flow through the plant stem was in good agreement with the independently measured water uptake by the roots. A separate analysis of the flow characteristics for two vascular bundles revealed that changes in volume flow of the xylem sap were accounted for by a change in linear-flow velocities in the xylem vessels. Multiple-spin echo experiments revealed two water fractions for different tissues in the plant stem; the spin-spin relaxation time of the larger fraction of parenchyma tissue in the center of the stem and the vascular tissue was down by 17% in the period after cooling the roots of the plant. This could point to an increased water permeability of the tonoplast membrane of the observed cells in this period of quick recovery from severe water los

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

Guest Editorial: Prevention of childhood injuries

No Abstrac

Guest Editorial: Prevention of childhood injuries (part 2)

No Abstrac

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

The history of paediatric trauma care in Cape Town

Trauma is a leading cause of morbidity, mortality and disability in childhood. In most developed countries where 18% of the population are in the age group 0 - 15 years, injury exceeds all other causes of childhood mortality. In the developing countries of Africa, however, children aged 0 - 15 years constitute 43% of the population and trauma has an even bigger impact on child health.There is an erroneous perception that trauma is not a major health problem in Africa, derived from undue emphasis on mortality statistics alone. Yet, the impact of trauma ought to be measured not only in terms of death, but also the tremendous morbidity and disability caused by injuries, and their socioeconomic consequences

Profile of children with head injuries treated at the trauma unit of Red Cross War Memorial Children's Hospital

Objective. To describe the profile of childhood head injury patients treated in a trauma unit. Design. A retrospective record-based study. Setting. The trauma unit of the Red Cross War Memorial Children’s Hospital. Subjects. Children (under 13 years of age) presenting with head injuries between January 1991 and December 2001. Results. Of the almost 94 000 records, more than one-third were children presenting with head injuries. Fifty-nine per cent were boys, with more than half the sample under 5 years of age. The majority of children presented with superficial lacerations and abrasions, mostly affecting the scalp and skull. Injuries were mainly caused by falls from a variety of heights, and traffic-related injuries. Almost twothirds of traffic-related injuries involved children as pedestrians being struck by a motor vehicle. More than 60% of injuries occurred in or around the child’s own home. Conclusions. Head injuries in children are a significant cause of morbidity. Prevention, especially in the home and on the streets, needs urgent attention

Is the golden hour optimally used in South Africa for children presenting with polytrauma?

BACKGROUND: The major paediatric public health problem worldwide is injury or trauma. In 2004, 950 000 children died as a result of injury. OBJECTIVE: The aim of this study was to evaluate the logistics of medical care after paediatric polytrauma within the first hours after arrival into a trauma unit - the so-called Golden Hour. METHODS: Children presenting with polytrauma to the Trauma Unit at the Red Cross War Memorial Children's Hospital between May 2011 and August 2011 were considered for inclusion in the study. RESULTS: Fifty-five children were included in the final analysis. The median duration of stay in the Trauma Unit was 205 minutes (interquartile range 135 - 274). CONCLUSION: Several factors were identified that unnecessarily prolonged the time that patients stayed in the trauma unit following arrival in hospital for polytrauma management