Isotope tracing of nitrate : lessons from Malta

Average concentrations of nitrate in Malta’s groundwaters are probably the highest among EU member states. This compromises the quality of an important resource -almost 60% of Malta’s water supply being provided by groundwater. An 15N/14N + 18O/16O isotope study was undertaken as a core part of wide-ranging investigations into the potential sources of the nitrate pollution, its likely future trends, and possible ameliorative actions. The dual isotope (15N/14N + 18O/16O) approach was important for identifying waters affected by denitrification. Excluding these, groundwater from three physically and hydrologically distinct aquifers, with a very wide range in nitrate concentrations (24 to 410 mg NO3 L-1), had remarkably similar isotope compositions: 90% of samples lying within d15N ≈ +8 to +12‰, and d18O ≈ +3 to +6‰. The d18O values are entirely consistent with those expected for microbial nitrification in the presence of surface or groundwaters, and together with 15N values rule out nitrate derivation directly from fertilizers or sewage. In other studies the relatively high d15N values for the waters would probably have been interpreted as indicative of nitrate derived from manure. In Malta, however, cultivated soils have high d15N values, ≈ +6 to +11‰, very similar to the values for nitrate in the groundwater, and argue for a soil-derived source. The implications of a soil-source of such high nitrate levels are discussed, and the study emphasised the importance of characterising the compositions of soils in addition to other sources – a factor often neglected in isotope studies of nitrate

The effect of shear and lap arrangement on reinforcement lap strength

The paper is concerned with the design of tension laps in reinforced concrete structures. The most recent design recommendations for laps are found in fib Model Code 2010 which is likely to influence the next revision of EN-1992. This is of concern to UK industry since laps designed to MC2010 can be significantly longer than laps designed to EN-1992 which UK designers already consider excessive compared with previous UK code requirements. Unlike the previous UK code, BS8110, EN-1992 requires adjacent laps to be offset by 0.3 of the lap length which complicates reinforcement detailing. The paper describes an experimental programme which was undertaken to assess the influence on lap performance of increasing lap length beyond that required for bar yield, shear and staggering of laps. The influence of shear was assessed by comparing the performance of laps of the same length positioned in zones of uniform and varying bending moment. Reinforcement strains were monitored and detailed measurements of crack development and crack widths were obtained with digital image correlation. Results show that very long laps are inefficient with the central half contributing little to force transfer between bars. Shear was found to have no significant influence on lap strength while lapping only 50% of bars at a section increased forces in the lapped bars leading to premature bond failure. Test results are compared with EN-1992 predictions, which are shown to be conservative for the tested laps

A whole-health-economy approach to antimicrobial stewardship: Analysis of current models and future direction.

Antimicrobial stewardship (AMS) strategies are widely implemented in single healthcare sectors and organisations; however, the extent and impact of integrated AMS initiatives across the whole health economy are unknown. Assessing degree of integration of AMS across the whole health economy and its impact is essential if we are to achieve a ‘One Health’ approach to addressing antimicrobial resistance (AMR), and therefore we searched systematically for and analysed published examples of integrated AMS initiatives to address this gap. Application of a system-level framework to analyse integration of AMS initiatives across and within healthcare sectors shows that integration is emerging but needs strengthening. Findings from a small number of evaluations in high-income countries suggest that antimicrobial prescribing and healthcare-associated infections can be reduced using a multisectoral integrated AMS approach. More robust research designs to evaluate and understand the impact of multisectoral integrated AMS are needed, particularly with respect to differing health systems in different countries and local organisational contexts. Our analysis highlights a number of challenges and ways forward for enhancing the delivery of AMS through an integrated approach

CONTROLLING CRACK WIDTHS IN WALLS RESTRAINED AT THEIR BASE AND ENDS

Following casting, concrete cracks if early-age thermal (EAT) and long-term (LT) shrinkage movement is restrained. Crack control is of particular importance in walls which rely solely on concrete for water tightness, such as retaining walls and water resisting tanks. It is well established that the cracking behaviour of end restrained members is very different from that of edge restrained walls. For this reason, both restraint types are considered separately in literature and in codes of practice such as Eurocode 2 (EN 1992). In reality, combined edge and end restraint is present in many reinforced concrete (RC) structures. In the absence of design recommendations for combined restraint, U.K. engineers commonly design crack control reinforcement for end restraint as it is the worst case. In the authors’ opinion, this is wasteful as it leads to the provision of unnecessary reinforcement. To this end, an experimental programme was conducted to investigate cracking in RC walls with combined base and end restraint. The measured and calculated crack widths are compared with the predictions of EN 1992 for edge and end restraint. The results suggest that crack widths in walls with combined edge and end restraint can be calculated with the EN 1992 equations for cracking in edge restrained walls

The application of multivariate analytical techniques to the study of marine benthic assemblages : a review with special reference to the Maltese Islands

In recent years there have been numerous studies made on the marine benthic assemblages of Maltese coastal waters, either as elements of the seascape, or in order to gain an understanding of the nature of these assemblages and of the factors which structure them, or to assess the potential of such assemblages as indicators of environmental change, principally that due to anthropogenic activities. The massive data sets generated by such studies can realistically only be analysed objectively using an array of sophisticated statistical techniques that it has only been possible to apply now that powerful computers are readily available. Starting with the basics of data analysis, this paper reviews the statistical techniques currently used for the analysis of benthic assemblages, particularly those that have been found suitable for the type and character of data from the Mediterranean. Emphasis is placed on multivariate techniques, since benthic data are usually highly multivariate. A brief review of the development of these techniques and of their application to benthic ecological research is also given. The objective is to provide a guide to techniques and to the literature which local workers may find useful as a starting point when designing an experimental, data collection, or analytical protocol.peer-reviewe

Generation of Distributed Programming Environments

This technical report consists of three related papers in the area of distributed programming environments. Incremental Attribute Evaluation in Distributed Language-Based Environments presents algorithms that extend existing technology for the generation of single-user language-based editors from attribute grammars to the cases of multiple-user concurrent and distributed environments. Multi-User Distributed Language-Based Environment, an extended abstract, provides additional information on how to apply the algorithms. Reliability in Distributed Programming Environments presents additional algorithms that extend our results to unreliable networks

integration of an organic rankine cycle and a photovoltaic unit for micro scale chp applications in the residential sector

Abstract The purpose of this work is to analyse the performance of a novel system for combined heat and power (CHP) generation in small-scale applications. The system is based on an Organic Rankine Cycle (ORC) fed with biomass and a photovoltaic (PV) unit. The ORC and PV sub-systems operate in parallel to produce the required electrical energy. A preliminary investigation is performed to define the proper size of the photovoltaic unit. Afterwards, the analysis is focused on the hybrid system and a comparison between the two configurations is carried out. This work demonstrates the potential for integrating biomass and solar energy resources: during daylight, solar radiation is significant and the ORC system can be switched off or operated at partial load. Furthermore, the adoption of biomass makes it possible to overcome the intermittency of solar resource, increase the self-consumed electrical energy, and produce thermal energy, thereby saving natural gas for heating purposes