Distribution of moisture in reconstructed oil paintings on canvas during absorption and drying: a neutron radiography and NMR study

Moisture is a driving factor in the long-term mechanical deterioration of canvas paintings, as well as for a number of physico–chemical degradation processes. Since the 1990s a number of publications have addressed the equilibrium hygroscopic uptake and the hygro-mechanical deformation of linen canvas, oil paint, animal glue, and ground paint. In order to visualise and quantify the dynamic behaviour of these materials combined in a painting mock-up or reconstruction, we have performed custom-designed experiments with neutron radiography and nuclear magnetic resonance (NMR) imaging. This paper reports how both techniques were used to obtain spatially and temporally resolved information on moisture content, during alternate exposure to high and low relative humidity, or in contact with liquids of varying water activities. We observed how the canvas, which is the dominant component in terms of volumetric moisture uptake, absorbs and dries rapidly, and, due to its low vapour resistance, allows for vapour transfer towards the ground layer. Moisture desorption was generally found to be faster than absorption. The presence of sizing glue leads to a local increase of moisture content. It was observed that lining a painting with an extra canvas results in a damping effect: i.e. absorption and drying are significantly slowed down. The results obtained by NMR are complementary to neutron radiography in that they allow accurate monitoring of water ingress in contact with a liquid reservoir. Quantitative results are in good agreement with adsorption isotherms. The findings can be used for risk analysis of paintings exposed to changing micro-climates or subjected to conservation treatments using water. Future studies addressing moisture-driven deformation of paintings can make use of the proposed experimental techniques

THE ROLE OF UMBRELLA AGREEMENTS IN ACHIEVING SUSTAINABILITY GOALS: ENERGY EFFICIENCY AT THE EMPIRE STATE BUILDING

In this paper we investigate whether innovative and flexible contractual arrangements can support the process of achieving ambitious sustainability goals. We explore this question through an analysis of the role of umbrella agreements in driving energy savings in the building sector. Drawing on a case study of the iconic Empire State building, we examine the typical challenges faced by clients and contractors in devising suitable agreements that facilitate managing contractual and performance risks, as well as the sharing of responsibilities and cooperation between multiple project stakeholders. We find that the project arrangements appear to exhibit the adoption of the key characteristics commonly found in umbrella agreements which incorporate sustainability measures that maximize income through efficient delivery of outcomes. Specifically, this means that they need to enable stakeholders to manage repeated review cycles, complex perceptions and expectations, and different tacit assumptions and codes of behaviour, as well as managing and communicating in networks and obtaining agreement also from non-contractual parties. Moreover, we demonstrate that umbrella agreements can facilitate a network perspective of business relationships by emphasizing value co-creation and the embeddedness of firms within a network of interactions

Assessing the Technical Impact of Integrating Largescale Photovoltaics to the Electrical Power Network of Bahrain

Electricity demand of Bahrain is met almost entirely by gas turbine power stations at present. The peak demand growth rate of around 6.5 % per year necessitates installing new generation in near future. Bahrain’s rich natural solar resource could be exploited to meet this need. However, so far, no detailed studies on the grid integration of large scale photovoltaics (PV) systems have been carried out. Potential impacts of integrating a 1MW PV plant to the power network of Bahrain is examined in this paper by means of a systematic modelling analysis using PVsyst and PSSE. Results demonstrate how PV systems can exploit the advantage provided by the weather of Bahrain to match the peak demand. Other concerns addressed in this work are impact of PV generation during times when electrical power network is more susceptible to voltage limit violations and impact of fault current contribution from the PV plant to the security of the network considered. The overarching view from the results of these grid integration studies is that the outlook for network integrated PV in the future In Bahrain is positive. It is hoped that the results of this work would inform Bahrain’s utility’s policies on PV systems

Mosquito larvicidal activities of Solanum villosum berry extract against the dengue vector Stegomyia aegypti

<p>Abstract</p> <p>Background</p> <p>Vector control is facing a threat due to the emergence of resistance to synthetic insecticides. Insecticides of botanical origin may serve as suitable alternative biocontrol techniques in the future. Although several plants have been reported for mosquitocidal activity, only a few botanicals have moved from the laboratory to field use, because they are poorly characterized, in most cases active principals are not determined and most of the works are restricted to preliminary screening. <it>Solanum villosum </it>is a common weed distributed in many parts of India with medicinal properties, but the larvicidal activity of this plant has not been reported so far.</p> <p>Methods</p> <p>Aqueous and polar/non-polar solvent extract of fresh, mature, green berries of <it>S. villosum </it>was tested against <it>Stegomyia aegypti</it>, a common vector of dengue fever. A phytochemical analysis of chloroform:methanol extract was performed to search for the active toxic ingredient. The lethal concentration was determined (log probit analysis) and compared with Malathion. The chemical nature of the active substance was also evaluated following ultraviolet-visual (UV-Vis) and infrared (IR) analysis.</p> <p>Results</p> <p>In a 72 hour bioassay experiment with the aqueous extract, the highest mortality was recorded in 0.5% extract. When the mortality of different solvent extracts was compared, the maximum (<it>p </it>< 0.05) mortality was recorded at a concentration of 50 ppm of chloroform:methanol extract (1:1, v/v). The larvicidal activity was lower when compared with the chemical insecticide, Malathion (<it>p </it>< 0.05). Results of regression analysis revealed that the mortality rate (<it>Y</it>) was positively correlated with the period of exposure (<it>X</it>) and the log probit analysis (95% confidence level) recorded lowest value (5.97 ppm) at 72 hours of exposure. Phytochemical analysis of the chlororm:methanol extract reported the presence of many bioactive phytochemicals. Two toxic compounds were detected having <it>R</it>_f= 0.82 (70% and 73.33% mortality in 24 and 48 hours, respectively) and <it>R</it>_f= 0.95 (40% and 50% mortality in 24 and 48 hours, respectively). IR analysis provided preliminary information about the steroidal nature of the active ingredient.</p> <p>Conclusion</p> <p><it>S. villosum </it>offers promise as potential bio control agent against <it>S. aegypti </it>particularly in its markedly larvicidal effect. The extract or isolated bioactive phytochemical could be used in stagnant water bodies for the control of mosquitoes acting as vector for many communicable diseases.</p