Chemical and physical characterisation of three NHL 2 binders and the relationship with the mortar properties

In conservation works, the physical properties of mortars, such as compressive strength and porosity, are by far the most important for compatibility with, and protection and durability of historic fabric. The classification of Natural Hydraulic Lime (NHL) binders by the EN 459-1, gives little information about these properties for mortars, due to the unrepresentative nature of the standard samples used to categorise these binders, especially after 28 days of aging. As a consequence, although important for quality assurance and consistency of binder production, the standard test tends not to reflect the performance of mortars as made and used on-site, since these use different aggregates and water/binder ratios.In this work, three types of NHL 2 were analysed. These binders were characterised by means of X-ray diffraction and X-ray fluorescence. In addition to chemical tests, the surface area and bulk density data were also obtained. Mortar samples were manufactured using a sand aggregate which is appropriate for a conservation mortar with 1:2 ratio (binder:aggregate by volume). Sufficient water was added to produce a spread by flow table of 16510 [mm]. The chemical and physical properties of the binders were related to the physical characteristics of the mortars.The chemical and physical properties of different binders with the same NHL classification were found to vary greatly as did the properties of mortars at ages of 7, 14, 28, 90 and 180 days made with those binders. The need to develop a model to predict the performance of aged mortars based on the chemical and physical properties of the binders was identified.<br/

Chemical and physical characterisation of some NHL binders and the correlation with the mechanical properties of conservation mortars

The chemical and physical properties of Natural Hydraulic Limes (NHL) from a given manufacturer can change over time. Some quarries are deactivated or the extracted raw material properties vary depending on their geographical location. These variations in property make it harder for practitioners to predict how changing new products can be best used to match the requirements of a mortar for heritage conservation in terms of mechanical performance and durability. NHL in the UK market have been show to meet the requirements of BS EN 459-1. Although important for a consistent production quality this requirement employs tests based on standard samples which are unrepresentative in their nature. As a consequence, these seldom reflect the performance of mortars produced and used ‘on-site’. Mortars formed from the same class of NHL often exhibit distinct variations in property. In this work, a selection of NHL binders were characterised using X-ray diffraction, X-ray fluorescence and thermo-gravimetric analysis. In addition physical properties including bulk density, surface area and particle size were obtained. Initial chemical and physical properties were correlated to the final mechanical properties of the mortars produced with a readily available sand in a 1:2 mix ratio (binder:aggregate by volume). Distinct mechanical properties at the ages of 7, 14, 28 and 90 days were measured for the same class of NHL. These initial studies will be used to develop a model to predict the final mortar performance from an understanding of the chemical and physical properties of lime binder

Heat capacity mapping mission project HCM-051

There are no author-identified significant results in this report

The socio-ecological dynamics of pastoralism and overstocking in the Dhofar Mountains of Oman

Achieving sustainable use of natural resources is the greatest challenge facing humanity today. Rangelands, which cover one-third to one-half of the earth's ice-free surface, are frequently mismanaged, vulnerable to climate change, and in a degraded state, and their inhabitants are some of the poorest and most marginalized communities on earth. Despite over a century of scientific attention, we still lack an adequate understanding of how rangeland socio-ecological systems operate and how rangeland vegetation responds to abiotic and biotic variables. The Dhofar Mountains represent a rather unique rangeland case study, with atypical social, cultural, political, economic and ecological situations, which could provide valuable insights for rangeland science. Moreover, the Dhofar mountain region is understudied, globally unique, supports a wealth of biodiversity and provides valuable ecosystem services to the local population, yet the threat of overstocking, despite being well-recognised, has received little scientific attention. Therefore, this interdisciplinary research which utilises contemporary methods from the social, ecological and rangeland sciences, aims to firstly understand the social processes driving overstocking in rural Dhofar and secondly, assess the impacts of overstocking on vegetation communities. Data collection methods included interviews, questionnaires, participatory mapping exercises, vegetation sampling and remote sensing. Analytical procedures included qualitative coding, the application of a socio-ecological systems framework, multivariate analysis of vegetation communities and GIS spatial analysis. The results provide the first detailed analysis of the socio-ecological system surrounding pastoralism in Dhofar. We find that livestock ownership is principally motivated by strong pastoral values rooted in cultural norms. But livestock ownership is expensive due to the requirement for daily feedstuff provisioning, which in turn makes local livestock prices uncompetitive against imported livestock. Few livestock are sold and the expense means some better-educated or wealthier individuals are losing interest. By applying a socio-ecological system framework we identify variables inhibiting self-organization, which can be summarised as too many resource users in an unproductive system with undervalued resources. Feedstuff provision is found to be a critical variable which deems many rangeland concepts inapplicable and maintains livestock populations beyond the carrying capacity of the environment. Subsequently, the rangelands, which receive reliable precipitation, exhibit equilibrium properties. Several decades of overbrowsing has increased the frequency of unpalatable species, decreased plant density, reduced advanced growth, altered population age structures, and altered plant phytomorphology through the damaging effects of management practises, bark stripping and browsing. We identify six new variants and a pre-described seventh variant of the Anogeissus forest. Our results suggest that two variants are the result of historical agricultural practises and deforestation, and long-term stocking rates are the primary driver of vegetation change across all variants. Finally, using a novel method, we calculate that seventeen percent of continuous-canopy forest has been lost in the study area and provide further evidence that unforested areas are the result of anthropogenic deforestation. Our findings contribute valuable insights for rangeland science and demonstrate the need for new case studies, and synthesis of concepts and theories, specific to pastoralism in the Middle East. Our findings highlight a requirement for an intervention to reduce livestock pressure on the rangelands in Dhofar. We propose a shift away from the status quo of unmanaged and unproductive overstocking to an economically and environmentally sustainable rural livestock production system through certification, sustainable intensification and marketization

Laboratory characterization of brick walls rendered with a pervious lime-cement mortar

A laboratory study investigating important thermal retrofitting solutions for simple and double (cavity) brick walls is presented. Test walls were modified using materials of current interest including an external pervious lime-cement mortar render and insulation board prior to evaluation. Laboratory simulations of steady-state winter and summer scenarios were performed using apparatus comprising two opposing climate chambers. Temperature, relative humidity and heat flux rate were monitored with surface sensors every 10 min until stabilization on each wall type, retrofitting solution and climate scenario. The temperature and relative humidity profiles, heat flux, surface temperature difference, thermal conductance, condensation risk and stabilization times were assessed. Comparisons between simple and double (cavity) brick walls showed significant differences and a high condensation risk in the non-ventilated air cavity of the double wall. The pervious lime-cement mortar render enhanced substantially the thermal performance of the single wall although increased the condensation risk of the double (cavity) wall. As expected, the insulation layer reduced the thermal conductance of the wall, although the improvement in a summer scenario was considerably lower than in winter. The different performance observed between winter and summer steady-state conditions emphasized the importance of the heat and mass transfer coupling effect. Therefore, this work proves that effective retrofitting depends on materials, wall layouts and climate conditions. These experimental results provide essential knowledge about assessing the effects of common retrofitting solutions especially under hot-dry summer scenarios.</p

Market-Based Alternatives for Managing Congestion at New York’s LaGuardia Airport

We summarize the results of a project that was motivated by the expiration of the “High Density Rule,” which defined the slot controls employed at New York’s LaGuardia Airport for more than 30 years. The scope of the project included the analysis of several administrative measures, congestion pricing options and slot auctions. The research output includes a congestion pricing procedure and also the specification of a slot auction mechanism. The research results are based in part on two strategic simulations. These were multi-day events that included the participation of airport operators, most notably the Port Authority of New York and New Jersey, FAA and DOT executives, airline representatives and other members of the air transportation community. The first simulation placed participants in a stressful, high congestion future scenario and then allowed participants to react and problem solve under various administrative measures and congestion pricing options. The second simulation was a mock slot auction in which participants bid on LGA arrival and departure slots for fictitious airlines.Auctions, airport slot auctions, combinatorial auctions

On the effects of using CO2 and F2 lasers to modify the wettability of a polymeric biomaterial.

Enhancement of the surface properties of a material by means of laser radiation has been amply demonstrated previously. In this work a comparative study for the surface modification of nylon 6,6 has been conducted in order to vary the wettability characteristics using CO2 and excimer lasers. This was done by producing 50 μm spaced (with depths between 1 and 10 μm) trench-like patterns using various laser parameters such as varying the laser power for the CO2 laser and number of pulses for the excimer laser. Topographical changes were analysed using optical microscopy and white light interferometry which indicated that both laser systems can be implemented for modifying the topography of nylon 6,6. Variations in the surface chemistry were evaluated using energy-dispersive X-ray spectroscopy and x-ray photoelectron spectroscopy analysis and showed that the O2 increased by up to 1.5% At. and decreased by up to 1.6% At. for the CO2 and F2 laser patterned samples, respectively. Modification of the wettability characteristics was quantified by measuring the advancing contact angle, which was found to increase in all instances for both laser systems. Emery paper roughened samples were also analysed in the same manner to determine that the topographical pattern played a major role in the wettability characteristics of nylon 6,6. From this, it is proposed that the increase in contact angle for the laser processed samples is due to a mixed intermediate state wetting regime owed to the periodic surface roughness brought about by the laser induced trench-like topographical patterns

Interaction of CO2 laser-modified nylon with osteoblast cells in relation to wettability

It has been amply demonstrated previously that CO2 lasers hold the ability to surface modify various polymers. In addition, it has been observed that these surface enhancements can augment the biomimetic nature of the laser irradiated materials. This research has employed a CO2 laser marker to produce trench and hatch topographical patterns with peak heights of around 1 μm on the surface of nylon 6,6. The patterns generated have been analysed using white light interferometery, optical microscopy and X-ray photoelectron spectroscopy was employed to determine the surface oxygen content. Contact angle measurements were used to characterize each sample in terms of wettability. Generally, it was seen that as a result of laser processing the contact angle, surface roughness and surface oxygen content increased whilst the apparent polar and total surface energies decreased. The increase in contact angle and reduction in surface energy components was found to be on account of a mixed intermediate state wetting regime owing to the change in roughness due to the induced topographical patterns. To determine the biomimetic nature of the modified and as-received control samples each one was seeded with 2×104 cells/ml normal human osteoblast cells and observed after periods of 24 hours and 4 days using optical microscopy and SEM to determine mean cell cover densities and variations in cell morphology. In addition a haeymocytometer was used to show that the cell count for the laser patterned samples had increased by up to a factor of 1.5 compared to the as-received control sample after 4 days of incubation. Significantly, it was determined that all laser-induced patterns gave rise to better cell response in comparison to the as-received control sample studied due to increased preferential cell growth on those surfaces with increased surface roughness

Six new variants of the Terminalia cloud forest in the Dhofar Mountains of Oman

Background and Aims: The Terminalia cloud forest is endemic to a 200-km stretch of coastal mountains in southern Arabia. This research aims to describe patterns of variation in the species composition of the Terminalia forest in Dhofar, Oman and examine causal environmental factors. Study area: The Jabal Qamar mountain range, Dhofar, Oman. Methods: Hierarchical cluster analysis and indicator species analysis were used to identify and describe variants of the Terminalia forest. Topoclimatic factors, vegetation characteristics and disturbance factors were compared between the variants using ordination and ANOVA or Kruskal-Wallis tests. Results: Six new variants of the Terminalia forest are described. These are the Dodonaea viscosa subsp. angustifolia shrubland variant, Cadia purpurea-Olea europaea forest variant, Euclea racemosa-Jasminum grandiflorum shrubland variant, Gymnosporia dhofarensis-Ficus sycomorus woodland variant, Jatropha dhofarica-Zygocarpum dhofarense sparse woodland variant and the Premna resinosa-Hybanthus durus forest variant. A seventh variant was identified, which was previously described by Kürschner et al. (2004); the broad-leaved Blepharispermum hirtum shrubland. The species composition and environmental conditions indicate that two variants are the result of anthropogenic disturbance, whilst the other variants are well separated along fog density and topographic position gradients. Conclusions: Distinct variants of the Terminalia forest in Jabal Qamar result from spatial variability in environmental conditions associated with the complex topography, monsoon fog distributions, and anthropogenic disturbance. The results of this study could assist practitioners to rapidly identify and prioritise these variants for conservation