Position Measurements Obeying Momentum Conservation

We present a hitherto unknown fundamental limitation to a basic measurement: that of the position of a quantum object when the total momentum of the object and apparatus is conserved. This result extends the famous Wigner-Araki-Yanase (WAY) theorem, and shows that accurate position measurements are only practically feasible if there is a large momentum uncertainty in the apparatus

Long Term Monitoring of CFA Energy Pile Schemes in the UK

Energy pile schemes involve the use of structural foundations as heat exchangers in a ground source heat pump system. Such schemes are attractive, as they reduce energy consumption compared with traditional building heating and cooling systems. As energy prices increase and governments introduce subsidies they are also proving increasingly economically attractive. Additionally, energy piles can contribute to reducing the carbon dioxide emissions associated with a development. However, this approach to heating and cooling building remains relatively novel and the lack of published long term performance data remains a barrier to further implementation. Two issues remain to be addressed by long term monitoring. First, the need for a database of operational energy piles schemes were the energy performance is proven over many years. Secondly, availability of long term datasets of pile thermal behavior that can be used to validate design approaches and tools and hence encourage less conservative design practices. This paper presents the initial results from a study aimed at tackling these issues through long term instrumentation and monitoring of two energy pile schemes in the United Kingdom

Economics of geotechnical asset deterioration, maintenance and renewal

Transport and other infrastructure systems are supported on, adjacent to and retained by extensive systems of earthworks of varying (and increasing) age, and of variable original construction quality. These earthworks are subject to natural deterioration, which can be accelerated and complicated by the effects of climate change. The ACHILLES research program is providing improved understanding of earthworks behavior, performance and deterioration. It is also developing methods and tools to analyze and provide decision support for the construction, maintenance and renewal of earthworks, with particular emphasis on the management of existing, deteriorating assets. The work described here aims to identify the most cost-effective timing and means of extending earthworks asset lives and maintaining their safety and serviceability. Conventional cost-benefit analysis methods, of the type used for new infrastructure projects, do not directly provide the decision support needed for the maintenance and renewal of existing earthworks assets. An alternative approach is proposed and applied to a modeled example, demonstrating the potential asset management benefits of early, pre-emptive intervention, the economic attraction of deferred intervention, and the means of identifying an intermediate whole-life cost ‘sweet spot’, based on a timely assessment of intervention options. The handling of the uncertainty associated with earthworks behavior, deterioration rates and times to failure is also considered, as is the extension of the single-asset approach to the management of multiple earthworks assets

Unraveling the role of protein dynamics in dihydrofolate reductase catalysis

Protein dynamics have controversially been proposed to be at the heart of enzyme catalysis, but identification and analysis of dynamical effects in enzyme-catalyzed reactions have proved very challenging. Here, we tackle this question by comparing an enzyme with its heavy (15N, 13C, 2H substituted) counterpart, providing a subtle probe of dynamics. The crucial hydride transfer step of the reaction (the chemical step) occurs more slowly in the heavy enzyme. A combination of experimental results, quantum mechanics/molecular mechanics simulations, and theoretical analyses identify the origins of the observed differences in reactivity. The generally slightly slower reaction in the heavy enzyme reflects differences in environmental coupling to the hydride transfer step. Importantly, the barrier and contribution of quantum tunneling are not affected, indicating no significant role for “promoting motions” in driving tunneling or modulating the barrier. The chemical step is slower in the heavy enzyme because protein motions coupled to the reaction coordinate are slower. The fact that the heavy enzyme is only slightly less active than its light counterpart shows that protein dynamics have a small, but measurable, effect on the chemical reaction rate

Termitaria as browsing hotspots for African megaherbivores in miombo woodland

Abstract: Thirteen termite mounds and 13 similar-sized control plots were surveyed in central Zimbabwe in order to study large mammalian browsing and vegetation characteristics. The mounds supported almost twice as many tree species as the control plots and the woody vegetation was denser on mounds compared with the woodland plots. Species of woody plants were recorded along with the percentage of branches browsed (cumulative browsing score) by black rhino, Diceros bicornis, elephant, Loxodonta africana and other browsers combined. In addition we measured how the cumulative browsing score on three woody plant species, Acacia nilotica, Colophospermum mopane and Dichrostachys cinerea, which were common both on and off mounds, was related to the distance from mound centre. Both black rhino and elephant cumulative browsing scores were significantly higher on the mound plants compared with the woodland plots. Cumulative browsing score was negatively related to distance from the mound centre for Dichrostachys cinerea, Colophospermum mopane and Acacia nilotica. We propose that termite mound construction in miombo woodland contributes to sustaining populations of megaherbivores and perhaps some woody species in these areas

Syndromic surveillance to assess the potential public health impact of the Icelandic volcanic ash plume across the United Kingdom, April 2010

The Eyjafjallajökull volcano in Iceland erupted on 14 April 2010 emitting a volcanic ash plume that spread across the United Kingdom and mainland Europe. The Health Protection Agency and Health Protection Scotland used existing syndromic surveillance systems to monitor community health during the incident: there were no particularly unusual increases in any of the monitored conditions. This incident has again demonstrated the use of syndromic surveillance systems for monitoring community health in real time

Comparison of two different models for pile thermal response test interpretation

Thermal response tests (TRTs) are regularly used to characterise the thermal resistance of borehole heat exchangers and to assess the thermal conductivity of the surrounding ground. It is becoming common to apply the same in situ testing technique to pile heat exchangers, despite international guidance suggesting that TRTs should be limited to hole diameters of 152 mm (6 in.). This size restriction arises from the increased thermal inertia of larger diameter heat exchangers, which invalidates the assumption of a steady state within the concrete needed to interpret the test data by traditional line source analysis techniques. However, new methods of analysis for pile heat exchangers have recently been developed that take account of the transient behaviour of the pile concrete. This paper applies these new methods to data from a multi-stage TRT conducted on a small diameter test pile. The thermal conductivity and thermal resistance determined using this method are then compared with those from traditional analytical approaches based on a line source analysis. Differences between the approaches are discussed, along with the observation that the thermal resistance may not be constant over the different test stages

Thermal Adaptation of Dihydrofolate Reductase from the Moderate ThermophileGeobacillus stearothermophilus

The thermal melting temperature of dihydrofolate reductase from Geobacillus stearothermophilus (BsDHFR) is 30 °C higher than that of its homologue from the psychrophile Moritella profunda. Additional proline residues in the loop regions of BsDHFR have been proposed to enhance the thermostability of BsDHFR, but site-directed mutagenesis studies reveal that these proline residues contribute only minimally. Instead, the high thermal stability of BsDHFR is partly due to removal of water-accessible thermolabile residues such as glutamine and methionine, which are prone to hydrolysis or oxidation at high temperatures. The extra thermostability of BsDHFR can be obtained by ligand binding, or in the presence of salts or cosolvents such as glycerol and sucrose. The sum of all these incremental factors allows BsDHFR to function efficiently in the natural habitat of G. stearothermophilus, which is characterized by temperatures that can reach 75 °C