26,977 research outputs found

    Smart & sustainable cities

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    The University of Strathclyde is creating a new Institute for Future Cities that aims to improve the quality of human life across the world through innovative research that enables cities to be understood in new ways, and innovative approaches to be developed for the way we live, work, learn and invest in cities. The new Institute will create a focus and strategy to coordinate academic research on urban themes, and partnerships with cities, businesses, research institutions and governments across the world. This paper outlines the wider context and issues for urban policy and research, and describes some of the key objectives and activities of the Institute for Future Cities - including the €3.7 million EU FP7 STEP UP project on sustainable city planning and implementation, a new ESRC research programme on crime prediction, and the City Observatory within the £24 million TSB Future City Demonstrator in Glasgow

    Centralized Oversight of the Regulatory State

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    Born out of a Reagan-era desire to minimize regulatory costs, and not fundamentally reconsidered since its inception, the centralized review of agency rulemakings has arguably become the most important institutional feature of the regulatory state. Yet it is a puzzling feature: although centralized review is sometimes justified on the ground it could harmonize the uncoordinated sprawl of the federal bureaucracy, the agency tasked with regulatory review, the Office of Management and Budget (OMB), has never embraced that role. It has instead doggedly clung to its original cost-reduction mission, justifying its function as a check on the federal bureaucracy with reference to the pervasive belief that agencies will systematically over-regulate. This article shows why this belief is wrong. The claim that agencies are systematically biased in favor of regulation finds little support in public choice theory, the political science literature, or elsewhere. In any event, theories predicting rampant over-regulation are no more plausible than alternative theories suggesting that agencies will routinely under regulate. Even if zealous agencies captured by powerful interest groups did characterize the regulatory state, OMB review is a curious and poorly designed counterweight. There is no reason to believe that OMB's location in the Executive Office of the President will inoculate OMB from the pathologies that afflict other agencies, and some reason to think that it will exacerbate them. As a response to these problems, we urge a reconsideration of the foundational role that centralized review should play in our regulatory state, and a revival and re-conceptualization of the neglected principles of harmonization that once ostensibly animated it.

    Passive control of a bi-ventricular assist device : an experimental and numerical investigation

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    For the last two decades heart disease has been the highest single cause of death for the human population. With an alarming number of patients requiring heart transplant, and donations not able to satisfy the demand, treatment looks to mechanical alternatives. Rotary Ventricular Assist Devices, VADs, are miniature pumps which can be implanted alongside the heart to assist its pumping function. These constant flow devices are smaller, more efficient and promise a longer operational life than more traditional pulsatile VADs. The development of rotary VADs has focused on single pumps assisting the left ventricle only to supply blood for the body. In many patients however, failure of both ventricles demands that an additional pulsatile device be used to support the failing right ventricle. This condition renders them hospital bound while they wait for an unlikely heart donation. Reported attempts to use two rotary pumps to support both ventricles concurrently have warned of inherent haemodynamic instability. Poor balancing of the pumps’ flow rates quickly leads to vascular congestion increasing the risk of oedema and ventricular ‘suckdown’ occluding the inlet to the pump. This thesis introduces a novel Bi-Ventricular Assist Device (BiVAD) configuration where the pump outputs are passively balanced by vascular pressure. The BiVAD consists of two rotary pumps straddling the mechanical passive controller. Fluctuations in vascular pressure induce small deflections within both pumps adjusting their outputs allowing them to maintain arterial pressure. To optimise the passive controller’s interaction with the circulation, the controller’s dynamic response is optimised with a spring, mass, damper arrangement. This two part study presents a comprehensive assessment of the prototype’s ‘viability’ as a support device. Its ‘viability’ was considered based on its sensitivity to pathogenic haemodynamics and the ability of the passive response to maintain healthy circulation. The first part of the study is an experimental investigation where a prototype device was designed and built, and then tested in a pulsatile mock circulation loop. The BiVAD was subjected to a range of haemodynamic imbalances as well as a dynamic analysis to assess the functionality of the mechanical damper. The second part introduces the development of a numerical program to simulate human circulation supported by the passively controlled BiVAD. Both investigations showed that the prototype was able to mimic the native baroreceptor response. Simulating hypertension, poor flow balancing and subsequent ventricular failure during BiVAD support allowed the passive controller’s response to be assessed. Triggered by the resulting pressure imbalance, the controller responded by passively adjusting the VAD outputs in order to maintain healthy arterial pressures. This baroreceptor-like response demonstrated the inherent stability of the auto regulating BiVAD prototype. Simulating pulmonary hypertension in the more observable numerical model, however, revealed a serious issue with the passive response. The subsequent decrease in venous return into the left heart went unnoticed by the passive controller. Meanwhile the coupled nature of the passive response not only decreased RVAD output to reduce pulmonary arterial pressure, but it also increased LVAD output. Consequently, the LVAD increased fluid evacuation from the left ventricle, LV, and so actually accelerated the onset of LV collapse. It was concluded that despite the inherently stable baroreceptor-like response of the passive controller, its lack of sensitivity to venous return made it unviable in its present configuration. The study revealed a number of other important findings. Perhaps the most significant was that the reduced pulse experienced during constant flow support unbalanced the ratio of effective resistances of both vascular circuits. Even during steady rotary support therefore, the resulting ventricle volume imbalance increased the likelihood of suckdown. Additionally, mechanical damping of the passive controller’s response successfully filtered out pressure fluctuations from residual ventricular function. Finally, the importance of recognising inertial contributions to blood flow in the atria and ventricles in a numerical simulation were highlighted. This thesis documents the first attempt to create a fully auto regulated rotary cardiac assist device. Initial results encourage development of an inlet configuration sensitive to low flow such as collapsible inlet cannulae. Combining this with the existing baroreceptor-like response of the passive controller will render a highly stable passively controlled BiVAD configuration. The prototype controller’s passive interaction with the vasculature is a significant step towards a highly stable new generation of artificial heart

    Cycle tourism development in the Peak District National Park, United Kingdom

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    ABSTRACT Protected areas are at the centre of nature-based tourism, which is increasingly popular across the world. As visitor numbers increase, so does awareness of the harmful effects that large crowds may have on both natural resources and individuals’ recreational experience. This volume considers the challenge of transportation to and within natural and protected areas, the improvement of which has already been recognised as having great potential for mitigating the environmental impacts of ecotourism. While several books have focused considerable attention to the management of protected areas in general, little has been said about the specific issue of sustainable transport, an emerging trend that is already reshaping visitation patterns in natural settings. This book provides current knowledge on issues associated with the transportation of visitors in natural and protected areas, and a comprehensive overview of the technical and strategic options available to tackle these issues. It approaches the subject via three main topics: preferences, or the visitors' attitudes towards transportation; practices, where current approaches are assessed through examples and case-studies of successful experiences and methodologies from around the world; and policies, where suggestions and recommendations are put forward for both local scale strategies and broad-scale regulatory action with global relevance. Contributors include academics in the field of natural resource management and tourism, with extensive experience in protected area management and active partnerships with natural park administrations

    Cultivar diversity as a means of ecologically intensifying dry matter production in a perennial forage stand

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    The relationship between genotypic diversity and productivity has not been adequately explored in perennial forage production systems despite strong theoretical and empirical evidence supporting diversity\u27s role in ecosystem functioning in other managed and unmanaged systems. We conducted a two-year field experiment with six cultivars of an agriculturally important forage grass, Lolium perenne L. (perennial ryegrass). Dry matter production of L. perenne and the weed community that emerged from the soil seed bank were measured each year in treatments that ranged from cultivar monocultures to three- and six-way cultivar mixtures, all sown at a constant seeding rate. Mean L. perenne dry matter production increased with increasing cultivar diversity and was highest in mixtures that contained cultivars representing the greatest additive trait range (calculated on rankings of three traits: winter hardiness, heading date, and tolerance to grazing). Mixtures had greater yields than those predicted by the mean of their component monoculture yields, but there was evidence that highly productive cultivars may have dampened over-yielding in mixtures. Weed abundance was correlated with L. perenne dry matter, but not L. perenne cultivar diversity. These results suggest that multi-cultivar mixtures may have utility as an approach to ecologically intensifying perennial forage production. Additional research will be necessary to determine the mechanisms responsible for the over-yielding observed in this study and the generality of these findings

    Rotationally Resolved Spectroscopy of Asteroid Pairs: No Spectral Variation Suggests Fission is followed by Settling of Dust

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    We examine the spectral properties of asteroid pairs that were disrupted in the last 2 Myrs to examine whether the site of the fission can be revealed. We studied the possibility that the sub-surface material, perhaps on one hemisphere, has spectral characteristics differing from the original weathered surface, by performing rotationally-resolved spectroscopic observations to look for local variations as the asteroid rotates. We observed 11 asteroids in pairs in the near-IR and visible range. Photometry was also conducted to determine the rotational phases of a spectrum on the asteroid lightcurves. We do not detect any rotational spectral variations within the signal-to-noise, which allow us to constrain the extent of any existing surface heterogeneity. For each observed spectrum of a longitudinal segment of an asteroid, we estimate the maximal size of an un-detected "spot" with a spectral signature different than the average. For 5 asteroids the maximal diameter of such a spot is smaller by a factor of two than the diameter of the secondary member. Therefore, the site of the fission is larger than any area with a unique spectral parameters and the site of the fission does not have a unique spectrum. In the case of an S-complex asteroid, where the site of fission is expected to present non-weathered spectra, a lack of a fission spot can be explained if the rotational-fission process is followed by the spread of dust that re-accumulates on the primary asteroid and covers it homogeneously. This is demonstrated for the young asteroid 6070 that presents an Sq-type spectrum while its inner material, that is presumably revealed on the surface of its secondary member, 54827, has a fresher, Q-type spectrum. The spread of dust observed in the disruption event of asteroid P/2013 R3, might be an example of such a process and an indication that it was indeed formed in a rotational-fission event.Comment: 16 pages, 15 figures, 6 Tables. Accepted for publication in Icaru

    Dynamical evolution of star forming regions - II. Basic kinematics

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    We follow the dynamical evolution of young star-forming regions with a wide range of initial conditions and examine how the radial velocity dispersion, σ\sigma, evolves over time. We compare this velocity dispersion to the theoretically expected value for the velocity dispersion if a region were in virial equilibrium, σvir\sigma_{\rm vir} and thus assess the virial state (σ/σvir\sigma / \sigma_{\rm vir}) of these systems. We find that in regions that are initially subvirial, or in global virial equilibrium but subvirial on local scales, the system relaxes to virial equilibrium within several million years, or roughly 25 - 50 crossing times, according to the measured virial ratio. However, the measured velocity dispersion, σ\sigma, appears to be a bad diagnostic of the current virial state of these systems as it suggests that they become supervirial when compared to the velocity dispersion estimated from the virial mass, σvir\sigma_{\rm vir}. We suggest that this discrepancy is caused by the fact that the regions are never fully relaxed, and that the early non-equilibrium evolution is imprinted in the one-dimensional velocity dispersion at these early epochs. If measured early enough (<<2 Myr in our simulations, or \sim20 crossing times), the velocity dispersion can be used to determine whether a region was highly supervirial at birth without the risk of degeneracy. We show that combining σ\sigma, or the ratio of σ\sigma to the interquartile range (IQR) dispersion, with measures of spatial structure, places stronger constraints on the dynamical history of a region than using the velocity dispersion in isolation.Comment: 20 pages, 14 figures, accepted for publication in MNRA
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