Showing papers in "Philosophical Transactions of the Royal Society A in 2010"
TL;DR: This work aims to review different strategies of surface modification and functionalization of inorganic colloidal nanoparticles with a special focus on the material systems gold and semiconductor nanoparticles, such as CdSe/ZnS.
Abstract: Inorganic colloidal nanoparticles are very small, nanoscale objects with inorganic cores that are dispersed in a solvent. Depending on the material they consist of, nanoparticles can possess a number of different properties such as high electron density and strong optical absorption (e.g. metal particles, in particular Au), photoluminescence in the form of fluorescence (semiconductor quantum dots, e.g. CdSe or CdTe) or phosphorescence (doped oxide materials, e.g. Y(2)O(3)), or magnetic moment (e.g. iron oxide or cobalt nanoparticles). Prerequisite for every possible application is the proper surface functionalization of such nanoparticles, which determines their interaction with the environment. These interactions ultimately affect the colloidal stability of the particles, and may yield to a controlled assembly or to the delivery of nanoparticles to a target, e.g. by appropriate functional molecules on the particle surface. This work aims to review different strategies of surface modification and functionalization of inorganic colloidal nanoparticles with a special focus on the material systems gold and semiconductor nanoparticles, such as CdSe/ZnS. However, the discussed strategies are often of general nature and apply in the same way to nanoparticles of other materials.
1,477 citations
TL;DR: There is room for optimism as long as the authors pursue paradigm shifts while keeping in mind the concept of materials sustainability, and relying on new ways to prepare electrode materials via eco-efficient processes, on the use of organic rather than inorganic materials or new chemistries will be discussed.
Abstract: Batteries are a major technological challenge in this new century as they are a key method to make more efficient use of energy. Although today's Li-ion technology has conquered the portable electronic markets and is still improving, it falls short of meeting the demands dictated by the powering of both hybrid electric vehicles and electric vehicles or by the storage of renewable energies (wind, solar). There is room for optimism as long as we pursue paradigm shifts while keeping in mind the concept of materials sustainability. Some of these concepts, relying on new ways to prepare electrode materials via eco-efficient processes, on the use of organic rather than inorganic materials or new chemistries will be discussed. Achieving these concepts will require the inputs of multiple disciplines.
718 citations
TL;DR: A new car-following model is proposed that also serves as the basis of an ACC implementation in real cars and eliminates the sometimes unrealistic behaviour of the IDM in cut-in situations with ensuing small gaps that regularly are caused by lane changes of other vehicles in dense or congested traffic.
Abstract: With an increasing number of vehicles equipped with adaptive cruise control (ACC), the impact of such vehicles on the collective dynamics of traffic flow becomes relevant. By means of simulation, we investigate the influence of variable percentages of ACC vehicles on traffic flow characteristics. For simulating the ACC vehicles, we propose a new car-following model that also serves as the basis of an ACC implementation in real cars. The model is based on the intelligent driver model (IDM) and inherits its intuitive behavioural parameters: desired velocity, acceleration, comfortable deceleration and desired minimum time headway. It eliminates, however, the sometimes unrealistic behaviour of the IDM in cut-in situations with ensuing small gaps that regularly are caused by lane changes of other vehicles in dense or congested traffic. We simulate the influence of different ACC strategies on the maximum capacity before breakdown and the (dynamic) bottleneck capacity after breakdown. With a suitable strategy, we find sensitivities of the order of 0.3, i.e. 1 per cent more ACC vehicles will lead to an increase in the capacities by about 0.3 per cent. This sensitivity multiplies when considering travel times at actual breakdowns.
696 citations
TL;DR: This review discusses advances that have been made in the study of defect-induced double-resonance processes in nanographite, graphene and carbon nanotubes, mostly coming from combining Raman spectroscopic experiments with microscopy studies and from the development of new theoretical models.
Abstract: This review discusses advances that have been made in the study of defect-induced double-resonance processes in nanographite, graphene and carbon nanotubes, mostly coming from combining Raman spectroscopic experiments with microscopy studies and from the development of new theoretical models The disorder-induced peak frequencies and intensities are discussed, with particular emphasis given to how the disorder-induced features evolve with increasing amounts of disorder We address here two systems, ion-bombarded graphene and nanographite, where disorder is represented by point defects and boundaries, respectively Raman spectroscopy is used to study the ‘atomic structure’ of the defect, making it possible, for example, to distinguish between zigzag and armchair edges, based on selection rules of phonon scattering Finally, a different concept is discussed, involving the effect that defects have on the lineshape of Raman-allowed peaks, owing to local electron and phonon energy renormalization Such effects can be observed by near-field optical measurements on the G ′ feature for doped single-walled carbon nanotubes
631 citations
TL;DR: The skin of fast-swimming sharks exhibits riblet structures aligned in the direction of flow that are known to reduce skin friction drag in the turbulent-flow regime.
Abstract: The skin of fast-swimming sharks exhibits riblet structures aligned in the direction of flow that are known to reduce skin friction drag in the turbulent-flow regime. Structures have been fabricated for study and application that replicate and improve upon the natural shape of the shark-skin riblets, providing a maximum drag reduction of nearly 10 per cent. Mechanisms of fluid drag in turbulent flow and riblet-drag reduction theories from experiment and simulation are discussed. A review of riblet-performance studies is given, and optimal riblet geometries are defined. A survey of studies experimenting with riblet-topped shark-scale replicas is also given. A method for selecting optimal riblet dimensions based on fluid-flow characteristics is detailed, and current manufacturing techniques are outlined. Due to the presence of small amounts of mucus on the skin of a shark, it is expected that the localized application of hydrophobic materials will alter the flow field around the riblets in some way beneficial to the goals of increased drag reduction.
551 citations
TL;DR: Prospects for the manufacture of patient-specific biomedical implants replacing hard tissues (bone), particularly knee and hip stems and large bone (femoral) intramedullary rods, using additive manufacturing (AM) by electron beam melting (EBM) are examined.
Abstract: In this paper, we examine prospects for the manufacture of patient-specific biomedical implants replacing hard tissues (bone), particularly knee and hip stems and large bone (femoral) intramedullary rods, using additive manufacturing (AM) by electron beam melting (EBM). Of particular interest is the fabrication of complex functional (biocompatible) mesh arrays. Mesh elements or unit cells can be divided into different regions in order to use different cell designs in different areas of the component to produce various or continually varying (functionally graded) mesh densities. Numerous design elements have been used to fabricate prototypes by AM using EBM of Ti-6Al-4V powders, where the densities have been compared with the elastic (Young) moduli determined by resonant frequency and damping analysis. Density optimization at the bone-implant interface can allow for bone ingrowth and cementless implant components. Computerized tomography (CT) scans of metal (aluminium alloy) foam have also allowed for the building of Ti-6Al-4V foams by embedding the digital-layered scans in computer-aided design or software models for EBM. Variations in mesh complexity and especially strut (or truss) dimensions alter the cooling and solidification rate, which alters the alpha-phase (hexagonal close-packed) microstructure by creating mixtures of alpha/alpha' (martensite) observed by optical and electron metallography. Microindentation hardness measurements are characteristic of these microstructures and microstructure mixtures (alpha/alpha') and sizes.
536 citations
TL;DR: A major change in the energy economy from fossil energy carriers to renewable energy fluxes is necessary to efficiently convert renewable energy into electricity and the storage of electricity or the production of a synthetic fuel.
Abstract: Since the beginning of the twenty-first century the limitations of the fossil age with regard to the continuing growth of energy demand, the peaking mining rate of oil, the growing impact of CO2 emissions on the environment and the dependency of the economy in the industrialized world on the availability of fossil fuels became very obvious. A major change in the energy economy from fossil energy carriers to renewable energy fluxes is necessary. The main challenge is to efficiently convert renewable energy into electricity and the storage of electricity or the production of a synthetic fuel. Hydrogen is produced from water by electricity through an electrolyser. The storage of hydrogen in its molecular or atomic form is a materials challenge. Some hydrides are known to exhibit a hydrogen density comparable to oil; however, these hydrides require a sophisticated storage system. The system energy density is significantly smaller than the energy density of fossil fuels. An interesting alternative to the direct storage of hydrogen are synthetic hydrocarbons produced from hydrogen and CO2 extracted from the atmosphere. They are CO2 neutral and stored like fossil fuels. Conventional combustion engines and turbines can be used in order to convert the stored energy into work and heat.
522 citations
TL;DR: An evaluation of the thermodynamic efficiency of the ceria-based thermochemical cycle suggests that, even in the absence of heat recovery, solar-to-fuel conversion efficiencies of 16 to 19 per cent can be achieved, assuming a suitable method for obtaining an inert atmosphere for the oxygen release step.
Abstract: We present a comprehensive thermodynamic and kinetic analysis of the suitability of cerium oxide (ceria) for thermochemical fuel production. Both portions of the two-step cycle, (i) oxygen release from the oxide at 1773 and 1873 K under inert atmosphere, and (ii) hydrogen release upon hydrolysis at 1073 K, are examined theoretically as well as experimentally. We observe gravimetric fuel productivity that is in quantitative agreement with equilibrium, thermogravimetric studies of ceria. Despite the non-stoichiometric nature of the redox cycle, in which only a portion of the cerium atoms change their oxidation state, the fuel productivity of 8.5–11.8 ml of H2 per gram of ceria is competitive with that of other solid-state thermochemical cycles currently under investigation. The fuel production rate, which is also highly attractive, at a rate of 4.6–6.2 ml of H_2 per minute per gram of ceria, is found to be limited by a surface-reaction step rather than by ambipolar bulk diffusion of oxygen through the solid ceria. An evaluation of the thermodynamic efficiency of the ceria-based thermochemical cycle suggests that, even in the absence of heat recovery, solar-to-fuel conversion efficiencies of 16 to 19 per cent can be achieved, assuming a suitable method for obtaining an inert atmosphere for the oxygen release step.
415 citations
TL;DR: It is clear now that wetting is not characterized by a single parameter, since several modes or regimes of wetting of a rough surface can exist, including the Wenzel, Cassie, lotus and petal.
Abstract: The wetting of rough surfaces remains a subject of active investigation by scientists. The contact angle (CA) is a traditional parameter used to characterize the hydrophobicity/philicity of a solid surface. However, it was found recently that high CAs can coexist with strong adhesion between water and a solid surface in the case of the so-called 'rose petal effect'. Several additional parameters have been proposed to characterize the interaction of water with a rough solid surface, including the CA hysteresis, the ability of water droplets to bounce off a solid surface, the tilt angle needed to initiate the flow of a droplet, and the normal and shear adhesion. It is clear now that wetting is not characterized by a single parameter, since several modes or regimes of wetting of a rough surface can exist, including the Wenzel, Cassie, lotus and petal. Understanding the wetting of rough surfaces is important in order to design non-adhesive surfaces for various applications.
389 citations
TL;DR: The paper briefly summarizes the approaches that different teams used in the 2007 DARPA Urban Challenge, with the goal of describing some of the challenges that the teams faced in driving in urban environments.
Abstract: The development of autonomous vehicles for urban driving has seen rapid progress in the past 30 years. This paper provides a summary of the current state of the art in autonomous driving in urban environments, based primarily on the experiences of the authors in the 2007 DARPA Urban Challenge (DUC). The paper briefly summarizes the approaches that different teams used in the DUC, with the goal of describing some of the challenges that the teams faced in driving in urban environments. The paper also highlights the long-term research challenges that must be overcome in order to enable autonomous driving and points to opportunities for new technologies to be applied in improving vehicle safety, exploiting intelligent road infrastructure and enabling robotic vehicles operating in human environments.
388 citations
TL;DR: This work provides a brief overview of an alternative mid- to long-term option, namely, the capture and conversion of CO2, to produce sustainable, synthetic hydrocarbon or carbonaceous fuels, most notably for transportation purposes, and highlights three possible strategies involving CO2 conversion by physico-chemical approaches.
Abstract: Our present dependence on fossil fuels means that, as our demand for energy inevitably increases, so do emissions of greenhouse gases, most notably carbon dioxide (CO2). To avoid the obvious consequences on climate change, the concentration of such greenhouse gases in the atmosphere must be stabilized. But, as populations grow and economies develop, future demands now ensure that energy will be one of the defining issues of this century. This unique set of (coupled) challenges also means that science and engineering have a unique opportunity-and a burgeoning challenge-to apply their understanding to provide sustainable energy solutions. Integrated carbon capture and subsequent sequestration is generally advanced as the most promising option to tackle greenhouse gases in the short to medium term. Here, we provide a brief overview of an alternative mid- to long-term option, namely, the capture and conversion of CO2, to produce sustainable, synthetic hydrocarbon or carbonaceous fuels, most notably for transportation purposes. Basically, the approach centres on the concept of the large-scale re-use of CO2 released by human activity to produce synthetic fuels, and how this challenging approach could assume an important role in tackling the issue of global CO2 emissions. We highlight three possible strategies involving CO2 conversion by physico-chemical approaches: sustainable (or renewable) synthetic methanol, syngas production derived from flue gases from coal-, gas- or oil-fired electric power stations, and photochemical production of synthetic fuels. The use of CO2 to synthesize commodity chemicals is covered elsewhere (Arakawa et al. 2001 Chem. Rev. 101, 953-996); this review is focused on the possibilities for the conversion of CO2 to fuels. Although these three prototypical areas differ in their ultimate applications, the underpinning thermodynamic considerations centre on the conversion-and hence the utilization-of CO2. Here, we hope to illustrate that advances in the science and engineering of materials are critical for these new energy technologies, and specific examples are given for all three examples. With sufficient advances, and institutional and political support, such scientific and technological innovations could help to regulate/stabilize the CO2 levels in the atmosphere and thereby extend the use of fossil-fuel-derived feedstocks.
TL;DR: Stable and unstable motions are described that may give the skeleton of traffic dynamics, and the effects of driver behaviour are emphasized in determining the emergent state in a vehicular system.
Abstract: This introductory paper reviews the current state-of-the-art scientific methods used for modelling, analysing and controlling the dynamics of vehicular traffic. Possible mechanisms underlying traffic jam formation and propagation are presented from a dynamical viewpoint. Stable and unstable motions are described that may give the skeleton of traffic dynamics, and the effects of driver behaviour are emphasized in determining the emergent state in a vehicular system. At appropriate points, references are provided to the papers published in the corresponding Theme Issue.
TL;DR: As a processing technique for the manufacture of biomaterials, freeze casting has great promise to synthesize materials that mimic both structure and mechanical performance of the natural tissue and permit strong tissue–implant interfaces to be formed.
Abstract: The functional requirements for synthetic tissue substitutes appear deceptively simple: they should provide a porous matrix with interconnecting porosity and surface properties that promote rapid tissue ingrowth; at the same time, they should possess sufficient stiffness, strength and toughness to prevent crushing under physiological loads until full integration and healing are reached. Despite extensive efforts and first encouraging results, current biomaterials for tissue regeneration tend to suffer common limitations: insufficient tissue-material interaction and an inherent lack of strength and toughness associated with porosity. The challenge persists to synthesize materials that mimic both structure and mechanical performance of the natural tissue and permit strong tissue-implant interfaces to be formed. In the case of bone substitute materials, for example, the goal is to engineer high-performance composites with effective properties that, similar to natural mineralized tissue, exceed by orders of magnitude the properties of its constituents. It is still difficult with current technology to emulate in synthetic biomaterials multi-level hierarchical composite structures that are thought to be the origin of the observed mechanical property amplification in biological materials. Freeze casting permits to manufacture such complex, hybrid materials through excellent control of structural and mechanical properties. As a processing technique for the manufacture of biomaterials, freeze casting therefore has great promise.
TL;DR: Electrophoretic mobility measurements made on turbid samples at high concentration using a novel cell with reduced path length are discussed and conclusions and recommendations are made from the zeta potential values obtained at high concentrations.
Abstract: Zeta potential is the key parameter that controls electrostatic interactions in particle dispersions. Laser Doppler electrophoresis is an accepted method for the measurement of particle electrophoretic mobility and hence zeta potential of dispersions of colloidal size materials. Traditionally, samples measured by this technique have to be optically transparent. Therefore, depending upon the size and optical properties of the particles, many samples will be too concentrated and will require dilution. The ability to measure samples at or close to their neat concentration would be desirable as it would minimize any changes in the zeta potential of the sample owing to dilution. However, the ability to measure turbid samples using light-scattering techniques presents a number of challenges. This paper discusses electrophoretic mobility measurements made on turbid samples at high concentration using a novel cell with reduced path length. Results are presented on two different sample types, titanium dioxide and a polyurethane dispersion, as a function of sample concentration. For both of the sample types studied, the electrophoretic mobility results show a gradual decrease as the sample concentration increases and the possible reasons for these observations are discussed. Further, a comparison of the data against theoretical models is presented and discussed. Conclusions and recommendations are made from the zeta potential values obtained at high concentrations.
TL;DR: This work shows that a quantization of the macroscopic turning flows into units of single vehicles is necessary to obtain realistic fluctuations in the traffic variables, and how this can be implemented in a fluid-dynamic model, and proposes a new method to simulate destination flows without the requirement of individual route assignments.
Abstract: Due to the complexity of the traffic flow dynamics in urban road networks, most quantitative descriptions of city traffic so far have been based on computer simulations. This contribution pursues a macroscopic (fluid-dynamic) simulation approach, which facilitates a simple simulation of congestion spreading in cities. First, we show that a quantization of the macroscopic turning flows into units of single vehicles is necessary to obtain realistic fluctuations in the traffic variables, and how this can be implemented in a fluid-dynamic model. Then, we propose a new method to simulate destination flows without the requirement of individual route assignments. Combining both methods allows us to study a variety of different simulation scenarios. These reveal fundamental relationships between the average flow, the average density and the variability of the vehicle densities. Considering the inhomogeneity of traffic as an independent variable can eliminate the scattering of congested flow measurements. The variability also turns out to be a key variable of urban traffic performance. Our results can be explained through the number of full links of the road network, and approximated by a simple analytical formula.
TL;DR: Some recent discoveries regarding ion adsorption in microporous carbon exhibiting pores in the nanometre range can help in designing the next generation of high-energy-density supercapacitors.
Abstract: Electrochemical capacitors, also known as supercapacitors, are energy storage devices that fill the gap between batteries and dielectric capacitors. Thanks to their unique features, they have a key role to play in energy storage and harvesting, acting as a complement to or even a replacement of batteries which has already been achieved in various applications. One of the challenges in the supercapacitor area is to increase their energy density. Some recent discoveries regarding ion adsorption in microporous carbon exhibiting pores in the nanometre range can help in designing the next generation of high-energy-density supercapacitors.
TL;DR: A parsimonious theory for congested freeway traffic that describes the spontaneous appearance of oscillations and their ensuing transformation into stop-and-go waves concludes that timid and aggressive driver behaviours are the cause for this transformation.
Abstract: This paper introduces a parsimonious theory for congested freeway traffic that describes the spontaneous appearance of oscillations and their ensuing transformation into stop-and-go waves. Based upon the analysis of detailed vehicle-trajectory data, we conclude that timid and aggressive driver behaviours are the cause for this transformation. We find that stop-and-go waves arise independently of the details of these behaviours. Analytical and simulation results are presented.
TL;DR: In the Industrial Revolution, energy usage increased massively and output rose accordingly as mentioned in this paper, which poses a problem for the future as fossil fuels are a depleting stock, whereas in pre-industrial time the energy source though limited, was renewed each year.
Abstract: Societies before the Industrial Revolution were dependent on the annual cycle of plant photosynthesis for both heat and mechanical energy. The quantity of energy available each year was therefore limited, and economic growth was necessarily constrained. In the Industrial Revolution, energy usage increased massively and output rose accordingly. The energy source continued to be plant photosynthesis, but accumulated over a geological age in the form of coal. This poses a problem for the future. Fossil fuels are a depleting stock, whereas in pre-industrial time the energy source, though limited, was renewed each year.
TL;DR: It is explained why two distinct momenta are needed to describe light in a medium and why each appears as the natural, and experimentally observed, momentum in appropriate situations.
Abstract: It is 100 years since Minkowski and Abraham first gave rival expressions for the momentum of light in a material medium. At the single-photon level, these correspond, respectively, either to multip...
TL;DR: It is shown here how the unique properties of individual AuNPs and AuNP assemblies can be used to create new functional materials for applications in a technical or biological environment.
Abstract: Ligand-stabilized gold nanoparticles (AuNPs) are of high interest to research dedicated to future technologies such as nanoelectronics or biomedical applications. This research interest arises from the unique size-dependent properties such as surface plasmon resonance or Coulomb charging effects. It is shown here how the unique properties of individual AuNPs and AuNP assemblies can be used to create new functional materials for applications in a technical or biological environment. While the term technical environment focuses on the potential use of AuNPs as subunits in nanoelectronic devices, the term biological environment addresses issues of toxicity and novel concepts of controlling biomolecular reactions on the surface of AuNPs.
TL;DR: The destabilization of gas hydrate reserves in permafrost areas is more certain as climate models predict that high-latitude regions will be disproportionately affected by global warming with temperature increases of over 12°C predicted for much of North America and Northern Asia.
Abstract: Gas hydrates are ice-like deposits containing a mixture of water and gas; the most common gas is methane. Gas hydrates are stable under high pressures and relatively low temperatures and are found ...
TL;DR: In this paper, the authors study weekly search volume data for various search terms from 2004 to 2010 that are offered by the search engine Google for scientific use, providing information about our economic life on an aggregated collective level.
Abstract: Search engine query data deliver insight into the behaviour of individuals who are the smallest possible scale of our economic life. Individuals are submitting several hundred million search engine queries around the world each day. We study weekly search volume data for various search terms from 2004 to 2010 that are offered by the search engine Google for scientific use, providing information about our economic life on an aggregated collective level. We ask the question whether there is a link between search volume data and financial market fluctuations on a weekly time scale. Both collective ‘swarm intelligence’ of Internet users and the group of financial market participants can be regarded as a complex system of many interacting subunits that react quickly to external changes. We find clear evidence that weekly transaction volumes of S&P 500 companies are correlated with weekly search volume of corresponding company names. Furthermore, we apply a recently introduced method for quantifying complex correlations in time series with which we find a clear tendency that search volume time series and transaction volume time series show recurring patterns.
TL;DR: Findings from this study elucidate scientists’ views on ‘sharable’ forms of data—the particular representation that they view as most valued for reuse by others within their own research areas—and the anticipated duration for such reuse.
Abstract: Results are presented from the Data Curation Profiles project research, on who is willing to share what data with whom and when. Emerging from scientists' discussions on sharing are several dimensions suggestive of the variation in both what it means 'to share' and how these processes are carried out. This research indicates that data curation services will need to accommodate a wide range of subdisciplinary data characteristics and sharing practices. As part of a larger set of strategies emerging across academic institutions, institutional repositories (IRs) will contribute to the stewardship and mobilization of scientific research data for e-Research and learning. There will be particular types of data that can be managed well in an IR context when characteristics and practices are well understood. Findings from this study elucidate scientists' views on 'sharable' forms of data-the particular representation that they view as most valued for reuse by others within their own research areas-and the anticipated duration for such reuse. Reported sharing incidents that provide insights into barriers to sharing and related concerns on data misuse are included.
TL;DR: A study of the use of Web 2.0 services by UK researchers and their use in novel forms of scholarly communication documents the contours of adoption, the barriers and enablers, and the dynamics of innovation in Web services and scholarly practices.
Abstract: Sharing research resources of different kinds, in new ways, and on an increasing scale, is a central element of the unfolding e-Research vision. Web 2.0 is seen as providing the technical platform to enable these new forms of scholarly communications. We report findings from a study of the use of Web 2.0 services by UK researchers and their use in novel forms of scholarly communication. We document the contours of adoption, the barriers and enablers, and the dynamics of innovation in Web services and scholarly practices. We conclude by considering the steps that different stakeholders might take to encourage greater experimentation and uptake.
TL;DR: This review will explore the natural and biomimetic AF surface strategies for marine systems, which may well provide new insights into designing and developing alternative, non-toxic, surface-active antifouling technologies.
Abstract: Marine biofouling is the accumulation of biological material on underwater surfaces, which has plagued both commercial and naval fleets. Biomimetic approaches may well provide new insights into designing and developing alternative, non-toxic, surface-active antifouling (AF) technologies. In the marine environment, all submerged surfaces are affected by the attachment of fouling organisms, such as bacteria, diatoms, algae and invertebrates, causing increased hydrodynamic drag, resulting in increased fuel consumption, and decreased speed and operational range. There are also additional expenses of dry-docking, together with increased fuel costs and corrosion, which are all important economic factors that demand the prevention of biofouling. Past solutions to AF have generally used toxic paints or coatings that have had a detrimental effect on marine life worldwide. The prohibited use of these antifoulants has led to the search for biologically inspired AF strategies. This review will explore the natural and biomimetic AF surface strategies for marine systems.
TL;DR: This paper presents two case studies (2003 heatwave, 2005 floods) that demonstrate some of the interlinkages between physical processes and human activity in climatically sensitive alpine regions that are responding to ongoing climate change and outlines future implications of climate change on mountain environments and its impact on hazards and hazard management in paraglacial mountain systems.
Abstract: Climate and environmental changes associated with anthropogenic global warming are being increasingly identified in the European Alps, as seen by changes in long-term high-alpine temperature, precipitation, glacier cover and permafrost. In turn, these changes impact on land-surface stability, and lead to increased frequency and magnitude of natural mountain hazards, including rock falls, debris flows, landslides, avalanches and floods. These hazards also impact on infrastructure, and socio-economic and cultural activities in mountain regions. This paper presents two case studies (2003 heatwave, 2005 floods) that demonstrate some of the interlinkages between physical processes and human activity in climatically sensitive alpine regions that are responding to ongoing climate change. Based on this evidence, we outline future implications of climate change on mountain environments and its impact on hazards and hazard management in paraglacial mountain systems.
University of Oxford1, University of Auckland2, University College London3, European Bioinformatics Institute4, University of Sheffield5, Catalan Institution for Research and Advanced Studies6, Pompeu Fabra University7, University of Melbourne8, Norwegian University of Life Sciences9, Polytechnic University of Milan10, École Polytechnique Fédérale de Lausanne11, Karolinska University Hospital12, University of Évry Val d'Essonne13, Centre national de la recherche scientifique14, University of Crete15, VU University Amsterdam16
TL;DR: The biomedical science, healthcare and information and communications technology challenges facing the project are considered and the VPH Institute is proposed as a means of sustaining the vision of VPH beyond the time frame of the NoE.
Abstract: European funding under framework 7 (FP7) for the virtual physiological human (VPH) project has been in place now for nearly 2 years. The VPH network of excellence (NoE) is helping in the development of common standards, open-source software, freely accessible data and model repositories, and various training and dissemination activities for the project. It is also helping to coordinate the many clinically targeted projects that have been funded under the FP7 calls. An initial vision for the VPH was defined by framework 6 strategy for a European physiome (STEP) project in 2006. It is now time to assess the accomplishments of the last 2 years and update the STEP vision for the VPH. We consider the biomedical science, healthcare and information and communications technology challenges facing the project and we propose the VPH Institute as a means of sustaining the vision of VPH beyond the time frame of the NoE.
TL;DR: This work describes several large slope failures in rock and ice in recent years in Alaska, New Zealand and the European Alps, and analyses weather patterns in the days and weeks before the failures to find one general temperature pattern.
Abstract: The number of large slope failures in some high-mountain regions such as the European Alps has increased during the past two to three decades. There is concern that recent climate change is driving this increase in slope failures, thus possibly further exacerbating the hazard in the future. Although the effects of a gradual temperature rise on glaciers and permafrost have been extensively studied, the impacts of short-term, unusually warm temperature increases on slope stability in high mountains remain largely unexplored. We describe several large slope failures in rock and ice in recent years in Alaska, New Zealand and the European Alps, and analyse weather patterns in the days and weeks before the failures. Although we did not find one general temperature pattern, all the failures were preceded by unusually warm periods; some happened immediately after temperatures suddenly dropped to freezing. We assessed the frequency of warm extremes in the future by analysing eight regional climate models from the recently completed European Union programme ENSEMBLES for the central Swiss Alps. The models show an increase in the higher frequency of high-temperature events for the period 2001-2050 compared with a 1951-2000 reference period. Warm events lasting 5, 10 and 30 days are projected to increase by about 1.5-4 times by 2050 and in some models by up to 10 times. Warm extremes can trigger large landslides in temperature-sensitive high mountains by enhancing the production of water by melt of snow and ice, and by rapid thaw. Although these processes reduce slope strength, they must be considered within the local geological, glaciological and topographic context of a slope.
TL;DR: The present review is intended to direct the reader’s attention to the important subjects of synthetic and natural polymers with HA for bone tissue engineering.
Abstract: The fracture of bones and large bone defects owing to various traumas or natural ageing is a typical type of tissue malfunction. Surgical treatment frequently requires implantation of a temporary or permanent prosthesis, which is still a challenge for orthopaedic surgeons, especially in the case of large bone defects. Mimicking nanotopography of natural extracellular matrix (ECM) is advantageous for the successful regeneration of damaged tissues or organs. Electrospun nanofibre-based synthetic and natural polymer scaffolds are being explored as a scaffold similar to natural ECM for tissue engineering applications. Nanostructured materials are smaller in size falling, in the 1–100 nm range, and have specific properties and functions related to the size of the natural materials (e.g. hydroxyapatite (HA)). The development of nanofibres with nano-HA has enhanced the scope of fabricating scaffolds to mimic the architecture of natural bone tissue. Nanofibrous substrates supporting adhesion, proliferation, differentiation of cells and HA induce the cells to secrete ECM for mineralization to form bone in bone tissue engineering. Our laboratory (NUSNNI, NUS) has been fabricating a variety of synthetic and natural polymer-based nanofibrous substrates and synthesizing HA for blending and spraying on nanofibres for generating artificial ECM for bone tissue regeneration. The present review is intended to direct the reader’s attention to the important subjects of synthetic and natural polymers with HA for bone tissue engineering.
TL;DR: Some new ideas on how to grasp the essentials of the mixing process are put forward and the influence of momentum transport on the invariants and on scaling and statistical properties of the unsteady turbulent mixing is considered.
Abstract: We review the theoretical developments in the field of Rayleigh-Taylor instabilities and turbulent mixing, discuss what is known and what is not known about the phenomenon, and outline the features of similarity of the turbulent mixing process. Based on the physical intuition and on the results of rigorous theoretical studies, we put forward some new ideas on how to grasp the essentials of the mixing process and consider the influence of momentum transport on the invariants and on scaling and statistical properties of the unsteady turbulent mixing.