Water availability in +2°C and +4°C worlds

While the parties to the UNFCCC agreed in the December 2009 Copenhagen Accord that a 2°C global warming over pre-industrial levels should be avoided, current commitments on greenhouse gas emissions reductions from these same parties will lead to a 50?:?50 chance of warming greater than 3.5°C. Here, we evaluate the differences in impacts and adaptation issues for water resources in worlds corresponding to the policy objective (+2°C) and possible reality (+4°C). We simulate the differences in impacts on surface run-off and water resource availability using a global hydrological model driven by ensembles of climate models with global temperature increases of 2°C and 4°C. We combine these with UN-based population growth scenarios to explore the relative importance of population change and climate change for water availability. We find that the projected changes in global surface run-off from the ensemble show an increase in spatial coherence and magnitude for a +4°C world compared with a +2°C one. In a +2°C world, population growth in most large river basins tends to override climate change as a driver of water stress, while in a +4°C world, climate change becomes more dominant, even compensating for population effects where climate change increases run-off. However, in some basins where climate change has positive effects, the seasonality of surface run-off becomes increasingly amplified in a +4°C climate.     

Agriculture and food systems in sub-Saharan Africa in a 4°C+ world

Agricultural development in sub-Saharan Africa faces daunting challenges, which climate change and increasing climate variability will compound in vulnerable areas. The impacts of a changing climate on agricultural production in a world that warms by 4°C or more are likely to be severe in places. The livelihoods of many croppers and livestock keepers in Africa are associated with diversity of options. The changes in crop and livestock production that are likely to result in a 4°C+ world will diminish the options available to most smallholders. In such a world, current crop and livestock varieties and agricultural practices will often be inadequate, and food security will be more difficult to achieve because of commodity price increases and local production shortfalls. While adaptation strategies exist, considerable institutional and policy support will be needed to implement them successfully on the scale required. Even in the 2°C+ world that appears inevitable, planning for and implementing successful adaptation strategies are critical if agricultural growth in the region is to occur, food security be achieved and household livelihoods be enhanced. As part of this effort, better understanding of the critical thresholds in global and African food systems requires urgent research.     

Climate-induced population displacements in a 4°C+ world

Massive population displacements are now regularly presented as one of the most dramatic possible consequences of climate change. Current forecasts and projections show that regions that would be affected by such population movements are low-lying islands, coastal and deltaic regions, as well as sub-Saharan Africa. Such estimates, however, are usually based on a 2°C temperature rise. In the event of a 4°C+ warming, not only is it likely that climate-induced population movements will be more considerable, but also their patterns could be significantly different, as people might react differently to temperature changes that would represent a threat to their very survival. This paper puts forward the hypothesis that a greater temperature change would affect not only the magnitude of the associated population movements, but also--and above all--the characteristics of these movements, and therefore the policy responses that can address them. The paper outlines the policy evolutions that climate-induced displacements in a 4°C+ world would require.     

Bone repair in the twenty-first century: biology, chemistry or engineering?

Increases in reconstructive orthopaedic surgery, such as total hip replacement and spinal fusion, resulting from advances in surgical practice and the ageing population, have lead to a demand for bone graft that far exceeds supply. Consequently, a number of synthetic bone-graft substitutes (BGSs) have been developed with mixed success and surgical acceptance. Skeletal tissue regeneration requires the interaction of three basic elements: cells, growth factors (GFs) and a permissive scaffold. This can be achieved by pre-loading a synthetic scaffold with GFs or pre-expanded cells; however, a 'simpler' approach is to design intrinsic 'osteoinductivity' into your BGS, i.e. the capability to recruit and stimulate the patient's own GFs and stem cells. Through investigation of the mechanisms controlling bone repair in BGSs, linking interactions between the local chemical and physical environment, scientists are currently developing osteoinductive materials that can stimulate bone regeneration through control of the scaffold chemistry and structure. Moreover, this body of research is providing the foundations for future generations of BGSs and bone-repair therapies and may ultimately contribute towards improving the quality of life through maintenance of the skeleton and reversal of disease states, as opposed to the mending of broken bones that we currently practice. Will we be able to grow our own bones in a bioreactor for use as autologous graft materials in the future? Could surgery be limited to accidental trauma cases, with greater restoration of function through biochemical or gene therapies? The technology and research probes necessary to this task are currently being developed with the advent of nanotechnology, genomics and proteomics: are we about to embark on a chemical revolution in medicine? This paper aims to discuss some of the current thinking on the mechanisms behind bioactivity and biocompatibility in bone and how a fuller understanding of the interactions between cells and the materials used today could bring about completely new approaches for the treatment of bone fracture and disease tomorrow.     

Rethinking adaptation for a 4°C world

With weakening prospects of prompt mitigation, it is increasingly likely that the world will experience 4°C and more of global warming. In such a world, adaptation decisions that have long lead times or that have implications playing out over many decades become more uncertain and complex. Adapting to global warming of 4°C cannot be seen as a mere extrapolation of adaptation to 2°C; it will be a more substantial, continuous and transformative process. However, a variety of psychological, social and institutional barriers to adaptation are exacerbated by uncertainty and long timeframes, with the danger of immobilizing decision-makers. In this paper, we show how complexity and uncertainty can be reduced by a systematic approach to categorizing the interactions between decision lifetime, the type of uncertainty in the relevant drivers of change and the nature of adaptation response options. We synthesize a number of issues previously raised in the literature to link the categories of interactions to a variety of risk-management strategies and tactics. Such application could help to break down some barriers to adaptation and both simplify and better target adaptation decision-making. The approach needs to be tested and adopted rapidly.     

The past is a guide to the future? Comparing Middle Pliocene vegetation with predicted biome distributions for the twenty-first century

During the Middle Pliocene, the Earth experienced greater global warmth compared with today, coupled with higher atmospheric CO2 concentrations. To determine the extent to which the Middle Pliocene can be used as a 'test bed' for future warming, we compare data and model-based Middle Pliocene vegetation with simulated global biome distributions for the mid- and late twenty-first century. The best agreement is found when a Middle Pliocene biome reconstruction is compared with a future scenario using 560 ppmv atmospheric CO2. In accordance with palaeobotanical data, all model simulations indicate a generally warmer and wetter climate, resulting in a northward shift of the taiga-tundra boundary and a spread of tropical savannah and woodland in Africa and Australia at the expense of deserts. Our data-model comparison reveals differences in the distribution of polar vegetation, which indicate that the high latitudes during the Middle Pliocene were still warmer than its predicted modern analogue by several degrees. However, our future scenarios do not consider multipliers associated with 'long-term' climate sensitivity. Changes in global temperature, and thus biome distributions, at higher atmospheric CO2 levels will not have reached an equilibrium state (as is the case for the Middle Pliocene) by the end of this century.     

The isothermal section of the Al-Si-B ternary system at 700 °C and its applications

The isothermal section of the Al−Si−B ternary system at 700 °C has been calculated using FactSage software and experimentally determined using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and x-ray powder diffraction(XRD). The calculated results show that there are six three-phase regions in the isothermal section: Liquid-Al+AlB₂+(Si), AlB₂+AlB₁₂+(Si), (Si)+AlB₁₂+SiB₃, AlB₁₂+SiB₃+SiB₆, AlB₁₂+SiB₆+SiB₁₄, AlB₁₂+SiB₁₄+(B). Four three-phase regions of Liquid-Al+AlB₂+(Si), AlB₂+AlB₁₂+(Si), (Si)+AlB₁₂+SiB₃ and AlB₁₂+SiB_n+(B) were confirmed experimentally, which are consistent with calculated results. The small AlB₂ particles in the Al-3B alloy have good refining effect on the primary α-Al phase in the Al-10Si alloy, which greatly refines the microstructure and improves the mechanical properties of the Al-10Si alloy.     

Automated 360° profilometry of a three-dimensional diffuse object and its reconstruction by use of the shading model

The 360° profilometry of a three-dimensional (3-D) diffuse object by use of the light intersection and its image reconstruction by surface shading are presented. The lack of data in one direction, which was due to occlusion, was compensated by the projection of two lines of light from different directions. Some experiments to profile objects and their reconstruction by computer are shown. The entire surface model was constructed, and a real shading image was obtained by means of computer graphics.     

Rapid oxidation of liquid tin and its alloys at 600 to 800°C

The behavior of liquid tin and its alloys in oxygen at temperature range 600 to 800°C were investigated. Rapid and nearly linear reaction kinetics were observed for pure tin at temperature higher than 700°C. Marker experiments, which determine the mode of mass transport through the scale, and wetting phenomena between the oxide and melts were studied to delineate the reaction mechanism of oxide growth. Moreover, the rates of oxidation of tin were markedly changed by alloying it with small amount of foreign elements. Significantly increased oxidation rates for binary tin alloys containing Mg, Ba, La or Ca were observed. TEM studies indicated that additional growth stresses were introduced into the SnO₂ scales by these additions.     

Pendent drop measurements of the polypropylene/polystyrene interfacial tension between 220°C and 270°C

The interfacial tensions of molten polypropylene/polystyrene have been measured using the pendent drop method between 220°C and 270°C. The obtained tension values are comparable with those of most of the molten polymer pairs, though their linear decrease as a function of temperature is steeper. The interaction parameter of Good and Girifalco lies within the range of values for all other polymer pairs.     

Compositional changes in minor phases present in 12CrMoVNb steels during thermal exposure at 550°C and 600°C

Abstract

One of the techniques considered promising in the assessment of the time–temperature history of creep resistant power plant steels is based on studies of compositional changes occurring in the minor phases during service exposure. Chemical compositions of alloy carbides and/or nitrides precipitated during quality heat treatment of high alloy steels are expected to be very close to equilibrium. However, since in practice the operating temperatures for these steels are usually much lower than the tempering temperatures used in their original heat treatments, changes in the compositions of their minor phases are likely to occur during service exposure. These changes depend on the differences between the respective equilibrium compositions of the minor phases at the tempering and service temperatures. The greater the difference between these temperatures, the greater will be the expected changes in the compositions of the minor phases during exposure at the service temperature. Since these changes are dependent on the time and temperature of exposure, any minor phase, which is present in the microstructure in the as received condition, as well as after prolonged service exposure, represents a potential indicator of time–temperature history of the material. In this paper the results of quantitative microstructural studies are reported on a series of martensitic 12CrMoVNb steels in their as received heat treated condition and following long term exposure at 550 and 600°C. The results of minor phase composition changes are discussed in terms of the equilibrium minor phase compositions calculated using the MTDATA computer program and the SGTE database, and their potentials as in service time–temperature history indicators for the materials are evaluated.     

Organic-inorganic interaction and the growth mechanism of hydroxyapatite crystals in gelatin matrices between 37 and 80 °C

The crystal development of hydroxyapatite[HAp] phase in gelatin[GEL] matrices was investigated in the temperature range 37 to 80 °C by using X-ray diffraction, scanning electron microscopy(SEM), thermoanalytical measurement(DT/TGA), Fourier-Transformed Infra-Red(FT-IR) spectroscopy, and transmission electron microscopy(TEM) with electron diffraction(ED). It was found that during the coprecipitation of apatite phase in GEL matrices and the next aging process the crystallites were formed and developed through the two reaction mechanisms of organic-inorganic interaction between apatite phase and GEL molecules, and thermodynamic reaction for the crystal growing. The analytical evidences showed that there was a definite competition between these two mechanisms with the reaction temperature. Below 50 °C the crystal development of HAp was greatly suppressed by the existence of the GEL molecules, indicating the heterogeneous nucleation by the supposed number of carboxyl groups in GEL. Above 50 °C the effective organic components as a template for the heterogeneous nucleation of apatite crystallites were greatly degraded and so more amount of inorganic ions could be favorably accredited on the preexisting crystallites in virtue of the limited nucleation chance, finally resulting in the crystal growth. At higher temperature pretty big HAp crystals were developed with the depletion of the organics to be bound with crystallites in the slurry solution. Presumably it is believed that the poisoning of the functional groups in GEL molecules was vigorously occurred in the phosphoric acid environment above ∼ 50 °C.     

Phase equilibria and crystal structures of solid solutions in the Sr-Fe-Ni-O system at 1100°C in air

The phase equilibria in the Sr-Fe-Ni-O system at 1100°C in air have been studied by x-ray diffraction, and the corresponding phase diagram at constant temperature and pressure has been constructed. The system has been shown to contain two solid-solution series at 1100°C in air: SrFe_{1 ? x} Ni _x O_{3 ? δ} (0 < x ≤ 0.075, sp. gr. Cmmm) and Sr₃(Fe_{1 ? y} Ni _y )₂O_{7 ? δ} (0 < y ≤ 0.15, sp. gr. I4/mmm). Neither Sr₄(Fe_{1 ? z} Ni _z )₆O₁₃ nor Sr(Fe_{1 ? z} Ni _z )₁₂O₁₉ solid solutions have been identified. The lattice constants and structural parameters of single-phase samples have been refined by the full profile Rietveld analysis method.