期外収縮後一過性収縮性増強の減衰過程を指数関数でカーブフィッティングすると心筋細胞内のカルシウム再循環率を過小評価する可能性がある：理論的・数学的解析

Marine cloud brightening (MCB) is one of several proposed solar radiation management (SRM) geoengineering schemes designed to ameliorate some of the undesirable effects of climate change, for example polar ice loss and associated increased sea levels. Satellite measurements over the last 40 years show a general reduction in polar sea ice area and thickness which is attributed to climate change. In our studies, HadGEM1, a fully coupled climate model, is used to predict changes in surface temperatures and ice cover as a result of implementing MCB in a double carbon dioxide concentration atmosphere. The meridional heat flux (MHF) is the mechanism within the earth system for the transport of energy from tropical to polar regions. This poleward transport of heat in a double carbon dioxide atmosphere amplifies the effects in polar regions, where it has a significant impact on both temperatures and ice cover. The results from this work show that MCB is capable of roughly restoring control temperatures and ice cover (where control is defined as 440 ppm carbon dioxide, a predicted 2020 level) in a double carbon dioxide atmosphere scenario. This work presents the first results on the impact of MCB on the MHF and the ability of the MCB scheme to restore the MHF to a control level

The impact of future climate change and potential adaptation methods on Maize yields in West Africa

International audienceMaize (Zea mays) is one of the staple crops of West Africa and is therefore of high importance with regard to future food security. The ability of West Africa to produce enough food is critical as the population is expected to increase well into the twenty-first century. In this study, a process-based crop model is used to project maize yields in Africa for global temperatures 2 K and 4 K above the preindustrial control. This study investigates how yields and crop failure rates are influenced by climate change and the efficacy of adaptation methods to mitigate the effects of climate change. To account for the uncertainties in future climate projections, multiple model runs have been performed at specific warming levels of + 2 K and + 4 K to give a better estimate of future crop yields. Under a warming of + 2 K, the maize yield is projected to reduce by 5.9% with an increase in both mild and severe crop failure rates. Mild and severe crop failures are yields 1 and 1.5 standard deviations below the observed yield. At a warming of + 4 K, the results show a yield reduction of 37% and severe crop failures which previously only occurred once in 19.7 years are expected to happen every 2.5 years. Crops simulated with a resistance to high temperature stress show an increase in yields in all climate conditions compared to unadapted crops; however, they still experience more crop failures than the unadapted crop in the control climate

Crop failure rates in a geoengineered climate: impact of climate change and marine cloud brightening

International audienceThe impact of geoengineering on crops has to date been studied by examining mean yields. We present the first work focusing on the rate of crop failures under a geoengineered climate. We investigate the impact of a future climate and a potential geoengineering scheme on the number of crop failures in two regions, Northeastern China and West Africa. Climate change associated with a doubling of atmospheric carbon dioxide increases the number of crop failures in Northeastern China while reducing the number of crop failures in West Africa. In both regions marine cloud brightening is likely to reduce the number crop failures, although it is more effective at reducing mild crop failure than severe crop failure. We find that water stress, rather than heat stress, is the main cause of crop failure in current, future and geoengineered climates. This demonstrates the importance of irrigation and breeding for tolerance to water stress as adaptation methods in all futures. Analysis of global rainfall under marine cloud brightening has the potential to significantly reduce the impact of climate change on global wheat and groundnut production

Consistency and differences between centrality measures across distinct classes of networks

The roles of different nodes within a network are often understood through centrality analysis, which aims to quantify the capacity of a node to influence, or be influenced by, other nodes via its connection topology. Many different centrality measures have been proposed, but the degree to which they offer unique information, and such whether it is advantageous to use multiple centrality measures to define node roles, is unclear. Here we calculate correlations between 17 different centrality measures across 212 diverse real-world networks, examine how these correlations relate to variations in network density and global topology, and investigate whether nodes can be clustered into distinct classes according to their centrality profiles. We find that centrality measures are generally positively correlated to each other, the strength of these correlations varies across networks, and network modularity plays a key role in driving these cross-network variations. Data-driven clustering of nodes based on centrality profiles can distinguish different roles, including topological cores of highly central nodes and peripheries of less central nodes. Our findings illustrate how network topology shapes the pattern of correlations between centrality measures and demonstrate how a comparative approach to network centrality can inform the interpretation of nodal roles in complex networks.Comment: Main text (25 pages, 8 figures, 1 table), supplementary information (16 pages, 2 tables) and supplementary figures (17 figures

Differential Liquidity Provision in Uniswap v3 and Implications for Contract Design

Decentralized exchanges (DEXs) provide a means for users to trade pairs of assets on-chain without the need of a trusted third party to effectuate a trade. Amongst these, constant function market maker (CFMM) DEXs such as Uniswap handle the most volume of trades between ERC-20 tokens. With the introduction of Uniswap v3, liquidity providers are given the option to differentially allocate liquidity to be used for trades that occur within specific price intervals. In this paper, we formalize the profit and loss that liquidity providers can earn when providing specific liquidity positions to a contract. With this in hand, we are able to compute optimal liquidity allocations for liquidity providers who hold beliefs over how prices evolve over time. Ultimately, we use this tool to shed light on the design question regarding how v3 contracts should partition price space for permissible liquidity allocations. Our results show that a richer space of potential partitions can simultaneously benefit both liquidity providers and traders.Comment: 48 pages, 13 figure

Watersheds in planetary health research and action

Watersheds (also known as water catchments and river basins) are recognised in contemporary science as important natural systems in which to investigate the complex socioecological foundations of health. A watershed is the spatially bound geophysical unit within which surface and shallow groundwater drain to a single collecting stream or river (see appendix). Watersheds are physical and abstract systems: they are open and hydrologically permeable, yet can be represented as functionally distinct. Collectively, watersheds comprise a complex hierarchical network, and thus exemplify the upstream and downstream nature of ecosystems. Watersheds include the social actors, relationships, and institutions located within their boundaries. This means that distant individuals residing within the same watershed might share a more common history of social and environmental exposure than nearer individuals located closer to each other, but in separate watersheds

Water-exchange MRI detects subtle blood-brain barrier breakdown in Alzheimer's disease rats

Blood-brain barrier (BBB) breakdown has been hypothesized to play a key role in the onset and progression of Alzheimer's disease (AD). However, the question of whether AD itself contributes to loss of BBB integrity is still uncertain, as many in-vivo studies have failed to detect signs of AD-related BBB breakdown. We hypothesize AD-related BBB damage is subtle, and that these negative results arise from a lack of measurement sensitivity. With the aim of developing a more sensitive measure of BBB breakdown, we have designed a novel MRI scanning protocol to quantify the trans-BBB exchange of endogenous water. Using this method, we detect increased BBB water permeability in a rat model of AD that is associated with reduced expression of the tight junction protein occludin. BBB permeability to MRI contrast agent, assessed using dynamic contrast-enhanced (DCE)-MRI, did not differ between transgenic and wild-type animals and was uncorrelated with occludin expression. Our data supports the occurrence of AD-related BBB breakdown, and indicates that such BBB pathology is subtle and may be undetectable using existing ‘tracer leakage’ methods. Our validated water-exchange MRI method provides a new powerful tool with which to study BBB damage in-vivo

Blood-brain barrier water exchange measurements using FEXI: Impact of modeling paradigm and relaxation time effects

PURPOSE: To evaluate potential modeling paradigms and the impact of relaxation time effects on human blood-brain barrier (BBB) water exchange measurements using FEXI (BBB-FEXI), and to quantify the accuracy, precision, and repeatability of BBB-FEXI exchange rate estimates at 3 T. METHODS: Three modeling paradigms were evaluated: (i) the apparent exchange rate (AXR) model; (ii) a two-compartment model (2CM) explicitly representing intra- and extravascular signal components, and (iii) a two-compartment model additionally accounting for finite compartmental T1 and T2 relaxation times (2CMr). Each model had three free parameters. Simulations quantified biases introduced by the assumption of infinite relaxation times in the AXR and 2CM models, as well as the accuracy and precision of all three models. The scan–rescan repeatability of all paradigms was quantified for the first time in vivo in 10 healthy volunteers (age range 23–52 years; five female) RESULTS: The assumption of infinite relaxation times yielded exchange rate errors in simulations up to 42%/14% in the AXR/2CM models, respectively. Accuracy was highest in the compartmental models; precision was best in the AXR model. Scan–rescan repeatability in vivo was good for all models, with negligible bias and repeatability coefficients in grey matter of RCAXR = 0.43 s −1, RC2CM = 0.51 s −1, and RC2CMr = 0.61 s −1. CONCLUSION: Compartmental modelling of BBB-FEXI signals can provide accurate and repeatable measurements of BBB water exchange; however, relaxation time and partial volume effects may cause model-dependent biases

Zero carbon transitions: a systematic review of the research landscape and climate mitigation potential

Academia has a crucial role to play in informing urgently needed actions on climate mitigation. It is vital to understand what is known about the potential contribution of climate mitigation options, the barriers that exist to achieving that contribution, and to quantify the research balance and geographic focus of these various approaches across the literature. This PRISMA-based systematic literature review aims to provide the reader with the following: Firstly, an overview of the post-Paris climate mitigation research landscape and secondly, an assessment of the climate mitigation potential of those options per the literature reviewed. Analysis of the research landscape demonstrated that supply-side research greatly outnumbers that on the demand-side, which totalled just half of that which focused on the supply-side. In terms of the geographic scale, the reviewed literature was dominated by national-level studies, with sub-national studies the least common, particularly those at a local government level. Given this, it can be concluded that two key areas would benefit from further research–that focusing on demand-side mitigation, and that carrying research out at more local levels. On climate mitigation potential, wind and solar energy were found to be the biggest contributors to a decarbonised energy supply, across a range of study areas. Discrepancies were identified between findings in the academic and grey literature for several options, chiefly bioenergy and nuclear power: bioenergy made significantly higher contributions in the academic literature versus grey literature, with the opposite true for nuclear. Demand-side options all demonstrated significant mitigation potential in the literature reviewed but received very limited coverage in comparison to many of their supply-side counterparts. Future research should pursue this knowledge gap to reach a better understanding of the contributions they can make and ensure that policymakers have the data necessary to chart a course to a zero-carbon future

The deployment of intercropping and agroforestry as adaptation to climate change

Food security is threatened by the combined pressures of increasing populations and climate change. Agricultural land is vulnerable to overexploitation and environmental change. Within this review, we identify the role of multiple cropping systems as an adaptation method towards climate change. Intercropping, the relay or simultaneous cultivation of two or more crops, and agroforestry, the incorporation of trees on at least 10% of agricultural land, provides an alternative cropping practice which can provide many advantages over industrial sole cropping. Examples from these systems are given to indicate how multiple cropping can provide increased yield, stability, ecosystem services and societal benefits when adopted. We also discuss instances where multiple cropping systems may be maladaptive or instances where desired benefits may not be achieved. Finally, we highlight the important considerations or constraints limiting the adoption of alternate systems and indicate how modelling approaches can be used to reduce the uncertainty of altering agricultural systems. This review challenges the traditional concept of how to increase industrial crop yields whilst maintaining sustainability. Future research should be aimed at overcoming the constraints limiting adoption of alternative cropping systems to revolutionise global crop production