Exploiting Geographical and Temporal Locality to Boost Search Efficiency in Peer-to-Peer Systems

As a hot research topic, many search algorithms have been presented and studied for unstructured peer-to-peer (P2P) systems during the past few years. Unfortunately, current approaches either cannot yield good lookup performance, or incur high search cost and system maintenance overhead. The poor search efficiency of these approaches may seriously limit the scalability of current unstructured P2P systems. In this paper, we propose to exploit two-dimensional locality to improve P2P system search efficiency. We present a locality-aware P2P system architecture called Foreseer, which explicitly exploits geographical locality and temporal locality by constructing a neighbor overlay and a friend overlay, respectively. Each peer in Foreseer maintains a small number of neighbors and friends along with their content filters used as distributed indices. By combining the advantages of distributed indices and the utilization of two-dimensional locality, our scheme significantly boosts P2P search efficiency while introducing only modest overhead. In addition, several alternative forwarding policies of Foreseer search algorithm are studied in depth on how to fully exploit the two-dimensional locality

Superconvergent postprocessing of C0C^0 interior penalty method

This paper focuses on the superconvergence analysis of the Hessian recovery technique for the $C^0$ Interior Penalty Method (C0IP) in solving the biharmonic equation. We establish interior error estimates for C0IP method that serve as the superconvergent analysis tool. Using the argument of superconvergence by difference quotient, we prove superconvergent results of the recovered Hessian matrix on translation-invariant meshes. The Hessian recovery technique enables us to construct an asymptotically exact ${\it a\, posteriori}$ error estimator for the C0IP method. Numerical experiments are provided to support our theoretical results

China actively promotes CO2 capture, utilization and storage research to achieve carbon peak and carbon neutrality

Global climate change is a common challenge facing mankind, which has evolved from a scientifific issue into a global economic and political issue of universal concern to the international community. Temperature increase, sea level rise, extreme weather and climate events caused by the climate change are becoming more and more prominent. The scientifific understanding of climate change in the international community has been deepening. The Intergovernmental Panel on Climate Change (IPCC, 2014) further strengthened the scientific conclusion that human-induced climate change is more than 95% likely to be attributed to emissions of greenhouse gases from human activities.The United Nations Climate Change Summit (held in September 2014) pointed out that climate change threatens the hard-won peace, prosperity and opportunities of all mankind, and that no one and no country is immune to its impact. Controlling global warming within 2℃ is an urgent and severe challenge faced by mankind in dealing with climate change. The awareness of all countries on the issue of climate change is gradually increasing. The 26th Conference of the Parties (held in November 2021 in Glasgow, UK) urged all countries to achieve the net zero carbon emissions by around 2050, and step up efforts to reduce carbon emission before 2030. Therefore, taking active measures to cope with climate change becomes the common aspiration and urgent need of all countries.Mitigating greenhouse gas emissions (represented by CO2) has become the consensus of the world. In September 2020, Chinese President Xi Jinping pledged at the General Debate of the 75th Session of The United Nations General Assembly that China aims to peak its CO2 emissions before 2030 and achieve carbon neutrality before 2060 (i.e., dual carbon goals), which demonstrates the responsibility of a major country.CO2 Capture, Utilization, and Storage (CCUS) is considered as an effective technology directly achieving carbon emissions mitigation, and has attracted widespread attention of the international community (Metz et al., 2005). The implementation of CCUS projects began in the 1970s, and was mainly carried out in the United States, Canada and some European countries. Those projects mainly focused on CO2 enhanced oil recovery, whereas projects with the pure purpose of CO2 sequestration are relatively rare due to their poor economy.CCUS projects in China started relatively late, and most of them were gradually implemented after 2000 (Guo et al., 2014). The initial technical routes of these projects were similar to those of projects carried out in European and American countries, which began with the geological sequestration of CO2 and enhanced oil recovery. In the past decade, CCUS projects in China began to develop in a diversified way, and there emerged a variety of carbon dioxide capture, storage and utilization technologies, including pre-combustion capture of power plants, CO2 chemical and biological utilization, etc.The realization of the dual carbon goals not only requires revolutionary changes in industrial technology, but also largely depends on the formulation of relevant policies and capital investment. The National Natural Science Foundation of China launched a special research program “Major Basic Science Issues and Countermeasures for National Carbon neutrality” in 2021 to meet the needs of basic science research for the national carbon neutrality strategy. Focusing on the two core issues of “carbon emission mitigation” and “carbon sink increase”, the special program includes a total of 28 research projects, with an average funding of about 3 million RMB per project.This special research program aims to reveal the oceans and terrestrial carbon sinks, the process mechanism, evolution trend and its mutual feedback mechanism with the climate system, delineate the geological process of carbon sequestration and the effectivity of fixing carbon. The program also has goals to increase the potential of CO2 storage, to assess the technology risk and management mode, to analyze the economic transformation, the optimal pathway, climate control, international cooperation management and policy issues. Interdisciplinary integration research is needed to condense key basic science issues and solutions for serving the national carbon-neutral strategy.It is foreseeable that China will further increase investment in realizing a carbon emission peak and its carbon-neutral strategy in the future. This is also a great opportunity for the development of CCUS-related technologies. The contribution of CCUS technology in carbon emission mitigation is generally low today. For instance, even in Norway, which has the highest proportion of carbon emissions treated by CCUS, the value is less than 5% (Cai et al., 2020). However, as the guaranteed technology of carbon peak strategy, the contribution ratio of CCUS in carbon emission mitigation is expected to significantly increase in the future.Although the CCUS technology has been implemented for many years and many projects have been carried out, there are still many challenges to be solved, such as:(i) CCUS related technology development and cost control The CCUS technology includes capture, transportation, utilization and storage, all of which need to consume a lot of energy. At present, the cost of the CCUS projects is still high. It is estimated that the cost of the whole CCUS process will be 150-540 RMB per ton of CO2 by 2025, of which CO2 capture cost accounts for more than two thirds of the total cost, about 100-480 RMB/ton. In comparison, the cost of CO2 sequestration is 50-60 RMB/ton, while the cost of CO2 transportation is very low, less than 1 RMB/ton (Cai et al., 2021). Obviously, the wider promotion of CCUS projects in the future largely depends on the further development of CO2 capture technology and the rapid reduction of cost.(ii) Effect of long-term CO2-water-rock interaction on rock structure and mechanical properties In the process of CO2 geological storage and utilization, the injected CO2 will inevitably change the pH of formation water, breaking the original water-rock balance and inducing a new water-rock reaction. Thus, the rock structure and mechanical properties of the caprock are likely to be changed over time, which affects the safety of the storage reservoirs. The current studies mostly focus on the effect of CO2-water-rock interaction on the leakage channels (porosity and permeability) of the caprock (Credoz et al., 2009; Liu et al., 2020). However, the study on the change of rock mechanical properties caused by chemical reactions requires further research attention. A few previous studies only simply correlated the evolution of rock mechanical properties with porosity, but without considering the influence of changes in mineral composition induced by CO2-water-rock interaction on the rock mechanical properties (Agarwal, 2019). Therefore, it is necessary to further deepen the relevant investigation and build a comprehensive rock mechanical parameter evolution model considering the changes of porosity, mineral composition and content, and other factors (Tian et al., 2019).(iii) CO2 leakage monitoring and risk assessment methods The leakage risk of CO2 after injection has been one of the main concerns, which directly affects the safety and feasibility of CCUS technology (Bachu, 2008). At this point, the construction of a CO2 leakage monitoring system is particularly important. However, the CO2 leakage process is usually characterized by sudden occurrence and weak surface response. Therefore, a single monitoring method is difficult to ensure the reliability of monitoring. In the future, it is necessary to combine various monitoring methods with their respective advantages.For a long-term (more than 100 years) CO2 leakage risk assessment, the most commonly used method at present is to employ the reactive transport modelling. However, due to the large time scale, parameter uncertainty and the difficulty of validation, the predicted results have high uncertainty. Some natural CO2 gas reservoirs have existed for more than thousands of years (Jonathan et al., 2018). Taking natural CO2 gas reservoirs as a natural analogue of CO2 geological sequestration can solve the problem that long-term simulated results are difficult to verify, thereby improving the reliability of long-term risk assessment (Xu et al., 2019). AcknowledgementThis work was performed in support of the National Natural Science Foundation of China (Grant Nos. 42141013 and 41772247). Conflict of interest The authors declare no competing interest.Open Access This article is distributed under the terms and conditions of the Creative Commons Attribution (CC BY-NC-ND) license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Cited as: Xu, T., Tian, H., Zhu, H., Cai, J. China actively promotes CO2 capture, utilization and storage research to achieve carbon peak and carbon neutrality. Advances in Geo-Energy Research, 2022, 6(1): 1-3. https://doi.org/10.46690/ager.2022.01.0

Recombinant human thioredoxin-1 promotes neurogenesis and facilitates cognitive recovery following cerebral ischemia in mice

AbstractCerebral ischemia (CI) can induce loss of hippocampal neurons, causing cognitive dysfunction such as learning and memory deficits. In adult mammals, the hippocampal dentate gyrus contains neural stem cells (NSCs) that continuously generate newborn neurons and integrate into the pre-existing networks throughout life, which may ameliorate cognitive dysfunction following CI. Recent studies have demonstrated that recombinant human thioredoxin-1 (rhTrx-1) could promote proliferation of human adipose tissue-derived mesenchymal stem cells and angiogenesis. To investigate whether rhTrx-1 also regulates hippocampal neurogenesis following CI and its underlying mechanisms, adult mice were subjected to bilateral common carotid arteries occlusion (BCCAO) to induce CI and treated with rhTrx-1 before reperfusion. Mice treated with rhTrx-1 showed shortened escape latencies in Morris water maze by 30 days and improvements in spatial memory demonstrated by probe trial test. Enhanced NSCs proliferation was observed at day 14, indicated by BrdU and Ki67 immunostaining. Doublecortin (DCX)+ cells were also significantly increased following rhTrx-1 treatment. Despite increases in BrdU+/NeuN+ cells by day 30, the double-labeling to total BrdU+ ratio was not affected by rhTrx-1 treatment. The promotive effects of rhTrx-1 on NSCs proliferation and differentiation were further confirmed in in vitro assays. Western blot revealed increased ERK1/2 phosphorylation after rhTrx-1 treatment, and the ERK inhibitor U0126 abrogated the effects of rhTrx-1 on NSCs proliferation. These results provide initial evidence that rhTrx-1 effects neurogenesis through the ERK signaling pathway and are beneficial for improving spatial learning and memory in adult mice following global CI

Activation of BNIP3-mediated mitophagy protects against renal ischemia-reperfusion injury

Acute kidney injury (AKI) is a syndrome of abrupt loss of renal functions. The underlying pathological mechanisms of AKI remain largely unknown. BCL2-interacting protein 3 (BNIP3) has dual functions of regulating cell death and mitophagy, but its pathophysiological role in AKI remains unclear. Here, we demonstrated an increase of BNIP3 expression in cultured renal proximal tubular epithelial cells following oxygen-glucose deprivation-reperfusion (OGD-R) and in renal tubules after renal ischemia-reperfusion (IR)-induced injury in mice. Functionally, silencing Bnip3 by specific short hairpin RNAs in cultured renal tubular cells reduced OGD-R-induced mitophagy, and potentiated OGD-R-induced cell death. In vivo, Bnip3 knockout worsened renal IR injury, as manifested by more severe renal dysfunction and tissue injury. We further showed that Bnip3 knockout reduced mitophagy, which resulted in the accumulation of damaged mitochondria, increased production of reactive oxygen species, and enhanced cell death and inflammatory response in kidneys following renal IR. Taken together, these findings suggest that BNIP3-mediated mitophagy has a critical role in mitochondrial quality control and tubular cell survival during AKI

Reflective plasmonic color filters based on lithographically patterned silver nanorod arrays

10.1039/c3nr01419cNanoscale5146243-624