A numerical investigation on the effectiveness of the actuator disc method in producing the interactions of multiple tidal stream devices via the 3D-RANS finite element model Telemac3D is explored. The methodology for...A numerical investigation on the effectiveness of the actuator disc method in producing the interactions of multiple tidal stream devices via the 3D-RANS finite element model Telemac3D is explored. The methodology for the implementation of the source term to represent an array of 20 m rotor diameter turbines deployed in an idealized channel is reviewed and discussed in detail. Flow interactions between multiple turbines are investigated for a single row arrangement with only two turbines and a two row arrangement containing three turbines. The results demonstrate that the non-hydrostatic solver shows better agreement when validated against published experimental data. Notably,the mesh density at the device location can strongly influence the simulated thrust from the disc. Although the actuator disc model can generally replicate the wake interactions well, the results indicate that it cannot accurately characterize the flow for regions with high turbulences. While a model setup with the largest lateral spacing(1.5D) demonstrates excellent agreement with the experimental data, the 0.5D model(smallest gap) deviates by up to 25%. These findings demonstrate the effectiveness of the applied source term in reproducing the wake profile, which is comparable with the published data, and highlight the inherent nature of the RANS and actuator disc models.展开更多
因暴雨、地震和岩羊踩踏等不确定因素,贺兰口沟口至"水关"处发育的34处孤石极易失稳滚落形成落石对岩画和游人安全构成严重威胁。通过对34处孤石数量、成因、分布、岩性和几何特征全面调查与分析的基础上,运用Rocfall软件分...因暴雨、地震和岩羊踩踏等不确定因素,贺兰口沟口至"水关"处发育的34处孤石极易失稳滚落形成落石对岩画和游人安全构成严重威胁。通过对34处孤石数量、成因、分布、岩性和几何特征全面调查与分析的基础上,运用Rocfall软件分析其失稳后的运动过程和能量变化进行分析,得出如下结论:(1)薄层状变质砂岩风化内凹的临空面、岩层层面与两组节理组合切割巨厚层砂岩失稳后堆积于坡面;(2)将落石划分为基岩裸露型、孤石带型和坡面泥石流型3种不同类型;(3)数值模拟结果显示,失稳后弹跳落点有52%~95%的概率在岩画赋存区,所具有能量为301~8412 k J;最终落点有51%~95%的概率在游客栈道,所具有能量为299~7698 k J;(4)监测结果表明,水剂比为0.32、平行布孔、间排距20 cm和抵抗线20 cm布置方案为最优,静态破碎结合人工搬运为岩画保护区落石源头治理的最佳方案。为贺兰口岩画保护区落石灾害的源头治理提供了新的途径与参考。展开更多
为了掌握南海钙质砂压缩变形特征及其微观机制,对3种不同粒组(S1:1.43~2 mm、S2:0.5~1 mm、S3:0.5~2 mm)的钙质砂进行100~3200 k Pa压力范围的压缩试验,利用自制的砂土微观结构提取装置和图像处理软件(PCAS)获得并分析了钙质砂压缩过程...为了掌握南海钙质砂压缩变形特征及其微观机制,对3种不同粒组(S1:1.43~2 mm、S2:0.5~1 mm、S3:0.5~2 mm)的钙质砂进行100~3200 k Pa压力范围的压缩试验,利用自制的砂土微观结构提取装置和图像处理软件(PCAS)获得并分析了钙质砂压缩过程中微观结构。结果表明:(1)钙质砂的大小、形状和级配对颗粒的破碎具有显著影响,当压力较低时(<800 k Pa),粒径较大的S1组以砂颗粒棱角破碎为主;粒径较小的S2组没有明显破裂,相对规则的颗粒形态使S2粒组在该压力范围内主要因颗粒的滚动与重分布导致压缩;级配良好的S3组除部分低宽度断肢状颗粒外其余大小、形态颗粒无明显破裂。(2)当压力较大时(>800 k Pa),S1组钙质砂逐渐转向以颗粒的整体破坏为主的破碎形式;S2、S3两组试样随着密实度的提高,砂颗粒的破坏以整体破碎为主。基于对破碎过程中试样微观结构变化的提取与分析,总结并提出了控制钙质砂颗粒破碎的4种接触模式:点-线接触、线-面接触、面-面接触和复合接触,可用于判断不同条件下的颗粒破碎形式。最后,讨论了钙质砂在破碎过程中颗粒几何参数的变化。展开更多
Hepatocellular carcinoma(HCC) is a common neoplasia which represents the second leading cause of cancer related death. Most cases occur in developing countries, but its incidence is rising in Western countries due to ...Hepatocellular carcinoma(HCC) is a common neoplasia which represents the second leading cause of cancer related death. Most cases occur in developing countries, but its incidence is rising in Western countries due to hepatitis C. Although hepatitis therapies have evolved and the HCC screening has increased in several areas, 40% present with advanced disease which is only amenable for palliative systemic treatment. HCC continues posing a challenge, in part due to the inherent chemoresistance of this neoplasia, the pharmacologic challenges due to an ill liver, difficulty in assessing radiological responses accurately, etc. Traditional chemotherapy have shown some responses without clear survival benefit, however, sorafenib demonstrated advantages in survival in advanced HCC when liver function is kept and recently immunotherapy seems to be a promising approach for some patients. This article will briefly expose the most relevant systemic treatment modalities to offer a general view from the past to the future.展开更多
BACKGROUND Hemorrhoidal disease is the most common anorectal disorder.Hemorrhoids can be classified as external or internal,according to their relation to the dentate line.External hemorrhoids originate below the dent...BACKGROUND Hemorrhoidal disease is the most common anorectal disorder.Hemorrhoids can be classified as external or internal,according to their relation to the dentate line.External hemorrhoids originate below the dentate line and are managed conservatively unless the patient cannot keep the perianal region clean,or they cause significant discomfort.Internal hemorrhoids originate above the dentate line and can be managed according to the graded degree of prolapse,as described by Goligher.Generally,low-grade internal hemorrhoids are effectively treated conservatively,by non-operative measures,while high-grade internal hemorrhoids warrant procedural intervention.AIM To determine the application of clinical practice guidelines for the current management of hemorrhoids and colorectal surgeon consensus in Australia and New Zealand.METHODS An online survey was distributed to 206 colorectal surgeons in Australia and New Zealand using 17 guideline-based hypothetical clinical scenarios.RESULTS There were 82 respondents(40%)to 17 guideline-based scenarios.Nine(53%)reached consensus,of which only 1(6%)disagreed with the guidelines.This was based on low quality evidence for the management of acutely thrombosed external hemorrhoids.There were 8 scenarios which showed community equipoise(47%)and they were equally divided for agreeing or disagreeing with the guidelines.These topics were based on low and moderate levels of evidence.They included the initial management of grade I internal hemorrhoids,grade III internal hemorrhoids when initial management had failed and the patient had recognised risks factors for septic complications;and finally,the decision-making when considering patient preferences,including a prompt return to work,or minimal post-operative pain.CONCLUSION Although there are areas of consensus in the management of hemorrhoids,there are many areas of community equipoise which would benefit from further research.展开更多
Hydrogen technologies and fuel cells offer an alternative and improved solution for a decarbonised energy future.Fuel cells are electrochemical converters;transforming hydrogen (or energy sources containing hydrogen) ...Hydrogen technologies and fuel cells offer an alternative and improved solution for a decarbonised energy future.Fuel cells are electrochemical converters;transforming hydrogen (or energy sources containing hydrogen) and oxygen directly into electricity.The hydrogen fuel cell,invented in 1839,permits the generation of electrical energy with high efficiency through a non-combustion,electrochemical process and,importantly,without the emission ofits point of use.Hitherto,despite numerous efforts to exploit the obvious attractions of hydrogen technologies and hydrogen fuel cells,various challenges have been encountered,some of which are reviewed here.Now,however,given the exigent need to urgently seek low-carbon paths for humankind’s energy future,numerous countries are advancing the deployment of hydrogen technologies and hydrogen fuel cells not only for transport,but also as a means of the storage of excess renewable energy from,for example,wind and solar farms.Furthermore,hydrogen is also being blended into the natural gas supplies used in domestic heating and targeted in the decarbonisation of critical,large-scale industrial processes such as steel making.We briefly review specific examples in countries such as Japan,South Korea and the People’s Republic of China,as well as selected examples from Europe and North America in the utilization of hydrogen technologies and hydrogen fuel cells.展开更多
Vasoactive intestinal peptide(VIP)secreting tumour(VIPoma)is a rare functional neuroendocrine tumour that typically arises from pancreatic islet cells.These present as sporadic,solitary pancreatic neoplasias with an e...Vasoactive intestinal peptide(VIP)secreting tumour(VIPoma)is a rare functional neuroendocrine tumour that typically arises from pancreatic islet cells.These present as sporadic,solitary pancreatic neoplasias with an estimated incidence of one in ten million individuals per year.Only around 5%of VIPomas are associated with multiple endocrine neoplasia type I syndrome.Excessive VIP secretion produces a clinical syndrome characterized by refractory watery diarrhoea,hypokalemia and metabolic acidosis.These coupled with elevated plasma levels of VIP are diagnostic.The majority of VIPomas are malignant and have already metastasized at the time of diagnosis(60%).Metastases occur most frequently in the liver,or regional lymph nodes,lungs,kidneys and bones.Some reports of skin metastases have been documented.Complete surgical resection continues to be the only potentially curative treatment.However,when the neoplasia cannot be excised completely,surgical debulking may provide palliative benefit.Other palliative options have included recently the peptide receptor radionuclide therapy which has shown to be effective and well-tolerated.This article will review all aspects of pancreatic VIPomas highlighting aspects such as clinical presentation,diagnosis and management.展开更多
AIM： To explore the trends in the ophthalmic literature over a 5-year period in relation to country, research expenditure and demographics. METHODS： Articles published between 2009 and 2013 by the 20 highest-con...AIM： To explore the trends in the ophthalmic literature over a 5-year period in relation to country, research expenditure and demographics. METHODS： Articles published between 2009 and 2013 by the 20 highest-contributing countries in the 20 top- ranked ophthalmology journals were identified by their country of affiliation. The number of articles published and mean impact factor were measured per country for each year and trends explored using regression analysis with 5-year and 10-year forecasts calculated. Data on research expenditure was collected and tested for correlation with the number of articles and mean impact factor. RESULTS： The analysis included 19 338 articles. The USA, UK and Europe accounted for 60.2% of articles published, with the USA contributing 7388 articles （34.0%）. The USA also demonstrated the highest mean impact factor （3.5）. Research expenditure was significantly correlated with both research output （r=0,86, P〈0.001） and scholarly impact （r=0.42, P〈0.001）. China （P〈0.01）, Korea （P〈0.01） and India （P〈0.02） demonstrated a significant growth in research output over the study period. The research contribution of these three countries combined is forecasted to overtake that of Europe within ten years, with China expected to be the second-largest contributor within five years. These countries were also among those demonstrating the greatest growth in research expenditure. CONCLUSION： While the USA and European countries are major contributors of ophthalmic research, the productivity of some Asian countries is growing impressively. The contribution of China, Korea and Indiais forecasted to outweigh that of Europe by 2023. Research expenditure is highly correlated with research productivity and these trends reflect the differing economic priorities across the world.展开更多
Aircraft ground movement plays a key role in improving airport efficiency,as it acts as a link to all other ground operations.Finding novel approaches to coordinate the movements of a fleet of aircraft at an airport i...Aircraft ground movement plays a key role in improving airport efficiency,as it acts as a link to all other ground operations.Finding novel approaches to coordinate the movements of a fleet of aircraft at an airport in order to improve system resilience to disruptions with increasing autonomy is at the center of many key studies for airport airside operations.Moreover,autonomous taxiing is envisioned as a key component in future digitalized airports.However,state-of-the-art routing and scheduling algorithms for airport ground movements do not consider high-fidelity aircraft models at both the proactive and reactive planning phases.The majority of such algorithms do not actively seek to optimize fuel efficiency and reduce harmful greenhouse gas emissions.This paper proposes a new approach for generating efficient four-dimensional trajectories(4DTs)on the basis of a high-fidelity aircraft model and gainscheduling control strategy.Working in conjunction with a routing and scheduling algorithm that determines the taxi route,waypoints,and time deadlines,the proposed approach generates fuel-efficient 4DTs in real time,while respecting operational constraints.The proposed approach can be used in two contexts:①as a reactive decision support tool to generate new trajectories that can resolve unprecedented events;and②as an autopilot system for both partial and fully autonomous taxiing.The proposed methodology is realistic and simple to implement.Moreover,simulation studies show that the proposed approach is capable of providing an up to 11%reduction in the fuel consumed during the taxiing of a large Boeing 747-100 jumbo jet.展开更多
AIM：To report the change in visual acuity and central macular thickness（CMT）following treatment with intravitreal aflibercept injections in patients with neovascular agerelated macular degeneration（n AMD）with sub...AIM：To report the change in visual acuity and central macular thickness（CMT）following treatment with intravitreal aflibercept injections in patients with neovascular agerelated macular degeneration（n AMD）with suboptimum response to ranibizumab.METHODS：This was a retrospective study. The inclusion criteria were patients with n AMD who responded poorly to ranibizumab. Patients then received either 3 consecutive aflibercept injections followed by pro re nata（PRN）treatment or PRN alone. Primary endpoints were mean change in bestcorrected visual acuity（BCVA）and CMT at 12 mo. Secondary endpoints were number of injections and adverse events.RESULTS：Forty-nine eyes from 49 patients met the inclusion criteria and completed 12-month follow up on aflibercept. Thirty-eight eyes received 3 consecutive aflibercept injections followed by PRN treatment and 11 eyes received PRN injections alone. At 12 mo,mean BCVA improved by one letters（log MAR 0.56±0.31 to 0.54±0.34）and mean CMT decreased from 303.9±82.1 to 259.2±108.3 μm.Four percent of eyes gained 15 letters or more,6% lost more than 15 letters and the remaining 90% had stable BCVA. The mean number of aflibercept injections was 6.There was one case of infectious endophthalmitis.CONCLUSION：Intravitreal aflibercept in patients with n AMD with a previous suboptimal response to ranibizumab resulted in an anatomical improvement in macular appearance at 12 mo without a corresponding improvement in visual acuity.展开更多
Rice fields are a major source of greenhouse gases,such as nitrous oxide (N_(2)O) and methane (CH_(4)).Organic fertilizers may potentially replace inorganic fertilizers to meet the nitrogen requirement for rice growth...Rice fields are a major source of greenhouse gases,such as nitrous oxide (N_(2)O) and methane (CH_(4)).Organic fertilizers may potentially replace inorganic fertilizers to meet the nitrogen requirement for rice growth;however,the simultaneous effects of organic fertilizers on N_(2)O and CH_(4)emissions and crop yield in paddy fields remain poorly understood and quantified.In this study,experimental plots were established in conventional double-cropping paddy fields in the Pearl River Delta,China,including an unfertilized control and five fertilizer treatments with fresh organic fertilizer (FOF),successively composted organic fertilizer (SOF),chemically composted organic fertilizer (COF),COF supplemented with inorganic fertilizer (COIF),and chemical fertilizers (CFs)(TFOF,TSOF,TCOF,TCOIF,and TCF,respectively).Paddy field soils behaved simultaneously as an N_(2)O sink (cumulative N_(2)O emission:-196 to-381 g N ha^(-1)) and as a CH_(4)source (cumulative CH_(4)emission:719 to 2 178 kg ha^(-1)).Compared to CFs,the effects of organic fertilizers on N_(2)O emission were not significant.In contrast,total annual CH_(4)emission increased by 157%,132%,125%,and 37%in TFOF,TCOF,TSOF,and TCOIF,respectively,compared to TCF.In TCOIF,rice yield was maintained,while CH_(4)emission was not significantly increased from the paddy fields characterized by a prolonged flood period.An important next step is to extend these field-based measurements to larger rice cultivation areas to quantify the regional and national-scale impacts on greenhouse gas emissions and to help determine the optimum practice for fertilizer use.展开更多
BACKGROUND Despite the improvement in the endoscopic hemostasis of non-variceal upper gastrointestinal bleeding(NVUGIB),rebleeding remains a major concern.AIM To assess the role of prophylactic transcatheter arterial ...BACKGROUND Despite the improvement in the endoscopic hemostasis of non-variceal upper gastrointestinal bleeding(NVUGIB),rebleeding remains a major concern.AIM To assess the role of prophylactic transcatheter arterial embolization(PTAE)added to successful hemostatic treatment among NVUGIB patients.METHODS We searched three databases from inception through October 19th,2020.Randomized controlled trials(RCTs)and observational cohort studies were eligible.Studies compared patients with NVUGIB receiving PTAE to those who did not get PTAE.Investigated outcomes were rebleeding,mortality,reintervention,need for surgery and transfusion,length of hospital(LOH),and intensive care unit(ICU)stay.In the quantitative synthesis,odds ratios(ORs)and weighted mean differences(WMDs)were calculated with the random-effects model and interpreted with 95%confidence intervals(CIs).RESULTS We included a total of 3 RCTs and 9 observational studies with a total of 1329 patients,with 486 in the intervention group.PTAE was associated with lower odds of rebleeding(OR=0.48,95%CI:0.29–0.78).There was no difference in the 30-d mortality rates(OR=0.82,95%CI:0.39–1.72)between the PTAE and control groups.Patients who underwent PTAE treatment had a lower chance for reintervention(OR=0.48,95%CI:0.31–0.76)or rescue surgery(OR=0.35,95%CI:0.14–0.92).The LOH and ICU stay was shorter in the PTAE group,but the difference was non-significant[WMD=-3.77,95%CI:(-8.00)–0.45;WMD=-1.33,95%CI:(-2.84)–0.18,respectively].CONCLUSION PTAE is associated with lower odds of rebleeding and any reintervention in NVUGIB.However,further RCTs are needed to have a higher level of evidence.展开更多
文摘A numerical investigation on the effectiveness of the actuator disc method in producing the interactions of multiple tidal stream devices via the 3D-RANS finite element model Telemac3D is explored. The methodology for the implementation of the source term to represent an array of 20 m rotor diameter turbines deployed in an idealized channel is reviewed and discussed in detail. Flow interactions between multiple turbines are investigated for a single row arrangement with only two turbines and a two row arrangement containing three turbines. The results demonstrate that the non-hydrostatic solver shows better agreement when validated against published experimental data. Notably,the mesh density at the device location can strongly influence the simulated thrust from the disc. Although the actuator disc model can generally replicate the wake interactions well, the results indicate that it cannot accurately characterize the flow for regions with high turbulences. While a model setup with the largest lateral spacing(1.5D) demonstrates excellent agreement with the experimental data, the 0.5D model(smallest gap) deviates by up to 25%. These findings demonstrate the effectiveness of the applied source term in reproducing the wake profile, which is comparable with the published data, and highlight the inherent nature of the RANS and actuator disc models.
文摘因暴雨、地震和岩羊踩踏等不确定因素,贺兰口沟口至"水关"处发育的34处孤石极易失稳滚落形成落石对岩画和游人安全构成严重威胁。通过对34处孤石数量、成因、分布、岩性和几何特征全面调查与分析的基础上,运用Rocfall软件分析其失稳后的运动过程和能量变化进行分析,得出如下结论:(1)薄层状变质砂岩风化内凹的临空面、岩层层面与两组节理组合切割巨厚层砂岩失稳后堆积于坡面;(2)将落石划分为基岩裸露型、孤石带型和坡面泥石流型3种不同类型;(3)数值模拟结果显示,失稳后弹跳落点有52%~95%的概率在岩画赋存区,所具有能量为301~8412 k J;最终落点有51%~95%的概率在游客栈道,所具有能量为299~7698 k J;(4)监测结果表明,水剂比为0.32、平行布孔、间排距20 cm和抵抗线20 cm布置方案为最优,静态破碎结合人工搬运为岩画保护区落石源头治理的最佳方案。为贺兰口岩画保护区落石灾害的源头治理提供了新的途径与参考。
文摘为了掌握南海钙质砂压缩变形特征及其微观机制,对3种不同粒组(S1:1.43~2 mm、S2:0.5~1 mm、S3:0.5~2 mm)的钙质砂进行100~3200 k Pa压力范围的压缩试验,利用自制的砂土微观结构提取装置和图像处理软件(PCAS)获得并分析了钙质砂压缩过程中微观结构。结果表明:(1)钙质砂的大小、形状和级配对颗粒的破碎具有显著影响,当压力较低时(<800 k Pa),粒径较大的S1组以砂颗粒棱角破碎为主;粒径较小的S2组没有明显破裂,相对规则的颗粒形态使S2粒组在该压力范围内主要因颗粒的滚动与重分布导致压缩;级配良好的S3组除部分低宽度断肢状颗粒外其余大小、形态颗粒无明显破裂。(2)当压力较大时(>800 k Pa),S1组钙质砂逐渐转向以颗粒的整体破坏为主的破碎形式;S2、S3两组试样随着密实度的提高,砂颗粒的破坏以整体破碎为主。基于对破碎过程中试样微观结构变化的提取与分析,总结并提出了控制钙质砂颗粒破碎的4种接触模式:点-线接触、线-面接触、面-面接触和复合接触,可用于判断不同条件下的颗粒破碎形式。最后,讨论了钙质砂在破碎过程中颗粒几何参数的变化。
文摘Hepatocellular carcinoma(HCC) is a common neoplasia which represents the second leading cause of cancer related death. Most cases occur in developing countries, but its incidence is rising in Western countries due to hepatitis C. Although hepatitis therapies have evolved and the HCC screening has increased in several areas, 40% present with advanced disease which is only amenable for palliative systemic treatment. HCC continues posing a challenge, in part due to the inherent chemoresistance of this neoplasia, the pharmacologic challenges due to an ill liver, difficulty in assessing radiological responses accurately, etc. Traditional chemotherapy have shown some responses without clear survival benefit, however, sorafenib demonstrated advantages in survival in advanced HCC when liver function is kept and recently immunotherapy seems to be a promising approach for some patients. This article will briefly expose the most relevant systemic treatment modalities to offer a general view from the past to the future.
文摘BACKGROUND Hemorrhoidal disease is the most common anorectal disorder.Hemorrhoids can be classified as external or internal,according to their relation to the dentate line.External hemorrhoids originate below the dentate line and are managed conservatively unless the patient cannot keep the perianal region clean,or they cause significant discomfort.Internal hemorrhoids originate above the dentate line and can be managed according to the graded degree of prolapse,as described by Goligher.Generally,low-grade internal hemorrhoids are effectively treated conservatively,by non-operative measures,while high-grade internal hemorrhoids warrant procedural intervention.AIM To determine the application of clinical practice guidelines for the current management of hemorrhoids and colorectal surgeon consensus in Australia and New Zealand.METHODS An online survey was distributed to 206 colorectal surgeons in Australia and New Zealand using 17 guideline-based hypothetical clinical scenarios.RESULTS There were 82 respondents(40%)to 17 guideline-based scenarios.Nine(53%)reached consensus,of which only 1(6%)disagreed with the guidelines.This was based on low quality evidence for the management of acutely thrombosed external hemorrhoids.There were 8 scenarios which showed community equipoise(47%)and they were equally divided for agreeing or disagreeing with the guidelines.These topics were based on low and moderate levels of evidence.They included the initial management of grade I internal hemorrhoids,grade III internal hemorrhoids when initial management had failed and the patient had recognised risks factors for septic complications;and finally,the decision-making when considering patient preferences,including a prompt return to work,or minimal post-operative pain.CONCLUSION Although there are areas of consensus in the management of hemorrhoids,there are many areas of community equipoise which would benefit from further research.
基金Professor Sir John Meurig Thomas FRS FREng,Department of Materials Science and Metallurgy,University of Cambridge.He is one of the founders of solid-state chemistry and the surface and materials chemistry of solids.He was one of the first chemists in the world to use electron microscopy as a chemical tool,which he initiated in the University of Wales(Bangor)in 1964.He has made numerous studies in heterogeneous catalysis and made significant contributions to the study of minerals,especially silicates,zeolites and clays as well as graphite and diamond.For his contributions to geochemistry,a new mineral,Meurigite,was named in his honour.He was once head of Physical Chemistry in the University of Cambridge and Director of the Royal Institution of Great BritainCorresponding author::Peter P.Edwards FRS ML holds the Statutory Chair of Inorganic Chemistry at Oxford and is the Co-Director of the KACST-Oxford Centre of Excellence in Petrochemicals,also at Oxford.He has previously held positions at Birmingham(Professor of Chemistry and of Materials),Cambridge(Lecturer in Chemistry and Director of Studies in Chemistry,Jesus College)and Cornell(British Fulbright Scholar and National Science Foundation Fellow).He was Co-Founder of the firstever UK Interdisciplinary Research Centre,that in Superconductivity at Cambridge and the UK Sustainable Hydrogen Energy Consortium(UKSHEC).He has been Chair of the European Research Council Advanced Investigators Award Panel on Chemical Synthesis and Advanced Materials.Edwards is Fellow of the Royal Society+1 种基金Einstein Professor of the Chinese Academy of SciencesMember,German Academy of Sciences,International Honorary Member of the US Academy of Arts and Sciences,International Member of the American Philosophical Society,and Member of the Academia Europaea.His current major interests include:Targeted reconstruction of plastic waste to hydrogen and starting monomers,converting carbon dioxide to carbon-neutral fuels and Green hydrogen from fossil hydrocarbon fuels,E-mail address:peter.edwards@chem.ox.ac.uk。
文摘Hydrogen technologies and fuel cells offer an alternative and improved solution for a decarbonised energy future.Fuel cells are electrochemical converters;transforming hydrogen (or energy sources containing hydrogen) and oxygen directly into electricity.The hydrogen fuel cell,invented in 1839,permits the generation of electrical energy with high efficiency through a non-combustion,electrochemical process and,importantly,without the emission ofits point of use.Hitherto,despite numerous efforts to exploit the obvious attractions of hydrogen technologies and hydrogen fuel cells,various challenges have been encountered,some of which are reviewed here.Now,however,given the exigent need to urgently seek low-carbon paths for humankind’s energy future,numerous countries are advancing the deployment of hydrogen technologies and hydrogen fuel cells not only for transport,but also as a means of the storage of excess renewable energy from,for example,wind and solar farms.Furthermore,hydrogen is also being blended into the natural gas supplies used in domestic heating and targeted in the decarbonisation of critical,large-scale industrial processes such as steel making.We briefly review specific examples in countries such as Japan,South Korea and the People’s Republic of China,as well as selected examples from Europe and North America in the utilization of hydrogen technologies and hydrogen fuel cells.
文摘Vasoactive intestinal peptide(VIP)secreting tumour(VIPoma)is a rare functional neuroendocrine tumour that typically arises from pancreatic islet cells.These present as sporadic,solitary pancreatic neoplasias with an estimated incidence of one in ten million individuals per year.Only around 5%of VIPomas are associated with multiple endocrine neoplasia type I syndrome.Excessive VIP secretion produces a clinical syndrome characterized by refractory watery diarrhoea,hypokalemia and metabolic acidosis.These coupled with elevated plasma levels of VIP are diagnostic.The majority of VIPomas are malignant and have already metastasized at the time of diagnosis(60%).Metastases occur most frequently in the liver,or regional lymph nodes,lungs,kidneys and bones.Some reports of skin metastases have been documented.Complete surgical resection continues to be the only potentially curative treatment.However,when the neoplasia cannot be excised completely,surgical debulking may provide palliative benefit.Other palliative options have included recently the peptide receptor radionuclide therapy which has shown to be effective and well-tolerated.This article will review all aspects of pancreatic VIPomas highlighting aspects such as clinical presentation,diagnosis and management.
文摘AIM： To explore the trends in the ophthalmic literature over a 5-year period in relation to country, research expenditure and demographics. METHODS： Articles published between 2009 and 2013 by the 20 highest-contributing countries in the 20 top- ranked ophthalmology journals were identified by their country of affiliation. The number of articles published and mean impact factor were measured per country for each year and trends explored using regression analysis with 5-year and 10-year forecasts calculated. Data on research expenditure was collected and tested for correlation with the number of articles and mean impact factor. RESULTS： The analysis included 19 338 articles. The USA, UK and Europe accounted for 60.2% of articles published, with the USA contributing 7388 articles （34.0%）. The USA also demonstrated the highest mean impact factor （3.5）. Research expenditure was significantly correlated with both research output （r=0,86, P〈0.001） and scholarly impact （r=0.42, P〈0.001）. China （P〈0.01）, Korea （P〈0.01） and India （P〈0.02） demonstrated a significant growth in research output over the study period. The research contribution of these three countries combined is forecasted to overtake that of Europe within ten years, with China expected to be the second-largest contributor within five years. These countries were also among those demonstrating the greatest growth in research expenditure. CONCLUSION： While the USA and European countries are major contributors of ophthalmic research, the productivity of some Asian countries is growing impressively. The contribution of China, Korea and Indiais forecasted to outweigh that of Europe by 2023. Research expenditure is highly correlated with research productivity and these trends reflect the differing economic priorities across the world.
基金This work was funded by the UK Engineering and Physical Sciences Research Council(EP/N029496/1,EP/N029496/2,EP/N029356/1,EP/N029577/1,and EP/N029577/2).
文摘Aircraft ground movement plays a key role in improving airport efficiency,as it acts as a link to all other ground operations.Finding novel approaches to coordinate the movements of a fleet of aircraft at an airport in order to improve system resilience to disruptions with increasing autonomy is at the center of many key studies for airport airside operations.Moreover,autonomous taxiing is envisioned as a key component in future digitalized airports.However,state-of-the-art routing and scheduling algorithms for airport ground movements do not consider high-fidelity aircraft models at both the proactive and reactive planning phases.The majority of such algorithms do not actively seek to optimize fuel efficiency and reduce harmful greenhouse gas emissions.This paper proposes a new approach for generating efficient four-dimensional trajectories(4DTs)on the basis of a high-fidelity aircraft model and gainscheduling control strategy.Working in conjunction with a routing and scheduling algorithm that determines the taxi route,waypoints,and time deadlines,the proposed approach generates fuel-efficient 4DTs in real time,while respecting operational constraints.The proposed approach can be used in two contexts:①as a reactive decision support tool to generate new trajectories that can resolve unprecedented events;and②as an autopilot system for both partial and fully autonomous taxiing.The proposed methodology is realistic and simple to implement.Moreover,simulation studies show that the proposed approach is capable of providing an up to 11%reduction in the fuel consumed during the taxiing of a large Boeing 747-100 jumbo jet.
文摘AIM：To report the change in visual acuity and central macular thickness（CMT）following treatment with intravitreal aflibercept injections in patients with neovascular agerelated macular degeneration（n AMD）with suboptimum response to ranibizumab.METHODS：This was a retrospective study. The inclusion criteria were patients with n AMD who responded poorly to ranibizumab. Patients then received either 3 consecutive aflibercept injections followed by pro re nata（PRN）treatment or PRN alone. Primary endpoints were mean change in bestcorrected visual acuity（BCVA）and CMT at 12 mo. Secondary endpoints were number of injections and adverse events.RESULTS：Forty-nine eyes from 49 patients met the inclusion criteria and completed 12-month follow up on aflibercept. Thirty-eight eyes received 3 consecutive aflibercept injections followed by PRN treatment and 11 eyes received PRN injections alone. At 12 mo,mean BCVA improved by one letters（log MAR 0.56±0.31 to 0.54±0.34）and mean CMT decreased from 303.9±82.1 to 259.2±108.3 μm.Four percent of eyes gained 15 letters or more,6% lost more than 15 letters and the remaining 90% had stable BCVA. The mean number of aflibercept injections was 6.There was one case of infectious endophthalmitis.CONCLUSION：Intravitreal aflibercept in patients with n AMD with a previous suboptimal response to ranibizumab resulted in an anatomical improvement in macular appearance at 12 mo without a corresponding improvement in visual acuity.
基金funded by the National Natural Science Foundation of China(No.41771291)the Jiangsu Agricultural Science and Technology Innovation Fund,China(No.CX(21)3183)+1 种基金the Jiangsu Specially Appointed Professor Program,Chinathe Jiangsu Six Talent Peaks Program,China(No.NY-083)。
文摘Rice fields are a major source of greenhouse gases,such as nitrous oxide (N_(2)O) and methane (CH_(4)).Organic fertilizers may potentially replace inorganic fertilizers to meet the nitrogen requirement for rice growth;however,the simultaneous effects of organic fertilizers on N_(2)O and CH_(4)emissions and crop yield in paddy fields remain poorly understood and quantified.In this study,experimental plots were established in conventional double-cropping paddy fields in the Pearl River Delta,China,including an unfertilized control and five fertilizer treatments with fresh organic fertilizer (FOF),successively composted organic fertilizer (SOF),chemically composted organic fertilizer (COF),COF supplemented with inorganic fertilizer (COIF),and chemical fertilizers (CFs)(TFOF,TSOF,TCOF,TCOIF,and TCF,respectively).Paddy field soils behaved simultaneously as an N_(2)O sink (cumulative N_(2)O emission:-196 to-381 g N ha^(-1)) and as a CH_(4)source (cumulative CH_(4)emission:719 to 2 178 kg ha^(-1)).Compared to CFs,the effects of organic fertilizers on N_(2)O emission were not significant.In contrast,total annual CH_(4)emission increased by 157%,132%,125%,and 37%in TFOF,TCOF,TSOF,and TCOIF,respectively,compared to TCF.In TCOIF,rice yield was maintained,while CH_(4)emission was not significantly increased from the paddy fields characterized by a prolonged flood period.An important next step is to extend these field-based measurements to larger rice cultivation areas to quantify the regional and national-scale impacts on greenhouse gas emissions and to help determine the optimum practice for fertilizer use.
基金by Economic Development and Innovation Operative Programme Grant,No.GINOP 2.3.2-15-2016-00048 and No.GINOP-2.3.4-15-2020-00010Human Resources Development Operational Programme Grant,No.EFOP-3.6.2-16-2017-00006 and No.EFOP-3.6.1.-16-2016-00004.
文摘BACKGROUND Despite the improvement in the endoscopic hemostasis of non-variceal upper gastrointestinal bleeding(NVUGIB),rebleeding remains a major concern.AIM To assess the role of prophylactic transcatheter arterial embolization(PTAE)added to successful hemostatic treatment among NVUGIB patients.METHODS We searched three databases from inception through October 19th,2020.Randomized controlled trials(RCTs)and observational cohort studies were eligible.Studies compared patients with NVUGIB receiving PTAE to those who did not get PTAE.Investigated outcomes were rebleeding,mortality,reintervention,need for surgery and transfusion,length of hospital(LOH),and intensive care unit(ICU)stay.In the quantitative synthesis,odds ratios(ORs)and weighted mean differences(WMDs)were calculated with the random-effects model and interpreted with 95%confidence intervals(CIs).RESULTS We included a total of 3 RCTs and 9 observational studies with a total of 1329 patients,with 486 in the intervention group.PTAE was associated with lower odds of rebleeding(OR=0.48,95%CI:0.29–0.78).There was no difference in the 30-d mortality rates(OR=0.82,95%CI:0.39–1.72)between the PTAE and control groups.Patients who underwent PTAE treatment had a lower chance for reintervention(OR=0.48,95%CI:0.31–0.76)or rescue surgery(OR=0.35,95%CI:0.14–0.92).The LOH and ICU stay was shorter in the PTAE group,but the difference was non-significant[WMD=-3.77,95%CI:(-8.00)–0.45;WMD=-1.33,95%CI:(-2.84)–0.18,respectively].CONCLUSION PTAE is associated with lower odds of rebleeding and any reintervention in NVUGIB.However,further RCTs are needed to have a higher level of evidence.
