Ports play a fundamental role in a sustainable integration of Africa in International trade. Both importers and exporters, shipping companies and government, however face high cost for sea transport and substantial in...Ports play a fundamental role in a sustainable integration of Africa in International trade. Both importers and exporters, shipping companies and government, however face high cost for sea transport and substantial inefficiency in port operations. This has resulted in congestion, higher dwell time, higher costs which affect the competitive ability in sub regional and global economy. This study investigates the main factors explaining poor container handling operations and limited competitive ability in Cameroonian Ports and aggregating this to the competitive position of Cameroonian ports in the West and Central African sub-regions (WCA). Using Analytic Hierarchy Process (A.H.P), the paper seeks to provide a basic understanding of container transportation and port’s terminal operations problems (constraints & ineffectiveness) in Cameroon.展开更多
This study examines the return connectedness between decentralized finance(DeFi)’s and the Association of Southeast Asian Nations(ASEAN)stock markets using the quantile vector autoregressive framework,which allows us...This study examines the return connectedness between decentralized finance(DeFi)’s and the Association of Southeast Asian Nations(ASEAN)stock markets using the quantile vector autoregressive framework,which allows us to investigate the connectedness at conditional quantiles.Our sample includes four major DeFi’s and six ASEAN stock markets,spanning from March 2018 to December 2022.The static results indicate a moderate level of return transmission between the system at mean and median quantile.This propagation increases substantially under extreme market conditions,establishing an asymmetric transmission across quantiles.Despite being a relatively new asset class,DeFi dominates the equity market and acts as the primary shock transmitter to the system in most instances.The dynamic analysis reveals that total system connectedness fluctuates over time and quantiles.The total system connectedness peaked during the COVID-19 and the Russia–Ukraine conflict period,indicating the impact of global events on system transmission.The optimal weight and hedge ratio estimated using the DCC-GARCH model indicate that DeFi is beneficial for portfolio construction and risk management.The rising trend in dynamic optimal weight and hedge ratio during the COVID-19 pandemic demonstrates that investors should decrease their investments in DeFi and increase hedging costs.Therefore,portfolio managers and investors should readjust their portfolio allocation in a timely manner according to different market states to build additional effective hedging and diversification strategies to avoid large losses and to reduce portfolio risk exposure.展开更多
Based on the author’s study and research in the virtual currency course at Columbia University’s Pre-College Summer Program,combined with discussions with American virtual currency experts,this paper systematically ...Based on the author’s study and research in the virtual currency course at Columbia University’s Pre-College Summer Program,combined with discussions with American virtual currency experts,this paper systematically analyzes the definition,operating mechanisms,types,regulatory policies,application scenarios,potential risks,future development,and relationship with the US dollar of stablecoins.The article uses ten core questions as the main thread,comprehensively exploring the position and prospects of stablecoins in the global digital financial landscape,aiming to provide readers with a panoramic understanding from concept to trend.展开更多
The rapid evolution of quantum computing poses significant threats to traditional cryptographic schemes,particularly in Decentralized Finance(DeFi)systems that rely on legacy mechanisms like RSA and ECDSA for digital ...The rapid evolution of quantum computing poses significant threats to traditional cryptographic schemes,particularly in Decentralized Finance(DeFi)systems that rely on legacy mechanisms like RSA and ECDSA for digital identity verification.This paper proposes a quantum-resilient,blockchain-based identity verification framework designed to address critical challenges in privacy preservation,scalability,and post-quantum security.The proposed model integrates Post-quantum Cryptography(PQC),specifically lattice-based cryptographic primitives,with Decentralized Identifiers(DIDs)and Zero-knowledge Proofs(ZKPs)to ensure verifiability,anonymity,and resistance to quantum attacks.A dual-layer architecture is introduced,comprising an identity layer for credential generation and validation,and an application layer for DeFi protocol integration.To evaluate its performance,the framework is tested on multiple real-world DeFi platforms using metrics such as verification latency,throughput,attack resistance,energy efficiency,and quantum attack simulation.The results demonstrate that the proposed framework achieves 90%latency reduction and over 35%throughput improvement compared to traditional blockchain identity solutions.It also exhibits a high quantum resistance score(95/100),with successful secure verification under simulated quantum adversaries.The revocation mechanism—implemented using Merkle-tree-based proofs—achieves average response times under 40 ms,and the system maintains secure operations with energy consumption below 9 J per authentication cycle.Additionally,the paper presents a security and cost tradeoff analysis using ZKP schemes such as Bulletproofs and STARKs,revealing superior bits-per-byte efficiency and reduced proof sizes.Real-world adoption scenarios,including integration with six major DeFi protocols,indicate a 25%increase in verified users and a 15%improvement in Total Value Locked(TVL).The proposed solution is projected to remain secure until 2041(basic version)and 2043(advanced version),ensuring long-term sustainability and future-proofing against evolving quantum threats.This work establishes a scalable,privacy-preserving identity model that aligns with emerging post-quantum security standards for decentralized ecosystems.展开更多
Celiac disease(CD) is now recognized as a common disorder among Middle Eastern(ME) and North African(NA) populations.The aim of this review is to assess the available data regarding CD in the ME and NA and to compare ...Celiac disease(CD) is now recognized as a common disorder among Middle Eastern(ME) and North African(NA) populations.The aim of this review is to assess the available data regarding CD in the ME and NA and to compare this information with that of Western countries.A literature review was performed using the electronic databases PubMed and Medline(1950-2008) as search engines,and "celiac disease" was used as a Mesh term.The search was limited to ME and NA countries.The prevalence of CD in ME and NA countries among low risk populations is similar to that of Western countries,but is higher in high risk populations such as those with type 1 diabetes.It is underestimated because of lack of clinical suspicion and lack of patient awareness.Clinical presentations in term of gastrointestinal,hematologic,skeletal,and liver manifestations are similar between both populations except for a high prevalence of short stature in some ME and NA countries.Few studies have addressed atypical or silent CD.As in the West,diagnosis is initially made by serological tests and is confirmed by small intestinal biopsies.Gluten-free diet is the main mode of treatment with a higher apparent adherence rate than in the West.Most disease complications result from malabsorption.The disease is strongly associated with HLA DQ2 and to a lesser extent with HLA DQ8 alleles.In conclusion,CD prevalence is underestimated,with little data available about its malignant complications.Disease parameters in the ME and NA are otherwise similar to those in Western countries.展开更多
BACKGROUND:Automated external defibrillators(AEDs)enable laypeople to provide early defi brillations to patients undergoing cardiac arrest,but scant information is available on the general public’s ability to use AED...BACKGROUND:Automated external defibrillators(AEDs)enable laypeople to provide early defi brillations to patients undergoing cardiac arrest,but scant information is available on the general public’s ability to use AEDs.This study assessed the ability of laypeople to operate AEDs,the effect of a 15-minute training,and whether skills differed by age.METHODS:From May 1 to December 31,2018,a prospective simulation study was conducted with 94 laypeople aged 18–65 years(32 aged 18–24 years,34 aged 25–54 years,and 28 aged 55–65 years)with no prior AED training.The participants’AED skills were assessed individually pretraining,post-training,and at a three-month follow-up using a simulated cardiac arrest scenario.The critical actions and time intervals were evaluated during the AED operating process.RESULTS:Only 14(14.9%)participants(eight aged 18–24 years,four aged 25–54 years,and two aged 55–65 years)successfully delivered defi brillations before training.AED operation errors were more likely to occur among the participants aged 55–65 years than among other age groups.After training,the proportion of successful defi brillations increased signifi cantly(18–24 years old:25.0%vs.71.9%,P<0.01;25–54 years old:11.8%vs.70.6%,P<0.01;55–65 years old:7.1%vs.67.9%,P<0.01).After three months,26.1%of the participants aged 55–65 years successfully delivered defi brillations,which was signifi cantly lower than that of participants aged 18–24 years(54.8%)and 25–54 years(64.3%)(P=0.02).There were no differences in time measures among three age groups in each test.CONCLUSIONS:The majority of untrained laypeople cannot effectively operate AEDs.More frequent training and refresher courses are crucial to improve AED skills.展开更多
Recent advancements in decentralized finance(DeFi)have resulted in a rapid increase in the use of Automated Market Makers(AMMs)for creating decentralized exchanges(DEXs).In this paper,we organize these developments by...Recent advancements in decentralized finance(DeFi)have resulted in a rapid increase in the use of Automated Market Makers(AMMs)for creating decentralized exchanges(DEXs).In this paper,we organize these developments by treating an AMM as a neoclassical black-box characterized by the conversion of inputs(tokens)to outputs(prices).The conversion is governed by the technology of the AMM summarized by an‘exchange function’.Various types of AMMs are examined,including:Constant Product Market Makers;Constant Mean Market Makers;Constant Sum Market Makers;Hybrid Function Market Makers;and,Dynamic Automated Market Makers.The paper also looks at the impact of introducing concentrated liquidity in an AMM.Overall,the framework presented here provides an intuitive geometric representation of how an AMM operates,and a clear delineation of the similarities and differences across the various types of AMMs.展开更多
BACKGROUND: To popularize the wide-spread use of automated external defi brillator(AED) to save life in sudden cardiac arrest, we compared the strength and weakness of different types of AEDs to enable a sound selecti...BACKGROUND: To popularize the wide-spread use of automated external defi brillator(AED) to save life in sudden cardiac arrest, we compared the strength and weakness of different types of AEDs to enable a sound selection based on regional requirement.METHODS: This was a retrospective descriptive study. Different types of AEDs were compared according to the information of AEDs from manuals and brochures provided by the manufacturers. Fifteen types of AEDs were divided into 3 groups, basic, intermediate and advanced.RESULTS: Lifeline? AUTO AED had the best performance in price, portability and user-friendly among AEDs of basic level. It required less time for shock charging. Samaritan PAD defi brillator was superior in price, portability, durability and characteristic among AEDs of intermediate level. It had the longest warranty and highest protection against water and dust. Lifeline? PRO AED had the best performance in most of the criteria among AEDs of advanced level and offered CPR video and manual mode for laypersons and clinicians respectively.CONCLUSION: Lifeline? AUTO AED, Samaritan PAD def ibrillator, Lifeline? PRO AED are superior in AEDs of basic, intermediate and advanced levels, respectively. A feasible AED may be chosen by users according to the regional requirement and the current information about the best available products.展开更多
Decentralized finance(DeFi)is a general term for a series of financial products and services.It is based on blockchain technology and has attracted people’s attention because of its open,transparent,and intermediary ...Decentralized finance(DeFi)is a general term for a series of financial products and services.It is based on blockchain technology and has attracted people’s attention because of its open,transparent,and intermediary free.Among them,the DeFi ecosystem based on Ethereum-based blockchains attracts the most attention.However,the current decentralized financial system built on the Ethereum architecture has been exposed to many smart contract vulnerabilities during the last few years.Herein,we believe it is time to improve the understanding of the prevailing Ethereum-based DeFi ecosystem security issues.To that end,we investigate the Ethereum-based DeFi security issues:1)inherited from the real-world financial system,which can be solved by macro-control;2)induced by the problems of blockchain architecture,which require a better blockchain platform;3)caused by DeFi invented applications,which should be focused on during the project development.Based on that,we further discuss the current solutions and potential directions ofDeFi security.According to our research,we could provide a comprehensive vision to the research community for the improvement of Ethereum-basedDeFi ecosystem security.展开更多
文摘Ports play a fundamental role in a sustainable integration of Africa in International trade. Both importers and exporters, shipping companies and government, however face high cost for sea transport and substantial inefficiency in port operations. This has resulted in congestion, higher dwell time, higher costs which affect the competitive ability in sub regional and global economy. This study investigates the main factors explaining poor container handling operations and limited competitive ability in Cameroonian Ports and aggregating this to the competitive position of Cameroonian ports in the West and Central African sub-regions (WCA). Using Analytic Hierarchy Process (A.H.P), the paper seeks to provide a basic understanding of container transportation and port’s terminal operations problems (constraints & ineffectiveness) in Cameroon.
文摘This study examines the return connectedness between decentralized finance(DeFi)’s and the Association of Southeast Asian Nations(ASEAN)stock markets using the quantile vector autoregressive framework,which allows us to investigate the connectedness at conditional quantiles.Our sample includes four major DeFi’s and six ASEAN stock markets,spanning from March 2018 to December 2022.The static results indicate a moderate level of return transmission between the system at mean and median quantile.This propagation increases substantially under extreme market conditions,establishing an asymmetric transmission across quantiles.Despite being a relatively new asset class,DeFi dominates the equity market and acts as the primary shock transmitter to the system in most instances.The dynamic analysis reveals that total system connectedness fluctuates over time and quantiles.The total system connectedness peaked during the COVID-19 and the Russia–Ukraine conflict period,indicating the impact of global events on system transmission.The optimal weight and hedge ratio estimated using the DCC-GARCH model indicate that DeFi is beneficial for portfolio construction and risk management.The rising trend in dynamic optimal weight and hedge ratio during the COVID-19 pandemic demonstrates that investors should decrease their investments in DeFi and increase hedging costs.Therefore,portfolio managers and investors should readjust their portfolio allocation in a timely manner according to different market states to build additional effective hedging and diversification strategies to avoid large losses and to reduce portfolio risk exposure.
文摘Based on the author’s study and research in the virtual currency course at Columbia University’s Pre-College Summer Program,combined with discussions with American virtual currency experts,this paper systematically analyzes the definition,operating mechanisms,types,regulatory policies,application scenarios,potential risks,future development,and relationship with the US dollar of stablecoins.The article uses ten core questions as the main thread,comprehensively exploring the position and prospects of stablecoins in the global digital financial landscape,aiming to provide readers with a panoramic understanding from concept to trend.
文摘The rapid evolution of quantum computing poses significant threats to traditional cryptographic schemes,particularly in Decentralized Finance(DeFi)systems that rely on legacy mechanisms like RSA and ECDSA for digital identity verification.This paper proposes a quantum-resilient,blockchain-based identity verification framework designed to address critical challenges in privacy preservation,scalability,and post-quantum security.The proposed model integrates Post-quantum Cryptography(PQC),specifically lattice-based cryptographic primitives,with Decentralized Identifiers(DIDs)and Zero-knowledge Proofs(ZKPs)to ensure verifiability,anonymity,and resistance to quantum attacks.A dual-layer architecture is introduced,comprising an identity layer for credential generation and validation,and an application layer for DeFi protocol integration.To evaluate its performance,the framework is tested on multiple real-world DeFi platforms using metrics such as verification latency,throughput,attack resistance,energy efficiency,and quantum attack simulation.The results demonstrate that the proposed framework achieves 90%latency reduction and over 35%throughput improvement compared to traditional blockchain identity solutions.It also exhibits a high quantum resistance score(95/100),with successful secure verification under simulated quantum adversaries.The revocation mechanism—implemented using Merkle-tree-based proofs—achieves average response times under 40 ms,and the system maintains secure operations with energy consumption below 9 J per authentication cycle.Additionally,the paper presents a security and cost tradeoff analysis using ZKP schemes such as Bulletproofs and STARKs,revealing superior bits-per-byte efficiency and reduced proof sizes.Real-world adoption scenarios,including integration with six major DeFi protocols,indicate a 25%increase in verified users and a 15%improvement in Total Value Locked(TVL).The proposed solution is projected to remain secure until 2041(basic version)and 2043(advanced version),ensuring long-term sustainability and future-proofing against evolving quantum threats.This work establishes a scalable,privacy-preserving identity model that aligns with emerging post-quantum security standards for decentralized ecosystems.
文摘Celiac disease(CD) is now recognized as a common disorder among Middle Eastern(ME) and North African(NA) populations.The aim of this review is to assess the available data regarding CD in the ME and NA and to compare this information with that of Western countries.A literature review was performed using the electronic databases PubMed and Medline(1950-2008) as search engines,and "celiac disease" was used as a Mesh term.The search was limited to ME and NA countries.The prevalence of CD in ME and NA countries among low risk populations is similar to that of Western countries,but is higher in high risk populations such as those with type 1 diabetes.It is underestimated because of lack of clinical suspicion and lack of patient awareness.Clinical presentations in term of gastrointestinal,hematologic,skeletal,and liver manifestations are similar between both populations except for a high prevalence of short stature in some ME and NA countries.Few studies have addressed atypical or silent CD.As in the West,diagnosis is initially made by serological tests and is confirmed by small intestinal biopsies.Gluten-free diet is the main mode of treatment with a higher apparent adherence rate than in the West.Most disease complications result from malabsorption.The disease is strongly associated with HLA DQ2 and to a lesser extent with HLA DQ8 alleles.In conclusion,CD prevalence is underestimated,with little data available about its malignant complications.Disease parameters in the ME and NA are otherwise similar to those in Western countries.
基金the National Natural Science Foundation of China(81703303)Shanghai Municipal Government Pujiang Research Development Program(17PJC070)+1 种基金HeartRescue Project China Programand Innovative Research Team of High-level Local Universities in Shanghai.
文摘BACKGROUND:Automated external defibrillators(AEDs)enable laypeople to provide early defi brillations to patients undergoing cardiac arrest,but scant information is available on the general public’s ability to use AEDs.This study assessed the ability of laypeople to operate AEDs,the effect of a 15-minute training,and whether skills differed by age.METHODS:From May 1 to December 31,2018,a prospective simulation study was conducted with 94 laypeople aged 18–65 years(32 aged 18–24 years,34 aged 25–54 years,and 28 aged 55–65 years)with no prior AED training.The participants’AED skills were assessed individually pretraining,post-training,and at a three-month follow-up using a simulated cardiac arrest scenario.The critical actions and time intervals were evaluated during the AED operating process.RESULTS:Only 14(14.9%)participants(eight aged 18–24 years,four aged 25–54 years,and two aged 55–65 years)successfully delivered defi brillations before training.AED operation errors were more likely to occur among the participants aged 55–65 years than among other age groups.After training,the proportion of successful defi brillations increased signifi cantly(18–24 years old:25.0%vs.71.9%,P<0.01;25–54 years old:11.8%vs.70.6%,P<0.01;55–65 years old:7.1%vs.67.9%,P<0.01).After three months,26.1%of the participants aged 55–65 years successfully delivered defi brillations,which was signifi cantly lower than that of participants aged 18–24 years(54.8%)and 25–54 years(64.3%)(P=0.02).There were no differences in time measures among three age groups in each test.CONCLUSIONS:The majority of untrained laypeople cannot effectively operate AEDs.More frequent training and refresher courses are crucial to improve AED skills.
文摘Recent advancements in decentralized finance(DeFi)have resulted in a rapid increase in the use of Automated Market Makers(AMMs)for creating decentralized exchanges(DEXs).In this paper,we organize these developments by treating an AMM as a neoclassical black-box characterized by the conversion of inputs(tokens)to outputs(prices).The conversion is governed by the technology of the AMM summarized by an‘exchange function’.Various types of AMMs are examined,including:Constant Product Market Makers;Constant Mean Market Makers;Constant Sum Market Makers;Hybrid Function Market Makers;and,Dynamic Automated Market Makers.The paper also looks at the impact of introducing concentrated liquidity in an AMM.Overall,the framework presented here provides an intuitive geometric representation of how an AMM operates,and a clear delineation of the similarities and differences across the various types of AMMs.
文摘BACKGROUND: To popularize the wide-spread use of automated external defi brillator(AED) to save life in sudden cardiac arrest, we compared the strength and weakness of different types of AEDs to enable a sound selection based on regional requirement.METHODS: This was a retrospective descriptive study. Different types of AEDs were compared according to the information of AEDs from manuals and brochures provided by the manufacturers. Fifteen types of AEDs were divided into 3 groups, basic, intermediate and advanced.RESULTS: Lifeline? AUTO AED had the best performance in price, portability and user-friendly among AEDs of basic level. It required less time for shock charging. Samaritan PAD defi brillator was superior in price, portability, durability and characteristic among AEDs of intermediate level. It had the longest warranty and highest protection against water and dust. Lifeline? PRO AED had the best performance in most of the criteria among AEDs of advanced level and offered CPR video and manual mode for laypersons and clinicians respectively.CONCLUSION: Lifeline? AUTO AED, Samaritan PAD def ibrillator, Lifeline? PRO AED are superior in AEDs of basic, intermediate and advanced levels, respectively. A feasible AED may be chosen by users according to the regional requirement and the current information about the best available products.
基金supported by the Key-Area Research and Development Program of Guangdong Province 2020B0101090003CCF-NSFOCUS Kunpeng Scientific Research Fund (CCFNSFOCUS 2021010)+4 种基金Innovation Fund Program of the Engineering Research Center for Integration and Application of Digital Learning Technology of Ministry of Education under Grant No.1221027National Natural Science Foundation of China (Grant Nos.61902083,62172115,61976064)Guangdong Higher Education Innovation Group 2020KCXTD007 and Guangzhou Higher Education Innovation Group (No.202032854)Guangzhou Fundamental Research Plan of“Municipal-School”Jointly Funded Projects (No.202102010445)Guangdong Province Science and Technology Planning Project (No.2020A1414010370).
文摘Decentralized finance(DeFi)is a general term for a series of financial products and services.It is based on blockchain technology and has attracted people’s attention because of its open,transparent,and intermediary free.Among them,the DeFi ecosystem based on Ethereum-based blockchains attracts the most attention.However,the current decentralized financial system built on the Ethereum architecture has been exposed to many smart contract vulnerabilities during the last few years.Herein,we believe it is time to improve the understanding of the prevailing Ethereum-based DeFi ecosystem security issues.To that end,we investigate the Ethereum-based DeFi security issues:1)inherited from the real-world financial system,which can be solved by macro-control;2)induced by the problems of blockchain architecture,which require a better blockchain platform;3)caused by DeFi invented applications,which should be focused on during the project development.Based on that,we further discuss the current solutions and potential directions ofDeFi security.According to our research,we could provide a comprehensive vision to the research community for the improvement of Ethereum-basedDeFi ecosystem security.
