The tail latency of end-user requests,which directly impacts the user experience and the revenue,is highly related to its corresponding numerous accesses in key-value stores.The replica selection algorithm is crucial ...The tail latency of end-user requests,which directly impacts the user experience and the revenue,is highly related to its corresponding numerous accesses in key-value stores.The replica selection algorithm is crucial to cut the tail latency of these key-value accesses.Recently,the C3 algorithm,which creatively piggybacks the queue-size of waiting keys from replica servers for the replica selection at clients,is proposed in NSDI 2015.Although C3 improves the tail latency a lot,it suffers from the timeliness issue on the feedback information,which directly influences the replica selection.In this paper,we analysis the evaluation of queuesize of waiting keys of C3,and some findings of queue-size variation were made.It motivate us to propose the Prediction-Based Replica Selection(PRS)algorithm,which predicts the queue-size at replica servers under the poor timeliness condition,instead of utilizing the exponentially weighted moving average of the state piggybacked queue-size as in C3.Consequently,PRS can obtain more accurate queue-size at clients than C3,and thus outperforms C3 in terms of cutting the tail latency.Simulation results confirm the advantage of PRS over C3.展开更多
Large-scale key-value stores are widely used in many Web-based systems to store huge amount of data as(key, value) pairs. In order to reduce the latency of accessing such(key, value) pairs, an in-memory cache system i...Large-scale key-value stores are widely used in many Web-based systems to store huge amount of data as(key, value) pairs. In order to reduce the latency of accessing such(key, value) pairs, an in-memory cache system is usually deployed between the front-end Web system and the back-end database system. In practice, a cache system may consist of a number of server nodes, and fault tolerance is a critical feature to maintain the latency Service-Level Agreements(SLAs). In this paper, we present the design, implementation, analysis, and evaluation of R-Memcached, a reliable in-memory key-value cache system that is built on top of the popular Memcached software. R-Memcached exploits coding techniques to achieve reliability, and can tolerate up to two node failures.Our experimental results show that R-Memcached can maintain very good latency and throughput performance even during the period of node failures.展开更多
1 Introduction Emerging byte-addressable storage technologies,such as NVM(Non-Volatile Memory),provide a more cost-effective and larger-capacity alternative to DRAM(Dynamic Random Access Memory)[1],presenting new oppo...1 Introduction Emerging byte-addressable storage technologies,such as NVM(Non-Volatile Memory),provide a more cost-effective and larger-capacity alternative to DRAM(Dynamic Random Access Memory)[1],presenting new opportunities to address the high cost,limited capacity,and volatility of in-memory key-value(KV)stores.Numerous efforts have been dedicated to redesigning conventional structures on NVM.However,they were challenged by the substantial engineering cost and increased complexity to be integrated into existing systems.Thus,a general framework to apply existing indexes to KV stores on NVM becomes more attractive[2].展开更多
The key-value store can provide flexibility of data types because it does not need to specify the data types to be stored in advance and can store any types of data as the value of the key-value pair.Various types of ...The key-value store can provide flexibility of data types because it does not need to specify the data types to be stored in advance and can store any types of data as the value of the key-value pair.Various types of studies have been conducted to improve the performance of the key-value store while maintaining its flexibility.However,the research efforts storing the large-scale values such as multimedia data files(e.g.,images or videos)in the key-value store were limited.In this study,we propose a new key-value store,WR-Store++aiming to store the large-scale values stably.Specifically,it provides a new design of separating data and index by working with the built-in data structure of the Windows operating system and the file system.The utilization of the built-in data structure of the Windows operating system achieves the efficiency of the key-value store and that of the file system extends the limited space of the storage significantly.We also present chunk-based memory management and parallel processing of WR-Store++to further improve its performance in the GET operation.Through the experiments,we show that WR-Store++can store at least 32.74 times larger datasets than the existing baseline key-value store,WR-Store,which has the limitation in storing large-scale data sets.Furthermore,in terms of processing efficiency,we show that WR-Store++outperforms not only WR-Store but also the other state-ofthe-art key-value stores,LevelDB,RocksDB,and BerkeleyDB,for individual key-value operations and mixed workloads.展开更多
随着互联网技术的迅猛发展,越来越多的非结构化数据涌入到人们的生活中,为这些数据建立高效的索引面临极大的挑战.键值数据库Key-Value以其结构简单和高扩展性而引起人们的广泛关注,已成为海量数据存储系统中的重要组成部分.由于Key-Va...随着互联网技术的迅猛发展,越来越多的非结构化数据涌入到人们的生活中,为这些数据建立高效的索引面临极大的挑战.键值数据库Key-Value以其结构简单和高扩展性而引起人们的广泛关注,已成为海量数据存储系统中的重要组成部分.由于Key-Value系统对吞吐量要求较高,而基于Flash的固态硬盘(solid state drive,SSD)能够提供很高的随机读性能,在SSD上构建Key-Value系统已成为海量数据存储领域的一大研究热点.鉴于Flash具有非定点更新、寿命有限等特性,基于SSD的KeyValue系统必须针对Flash的特性作专门优化.以一种称为SkimpyStash的基于SSD的Key-Value系统为基础,提出了一种新的Key-Value系统低延迟存储系统(low latency store,LLStore).LLStore使用内存文件映射技术来减少针对SSD的IO请求,除此之外,针对SkimpyStash中低效的压缩策略,提出一种改进方法,可以在少量增加内存开销的情况下极大地减少查询时间.通过与原系统的性能比较实验,LLStore在平均查询时间上可以获得至少12%的加速.展开更多
This assignment will critically examine the competitive strategies of four selected department stores in Hangzhou and the reasons why the choice of them depends on different customer values.It will also highlight the ...This assignment will critically examine the competitive strategies of four selected department stores in Hangzhou and the reasons why the choice of them depends on different customer values.It will also highlight the capabilities that companies used to realize their strategies.展开更多
NoSQL系统因其高性能、高可扩展性的优势在大数据管理中得到广泛应用,而key-value(KV)模型则是NoSQL系统中使用最广泛的一种存储模型.KV型本地存储系统对于以机械磁盘为持久化存储的情形,存在许多性能优化技术,但这些优化技术面对当前...NoSQL系统因其高性能、高可扩展性的优势在大数据管理中得到广泛应用,而key-value(KV)模型则是NoSQL系统中使用最广泛的一种存储模型.KV型本地存储系统对于以机械磁盘为持久化存储的情形,存在许多性能优化技术,但这些优化技术面对当前的硬件发展新趋势,如多核处理器、大内存和低延迟闪存、非易失性内存NVM(Non-Volatile Memory)等,难以充分发挥新硬件的优势,如数据索引、并发控制、事务日志管理等技术在多核架构下存在多核扩展性问题,又如数据存储策略不适应闪存SSD(Solid State Drive)的新存储特性而产生了IO利用率低效的问题.针对多核处理器、大内存和闪存、NVM等硬件发展新趋势,文中面向当前的大数据应用背景,综述了KV型本地存储系统在索引技术、并发控制、事务日志管理和数据放置等核心模块上的最新优化技术和系统研究成果.从处理器、内存和持久化存储的角度概括了KV型本地存储系统当前存在的最优技术,总结了当前研究尚未解决的技术挑战,并对KV型本地存储系统在CPU缓存高效性、事务日志扩展性和高可用性等方面的研究进行了展望.展开更多
BACKGROUND： Most of the currently available information on purinergic receptors （P2Rs） involved in pain transmission is based on results obtained in dorsal root ganglion or the spinal cord. However, the mechanism o...BACKGROUND： Most of the currently available information on purinergic receptors （P2Rs） involved in pain transmission is based on results obtained in dorsal root ganglion or the spinal cord. However, the mechanism of P2Rs in trigeminal neuralgia remains unclear. OBJECTIVE： To investigate changes in the P2R-mediated calcium signaling pathway in nociceptive trigemJnal ganglion neurons. DESIGN, TIME AND SETTING： In vitro experiments were conducted at the Patch-Clamp Laboratory of Comprehensive Experiment Center of Anhui Medical University, China from September 2008 to June 2009. MATERIALS： Thapsigargin, caffeine, suramin, and adenosine 5＇-triphosphate were purchased from Sigma, USA. METHODS： Using Fura-2-based microfluorimetry, intracellular calcium concentration （[Ca^2＋]i） was measured in freshly isolated adult rat small trigeminal ganglion neurons before and after drug application. MAIN OUTCOME MEASURES： Fluorescent intensities were expressed as the ratio F340/F380 to observe [Ca^2＋]i changes. RESULTS： In normal extracellular solution and Ca^2＋-free solution, application of thapsigargin （1 μmol/L）, a sarcoplasmic reticulum Ca^2＋ pump adenosine 5＇-triphosphate inhibitor, as well as caffeine （20 mmol/L）, a ryanodine receptor agonist, triggered [Ca^2＋]i increase in small trigeminal ganglion neurons. A similar response was induced by application of adenosine 5＇-triphosphate （100 μmol/L）. In Ca^2＋-free conditions, adenosine 5＇-triphosphate-induced [Ca^2＋]i transients in small trigeminal ganglion neurons were inhibited in cells pre-treated with thapsigargin （P 〈 0.01）, but not by caffeine （P 〉 0.05）. In normal, extracellular solution, adenosine 5＇-triphosphate-induced [Ca^2＋]i transients in small trigeminal ganglion neurons were partly inhibited in cells pre-treated with thapsigargin （P 〈 0.05）. CONCLUSION： Inositol-1,4, 5-triphosphate （IP3）- and ryanodine-sensitive Ca^2＋ stores exist in rat nociceptive trigeminal ganglion neurons. Two pathways are involved in the purinoreceptor-mediated [Ca^2＋]i rise observed in nociceptive trigeminal ganglion neurons. One pathway involves the metabotropic P2Y receptors, which are associated with the IP3 sensitive Ca^2＋store, and the second pathway is coupled to ionotropic P2X receptors that induce the Ca^2＋ influx.展开更多
Tropical montane cloud forest is one of the ecosystems with the highest biomass worldwide, representing an important carbon store. Globally its deforestation index is –1.1%, but in Mexico it is higher than –3%. Carb...Tropical montane cloud forest is one of the ecosystems with the highest biomass worldwide, representing an important carbon store. Globally its deforestation index is –1.1%, but in Mexico it is higher than –3%. Carbon estimates are scarce globally, particularly in Mexico. The objective of this study was to simulate future land-cover scenarios for the Sierra Madre Oriental in Mexico, by analyzing past forest cover changes. Another objective was to estimate stored carbon in the two study areas. These objectives involve the generation of information that could be useful inputs to anti-deforestation public policy such as the REDD+ strategy. Remote sensing was used to measure land cover change and estimate carbon stocks. Satellite images from 2015, 2000 and 1986 were used, and Dinamica EGO freeware generatedmodels of future projections. Between 1986 and 2015, 5171 ha of forest were converted to pasture. The annual deforestation rates were –1.5% for Tlanchinol and –1.3% for the San Bartolo Tutotepec sites. Distance to roads and marginalization were highly correlated with deforestation. By 2030, an estimated 3608 ha of forest in these sites will have been converted to pasture. Stored carbon was estimated at 16.35 Mg C ha-1 for the Tlanchinol site and 12.7 Mg C ha-1 for the San Bartolo site. In the Sierra Madre Oriental deforestation due to land cover change(–1.4%) is higher than levels reported worldwide. Besides having high values of stored carbon(14.5 Mg C ha-1), these forests have high biodiversity. The models' outputs show that the deforestation process will continue if action is not taken to avoid the expansion of livestock pasturing. This can be done by paying incentives for forest conservation to the owners of the land. The results suggest that REDD+ is currently the most viable strategy for reducing deforestation rates in tropical montane cloud forests in Sierra Madre Oriental.展开更多
In many animals,catabolic and anabolic periods are temporally separated.Migratory birds alternate energy expenditure during flight with energy accumulation during stopover.The size of the energy stores at stopover aff...In many animals,catabolic and anabolic periods are temporally separated.Migratory birds alternate energy expenditure during flight with energy accumulation during stopover.The size of the energy stores at stopover affects the decision to resume migration and thus the temporal organization of migration.We now provide data suggesting that it is not only the size of the energy stores per se that may influence migration scheduling,but also the physiological consequences of flying.In two subspecies of the northern wheatear Oenanthe oenanthe,a long-distance migrant,estimated energy stores at a stopover during autumn migration were positively related with both constitutive innate and acquired immune function,and negatively related with oxidative damage to lipids.In other words,migrants'physiological condition was associated with their energetic condition.Although time spent at stopover before sampling may have contributed to this relationship,our results suggest that migrants have to trade-off the depletion of energy stores during flight with incurring physiological costs.This will affect migrants'decisions when to start and when to terminate a migratory flight.The physiological costs associated with the depletion of energy stores may also help explaining why migrants often arrive at and depart from stopover sites with larger energy stores than expected.We propose that studies on the role of energy stores as drivers of the temporal organization of(avian)migration need to consider physiological condition,such as immunological and oxidative states.展开更多
Data storage solutions are a crucial aspect of any application, significantly impacting data management and system performance. This article explores the rationale behind utilizing both SQL and NoSQL databases, addres...Data storage solutions are a crucial aspect of any application, significantly impacting data management and system performance. This article explores the rationale behind utilizing both SQL and NoSQL databases, addressing key questions about when each type is preferable. The background emphasizes the importance of selecting the appropriate database technology to meet specific application requirements. The purpose of this research is to provide a comprehensive guide for choosing between SQL and NoSQL databases based on various factors, including workload characteristics, scalability needs, and consistency requirements. To achieve this, we examine different strategies for implementing SQL and NoSQL databases in large-scale distributed applications and systems. The research method involves a comparative analysis of the features, advantages, and limitations of both database types. We specifically focus on scenarios involving read-heavy versus write-heavy systems and the trade-offs between availability and consistency. The results of this research indicate that SQL databases, with their relational structure and ACID compliance, are ideal for applications requiring complex queries and data integrity. In contrast, NoSQL databases, offering schema flexibility and horizontal scalability, are better suited for managing extensive datasets and high-velocity data ingestion. In conclusion, the selection of a database depends on the specific needs of the application. SQL databases are preferred for transactional systems with complex relationships, while NoSQL databases excel in scenarios demanding flexibility and scalability. The study provides insights into hybrid approaches, leveraging both database types to optimize system performance.展开更多
This study attempted to examine the importance of storeenvironment in affecting consumers’store choice deci-sion;the relative importance among the three environ-mental factors;and consumers’expectations on store en-...This study attempted to examine the importance of storeenvironment in affecting consumers’store choice deci-sion;the relative importance among the three environ-mental factors;and consumers’expectations on store en-vironment for the casual-wear chain stores in HongKong.Julie Baker’s Three-category framework onstore environments namely ambient,design and socialfactors was adopted for investigation.The results indi-cated that the store environment was important in affect-ing consumers’selection of store for shopping.It alsorevealed that social factor was perceived relatively im-portant than ambient and design factors.Nine store ex-pectation dimensions were categorised and the resultdemonstrated that most respondents were concerned onthe social aspect in their expectation of having a satisfy-ing store environment.展开更多
文摘The tail latency of end-user requests,which directly impacts the user experience and the revenue,is highly related to its corresponding numerous accesses in key-value stores.The replica selection algorithm is crucial to cut the tail latency of these key-value accesses.Recently,the C3 algorithm,which creatively piggybacks the queue-size of waiting keys from replica servers for the replica selection at clients,is proposed in NSDI 2015.Although C3 improves the tail latency a lot,it suffers from the timeliness issue on the feedback information,which directly influences the replica selection.In this paper,we analysis the evaluation of queuesize of waiting keys of C3,and some findings of queue-size variation were made.It motivate us to propose the Prediction-Based Replica Selection(PRS)algorithm,which predicts the queue-size at replica servers under the poor timeliness condition,instead of utilizing the exponentially weighted moving average of the state piggybacked queue-size as in C3.Consequently,PRS can obtain more accurate queue-size at clients than C3,and thus outperforms C3 in terms of cutting the tail latency.Simulation results confirm the advantage of PRS over C3.
基金supported in part by Hong Kong GRF grant HKBU 210412 and HKBU grant FRG2/14-15/059
文摘Large-scale key-value stores are widely used in many Web-based systems to store huge amount of data as(key, value) pairs. In order to reduce the latency of accessing such(key, value) pairs, an in-memory cache system is usually deployed between the front-end Web system and the back-end database system. In practice, a cache system may consist of a number of server nodes, and fault tolerance is a critical feature to maintain the latency Service-Level Agreements(SLAs). In this paper, we present the design, implementation, analysis, and evaluation of R-Memcached, a reliable in-memory key-value cache system that is built on top of the popular Memcached software. R-Memcached exploits coding techniques to achieve reliability, and can tolerate up to two node failures.Our experimental results show that R-Memcached can maintain very good latency and throughput performance even during the period of node failures.
基金grant funded by the Ministry of Education(Singapore)(Title:inPMdb:An in-Persistent Memory Database System,WBS NO:A8000082-00-00)Shanghai Engineering Research Center of Big Data Management.
文摘1 Introduction Emerging byte-addressable storage technologies,such as NVM(Non-Volatile Memory),provide a more cost-effective and larger-capacity alternative to DRAM(Dynamic Random Access Memory)[1],presenting new opportunities to address the high cost,limited capacity,and volatility of in-memory key-value(KV)stores.Numerous efforts have been dedicated to redesigning conventional structures on NVM.However,they were challenged by the substantial engineering cost and increased complexity to be integrated into existing systems.Thus,a general framework to apply existing indexes to KV stores on NVM becomes more attractive[2].
文摘The key-value store can provide flexibility of data types because it does not need to specify the data types to be stored in advance and can store any types of data as the value of the key-value pair.Various types of studies have been conducted to improve the performance of the key-value store while maintaining its flexibility.However,the research efforts storing the large-scale values such as multimedia data files(e.g.,images or videos)in the key-value store were limited.In this study,we propose a new key-value store,WR-Store++aiming to store the large-scale values stably.Specifically,it provides a new design of separating data and index by working with the built-in data structure of the Windows operating system and the file system.The utilization of the built-in data structure of the Windows operating system achieves the efficiency of the key-value store and that of the file system extends the limited space of the storage significantly.We also present chunk-based memory management and parallel processing of WR-Store++to further improve its performance in the GET operation.Through the experiments,we show that WR-Store++can store at least 32.74 times larger datasets than the existing baseline key-value store,WR-Store,which has the limitation in storing large-scale data sets.Furthermore,in terms of processing efficiency,we show that WR-Store++outperforms not only WR-Store but also the other state-ofthe-art key-value stores,LevelDB,RocksDB,and BerkeleyDB,for individual key-value operations and mixed workloads.
文摘随着互联网技术的迅猛发展,越来越多的非结构化数据涌入到人们的生活中,为这些数据建立高效的索引面临极大的挑战.键值数据库Key-Value以其结构简单和高扩展性而引起人们的广泛关注,已成为海量数据存储系统中的重要组成部分.由于Key-Value系统对吞吐量要求较高,而基于Flash的固态硬盘(solid state drive,SSD)能够提供很高的随机读性能,在SSD上构建Key-Value系统已成为海量数据存储领域的一大研究热点.鉴于Flash具有非定点更新、寿命有限等特性,基于SSD的KeyValue系统必须针对Flash的特性作专门优化.以一种称为SkimpyStash的基于SSD的Key-Value系统为基础,提出了一种新的Key-Value系统低延迟存储系统(low latency store,LLStore).LLStore使用内存文件映射技术来减少针对SSD的IO请求,除此之外,针对SkimpyStash中低效的压缩策略,提出一种改进方法,可以在少量增加内存开销的情况下极大地减少查询时间.通过与原系统的性能比较实验,LLStore在平均查询时间上可以获得至少12%的加速.
文摘This assignment will critically examine the competitive strategies of four selected department stores in Hangzhou and the reasons why the choice of them depends on different customer values.It will also highlight the capabilities that companies used to realize their strategies.
文摘NoSQL系统因其高性能、高可扩展性的优势在大数据管理中得到广泛应用,而key-value(KV)模型则是NoSQL系统中使用最广泛的一种存储模型.KV型本地存储系统对于以机械磁盘为持久化存储的情形,存在许多性能优化技术,但这些优化技术面对当前的硬件发展新趋势,如多核处理器、大内存和低延迟闪存、非易失性内存NVM(Non-Volatile Memory)等,难以充分发挥新硬件的优势,如数据索引、并发控制、事务日志管理等技术在多核架构下存在多核扩展性问题,又如数据存储策略不适应闪存SSD(Solid State Drive)的新存储特性而产生了IO利用率低效的问题.针对多核处理器、大内存和闪存、NVM等硬件发展新趋势,文中面向当前的大数据应用背景,综述了KV型本地存储系统在索引技术、并发控制、事务日志管理和数据放置等核心模块上的最新优化技术和系统研究成果.从处理器、内存和持久化存储的角度概括了KV型本地存储系统当前存在的最优技术,总结了当前研究尚未解决的技术挑战,并对KV型本地存储系统在CPU缓存高效性、事务日志扩展性和高可用性等方面的研究进行了展望.
基金the National Natural Science Foundation of China, No.30670694 the Natural Science Foundation of Anhui Province Department of Education in China, No.2006KJ361B+2 种基金 the National Science Fund for Distinguished Young Scholars of Anhui Medical University, No.GJJQ-0801 the Scientific Research Foundation for Doctor of Anhui Medical University, No. XJ2005006the Special Foundation for Young Scientists in Higher Education Institutions of Anhui Province, No.2010SQRL078
文摘BACKGROUND： Most of the currently available information on purinergic receptors （P2Rs） involved in pain transmission is based on results obtained in dorsal root ganglion or the spinal cord. However, the mechanism of P2Rs in trigeminal neuralgia remains unclear. OBJECTIVE： To investigate changes in the P2R-mediated calcium signaling pathway in nociceptive trigemJnal ganglion neurons. DESIGN, TIME AND SETTING： In vitro experiments were conducted at the Patch-Clamp Laboratory of Comprehensive Experiment Center of Anhui Medical University, China from September 2008 to June 2009. MATERIALS： Thapsigargin, caffeine, suramin, and adenosine 5＇-triphosphate were purchased from Sigma, USA. METHODS： Using Fura-2-based microfluorimetry, intracellular calcium concentration （[Ca^2＋]i） was measured in freshly isolated adult rat small trigeminal ganglion neurons before and after drug application. MAIN OUTCOME MEASURES： Fluorescent intensities were expressed as the ratio F340/F380 to observe [Ca^2＋]i changes. RESULTS： In normal extracellular solution and Ca^2＋-free solution, application of thapsigargin （1 μmol/L）, a sarcoplasmic reticulum Ca^2＋ pump adenosine 5＇-triphosphate inhibitor, as well as caffeine （20 mmol/L）, a ryanodine receptor agonist, triggered [Ca^2＋]i increase in small trigeminal ganglion neurons. A similar response was induced by application of adenosine 5＇-triphosphate （100 μmol/L）. In Ca^2＋-free conditions, adenosine 5＇-triphosphate-induced [Ca^2＋]i transients in small trigeminal ganglion neurons were inhibited in cells pre-treated with thapsigargin （P 〈 0.01）, but not by caffeine （P 〉 0.05）. In normal, extracellular solution, adenosine 5＇-triphosphate-induced [Ca^2＋]i transients in small trigeminal ganglion neurons were partly inhibited in cells pre-treated with thapsigargin （P 〈 0.05）. CONCLUSION： Inositol-1,4, 5-triphosphate （IP3）- and ryanodine-sensitive Ca^2＋ stores exist in rat nociceptive trigeminal ganglion neurons. Two pathways are involved in the purinoreceptor-mediated [Ca^2＋]i rise observed in nociceptive trigeminal ganglion neurons. One pathway involves the metabotropic P2Y receptors, which are associated with the IP3 sensitive Ca^2＋store, and the second pathway is coupled to ionotropic P2X receptors that induce the Ca^2＋ influx.
基金support with doctorate fellowship CONACy T(No.266708)Postgraduate Sciences in Biodiversity and Conservation of the Center for Biological Research,UAEH
文摘Tropical montane cloud forest is one of the ecosystems with the highest biomass worldwide, representing an important carbon store. Globally its deforestation index is –1.1%, but in Mexico it is higher than –3%. Carbon estimates are scarce globally, particularly in Mexico. The objective of this study was to simulate future land-cover scenarios for the Sierra Madre Oriental in Mexico, by analyzing past forest cover changes. Another objective was to estimate stored carbon in the two study areas. These objectives involve the generation of information that could be useful inputs to anti-deforestation public policy such as the REDD+ strategy. Remote sensing was used to measure land cover change and estimate carbon stocks. Satellite images from 2015, 2000 and 1986 were used, and Dinamica EGO freeware generatedmodels of future projections. Between 1986 and 2015, 5171 ha of forest were converted to pasture. The annual deforestation rates were –1.5% for Tlanchinol and –1.3% for the San Bartolo Tutotepec sites. Distance to roads and marginalization were highly correlated with deforestation. By 2030, an estimated 3608 ha of forest in these sites will have been converted to pasture. Stored carbon was estimated at 16.35 Mg C ha-1 for the Tlanchinol site and 12.7 Mg C ha-1 for the San Bartolo site. In the Sierra Madre Oriental deforestation due to land cover change(–1.4%) is higher than levels reported worldwide. Besides having high values of stored carbon(14.5 Mg C ha-1), these forests have high biodiversity. The models' outputs show that the deforestation process will continue if action is not taken to avoid the expansion of livestock pasturing. This can be done by paying incentives for forest conservation to the owners of the land. The results suggest that REDD+ is currently the most viable strategy for reducing deforestation rates in tropical montane cloud forests in Sierra Madre Oriental.
基金The study was supported with grants from the Deutsch Forschungsgemeinschaft(DFG)awarded to C.E.(EI 1048/3-1)to Heiko Schmaljohann(SCHM 2647/3-1)+2 种基金the Swedish Research Council C 0361301(to C.I.)Marie Curie Career Integration Grant FP7-CIG ID:322217(to C.I.)A.H.is associated with the Centre for Animal Movement Research(CAnMove)which is financed by a Linnaeus grant(349-2007-8690)from the Swedish Research Council and Lund University.
文摘In many animals,catabolic and anabolic periods are temporally separated.Migratory birds alternate energy expenditure during flight with energy accumulation during stopover.The size of the energy stores at stopover affects the decision to resume migration and thus the temporal organization of migration.We now provide data suggesting that it is not only the size of the energy stores per se that may influence migration scheduling,but also the physiological consequences of flying.In two subspecies of the northern wheatear Oenanthe oenanthe,a long-distance migrant,estimated energy stores at a stopover during autumn migration were positively related with both constitutive innate and acquired immune function,and negatively related with oxidative damage to lipids.In other words,migrants'physiological condition was associated with their energetic condition.Although time spent at stopover before sampling may have contributed to this relationship,our results suggest that migrants have to trade-off the depletion of energy stores during flight with incurring physiological costs.This will affect migrants'decisions when to start and when to terminate a migratory flight.The physiological costs associated with the depletion of energy stores may also help explaining why migrants often arrive at and depart from stopover sites with larger energy stores than expected.We propose that studies on the role of energy stores as drivers of the temporal organization of(avian)migration need to consider physiological condition,such as immunological and oxidative states.
文摘Data storage solutions are a crucial aspect of any application, significantly impacting data management and system performance. This article explores the rationale behind utilizing both SQL and NoSQL databases, addressing key questions about when each type is preferable. The background emphasizes the importance of selecting the appropriate database technology to meet specific application requirements. The purpose of this research is to provide a comprehensive guide for choosing between SQL and NoSQL databases based on various factors, including workload characteristics, scalability needs, and consistency requirements. To achieve this, we examine different strategies for implementing SQL and NoSQL databases in large-scale distributed applications and systems. The research method involves a comparative analysis of the features, advantages, and limitations of both database types. We specifically focus on scenarios involving read-heavy versus write-heavy systems and the trade-offs between availability and consistency. The results of this research indicate that SQL databases, with their relational structure and ACID compliance, are ideal for applications requiring complex queries and data integrity. In contrast, NoSQL databases, offering schema flexibility and horizontal scalability, are better suited for managing extensive datasets and high-velocity data ingestion. In conclusion, the selection of a database depends on the specific needs of the application. SQL databases are preferred for transactional systems with complex relationships, while NoSQL databases excel in scenarios demanding flexibility and scalability. The study provides insights into hybrid approaches, leveraging both database types to optimize system performance.
文摘This study attempted to examine the importance of storeenvironment in affecting consumers’store choice deci-sion;the relative importance among the three environ-mental factors;and consumers’expectations on store en-vironment for the casual-wear chain stores in HongKong.Julie Baker’s Three-category framework onstore environments namely ambient,design and socialfactors was adopted for investigation.The results indi-cated that the store environment was important in affect-ing consumers’selection of store for shopping.It alsorevealed that social factor was perceived relatively im-portant than ambient and design factors.Nine store ex-pectation dimensions were categorised and the resultdemonstrated that most respondents were concerned onthe social aspect in their expectation of having a satisfy-ing store environment.
