Salinity is a fundamental variable of watermass chemistry,often varying strongly in coastal,estuarine,lagoonal,restricted-marine basinal,and non-freshwater lacustrine systems(Figure 1).Salinity variation commonly cont...Salinity is a fundamental variable of watermass chemistry,often varying strongly in coastal,estuarine,lagoonal,restricted-marine basinal,and non-freshwater lacustrine systems(Figure 1).Salinity variation commonly controls other watermass properties(e.g.,redox,temperature,p H,and chemical composition)as well as nutrient levels(and thus bioproductivity).展开更多
Global closed basins,occupying almost one fifth of the world's land area,spatially coincide with arid and semiarid areas.Paleoclimatic proxies can indicate basin-wide environmental change and human activity.Howeve...Global closed basins,occupying almost one fifth of the world's land area,spatially coincide with arid and semiarid areas.Paleoclimatic proxies can indicate basin-wide environmental change and human activity.However,previous studies have not approached the use of proxies in the same way to reconstruct natural and anthropogenic processes at regional and global scales.Here we present a regional study to investigate the basic processes of paleoclimatic proxies,from a typical closed-basin system in arid China.We use multiple paleoclimatic proxies of surface samples and sediments,as well as groundwater and sediment ages to study environmental change and human activity.We then establish a dataset for paleoclimatic proxies from global closed basins and do a numerical analysis on it.Regional studies verify that human activity greatly impacts paleoclimatic proxies,especially with regard to surface samples,as well as groundwater age,but Holocene sediments are less affected.Results from global studies indicate that the major changing trend of the wet/dry status of closed basins is associated with the movement of the westerly jet streams controlled by long-term changes in winter insolation.There is an abrupt change between 1800 AD and 1900 AD,according to a numerical synthesis of paleoclimatic proxies from global closed basins,which can be linked to human impact.We suggest this time period can be considered as a start point for the Anthropocene based on the sedimentary evidence of closed basins,globally.展开更多
The recent evolution of the Internet towards "Information-centric" transfer modes has renewed the interest in exploiting proxies to enhance seamless mobility. In this work, we focus on the case of multiple l...The recent evolution of the Internet towards "Information-centric" transfer modes has renewed the interest in exploiting proxies to enhance seamless mobility. In this work, we focus on the case of multiple levels of proxies in ICN architectures, in which content requests from mobile subscribers and the corresponding items are proactively cached to these proxies at different levels. Specifically, we present a multiple-level proactive caching model that selects the appropriate subset of proxies at different levels and supports distributed online decision procedures in terms of the tradeoff between delay and cache cost. We show via extensive simulations the reduction of up to 31.63% in the total cost relative to Full Caching, in which caching in all 1-level neighbor proxies is performed, and up to 84.21% relative to No Caching, in which no caching is used. Moreover, the proposed model outperforms other approaches with a flat cache structure in terms of the total cost.展开更多
This paper examines the relationship among organic geochemical proxies （TOC, C/N ratio and ~13C） and pollen assemblages in Zhuye Lake sediments since the Late Glacial. Results show that the reaction extent of organi...This paper examines the relationship among organic geochemical proxies （TOC, C/N ratio and ~13C） and pollen assemblages in Zhuye Lake sediments since the Late Glacial. Results show that the reaction extent of organic geochemical proxies and pollen as- semblages to environment changes are different. Organic geochemical proxies are sensitive to overall environmental change, while pollen assemblages indicate detailed information of environmental change. For the entire sedimentary section （except the sand layer fi＇om the bottom of the section）, when values of TOC, C/N ratio and total pollen concentrations are high, 813C values are low, and vice versa. The different responses of organic geochemical proxies and pollen records in Zhuye Lake are mainly due to their different sensitivity and diverse influencing factors in different environmental conditions.展开更多
Introduction: In older populations, the help of a third person may be necessary for a certain number of individuals in order to fill in questionnaires. The influence of this assistance on the collected information can...Introduction: In older populations, the help of a third person may be necessary for a certain number of individuals in order to fill in questionnaires. The influence of this assistance on the collected information can raise questions, among others concerning the concordance between the information provided by the persons themselves and by their proxies, or the introduction of a potential bias. Our study’s objective is to examine, among older people, the differences in the reported frequency of falls, fear of falling and activity restriction due to fear of falling, according to the fact that people had filled in a questionnaire with or without the help of a third person. Methods: The data used come from the secondary analysis of a cross-sectional survey using a self-administered questionnaire and conducted in 2006 in a Belgian semi-rural town among non-institutionalised persons aged 65 years and over. Results: Among the 501 questionnaires, 16.4% were filled in with the help of another person. In bivariate analysis, the persons who needed help reported fall history, fear of falling and activity restriction significantly more often. In multivariable analysis, when considering concurrently the covariates (sex, age, living alone and fall history for fear of falling and for activity restriction), the influence of having received help to fill in the survey was only significant for activity restriction. Conclusion: Our study shows that it is important to know whether or not a person has received help to fill in a questionnaire. This can actually influence the reported frequency of certain outcomes, even, for activity restriction, when considering simultaneously the effect of other covariates. Given the current and future ageing of our populations, it seems that more extensive exploration is needed of the influence of proxies on the collected information about falls, fear of falling and activity restriction among older people.展开更多
Sedimentary TOC （total organic carbon）, TN （total nitrogen） and C/N （carbon/nitrogen） at selected sites of Lake Victoria basin have provided evidence of phytoplankton productivity, input of nitrates and allochth...Sedimentary TOC （total organic carbon）, TN （total nitrogen） and C/N （carbon/nitrogen） at selected sites of Lake Victoria basin have provided evidence of phytoplankton productivity, input of nitrates and allochthonous （land） plant materials/catchment destruction in the basin during the late Holocene period （last 4,000 years to present）. TOC and TN in the sediment cores were determined using EuroEA3000 Series Elemental Analyser and radiocarbon dating done using AMS （accelerator mass spectrometry） standard method. Results showed that TOC （13.45%-20.78%） and TN （1.07%-1.92%） values were higher at Napoleon Gulf from about 4,186 years before present （ca. 4,186 yr. BP） to present than at inlet of river Kagera （TOC： 3.27%-6.32% and TN： 0.30%-0.59%） from about 190 years before present （ca. 190 yr. BP） to present. Generally TOC and TN had a negative correlation （r = -0.37, p = 0.04, n = 32） at Napoleon Gulf in the last 4,186 years to present signifying that C/N ratios were governed mostly by phytoplankton productivity which markedly increased during some periods in the last 370 years to present possibly as a result of increased input of nitrates. However, the periods from about 4,186 years to 1,684 years before present （ca. 4,186 yr. BP to 1,684 yr. BP） and some periods between the last 370 years to present indicated increased input of allochthonous plant materials/catchment destruction. On overall, there was a positive correlation between C/N and TOC at inlet of river Kagera （r = 0.57, p = 0.01, n = 20） in the last 190 years to present possibly signifying that C/N ratios were governed mainly by input of allochthonous plant materials hence increased catchment destruction. Input of land plant materials （catchment destruction） along Kagera basin declined during some period after 1950 AD. However the most recent years have shown increased input of land plant materials （catchment destruction） in Kagera basin.展开更多
Objective Located at the interface of terrestrial and marine ecosystems, mangroves are particularly sensitive to environmental changes. They provide a sedimentary sink for organic carbon, whereby core samples could p...Objective Located at the interface of terrestrial and marine ecosystems, mangroves are particularly sensitive to environmental changes. They provide a sedimentary sink for organic carbon, whereby core samples could provide detailed records of mangrove evolution. Human induced, rapid environmental changes in recent years require a better understanding of the mangrove ecosystems evolution in the past, by reconstructing the past mangrove dynamics using triterpenols recorded in sediments. The aim of our work is to improve the application of triterpenols as biomarkers for mangrove development in long term in China.展开更多
Usage of methods for determination of long-term trends of the dynamics of vegetation formation on the background of climate changes becomes more and more important at modern stage of the assessment of natural systems ...Usage of methods for determination of long-term trends of the dynamics of vegetation formation on the background of climate changes becomes more and more important at modern stage of the assessment of natural systems development. This causes to researchers a series of problems from choice of conceptual base to notions and terms of the processes identified and of state of vegetation of different environments. Solution of such a task results inevitably in necessity to correct the understanding of existing processes occurring in the vegetation cover. It allows establishing a direction of their development in the system of natural factors of any territory. As a result, we have base for determination of age, site and role of current state of phytocenoses in successional systems. It is necessary for this to reveal the peculiarities of phytocenoses composition and formation due to climate dynamics and to determine a period of ecosystems homeostasis, especially for phytocenoses of contact natural conditions. Optimal values of phytocenoses diversity, like one of whole biosystems, depend on the amount of resource in the environment, on stability degree and on evolutional development of cenoses due to ecological, micro-evolutional and evolutional processes.展开更多
Currently available proxies were studied as networks for building reconstruction models of the Atlantic Multidecadal Oscillation (AMO). Only proxies that would double the current record length (backwards in time from ...Currently available proxies were studied as networks for building reconstruction models of the Atlantic Multidecadal Oscillation (AMO). Only proxies that would double the current record length (backwards in time from AD 1564) were included. We present two proxy networks and corresponding reconstruction (transfer) models, one for tree-growth based proxies only and another for multiproxies. Both of them show a useful match in timing as well as amplitude with the AMO. These model structures demonstrated reasonable model performance (overall r<sup>2</sup> = 0.45 - 0.36). The time stability of proxy-AMO relationships was also validated. The new models produced acceptable results in cross-calibration-verification (reduction of error and coefficient of efficiency statistics in 1856-1921 and 1922-1990 vary between 0.41 and 0.21). The spatial distribution of these data series indicate that proxies respond to an AMO-like climatic oscillation over much of the Northern Hemisphere.展开更多
Four extreme ultraviolet(EUV)solar radiation proxies(Magnesium II core-to-wing ratio(MgII),Lymanαflux(Fα),10.7-cm solar radio flux(F10.7),and sunspot number(Rz))were analyzed during the last four consecutive solar a...Four extreme ultraviolet(EUV)solar radiation proxies(Magnesium II core-to-wing ratio(MgII),Lymanαflux(Fα),10.7-cm solar radio flux(F10.7),and sunspot number(Rz))were analyzed during the last four consecutive solar activity minima to investigate how they differ during minimum periods and how well they represent solar EUV radiation.Their variability within each minimum and between minima was compared by considering monthly means.A comparison was also made of their role in filtering the effect of solar activity from the critical frequency of the ionospheric F2 layer,foF2,which at mid to low latitudes depends mainly on EUV solar radiation.The last two solar cycles showed unusually low EUV radiation levels according to the four proxies.Regarding the connection between the EUV“true”variation and that of solar proxies,according to the foF2 filtering analysis,MgII and Fαbehaved in a more stable and suitable way,whereas Rz and F10.7 could be overestimating EUV levels during the last two minima,implying they would both underestimate the inter-minima difference of EUV when compared with the first two minima.展开更多
Using artificial intelligence(AI) and machine learning(ML) techniques, we developed and validated the smart proxy models for history matching of reservoir simulation, sensitivity analysis, and uncertainty assessment b...Using artificial intelligence(AI) and machine learning(ML) techniques, we developed and validated the smart proxy models for history matching of reservoir simulation, sensitivity analysis, and uncertainty assessment by artificial neural network(ANN). The smart proxy models were applied on two cases, the first case study investigated the application of a proxy model for calibrating a reservoir simulation model based on historical data and predicting well production while the second case study investigated the application of an ANN-based proxy model for fast-track modeling of CO2 enhanced oil recovery, aiming at the prediction of the reservoir pressure and phase saturation distribution at injection stage and post-injection stage. The prediction effects for both cases are promising. While a single run of basic numerical simulation model takes hours to days, the smart proxy model runs in a matter of seconds, saving 98.9% of calculating time. The results of these case studies demonstrate the advantage of the proposed workflow for addressing the high run-time, computational time and computational cost of numerical simulation models. In addition, these proxy models predict the outputs of reservoir simulation models with high accuracy.展开更多
Geochemical ratios in coral reef skeletons could be used as proxies to reconstruct past climatological and environmental records in data-poor regions. Using a 103-year data set(1902 to 2005), the annual variations in ...Geochemical ratios in coral reef skeletons could be used as proxies to reconstruct past climatological and environmental records in data-poor regions. Using a 103-year data set(1902 to 2005), the annual variations in Ba/Ca and Mn/Ca ratios of Porites lutea skeletons at an eastern offshore area of Hainan Island(19?12'28.4''N, 110?37'38.8''E) were analyzed using inductively coupled plasma-optic emission spectrometry(ICP-OES). The analysis results showed that Ba/Ca ratios varied from a minimum of 3.120 μmol mol^(-1) in 1903 to a maximum of 10.064 μmol mol^(-1) in 1944, with an average of 5.256 μmol mol^(-1). Mn/Ca ratios varied from 0.206 to 5.708 μmol mol^(-1) with an annual average of 1.234 μmol mol^(-1), with peak values in 2001, 1964 and 1932, that correlated with strong rainfall events caused by typhoons. Variation in Ba/Ca and Mn/Ca ratios were compared with available river discharge and precipitation records, providing insight into past climatological events. Human activities and their indirect effects could impact the strength of the relationship between Ba/Ca and Mn/Ca ratios and observed precipitation and terrestrial input in the future.展开更多
Based on multiple proxies from the Southern Hemisphere, an austral summer (December-January-February: DJF) Antarctic Oscillation Index (AAO) since 1500 A.D. was reconstructed with a focus on interannual to interdecada...Based on multiple proxies from the Southern Hemisphere, an austral summer (December-January-February: DJF) Antarctic Oscillation Index (AAO) since 1500 A.D. was reconstructed with a focus on interannual to interdecadal variability (<50 a). By applying a multivariate regression method, the observational AAO-proxy relations were calibrated and cross-validated for the period of 1957 89. The regressions were employed to compute the DJF-AAO index for 1500 1956. To verify the results, the authors checked the explained variance (r 2 ), the reduction of error (RE), and the standard error (SE). Cross-validation was performed by applying a leave-one-out validation method. Over the entire reconstruction period, the mean values of r 2 , RE, and SE are 59.9%, 0.47, and 0.67, respectively. These statistics indicate that the DJF-AAO reconstruction is relatively skillful and reliable for the last ～460 years. The reconstructed AAO variations on the interannual and interdecadal timescales compare favorably with those of several shorter sea level pressure (SLP)-based AAO indices. The leading periods of the DJF-AAO index over the last 500 years are ～2.4, ～2.6, ～6.3, ～24.1, and ～37.6 years, all of which are significant at the 95% level as estimated by power spectral analysis.展开更多
This paper discusses an approach to share a smart card in one machine with other machines accessible on the local network or the Internet. This allows a user at a browser to use the shared card remotely and access web...This paper discusses an approach to share a smart card in one machine with other machines accessible on the local network or the Internet. This allows a user at a browser to use the shared card remotely and access web applications that requiresmart card authentication. This also enables users to access these applications from browsers and machines that do not have the capability to use a smart card. The approach uses proxies and card reader code to provide this capability to the requesting device.Previous work with remote or shared smart card use either requires continuous access to the smart card machine or specific client software. The approach in this paper works for any device and browser that has proxy settings, creates minimal network traffic and computation on the smart card machine, and allows the client to transfer from one network to another while maintaining connectivity to a server. This paper describes the smart card sharing approach, implementation and validation of the approach using real systems, and security implications for an enterprise using smart cards.展开更多
We reconstruct the environmental evolution of the East China Sea in the past 14 kyr based on glycerol dialkyl glycerol tetraethers(GDGTs) in a sediment core from the subaqueous Yangtze River Delta. Two primary phases ...We reconstruct the environmental evolution of the East China Sea in the past 14 kyr based on glycerol dialkyl glycerol tetraethers(GDGTs) in a sediment core from the subaqueous Yangtze River Delta. Two primary phases are recognized. Phase I(13.8–8 cal kyr BP) reflects a predominantly continental influence, showing distinctly higher concentrations of branched GDGTs(averaged 143 ng/g dry sediment weight, dsw) than isoprenoid GDGTs(averaged 36 ng/g dsw), high BIT index(branched vs. isoprenoid tetraethers) values(>0.78) and a fluctuating GDGT-0/crenarchaeol ratio(R_(0/5), varied from 0.52 to 3.81). Within this interval, temporal increases of terrestrial and marine influence are attributed to Younger Dryas(YD)(ca. 12.9–12.2 cal kyr BP) cold event and melt-water pulse(MWP)-1B(11.5–11.1 cal kyr BP), respectively. The prominent transition from 8 to 7.9 cal kyr BP shows a sharp decrease in BIT index value(<0.4) and increase in crenarchaeol, which marks the beginning of phase II. Afterwards, the proxies remain relatively constant, which indicates that phase II(7.9 cal kyr BP-present) is a shelf sedimentary environment with high stand of sea level. Overall, the BIT index in our record serves as a good marker for terrestrial influence at the site, and likely reflects the flooding history of the region. The TEX_(86)(Tetra Ether Index of tetraethers consisting of 86 carbons) proxy is not applicable in phase I because of an excess terrestrial influence; but it seems to be valid for revealing the annual SST in phase II(21.6±0.9°C, n=49). In contrast, the MBT'/CBT(Methylation of Branched Tetraethers and Cyclization of Branched Tetraethers) proxy appears to faithfully record the annual mean air temperature(MAT)(14.3±0.63°C, n=68) and presents an integrated signal over the middle and lower Yangtze River drainage basin.展开更多
Cloud services,favored by many enterprises due to their high flexibility and easy operation,are widely used for data storage and processing.However,the high latency,together with transmission overheads of the cloud ar...Cloud services,favored by many enterprises due to their high flexibility and easy operation,are widely used for data storage and processing.However,the high latency,together with transmission overheads of the cloud architecture,makes it difficult to quickly respond to the demands of IoT applications and local computation.To make up for these deficiencies in the cloud,fog computing has emerged as a critical role in the IoT applications.It decentralizes the computing power to various lower nodes close to data sources,so as to achieve the goal of low latency and distributed processing.With the data being frequently exchanged and shared between multiple nodes,it becomes a challenge to authorize data securely and efficiently while protecting user privacy.To address this challenge,proxy re-encryption(PRE)schemes provide a feasible way allowing an intermediary proxy node to re-encrypt ciphertext designated for different authorized data requesters without compromising any plaintext information.Since the proxy is viewed as a semi-trusted party,it should be taken to prevent malicious behaviors and reduce the risk of data leakage when implementing PRE schemes.This paper proposes a new fog-assisted identity-based PRE scheme supporting anonymous key generation,equality test,and user revocation to fulfill various IoT application requirements.Specifically,in a traditional identity-based public key architecture,the key escrow problem and the necessity of a secure channel are major security concerns.We utilize an anonymous key generation technique to solve these problems.The equality test functionality further enables a cloud server to inspect whether two candidate trapdoors contain an identical keyword.In particular,the proposed scheme realizes fine-grained user-level authorization while maintaining strong key confidentiality.To revoke an invalid user identity,we add a revocation list to the system flows to restrict access privileges without increasing additional computation cost.To ensure security,it is shown that our system meets the security notion of IND-PrID-CCA and OW-ID-CCA under the Decisional Bilinear Diffie-Hellman(DBDH)assumption.展开更多
Cloud data sharing is an important issue in modern times.To maintain the privacy and confidentiality of data stored in the cloud,encryption is an inevitable process before uploading the data.However,the centralized ma...Cloud data sharing is an important issue in modern times.To maintain the privacy and confidentiality of data stored in the cloud,encryption is an inevitable process before uploading the data.However,the centralized management and transmission latency of the cloud makes it difficult to support real-time processing and distributed access structures.As a result,fog computing and the Internet of Things(IoT)have emerged as crucial applications.Fog-assisted proxy re-encryption is a commonly adopted technique for sharing cloud ciphertexts.It allows a semitrusted proxy to transforma data owner’s ciphertext into another re-encrypted ciphertext intended for a data requester,without compromising any information about the original ciphertext.Yet,the user revocation and cloud ciphertext renewal problems still lack effective and secure mechanisms.Motivated by it,we propose a revocable conditional proxy re-encryption scheme offering ciphertext evolution(R-CPRE-CE).In particular,a periodically updated time key is used to revoke the user’s access privileges while an access condition prevents a malicious proxy from reencrypting unauthorized ciphertext.We also demonstrate that our scheme is provably secure under the notion of indistinguishability against adaptively chosen identity and chosen ciphertext attacks in the random oracle model.Performance analysis shows that our scheme reduces the computation time for a complete data access cycle from an initial query to the final decryption by approximately 47.05%compared to related schemes.展开更多
Hemipelagic to pelagic(H/P)marls,representing pelitic deposits,accumulated within the foredeep sub-basin of the Dinaric Foreland Basin(northern Neotethyan margin,present-day Croatia)during the Middle to Late Eocene.Sy...Hemipelagic to pelagic(H/P)marls,representing pelitic deposits,accumulated within the foredeep sub-basin of the Dinaric Foreland Basin(northern Neotethyan margin,present-day Croatia)during the Middle to Late Eocene.Syn-sedimentary tectonic movements,paleogeographic position and exchanges of short-lived hyperthermal episodes affected the sedimentation and related mineral and geochemical record of these deposits.Mineral(clay)assemblages bear signature of prevailing physical weathering with significant illite and chlorite content,but climatic seasonality is suggested by smectite-interlayered phases and sporadical increase of kaolinite content.Illite crystallinity varies significantly,and the lowest crystallinity is recorded by the Lutetian samples.Illite chemistry index is always bellow 0.5,being characteristic for Fe-Mg-rich illite.The geochemical records are the most prominent(CIA up to 76,CIW up to 91)for the Istrian Lutetian(42.3-40.5 Ma),but also for Priabonian(35.8-34.3 Ma)samples of Hvar Island.The ICV values(the lowest 1.40 and the highest 10.85)of all studied samples fall above PAAS(ICV=0.85)and point to their chemical immaturity.The Ga/Rb ratios are lower than 0.2 and K_(2)O/Al_(2)O_(3) ratios are also low(0.16-0.22),implying transition between cold and dry,and warm and humid climate,obviously trending among several warming episodes.展开更多
Research on changes in the redox conditions of bottom waters is essential for understanding deep water circulation,global ocean currents,climate change,and ecosystem health.Through sedimentary geological methods,a dee...Research on changes in the redox conditions of bottom waters is essential for understanding deep water circulation,global ocean currents,climate change,and ecosystem health.Through sedimentary geological methods,a deeper understanding of the complex relationships between various environmental changes can be achieved,providing detailed evidence and theoretical support for global climate change research.The Ross Sea in Antarctica plays a key role in the formation of Antarctic bottom water(AABW),and the complex climate changes since the last glacial maximum(LGM)make it particularly significant for study.This research analyzes core ANT32-RB16C from the Ross Sea using geochemical proxies such as major and trace elements,grain size,and redox-sensitive indicators like Mn/Ti,Co/Ti,Mo/Ti,Cd/Ti,U/Th,and Ni/Co molar concentration ratios.Combining this data with a previously established chronological framework,the study explores the evolution of redox conditions in the Ross Sea’s deep waters since the LGM.The results show that the deep waters have remained oxygen-rich since the LGM,with significant changes in four stages.Stage 1(24.7–15.7 cal ka BP):Strong oxidizing conditions,likely due to enhanced formation of Ross Sea bottom water(RSBW),increasing oxygen levels.Stage 2(15.7–4.5 cal ka BP):Weakened oxidizing conditions as temperatures rose and ice shelves retreated,increasing primary productivity and depleting oxygen.Stage 3(4.5–1.5 cal ka BP):Continued decline in oxidizing conditions,possibly linked to high primary productivity and oxygen consumption.Stage 4(1.5 cal ka BP to present):A rapid recovery of oxidizing conditions,likely driven by temperature drops,increased RSBW formation,and decreased productivity.展开更多
With the rapid development of web3.0 applications,the volume of data sharing is increasing,the inefficiency of big data file sharing and the problem of data privacy leakage are becoming more and more prominent,and the...With the rapid development of web3.0 applications,the volume of data sharing is increasing,the inefficiency of big data file sharing and the problem of data privacy leakage are becoming more and more prominent,and the existing data sharing schemes have been difficult to meet the growing demand for data sharing,this paper aims at exploring a secure,efficient and privacy-protecting data sharing scheme under web3.0 applications.Specifically,this paper adopts interplanetary file system(IPFS)technology to realize the storage of large data files to solve the problem of blockchain storage capacity limitation,and utilizes ciphertext policy attribute-based encryption(CP-ABE)and proxy re-encryption(PRE)technology to realize secure multi-party sharing and finegrained access control of data.This paper provides the detailed algorithm design and implementation of data sharing phases and processes,and analyzes the algorithms from the perspectives of security,privacy protection,and performance.展开更多
文摘Salinity is a fundamental variable of watermass chemistry,often varying strongly in coastal,estuarine,lagoonal,restricted-marine basinal,and non-freshwater lacustrine systems(Figure 1).Salinity variation commonly controls other watermass properties(e.g.,redox,temperature,p H,and chemical composition)as well as nutrient levels(and thus bioproductivity).
基金The National Key Research and Development Program of China,No.2019YFC0507401National Natural Science Foundation of China,No.42077415,No.41822708+1 种基金The Second Tibetan Plateau Scientific Expedition and Research Program(STEP),No.2019QZKK0202The Strategic Priority Research Program of Chinese Academy of Sciences,No.XDA20100102。
文摘Global closed basins,occupying almost one fifth of the world's land area,spatially coincide with arid and semiarid areas.Paleoclimatic proxies can indicate basin-wide environmental change and human activity.However,previous studies have not approached the use of proxies in the same way to reconstruct natural and anthropogenic processes at regional and global scales.Here we present a regional study to investigate the basic processes of paleoclimatic proxies,from a typical closed-basin system in arid China.We use multiple paleoclimatic proxies of surface samples and sediments,as well as groundwater and sediment ages to study environmental change and human activity.We then establish a dataset for paleoclimatic proxies from global closed basins and do a numerical analysis on it.Regional studies verify that human activity greatly impacts paleoclimatic proxies,especially with regard to surface samples,as well as groundwater age,but Holocene sediments are less affected.Results from global studies indicate that the major changing trend of the wet/dry status of closed basins is associated with the movement of the westerly jet streams controlled by long-term changes in winter insolation.There is an abrupt change between 1800 AD and 1900 AD,according to a numerical synthesis of paleoclimatic proxies from global closed basins,which can be linked to human impact.We suggest this time period can be considered as a start point for the Anthropocene based on the sedimentary evidence of closed basins,globally.
基金supported by National Natural Science Foundation of China (Grant Nos. 61302078 and 61372108)National High-tech R&D Program of China (863 Program) (Grant Nos. 2011AA01A102)+1 种基金National S&T Major Project (Grant Nos. 2011ZX 03005-004-02)Beijing Higher Education Young Elite Teacher Project (Grant Nos. YETP0476)
文摘The recent evolution of the Internet towards "Information-centric" transfer modes has renewed the interest in exploiting proxies to enhance seamless mobility. In this work, we focus on the case of multiple levels of proxies in ICN architectures, in which content requests from mobile subscribers and the corresponding items are proactively cached to these proxies at different levels. Specifically, we present a multiple-level proactive caching model that selects the appropriate subset of proxies at different levels and supports distributed online decision procedures in terms of the tradeoff between delay and cache cost. We show via extensive simulations the reduction of up to 31.63% in the total cost relative to Full Caching, in which caching in all 1-level neighbor proxies is performed, and up to 84.21% relative to No Caching, in which no caching is used. Moreover, the proposed model outperforms other approaches with a flat cache structure in terms of the total cost.
基金supported by the National Natural Science Foundation of China(Grant Nos.41371009 and 41001116)the Fundamental Research Fund for the Central Universities(Grant Nos.lzujbky-2013-127 and lzujbky-2013-129)
文摘This paper examines the relationship among organic geochemical proxies （TOC, C/N ratio and ~13C） and pollen assemblages in Zhuye Lake sediments since the Late Glacial. Results show that the reaction extent of organic geochemical proxies and pollen as- semblages to environment changes are different. Organic geochemical proxies are sensitive to overall environmental change, while pollen assemblages indicate detailed information of environmental change. For the entire sedimentary section （except the sand layer fi＇om the bottom of the section）, when values of TOC, C/N ratio and total pollen concentrations are high, 813C values are low, and vice versa. The different responses of organic geochemical proxies and pollen records in Zhuye Lake are mainly due to their different sensitivity and diverse influencing factors in different environmental conditions.
文摘Introduction: In older populations, the help of a third person may be necessary for a certain number of individuals in order to fill in questionnaires. The influence of this assistance on the collected information can raise questions, among others concerning the concordance between the information provided by the persons themselves and by their proxies, or the introduction of a potential bias. Our study’s objective is to examine, among older people, the differences in the reported frequency of falls, fear of falling and activity restriction due to fear of falling, according to the fact that people had filled in a questionnaire with or without the help of a third person. Methods: The data used come from the secondary analysis of a cross-sectional survey using a self-administered questionnaire and conducted in 2006 in a Belgian semi-rural town among non-institutionalised persons aged 65 years and over. Results: Among the 501 questionnaires, 16.4% were filled in with the help of another person. In bivariate analysis, the persons who needed help reported fall history, fear of falling and activity restriction significantly more often. In multivariable analysis, when considering concurrently the covariates (sex, age, living alone and fall history for fear of falling and for activity restriction), the influence of having received help to fill in the survey was only significant for activity restriction. Conclusion: Our study shows that it is important to know whether or not a person has received help to fill in a questionnaire. This can actually influence the reported frequency of certain outcomes, even, for activity restriction, when considering simultaneously the effect of other covariates. Given the current and future ageing of our populations, it seems that more extensive exploration is needed of the influence of proxies on the collected information about falls, fear of falling and activity restriction among older people.
文摘Sedimentary TOC （total organic carbon）, TN （total nitrogen） and C/N （carbon/nitrogen） at selected sites of Lake Victoria basin have provided evidence of phytoplankton productivity, input of nitrates and allochthonous （land） plant materials/catchment destruction in the basin during the late Holocene period （last 4,000 years to present）. TOC and TN in the sediment cores were determined using EuroEA3000 Series Elemental Analyser and radiocarbon dating done using AMS （accelerator mass spectrometry） standard method. Results showed that TOC （13.45%-20.78%） and TN （1.07%-1.92%） values were higher at Napoleon Gulf from about 4,186 years before present （ca. 4,186 yr. BP） to present than at inlet of river Kagera （TOC： 3.27%-6.32% and TN： 0.30%-0.59%） from about 190 years before present （ca. 190 yr. BP） to present. Generally TOC and TN had a negative correlation （r = -0.37, p = 0.04, n = 32） at Napoleon Gulf in the last 4,186 years to present signifying that C/N ratios were governed mostly by phytoplankton productivity which markedly increased during some periods in the last 370 years to present possibly as a result of increased input of nitrates. However, the periods from about 4,186 years to 1,684 years before present （ca. 4,186 yr. BP to 1,684 yr. BP） and some periods between the last 370 years to present indicated increased input of allochthonous plant materials/catchment destruction. On overall, there was a positive correlation between C/N and TOC at inlet of river Kagera （r = 0.57, p = 0.01, n = 20） in the last 190 years to present possibly signifying that C/N ratios were governed mainly by input of allochthonous plant materials hence increased catchment destruction. Input of land plant materials （catchment destruction） along Kagera basin declined during some period after 1950 AD. However the most recent years have shown increased input of land plant materials （catchment destruction） in Kagera basin.
基金granted by the National Natural Science Foundation of China(grants No.41306064 and 41376075)
文摘Objective Located at the interface of terrestrial and marine ecosystems, mangroves are particularly sensitive to environmental changes. They provide a sedimentary sink for organic carbon, whereby core samples could provide detailed records of mangrove evolution. Human induced, rapid environmental changes in recent years require a better understanding of the mangrove ecosystems evolution in the past, by reconstructing the past mangrove dynamics using triterpenols recorded in sediments. The aim of our work is to improve the application of triterpenols as biomarkers for mangrove development in long term in China.
文摘Usage of methods for determination of long-term trends of the dynamics of vegetation formation on the background of climate changes becomes more and more important at modern stage of the assessment of natural systems development. This causes to researchers a series of problems from choice of conceptual base to notions and terms of the processes identified and of state of vegetation of different environments. Solution of such a task results inevitably in necessity to correct the understanding of existing processes occurring in the vegetation cover. It allows establishing a direction of their development in the system of natural factors of any territory. As a result, we have base for determination of age, site and role of current state of phytocenoses in successional systems. It is necessary for this to reveal the peculiarities of phytocenoses composition and formation due to climate dynamics and to determine a period of ecosystems homeostasis, especially for phytocenoses of contact natural conditions. Optimal values of phytocenoses diversity, like one of whole biosystems, depend on the amount of resource in the environment, on stability degree and on evolutional development of cenoses due to ecological, micro-evolutional and evolutional processes.
文摘Currently available proxies were studied as networks for building reconstruction models of the Atlantic Multidecadal Oscillation (AMO). Only proxies that would double the current record length (backwards in time from AD 1564) were included. We present two proxy networks and corresponding reconstruction (transfer) models, one for tree-growth based proxies only and another for multiproxies. Both of them show a useful match in timing as well as amplitude with the AMO. These model structures demonstrated reasonable model performance (overall r<sup>2</sup> = 0.45 - 0.36). The time stability of proxy-AMO relationships was also validated. The new models produced acceptable results in cross-calibration-verification (reduction of error and coefficient of efficiency statistics in 1856-1921 and 1922-1990 vary between 0.41 and 0.21). The spatial distribution of these data series indicate that proxies respond to an AMO-like climatic oscillation over much of the Northern Hemisphere.
基金Research Project Numbers PIUNT E642 and PIP 2957supported by National Science Foundation Grant Number AGS-2152365
文摘Four extreme ultraviolet(EUV)solar radiation proxies(Magnesium II core-to-wing ratio(MgII),Lymanαflux(Fα),10.7-cm solar radio flux(F10.7),and sunspot number(Rz))were analyzed during the last four consecutive solar activity minima to investigate how they differ during minimum periods and how well they represent solar EUV radiation.Their variability within each minimum and between minima was compared by considering monthly means.A comparison was also made of their role in filtering the effect of solar activity from the critical frequency of the ionospheric F2 layer,foF2,which at mid to low latitudes depends mainly on EUV solar radiation.The last two solar cycles showed unusually low EUV radiation levels according to the four proxies.Regarding the connection between the EUV“true”variation and that of solar proxies,according to the foF2 filtering analysis,MgII and Fαbehaved in a more stable and suitable way,whereas Rz and F10.7 could be overestimating EUV levels during the last two minima,implying they would both underestimate the inter-minima difference of EUV when compared with the first two minima.
文摘Using artificial intelligence(AI) and machine learning(ML) techniques, we developed and validated the smart proxy models for history matching of reservoir simulation, sensitivity analysis, and uncertainty assessment by artificial neural network(ANN). The smart proxy models were applied on two cases, the first case study investigated the application of a proxy model for calibrating a reservoir simulation model based on historical data and predicting well production while the second case study investigated the application of an ANN-based proxy model for fast-track modeling of CO2 enhanced oil recovery, aiming at the prediction of the reservoir pressure and phase saturation distribution at injection stage and post-injection stage. The prediction effects for both cases are promising. While a single run of basic numerical simulation model takes hours to days, the smart proxy model runs in a matter of seconds, saving 98.9% of calculating time. The results of these case studies demonstrate the advantage of the proposed workflow for addressing the high run-time, computational time and computational cost of numerical simulation models. In addition, these proxy models predict the outputs of reservoir simulation models with high accuracy.
基金supported by the National Ocean Welfare Research Funds of State Ocean Administration (No.201105012)
文摘Geochemical ratios in coral reef skeletons could be used as proxies to reconstruct past climatological and environmental records in data-poor regions. Using a 103-year data set(1902 to 2005), the annual variations in Ba/Ca and Mn/Ca ratios of Porites lutea skeletons at an eastern offshore area of Hainan Island(19?12'28.4''N, 110?37'38.8''E) were analyzed using inductively coupled plasma-optic emission spectrometry(ICP-OES). The analysis results showed that Ba/Ca ratios varied from a minimum of 3.120 μmol mol^(-1) in 1903 to a maximum of 10.064 μmol mol^(-1) in 1944, with an average of 5.256 μmol mol^(-1). Mn/Ca ratios varied from 0.206 to 5.708 μmol mol^(-1) with an annual average of 1.234 μmol mol^(-1), with peak values in 2001, 1964 and 1932, that correlated with strong rainfall events caused by typhoons. Variation in Ba/Ca and Mn/Ca ratios were compared with available river discharge and precipitation records, providing insight into past climatological events. Human activities and their indirect effects could impact the strength of the relationship between Ba/Ca and Mn/Ca ratios and observed precipitation and terrestrial input in the future.
基金supported by the National Natural Science Foundation of China (Grant No. 40675035)the National High Technology Research and Development Program of China (Grant No. 2008AA121704)the National Key Technologies R&D Program of China (Grant No. 2009BAC51B05)
文摘Based on multiple proxies from the Southern Hemisphere, an austral summer (December-January-February: DJF) Antarctic Oscillation Index (AAO) since 1500 A.D. was reconstructed with a focus on interannual to interdecadal variability (<50 a). By applying a multivariate regression method, the observational AAO-proxy relations were calibrated and cross-validated for the period of 1957 89. The regressions were employed to compute the DJF-AAO index for 1500 1956. To verify the results, the authors checked the explained variance (r 2 ), the reduction of error (RE), and the standard error (SE). Cross-validation was performed by applying a leave-one-out validation method. Over the entire reconstruction period, the mean values of r 2 , RE, and SE are 59.9%, 0.47, and 0.67, respectively. These statistics indicate that the DJF-AAO reconstruction is relatively skillful and reliable for the last ～460 years. The reconstructed AAO variations on the interannual and interdecadal timescales compare favorably with those of several shorter sea level pressure (SLP)-based AAO indices. The leading periods of the DJF-AAO index over the last 500 years are ～2.4, ～2.6, ～6.3, ～24.1, and ～37.6 years, all of which are significant at the 95% level as estimated by power spectral analysis.
文摘This paper discusses an approach to share a smart card in one machine with other machines accessible on the local network or the Internet. This allows a user at a browser to use the shared card remotely and access web applications that requiresmart card authentication. This also enables users to access these applications from browsers and machines that do not have the capability to use a smart card. The approach uses proxies and card reader code to provide this capability to the requesting device.Previous work with remote or shared smart card use either requires continuous access to the smart card machine or specific client software. The approach in this paper works for any device and browser that has proxy settings, creates minimal network traffic and computation on the smart card machine, and allows the client to transfer from one network to another while maintaining connectivity to a server. This paper describes the smart card sharing approach, implementation and validation of the approach using real systems, and security implications for an enterprise using smart cards.
基金supported by the National Key Basic Research Program of China (Grant No. 2013CB955703), National Key Basic Research Program of China (Grant No. 2013CB429701)the National Natural Science Foundation of China (Grant No. 91028005)+4 种基金the China Geological Survey (Grant No. GZH201100203)the Fundamental Research Funds for the Central Universitiesthe "National Thousand Talents" Program through the State Key Laboratory of Marine Geology at Tongji Universitythe DFG to GJMV Heisenberg Grant (Grant No. VE486/2-2)the Project of Shanghai Engineering Research Center of Hadal Science and Technology (Grant No. 14DZ2250900)
文摘We reconstruct the environmental evolution of the East China Sea in the past 14 kyr based on glycerol dialkyl glycerol tetraethers(GDGTs) in a sediment core from the subaqueous Yangtze River Delta. Two primary phases are recognized. Phase I(13.8–8 cal kyr BP) reflects a predominantly continental influence, showing distinctly higher concentrations of branched GDGTs(averaged 143 ng/g dry sediment weight, dsw) than isoprenoid GDGTs(averaged 36 ng/g dsw), high BIT index(branched vs. isoprenoid tetraethers) values(>0.78) and a fluctuating GDGT-0/crenarchaeol ratio(R_(0/5), varied from 0.52 to 3.81). Within this interval, temporal increases of terrestrial and marine influence are attributed to Younger Dryas(YD)(ca. 12.9–12.2 cal kyr BP) cold event and melt-water pulse(MWP)-1B(11.5–11.1 cal kyr BP), respectively. The prominent transition from 8 to 7.9 cal kyr BP shows a sharp decrease in BIT index value(<0.4) and increase in crenarchaeol, which marks the beginning of phase II. Afterwards, the proxies remain relatively constant, which indicates that phase II(7.9 cal kyr BP-present) is a shelf sedimentary environment with high stand of sea level. Overall, the BIT index in our record serves as a good marker for terrestrial influence at the site, and likely reflects the flooding history of the region. The TEX_(86)(Tetra Ether Index of tetraethers consisting of 86 carbons) proxy is not applicable in phase I because of an excess terrestrial influence; but it seems to be valid for revealing the annual SST in phase II(21.6±0.9°C, n=49). In contrast, the MBT'/CBT(Methylation of Branched Tetraethers and Cyclization of Branched Tetraethers) proxy appears to faithfully record the annual mean air temperature(MAT)(14.3±0.63°C, n=68) and presents an integrated signal over the middle and lower Yangtze River drainage basin.
基金supported in part by the National Science and Technology Council of Taiwan under the contract numbers NSTC 114-2221-E-019-055-MY2 and NSTC 114-2221-E-019-069.
文摘Cloud services,favored by many enterprises due to their high flexibility and easy operation,are widely used for data storage and processing.However,the high latency,together with transmission overheads of the cloud architecture,makes it difficult to quickly respond to the demands of IoT applications and local computation.To make up for these deficiencies in the cloud,fog computing has emerged as a critical role in the IoT applications.It decentralizes the computing power to various lower nodes close to data sources,so as to achieve the goal of low latency and distributed processing.With the data being frequently exchanged and shared between multiple nodes,it becomes a challenge to authorize data securely and efficiently while protecting user privacy.To address this challenge,proxy re-encryption(PRE)schemes provide a feasible way allowing an intermediary proxy node to re-encrypt ciphertext designated for different authorized data requesters without compromising any plaintext information.Since the proxy is viewed as a semi-trusted party,it should be taken to prevent malicious behaviors and reduce the risk of data leakage when implementing PRE schemes.This paper proposes a new fog-assisted identity-based PRE scheme supporting anonymous key generation,equality test,and user revocation to fulfill various IoT application requirements.Specifically,in a traditional identity-based public key architecture,the key escrow problem and the necessity of a secure channel are major security concerns.We utilize an anonymous key generation technique to solve these problems.The equality test functionality further enables a cloud server to inspect whether two candidate trapdoors contain an identical keyword.In particular,the proposed scheme realizes fine-grained user-level authorization while maintaining strong key confidentiality.To revoke an invalid user identity,we add a revocation list to the system flows to restrict access privileges without increasing additional computation cost.To ensure security,it is shown that our system meets the security notion of IND-PrID-CCA and OW-ID-CCA under the Decisional Bilinear Diffie-Hellman(DBDH)assumption.
基金supported in part by the National Science and Technology Council of Republic of China under the contract numbers NSTC 114-2221-E-019-055-MY2NSTC 114-2221-E-019-069.
文摘Cloud data sharing is an important issue in modern times.To maintain the privacy and confidentiality of data stored in the cloud,encryption is an inevitable process before uploading the data.However,the centralized management and transmission latency of the cloud makes it difficult to support real-time processing and distributed access structures.As a result,fog computing and the Internet of Things(IoT)have emerged as crucial applications.Fog-assisted proxy re-encryption is a commonly adopted technique for sharing cloud ciphertexts.It allows a semitrusted proxy to transforma data owner’s ciphertext into another re-encrypted ciphertext intended for a data requester,without compromising any information about the original ciphertext.Yet,the user revocation and cloud ciphertext renewal problems still lack effective and secure mechanisms.Motivated by it,we propose a revocable conditional proxy re-encryption scheme offering ciphertext evolution(R-CPRE-CE).In particular,a periodically updated time key is used to revoke the user’s access privileges while an access condition prevents a malicious proxy from reencrypting unauthorized ciphertext.We also demonstrate that our scheme is provably secure under the notion of indistinguishability against adaptively chosen identity and chosen ciphertext attacks in the random oracle model.Performance analysis shows that our scheme reduces the computation time for a complete data access cycle from an initial query to the final decryption by approximately 47.05%compared to related schemes.
基金supported by Croatian Science Foundation Research Project Dinaridic Foreland Basin between Two Eocene Thermal Optima:A Possible Scenario for the Northern Adriatic BREEMECO(No.2019-04-5775)。
文摘Hemipelagic to pelagic(H/P)marls,representing pelitic deposits,accumulated within the foredeep sub-basin of the Dinaric Foreland Basin(northern Neotethyan margin,present-day Croatia)during the Middle to Late Eocene.Syn-sedimentary tectonic movements,paleogeographic position and exchanges of short-lived hyperthermal episodes affected the sedimentation and related mineral and geochemical record of these deposits.Mineral(clay)assemblages bear signature of prevailing physical weathering with significant illite and chlorite content,but climatic seasonality is suggested by smectite-interlayered phases and sporadical increase of kaolinite content.Illite crystallinity varies significantly,and the lowest crystallinity is recorded by the Lutetian samples.Illite chemistry index is always bellow 0.5,being characteristic for Fe-Mg-rich illite.The geochemical records are the most prominent(CIA up to 76,CIW up to 91)for the Istrian Lutetian(42.3-40.5 Ma),but also for Priabonian(35.8-34.3 Ma)samples of Hvar Island.The ICV values(the lowest 1.40 and the highest 10.85)of all studied samples fall above PAAS(ICV=0.85)and point to their chemical immaturity.The Ga/Rb ratios are lower than 0.2 and K_(2)O/Al_(2)O_(3) ratios are also low(0.16-0.22),implying transition between cold and dry,and warm and humid climate,obviously trending among several warming episodes.
基金The National Key R&D Program of China under contract No. 2023YFC28 11305the Scientific Research Fund of the Second Institute of Oceanography,MNR under contract No. SZ2405the Impact and Response of Antarctic Seas to Climate Change under contract No. IRASCC
文摘Research on changes in the redox conditions of bottom waters is essential for understanding deep water circulation,global ocean currents,climate change,and ecosystem health.Through sedimentary geological methods,a deeper understanding of the complex relationships between various environmental changes can be achieved,providing detailed evidence and theoretical support for global climate change research.The Ross Sea in Antarctica plays a key role in the formation of Antarctic bottom water(AABW),and the complex climate changes since the last glacial maximum(LGM)make it particularly significant for study.This research analyzes core ANT32-RB16C from the Ross Sea using geochemical proxies such as major and trace elements,grain size,and redox-sensitive indicators like Mn/Ti,Co/Ti,Mo/Ti,Cd/Ti,U/Th,and Ni/Co molar concentration ratios.Combining this data with a previously established chronological framework,the study explores the evolution of redox conditions in the Ross Sea’s deep waters since the LGM.The results show that the deep waters have remained oxygen-rich since the LGM,with significant changes in four stages.Stage 1(24.7–15.7 cal ka BP):Strong oxidizing conditions,likely due to enhanced formation of Ross Sea bottom water(RSBW),increasing oxygen levels.Stage 2(15.7–4.5 cal ka BP):Weakened oxidizing conditions as temperatures rose and ice shelves retreated,increasing primary productivity and depleting oxygen.Stage 3(4.5–1.5 cal ka BP):Continued decline in oxidizing conditions,possibly linked to high primary productivity and oxygen consumption.Stage 4(1.5 cal ka BP to present):A rapid recovery of oxidizing conditions,likely driven by temperature drops,increased RSBW formation,and decreased productivity.
基金supported by the National Natural Science Foundation of China(Grant No.U24B20146)the National Key Research and Development Plan in China(Grant No.2020YFB1005500)Beijing Natural Science Foundation Project(No.M21034).
文摘With the rapid development of web3.0 applications,the volume of data sharing is increasing,the inefficiency of big data file sharing and the problem of data privacy leakage are becoming more and more prominent,and the existing data sharing schemes have been difficult to meet the growing demand for data sharing,this paper aims at exploring a secure,efficient and privacy-protecting data sharing scheme under web3.0 applications.Specifically,this paper adopts interplanetary file system(IPFS)technology to realize the storage of large data files to solve the problem of blockchain storage capacity limitation,and utilizes ciphertext policy attribute-based encryption(CP-ABE)and proxy re-encryption(PRE)technology to realize secure multi-party sharing and finegrained access control of data.This paper provides the detailed algorithm design and implementation of data sharing phases and processes,and analyzes the algorithms from the perspectives of security,privacy protection,and performance.
