Fan-Delta,Braid Delta and the Classification of Delta Systems

This paper mainly discusses the origin and deposhional features of fan-deltas and braid deltas. Fan-del-tas are storm discharge-dominated, while braid deltas are usually flashy flood-dominated. The two types ofdelta, like common deltas, were reworked by marine processes. Delta systems are classified into nine deltatypes on the basis of the subaerial depositional processes and the nature of marine reworking. Fan-deltas and braid deltas are of great significance for petroleum exploration. In divergent-marginforeland and intraplate rift-subsided basin settings fan-deltas often form combination traps for petroleum ac-cumulation.

Harmonic Propagation from the Low Voltage Four-Wire Delta Systems

The electric networks for the distribution to low voltage costumers can be configured in different layouts. Two main approaches are used: the European system composed by three-phase distribution transformers or the North American system composed by single-phase distribution transformers and three-phase transformer banks of single-phase transformers. With respect to harmonic analysis, much more attention has been focused on the three-phase balanced systems arrangements than on the unbalanced four-wire delta system extensively used to supply low voltage loads of 120/240 V. Different authors have shown the three-phase power systems modeling on a phase-coordinates frame. However, the presence of significant asymmetries in the network forces the need of adding a new phase-coordinates model to represent the three-phase transformers banks of two or three single-phase transformers in its various connections. Several papers treat the use of harmonic analysis programs based on a phase-coordinates frame to study the Wye or Delta connected three-phase systems. However, the commonly used four-wire delta connected systems are not fully treated in literature. This paper presents a phase-coordinates model for the representation of the commonly used three-phase transformer banks of three or two single-phase transformers, and single-phase distribution transformers for the harmonic analysis of the four-wire delta connected systems. The harmonic analysis method based on the presented model is used to examine the characteristics of this kind of distribution system with respect to the penetration of harmonics currents from loads to the primary system.

Control of slope-pattern on the deposition of fan-delta systems:a case study of the Upper Karamay Formation,Junggar Basin

The Mesozoic fan deltas in the north-west margin of the Junggar Basin,as important petroleum reservoirs,exhibited complex facies change and internal structures with strong heterogeneity which were controlled by the transformation of slope-patterns,bringing great challenges to the study of sedimentary characteristics.The Upper Karamay Formation at north-west margin of the Junggar Basin was the objective in this paper which attempts to clarify the mechanism of sedimentary response and sand-body distribution of fan delta systems under the control of slope-pattern change.Based on a data set of cores,well logs and seismic,two types of slope-pattern were identified in the study area,which include steep-to-gentle in the south and gentle-to-steep in the north.The control of difference slope-patterns on the sand-body distribution was clarified based on the analysis of the sedimentary dynamics,facies characteristics,and depositional evolution of the fan deltas.The study shows that the transport mechanism of sediments on the steep-slope was dominated by debris flows,developing coarse-grained,thick-bedded lobes with poor structural maturity of clasts.On the gentle-slope,the deposition was dominated by hyperconcentrated-traction currents,forming relatively fine-grained,thin-bedded lobes with increased sandy matrix.The sand-bodies show frequent bar-channel transformation and channel down-cutting under the steep slope setting,which exhibit migration of isolated river channels on the gentle slopes.Under the steep-to-gentle pattern,the coase-grained sediments were mainly accumulated at slope toe,generally developed equiaxial lobes.However,the coarse-grained clasts were preserved both at proximal and distal lobes on the gentle-to-steep slopes,showing obvious lateral extension of the fan delta.The slope patterns controlled sedimentary respond rates of the fan deltas during lake level change.By comparing the modern cases of fan systems worldwide,the control of slope patterns on deposition of coarse-grained fans was clarified,providing insight into hydrocarbon exploration on basin margins.

Impacts of multi-scenario land use change on ecosystem services and ecological security pattern: A case study of the Yellow River Delta

The Yellow River Delta(YRD), a critical economic zone along China's eastern coast, also functions as a vital ecological reserve in the lower Yellow River. Amidst rapid industrialization and urbanization, the region has witnessed significant land use/cover changes(LUCC), impacting ecosystem services(ES) and ecological security patterns(ESP). Investigating LUCC's effects on ES and ESP in the YRD is crucial for ecological security and sustainable development. This study utilized the PLUS model to simulate 2030 land use scenarios, including natural development(NDS), economic development(EDS), and ecological protection scenarios(EPS). Subsequently, the InVEST model and circuit theory were applied to assess ES and ESP under varying LUCC scenarios from 2010 to 2030. Findings indicate:(1) Notable LUCC from 2010 to 2030, marked by decreasing cropland and increasing construction land and water bodies.(2) From 2010 to 2020, improvements were observed in carbon storage,water yield, soil retention, and habitat quality, whereas 2020–2030 saw increases in water yield and soil retention but declines in habitat quality and carbon storage. Among the scenarios, EPS showed superior performance in all four ES.(3) Between 2010 and 2030, ecological sources, corridors, and pinchpoints expanded, displaying significant spatial heterogeneity. The EPS scenario yielded the most substantial increases in ecological sources,corridors, and pinchpoints, totaling 582.89 km^(2), 645.03 km^(2),and 64.43 km^(2), respectively. This study highlights the importance of EPS, offering insightful scientific guidance for the YRD's sustainable development.

Land Use Dynamics and Ecosystem Service Value Changes in the Yangtze River Delta Urban Agglomeration Under Different Scenarios

Urban agglomerations,serving as pivotal centers of human activity,undergo swift alterations in ecosystem services prompted by shifts in land utilization.Strengthening the monitoring of ecosystem services in present and future urban agglomerations contributes to the rational planning of these areas and enhances the well-being of their inhabitants.Here,we analyzed land use conversion in the Yangtze River Delta(YRD)urban agglomeration during 1990-2020 and discussed the spatiotemporal response and main drivers of changes in ecosystem service value(ESV).By considering the different development strategic directions described in land use planning policies,we predicted land use conversion and its impact on ESV using the Future Land Use Simulation(FLUS)model in three scenari-os in 2025 and 2030.Results show that:1)from 1990 to 2020,land use change is mainly manifested as the continuous expansion of con-struction land to cultivated land.Among the reduced cultivated land,82.2%were occupied by construction land.2)The land use types conversion caused a loss of 21.85 billion yuan(RMB)in ESV during 1990-2020.Moreover,the large reduction of cultivated land area led to the continuous decline of food production value,accounting for 13%of the total ESV loss.3)From 2020 to 2030,land use change will mainly focus on Yangzhou and Zhenjiang in central Jiangsu Province and Taizhou in southern Zhejiang Province.Under the BAU(natural development)and ED(cultivated land protection)scenarios,construction land expansion remains dominant.In contrast,under the EP(ecological protection)scenario,the areas of water bodies and forest land increase significantly.Among the different scenarios,ESV is highest in the EP scenario,making it the optimal solution for sustainable land use.It can be seen that the space use conflict among urban,agriculture and ecology is a key factor leading to ESV change in the urban agglomeration of Yangtze River Delta.There-fore,it is crucial to maintain spatial land use coordination.Our findings provide suggestions for scientific and rational land use planning for the urban agglomeration.

基于多模型和改进WOA算法的Delta机器人柔性夹持器抓取方法研究

[目的]解决Delta机器人柔性夹持器抓取方法存在的控制精度和适应性较差等问题。[方法]以Delta机器人柔性夹持器为研究对象,提出一种多模型和改进鲸鱼算法相结合的Delta机器人柔性夹持器抓取方法。建立稳定抓取优化模型,在抓持对象表面寻求最佳接触位置。建立无损抓取优化模型,在确保稳定抓起物体的前提下使接触力尽可能地小。结合粒子群算法和鲸鱼算法求解模型。通过试验验证了所提抓取方法的优越性。[结果]所提方法不仅具有良好的控制精度,还能够适应不同形状和大小的物体,具有较高的灵活性和适应性,抓取成功率>96%,抓取损伤率为0。[结论]所提方法有效提高了Delta机器人柔性夹持器抓取方法的性能,适用于果蔬和易碎物品的分拣工作。

Delta大通道内镜辅助下后路椎管减压椎间植骨融合术治疗退变性腰椎疾病的临床疗效

目的:探讨Delta大通道内镜辅助下后路椎管减压椎间植骨融合术治疗退变性腰椎疾病的效果。方法:回顾性分析2021年9月~2022年9月我院收治的80例退变性腰椎疾病患者的病历资料,根据患者治疗方式分为观察组(38例,男17例,女21例,年龄61.0±4.9岁)和对照组(42例,男20例,女22例,年龄60.5±5.4岁),观察组患者采取Delta大通道内镜下Endo-PLIF治疗,对照组采取开放后路腰椎椎间融合术治疗,记录两组患者术中出血量、术后引流量、手术时间、手术切口长度、住院时间,比较患者并发症发生情况。于术前、术后1周、1个月、3个月、6个月使用视觉模拟量表(visual analogue scale,VAS)评分评估患者腰痛情况,并采用Oswestry功能障碍指数(Oswestry disability index,ODI)评估患者腰椎功能;使用改良Macnab标准对患者进行疗效评估。根据患者术后1年随访时的腰椎影像学复查结果,使用Bridwell椎间融合标准对患者手术节段融合情况进行评估。结果:观察组患者的术中出血量及术后引流量分别低于对照组(88.46±10.98mL vs 112.99±12.01mL、159.73±18.42mL vs 201.36±23.06mL,P<0.05),手术切口及住院时间分别短于对照组(1.54±0.36cm vs 5.43±1.01cm、6.79±1.22d vs 8.03±1.43d,P<0.05),手术时间长于对照组(162.33±19.57min vs 126.87±23.15min,P<0.05)。80例患者术后均获随访,随访时间15~40个月(19.0±6.3个月)。观察组患者术后1周、术后1个月的VAS评分分别为2.46±0.51分、1.21±0.38分,ODI分别为(17.84±4.15)%、(10.69±1.88)%,均低于对照组[VAS评分分别为3.68±0.62分、2.01±0.41分,ODI分别为(21.33±3.48)%、(12.33±2.17)%,均P<0.05],两组患者术后3个月、术后6个月的VAS评分比较无统计学差异(P>0.05)。观察组治疗优良率为92.11%,与对照组的85.71%比较无统计学意义(P=0.487)。两组患者融合分级比较,差异无统计学意义(Z=0.487,P=0.624)。观察组术后并发症发生率为5.26%,与对照组的9.52%比较无统计学差异(P=0.678)。结论:Delta大通道内镜辅助下后路椎管减压椎间植骨融合术治疗退变性腰椎疾病效果良好,可以减少术中出血量,缩短手术切口和住院时间,更快改善患者术后短期内疼痛、腰椎功能,安全性较好。

单边双通道内镜与Delta大通道内镜技术治疗L5/S1椎间盘突出并椎管狭窄的临床疗效分析

目的 探讨Delta大通道内镜技术与单边双通道内镜技术(unilateral biportal endoscopy, UBE)治疗L5/S1单节段椎间盘突出并椎管狭窄的疗效。方法 回顾性分析2018年1月至2022年8月手术治疗的60例L5/S1单节段腰椎间盘突出并椎管狭窄患者的临床资料,其中32例采用Delta大通道内镜技术行经皮椎板间入路内镜下椎间盘切除术(Delta内镜组),28例采用UBE内镜技术行椎管减压髓核摘除术(UBE组)。比较两组围手术期指标、腰腿痛VAS评分、 ODI及并发症情况,末次随访时按Macnab标准评价疗效。结果 两组患者均顺利完成手术。Delta内镜组术中出血量少于UBE组,手术时间、住院时间短于UBE组(P<0.001)。两组患者术后腰腿痛VAS评分及ODI均较术前明显降低,且Delta内镜组术后3 d腰痛VAS评分及术后1月腿痛VAS评分均低于UBE组(P<0.05)。术后随访6个月,末次随访按Macnab标准评价疗效:Delta内镜组优30例,可2例,优良率为93.75%;UBE组优27例,可1例,优良率为96.43%;组间比较差异无统计学意义(P>0.05)。Delta内镜组硬膜撕裂1例,因撕裂处较小仅严密缝合手术切口;UBE组出现腿部疼痛加重1例。结论 Delta大通道内镜技术与UBE治疗L5/S1单节段椎间盘突出并椎管狭窄均可获得良好的近期效果,但Delta内镜手术术中出血少,软组织损伤小,操作时间短,术后短期疼痛缓解明显,患者恢复快,而UBE适应证范围相对广泛。

Delta并联机器人运动学性能分析与结构参数优化

Delta并联机器人具有速度快、结构简单、承载力强等优点,在钵苗移栽、产品分拣与包装中应用广泛。针对目前Delta并联机器人各结构参数对运动学性能的影响及系统性结构参数优化设计缺乏完整理论体系的问题,本文分析可达工作空间雅可比矩阵条件数分布规律、结构参数约束关系、运动学性能随结构参数的变化规律及相关性,获得条件数分布特性和失真约束条件,在此基础上得出动静平台半径差和主动臂长度增加和从动杆长度减小能够使得机构性能较优。给定设计工作空间,对原结构进行参数优化设计,通过建立包络惩罚函数,采用多元非线性拟合与线性加权组合法得到运动学性能评价函数,结合条件数分布特性和失真约束条件建立优化模型,利用遗传算法进行优化。相较于优化前,优化后可达工作空间体积减小14.26%,设计工作空间的全局条件数均值和全局条件数标准差分别减小31.20%和11.78%,且设计工作空间各截面条件数分布规律验证了条件数分布特性的可靠性。

Delta型FDM打印设备结构参数设定及运动学研究

FDM打印设备的扫描路径、打印速度、温度、层厚等问题是影响制件外形精度和成型效率的工艺参数的重要因素。Delta型结构作为最常用的FDM设备结构型式之一,其末端打印头的运动由多杆共同作用,运动分析较繁琐,为设备的参数设定增添了很大的难度,存在参数设定和运动分析难的问题。从Delta型的结构分析出发,重点研究了各结构尺寸之间的关联,总结了参数设定和计算的依据。考虑到Delta结构的打印头与3个滑车之间坐标的对应关系并不能通过简单推算得出,需要大量的三角函数运算,建立了Delta型结构的正、逆解运动学模型,结合几何的方式详细推导了运动学反解和正解的解法,分析和求解的结果为设定Delta型设备参数和确定控制程序算法提供了理论依据。经过分析与计算,基于并联机构内核的Delta结构采用正运动求解更便于规避正解集合中的不合理结果。

基于Delta分位数映射法的青藏高原中东部IMERG卫星降水误差订正

可靠的降水资料对理解青藏高原水量平衡和水循环过程尤为重要。IMERG(Integrated MultisatellitE Retrievals for Global Precipitation Measurement)是新一代卫星降水产品,具有更广的覆盖范围与更高的时空分辨率,但在高原复杂地形条件下仍然存在较大的不确定性。鉴于此,本研究应用Delta分位数映射法(Quantile Delta Mapping,QDM),对IMERG日降水数据进行偏差订正,使用2001-2010年的中国区域地面气象要素数据集(China Meteorological Forcing Dataset,CMFD)降水数据和IMERG日降水产品分季节建立传递函数,对2011-2014年的IMERG逐日降水进行订正。研究结果表明:(1)Delta分位数映射法能够有效订正IMERG的降水频率、数值和空间分布,对极端降水和负偏差较大区域的订正效果更为明显。订正后的IMERG降水概率分布更加接近观测概率分布,降水偏差也更符合正态分布,改进了对全年和季节降水空间分布的刻画,提高了月降水的精度。(2)订正后日降水量均方根误差由1.49 mm·d^(-1)降低到1.26 mm·d^(-1),精度提高了15.44%;订正后的日降水在不同降水量级的临界成功指数CSI、命中率POD、误报率FAR、准确率Precision和F评分Fscore均有提高,降低了微量和暴量降水的空报率。(3)对极端降水的订正效果显著,降水强度SDII以及极强降水量R95p和R99p的均值更接近观测值;有效提高了对极端降水空间分布的表征,极端降水偏差从30%以上降低到5%以内;SDII、R95p和R99p的均方根误差从1.59 mm·d^(-1)、6.54 mm·d^(-1)、14.89 mm·d^(-1)降为0.65 mm·d^(-1)、3.01 mm·d^(-1)、8.99 mm·d^(-1),精度分别提高了59.12%、53.98%和39.62%。本研究验证了Delta分位数映射法在青藏高原的适用性,有利于为青藏高原气象和水文研究获取更精确的降水数据。

一种具有1~128倍可变增益放大器的低功耗Sigma⁃Delta ADC

为满足传感器应用的低功耗需求,设计并实现了一种低功耗Sigma⁃Delta模数转换器(ADC)芯片。该ADC采用一阶全差分开关电容Sigma⁃Delta调制器,且集成了可编程增益放大器(PGA)和Bandgap;使用1.5 bit量化结构,相较于1 bit量化结构减小了3 dB的量化误差;使用优化的反馈电路,减小了电容失配引入的误差;PGA采用轨到轨的运放电路拓扑,增大了整个芯片的电压适应范围。基于180 nm CMOS工艺对该ADC进行了设计和流片。测试结果表明:该Sigma⁃Delta ADC在采样频率512 kHz、过采样率(OSR)为256时,峰值信噪谐波失真比(SNDR)和有效位数(ENOB)分别为75.29 dB和12.21 bit,芯片功耗仅为0.92 mW。芯片能在2.3~5.5 V宽电源电压范围内正常工作,可实现最大128 V/V的增益。适用于小型传感器的信号测量应用,可以满足小型传感器低功耗、高精度的需求。

Palaeogeographical development of two merging delta systems(Eocene Shahejie Formation)in the Bohai Bay Basin,E China and implications for hydrocarbon exploration

Two deltas developed simultaneously during the Eocene on the eastern side of a large lake that existed in the Dongying Sub-basin,which forms part of the Bohai Bay Basin in eastern China.The rivers that built the deltas had different catchment areas,which resulted in sediments with different permeability and porosity,due to differences in sorting and mud content.Both deltas prograded,and mass flows that originated frequently on their fronts formed lobes that expanded laterally.This eventually led to merging of both deltas,a feature that has rarely been described from ancient deposits thus far.Core analysis and seismic reflection data show that the merging of the two deltas took place in nine phases,determined by phases of slower progradation or even temporary retrogradation in between.The alternation of sediments from both deltas and their eventual mixing makes the architecture of the merged deltas much more complex than that of'classical'single deltas.This affects the predictability of the spatial distribution of possible reservoir characteristics significantly,but detailed core analysis shows that the best hydrocarbon reservoirs consist of sand bodies formed in distributary channels on the delta plains,and of sandy turbidites formed in the deep-lacustrine environment in front of the merged deltas.

首次从湖南猪源大肠杆菌中检出mcr-1阳性IncI2(Delta)质粒

近年来,由于抗生素耐药基因的广泛传播及多重耐药细菌的出现,导致抗生素的使用面临严峻挑战,致使毒性较强的多黏菌素又重新引起业界的重视,为此对多黏菌素耐药情况的研究也变得十分重要。为了调查畜牧场中多黏菌素耐药基因mcr-1的流行情况,本研究选择我国湖南省某猪场240份肠肛拭子样品,培养分离鉴定出含有mcr-1耐药基因的大肠杆菌菌株,选取多黏菌素等10种抗菌药物对分离的菌株进行耐药性试验,对所有含mcr-1耐药基因的大肠杆菌阳性株进行全基因组测序(whole-genome sequencing,WGS),采用多位点序列分型(multi-locus sequence typing,MLST)技术进行大肠杆菌的遗传多样性分析。研究结果表明,在分离出的172株大肠杆菌中,来自不同个体的9株携带mcr-1基因的大肠杆菌均表现出多重耐药现象;MLST分析共鉴定出ST10、ST196、ST46和ST5229共4种分型和4种血清型(O83:H5,O16:H7,O16:H51,O9:H4)。生物信息学分析显示,所有阳性菌株均未发现与mcr-1基因传播有关的典型可移动遗传元件ISApl1,但均检出可能会导致mcr-1传播的IV型分泌系统基因。质粒接合转移试验与单倍型的MLST多态性结果表明,mcr-1基因主要以质粒介导的水平传播为主。本研究是国际上首次在猪源细菌中检出常见于人医临床细菌的携带有mcr-1抗性基因的IncI2(Delta)质粒。

Delta超声组学对早期乳腺癌新辅助治疗疗效的预测价值

目的探讨Delta超声组学对乳腺癌新辅助治疗(NAT)后疗效的预测价值。方法将140例乳腺癌新辅助治疗患者按照软件中的随机种子数以7∶3比例分成训练集(98例)及验证集(42例)。基于肿瘤NAT治疗前、NAT治疗2个疗程后最大径相对退缩值构建传统影像模型;基于治疗前与2个疗程后的超声图像提取和筛选相应影像组学特征并计算其Delta,构建Delta超声组学模型并计算其影像组学得分(Radscore);基于有意义的临床病理指标结合Radscore构建综合模型,采用受试者操作特征曲线(ROC)评估模型预测乳腺癌NAT后病理完全缓解(pCR)的效能,比较它们的曲线下面积(AUC)、准确度、灵敏度、特异度。使用临床校正曲线与临床决策曲线对模型进行评估与对比。结果综合模型预测pCR的效能最佳,其AUC值在训练集与验证集分别达0.92、0.85;其次为Delta超声组学模型,AUC分别为0.80、0.82;传统影像模型效能最低,AUC分别为0.67、0.72。临床校准曲线显示综合模型预测值与实际值一致性较高,临床决策曲线显示综合模型优于其他两种模型。结论Delta超声组学是早期预测乳腺癌NAT疗效的标记物。基于Delta超声组学结合临床病理指标构建的综合模型可作为早期准确预测NAT疗效的评估手段。

Numerical study on local scour characteristics around submarine pipelines in the Yellow River Delta silty sandy soil under waves and currents

Due to their high reliability and cost-efficiency,submarine pipelines are widely used in offshore oil and gas resource engineering.Due to the interaction of waves,currents,seabed,and pipeline structures,the soil around submarine pipelines is prone to local scour,severely affecting their operational safety.With the Yellow River Delta as the research area and based on the renormalized group(RNG)k-εturbulence model and Stokes fifth-order wave theory,this study solves the Navier-Stokes(N-S)equation using the finite difference method.The volume of fluid(VOF)method is used to describe the fluid-free surface,and a threedimensional numerical model of currents and waves-submarine pipeline-silty sandy seabed is established.The rationality of the numerical model is verified using a self-built waveflow flume.On this basis,in this study,the local scour development and characteristics of submarine pipelines in the Yellow River Delta silty sandy seabed in the prototype environment are explored and the influence of the presence of pipelines on hydrodynamic features such as surrounding flow field,shear stress,and turbulence intensity is analyzed.The results indicate that(1)local scour around submarine pipelines can be divided into three stages:rapid scour,slow scour,and stable scour.The maximum scour depth occurs directly below the pipeline,and the shape of the scour pits is asymmetric.(2)As the water depth decreases and the pipeline suspension height increases,the scour becomes more intense.(3)When currents go through a pipeline,a clear stagnation point is formed in front of the pipeline,and the flow velocity is positively correlated with the depth of scour.This study can provide a valuable reference for the protection of submarine pipelines in this area.

基于事件触发的Delta算子网络控制系统故障检测

针对网络控制系统在高速采样情况下,网络中由于通信网络带宽受限发生时延和丢包所引起的故障问题,文中采用了基于事件触发机制和Delta算子相结合的故障检测方法。在对故障检测滤波器和控制器进行协同设计的同时,在Delta算子滤波器模型中加入构造向量,避免了参数设计时双线性项的产生。构造δ域的Lyapunov-Krasovskii泛函,对残差系统的稳定性和H∞性能进行分析。数值仿真实例验证了文中所提事件触发机制的有效性,并通过残差评价函数证明了其对故障的灵敏度较高。

油茶果动态抓取Delta机器人正运动学特性研究

针对传统D-H参数法求解机械臂运动学时过程比较复杂的问题,为满足油茶果动态抓取的要求,提出了一种基于旋量理论构建3-R(SS)2Delta机器人正运动学方程的方法。针对3-R(SS)2Delta机器人的结构进行分析;通过旋量理论的指数积公式对该机器人的正运动学特性进行研究,获得机器人的位姿变换矩阵;最后,通过搭建的Delta机器人试验平台运行标准门型轨迹,结果表明:Delta机器人末端执行器能够精准地对传送带上移动的油茶果进行抓取。对比分析正运动学方程的计算值和Delta机器人试验平台试验测量值,得到末端执行器位置值的位置误差为±0.3mm,验证了所提出方法对构建油茶果动态抓取Delta机器人正运动学方程的正确性及可行性,旨在为后续进行油茶果动态抓取的轨迹规划研究奠定基础。

Real-world effectiveness of mRNA COVID-19 vaccines in the elderly during the Delta and Omicron variants:Systematic review

BACKGROUND As of 31 December 2022,there were over 6.6 million coronavirus disease 2019(COVID-19)deaths and over 651 million cases across 200 countries worldwide.Despite the increase in vaccinations and booster shots,COVID-19 cases and deaths continue to remain high.While the effectiveness of these vaccines has already been established by different manufacturers,the fact remains that these vaccines were created quickly for global emergency use,tested under controlled clinical conditions from voluntary subjects and age groups whose general characteristics may differ from the actual general population.AIM To conduct a systematic review to determine the real-world effectiveness of mRNA COVID-19 vaccines in the elderly during the predominance of Delta and Omicron variants in preventing COVID-19 related infection,hospital,intensive care unit(ICU)admission and intubation,and death.METHODS A combination of Medical Subject Headings and non–Medical Subject Headings was carried out to identify all relevant research articles that meets the inclusion and exclusion criteria from PubMed,Cochrane,CINAHL,Scopus,ProQuest,EMBASE,Web of Science,and Google Scholar databases,as well as qualified research studies from pre–print servers using medRxiv and Research Square,published from January 1,2021-December 31,2022.RESULTS As per the inclusion and exclusion criteria,the effectiveness of Pfizer-BioNTech and Moderna vaccines were evaluated from an estimated total study population of 26535692 using infection,hospital,ICU admission and intubation,and death as outcome measures from studies published between 2021 and 2022,conducted in New York,Finland,Canada,Costa Rica,Qatar,Greece,and Brazil.The risk of bias was evaluated using risk of bias in nonrandomized studies of interventions(ROBINS-I)tool for cohort,case-control,and cross-sectional studies.While clinical trial data on Pfizer-BioNTech and Moderna vaccines demonstrated 94%vaccine effectiveness in the elderly,the results in this study showed that vaccine effectiveness in real-world settings is marginally lower against infection(40%-89%),hospitalization(92%),ICU admission and intubation(98%-85%),and death(77%-87%)with an indication of diminished effectiveness of vaccine over time.Furthermore,2 doses of mRNA vaccines are inadequate and only provides interim protection.CONCLUSION Because of the natural diminishing effectiveness of the vaccine,the need for booster dose to restore its efficacy is vital.From a research perspective,the use of highly heterogeneous outcome measures inhibits the comparison,contrast,and integration of the results which makes data pooling across different studies problematic.While pharmaceutical intervention like vaccination is important to fight an epidemic,utilizing common outcome measurements or carrying out studies with minimal heterogeneity in outcome measurements,is equally crucial to better understand and respond to an international health crisis.

Occurrence,Spatial Distribution,Sources and Risk Assessment of Per-and Polyfluoroalkyl Substances in Surface Sediments of the Yellow River Delta Wetland

Per-and polyfluoroalkyl substances(PFASs)are emerging persistent organic pollutants(POPs).In this study,47 surface sediment samples were collected from the Yellow River Delta wetland(YRDW)to investigate the occurrence,spatial distribution,potential sources,and ecological risks of PFASs.Twenty-three out of 26 targeted PFASs were detected in surface sediment samples from the YRDW,with totalΣ23PFASs concentrations ranging from 0.23 to 16.30 ng g^(-1) dw and a median value of 2.27 ng g^(-1) dw.Perfluorooctanoic acid(PFOA),perfluorobutanoic acid(PFBA)and perfluorooctanesulfonic acid(PFOS)were the main contaminants.The detection frequency and concentration of perfluoroalkyl carboxylic acids(PFCAs)were higher than those of perfluoroal-kanesulfonic acids(PFSAs),while those of long-chain PFASs were higher than those of short-chain PFASs.The emerging PFASs substitutes were dominated by 6:2 chlorinated polyfluoroalkyl ether sulfonic acid(6:2 Cl-PFESA).The distribution of PFASs is significantly influenced by the total organic carbon content in the sediments.The concentration of PFASs seems to be related to human activities,with high concentration levels of PFASs near locations such as beaches and villages.By using a positive matrix factorization model,the potential sources of PFASs in the region were identified as metal plating mist inhibitor and fluoropolymer manufacturing sources,metal plating industry and firefighting foam and textile treatment sources,and food packaging material sources.The risk assessment indicated that PFASs in YRDW sediments do not pose a significant ecological risk to benthic organisms in the region overall,but PFOA and PFOS exert a low to moderate risk at individual stations.