Exploring the associations between skeletal muscle echogenicity and physical function in aging adults:A systematic review with meta-analyses

Background:Assessment and quantification of skeletal muscle within the aging population is vital for diagnosis,treatment,and injury/disease prevention.The clinical availability of assessing muscle quality through diagnostic ultrasound presents an opportunity to be utilized as a screening tool for function-limiting diseases.However,relationships between muscle echogenicity and clinical functional assessments require authoritative analysis.Thus,we aimed to(a) synthesize the literature to assess the relationships between skeletal muscle echogenicity and physical function in older adults(≥60 years),(b) perform pooled analyses of relationships between skeletal muscle echogenicity and physical function,and(c) perform sub-analyses to determine between-muscle relationships.Methods:CINAHL,Embase,MEDLINE,PubMed,and Web of Science databases were systematically searched to identify articles relating skeletal muscle echogenicity to physical function in older adults.Risk-of-bias assessments were conducted along with funnel plot examination.Meta-analyses with and without sub-analyses for individual muscles were performed utilizing Fisher's Z transformation for the most common measures of physical function.Fisher's Z was back-transformed to Pearson's r for interpretation.Results:Fifty-one articles(n=5095,female=~2759,male=~2301,72.5± 5.8 years,mean±SD(1 study did not provide sex descriptors))were extracted for review,with previously unpublished data obtained from the authors of 13 studies.The rectus femoris(n=34) and isometric knee extension strength(n=22) were the most accessed muscle and physical qualities,respectively.The relationship between quadriceps echogenicity and knee extensor strength was moderate(n=2924,r=-0.36(95% confidence interval:-0.38 to-0.32),p <0.001),with all other meta-analyses(grip strength,walking speed,sit-to-stand,timed up-and-go) resulting in slightly weaker correlations(r:-0.34 to-0.23,all p <0.001).Sub-analyses determined minimal differences in predictive ability between muscle groups,although combining muscles(e.g.,rectus femoris+vastus lateralis) often re sulted in stronger correlations with maximal strength.Conclusion:While correlations are modest,the affordable,portable,and noninvasive ultrasonic assessment of muscle quality is a consistent predictor of physical function in older adults.Minimal between-muscle differences suggest that echogenicity estimates of muscle quality are systemic.Therefore,practitioners may be able to scan a single muscle to estimate full-body skeletal muscle quality/composition,while researchers should consider combining multiple muscles to strengthen the model.

Multi-scale Modeling and Finite Element Analyses of Thermal Conductivity of 3D C/SiC Composites Fabricating by Flexible-Oriented Woven Process

Thermal conductivity is one of the most significant criterion of three-dimensional carbon fiber-reinforced SiC matrix composites(3D C/SiC).Represent volume element(RVE)models of microscale,void/matrix and mesoscale proposed in this work are used to simulate the thermal conductivity behaviors of the 3D C/SiC composites.An entirely new process is introduced to weave the preform with three-dimensional orthogonal architecture.The 3D steady-state analysis step is created for assessing the thermal conductivity behaviors of the composites by applying periodic temperature boundary conditions.Three RVE models of cuboid,hexagonal and fiber random distribution are respectively developed to comparatively study the influence of fiber package pattern on the thermal conductivities at the microscale.Besides,the effect of void morphology on the thermal conductivity of the matrix is analyzed by the void/matrix models.The prediction results at the mesoscale correspond closely to the experimental values.The effect of the porosities and fiber volume fractions on the thermal conductivities is also taken into consideration.The multi-scale models mentioned in this paper can be used to predict the thermal conductivity behaviors of other composites with complex structures.

Thermodynamic,Economic,and Environmental Analyses and Multi-Objective Optimization of Dual-Pressure Organic Rankine Cycle System with Dual-Stage Ejector

A novel dual-pressure organic Rankine cycle system(DPORC)with a dual-stage ejector(DE-DPORC)is proposed.The system incorporates a dual-stage ejector that utilizes a small amount of extraction steam from the highpressure expander to pressurize a large quantity of exhaust gas to performwork for the low-pressure expander.This innovative approach addresses condensing pressure limitations,reduces power consumption during pressurization,minimizes heat loss,and enhances the utilization efficiency of waste heat steam.A thermodynamic model is developed with net output work,thermal efficiency,and exergy efficiency(W_(net,ηt,ηex))as evaluation criteria,an economicmodel is established with levelized energy cost(LEC)as evaluation index,anenvironmentalmodel is created with annual equivalent carbon dioxide emission reduction(AER)as evaluation parameter.A comprehensive analysis is conducted on the impact of heat source temperature(T_(S,in)),evaporation temperature(T_(2)),entrainment ratio(E_(r1),E_(r2)),and working fluid pressure(P_(5),P_(6))on system performance.It compares the comprehensive performance of the DE-DPORC system with that of the DPORC system at TS,in of 433.15 K and T2 of 378.15 K.Furthermore,multi-objective optimization using the dragonfly algorithm is performed to determine optimal working conditions for the DE-DPORC system through the TOPSIS method.The findings indicate that the DEDPORC system exhibits a 5.34%increase inWnet andηex,a 58.06%increase inηt,a 5.61%increase in AER,and a reduction of 47.67%and 13.51%in the heat dissipation of the condenser andLEC,compared to theDPORCsystem,highlighting the advantages of this enhanced system.The optimal operating conditions are TS,in=426.74 K,T_(2)=389.37 K,E_(r1)=1.33,E_(r2)=3.17,P_(5)=0.39 MPa,P_(6)=1.32 MPa,which offer valuable technical support for engineering applications;however,they are approaching the peak thermodynamic and environmental performance while falling short of the highest economic performance.

Design,preparation,application of advanced array structured materials and their action mechanism analyses for high performance lithium-sulfur batteries

Lithium-sulfur battery(LSB)has brought much attention and concern because of high theoretical specific capacity and energy density as one of main competitors for next-generation energy storage systems.The widely commercial application and development of LSB is mainly hindered by serious“shuttle effect”of lithium polysulfides(Li PSs),slow reaction kinetics,notorious lithium dendrites,etc.In various structures of LSB materials,array structured materials,possessing the composition of ordered micro units with the same or similar characteristics of each unit,present excellent application potential for various secondary cells due to some merits such as immobilization of active substances,high specific surface area,appropriate pore sizes,easy modification of functional material surface,accommodated huge volume change,enough facilitated transportation for electrons/lithium ions,and special functional groups strongly adsorbing Li PSs.Thus many novel array structured materials are applied to battery for tackling thorny problems mentioned above.In this review,recent progresses and developments on array structured materials applied in LSBs including preparation ways,collaborative structural designs based on array structures,and action mechanism analyses in improving electrochemical performance and safety are summarized.Meanwhile,we also have detailed discussion for array structured materials in LSBs and constructed the structure-function relationships between array structured materials and battery performances.Lastly,some directions and prospects about preparation ways,functional modifications,and practical applications of array structured materials in LSBs are generalized.We hope the review can attract more researchers'attention and bring more studying on array structured materials for other secondary batteries including LSB.

The need to develop tailored tools for improving the quality of thematic bibliometric analyses: Evidence from papers published in Sustainability and Scientometrics

Purpose: The aim of this article is to explore up to seven parameters related to the methodological quality and reproducibility of thematic bibliometric research published in the two most productive journals in bibliometrics, Sustainability(a journal outside the discipline) and Scientometrics, the flagship journal in the field.Design/methodology/approach: The study identifies the need for developing tailored tools for improving the quality of thematic bibliometric analyses, and presents a framework that can guide the development of such tools. A total of 508 papers are analysed, 77% of Sustainability, and 23% published in Scientometrics, for the 2019-2021 period.Findings: An average of 2.6 shortcomings per paper was found for the whole sample, with an almost identical number of flaws in both journals. Sustainability has more flaws than Scientometrics in four of the seven parameters studied, while Scientometrics has more shortcomings in the remaining three variables.Research limitations: The first limitation of this work is that it is a study of two scientific journals, so the results cannot be directly extrapolated to the set of thematic bibliometric analyses published in journals from all fields.Practical implications: We propose the adoption of protocols, guidelines, and other similar tools, adapted to bibliometric practice, which could increase the thoroughness, transparency, and reproducibility of this type of research.Originality/value: These results show considerable room for improvement in terms of the adequate use and breakdown of methodological procedures in thematic bibliometric research, both in journals in the Information Science area and journals outside the discipline.

Mechanical stress and deformation analyses of pressurized cylindrical shells based on a higher-order modeling

In this research,mechanical stress,static strain and deformation analyses of a cylindrical pressure vessel subjected to mechanical loads are presented.The kinematic relations are developed based on higherorder sinusoidal shear deformation theory.Thickness stretching formulation is accounted for more accurate analysis.The total transverse deflection is divided into bending,shear and thickness stretching parts in which the third term is responsible for change of deflection along the thickness direction.The axisymmetric formulations are derived through principle of virtual work.A parametric study is presented to investigate variation of stress and strain components along the thickness and longitudinal directions.To explore effect of thickness stretching model on the static results,a comparison between the present results with the available results of literature is presented.As an important output,effect of micro-scale parameter is studied on the static stress and strain distribution.

基于光谱特征的多重金属离子与DOM结合特性

通过淬灭滴定实验,文章采用同步荧光光谱和傅里叶红外光谱(FTIR)结合二维相关光谱分析,探究Cu^(2+)和Cd^(2+)多重离子与溶解态有机质(DOM)结合特性。研究结果表明,(1)DOM与Cu^(2+)和Cd^(2+)结合稳定常数(lg KM)分别为4.75~5.18和3.71~4.12,Cu^(2+)与DOM的结合能力要强于Cd^(2+)。(2)Cd^(2+)浓度为0和100μmol/L时,DOM点位与Cu^(2+)的结合顺序均为430~500 nm>330~420 nm,且Cd^(2+)存在时Cu^(2+)与DOM的lg KM为4.56~4.95。对比结果表明Cd^(2+)的存在并未影响DOM点位与Cu^(2+)的结合顺序,但减弱了DOM与Cu^(2+)的结合能力。(3)FTIR结果表明,Cd^(2+)浓度为0和100μmol/L时DOM官能团与Cu^(2+)结合顺序依次为酚类C-O>酰胺N-H>酰胺C=O>羧基C=O>芳香族C-H>多糖C-O和酰胺N-H>酰胺C=O>酚类C-O>芳香族C-H>多糖C-O。Cd^(2+)与酚类C-O结合后影响了Cu^(2+)与DOM中酚类C-O和羧基C=O官能团的结合。水环境中多重金属离子共存时的生物有效性和生态风险应受到关注。

呼吸科住院患者风险感知与创伤后应激障碍的相关性研究

目的探究呼吸科住院患者风险感知与创伤后应激障碍(PTSD)的现状,分析其相关性,为患者心理危机早期预防和干预提供理论依据。方法选择南阳市中心医院2023年1月~3月呼吸科住院的发热患者为研究对象,收集患者的一般资料、风险感知量表(PRQ)及创伤后应激障碍自评量表(PCL-C)评分,并进行统计学分析。结果共回收182份有效问卷,患者一般资料与PRQ、PCL-C评分比较,差异无统计学意义(P>0.05)。患者中、重度PTSD发生率为71.98%,回归分析显示,PRQ评分与PCL-C评分呈显著正相关(P<0.01),风险感知可以解释PTSD 39.00%的变化原因。结论呼吸科发热患者PTSD发生率较高,有必要对患者实施风险感知的管理或干预,从而减轻患者心理压力,以降低创伤后应激障碍的发生。

不同温度下再生骨料沥青混凝土动态抗压性能研究

为进一步研究再生骨料沥青混凝土在水工建筑物中的适用性,本文在不同温度环境中对再生骨料水工沥青混凝土的动态力学特性进行试验研究。对再生骨料水工沥青混凝土在温度为-10℃~10℃和应变速率为10^(-5)~10^(-2)s^(-1)的条件下进行动态抗压性能试验研究。试验结果表明:再生骨料水工沥青混凝土的抗压强度和弹性模量与温度成反比关系,与加载速率成正比关系;峰值应变与温度成正比关系,与加载速率成反比关系。通过温度影响因子和相关性系数分析,发现抗压强度和弹性模量随着温度升高逐渐减小并趋于某一定值。

基于整车路面谱的副车架开裂台架试验及仿真

针对前悬架稳定杆与副车架连接处在整车试验场耐久测试过程中出现的疲劳破坏问题,通过对稳定杆进行贴片标定,获得了试验场环境下稳定杆的连杆力和稳定杆扭转相对位移的强化耐久路谱,设计搭建了稳定杆副车架系统的物理台架,并按照耐久性规范进行了台架试验。试验结果表明:该台架试验装置能良好地再现整车耐久路试下的断裂位置,疲劳寿命相对于整车耐久路试的疲劳寿命偏差仅为2.5%。在此基础上,建立了稳定杆与副车架多体的仿真模型,设定了与系统试验台架相同的约束边界,通过虚拟迭代的方法及准静态有限元疲劳寿命分析法对系统进行了仿真分析。仿真得到稳定杆连杆力和稳定杆扭转相对位移信号,与测试结果进行对比分析可以看出,时域下相位和幅值重合度良好,频域下的PSD谱重合度较高,穿级计数载荷统计基本一致,载荷相对损伤均在1附近,相关风险位置处的仿真疲劳寿命与整车耐久试验寿命偏差比为6.25%,获得了较高精度的风险位置载荷,实现了耐久风险位置的复现。最后,基于仿真模型对副车架风险位置处进行了结构优化设计,改进后的方案顺利通过了后续的台架试验和整车耐久路试。

欧洲温室型黄瓜种质资源主要农艺性状遗传多样性分析

为了研究欧洲温室型黄瓜农艺性状遗传多样性、亲缘关系,明确种质资源的特征特性,为欧洲温室型黄瓜新品种选育提供参考,对搜集并纯化的41份欧洲温室型黄瓜自交系进行了第一雌花节位、叶长、叶宽等18个农艺性状鉴定,并进行遗传多样性、相关性和聚类分析。18个农艺性状间变异系数在13.36%~76.48%之间,变异系数最大的性状为第一雌花节位,达到76.48%;变异系数最小的性状为植株生长势,为13.36%、平均变异系数为27.78%。单瓜质量和单株产量均与第一雌花节位呈显著正相关;果皮颜色与果皮硬度呈显著正相关,与心腔比呈极显著负相关。在遗传相似系数(GS)为1.86时,分为三大类,第一类含有23份黄瓜种质资源,占供试材料的56%;第二类含有4份黄瓜种质资源;第三类含有14份黄瓜种质资源。41份欧洲温室型黄瓜材料遗传差异较大,有丰富的遗传多样性,具有较大的育种目标选择潜力,为欧洲温室型黄瓜新品种选育提供了优良资源。

脑肿瘤与癫痫的临床及影像相关性探究

目的分析脑肿瘤的临床及影像特征,探讨脑肿瘤与其继发癫痫的相关性。方法选取笔者所在医院34例脑肿瘤且合并癫痫患者作为观察组,随机选取同时期脑肿瘤不伴癫痫症状患者34例作为对照组,统计两组间年龄、性别、肿瘤组织类型、肿瘤部位及影像特征差异,分析两者之间的相关性。结果两组间年龄、性别以及肿瘤组织类型差异没有明显统计学意义,两组间肿瘤分布情况在额叶组中存在统计学差异(P=0.078),两组肿瘤影像学特征在伴局部脑萎缩组中存在统计学差异(P=0.032)。结论脑肿瘤与癫痫发生存在一定相关性,充分运用影像学检查指导这类患者的诊疗能有效地减少癫痫带来的继发损害和潜在危害。

基于灰色关联度分析挺水植物模拟生活污水的净化能力

以17种挺水植物为研究对象,对挺水植物进行驯化处理,随后移植在模拟生活污水中培养,在不同的时间段内采集水质,并对水质中的总氮、总磷、氨氮和化学需氧量以及pH进行监测,采用灰色关联度分析评价挺水植物的综合净化水质的能力。结果表明,不同的挺水植物对单个水质指标的去污能力差异较大;灰色关联度分析17种挺水植物综合去污能力优等的有3种,分别是旱伞草、紫芋和灯芯草;综合去污能力良好的有6种,分别是海寿花、水葱、溪荪、水生美人蕉、花叶芦竹、再力花;综合去污能力中等的有5种,分别是香蒲、水芹、慈姑、纸莎草、泽泻;综合去污能力较低的有3种,分别是千屈菜、黄菖蒲、菰。初步筛查出9种挺水植物具有良好的综合去污效果,试验结果可为后续小微湿地水生植物示范与推广提供基础数据。

西南地区优良观赏白及属花色色差测定与分析

对西南地区优良观赏白及属花色色差进行测定和分析,探究其与生长特性的相关性。收集西南地区白及、黄花白及、小白及种质资源,测量表观性状并在标准光源D65下测定花瓣颜色,利用CIELab颜色系统进行分类。结果表明:可划分为紫色、深紫、粉紫、淡紫、粉、淡橙、淡黄和黄色等8个色系。花色色差与花期、株高、花茎高具备显著的相关性,色差评价模型的建立可以为观赏白及属良种选育与亲本筛选提供参考依据。

不同包装方式对冷鲜猪肉品质及假单胞菌生长的影响

【目的】探索冷鲜猪肉贮藏期间品质劣变情况及假单胞菌生长状况,为冷鲜肉贮藏期品质判断提供依据。【方法】采用真空、保鲜盒和热收缩膜3种方式包装冷鲜猪肉,检测4℃下贮藏第0、2、4、6、8天时肉样中假单胞菌菌落数及细菌菌落总数、感官指标、pH值、色差、水分活度值、TVB-N值的变化。【结果】相对于保鲜盒包装,真空包装和热收缩膜包装均能抑制冷鲜猪肉中菌落总数及假单胞菌菌落数增长;贮藏第4天,保鲜盒组肉样的菌落总数达到6.99 lg(CFU·g-1),真空包装组第6天才达到6.46 lg(CFU·g-1);贮藏第6天,保鲜盒组肉样中假单胞菌数最高达到7.58 lg(CFU·g-1),真空包装组和热收缩膜组分别达到了5.00 lg(CFU·g-1)、6.27 lg(CFU·g-1),显著低于保鲜盒组;贮藏期间,3组肉样的TVB-N值均呈现出上升的趋势,保鲜盒组第6天TVB-N值达到158.7 mg·kg-1,真空包装组和热收缩膜组在贮藏第8天时超过150 mg·kg-1;水分活度测定中,第4天真空包装组和热收缩膜包装组AW值大于保鲜盒包装组,贮藏第6天起,各组肉样的水分活度趋于稳定差异不显著(p>0.05);贮藏前2 d,保鲜盒组肉样L*值较高,而贮藏后期,热收缩膜组和真空包装组能维持较高的L*值;保鲜盒组肉样的a*值均整体先上升后下降趋势,热收缩膜组和真空包装组呈下降趋势,真空包装能较好延缓a*值下降;第8天,保鲜盒组肉样pH值最高,已接近7.0,热收缩膜组与真空包装组肉样pH值差异不显著(p>0.05),且均低于6。在反映肉质新鲜度上,猪肉的感官与a*值、pH值、AW值、TVB-N值、假单胞菌数相关性比较大。【结论】真空包装可以能抑制冷鲜猪肉细菌的增长、延缓TVB-N值的增长,在短期内能更好维护冷鲜猪肉的品质。

缺血性脑卒中患者伤残接受度的相关影响因素分析

目的 研究影响缺血性脑卒中患者伤残接受度的相关影响因素。方法 选取2021年1月至2022年10月河北医科大学第二医院神经内科住院的缺血性脑卒中患者696例,采用一般资料调查表、伤残接受度量表、自我管理能力量表、社会支持量表及焦虑自评量表进行调查。结果 缺血性脑卒中患者伤残接受度量表得分为(65.63±11.30)分。多元线性回归结果显示,影响缺血性脑卒中患者伤残接受度的主要因素为文化程度、经济水平、对病情了解情况(P<0.05),自我管理能力与其伤残接受度呈正相关(r=0.557,P<0.01),社会支持度与其伤残接受度呈正相关(r=0.363,P<0.05),焦虑与其伤残接受度呈负相关(r=-0.665,P<0.01)。结论 缺血性脑卒中患者伤残接受度接受水平较低,与患者自我管理能力、社会支持呈正相关,与焦虑呈负相关,医务人员应给予重视,及时对患者进行心理干预,促进伤残接受度水平的提高,改善其身心健康。

淡水养殖池塘水质评价及与底质相关性分析

在哈尔滨地区面积6 600 m^(2)、平均水深1.2 m、多年未清淤的泥沙底质典型淡水精养池溏中混养鲤(Cyprinus carpio)、鲇(Silurus asotus)、草鱼(Ctenopharyngodon idella)和鲢(Hypophthalmichthys molitrix),春季(4—5月)、夏季(6—8月)和秋季(9月)不同时间采集池塘水体和表层底泥样品,监测养殖周期内水质总氮(TN)、总磷(TP)、氨氮(NH_(4)^(+)-N)、亚硝酸盐氮(NO_(2)^(-)-N)、硝酸盐氮(NO_(3)^(-)-N)和总有机碳(TOC)含量及高锰酸盐指数(COD_(Mn))、p H的季节性变化,利用单项污染指数法、综合污染指数法评价水体污染程度,利用主成分分析法解析水质污染的主要驱动因子,并结合底质指标绘制网络关系图。结果表明:池塘水质整体处于严重污染水平,春季优于夏季和秋季。参与评价时池塘水质为Ⅳ类、Ⅴ类和劣Ⅴ类,水质超标数随着养殖时间延长而增加,TN在全养殖周期内均超出警戒水平;TN、TP、NH_(4)^(+)-N和COD_(Mn)是池塘水体的主要污染物。因子分析结果表明,池塘水质主要受鱼类的生长代谢、溶解氧和投饵的影响,污染物以N、P营养盐为主。水体TP、TN、NH_(4)^(+)-N和底泥NO_(2)^(-)-N呈极显著正相关关系(P<0.01),与底泥TOC呈显著正相关关系(P<0.05)。池塘水体和底泥中的有机物污染具有共现性,水体TOC和底泥TOC呈极显著正相关关系(P<0.01)。

半干旱地区燕麦种子产量及其相关农艺性状

本研究选取19个燕麦(Avena sativa)品种(系)的产量相关性状指标,采用相关性分析、通径分析、灰色关联度分析以及聚类分析,探讨甘肃中部半干旱地区燕麦种子产量影响因素并筛选综合性状优良的燕麦种质。结果表明:燕麦种子产量为3 283.33~5 833.33 kg·hm^(-2),其中‘Cinskinaly’的产量最高。种子产量与千粒重、成穗数极显著正相关(P <0.01),与单株穗粒重显著正相关(P <0.05),而与株高显著负相关(P <0.05);通径分析结果表明,单株穗粒数、单株穗粒重、千粒重是决定种子产量的重要因素。聚类分析将19份燕麦材料析划分为4个类群:第Ⅰ类可作饲草资源加以筛选利用;第Ⅱ类适合作高产抗倒伏产籽型品种;第Ⅲ类为优选裸燕麦材料;而第Ⅳ类生产适应性和田间表现差,可直接淘汰。筛选出综合表现较佳的两个裸燕麦品系‘201006-01-01-9’‘201003-06-5’和1个皮燕麦品系‘201113-03-05’,可提升到甘肃省区域试验。

欧李果实发育过程中钙与有机酸含量的变化及相关性分析

【目的】探讨欧李果实发育过程中不同形态钙及有机酸代谢的变化及二者之间的关系,以期为解析欧李果实钙素吸收积累机制及进一步研究调控提供理论依据。【方法】以内蒙古地区高钙和低钙两种钙素水平欧李果实为试材,比较研究果实发育成熟过程中不同形态钙以及有机酸代谢相关指标的变化,并进行相关性分析。【结果】(1)在果实发育成熟过程中,两种钙素水平欧李果实中水溶性钙含量表现为先降后升,整体为上升趋势;总钙、果胶钙、磷酸钙和草酸钙含量均表现为先升后降,整体为下降趋势;残渣钙含量表现为持续下降。(2)两种钙素水平欧李果实中苹果酸脱氢酶(NAD-MDH)活性、苹果酸含量及有机酸总量的变化一致,均表现为先升后降,在硬熟期达到最高值,整体呈明显上升趋势,且以上三者活性或含量均表现为低钙果实高于高钙果实;苹果酸酶(NADP-ME)活性整体表现为下降;柠檬酸含量表现为先升后降,在硬核期达到最高值,整体呈下降趋势,且高钙果实中柠檬酸含量高于低钙果实。(3)相关性分析表明,两种钙素水平欧李果实中NAD-MDH活性、苹果酸含量、有机酸总量与水溶性钙含量均呈极显著正相关,与其他组分钙及总钙含量均呈不同程度的负相关;NADP-ME活性和柠檬酸含量与水溶性钙含量均呈显著或极显著负相关,与其他组分钙及总钙含量均呈不同程度的正相关。【结论】在欧李果实发育成熟过程中钙素积累与有机酸代谢有关,苹果酸是欧李果实中主要的有机酸,苹果酸合成代谢增强有利于水溶性钙含量的增加,柠檬酸含量增加则趋向于促进非水溶性钙类果胶钙、磷酸钙和草酸钙的积累。

石羊河流域气候变化及其对植被指数的影响

研究气候变化对植被覆盖的影响,对干旱区生态环境保护具有重要意义。以石羊河流域2000-2020年逐月气温、降水、日照、蒸发和NASA GIMMS归一化植被指数(NDVI)资料为基础,首先运用线性趋势法分析了气温、降水量、日照时数、蒸发量与NDVI的年、季节变化趋势,然后采用相关系数法研究了气候要素对NDVI的影响。结果表明:石羊河流域及各地年气温呈明显上升趋势,春、夏、秋季气温呈上升趋势,冬季(除民勤外)呈下降趋势;全流域及永昌、古浪、天祝年降水量呈增多趋势,民勤、凉州呈减少趋势,各季节降水量变化趋势不太一致;年日照时数除古浪呈增多趋势外,全流域及其他各地呈减少趋势,各季节日照时数变化趋势很不一致;年蒸发量除凉州呈减少趋势外,全流域及其他各地呈增多趋势,各季节蒸发量变化趋势也不太一致。石羊河流域及各地年NDVI呈显著增长趋势,除凉州春季外,各季节也呈增长趋势。年、季气温和降水量与NDVI基本呈正相关,气温、降水量对NDVI具有正贡献。年、季日照时数和蒸发量与NDVI相关性的正负差异较大,总体来看,日照时数对NDVI具有负贡献,蒸发量对NDVI具有正贡献。研究结果将为石羊河流域提高气候资源的利用率、调整种植结构和改善生态环境提供科学的参考依据。