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Method to measure tree-ring width,density,elemental composition,and stable carbon and oxygen isotopes using one sample 被引量:1
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作者 Chenxi Xu Yaru Zhao +4 位作者 Wenling An Qingyu Zhao Yucheng Liu Masaki Sano Takeshi Nakatsuka 《Journal of Forestry Research》 SCIE EI CAS CSCD 2024年第3期167-174,共8页
Tree-ring width(RW),density,elemental com-position,and stable carbon and oxygen isotope(δ^(13)C,δ^(18)O)are widely used as proxies to assess climate change,ecology,and environmental pollution;however,a specific pret... Tree-ring width(RW),density,elemental com-position,and stable carbon and oxygen isotope(δ^(13)C,δ^(18)O)are widely used as proxies to assess climate change,ecology,and environmental pollution;however,a specific pretreat-ment has been needed for each proxy.Here,we developed a method by which each proxy can be measured in the same sample.First,the sample is polished for ring width meas-urement.After obtaining the ring width data,the sample is cut to form a 1-mm-thick wood plate.The sample is then mounted in a vertical sample holder,and gradually scanned by an X-ray beam.Simultaneously,the count rates of the fluorescent photons of elements(for chemical characteriza-tion)and a radiographic grayscale image(for wood density)are obtained,i.e.the density and the element content are obtained.Then,cellulose is isolated from the 1-mm wood plate by removal of lignin,and hemicellulose.After producing this cellulose plate,cellulose subsamples are separated by knife under the microscope for inter-annual and intra-annual stable carbon and oxygen isotope(δ^(13)C,δ^(18)O)analysis.Based on this method,RW,density,elemental composition,δ^(13)C,and δ^(18)O can be measured from the same sample,which reduces sample amount and treatment time,and is helpful for multi-proxy comparison and combination research. 展开更多
关键词 tree-ring width tree-ring density tree-ring elemental composition tree-ring stable carbon and oxygenisotopes
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Relationships between tree-ring width index and NDVI of grassland in Delingha 被引量:13
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作者 HE Jicheng1,3 & SHAO Xuemei1,21. Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China 2. Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100085, China 3. Graduate School of Chinese Academy of Sciences, Beijing 100039, China 《Chinese Science Bulletin》 SCIE EI CAS 2006年第9期1106-1114,共9页
Using five well-replicated Qilian juniper (Sabina przewalskii Kom.) tree-ring width index se- ries, monthly normalized difference vegetation index (NDVI) of grassland, and climatic data from 1982 to 2001, the relation... Using five well-replicated Qilian juniper (Sabina przewalskii Kom.) tree-ring width index se- ries, monthly normalized difference vegetation index (NDVI) of grassland, and climatic data from 1982 to 2001, the relationships between tree-ring width index, NDVI of grassland, and climatic data were analyzed firstly. Then, the relationship between tree-ring width index and NDVI of grassland was explored. The re- sults showed that: (1) Temperature and precipitation in June influenced tree-ring width index and NDVI of grassland deeply in Delingha. (2) There were sig- nificant relationships between five tree-ring width index series (DLH1-DLH5) and monthly NDVI of grassland from June to September, with the most significant relationship being between tree-ring width index series and NDVI of grassland in August. (3) The PC1 (the first principal component derived from DLH1-DLH5 series) exhibited good agreement with monthly NDVI of grassland in the grass growth sea- son (from June to September) and the averaged NDVI in the growth season, which was attributed to their common responses to water-supply limit in Delingha. This study may allow an increase in studying the past dynamics of grassland in Delingha in that the variation of grassland NDVI during the last millennium has been reconstructed from PC1. 展开更多
关键词 圆柏 祁连山 NDVI 草原 年轮宽度指数
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January to August temperature variability since 1776 inferred from tree-ring width of Pinus tabulaeformis in Helan Mountain 被引量:6
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作者 CAI Qiufang LIU Yu 《Journal of Geographical Sciences》 SCIE CSCD 2007年第3期293-303,共11页
Tree-ring standardized chronologies are developed by 78 cores collected from the eastern and western Helan Mountain. Statistical analysis shows that both the STD and RES chronologies correlate negatively with the temp... Tree-ring standardized chronologies are developed by 78 cores collected from the eastern and western Helan Mountain. Statistical analysis shows that both the STD and RES chronologies correlate negatively with the temperature of different periods of early half year, especially with January to August mean (JA) temperature, which means that JA temperature is one of the predominant limiting factors of tree growth in the Helan Mountain. Based on this analysis, we reconstructed JA temperature, and the explained variance is 43.3% (F=21.422, p〈0.001 ). The comparatively high temperature periods in the reconstruction were: 1805-1818 1828-1857, 1899-1907, 1919-1931 and 1968-1995; and the comparatively low temperatu re periods happened in 1858-1872, 1883-1895 and 1935-1953. Ten-year moving average curve shows three slow uplifting trends: 1766-1853, 1862-1931 and 1944-1995. Each temperature increase was followed by a sudden temperature decrease about 10 years, that is to say, the JA temperature in the Helan Mountain is characterized by slow increase and sudden decrease. The 70- and 10.77-year periodicities detected in the temperature series correspond to the Gleissberg (80-year) and Schwabe (11-year) periodicities of solar activity respectively, the 2.11-2.62 years cycles are considered to be influenced by QBO (Quasi-Biennial-Oscillation) and the local environmental change. 展开更多
关键词 Helan Mountain tree-ring width temperature reconstruction
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Reconstructing the annual precipitation variation since 1899 based on tree-ring width in the western Hedong sandy land of Ningxia 被引量:3
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作者 Wang, YaJun Gao, ShangYu +3 位作者 Ma, YuZhen Lu, RuiJie Sang, YanLi Meng, HongWei 《Journal of Arid Land》 SCIE 2010年第4期286-294,共9页
Based on the analysis of the correlation between the tree-ring width of Pinus tabulaeformis and the climate factors in the western Hedong sandy land of Ningxia, a conversion equation between the annual precipitation a... Based on the analysis of the correlation between the tree-ring width of Pinus tabulaeformis and the climate factors in the western Hedong sandy land of Ningxia, a conversion equation between the annual precipitation and the tree-ring width since 1899 was reconstructed. The results of cross verification indicated that the conversion equation is stable and the reconstructed results are reliable. The result of reconstructed annual precipitation showed the remarkable fluctuation of precipitation and dry-to-wet variation before the 1940s. The smaller fluctuation and high frequent changes of precipitation occurred during the period of 1940s-1980s and after the 1980s the change trend of the precipitation became high periodic extent and low frequent. The study found that there were some coincidences with the climate change in Changling Mountains, Helan Mountains and the east of Qilian Mountains. The relatively dry periods in the beginning of 20th century, 1920s to 1930s, the end of the 20th century and 2004 to 2006 in the western Hedong sandy land of Ningxia accelerated the desertification, while the relatively humid period during the periods of the 1910s-1920s, 1930s-1940s and 1990s is favorable to prevent and control the desertification, and to weaken the climate warming and drying. The periods of annual precipitation variation in the western Hedong sandy land of Ningxia since 1899 are approximately 2-4 years, 5-7 years and 10 years. 展开更多
关键词 Hedong sandy land of Ningxia tree-ring width annual precipitation CORRELATION
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Dynamics of moisture regime and its reconstruction from a tree-ring width chronology of Pinus sylvestris in the downstream basin of the Selenga River, Russia 被引量:1
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作者 Liliana BELOKOPYTOVA Dina ZHIRNOVA +1 位作者 Tatiana KOSTYAKOVA Elena BABUSHKINA 《Journal of Arid Land》 SCIE CSCD 2018年第6期877-891,共15页
Regional tree-ring width chronology of the Scots pine (Pinus sylvestris L.) was constructed from 8 sites in the forest-steppe belt situated in the foothills of the Selenga River basin, Russia. Moisture information con... Regional tree-ring width chronology of the Scots pine (Pinus sylvestris L.) was constructed from 8 sites in the forest-steppe belt situated in the foothills of the Selenga River basin, Russia. Moisture information contained in tree-ring width chronology was obtained through linear regression reconstruction models of annual August–July precipitation and annual water discharge of the Selenga River during the period 1767–2015. Comparison of the smoothed series allowed estimating long-term variation component of these moisture regime parameters with a high precision. At the same time, regional drought indices are less correlated with pine radial growth, because they have contribution of the other environmental variables, which are much less reflected in the tree-ring of the investigated pine forest stands. Reconstructed dynamic of the moisture regime parameters is supported by documental evident of many socially significant events in the regional history, such as crop failures caused by both droughts and floods, and catastrophic fire in the Irkutsk City in 1879. Also, dependence of the amount of precipitation in the study area on the atmospheric circulation in Central Asia is revealed to have a similar pattern with other regions, i.e., a negative relationship of precipitation with the development of large high atmospheric pressure area within its center in the Altai and Tianshan mountains. 展开更多
关键词 tree-ring width Pinus sylvestris climate HYDROLOGY precipitation reconstruction model
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Climatic response of Pinus sylvestris var. mongolica tree-ring width and precipitation reconstruction for the northern Greater Higgnan Mountains, China, since 1720
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作者 TongWen Zhang YuJiang Yuan +6 位作者 WenShou Wei RuiBo Zhang ShuLong Yu Feng Chen HuaMing Shang Li Qin ZiAng Fan 《Research in Cold and Arid Regions》 CSCD 2014年第6期546-555,共10页
August-June precipitation has been reconstructed back to AD 1720 for the northern Greater Higgnan Mountains, China, by use ofPinus sylvestris var. mongolica tree-ring width. The reconstruction explains the variance of... August-June precipitation has been reconstructed back to AD 1720 for the northern Greater Higgnan Mountains, China, by use ofPinus sylvestris var. mongolica tree-ring width. The reconstruction explains the variance of 39% in observed precipitation from 1973 to 2008. Some extremely dry/wet signals in historical documents and other precipitation reconstructions in previous studies are precisely captured in our reconstruction. Wet periods occurred during the periods of 1730 to 1746, 1789 to 1812, 1844 to 1903, 1920 to 1930, 1942 to 1961, and 1985 to 1998; while periods of 1747 to 1788, 1813 to 1843, 1904 to 1919, 1931 to 1941, and 1962 to 1984 were relatively dry. Power spectral and wavelet analyses demon- strated the existence of significant 24-year, 12-year, and 2-year cycles of variability. 展开更多
关键词 Greater Higgnan Mountains Pinus sylvestris var. mongolica tree-ring width precipitation reconstruction
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Reconstruction of hydrological changes based on tree-ring data of the Haba River, northwestern China 被引量:12
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作者 zhang tongwen yuan yujiang +4 位作者 chen feng yu shulong zhang ruibo qin li jiang shengxia 《Journal of Arid Land》 SCIE CSCD 2018年第1期53-67,共15页
Reconstructing the hydrological change based on dendrohydrological data has important implications for understanding the dynamic distribution and evolution pattern of a given river. The widespread, long-living conifer... Reconstructing the hydrological change based on dendrohydrological data has important implications for understanding the dynamic distribution and evolution pattern of a given river. The widespread, long-living coniferous forests on the Altay Mountains provide a good example for carrying out the dendrohydrological studies. In this study, a regional composite tree-ring width chronology developed by Lariat sibirica Ledeb. and Picea obovata Ledeb. was used to reconstruct a 301-year annual (from preceding July to succeeding June) streamflow for the Haba River, which originates in the southern Altay Mountains, Xinjiang, China. Results indicated that the reconstructed streamflow series and the observations were fitting well, and explained 47.5% of the variation in the observed streamflow of 1957-2008. Moreover, floods and droughts in 1949-2000 were precisely captured by the streamflow reconstruction. Based on the frequencies of the wettest/driest years and decades, we identified the 19th century as the century with the largest occurrence of hydrological fluctuations for the last 300 years. After applying a 21-year moving average, we found five wet (1724-1758, 1780-1810, 1822-1853, 1931-1967, and 1986-2004) and four dry (1759-1779, 1811-1821, 1854-1930, and 1968-1985) periods in the streamflow reconstruction. Furthermore, four periods (1770-1796, 1816-1836, 1884-1949, and 1973-1997) identified by the streamflow series had an obvious increasing trend. The increasing trend of streamflow since the 1970s was the biggest in the last 300 years and coincided with the recent warming-wetting trend in northwestern China. A significant correlation between streamflow and precipitation in the Altay Mountains indicated that the streamflow reconstruction contained not only local, but also broad-scale, hydro-climatic signals. The 24-year, 12-year, and 2.2-4.5-year cycles of the reconstruction revealed that the streamflow variability of the Haba River may be influenced by solar activity and the atmosphere-ocean system. 展开更多
关键词 Larzx sibiffca Ledeb. Picea obovata Ledeb. streamflow reconstruction tree-ring width Altay Mountains
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Tree-ring response of Larix chinensis on regional climate and sea-surface temperature variations in alpine timberline in the Qinling Mountains 被引量:4
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作者 Boqian Yan Jian Yu +2 位作者 Qijing Liu Lihua Wang Lile Hu 《Journal of Forestry Research》 SCIE CAS CSCD 2020年第1期209-218,共10页
Tree-ring width chronologies of Larix chinensis were developed from the northern and southern slopes of the Qinling Mountains in Shaanxi Province,and climatic factors affecting the tree-ring widths of L.chinensis were... Tree-ring width chronologies of Larix chinensis were developed from the northern and southern slopes of the Qinling Mountains in Shaanxi Province,and climatic factors affecting the tree-ring widths of L.chinensis were examined.Correlation analysis showed that similar correlations between tree-ring width chronologies and climatic factors demonstrated that radial growth responded to climate change on both slopes.The radial growth of L.chinensis was mainly limited by temperature,especially the growing season.In contrast,both chronologies were negatively correlated with precipitation in May of the previous year and April of the current year.Spatial climate-correlation analyses with gridded land-surface climate data revealed that our tree-ring width chronologies contained a strong regional temperature signal over much of northcentral and eastern China.Spatial correlation with seasurface temperature fields highlights the influence of the Pacific Ocean,Indian Ocean,and North Atlantic Ocean.Wavelet coherence analysis indicated the existence of some decadal and interannual cycles in the two tree-ring width chronologies.This may suggest the influences of El Nin˜o-Southern Oscillation and solar activity on tree growth in the Qinling Mountains.These findings will help us understand the growth response of L.chinensis to climate change in the Qinling region,and they provide critical information for future climate reconstructions based on this species in semi-humid regions. 展开更多
关键词 Climate response Dendroclimatic tree-ring width L.chinensis Qinling Mountains
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Red cell distribution width: A predictor of the severity of hypertriglyceridemia-induced acute pancreatitis 被引量:2
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作者 Yong-Cai Lv Yan-Hua Yao +2 位作者 Juan Zhang Yu-Jie Wang Jing-Jing Lei 《World Journal of Experimental Medicine》 2023年第5期115-122,共8页
BACKGROUND Compared with patients with other causes of acute pancreatitis,those with hypertriglyceridemia-induced acute pancreatitis(HTG-AP)are more likely to develop persistent organ failure(POF).Therefore,recognizin... BACKGROUND Compared with patients with other causes of acute pancreatitis,those with hypertriglyceridemia-induced acute pancreatitis(HTG-AP)are more likely to develop persistent organ failure(POF).Therefore,recognizing the individuals at risk of developing POF early in the HTG-AP process is a vital for improving outcomes.Bedside index for severity in acute pancreatitis(BISAP),a simple parameter that is obtained 24 h after admission,is an ideal index to predict HTG-AP severity;however,the suboptimal sensitivity limits its clinical application.Hence,current clinical scoring systems and biochemical parameters are not sufficient for predicting HTG-AP severity.AIM To elucidate the early predictive value of red cell distribution width(RDW)for POF in HTG-AP.METHODS In total,102 patients with HTG-AP were retrospectively enrolled.Demographic and clinical data,including RDW,were collected from all patients on admission.RESULTS Based on the Revised Atlanta Classification,37(33%)of 102 patients with HTG-AP were diagnosed with POF.On admission,RDW was significantly higher in patients with HTG-AP and POF than in those without POF(14.4%vs 12.5%,P<0.001).The receiver operating characteristic curve demonstrated a good discrim-inative power of RDW for POF with a cutoff of 13.1%,where the area under the curve(AUC),sensitivity,and specificity were 0.85,82.4%,and 77.9%,respectively.When the RDW was≥13.1%and one point was added to the original BISAP to obtain a new BISAP score,we achieved a higher AUC,sensitivity,and specificity of 0.89,91.2%,and 67.6%,respectively.CONCLUSION RDW is a promising predictor of POF in patients with HTG-AP,and the addition of RDW can promote the sensitivity of BISAP. 展开更多
关键词 Red cell distribution width Bedside index for severity in acute pancreatitis Persistent organ failure Hypertriglyceridemia-induced acute pancreatitis
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术前血小板分布宽度联合系统性炎症指数对结肠癌术后复发转移的预测价值 被引量:1
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作者 宗旭芳 崔磊 +1 位作者 党胜春 陈金才 《新疆医科大学学报》 CAS 2024年第1期73-77,85,共6页
目的研究术前血小板分布宽度(Platelet volume distribution width,PDW)联合系统性炎症指数(Systemic inflammation response index,SIRI)对结肠癌术后复发转移的预测价值。方法以2020年1月-2021年6月江苏大学附属医院胃肠外科就诊并接... 目的研究术前血小板分布宽度(Platelet volume distribution width,PDW)联合系统性炎症指数(Systemic inflammation response index,SIRI)对结肠癌术后复发转移的预测价值。方法以2020年1月-2021年6月江苏大学附属医院胃肠外科就诊并接受根治性切除手术治疗的194例结肠癌患者为结肠癌组,选择同期在本院体检中心招募的100例健康体检者为对照组。术前检测并记录PDW和SIRI,收集患者的一般资料包括:性别、年龄、身高、体重、家族肿瘤史、是否吸烟、酗酒、体质指数(Body mass index,BMI)、肿瘤最大径、TNM分期(Tumor node metastasis,TNM)和分化程度。对患者随访2年,记录结肠癌复发转移情况。采用ROC曲线确定相关变量的临界最佳值,通过AUC(ROC曲线下面积)评价其预后的准确性。结果与对照组比较,结肠癌组PDW和SIRI均显著增高,差异有统计学意义(P<0.05)。术后发生复发转移患者术前PDW与SIRI高于术后未发生复发转移的患者,差异有统计学意义(P<0.05)。TNM分期Ⅲ~Ⅳ期和中低分化程度术后复发转移患者的PDW高于Ⅰ~Ⅱ期患者和高分化程度患者,差异有统计学意义(P<0.05)。肿瘤最大径≥5 cm、TNM分期Ⅲ~Ⅳ期和中低分化程度术后复发转移患者的PDW高于肿瘤最大径<5 cm、TNM分期Ⅰ~Ⅱ期和高分化程度的患者,差异有统计学意义(P<0.05)。PDW、SIRI及两者联合预测结肠癌术后复发转移的曲线下面积(Area under curve,AUC)分别为0.761(95%CI:0.691~0.831),0.836(95%CI:0.775~0.897)和0.918(95%CI:0.876~0.960)。术后复发转移患者的PDW与SIRI呈显著正相关关系(r=0.574,P=0.003)。结论PDW、SIRI与结肠癌患者临床病理特征和术后复发转移有关,两者联合预测术后复发转移的效能较好,可为临床应用提供一定参考价值。 展开更多
关键词 结肠癌 血小板分布宽度 系统性炎症指数 肿瘤复发 肿瘤转移
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红细胞分布宽度、系统免疫炎症指数与重性抑郁障碍的相关性研究
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作者 金曼 梁浩 +5 位作者 张石盼 张雪茹 井朋 杨越 王春阳 吕佩源 《中国神经精神疾病杂志》 CAS CSCD 北大核心 2024年第7期409-414,共6页
目的探讨外周血红细胞分布宽度(red blood cell distribution width,RDW)、系统免疫炎症指数(systemic immune-inflammation index,SⅡ)与重性抑郁障碍(major depressive disorder,MDD)的相关性。方法回顾性分析2020-2022年于我院临床... 目的探讨外周血红细胞分布宽度(red blood cell distribution width,RDW)、系统免疫炎症指数(systemic immune-inflammation index,SⅡ)与重性抑郁障碍(major depressive disorder,MDD)的相关性。方法回顾性分析2020-2022年于我院临床心理科住院的176例MDD患者和常规体检的209例非MDD对照者的临床资料。从血液分析结果中,得到RDW、SⅡ、红细胞分布宽度与血小板计数比值(RDW to platelet ratio,RPR)。绘制受试者操作特征(receiver operator characteristic,ROC)曲线以确定RDW区分患者与对照的最佳临界值及曲线下面积(area under the curve,AUC)。结果MDD组患者的RDW[中位数及四分位数:13.20(12.70,13.98)vs.12.80(12.40,13.35)]、SⅡ水平[中位数及四分位数:510.87(350.95,878.12)vs.405.33(313.74,539.92)]高于非MDD组对照者,差异有统计学意义(P<0.05),两组间RPR差异无统计学意义(P>0.05)。多因素logistic回归分析结果显示,调整混杂因素后,RDW与MDD呈正关联(OR=3.086,95%CI:1.926~4.944)。ROC曲线结果显示,RDW区分MDD与非MDD的最佳临界值为12.85,AUC为0.647(95%CI:0.592~0.702;P<0.001)。结论高RDW可能是MDD发生的危险因素,是对MDD诊断有价值的重要参数。 展开更多
关键词 红细胞分布宽度 重性抑郁障碍 系统免疫炎症指数 红细胞分布宽度与血小板计数比值 炎症反应 相关性研究 危险因素
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红细胞分布宽度/白蛋白比值对重症社区获得性肺炎不良结局预测价值 被引量:1
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作者 李川 唐伟伟 方长太 《分子诊断与治疗杂志》 2024年第4期713-716,720,共5页
目的 探讨红细胞分布宽度/白蛋白(RDW/ALB)比值对重症社区获得性肺炎(sCAP)不良结局的预测价值。方法 分析107例sCAP患者的临床资料,根据30 d预后情况分为预后不良组和预后良好组。采用单因素和多因素Logistic回归分析,揭示预后的影响... 目的 探讨红细胞分布宽度/白蛋白(RDW/ALB)比值对重症社区获得性肺炎(sCAP)不良结局的预测价值。方法 分析107例sCAP患者的临床资料,根据30 d预后情况分为预后不良组和预后良好组。采用单因素和多因素Logistic回归分析,揭示预后的影响因素。采用受试者特征工作(ROC)曲线分析RDW/ALB比值预测预后的能力。结果 sCAP患者预后不良组RDW/ALB比值的中位数显著高于预后良好组(P<0.05),RDW/ALB比值越高,30 d预后不良发生率越高(OR=1.155,95%CI:1.007~2.430,P<0.05)。计算RDW/ALB比值曲线下面积(AUC)为0.761(95%CI:0.665~0.857),高于肺炎严重程度指数(PSI)评分的0.740(95%CI:0.643~0.837)(P<0.05)。当RDW/ALB比值与PSI评分结合时,AUC值增加到0.817(95%CI:0.736~0.899),高于PSI评分或单独的RDW/ALB比值(P<0.05)。结论 RDW/ALB比值具有较好预测重症社区获得性肺炎不良结局的价值。 展开更多
关键词 重症社区获得性肺炎 白蛋白 红细胞分布宽度 红细胞分布宽度/白蛋白比值 肺炎严重程度指数
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Resilience and response:Unveiling the impacts of extreme droughts on forests through integrated dendrochronological and remote sensing analyses 被引量:1
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作者 Han Shi Xi Peng +6 位作者 Yong-Jiao Zhou Ai-Ying Wang Xue-Kai Sun Na Li Quan-Sheng Bao Gude Buri Guang-You Hao 《Forest Ecosystems》 SCIE CSCD 2024年第4期491-501,共11页
Extreme droughts are anticipated to have detrimental impacts on forest ecosystems,especially in water-limited regions,due to the influence of climate change.However,considerable uncertainty remains regarding the patte... Extreme droughts are anticipated to have detrimental impacts on forest ecosystems,especially in water-limited regions,due to the influence of climate change.However,considerable uncertainty remains regarding the patterns in species-specific responses to extreme droughts.Here,we conducted a study integrating dendrochronology and remote sensing methods to investigate the mosaic-distributed maple-oak(native)natural forests and poplar plantations(introduced)in the Horqin Sandy Land,Northeast China.We assessed the impacts of extreme droughts on tree performances by measuring interannual variations in radial growth and vegetation index.The results showed that precipitation and self-calibrated palmer drought severity index(scPDSI)are the major factors influencing tree-ring width index(RWI)and normalized difference vegetation index(NDVI).The severe droughts between 2000 and 2004 resulted in reduced RWI in the three studied tree species as well as led to NDVI reductions in both the maple-oak natural forests and the poplar plantations.The RWI reached the nadir during the2000-2004 severe droughts and remained at low levels two years after the severe drought,creating a legacy effect.In contrast to the lack of significant correlation between RWI and scPDSI,NDVI exhibited a significant positive correlation with scPDSI indicating the greater sensitivity of canopy performance to droughts than radial growth.Furthermore,interspecific differences in RWI and NDVI responses were observed,with the fast-growing poplar species experiencing a more significant RWI decrease and more negative NDVI anomaly during severe droughts than native species,highlighting the species-specific trade-offs between drought resilience and growth rate.This study emphasizes the importance of combining tree-level radial growth with landscape-scale canopy remote sensing to understand forest resilience and response.Our study improves our understanding of forest responses to extreme drought and highlights species differences in climate responses,offering crucial insights for optimizing species selection in sustainable afforestation and forest management in water-limited regions under the influence of climate change. 展开更多
关键词 Introduced tree species Native tree species NDVI Severe drought tree-ring width
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鱼类自主游动推进机理与游动性能二维数值模拟研究
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作者 贾瑞 杨光 +3 位作者 万宇 张鹏 杜洪波 李文杰 《船舶力学》 EI CSCD 北大核心 2024年第10期1559-1569,共11页
推进机理及游动性能研究对鱼类洄游通道建设具有重要意义。利用计算流体动力学方法结合重叠网格技术,通过编译控制鱼体摆动的UDF程序,对二维鱼类自主游动进行模拟,分析鱼体压力场分布及反卡门涡街结构演化过程与参数变化情况,开展不同... 推进机理及游动性能研究对鱼类洄游通道建设具有重要意义。利用计算流体动力学方法结合重叠网格技术,通过编译控制鱼体摆动的UDF程序,对二维鱼类自主游动进行模拟,分析鱼体压力场分布及反卡门涡街结构演化过程与参数变化情况,开展不同摆尾频率、摆尾幅度、鱼体体形及尾鳍尺寸等参数下鱼类游动性能及鱼体受力的变化情况,揭示鱼类自主游动过程中的游动机理。研究结果表明:(1)鱼体尾鳍周期性往复摆动下漩涡脱落形成反卡门涡街,是鱼体前进推力的主要来源,且随着摆尾频率、摆尾幅度的增加,鱼体尾部涡街长度、涡街强度逐渐增加,而摆尾幅度对涡街宽度的影响较大;(2)随着摆尾频率、摆尾幅度的增加,纵向平均合力系数和最大侧向力系数均增大,使得鱼类获得较大的游动速度,但摆尾频率改变时平均合力系数和游动速度的增加更为明显,摆尾幅度改变时最大侧向力系数的增加更为明显;(3)随着体宽指数的增加,纵向平均合力系数逐渐减小,需克服的游动阻力增加,使得鱼类游动速度逐渐减小,而最大侧向力系数逐渐增加;(4)随着尾鳍指数的增加,纵向平均合力系数和最大侧向力系数均增大,使得鱼类游动速度逐渐增大。研究成果可为鱼类生境恢复营造提供支撑。 展开更多
关键词 推进机理 游动性能 摆尾频率 摆尾幅度 体宽指数 尾鳍指数
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沿黑体辐射线类太阳光LED调光系统调配及优化
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作者 张爱奎 朱友华 +2 位作者 孙智江 李毅 郭兴龙 《半导体技术》 CAS 北大核心 2024年第11期953-960,共8页
为了使发光二极管(LED)光源光谱在可见光波段更接近太阳光光谱,且相关色温实现沿黑体辐射线连续可调,选取不同峰值波长LED芯片及荧光粉,覆盖可见光波段;采用相应LED芯片激发相应荧光粉,获得多个调光光源并记录色点及相对光谱;根据光谱... 为了使发光二极管(LED)光源光谱在可见光波段更接近太阳光光谱,且相关色温实现沿黑体辐射线连续可调,选取不同峰值波长LED芯片及荧光粉,覆盖可见光波段;采用相应LED芯片激发相应荧光粉,获得多个调光光源并记录色点及相对光谱;根据光谱叠加性原理,混合光源色点位于调光光源在CIE 1931色坐标图中围成的区域内。对四色光源混合调光进行了系统的调配优化,基于脉宽调制(PWM)调光模式,使用LED驱动模块控制各调光LED的光通量,实现了光源沿黑体辐射线色温可连续调节。模拟与实测结果显示,在常用照明色温2700~6500 K时,LED光源的一般显色指数大于98,且各特殊显色指数均大于90。光谱特性与太阳光类似,填补了LED白光中青光波段的凹陷,去除了短波长蓝光危害。 展开更多
关键词 发光二极管(LED) 黑体辐射线 脉宽调制(PWM) 显色指数 可调色温
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全身免疫炎症指数和红细胞分布宽度在儿童过敏性紫癜合并肾损害中的变化及意义
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作者 裘艺莎 吴锴 +1 位作者 胡剑 孙兴珍 《中国妇幼健康研究》 2024年第11期13-19,共7页
目的探讨全身免疫炎症指数(SII)和红细胞分布宽度(RDW)在预测儿童过敏性紫癜(HSP)合并肾损害中的临床价值。方法选取2018年6月至2022年12月在南京医科大学附属淮安第一医院住院治疗的191例HSP患儿为研究对象,其中77例为肾损害组,114例... 目的探讨全身免疫炎症指数(SII)和红细胞分布宽度(RDW)在预测儿童过敏性紫癜(HSP)合并肾损害中的临床价值。方法选取2018年6月至2022年12月在南京医科大学附属淮安第一医院住院治疗的191例HSP患儿为研究对象,其中77例为肾损害组,114例为无肾损害组。分析两组患儿的一般资料和实验室检查结果,通过多因素Logistic回归分析HSP合并肾损害的危险因素;以Spearman相关性分析SII和RDW与24小时尿蛋白定量(24h-UPRO)之间的相关性;利用受试者工作特征(ROC)曲线评估SII和RDW对HSP合并肾损害的预测价值。结果两组患儿的年龄(t=-2.449)、白细胞计数(t=-3.057)、血红蛋白(t=-2.304)、红细胞压积(t=-2.630)、RDW(t=-8.617)、中性粒细胞计数(t=-2.788)、中性粒细胞/淋巴细胞比值(Z=-2.887)、SII(Z=-3.325)比较差异均有统计学意义(P<0.05)。多因素Logistic回归分析显示,RDW(OR=1.861,95%CI:1.526~2.270,P<0.001)、SII(OR=1.003,95%CI:1.001~1.005,P=0.008)均是HSP患儿发生肾损害的独立危险因素。RDW、SII水平与24h-UPRO水平均呈正相关(r值分别为0.256、0.429,P<0.05)。ROC曲线评估显示,RDW预测HSP患儿合并肾损害的曲线下面积(AUC)为0.817(95%CI:0.757~0.877,P<0.001),最佳截断值为38.85fL,灵敏度和特异度分别为80.52%和70.18%;SII预测HSP患儿合并肾损害的AUC为0.642(95%CI:0.562~0.721,P=0.001),最佳截断值为401.67×10^(9)/L,灵敏度和特异度分别为81.82%和43.86%;二者联合预测HSP患儿合并肾损害的AUC为0.845(95%CI:0.790~0.900,P<0.001),灵敏度和特异度分别为87.01%和71.93%。结论SII和RDW对预测HSP患儿合并肾损害有一定的临床应用价值。 展开更多
关键词 全身免疫炎症指数 红细胞分布宽度 过敏性紫癜 肾损害 儿童
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Interpreting Larix principis-rupprechtii radial growth in northern China based on the Vaganov-Shashkin model
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作者 Jiachuan Wang Shuheng Li +4 位作者 Qiang Li Yili Guo Yijie Han Qi Liu Yiqi Zhao 《Journal of Forestry Research》 SCIE EI CAS CSCD 2024年第3期99-110,共12页
Changes in annual radial growth is an important indication of climate change. Dendroclimatology studies in northern China have focused on linear statistical analysis,but lacking studies based on the process of ring fo... Changes in annual radial growth is an important indication of climate change. Dendroclimatology studies in northern China have focused on linear statistical analysis,but lacking studies based on the process of ring formation to clarify the radial growth of trees. Tree-ring width standard chronology(STD) was established using samples of Larix principis-rupprechtii collected at 2303 m altitude on Luya Mountain. Using the Vaganov-Shashkin(VS) model to simulate growth and development, the internal physiological mechanism of radial growth is identified. It was concluded that:(1) the growing season of L. principis-rupprechtii was May to September;(2) soil moisture was a significant factor in the early and late growing seasons, and temperature was the dominant factor in its main growth period;and(3) formation of narrow ring widths was closely related to drought stress, the development of wide ring widths will be restricted by increasing future temperatures. The VS model is applicable for radial growth simulation of subalpine coniferous forests and for guiding the cultivation of local tree species in the future. 展开更多
关键词 Vaganov-Shashkin model Larix principis-rupprechti tree-ring width Annual growth
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老年脓毒症患者住院期间死亡风险预测模型的建立与验证
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作者 邢冬梅 隋冰冰 王磊 《实用临床医药杂志》 CAS 2024年第8期39-44,共6页
目的建立并验证可预测老年脓毒症患者住院死亡风险的模型。方法回顾性纳入2019年1月—2022年12月哈尔滨医科大学附属第一医院重症医学科住院治疗的238例脓毒症患者,以住院期间转归情况为主要结局指标,分为死亡组68例(28.57%)和生存组170... 目的建立并验证可预测老年脓毒症患者住院死亡风险的模型。方法回顾性纳入2019年1月—2022年12月哈尔滨医科大学附属第一医院重症医学科住院治疗的238例脓毒症患者,以住院期间转归情况为主要结局指标,分为死亡组68例(28.57%)和生存组170例(71.43%)。采用多因素Logistic回归法筛选脓毒症患者住院死亡的独立危险因素,并根据影响因素构建预测脓毒症患者住院死亡风险的模型。采用受试者工作特征(ROC)曲线对预测模型的性能进行评定,结果以曲线下面积(AUC)表示;基于2016年1月—2018年12月的176例脓毒症患者的临床资料进行外部验证。结果单因素分析显示,与生存组比较,死亡组年龄>70岁的比率、急性肾损伤(AKI)Ⅲ期比率及红细胞分布宽度(RDW)、纤维蛋白原、乳酸、血肌酐、英国早期预警评分(NEWS)、快速序贯器官衰竭评分(qSOFA)升高,氧合指数、白蛋白降低,差异均有统计学意义(P<0.05)。多因素Logistic回归分析结果显示,年龄>70岁(OR=1.426,95%CI:1.055~1.928)、乳酸>6 mmol/L(OR=1.436,95%CI:1.105~1.867)、RDW>16%(OR=1.354,95%CI:1.080~1.698)、AKIⅢ期(OR=1.982,95%CI:1.407~2.791)、qSOFA>2分(OR=1.853,95%CI:1.255~2.738)是脓毒症患者住院期间死亡的独立危险因素(P<0.05)。根据回归分析结果,建立脓毒症患者死亡风险方程,一致性指数(Cindex)=-1.694+0.355×年龄+0.303×RDW+0.362×乳酸+0.684×AKIⅢ期+0.617×qSOFA。ROC曲线显示,内部验证时Cindex预测脓毒症患者住院期间死亡的AUC为0.882(95%CI:0.834~0.929),灵敏度为83.82%,特异度为77.06%;外部验证时Cindex预测脓毒症患者住院期间死亡的AUC为0.823(95%CI:0.757~0.889),灵敏度为74.13%,特异度为81.36%。结论年龄、乳酸、RDW、AKI分期、qSOFA与老年脓毒症死亡风险具有相关性,基于这些参数构建的模型可能有助于预测老年脓毒症住院期间全因死亡风险。 展开更多
关键词 脓毒症 死亡风险 预测模型 老年人 一致性指数 红细胞分布宽度 急性肾损伤 快速序贯器官衰竭评分
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异种胶原基质在种植体周角化黏膜增宽中的美学效果评价
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作者 杨艳 张佳 +3 位作者 马雪纯 蔡安东 周文娟 柳忠豪 《口腔疾病防治》 2024年第2期108-115,共8页
目的评价异种胶原基质在种植体周角化黏膜增宽中的稳定性及美学效果,为异种胶原基质材料的临床应用提供参考依据。方法获得医院伦理委员会审批及患者知情同意,收集2020年7月至2022年9月于滨州医学院附属烟台口腔医院因种植位点颊侧角化... 目的评价异种胶原基质在种植体周角化黏膜增宽中的稳定性及美学效果,为异种胶原基质材料的临床应用提供参考依据。方法获得医院伦理委员会审批及患者知情同意,收集2020年7月至2022年9月于滨州医学院附属烟台口腔医院因种植位点颊侧角化黏膜宽度(keratinized mucosa width,KMW)<2 mm行角化黏膜增宽的20例患者,共纳入36颗种植体,年龄(52.0±10.4)岁,其中女性18例,男性2例。根据移植材料的不同分为游离龈移植(free gingival graft,FGG)对照组和异种胶原基质试验组。测量术后1、3个月种植体颊侧KMW的增量效果及黏膜收缩率,评价术后黏膜瘢痕指数(mucosal scarring index,MSI)。结果术后3个月对照组的KMW为(3.67±1.06)mm,试验组的KMW为(2.96±0.98)mm,差异有统计学意义(t=2.076,P<0.05)。术后1个月试验组KMW收缩率为(33.34±16.30)%,对照组为(22.05±15.47)%,差异有统计学意义(P<0.05);术后3个月试验组KMW收缩率为(51.95±12.60)%,对照组为(37.44±16.30)%,差异有统计学意义(P<0.05)。术后3个月试验组在瘢痕5项指标中(瘢痕宽度、瘢痕凸度、瘢痕颜色、缝合痕迹、整体外观)均优于对照组,差异具有统计学意义(P<0.05)。结论异种胶原基质在种植体周角化黏膜增宽中可以增加KMW,同时获得更加自然协调的软组织美学效果,但具有较大的收缩率。 展开更多
关键词 牙种植 角化黏膜 角化黏膜宽度 种植体周角化黏膜增宽 游离龈移植术 异种胶原基质 角化黏膜收缩率 黏膜瘢痕指数 美学效果
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Blown Film Extrusion Process for Polybags: Technical Overview and Applications
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作者 Sunil Badgujar Sudeep Asthana +6 位作者 Ravindra Kanawade Krunal Suthar Ankit Solanki Karuppiah Nagaraj Mahaveer Singh Bilkhu Harekrushna Sutar Swapna Rekha Panda 《Advances in Chemical Engineering and Science》 CAS 2024年第4期188-201,共14页
The choice of extrusion process is a decisive factor that affects the finished product quality for polybag manufacturing. One important component influencing the quality of the finished product is the selection of the... The choice of extrusion process is a decisive factor that affects the finished product quality for polybag manufacturing. One important component influencing the quality of the finished product is the selection of the extrusion technique. Two popular procedures that vary in the kind of dye used and the final product’s texture are cast film and blown film. In the horizontal extrusion moulding method known as “cast film”, heated resin is injected into a flat dye and allowed to cool on chill rolls. The film produced is clear, lightweight, and appropriate for lamination;its thickness varies based on the winding speed and the film is slower to crystallize and has less clarity but more durability because the resin molecules have reoriented, facing limitation of high wastage generation. This study primarily focused on the preparation of polybag film using the blown film extrusion process, utilizing high-quality polymer resins such as polyester polyethylene (PP) and linear low-density polyethylene (LLDPE) to minimize waste generation. The novelty of the process was reflected in minimising the waste generation. The control parameters considered in this study are temperature, pressure, and air intake volume. We investigated the influence of these critical process control parameters on the gauge thickness, optical properties, and mechanical strength of the polybag film produced through blown film extrusion. Additionally, we replicated the blown film process using simulation software developed at Pennsylvania College of Technology. The simulation results confirmed the overall stability of the polybag film produced through the blown film extrusion process. 展开更多
关键词 LLDPE Melt Flow index Blow-Up Ratio Lay-Flat width Draw-Down Ratio
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