There are differing views regarding the climatic factors that limit radial growth of Qilian juniper （Juniperus przewalskii Kom.） at the upper treelines on the northeastern Tibetan Plateau. In this study, trees from ...There are differing views regarding the climatic factors that limit radial growth of Qilian juniper （Juniperus przewalskii Kom.） at the upper treelines on the northeastern Tibetan Plateau. In this study, trees from an upper tree northeastern Tibetan Plateau were selected to limits the radial growth of Qilian juniper. Using ine site in the Anyemaqen Mountains of the present new evidence that low temperature a signal-free regional curve standardization （SF-RCS） method, a ring-width chronology for Qilian juniper was developed extending from AD 1082 to 2010. The results of correlation analysis between tree-ring index and instrumental climatic variables showed that both winter （December in the previous year and January in the current year） and summer （July and August in the current year） temperatures were signifi- cantly and positively correlated with the tree-ring index. Precipitation in June was also significantly and positively correlated with the tree-ring index, but was not as important as low temperature in controlling tree growth. To test the key limiting climatic factor for tree radial growth at different altitudes, an indicator termed the ＂relative distance to upper treeline＂ （RDUT） was developed to quantify the representativeness of collected samples for the forest＇s upper treeline. The RDUT showed that the upper 20% of the forest belt may be an important boundary in terms of capturing the temperature signal from tree-ring width at the upper treelines on the northeastern Tibetan Plateau. Our findings enhance the existing understanding that temperature is the limiting factor at upper treelines on the northeastern Tibetan Plateau, and will be useful in the reconstruction of past temperature in future studies.展开更多
目的评估高原地区血小板分布宽度（platelet distribution width, PDW）在脑梗死（cerebralinfarct，CI）患者中的临床价值。方法青海省人民医院收治并明确诊断为脑梗死的患者98例，根据斯坎迪纳维亚神经卒中量表评分（SNSS）分为低危...目的评估高原地区血小板分布宽度（platelet distribution width, PDW）在脑梗死（cerebralinfarct，CI）患者中的临床价值。方法青海省人民医院收治并明确诊断为脑梗死的患者98例，根据斯坎迪纳维亚神经卒中量表评分（SNSS）分为低危组、中危组、高危组和极高危组，收集人口学参数和PDW数据，另选取同时期来我院体检的健康者50例为对照组，分析四组患者PDW水平与病情严重程度、梗死面积之间的相关性，并以改良Rankin残障量表（mRS）进行预后评估，应用ROC曲线下面积（AUC）检验PDW及SNSS评分对脑梗死不良预后的预测价值。结果CI发病时，PDW与脑梗死病情严重程度（P〈0．05）和梗死面积显著相关（P〈0．01），PDW及SNSS评分的AUC分别为0．811、0．874。结论PDW对判断高原地区CI病情严重程度、梗死面积有一定临床意义，并且对不良预后具有预测价值。展开更多
Experiments were conducted on the Tibetan Plateau to investigate the effects of sample width (W) on flame spread over horizontal charring solid surfaces. The results show that the rate of spread is influenced by the c...Experiments were conducted on the Tibetan Plateau to investigate the effects of sample width (W) on flame spread over horizontal charring solid surfaces. The results show that the rate of spread is influenced by the combined effects of convection heat transfer and flame radiation. Moreover, two different regimes depending on sample width were found in flame spread behavior. The rate of spread decreased with width in the convective regime (W≤3 cm) but increased in the radiative regime (W>3 cm). Similar results were observed in comparative experiments conducted on a plain in Hefei, with the rate of spread reaching its minimum value at W=4 cm rather than 3 cm.展开更多
This paper presents a 457-year reconstruction of precipitation in the southeastern Qinghai-Tibet Plateau using tree-ring records.Tree-ring samples were collected from the Hengduan Mountains in the southeastern part of...This paper presents a 457-year reconstruction of precipitation in the southeastern Qinghai-Tibet Plateau using tree-ring records.Tree-ring samples were collected from the Hengduan Mountains in the southeastern part of the Qinghai-Tibet Plateau,China.A nearly 500-year chronology was developed using tree-ring width records.Correlation analysis shows moisture is the main factor limiting tree growth in this region.Ring-widths were significantly positively correlated with the Palmer Drought Severity Index(PDSI) and precipitation in many months.The highest correlation coefficient was found between the annual growth of trees and precipitation from the previous September to the current June(0.738).Based on this relationship,we reconstructed the precipitation history from 1509 to 2006.The reconstruction explains 54.4%(Radj2=53.5%,N=49,F=56.12) of the actual precipitation variation during the calibration period(1958-2006).During the reliable period of the reconstruction(1549-2006),some low-frequency climate signals are included,indicating this region has been getting wetter in the last 20 years.The reconstruction documents six apparently dry and five pluvial periods and the 17th century dry period lasted longer than any other.When compared with other recent studies,this study and these earlier reconstructions show a similar trend in the variation of drought and pluvial.Further spatial correlation analysis confirms that the reconstructed precipitation adequately represents the rainfall history of the entire Hengduan Mountain area.The Multi-taper method,a type of spectral analysis,reveals that precipitation in this area had significant(P<0.01) spectral peaks at 3-5 a,60 a and 79-85 a.展开更多
基金The Strategic Priority Research Program from the Chinese Academy of Sciences No.XDA05080201 National Natural Science Foundation of China, No.41071061
文摘There are differing views regarding the climatic factors that limit radial growth of Qilian juniper （Juniperus przewalskii Kom.） at the upper treelines on the northeastern Tibetan Plateau. In this study, trees from an upper tree northeastern Tibetan Plateau were selected to limits the radial growth of Qilian juniper. Using ine site in the Anyemaqen Mountains of the present new evidence that low temperature a signal-free regional curve standardization （SF-RCS） method, a ring-width chronology for Qilian juniper was developed extending from AD 1082 to 2010. The results of correlation analysis between tree-ring index and instrumental climatic variables showed that both winter （December in the previous year and January in the current year） and summer （July and August in the current year） temperatures were signifi- cantly and positively correlated with the tree-ring index. Precipitation in June was also significantly and positively correlated with the tree-ring index, but was not as important as low temperature in controlling tree growth. To test the key limiting climatic factor for tree radial growth at different altitudes, an indicator termed the ＂relative distance to upper treeline＂ （RDUT） was developed to quantify the representativeness of collected samples for the forest＇s upper treeline. The RDUT showed that the upper 20% of the forest belt may be an important boundary in terms of capturing the temperature signal from tree-ring width at the upper treelines on the northeastern Tibetan Plateau. Our findings enhance the existing understanding that temperature is the limiting factor at upper treelines on the northeastern Tibetan Plateau, and will be useful in the reconstruction of past temperature in future studies.
文摘目的评估高原地区血小板分布宽度（platelet distribution width, PDW）在脑梗死（cerebralinfarct，CI）患者中的临床价值。方法青海省人民医院收治并明确诊断为脑梗死的患者98例，根据斯坎迪纳维亚神经卒中量表评分（SNSS）分为低危组、中危组、高危组和极高危组，收集人口学参数和PDW数据，另选取同时期来我院体检的健康者50例为对照组，分析四组患者PDW水平与病情严重程度、梗死面积之间的相关性，并以改良Rankin残障量表（mRS）进行预后评估，应用ROC曲线下面积（AUC）检验PDW及SNSS评分对脑梗死不良预后的预测价值。结果CI发病时，PDW与脑梗死病情严重程度（P〈0．05）和梗死面积显著相关（P〈0．01），PDW及SNSS评分的AUC分别为0．811、0．874。结论PDW对判断高原地区CI病情严重程度、梗死面积有一定临床意义，并且对不良预后具有预测价值。
基金supported by the National Natural Science Foundation of China (50976110)the National Science Foundation for Post-doctoral Scientists of China (20090450703)
文摘Experiments were conducted on the Tibetan Plateau to investigate the effects of sample width (W) on flame spread over horizontal charring solid surfaces. The results show that the rate of spread is influenced by the combined effects of convection heat transfer and flame radiation. Moreover, two different regimes depending on sample width were found in flame spread behavior. The rate of spread decreased with width in the convective regime (W≤3 cm) but increased in the radiative regime (W>3 cm). Similar results were observed in comparative experiments conducted on a plain in Hefei, with the rate of spread reaching its minimum value at W=4 cm rather than 3 cm.
基金supported by the National Natural Science Foundation of China (41171039 and 40890051)the Chinese NSFC Innovation Team Project (41021091)+1 种基金the One Hundred Talents Program of Chinese Academy of Sciences (29O827B11)the Program of Introducing Talents of Discipline to Universities from China’s Ministry of Education (B06026)
文摘This paper presents a 457-year reconstruction of precipitation in the southeastern Qinghai-Tibet Plateau using tree-ring records.Tree-ring samples were collected from the Hengduan Mountains in the southeastern part of the Qinghai-Tibet Plateau,China.A nearly 500-year chronology was developed using tree-ring width records.Correlation analysis shows moisture is the main factor limiting tree growth in this region.Ring-widths were significantly positively correlated with the Palmer Drought Severity Index(PDSI) and precipitation in many months.The highest correlation coefficient was found between the annual growth of trees and precipitation from the previous September to the current June(0.738).Based on this relationship,we reconstructed the precipitation history from 1509 to 2006.The reconstruction explains 54.4%(Radj2=53.5%,N=49,F=56.12) of the actual precipitation variation during the calibration period(1958-2006).During the reliable period of the reconstruction(1549-2006),some low-frequency climate signals are included,indicating this region has been getting wetter in the last 20 years.The reconstruction documents six apparently dry and five pluvial periods and the 17th century dry period lasted longer than any other.When compared with other recent studies,this study and these earlier reconstructions show a similar trend in the variation of drought and pluvial.Further spatial correlation analysis confirms that the reconstructed precipitation adequately represents the rainfall history of the entire Hengduan Mountain area.The Multi-taper method,a type of spectral analysis,reveals that precipitation in this area had significant(P<0.01) spectral peaks at 3-5 a,60 a and 79-85 a.
