珠穆朗玛峰北坡桤木属大气花粉传输路径与来源

认识区域大气花粉组成及其形成条件有利于明确不同类型花粉组合的气候与环境意义。利用布卡大气花粉采样器在珠穆朗玛峰北坡开展了连续2年(2012—2013年)的大气花粉观测研究。基于后向轨迹和潜在来源区域模型,探讨了秋季主要组分桤木属花粉的传输路径与潜在来源区域,分析了桤木属花粉与其植物分布和大气环流的关系及气候指示意义。结果显示:(1)桤木属花粉季气团传输路径主要来自于采样点西南方向;(2)桤木属花粉潜在来源区域与其气团传输路径基本一致,主要是喜马拉雅山脉中段,包括尼泊尔中部和东部以及西藏南部等地区;(3)桤木属花粉数量、传输路径和来源区域的年际变化与大气环流有关,受高空西风影响的西南气团对桤木属花粉影响更大。研究结果可以为认识珠穆朗玛峰北坡外来花粉的气候意义提供科学依据。

模仿目标临床试验在脑血管疾病领域的应用现状及展望

模仿目标临床试验是一种利用观察性研究数据来模仿随机临床试验结果的方法,近年来在临床研究中得到了广泛应用。模仿目标临床试验在脑血管疾病研究领域的应用,可以补充随机临床试验的不足,提高研究效率和可靠性,减少试验成本和时间,同时还可以扩大研究样本量,提高研究结果的可解释性和可推广性。未来,模仿目标临床试验在脑血管疾病研究中的应用还有待进一步发展和完善,从而更好地为脑血管疾病的治疗和预防提供科学依据。本文针对模仿目标临床试验在脑血管疾病领域的应用现状及未来展望进行了综述。

Climatic and lake environmental changes in the Serling Co region of Tibet over a variety of timescales

The Serling Co region is located at the transitional zone of the interaction between the Indian monsoon and the westerlies over the Tibetan Plateau. The Serling Co lake covers a water area of2,389 km2(June 2017) in a 45,530 km2drainage basin. Under the dramatic hydro-meteorological changes on the Tibetan Plateau in recent decades, and complex hydrological compositions of rivers and lakes in the basin, the lake area expanded by 43%, from1,667 km2in 1976, to 2,389 km2in 2017 (1)In 2014 it surpassed Nam Co as the largest lake on the Tibetan Plateau [2], and exerts significant effect on regional environmental conditions.

Pollen-inferred Holocene vegetation and climate histories in Taro Co,southwestern Tibetan Plateau

A 310-cm-long sediment core,covering the last10,200 years,was collected from Taro Co on the southwestern Tibetan Plateau and analyzed for pollen,grain size and total inorganic carbon content.The pollen data showed that vegetation changed from alpine steppe to alpine meadow during 10,200–8,900 cal a BP,to alpine steppe dominated by Artemisia during 8,900–7,400 cal a BP,to alpine meadow during 7,400–3,300 cal a BP and to alpine steppe after 3,300 cal a BP.Correspondingly,the pollen,grain size and total inorganic carbon content results revealed climatic change in this area over four stages.The initial stage was from 10,200 to 8,900 cal a BP,during which the climate changed from cold-dry to warm-humid.The second stage(8,900–7,400 cal a BP)was characterized by a warm and dry climate.However,at approximately7,400 cal a BP,the climate began to become cold and humid,which continued until 3,300 cal a BP.The last stage,from 3,300 cal a BP to present,was characterized as cold and increasingly arid.Climatic events of the early and mid-late Holocene showed that the area was significantly affected by the westerlies.However,the mid-Holocene climate in Taro Co was controlled by the Indian monsoon.The mid-late Holocene depositional environment record of Taro Co was very important to further elaborate the degree of influence by the westerlies or Indian monsoon.

Climatic significance of n-alkanes and their compound-specific dD values from lake surface sediments on the Southwestern Tibetan Plateau

The content and hydrogen isotope ratios of n-alkanes extracted from recent lake surface sediments sampled from nine lakes in three different climate zones on the Southwestern Tibetan Plateau were analyzed.Values were compared with n-alkanes in plants from lake drainages,and dD values of meteoric water,lake water,and mean annual precipitation.The results showed that n-C23was predominantly derived from aquatic plants,and n-C27–n-C33from terrestrial higher plants.The average carbon chain length of n-C27–n-C33(ACL27–33)was positively correlated with the mean annual precipitation.dD values of the long-chain n-alkanes n-C29and n-C31of terrestrial origin(varying between-214%and-169%,and-226%and-185%,respectively)were inversely correlated with mean annual precipitation;but in accordance with the average annual variations in dD(OIPC),dD values of n-C31were strongly related to the dD values of growing season meteoric water(R2=0.74).The large difference between dD values of n-C23of aquatic origin and n-C31(an average of about 27%)demonstrates the enrichment of the lake water dD compared to precipitation,caused by strong evaporation in the semiarid–arid areas of the southwestern Tibetan Plateau.Average value of en C25 31=p(-95%)is evidently higher than the value observed in European wet regions(-128%);besides,en C31(about-116%)is constant along the study transect(SD=9),which indicates that n-C31is a useful proxy for the environment.

The decrease of salinity in lakes on the Tibetan Plateau between 2000 and 2019 based on remote sensing model inversions

Salinity is an essential factor of lake water environments and aquatic systems.It is also sensitive to climatic changes and human activities based on concentration variations of solved minerals.However,there are few consecutively temporal studies on lake salinity variations on the Tibetan Plateau because the harsh environmental conditions make it diffcult to carry out in-situ observations for several lakes.In this study.we constructed a remote sensing retrieval model for lake salinity based on 87 in-situ lake investigations;moreover,interannual lake salinity and associated variations from 152 lakes larger than 50 km2 were analyzed on the Tibetan Plateau.A significant decreasing trend in lake salinity was observed between 2000 and 2019(p<0.01).The spatial variation of lake salinity was negatively correlated with lake area changes,and the optical characteristics of salt mineral solutions were generally positively correlated with mineral concentration based on the absorption coefficients of ionic solutions.The decreasing trend of lake salinity was not directly affected by the.precipitation,but was,potentially dominated by the expanding lake water volume.This study improves the understanding of regional water environmental changes and management efficacy of water resources.

Loss of life expectancy due to stroke and its subtypes in urban and rural areas in China,2005-2020

Stroke is characterised by high mortality and disability rate in China.This study aimed to explore the temporal trends in years of life lost(YLL)and loss of life expectancy due to stroke and its subtypes in urban and rural areas in China during 2005-2020.Data were obtained from China National Mortality Surveillance System.Abbreviated life and stroke-eliminated life tables were generated to calculate loss of life expectancy.The YLL and loss of life expectancy due to stroke in urban and rural areas at both national and provincial level during 2005-2020 were estimated.In China,the age-standardised YLL rate due to stroke and its subtypes were higher in rural areas than in urban areas.The YLL rate due to stroke showed a downward trend in both urban and rural residents from 2005 to 2020,decreased by 39.9%and 21.5%,respectively.Loss of life expectancy caused by stroke decreased from 1.75 years to 1.70 years from 2005 to 2020.During which,loss of life expectancy due to intracerebral haemorrhage(ICH)decreased from 0.94 years to 0.65 years,while that of ischaemic stroke(IS)increased from 0.62 years to 0.86 years.A slightly upward trend was observed in loss of life expectancy caused by subarachnoid haemorrhage(SAH),from 0.05 years to 0.06 years.Loss of life expectancy due to ICH and SAH was always higher in rural areas than in urban areas,whereas that of IS was higher in urban areas than in rural areas.Rural males suffered the greatest loss of life expectancy due to ICH and SAH,while the highest loss of life expectancy caused by IS was found in urban females.Furthermore,Heilongjiang(2.25 years),Tibet(2.17 years)and Jilin(2.16 years)were found to have the highest loss of life expectancy caused by stroke in 2020.Loss of life expectancy caused by ICH and SAH was higher in western China,while the disease burden of IS was heavier in northeast China.Stroke remains a major public health problem in China,although the age-standardised YLL rate and loss of life expectancy due to stroke decreased.Evidence-based strategies should be conducted to reduce the premature death burden caused by stroke and prolong life expectancy in Chinese population.

In-situ water quality investigation of the lakes on the Tibetan Plateau

The lakes on the Tibetan Plateau(TP)account for 57%of the total lake area in China[1],which is a key component of the Asia water tower[2-4].A recent study showed that there are 1424 lakes greater than 1 km^(2) on the TP,while the total lake area reached 5.0-10^(4)±791.4 km^(2) in 2018[5].Most lakes on the TP are closed and are less disturbed by human activities than the other inland water bodies in China.

Fifty years of Quaternary palynology in the Tibetan Plateau

Quaternary palynology in the Tibetan Plateau(TP)was initiated in the 1960s to meet the needs of economic development in western China.Pollen analysis was conducted for the first time on a 200-m long core of Quaternary lacustrine sediments taken from the main body of the TP in order to study pollen assemblages as well as vegetation and climate changes of glacial(cold)/interglacial(warm)periods.Pollen analysis of alpine snow and ice began at the first scientific expedition to the TP in the 1970s.After the 1980s,a series of international collaborative programs were carried out under Sino-French,Sino-German,Sino-Australian,and Sino-American cooperation,marking the integration of Chinese Quaternary palynology society with the international community.New methods for Quaternary palynology were gradually promoted and applied,changing the vegetational and climatic interpretation of Quaternary palynology from qualitative to quantitative.Since the 1990s,many palynologists have carried out extensive Quaternary palynological studies on fossil pollen sites of more than 60 lakes/sections and alpine glaciers in the TP to discuss the spatiotemporal vegetation changes and climatic and environmental evolution of the TP since the Pleistocene.Over the past half-century,Quaternary palynology in the TP has contributed to the establishment of the Chinese Quaternary pollen database and the study of vegetation and climate evolution since the Last Glacial Maximum(LGM)in the TP.Currently available pollen records revealed the spatial and temporal distribution of vegetation in the TP since the LGM,exhibiting expansions and shrinkages of forest,meadow,grassland and desert in different periods such as the LGM,the last deglaciation,and Holocene optimum period.The paleomonsoon reflected by paleovegetation since the LGM has undergone the changes of weak-strengthening-strong-weakening but still active-shrinking,which is mainly affected by solar insolation.