Lateral interaction by Laplacian‐based graph smoothing for deep neural networks

Lateral interaction in the biological brain is a key mechanism that underlies higher cognitive functions.Linear self‐organising map(SOM)introduces lateral interaction in a general form in which signals of any modality can be used.Some approaches directly incorporate SOM learning rules into neural networks,but incur complex operations and poor extendibility.The efficient way to implement lateral interaction in deep neural networks is not well established.The use of Laplacian Matrix‐based Smoothing(LS)regularisation is proposed for implementing lateral interaction in a concise form.The authors’derivation and experiments show that lateral interaction implemented by SOM model is a special case of LS‐regulated k‐means,and they both show the topology‐preserving capability.The authors also verify that LS‐regularisation can be used in conjunction with the end‐to‐end training paradigm in deep auto‐encoders.Additionally,the benefits of LS‐regularisation in relaxing the requirement of parameter initialisation in various models and improving the classification performance of prototype classifiers are evaluated.Furthermore,the topologically ordered structure introduced by LS‐regularisation in feature extractor can improve the generalisation performance on classification tasks.Overall,LS‐regularisation is an effective and efficient way to implement lateral interaction and can be easily extended to different models.

Prognostic value of systemic immune.inflammation index in patients with gastric cancer

Background:Inflammation-based indexes have been used to predict survival and recurrence in cancer patients.Systemic immune-inflammation index(Sll) was reported to be associated with prognosis in some malignant tumors.In the present study,we aimed to explore the association between Sll and the prognosis of patients with gastric cancer.Methods:We retrospectively analyzed data from 444 gastric cancer patients who underwent gastrectomy at the First Affiliated Hospital of Sun Yat-sen University between January 1994 and December 2005.Preoperative Sll was calculated.The Chi square test or Fisher's exact test was used to determine the relationship between preoperative Sll and clinicopathologic characteristics.Overall survival(OS) rates were estimated using the Kaplan-Meier method,and the effect of Sll on OS was analyzed using the Cox proportional hazards model.Receiver operating characteristic(ROC)curves were used to compare the predictive ability of Sll,NLR,and PLR.Results:Sll equal to or higher than 660 was significantly associated with old age,large tumor size,unfavorable Borrmann classification,advanced tumor invasion,lymph node metastasis,distant metastasis,advanced TNM stage,and high carcino-embryonic antigen level,high neutrophil-lymphocyte ratio,and high platelet-lymphocyte ratio(all P<0.05).High Sll was significantly associated with unfavorable prognosis(P<0.001) and Sll was an independent predictor for OS(P=0.015).Subgroups analysis further showed significant associations between high Sll and short OS in stage Ⅰ,Ⅱ,Ⅲ subgroups(all P<0.05).Sll was superior to NLR and PLR for predicting OS in patients with gastric cancer.Conclusion:Preoperative Sll level is an independent prognostic factor for OS in patients with gastric cancer.

多官能团端乙烯基酯基-环氧树脂的合成与结构表征

通过控制N,N,N′,N′-四缩水甘油基-4,4’-二氨基二苯甲烷(TGDDM)和丙烯酸(AA)的摩尔比(n(AA)/n(TGDDM)=1∶1、2∶1、3∶1、4∶1),合成了一系列多官能团端乙烯基酯基-环氧树脂(MVE-EPs)。采用端基分析、傅里叶变换红外光谱(FT-IR)分析了反应过程中环氧基和乙烯基酯基的变化规律。结果表明,反应体系中环氧基含量逐渐降低而乙烯基酯基含量逐渐升高,TGDDM的分子链上部分环氧基转化为乙烯基酯基,生成既含环氧基又含乙烯基酯基的MVE-EPs树脂。采用FT-IR、核磁共振氢谱(~1H-NMR)和凝胶渗透色谱(GPC)等测试表征了不同MVE-EPs树脂的结构。结果表明,随着原料配比中AA含量增加,MVE-EPs中乙烯基酯基含量逐渐增加,环氧基含量逐渐降低,MVE-EPs的相对分子质量逐渐升高,其中多官能团环氧乙烯基酯树脂(MVER)的数均相对分子质量(M_n)最大,MVE-EP 2的多分散性指数最大。

Ecological Risk Assessment of Shan Xin Mining Area Based on Remote Sensing and Geography Information System Technology

In this paper, introducing new remote sensing and geographic information technology to solve the problem of data collection and analysis, this makes the study of ecological risk assessment very quick and accurate. Taking the Shan Xin mining area of the tin mine in Lengshuijiang of Hunan Province as the research object, using the remote sensing image data of three periods in 2005, 2010 and 2015, the remote sensing image is classified carefully and the landscape classification map of the mining area is obtained. The ecological risk index is introduced and the ecological risk values are sampled and interpolated on the ArcGIS platform. The ecological risk spatial distribution map based on the landscape pattern index was obtained. The ecological risk was divided into 5 levels by using the Jenks natural classification method, and each ecological risk grade area was counted. The research results show that: from year 2005 to year 2010, landscape ecological risk trend of the mining area is growing up;the trend rising area of landscape ecological risk is mainly in the southwest and northeast of the Shan Xin mining field;the area of higher and high ecological risk is increasing year by year;and the trend of dispersed development in space is obvious;the development trend of ecological risk in the mining area is rapidly increasing;in 2010 - 2015, the higher and high ecological risk area decrease slightly with the increasing of area of grassland and residential low vulnerability of landscape types;the ecological risk area showed a slow decreasing trend. The research results provide an objective reference for decision making of ecological environment governance.

Hierarchical Merging &Generalization Method of Three-Dimension City Model Group Based on the Theory of Spatial Visual Cognition

In order to simplify the three-dimensional building group model, this paper proposes a clustering generalization method based on visual cognitive theory. The method uses road elements to roughly divide scenes, and then uses spatial cognitive elements such as direction, area, height and their topological constraints to classify them precisely, so as to make them conform to the urban morphological characteristics. Delaunay triangulation network and boundary tracking synthesis algorithm are used to merge and summarize the models, and the models are stored hierarchically. The proposed algorithm should be verified experimentally with a typical urban complex model. The experimental results show that the efficiency of the method used in this paper is at least 20% higher than that of previous one, and with the growth of test data, the higher efficiency is improved. The classification results conform to human cognitive habits, and the generalization levels of different models can be relatively unified by adaptive control of each threshold in the clustering generalization process.

Holocene Hydroclimatic Variations in the Asian Drylands:Current Understanding and Future Perspectives

0 INTRODUCTION.The intensification of global warming is generating increasing risks to human society and sustainable development,which are of growing concern to the international scientific community and policymakers(Sun,2023).The ecosystems of the Asian drylands are fragile and highly sensitive to global changes;moreover,while these drylands are the most important areas of oasis agriculture on Earth,their water resources are being adversely impacted by ongoing climate change(Zhang et al.,2023).Hence,an improved understanding of the patterns of climate change in this region is important and attracting increasing research attention.

气候变化以两种不同方式驱动了丝绸之路路线的变迁

Although climate change has convincingly been linked to the evolution of human civilization on different temporal scales,its role in influencing the spatial patterns of ancient civilizations has rarely been investigated,The northward shift of the ancient Silk Road(SR)route from the Tarim Basin(TB)to the Junggar Basin during~420-850 CE provides the opportunity to investigate the relationship between climate change and the spatial evolution of human societies.Here,we use a new high-resolution chironomidbased temperature reconstruction from arid China,combined with hydroclimatic and historical datasets,to assess the possible effects of climate fluctuations on the shift of the ancient SR route,We found that a cooling/drying climate in the TB triggered the SR route shift during~420-600 CE,However,a warming/wetting climate during~600-850 CE did not inhibit this shift,but instead promoted it,because of the favorable climate-induced geopolitical conflicts between the Tubo Kingdom and the Tang Dynasty in the TB.Our findings reveal two distinct ways in which climate change drove the spatial evolution of human civilization,and they demonstrate the flexibility of societal responses to climate change.

Neuroimmune regulation in the pancreas

The pancreas exerts endocrine and exocrine functions in energy balance.The neural innervation and immune milieu are both crucial in supporting pancreatic homeostasis.The neuronal network connects the pancreas with the central nervous system(CNS)and the enteric nervous system(ENS)and sustains metabolic activities.The nerves in the pancreas are categorized as spinal sensory afferent fibers,vagal sensory afferent nerves,autonomic fibers of both sympathetic and parasympathetic divisions,and fibers from the ENS and intrapancreatic ganglia.They innervate different regions and various cell types,which collectively determine physiological functions.Studies have established that the diverse pathological conditions,including pancreatitis,diabetes,and pancreatic tumor,are attributed to aberrant immune reactions;however,it is largely not clear how the neuronal network may influence the disease conditions.Enlightened by the recent advances illuminating the organ-wide neuronal architecture and the dysfunctions in pancreatic disorders,this review will highlight emerging opportunities to explore the cellular interrelationship,particularly the neuroimmune components in pancreatic health and diseases.

A cell wall invertase modulates resistance to fusarium crown rot and sharp eyespot in common wheat

Fusarium crown rot(FCR) and sharp eyespot(SE)are serious soil-borne diseases in wheat and its relatives that have been reported to cause wheat yield losses in many areas. In this study, the expression of a cell wall invertase gene, TaCWI-B1,was identified to be associated with FCR resistance through a combination of bulk segregant RNA sequencing and genome resequencing in a recombinant inbred line population. Two biparental populations were developed to further verify TaCWI-B1 association with FCR resistance.Overexpression lines and ethyl methanesulfonate(EMS) mutants revealed TaCWI-B1 positively regulating FCR resistance. Determination of cell wall thickness and components showed that the TaCWI-B1-overexpression lines exhibited considerably increased thickness and pectin and cellulose contents. Furthermore, we found that TaCWI-B1 directly interacted with an alphagalactosidase(TaGAL). EMS mutants showed that TaGAL negatively modulated FCR resistance. The expression of TaGAL is negatively correlated with TaCWI-B1 levels, thus may reduce mannan degradation in the cell wall, consequently leading to thickening of the cell wall. Additionally, TaCWI-B1-overexpression lines and TaGAL mutants showed higher resistance to SE;however, TaCWI-B1 mutants were more susceptible to SE than controls.This study provides insights into a FCR and SE resistance gene to combat soil-borne diseases in common wheat.

Temperature variations along the Silk Road over the past 2000 years:Integration and perspectives

Reconstructing temperature changes along the Silk Road(SR)over the last two millennia can provide insights into past global changes and their impact on the rise and fall of ancient civilizations in this region.Numerous high-quality single-site paleotemperature records have been produced for the eastern part of the SR(mainly for the Xinjiang region and its surrounding areas),which provide the data basis for a comprehensive synthesis.In this study,we used objective criteria to select 10 highquality ones from 30 temperature reconstructions derived from various geological archives including lacustrine sediments,ice cores,and tree rings in this region.Our aims are to summarize the pattern of temperature change over the past 2000 years,to provide a long-term viewpoint on the present warming,and to evaluate the impact of climate change on civilizations along the SR.The principal results are as follows:(1)The temperature variations over the last millennium are mutually consistent within these records.The study area experienced typical climate anomalies during the Medieval Warm Period(MWP,AD 1000-1250),the Little Ice Age(LIA,AD 1450-1850),and the Current Warm Period(CWP,AD 1850 to present);however,contrary to previous knowledge,the amplitude of climatic warming during the CWP did not exceed that during the MWP.(2)Fewer temperature records were available for the interval AD 1–1000,and there were large differences between them.For example,the reconstructed climate during both the Han Dynasty and the Sui-Tang Dynasties was either warm or cold,without prevailing consensus.(3)The warming during the MWP favored the rapid development of the SR route along the northern slopes of the Tianshan Mountains,and the cooling during the LIA contributed to the decline of the SR marked by the closure of the Jiayuguan Pass.Notably,the scarcity of temperature records and the discrepancies between them during AD 1-1000 in the eastern part of the SR have hindered our understanding of the hydroclimatic changes and their influence on the development of civilizations along the SR.Thus,it is important to obtain an increased number of high-quality reliable records spanning the past 2000 year,and to examine the occurrence of local signals of temperature changes during the period of AD 1-1000.On the other hand,the paleotemperature investigation on the western part of the SR over the last two millennia is wholly insufficient,and thus more high-quality single-site and integrated studies are needed,to facilitate more comprehensive insights into the coupled relationship between climate change and the rise and fall of civilizations along the entire length of the Silk Road.

Organic Passivation of Deep Defects in Cu(In,Ga)Se_(2) Film for Geometry-Simplified Compound Solar Cells

Diverse defects in copper indium gallium diselenide solar cells cause nonradiative recombination losses and impair device performance.Here,an organic passivation scheme for surface and grain boundary defects is reported,which employs an organic passivation agent to infiltrate the copper indium gallium diselenide thin films.A transparent conductive passivating(TCP)film is then developed by incorporating metal nanowires into the organic polymer and used in solar cells.The TCP films have a transmittance of more than 90%in the visible and nearinfrared spectra and a sheet resistance of~10.5Ω/sq.This leads to improvements in the open-circuit voltage and the efficiency of the organic passivated solar cells compared with control cells and paves the way for novel approaches to copper indium gallium diselenide defect passivation and possibly other compound solar cells.

Opioid growth factor receptor promotes adipose tissue thermogenesis via enhancing lipid oxidation

The thermogenic brown and beige adipocytes consume fatty acids and generate heat to maintain core body temperature in the faceof cold challenges.Since their validated presence in humans,the activation of thermogenic fat has been an attractive target fortreating obesity and related metabolic diseases.Here,we reported that the opioid growth factor receptor(Ogfr)was highly expressedin adipocytes and promoted thermogenesis.The mice with genetic deletion of Ogfr in adipocytes displayed an impaired capacity tocounter environmental cold challenges.Meanwhile,Ogfr ablation in adipocytes led to reduced fatty acid oxidation,enhanced lipidaccumulation,impaired glucose tolerance,and exacerbated tissue inflammation under chronic high-fat diet(HFD)-fed conditions.At the cellular level,OGFr enhanced the production of mitochondrial trifunctional protein subunitα(MTPα)and also interacted withMTPα,thus promoting fatty acid oxidation.Together,our study demonstrated the important role of OGFr in fatty acid metabolismand adipose thermogenesis.

AMH在NOA患者显微取精术前评估中的应用

目的探讨血清抗苗勒管激素(anti-Müllerian hormone,AMH)测定在评估非梗阻性无精子症(non-obstructive azoospermia,NOA)患者显微取精成功率中的价值。方法采用回顾性病例对照研究分析2014年9月至2022年5月期间于中山大学附属第六医院生殖医学中心接受显微取精手术的502例NOA患者的临床资料,根据手术结果分为获精组和未获精组,根据取精术中生精小管是否出现可辨别的差异分为差异可辨组和差异不可辨组,比较各组年龄、睾丸体积、血清AMH以及卵泡刺激素(follicle-stimulating hormone,FSH)、睾酮水平的差异,根据NOA病因分为睾丸炎组(特发性或腮腺炎继发)、AZFc区基因缺失组、隐睾下降固定术后组、克氏综合征(Klinefelter’s syndrome,KS)组、特发性NOA组,比较不同病因NOA患者获精率(sperm retrieval rate,SRR)与AMH水平的差异。结果270例患者成功获取到精子,SRR为53.8%;获精组AMH水平显著低于未获精组[0.81(0.16,3.26)μg/L比1.37(0.21,4.84)μg/L,P<0.001],两组间年龄、睾丸体积、FSH、睾酮水平差异均无统计学意义(均P>0.05)。不同病因NOA的血清AMH水平差异有统计学意义(P<0.001),睾丸炎、AZFc缺失、隐睾下降、KS和特发性NOA的AMH水平分别为0.15(0.01,0.41)μg/L、5.71(3.57,8.26)μg/L、2.29(1.36,3.81)μg/L、0.15(0.05,0.39)μg/L、2.46(0.75,5.49)μg/L。在特发性NOA患者中,显微取精获精组的年龄高于未获精组[(35.2±8.9)岁比(32.5±5.5)岁,P=0.010],睾酮、AMH水平显著低于未获精组[(3.1±1.4)μg/L比(3.7±2.1)μg/L,P=0.029;1.63(0.35,3.84)μg/L比3.00(1.20,6.68)μg/L,P=0.001],两组睾丸体积与FSH水平差异均无统计学意义(均P>0.05);AMH水平对显微取精SRR的受试者工作特征(receiver operating characteristic,ROC)曲线分析,AMH切点值为2.96μg/L、敏感度为0.710、特异度为0.523、曲线下面积(area under the curve,AUC)为0.649。生精小管差异可辨组的AMH水平显著低于差异不可辨组[0.55(0.12,2.05)μg/L比2.99(0.76,6.11)μg/L,P<0.001],而SRR高于差异不可辨组[75.9%(236/311)比17.8%(34/191),P<0.001]。结论对NOA患者实施显微取精时,低AMH水平病例更易于观察到生精小管之间的差异,并有更好的SRR,测定AMH的价值在特发性NOA患者中尤其明显。

无过渡金属参与杂环甲基化合物与醇的选择性有氧碳-烷基化反应

研究发现,使用适当的碱并将反应在空气下进行,不使用任何外加催化剂即可高效实现杂环甲基化合物与各种醇的选择性脱水碳-烷基化反应.控制实验说明该反应的确不需要过渡金属催化剂,机理研究也显示了碱和空气在反应中的关键作用:该反应实际上通过碱促进下空气将醇氧化为羰基化合物的方式启动,生成的羰基化合物中间体进而催化烷基化反应的顺利进行、从而选择性地得到烷基化产物,羰基化合物可在反应中再生、回收、完成催化循环.该方法具有底物适用范围广、无需过渡金属催化剂及配体、无需惰性气体保护、操作简单、成本较低、产物无过渡金属残留等优点,因此是一种较为实用的杂环化合物的官能团化方法.

Major advances in studies of the physical geography and living environment of China during the past 70 years and future prospects

The natural environment provides material essentials for human survival and development. The characteristics,processes, regional differentiation and forcing mechanisms of the elements of the natural environment(e.g. geomorphology,climate, hydrology, soil, etc.) are the main objects of research in physical geography. China has a complex natural environment and huge regional differentiation and therefore it provides outstanding reserach opportunities in physical geography. This review summarizes the most important developments and the main contributions of research in the physical geography and human living environment in China during the past 70 years. The major topics addressed are the uplift of the Tibetan Plateau and the evolution of its cryosphere, the development of fluvial systems, the acidification of the vast arid region of the Asian interior, variations in the monsoon and westerly climate systems on multiple timescales, the development of lakes and wetlands, the watershed system model, soil erosion, past human-environment interactions, biogeography, and physical geographic zonality. After briefly introducing international research developments, we review the history of research in physical geography in China, focusing on the major achievements and major academic debates, and finally we summarize the status of current research and the future prospects. We propose that in the context of the national demand for the construction of an ecological civilization, we should make full use of the research findings of physical geography, and determine the patterns and mechanisms of natural environmental processes in order to continue to promote the continued contribution of physical geography to national development strategies, and to further contribute to the theory of physical geography from a global perspective.

Spatiotemporal variations of aridity in China during 1961–2015: decomposition and attribution

Changes in global climate intensify the hydrological cycle, directly influence precipitation, evaporation,runoff, and cause the re-distribution of water resources in time and space. The aridity index (AI), defined as the ratio of annual precipitation to annual potential evapotranspiration, is a widely used numerical indicator to quantify the degree of dryness at a given location. This study examined the effects of climate change on AI in China during 1961–2015. The results showed that the nationally averaged AI experienced a notable interdecadal transition in 1993, characterized by increasing AI (wetter) between 1961 and 1993,and decreasing AI (drier) after 1993. Overall, the decreased solar radiation (solar dimming) was the main factor affected the nationally averaged AI during 1961–1993, while the relative humidity dominated the variations of nationally averaged AI during 1993–2015. However, the roles of individual factors on the changes in AI vary in different subregions. Precipitation is one of the important contributing factors for the changes of AI in almost all subregions, except the Mid-Lower Yangtze and Huaihe basins. Solar radiation has been significantly decreased during 1961–1993 in South China, Southwest China, Mid-Lower Yangtze and Huaihe basins, and the Tibetan Plateau. Therefore, it dominated the trends of AI in these subregions.The relative humidity mainly affected the Mid-Lower Yangtze and Huaihe basins, Southwest China, and the Tibetan Plateau during 1993–2015, hence dominated the trends of AI in these subregions. The changes of temperature and wind speed, however, played a relatively weak role in the variations of AI.

中国北方全新世沙尘暴演化:从自然驱动转向人为驱动

亚洲强沙尘暴事件能显著地降低空气质量,改变到达地面的太阳辐射,对人体健康产生严重的潜在危害,受到国内外的广泛关注.然而,目前对于全新世不同时间尺度亚洲沙尘暴的驱动机制以及是否存在由自然驱动向人为驱动的转变仍不清楚.黄土高原是世界上最大的粉尘堆积区,该区域未受人类活动直接影响的湖泊沉积是研究沙尘暴变化的理想载体.基于黄土高原上的高山湖泊岩芯,我们发现全新世沙尘暴频率总体呈增加趋势,并在过去2000年达到最高值且伴随着剧烈波动.其中,11~2 cal ka BP沙尘暴频率与东亚夏季风降水、植被覆盖、东亚冬季风强度均呈负相关,揭示出不同于冬季风控制沙尘暴变化的观点,认为东亚夏季风是控制千年尺度沙尘暴变化的自然驱动因子.从~2 cal ka BP开始,沙尘暴频率与粉尘源区人口数量、季风降雨量同步变化,人类活动的增强使得在强夏季风阶段却出现强沙尘暴现象,揭示出年代际尺度人类活动对地表系统的影响已超过夏季风的影响.沙尘暴由自然驱动向人为驱动的转变,支持中国北方"早期人为假说",可能至少开始于~2 cal ka BP.

中国目前和未来水文气候模态的变化特征

过去千年我国暖季的干湿变化呈现出三极子模态,即新疆地区和华南地区的干湿变化趋势与华北地区相反.本文利用中国的台站观测资料及CMIP5的模拟数据构建干燥度指数(AI),对目前和未来中国水文气候三级子模态的变化特征及归因进行了分析.结果表明,1993~2015年期间,长期存在的三极子模态已经消失.在未来RCP8.5排放情景下,21世纪中期当全球升温低于2℃时,该模态可以恢复;但是在21世纪末,三级子模态将再次消失.归因分析表明,未来气温升高将导致新疆和华南地区变干.除温度外,相对湿度的变化也是造成未来华南地区变干的重要因子.而华北地区AI对全球变暖的响应则取决于升温程度.当未来升温低于2℃时,降水的增加使得华北地区变湿,而在21世纪末,升温高于2℃时,温度的升高将导致华北地区变干.

眼科专业研究生抑郁情绪与学术产出的关联及学术行为自我效能感的中介作用

目的 :调查临床不同类型眼科专业研究生的抑郁情绪现状,并探讨其与学术产出的关系及学术行为自我效能感的中介效应。为解决研究生教育中的心理健康与学术产出的平衡提供重要参考。方法 :采用前瞻性研究设计,对376名眼科研究生进行调查。使用自编一般情况调查表、抑郁自评量表(SDS)、学术行为自我效能感量表(ABSS)在2020年初对眼科学专业研究生进行心理调查,统计其1年后学术产出情况。结果 :存在抑郁情绪研究生的构成比为26.33%,SDS平均分(45.95±15.08)低于全国常模;ABSS平均分(106.45±16.97);有学术产出研究生人数占49.73%;抑郁情绪与学术产出呈显著负相关;学术行为自我效能感与学术产出显著正相关;学术行为自我效能感在抑郁情绪与学术产出之间起完全中介作用。结论 :眼科专业研究生抑郁情绪不利于学术产出,抑郁情绪可通过学术行为自我效能感影响其后期的学术产出。可以通过缓解其抑郁情绪提高其学术行为自我效能感,从而提高其学术产出。

超级大旱与史前丝绸之路上的文化交流

中亚干旱区是丝绸之路的核心区,也是史前人类扩散和东西方文化交流的重要通道.该区气候干旱,植被和生态群落受制于水文因素.由于缺乏精确年代控制的高分辨率古气候记录,中亚地区全新世水文变化及极端干旱事件在史前人口迁移和跨欧亚大陆文化交流中扮演的角色还不清楚.本文基于来自吉尔吉斯斯坦的石笋多指标记录,重建了中亚干旱区目前年代最精确(测年误差~6‰)、分辨率最高(~3年)、涵盖中晚全新世的降水变化序列.结果显示在5820~5180 a BP期间,该区存在一次持续时间为640年的超级干旱事件,主要受西风带北移的影响.这次干旱事件对中亚史前文化的发展产生了重要影响,很可能阻碍了史前东西方文化沿中亚绿洲路线上的相向扩散,使得最早的跨欧亚大陆文化交流在5000~4000 a BP沿着北方草原路线开展.随着大干旱后降水的逐渐增加和生态环境的恢复,中亚绿洲和河谷中增加的定居人口促进了不同绿洲之间的相互联系,进一步在4000~3000 a BP开辟了跨大陆文化交流的史前丝绸之路,为历史时期丝绸之路的最终开通奠定了基础.