Effects of Periodic Temperature Changes on Stress Relaxation of Chemically Treated Wood

In order to clarify the relationship between the microstructural changes and the rheological behaviors of four chemically treated woods (delignified wood, hemicellulose-removed wood, DMSO swollen and decrystallization treated wood), the stress relaxation of wood with three different moisture contents was determined during periodic temperature changes. The experi- mental results show that after wood relaxation for 4 h at 25 °C, the stress decays sharply when the temperature increases and 2 h later the stress recovers again when the temperature drops back to the original point. The additional stress relaxation, produced after tem- perature begins to increase, is mainly caused by the thermal swelling, molecular thermal movement and the break of a part of residual hydrogen bonds. The number of hydrogen bonds and the size and amount of cavities in various treated woods greatly affect the magnitude of the additional relaxed stress and the recovery stress.

Climate change during the last glacial period on the southeast margin of Badain Jaran Desert, Northwest China

Reconstruction of the desert paleoclimate is important to understand the mechanisms that triggered and/or enhanced climate change.Through optically stimulated luminescence(OSL)dating,grain size,magnetic susceptibility,X-ray powder diffraction(XRD)and geochemical indicators,we provide a welldated record of a sedimentary outcrop on the southeast margin of the Bardain Jaran Desert,Northwest China,during the last glacial period.Four Qz-OSL ages are obtained,41.0±3.4 ka,54.7±4.4 ka,59.5±5.0 ka and 66.8±5.8 ka,corresponding to the depths of 35 cm,70 cm,150 cm and 200 cm respectively.Indicators like grain size,clay content,magnetic susceptibility,XRD and geochemical index(e.g.Sr,Ba,Sr/Ca)jointly indicate abrupt climate changes at the depth of 35 cm(age,ca.41.0 ka)and200 cm(age,ca.67 ka).Namely,the 280 cm sedimentary outcrop perfectly records a warm wet climate stage,corresponding to the late Marine Isotope Stages(MIS)4 to the early MIS 3.Besides,there is a trend of grain size increase after around 40ka BP,which is most likely a signal of wind strength change.Our research supports that enhancing Siberian High pressure system during the late MIS 3played a key role in NW East Asia climate evolution.

Characteristics of Temperature Change in China over the Last 2000 years and Spatial Patterns of Dryness/Wetness during Cold and Warm Periods

This paper presents new high-resolution proxies and paleoclimatic reconstructions for studying climate changes in China for the past 2000 years. Multi-proxy synthesized reconstructions show that temperature variation in China has exhibited significant 50–70-yr, 100–120-yr, and 200–250-yr cycles. Results also show that the amplitudes of decadal and centennial temperature variation were 1.3℃ and 0.7℃, respectively, with the latter significantly correlated with long-term changes in solar radiation, especially cold periods, which correspond approximately to sunspot minima. The most rapid warming in China occurred over AD 1870–2000, at a rate of 0.56°± 0.42℃（100 yr）^（-1）; however, temperatures recorded in the 20 th century may not be unprecedented for the last 2000 years, as data show records for the periods AD 981–1100 and AD1201–70 are comparable to the present. The ensemble means of dryness/wetness spatial patterns in eastern China across all centennial warm periods illustrate a tripole pattern： dry south of 25°N, wet from 25°–30°N, and dry to the north of 30°N. However, for all centennial cold periods, this spatial pattern also exhibits a meridional distribution. The increase in precipitation over the monsoonal regions of China associated with the 20 th century warming can primarily be attributed to a mega El Nino–Southern Oscillation and the Atlantic Multidecadal Oscillation. In addition, a significant association between increasing numbers of locusts and dry/cold conditions is found in eastern China. Plague intensity also generally increases in concert with wetness in northern China, while more precipitation is likely to have a negative effect in southern China.

Social development and living environment changes in the Northeast Tibetan Plateau and contiguous regions during the late prehistoric period

The relationship between the evolution of human societies and their living environments has been discussed intensively in recent decades.It is important to understand the patterns and mechanisms of human–environment interaction and evolution in order to cope with rapidly changing environments in the modern world.We reviewed the results of dating,archaeobotanical,and zooarchaeological studies from 139 prehistoric sites in the Northeast Tibetan Plateau(NETP)and contiguous regions(NETP-CR:i.e.,the Hexi Corridor and western margin of the Chinese Loess Plateau)and compared them with paleoenvironmental records to study variations in spatiotemporal patterns of social development in the area and their relationships with climate and vegetation changes.Our results show that hunter-gatherer groups occupied vast areas of the NETP at low intensities during^15,000–5500 BP(years before present).This was directly related to forest cover and climate change.An increase in temperature and precipitation turnover of vegetation from desert steppe to alpine meadow/subalpine shrub,and recovery of animal population on the Tibetan Plateau created more food resources and space for hunter-gatherers.Millet farmers settled extensively below 2500 m a.s.l.(meters above sea level)in the NETP-CR between^5500 and 3600 BP,and might have coexisted with hunting groups above 2500 m a.s.l.via subsistence exchange.The distribution of human settlements during that period was affected by climate change,with the relatively warm and wet climate promoting the expansion of millet agriculture to the NETP-CR during 5500–4500 BP,while climate deterioration caused humans to retreat to lower altitudes.During 3600–2200 BP,a range of livelihoods emerged in different regions of the NETPCR.This was promoted by early trans-Eurasian exchange and the development of an agro-pastoral economy that utilized cold-tolerant crops and livestock.This eventually promoted the expansion of permanent human settlements to high-altitude areas in the NETP.This study found that human societies adopted various strategies to adapt to the changing living environment throughout late prehistoric times in the NETP-CR.The results provide a long-term perspective on the trajectory of regional socio-environmental co-evolution.

Joint Distribution of Wave Periods and Rate of Change of Wave Surface Elevation

The rate of change of wave surface elevation is of much importance in ocean engineering, especially for the determination of the limitation of wave breaking. This paper gives a kind of joint distribution of wave periods and the rate of change of wave surface elevation by means of calculation of the two-order to four-order moment of the frequency spectrum based on the linear wave theory. For the first time, the distribution density function of wave periods determined by peaks is provided, and the conclusion is drawn that the rate of change of wave surface elevation obeys the Rayleigh distribution.

Climate Change Characteristics and Return Periods of Heavy Precipitation in the Northeast Side of Qinghai-Tibet Plateau

[ Objective] The study aimed to discuss analyze climate change characteristics and return periods of heavy precipitation in the northeast side of Qinghai-Tibet Plateau. [ Method] Based on the data of daily precipitation from 1943 to 2008 in 6 representative meteorological stations in Linxia located in the northeast side of Qinghai-Tibet Plateau, the climate change characteristics of heavy precipitation were analyzed, and the return periods of heavy precipitation were calculated by Pearson-Ill probability distribution method. [ Result] Days of heavy precipitation in Linxia region in- creased conspicuously since the 1990s. The return periods of heavy precipitation in the six stations on August 20, 2008 were consistent with the re- sults of artificial estimation. [ Conclusion] The research could provide scientific references for the reasonable utilization of climate resources, disas- ter prevention and rational arranqement of anricultural plantina svstems in Linxia reaion.

Analysis on Change Tendency of the Precipitation Resource during Growth Period of the Conventional Crops in Plain Area before Taihang Mountains

[Objective] The aim was to study change tendency of the precipitation resource during growth period of the conventional crops in plain area before Taihang Mountains. [ Method] Based on daily precipitation data at Shijiazhuang meteorological station in recent 51 years, average rainfall dudng growth periods of the 9 kinds of conventional crops was obtained. Precipitation tendency dudng growth periods of the 9 kinds of conventional crops in plain area before Taihang Mountains was analyzed by Mann-Kendall nonparametric test. [ Result] Seen from rainfall during growth pedods of the different crops, rainfall was the least during the growth period of winter wheat, followed by summer corn. Rainfall during growth peri- ods of the cotton, oil plant, vegetable, fruit tree, potato, rice and legumes was more. Under different guaranteed rates, precipitation change also had difference. Rainfall change during growth periods of the wheat and corn was bigger, and rainfall change during growth period of the rice was smaller. Change degree of the precipitation during growth periods of the cotton, oil plant, vegetable, fruit tree and legumes was equivalent, while precipitation change during growth period of the potato was the biggest. Seen from change tendency of the precipitation during growth periods of the different crops, precipitation in the growth period of winter wheat was increasing at a speed of 0.62 mm/a. However, precipitation in growth periods of the other crops had a decreasing tendency. Precipitation in the growth periods of summer corn and legumes decreased at the same speed which was 2.11 mm/a, while precipitation in growth periods of the cotton, oil plant, vegetable, fruit tree, potato and rice decreased insignificantly. [ Con dusion] The study laid foundation for determination of the agricultural irrigation water and provided theoretical reference for regional agricultural water-saving.

Assessing the Crop Growing Period According to the Climate Change Forecasts for Marina Baixa (SE Spain)

The present work aims to assess the likely effects of climate change on the length of growing period (LGP) of crops in Marina Baixa (SE, Spain). LGP can be assessed by a balance between preci- pitation and reference evapotranspiration. Less rainfall and an increased evapotranspiration, forecast by Global Climate Models (GCMs), are considered as a high risk for agriculture. This area is located in a semiarid climate region where water is a very limited resource. It is a typical example of areas where the agricultural sector has to compete for water with the tourism industry. In this context, by using observed and projected precipitation data set (model HadCM3, Scenario A2), calculating reference evapotranspiration (ETo), and applying the frequency analysis of a probability-type method, we estimated the growing period length in the observed period (1961-1990) and three 30-year future periods (2011-40, 2041-70 and 2071-99) in the study area. The results show a drop in annual precipitations (&#45?30%) and an increased ETo (+18%) towards the end of this century with respect to the observed period (mean annual rainfall: 356 mm;mean ETo: 1476 mm). The results also show a decrease in the number of decades (10 days) when precipitation exceeds half of the ETo, which means shorter growing periods as the 21st century advances. This expected reduction in growing period length towards the end of the present century will imply that many rainfed crops, like olives, almonds and cereals, will require a higher irrigation water supply to maintain suitable growth and performance levels. The results are an early warning to manage water resources in Marina Baixa in a sustainable way.

Numerical Study for Characteristic Change of Asian Summer Monsoon Circulation and Its Influence Mechanism during the EI Nino Period

In this paper, the relation between Asian summer monsoon circulation and sea surface temperature anomalies over equatorial central-eastern Pacific is investigated by using a global spectral model. This model has nine layers in the vertical and the model variables are represented in the horizontal as truncated expansions of the surface spherical harmonics with rhomboidal truncation at wave number 15. The model involves comparatively complete physical processes and parameterizations with mountains.Using the above model, two experimental schemes are designed, namely control case and anomalous sea surface temperature case. The above two schemes are respectively integrated for forty days and the simulated results are obtained from the last 30-day averaged simulations.The simulations show that positive SST anomalies over equatorial central-eastern Pacific weakens Indian monsoon circulation,decreases precipitation in Indian sub-continent whereas it intensifies East Asian monsoon circulation and increases precipitation in East Asian area. All these results reflect the characteristics of Asian summer monsoon during the El Nino period. In this paper, SST anomalies over equatorial central-eastern Pacific have a direct influence on the intensity and position of subtropical high via the wave train over Northern Hemisphere, which is similar to that suggested by Nitta(1987) and the wave train over Southern Hemisphere has an influence on the intensity of Muscarene high and Australia high resulting in affecting cross equatorial flow. As a result, atmospheric interior heat sources and sinks are redistributed because of the change of cross equatorial flow. And the response of atmosphere to the new heat source and sink has a significant influence on Asian summer monsoon.

Changes of the Period and the Light Curves of the Contact Binary V1073 Cygni

Observational evidence of unstable behavior for the W UMa type binary system V1073 Cygni is presented in this paper. Around 1939 the period of the binary suddenly decreased by 0 580 seconds and again suddenly decreased by 0 746 seconds around 1981.Obvious variable O’ Connell effect of the light curves in V can be seen. The relation between the changes in the orbital period and variation in the O’ Connell effect and possible reasons for the unstable behavior of V1073 Cyg were discussed.

Palaeoclimatic Cycles, Global Environmental Changes and New Glacial Periods Induced by the Impact of Extraterrestrial Bodies

In terms of Earth\|Sun geometry, the Milankovitch theory has successfully explained most of the cyclic palaeoclimatic variations during the history of the Earth, especially in the Quaternary. In this paper, the authors suggest that the impact of extraterrestrial bodies on the Earth may be another mechanism to cause palaeoclimatic cycles, global environmental changes and new glacial periods. Based on geological and geochemical records in the boundary layers produced by six huge Cenozoic bolide\|impact events (65, 34, 15, 2.4, 1.1, 0.73 Ma B.P.), including those at 34, 15, 1.1 and 0.73 Ma B.P. which are represented by four famous tektite\|strewn fields, the process and mechanics of palaeoclimatic cycles and global environmental catastrophes induced by extraterrestrial impact are discussed in detail. Impact\|generated dust, soot and aerosol floating in the stratosphere could result in short\|term (<1 year), rapid drop in temperature immediately after impact. Through self\|regulation of the Earth’s climate system, the temperature at the surface slowly went up within 100a and maintained stable for a long time at 250K. If there were no other factors leading to the break\|down of the newly\|established equilibrium, a new glacial period would be initiated. Estimating from the thickness of \{δ\{\}\+\{13\}C\} and \{δ\{\}\+\{18\}O\} anomalies in sediments across the impact boundary layer and deposition rate, the duration of two stages of the palaeoclimate cycle in the form of cold weather—greenhouse effect—normal weather was 10\+4-10\+5a, respectively. The conclusion deduced from the above model is supported by palaeotemperature change recorded by oxygen isotope in sediments across the impact boundary layer.

末次冰期东海嵊山岛黄土粒度端元分析及其环境意义

【目的】东海岛屿晚更新世风尘黄土堆积是我国黄土在东部长三角及外延海域重要的拓展,深化这一区域风尘黄土沉积的物源特征和后期演化问题研究,对于认识晚更新世区域古环境变化尤为重要。【方法】在OSL测年和磁化率测试基础上,基于东海岛屿典型风尘黄土剖面(嵊山岛黄土)的粒度分析,开展了粒度组成的端元分析,探讨了其蕴含的古环境信息。【结果与结论】嵊山岛黄土沉积可提取出3个粒度端元(EM1~EM3),进一步分析发现EM1可能代表通过高空西风气流传输的远源黏粒组分,EM2可能代表以浮尘形式远距离悬浮搬运并随风力减弱而沉降堆积的细粉砂组分,EM3可能代表冬季风驱动下的近地表短距离搬运堆积的粗粉砂组分。粒度端元分析结果表明,高空西风输送的黏粒端元组分和远距离悬浮运移的浮尘端元组分可能是沉积剖面主要粉尘来源;综合年代学结果、百分频率磁化率和颗粒中值粒径等参数分析,认为东海嵊山岛黄土沉积过程在MIS3阶段先后经历暖湿—冷干—暖湿的旋回波动;并且,所记录的MIS3阶段气候波动以及MIS2阶段末次冰盛期和冰消期的古环境变化同深海氧同位素和古海平面变化趋势相对应,说明东海陆架区域该时期环境演变与全球性气候波动相协同。

近62 a三峡地区区域性暴雨过程气候特征及长期变化规律

【目的】充分认识三峡地区区域暴雨过程的气候特征及长期变化规律对于科学防汛以及合理利用水资源具有重要意义。【方法】基于三峡地区33个国家级气象观测站1961—2022年逐日降水量资料和目前重庆市气候中心业务采用的区域性暴雨过程监测指标,对三峡地区区域性暴雨过程进行客观识别,并利用多种数理统计方法分析区域性暴雨过程的气候特征和长期变化规律。【结果】结果表明:(1)三峡地区近三分之二的暴雨以区域性过程形式出现,平均每年区域性暴雨过程有8.4次,主要出现在5—9月,尤以6—7月为集中发生时段。区域性暴雨过程首次开始日期多年平均为5月8日,末次结束日期为9月17日。平均每次过程的暴雨覆盖范围为8.6站,持续时间1.3 d,平均暴雨强度为74.7 mm/d。(2)三峡地区区域性暴雨过程年频次存在2~3 a和8 a左右的变化周期,年平均区域性暴雨过程覆盖范围存在4~6 a和8~11 a周期变化。(3)近62 a三峡地区区域性暴雨过程的首次开始日期显著提前,末次结束日期无明显变化,发生期显著变长;发生频次没有明显变化趋势、平均持续时间、平均覆盖范围、平均综合强度也均没有明显变化趋势,但平均暴雨强度呈增强趋势。(4)近62 a,三峡地区区域性暴雨过程的各项指标均未发生突变现象。【结论】研究成果为三峡地区防汛减灾、水资源管理以及回应三峡工程对局地气候影响的社会关切等提供科学支撑。

The change of the cationic peroxidase in the leaves at the fertile transformation period in Nongken 58s

Nongken 58s is a type of photoperiod sensitivegenie male sterile rice which gives rice to malesterility when illuminated time is longer than13.75 h/d.The photoperiod sensitive stagesare from the differentiation of primary branchprimordum(Ⅱ)in young ears to fullness ofcontents of the pollen(Ⅶ).The changes ofactivity and isoenzymes in cation peroxidase atph0toperiod sensitive stages and the relation-ship between this enzyme and feritility of rice

从“氏族之人”到“编户齐民”——试论先秦时期社会成员身份的变迁

夏商西周时期,社会上几乎所有的人都生活于“族”之中。这些族,夏商时期称为“氏族”,西周时期则多称为“宗族”。春秋战国时期,虽然“人”“民”多混用无别,但两者的使用却出现了有所侧重的情况。“民”能够以地域为称,但并不以族为称,它所表现的是社会成员的地域特征,而“人”则可以表现其作为某族的血缘关系特征。社会成员间血缘关系的影响在削弱,而国家地域关系的影响在增强。社会成员身份的巨大变化是由氏族(宗族)之人,变成了国家控制下的编户齐民。“编户齐民”肇端于战国时期诸国授田制度的实施,到秦代则成为国家控制天下民众的最主要的制度。这种居民身份的变化深刻地影响着古代中国的历史发展。

中国人口流动的健康轨迹研究

人口的高流动性和流动人口快速老化已成为中国人口发展的显著特征。研究人口流动对我国城乡居民健康的影响及其变动趋势,对于理解和实现健康老龄化,改善人口健康水平具有重要意义。现有研究较多分析流动人口相比于城镇居民的健康状况,而对流动人口和农村居民的健康差异的研究相对缺乏;对于流动人口在老年阶段的健康状况与户籍人口的差异以及流动对人口健康的影响等关键问题尚没有确定结论。本文旨在探讨人口流动与个体健康的因果关系以及流动人口和城乡户籍人口之间随时间和年龄变化的健康差异。本文利用中国家庭动态追踪调查(CFPS)2010-2020年连续六次调查的面板数据,采用固定效应模型和线性回归模型分析人口流动的健康效应和年龄效应。研究发现2012-2020年流动对人口健康的总体影响为负,验证了流动具有健康损耗效应,存在“流行病学悖论”。从时期维度看,流动对人口健康的影响呈现由健康优势转为健康劣势的趋势,人口流动的健康选择效应和流动经历的内在健康损耗效应并存。初期流动人口具有健康优势,健康自评状况优于城乡户籍人口。随着时间推进,健康优势逐渐收敛,健康损耗效应逐渐显现。从年龄维度看,流动人口和城乡户籍人口的自评健康水平随着年龄增加都呈下降趋势,但流动人口的下降速度显著慢于城乡户籍人口,其健康优势在老年阶段逐渐消失。上述发现的政策含义是:在人口老龄化不断加深和流动人口规模保持高位,流动人口老化愈加明显的背景下,流动人口的健康老龄化成为重要挑战,在政策实践层面应关注流动经历对个体生命周期的持续影响,尤其是要重视城镇中的高龄流动人口返乡回流将健康风险转移到农村,从而增加农村整体的健康脆弱性和健康照护成本,应将人口流动因素作为优化城乡卫生健康资源配置的重要考量。

气候变化与物候期的关系及农户感知研究——以三江平原为例

通过研究物候期对气候变化的响应,评估农户对气候变化认知水平,实施气象为农服务提质增效行动,基于三江平原佳木斯市1993—2022年的物候期、1961—2022年气温和降水量、农户气候变化感知数据,利用数理统计方法,分析气候变化与物候期关系及农户对气候变化的感知。近30 a三江平原春季物候期变化均呈提前趋势,秋季物候期变化均呈延后趋势,蒲公英物候期趋势变化最为显著,蒲公英萌芽日期提前,变化速率为5.5 d/10 a,黄枯日期延后,变化速率为10.6 d/10 a;春秋季温度、降水和春秋季物候期之间的相关系数,共有8对极显著相关和6对显著相关,其中正相关有7对,负相关有7对,春季物候期的变化主要是受温度影响,秋季物候期变化则是降水量影响;农户对温度变化感知结果与实测数据基本一致,准确率达到80%以上,农户感知到的降水变化趋势与气象实测数据存在差异,准确率达到58.0%,自然现象物候期感知结果准确性低于温度和降水变化感知结果。三江平原物候期随着温度升高及降水增加,出现日期提前,结束日期延后,物候期呈延长趋势,农户对农业生产相关的气候变化感知更为敏感,也相对准确。研究结果为农业生产制定有效的气候变化适应政策提供科学依据与借鉴。

不同种植年限水稻土有机碳矿化对周期性变温的响应

为了探讨陕北中部黄土丘陵沟壑区不同种植年限水稻土有机碳矿化对周期性温度变化的响应,以陕北南泥湾水稻种植基地不同种植年限(78 a、30 a、3 a)的稻田土壤为研究对象,基于室内35 d培养试验与矿化动态模型研究方法,解析温度变化对土壤有机碳矿化的影响。结果表明:恒温以及周期性变温处理的土壤累积矿化量在前7 d增加较快,达到整个培养期的39.2%~47.6%,7 d后至培养结束时增加缓慢。培养前7 d,土壤有机碳矿化速率快速下降,直至21 d时趋于稳定状态。78 a、30 a、3 a水稻土和玉米地的累积矿化量分别为3126.75、2737.63、2547.42和2173.88 mg/kg,水稻土累积矿化量比玉米地高28.94%。变温条件下的有机碳累积矿化量较恒温条件下增加4.95%。变温条件下,0~20 cm和20~40 cm土壤有机碳矿化量比恒温下分别高5.69%和4.20%。水稻土在周期性变温条件下14 d的微生物生物量碳(MBC)下降幅度(41.49%)高于恒温培养(32.22%),35 d的MBC下降幅度(50.20%)低于恒温培养(54.23%),溶解性有机碳(DOC)下降幅度规律与之相反。0~20 cm和20~40 cm土壤潜在矿化量占总有机碳的比例(C 0/SOC)均表现为15℃/35℃高于25℃恒温,说明表层土壤易于矿化,土壤碳固存能力随温度周期性改变而降低。变温与恒温的土壤有机碳矿化速率、累积矿化量、潜在可矿化有机碳量无明显差异,说明在本试验条件下,在积温相同的情况下,周期性变温对土壤有机碳的矿化无显著影响。

基于ITHBC理论AVF肾病患者围透析期自我管理方案的构建

目的构建科学、可行的自体动静脉内瘘(AVF)肾病患者围透析期自我管理方案。方法通过文献检索,以健康行为改变整合理论(ITHBC)为理论基础初步构建AVF肾病患者围透析期自我管理方案,应用德尔菲法对24名专家进行2轮专家咨询,对各级指标进行评定与修改。结果2轮专家咨询问卷回收率均为100%(24/24),专家权威系数(Cr)分别为0.895、0.915,专家协调系数Kendall's W分别为0.153、0.221。第2轮专家意见变异系数为0.010~0.099,均小于0.250。2轮德尔菲专家咨询确定3个一级指标、10个二级指标和22个三级指标。结论基于ITHBC理论构建AVF肾病患者围透析期自我管理方案具有较好的科学性与可操作性,能够为AVF肾病患者围透析期间自我管理提供依据和指导。