Decomposition of hydroxy amino acids in foraminiferal tests; kinetics,mechanism and geochronological implications     

Jeffrey L. Bada  Ming-Yung Shou  Eugene H. Man  Roy A. Schroeder 《Earth and Planetary Science Letters》1978,41(1):67-76

The diagenesis of the hydroxy amino acids serine and threonine in foraminiferal tests has been investigated. The decomposition pathways of these amino acids are complex; the principal reactions appear to be dehydration, aldol cleavage and decarboxylation. Stereochemical studies indicate that the α-amino-n-butyric acid (ABA) detected in foraminiferal tests is the end product of threonine dehydration pathway. Decomposition of serine and threonine in foraminiferal tests from two well-dated Caribbean deep-sea cores, P6304-8 and -9, has been found to follow irreversible first-order kinetics. Three empirical equations were derived for the disappearance of serine and threonine and the appearance of ABA. These equations can be used as a new geochronological method for dating foraminiferal tests from other deep-sea sediments. Preliminary results suggest that ages deduced from the ABA kinetics equation are most reliable because “species effect” and contamination problems are not important for this nonbiological amino acid. Because of the variable serine and threonine contents of modern foraminiferal species, it is likely that the accurate age estimates can be obtained from the serine and threonine decomposition equations only if a homogeneous species assemblage or single species sample isolated from mixed natural assemblages is used.  相似文献   

中国西部大城市开发区企业投资决策的驱动因素——以成都、西安高新区为例     

李建新  杨永春  梁曼 《地域研究与开发》2021,40(1):50-54,66

基于成都、西安高新区企业调研数据,在构建企业投资决策驱动指标体系的基础上,采用因子分析法考察企业投资决策的驱动因素,并运用单因素方差分析和相关性检验进一步探究企业异质性与投资决策驱动因素的关系。结果表明:(1)信息通信水平、获取高素质人才、人际关系网络等构成企业投资决策的关键驱动指标,而跨国公司集聚、获取自然资源、决策者偏好等指标的解释力度最小。(2)企业投资决策由6个维度因子构成,其重要程度由高至低依次为政策、产业集群与人力资源、城市环境、城市区位、企业集聚以及关系因子。(3)入园越早、规模越大、总部型及出口型企业均更加依赖政策驱动;私企与外企、一般服务业企业与高级服务业企业、部分迁移企业与非迁移企业、办公区企业与科技园企业、办公区企业与厂区企业分别形成了基本对立的投资驱动偏好。  相似文献   

Variegated transnational partnerships: Multi-scalar actor networks in China’s overseas industrial parks     

SONG Tao  SUN Man  LIANG Yutian  Soavapa NGAMPRAMUAN  WUZHATI Yeerken  ZHOU Keyang 《地理学报(英文版)》2021,31(5):664-680

The development of overseas industrial parks is a key component of the Belt and Road Initiative and a practical way of promoting inclusive globalization by introducing new forms of cooperation between China and the host countries.In this paper,the Thai-Chinese Rayong Industrial Zone(TCRIZ),and the China-Indonesia Economic and Trade Cooperation Zone(KITIC)are discussed in the context of the evolving development strategies and tra-jectories through three interrelated conceptual lenses-policy mobility,actor networks,and partnerships.The actor-network theory provides a lens to analyze how policy mobility and partnerships develop for two industrial zone case studies.The development,which involves a multi-scalar process,is shaped by the interactions among the national states,the regional governments and corporations against a background of globalization.Three types of trans-national actor partnership networks have been identified,namely,hierarchical partnership,spontaneous partnership,and hybrid partnership.A highlight of the study is the role that the partnerships play in the process of policy mobility when it comes to the overseas industrial zones.It is argued that the partnerships are the key to achieving technology transfer on a cross-national basis,and the effectiveness of the technology transfer is dependent on partner selection and the roles of the actors in policy mobility.  相似文献   

基于岩土材料软化特性的滑坡多级滑动面分析方法研究     

薛海斌  党发宁  尹小涛  雷曼  杨超 《岩土力学》2015,36(11):3235-3242

在实际工程中,滑坡经常呈现出多级破坏的特征,而一般计算和设计中仅关注最危险的滑动面及对应的最小安全系数,这往往遗留安全隐患。在考虑岩土材料软化特性的基础上,借助FLAC3D和Matlab软件平台构建了无需人工干预便可有效模拟与评价滑坡多级破坏的理论框架。以旬阳县党家坝廉租房小区滑坡为例,通过对塑性剪应变、塑性拉应变、剪切应变增量等特征变量的渐进发展规律分析发现：滑坡多级滑动面的形成,其时间和空间顺序并不一定相对应。各级滑动面在时间上按产生的先后顺序依次为第1级主滑面、第2级主滑面、次级滑面;而在空间上按照从前到后的顺序依次为第1级主滑面、次级滑面、第2级主滑面。从计算所得的滑坡最终破坏形态中发现,坡体内部出现的滑动面条数与现场采集的拉裂缝数基本保持一致;第1级主滑面的入口位置与滑坡前缘拉裂缝位置基本吻合;而第2级主滑面及次级滑面的位置与现场勘查到的拉裂缝位置出现偏差。从材料参数的渐进发展规律中发现,滑面上强度参数的分布及大小均随着滑面的产生、发展而逐渐变化,其变化区间为峰值强度到残余强度,这是此方法可以有效模拟多级滑动面形成过程与各级滑动面之间相互影响的核心所在。借助矢量和法成功地实现了基于滑面上强度参数渐进发展规律的安全系数演化过程的确定。通过对安全系数演化过程的分析发现,在滑坡多级滑动面的形成过程中安全系数大小顺序呈现出3种不同的状态,这很好地揭示了各级滑动面在形成过程中的主、被动关系。  相似文献   

地震报道中死亡人数估计方法的适用性分析     

董曼  杨天青  陈通  魏文薪 《地震》2014,34(3):140-148

基于国内外8次地震报道死亡人数的统计数据,采用修正指数曲线、龚铂茨曲线、罗吉斯蒂曲线分别进行震后死亡人数估计。对比分析表明三种模型均适合地震报道死亡人数估计;用剔除前两个拟合值后的拟合精度作为预测误差在实际应用中具有实际参考价值。对中国3次强震报道死亡人数拟合结果分析显示,联合三种模型,采用相对误差较小的模型为主、另两种模型为参考的方法进行最终死亡人数预测,可为抗震救灾指挥部署提供参考依据。  相似文献   

Application of food waste based diets in polyculture of low trophic level fish: Effects on fish growth,water quality and plankton density     

Wing Yin Mo  Zhang Cheng  Wai Ming Choi  Yu Bon Man  Yihui Liu  Ming Hung Wong 《Marine pollution bulletin》2014

Food waste was collected from local hotels and fish feed pellets were produced for a 6 months long field feeding trial. Three types of fish feed pellets (control diet: Jinfeng® 613 formulated feed, contains mainly fish meal, plant product and fish oil; Diet A: food waste based diet without meat and 53% cereal; Diet B: food waste based diet with 25% meat and 28% cereal) were used in polyculture fish ponds to investigate the growth of fish (grass carp, bighead and mud carp), changes in water quality and plankton density. No significant differences in the levels of nitrogen and phosphorous compounds of water body were observed between 3 fish ponds after the half-year feeding trial, while pond receiving Diet A had the highest density of plankton. The food waste combination of Diet B seems to be a better formulation in terms of the overall performance on fish growth.  相似文献   

塔里木河下游垦区绿洲景观格局变化分析   总被引：14，自引：4，他引：10  

许英勤  徐曼 《干旱区地理》2004,27(2):193-198

以塔里木河下游垦区为研究区,对其1986～2000年的景观变化进行了研究。结果表明,景观变化主要体现在：(1)随着人类土地开发利用的程度提高,区域景观趋于多样化和均匀化,主要是以人类活动造成的灌木疏林地、低质草地和草地的退化为主;其次,人工绿洲的开垦多在这三类用地上;此外,水库蓄水面积的增大,淹没了部分这类用地。(2)从斑块的绝对面积来看,始终是以荒地和低质草地为主,且荒地、水浇地、水田、水域和沼泽在两个灌区都是逐步增加的,荒地面积的增加反映了研究区生态退化趋势较为严重。(3)从斑块转移概率来看,研究区居民地、荒地、低质草地以及水浇地至少有94％以上的面积是保持其原来状况的;而沼泽的转移概率达到84％以上,主要转移为水域。反映了区域绿洲景观的主体仍然是以荒漠为背景的强烈人为干扰的人工绿洲景观．以及人工绿洲对水资源的依赖。  相似文献   

Effect of model error representation in the Yellow and East China Sea modeling system based on the ensemble Kalman filter   总被引：1，自引：1，他引：0  

Kyung Man Kwon  Byoung-Ju Choi  Sang-Ho Lee  Young Ho Kim  Gwang-Ho Seo  Yang-Ki Cho 《Ocean Dynamics》2016,66(2):263-283

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Sorption and Desorption of Copper and Cadmium in a Contaminated Soil Affected by Soil Amendments          下载免费PDF全文

Ping Li  Man Lang  Xing‐Xiang Wang  Tao‐Lin Zhang 《洁净——土壤、空气、水》2016,44(11):1547-1556

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19世纪中叶北京高分辨率沙尘天气记录：《翁心存日记》初步研究^*          下载免费PDF全文

杨煜达  成赛男  满志敏 《古地理学报》2013,15(4):565-574

《翁心存日记》是迄今为止发现的记录天气现象最为详细的历史天气日记,保留了难得的19世纪中叶北京的沙尘天气记录。归纳了对历史文献记录中的沙尘天气进行分类的方法,通过《翁心存日记》,重建了19世纪中叶北京沙尘天气情况。分析发现当时北京年平均沙尘日多达31.36天,高于近60年来北京沙尘天气的平均水平。而19世纪中叶的北京沙尘天气中扬沙、浮尘和沙尘暴天气的构成和现代基本相似,年内分布特征也较相似。但19世纪中叶夏季沙尘比例较现代明显偏多46％,而冬季沙尘比例仅为现代比例的75％,这说明古今间沙尘天气的季节分布可能存在较大差异。另外,19世纪的沙尘天气同样存在明显的年际变化,且本地降水是影响年际变化的因素之一。  相似文献