Environmental Factors Governing Soil Water Repellency Dynamics in a Pinus Pinaster Plantation in NW Spain

Soil water repellency (SWR) is a dynamic property that changes throughout the year. The objective of this work was to identify the environmental factors governing the temporal patterns in SWR in a pine plantation in northwest Spain with a view of predicting its occurrence and persistence. For this purpose, 24 samples were collected from the soil surface (0–5 cm) at 25 different times over a 1‐year period and analysed for SWR by using water drop penetration time test and soil moisture measurements. Temporal variations in SWR exhibited a well‐defined seasonal pattern. The soil surface was largely wettable from late autumn to early spring and extremely water repellent during summer and early autumn. Repellency persistence was rather variable during spring. There was highly significant correlation between SWR and soil moisture content. The moisture range defining the presence or absence of repellency under field conditions was 22–57%. There were also significant correlations with the target variables (maximum temperature, minimum temperature, precipitation and water balance during variably long antecedent periods), with coefficients that increased with increasing length of the antecedent period considered. The moisture content of soil at the time of sampling and the average maximum temperature for the 28 days before sampling are the best predictors of occurrence of SWR and its persistence in different seasons. Copyright © 2015 John Wiley & Sons, Ltd.     

温度对光敏感雄性核不育水稻育性转换的影响研究

在北京(N39°56′)自然变温和人工控温条件下分别对比观察光敏感雄性核不育(pgms)水稻的育性对10小时、16(或15)小时两种光周期的反应。试验结果指出: 1.在适宜水稻发育的温度范围内,pgms水稻均有因光周期不同而发生的育性转换。而且光周期效应远大于温度不同所引起的育性变化。 2.温度变化可诱发长日光周期状态下pgms水稻的     

Superconductivity of Single-Walled Carbon Nanotubes

The electric-arc technique used to generate single-walled carbon nanotubes (SWCNTs) is introduced. Especially, the superconductivity of SWCNTS is concerned. The samples of single-walled carbon nanotubes are suspended between two superconducting electrodes and their super-currents may be observed under special conditions. It is called 'proximity-induced method'. With the method, some experiments show that SWCNTs have higher critic super-currents, and the temperature and magnetic field dependence of the critic currents exhibits unusual features.     

GLONASS Transition Between GLONASS and GPS

In this paper, the GLONASS system is introduced, then the coordinates adopted in both GLONASS and GPS are discussed. The authors present a mathematic model of conversion between PZ-90 and WGS-84.This paper lays emphasis on the expounding the solution of converting parameters,then,the converting formula suitable for use in China is also presented. After that, in this paper starting from the converting formula to discuss the WGS-84 ground coordinate system and space-ground coordinate system as well as the PZ-90 space-ground coordinate system and ground coordinate system are discussed.Finally, the data used in China in the process of WGS-84 converting into PZ-90 are analyzed.     

碳达峰背景下遵义市土地利用转型的生态环境效应及预测

[目的]研究土地利用转型的生态环境效应及其发展趋势,为促进土地利用转型、低碳循环发展及实现“双碳”目标提供依据。[方法]基于贵州省遵义市2005,2010,2015,2020年4期的土地利用数据,运用空间分析技术,对该区土地利用转型的生态环境效应及其发展趋势进行研究。[结果](1)2005—2020年土地转型主要表现为碳汇用地之间的相互转换,以及碳汇用地向碳源用地转型。(2)净碳排放量由2005年的5.99×10⁵ t增加到2020年的9.87×10⁶ t,增加了9.27×10⁶ t,增幅达1 548.15%。但增量却呈逐渐减少的趋势,增幅也逐渐降低。(3)遵义市生态系统服务价值量由2005年的7.64×10¹⁰元增加到2020年的7.73×10¹⁰元,呈波动上升趋势,共增加了9.14×10⁸元,增长率为1.2%。(4)通过灰色预测模型得出遵义市未来净碳排放量和生态系统服务价值量会持续增加,且都呈规律上升趋势。[结论]遵义市在生态环境方面仍面临着不小的压力...     

碳中和目标下的广西边境地区“三生”空间转型及碳储量效应

[目的] 系统分析“三生”空间转型下的碳储量效应,以期优化空间布局与提升边区生态系统固碳能力,助推国家实现“碳中和”的战略目标。[方法] 采用“三生”空间动态度、“三生”空间转移矩阵刻画边境“三生”空间分布格局和转型特征,借助InVEST模型和“三生”空间碳储量贡献率揭示边境1990—2020的碳储量时空分异及“三生”空间转型对碳储量的影响。[结果] ①1990—2020年边境地区以绿被生态空间占绝对主体,农业生产空间和水域生态空间为辅的组合特点,分布上呈现“南北两翼高,中部低”特征。 ②研究期内边境地区“三生”空间转型呈现出初期稳定、中期波动、后期剧烈的发展态势,除水域生态空间外,其余空间均于2010—2020年动态度变化最为显著。 ③1990—2020年,边境地区碳储量整体呈现逐期持续递减,研究初期与中期变动幅度不大,末期碳储量深刻变化;40 a间碳储量共计损失4.13×10⁶ t,绿被生态空间与农业生产空间的相互转换主导着广西边境地区碳储量的变化。[结论] 应调整与优化区域“三生”空间用地结构,促进“三生”空间融合,并以“碳中和”为目标导向,强化空间用途管制,为提升区域碳储资源提供精确保障。     

科技档案发展历程回顾

科技档案事业经历了创建、恢复整顿、调整转型和改革发展时期,在不同时期,科技档案都做了大量的工作,本文回顾了科技档案在不同的发展阶段所做的主要工作以及这些工作对科技档案事业发展的重要作用。     

南过渡带混播草坪组合研究

在南过渡带的生境及一定的养护条件下,对多种混播草坪组合设计进行了评比,结果表明:混播组合高羊茅(Festuca arundinacea)凌志40%+高羊茅锐步30%+早熟禾(Poa pratensis)男爵20%+黑麦草(Lolium perenne)顶峰10%表现最好,其次为高羊茅凌志30%+高羊茅锐步30%+早熟禾巴润20%+黑麦草顶峰20%;其余表现不好。从苗期表现来看,黑麦草及高羊茅的比例高者表现好。从成坪后期来看,黑麦草的比例不宜过多,最好不超过20%。混播组合中,随着草坪利用年限的延长,高羊茅的比例稳定,开始时黑麦草及早熟禾的比例有所下降,但早熟禾的比例在后期又有所增加。翦股颖(Agrostis stolonifera)宜作单播草种,狗牙根(Cynodon dactylon)可与高羊茅或早熟禾混播使用。综合考虑成坪速度、草坪质量及病虫害等各方面的因素,混播比例最佳配合为高羊茅∶早熟禾∶黑麦草=7∶2∶1;混播组合为高羊茅∶早熟禾∶黑麦草=6∶2∶2表现也很好,建议使用。高羊茅由多个品种组成的表现更佳。     

线粒体通透性转换孔及其与细胞凋亡的关系

线粒体通透性转换孔,又称线粒体巨型通道,是横跨线粒体内外膜之间的非选择性高导电性通道,由多种蛋白质复合组成。多数理论认为,它的开放所导致的线粒体膜通透性转换是线粒体导致细胞凋亡众多途径中关键的一个。现阶段对线粒体通透性转换孔有各种方向的研究。论文对其结构、作用机制及其与细胞凋亡的关系进行了综述。     

Hierarchical control method of low voltage looped microgrid

The low voltage (LV) looped microgrid has high reliability of power supply and good accessibility of the DG. The medium voltage distribution network with single loop network and multi sectioned & multi linked is studied to analyze the wiring mode of the LV looped microgrid. A research on the two hierarchical control scheme of the looped microgrid is conducted, and the sub microgrid, which meets island operation requirements, is divided according to their segments. Then the incidence matrix is formed based on the connection relation of different segments and components, and the plan for switching the microgrid operation status is concluded from the reform of incidence matrix on the basis of the judgment of island and reconnection segments. A resynchronization strategy using microgrid central controller is proposed. The MATLAB/SIMULINK simulation software is used to analyze the dynamic characteristics of different operation status switching and synchronizing, and the results verify the effectiveness and correctness of the proposed control method.