陕西渭北旱塬种植业结构调整的水资源问题及对策   总被引：14，自引：4，他引：10  

宋孝玉  刘贤赵  沈冰  史文娟 《干旱区地理》2004,27(2):199-201

陕西渭北旱塬地处西北内陆黄土高原腹地,是陕西省小麦主产区．也是中低产区,该区属暖温带半湿润易旱区,年降水量420mm～700mm,降水时空分布不均且变率较大,与冬小麦的需水规律不相吻合,加之田间蒸发量大,使得田间水分相对不足,限制了渭北旱塬小麦产量的进一步提高。由于果树产量高、经济效益好,自20世纪80年代中后期以来,渭北旱塬农村种植业由传统的粮食生产转为大面积的栽种果树。但由于种植业结构的调整,农田大面积改种果树,势必加重区域水资源的供需矛盾,导致水分生态的新态势。在分析渭北旱塬作物种植业结构调整引起的水资源问题基础上,指出：渭北旱塬种植业结构调整必须以水资源为约束。  相似文献   

Biodegraded Oil and Its High Molecular Weight (C_(35+)) n-alkanes in the Qianmiqiao Region in the Bohai Bay Basin, Northern China     

WANG Tieguan  ZHU Dan  LU Hong  ZHANG Zhihuan  YANG Chiyin The Key Laboratory of Petroleum Accumulation Mechanism of the Education Ministry  University of Petroleum  Beijing  Guangzhou Institute of Geochemistry  Chinese Academy of Sciences  Guangzhou  Guangdong Geological Research Institute  Dagang Oilfield 《《地质学报》英文版》2004,78(4):993-1001

With a production of 208.2 m3/d, heavy oil was produced by drill stem test (DST) from three shallow reservoirs in Sand Group Nos. Ⅰ and Ⅲ of the Neogene Guantao Formation (NgⅠ and NgⅢ) and the Eogene Dongying Formation (Ed) in an exploratory well Ban-14-1 within the Qianmiqiao region, Bohai Bay Basin, northern China. Based on the GC and GC-MS data of the NgⅠ and NgⅢ heavy oil samples, all n-alkanes and most isoprenoid hydrocarbons are lost and the GC baseline appears as an evident "hump", implying a large quantity of unresolved complex mixture (UCM), which typically revealed a result of heavy biodegradation. However, there still is a complete series of C14-C73 n-alkanes in the high-temperature gas chromatograms (HTGC) of the heavy oil, among which, the abundance of C30- n-alkanes are drastically reduced. The C35-C55 high molecular weight (HMW) n-alkanes are at high abundance and show a normal distribution pattern with major peak at C43 and an obvious odd-carbon-number predominance with CPI37-55 and  相似文献   

Primordial magnetic fields and formation of molecular hydrogen     

Shiv K. Sethi  Biman B. Nath  Kandaswamy Subramanian 《Monthly notices of the Royal Astronomical Society》2008,387(4):1589-1596

We study the implications of primordial magnetic fields for the thermal and ionization history of the post-recombination era. In particular, we compute the effects of dissipation of primordial magnetic fields owing to ambipolar diffusion and decaying turbulence in the intergalactic medium (IGM) and the collapsing haloes, and compute the effects of the altered thermal and ionization history on the formation of molecular hydrogen. We show that, for magnetic field strengths in the range  2 × 10⁻¹⁰≲ B ₀≲ 2 × 10⁻⁹ G  , the molecular hydrogen fraction in IGM and collapsing halo can increase by a factor of 5 to 1000 over the case with no magnetic fields. We discuss the implication of the increased molecular hydrogen fraction on the radiative transfer of ultraviolet photons and the formation of first structures in the universe.  相似文献   

Star-forming region BBW 36 in puppis     

A. L. Gyulbudahgian  J. May 《Astrophysics》2008,51(3):394-402

Recent studies of the star formation region BBW 36 and associated molecular clouds are presented. The ¹²CO (1-0) observations, carried out with the 15-m SEST (Swedish-ESO) telescope (Cerro La Silla, Chile), revealed the existence of cloud a, connected with BBW 36 and of cloud b, having elongation in SE-NW direction. A red-shifted molecular outflow with velocity ∼+5 km/s (with respect to cloud a), having a direction parallel to the line of sight, was also observed. VLA observations showed the presence of a source VLA 2 at 3.6 cm with an elongation in the N-S direction. It is suggested that the VLA 2 source coincides with a dust disc (surrounding the object BBW 36). The star 3, which is one of the YSOs in the star-forming region BBW 36 and is connected with a bright comma-like nebula, can be the source of the molecular outflow. The star 3 has very high IR colors and is associated with an IRAS point source IRAS 07280-1829, which has IR colors, typical for an IRAS point source, connected with a water maser. On the 2MASS K image of BBW 36 we can see the existence of a bright nebula; a group of stars is embedded in that nebula, and among these stars there are stars with dust discs (or envelopes). On the 2MASS K image several spiral jets are also present, some of them with a condensation at the end. Published in Astrofizika, Vol. 51, No. 3, pp. 469–477 (August 2008).  相似文献   

非水溶性钾矿制取碳酸钾研究:副产13X型分子筛   总被引：15，自引：0，他引：15  

马鸿文  白志民  杨静  王英滨  戚洪彬  白峰  章西焕 《地学前缘》2005,12(1):137-155

非水溶性钾矿通常以钾长石为主要矿物相。对其进行粉碎、摇床重选、湿法磁选和化学酸浸除铁等预处理,可制得纯度达75%~95%的钾长石粉体。以碳酸钠为助剂,在760~860 ℃的中温下钾长石发生固相分解反应,生成偏硅酸钠、偏铝酸钾(钠)前体化合物,用于水热合成13X 沸石分子筛。滤液为富含[SiO2(OH)2]2-、Na+、K+的碱性溶液,通入CO2 进行酸化反应,生成SiO3·nH2O胶体沉淀,经250 ℃下煅烧即制成白炭黑。剩余滤液为NaHCO3 KHCO3 H2O三元水盐体系,再经浓缩、分离、纯化、结晶,制取碳酸钠和碳酸钾。由此,原矿中SiO2、Al2O3、K2O 3 种主要组分均可制成高值产品,可达到钾长石资源利用率接近100%、“三废”近于零排放的高效节能、清洁生产的“绿色过程”要求。本项技术实现规模化工业生产,将有利于缓解我国水溶性钾盐资源极缺的矛盾,平衡钾盐市场,提高国民经济可持续发展中钾盐资源的保证程度。  相似文献   

Fe2O3对13X沸石分子筛合成条件及性能的影响研究   总被引：4，自引：0，他引：4  

章西焕  马鸿文  杨静  戚洪彬 《地学前缘》2005,12(1):157-164

对江苏丰县的富钾页岩进行预处理,得到不同Fe2O3 质量分数的钾长石粉体原料FXY1、FXY2,经中温焙烧得到偏铝硅酸盐前体化合物,水热晶化合成了13X沸石分子筛。采用正交实验法,确定了水热晶化反应的优化工艺条件,原料中Fe2O3 质量分数的不同导致水热晶化反应的工艺参数有所不同。合成的两种沸石的性能与13X沸石分子筛的工业产品相似,吸附量均达到国家化学工业产品标准HG/T 2690 95的要求。对比实验表明,原料中Fe2O3 质量分数的降低可使其在更宽的碱度范围内合成性能更优的13X沸石产品。由低Fe2O3 质量分数的FXY2为原料合成的沸石,其物相纯度、热稳定性、白度、比表面积、吸附性等性质更优。合成沸石均可用于对含重金属离子废水的深度净化处理,由FXY2为原料合成的13X沸石还可用作洗涤助剂。  相似文献   

用于单体氢同位素分析的混合溶剂洗脱5分子筛吸附正构烷烃的方法   总被引：1，自引：1，他引：0  

陈莎莎  朱信旭  贾望鲁  于赤灵  彭平安 《岩矿测试》2017,36(4):413-419

混合溶剂萃取洗脱5分子筛吸附正构烷烃的方法在单体碳同位素分析研究中已得到了应用。由于5分子筛在长时间加热条件下可能对有机分子的氢交换反应具有一定的催化作用,因此对于该方法能否用于正构烷烃的单体氢同位素分析需要做进一步研究。本文以两种不同类型原油的饱和烃和正构烷烃混合标准样品为对象,采用环己烷-正戊烷溶剂和氢氟酸溶解-正戊烷溶剂洗脱5分子筛吸附的正构烷烃,对比分析两种萃取方式的分离效果,并分别测定了正构烷烃的单体氢同位素比值。结果表明:两种萃取方式都得到了纯化效果良好的正构烷烃组分,氢同位素测定结果的差值总体上小于4‰,在仪器分析误差范围内。经过三次环己烷-正戊烷洗脱方式获得正构烷烃回收率平均值为58%,氢氟酸溶解-正戊烷洗脱方式经过多次萃取操作获得正构烷烃回收率平均值为68%。尽管环己烷-正戊烷洗脱方式提取正构烷烃的效率较低,并且涉及在分子筛条件下多次较长时间的加热过程,但这两个因素没有导致氢同位素发生明显的分馏或交换过程,适合用于正构烷烃分离、纯化以及单体氢同位素测定。  相似文献   

全缘马尾藻(Sargassum integerrimum)生殖细胞排放规律及人工促排条件   总被引：1，自引：0，他引：1  

欧泽奎  刘东超  谢恩义  吴启藩 《海洋与湖沼》2017,48(1):67-78

在全缘马尾藻生殖细胞同步成熟的基础上,研究了生殖细胞的排放规律以及人工促排的条件。结果表明:(1)在温度(25±0.5)°C,光照强度(3000±100)lx,光照周期12h︰12h[光照(L)︰黑暗(D)],盐度33±0.5,pH值8.2±0.2、静置暂养条件下,雄生殖托排放精子与雌生殖托排放卵细胞基本同步;雌生殖托排放卵细胞集中在夜间,为间断式排卵,完成整个排卵过程约需3d;雌生殖托的排卵量与其重量呈正相关,3d内排出卵细胞(14431±1288)个/g;卵细胞在排出后4h内完成受精,得到受精卵8358±734个/g;雌生殖托表面的"挂卵"量约为10000个/g,受精卵的脱落量与排卵量相关。(2)在光照周期0h:24h(L︰D)、pH值8.2培养条件的基础上,最适生殖细胞促排条件分别为温度31°C,盐度33±1,水流速度(6±1)cm/s,在该条件下得到的脱落受精卵量最多,所需促排及排放时间最短。在最适条件下,将雌、雄生殖托混合的重量比例改变为1︰6,受精率可提高至(94.4±0.3)%,相比暂养条件下的排卵过程,排卵提前4d,排卵周期缩短2d。  相似文献   

Genetic differentiation of the soft shore barnacle Fistulobalanus albicostatus (Cirripedia: Thoracica: Balanomorpha) in the West Pacific          下载免费PDF全文

Yen Wei Chang  Joanna S. M. Chan  Ryota Hayashi  Takuho Shuto  Ling Ming Tsang  Ka Hou Chu  Benny K. K. Chan 《Marine Ecology》2017,38(2)

This study examined the phylogeography of the barnacle Fistulobalanus albicostatus, which inhabits mangroves and estuarine shores in the West Pacific. Differentiation in the mitochondrial cytochrome c oxidase subunit I (COI) and 12S ribosomal RNA (12S) genes of 401 specimens of F. albicostatus was examined in samples from 16 locations in the West Pacific, ranging from Honshu to Southern China. Our results revealed that F. albicostatus comprises two major clades exhibiting a COI divergence ranging from 1.25% to 2.8%. Clade A demonstrated the widest distribution, ranging from Japan to China, and was divided into three subclades occurring in the South China Sea (A1), Okinawa (A2), and Honshu, Korea and Qingdao (A3). Clade B was determined to be endemic to Okinawa; i.e. two endemic lineages occur in this island. Thus, F. albicostatus resembles several inter‐tidal species in having clades that are endemic to Okinawan waters. Nevertheless, in contrast to the rocky inter‐tidal barnacles Tetraclita spp. and Chthamalus malayensis, F. albicostatus was not found to be separated into continental and oceanic populations, but instead is divided into northern and southern clades, probably because of the Yangtze River discharge, which limits gene flow between the northern and southern populations.  相似文献   

七鳃鳗鸟嘌呤转移因子Vav2分子克隆、表达及系统发育分析研究     

韩英伦  李军  徐磊  马庆华  勾萌  逄越  刘欣  李庆伟 《海洋学报(英文版)》2017,36(12):24-30

鸟嘌呤转移因子Vav2为Vav家族成员,其在Ras-related GTP酶活性调节过程中发挥重要作用。本文首次从七鳃鳗体内克隆并表达出七鳃鳗Vav2分子（Lj-Vav2）。系统发育分析结果阐明,Lj-Vav2为脊椎动物Vav2基因家族的直系同源基因。进化动力学分析指明,CH结构域、DH结构域、PH结构域、C1结构域、SH3结构域、SH2结构域贯穿于脊椎动物Vav2家族的进化历程。实时定量PCR结果表明,Lj-Vav2分布于七鳃鳗心脏、肾脏、髓样组织、肝脏、鳃以及类淋巴细胞中,同时经过LPS刺激后淋巴细胞中Lj-Vav2的表达水平呈现明显上调趋势。综上,Lj-Vav2在七鳃鳗体内免疫防御过程中发挥重要作用。此外,我们的研究将为今后更好地阐明Lj-Vav2生物学功能奠定坚实的物质基础。  相似文献