蔬菜温室土壤某些化学性质的演变特征

To explore the changes of soil chemical properties in vegetable greenhouse,a comparative study was carried out with the samples gathered from vegetable greenhouse fields and their adjacent upland fields in Damintun Town,Xinming County,Liaoning Province.The results showed that compared with upland fields,the contents of soil organic carbon and total nitrogen in greenhouse fields increased significantly.At the depth of 0～30 cm,soil organic carbon in greenhouses of 1-,4-and 10-year increased by 31.09%,35.44%,and 66.80%,respectively,compared with the upland soil.Soil nitrate content at the depth of 0～30 cm in greenhouse fields was 5.05～12.49 times as much as that in upland fields.The nitrate content in different soil layers increased with the increasing age of greenhouse field.,e.g.,at the depth of 20～30 cm,soil nitrate content was significantly higher in 10-year than in 1-and 4-year greenhouse field,with an increase of 65.73% and 50.89%,respectively,and 6.55 times as much as that in upland field,which indicated that soil nitrate transported downwards,and obviously enriched in deeper soil layers under heavy application of fertilizer.Also with the increasing age of greenhouse field,soil pH decreased,while soil soluble salts accumulated.

Analysis on fluorescence intensity reverse photonic phenomenon between red and green fluorescence of oxyfluoride nanophase vitroceramics

An interesting fluorescence intensity reverse photonic phenomenon between red and green fluorescence is investigated. The dynamic range. of intensity reverse between red and green fluorescence of Er( 0.5) Yb( 3): FOV oxyfluoride nanophase vitroceramics, when excited by 378.5nm and 522.5nm light respectively, is about 4.32 x 10(2). It is calculated that the phonon- assistant energy transfer rate of the electric multi- dipole interaction of {(4)G(11/2)( Er3+) -> F-4(9/2)( Er3+), F-2(7/2)( Yb3+). F-2(5/2)( Yb3+)} energy transfer of Er( 0.5) Yb( 3): FOV is around 1.380 x 10(8) s(-1), which is much larger than the relative multiphonon nonradiative relaxation rates 3.20 x 10(5) s(-1). That energy transfer rate for general material with same rare earth ion's concentration is about 1.194 x 10(5) s(-1). These are the reason to emerge the unusual intensity reverse phenomenon in Er( 0.5) Yb( 3): FOV. (C) 2007 Optical Society of America.

中国近海典型海域沉积物中无机碳的形态研究

碳循环是影响地球环境中能量循环和物质流动的重要过程，而由于人类活动带来的大气CO2浓度升高对生态环境带来一系列的影响，如温室效应、海水酸化及全球灾害性气候增加等。海洋是地球上巨大的碳库，近海海域是连接陆地和海洋两大生态系统的关键环节，它接受着河流输入的大量陆源物质，并通过物理、化学和生物过程与大洋进行各种物质和能量交换。经过对海洋碳循环的多年研究，人们对碳在大洋中的迁移转化获得了比较清晰的认识，但对生物地球化学过程极为复杂的近海的研究还存在较多的不确定性。 元素的存在形态对其迁移转化有着重要影响，为研究近海不同形态无机碳，本文采用连续浸取方法，根据无机碳在沉积物中的结合强度，将无机碳分为交换态、弱碱结合态、强碱结合态、弱酸结合态和残渣态，分析了渤海湾、四十里湾附近海域、大亚湾和南海北部海域等中国典型近海海域表层及柱状沉积物中不同形态的无机碳含量，并讨论了其与各地球化学参数之间的关系，得到如下结论： 在各个研究区，沉积物中总无机碳的平均含量分别为：渤海湾6.16 mg/g，四十里湾附近海域7.51 mg/g，大亚湾3.08 mg/g，南海北部海域11.66 mg/g。渤海湾潮间带沉积物的无机碳含量普遍高于潮下带沉积物，四十里湾附近海域柱状样沉积物中无机碳含量一般随埋藏深度的增加而增加，大亚湾沉积物低的无机碳含量可能与低的陆源物质输入有关，南海北部海域表层沉积物无机碳含量分布表现出明显的近岸低深海高的分布特征，高的无机碳含量明显受生物活动影响。 渤海湾沉积物中各相无机碳的平均含量为氯化钠相0.63 mg/g、氨水相0.74 mg/g、氢氧化钠相0.28 mg/g、盐酸羟胺相3.13 mg/g、残渣相1.38 mg/g。四十里湾附近海域沉积物柱状样各形态无机碳含量为氯化钠相0.54 mg/g、氨水相0.36 mg/g、氢氧化钠相0.13 mg/g、盐酸羟胺相6.46 mg/g、残渣相0.02 mg/g。大亚湾沉积物中各相无机碳的平均含量为氯化钠相0.45 mg/g、氨水相0.50 mg/g、氢氧化钠相0.46 mg/g、盐酸羟胺相1.51 mg/g、残渣相0.16 mg/g。南海北部沉积物中各相无机碳的平均含量为氯化钠相0.52 mg/g、氨水相0.30 mg/g、氢氧化钠相0.17 mg/g、盐酸羟胺相3.79 mg/g、残渣相6.88 mg/g。在所研究的大部分近海沉积物中，盐酸羟胺相是沉积物无机碳的主要形态，只有南海北部海域表层沉积物比较特殊。 渤海湾潮下带沉积物中，碱浸取相（氢氧化钠相和氨水相）无机碳与沉积物总有机碳（TOC）和总氮（TN）之间存在较为紧密的联系；潮间带沉积物中，含水率、TOC、TN和粒度等地球化学参数与前3相及残渣相无机碳均有较紧密的联系。四十里湾附近海域柱状沉积物中，沉积物各参数对不同柱状样各形态无机碳的影响差异较大，位于芝罘岛附近的柱状样B主要受粒度影响，含水率、TOC和TN对离岸较近的柱状样D的前两相无机碳和崆峒岛北侧的柱状样E的氯化钠相无机碳有较大影响，沉积物各参数对崆峒岛南侧的柱状样C和离岸最远的柱状样S的影响相对较小。大亚湾沉积物各形态无机碳受环境影响的程度比其它海域弱。南海北部沉积物中，TOC对各形态无机碳影响较强，其中的氨水相无机碳与沉积物各参数间存在较为紧密的联系。 对比各海域的研究结果发现，不同无机碳形态之间，碱浸取相无机碳之间常存在正相关关系，氯化钠相作为比较活泼的无机碳形态，与其它各相之间的关系具有不确定性，弱酸浸取相无机碳与无机碳总量的关系较为紧密，残渣相与其它无机碳形态的关系一般较弱，说明此相无

真核生物mRNA二级结构与内含子剪接

对68个外显子-内含子-外显子序列片段以及相应的外显子-外显子序列片段的二级结构进行分析后发现,内含子5^端和3^端的碱基G(剪接位点)中大约90%位于二级结构的环区或是茎区的端部并靠近环,而且位于环区的G也多靠近环的基部;92%的外显子拼接位点也有类似性质。约82%的分枝点A位于环区或环与茎的连接部位。折叠结构的形成使剪接位点和分枝点在空间上彼此靠近。

粪便收集时间和饲料中肉骨粉含量对异育银鲫(Carassius auratus gibelio)消化率的影响(英文)

本研究探讨了通过收集器不同粪便收集时间和饲料中肉骨粉( MBM)含量对异育银鲫干物质、蛋白、能量、磷的表观消化率(ADC)影响。不同梯度(0 ,20 ,40 ,60 ,80 ,100 %)的肉骨粉替代鱼粉(FM)蛋白配制成六种等氮(粗蛋白:410 g/kg)等能(总能:18 kJ/g)的饲料,通过11周的饲养实验,实验开始后2周开始收集粪便,收集时间分别是:排粪后1 min,投喂后4h和16h。结果表明,干物质、蛋白、能量、磷的消化率明显随粪便收集时间增加而升高(p<0 .05) ,但在高肉骨粉替代饲料中

太阳能空气饱和蒸馏器的试验研究

研究得到了太阳能空气饱和蒸馏器在稳态情况下和不同海水加热温度下的蒸发速度实验式:lgD=7.062+3.446t_0海水加热温度是影响淡水产量的主要因素，以46.2℃为转折，超过此温度，蒸发速度急促增加。液-气两相重量流量比(W/G)，必须与海水加热温度相适应。温度较高，(W/G)值也应较大，这样才能最大限度地提高产水量和降低产水的耗热量。当t_0=96℃时，(W/G)_(最佳)=12;当(W/G)=11时，t_(0最佳)=90℃。在一般太阳辐射条件下，t_0=60℃，(W/G)=1.67—3.0时，热耗值最低。过多地通入空气是空气饱和蒸馏器动力消耗较大的重要原因。在适当工况下进行操作，所需空气量较小。这样，不但产水量高、热耗值低、系统阻力减少，而且能耗大幅度降低。 模拟试验表明:太阳能空气饱和蒸馏器在太阳辐射日总量4500〔千卡/米~2〕时，每平方米集热器面积，每日可产淡水5—7公斤，所需翅片冷凝器换热面积为0.21〔米~2/时·公斤淡水〕。

煤层气与常规天然气测试技术的异同

煤层气测试资料的分析成果对确定煤层气的排采制度和制订合理的开发方案是至关重要的,研究该问题的目的在于解决目前只能利用常规方法进行测试、常规软件进行测试资料解释的问题。煤储层在成份、结构及其物理力学性质上与常规储层(如砂岩)有着明显的差异;煤层气的赋存和采出机理与砂岩中天然气也有着本质区别。要获取煤层准确参数、正确评价煤层,必须研究煤层气测试的相关理论方法。但目前对煤层气测试的认识较少。从常规天然气测试与煤层气测试的差异对比的角度出发,给出了煤层气测试的诸多特征。从研究对象的储层特征、煤层气的赋存特征以及不同开发阶段的流体分布及流动特征等方面,论述了煤层气与常规天然气测试技术异同的根本原因。从测试方法、测试工艺、解释模型和资料分析方法等方面,分析了煤层气与常规天然气测试技术的差异。研究成果对充分认识和理解煤层气测试的重要作用有积极的意义。

天然物质复配铁型絮凝剂及其处理味精废水的研究

采用不同天然物质(城市草炭土、草甸土、火山灰和红壤)与聚合硫酸铁复配,制备一种更为经济的新型絮凝剂,利用其对高浓度有机味精废水进行絮凝实验,并讨论了各组分的不同投加量比例及其絮凝的影响因素.研究结果表明:此种天然物质-聚合硫酸铁复配絮凝剂处理味精废水表现出优良的絮凝性能.其中以草甸土、红壤为天然复配材料处理效果最为显著,其最佳投加量比例为草甸土(g)∶聚合硫酸铁(m l)∶助剂(g)=11∶4∶6,最佳pH为7.0—8.0;红壤(g)∶聚合硫酸铁(m l)=10∶6,最佳pH为1.0—2.0.在此条件下,该天然复配铁型絮凝剂对味精废水的CODcr去除率远远高于聚合硫酸铁(PFS)本身,分别可达到71.1%和55.0%.

Study on stimulated emission of Eu2+ in crystal KMgF3 : Eu2+

The line emission peak of Eu2+ ion in crystal KMgF3 is at 360 nm. The probability of stimulated emission on 4f(7) (P-6(7/2))-> 4f(7)(S-8(7/2)) transition was predicted with a four-level decay model of Eu2+6P7/2 excited states proposed by the authors. Optic gain and net gain coefficient (g = 11.4 +/- 3.2)cm(-1) of 360 nm emission in crystal KMgF3 : Eu2+ were measured by ASE method, and the predication was proved by experiment. The net gain coefficient can be increased by annealing or doping crystal KMgF3 : Eu2+ with Gd3+ or Ce3+.

应用便携式微机伏安仪测定钯

用便携式微机伏安仪对贵金属Pd的电化学性能和测定进行了研究。在1 mol/L HCl溶液中Pd(Ⅱ)浓度2.5ng/ml～60μg/ml范围峰高是线性增加的。回收范围82％～105％。相对标准偏差为(n=8)3.8％。本法应用于贵金属回收液中Pd的测定,获得较为满意的结果。

基于加速度传感器的丝杠传动系统建模及控制研究

提出了基于加速度传感器的丝杠传动系统建模及控制策略 ,可以通过实验测量存在结构非刚性因素时丝杠系统的模型。基于该模型可以进一步设计基于加速度传感器的控制策略 ,加速度反馈可以抑制系统的扰动力对丝杠传动系统控制精度的影响 ,实验结果表明提出的方法可以有效地提高丝杠系统的性能。

贵州遵义牛蹄塘组黑色岩系的硒同位素变化及其环境指示初探质系，厄巴纳61801美国

西南早寒武世牛蹄塘组是分布在中国南方扬子地台的一套黑色岩系，区域上发育有典型富集多金属元素的硫化物矿化层。选取遵义松林小竹牛蹄塘组下部富硒、钼、镍等元素的黑色岩系剖面，利用Se同位素初步探讨了该剖面岩石的沉积环境和硒的可能来源。结果表明，小竹牛蹄塘组下部剖面黑色岩系的δ^82/76SeSRM 3149比值变化较大，下部底层含碳斑脱岩与磷块岩的变化范围在-4．35％～＋4．11‰之间；中间镍钼层及碳质页岩、碳质碳酸盐岩的占82δ^82/76SeSRM 3149变化范围窄，平均值为0．91700±0．23700（n=4）；上层碳质页岩为-1．24‰。结合已发表的钼同位素数据，认为中间岩石沉积于缺氧／无氧环境，但存在盆地海水与热液或充氧水团的混合；下层的岩石曾一度位于充氧与贫氧环境的边界面，局部岩石曾暴露地表经历了较强的风化和蚀变作用，海水中硒有可能来自底部富硒斑脱岩的氧化淋滤或海底热液。据此推测遵义松林小竹牛蹄塘组下部岩石的沉积环境极可能处在局限盆地靠近陆地的边缘部分，经历了充氧→贫氧→缺氧／无氧→贫氧的演化阶段.

Shell effect on stabilization processes following multi-electron transfer in slow Arq+-Ar (g=6-9, 11) collisions

We experimentally investigate the shell effect on the stabilization processes following the multi-electron transfer in slow collisions of Arq+-Ar (q = 6-9, It) The relative cross-section ratios of multi-electron transfer and of the subsequent stabilization with respect to single-electron capture are measured meanwhile compared with the theoretical results predicted by the classical over-barrier model. Our result indicates that the multi-electron transfer is dominant when the projectile charge is large and the subsequent stabilization shows a dramatic variation if the projectile L-shell configuration becomes open. It shows that the subsequent stabilization processes of multiply excited scattering ions have a strong dependence on the projectile shell. (C) 2010 Elsevier BV All rights reserved.

源于G.I.Taylor工作的现代经典物理学

一位科学家的工作提供了一门完整课程的素材，涉及从流体动力学稳定性、湍流到流体电动力学、微生物的运动．

Starting Nozzle Flow Simulation Using K-G Two-Equation Turbulence Model

The starting process of two-dimensional nozzle flows has been simulated with Euler, laminar and k - g two-equation turbulence Navier-Stokes equations. The flow solver is based on a combination of LUSGS subiteration implicit method and five spatial discretized schemes, which are Roe, HLLE, MHLLE upwind schemes and AUSM+, AUSMPW schemes. In the paper, special attention is for the flow differences of the nozzle starting process obtained from different governing equations and different schemes. Two nozzle flows, previously investigated experimentally and numerically by other researchers, are chosen as our examples. The calculated results indicate the carbuncle phenomenon and unphysical oscillations appear more or less near a wall or behind strong shock wave except using HLLE scheme, and these unphysical phenomena become more seriously with the increase of Mach number. Comparing the turbulence calculation, inviscid solution cannot simulate the wall flow separation and the laminar solution shows some different flow characteristics in the regions of flow separation and near wall.