990 resultados para low level


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通过测定黄土高原不同区域、不同类型土壤全锌和有效锌含量,研究了黄土高原土壤锌含量及影响有效锌的因素。结果表明,供试土壤全锌主要分布在50~100mg·kg-1之间,有效锌含量较低,其中20.69%在临界值(0.5mg·kg-1)之下,37.93%为低(0.5~1.0mg·kg-1)水平。用直线、幂函数和指数函数回归方程对影响有效锌的主要土壤因素进行回归拟合。发现土壤有效锌与全锌、全氮、全磷、有机质呈显著正相关,与土壤pH值呈显著负相关;幂函数可以较好地拟合有效锌与土壤全氮、有机质的相关关系,有效锌与全锌、全磷、pH值宜用指数函数表示其相关性。通径分析表明土壤性质对有效锌的直接作用系数大小次序为全氮>全锌>pH>全磷,土壤全氮对锌有效性的直接作用最明显。

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应用时空互代方法,以柠条林为例,对黄土丘陵沟壑区不同利用年限人工林土壤养分特征、空间变异及其演变进行了系统的研究。结果表明,该区人工林土壤肥力处于较低水平;人工林表层土壤养分中速效磷和速效钾的空间变异性较大;各环境因子对土壤养分有一定的影响,海拔、坡度和坡向等环境因子与人工林地土壤养分间呈负相关关系,坡位和地形与人工林地土壤养分间呈正相关关系。随着利用年限的增加,人工林土壤养分各指标含量均增加,与利用年限有显著的相关性。有机质、全氮、有效氮和速效磷的增加量不明显,全磷含量保持相对稳定的水平,速效钾经过多年积累有明显的增加。从土壤养分指数模型可以算出该区的人工林土壤有机质、全氮、有效氮约需35a能达到中上等养分水平,速效钾则约需27a才能达到中上等养分水平。

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The nutrient cycling in the reed field has been studied via field investigation and laboratory analysis. The results indicate that N absorption in higher reed productvity field is 0.6044% (high level); The P absorption is 0.1100% (intermediate); The K absorption is 0.0153% (low level).the cycling coefficiencies for N,P and K are 0.16、 0.15 and 0.12,respectively. They are all at low levels.

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With the digital all-sky imager (ASI) emergence in aurora research, millions of images are captured annually. However, only a fraction of which can be actually used. To address the problem incurred by low efficient manual processing, an integrated image analysis and retrieval system is developed. For precisely representing aurora image, macroscopic and microscopic features are combined to describe aurora texture. To reduce the feature dimensionality of the huge dataset, a modified local binary pattern (LBP) called ALBP is proposed to depict the microscopic texture, and scale-invariant Gabor and orientation-invariant Gabor are employed to extract the macroscopic texture. A physical property of aurora is inducted as region features to bridge the gap between the low-level visual features and high-level semantic description. The experiments results demonstrate that the ALBP method achieves high classification rate and low computational complexity. The retrieval simulation results show that the developed retrieval system is efficient for huge dataset. (c) 2010 Elsevier Inc. All rights reserved.

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Rare earth oxide, neodymium oxide (Nd2O3), CO-catalyzed melt grafting of maleic anhydride (MAH) onto co-polypropylene (co-PP) in the presence of dicumyl peroxide (DCP) was carried out by reactive extrusion. The experimental results reveal that the addition of Nd2O3 as a coagent leads to an enhancement in both MFR and the grafting degree of MAH, along with a simultaneous decrease in the gel content. When the Nd2O3 concentration is 6.0 mmol%, the increment of the grafting degree of MAH maximally is up to about 20% compared with the related system without adding Nd2O3, and the gel content decreases simultaneously to a very low level of about 3%. Attenuated total reflection FTIR (ATR-FTIR) indicates that the gel in the graft copolymers mainly arise from the cross-linking reaction between ethylene units of co-PP. A reasonable reaction mechanism has been put forward on the basis of our experimental results and other mechanisms reported in the literature. We also tentatively explain above results by means of synergistic effect between DCP and Nd2O3, which causes a higher concentration of the macroradical, in particular the tertiary macroradical.

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In this study, the background activity of beta-glucuronidase (GUS) was analyzed histochemically and fluorometrically in the negative control of Laminaria japonica (Phaeophyta) thalli, showing low level of activity. GUS gene transformation without selectable gene in L. japonica was performed using four different promoters, i.e., Cauliflower mosaic virus 35S promoter (CaMV35S) from cauliflower mosaic virus, ubiquitin promoter (UBI) from maize, adenine-methyl transfer enzyme gene promoter (AMT) from virus in green alga Chlorella, and fucoxanthin chlorophyll a/c-binding protein gene promoter (FCP) from diatom Phaeodactylum tricornutum. The GUS transient activity was determined fluorometrically after bombarding sliced parthenogenetic sporophytes explants, and it was found that the activity resulting from CaMV35S and FCP promoters (in 114.3 and 80.6 pmol MU min(-1) (mg protein)(-1), respectively) was higher than for the other two promoters. The female gametophytes were bombarded and regenerated parthenogenetic sporophytes. FCP was the only promoter that resulted in detectable GUS chimeric expression activity during histochemical staining and polymerase chain reaction. Results of Southern blot showed that GUS gene was integrated with the L. japonica genome.

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The color mutations in Bangiaceae were investigated by treating the blades, conchocelis and conchospores phase of Bangia sp., Porphyra yezoensis, and P. haitanensis sampled in China with mutagen N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). A high percentage of mutation in different expression characteristics in all three phases were shown within optimum mutagen concentrations. Among mutagenized blades, mutations occurred on single cells, which is a direct outcome of mutation of haploid cells. The mutation of mutagenized conchocelis resulted in a two-step process: low-level expression in conchocelis phase, and high-level expression in progeny, explaining that mutation took place in diploid cells. The mutations of conchospores were expressed immediately at germination of spores, indicating a change in ploidy. This paper reports the process of meiosis and its effect on frond development, and the relation between color mutations and morphological characteristics expressed by mutations in Bangiaceae.

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本文主要运用稳定加液-反应系统对海水中方解石和文石形成时稀土元素的共沉淀现象进行了分析,研究了稀土元素在固-液体系中的迁移、转化和分配。进而在对其定量描述的前提下,研究了稀土元素共沉淀对各种反应条件的响应,并对共沉淀行为的机制进行了探讨。 本实验首先运用pH测试、高精度滴定分析等手段测定了实验中的一些基本参数,如[H+]、碱度和[Ca2+],根据计算结果获得了各碳酸体系要素,并以此为基础建立了5℃、15℃和25℃及pCO2=0.003atm下海水中方解石或文石的沉淀动力学方程。实验结果表明: 1)在各条件下,方解石或文石的沉淀速率(R)和其在海水中过饱和度(Ω)存在很好的线性相关性,即海相碳酸盐的沉淀动力学方程可以通过下面的基本表达式来表示:LogR=k*Log(Ω-1)+b ; 2)过高的稀土元素浓度会对文石或方解石的沉淀产生抑制作用,进而对共沉淀过程中YREEs的分异和分馏产生一定的影响。相比方解石而言,文石的沉淀动力学过程承受稀土元素的干扰能力更强; 3)不同温度下得到的方解石或文石各自的沉淀动力学方程存在明显的差异,表明这一过程受热力学因素控制。相对于方解石而言,温度对文石的沉淀动力学的影响更为显著。 与前人研究不同的是,本实验中YREEs的浓度设定在非常低的范围内,从而避免了过高浓度YREEs对方解石或文石沉淀动力学过程的干扰。在最终的反应液中,各种实验条件非常接近自然环境。有关稀土元素的共沉淀行为主要得出以下定性或定量化结论: 1)YREEs在随方解石或文石的共沉淀过程中,均发生了强烈的分异作用。在方解石实验中,稀土元素的分异系数分布曲线呈凸状分布;而在文石实验中,稀土元素的分异系数随原子序数的增加逐渐减小,遵循镧系收缩的规律。总的来说,稀土元素,尤其轻稀土元素在文石中的分异作用要强于方解石。 2)无论是方解石还是文石,沉淀速率对YREEs的分异作用都有着明显的影响。在方解石中,YREEs的分异系数随沉淀速率的增加呈一致性递减趋势;而在文石中,其分异系数对文石沉淀速率有着截然不同的响应:轻稀土元素(La, Ce, Nd, Sm, Eu, Gd)的分异系数随文石沉淀速率的增加而下降,而重稀土元素(Ho, Y, Tm, Yb , Lu)的分异系数则随文石沉淀速率的增加呈上升趋势。 3)在方解石中YREEs的分异系数之间存在非常好的相互关系,表明这些元素是以成比例的方式参与共沉淀。整个谱系呈现中等强度的分馏,MREE相对于LREE和HREE要更为富集;在文石中由于沉淀速率的作用不同,只有Y、Ho、Yb、Lu等元素的分异系数之间有较好的相互关系。YREEs出现了差异性的强烈分馏,在新生成沉淀中轻稀土元素相对于重稀土元素强烈富集。 4)YREEs在溶液中和碳酸盐晶体表面的碳酸根配位形式对YREEs在共沉淀过程中的分异作用极为重要,YREEs在碳酸盐晶体表面的吸附是整个谱系发生分馏效应的关键环节。对于文石来讲,晶体中有效YREE离子和Ca离子半价大小之间的相近程度是其分馏效应的关键因素;而对于方解石来说,YREEs在方解石晶格中的安置就是其分馏效应的关键控制因子,但在晶格安置中起到关键作用的是YREEs和方解石中O原子之间离子键M-O的键长,而非离子半径。 5)综合YREEs在方解石中的分异作用和分馏效应,我们认为M2(CO3)3-CaCO3和MNa(CO3)2-CaCO3是最为可能的两种固体溶液形成模式。 最为重要的是,对比我们的实验结果与前人在灰岩、叠层石、微生物成因碳酸盐等方解石质载体中的研究成果,两者之间出现了非常好的一致性。我们认为方解石质载体将是重建古海水中稀土元素相关信息的重要工具。相比之下,文石质载体不适合作为类似的载体。

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The vertical distribution and stage-specific abundance of Calanus sinicus were investigated on three key transects in the southern Yellow Sea and the northern East China Sea in August 1999. The results showed that in summer C. sinicus shrank its distribution area to the central cold (less than or equal to10degreesC) bottom water in the Yellow Sea, i.e. the Yellow Sea Cold Bottom Water, remaining in high abundance (345.7 ind m(-3)). In the northern East China Sea on a transect from the mouth of the Yangtze River to the Okinawa trench, only a few individuals appeared in the inner side and none had been found either in the upper layer or in the deep layer of the outer shelf area. The population of C. sinicus in YSCBW consisted of mainly adults (46.83%) and C5 (37.41%). C1-C4 only accounted for 15.76%. The low proportion of the earlier copepodite stages and the high female:male ratio (11.39) indicated that the reproduction of C. sinicus in YSCBW was at a very low level due to the low temperature and low food concentration. It is concluded that the dramatic decrease of C. sinicus population in the shelf area of China seas in summer is caused by the shrinkage of its distribution area and the YSCBW served as an oversummering site.

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Due to the influence of human activities, nutrient concentrations, nutrient ratios and phytoplankton composition have notably changed in Jiaozhou Bay, China since the 1960s. From the 1960s to the 1990s, nutrient concentrations have increased 1.4 times for PO4-P, 4.3 times for NO3-N, 4.1 times for NH4-N and 3.9 times for DIN. The atomic ratio of DIN:PO4-P increased very rapidly from 15.9 +/- 6.3 for the 1960s, to 37.8 +/- 22.9 for the 1990s. SiO3-Si concentration has remained at a very low level from the 1980s to the 1990s. The high ratio of DIN: PO4-P and low ratios of SiO3-Si:PO4-P (7.6 +/- 8.9) and SiO3-Si:DIN (0.19 +/- 0.15) showed the nutrient structure of Jiaozhou Bay has changed from more balanced to unbalanced during the last 40 years. The possibility that DIN and/or PO4-P as limiting factors of Jiaozhou Bay phytoplankton has been lessened or eliminated and that of SiO3-Si limiting has been increased. The changes in nutrient structure may have led to the decrease of large diatoms and a shift of phytoplankton species composition. It is likely that there is a trend from large diatoms to smaller cells in Jiaozhou Bay. (C) 2001 Academic Press.

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Random amplified polymorphic DNA ( RAPD) markers were used to measure genetic diversity of Coelonema draboides ( Brassicaceae), a genus endemic to the Qilian Mountains of the Qinghai-Tibet Plateau. We sampled 90 individuals in 30 populations of Coelonema draboides from Datong and Huzhu counties of Qinghai Province in P. R. China. A total of 186 amplified bands were scored from the 14 RAPD primers, with a mean of 13.3 amplified bands per primer, and 87% ( 161 bands) polymorphic bands (PPB) was found. Analysis of molecular variance (AMOVA) shows that a large proportion of genetic variation (84.2%) resides among individuals within populations, while only 15.8% resides among populations. The species shows higher genetic diversity between individuals than other endemic and endangered plants. The RAPDs provide a useful tool for assessing genetic diversity of rare, endemic species and for resolving relationships among populations. The results show that the genetic diversity of this species is high, possibly allowing it to adapt more easily to environmental variations. The main factor responsible for the high level of differentiation within populations and the low level of diversity among populations is probably the outcrossing and long-lived nature of this species. Some long-distance dispersal, even among far separated populations, is also a crucial determinant for the pattern of genetic variation in the species. This distributive pattern of genetic variation of C. draboides populations provides important baseline data for conservation and collection strategies for the species. It is suggested that only populations in different habitats should be studied and protected, not all populations, so as to retain as much genetic diversity as possible.

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设计了一种基于多微处理器的智能超声探测系统。该系统采用由上位工作模式控制单元和下位智能超声传感器阵列组成的分布式结构。每个超声传感器均由独立的微处理器控制,并完成实时数据处理、抗干扰处理、故障报警以及数据通信等功能。上位控制单元根据移动机器人的运动状态采用不同的控制策略,使下位传感器阵列分组并行工作,提高了探测系统的实时性;下位传感器采用"阈值比较法"、"改进型递推均值滤波"算法和模糊信息处理技术,提高了探测系统的准确性、可靠性。将该探测系统安装于RIRA-II移动机器人上,进行了基于主动视觉和超声信息的运动目标跟踪实验,实验表明超声探测系统运行可靠、稳定。

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Now low porosity and low permeability reservoir is one of the main targets of exploration for the onshore oilfields of China. Most of the reservoirs are none flowing because of bad formation percolation condition, poor gas oil ratio , low formation pressure coefficient and other factors. In the recent years, a number of domestic oilfields have carried out some research work and achieved some success on oil testing and production technology in such formation. But by now, there is still no systematic and mature technology, particularly testing technology in none flowing formation is still needed further study. Based on study the key problem of well testing and interpretation technology in none flowing formation, solve the important problems in well testing technology, continuously improve and innovate geological information acquisition technology for none flowing reservoir, accurately acquire boundary information and evaluate reservoir flow characteristics. Its wide application remarkable result has shown. The main results and cognitions obtained from research are as follows: 1. This new technology research results help solve the occurrent problems in well testing process for none flowing formations, such as small investigation radius, poor representative of interpretation results from the poor data, low level application of interpretation results. This new technology helps create favorable conditions for early precise reservoir evaluation and reduction of the risk of exploration. 2. The technological difficulties for none flowing well testing are successfully solved by using none flowing formation combined mechanical tool string .This method has been proved by its applications to be able to improve the efficiency of the testing and the quantity of the acquired test data ,and so as to enhance the application of the interpretation results of the test in development of oil fields. 3. The application of the rotary formation tester, selective test valve, well testing string and their allier tools help to resolve problems such as the operation of opening and shutting-in the well under different well conditions, to broaden the scope of well test technology for none flowing formations. 4. Refined Testing Technique for production Wells has greatly shortened the testing dwration and improved the efficiency and accuracy of operation, enriched test results, and at the same time created conditions for conducting multi-well interference well testing.

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The surface of the Earth is continuously undergoing changes as a result of weathering-erosion, plate tectonics and volcanic processes. Continental weathering-erosion with its complex rock-water interactions is the central process of global biochemical cycling of elements, and affects the long-term ocean atmosphere budget of carbon dioxide both through the consumption of carbonic acid during silicate weathering and through changes in the weathering and burial rates of organic carbon. Rates of the weathering-erosion depend on a variety of factors, in particular rock properties and chemical composition, climate (especially rainfall), structure, and elevation. They are quite variable on a regional scale. Thus, environmental changes in a region could be indicated by the history of weathering-erosion in the region. Recent attention has focused on increased silicate weathering of tectonically uplifted areas in the India-Asia collision zone as a possible cause for falling atmospheric CO_2 levels in the Cenozoic era. The wind blown dust deposits in the Loess Plateau is derived from the arid and semiarid regions in northwestern China, in turn, where the deposits have been derived from the Qinghai-Xizang Plateau and the high mountains around. Therefore, geochemistry of the wind blown loess-paleosol and red clay sequences may provide insight both to paleoenvironmental changes on the Loess Plateau, and to the uplift and weathering-erosion histories of the Qinghai-Xizang Plateau. In this paper, uranium-thorium series nuclides and cosmogenic ~(10)Be have been employed as tracers of weathering intensities and histories of the dust sediments in the Loess Plateau. Major elements, such as Na, Al, Fe etc., are also used to estimate degree of chemical alteration of the dust sediments and to rebuild the history of weathering on the Loess Plateau. First of all, using a low-level HPGe γ-ray detector, we measured U and Th series nuclides in 170 loess and paleosol samples from five sites in the Loess Plateau, going back 2.6 Ma. The results show that ~(238)U activities are disequilibrium with its daughter nuclide ~(230)Th in young loess-paleosol sequence, indicating that weathering was happened both in dust deposition site and in dust source regions. Using concentrations of ~(238)U and ~(232)Th in the samples, we estimated the amounts of ~(238)U leached out of from paleosols due to weathering. Further, based on analyses of ~(230)Th in paleosols deposited in the past ca. 140 ka, we determined when the paleosols weathered in the source regions. We conclude that most of the weathering in the dust-source regions may have occurred during the interglacials before dust deposition.

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Superfine mineral materials are mainly resulted from the pulverization of natural mineral resources, and are a type of new materials that can replace traditional materials and enjoy the most extensive application and the highest degree of consumption in the present day market. As a result, superfine mineral materials have a very broad and promising prospect in terms of market potential. Superfine pulverization technology is the only way for the in-depth processing of most of the traditional materials, and is also one of the major means for which mineral materials can realize their application. China is rich in natural resources such as heavy calcite, kaolin, wollastonite, etc., which enjoy a very wide market of application in paper making, rubber, plastics, painting, coating, medicine, environment-friendly recycle paper and fine chemical industries, for example. However, because the processing of these resources is generally at the low level, economic benefit and scale for the processing of these resources have not been realized to their full potential even up to now. Big difference in product indices and superfine processing equipment and technologies between China and advanced western countries still exists. Based on resource assessment and market potential analysis, an in-depth study was carried out in this paper about the superfine pulverization technology and superfine pulverized mineral materials from the point of mineralogical features, determination of processing technologies, analytical methods and applications, by utilizing a variety of modern analytical methods in mineralogy, superfine pulverization technology, macromolecular chemistry, material science and physical chemistry together with computer technology and so on. The focus was placed on the innovative study about the in-depth processing technology and the processing apparatus for kaolin and heavy calcite as well as the application of superfine products. The main contents and the major achievements of this study are listed as follows: 1. Superfine pulverization processing of mineral materials shall be integrated with the study of their crystal structures and chemical composition. And special attention shall be put on the post-processing technologies, rather than on the indices for particle size, of these materials, based on their fields of application. Both technical feasibility and economic feasibility shall be taken into account for the study about superfine pulverization technologies, since these two kinds of feasibilities serve as the premise for the industrialized application of superfine pulverized mineral materials. Based on this principle, preposed chemical treatment method, technology of synchronized superfine pulverization and gradation, processing technology and apparatus of integrated modification and depolymerization were utilized in this study, and narrow distribution in terms of particle size, good dispersibility, good application effects, low consumption as well as high effectiveness of superfine products were achieved in this study. Heavy calcite and kaolin are two kinds of superfine mineral materials that enjoy the highest consumption in the industry. Heavy calcite is mainly applied in paper making, coating and plastics industries, the hard kaolin in northern China is mainly used in macromolecular materials and chemical industries, while the soft kaolin in southern China is mainly used for paper making. On the other hand, superfine pulverized heavy calcite and kaolin can both be used as the functional additives to cement, a kind of material that enjoys the biggest consumption in the world. A variety of analytical methods and instruments such as transmission and scanning electron microscopy, X-ray diffraction analysis, infrared analysis, laser particle size analysis and so on were applied for the elucidation of the properties and the mechanisms for the functions of superfine mineral materials as used in plastics and high-performance cement. Detection of superfine mineral materials is closely related to the post-processing and application of these materials. Traditional detection and analytical methods for superfine mineral materials include optical microscopy, infrared spectral analysis and a series of microbeam techniques such as transmission and scanning electron microscopy, X-ray diffraction analysis, and so on. In addition to these traditional methods, super-weak luminescent photon detection technology of high precision, high sensitivity and high signal to noise ratio was also utilized by the author for the first time in the study of superfine mineral materials, in an attempt to explore a completely new method and means for the study of the characterization of superfine materials. The experimental results are really exciting! The innovation of this study is represented in the following aspects: 1. In this study, preposed chemical treatment method, technology of synchronized superfine pulverization and gradation, processing technology and apparatus of integrated modification and depolymerization were utilized in an innovative way, and narrow distribution in terms of particle size, good dispersibility, good application effects, low consumption as well as high effectiveness of superfine products were achieved in the industrialized production process*. Moreover, a new modification technology and related directions for producing the chemicals were invented, and the modification technology was even awarded a patent. 2. The detection technology of super-weak luminescent photon of high precision, high sensitivity and high signal to noise ratio was utilized for the first time in this study to explore the superfine mineral materials, and the experimental results can be compared with those acquired with scanning electron microscopy and has demonstrated its unique advantages. It can be expected that further study may possibly help to result in a completely new method and means for the characterization of superfine materials. 3. During the heating of kaolinite and its decomposition into pianlinite, the diffraction peaks disappear gradually. First comes the disappearance of the reflection of the basal plane (001), and then comes the slow disappearance of the (hkl) diffraction peaks. And this was first discovered during the experiments by the author, and it has never before reported by other scholars. 4. The first discovery of the functions that superfine mineral materials can be used as dispersants in plastics, and the first discovery of the comprehensive functions that superfine mineral materials can also be used as activators, water-reducing agents and aggregates in high-performance cement were made in this study, together with a detailed discussion. This study was jointly supported by two key grants from Guangdong Province for Scientific and Technological Research in the 10th Five-year Plan Period (1,200,000 yuan for Preparation technology, apparatus and post-processing research by using sub-micron superfine pulverization machinery method, and 300,000 yuan for Method and instruments for biological photon technology in the characterization of nanometer materials), and two grants from Guangdong Province for 100 projects for scientific and technological innovation (700,000 yuan for Pilot experimentation of superfine and modified heavy calcite used in paper-making, rubber and plastics industry, and 400,000 yuan for Study of superfine, modified wollastonite of large length-to-diameter ratio).