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1.
水平测试样品的均匀性保证   总被引:1,自引:0,他引:1  
为确保水平测试样品的均匀性,文中阐述了水平测试、样品制备、均匀性检验的取样数量、取样方式、最小取样量、测量方法和统计方法,重点介绍了均匀性检验的统计方法。  相似文献   

2.
为了揭示禁食应激与组织内Fe、Mg代谢的内在规律,本实验观察了禁食对豚鼠不同组织内Fe、Mg水平的影响。结果显示:1.大脑、心、肝和肾脏等组织内Fe、Mg水平随着禁食时间延长呈下降趋势。2.间脑和肾上腺组织内Fe水平及间脑组织内Mg水平在禁食早期上升,以后则下降;肾上腺组织内Mg水平则先下降,以后逐渐恢复。3.血浆Fe水平早期增高,而Mg水平则变化不明显。提示:1.禁食可明显影响机体内部Fe、Mg  相似文献   

3.
用量子化学密度泛函理论(DFT)方法,对COS与O2的反应进行了理论研究.在UB3LYP/6—31G^*,UB3LYP/6—311++G^**水平上,优化了反应势能面上各驻点(反应物、产物、中间体和过渡态)的几何构型,在UB3LYP/6—31G^*水平上通过内禀反应坐标(IRC)计算和振动分析,对过渡态进行了确认.在CCSD(T)/6—311++G(2d,2p)水平上进行了单点能量计算,并确定了反应机理.研究结果表明,反应主要产物为CO2和SO.  相似文献   

4.
血清铁、锌、钙、镁、磷与妊娠的关系探讨   总被引:5,自引:1,他引:5  
为探讨血清铁、锌、钙、镁、磷在孕妇体内的水平,做好围产期孕妇的保健工作,提高孕产妇的健康水平和新生儿健康素质,抽取125例孕中期妇女空腹静脉血,采用透射比浊法测定了其血清铁、锌、钙、镁、磷的含量。结果表明,铁、锌、钙、镁、磷的异常在孕妇中有一定的发生率,其中尤以钙与锌的缺乏最为多见。提示应定期检测孕妇血清铁、锌、钙、镁、磷水平,并采取相府的防治措施.以提高孕产妇及新生儿的健康水平。  相似文献   

5.
简述了我国国家标准的制定水平、采用国际标准的程度、国家标准的更新,以及参与国际标准制定等现状,指出了存在的不足,并提出了提高国家标准的起点水平,积极参与国际标准制定等建议。  相似文献   

6.
给出了内蒙古段黄河水平中总α,总β,^90Sr,^137Cs,^40K,^3H,^210Pb,^210Po,^238U,^232Th、^226Ra放射性水平,结果基本为正常水平,找出了污染源,为内蒙古段黄河水中放射性监督监测建立了全面的背景材料。  相似文献   

7.
为揭示应激对体内微量元素代谢的影响和机制,预先给予大鼠不同水平的铜3周后,采用冷束缚法使大鼠产生应激,测定了血清铜、锌水平及超氧化物歧化酶(SOD)活性、还原型谷胱甘肽(GSH)和丙二醛(MDA)含量。结果表明,高铜给予没有对清洁级大鼠生长产生明显的影响.血清铜、锌及铜锌比值变化不明显,但适量的铜给予能显著提高血清中SOD活性和GSH含量;冷应激处理后大鼠血清中Cu水平下降,Zn水平升高,同时SOD消耗降低,而GSH含量显著升高。表明冷应激可使大鼠体内铜锌代谢及SOD活性和GSH含量发生变化,适量的铜给予在应激状况下才发挥出积极的生理作用。  相似文献   

8.
设计并实践了新的分析化学实验教学方法和考评方法。将案例分析与翻转课堂相结合,进行线上线下混合式教学。课前教师选择案例并设计问题,学生分组预习;课堂上学生讨论分析为主,教师查漏补缺为辅;课后学生撰写报告上传至线上平台,教师批阅并反馈问题。新的考评方法中,突出对学生表达能力、逻辑思维能力、团队协作能力、实验操作水平、实验台与实验室整洁水平的考查评价。实践表明,新的教学方法有助于提升学生的表达能力和实验操作水平,激发学生学习的积极性和挑战高难度学习任务的热情。新的考评方法为评价学生能力提供了可执行的标准。  相似文献   

9.
美国、日本和国产香烟中铅含量的比较   总被引:8,自引:0,他引:8  
测定和比较了来自美国、日本和国产香烟的铅含量,结果表明,不同产地的烟中铅含量差别很大,并足以造成被动吸烟者血铅水平增高。  相似文献   

10.
人类铅暴露的历史回顾   总被引:1,自引:0,他引:1  
回顾了环境铅污染史和人类铅接触史,包括世界铅产量的历史演变,人类血铅水平的历史演变,近二十年来人类血铅水平的变化和铅中毒诊断标准的变化。  相似文献   

11.
Investigations dealing with fundamental aspects of the interaction between covalently cross-linked polyelectrolyte gels and oppositely charged surfactants are reviewed. For reference, a brief summary of results from recent studies of associative phase separation in linear polyelectrolyte/surfactant mixtures is also included. It is found that great progress has been made in several sub-areas since the first reports appeared in the early 1990's. The frequently observed surfactant-induced volume transition has been studied in detail. Its relation to associative phase separation in solutions and the important role of polyion-mediated micelle–micelle attractions have been clarified. Phase separation in gels, in particular core/shell structures, has been studied in great detail. The importance of network mediated elastic forces between two phases coexisting in the same gel has been demonstrated and some of their consequences have been clarified. Hydrophobic interactions between polyion and micelle have been found to have strong effects on both binding and swelling isotherms. The effect of salt, which has been found to sometimes disfavor, sometimes promote surfactant binding, is quite well understood. The microstructure of gels in the collapsed state has been studied in great detail and is often found to be highly ordered, resembling liquid crystalline phases common to surfactant/water systems. The kinetics of surfactant binding and the associated volume change has been investigated to some extent. Progress has been made for gels displaying phase separation during the volume transition.  相似文献   

12.
Carbonaceous nanomaterials and their derivatives have been inspired tremendous enthusiasm in the scientific community. They have been excogitated as the encouraging attributes and the qualified dispersed phase to develop multi-functional composites. Particularly, graphene and carbon nanotube (anisotropic fillers) have gained substantial research interest owing to their promising characteristics. This highlights an innovative technique to synthesize hybridized nanotube and nanosheet. Initially, parent materials have been synthesized: The pristine CNT has been modified by acid mixture solution, and reduced graphene oxide has been prepared by chemical reduction method. Henceforth, the self-assembly in situ sol–gel technique has been endorsed here. The synthesized nanohybrids have been characterized by different spectroscopic techniques: FTIR, Raman, UV, and XPS to confirm the attachment of multifunctionalities; meanwhile, the composition and stability have been investigated from XRD and TGA plots. The magnitude of surface charge and particle size distribution have been evaluated for the parent and hybridized products; further, morphology of all the samples has been authenticated from FESEM and TEM.  相似文献   

13.
For (ethylene-vinyl acetate copolymer)-tetraethoxysilane and (ethylene-vinyl acetate copolymer)-polydimethylsiloxane systems, the solubility of components has been studied in a wide range of temperatures and compositions. Phase diagrams have been constructed, pair interaction parameters have been calculated, and diffusion coefficients and activation energies of diffusion have been estimated. The temperature and concentration ranges of a change in solubility related to chemical interactions between the components have been revealed, and the structure of the modified copolymers has been studied. On the basis of the kinetic data on the movement of isoconcentration planes in diffusion zones of component mixing, time intervals corresponding to the onset of the chemical reaction between the components have been determined and the apparent activation energies of the process have been computed. Complex-shaped binodal and boundary curves have been interpreted within the framework of the classical Flory-Huggins theory.  相似文献   

14.
Pyridine, pyridine imine, and bipyridine imine ligands functionalized by a phenol have been synthesized and characterized, in many cases by X-ray diffraction. Several of these N-, N,N-, and N,N,N,-ligands have been grafted onto the surface of phosphorhydrazone dendrimers, from generation 1 to generation 3. The complexation ability of these monomers and dendrimers towards palladium(II) has been assayed. The corresponding complexes have been either isolated or prepared in situ. In both cases, the monomeric and dendritic complexes have been tested as catalysts in Heck couplings and in Sonogashira couplings. In some cases, a positive dendritic effect has been observed, that is, an increase of the catalytic efficiency proportional to the dendrimer generation.  相似文献   

15.
Improvement of prediction accuracy of the protein secondary structure is essential for further developments of the whole field of protein research. In this paper, the expertness of protein secondary structure prediction engines has been studied in three levels and a new criterion has been introduced in the third level. This criterion could be considered as an extension of the previous ones based on amino acid index. Using this new criterion, the expertness of some high score secondary structure prediction engines has been reanalyzed and some hidden facts have been discovered. The results of this new assessment demonstrated that a noticeable harmony has been existed among each amino acid prediction behavior in all engines. This harmony has also been seen between single global propensity and prediction accuracy of amino acid types in each secondary structure class. Moreover, it is shown that Proline and Glycine amino acids have been predicted with less accuracy in alpha helices and beta strands. In addition, regardless of different approaches used in prediction engines, beta strands have been predicted with less accuracy.  相似文献   

16.
相变储能材料的研究进展   总被引:38,自引:0,他引:38  
综述了相变材料的研究进展状况 ,介绍了相变材料的分类以及各类相变材料的性能、储能机理和优缺点 ,并介绍了一些新型的相变材料 ,指出了该领域中有待解决的问题 ,展望了未来相变材料的发展前景。  相似文献   

17.
The evaluation of a macrocyclic glycopeptide antibiotic, eremomycin, as a chiral selector in capillary electrophoresis (CE) has been performed. The stability of eremomycin in solution and capillary electrolyte, as well as its optical and electrophoretic properties have been discussed. The effect of experimental parameters influencing the enantioseparation of several profens has been studied. Excellent enantioseparation of profens has been achieved and migration order has been validated. Comparison of enantioseparations of profens in CE by using eremomycin-mediated electrolytes and in HPLC with eremomycin immobilized on silica has revealed similar trends for both methods.  相似文献   

18.
An apparatus and procedure for real-time in situ investigations of monomer electropolymerization in solution using optical microscopy with differential interference and phase contrast have been designed. The kinetics of electropolymerization of an acrylamide-formaldehyde monomer mixture in aqueous solution has been studied. An induction period of electropolymerization was fixed and evaluated for the first time. Growth of the polymer film after disconnection has been visualized. The dynamics of this phenomenon is evaluated, and possible reasons are discussed. Anisotropic mechanical stresses, arising in the polymer film during electropolymerization, have been found and characterized. The mechanism that is responsible for the formation of a dense near-cathode layer has been revealed. The formation of a zinc sublayer during electropolymerization has been examined. Reasons for the roughness of the near-electrode surface of the polymer film and for high adhesion of the electrodeposited polymer film to the metal have been established.  相似文献   

19.
The EGS4 a Monte Carlo electron-photon transport simulation package together with a locally developed computer program “GCELL” has been used to simulate the transport of the gamma rays in Gammacell 220. An additional lead attenuator has been inserted in the chamber, has been included for those cases where lower dose rates were required.

For three cases of 0, 1.35 and 4.0 cm thickness of added lead attenuators, the gamma spectrum, and dose rate distribution inside the chamber have been determined. For the case of no attenuator present, the main shield around the source cage has been included in the simulation program and its albedo effects have been investigated.

The calculated dose rate distribution in the Gammacell chamber has been compared against measurements carried out with Fricke, PMMA and Gafchromic film dosimeters.  相似文献   


20.
The extraction process of ternary ion-association complexes of molybdenum (VI) with some polyphenols (4-nitrocatechol, 2,3-dihydroxy naphthalene) and thiazolyl blue has been investigated by using an extraction-spectrophotometric method. The optimum conditions for their quantitative preparation in aqueous medium and subsequent extraction into an organic solvent have been found. The extraction, distribution and association constants, and the recovery factors have been calculated. The composition of the complexes has been determined. A precise, sensitive and simple extraction-spectrophotometric method for determination of molybdenum in products from ferrous metallurgy has been developed.  相似文献   

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