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71.
采用紫露草四分体微核技术,对莆田木兰溪下游河溪水和饮用的浅井水进行致突变性监测。结果表明,10份河溪水能明显诱发紫露草四分体微核率的增高;与对照组相比10份浅井水也均不同程度提高了四分体微核效应,8份已达到显著或极显著水平(P〈0.05或P〈0.01),且与诱发的紫竹梅四分体微核效应显著相关,r=0.9777。说明浅井水内存在致植物细胞染色体畸变物质,提示当地居民上消化道肿瘤高发与饮水污染有一定相 相似文献
72.
对化学法清洗硅片过程中消除颗粒的机理作了定量的探讨。颗粒的清除是由于化学蚀刻和颗粒与表面排斥力共同作用的结果。首次提出了最浅蚀刻深度和最小蚀刻速度的概念。最浅蚀刻深度可通过颗粒与表面间作用能的关系进行计算。是小蚀刻速度则可通过蚀刻侧形进行计算。研究结果对于优化化学法清洗过程和设计高性能清洗液都具有重要意义。 相似文献
73.
Recent results obtained on determining the extraction efficiency and composition of organic volatiles in Oregano Water obtained from Origanum onites L. are described. Oregano Water was subjected to liquid-liquid extraction with a range of solvents with different polarities and each extract was analyzed by GC/MS. 相似文献
74.
《Electroanalysis》2004,16(5):355-359
Water present in undiluted acetic acid can be monitored in situ with Pt and Au microelectrodes using differential pulse and square‐wave voltammetries. Both reduction and oxidation peaks can be obtained. The best quantitative analytical results were obtained for the anodic peak, the Pt microelectrode, and differential pulse voltammetry. The anodic water peak is located at +1.55 V vs. the quasi reference Pt electrode. The voltammetric peak obtained at Pt electrode is apparently not a diffusional one, however, the calibration plot obtained by employing this peak is linear over a wide concentration range, up to 4 mol dm?3. The detection limit has been estimated as 2.3 mM or 0.0043 v/v%. The developed method may be particularly useful, since the Karl Fischer method can not be used to determine water in glacial acetic acid due to the estrification reaction of acetic acid with methanol. A voltammetric wave of undiluted acetic acid could not be obtained in the positive and negative ranges of potential. 相似文献
75.
Pb(II) interactions with the surface of suspended matter from a polluted river was studied using differential pulse anodic stripping voltammetry (DPASV) technique. Three sampling sites were selected and studies have been done with samples collected in different times of the year (winter, autumn and summer). The values have been compared with those obtained in spring in the same conditions [Sci. Total Environ. 151 (1994) 101].Particles were separated by centrifugation and suspensions of the freeze-dried particles were titrated with Pb(II), being measured the labile metal fraction by DPASV. For comparison, suspensions of river water without any separation have also been titrated.Results show that surface metal complexes are inert, within the time scale of the analytical technique and desorbed organics from surfaces, form labile Pb(II) complexes in solution. For each sample it was determined the capacity for Pb complexation of particles and desorbed organics and the differential function has been estimated. Despite the heterogeneity of ligands, the systems interpreted in a discontinuous way, present one or two kinds of dominant ligands with Pb affinity. 相似文献
76.
Torsten Barfels Bernd Schmidt Andreas von Czarnowski Hans-Joachim Fitting 《Mikrochimica acta》2002,139(1-4):11-16
For investigation of the luminescent center profile cathodoluminescence measurements are used under variation of the primary
electron energy E
0 = 2…30 keV. Applying a constant incident power regime (E
0·I
0 = const), the depth profiles of luminescent centers are deduced from the range of the electron energy transfer profiles dE/dx.
Thermally grown SiO2 layers of thickness d = 500 nm have been implanted by Ge+-ions of energy 350 keV and doses (0.5–5)1016 ions/cm2. Thus Ge profiles with a concentration maximum of (0.4 – 4) at% at the depth of dm≅240 nm are expected. Afterwards the layers have been partially annealed up to T
a = 1100 °C for one hour in dry nitrogen. After thermal annealing, not only the typical violet luminescence (λ = 400 nm) of
the Ge centers is strongly increased but also the luminescent center profiles are shifted from about 250 nm to 170 nm depth
towards the surface. This process should be described by Ge diffusion processes, precipitation and finally Ge nanocluster
formation. Additionally, a Ge surface layer is piled-up extending to a depth of roughly 25 nm. 相似文献
77.
The adsorption equilibrium of water on microporous adsorbents (zeolites of NaA-, NaY- and NaX-type as well as their ion exchanged
forms) and on mesoporous adsorbents (different silica gels and composite material i.e. silica gel + salt hydrate) has been
studied experimentally and theoretically. Using the Dubinin theory of pore filling the characteristic curves of the adsorption
systems and other relevant dependences such as isotherms, isobars, isosteres and the curve of the differential heat of adsorption
were calculated. For all systems investigated the adsorption were calculated. Aads and the desorption potential Ades of the closed heat storage system were estimated. These values define the working range of the adsorption/desorption cycle
and allow to calculate the specific heat storage density Δ hsp. On the basis of Δ hsp the different adsorbents were compared in order to select the optimal porous storage material for a given application.
The presented experimental and theoretical investigations show that the adsorption systems water-zeolite and water-composites
are promising working pairs for thermochemical heat storage processes for hot tap water supply and space heating of single
family dwellings. The advantage of the water-composite system is the low desorption temperature (solar energy) the main shortcoming
the low temperature lift. The advantage of the water zeolite system is the high temperature lift, the shortcoming are the
relative high desorption temperatures. 相似文献
78.
The influence of surface structure of technical materials on results and statements of surface analytical methods has been investigated. Especially surface roughness as a typical property of rolled products has been observed. For this purpose samples of steel (technical surface, roughness up to 5 m) and silicon wafers (polished surface) have been analyzed by SNMS and GDOS in order to get information about changes of the surface roughness as function of the sputtering time and their influence on the statements about the depth profiles obtained. 相似文献
79.
G. A. Jeffrey 《Journal of inclusion phenomena and macrocyclic chemistry》1984,1(3):211-222
There are three general classes of hydrate inclusion compounds: the gas hydrates, the per-alkyl onium salt hydrates, and the alkylamine hydrates. The first are clathrates, the second are ionic inclusion compounds, the third are semi-clathrates. Crystallization occurs because the H2O molecules, like SiO2, can form three-dimensional four-connected nets. With water alone, these are the ices. In the inclusion hydrates, nets with larger voids are stabilized by including other guest molecules. Anions and hydrogen-bonding functional groups can replace water molecules in these nets, in which case the guest species are cations or hydrophobic moieties of organic molecules. The guest must satisfy two criteria. One is dimensional, to ensure a comfortable fit within the voids. The other is functional. The guest molecules cannot have either a single strong hydrogen-bonding group, such as an amide or a carboxylate, or a number of moderately strong hydrogen-bonding groups, as in a polyol or a carbohydrate.The common topological feature of these nets is the pentagonal dodecahedra: i.e., 512-hedron. These are combined with 51262-hedra, 51263-hedra, 51264-hedra and combinations of these polyhedra, to from five known nets. Two of these are the well-known 12 and 17 Å cubic gas hydrate structures,Pm3n, Fd3m; one is tetragonal,P4
2/mnm, and two are hexagonal,P6
3/mmc andP6/mmm. The clathrate hydrates provide examples of the two cubic and the tetragonal structures. The alkyl onium salt hydrates have distorted versions of thePm3n cubic, the tetragonal, and one of the hexagonal structures. The alkylamine hydrate structures hitherto determined provide examples of distorted versions of the two hexagonal structures.There are also three hydrate inclusion structures, represented by single examples, which do not involve the 512-hedra. These are 4(CH3)3CHNH2·39H2O which is a clathrate; HPF6·6H2O and (CH3)4NOH·5H2O which are ionic-water inclusion hydrates. In the monoclinic 6(CH3CH2CH2NH2)·105H2O and the orthorhombic 3(CH2CH2)2NH·26H2O, the water structure is more complex. The idealization of these nets in terms of the close-packing of semi-regular polyhedra becomes difficult and artificial. There is an approach towards the complexity of the water salt structures found in the crystals of proteins. 相似文献
80.