共查询到20条相似文献，搜索用时 31 毫秒
1.
研究了在硫酸环境中８－羟基喹啉对碘催化亚砷酸与硫酸铈氧化还原反应的抑制作用及其动力学条件。据此建立了动力学的直接光度法测定痕量８－羟基喹啉的新方法。结果表明,在０２２５ｍｏｌ／ＬＨ２ＳＯ４,０００１２５ｍｏｌ／ＬＡｓ２Ｏ３,０００１ｍｏｌ／ＬＣｅ（ＳＯ４）２,００１ｍｇ／ＬＩ,０５ｇ／ＬＮａＣｌ环境中测定８－羟基喹啉,其线性范围为００２０～０２７ｍｇ／Ｌ,表观摩尔吸光系数为２７×１０５Ｌ·ｍｏｌ１·ｃｍ１,Ｓａｎｄｅｌ灵敏度为０５３８μｇ／ｃｍ２。用本法对药物硫酸羟基喹啉钾中的８－羟基喹啉含量的测定,结果满意。 相似文献
2.
Meyer RR Sloan J Dunin-Borkowski RE Kirkland AI Novotny MC Bailey SR Hutchison JL Green ML 《Science (New York, N.Y.)》2000,289(5483):1324-1327
The complete crystallography of a one-dimensional crystal of potassium iodide encapsulated within a 1.6-nanometer-diameter single-walled carbon nanotube has been determined with high-resolution transmission electron microscopy. Individual atoms of potassium and iodine within the crystal were identified from a phase image that was reconstructed with a modified focal series restoration approach. The lattice spacings within the crystal are substantially different from those in bulk potassium iodide. This is attributed to the reduced coordination of the surface atoms of the crystal and the close proximity of the van der Waals surface of the confining nanotube. 相似文献
3.
[目的]以试纸作为载体,建立了食品中有害重金属镉的快速检测方法。[方法]以马铃薯为样品,在试样中加入抗坏血酸和碘化钾,用硫酸调节p H,取混合试样与制作好的镉试纸片反应后,与标准比色板比较。[结果]以0.3%乙醇溶液配制的0.002%维多利亚蓝B作为显色剂溶液,使用快速定量滤纸浸泡在配制好的显色剂溶液中,在40~45℃恒温浸泡80~90 min后避光晾干制作成镉试纸。用干灰化法处理样品,在消化处理后的试样中加入少量0.06 mol/L抗坏血酸溶液和1.20 mol/L碘化钾溶液并混匀,使用浓硫酸2.0 m L调节试液的p H,最后测出的马铃薯中有害重金属镉的含量约为0.041 6 mg/kg。[结论]该研究建立的方法具有检测灵敏、快速方便等特点,可用于食品中镉含量的快速检测。 相似文献
4.
SDS和TX100及其混合体系水溶液在石蜡面上的吸附润湿行为表明,适当比例的混合体系水溶液其降低接触角,改善固体表面亲液性等性能优于单组分表面活性剂水溶液。因而适当比例的混合表面活性剂水溶液用作低能固体表面铺展剂具有润湿效果良好,成本低廉的特点,具有实际应用价值。该实验现象用分子相互作用理论得到初步解释。 相似文献
5.
Nanowires are conventionally assumed to grow via the vapor-liquid-solid process, in which material from the vapor is incorporated into the growing nanowire via a liquid catalyst, commonly a low-melting point eutectic alloy. However, nanowires have been observed to grow below the eutectic temperature, and the state of the catalyst remains controversial. Using in situ microscopy, we showed that, for the classic Ge/Au system, nanowire growth can occur below the eutectic temperature with either liquid or solid catalysts at the same temperature. We found, unexpectedly, that the catalyst state depends on the growth pressure and thermal history. We suggest that these phenomena may be due to kinetic enrichment of the eutectic alloy composition and expect these results to be relevant for other nanowire systems. 相似文献
6.
[目的]研究不同浓度(0～4 mg/kg)和不同形态的碘(碘离子和碘酸根离子)对菠菜地上可食部分(叶)中VC含量和硝酸盐含量的影响。[方法]开展菠菜盆栽试验。[结果]施用碘酸钾处理对菠菜地上可食部分生物量影响达0.05显著水平。施用碘化钾影响不明显,并且低浓度碘可促进菠菜生长,高浓度碘则抑制菠菜的生长。不同浓度的碘对菠菜叶中VC含量和硝酸盐含量无明显影响。在碘酸根离子处理条件下,菠菜叶中VC和硝酸盐含量高于碘离子处理。[结论]研究结果可为富碘蔬菜的栽培和筛选提供理论依据。 相似文献
7.
Luo G Malkova S Yoon J Schultz DG Lin B Meron M Benjamin I Vanysek P Schlossman ML 《Science (New York, N.Y.)》2006,311(5758):216-218
Mean field theories of ion distributions, such as the Gouy-Chapman theory that describes the distribution near a charged planar surface, ignore the molecular-scale structure in the liquid solution. The predictions of the Gouy-Chapman theory vary substantially from our x-ray reflectivity measurements of the interface between two electrolyte solutions. Molecular dynamics simulations, which include the liquid structure, were used to calculate the potential of mean force on a single ion. We used this potential of mean force in a generalized Poisson-Boltzmann equation to predict the full ion distributions. These distributions agree with our measurements without any adjustable parameters. 相似文献
8.
Spectra of the region just above the bright limb of the Moon show weak emission features that are attributed to resonant scattering of sunlight from sodium and potassium vapor in the lunar atmosphere. The maximum omnidirectional emission flux above the bright limb is 3.8 +/- 0.4 kilorayleighs for sodium and 1.8 +/- 0.4 kiloray-leighs for potassium. The zenith column densities above the subsolar point are estimated to be 8 +/- 3 x 10(8) atoms cm(-2) for sodium 1.4 +/- 0.3 x 10(8) atoms cm(-2) for potassium. Corresponding surface densities are 67 +/- 12 atoms cm(-3) and 15 +/- 3 atoms cm(-3), respectively. The scale height for the sodium atmosphere is 120 +/- 42 kilometers, and for potassium 90 +/- 20 kilometers, which implies that the effective temperature of the sodium and potassium is close to the lunar surface temperature. The sodium density at the south polar region was found to be similar to that at the subsolar point, indicating wide-spread distribution of sodium vapor over the lunar surface. The ratio of the density of sodium to the density of potassium is (6 +/- 3) to 1, which is close to the sodium to potassium ratio in the lunar surface, suggesting that the atmosphere originates from the vaporization of surface minerals. 相似文献
9.
商丘市人工增雨潜力及效益分析 总被引：1，自引：1，他引：0
[目的]分析商丘春秋两季的空中水资源分布特征、人工增雨潜力及效益。[方法]通过计算、分析代表站的各标准层等压面的水汽含量研究商丘市的人工增雨潜力及效益。[结果]3月份的水汽含量不到是5月份的一半,9月份的水汽含量是11月份的2～3倍。Ⅰ区的水汽含量比Ⅱ区少2～4k∥m^2。在春季Ⅰ区的整层水汽含量为44．92kg／m^2,Ⅱ区的整层水汽含量为56．34kg／m^2,Ⅰ区和Ⅱ区的水汽含量差异为11．42kg/m^2。在秋季,Ⅰ区的整层水汽含量为39．74kg／m^2,Ⅱ区的整层水汽含量为53．25kg／m^2,I区和Ⅱ区的水汽含量差异为13．51kg／m^2。适宜增雨作业的云层高度为3000～5500rn。6月份的增雨潜力最大,8月份的增雨潜力最小。[结论]人工增雨是一条综合利用空中水资源补充地表水资源的有效途径。 相似文献
10.
Electron solvation dynamics in photoexcited anion clusters of I-(D2O)n=4-6 and I-(H2O)4-6 were probed by using femtosecond photoelectron spectroscopy (FPES). An ultrafast pump pulse excited the anion to the cluster analog of the charge-transfer-to-solvent state seen for I- in aqueous solution. Evolution of this state was monitored by time-resolved photoelectron spectroscopy using an ultrafast probe pulse. The excited n = 4 clusters showed simple population decay, but in the n = 5 and 6 clusters the solvent molecules rearranged to stabilize and localize the excess electron, showing characteristics associated with electron solvation dynamics in bulk water. Comparison of the FPES of I-(D2O)n with I-(H2O)n indicates more rapid solvation in the H2O clusters. 相似文献
11.
杉木人工林近自然化改造对林下植被多样性和土壤理化性质的影响 总被引：1，自引：1，他引：0
12.
Whetten JT 《Science (New York, N.Y.)》1966,152(3725):1057-1058
The mineral and chemical composition of sediments deposited in the three lowermost reservoirs of the Columbia River is remarkably similar to the composition of many graywackes. Lithic fragments are abundant. In comparison with an "average" sandstone, the sediments have low concentrations of silica and high concentrations of all other major constituents, except calcium. Sodium is more abundant than potassium. The sediments are generally better sorted than graywackes. If graywacke texture is post-depositional in origin, Columbia River-type sediments could be expected to form graywackes upon deep burial without any significant addition or removal of material. 相似文献
13.
曝气池内气液两相流CFD模拟 总被引：2，自引：0，他引：2
对曝气池反应器内的气液两相流动进行了三维瞬态数值模拟,模拟采取了双流体模型,液相湍流采用标准k-ε方程,两相间的动量传递只考虑曳力作用。模拟获得了曝气池内的液速及不同径向位置的轴向液速分布、气含率分布等,结果表明,气泡刚开始以直线垂直上升,过一段时间后,气泡的运动开始偏离轴中心,气泡群开始发生了摆动;随着气体速度增大,气含率分布变宽,气含率增大,液体循环液速也在增大,气液之间混合越充分,曝气效果越好。 相似文献
14.
Variable coloration was displayed by Rosa hybrida, var. Better Times, grown in solutions of various concentrations of nitrogen and potassium. As revealed by measuring the color in Hunter values, growth in high potassium and low nitrogen concentrations resulted in less reddish and more bluish roses, while cultivation in a low nitrogen concentration, irrespective of the N/ K ratio, resulted in roses which were more lightly colored than those grown in high concentrations of nitrogen and potassium. The results were statistically significant at the 1 percent probability level. 相似文献
15.
利用中国气象局MICAPS资料,对长江中下游2008年1月19日降水增幅过程进行了天气动力学方面的成因分析。结果表明,冷暖空气交汇是降水增幅的基本条件;地面倒槽、850～700 hPa暖切变和850～500 hPa低槽是降水增幅的影响系统;西南、东南低空急流是降水增幅的重要动力机制;西南低空急流为降水增幅输送了充沛的水汽。 相似文献
16.
[目的]确认并探究影响硫代硫酸钠标定结果的偏差所在。[方法]研究了影响硫代硫酸钠标准溶液稳定性的因素,剖析该溶液标定过程中的关键环节,并对相应关键点进行试验,控制其标定结果的相对偏差。[结果]试验表明,参与硫代硫酸钠标定过程的水必须不含CO2和O2,是煮沸冷却水或新制备水,减少用水干扰;制备的溶液及静置过程中的溶液均需放置在避光条件下,避免环境对溶液造成影响;标定过程中静置完毕后应立即加水终止反应,确保结果的稳定,降低偏差;采用滴定一个样品加入一个碘化钾的方式进行试验,对控制偏差效果显著。[结论]研究可为硫代硫酸钠标准溶液的制备提供参考。 相似文献
17.
Manolopoulos DE Stark K Werner HJ Arnold DW Bradforth SE Neumark DM 《Science (New York, N.Y.)》1993,262(5141):1852-1855
The transition state region of the F + H(2) reaction has been studied by photoelectron spectroscopy of FH(2)(-). New para and normal FH(2)(-)photoelectron spectra have been measured in refined experiments and are compared here with exact three-dimensional quantum reactive scattering simulations that use an accurate new ab initio potential energy surface for F + H(2). The detailed agreement that is obtained between this fully ab initio theory and experiment is unprecedented for the F + H(2) reaction and suggests that the transition state region of the F + H(2) potential energy surface has finally been understood quantitatively. 相似文献
18.
沼液对酒用有机高粱产量和地力的影响试验结果表明:施用沼液原液、清粪水可使高粱穗粒数和千粒重增加,沼液原液比对照增产672.39 kg/hm2,增产17.55%,施用清粪水比对照增产596.27 kg/hm2,增产15.56%;同时增加了土壤有机质、全氮、碱解氮、有效磷和速效钾的含量,因此沼液能增强土壤肥力,改善土壤结构,但对pH值无影响。 相似文献
19.
实验结果表明，在ｎｃ＝１０～１６范围内，烷基三甲基溴化铵表面活性剂在水溶液表面的吸附和在水溶液中的胶团化作用均随着其碳氢链长的增加而呈不同程度的增强．在实际应用中，结合使用效果和经济效益，当强调表面吸附时，以Ｃ１２ＴＡＢ较好；若希望利用其胶团性质，则应更多地使用价廉的Ｃ１６ＴＡＢ． 相似文献
20.
汞对外生菌根真菌生长及其氮磷钾含量的影响 总被引：1，自引：0，他引：1
为筛选抗汞污染能力强、养分利用效率高的优良菌株,在液体培养条件下,研究了不同浓度汞处理对4个外生菌根真菌菌株生长速率和氮、磷、钾含量的影响。结果表明,外生菌根真菌的生长在不同程度上受到汞的抑制,其中,土生空团菌菌株CgSIV生长速率下降最少,在高汞处理时仍达对照的90.3%;松乳菇菌株Ld-1在Hg浓度为0~50μmol/L时,其生长速率差异不显著;彩色豆马勃菌株Pt715生长速率降幅最大。除CgSIV外,其余3个菌株含氮量均随汞浓度上升而增大,表现出良好的氮营养状况。各菌株磷的吸收受汞浓度影响较小。4个菌株含钾量均随汞浓度的升高而增加,推测与重金属胁迫促进菌丝体分泌氢离子,进而同钾离子进行交换有关。Ld-1和CgSIV表现出较强的耐汞性,且氮、磷、钾吸收受汞胁迫影响较小。若用于接种汞污染土壤种植的树木,有利于提高植物对汞的抗性,促进生长。 相似文献