氟的比色测定法 Ⅱ.用2,4-二羟基苯乙酮和铁(Ⅲ)作试剂

本文报告以2,4-二羟基苯乙酮和鉄(III)作试剂测定氟的适宜pH范围为1.95—2.5。试剂中鉄量减少则可测度降低和使用范围缩小。可测度约为鉄试剂之半(更灵敏)。使用范围不及鉄试剂广。所受干扰亦较鉄试剂为烈。氯离子和硝酸根的干扰不大。硫酸根影响颇巨。硫离子,碳酸氢根和氰根应除去。四价钛及锆亦不应存于试液中。 2,4-二经基苯乙酮和三价鉄所成络合物之最大吸收峰在470mμ(此时有机试剂之吸收几等于零),不带电荷,其中鉄与有机试剂之比为2:3。     

BA对大豆子叶培养物器官分化的影响及其与子叶离体时苗龄的关系

苗龄显著影响大豆子叶培养物器官分化的能力,其中３ｄ苗龄子叶的器官分化率最高．ＢＡ促进不定芽和抑制不定根形成的作用没有改变苗龄对子叶器官发生的影响趋势．ＢＡ对器官发生的影响幅度随苗龄而异,表明不同苗龄子叶对ＢＡ的反应不同．子叶器官发生的适宜苗龄和ＢＡ生理影响幅度最大的苗龄是有区别的．     

二阶线性椭圆型和抛物型方程广义解最大模的估计

证明椭圆型方程边值问题解的存在性,需要对有关问题的未知解作出它在适当泛函空间中的必需的先验估计.关于二阶线性椭圆型方程广义解最大模的估计,已经由不同作者用不同方法建立.下面给出(关于椭圆型广义解的最大模的估计)定理1,在[2]中是用Moser迭代法得到的,本文则用不同的方法得到。我们的方法也同样适用于抛物型方程,故也一并把抛物型方程广义解的最大模的估计给出(定理2).定理2最早由     

全氟和多氟型有机化合物的化学特性——全氟叔丁基碘以及全氟烷基的诱导效应顺序

利用Krespan法合成全氟叔丁基碘(I),并证明它的结构.以溴代碘可进一步发展Krespan法,合成全氟叔丁基溴(II).碘化物(I)[或溴化物(II)]与二乙基胺或乙醇-氢氧化钾反应时,其第一步为亲核试剂直接对碘(或溴)原子进攻的类S_N2型反应,产物与由全氟异丁烯和有关试剂直接反应所得者相同.测定(CF_3)_3CI,(CF_3)_2CFI及CF_3CF_2CF_2I之紫外光谱溶剂位移值δ(H-B),所得之值为各全氟型烷基的吸电性诱导效应顺序(CF_3)_3C>(CF_3)_2CF>CF_3CF_2>CF_3初步提供论据.本文并讨论各种顺序的观点.     

利用透光率-时间曲线来进行一级反应催化比色的探讨

在一级反应的催化比色方法中,通常使用lg(1/E)-C函数方式来绘制工作曲线,在操作上带来许多不便,并影响到测量的准确度。本文证明:吸光度E在0.700～0.222范围内时,lg(1/E)和透光率T有十分近似的正比关系。因此可用透光率T来代替函数lg(1/E),并提出用T-t曲线的斜率tgα对浓度C作图来代替通常方法中的lg1/E-C工作曲线,从而可以通过记录器来自动记录T-t曲线,使催化比色的操作得到简化,并且有效地提高了测量的准确度。     

Electron resonance-transmission through a driven quantum well with spin--orbit coupling

We have studied the spin-dependent electron transmission through a quantum well driven by both dipole-type and homogeneous oscillating fields. The numerical evaluations show that Dresselhaus spin-orbit coupling induces the splitting of asymmetric Fano-type resonance peaks in the conductivity, in which the dipole modulation and the homogeneous modulation are equivalent. Therefore, we predict that the dipole-type oscillation, which is more practical in the experimental setup, can be used to realize the tunable spin filters by adjusting the field oscillation-frequency and the amplitude as well.     

Field-assisted electron transport through a symmetric double-well structure with spin--orbit coupling and the Fano-resonance induced spin filtering

We have investigated theoretically the field-driven electron-transport through a double-quantum-well semiconductor-heterostructure with spin-orbit coupling. The numerical results demonstrate that the transmission spectra are divided into two sets due to the bound-state level-splitting and each set contains two asymmetric resonance peaks which may be selectively suppressed by changing the difference in phase between two driving fields. When the phase difference changes from 0 to π, the dip of asymmetric resonance shifts from one side of resonance peak to the other side and the asymmetric Fano resonance degenerates into the symmetric Breit-Wigner resonance at a critical value of phase difference. Within a given range of incident electron energy, the spin polarization of transmission current is completely governed by the phase difference which may be used to realize the tunable spin filtering.     

Surface oxidation of vanadium dioxide films prepared by radio frequency magnetron sputtering

This paper reports that the thermochromic vanadium dioxide films were deposited on various transparent substrates by radio frequency magnetron sputtering, and then aged under circumstance for years. Samples were characterized with several different techniques such as x-ray diffraction, x-ray photoelectron spectroscopy, and Raman, when they were fresh from sputter chamber and aged after years, respectively, in order to determine their structure and composition. It finds that a small amount of sodium occurred on the surface of vanadium dioxide films, which was probably due to sodium ion diffusion from soda-lime glass when sputtering was performed at high substrate temperature. It also finds that aging for years significantly affected the nonstoichiometry of vanadium dioxide films, thus inducing much change in Raman modes.     

二维配位聚合物[Tb(1,4⁃bdc)1.5(phen)(H2O)]n的合成、晶体结构及对Fe3+离子的荧光检测

通过溶剂热反应成功合成出一种新型2D配位聚合物[Tb(1,4-bdc)_1.5(phen)(H₂O)]_n(1)(1,4-H₂bdc=对苯二甲酸;phen=菲咯啉)。对其进行了单晶X射线衍射、粉末X射线衍射、红外光谱、元素分析、荧光光谱表征。X射线衍射晶体学分析表明,配合物1结晶于三斜晶系P1空间群,2个相邻的Tb(Ⅲ)离子与4个1,4-bdc^2-通过—O—C—O—桥联成双核单元,并进一步通过1,4-bdc^2-桥联成二维层状结构。荧光实验证明配合物1可以通过荧光猝灭机制检测Fe₃₊,Ksv=8.39×10³ L·mol-1,检测限为0.017μmol·L^-1。     

合金吸气剂除杂-气相色谱法测定混合气体中氪、氙的含量北大核心CSCD

提出了合金吸气剂除杂-气相色谱法测定混合气体中氪、氙含量的方法。样品通过减压进样装置进入气相色谱仪,选用管径为3.18 mm、长度为100 cm的不锈钢管为除杂柱,填装合金吸气剂,以消除氮气、氢气等杂质气体对氪、氙测定的干扰。结果显示:氪、氙的体积分数分别在4.55×10^(-4)%~2.65×10^(-3)%,5.60×10^(-5)%~3.29×10^(-4)%内与其对应的峰面积呈线性关系,检出限(3S/N)分别1.71×10^(-6)%,1.65×10^(-6)%;对混合标准气体重复测定6次,峰面积的相对标准偏差均不大于1.0%;按照试验方法与文献报道的气相色谱-质谱法对6个混合气体样品进行测定,相对偏差的绝对值均不大于1.0%。