X射线荧光光谱粉末法监控蓝晶石生产流程

利用已有准确结果的蓝晶石选矿流程试样制备两个标准系列(原、尾矿和精矿),试样经机械研磨至~#300目(50μm)及用经验系数法校正矿物效应,颗粒效应及基体效应。本法有快速、简易、成本低等特点,所得结果与化学分析相吻合。可满足生产要求。     

The nonpolar resonance effects and the non-Hammett behaviors

In the study we tried to unify the observed non-Hammett behaviors in various fields by proposing the nonpolar resonance effect. This effect was shown to be important not only for carbon radicals but also for some closed-shell systems. Therefore, the odd electron or spin is not the essential cause of the effect. The real origin of the non-Hammett effect should be the HOMO(reaction-center)-LUMO(acceptor) and LUMO(reaction-center)-HOMO(donor) interactions. This means that the nonpolar resonance effect is a universal effect. However, we found that the nonpolar resonance effect could not be well exhibited in many systems because of the serious competition from the polar Hammett effect. Finally, we showed that our proposal of the nonpolar resonance effect was valuable from a practical point of view, because using it we could perform much better correlation studies on some "tough" problems such as radical and multiple bond stabilities, UV and IR spectra, and molecular structures.     

Evaluation of the contribution to hydration of nonelectrolytes from the hydrophobic effect

A new method was suggested for estimating the hydrophobic effect of contributions to the Gibbs energies and enthalpies of hydration of hydrocarbons, inorganic gases and rare gases. In accordance with this method the hydrophobic effect contribution to the Gibbs energy was evaluated from the difference between the hydration Gibbs energy of a solute and the non hydrophobic contribution. To estimate the latter value, the known dependence connecting the Gibbs energies of solvation of a solute in a number of aprotic solvents to the Hildebrand solubility parameter for these solvents was used. The non hydrophobic contribution to the Gibbs energy of hydration was calculated for various solutes from such dependences extended to water as solvent. The Hildebrand solubility parameter for water used in the calculation was corrected for the effect of association through hydrogen bonding. This correction was made by subtraction of the water self-association enthalpy from the enthalpy of vaporization of water. The evaluated Gibbs energies of the hydrophobic effect are positive for saturated hydrocarbons, inorganic gases and rare gases and linearly depend on the solute molecular refraction. The hydrophobic contribution to the hydration enthalpies of the solutes was calculated in the same manner as was made to calculate the hydrophobic contribution to Gibbs energies of hydration. Enthalpies of the hydrophobic effect for the solutes under study are negative.     

The alkali cation effect on the 1H NMR chemical shifts of the indenyl carbanion

The complex character of the temperature dependence of the ¹H NMR chemical shifts of indenyl-lithium and -sodium in dimethoxyethane is explained. It is shown that the cation causes a polarisation of the C? H bonds and thus influences the proton shifts of the anion, both directly by its electric field along the bonds (the direct effect) and indirectly via its effect on the π-electron distribution (the indirect effect). The indirect effect is inferred from ¹³C NMR chemical shift data. By subtracting the temperature dependent contribution of the indirect effect from the experimental ¹H data, the direct effect is visualised. It appears that information on ion paris obtained by ¹H and ¹³C NMR on the one hand and optical spectroscopy on the other hand is complementary. Apparently, aggregation of ion pairs does not seriously affect the chemical shift data.     

A method for calculating the enthalpy of hydrophobic effect

A new method for calculating the enthalpy of hydrophobic effect for compounds incapable of specific interactions with water was suggested. The method is based on separating the enthalpy of hydration into the contributions from nonspecific hydration and hydrophobic effect. The contribution from nonspecific hydration was determined by a method described previously. The enthalpies of hydrophobic effect for inert gases, alkanes, aromatic hydrocarbons, and their derivatives were determined. It was found that the enthalpy of hydrophobic effect for inert gases and alkanes is negative and independent of the size of the molecule dissolved in water. For aromatic compounds, the enthalpy is positive; it increases with the molecular size.     

Diastereotopy in some 3,4-dihydroisocoumarins--effect of changing the substituents on the chiral centre

Diastereotopy has been investigated in eight different derivatives of 3,4-dihydroisocoumarins by changing the substituent on the pyran ring chiral centre, C-3. A diastereotopic NMR effect is observed for the prochiral methylene protons on the benzopyran ring and the effect is greatly influenced by the pi-electron system of the substituent. The effect is also observed for the substituents, however, the extent of diastereotopy depends upon their nature and the separation of methylene groups from the chiral centre.     

Orientated-assembly of rod-like silica particles based on sandwich structure from the superhydrophobic template and the superhydrophilic substrates

The paper demonstrated a facile approach for the orientated assembly of the rod-like silica particles by sandwich structure from the combined effect of superhydrophobic template and the superhydrophilic substrates. The rod-like particles can be arranged in ring-like, square-like and etc from the confined effect of the template, which will produce an important insight for the oriented assembly of anisotropic particles and the development of the novel functional materials and devices.     

Characterization of the electroclinic effect of smectic LCs in terms of the transitional dielectric constant in the SA phase

The electric-field dependence of the dielectric constant of some materials which show a strong electroclinic effect in the S_A phase, has been studied by measurement of the transitional dielectric constant. We suggest that the observed variation of the dielectric constant may originate from the electric field induced dielectric biaxiality; this is inherent in a material that exhibits the electroclinic effect.     

单粒子表面增强拉曼光谱的二维成像研究

以单个椭球形Fe₂O₃@Au核壳粒子作为SERS活性基底, 苯硫酚(TP)作为探针分子, 研究了椭球形粒子表面SERS效应的分布, 对比了粒子尖端以及中间SERS效应的差别. 为了得到单个粒子表面不同部分对SERS强度的贡献差别, 通过数学模拟和解析了探针分子SERS的二维成像(2D-mapping)信号, 获得了粒子边缘不同点的SERS效应. 模拟分析结果表明, 当xy平面内粒子在垂直入射(z轴)平面波作用下, 单个椭球形Fe₂O₃@Au核壳粒子表面单位面积上的SERS强度相差极大, 粒子长轴方向端点附近单位面积上的SERS效应最大, 而其它表面部分较弱, 其中与短轴平行方向的表面附近为最弱, 差异可达到约2~3个数量级. 若考虑SERS增强主要为电磁场增强的尖端效应, 则单个椭球形粒子尖端的局域感应电磁场为垂直方向的5倍.     

On the relation of the non-linear dielectric effect to the kerr effect: closing a gap

A simple and uniform procedure is used to determine the non-linear dielectric effect in static fields, for probing fields with frequency either below or above the rotational relaxation region. Contributions from the permanent moment and the linear and non-linear polarizability of non-interacting particles are considered. A quantitative link with the Kerr effect is established. The different weight of contributions due to anisotropic polarizability and hyperpolarizability in both effects is emphasized.     

Mechanistic study of the aluminum interference in the determination of arsenic by electrothermal atomic absorption spectrometry

The interference effect derived from the presence of aluminum in the wall and platform atomization of arsenic using two sampling modes (aerosol vs. liquid drop) was revisited. The mechanistic action of the Al interference seems to be the result of the formation of some gas phase Al oxide, which would absorb at the arsenic analytical wavelength. A vaporization/condensation process for aluminum oxide seems to exist into the graphite tube with temperature. The effect of protons (as nitric acid) and activated carbon on the behavior of the Al interference was tested. A beneficial effect of overcoming the Al interference was derived from the presence of activated carbon. The mechanistic action of both, protons and activated carbon, was also proposed.     

Hammett constants of the pyrroline-2, 5-dione ring

The electronic effect of the pyrroline-2,5-dione ring on the benzene ring in the case of N-aryl compounds is close to the effect exerted by halogens. The overall electron-acceptor effect depends markedly on the nature of the solvent. The electron-donor effect of conjugation is small.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 906–910, July, 1976.     

Nuclear quadrupole contribution to the equilibrium isotope effect

It has been shown that besides the overall assessment of the new isotope effect of “size and shape” of nuclei, discovered by Prof. J. Bigeleisen, a specific effect of the nuclear quadrupole can be distinguished from the effect of “size” and analyzed separately. This effect is significant only for those nuclei that have a non-zero quadrupole effect. It has been shown by means of analysis of the experimental data on separation of uranium isotopes in industrial processes ASAHI and CHEMEX that the relative value of the contribution of the quadrupole effect to ln(s/s′) can be as large as 20% of the overall (“size”+“shape”) effect.     

Measurement of the mechanocaloric effect in rubber

An apparatus for measurement of mechanocaloric effect in rubber has been constructed and tested by measuring the thermal response of three rubber materials to mechanical strain. The results obtained were satisfactory. Detailed measurement has been performed on these materials. The entropy changes that accompany elongation were calculated from the experimental results and compared with those derived from literature data and statistical theory of the macromolecular chain. A dissipative effect was found to accompany the rapid deformation of rubber and attributed to viscoelastic irreversibility. An experimental procedure to eliminate this effect was identified. The apparatus, assembled with the readily available components, will be a useful device for introducing the entropy concept in thermodynamics courses.     

Spin dynamics of the radical pair in a low magnetic field studied by the transient absorption detected magnetic field effect on the reaction yield and switched external magnetic field

The spin dynamics of the radical pair generated from the photocleavage reaction of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide (TMDPO) in micellar solutions was studied by the time-resolved magnetic field effect (MFE) on the transient absorption (TA) and by a novel technique, absorption detected switched external magnetic field (AD-SEMF). Thanks to the large hyperfine coupling constant (A = 38 mT), a characteristic negative MFE on the radical yield was observed at a magnetic field lower than 60 mT whereas a positive effect due to the conventional hyperfine (HFM) and relaxation mechanisms (RM) was observed at higher magnetic field. The negative effect can be assigned to the mechanism "so-called" low field effect (LFE) mechanism and has been analyzed thoroughly using a model calculation incorporating a fast spin dephasing process. The time scale of the spin mixing process of LFE studied by AD-SEMF is shorter than the lifetime of the recombination kinetics of the radical pair. These results indicate that the LFE originates from the coherent spin motion. This can be interfered from the fast spin dephasing caused by electron spin interaction fluctuations.     

A laser photolysis study of the effect of a magnetic field on the kinetics of the recombination of radical and radicalion pairs in micelles

Conclusions The recombination of the radical pairs formed upon the transfer of a hydrogen atom from phenols and amines to triplet quinones in micelles is hindered upon the application of an external magnetic field and accelerated in the presence of atmospheric oxygen. The magnetic field effect is explained within the framework of a relaxation mechanism. The magnetic field has no effect on the kinetics of the deactivation of triplet exciplexes in micelles.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 464–467, February, 1986.     

Impact of the sample matrix composition on the signal enhancement in the capillary electrophoretic separation of poliovirus samples

The development of capillary electrophoretic applications aiming to provide reliable stability assessment of viral suspensions, to detect subviral particles from cell extracts or to study the interactions between virus particles and various biomolecules, cannot be done without a thorough understanding of the sample matrix contribution to the observed electrophoretic behaviour. The present study thoroughly investigates the effect of the sample matrix on the electrophoretic behaviour of poliovirus injected as sample plugs of 1%, 5% and 12% effective capillary length. The effect of the sample matrix for three different poliovirus batches was evaluated. Additionally, simulated samples, obtained from concentrated poliovirus suspensions of high purity and diluted with commonly used lab buffers in order to obtain samples with either high or low conductivities, were also investigated. The goal of the study was to obtain a better understanding of the effect of the sample matrix on the signal enhancement, in order to define a general approach allowing a repeatable capillary electrophoretic (CE) separation of poliovirus from complex samples. This study clearly demonstrates that the sample matrix has an important influence on the sensitivity of the CE poliovirus separations. Translation of these observations into routine practice involves several compromises and a set of rules in order to reduce day-to-day variation and to maximize sensitivity.     

Voltammetry of redox reactions using the general form of the oxidized or reduced species adsorption isotherm

The theory of linear-sweep voltammetry (LSV) applied to heterogeneous redox reactions accompanied by the nondissociative adsorption of the reactant or the product is developed. The basic criterial relationships of LSV in this case are invariant with respect to the type of adsorption isotherm and the number of adsorption sites occupied by one species. The degree of irreversibility of the discharge-ionization step can be evaluated from the effect of the potential scan rate on the peak potential. The nature of the adsorbate can be deduced from the effect of the reactant concentrations on the peak current.     

The contribution of the pressure drop to analyte retention in coupled column supercritical fluid chromatography of lipids

Summary This paper reports the qualitative and quantitative effects of the column pressure drop on the retention of lipid components in a serially coupled capillary column SFC system. The contribution of the pressure drop consists of two components, the density effect and the flow effect. The magnitude of the flow effect,i. e. the change in retention which results from changes in the flow-rate when column pressures are changed, is determined by the difference in single column analyte k values. The effect will be positive compared with the uncorrected retention values when the column with largest k value is closest to the injector. With the columns in reversed order, the effect will be negative. The contribution from the density effect always resulted in larger coupled column k values and was in most instances of more significance than the flow effect component. Values calculated with and without pressure drop correction have been compared and it has been shown that for most of the eighteen model lipid compounds investigated, the deviations from the experimental retention factors were smaller when pressure drop corrections were made.