Observation of vibration-electronic exchange in gas-surface collisions

Intensity increase of exoelectronic emission in the interaction of vibrationally excited hydrogen beam (v1) with emitter surface (CaSO₄) has been found. The effect proves to be due to the transfer of vibrational energy from molecules to trapped electrons, i.e. to the v-e transition in gas-surface collisions.

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- (v1) (CaSO₄). , .. v-e- -.

     

Titanosilicates as Supports for an Enzymatic Alcoholysis Reaction

Novel [Cr^III(amp)(bipy)(Cl)] (1) (H₂amp = N-(hydroxyphenyl)salicyldimine; bipy = 2,2-bipyridyl) and [Cr^III(app)(bipy)(Cl)]⁺ (2) (H₂app = N-(hydroxyphenyl)pyridine-2-carboxaldimine; bipy = 2,2-bipyridyl) complexes have been synthesized and characterized by physico-chemical methods. Complexes 1 and 2 have been employed as catalysts in the oxidation of both saturated and unsaturated hydrocarbons using tert-butylhydroperoxide (t-BuOOH). The significance of the results with respect to oxo-functionalization of C-H bonds both in unsaturated and saturated hydrocarbons is noted.     

Statistical evaluation of the influence of several sample pretreatment methods on the mercury content detectable by chemical analysis of contaminated soil samples under practical conditions

The estimation of the environmental risk of contaminated sites caused by hazardous components may be obtained, for instance, by means of a soil survey. There unavoidable errors by sampling, sample preparation and chemical analysis occur. Furthermore, in case of mercury contaminations, the mercury content detectable by chemical analysis can be falsified, if between sampling, on the one hand, and sample preparation and sample decomposition for chemical analysis, on the other hand, volatile components or elementary metallic mercury escape from the sample. Thus, in these cases, handling of samples such as air drying, storing in plastic bags or thermal evaporation, generally termed sample pretreatment, is a further source of error in evaluating a material. However, the measuring results are influenced not only by sampling, sample pretreatment, sample preparation by homogenization and splitting, and chemical analysis; they must also reflect the intrinsic properties of the soil sample subject to both global fluctuations and local heterogeneities. The present work shows by example of a non-uniformly contaminated site to what extent the analytically detectable mercury content is changed by the method of handling of soil samples in the period between sampling and chemical analysis. A hierarchical experimental design was realized in order to separately quantify the different sources of variation of the measured mercury contents, which are caused by global variations, local heterogeneities, sample preparation, sample pretreatment as well as chemical analysis. As turned out by variance analysis, the variance portion contributed to the total variance by sample pretreatment is highly significant and lies in the same order of magnitude as the variance caused by local heterogeneities of the soil. That means that the type of sample pretreatment influences the analytical results essentially. In order to quantify the effect of a definite pretreatment method in comparison with the mercury content of the unchanged original soil sample, the probable systematic error of a method was introduced. Investigations were only carried out at two sampling locations of the contaminated site because of the relatively high labour; the mean values and variances obtained cannot be immediately transferred to other sites. However, the general knowledge can be used as methodical basis for further investigations. Particularly, the consequence arises that the regulations existing for the treatment of mercury-contaminated samples between sampling and chemical analysis must be revised to obtain comparable criteria of evaluation.Symbols used level of error in statistical tests, - _i random effect of the i-th sampling location with respect to the mercury content, effect of global fluctuations - _ij random effect of the j-th primary sample (composite sample) at the i-th sampling location, effect of local heterogeneity, sampling error - _ijk random effect of the k-th subsample within the respective j-th primary sample (composite sample) at the i-th sampling location, sample preparation error - _ijkl random effect of the l-th pretreated sample belonging to the respective k-th subsample of the j-th primary or composite sample at the i-th sampling location, sample pretreatment effect - _1– probable relative systematic error of a pretreatment methods as compared with the original material at the coverage probability 1– - overall expected mercury content of the sampling results - _i expected mercury content of the i-th pretreated composite sample at a fixed location - û_{1.1 –} lower limit of a confidence interval for the unknown expected mercury content of unchanged original material at the confidence probability 1– - _i intraclass correlation coefficient - ² , ² , ² , ² , _Z ² variance components caused by global variability, local heterogeneity, sample preparation, sample pretreatment and analytical error, respectively - _total ² total variance of mercury content - D² operator of the variance of a random variable - E operator of the mathematical expectation of a random variable - F_i mean squared sum quotient of the Fisher's F-distribution - F_1–/2(fg_i, fg_j) critical value of the F-distribution at fg_i and fg_j degrees of freedom, respectively - fg_i degree of freedom of a (mean) sum of squared deviations - H_i hypothesis regarding a statistical law - I_1– confidence interval for the unknown expected value difference of two methods compared at the probability 1–, probable systematic error of a pretreatment method as compared with the unchanged original material at the coverage probability 1– - MQ_i, mq_i mean squared deviations as explained in the context - n_i number of sampling locations, primary samples per location, subsamples per primary sample, pretreatment methods and measuring values per pretreated sample, respectively - S _i ² , s _i ² variance estimation obtained by chemical analysis - SQ_i, sq_i sum of squared deviations - S(|Y₁–Y_i|) mean error of the absolute mean value difference |Y₁–Y_i|) - t_1–/2;m critical value of the Student's t-distribution at m degrees of freedom and the probability 1–/2 - Y_ijklm mercury content obtained on the m-th final sample of the l-th pretreated sample belonging to the k-th subsample of the j-th primary sample at the i-th sampling location - Y_i, y_i,... mean values obtained by sampling and chemical analysis - Z_ijklm random error of the ijklm-th measuring value (final sample value) Y_ijklm.     

Immobilized sol of cobalt(III) hydroxide as an efficient catalyst of water oxidation to dioxygen by the Ru(bpy)33+ complex

Catalysts of water oxidation to dioxygen by Ru(bpy) ₃ ³⁺ have been obtained by immobilization of colloidal Co(III) hydroxide on supports of the hydroxide types. These supports are found to be able either to enhance (Al(III), Bi(III), Sn(IV) and Ce(IV) hydroxides) or to weaken (Fe(III) and Mn(IV) hydroxides) the catalytic efficiency of the initial sol. The possible nature of the influence of the support is discussed.

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Ru(bpy) ₃ ³⁺ Co(III). - , ( Al(III), Bi(III), Sn(IV), Ce(IV)), ( Fe(III), Mn(IV)) . .

     

The photoconversion R-CH3 → R-CHO in indazole derivatives

The UV irradiation of 1-(p-nitrophenyl)-3-methyl-indazole leads to the formation of the corresponding 3-formyl derivative as product of the photooxidation R-CH₃ → R-CHO. This method was applied to a series of substituted indazoles and the same reaction was observed with methyl groups attached to the pyrazole and to the benzene ring of the indazole.     

Analytical aspects of some organic acids

Summary A direct titrimetric method for the estimation of iron(III) has been developed, which involves the adjustment of concentration of iron(III) andPh, dilution, addition of 1 ml of 2% indicator solution and titration with EDTA (30° to 35° C). It is based on the fact that the iron(III) forms a blue coloured complex which is destroyed at the 11 molar ratio making the end-point of the titration. Quantity of iron(III) as small as 23.2 mg can be titrated accurately when present in a volume of 100 ml. Study of interferences revealed that quite a number of elements like Be²⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, UO₂ ²⁺ and Mn²⁺ does not interfere, whereas much interference is caused by Cu²⁺, Zn²⁺, Pb²⁺, Fe²⁺, Co²⁺, Ni²⁺, ZrO²⁺, V0²⁺, Al³⁺, Cr³⁺, Ti⁴⁺, Ce⁴⁺ and Th⁴⁺. The method proposed for iron(III) is selective and should be of considerable use in many cases.Part III: See Z. analyt. Chem. 167, 332 (1959).     

Kinetics and mechanism of oxidation of substituted benzaldehydes by quinolinium fluorochromate

The kinetics of oxidation of a number of meta- and para-substituted benzaldehydes by quinolinium fluorochromate, QFC has been studied in aqueous acetic acid medium in the presence of acid. The products of oxidation are the corresponding benzoic acids. The reaction is first order each in substrate, QFC and HClO₄. Electron-withdrawing substituents increase the rate, while electron-releasing substituents decrease it and the rate data obey Hammett's relationship. The reaction constant for the oxidation has a value of 1.16±0.07 at 30°C. The activation enthalpies and entropies are calculated and the possible mechanism for oxidation is discussed.     

Investigation on structure and morphology of the thermally treated glassy alloy (Fe,Cr)80(P,C,Si)20 by means of ESCA and SEM/EDXA

Metallic glass ribbons of the chemical composition (Fe,Cr)₈₀(P,C,Si)₂₀ have been thermally treated in the region between 530 and 980°C for 72 h. The SEM/EDXA investigations indicate that a phase transformation takes place between 575 and 980°C in a surface layer of 5 m thickness. Thus, a Cr-rich phase occurs between 760 and 800°C which is converted into an open-pore system between 850 and 900°C. The oxidation process reaches its maximum at 760°C. The ESCA spectra of the material in the as received state and of the thermally treated samples indicate that different oxygen species are formed within the analysed surface layer of 10 nm. The oxygen of the original material is incorporated as hydroxyl groups in species such as FeO(OH) and CrO(OH). After thermal treating the hydroxyl content decreases and the oxide content increases. Species of Si exist in the surface layer as SiO_x-like compounds (peak at BE=102.0 eV). A majority phase of transition metal phosphide species is coexisting with oxidised phosphate species.     

Wannier-Stark effect on surface states

A recursive Green-function (RGF) technique is used to study the surface states of an electrified solid. The concatenating nature of the method leads to a continued-fraction form of the RGF, which can be expressed as a ratio of Bessel functions. The surface density of states (SDOS), derived from the RGF, reveals a quasi-Stark-ladder distribution of the energy levels at the surface atom. The dependence of the SDOS on the applied field and surface perturbation parameters is discussed.     

氯过氧化物酶的手性催化活性在有机合成中的应用

氯过氧化物酶（CPO）作为过氧化物酶家族中的一员对多种有机底物表现出了广泛的催化活性。自上世纪60年代被发现以来，CPO在有机合成中的应用一直是一个研究热点。它作为一种生物催化剂能催化广泛的底物合成手性化合物，且有高的产率和高的对映选择率。本文综述了氯过氧化物酶在手性有机合成中的应用，重点关注了卤化、醇氧化、羟基化、环氧化、磺化氧化等反应，并讨论了目前在该领域所面临的问题及今后的发展趋势。