Determination of ni,zn and al in bronzes and brasses after determining cu-pb-sn-sb by controlled-potential electrolysis

A method is given, which allows nickel, zinc and aluminium to be determined in the solution remaining after the determination of copper, lead, tin and antimony by controlled-potential electrolysis. Nickel is precipitated by dimethylglyoxime, zinc is deposited by controlled-potential electrolysis and aluminium is precipitated first by oxine and then by ammonium benzoate.     

丙烷在金属铁表面还原NO的实验研究

在程序控温电加热水平陶瓷管反应器、N2气氛和模拟烟气气氛以及300~1 100℃时,对丙烷在金属铁表面还原NO的特性进行了实验研究,并且与相同条件下甲烷在金属铁表面脱硝的效率进行了对比。结果表明,丙烷在金属铁表面能够高效地还原NO。N2气氛中在500~900℃,丙烷在金属铁表面的脱硝效率高于相同含量的甲烷脱硝效率,900℃以上丙烷在金属铁表面的脱硝效率超过95%,并且与甲烷的脱硝效率差别很小。模拟烟气条件下,当过量空气系数SR1小于1.0时,温度超过900℃后丙烷在金属铁表面还原NO的效率能够达到90%以上,且有、无燃尽的情况下,NO的还原率相差不大。在相同的条件下,丙烷在金属铁表面的脱硝效率高于相同条件下甲烷的脱硝效率。SO2对丙烷在金属铁表面还原NO的效率影响很小,可以忽略。     

A theory of measurement with applications to spectrometry

An analytic function operating on experimental data is optimized for making the most accurate measurement of a parameter of the expected data, under the conditions of non-stationary shot noise. The value of the parameter is obtained by equating the operation on experimental data with the same operation on the expected data which contains the parameter as an unknown value. If the operation is represented by a weighting function, the form of the optimum weighting function depends on the initial transformation of the experimental data by the measuring instrument. The optimum weighting function always contains the derivative of the expected signal with respect to the unknown parameter, divided by the time-dependent variance of the received signal. Weighting functions for the logarithmic output of a spectrophotometer are described. The superiority over least-squares curve-matching is shown. A method for determination of peak position by optimum slope measurement is derived. In general, the optimum weighting function is not a matched filter. The optimum result is the same for center-of-gravity measurements. The optimum parameter measurement is equivalent to a least-squares error minimization weighted by the inverse variance or mean-square noise level. This variance weighting is significant in photometric measurements limited by shot noise or other measurements described by Poisson statistics, such that the mean-square noise level varies with time. The form of the optimum filter, for non-white, non-stationary noise is derived.     

有机化合物血卟啉及其衍生物被物理因素--超声激活机理研究

利用1,3-二苯基异苯并呋喃(DPBF)作为单线态氧捕获剂,研究了超声激活血卟啉的机理,通过用紫外-可见分光光度计测量了超声辐照配制好的血卟啉和DPBF溶液后的DPBF相对消耗量,表明了单线态氧的存在量．实验结果显示了DPBF的消耗量随超声照射时间和强度的增加而增加．从而支持了超声激活血卟啉产生单线态氧的说法．并提出了采用各向同性集光球把声致发光和声场分开的方法,进一步研究了是超声空化产生的荧光,还是高温热点激活血卟啉产生单线态氧．与白光对比结果表明,声致发光虽能使照相底版感光,但不足以激活血卟啉产生单线态氧．     

几种建筑材料的氡射气系数研究

通过天然γ能谱测量方法测定建材样品中的镭含量,计算理论上衰变产生的氡密度,以及用硫化锌闪烁法测定由样品释放到空气中的氡密度的方法来计算氡的射气系数。通过改变样品的颗粒度大小,以及改变样品的灼烧温度等条件,来研究氡射气系数的变化规律。结果表明,土坯砖射气系数在8.5%~29.4%,红砖射气系数在0.031%~3.5%之间,瓷砖射气系数在0.74%~4.5%之间;建筑材料的氡射气系数随着其自身颗粒度的增大而减小,随加工(灼烧)温度升高而减小。     

Relation between melting behavior and physical structure in polymers

The phenomenon of double melting, as manifested by two characteristic endotherms in the melting region on a differential thermal analysis (DTA) scan, has been studied in nylon 66 and polystyrene as a function of sample treatment by annealing or drawing. A variety of techniques were used in these studies including DTA, x-ray diffraction, electron microscopy, and mechanical testing. It is shown that the two endotherms are not caused by a bimodal crystal size distribution, by recrystallization, by orientation changes, or by phase changes. It is proposed that one endotherm is caused by the melting of foldedchain crystals, while the other is due to the melting of less perfect bundle crystals. This view is well supported by the results, especially by the DTA measurements made at different heating rates. Published data on the thermal behavior of annealed and drawn poly(ethylene terephthalate) and on polyethylene crystallized at various pressures may also be explained on this basis if it is allowed that in polyethylene the chains may be more extended.     

Separation of Cr(III) and Cr(VI) using melamine-formaldehyde resin and determination of both species in water by FAAS

A method is described for the determination of Cr(VI) and total chromium by FAAS. Cr(VI) is separated from Cr(III) by adsorption on melamine-formaldehyde resin. After elution of Cr(VI) with 0.1 mol/l NaAc solution, it is analysed by FAAS. Total chromium is determined by FAAS after conversion of Cr(III) to Cr(VI) by oxidation with hydrogen peroxide, total Cr(VI) is concentrated as above. If the total concentration of chromium is sufficient, the determination can be directly made by FAAS. Cr(III) can then be calculated by subtracting Cr(VI) from the total Cr. This method was successfully applied to the determination of chromium in lake water.     

Thermal activation of photoactivatable urocanase from Pseudomonas putida

The dark inactivation of urocanase from Pseudomonas putida is caused by the formation of a sulfite adduct of the tightly bound coenzyme, nicotinamide adenine dinucleotide. Photodissociation of this adduct by UV radiation restores the enzyme activity. Based on cold exhaustive dialysis the modification reaction appeared to be irreversible. However, we now report that sulfite modification of urocanase is reversible at higher temperatures. An Arrhenius plot of the thermal activation is linear (20-38 degrees C). The activation energy for the enzyme activation is 114 kJ mol-1. The substance that is photodissociated from inactive urocanase reacts with urocanase to reform the modified enzyme indicating that sulfite is not oxidized, or otherwise changed through these processes. Nucleophiles (sulfite, hydroxylamine, hydride, cyanide) are known to inhibit urocanase by forming adducts with nicotinamide adenine dinucleotide. Urocanase inactivated by hydride or cyanide is not reactivated thermally or photochemically. Urocanase inactivated by hydroxylamine and by glycylglycine can be reactivated by a thermal reaction. In conclusion, sulfite-modified urocanase, which is formed in cells, can be reactivated not only by sunlight but also at physiological temperatures.     

Determination of creatinine in undiluted blood serum enzymatic flow injection analysis with optosensing

A specific enzymatic assay for creatinine in undiluted serum samples is described, exploiting the generation of ammonia from creatinine by immobilized creatinine iminohydrolase. The ammonia produced is separated from the sample matrix by gas diffusion into an acceptor stream containing a pH-sensitive indicator. The creatinine content is quantified by monitoring the resulting colour change of the indicator by means of reflectance measurement via optical fibers, the hydrophobic gas-permeable membrane serving as a diffuse reflector. Two approaches are used to overcome the interference caused by endogenous ammonia. The first is based on enzymatic abatement of endogenous ammonia by immobilized glutamate dehydrogenase. In the second, preferable, approach, endogenous ammonia, itself a parameter of clinical interest, is measured separately prior to the enzymatic degradation by creatinine iminohydrolase. Each assay requires only 30 μl of sample solution, and the sampling frequency is 60 h^?1. The relative standard deviation is approximately 3%.     

丝氨酸热分解机理的研究

用热重法(TG)、差热分析(DTA)和红外光谱(IR)方法测试了丝氨酸的热分解过程,用量子化学方法在RHF/6-21G水平上全优化计算了丝氨酸及其热分解中间产物、产物分子的几何构型,得到其总能量和Mulliken集居数等数据.从理论上证明了环氧中间产物的存在.通过对实验结果和计算结果如Mulliken集居数的分析,提出了丝氨酸的热分解反应机理是先失去CO2为主要反应通道,同时伴有先失去NH3而生成环氧中间产物的副反应发生.     

TiO2-Al2O3复合载体的比较研究

对用混胶法和共沉淀法分别制备的ＴｉＯ２－Ａｌ２Ｏ３复合载体（ＴｉＯ２含量为０．０８ｇ／ｇγ－Ａｌ２Ｏ３）进行了对比研究，采用的表征方法有ＸＲＤ，ＸＲＳ，ＬＲＳ等，得出的结论如下：两种载体均保持了γ－Ａｌ２Ｏ３的骨架结构，但ＴｉＯ２的分散状态不尽相同，混胶样品中ＴｉＯ２主要以表面富集的形式分散在γ－Ａｌ２Ｏ３表面，这有利于集二者的优点于一体，共沉淀样品中ＴｉＯ２趋于整个体相均匀分散，这有利于相互作用     

Monitoring of Fluorescent-Labelled Main Progesterone Metabolite in Marmoset Monkeys

Abstract

5α-pregnane-3α, 7α-diol-20-one, the main progesterone derivative in marmoset monkeys, shows a very low absorption in UV-light. Labelling of this metabolite prior to HPLC and subsequent monitoring by an UV-detector is essential. We used dansyl-hydrazine for the formation of a fluorescent derivative. The optimum conditions for the reaction of dansyl-hydrazone with hydroxypregnanolone were controlled by HPTLC, chromatographic separation is carried out by HPLC and HPTLC and is described in this paper. When the quantitation of the dansylhydrazones is carried out by HPTLC, the fluorescence intensity of the derivative can be increased by a factor up to 5 by dipping the HPTLC plate into a mixture of paraffin/n-hexane or after treatment with triethanolamin/isopropanol (1:4; by vol). Hydroxypregnanolone from marmoset urine is detected for the first time by liquid chromatography. The derivative is of practical use to determine ovulation and pregnancy in the marmoset monkey. Quantitation by HPLC and thin-layer chromatography is possible in the range of 10 to 1000 ng. The concentrations in marmoset urine during the luteal phase is in the range of 50 to 400 ng/mg creatinine.     

N-硬脂酰基亮氨酸的合成

采用酰氯化反应与缩合反应两步法合成N -硬脂酰基亮氨酸。以硬脂酸和亚硫酰氯为原料 ,n(硬脂酸 )∶n(亚硫酰氯 ) =1∶1 .5 ,在 80℃下冷凝回流 6h酰氯化反应合成硬脂酰氯 ,硬脂酰氯经减压蒸馏收集 1 70～2 0 0℃的馏分得到。硬脂酰氯收率为 65 %。硬脂酰氯再与亮氨酸的氢氧化钠溶液在冰水浴中进行Schotten -Baumann缩合反应制得N -硬脂酰基亮氨酸。缩合反应最佳工艺条件是反应溶液pH值控制为 9.0。反应后滴加1mol/L盐酸至pH =5 .0～ 6.0 ,加入正己烷使N -硬脂酰基亮氨酸处于水层中 ,分离并蒸干水层溶液得含NaCl的混合物。用无水乙醇萃取混合物 ,萃取液蒸干得产物。N -硬脂酰基亮氨酸收率为 75 %     

超细4A分子筛的超声波低温快速合成

在低温条件下用超声波快速合成了4A分子筛.产物分别用XRD,IR,SEM和DSC等进行了表征.结果表明,用超声波法合成4A分子筛的速度是常规法的24倍.合成产物的白度为95%,钙离子交换容量为335mgCaCO₃/g4A分子筛,平均粒径为280nm.与采用常规方法合成的产物相比,超声波法合成的产物热稳定性有所下降.     

PHOTOINACTIVATION OF SPINACH NITRATE REDUCTASE SENSITIZED BY FLAVIN MONONUCLEOTIDE. EVIDENCE FOR THE INVOLVEMENT OF SINGLET OXYGEN

Abstract All the activities of the nitrate reductase complex from spinach are irreversibly inactivated by irradiation of the enzyme with blue light in the presence of flavin mononucleotide. The photoinactivation requires oxygen and is prevented by ethylenediaminetetraacetic acid and by reduced nicotinamide adenine dinucleotide, but not by superoxide dismutase plus catalase. On the other hand, the inactivation is markedly enhanced in 77% deuterated water and it is suppressed by the singlet oxygen quenchers azide, histidine and tryptophan. All these results suggest that singlet oxygen generated by light absorption by flavin mononucleotide, rather than excited flavin mononucleotide or other oxygen species, is the primary agent involved in the photooxidative inactivation of the enzyme.     

Chronocoulometric study of the electrochemistry of Prussian blue

During the electrochemical oxidation of Prussian blue (PB) to Prussian yellow (PY), an electrocatalytic oxygen production proceeds at the electrode when aqueous electrolyte solutions are used. The formed oxygen is scavenged by the PY, probably by absorption, and it is consumed during the electrochemical reduction of PY to PB by a heterogeneous chemical reaction of PB with oxygen to PY and hydrogen peroxide. Because of this catalytic regeneration of PY, it is impossible to determine the amount of low-spin iron by chronocoulometry using a potential program in which PB is first oxidized to PY and then the charge is measured to reduce PY to PB. The latter charge is biased by the electrocatalytic PY regeneration.     

Problems encountered with the routine application of HPLC to the analysis of carbamate pesticides

Summary This paper describes the determination of all carbamate pesticides mentioned in the Austrian regulations for pesticides and of some other carbamates commonly used in the EEC. Clean-up procedure is carried out by ethyl acetate extraction. Purification is by a liquid-liquid extraction step followed by use of a florisil column. Final detection of the carbamates is carried out by HPLC on silica gel and GLC respectively The method works well for all carbamates under consideration. Only benzimidazolamine-2, the decomposition product of benomyl and carbendazime cannot be determined by the method described. Therefore determination of benomyl, carbendazime and benzimidazolamine-2 was by hydrolysis of benomyl and carbendazime to benzimidazolamine-2, which is then determined by reversed-phase chromatography.     

A computer program system — new chemics — for structure elucidation of organic compounds by spectral and other structural information

Computer-assisted structure elucidation is improved by the introduction of substructures selected by the user, in addition to analyses of the spectral data of an unknown organic compound. The substructure is called a 'macrocomponent' in the system. The macrocomponent which is input at will is authenticated by comparison with the set of components assembled by the automated analyses of the spectra before it is used for structure construction. It is shown that the introduction of the macrocomponent enhances the correctness and practicality of structure elucidation by computer.     

Back-electron transfer suppresses the periodic length dependence of DNA-mediated charge transport across adenine tracts

DNA-mediated charge transport (CT) is exquisitely sensitive to the integrity of the bridging pi-stack and is characterized by a shallow distance dependence. These properties are obscured by poor coupling between the donor/acceptor pair and the DNA bridge, or by convolution with other processes. Previously, we found a surprising periodic length dependence for the rate of DNA-mediated CT across adenine tracts monitored by 2-aminopurine fluorescence. Here we report a similar periodicity by monitoring N 2-cyclopropylguanosine decomposition by rhodium and anthraquinone photooxidants. Furthermore, we find that this periodicity is attenuated by consequent back-electron transfer (BET), as observed by direct comparison between sequences that allow and suppress BET. Thus, the periodicity can be controlled by engineering the extent of BET across the bridge. The periodic length dependence is not consistent with a periodicity predicted by molecular wire theory but is consistent with a model where multiples of four to five base pairs form an ideal CT-active length of a bridging adenine domain.     

An ESR study of radiation damage of bisphenol-A-based epoxy resin at low temperature: Selective hydrogen addition to benzene-ring-forming cyclohexadienyl-type radical

In the γ-irradiated aromatic epoxy resin, diglycidylether of bisphenol A cured with diaminodiphenylmethane, the cyclohexadienyl-type radical is produced as one of the main radical species. Although both the resin and the hardener contain benzene rings, it is concluded that the cyclohexadienyl-type radical is formed by selective addition of the OH hydrogen to the benzene ring on the resin side. The selectivity is accounted for in terms of electron capture by the benzene ring followed by proton transfer from the OH group which is located in front of the benzene ring. This reaction scheme is further supported by the effect of the addition of an electron scavenger on the radical yield as well as by the photobleaching behavior of the radicals involved.