ON THE PHOTOIONIZATION ENERGY THRESHOLD OF TRYPTOPHAN IN AQUEOUS SOLUTIONS

Abstract— To investigate the existence and energy position of a photoionization threshold. tryptophan (Trp) has been photoionized in desecrated neutral aqueous or alcoholic solution under monochromatic light of variable frequency, in presence of N₂O to scavenge the photoelectron.
Present findings and some literature data converge to show the existence of a threshold for the one photon ionization process. This threshold is located at 4.5 ± 0.1 eV and 4.85 ± 0.1 cV for Trp in aqueous and ethanol solutions. respectively, which corresponds to a lowering with respect to the gas phase ionization potential of 3.4 and 3.0 eV.
The photoionization quantum yields for Trp is found about 4 times greater at 250 nm than at Λ_cx= 265 nm, where φe^-_4M=0.080±0.025. In such spectral range. at most one photoelectron out of 4–5 escaping geminate recombination would lead to Trp photodegradation in acrated solutions.
These results also point out that the neutral radical Trp. which has been previously observed for Λ_cx > 275 nm, i.e. below the ionization threshold energy—would not necessarily derive from Trp ⁺ deprotonation or cation-electron dissociative recombination. Similarly, the opening of the indole ring with formylkynurenine (FK) formation which is observed under aerobic conditions and Λ_cx >, 280 nm would not imply an electron attachment on O₂ but reactions such as Trp +³O₂ or Trp*+³O₂ or else
     

DEMULSIFICATION OF WATER IN OIL EMULSIONS USING WATER SOLUBLE DEMULSIFIERS

The possibility of using a water soluble,as opposed to the conventional oil soluble demulsifier, to destabilize a w/o emulsion in crude oil has been explored. It was found experimentally that a surfactant soluble in the water (dispersed) phase could destabilize the emulsion. Polymer molecules with varying HLB's and molecular weights and structure were synthesized and these compounds were added to the water phase to destabilize the water/crude oil emulsions. Molecules with a high percentage of hydrophilic groups and low molecular weights showed very good demulsifying abilities.     

STABILITY OF HATER IN OIL EMULSIONS USING HIGH MOLECULAR WEIGHT EMULSIFIERS

Excellent stability of water-in-oil emulsions could be obtained by partial crosslinking of the fatty chain in several polyglycerol fatty esters. Such products were capable of emulsifying and stabilizing up to 50 wt% water in vegetable oils at a level of 3-5% emulsifier per total emulsion weight. The corresponding non-crosslinked products require at least 20-25% emulsifier to give the sane level of stability, with much higher viscosity.

Degree of polymerization, molecular weight distribution, viscosity, dielectric constant and refractive index of the emulsifier were correlated to the emulsion stability. The most remarkable result is a clear correlation between the molecular weight of the emulsifier and emulsion stability; best emulsions were prepared with polymeric emulsifier with MW of Ca. 40000.     

丙烯酰胺型阴离子表面活性单体与丙烯酰胺共聚物水溶液的流变特性

以丙烯酰胺型阴离子表面活性单体2-丙烯酰胺基十四烷基磺酸钠(NaAMC14S)为共单体,与丙烯酰胺(AM)的水溶液均相共聚合,使NaAMC14S的浓度分别处于临界胶束浓度上下,分别制备了具有无规结构与微嵌段结构的两类共聚物;用红外光谱法对共聚物的结构进行了表征,使用乌氏粘度法测定了特性粘数,相对表示出了共聚物的分子量;采用荧光探针法与表观粘度法重点研究了两类共聚物的疏水缔合性与水溶液的流变特性.研究结果表明,具有微嵌段结构的共聚物具有很强的疏水缔合性,当其水溶液的浓度达0.2wt%后,表观粘度迅速提高;其水溶液的切力变稀行为具有明显的可逆性,表现出强的抗剪切性能.本研究中特别发现,具有微嵌段结构的共聚物其盐水溶液的表观粘度远高于纯水溶液的表观粘度,当共聚物浓度为0.3wt%、CaCl2浓度为2wt%时,溶液的表观粘度竟然提高了3个数量级,表现出独特的正性盐敏性(即遇盐变稠).     

THE ''Q-BAND'' ABSORPTION spECTRA OF HEMATOPORPHYRIN MONOMER AND AGGREGATE IN AQUEOUS SOLUTION

Abstract The resolution of the absorption spectra in the Q band (480 nm-620 nm) spectral region of monomeric and dimeric hematoporphyrin species present in aqueous solutions has been achieved using absorption, fluorescence and computer analysis methods. The absorption maxima of the dimer in this spectral region are red shifted about 12 nm with respect to those of the monomer. The significance of this finding in relationship to the well documented blue shift of hematoporphyrin aggregate observed in the Soret band region (λ_malx∼400 nm) of the absorption spectrum is discussed.     

ADSORPTION PROPERTIES OF THE STEARIC ACID-OCTADECANE PARTICLES IN AQUEOUS SOLUTIONS

The adsorption properties and surface charge creation for the stearic acid and octadecane/aqueous electrolyte solutions are considered. The hairy structure of surface charge for these systems was confirmed on the basis of potentiometric titration, ion adsorption and electrophoretic measurement data. For the system with stearic acid the reaction of ionization and complexation of carboxyl groups of stearic acid molecules from subsurface layer are responsible for the creation of surface charge and adsorption properties. The surface charge at octadecane particle is probably the results in adsorption and orientation of water molecules at the interface.     

EFFECTS OF INTERFACIAL POLYUREA FILM ON THE STABILITY OF OIL IN WATER EMULSIONS

The stability of oil in water emulsions containing a triisocyanate soluble in the oil phase was investigated. The oil component was either di-n-butyl phthalate (DBP) or a mixture of DBP with liquid paraffin. The time required for the average size parameter to reach a constant value was studied. It was found that the polyurea film produced by an interfacial polymerization reaction between water and a triisocyanate contributed to make the stable emulsions. The effects of drop size, temperature, polarity of oil phase, triisocyanate concentration, and mechanical stirring on the stability of the emulsions were established in this study. The film thickness at the point where the average size parameter reached a constant value was found to be of the order of 0. 002 ～ 0. 004μ.     

CARBOXYLATION OF FORMIC ACID IN AQUEOUS SOLUTIONS UNDER THE INFLUENCE OF U.V.-LIGHT

Abstract— Carboxylation of various organic substances by dissolved carbon dioxide or bicarbonate is achieved by the action of U.V. -Light of 184.9 and 253.1 mμ on water. The transformation of formic acid to oxalic acid was investigated in more detail as a function of u.v.-dose, pH-values and the formate concentration. For an irradiation period of 12 hr of 0.1 M formate, a yield of about 2 m mol.1^--¹ oxalic acid was obtained. A reaction mechanism for the photochemical carboxylation process is presented. The results are of some interest in respect of the synthesis of organic compounds under the primitive earth conditions.     

pH DEPENDENCE OF SINGLET OXYGEN PRODUCTION IN AQUEOUS SOLUTIONS USING THIAZINE DYES AS PHOTOSENSITIZERS

Abstract— The production of singlet oxygen by thiazine dye photosensitization, as measured by the rate of photooxidation of tryptophan, was found to be very sensitive to changes of pH in the range 5–9. For methylene blue in aerated solutions, the production of ¹O₂* is approximately five times more efficient in basic than in acidic medium. This was shown to be related to the p K 's of the triplet dyes, by evaluating the yields of ¹O₂* from the lifetimes and the quenching rate constants for the two ionic species of sensitizer triplets measured by laser flash photolysis. Changes in the quenching rate constants of the thiazine triplet states can be correlated with the triplet energies.     

溴代十四烷基吡啶胶团长大的光子相关谱研究

本文用光子相关谱方法在15—85 ℃温度范围内, 研究了溴代十四烷基吡啶(TPB)胶团在高盐量介质(0.5—2.0M NaBr)中的长大规律。自光子相关实验测定了胶团的平均流体力学半径。增加盐量、降低温度和增大活性剂浓度均使胶团变大。TPB胶团长大时由球转变为棒。自实验测量结果求算了在0.5 M和1.0 M盐中支配球-棒转变的平衡常数及热力学函数值。本文检验了梯子模型对TPB体系的适用性, 并对2 M盐介质中TPB胶团的长大具有不同的特征作了讨论。     

脂肪酸钠盐对于苯甲酸在水中溶度的影响

在25°脂肪酸钠盐对正戊酸在水中溶度的影响是不规则的盐溶和盐析作用,其原因是排代出的新酸分布于正戊酸相和盐溶液相间^[1]。黄子卿等^[2]曾在25°研究脂肪酸盐(甲酸钠至戊酸钠)对正己酸在水中溶度的影响,除甲酸钠外,盐溶随盐的碳原子数目的增加而下降。Philip等^[3]曾在25°测定苯甲酸在甲酸钠和乙酸钠水溶液中的溶度。在本文中,作者测定在25°苯甲酸在五种脂肪酸钠(甲酸钠至戊酸钠)水溶液中的溶度。     

KINETICS OF COALESCENCE OF WATER DROPLETS IN WATER-IN-CRUDE OIL EMULSIONS

Water from water-in-crude oil emulsions is separated by chemical demul-sification. Coalescence rates of water droplets have been studied in the presence of a demulsifier. Droplet size measurement was carried out by photomicrography. Fastest coalescence rate was observed during first one minute. Binary coalescence time during this period was 5·4 seconds when 50 mg/1 of demulsifier was added and 4·2 seconds in the presence of 100 mg/1 of demulsifier.     

A NEW METHOD FOR THE DETECTION OF SINGLET OXYGEN IN AQUEOUS SOLUTIONS

Abstract— In experiments on the interception of reactive intermediates of strongly oxidizing character in dye (S) sensitized photooxidations using p -nitrosodimethylaniline (RNO) as a selective scavenger, it has been observed that some substrates (A) or ¹O₂ acceptors (like imidazole derivatives) induce the bleaching of RNO as followed spectrophotometrically at 440 nm. Since singlet oxygen (¹O₂) does not react chemically with RNO, this bleaching is a consequence of ¹O₂ capture by the imidazole ring which results in the formation of a trans-annular peroxide intermediate [¹O₂] capable of inducing the bleaching of RNO (-RNO). In the absence of RNO, [¹O₂] decomposes or rearranges into the final oxygenation product ¹O₂: ¹Δ_g Thus, the system imidazole plus RNO can be used as a sensitive and selective test for the presence of ¹O₂ in aqueous solutions. The method can also be applied in the presence of sensitizing dyes which, under visible irradiation, can partially bleach RNO even in the absence of imidazole derivatives. In such a case, the bleaching of RNO is strongly increased by the presence of imidazoles with a characteristic dependence on their concentration. The separation of the product of RNO bleaching by thin layer chromatography can serve as additional proof of the presence of ¹O₂ in the system. The imidazole plus RNO method has been applied to a number of sensitizing and non-sensitizing dyes.     

PREPARATION OF CLOUDY COCONUT OIL EMULSIONS CONTAINING DISPERSED TiO2 USING ATOMIZER

ABSTRACT

Food Grade Rutile TiO₂ was dispersed in coconut oil with the help of hydrophobic emulsifiers such as sorbitan esters and lecithin. The dispersed mixture was melted and blended with hydrophilic emulsifiers such as ethoxylated sorbitan esters and the preheated (60°C) blend was further sprayed by atomizer into cold water (20°C). The oil in water emulsions contained encapsulated TiO₂ in the internal phase. The technique is simple and allows preparation of stable emulsions with average droplets size of 1-10 microns.     

Zn在KOH水溶液中的阳极溶解和钝化机理

本文用旋转圆盘电极、稳态极化曲线、交流阻抗及恒电流充电曲线等方法研究了Zn在常温(30℃)和低温(-20℃)的KOH水溶液中阳极溶解和钝化过程的规律。从而提出其反应机理,并用最优化程序在TRS-80微型计算机上计算了反应机理中基元反应的速度和动力学参数的最佳值。由动力学参数计算的φ～i关系定量地符合从阳极溶解至钝化前整条极化曲线实验数据。旋转圆盘电极的转速效应、交流阻抗值以及恒电流充电电量值也都与提出的反应机理相符合。     

PREPARATION OF CLOUDY COCONUT OIL EMULSIONS CONTAINING DISPERSED Ti02 USING ATOMIZER

Food Grade Rutile TiO₂ was dispersed in coconut oil with the help of hydrophobic emulsifiers such as sorbitan esters and lecithin. The dispersed mixture was melted and blended with hydrophilic emulsifiers such as ethoxylated sorbitan esters and the preheated (60°C) blend was further sprayed by atomizer into cold water (20°C). The oil-in-water emulsions contained encapsulated TiO₂ in the internal phase. The technique is simple and allows preparation of stable emulsions with average droplet size of 1-10 microns.     

在水溶液中用原碲酸根阴离子稳定铽(Ⅳ)的研究

在镧系元素中,除铈以外镨和铽也可以以正四价氧化态存在这一事实早已为人们所熟知。     

ELECTROCHEMICAL PROPERTIES OF ASPHALTENE PARTICLES IN AQUEOUS SOLUTIONS

The electrical properties of colloidal asphaltene/water solution interface were determined by carrying out the potentiometric titration and electrokinetic measurements. Asphaltenes in aqueous solutions exhibit typical organic colloid properties i.e. surface charge and electrophoretic mobility. It was considered that the surface charge at the asphaltene particles is a result of protonation and dissociation reactions of surface functional groups. On the base of the surface charge density data vs. pH the surface reaction constants were calculated by numerical method. The agreement of these values with calculated ones, on the base of ζ potential data, is noticeable.

The characteristic feature of the investigated systems is the maximum, appearing on the curve ζ potential vs. electrolyte concentration. This behaviour is explained by _”hair layer ” structure of the asphaltene surface