A quantitative study of the pathways involved in the formation of radiolysis products in ethyl palmitate

The various compounds produced by irradiation in ethyl palmitate have been determined by direct mass spectrometry and gas chromatography mass spectrometry. Postulated mechanisms for their formation have been confirmed by a comparison of product yields, and a material balance is shown between the G-values for products and their putative precursors. The total product yield is seen to be nearly equal to the amount of radiation absorbed. Three new radiolysis products, viz. ethyl α-ethylpalmitate, ethyl hexadecen-2-oate and butyl palmitate are reported.     

Evidence for the mechanisms of formation of radiolysis products using a deutero labeled triglyceride

Several previous studies of the radiolysis of fats and related compounds such as pure triglycerides, fatty acid methyl esters, and free fatty acids, have led to the hypothesis that radiolytic products result from selective cleavages at specific locations. This hypothesis is confirmed by the results of mass spectrometric analysis of the compounds formed upon gamma irradiation of tributyrin labeled with deuterium in the glycerol moiety. Compounds derived from alkyl, acyl, and acyloxy cleavages are characterized by the absence of deuterium whereas those involving the glyceryl moiety are found to carry the deuterium labels.     

A quantitative comparison of the yields of radiolysis products in various meats and their relationship to precursors

A detailed analysis has been made of the composition of radiolysis products formed in beef, pork, ham, and chicken. The yields of the various compounds are related linearly to irradiation dose, and the fat, fatty acid and triglyceride composition of the meats.     

Recombination products from the radiolysis of tricaproin

A low molecular weight triglyceride, tricaproin, has been selected to study the higher molecular weight products produced by irradiation. In a previous publication the identification of the primary radiolytic products in tricaproin was reported. In the present work, 28 compounds considered to have been produced by the combination of free radicals have been identified. Among these are hydrocarbons, ketones, esters, alkanediol diesters and glyceryl ether diesters. Reaction mechanisms for the production of these compounds are discussed.     

Effect of various parameters on the level of mixing in continuous flow systems

Variations of the level of mixing in a flow system have been investigated as a function of the following parameters: diameter, shape and speed of the agitator, feed rate and position of the feed inlet. At agitator speeds inferior to a critical value, a minimum level of mixing is observed which depends on the position of the feed inlet. At speeds superior to the critical value, the level of mixing increases linearly with agitator speed, at a given feed rate, until conditions of perfect mixing are reached. The critical agitator speed and the position of each straight line depend on the agitator size. A modified Reynolds number makes possible a more general correlation. At a given agitator speed, superior to the critical value, the level of mixing decreases as the feed rate increases, due to the smaller amount of energy imparted by the agitator per unit mass of feed. The effect of agitator shape on the level of mixing is rather pronounced as it affects the flow patterns inside the reservoir.     

Identification of adduct radiolysis products from pork fat

Mass spectrometric evidence is given to show the formation of adduct radiolysis products in pork fat. A variety of adduct radiolysis products were identified. Only the major recombination products are considered and discussed herein. These compounds consist of triglyceride dimers, propanedioldiester-triglyceride adducts, propanedioldiester dimers and branched alkyl substituted triglycerides.     

Effects of anodization parameters on the formation of titania nanotubes in ethylene glycol

The effects of fluoride concentration, anodization temperature, and anodization applied potential difference on the formation and dimensions of the titania nanotubes in ethylene glycol/water systems were investigated. It was found that fluoride concentration and anodization temperature were the two critical parameters for controlling the nanotube formation whilst anodization applied potential difference mainly contributes to tuning the dimension of the nanotubes. Electrolytes containing a low fluoride concentration are beneficial for initiating nanotube formation, whilst a higher anodization temperature is helpful to the rapid growth of the nanotubes. It is shown that the current-time curve obtained during the anodization can be used as an effective tool to predict the morphology of titania nanotubes. A model based on the competition between electrochemical oxidation of the titanium and chemical dissolution by fluoride ions is developed to explain the experimental observations.     

Study of structure formation of products in SHS nickel-aluminum-alloying component systems

A previously proposed model for the interaction in theNi-Al system is developed as applied to ternary reaction systems, which are promising for preparing materials for gasothermal application of protective coatings. In this investigation a correlation is made between the features of the thermal profile of a combustion wave with structural analysis data for the interaction products and the quenching zone. The developed qualitative models of the interaction are shown to fit adequatly the structure and phase composition of products obtained over a wide range of concentrations of dopants(Fe, Ti), which form constitution diagrams of various types with the components of the base system, and also the initial conditions of synthesis.Translated from Fizika Goreniya i Vzryva, Vol. 32, No. 2, pp. 55–63, March–April, 1996.     

Effects of various factors on the formation of high molecular weight polyamic acid

The reaction of pyromellitic dianhydride (PMDA) and aromatic diamine in an aprotic solvent such as dimethylacetamide (DMAc) gives a solution of poly(amic acid). The effects of certain variables on the polymerization and some additives on the stability and imidization of the poly(amic acid)s were studied. It was found that the addition of PMDA portionwise to the solution of diamine always keeps the excess diamine in solution and enables one to obtain the highest molecular weight of poly(amic acid). When the addition process was reversed, either by the change or dehydration of solvent, a high molecular weight was not attained. The inevitable water in the solvent or the reaction medium is the major factor, and the more the water content in the solvent or the reaction medium, the larger is the probability of destruction of PMDA during the reaction and hence low molecular weight is obtained. If very pure monomers were used in the polymerization, the 1:1 of molar ratio is the optimum value. Excess diamine or dianhydride results in the exchange reaction with poly(amic acid) and causes a rapid degradation of polymer chain. This exchange reaction was proved by NMR measurements. The presence of electrophilic agents or the nucleophilic agents containing active protons in the poly(amic acid) solution promotes the decomposition of polymer and causes the brittleness of polyimide film in the curing process. Using acetic anhydride (A) to convert the poly(amic acid) to polyimide, pyridine (P) can protect the polymer chain from the nucleophilic attack by the anhydride. The mixture with proper ratio of A/P (1/1–15/1) can be used as good dehydrating agents. Meanwhile, according to the results to the results of experiments, we suggested the probable reaction mechanisms about how the water, amine, and anhydride destroy the polyamic acid chains.     

Influence of initial parameters of reacting systems on the porosity structure of self-propagating high-temperature synthesis products

The effects of the particle size of powder components, the relative density of the sample, and the degree of dilution of the mixture by thermally inert materials on the pore structure of self-propagating high-temperature synthesis products obtained in the combustion process involving melt were experimentally studied using the (Ti + 26% Si)-Al₂O₃ system as an example. Special techniques of quantitative metallographic analysis allowing for the analysis of materials with complex pore space structure were used.     

Effects of various parameters in differential scanning calorimetry of hydrogen-peroxide-treated lignocellulose

Differential scanning calorimetric (DSC) analyses of mixtures of hydrogen peroxide and lignocellulosic materials have been performed. The influence of chamber atmosphere composition, heating rate, pinhole size, lignocellulose particle size, and hydrogen peroxide-to-lignocellulose ratio were examined. With the exception of particle size, the variables produced significant effects on the DSC curves. These effects were mainly connected with changes in the atmosphere surrounding the sample, sample density, heat capacity, and heat conductance.     

Influence of native antioxidants on the formation of fatty acid hydroperoxides in model systems

The effect of alpha‐tocopherol (alpha‐T) and quercetin on the formation of hydroperoxides of linoleic and linolenic acids during autoxidation at 60 ± 1 °C was investigated. Three isomers of hydroperoxides were detected using HPLC. Of isomers of linoleic acid hydroperoxides, 13‐hydroperoxy‐octadecadienoic acid trans‐trans (13‐HPODE t‐t), 9‐HPODE cis‐trans (9‐HPODE c‐t) and 9‐HPODE trans‐trans (9‐HPODE t‐t) were identified, constituting 64, 19 and 17% of the total amount, respectively. For linolenic acid, the components 13‐hydroperoxy‐octadecatrienoic acid trans‐trans (13‐HPOTE t‐t), 9‐HPOTE c‐t and 9‐HPOTE t‐t contributed 7, 33 and 60% to the total, respectively. The different dominant hydroperoxide isomers detected in linoleic and linolenic acids during oxidation are related to their chemical structure and the microenvironment of emulsion droplets. The ratios between specific isomers for both fatty acid hydroperoxides did not change during oxidation with or without antioxidants. Alpha‐T effectively inhibited the oxidation of fatty acids and reduced the formation of hydroperoxides. The total amount of the hydroperoxides decreased along with the increase in the concentration of alpha‐T, 1–40 µM. Quercetin inhibited the oxidation of both fatty acids at similar efficiency only at 40 µM concentration. A synergistic antioxidant effect of quercetin with alpha‐T in a binary system on both fatty acids was observed.     

Effects of processing parameters on formation of sinkmarks on injection moulded parts

Abstract

The effects of different processing parameters on sinkmarks, which occur on the surface of injection moulded parts, have been investigated. An L'18 orthogonal array design based on the Taguchi method was conducted to minimise the sinkmarks of injection moulded thermoplastic parts and the relative significance of each processing parameter on the sinkmarks was considered. The polymeric material used was polypropylene and a plate cavity with various ribs was used for moulding. Experiments were carried out on a reciprocating injection moulding machine. After moulding, sinkmarks on the surface of moulded parts were measured using a profile meter. For the factors selected in the main experiments, the size of the gate, the melt temperature, and the width of the rib were found to be the principal parameters affecting sinkmark formation on injection moulded polypropylene. In this way experimental investigation can help in the understanding of the formation mechanism of sinkmarks, so that steps can be taken to optimise the surface quality of moulded parts.     

Effects of salt content on secondary formation of hydrates in complex systems

The phenomenon of ‘memory effect’ exists in the secondary generation of natural gas hydrates, which is mainly manifested in the fact that the induction time required for the nucleation of hydrates in the secondary generation of hydrates is significantly shorter than that of the primary generation, thus accelerating the generation of hydrates. At present, the research on the memory effect phenomenon has been proven to exist, and its influencing factors have become a research hotspot. In order to study the influence of decomposition time and salt content on the memory effect, the hydrate was generated under the system of porous medium alumina complexed with surfactant SDS, and hydrate secondary generation experiments were carried out by adding different contents of NaCl according to four different decomposition times. The influence of four different decomposition times on the memory effect phenomenon in the secondary generation of hydrates and the influence of different salt contents on the memory effect phenomenon were analyzed by observing the pressure drop changes in the reactor during the hydrate generation process and calculating the methane gas consumption. The experimental results show that different decomposition times can affect the effect and time of the memory effect, and the effect of decomposition time on the memory effect does not show a linear relationship. The addition of salt may have an inhibitory effect on the memory effect.     

Effects of parameters on nanofiber diameter determined from electrospinning model

In this paper the effects of 13 material and operating parameters on electrospun fiber diameters are determined by varying the parameter values in an electrospinning theoretical model. The complexity of the electrospinning process makes empirical determination of the effects of parameters very difficult. The results show that the five parameters (volumetric charge density, distance from nozzle to collector, initial jet/orifice radius, relaxation time, and viscosity) have the most significant effect on the jet radius. The other parameters (initial polymer concentration, solution density, electric potential, perturbation frequency, and solvent vapor pressure) have moderate effects on the jet radius. Parameters relative humidity, surface tension, and vapor diffusivity have minor effects on the jet radius. Knowing the relative effects of parameters on jet radius should be useful for process control and prediction of electrospun fiber production.     

Identification of adduct radiolysis products from ethyl palmitate and ethyl oleate

Radiolysis induced adduct products have been separated and identi-fied from irradiated ethyl palmitate, ethyl α-d₂-palmitate and ethyl oleate. In the saturated compounds, adduct formation was observed mainly at the position α to the carbonyl group. The three major adduct products identified in irradiated ethyl palmitate were ethyl α-tetradecylpalmitate, ethyl α-pentadecylpalmitate and the α,α′- dimer of ethyl palmitate. Corresponding compounds were identified from the irradiated ethyl α-deuteropalmitate. Adduct radiolysis products formed in ethyl oleate were identified as the monoene and diene dimers.     

Effects of the electrospray ionization parameters on the formation and morphology of colloidal microspheres of polyacrylonitrile

Polyacrylonitrile colloidal microspheres have been successfully prepared with different concentrations of electrospraying polyacrylonitrile solutions. The morphology of the colloidal spheres has two kinds of structures and is strongly affected by electrospray‐ionization parameters, such as the polymer concentration, applied voltage, and distance between the electrodes. The solvent can also affect the morphology of polyacrylonitrile. The optimum conditions for preparing colloidal spheres have been found, and differential scanning calorimetry results indicate that polyacrylonitrile colloid spheres are amorphous. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2889–2893, 2006     

城市生活垃圾焚烧炉各工艺参数对二噁英生成的影响

二英的致命毒性及其对人体可能产生的影响已经引起了广大研究者的关注。城市生活垃圾的焚烧是二英形成的主要途径之一 ,因此如何控制垃圾焚烧中二英的形成和排放是目前研究的热点问题之一。介绍了二英的性质以及各工艺参数 (燃烧温度、形成二英的母体物质、碳源和氯源、表面材料、反应时间、金属离子催化剂以及气体组成和水分等 )对二英生成的影响     

城市生活垃圾焚烧炉各工艺参数对二英生成的影响

二英的致命毒性及其对人体可能产生的影响已经引起了广大研究者的关注.城市生活垃圾的焚烧是二噁英形成的主要途径之一,因此如何控制垃圾焚烧中二噁英的形成和排放是目前研究的热点问题之一.介绍了二噁英的性质以及各工艺参数(燃烧温度、形成二英的母体物质、碳源和氯源、表面材料、反应时间、金属离子催化剂以及气体组成和水分等)对二噁英生成的影响.