Studying the formation process of chromate conversion coatings on aluminium using continuous electrochemical noise resistance measurements

A unique electrochemical technique, namely continuous noise resistance calculation (CNRC), was used to obtain electrochemical kinetic information from the formation process of chromate conversion coatings (CCC) on aluminium electrodes. It was found that the noise resistance (R_n) of aluminium electrodes remained almost unchanged during electrodes' immersion in a chromate containing acidic solution where the CCC films were supposed to form rapidly. This result indicates that the formation of CCC was associated with continuous corrosion of the aluminium electrodes and that the CCC films formed on aluminium surface were not intact barrier films, but most likely porous layers. The CCCs became protective only after they were aged in the environment. Based on these findings, the formation and inhibition mechanisms of CCC have been discussed.     

Stearyl CoA as a precursor of oleic acid and glycerolipids in mammary microsomes from lactating bovine: Possible regulatory step in milk triglyceride synthesis

The stearyl desaturase of lactating bovine mammary tissue is located in the microsomes and requires activated fatty acid and NADH for activity. Other enzymes, acyl-transferase(s) and deacylase which apparently compete with the desaturase for substrate are also present. Both the substrate 1-¹⁴C-stearyl CoA and the oleic acid produced by desaturase are esterified into the various lipid classes. The oleic acid is preferentially acylated into positionsn-3 of the triglycerides andsn-2 of the phosphatidylcholine. Experimental conditions causing reduced desaturase activity depressed triglyceride synthesis, and stimulation of desaturation by NADH L^−α GP, acidic pH, 5.6, was accompanied by increased incorporation of radioactive fatty acids into the triglycerides. These data indicated that desaturase and glyceride acyl transferase were located contiguously within the microsomal membranes. The possibility that desaturase activity might control triglyceride synthesis in vivo is discussed. It was observed that mammary tissue from nonlactating cows 1–2 weeks and 2 days prior to calving lacked or possessed very low stearyl desaturase activity.     

Lipids and fatty acids of important finfish: New data for nutrient tables

There is an urgent need for thorough and reliable information on the lipid content and fatty acid composition of food. Data on fish lipids (1960 to the present) have been collected and evaluated for the preparation of nutrient and food composition tables for this important commodity. Some factors affecting these data include the lack of standardization in fish nomenclature, cut of fish, season and location of catch, and variability of methods of analysis. The derivation and use of conversion factors relating wt percent methyl ester data in the literature to g fatty acid/100 g fish are described. Tabulated data are presented for total lipid and 14 fatty acids in 11 important finfish.     

Tissue culture of cocoa bean (Theobroma cacao L.): changes in lipids during maturation of beans and growth of cells and calli in culture

Callus cultures ofTheobroma cacao L., initiated from explants of immature cocoa bean cotyledons, contained 5.3%–6.4% lipids (dry wt basis). The major fatty acids were palmitic, oleic and linoleic acids. Cell suspensions contained 5.7–7.7% total lipids which had a higher polyunsaturated fatty acid content than total lipids of the calli. Phospholipids and glycolipids were the predominant lipid classes of calli and cell suspensions. Immature cocoa beans at early stages of development contained much higher polyunsaturated fatty acids, higher polar lipids and lower triglycerides than did mature ripe beans. Ripe cocoa beans contained 54% total lipids of which 96.8% where triglycerides. The fatty acid composition of total lipids of calli and cell suspensions were similar to those of the immature cocoa beans.     

A quantitative risk assessment of a domestic property connected to a hydrogen distribution network

The increased reliance on natural gas for heating worldwide makes the search for carbon-free alternatives imperative, especially if international decarbonisation targets are to be met. Hydrogen does not release carbon dioxide (CO₂) at the point of use which makes it an appealing candidate to decarbonise domestic heating. Hydrogen can be produced from either 1) the electrolysis of water with no associated carbon emissions, or 2) from methane reformation (using steam) which produces CO₂, but which is easily captured and storable during production. Hydrogen could be transported to the end-user via gas distribution networks similar to, and adapted from, those in use today. This would reduce both installation costs and end-user disruption. However, before hydrogen can provide domestic heat, it is necessary to assess the ‘risk’ associated with its distribution in direct comparison to natural gas. Here we develop a comprehensive and multi-faceted quantitative risk assessment tool to assess the difference in ‘risk’ between current natural gas distribution networks, and the potential conversion to a hydrogen based system. The approach uses novel experimental and modelling work, scientific literature, and findings from historic large scale testing programmes. As a case study, the risk assessment tool is applied to the newly proposed H100 demonstration (100% hydrogen network) project. The assessment includes the comparative risk of gas releases both upstream and downstream of the domestic gas meter. This research finds that the risk associated with the proposed H100 network (based on its current design) is lower than that of the existing natural gas network by a factor 0.88.     

Fatty acid content and composition of freshwater finfish

The fatty acid content and composition of 18 species of freshwater fish filets were determined. The fat content and composition varied with anatomical location. The anterior ventral regions of trout and salmon contained more lipids than the posterior dorsal sections. Marked variations in fatty acid composition between species were observed. Palmitic (C16:0), palmitoleic (C16:1), oleic (C18:l), eicosapentaenoic (C20:5 ω3), and docosahexaenoic (C22:6 ω3) were the most abundant fatty acids. The fatty acids were tabulated according to the number and positions of the double bonds. Significant quantities of ω6 C18:2 and C20:4 fatty acids were found in several species.     

Docosahexaenoic acid and other dietary polyunsaturated fatty acids suppress leukotriene synthesis by mouse peritoneal macrophages

The efficacy of individual ω-t-3 polyunsaturated fatty acids (PUFA) in altering eicosanoid synthesis in peritoneal macrophages was studied by feeding mice for 10 days a diet containing 2 wt% fat, which included 0.5 wt% ethyl esters of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) or linolenic acid (LNA). Upon stimulation with calcium ionophore A23187, macrophages from these animals produced significantly lower amounts of leukotriene C₄, leukotriene B₄ and 12-hydroxyeicosatetraenoic acid, prostaglandin E₂ and 6-keto prostaglandin F_1α compared with those obtained from animals on the diets containing olive oil or safflower oil. The decrease in leukotriene synthesis was similar in the animals fed DHA, EPA or LNA diets. This depression of eicosanoids by DHA and EPA was associated with decreased levels of arachidonic acid (AA); however, LA that altered eicosanoids did not have the same effect on AA levels.     

Silicon-doped hydroxyapatite prepared by a thermal technique for hard tissue engineering applications

Hydroxyapatite (HA, Ca₅(PO₄)₃OH) has been extensively used for bone implantation due to its similarity to the mineral component of bone, which makes it strongly osteoconductive. However, HA has low resorbability, and it is difficult to replace by a newly regenerated bone. Si doping can enhance the resorbability of HA by modifying its crystal structure. Here, we developed a simple thermal technique for preparing Si-doped HA from silica (SiO₂) and HA precursors, both of which are inexpensive and commercially available. This method included the physical binding of SiO₂ and HA particles, followed by pressing and sintering the mixture at an elevated temperature, which enhanced the atomic diffusion of Si into HA unit cells. We also evaluated the simulated body fluid (SBF) activity of the Si-doped HA prepared by this technique and showed that it significantly had higher resorbability and mineralizing potential compared to the pure HA. Our experimental design including, the individual precipitation and resorption assays enabled us to explain the mechanism behind the improved activity of Si-doped HA in SBF. This was attributed to the formation of new phases, such as β-tricalcium phosphate (β-TCP) and calcium silicate (Ca₂SiO₄) with higher solubility than HA on the SiO₂-contating HA during the sintering stage. This can provide some guidelines for designing new calcium phosphate-based materials for hard tissue engineering applications.