Key Engineering Materials Vol. 800

Abstract: Today, artificial implants (AI) industry depends strongly on tribological constitution of the material (s) of the implant. Erosion, corrosion, tribocorrosion and biocorrosion are essential factors to determine both functionality and lifetime of the AIs. Histo-Biocompatibility is also an additional constraint, indispensable for implant manufacturing process. The prediction of durability, based on the computational and experimental study of constituents of AI material (s) are key factors to obtain objective data of any AI characteristics. This contribution deals with a computational comparative analysis of materials for hip implants using Archard’s model mainly. Selected hip implant material hardness are Co-Cr alloy and Titanium types. Method is carried out with specific material data, e.g., hardness or wear constants, nonlinear optimization and graphical subroutines. Results presented are both numerical and graphical. Particular interest is focused on application of the 3D Graphical Optimization method.

Abstract: The aim of the study was to characterize antioxidative properties and antiradical activity of the herbal syrups collection in Latvia. Spectrophotometry was used to characterize antioxidant properties of herbal syrups. Antiradical activity, total phenols and content of flavonoids were determined spectrophotometrically. The antiradical scavenging activity was measured by the DPPH (2.2-diphenyl-1-picrylhydrazyl) reaction. The herbal syrups antiradical scavenging activity was estimated by the amount of DPPH of reagent using in reaction with a sample of vegetable syrup (in percent) and by Trolox equivalent. The total phenolic compounds were determined by using the Folin – Ciocalteu method. The total phenolic content was expressed in mg of the gallic acid equivalents. The content of flavonoids was determined by using reaction between the AlCl₃ and flavonoids. Antiradical scavenging activity by Trolox equivalent of the herbal syrups was found from 81 to be 130 mg 100 g^-1 herbal syrups. The content of total phenols was found from 22 to be 282 mg GAE 100 g^-1, but content of total flavonoids by quercetin equivalent was found from 1 to 44 mg QE 100 g^-1. In case of increased disease problems, syrups with increased antioxidant content should be used. However, the specificity of each disease should be taken into account as well as the content of certain compounds in the plants.

Abstract: Oral rehydration fluids (ORS) are used to reverse dehydration that, in case of children, mostly is due to acute gastroenteritis. The key of successful dehydration treatment is to replenish the lost water and electrolytes. This is best done by consuming oral rehydration solution, containing both salt and sugar. ORS enhances fluid absorption because sodium and glucose transport in the small intestine are coupled, and glucose promotes absorption of both sodium ions and water. Studies show that children refuse ORS due to its salty-sweet taste and unpalatability. To improve oral rehydration therapy, we hypothesized that freezing ORS containing a fruit/berry juice to a likeable texture in “gelato” form could promote oral rehydration. The results provide a basis for further development of the ORS gelato with attention to flavor, sweetness and texture.

Abstract: Brushite cement has advantages such as fast setting, high reactivity and good injectability over apatitic cements. To induce the bioactivity of brushite cements, the goal was to convert it into a bone-like low crystalline carbonate apatite. To achieve this induced transformation, potassium and magnesium were used as dopants which were claimed to be effective in the literature. The cements were immersed for 2 periods of time: 1 day and 6 weeks in Tas-Simulated-Body-Fluid (Tas-SBF) due to its excellent biomimetic properties with its adjusted HCO3- and Cl- ionic rates according to human-blood-plasma. 5% of potassium (to calcium sites) seemed to be more effective over magnesium modification. The aim of this study is to define an optimal composition in terms of transforming brushite into apatite.

Abstract: The incorporation of protein based polymeric materials with calcium phosphate (CaP) coatings can provide excellent biological characteristics and biocompatibility with its bone-like protein-CaP composition. Calcium chloride-ethanol catalysed hydrolysis reaction and wet precipitation method was used to prepare silk solution and to precipitate brushite respectively to produce the brushite/silk composite powder. FTIR analyses showed that brushite absorption bands were prominent, overlapping the less intense N-H bands in silk. The most distinct absorptions from the silk were N-H bands. 1g of silk additive to the 300 ml of solution media resulted in arbitrary particle attachment onto brushite crystal surface; most of the brushite particles were covered by the silk β-sheets phase.

Abstract: By the investigation and comparison of different interesterification reactions at fixed reaction time researchers usually selected 1 hour as a characteristic time for the synthesis stage of industrial biodiesel production. Investigation performed in this work shows that the equilibrium of interesterification reaction mixture of rapeseed oil with methyl acetate in molar ration of 1:18 in presence of potassium tert-butoxide in tert-butanol at molar ratio to oil 0.08 at 25 °C reach the equilibrium approximately after 50 min but at 55 °C after 10 min. The equilibrium compositions of the reaction mixtures at different temperatures are different. The concentrations of TG, FAME and TA during the interesterification reaction at 25 °C obey the pseudo-first order law which do not reflect the stoichiometry of this multiple elementary steps reaction.

Abstract: 1,2-Propanediol selective oxidation with molecular oxygen in presence of heterogeneous catalyst is one of the most nature friendly 1,2-propanediol conversion methods. This work demonstrates Au, Pt and Pd containing catalysts’ activity and selectivity in a 1,2-propanediol oxidation process. The main product of the 1,2-propanediol catalytic oxidation was lactic acid, by-products were acetic and formic acids. It was found that Au based catalysts are best for 1,2-propanediol oxidation in alkaline water solutions. The best result was achieved using the 4.8wt%Au/Al₂O₃ catalyst: selectivity by lactic acid was 94% with 1,2-propanediol conversion 100% (c₀(1,2-propanediol) = 0.3 mol/L, P(O₂) = 6 atm, n (1,2-propanediol)/n (Au) = 500, t = 60°C, c₀(NaOH) = 1.5 mol/L).

Abstract: Chemical interesterification is one possible way to produce biofuel from vegetable oils. Rapeseed oil interesterification with methyl formate using 1M tBuOK catalyst in tBuOH yields product in two layers. The upper layer contains fatty acid esters. Analysis of lower layer by ¹³C NMR method shows that it contains glycerol and glycerol formates. To develop quantitative determination methods using HPLC and GC, glycerol formates are synthesized in Fisher esterification reaction and used as standards. HPLC analysis is fast, but suitable only for determination of diformin and triformin. GC analysis gives content for all components but is more time consuming.

Abstract: In the present study, the Fucus vesiculosus is considered as perspective feedstock for obtaining fertilizers and valuable biologically active compounds. Polyphenols (phlorotannin) and sulfated polysaccharide (fucoidan) were isolated using sequential extraction from the above-mentioned seaweed. The total content of polyphenolics in hydrophilic extracts is 680 GAE/g. The yield of fucoidan from brown algae was 7 % on the oven dry seaweed. The assessment of biological activity of Fucus vesiculosus was performed using germination test and vegetation test. The results of the tests revealed that the Fucus vesiculosus promotes the growth of the agricultural plants, is not phytotoxic, and has a good potential in sustainable agriculture

Abstract: Often we are faced with the need for thermal treatment of honey. Traditionally this is done by heating the honey. This process requires certain time consumption. Thermal treatment can be greatly accelerated by the use of microwaves. Indicators for thermal treatment and storage of honey traditionally are hydroxymethylfurfural (HMF) content and activity of enzymes. HMF is organic compound, which is created when carbohydrates are dehydrated. HMF content increases when honey is stored for long time or is thermally treated. Our objective of the study was to find out how the different types of honey heat treatment affect the honey enzyme, invertase, activity and HMF content. HMF content in honey was determined using high pressure liquid chromatography. Invertase activity is determined by spectrophotometry. The study results proved that using microwaves to thermally treat honey significantly impacts honey invertase activity and HMF content increases. Invertase activity reduction is more severe compared to the HMF content increase. Thermally treating honey with microwaves, even treating it only 10 seconds, affects the quality of honey.