Investigation of Thermophysical Properties of Thermal Degraded Biodiesels

Biofuels are an alternative to fossil fuels and can be made from many different raw materials. The use of distinct catalyst and production processes, feedstocks, and types of alcohol results in biofuels with different physical and chemical properties. Even though these diverse options for biodiesel production are considered advantageous, they may pose a setback when quality specifications are considered, since different properties are subject to different reactions during usage, storage and handling. In this work, we present a systematic characterization of biodiesels to investigate how accelerated thermal degradation affects fuel properties. Two different types of biodiesel, commercially obtained from distinct feedstocks, were tested. The thermal degradation process was performed by maintaining the temperature of the sample at \(140 \,^{\circ }\hbox {C}\) under constant air flux for different times: 0 h, 3 h, 6 h, 9 h, 12 h, 24 h and 36 h. Properties such as density, viscosity, activation energy, volumetric thermal expansion coefficient, gross caloric value, acid value, infrared absorption, and temperature coefficient of the refractive index were used to study the thermal degradation of the biodiesel samples. The results show a significant difference in fuel properties before and after the thermal degradation process suggesting the formation of undesirable compounds. All the properties mentioned above were found to be useful to determine whether a biodiesel sample underwent thermal degradation. Moreover, viscosity and acid value were found to be the most sensitive characteristics to detect the thermal degradation process.     

The Physicochemical Characterization and In Vitro/In Vivo Evaluation of Natural Surfactants-based Emulsions as Vehicles for Diclofenac Diethylamine

ABSTRACT

Two sugar-based emulsifiers, cetearyl alcohol & cetearyl glycoside and sorbitan stearate & sucrose cocoate, known as potential promoters of lamellar liquid crystals/gel phases, were investigated in order to formulate an optimal vehicle for amphiphilic drug—diclofenac diethylamine (DDA).

Physico-chemical characterization and study of vehicle's physical stability were performed. Then, the in vitro DDA liberation profile, dependent on the mode of drug incorporation to the system, and the in vivo, short-term effects of chosen samples on skin parameters were examined.

Droplets size distribution and rheological behavior indicated satisfying physical stability of both types of vehicles. Unexpectedly, the manner of DDA incorporation to the system had no significant influence on DDA release. In vivo study pointed to emulsion's favorable potential for skin hydration and barrier improvement, particularly in cetearyl glycoside-based vehicle.     

A Flexible Approach for the Reinforcement of Water Networks Using Multi-Criteria Decision Analysis

Water Resources Management - This work proposes a multi-criteria decision analysis (MCDA) as a useful tool for supporting interventions to overcome problems faced by water utilities due to...     

Flexible and configurable verification policies with Omnibus

The three main assertion-based verification approaches are: run-time assertion checking (RAC), extended static checking (ESC) and full formal verification (FFV). Each approach offers a different balance between rigour and ease of use, making them appropriate in different situations. Our goal is to explore the use of these approaches together in a flexible way, enabling an application to be broken down into parts with different reliability requirements and different verification approaches used in each part. We explain the benefits of using the approaches together, present a set of guidelines to avoid potential conflicts and give an overview of how the Omnibus IDE provides support for the full range of assertion-based verification approaches within a single tool.     

Enhanced stability in CO2 of Ta doped BaCe0.9Y0.1O3−δ electrolyte for intermediate temperature SOFCs

The influence of Ta concentration on the stability of BaCe_0.9−xTa_xY_0.1O_3−δ (where x=0.01, 0.03 and 0.05) powders and sintered samples in CO₂, their microstructure and electrical properties were investigated. The ceramic powders were synthesized by the method of solid state reaction, uniaxially pressed and sintered at 1550 °C to form dense electrolyte pellets. A significant stability in CO₂ indicated by the X-ray analysis performed was observed for the samples with x≥0.03. The electrical conductivities determined by impedance measurements in the temperature range of 550–750 °C and in various atmospheres (dry argon, wet argon and wet hydrogen) increased with temperature but decreased with Ta concentration. The highest conductivities were observed in the wet hydrogen atmosphere, followed by those in wet argon, while the lowest were obtained in the dry argon atmosphere for each dopant concentration. The composition with Ta content of 3 mol% showed satisfactory characteristics: good resistance to CO₂ in extreme testing conditions, while a somewhat reduced electrical conductivity is still comparable with that of BaCe_0.9Y_0.1O_3−δ.     

Antioxidant activity of strawberry (Fragaria × ananassa Duch.) leaves

Antioxidant activity of aqueous extracts from two cultivated strawberry leaves, Senga Sengana and Mount Everest, obtained by maceration, reflux extraction and ultrasonic extraction, was investigated. Antioxidant activity of extracts was assessed by DPPH, FRAP, FIC and H₂O₂ test; total phenolics and flavonoids were assessed by Folin–Ciocalteu and aluminium chloride methods, respectively. Extract obtained from Senga Sengana by reflux extraction, containing higher amounts of extractive matter, total phenolics and flavonoids, has shown higher antioxidant activity (EC_50(DPPH) = 10.4 μg/mL; FRAP = 258.61 mgFe²⁺/g dry extract.; FIC activity = 62.6% in concentration of 2 mg/mL; H₂O₂ scavenging = 25.43% in concentration of 0.5 mg/mL) compared to extracts obtained by other extraction techniques. Rutin, coumaroyl-galloyl-glucopyranoside, hydroxyphenylethyl-coumaroyl-glucopyranoside, derivates of hydroxyphenylethyl-coumaroyl-glucopyranoside, chlorogenic acid and p-coumaroylhexose have been identified by UHPLC–DAD–HESI–MS analysis.