Numerical Studies on Supersonic Mixing and Combustion Phenomena

A numerical study is conducted to investigate the mixing, combustion, and flow characteristics of different scramjet-combustor configurations. Three-dimensional models for the combustors have been used. Numerical results are obtained using a finite volume computational fluid dynamics (CFD) code with unstructured grids with sizes between 200,000 and 400,000 cells. In the first part of the current study, the effects of the side angle of the fuel injectors in both mixing and combustion processes are investigated. Raised (compression) and relieved (expansion) wall-mounted ramps are used with side angles of 0 (unswept), 5, and 10 degrees. Results are obtained for nonreacting flows as well as for reacting flows. Hydrogen is used as the fuel in all reacting cases. It is noted that the side angle highly affects the mixing process. The results show clearly that increasing the side angle of the ramps leads to better mixing and further increase of the angle will slightly improve the mixing rate. In the second part, two dual-mode scramjet-combustor models are investigated. In the first model, fuel is injected through a single unswept wall-mounted ramp parallel to the airstream. In the second model, fuel is injected behind a rearward facing step normal to the airstream. The effects of the combustor length, the equivalence ratio, the number, and the arrangements of the fuel injectors are investigated. Also, the effect of the initial boundary layer thickness is studied. Results show that improved combustion efficiency is obtained by increasing the length of the combustor. For the same amount of injected fuel, increasing the number of injectors improves the combustion efficiency. Asymmetric flow and significant upstream interaction are seen in the isolator section of the second model when using initial boundary layer at the inlets. Furthermore, high degree of upstream interaction is obtained by increasing the number of injectors

Citric acid strongly inhibits visceral pain response in mice

Citric acid introduced into the stomach of mice at increasing concentrations of 0.1, 1 or 10 % (4.8 µM-0.48 mM; 95 µmol/kg-9.5 mmol/kg, 0.5 ml) caused dose-dependent inhibition of abdominal constrictions induced 1 h later by i. p. acetic acid injection by -51 % to -69.5 %. When administered at 10 % (0.48 mM, 0.5 ml) 15 min before nociceptive challenge, citric acid inhibited the nociceptive response by 96.8 %. Inhibition of the acetic acid-induced abdominal constrictions was also observed when lower doses of citric acid were introduced into the stomach (0.2 ml of 0.1-1 %; 38.1 µmol/kg-0.38 mmol/kg). The effect was evident as early as 5 min after administration of citric acid into the stomach and with the maximal effect being at 15-30 min after dosing. Lidocaine given orally 5 min prior to citric acid (1 %, 48 µM; 0.38 mmol/kg, 0.2 ml) prevented antinociception by citric acid, but lidocaine given 15 min before oral introduction of citric acid enhanced the citric acid-induced inhibition of the nociceptive response to acetic acid. The antinociceptive effect of orally administered citric acid (1 %, 48 µM; 0.38 mmol/kg, 0.2 ml) was increased by pre-treatment with propranolol (4 mg/kg, s. c.), yohimbine (4 mg/kg, s. c.), guanethidine (32 mg/kg, s. c.), but reduced after treatment with atropine (3 mg/kg, s. c.), which itself increased the nociceptive behavior. Similar inhibition of the acetic acid-induced nociceptive behavior was also observed when sodium citrate (pH 7.21) or 0.1 N HCl (pH 3) or 1 % sucrose solution (0.2 ml) was intragastrically given. It is suggested that citric acid might act to stimulate sensory afferents and that transmission of nociceptive information centrally leads to the activation of descending antinociceptive mechanism to a noxious stimulus

Investigation of the nanocrytalline SnO2 Synthesized by Homogeneous Precipitation

Nanocrystalline tin dioxide synthesized by the homogeneous pre cipitation method using the reaction of tin tetrachloride pentahydrate and urea solutions has been investigated. The nanocrystalline powder has been traced at different calcination temperatures (300ºC-1050ºC), and then characterized by using   Thermogravemetric analysis, differential thermal analysis and x-ray diffraction. The microstructure of the obtained nanoparticles has been examined by scanning and transmission electron microscopy. The average crystallite size, determined by x-ray diffraction, was found to be in the range of 3 –30 nm. The analysis exhibited a tetragonal phase.  Optical properties were investigated by a UV–vis absorption spectrophotometer. The calculated optical band gap lies between 4.47–3.71 eV as a result of increasing the calcination temperatures and crystallite size. Surface area and porosity of SnO2 nanoparticles are measured. Specific surface area which is related to pore volume and decreases from 155 m2/g at 100ºC to 3.3 m2/g at 1050ºC.Â

Statistical analysis for the impact of smoking on the behavior and health of Qatari adolescents

The links between the use of tobacco and health risks are well known. Most of the younger smokers reside in Asia which includes Qatar, the focus country of this study. Cigarette smoking among children is rising at an alarming rate worldwide including Qatar. As youth make up a significant percentage of the population and to achieve the health objectives of the Qatar Vision 2030, it is essential to ensure the health and well-being of adolescents, as they are the future of Qatar. This study focuses on exploring the patterns of tobacco use and its impacts on the adolescents by conducting a survey in different schools across Qatar. The questionnaire was administered in five schools, selected by proportional random sampling. The responses were recorded from the sample for general questions regarding interest in physical activities, relationship with family and friends, mental satisfaction, health, academics and access to cigarettes. 2018 Walter de Gruyter GmbH, Berlin/Boston 2018.Scopu

Optimirana i validirana protočna injekcijska spektrofotometrijska analiza topiramata, piracetama i levetiracetama u farmaceutskim pripravcima

Application of a sensitive and rapid flow injection analysis (FIA) method for determination of topiramate, piracetam, and levetiracetam in pharmaceutical formulations has been investigated. The method is based on the reaction with ortho-phtalaldehyde and 2-mercaptoethanol in a basic buffer and measurement of absorbance at 295 nm under flow conditions. Variables affecting the determination such as sample injection volume, pH, ionic strength, reagent concentrations, flow rate of reagent and other FIA parameters were optimized to produce the most sensitive and reproducible results using a quarter-fraction factorial design, for five factors at two levels. Also, the method has been optimized and fully validated in terms of linearity and range, limit of detection and quantitation, precision, selectivity and accuracy. The method was successfully applied to the analysis of pharmaceutical preparations.Opisana je osjetljiva i brza protočna injekcijska analiza (FIA) za određivanje topiramata, piracetama i levetiracetama u farmaceutskim pripravcima. Metoda se temelji na reakciji ortho-ftalaldehida i 2-merkaptoetanola u bazičnom puferu i mjerenju apsorbancije na 295 nm u protočnim uvjetima. U svrhu povećanja osjetljivosti i dobivanja reproducibilnih rezultata optimirane su varijable koje utječu na određivanje kao što su volumen injektiranog uzorka, pH, ionska jakost, koncentracija reagensa, brzina protoka reagensa i drugi FIA parametri koristeći četvrt-frakcijski faktorijalni dizajn, za pet faktora na dva nivoa. Metoda je optimirana i potpuno validirana (linearnost, područje određivanja, granica detekcije i kvantifikacije, preciznost, selektivnost i točnost). Metoda je uspješno primijenjena za analizu farmaceutskih pripravaka

Hepatoprotective effects of citric acid and aspartame on carbon tetrachloride-induced hepatic damage in rats

The aim of this study was to investigate the effect of citric acid or the sweetening agent aspartame on the CCl4-induced hepatic injury in rats. Citric acid (10 mg/kg, 100 mg/kg or 1000 mg/kg), aspartame (0.625 or 1.25 mg/kg) or silymarin (25 mg/kg) was given once daily orally simultaneously with CCl4 and for one week thereafter. The administration of citric acid at 100 mg/kg or 1000 mg/kg to CCl4-treated rats reduced elevated plasma ALT by 44.1-63.3 %, AST by 47.8-70.6 %, ALP by 41.7-67.2 %, respectively compared to controls. Aspartame at 0.625 or 1.25 mg/kg reduced plasma ALT by 39.8-52.0 %, AST by 43.2-52.4 % and ALP by 50.0-68.5 %, respectively. Meanwhile, silymarin at 25 mg/kg reduced ALT, AST and ALP levels by 52.7, 62.2 and 64.7 %, respectively. On histology, citric acid at 1000 mg/kg resulted in near normalization of liver tissue. Vacuolar degeneration and necrosis were markedly reduced by 1.25 mg/kg aspartame. These results indicate that treatment with citric acid or the sweetening agent aspartame protects against hepatocellular necrosis induced by CCl4

Linking Urban Regeneration to Sustainable Urban Development of Smart Cities

Urban regeneration involves the revitalisation of distressed urban areas, through actions such as rehabilitation of historic areas, improvement of living conditions in residential districts, redevelopment of public spaces, and modernisation of urban infrastructure (Alpopi & Manole, 2013). The label 'smart city' has an impact on urban strategies in both large and small towns. It helps to face the increasing problems of urban areas, local public government, companies, non-profit organisations, and the citizens themselves. They all embraced the idea of a smarter city, using more technologies, creating better life conditions and safeguarding the environment for a better quality of life (Dameri & Rosenthal-Sabroux, 2014). This research focuses on adopting an inductive methodology of sustainable urban development in smart cities through a specific framework to be applied on the urban regeneration of city centres in cities with historical background. This will be carried out through the analysis of the interrelationship between the key principles of both urban regeneration and smart cities with the aim to compile a comprehensive list ofprinciples. This inductive methodology will be validated through a comparative study of selected relevant examples. After that the development framework will be used to apply the compiled ideas and principles, and to verify its potential to formulate multiple scenarios of urban regeneration of city centres. After that, the scenarios of development will be tested on a case study of the city of Alexandria in Egypt, by using multiple research methods such as focused interviews, structured questionnaires, personal observation and assessment. This study aims to conclude with a set of guidelines for intervention in similar urbancontexts in general, as well as in the specific case of Alexandria with its particular conditions