Performance of Silicotungstic Acid Incorporated Mesoporous Catalyst in Direct Synthesis of Dimethyl Ether from Syngas in the Presence and Absence of CO2

Dimethyl ether (DME), which is an excellent green diesel fuel alternate, is synthesized following a direct synthesis route from synthesis gas, by using a bi-functional catalyst mixture, which was composed of a silicotungstic acid incorporated mesoporous catalyst [TRC-75(L)] and a commercial Cu–Zn based catalyst. Higher DME selectivity values were obtained by using TRC-75(L), than commercial γ-alumina at 50 bars. Presence of CO₂ in the feed stream caused significant enhancement in DME selectivity. Results showed that DME selectivity of about 0.85 was obtained in a temperature range 250–275 °C in the presence of 10 % CO₂. In fact, CO₂ was also used as a resource to produce DME at lower temperatures. Reverse dry reforming and ethanol formation reactions were observed as side reactions, especially at higher temperatures. Results also proved that direct synthesis of DME from syngas has major CO conversion and DME selectivity advantages over the two step process involving consecutive methanol synthesis and dehydration steps.     

The effects of water flow rate on shear bond strength of self etch resin cement to dentin surface after Er,Cr:YSGG laser etching

The aim of the present study was to evaluate the effect of water flow rate on the morphological features of dentin and shear bond strength (SBS) of self-etching resin cement after Er,Cr:YSGG laser etching. Dentin specimens obtained from extracted human third molars were randomly assigned to four groups (n = 23), including one that received no laser irradiation (control-group D) and three others with different laser parameters: 2.25 W, 50 Hz, 60% air with water flow rates of 19 mL/min-100% water (group A), 2.25 W, 50 Hz, 6.75 mL/min-50% water (group B), and 2.25 W, and 50 Hz, 2.75 mL/min-25% water (group C). The morphological features of each group were examined with scanning electron microscopy and atomic force microscopy. The SBS of resin cement disks (Panavia F2.0, Kuraray; Tokyo, Japan) (3 mm in diameter and 2 mm in height) to the dentin specimens was measured using a universal testing machine at a cross head speed of 0.5 mm/min. Bond strength values were analyzed with one-way ANOVA/Tukey tests. There were no significant differences between the SBS values of groups A and B (p > 0.05). However, the SBS values of these groups were significantly higher when compared to groups C and D (p < 0.001). Er,Cr:YSGG laser application with water flow rates of 6.75 or 19 mL/min resulted in better dentin surface alterations and increased the SBS of self-etching resin cement to dentin.     

A high pressure ignition delay time study of 2-methylfuran and tetrahydrofuran in shock tubes

Ignition delay time studies for tetrahydrofuran (THF) and 2-methylfuran (2MF) as well as optical investigations of combustion for 2MF have been carried out using two shock tubes. The experiments with undiluted THF/air mixtures were performed at 20 and 40 bar in a high pressure shock tube (HPST) at an equivalence ratio of Ф = 1 covering an overall temperature range of 780–1100 K and 691–1006 K, respectively. Undiluted 2MF/air mixtures (Ф = 1) were also investigated in the HPST at 40 bar in the temperature range of 820–1215 K. The experimental data of 2MF obtained at 40 bar were supported with kinetic simulations of existing models from literature. Additionally, sensitivity analyses of 2MF at several temperatures were performed for finding out the most sensitive reactions. Schlieren imaging was employed in a rectangular shock tube (RST) utilizing a high speed video camera through which the ignition process was captured for a stoichiometric 2MF/O₂/Ar mixture at pressures of about 10 bar and in the temperature range of 871–1098 K.     

Growth and development impact of sustainable nutrition education: An experimental study

Healthy societies are formed by learning and maintaining sustainable healthy eating behaviors from childhood. The aim of this study was to determine the effect of short-term sustainable nutrition education on growth and development parameters of preschool children. This study is an experimental design with pretest–posttest control group. This study was carried out in two kindergartens between February 2022 and June 2023 in Turkey. The education group received 4 months of dietary behavior training. The dietary scale and anthropometric measurements were administered at the first and last meetings. Data were analyzed with 95% confidence interval. The study was completed with 174 children. A statistically significant difference was found, especially in body weight (p < 0.05) and body weight percentile values (p < 0.05) in the posttest of the education group. A statistically significant difference (p < 0.05) was found between the groups in the eating behavior scale posttest score. Nutrition education in schools is important in promoting healthy eating habits. Nutrition education improves eating behavior positively. To maintain healthy eating behaviors, however, the continuity of education is necessary. In addition, as growth and development are physical processes, it is recognized that growth and development cannot be assessed by nutrition alone.