A Study of nozzle angle in stone surface treatment with water jets

The stone surface treatment with water jet is a recently introduced method. It is used to increase the roughness to improve its antislip properties while preserving esthetic appearance of the stone without having thermal shock, mechanical stress and the production of fumes and dust. Nozzle angle is one of the important parameters affecting treatment of surface. This study is an attempt to assess the effect of nozzle angle on surface treatment quality with water jet and to determine the most suitable nozzle angle value. For this purpose, surfaces of Sardinian Basalt samples are treated with pure water jet in six different nozzle angles (15°, 30°, 45°, 60°, 75° and 90°). The roughness is measured on all the treated surfaces by various roughness parameters. The experimental studies showed that treatment with nozzle angle between 30° and 75° gives the surfaces with similar regular variation.     

Why does signaling enhance multimedia learning? Evidence from eye movements

Previous studies have suggested that signaling enhances multimedia learning. However, there is not enough evidence showing why signaling leads to better performance. The goal of this study was to examine the effects of signaling on learning outcomes and to reveal the underlying reasons for this effect by using eye movement measures. The participants were 40 undergraduate students who were presented with either signaled or nonsignaled multimedia materials. Labels in the illustration were signaled by temporarily changing the color of the items. The results suggest that the signaled group outperformed the nonsignaled group on transfer and matching tests. Eye movement data shows that signaling guided attention to relevant information and improved the efficiency and effectiveness of finding necessary information.     

Synthesis of ZnO nanoparticles by an aerosol process

Spherical nano-sized zinc oxide (ZnO) particles were produced by a spray pyrolysis method using the aerosol technique described in this study. The effects of reaction temperatures of 600, 800 and 1000 °C and collection locations of the particles, such as the flask collector and the tube exit, on the morphology and crystal structure of the ZnO particles were investigated. X-ray diffraction (XRD) studies showed that the crystallinity of the particles was increased by increasing the reaction temperature from 600 °C to 1000 °C. Fourier transform infrared spectroscopy (FTIR) measurements revealed that the particles were pure and similar to each other. Scanning electron microscopy (SEM) revealed that the synthesized nanoparticles had sizes between 200 nm and 400 nm, with uniform morphologies. A computational fluid dynamics (CFD) model of the horizontally positioned tube reactor was developed. Simulation results provided information about the residence time and the temperature distribution along the tube, which were found to be correlated to the particle morphology.     

Cross-linked electrospun polyvinyl alcohol/sodium caseinate nanofibers for antibacterial applications

In this study, the polyvinyl alcohol (PVA) and sodium caseinate (SC) nanofibers were produced by a single-fluid electrospinning method from their blends. Afterward, the cross-linking process with two different methods was applied to the PVA/SC (70/30, v/v) ratio, which was selected according to the surface and mechanical properties of the electrospun mat. In the first method, different ratios (15%, 20%, 25%, and 30%) of glutaraldehyde (GLA) cross-linking agents were added to the PVA/SC solution and then, PVA/SC/GLA nanofibers were obtained. In the second method (in-situ method), the nanofibers obtained from the PVA/SC solution were cross-linked by dipping into the cross-linking solution. After, PVA/SC/GLA/Zinc oxide nanoparticles (ZnO NP) mats were obtained by adding ZnO NP at different rates to the PVA/SC/GLA (7030-25GLA) solution, which was chosen according to the results of thermal, mechanical, and moisture test. In addition, performing tests, a cytotoxicity test for fibroblast cell line (L929), and in vitro antibacterial test for Escherichia coli and Staphylococcus aureus were also applied to them. Therefore, the usability of PVA/SC/GLA/ZnO NP nanofibers as an antibacterial effective wound dressing was investigated. Due to the high toxic effect of GLA, it was found that PVA/SC/ZnO cross-linked nanofibers are not suitable for wound dressing use. However, it was determined that the PVA/SC nanofiber cross-linked by the in-situ method had high cell viability according to the cytotoxicity test result and thus could be used as a fibroblast tissue scaffold.