Polymerization and characterization of various di(pyridine)bis(trihalophenolato)cobalt(II) complexes in solid and melt states

The syntheses of distorted tetrahedral bis(pyridine)bis(trihalophenolato)cobalt(II) complexes from an aqueus solution were achieved and their characterization by FT‐IR, X‐ray, DSC, UV‐visible and elemental analysis in solid state or in melt form is reported. Polymerizations of these complexes were accomplished either at constant temperature, employing different time intervals or constant decomposition times while varying the temperature range. The slow decomposition at constant temperature leads to long chain products, whereas long chains formed at higher temperatures were during a constant time. The resulting poly(dihalophenylene oxide)s were characterized by FT‐IR, ¹H NMR, ¹³C NMR spectral analysis, differential scanning calorimetry and molecular weight determinations by viscometric method. © 2001 Society of Chemical Industry     

Effect of Er,Cr:YSGG laser surface conditioning on the adhesion of fiber- reinforced composite and zirconia intraradicular posts to the root dentin

This study evaluated the influence of Er,Cr:YSGG laser surface conditioning on push-out bond strength of different root posts to the root dentin. Extracted (N = 27, n = 9 per group) and endodontically treated human mandibular premolars were prepared to receive the posts. Three types of posts, namely quartz fiber (D), glass fiber (S), and zirconium dioxide post (C) were luted with resin cement. The posts were randomly assigned to one of the surface conditioning method: (a) No conditioning, control (L0), (b) Er,Cr:YSGG laser at 175 mJ, 3.5 W for 60 s (L1), and (c) at 225 mJ, 4.5 W for 60 s, with 60 μs pulse duration and repetition rate was 20 Hz (L2) irradiation. Six sections (two coronal, two middle, and two apical) were made in each tooth yielding to 1 mm thick specimens. The specimens were stored in distilled water at 37?°C for 24 h and push-out bond strength (MPa) was tested in a Universal Testing Machine (1 mm/min). Data were analyzed using Kruskall–Wallis and Dunns`s post hoc tests (α = 0.05). In group D, both laser treated groups (L1:16.16 ± 19.89; L2:8.24 ± 9.26) presented significantly less bond strength compared to control group (L0:28.3 ± 16.8) (p < 0.001). Mean push-out bond strength values did not significantly differ according to the root segments (coronal, middle, and apical) (p = 0.106). Application of Er,Cr:YSGG laser, with the parameters tested, did not increase the bond strength of zirconium glass fiber and zirconium oxide posts. Laser surface conditioning decreased the bond strength of quartz fiber posts in the root canal.     

Antibacterial PVP/cinnamon essential oil nanofibers by emulsion electrospinning

This study presents the production of antibacterial Polyvinylpyrrolidone/cinnamon essential oil (PVP/CEO) nanofibers by oil-in-water emulsion electrospinning, with solution properties such as GC-MS, conductivity, viscosity, and characterization using SEM (fiber morphology), FT-IR (chemical structure), UV-vis (release properties of CEO). In addition, the antimicrobial properties of the nanofibers are also investigated by the disc diffusion method (antimicrobial properties) using Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans. According to the results, the viscosity values increase with the addition of surfactant and with increased CEO concentration, but the conductivity increases until PVP1 then has decrease tendency. As concerns the fiber properties, the average fiber diameter increased with surfactant addition and CEO concentration except for PVP4. Also, the spinnability and fiber smoothness were enhanced significantly with surfactant and CEO. FT-IR analysis results verified the existence of CEO and PVP in the structure of the nanofibers. The absorbance values increased with the CEO concentration except for PVP4. Lastly, the antimicrobial results showed that 2, 3, and 4 wt% CEO concentration values are suitable for good antibacterial properties, while there is no zone formation with 1 wt% CEO concentration of PVP nanofibers. It is another important result that the antibacterial activity increases with the size of the nanofibrous material.     

Analysis of cognitive learning strategies and computer attitudes,according to college students’ gender and locus of control

This study explored variations in cognitive learning strategies and computer attitudes among college students, based on gender and locus of control. The study groups were comprised of 263 preservice teachers. The results demonstrated that the level of adherence to cognitive learning strategies on the part of female college students was significantly higher than those of male college students, especially in terms of memorization, analytical, and explanation. This study found that college students’ gender has an effect on cognitive learning strategies and computer attitudes. In terms of locus of control, college students’ cognitive learning strategies and computer attitudes were found statistically significant in the following levels: small in application, small in memorization, weaker in analytical, small in summarization, small in rehearsal, weaker in explanation, and small in computer attitude. Observance of cognitive learning strategies was found to be significantly higher for college students with internal locus of control than for those with external locus of control in terms of summarization and rehearsal.