Poly (hydroxyethyl methacrylate-glycidyl methacrylate) films modified with different functional groups: In vitro interactions with platelets and rat stem cells

Copolymerization of 2-hydroxyethylmethacrylate (HEMA) with glycidylmethacrylate (GMA) in the presence of α-α′-azoisobisbutyronitrile (AIBN) resulted in the formation of hydrogel films carrying reactive epoxy groups. Thirteen kinds of different molecules with pendant NH₂ group were used for modifications of the p(HEMA-GMA) films. The NH₂ group served as anchor binding site for immobilization of functional groups on the hydrogel film via direct epoxy ring opening reaction. The modified hydrogel films were characterized by FTIR, and contact angle studies. In addition, mechanical properties of the hydrogel films were studied, and modified hydrogel films showed improved mechanical properties compared with the non-modified film, but they are less elastic than the non-modified film. The biological activities of these films such as platelet adhesion, red blood cells hemolysis, and swelling behavior were studied. The effect of modified hydrogel films, including NH₂, (using different aliphatic CH₂ chain lengths) CH₃, SO₃H, aromatic groups with substituted OH and COOH groups, and amino acids were also investigated on the adhesion, morphology and survival of rat mesenchymal stem cells (MSCs). The MTT colorimetric assay reveals that the p(HEMA-GMA)-GA-AB, p(HEMA-GMA)-GA-Phe, p(HEMA-GMA)-GA-Trp, p(HEMA-GMA)-GA-Glu formulations have an excellent biocompatibility to promote the cell adhesion and growth. We anticipate that the fabricated p(HEMA-GMA) based hydrogel films with controllable surface chemistry and good stable swelling ratio may find extensive applications in future development of tissue engineering scaffold materials, and in various biotechnological areas.     

Determination of textural deterioration in fish meat processed with electrospun nanofibers

Nano-applications are named as one of the novel methods, which provide many advantages like a larger contact area on the surface of fish fillets with less material. The goal of the study was to reveal the textural profile changes correlated with TPB growth of fish fillets coated with nanofibers having 2.47 ± 0.68 mV zeta potential value and 172 nm diameter. The difference of TPB count between control (CS) and the fish fillets treated with nanofibers (NG) reached 3.45 log CFU/g (p < .05) on the sixth day. The hardness value of CS was decreased (p < .05) (the decline: 68%) while the hardness of NG was found to be much more stable (the change: 42%). The highest change in springiness for CS and NG samples was determined as ~24 and ~15%, respectively, for 12 days. Cohesiveness values of CS were slightly increased, but those of the fish fillets coated with nanofibers were remarkably decreased. The coefficient of correlation analysis between TPB count and cohesiveness values was determined as “r = −.026 and r = .796” for CS and NG, respectively. Chewiness values of CS were significantly decreased (p < .05). However, chewiness values of the fish fillets coated with nanofibers were found as much more stable (p > .05). The results revealed that nanofiber coating limited the increase of TPB in fish fillets; it also better kept the textural profile of fish fillets as compared to CS stored at 4°C. The study could play a guiding role in further food nanotechnology applications in the industry and food science.     

Effect of microstructure on internal friction and Young's modulus of aged Cu–Be alloy

This study is intended to determine the effect of microstructure on internal friction and Young's modulus as a function of stress in the elastic region of an aged Cu–Be alloy and to investigate the influence of transformed phases caused by precipitation hardening on both properties. Results show that internal friction and Young's modulus were influenced by different precipitates. Transformed phases and micromechanical mechanisms could be responsible for the changes in internal friction and Young's modulus. The microstructure of the alloy having Guinier–Preston zones appears to have low internal friction and dependence on stress after aging at 315 °C for 2 h. The Young's moduli of the long-term aged samples increased by approximately 2 GPa compared to that for the short-term aged samples and elastic instability up to a stress of 20% of the yield strength was observed.     

Preparation of low cost activated carbons from various biomasses with microwave energy

Activated carbons are generated from various waste biomass sources such as waste tea, almond shells, tomato stems and leaves. Porous materials were prepared with phosphoric acids activation by microwave energy in a covered Teflon reactor for 1, 2, 3, and 4?min. The activated carbons were characterised in terms of surface area, pore size distribution, pore volume, FTIR analysis. The highest surface areas were obtained using almond shells (1,002?m²/g), waste tea (702?m²/g), tomato stems (813?m²/g) and tomato leaves (117?m²/g), respectively. The type of the raw material has significant effects on the characteristics of the final product. It was shown that porous carbons with high surface area could be prepared by short microwave radiation periods such as 2?C3?min.     

Arsenite removal from groundwater in a batch electrocoagulation process: Optimization through response surface methodology

In this study, influences of seven process variables such as initial pH (pH_i), applied current (i), operating time (t_EC), initial As(III) concentration (C_o), diameter of Fe ball anode (d_p), column height in the electrocoagulation (EC) reactor (h) and airflow rate (Q_air) for removal of As(III) from groundwater by a new air-fed fixed-bed EC reactor were evaluated with a response surface methodology (RSM). The proposed quadratic model fitted very well with the experimental data for the responses. The removal efficiencies and operating costs were determined to be 99% and 0.01 $/m³ at the optimum operating conditions (a pH_i of 8.5, 0.05 A, 4.94 min, d_p of 9.24 mm, h of 7.49 cm, Q_air of 9.98 L/min for 50 µg/L). This study clearly showed that the RSM in the EC process was a very suitable method to optimize the operating conditions at the target value of effluent As(III) concentration (10 µg/L) while keeping the operating cost to minimal and maximize the removal efficiency.     

Enhancement of direct methanol fuel cell performance through the inclusion of zirconium phosphate

Nafion/zirconium hydrogen phosphate (ZrP) composite membranes containing 2.5 wt.% ZrP (NZ-2.5) or 5 wt.% ZrP (NZ-5) were prepared to improve the performance of a direct methanol fuel cell (DMFC). The influence of ZrP content on the Nafion matrix is assessed through characterization techniques, such as Thermogravimetric Analysis (TGA), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Electrochemical Impedance Spectroscopy (EIS), and water uptake measurement. Performance testings of the DMFCs based on these composite membranes as well as commercial Nafion^® 115 membrane were performed using a computer aided fuel cell test station for different values of cell temperature (40 °C, 60 °C, 80 °C, and 100 °C) and methanol concentration (0.75 M, 1.00 M, and 1.50 M). Characterization studies indicated that incorporation of ZrP into polymer matrix enhanced the water uptake and proton conductivity values of Nafion membrane. The results of the performance tests showed that the Membrane Electrode Assembly (MEA) having NZ-2.5 provided the highest performance with the peak power density of 551.52 W/m² at 100 °C and 1.00 M. Then, the performances of the MEAs having the same NZ-2.5 membrane but different cathode catalysts were investigated by fabricating two different MEAs using cathode catalysts made of Pt/C–ZrP and Pt/C (HiSPEC^® 9100). According to the results of these experiments, the MEA having NZ-2.5 membrane and Pt/C (HiSPEC^® 9100) cathode catalyst containing 10 wt.% of ZrP exhibited the highest performance with the peak power density of 620.88 W/m² at 100 °C and 1.00 M. In addition, short-term stability tests were conducted for all the MEAs. The results of the stability tests revealed that introduction of ZrP to commercial (HiSPEC^® 9100) cathode catalyst improves its stability characteristics.     

A novel method for production of activated carbon from waste tea by chemical activation with microwave energy

This study presents the production of activated carbon from waste tea. Activated carbons were prepared by phosphoric acid activation with and without microwave treatment and carbonisation of the waste tea under nitrogen atmosphere at various temperatures and different phosphoric acid/precursor impregnation ratios. The surface properties of the activated carbons were investigated by elemental analysis, BET surface area, SEM, FTIR. Prior to heat treatment conducted in a furnace, the mixture of the waste tea and H₃PO₄ was treated with microwave heating. The maximum BET surface area was 1157 m²/g for the sample treated with microwave energy and then carbonised at 350 °C. In case of application of conventional method, the BET surface area of the resultant material was 928.8 m²/g using the same precursor and conditions. According to the Dubinin–Radushkevich (DR) method the micropore surface area for the sample treated with microwave energy was higher than the sample obtained from the conventional method. Results show that microwave heating reasonably influenced the micropore surface area of the samples as well as the BET surface area.The samples activated were also characterised in terms of the cumulative pore and micropore volumes according to the BJH, DR and t-methods, respectively.