What are tutors' perceptions of an online tutoring project-Digital Learning Companion-During the COVID-19 pandemic? A case study in Taiwan.

The COVID-19 outbreak has had serious impact on remote education and service-learning implementation in Taiwan. To alleviate these impacts, the Digital Learning Companion, an online tutoring project, was proposed to bridge the digital divide and learning gap among remote children, while offering university students an online service-learning environment. This project recruited international students as tutors for local children. To explore tutors' perceptions of this project during the COVID-19 pandemic, qualitative research, particularly a case study, was conducted. Adopting purposive sampling, 15 participants were chosen for interviews at the end of the project, and 10 reflective videos were used to reveal further information to supplement the interview results. Content analysis was employed to analyse the data. The findings implied that using JoinNet and tutoring journals significantly facilitated the tutoring process, which led to tutors' remarkable development in skills, social relationships, multicultural experience, altruism, social responsibility, self-efficacy, and affective values. However, they encountered some challenges, such as technical problems, communication barrier, lack of tutee information, and short tutoring duration. The solutions to these challenges and insightful suggestions for the project development are pointed out. The results of this study contribute to tutors' cognitive, social, and motivational development, and support the online service-learning-integrated curriculum, which can become a reference for further studies regarding online service-learning implementation to bridge the research gap.

Solution Equilibrium Study of Divalent Metal Ions with Phenylpropanoid Derivatives and Acetylcysteine Ligands.

Solution equilibrium of divalent metal ions (M=Mn2+, Co2+, Ni2+, Cu2+ and Zn2+) with caffeic acid (ligand C) or dihydrocaffeic acid (ligand D) in binary system, and with acetylcysteine (ligand N) in ternary system were investigated at condition similar to human physiological temperature of 310.15 K and ionic strength of 0.15 mol·dm-3 NaCl. Potentiometry technique was used for the determination of formation constant (log ß) assisted by spectrophotometry technique. The results indicated the formation of [ML], [MLH], [ML2], [ML2H] in binary species and [MLN], [MNLH], [MNLH2] in ternary species, where L represents ligands C or D. It was found that ligand D formed more stable complexes than that of ligand C, which were affected by the presence of double bond in the carboxylate moiety of ligand C. The speciation diagrams were simulated by HySS and discussed briefly, additionally the tendency of ternary complexes was evaluated from parameters Δ log KM and log X.

Facile synthesis of superparamagnetic thiamine/Fe3O4 with enhanced adsorptivity toward divalent copper ions.

The development of environmentally friendly adsorbents has been extensively carried out to overcome the detrimental effects of heavy metal accumulation, which has persistently become a global ecological problem. In pursuit of generating eco-friendly adsorbents, a green method for synthesizing thiamine functionalized-Fe3O4 (FT) was developed in this study. A one-step chemical oxidation and functionalization technique was used to prepare FT using the ammonia-containing solvent. A molar ratio of ammonia:Fe:thiamine of 15:1:1 was shown to produce FT15 with high yield, adsorptivity, and purity. XRD, XPS, FTIR, SEM, and SQUID characterization of FT15 revealed the formation of superparamagnetic thiamine functionalized Fe3O4 in their particles. This superparamagneticity facilitates the easy recovery of FT15 particles from the waste-containing solution by using an external magnetic force. The batch adsorption of Cu(II) onto FT15 showed the best fit with the Sips adsorption isotherm model with a maximum adsorption capacity of 426.076 mg g-1, which is 5.69-fold higher capacity than the control unmodified Fe3O4 (F15). After five adsorption-desorption cycles, the FT15 can maintain up to 1.95-fold higher capacity than the freshly synthesized F15. Observation on the physicochemical properties of the post-adsorption materials showed the contribution of an amine group, pyrimidine ring, and the thiazolium group of thiamine in boosting its adsorption capacity. This study provides important findings to advance the adsorptivity of magnetic adsorbents with promising recoverability from aqueous solution by employing naturally available and environmentally friendly compounds such as thiamine.

Evaluation of silicone hydrogel contact lenses based on poly(dimethylsiloxane) dialkanol and hydrophilic polymers.

Silicone hydrogel lenses were prepared by copolymerizing PDMS-PEGMA macromer (PGP) with various combinations of DMA, NVP, and PEGMA through UV initiated polymerization process. The resultant PGP macromer were characterized by gel permeation chromatography (GPC), and scanning electron microscope (SEM-EDS). Characterization of all the resultant co-polymers included Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), equilibrium water content (EWC), oxygen permeability (Dk), optical transparency, contact angle, mechanical properties, zeta potential, protein deposition, and cytotoxicity. The results show that higher content of hydrophilic polymers increased water uptake ability as well as improved hydrophilicity and modulus of silicone hydrogel lenses; however, oxygen permeability decreased with the decrease of PDMS content (145 barrers of PGP to 37 barrers of DP0). In addition, these silicone hydrogel lenses exhibited relatively optical transparency, anti-protein deposition, and non-cytotoxic according to an in vitro L929 fibroblast assay. Therefore, these silicone hydrogel polymers would be applicable for making contact lens.

TiO2/guar gum hydrogel composite for adsorption and photodegradation of methylene blue.

The development of porous adsorbent materials from renewable resources for water and wastewater treatment has received considerable interest from academia and industry. This work aims to synthesize composite hydrogel from the combination of guar gum (a neutral galactomannan polysaccharide) and TiO2. The TiO2-embedded guar gum hydrogel (TiO2@GGH) was utilized to remove methylene blue through adsorption and photodegradation. The presence of TiO2 particles in the hydrogel matrix (TiO2@GGH) was confirmed by scanning electron microscopy-energy dispersive X-ray and X-ray photoelectron spectroscopy analysis. The mercury intrusion and N2 sorption isotherm indicate the macroporous structure of the TiO2@GGH composite, showing the presence of pore sizes ~420 µm. The dye removal efficiency of the GGH and TiO2@GGH was evaluated in batch mode at ambient temperature under varying pH. The effect of UV radiation on the dye removal efficiency was also assessed. The results demonstrated that the highest dye removal was recorded at pH 10, with the equilibrium condition achieved within 5 h. UV radiation was shown to enhance dye removal. The maximum adsorption capacity of TiO2@GGH is 198.61 mg g-1, while GGH sorbent is 188.53 mg g-1. The results imply that UV radiation gives rise to the photodegradation effect.

One-step synthesis of nitrogen-grafted copper-gallic acid for enhanced methylene blue removal.

Nitrogen-grafting through the addition of glycine (Gly) was performed on a metal- phenolic network (MPN) of copper (Cu2+) and gallic acid (GA) to increase its adsorption capacity. Herein, we reported a one-step synthesis method of MPN, which was developed according to the metal-ligand complexation principle. The nitrogen grafted CuGA (Ng-CuGA) MPN was obtained by reacting Cu2+, GA, and Gly in an aqueous solution at a molar ratio of 1:1:1 and a pH of 8. Several physicochemical measurements, such as Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), N2 sorption, X-ray diffraction (XRD), and thermal gravimetry analysis (TGA), were done on Ng-CuGA to elucidate its characteristics. The analysis revealed that the Ng-CuGA has non-uniform spherical shaped morphology with a pore volume of 0.56 cc/g, a pore size of 23.25 nm, and thermal stability up to 205 °C. The applicational potential of the Ng-CuGA was determined based on its adsorption capacity against methylene blue (MB). The Ng-CuGA was able to adsorb 190.81 mg MB per g adsorbent at a pH of 6 and temperature of 30 °C, which is 1.53 times higher than the non-grafted CuGA. Detailed assessment of Ng-CuGA adsorption properties revealed their pH- and temperature-dependent nature. The adsorption capacity and affinity were found to decrease at a higher temperature, demonstrating the exothermic adsorption behavior.

Aqueous synthesis of highly adsorptive copper-gallic acid metal-organic framework.

A greener route to synthesize mesoporous copper-gallic acid metal-organic framework (CuGA MOF) than the conventional method using harmful DMF solvent was proposed in this study. Various synthesis attempts were conducted by modifying the synthesis conditions to produce CuGA MOF with comparable physical properties to a reference material (DMF-synthesized CuGA NMOF). The independent variables investigated include the molar ratio of NaOH to GA (1.1 to 4.4) and the synthesis temperature (30, 60, 90 °C). It was found that proper NaOH addition was crucial for suppressing the generation of copper oxide while maximizing the formation of CuGA MOF. On the other hand, the reaction temperature mainly affected the stability and adsorption potential of CuGA MOF. Reacting Cu, GA, and NaOH at a molar ratio of 1:1:2.2 and a temperature of 90 °C, produced mesoporous MOF (CuGA 90-2.2) with a surface area of 198.22 m2/g, a pore diameter of 8.6 nm, and a thermal stability of 219 °C. This MOF exhibited an excellent adsorption capacity for the removal of methylene blue (124.64 mg/g) and congo red (344.54 mg/g). The potential usage of CuGA 90-2.2 as a reusable adsorbent was demonstrated by its high adsorption efficiency (> 90%) after 5 adsorption-desorption cycles.

Transesterification of activated sludge in subcritical solvent mixture.

Most previous studies reported in literature on biodiesel production from sludge were performed by acid catalyzed transesterification that required long reaction time (about 24h) and high methanol loading. The objective of this study was to investigate the in situ transesterification of sludge in subcritical mixture of methanol and acetic acid. At 250°C and a solvent (85% methanol and 15% acetic acid) to sludge ratio of 5 (mLg(-1)), a FAME yield of 30.11% can be achieved in 30min, compared to the yield of 35% obtained by the acid-catalyzed (4% H2SO4) transesterification which required 24h at 55°C and a methanol to sludge ratio of 25 (mLg(-1)). The method developed in this study avoided using mineral acid, significantly reduced reaction time and methanol loading to achieve comparable FAME yield.

Effect of extraction solvent on total phenol content, total flavonoid content, and antioxidant activity of Limnophila aromatica.

Limnophila aromatica is commonly used as a spice and a medicinal herb in Southeast Asia. In this study, water and various concentrations (50%, 75%, and 100%) of methanol, ethanol, and acetone in water were used as solvent in the extraction of L. aromatica. The antioxidant activity, total phenolic content, and total flavonoid content of the freeze-dried L. aromatica extracts were investigated using various in vitro assays. The extract obtained by 100% ethanol showed the highest total antioxidant activity, reducing power and DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity. The same extract also exhibited the highest phenolic content (40.5 mg gallic acid equivalent/g of defatted L. aromatica) and the highest flavonoid content (31.11 mg quercetin equivalent/g of defatted L. aromatica). The highest extraction yield was obtained by using 50% aqueous acetone. These results indicate that L. aromatica can be used in dietary applications with a potential to reduce oxidative stress.

Impact of pretreatments on morphology and enzymatic saccharification of shedding bark of Melaleuca leucadendron.

The effects of subcritical water (SCW) and dilute acid pretreatments on the shedding bark of Melaleuca leucadendron (paper bark tree, PBT) biomass morphology, crystallinity index (CrI) and enzymatic saccharification were studied. The morphology of PBT bark was characterized by X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy. SCW pretreatment mainly extracted amorphous parts of the biomass hence its CrI increased, partial decrystallization of cellulose and exposing of intact nanofibers of cellulose were observed for SCW pretreatment at 180°C. On the other hand, dilute acid pretreatment at 160°C exhibited a large decrease in CrI, an increase in surface area, a decrease in lignin content and decrystallization of cellulose as well as the peel-off and degradation of some nanofiber bundles. Dilute acid and SCW pretreatments of PBT biomass resulted in about 4.5 fold enhancement in glucose release relative to the untreated one.

Catalyst-free fatty acid methyl ester production from wet activated sludge under subcritical water and methanol condition.

Wet activated sludge was converted directly into biodiesel using water as hydrolysis reagent to enhance the extraction of lipid in activated sludge, and as catalyst for the conversion of neutral lipids into biodiesel under subcritical conditions. At 175°C, 3.5MPa, a methanol to sludge ratio of 30 (mL/g) and a sludge water content of 84wt.%, about 90% conversion to fatty acid methyl esters was achieved within 24h without the need for conventional catalysts such as KOH and H(2)SO(4). Since water is employed as a catalyst, its removal is not required; therefore, the processing costs for producing biodiesel from activated sludge are reduced. The method has the potential for applications to other feedstock with high water contents such as micro-algae.