Chitosan was chemically modified with bulky structure, cis-5-norbornene-2, 3-dicarboxylic anhydride and the characteristic of this modified chitosan was studied. The resulting material was analyzed by FTIR, TGA, DSC, XRD and SEM to study the effect of N-acylation to the polysaccharide structure. FTIR results show that the anhydride monomer was successfully bound to amine group of chitosan. Thermal analysis of the modified structure provides the chitosan fibers with thermal stability while XRD and SEM show the lost of crystallinity of modified chitosan. XRD of modified chitosan shows broader peak pattern and a considerable increase in a dimension while SEM of chitosan presented the single particle morphology while norbornene-chitosan shows aggromolarate behaviour due to the hydrophobic nature of norbornene pendant group which induced aggromolaration of the particles in modified structure.
Graphene oxide (GO) is a reliable additive used to improve the wax crystal inhibition performance of pour point depressant (PPD). In understanding the lateral size effect on wax crystal inhibition, PPD emulsions containing graphene oxide of different lateral sizes were prepared. The parameters of pour point reduction (PPR) and dissipated wax crystallisation enthalpy were considered in the assessment of wax inhibition performance. PPR was measured using a pour point tester in accordance to ASTM D-97, while the enthalpy dissipation was evaluated via differential scanning calorimetry (DSC) under cooling cycle. The study revealed that the addition of GO lowered the wax crystallisation enthalpy, as indicated by the lesser amount of precipitated wax present in the model oil. The enthalpy underwent a decrease from 25.04 to 23.97 Jg-1 with decreasing GO lateral size. It is evident from the pour point test that the use of different GO lateral sizes significantly affects the wax inhibition, as verified through the highest PPR of 10o C displayed by the EJGO5 sample (with addition of the smallest lateral size of 1 µm). In short, manipulating the GO lateral size in sonicated samples boosted the PPR up to 100% compared to the unsonicated sample (EJGO1). Furthermore, smaller lateral size provides more nucleation site for wax co-crystallisation, hence preventing the neighbouring wax crystals from attaching and forming a looser crystal structure. The thermal characteristics of the PPD emulsions were also examined through DSC technique, which revealed that the emulsions thermal properties were unaffected by the addition of GO.
This study explored the impact of online lectures that were developed using principles of cognitive load theory (CLT) and cognitive theory of multimedia learning (CTML) on health profession students' lecture comprehension, cognitive load, cognitive engagement, and intrinsic motivation in learning. A total of 215 first-year undergraduate students in medical, dentistry, and nutrition programs participated in this pre-post quasi experimental study. The students attended a typical face-to-face lecture on Day-1 of the intervention, followed by a CLT-based online lecture 8 weeks thereafter. Their comprehension of the lecture topics was measured through pre- and post-lecture assessments, and their cognitive load, cognitive engagement, and motivation were measured immediately after each lecture session. The analysis revealed that the CLT-based online lectures promoted the students' comprehension of the lecture content (p < 0.001), self-perceived learning (p < 0.001), engagement toward the learning material, and motivation to learn (p = 0.025). It was also effective at reducing the students' intrinsic and extraneous cognitive loads (p < 0.001). Hence, designing online lectures using CLT and CTML principles could be an effective method to promote students' knowledge and comprehension, cognitive engagement, and learning motivation. However, further research is needed to investigate the applicability and impact of CLT-based online lectures in non-health profession disciplines.