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关键词： Upper-Division Undergraduate   Physical Chemistry   Distance Learning/Self Instruction   Testing/Assessment   IR Sspectroscopy   Kinetics   Quantum Chemistry   Spectroscopy   Thermodynamics   Statistical Mechanics  

摘要： A fast track into online teaching in response to the COVID-19 crisis resulted in the author learning to use online platforms and tools to teach thermodynamics and quantum mechanics courses. These resources were used effectively to teach highly mathematical and challenging concepts, as presented in this communication. Student assessment using traditional (exams) and novel (projects) approaches are highlighted, especially the use of projects that examined students ability to apply their knowledge to solve real world problems. A survey of students responses to online learning revealed that they felt supported during the COVID-19 crisis and the teaching tools described in this work were successful in helping them learn. These students who completed parts of the two courses in face-to-face classes in previous quarters overwhelmingly preferred in-person instruction. The pedagogical approaches described in the communication were shared informally with fellow science faculty at the college. They may be successful in teaching other chemistry courses and STEM fields. The author feels better prepared for teaching online in the future as a result of this teaching experience.

关键词： First-Year Undergraduate/General   Physical Chemistry   Internet/Web-Based Learning  

摘要： The COVID-19 pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has disrupted normal activities all over the world. Education at all levels has been particularly hard hit, and this has resulted in the suspension of face-to-face discourse, instruction, and student assessment worldwide, with the necessity of social distancing preventing the social gatherings common to all learning environments. This has prompted a shift to online modes of teaching and assessment, with varying degrees of success and possibly much discomfort. In this communication, reflections and comments on the results of asynchronous online assessment of physical chemistry courses at the Cave Hill campus of the University of the West Indies are presented. We hope this paper will be useful in delineating some of the challenges faced in the delivery of unsupervised online assessments, especially in situations where limited internet connectivity may disadvantage some students.

关键词： First-Year Undergraduate/General   Physical Chemistry   Internet/Web-Based Learning   Administrative Issues  

摘要： The disruptions of the COVID-19 pandemic caused academic staff from around the world to convert to online methods of teaching. At the University of Western Australia, this transition was implemented half way through semester one. This commentary provides an overview of the changes made for a physical chemistry first year unit. We provide analysis into the lessons that we learned having gone through the process and how we can use this experience to improve the unit in the future.

关键词： Upper-Division Undergraduate   Physical Chemistry   Curriculum   Internet/Web-Based Learning   Learning Theories  

摘要： This communication reports the curriculum changes and how they worked when an upper-level experimental physical chemistry course had to switch from face-to-face to online teaching within a matter of days. Although several of the learning goals of the laboratory-based course could still be met in the online environment, others required modifications in order to reduce the educational losses. The use of videos, icebreakers, homework, prelab quizzes, in-lab questions, and synchronous meetings helped to keep the students engaged and maximize the achievement of learning goals. The technology challenge when internet connections were poor was swiftly addressed by the students ching to cell phone data plans. Academic integrity was managed through the use of an open-book exam using original problems that required critical thinking and problem-solving skills rather than only regurgitation of knowledge that could be copied from textbooks or found online. Although gains were obtained through writing lab reports, solving the homework, prelab quizzes, and in-lab questions as well as generating questions about the laboratory experiments, the development of problem solving skills to address challenges during the actual instrument operation and planning and conducting an authentic research experiment were lost because instruction was not face-to-face.

关键词： First-Year Undergraduate/General   Second-Year Undergraduate   Chemical Engineering   Physical Chemistry   Surface Science   Thermodynamics   UV-vis Spectroscopy   Hands-On Learning/Manipulatives   Laboratory Instruction  

摘要： We present our experience with transferring a four-day photometry and dye-adsorption laboratory experiment to the kitchens of students of Applied Thermodynamics from our degree in "Industrial Chemical Process Engineering". The students designed and built a double-beam photometer using their smartphones and household materials, then prepared a series of dye-solutions with well-known relative concentrations and measured the absorbance concentration calibration curve. After 24 h of adsorption to kitchen absorbent paper the solutions were visibly decolored. The students were able to determine the equilibrium dye concentrations from absorbance measurements and to calculate the adsorption isotherm. This home-lab experiment allowed them to keep on track with their lessons during the severe lock down in Spain due to COVID-19. They were highly motivated and achieved the learning objectives to a similar degree as in years before with conventional lab equipment.

关键词： Detergents   Monomers   Surfmers   Extraction   Membrane proteins  

摘要： Three monomers with a maltose polar head, an alkyl hydrogenated chain, and an acrylamide-based polymerizable moiety were synthesized. The self-assembly properties in aqueous solutions of these monomers were studied by means of isothermal titration calorimetry (ITC), surface tension (SFT) measurements, and dynamic light scattering (DLS), which indicated the formation of small micellar aggregates of about 6 nm diameter. The critical micellar concentration (CMC) was found to depend on the length of the alkyl chain and on the nature of the polymerizable moiety, ranging from 0.35 mmto ca. 10 mm. The monomers were found to solubilize phospholipid vesicles and to extract a broad range of proteins fromEscherichia colimembranes. Finally, the extraction of two membrane proteins, namely, the full-length, wild-type human G-protein-coupled receptor (GPCR) adenosine A2A receptor (A(2A)R) and the bacterial transporter AcrB was demonstrated.

关键词： Cellulose  

摘要： Cellulose nanocrystals (CNCs) are bio-based rod-like nanoparticles with a quickly expanding market. Despite the fact that a variety of production routes and starting cellulose sources are employed, all industrially produced CNCs consist of cellulose I (CNC-I), the native crystalline allomorph of cellulose. Here a comparative study of the physico-chemical properties and liquid crystalline behavior of CNCs produced from cellulose II (CNC-II) and typical CNC-I is reported. CNC-I and CNC-II are isolated by sulfuric acid hydrolysis of cotton and mercerized cotton, respectively. The two allomorphs display similar surface charge densities and zeta-potentials and both have a right-handed twist, but CNC-II have a slightly smaller average length and aspect ratio, and are less hygroscopic. Interestingly, the self-assembly behavior of CNC-I and CNC-II in water is different. Whilst CNC-I forms a chiral nematic phase, CNC-II initially phase separates into an upper isotropic and a lower nematic liquid crystalline phase, before a slow reorganization into a large-pitch chiral nematic texture occurs. This is potentially caused by a combination of factors, including the inferred faster rotational diffusion of CNC-II and the different crystal structures of CNC-I and CNC-II, which are responsible for the presence and absence of a giant dipole moment, respectively.

关键词： Physicochemical properties  

摘要： High temperature is the main factor responsible for degrading the lubrication and antiwear properties of aero-lubricating oils. Accordingly, this study assessed the effects of thermal treatment of diester aviation lubricating oil and the associated mechanism. Fourier-transform infrared spectroscopy and gas chromatography/mass spectrometry analyses showed that low-molecular-weight compounds, such as monoesters, diesters, alcohols, and olefins, were the primary degradation products. An assessment of the degradation mechanism of bis(2-ethylhexyl)decanedioate showed that pyrolysis, resulting in the cleavage of beta-C-H and C-C bonds, was the main process involved. Additional investigation using advanced polymer chromatography showed that the molecular weights of oil samples changed slightly at high temperatures, while the viscosity and viscosity-temperature index values were relatively stable. High-pressure differential scanning calorimetry established that the thermal oxidation stability of these oils decreased above 250 degrees C. Finally, variations in the chemical compositions of the oil samples were found to be highly correlated with changes in physicochemical properties during thermal processing, with the formation of low-molecular-weight polar compounds greatly increasing the acid numbers of the oils.

关键词： Oreochromis niloticus   shelf life   ice storage   ozonated water   quality changes  

摘要： Quality changes in commercial-sized Nile tilapia fillets sterilized by 4.0 mg/L ozonated water for 30-min and stored in ice for 18 days were evaluated. Malondialdehyde content increased from 1.54 +/- 0.06 to 1.94 +/- 0.14 nmol/mgprot after treatment at day 18, while drip loss rate, lightness, chroma, whiteness index and whilst hue values in the treated group were significantly higher (P < .05). These changes indicated that treatment had some adverse effects on fillet quality. Total volatile basic nitrogen (TVB-N) decreased from 27.67 +/- 1.39 to 22.79 +/- 2.77 mg/100g after 18 days storage. Hardness and chewiness increased from 73.78 +/- 10.78 to 81.44 +/- 16.54 g and 45.61 +/- 14.81 to 49.85 +/- 13.52 g mm respectively by the treatment at day 0. Besides, pH showed no significant differences between both groups throughout the storage period. Based on microbiological analysis and sensory evaluation, the shelf-life of treated and control fillets was 14 and 11 days, respectively. The results of this study indicate that ozonated water treatment is effective in enhancing textural properties, reducing total viable counts and extending shelf-life during ice storage.

关键词： Sensory attributes   consumer likeness   Young's modulus   bread staling   PCA  

摘要： The aim of this work was to evaluate the physicochemical and sensory characteristics of sliced pan breads and to investigate their possible correlation. Five commercial sliced pan breads from different brands (C1-C5) were examined for four weeks. A two-way ANOVA revealed significant differences in the moisture content, Young's modulus and mean cell area among the different brands. Principal Component Analysis showed a good agreement between sensory and instrumental measurements. MaxDiff analysis revealed that the sliced pan bread of the brand C1 is considered as the most favored bread by the consumers whereas the bread of brand C2 as the least favored one.