Understanding interactions in face-to-face and remote undergraduate science laboratories

This paper reviews the ways in which interactions have been studied, and the findings of such studies, in science education in both face-to-face and remote laboratories. Guided by a systematic selection process, 27 directly relevant articles were analysed based on three categories: the instruments used for measuring interactions, the research findings on student interactions, and the theoretical frameworks used in the studies of student interactions. In face-to-face laboratories, instruments for measuring interactions and the characterisation of the nature of interactions were prominent. For remote laboratories, the analysis of direct interactions was found to be lacking. Instead, studies of remote laboratories were mainly concerned with their practical scope. In addition, it is found that only a limited number of theoretical frameworks have been developed and applied in the research design. Existent theories are summarised and possible theoretical frameworks that may be implemented in studies of interactions in undergraduate laboratories are proposed. Finally, future directions for research on the interrelationship between student interactions and laboratory learning are suggested

Vibrio cholerae strains with inactivated cqsS gene overproduce autoinducer-2 which enhances resuscitation of dormant environmental V. cholerae.

BACKGROUND: Toxigenic Vibrio cholerae resides in aquatic reservoirs of cholera-endemic areas mostly in a dormant form known as conditionally viable environmental cells (CVEC) in which the bacteria remain embedded in an exopolysaccharide matrix, and fail to grow in routine bacteriological culture. The CVEC can be resuscitated by supplementing culture media with either of two autoinducers CAI-1 and AI-2, which are signal molecules controlling quorum sensing, a regulatory network of bacterial gene expression dependent on cell density. This study investigated possible existence of variant strains that overproduce AIs, sufficient to resuscitate CVEC in environmental waters. METHODS: Environmental V. cholerae isolates and Tn insertion mutants of a V. cholerae strain C6706 were screened for production of AIs using bioluminescent reporter strains. Relevant mutations in environmental strains which overproduced AI-2 were characterized by nucleotide sequencing and genetic complementation studies. Effect of AIs produced in culture supernatants of relevant strains on reactivation of CVEC in water was determined by resuscitation assays. RESULTS: Two of 54 environmental V. cholerae isolates were found to overproduce AI-2. Screening of a Tn-insertion library of V. cholerae strain C6706, identified a mutant which overproduced AI-2, and carried Tn insertion in the cqsS gene. Nucleotide sequencing also revealed mutations inactivating the cqsS gene in environmental isolates which overproduced AI-2, and this property was reversed when complemented with a wild type cqsS gene. Culture of river water samples supplemented with spent medium of these mutants resuscitated dormant V. cholerae cells in water. SIGNIFICANCE: V. cholerae strains with inactivated cqsS gene may offer a convenient source of AI-2 in enhanced assays for monitoring bacteriological quality of water. The results also suggest a potential role of naturally occurring cqsS mutants in the environmental biology of V. cholerae. Furthermore, similar phenomenon may have relevance in the ecology of other waterborne bacterial pathogens beyond V. cholerae

Evaluation of oxygenated n-butanol-biodiesel blends along with ethyl hexyl nitrate as cetane improver on diesel engine attributes

In the present investigation, an attempt has been made to study the fuel properties, engine performance and emission of a diesel engine by mixing ethyl hexyl nitrate (EHN) with n-butanol-diesel-biodiesel blends. The engine test was carried out at full throttle opening in a single cylinder direct injection diesel engine. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis was done to evaluate the thermal properties of the test fuels. Experimental results revealed that the density, viscosity, and other properties are developed well. Notably, the cetane number of the blends increased 4.74% to 11.82% are promising. Alcohol along with cetane improver make the diesel-biodiesel blends thermally more strong. Moreover, introducing the EHN in the blends increased the carbon monoxide (CO) up to 16.64%, hydrocarbon (HC) emissions up to 27.46%, brake power (BP) up to 5.62% and brake thermal efficiency (BTE) up to 2.5% compared to the n-butanol added biodiesel blends. On the other hand, the brake specific fuel consumption (BSFC), nitric oxide (NO) and smoke reduced from 1.44% to 2.8%, 2.53% to 5.27% and 7.08% to 14.11% respectively with the addition of EHN into the n-butanol mixed biodiesel blends. Hence it can be concluded that the addition of cetane improver to oxygenated alcohol treated biodiesel blends is well efficient for a diesel engine

Experimental assessment of non-edible candlenut biodiesel and its blend characteristics as diesel engine fuel.

Exploring new renewable energy sources as a substitute of petroleum reserves is necessary due to fulfilling the oncoming energy needs for industry and transportation systems. In this quest, a lot of research is going on to expose different kinds of new biodiesel sources. The non-edible oil from candlenut possesses the potential as a feedstock for biodiesel production. The present study aims to produce biodiesel from crude candlenut oil by using two-step transesterification process, and 10%, 20%, and 30% of biodiesel were mixed with diesel fuel as test blends for engine testing. Fourier transform infrared (FTIR) and gas chromatography (GC) were performed and analyzed to characterize the biodiesel. Also, the fuel properties of biodiesel and its blends were measured and compared with the specified standards. The thermal stability of the fuel blends was measured by thermogravimetric analysis (TGA) and differential scan calorimetry (DSC) analysis. Engine characteristics were measured in a Yanmar TF120M single cylinder direct injection (DI) diesel engine. Biodiesel produced from candlenut oil contained 15% free fatty acid (FFA), and two-step esterification and transesterification were used. FTIR and GC remarked the biodiesels' existing functional groups and fatty acid methyl ester (FAME) composition. The thermal analysis of the biodiesel blends certified about the blends' stability regarding thermal degradation, melting and crystallization temperature, oxidative temperature, and storage stability. The brake power (BP), brake specific fuel consumption (BSFC), and brake thermal efficiency (BTE) of the biodiesel blends decreased slightly with an increasing pattern of nitric oxide (NO) emission. However, the hydrocarbon (HC) and carbon monoxides (CO) of biodiesel blends were found decreased

Multi-Color Excitonic Emissions in Chemical Dip-Coated Organolead Mixed-Halide Perovskite

© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Organolead mixed-halide perovskites capable of emitting multiple colors not only allow the fabrication of compact devices but also improves the functionality of light emitting devices beyond conventional displays. Here we demonstrate a cost-effective chemical dip-coating technique to grow highly reproducible methylammonium-lead-halide perovskite film, which exhibits highly efficient multi-color emissions of red, green and ultraviolet. The power- and temperature-resolved cathodoluminescence analyses reveal that these emissions are attributed to localized excitions with thermal activation energies of 27, 29 and 57 meV. The non-linear fitting of these emission band widths within the frame work of Boson model reveals that excitons are strongly coupled to the lattice with energy of 28 meV, which is consistent with the Raman measurement. This work presents an effective method for the deposition of high-quality and large-area perovskite film, which could be useful for high-performance multi-color display devices

Indigenous people's responses to drought in northwest Bangladesh

Bangladesh is highly disaster-prone, with drought being a major hazard which significantly impacts water, food, health, livelihoods, and migration. In seeking to reduce drought vulnerabilities and impacts while improving responses, existing literature pays limited attention to community-level views and actions. This paper aims to contribute to filling in this gap by examining how an indigenous group, the Santal in Bangladesh’s northwest, responds to drought through local strategies related to water, food, and migration which in turn impact health and livelihoods. A combination of quantitative data through a household survey and qualitative data through participatory rural appraisal is used. The results suggest that the Santal people have developed and applied varied mechanisms for themselves to respond to drought. The categories of responses found are water collection and storage, crop and livestock selection, and migration. These responses might not be enough to deal with continuing droughts, yielding lessons for Bangladesh and beyond