Massive Open Online Courses (MOOCs) have recently experienced rapid development and garnered significant attention from various populations. Despite the wide recognition of MOOCs as an important opportunity within educational practices, there are still many questions as to how we might satisfy students' needs, as evidenced by very high dropout rates. Researchers lack a solid understanding of what student needs are being addressed by MOOCs, and how well MOOCs now address (or fail to address) these needs. To help in building such an understanding, we conducted in-depth interviews probing student motivations, learning perceptions and experiences towards MOOCs, paying special attention to the MOOC affordances and experiences that might lead to high drop rates. Our study identified learning motivations, learning patterns, and a number of factors that appear to influence student retention. We proposed that the issue of retention should be addressed from two perspectives: retention as a problem but also retention as an opportunity.
Active drug efflux by the adenosine triphosphate-binding cassette (ABC) transporter ABCG2 is one of the common mechanisms causing multiple drug resistance in various human cancers. In the intrinsic drug resistance of hepatocellular carcinoma (HCC), the role of ABCG2 is closely associated with 'side population (SP)', a minor subset of cancer stem-like cells with unique capacity to extrude lipophilic dye Hoechst 33342 and many chemotherapeutic agents. In this study, we showed that ABCG2 was intrinsically expressed in a subgroup of HCC tissues and its expression pattern significantly influenced the levels of drug efflux from HCC cell lines. In MHCC-97L HCC cell line with intrinsic ABCG2 expression, we confirmed the importance of SP cells to the drug efflux-related chemotherapy resistance and found that the SP analysis provided an efficient method to evaluate the functional activity of ABCG2 transporter. In this cell line, we discovered that the SP proportion was modulated by the treatments of Akt signaling inhibitors and serum supplement, which led to the finding that Akt signaling was able to regulate the SP cells' efflux activity via altering the subcellular localization of ABCG2 transporter. We further demonstrated that the Akt signaling inhibition attenuated the doxorubicin efflux from MHCC-97L cells and increased the drug efficacy. Our results indicate the protective role of intrinsic ABCG2 expression in HCC cells and suggest that suppressing Akt signaling could help overcome the drug efflux by ABCG2 transporter.
Well-defined manganese complexes based on inexpensive, readily available ligands, 2,2':6',2''-terpyridine and its derivatives have been prepared and employed for the selective hydroboration of alkenes, ketones and aldehydes. Highly Markovnikov regioselective hydroboration of styrenes as well as excellent chemoselective hydroboration of ketones over alkenes were achieved, for the first time, by an earth-abundant manganese catalyst.
An ionic cobalt-PNP complex is developed for the efficient α-alkylation of ketones with primary alcohols for the first time. A broad range of ketone and alcohol substrates were employed, leading to the isolation of alkylated ketones with yields up to 98%. The method was successfully applied to the greener synthesis of quinoline derivatives while using 2-aminobenzyl alcohol as an alkylating reagent.
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