In 2015, 35 million learners participated online in 4,200 MOOCs organised by over 500 universities. Learning designers orchestrate MOOC content to engage learners at scale and retain interest by carefully mixing videos, lectures, readings, quizzes, and discussions. Universally, far fewer people actually participate in MOOCs than originally sign up with a steady attrition as courses progress. Studies have correlated social engagement to completion rates. The FutureLearn MOOC platform specifically provides opportunities to share opinions and to reflect by posting comments, replying, or following discussion threads. This paper investigates learners' social behaviours in MOOCs and the impact of engagement on course completion. A preliminary study suggested that dropout rates will be lower when learners engage in repeated and frequent social interactions. We subsequently reviewed the literature of prediction models and applied social network analysis techniques to characterise participants' online interactions examining implications for participant achievements. We analysed discussions in an eight week FutureLearn MOOC, with 9855 enrolled learners. Findings indicate that if learners starts following some , the probability of their finishing the course is increased; if learners also interact with those they follow, they are highly likely to complete, both important factors to add to the prediction of completion model.

It seems self-evident that life for teachers would be simplified if there existed a large corpus of relevant resources that was available for them to reuse and for inquisitive students to download. The learning object community has worked for the past decade and more to provide the necessary infrastructure, standards, and specifications to facilitate such beneficial activity, but the take-up has been disappointingly small, particularly in University and Higher Education, which is the subject of this research. The problem has been that practitioners have not deposited their teaching resources, or have not made them openly available, in the quantity that would achieve critical mass for uptake. EdShare and the Language Box are two initiatives that have concentrated on the issue of facilitating and improving the practice of sharing, the former in an institutional setting and the latter in a subject community of practice. This paper describes and analyzes the motivations for these projects, the design decisions they took in implementing their repositories, the approaches they took to change agency and practice within their communities, and the changes, in practice, that have so far been observed. The contribution of this paper is an improved understanding of how to encourage educational communities to share.

Conversion of Candida albicans from yeast to mycelial growth is believed to be associated with the organism's virulence. We investigated the role of mammalian hormones in initiating this transformation. Three clinical isolates of Candida albicans were tested for their ability to produce germ tubes under various conditions. Controlled hormonal conditions were provided by stripping rabbit serum with activated charcoal. Steroid compounds under investigation were added back to the stripped serum and yeast were inoculated into the test materials. Microscopic counts of germinated versus ungerminated cells were used as an indicator of morphogenic transformation. The percent of yeast cells germinating was profoundly reduced in stripped compared to unstripped serum. The addition of 1 microM estradiol, cholesterol or testosterone only slightly increased levels of germination above that seen in controls. Estradiol at concentrations 100 times less, however, proved a strong inducer of germination. Cholesterol did not synergize germination when combined with estradiol and the alpha isomer of estradiol had almost no activity as an inducer of morphogenic change in Candida albicans. We conclude that beta estradiol was a morphogenic inducer in three clinical isolates of Candida albicans but only at concentrations typical in vivo.

The structure of helix I of the 5S rRNA from Escherichia coli has been determined using a nucleolytic digest fragment of the intact molecule. The fragment analyzed, which corresponds to bases (-1)-11 and 108-120 of intact 5S rRNA, contains a G-U pair and has unpaired bases at its termini. Its proton resonances were assigned by two-dimensional NMR methods, and both NOE distance and coupling constant information have been used to calculate structural models for it using the full relaxation matrix algorithm of the molecular dynamics program XPLOR. Helix I has A-type helical geometry, as expected. Its most striking departure from regular helical geometry occurs at its G-U, which stacks on the base pair to the 5' side of its G but not on the base pair to its 3' side. This stacking pattern maximizes interstrand guanine-guanine interactions and explains why the G-U in question fails to give imino proton NOE's to the base pair to 5' side of its G. These results are consistent with the crystal structures that have been obtained for wobble base pairs in tRNAPhe [Mizuno, H., & Sundaralingam, M. (1978) Nucleic Acids Res. 5, 4451-4461] and A-form DNA [Rabbinovich, D., Haran, T., Eisenstein, M., & Shakked, Z. (1988) J. Mol. Biol. 200, 151-161]. The conformations of the terminal residues of helix I, which corresponds to bases (-1)-11 and 108-120 of native 5S RNA, are less well-determined, and their sugar puckers are intermediate between C2' and C3'-endo, on average.

A set of four RNA hairpin helices has been prepared by in vitro transcription with T7 RNA polymerase. The hairpins all contain the same nine base pair helix, but with an extra A, C, or U residue forming a bulge at one position; the fourth hairpin is a perfect helix with no bulge. The helix with a bulged A duplicates six base pairs of a helix in the 16S rRNA known to have an unusually high affinity for ethidium bromide [J. M. Kean, S. A. White, and D. E. Draper, Biochemistry 24, 5062 (1985)]. Binding and chemical cleavage studies with ethidium or the reagent methidiumpropylEDTA-Fe(II) [MPE-Fe(II)] showed that the sequence CpG is a preferred intercalation site whether or not a bulge is present; all three bulged bases enhance intercalation at the CpG sequence by an order of magnitude; and intercalation in a bulged helix results in a concerted conformational change involving the entire helix backbone, again dependent on the presence of a bulge but independent of the particular base. These results suggest that an extra sugar-phosphate residue in an RNA helix backbone has a dramatic effect on the ability of the RNA to adopt new conformations. This effect could be an important reason for the conservation of bulges at certain positions in ribosomal and other RNAs.