604 research outputs found
The Internet supporting an aspect of designing and making : a mini case study
The Internet supporting an aspect of designing and making : a mini case stud
Engagement as the key feature of the successful use of the Internet for information
Engagement as the key feature of the successful use of the Internet for informatio
Pandering to the PANDA : the introduction of threshold policy and performance pay into English schools (and why it matters to us)
EThOS - Electronic Theses Online ServiceGBUnited Kingdo
The circulation near the head of Chesapeake Bay
Three-month long current records are examined for a position near the head of the Chesapeake Bay. For time scales longer than 5 days the flow was determined by the strength of the Susquehanna discharge. A major event was Tropical Storm Eloise which occurred near the middle of the observation period and whose influence dominated the current spectra...
Differential expression of glutathione S-transferase (GST) by adult Heligmosomoides polygyrus during primary infection in fast and slow responding hosts
Solvent effects in gold-catalysed A3-coupling reactions
AbstractGold-catalysed A3-reactions proceed efficiently when conducted in 2,2,2-trifluoroethanol as solvent. The rates of these reactions are accelerated considerably when conducted in a microwave reactor
A lower limit of dz > 0.06 for the duration of the reionization epoch
Observations of the 21-centimetre line of atomic hydrogen in the early
Universe directly probe the history of the reionization of the gas between
galaxies. The observations are challenging, though, because of the low expected
signal strength (~10 mK), and contamination by strong (>100 K) foreground
synchrotron emission in the Milky Way and extragalactic continuum sources2. If
reionization happened rapidly, there should be a characteristic signature
visible against the smooth foreground in an all-sky spectrum. Here we report an
all-sky spectrum between 100 and 200 MHz, corresponding to the redshift range 6
< z < 13 for the 21-centimetre line. The data exclude a rapid reionization
timescale of dz < 0.06 at the 95% confidence level.Comment: 8 pages, 2 figures, Published in Nature, Volume 468, Issue 7325, pp.
796-798 (2010
Empirical and Bayesian approaches to fossil only divergence times: A study across three reptile clades
Estimating divergence times on phylogenies is critical in paleontological and neontological studies. Chronostratigraphically-constrained fossils are the only direct evidence of absolute timing of species divergence. Strict temporal calibration of fossil-only phylogenies provides minimum divergence estimates, and various methods have been proposed to estimate divergences beyond these minimum values. We explore the utility of simultaneous estimation of tree topology and divergence times using BEAST tip-dating on datasets consisting only of fossils by using relaxed morphological clocks and birth-death tree priors that include serial sampling (BDSS) at a constant rate through time. We compare BEAST results to those from the traditional maximum parsimony (MP) and undated Bayesian inference (BI) methods. Three overlapping datasets were used that span 250 million years of archosauromorph evolution leading to crocodylians. The first dataset focuses on early Sauria (31 taxa, 240 chars.), the second on early Archosauria (76 taxa, 400 chars.) and the third on Crocodyliformes (101 taxa, 340 chars.). For each dataset three time-calibrated trees (timetrees) were calculated: a minimum-age timetree with node ages based on earliest occurrences in the fossil record; a ‘smoothed’ timetree using a range of time added to the root that is then averaged over zero-length internodes; and a tip-dated timetree. Comparisons within datasets show that the smoothed and tip-dated timetrees provide similar estimates. Only near the root node do BEAST estimates fall outside the smoothed timetree range. The BEAST model is not able to overcome limited sampling to correctly estimate divergences considerably older than sampled fossil occurrence dates. Conversely, the smoothed timetrees consistently provide node-ages far older than the strict dates or BEAST estimates for morphologically conservative sister-taxa when they sit on long ghost lineages. In this latter case, the relaxed-clock model appears to be correctly moderating the node-age estimate based on the limited morphological divergence. Topologies are generally similar across analyses, but BEAST trees for crocodyliforms differ when clades are deeply nested but contain very old taxa. It appears that the constant-rate sampling assumption of the BDSS tree prior influences topology inference by disfavoring long, unsampled branches.AHT was supported under National
Science Foundation Awards EAR 1349654 and DEB
1257485. ACP was supported under an National
Science Foundation Doctoral Dissertation
Improvement Grant Award (DEB 1501851) to AHT
and ACP. NJM was supported by a NIMBioS
fellowship under National Science Foundation
Award #EFJ0832858, Australian Research Council DECRA fellowship DE150101773, and his work on
BEASTmasteR began while supported by National
Science Foundation 0919124
Researching for better instructional methods using AB experiments in MOOCs: results and challenges
We conducted two AB experiments (treatment vs. control) in a massive open online course. The first experiment evaluates deliberate practice activities (DPAs) for developing problem solving expertise as measured by traditional physics problems. We find that a more interactive drag-and-drop format of DPA generates quicker learning than a multiple choice format but DPAs do not improve performance on solving traditional physics problems more than normal homework practice. The second experiment shows that a different video shooting setting can improve the fluency of the instructor which in turn improves the engagement of the students although it has no significant impact on the learning outcomes. These two cases demonstrate the potential of MOOC AB experiments as an open-ended research tool but also reveal limitations. We discuss the three most important challenges: wide student distribution, “open-book” nature of assessments, and large quantity and variety of data. We suggest possible methods to cope with those.Google (Firm)Massachusetts Institute of Technolog
Ascaris suum-Derived Products Induce Human Neutrophil Activation via a G Protein-Coupled Receptor That Interacts with the Interleukin-8 Receptor Pathway
Infection with tissue-migrating helminths is frequently associated with intense granulocyte infiltrations.
Several host-derived factors are known to mediate granulocyte recruitment to the tissues, but less attention has
been paid to how parasite-derived products trigger this process. Parasite-derived chemotactic factors which
selectively recruit granulocytes have been described, but nothing is known about which cellular receptors
respond to these agents. The effect of products from the nematodes Ascaris suum, Toxocara canis, and Anisakis
simplex on human neutrophils were studied. We monitored four parameters of activation: chemotaxis, cell
polarization, intracellular Ca21 transients, and priming of superoxide anion production. Body fluids of A. suum
(ABF) and T. canis (TcBF) induced strong directional migration, shape change, and intracellular Ca21
transients. ABF also primed neutrophils for production of superoxide anions. Calcium mobilization in response
to A. suum-derived products was completely abrogated by pretreatment with pertussis toxin, implicating
a classical G protein-coupled receptor mechanism in the response to ABF. Moreover, pretreatment with
interleukin-8 (IL-8) completely abrogated the response to ABF, demonstrating desensitization of a common
pathway. However, ABF was unable to fully desensitize the response to IL-8, and binding to CXCR1 or CXCR2
was excluded in experiments using RBL-2H3 cells transfected with the two human IL-8 receptors. Our results
provide the first evidence for a direct interaction between a parasite-derived chemotactic factor and the host’s
chemotactic network, via a novel G protein-coupled receptor which interacts with the IL-8 receptor pathway
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