A content analysis method to measure critical thinking in face-to-face and computer supported group learning

This paper gives a detailed account of the content analysis method developed at Queen's University Belfast to measure critical thinking during group learning, as used in our controlled comparisons between learning in face-to-face and computer conference seminars. From Garrison's 5 stages of critical thinking, and Henri's cognitive skills needed in CMC, we have developed two research instruments: a student questionnaire and this content analysis method. The content analysis relies on identifying, within transcripts, examples of indicators of obviously critical and obviously uncritical thinking, from which several critical thinking ratios can be calculated.

Multiple Enzymatic Activities Associated with Severe Acute Respiratory Syndrome Coronavirus Helicase

Severe acute respiratory syndrome coronavirus (SARS-CoV), a newly identified group 2 coronavirus, is the causative agent of severe acute respiratory syndrome, a life-threatening form of pneumonia in humans. Coronavirus replication and transcription are highly specialized processes of cytoplasmic RNA synthesis that localize to virus-induced membrane structures and were recently proposed to involve a complex enzymatic machinery that, besides RNA-dependent RNA polymerase, helicase, and protease activities, also involves a series of RNA-processing enzymes that are not found in most other RNA virus families. Here, we characterized the enzymatic activities of a recombinant form of the SARS-CoV helicase (nonstructural protein [nsp] 13), a superfamily 1 helicase with an N-terminal zinc-binding domain. We report that nsp13 has both RNA and DNA duplex-unwinding activities. SARS-CoV nsp13 unwinds its substrates in a 5'-to-3' direction and features a remarkable processivity, allowing efficient strand separation of extended regions of double-stranded RNA and DNA. Characterization of the nsp13-associated (deoxy)nucleoside triphosphatase ([dNTPase) activities revealed that all natural nucleotides and deoxynucleotides are substrates of nsp13, with ATP, dATP, and GTP being hydrolyzed slightly more efficiently than other nucleotides. Furthermore, we established an RNA 5'-triphosphatase activity for the SARS-CoV nsp13 helicase which may be involved in the formation of the 5' cap structure of viral RNAs. The data suggest that the (d)NTPase and RNA 5'-triphosphatase activities of nsp13 have a common active site. Finally, we established that, in SARS-CoV-infected Vero E6 cells, nsp13 localizes to membranes that appear to be derived from the endoplasmic reticulum and are the likely site of SARS-CoV RNA synthesis.

Boron abundances in B-type stars: A test of rotational depletion during main-sequence evolution

Boron abundances have been derived for seven main-sequence B- type stars from Hubble Space Telescope STIS spectra around the B III lambda2066 line. In two stars, boron appears to be undepleted with respect to the presumed initial abundance. In one star, boron is detectable but is clearly depleted. In the other four stars, boron is undetectable, implying depletions of 1-2 dex. Three of these four stars are nitrogen enriched, but the fourth shows no enrichment of nitrogen. Only rotationally induced mixing predicts that boron depletions are unaccompanied by nitrogen enrichments. The inferred rate of boron depletion from our observations is in good agreement with these predictions. Other boron-depleted nitrogen-normal stars are identified from the literature. In addition, several boron- depleted nitrogen-rich stars are identified, and while all fall on the boron-nitrogen trend predicted by rotationally induced mixing, a majority have nitrogen enrichments that are not uniquely explained by rotation. The spectra have also been used to determine iron group (Cr, Mn, Fe, and Ni) abundances. The seven B-type stars have near-solar iron group abundances, as expected for young stars in the solar neighborhood. We have also analyzed the halo B-type star PG 0832 + 676. We find [Fe/H] = -0.88 +/- 0.10, and the absence of the B III line gives the upper limit [B/H] <-2.5. These and other published abundances are used to infer the star's evolutionary status as a post-asymptotic giant branch star.

Chemical composition of B-type supergiants in the OB 8, OB 10, OB 48, OB 78 associations of M 31

Absolute and differential chemical abundances are presented for the largest group of massive stars in M31 studied to date. These results were derived from intermediate resolution spectra of seven B-type supergiants, lying within four OB associations covering a galactocentric distance of 5-12 kpc. The results are mainly based on an LTE analysis, and we additionally present a full non-LTE, unified model atmosphere analysis of one star (OB 78-277) to demonstrate the reliability of the differential LTE technique. A comparison of the stellar oxygen abundance with that of previous nebular results shows that there is an off set of between similar to0.15-0.4 dex between the two methods which is critically dependent on the empirical calibration adopted for the R 23 parameter with [O/H]. However within the typical errors of the stellar and nebular analyses (and given the strength of dependence of the nebular results on the calibration used) the oxygen abundances determined in each method are fairly consistent. We determine the radial oxygen abundance gradient from these stars, and do not detect any systematic gradient across this galactocentric range. We find that the inner regions of M31 are not, as previously thought, very "metal rich". Our abundances of C, N, O, Mg, Si, Al, S and Fe in the M31 supergiants are very similar to those of massive stars in the solar neighbourhood.