3,802 research outputs found
Pre-Matrix Balancing of Challenging Chemical Equations with a Simple Formula Register and Middle School Arithmetic
This paper describes a procedure employing basic relational concepts (analogous to certain matrix algebra concepts), but structured by a simple formula register and using only middle school arithmetic to balance chemical equations ranging from easy to moderate to difïŹcult redox reactions. This procedure allows average students and below average students to experience ready success in balancing, thus avoiding a traditional source of frustration and failure which might contribute to their losing interest in chemistry. One interesting serendipity of this procedure is how quickly it turns able pre-matrix students into extremely fast and accurate balaneers
QSOs in the combined SDSS/GALEX database
We discuss selection of QSO candidates from the combined SDSS and GALEX
catalogues. We discuss properties of QSOs within the combined sample, and note
uncertainties in number counts and completeness, compared with other SDSS-based
samples. We discuss colour and other properties with redshift within the sample
and the SEDs for subsets. We estimate the numbers of faint QSOs that are
classified as extended objects in the SDSS, and consequent uncertainties that
follow.Comment: To appear in PAS
Galaxy population properties in the rich clusters MS0839.8+2938, 1224.7+2007 and 1231.3+1542
This paper discusses the galaxy populations of three rich clusters, with
redshift 0.19 (0839+29), 0.24 (1231+15), and 0.32 (1224+20), from the database
of the CNOC1 consortium. The data consist of spectra of 52 cluster members for
0839+29, 30 members for 1224+15, and 82 members for 1231+15, and there are
comparable numbers of field galaxy spectra. 0839+29 is compact with no strong
radial gradients, and possibly dusty. 1224+20 is isolated in redshift, has low
velocity dispersion around the cD galaxy, and low 4000A break. 1231+15 is
asymmetrical and we discuss the possibility that it may be a recent merger of
two old clusters. We find few galaxies in 0839+29 and 1231+15 with ongoing or
recently truncated star-formation.Comment: 16 pages and 20 diagrams, to appear in A
A financial analysis of the effect of the mix of crop and sheep enterprises on the risk profile of dryland farms in south-eastern Australia
This study analyses the financial risk faced by representative mixed-enterprise farm businesses in four regions of south-eastern Australia. It uses discrete stochastic programming to optimise the ten-year cash flow margins produced by these farms operating three different farming systems. Monte Carlo analysis is used to produce a risk profile for each scenario, derived from multiple runs of this optimised model, randomised for commodity prices and decadal growing season rainfall since 1920. This analysis shows that the performance of the enterprise mixes at each site is characterised more by the level of variability of possible outcomes than by the mean values of financial outputs. It demonstrates that relying on mean values for climate and prices disguises the considerable risks involved with cropping in this area. Diversification into a Merino sheep enterprise marginally reduced the probability of financial loss at all sites. This study emphasises the fact that the variability, or risk, associated with all scenarios far exceeds the likely change in cash margins due to innovation and good management. It further shows that farm managers should give a higher priority to adopting innovations which reduce costs, rather than increase productivity, in order to reduce risk. Further analysis shows that the current static measures of financial performance (gross margins, profit and cash margins) do not characterise the risk-adjusted performance of the various farming systems and almost certainly result in a flawed specification of best-practice farm management in south-eastern Australia.Farm Management,
Political Context, Issue Salience, and Selective Attentiveness: Constituent Knowledge of the Clarence Thomas Confirmation Vote
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72941/1/0022-3816.00090.pd
The Resolved Outer Population of NGC6822 with WFPC2
We present F336W (U), F439W (B), F555W (V), and F675W (R) Wide Field
Planetary Camera 2 (WFPC2) photometry of two outer regions of the Local Group
dwarf irregular galaxy NGC6822. The NE region is ~13 arcmin from the galaxy
centre, while the W region lies 10 arcmin out, and within the wispy low surface
brightness outer regions of the galaxy. The fields are not crowded and contain
few NGC 6822 stars. We discuss errors and uncertainties and find that the W
region contains a main sequence that extends to stars of about 2 solar masses,
with an age of about 200 Myr. The NE region has no main sequence or stars
younger than 1 Gyr, but does contain some luminous red stars that are not
matched in the W field. These stars are not clumped in the field. The results
suggest that the W region may be a trace of a tidal event that triggered the
current star-formation in this isolated galaxy.Comment: 12 pages including 2 tables, plus 4 figures (#1 omitted) To appear in
PAS
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