12,912 research outputs found
NOTES ON A COLLECTION OF DRAGONFLIES (ORDER ODONATA) FROM. THE DUTCH EAST INDIES AND DESCRIPTIONS OF FOUR NEW SPECIES FROM THE NEIGHBOURING CONTINENT
abstract not avaialabl
Obituary: Arthur Cruickshank 1932 - 2011. A native Gondwanan, who studied the former continent's fossil tetrapods
Dr Arthur Richard Ivor Cruickshank died
on 4th December 2011, aged 79, in the
Borders General Hospital, Melrose, Scotland.
Arthur Cruickshank was part of the post-war
generation of palaeontologists who laid the
foundations on which today’s researchers
build. Appropriately for someone from
an expatriate Scots family living in Kenya,
much of his work was on the extinct reptiles
of the great southern palaeocontinent of
Gondwana
The nebular spectra of SN 2012aw and constraints on stellar nucleosynthesis from oxygen emission lines
We present nebular phase optical and near-infrared spectroscopy of the Type
IIP supernova SN 2012aw combined with NLTE radiative transfer calculations
applied to ejecta from stellar evolution/explosion models. Our spectral
synthesis models generally show good agreement with the ejecta from a MZAMS =
15 Msun progenitor star. The emission lines of oxygen, sodium, and magnesium
are all consistent with the nucleosynthesis in a progenitor in the 14 - 18 Msun
range. We also demonstrate how the evolution of the oxygen cooling lines of [O
I] 5577 A, [O I] 6300 A, and [O I] 6364 A can be used to constrain the mass of
oxygen in the non-molecularly cooled ashes to < 1 Msun, independent of the
mixing in the ejecta. This constraint implies that any progenitor model of
initial mass greater than 20 Msun would be difficult to reconcile with the
observed line strengths. A stellar progenitor of around MZAMS = 15 Msun can
consistently explain the directly measured luminosity of the progenitor star,
the observed nebular spectra, and the inferred pre-supernova mass-loss rate. We
conclude that there is still no convincing example of a Type IIP explosion
showing the nucleosynthesis expected from a MZAMS > 20 Msun progenitor.Comment: Accepted for publication in MNRA
A NEW CHONDRODYSTROPHIC MUTANT IN MICE : Electron Microscopy of Normal and Abnormal Chondrogenesis
The occurrence of a new mutation affecting cartilage and bone in mice is reported. The gene is lethal, shows autosomal recessive inheritance, and has high penetrance. It is not allelic to shorthead and probably not to phocomelia or achondroplasia. It results in a foreshortened face, cleft palate, defective trachea, and shortened long bones with flared metaphyses. Chondrocytes of epiphyseal cartilage from the mutant are not aligned in columns, and there is a decrease in the usual staining of the cartilage matrix. Electron microscope observations show large, wide collagen fibrils with "native" banding in the matrix of mutant cartilage, which are not present in normal cartilage. Possible explanations for the expression of this genetic disorder of cartilage development are put forward
Intercomparison of ground-based ozone and NO2 measurements during the MANTRA 2004 campaign
The MANTRA (Middle Atmosphere Nitrogen TRend Assessment) 2004 campaign took place in Vanscoy, Saskatchewan, Canada (52° N, 107° W) from 3 August to 15 September, 2004. In support of the main balloon launch, a suite of five zenith-sky and direct-Sun-viewing UV-visible ground-based spectrometers was deployed, primarily measuring ozone and NO2 total columns. Three Fourier transform spectrometers (FTSs) that were part of the balloon payload also performed ground-based measurements of several species, including ozone. Ground-based measurements of ozone and NO2 differential slant column densities from the zenith-viewing UV-visible instruments are presented herein. They are found to partially agree within NDACC (Network for the Detection of Atmospheric Composition Change) standards for instruments certified for process studies and satellite validation. Vertical column densities of ozone from the zenith-sky UV-visible instruments, the FTSs, a Brewer spectrophotometer, and ozonesondes are compared, and found to agree within the combined error estimates of the instruments (15%). NO2 vertical column densities from two of the UV-visible instruments are compared, and are also found to agree within combined error (15%)
Influence of pulse crops on arbuscular mycorrhizal fungi in a durum-based cropping system
Non-Peer ReviewedPulses are an important component in crop rotations in southern Saskatchewan. Besides their capability to fix nitrogen, pulse crops establish a symbiotic relationship with arbuscular mycorrhizal fungi, which have been shown to increase nutrient and water uptake through hyphal extensions in the soil. This 2 year study is designed to evaluate the impact of pulses in crop rotations on the biodiversity of AMF communities and their dynamics. Plant N and P uptake and the available soil N and P pools under a durum crop are also measured to assess if there is any correlation with AMF communities. The sampling and analysis is completed on the durum phase of the rotation with preceding crops of pea, lentil, chickpea, canola and durum. The final results will be explained by: (1) the size, nature, and physiological state of the soil microbial community and (2) the nature of the preceding crop residues. Preliminary results from the 2004 season indicate that higher plant P uptake is related to AMF colonization, while no significant change was detected in the soil N and P pools
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