'I wouldn't want to be the animal in use nor the patient in need' - the role of issue familiarity in students' socioscientific argumentation

Students’ argumentation skills are considered a central tool to contribute to scientific controversies in the science classroom. Scientific controversies of social relevance (socioscientific issues; SSI) are subject to multiple viewpoints that are often rooted in diverse disciplines. However, the relationship between issue familiarity and students’ multidisciplinary argumentation is still a matter under discussion. This study: (1) explores whether the selection of a particular issue (animal testing) enables students’ engagement in multidisciplinary argumentation without additional issue familiarisation, i.e., using only their existing knowledge; and (2) clarifies the relationship between increased issue familiarity and students’ multidisciplinary argumentation. One hundred and sixty three ninth and tenth graders participated in this study, of whom one hundred and six took part in a teaching unit to familiarise themselves with the issue of animal testing. The study’s results demonstrate that animal testing constitutes an effective issue to engage students with the complexity of SSI without requiring more than basic familiarity prior to engagement. The results further demonstrate that increased issue familiarity can enhance the overall diversity of discipline-related arguments amongst students; however, not all disciplines were enhanced equally. The findings suggest that more instructional guidance seems to be needed to assist students in broadening their arguments

Stable gene replacement in barley by targeted double-strand break induction

Gene targeting is becoming an important tool for precision genome engineering in plants. During gene replacement, a variant of gene targeting, transformed DNA integrates into the genome by homologous recombination (HR) to replace resident sequences. We have analysed gene targeting in barley (Hordeum vulgare) using a model system based on double-strand break (DSB) induction by the meganuclease I-SceI and a transgenic, artificial target locus. In the plants we obtained, the donor construct was inserted at the target locus by homology-directed DNA integration in at least two transformants obtained in a single experiment and was stably inherited as a single Mendelian trait. Both events were produced by one-sided integration. Our data suggest that gene replacement can be achieved in barley with a frequency suitable for routine application. The use of a codon-optimized nuclease and co-transfer of the nuclease gene together with the donor construct are probably the components important for efficient gene targeting. Such an approach, employing the recently developed synthetic nucleases/nickases that allow DSB induction at almost any sequence of a genome of interest, sets the stage for precision genome engineering as a routine tool even for important crops such as barley

SN1997cy/GRB970514 - A New Piece in the GRB Puzzle?

We present observations of SN1997cy, a supernova discovered as part of the Mount Stromlo Abell Cluster SN Search, which does not easily fit into the traditional classification scheme for supernovae. This object's extraordinary optical properties and coincidence with GRB970514, a short duration gamma ray burst, suggest a second case, after SN1998bw/GRB980425, for a SN-GRB association. SN1997cy is among the most luminous SNe yet discovered and has a peculiar spectrum. We present evidence that SN1997cy ejected approximately 2 solar masses of 56Ni, supported by its late-time light curve, and FeII/[FeIII] lines in its spectrum, although it is possible that both these observations can be explained via circumstellar interaction. While SN1998bw and SN1997cy appear to be very different objects with respect to both their gamma ray and optical properties, SN1997cy and the optical transient associated with GRB970508 have roughly similar late-time optical behavior. This similarity may indicate that the late-time optical output of these two intrinsically bright transient events have a common physical process. Although the connection between GRB970514 and SN1997cy is suggestive, it is not conclusive. However, if this association is real, followup of short duration GRBs detected with BATSE or HETE2 should reveal objects similar to SN1997cy.Comment: 26 pages including 6 postscript figures and 3 tables. Submitted to ApJ. Re-calibrated photometry - objects are about 0.3mags brighter than in original versio

Effects of environmental factors on development of Pyrenopeziza brassicae (light leaf spot) apothecia on oilseed rape debris

Publication no. P-2001-0221-01R. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 2001The development of Pyrenopeziza brassicae (light leaf spot) apothecia was studied on petiole debris from artificially infected oilseed rape leaves incubated at temperatures from 6 to 22 degreesC under different wetness regimes and in 16 h light/8 h dark or continuous darkness. There was no significant difference between light treatments in numbers of apothecia that developed. Mature apothecia developed at temperatures from 5 to 18 degreesC but not at 22 degreesC. The rate of apothecial development decreased as temperature decreased from 18 to 5 degreesC; mature apothecia were first observed after 5 days at 18 degreesC and after 15 days at 6 degreesC. Models were fitted to estimates of the time (days) for 50% of the maximum number of apothecia to develop (t(1); model 1, t(1) = 7.6 + 55.8(0.839)(T)) and the time for 50% of the maximum number of apothecia to decay (t(2); model 2, t(2) = 24.2 + 387(0.730)(T)) at temperatures (T) from 6 to 18 degreesC. An interruption in wetness of the petiole debris for 4 days after 4, 7, or 10 days of wetness delayed the time to observation of the first mature apothecia for approximate to4 days and decreased the number of apothecia produced (by comparison with continuous wetness). A relationship was found between water content of pod debris and electrical resistance measured by a debris-wetness sensor. The differences between values of tl predicted by model 1 and observed values of t(1) were 1 to 9 days. Model 2 did not predict t(2); apothecia decayed more quickly under natural conditions than predicted by model 2.Peer reviewe

Stability of Circular Orbits in General Relativity: A Phase Space Analysis

Phase space method provides a novel way for deducing qualitative features of nonlinear differential equations without actually solving them. The method is applied here for analyzing stability of circular orbits of test particles in various physically interesting environments. The approach is shown to work in a revealing way in Schwarzschild spacetime. All relevant conclusions about circular orbits in the Schwarzschild-de Sitter spacetime are shown to be remarkably encoded in a single parameter. The analysis in the rotating Kerr black hole readily exposes information as to how stability depends on the ratio of source rotation to particle angular momentum. As a wider application, it is exemplified how the analysis reveals useful information when applied to motion in a refractive medium, for instance, that of optical black holes.Comment: 20 pages. Accepted for publication in Int. J. theor. Phy

Prevalence, genetic diversity and potential clinical impact of blood-borne and enteric protozoan parasites in native mammals from northern Australia

A molecular survey was conducted to provide baseline information on the prevalence, genetic diversity and potential clinical impacts of blood-borne and enteric protozoans in native wild mammals from the Northern Territory (NT). A total of 209 blood and 167 faecal samples were collected from four target species; the northern brown bandicoot (Isoodon macrourus), common brushtail possum (Trichosurus vulpecula), northern quoll (Dasyurus hallucatus) and brush-tailed rabbit-rat (Conilurus penicillatus). Blood samples were screened by PCR at the 18S rRNA gene for trypanosomes, piroplasms and haemogregarines, with faecal samples tested for Cryptosporidium spp. at the 18S rRNA locus, and for Giardia spp. at the glutamate dehydrogenase (gdh) and 18S rRNA loci. The potential clinical impact was investigated by associating clinical, haematological and biochemical parameters with presence or absence of infection. Overall, 22.5% (95% CI: 17.0-28.8%) of the animals tested were positive for haemoprotozoans. Trypanosomes were found in 26.6% (95% CI: 18.7-35.7%) of the bandicoots and were identified as Trypanosoma vegrandis G6, except for one unique genotype, most similar to T. vegrandis G3 (genetic distance = 7%). The prevalence of trypanosomes in possums was 23.7% (95% CI: 11.4-40.2%), and the genotypes identified clustered within the T. noyesi clade. The presence of Babesia sp. and Hepatozoon sp. was confirmed in bandicoots only, both at a prevalence of 9.7% (95% CI: 2.7-9.2%). The total prevalence of intestinal protozoan parasites observed was relatively low (3%; 95% CI: 1.0-6.9%). No evidence of clinical disease associated with protozoan parasitic infection was observed, however bandicoots positive for Trypanosoma exhibited a significantly lower packed cell volume (PCV) compared to negative bandicoots (p = 0.046). To the authors' knowledge, this is the first research conducted in the NT to characterise protozoan parasites in threatened native mammals using both molecular and morphological tools; and to assess the potential clinical impacts of these agents. The absence of clear signs of major morbidity in infected animals seems to exclude a direct association between infections with these agents and possible population decline events in northern Australian native mammals. However until the cause(s) of population decline are ascertained for each individual mammal species, further studies are required. The outcome of the present investigation may be used to inform wildlife conservation and zoonotic disease programs

Analysis of Granular Flow in a Pebble-Bed Nuclear Reactor

Pebble-bed nuclear reactor technology, which is currently being revived around the world, raises fundamental questions about dense granular flow in silos. A typical reactor core is composed of graphite fuel pebbles, which drain very slowly in a continuous refueling process. Pebble flow is poorly understood and not easily accessible to experiments, and yet it has a major impact on reactor physics. To address this problem, we perform full-scale, discrete-element simulations in realistic geometries, with up to 440,000 frictional, viscoelastic 6cm-diameter spheres draining in a cylindrical vessel of diameter 3.5m and height 10m with bottom funnels angled at 30 degrees or 60 degrees. We also simulate a bidisperse core with a dynamic central column of smaller graphite moderator pebbles and show that little mixing occurs down to a 1:2 diameter ratio. We analyze the mean velocity, diffusion and mixing, local ordering and porosity (from Voronoi volumes), the residence-time distribution, and the effects of wall friction and discuss implications for reactor design and the basic physics of granular flow.Comment: 18 pages, 21 figure