ALBERT

Description: Water deficit associated with drought can severely affect plants and influence ecological interactions involving plant secondary metabolites. We tested the effect of mild water deficit and rewatering on physiological, morphological and chemical traits of juvenile Eucalyptus globulus Labill. and Eucalyptus viminalis Labill. We also tested if responses of juvenile eucalypts to water deficit and rewatering varied within species using provenances across a rainfall gradient. Both species and all provenances were similarly affected by mild water deficit and rewatering, as only foliar abscisic acid levels differed among provenances during water deficit. Across species and provenances, water deficit decreased leaf water potential, above-ground biomass and formylated phloroglucinol compound concentrations, and increased condensed tannin concentrations. Rewatering reduced leaf carbon : nitrogen, and total phenolic and chlorogenic acid concentrations. Water deficit and rewatering had no effect on total oil or individual terpene concentrations. Levels of trait plasticity due to water deficit and rewatering were less than levels of constitutive trait variation among provenances. The overall uniformity of responses to the treatments regardless of native provenance indicates limited diversification of plastic responses when compared with the larger quantitative variation of constitutive traits within these species. These responses to mild water deficit may differ from responses to more extreme water deficit or to responses of juvenile/mature eucalypts growing at each locality.

Description: The mouse liver tumorigenic conazole fungicides triadimefon and propiconazole have previously been shown to be in vivo mouse liver mutagens in the Big Blue™ transgenic mutation assay when administered in feed at tumorigenic doses, whereas the nontumorigenic conazole myclobutanil was not mutagenic. DNA sequencing of the mutants recovered from each treatment group as well as from animals receiving control diet revealed that propiconazole- and triadimefon-induced mutations do not represent general clonal expansion of background mutations, and support the hypothesis that they arise from the accumulation of endogenous reactive metabolic intermediates within the liver in vivo . We therefore measured the spectra of endogenous DNA adducts in the livers of mice from these studies to determine if there were quantitative or qualitative differences between mice receiving tumorigenic or nontumorigenic conazoles compared to concurrent control animals. We resolved and quantitated 16 individual adduct spots by 32 P postlabelling and thin layer chromatography using three solvent systems. Qualitatively, we observed the same DNA adducts in control mice as in mice receiving conazoles. However, the 13 adducts with the highest chromatographic mobility were, as a group, present at significantly higher amounts in the livers of mice treated with propiconazole and triadimefon than in their concurrent controls, whereas this same group of DNA adducts in the myclobutanil-treated mice was not different from controls. This same group of endogenous adducts were significantly correlated with mutant frequency across all treatment groups ( P = 0.002), as were total endogenous DNA adduct levels ( P = 0.005). We hypothesise that this treatment-related increase in endogenous DNA adducts, together with concomitant increases in cell proliferation previously reported to be induced by conazoles, explain the observed increased in vivo mutation frequencies previously reported to be induced by treatment with propiconazole and triadimefon.

Description: Studies incorporating technology into the teaching of trigonometry, although sparse, have demonstrated positive effects on student achievement. The optimal sequence for integrating technology with teacher-led mathematics instruction has not been determined. Our research investigated whether technology has a greater impact on student achievement and attitudes if it is implemented before or after whole class teaching. The curriculum context of the study was a set of learning objects (CLIPS: Trig) designed to support student learning of transformations of trigonometric functions. The software includes functional features identified in prior research: it relieves students of the tedium of creating graphs by hand; sliders give students control of the simulations within program parameters; there are easy transitions between algebraic and graphic representations; the environment is dynamic; animation and visualization are included with graphing functions. Twenty Canadian classrooms ( N = 489 grade 11–12 students, aged 17–18 years) were randomly assigned to two instructional sequences: CLIPS: Trig followed by whole-class teaching (CLIPS early treatment) and whole-class teaching followed by CLIPS: Trig (CLIPS late treatment). We found that in the pre-test to post-test comparisons, students who experienced CLIPS: Trig after whole-class teaching of core concepts learned more than students who began the unit with technology-supported simulations. However, there were no statistically significant differences in the pre-test to delayed post-comparisons. Beginning the trigonometry unit with CLIPS: Trig enhanced the impact of whole-class teaching, while beginning with whole-class teaching enriched students’ technology experience. The findings suggest that a tight integration of whole-class and technology-assisted instruction is preferable.

Description: Migratory animals often go to extraordinary lengths to follow broad-scale changes in the spatial distributions of food resources over time. An example is the molt-migration system of songbirds in the central and western United States, wherein birds interrupt migratory movements to molt their feathers in the ephemerally productive North American monsoon region in Northwestern Mexico. Within this large-scale migration system, the efficacy of individual migration behaviors relative to dynamics of primary productivity en route is unknown. We performed a comparison of real migration tracks from a common molt migrant, the painted bunting ( Passerina ciris ), with the results from millions of random-walk simulations to determine if real birds demonstrate optimal migratory behavior with respect to seasonal changes in primary productivity across the landscape. We scored migration routes of both real and simulated birds using an index of new plant growth, wherein daily values for each day of the autumn migration period were summed to indicate the total exposure to primary productivity. We then compared the highest-scoring simulated routes with real bird tracks and observed a high degree of correspondence between them, with the monsoon region featuring prominently in most of the high-ranking simulations. However, real birds generally left the breeding grounds later than virtual birds, perhaps because of life-history constraints not represented in the simulations. Our work supports the contention that painted bunting migration maximizes exposure to new plant growth and provides a novel approach for exploring migratory behaviors in other species and other regions.

Description: Studies of the distribution of ammonia oxidising archaea (AOA) and bacteria (AOB) suggest distinct ecological niches characterised by ammonia concentration and pH, arising through differences in substrate affinity and ammonia tolerance. AOA form five distinct phylogenetic clades, one of which, the ‘ Nitrososphaera sister cluster’, has no cultivated isolate. A representative of this cluster, named ‘ Candidatus Nitrosocosmicus franklandus’, was isolated from a pH 7.5 arable soil and we propose a new cluster name: ‘Nitrosocosmicus’ . While phylogenetic analysis of amoA genes indicates its association with the Nitrososphaera sister cluster, analysis of 16S rRNA genes provided no support for a relative branching that is consistent with a ‘sister cluster’, indicating placement within a lineage of the order Nitrososphaerales . ‘ Ca. N. franklandus’ is capable of ureolytic growth and its tolerances to nitrite and ammonia are higher than in other AOA and similar to those of typical soil AOB. Similarity of other growth characteristics of ‘ Ca. N. franklandus’ with those of typical soil AOB isolates reduces support for niche differentiation between soil AOA and AOB and suggests that AOA have a wider physiological diversity than previously suspected. In particular, the high ammonia tolerance of ‘ Ca. N. franklandus’ suggests potential contributions to nitrification in fertilised soils.

Description: We consider a notion of balanced metrics for triples ( X , L , E ) which depend on a parameter α, where X is a smooth complex manifold with an ample line bundle L and E is a holomorphic vector bundle over X . For generic choice of α, we prove that the limit of a convergent sequence of balanced metrics leads to a Hermitian–Einstein metric on E and a constant scalar curvature Kähler metric in c 1 ( L ). For special values of α, limits of balanced metrics are solutions of a system of coupled equations relating a Hermitian–Einstein metric on E and a Kähler metric in c 1 ( L ).

Description: To study mitochondrial–nuclear genetic interactions in the nematode Caenorhabditis briggsae , our three laboratories independently created 38 intra-species cytoplasmic–nuclear hybrid (cybrid) lines. Although the cross design combines maternal mitotypes with paternal nuclear genotypes, eight lines (21%) unexpectedly contained paternal mitotypes. All eight share in common ancestry of one of two genetically related strains. This unexpected parallel observation of paternal mitochondrial transmission, undesirable given our intent of creating cybrids, provides a serendipitous experimental model and framework to study the molecular and evolutionary basis of uniparental mitochondrial inheritance.

Description: We determine how MRI (magnetorotational instability)-turbulent stresses depend on gas pressure via a suite of unstratified shearing box simulations. Earlier numerical work reported only a very weak dependence at best, results that call into question the canonical α-disc model and the thermal stability results that follow from it. Our simulations, in contrast, exhibit a stronger relationship, and show that previous work was box-size limited: turbulent ‘eddies’ were artificially restricted by the numerical domain rather than by the scaleheight. Zero-net-flux runs without physical diffusion coefficients yield a stress proportional to P 0.5 , where P is pressure. The stresses are also proportional to the grid length and hence remain numerically unconverged. The same runs with physical diffusivities, however, give a result closer to an α-disc: the stress is P 0.9 . Net-flux simulations without explicit diffusion exhibit stresses P 0.5 , but stronger imposed fields weaken this correlation. In summary, compressibility is important for the saturation of the MRI, but the exact stress–pressure relationship is difficult to ascertain in local simulations because of numerical convergence issues and the influence of any imposed flux. As a consequence, the interpretation of thermal stability behaviour in local simulations is a problematic enterprise.

Description: Jets, from the protostellar to the AGN context, have been extensively studied but their connection to the turbulent dynamics of the underlying accretion disc is poorly understood. Following a similar approach to Lesur, Fereira & Ogilvie, we examine the role of the magnetorotational instability (MRI) in the production and acceleration of outflows from discs. Via a suite of 1D shearing-box simulations of stratified discs, we show that magnetocentrifugal winds exhibit cyclic activity with a period of 10–20 –1 , a few times the orbital period. The cycle seems to be more vigorous for strong vertical field; it is robust to the variation of relevant parameters and independent of numerical details. The convergence of these solutions (in particular the mass-loss rate) with vertical box size is also studied. By considering a sequence of magnetohydrostatic equilibria and their stability, the periodic activity may be understood as the succession of the following phases: (a) a dominant MRI channel mode, (b) strong magnetic field generation, (c) consequent wind launching, and ultimately (d) vertical expulsion of the excess magnetic field by the expanding and accelerating gas associated with the wind. We discuss potential connections between this behaviour and observed time-variability in disc–jet systems.

Description: Feedback from radio jets associated with active galactic nuclei (AGNs) plays a profound role in the evolution of galaxies. Kinetic power of these radio jets appears to show temporal variation, but the mechanism(s) responsible for this process are not yet clear. Recently, the LOw Frequency ARray (LOFAR) has uncovered large populations of active, remnant, and restarted radio jet populations. By focusing on LOFAR data in the Lockman Hole, in this work we use the Radio AGNs in Semi-Analytic Environments (RAiSE) dynamical model to present the first self-consistent modelling analysis of active, remnant, and restarted radio source populations. Consistent with other recent work, our models predict that remnant radio lobes fade quickly. Any high (〉10 per cent) observed fraction of remnant and restarted sources therefore requires a dominant population of short-lived jets. We speculate that this could plausibly be provided by feedback-regulated accretion.