Gymnostoma tasmanianum sp nov., a fossil Casuarinaceae from the Early Oligocene of Little Rapid River, Tasmania, Australia

Int. J Plant Sci. 164(4):629–634. 2003. © 2003 by The University of ChicagoMacrofossils of Casuarinaceae from Early Oligocene sediments at Little Rapid River, Tasmania, are assigned to a new species, Gymnostoma tasmanianum. This is only the second species of fossil Gymnostoma to be formally described and the first species of Gymnostoma to be described from Tasmania. The species is known from both vegetative and reproductive organs. The new taxon is distinguished from other known species by its small stomata, short article length and tooth width, small length:width ratio of articles, glabrous articles, stomata in two to five rows, and teeth elongate with acute apices and sinuses. The fossil record shows that Gymnostoma once had a much wider distribution in Australia than its current occurrence in far north Queensland.Greg Guerin and Robert S. Hil

Adjustment of Parametric Dynamic Scheduling Heuristics for Heterogeneous Systems to Account for Heterogeneity

Modern computing applications are becoming increasingly data-hungry and computationally expensive. This trend continues even as hardware performance constraints loom with the impending death of Moore\u27s law. Hence, systems have become increasingly heterogeneous in the pursuits of improving performance and reducing power consumption. Such a heterogeneous system relies on a variety of different specialized processors with differing architectures, rather than processing units of a single type. Given their architectural differences, any given computation will not perform equally on all processors. As such, efficient scheduling of computations to processors is an essential design consideration. In this thesis work, a simulation of an existing dynamic scheduling heuristic - Alternative Processor within Threshold (APT) - was used to model the execution of a variety of heterogeneous workloads and heterogeneous systems. An extended version of this scheduler (APTX) was analyzed in a similar way, as was a simplified version of the existing K-Percent Best (KPB) scheduler. Each of these schedulers has a numeric parameter constraining its behavior. In existing analyses, these scheduling heuristics were tested only with a small set of arbitrary values for these parameters. The goal of this research was to use a stochastic method to optimize said parameters for the minimum finishing time of any given set of computations on any given heterogeneous system. An analytical expression to estimate the ideal parameter of each scheduler was developed. Each was based on the statistical analysis of the results of a set of randomly-generated simulations. After these expressions were developed, these optimized APT, APTX, and KPB schedulers were evaluated against three other dynamic schedulers - Minimum Execution Time (MET), Serial Scheduling (SS), and Shortest Process Next (SPN) - by running the randomly-generated simulations on all six. For the most common type of heterogeneous system, APT and APTX were found to have the earliest finish time on average, while MET and KPB generally performed poorly. Ultimately, this research not only demonstrated the advantages of APT and APTX over other dynamic schedulers in a fair comparison, but it also demonstrated a method by which any parametric scheduler can be tuned

Thermally stable low current consuming gallium and germanium chalcogenides for consumer and automotive memory applications

The phase change technology behind rewritable optical disks and the latest generation of electronic memories has provided clear commercial and technological advances for the field of data storage, by virtue of the many well known attributes, in particular scaling, cycling endurance and speed, that chalcogenide materials offer. While the switching power and current consumption of established germanium antimony telluride based memory cells are a major factor in chip design in real world applications, often the thermal stability of the device can be a major obstacle in the path to the full commercialisation. In this work we describe our research in material discovery and characterization for the purpose of identifying more thermally stable chalcogenides for applications in PCRAM

Weed abundance is positively correlated with native plant diversity in grasslands of southern Australia

Published: June 1, 2017Weeds are commonly considered a threat to biodiversity, yet interactions between native and exotic species in grasslands are poorly understood and reported results vary depending on the spatial scale of study, the factors controlled for and the response variables analysed. We tested whether weed presence and abundance is related to declines in biodiversity in Australian grasslands. We employed existing field data from 241 plots along a disturbance gradient and correlated species richness, cover and Shannon diversity for natives and exot- ics, controlling for seasonal rainfall, climatic gradients and nutrient status. We found no neg- ative relationships in terms of emergent diversity metrics and occupation of space, indeed, many positive relationships were revealed. When split by land-use, differences were found along the disturbance gradient. In high-moderately disturbed grasslands associated with land-uses such as cropping and modified pastures, positive associations were enhanced. Tolerance and facilitation mechanisms may be involved, such as complementary roles through different life history strategies: the exotic flora was dominated mainly by annual grasses and herbs whereas the native flora represented more diverse growth-forms with a higher proportion of perennials. The positive relationships existing between native and exotic plant species in high-moderately disturbed grasslands of South Australia are most likely due to facilitation through different strategies in occupation of space given that the effect of habitat suitability was controlled for by including environmental and disturbance fac- tors. Consequently, although particular weeds may negatively impact biodiversity, this can- not be generalised and management focusing on general weed eradication in grasslands might be ineffectual.Irene Martín-Forés, Greg R. Guerin, Andrew J. Low

Genetic heterogeneity of hepatitis E virus in Darfur, Sudan, and neighboring Chad.

The within-outbreak diversity of hepatitis E virus (HEV) was studied during the outbreak of hepatitis E that occurred in Sudan in 2004. Specimens were collected from internally displaced persons living in a Sudanese refugee camp and two camps implanted in Chad. A comparison of the sequences in the ORF2 region of 23 Sudanese isolates and five HEV samples from the two Chadian camps displayed a high similarity (>99.7%) to strains belonging to Genotype 1. But four isolates collected in one of the Chadian camps were close to Genotype 2. Circulation of divergent strains argues for possible multiple sources of infection

Une approche sylvopastorale incontournable pour la mise en valeur des milieux boisés difficiles

De vastes espaces boisés sont issus de l’abandon des pratiques anciennes (cultures, pâturage, cueillettes diverses). Les utilisations spécialisées y sont rares : taillis vieillissants et peu de produits « nobles » ou pâturage d’appoint sans pérennité visible. Ces types de couverts très répandus ne pourront être mis en valeur qu’en combinant interventions sur les arbres et impacts du pâturage. Ce n’est qu’à ce prix que la combinaison des différentes activités sera rentable. Le peuplement boisé en sort bonifié et les qualités écologiques de ces milieux sont améliorées

Optical parametric oscillation with distributed feedback in cold atoms

There is currently a strong interest in mirrorless lasing systems, in which the electromagnetic feedback is provided either by disorder (multiple scattering in the gain medium) or by order (multiple Bragg reflection). These mechanisms correspond, respectively, to random lasers and photonic crystal lasers. The crossover regime between order and disorder, or correlated disorder, has also been investigated with some success. Here, we report one-dimensional photonic-crystal lasing (that is, distributed feedback lasing) with a cold atom cloud that simultaneously provides both gain and feedback. The atoms are trapped in a one-dimensional lattice, producing a density modulation that creates a strong Bragg reflection with a small angle of incidence. Pumping the atoms with auxiliary beams induces four-wave mixing, which provides parametric gain. The combination of both ingredients generates a mirrorless parametric oscillation with a conical output emission, the apex angle of which is tunable with the lattice periodicity

De la forêt pâturée au sylvopastoralisme

Historiquement très intégrées, les différentes activités en forêt ont été désarticulées et spécialisées par la modernisation des filières. L'espace boisé, particulièrement dans le Sud, recouvre en réalité de nombreuses fonctions dont la première production est sans doute celle de viande! Pendant des décennies, la coopération entre forestiers et pastoralistes est restée limitée à un équilibre précaire entre leurs attentes respectives. Plus récemment, ce pâturage en forêt a évolué vers la recherche plus affirmée d'une combinaison des activités, intéressante pour chacun : consolider l'activité pastorale et, aussi, revisiter les possibilités de valorisation sylvicole grâce à la contribution du pâturage