1,678 research outputs found
The Canadian ‘Model Forest’ approach : a way forward for Tasmania?
Forest policy and forestry management in Tasmania have undergone a number of changes in the last thirty years, many explicitly aimed at improving industry sustainability, job security, and forest biodiversity conservation. Yet forestry remains a contentious issue in Tasmania, due to a number of interacting factors, most significant of which is the prevalence of a ‘command and control’ governance approach by policymakers and managers. New approaches such as multiple-stakeholder decision-making, adaptive management, and direct public participation in policymaking are needed. Such an approach has been attempted in Canada in the last decade, through the Canadian Model Forest Program, and may be suitable for Tasmania. This paper seeks to describe what the Canadian Model Forest approach is, how it may be implemented in Tasmania, and what role it may play in the shift to a new forestry paradigm. Until such a paradigm shift occurs contentions and confrontations are likely to continue
The contrasting physiological and subjective effects of chewing gum on social stress
Uncertainty exists with respect to the extent to which chewing gum may attenuate stress-induced rises in cortisol secretion (Scholey et al., 2009; Smith, 2010; Johnson et al., 2011). The present study used the Trier Social Stress Task (TSST: Kirschbaum et al., 1993), a task known to elevate cortisol secretion (Kudielka et al., 2004), in order to examine the moderating physiological and subjective effects of chewing gum on social stress. Forty participants completed the TSST either with or without chewing gum. As expected, completion of the TSST elevated both cortisol and subjective stress levels, whilst impairing mood. Although gum moderated the perception of stress, cortisol concentrations were higher following the chewing of gum. The findings are consistent with Smith (2010) who argued that elevations in cortisol following the chewing of gum reflect heightened arousal. The findings suggest that chewing gum only benefits subjective measures of stress. The mechanism remains unclear; however, this may reflect increased cerebral blood flow, cognitive distraction, and/or effects secondary to task facilitation
Tungsten Behavior at High Temperature and High Stress
Recently reported results on the tungsten lifetime/fatigue tests under conditions expected in the Neutrino Factory target have strengthened the case of solid target option for a Neutrino Factory. This paper gives description of the detailed measurements of the tungsten properties at high temperature and high stress. We have performed extensive set of measurements of the surface displacement and velocity of the tungsten wires that were stressed by passing a fast, high current pulse through a thin sample. Radial and longitudinal oscillations of the wire were measured by a Laser Doppler Vibrometer. The wire was operated at temperatures of 300-2500 K by adjusting the pulse repetition rate. In doing so we have tried to simulate the conditions (high stress and temperature) expected at the Neutrino Factory. Most important result of this study is an experimental confirmation that strength of tungsten remains high at high temperature and high stress. The experimental results have been found to agree very well with LS-DYNA modelling results
High-pressure annealing of a prestructured nanocrystalline precursor to obtain tetragonal and orthorhombic polymorphs of Hf3N4
Transition metal nitrides containing metal ions in high oxidation states are a significant goal for the discovery of new families of semiconducting materials. Most metal nitride compounds prepared at high temperature and high pressure from the elements have metallic bonding. However amorphous or nanocrystalline compounds can be prepared via metal-organic chemistry routes giving rise to precursors with a high nitrogen:metal ratio. Using X-ray diffraction in parallel with high pressure laser heating in the diamond anvil cell this work highlights the possibility of retaining the composition and structure of a metastable nanocrystalline precursor under high pressure-temperature conditions. Specifically, a nanocrystalline Hf3N4 with a tetragonal defect-fluorite structure can be crystallized under high-P,T conditions. Increasing the pressure and temperature of crystallization leads to the formation of a fully recoverable orthorhombic (defect cottunite-structured) polymorph. This approach identifies a novel class of pathways to the synthesis of new crystalline nitrogen-rich transition metal nitrides
Origins and evolution of stomatal development
The fossil record suggests stomata-like pores were present on the surfaces of land plants over 400 million years ago.
Whether stomata arose once or whether they arose independently across newly evolving land plant lineages has long been
a matter of debate. In Arabidopsis, a genetic toolbox has been identified that tightly controls stomatal development and
patterning. This includes the basic helix-loop-helix (bHLH) transcription factors SPEECHLESS (SPCH), MUTE, FAMA, and
ICE/SCREAMs (SCRMs), which promote stomatal formation. These factors are regulated via a signaling cascade, which
includes mobile EPIDERMAL PATTERNING FACTOR (EPF) peptides to enforce stomatal spacing. Mosses and hornworts,
the most ancient extant lineages to possess stomata, possess orthologs of these Arabidopsis (Arabidopsis thaliana) stomatal
toolbox genes, and manipulation in the model bryophyte Physcomitrella patens has shown that the bHLH and EPF
components are also required for moss stomatal development and patterning. This supports an ancient and tightly
conserved genetic origin of stomata. Here, we review recent discoveries and, by interrogating newly available plant
genomes, we advance the story of stomatal development and patterning across land plant evolution. Furthermore, we
identify potential orthologs of the key toolbox genes in a hornwort, further supporting a single ancient genetic origin of
stomata in the ancestor to all stomatous land plants
Stomata and sporophytes of the model moss physcomitrium patens
Mosses are an ancient land plant lineage and are therefore important in studying the evolution of plant developmental processes. Here, we describe stomatal development in the model moss species Physcomitrium patens (previously known as Physcomitrella patens) over the duration of sporophyte development. We dissect the molecular mechanisms guiding cell division and fate and highlight how stomatal function might vary under different environmental conditions. In contrast to the asymmetric entry divisions described in Arabidopsis thaliana, moss protodermal cells can enter the stomatal lineage directly by expanding into an oval shaped guard mother cell (GMC). We observed that when two early stage P. patens GMCs form adjacently, a spacing division can occur, leading to separation of the GMCs by an intervening epidermal spacer cell. We investigated whether orthologs of Arabidopsis stomatal development regulators are required for this spacing division. Our results indicated that bHLH transcription factors PpSMF1 and PpSCRM1 are required for GMC formation. Moreover, the ligand and receptor components PpEPF1 and PpTMM are also required for orientating cell divisions and preventing single or clustered early GMCs from developing adjacent to one another. The identification of GMC spacing divisions in P. patens raises the possibility that the ability to space stomatal lineage cells could have evolved before mosses diverged from the ancestral lineage. This would have enabled plants to integrate stomatal development with sporophyte growth and could underpin the adoption of multiple bHLH transcription factors and EPF ligands to more precisely control stomatal patterning in later diverging plant lineages. We also observed that when P. patens sporophyte capsules mature in wet conditions, stomata are typically plugged whereas under drier conditions this is not the case; instead, mucilage drying leads to hollow sub-stomatal cavities. This appears to aid capsule drying and provides further evidence for early land plant stomata contributing to capsule rupture and spore release
Origins and evolution of stomatal development
The fossil record suggests stomata-like pores were present on the surfaces of land plants over 400 million years ago.
Whether stomata arose once or whether they arose independently across newly evolving land plant lineages has long been
a matter of debate. In Arabidopsis, a genetic toolbox has been identified that tightly controls stomatal development and
patterning. This includes the basic helix-loop-helix (bHLH) transcription factors SPEECHLESS (SPCH), MUTE, FAMA, and
ICE/SCREAMs (SCRMs), which promote stomatal formation. These factors are regulated via a signaling cascade, which
includes mobile EPIDERMAL PATTERNING FACTOR (EPF) peptides to enforce stomatal spacing. Mosses and hornworts,
the most ancient extant lineages to possess stomata, possess orthologs of these Arabidopsis (Arabidopsis thaliana) stomatal
toolbox genes, and manipulation in the model bryophyte Physcomitrella patens has shown that the bHLH and EPF
components are also required for moss stomatal development and patterning. This supports an ancient and tightly
conserved genetic origin of stomata. Here, we review recent discoveries and, by interrogating newly available plant
genomes, we advance the story of stomatal development and patterning across land plant evolution. Furthermore, we
identify potential orthologs of the key toolbox genes in a hornwort, further supporting a single ancient genetic origin of
stomata in the ancestor to all stomatous land plants
Conjugate gradient algorithms and the Galerkin boundary element method
Original article can be found at: http://www.sciencedirect.com/science/journal/08981221 Copyright Elsevier Ltd. DOI: 10.1016/j.camwa.2004.02.002Peer reviewe
Studies on a bovine Babesia transmitted by Hyalomma marginatum rufipes Koch, 1844
A Babesia sp. was recently observed in Hyalomma marginatum rufipes and found to be transmissible to bovines. Further observations were carried out on this parasite and a study made of the morphology of stages in both erythrocytes and tick haemolymph. Apart from Babesia divergens intra-erythrocytic parasites were not readily distinguishable from bovine Babesia spp. Merozoites in tick haemolymph morphologically resembled those of Babesia bigemina, but they were significantly larger. This Babesia sp. proved to be highly infective for adult H. m. rufipes, with transmission taking place transovarially and next generation nymphae and adults transmitting the infection.
Features of the infection were its very low pathogenicity, even in splenectomized animals, and the tendency of parasitized erythrocytes to accumulate in capillaries.
Serologically, this species could be differentiated from Babesia bigemina, B. divergens, B. bovis and B. major. A serological survey of 25 farms showed a wide distribution of this species in South Africa and its high rate of transmission on most properties. It was concluded that this is a true but hitherto undescribed bovine Babesia sp. and the name Babesia occultans n. sp. is proposed.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi.
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format
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