http://www.researchonline.mq.edu.au/vital/access/services/Feed ${session.getAttribute("locale")} 5 http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:25582 An apparatus for measuring the complex impedance of samples with high impedances is described. Complex impedance spectra were collected from a range of borosilicate glasses of composition (B₂O₃)₄(Li₂O)(LiBr)ₓ(NaBr)₁₋ₓ at pressures and temperatures ranging from 1 to 5 GPa and 350 to 450 °C, respectively. These data were used to determine AC conductivities and activation energies in order to test the Modified Random Network model of glass structure. Our results are in line with the predictions of this theory. 2013-05-15T14:20:06.410Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:25515 We present isothermal volume compression behavior of two polycrystalline (Mg,Fe)O samples with FeO = 39 and 78 mol% up to ~90 GPa at 300 K using synchrotron X-ray diffraction and neon as a pressure-transmitting medium. For the iron-rich (Mg₀․₂₂Fe₀․₇₈)O sample, a structural transition from the B1 structure to a rhombohedral structure was observed at 41.6 GPa, with no further indication of changes in structural or compression behavior changes up to 93 GPa. In contrast, a change in the compression behavior of (Mg₀․₆₁Fe₀․₃₉)O was observed during compression at P ≥ 71 GPa and is indicative of a spin crossover occurring in the Fe²⁺ component of (Mg₀․₆₁Fe₀․₃)O. The low-spin state exhibited a volume collapse of ~3.5%, which is a larger value than what was observed for a similar composition in a laser-heated NaCl medium. Upon decompression, the volume of the high-spin state was recovered at approximately 65 GPa. We therefore bracket the spin crossover at 65 ≤P (GPa) ≤77 at 300 K (Mg₀․₆₁Fe₀․₃)O. We observed no deviation from the B1 structure in (Mg₀․₆₁Fe₀․₃)O throughout the pressure range investigated. 2013-05-13T00:20:12.296Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:24546 15 pages(s) 2013-03-04T05:00:13.709Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:24351 This study examined attentional biases for emotional faces in borderline personality disorder (BPD). Twenty-one outpatient youth (aged 15-24 years) meeting three or more DSM-IV BPD criteria and 20 community-derived participants (aged 15-24 years) with no history of psychiatric problems and not meeting any BPD criteria completed a modified dot-probe task that tested automatic (30 ms) and controlled (500 ms) stages of information processing. The findings indicate that, compared with healthy controls, youth with borderline features were faster to respond to congruent rather than incongruent fear stimuli. This effect was independent of state anxiety and was observed during the 30 ms presentation of fearful faces. There was no significant effect for happy or angry faces. Youth with borderline features were also slower to respond to incongruent rather than paired neutral trials, indicating difficulties in disengaging attention from the perceived threat. Such differences were not found for the healthy controls. Thus, youth with borderline features had an attentional bias for fearful faces that reflected difficulty in disengaging attention from threatening information during preconscious stages of attention. This finding extends previous research highlighting the diminished capacity for affect regulation and subsequent engagement in behavioural strategies to avoid distress in BPD. Future research should explore the relationship between information processing, emotion regulation in adult BPD samples. 2013-02-27T05:25:33.741Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:22198 1. Introduction -- 2. Proximal and Distal Causes of Individual Differences in Reading -- 3. Dual-Route Theories of Reading -- 4. Acquired Dyslexia -- 5. Reading Acquisition -- 6. Reading Acquisition Difficulties -- 7. Precocious Reading -- 8. Conclusions. 2012-10-23T00:32:43.277Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:21567 The methods used by the Australian Bureau of Statistics (ABS) to estimate life expectancies of Aboriginal and Torres Strait Islander peoples in 2009 have been controversial and require critical and sensitive analysis. The introduction by ABS of the direct method for estimating Indigenous life expectancies, based on estimated deaths and populations, has been generally welcomed. But the way this method has been applied and, in particular, death estimates used by the ABS, warrant scrutiny. These estimates were based on a first ever linkage between Indigenous deaths and census records following the 2006 census. Census-based identification was used in place of identification in the death registrations, rather than as a supplementary data source. The various national, state and regional life expectancy estimates published may have been biased upwards by this process. Because the impact of the methodology varies across Australia, regional differentials reported appear substantial but are not soundly based. The questionable ABS results are highlighted and discussed. Analysis based on more comprehensive linkage of death records in New South Wales over 5 years suggests that the ABS methods have understated Indigenous deaths and so overstated life expectancy. The effect of an alternative ABS approach is also discussed. ABS estimates published in 2009 are not necessarily definitive and may well overestimate Aboriginal and Torres Strait Islander life expectancy and underestimate the life expectancy gap. Estimates should be based on accurate estimates of deaths and population. Consultation and a thorough review are essential before the next round of estimates following the findings of the 2011 population census. Closing the Gap commitments focus on eliminating the life expectancy gap between Aboriginal and Torres Strait Islander peoples and other Australians. Life expectancy estimates need to be based on methods and data that are well understood and broadly supported. The alternative is unproductive debate about statistics rather than the range of policies and resourcing issues needed to improve Indigenous health. 2012-09-21T05:50:15.241Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:19890 Lineages undergoing rapid radiations provide exceptional opportunities for studying speciation and adaptation, but also represent a challenge for molecular systematics because retention of ancestral polymorphisms and the occurrence of hybridization can obscure relationships among lineages. Dolphins in the subfamily Delphininae are one such case. Non-monophyly, rapid speciation events, and discordance between morphological and molecular characters have made the inference of phylogenetic relationships within this subfamily very difficult. Here we approach this problem by applying multiple methods intended to estimate species trees using a multi-gene dataset for the Delphininae (Sousa, Sotalia, Stenella, Tursiops, Delphinus and Lagenodelphis). Incongruent gene trees obtained indicate that incomplete lineage sorting and possibly hybridization are confounding the inference of species history in this group. Nonetheless, using coalescent-based methods, we have been a ble to extract an underlying species-tree signal from divergent histories of independent genes. This is the first time a molecular study provides support for such relationships. This study further illustrates how methods of species-tree inference can be very sensitive both to the characteristics of the dataset and the evolutionary processes affecting the evolution of the group under study. 2012-06-18T09:43:42.720Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:19805 Aims To assess the impact of retail displays of tobacco on tobacco smoking and purchase by smokers and attempting quitters. Design Population-based diary style survey. Setting NSW, Australia. Participants A total of 998 smokers and 111 attempting quitters. Measurements Demographic measures and 4-hourly records over 4 days: number of cigarettes smoked and bought; exposure to cigarette smoking by friends/family or other smokers; and exposure to retail displays of tobacco. Findings Subjects reported seeing cigarettes for sale in more than 40% of the time-periods when they were outside their home. After allowing for factors which are known to increase smoking, people who saw cigarettes for sale were more likely to smoke, and smoked more cigarettes, even if they did not buy cigarettes in the same time-period. There was marginally significant evidence that people exposed to retail displays of tobacco in one time-period were more likely to buy in the following time-period. Conclusions In an environment which permits point-of-sale displays, smokers were found to see tobacco displays in more than 40% of the 4-hour periods that they were outside the home. Exposure to such tobacco displays was associated with a higher probability of smoking, and with higher levels of smoking, even when subjects did not purchase cigarettes. 2012-06-14T08:04:35.797Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:18864 EMU is a wide-field radio continuum survey planned for the new Australian Square Kilometre Array Pathfinder (ASKAP) telescope. The primary goal of EMU is to make a deep (rms ∼10Jy/beam) radio continuum survey of the entire Southern sky at 1.3GHz, extending as far North as +30 declination, with a resolution of 10arcsec. EMU is expected to detect and catalogue about 70million galaxies, including typical star-forming galaxies up to z∼1, powerful starbursts to even greater redshifts, and active galactic nuclei to the edge of the visible Universe. It will undoubtedly discover new classes of object. This paper defines the science goals and parameters of the survey, and describes the development of techniques necessary to maximise the science return from EMU. 2012-04-30T05:13:23.949Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:18896 Rhou encodes a Cdc42-related atypical Rho GTPase that influences actin organization in cultured cells. In mouse embryos at earlysomite to early-organogenesis stages, Rhou is expressed in the columnar endoderm epithelium lining the lateral and ventral wall of the anterior intestinal portal. During foregut development, Rhou is down regulated in regions where the epithelium acquires a multilayered morphology heralding the budding of organ primordia. In embryos generated from Rhou knockdown embryonic stem (ES) cells, the embryonic foregut displays an abnormally flattened shape. The epithelial architecture of the endoderm is disrupted, the cells are depleted of microvilli and the phalloidin-stained F-actin content of their sub-apical cortical domain is reduced. Rhou-deficient cells in ES cell-derived embryos and embryoid bodies are less efficient in endoderm differentiation. Impaired endoderm differentiation of Rhou-deficient ES cells is accompanied by reduced expression of c-Jun/AP-1 target genes, consistent with a role for Rhou in regulating JNK activity. Down regulation of Rhou in individual endoderm cells results in a reduced ability of these cells to occupy the apical territory of the epithelium. Our findings highlight epithelial morphogenesis as a required intermediate step in the differentiation of endoderm progenitors. In vivo, Rhou activity maintains the epithelial architecture of the endoderm progenitors, and its down regulation accompanies the transition of the columnar epithelium in the embryonic foregut to a multilayered cell sheet during organ formation. 2012-04-30T05:11:02.402Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:18095 This is the first description of the natural history and behaviour of Stenolemus giraffa Wygodzinsky, an emesine assassin bug (Reduviidae; Emesinae) from Australia. Field data from sites in the Northern Territory and Western Australia, complemented by observations from staged predatory interactions in the laboratory, show that this species is a web-invading araneophage. In the field, S. giraffa was found on rock escarpments, associated with 10 spider species. Spiders of the genus Trichocyclus (Pholcidae) dominated this species' natural diet at all field locations. Predatory sequences appear to emphasise stealth and were characterised by S. giraffa slowly stalking the resident spider until within striking range. Stenolemus giraffa approached the spiders by breaking silk threads in its path while walking across the rock substrate beneath the web or hanging directly from the web. Observations of S. giraffa being attacked, and sometimes killed, by spiders illustrate that araneophagy is a dangerous strategy for these insects. Natural history and behaviour of most emesine species is currently unknown and so the present study provides an important landmark. Findings from this study add to growing evidence that araneophagy is prevalent in the emesine genus Stenolemus and that considerable variation in predatory tactics occur within this genus. © 2011 The Royal Society of New Zealand. 2012-03-14T15:00:29.989Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:18097 Predatory arthropods that specialize in invading webs and preying on the resident spiders ('araneophagic predators') face special challenges. As webs are exceedingly good at transmitting vibrations, it is difficult for a web invader to move through the web and remain undetected by the spider. An araneophagic predator that generates vibrations in the web may risk prey escaping or even counterattacking. To increase the chances of an undetected approach, predators may exploit episodes of environmental noise to approach, while their prey's ability to detect them is compromised ('opportunistic smokescreen behaviour'). Here we provide the first experimental evidence of convergent opportunistic smokescreen behaviour in an araneophagic insect, Stenolemus bituberus Stål (Reduviidae), which preys on web-building spiders. We tested how two common types of environmental noise, wind and localized vibrations in the web, influence the predatory behaviour and success of assassin bugs when hunting spiders. We found that assassin bugs were more likely to catch the spider in the presence of wind. During episodes of environmental noise, assassin bugs stepped more often and walked in a more continuous manner, apparently exploiting the opportunity to approach while the prey's sensory system is less able to detect the predator. Changes in predatory behaviour in the presence of environmental noise were not evident when S. bituberus was in an unoccupied spider web. This supports our hypothesis that noise-related timing of behaviour reflects decisions made as part of a predatory strategy, rather than responses to physical disturbance. 2012-03-14T15:00:16.320Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:17303 Despite a variety of long-standing tobacco control policies in most countries, smoking remains a source of considerable economic and health costs, resulting in ongoing discussion of potential policy changes. The contribution of retail tobacco distribution to prompting, facilitating and normalising smoking has received increasing attention, but the effect of retail outlets on tobacco consumption is relatively under-researched. In particular, there has been almost no empirical research on whether different retail outlets types have different effects on tobacco consumption by different types of smokers. This paper reports on two large studies examining the purchase behaviour of independent samples of smokers. The results provide the first evidence on the frequency of exposure of adult smokers to tobacco outlets, and show differences in tobacco purchase size across different retailers, and differences in the use of tobacco retailers by different smoker types. Implications for public health and tobacco control policy are discussed. 2012-02-05T17:22:27.619Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:16759 Copper isotope fractionation factors have been determined experimentally at temperatures of 250 and 300°C for fluid salinities of 1, 3, 5 and 7 molal Cl-, and starting acidity of 0, 0.01, 0.1, 0.2 and 0.6 molar HCl. The experiments, which follow a partial dissolution of natural chalcopyrite in a hydrothermal fluid from 7 to 30days, yield a significant range of leached copper-residual chalcopyrite isotopic fractionations. These appear to be pH, temperature and salinity dependent, with pH showing the greatest apparent control over the magnitude of fractionation. For weakly acidic conditions, preferential incorporation of the light isotope into the leached phase(s) generally occurred. Experiments gained a maximum fractionation magnitude at intermediate pH (4-7), where the leached copper-chalcopyrite fractionation magnitude reached to -1‰, depending on fluid salinity and temperature. Fractionation decreased at higher and lower solubility (pH) conditions. The highest pH experiments showed a small positive fractionation (approx. +0.2 to 0.3‰). Limited reproducibility of the experiments is related to unconstrained physicochemical conditions (primarily pH and fO2). A major control on the fractionation magnitude appears to be the degree of partitioning of Cu between vapor and liquid phases, which is controlled by pH and salinity. The copper-bearing vapor species permitting significant mass transfer to the vapor apparently differ with salinity and temperature. Under certain experimental conditions one or more vapor species forms and produces significant isotopic fractionation between the copper in the liquid and copper in the vapor. The experiments indicate that the likelihood of observing significant isotopic fractionation in hypogene ore forming systems depends on the pH of the mineralizing fluid and the controls over partitioning of Cu between a vapor and liquid phase. 2012-01-10T00:11:23.527Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:16668 Objective: To investigate the potential of record linkage between the Australian Bureau of Statistics (ABS) mortality data and the NSW Admitted Patient Data Collection (APDC) to improve reporting of deaths among Aboriginal and Torres Strait Islander peoples. Methods: ABS mortality data for 2002 to 2006 were linked with APDC records for 2001 to 2006. Six algorithms were developed to enumerate deaths. Possible biases by age, sex and geographic remoteness were investigated. Results: Levels of reporting ranged from baseline reporting on the ABS mortality data to the largest enhancement with the ‘ever reported as Aboriginal or Torres Strait Islander’ algorithm. Enhancement was more likely in females, older people and residents of major cities. Conclusions: Data linkage substantially improved reporting of Aboriginal and Torres Strait Islander deaths. An algorithm that includes both the number of APDC records and the number of facilities reporting a person as Aboriginal or Torres Strait Islander was considered most promising. Implications: Inclusion of other datasets in the enhancement process is warranted to further improve reporting and address possible bias produced by using APDC records only. Further work should take into account the possibility that a person may be falsely reported as Aboriginal or Torres Strait Islander or not reported in either hospital or death records. 2012-01-05T14:32:37.186Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:3665 Background: All vectors of human malaria, a disease responsible for more than one million deaths per year, are female mosquitoes from the genus Anopheles. Evarcha culicivora is an East African jumping spider (Salticidae) that feeds indirectly on vertebrate blood by selecting blood-carrying female mosquitoes as preferred prey. Methodology/Principal Findings: By testing with motionless lures made from mounting dead insects in lifelike posture on cork discs, we show that E. culicivora selects Anopheles mosquitoes in preference to other mosquitoes and that this predator can identify Anopheles by static appearance alone. Tests using active (grooming) virtual mosquitoes rendered in 3-D animation show that Anopheles' characteristic resting posture is an important prey-choice cue for E. culicivora. Expression of the spider's preference for Anopheles varies with the spider's size, varies with its prior feeding condition and is independent of the spider gaining a blood meal. Conclusions/Significance: This is the first experimental study to show that a predator of any type actively chooses Anopheles as preferred prey, suggesting that specialized predators having a role in the biological control of disease vectors is a realistic possibility. 2011-11-15T04:43:43.783Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:15870 We present a narrow-linewidth, linearly polarized neodymium-doped fiber laser that incorporates a point-by-point Bragg grating inscribed into the core of a single-polarization all-solid photonic bandgap fiber. The Bragg grating was written within a single-polarization wavelength band of the fiber; thus, the Bragg reflection was polarized. This all-fiber laser produced 7.2W, linearly polarized output with 25pm FWHM and 19.6 dB polarization extinction ratio. 2011-11-09T03:10:36.297Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:15805 If Borderline Personality Disorder (BPD) is characterized by an underlying emotional sensitivity, individuals with this disorder would be expected to demonstrate accurate identification of emotional expressions at earlier stages of expression (i.e., lower thresholds of facial expressivity across all emotional valences). Twenty-one outpatient youth (aged 15-24. years) meeting 3 or more DSM-IV BPD criteria and 20 community-derived participants (aged 15-24. years) with no history of psychiatric problems were tested on a measure of emotional sensitivity, the Face Morph Task. In this test faces morph from neutral to each of the six basic emotional expressions. The BPD group showed no evidence of heightened sensitivity to emotional facial expressions compared to the community control group (all P> 0.05 and effect sizes ranging from 0 to 0.6). They require comparable levels of emotional expressivity in order to correctly identify emotions. Therefore, emotional sensitivity might not be apparent early in the course of BPD. Rather, it might develop later in the course of the disorder or be present only in severe BPD. 2011-11-05T12:11:24.411Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:15678 Climate change is predicted to become a major threat to biodiversity in the 21st century, but accurate predictions and effective solutions have proved difficult to formulate. Alarming predictions have come from a rather narrow methodological base, but a new, integrated science of climate-change biodiversity assessment is emerging, based on multiple sources and approaches. Drawing on evidence from paleoecological observations, recent phenological and microevolutionary responses, experiments, and computational models, we review the insights that different approaches bring to anticipating and managing the biodiversity consequences of climate change, including the extent of species' natural resilience. We introduce a framework that uses information from different sources to identify vulnerability and to support the design of conservation responses. Although much of the information reviewed is on species, our framework and conclusions are also applicable to ecosystems, habitats, ecological communities, and genetic diversity, whether terrestrial, marine, or fresh water. 2011-10-25T05:50:26.626Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:3669 Field data suggest that ants may be important predators of mantises which, in turn, may be important predators of jumping spiders (Salticidae). Using a tropical fauna from the Philippines as a case study, the reactions of mantises to ants, myrmecomorphic salticids (i.e. jumping spiders that resemble ants) and ordinary salticids (i.e. jumping spiders that do not resemble ants) were investigated in the laboratory. Three mantis species (Loxomantis sp., Orthodera sp., and Statilia sp.) were tested with ten ant species, five species of Myrmarachne (i.e. myrmecomorphic salticids), and 23 ordinary salticid species. Two categories of the myrmecomorphic salticids were recognized: (1) 'typical Myrmarachne' (four species with a strong resemblance to ants) and (2) Myrmarachne bakeri (a species with less strong resemblance to ants). Ants readily killed mantises in the laboratory, confirming that, for the mantises studied, ants are dangerous. In alternate-day testing, the mantises routinely preyed on the ordinary salticids, but avoided ants. The mantises reacted to myrmecomorphic salticids similarly to how they reacted to ants (i.e. myrmecomorphic salticids appear to be, for mantises, Batesian mimics of ants). Although myrmecomorphic salticids were rarely eaten, M. bakeri was eaten more often than typical Myrmarachne. Because the mantises had no prior experience with ants, ant mimics or ordinary salticids, our findings suggest that mantises have an innate aversion to attacking ants and that this aversion is generalized to myrmecomorphic salticids even in the absence of prior experience with ants. 2011-07-04T09:32:12.138Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:12183 Many predators are averse to attacking ants and many palatable arthropods are Batesian mimics of ants. We considered whether aggregating Batesian mimics of ants can become more repelling to ant-averse predators by, as a group, resembling groups of ants (collective mimicry). Myrmarachne melanotarsa is a gregarious ant-like jumping spider (Salticidae) that resembles and associates with the ant Crematogaster sp. We used three large ant-averse salticids as predators in experiments. Besides M. melanotarsa and Crematogaster we used midges (Chaoborus sp.) and a small nonant-like, but gregarious, salticid (Menemerus sp.) as prey. The predators readily attacked both live midges and the nonant-like salticids that were presented singly or in groups but rarely attacked ants or ant mimics. Predators attacked ants and ant mimics presented in groups less often than they attacked solitary ants and ant mimics. In another experiment, motionless lures (groups of arthropods mounted in lifelike posture) were used. The findings showed that, independent of prey behaviour and movement, the predators were averse to being in close proximity to groups of ants and ant mimics, but had no evident aversion to the close proximity of groups of nonant-like salticids. Palatability tests demonstrated that the predators fed for long periods on M. melanotarsa, Menemerus and Chaoborus, but released Crematogaster almost immediately. Our results suggest that these predators have an innate aversion to ants and ant mimics and also that they are innately predisposed to perceive a group of ants (or ant mimics) as more repelling than solitary ants or ant mimics. 2011-04-04T07:02:10.733Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:12335 Batesian mimicry is classically studied under the premise that aversion to noxious or dangerous animals is learned and is extended to the mimics, benefiting the mimics through reduced predation. We extend this model to include innate aversion to dangerous models (ants) and their mimics (jumping spiders in the genus Myrmarachne). We show that mantises with no prior experience with ants, or spiders, are averse to both ants and Myrmarachne, but not to ‘ordinary’ jumping spiders. We show that specialist spider-eating spiders are also averse to Myrmarachne, but that specialist ant-eating spiders are attracted to Myrmarachne, thus providing a rare empirical example of the costs associated with mimicry. Furthermore, Myrmarachne are sexually dimorphic. Although adult females and juveniles of both sexes are distinctly ant-like in appearance, Myrmarachne males have elongated chelicerae that might appear to detract from their resemblance to ants. Experimental findings suggest that the Myrmarachne male’s solution is to adopt compound mimicry; the male’s model seems to be not simply an ant worker but a combination of an ant and something carried in the ant’s mandibles. By becoming a mimic of a particular subset of worker ants, Myrmarachne males appear to have retained their Batesian-mimicry defence against ant-averse predators, but at the price of receiving the unwanted attention of ant-specialist predators for which encumbered ants are preferred prey. 2011-03-31T19:10:54.706Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:12051 Fibre Bragg gratings inscribed with the point-by-point method using a Ti-sapphire femtosecond laser operating at 800 nm are shown to display strong increasing attenuation towards shorter wavelengths with a large and spectrally sharp recovery observed below 400 nm. The origin of this loss is shown to be Mie scattering, and the sharp recovery in the transmission results from wavelength dependent scattering within the numerical aperture of the core. The permanent losses from these Type II gratings have implications for high temperature sensors and fibre lasers. 2011-03-03T08:20:56.439Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:4329 We have confirmed the suggestion of Gibson and Österberg [Opt. Lett. 30, 1827 (2005)] that the lasing action observed in Rhodamine 6G-doped microstructured polymer fibers [Argyros et al., Opt. Lett. 29, 1882 (2004)] is due to stimulated Raman scattering. The Raman scattering occurs in the poly(methyl methacrylate) host material, and upon further investigation emission up to the third Stokes order was observed. Lasing of the dye in a microstructured polymer fiber was achieved with a modification of the fiber properties. 2011-02-02T06:23:05.406Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:11352 1 page(s) 2011-01-18T19:50:29.146Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:11353 The distribution of Ni in geological materials is controlled by a number of key processes depending on the geological context: these include partial melting for mantle materials and mantle-derived magmas, and shallow fluid-related processes during ore-body genesis. The measurement of the stable isotopes of Ni could provide data that may be useful to understand these processes and for geochemical fingerprinting. So far this has been hampered by the lack of a reliable and simple separation technique to produce high-purity Ni solutions. We have undertaken development of a separation technique to separate Ni from rock matrices to measure Ni isotopes by plasma source mass spectrometry. Tests show that Ni can be isolated from geological materials using a simple two-column procedure. An Icelandic basalt, BIR-1, was digested and used during the development of this method. The sample was first passed through Biorad anion exchange resin AG MP1-M in HCl form in order to remove the Fe and Cu from the sample. The Ni is eluted with the bulk matrix elements and 100% of the Cu and Fe are retained on the column. The sample fraction containing the Ni and matrix elements was then passed through Eichrom Ni specific resin in an HCl and ammonium citrate solution with a pH of 8-9. The Ni in the form of a dimethylglyoxime complex was stripped with 3 M HNO₃. It was found that the preliminary removal of Fe and Cu is essential, as these elements are eluted with Ni and would prove to be a problem during subsequent isotope analysis. Multi-elemental scans of sample solutions on an Agilient 7500CS quadropole ICPMS revealed the Ni is isolated from matrix elements using this protocol. The proposed method provides a 95± 2% recovery of Ni. Continuing refinement for this method relevant to different types of geological samples is in progress. 2011-01-18T19:50:28.863Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:11354 Quantitative trace-element analyses of >40 elements in >500 diamonds have been carried out by LAM-ICPMS, using a multi-element-doped cellulose standard; detection limits range to low-ppb levels for many elements [1]. The trace-element patterns of polycrystalline (framesite, diamondite) and fibrous/particulate diamonds are consistent with crystallisation directly from kimberlitic-carbonatitic melts, which show significant compositional variation from locality to locality. However, many fibrous/particulate diamonds show an abrupt change in trace-element patterns as crystallisation proceeds. Large decreases in Nb/Ta and Zr/Hf are difficult to explain by fractional crystallisation, but can be modelled as the result of liquid immiscibility: a separation into broadly hydrous-silicate and carbonatite fluids. The ubiquitous development of pronounced negative Y anomalies (relative to Ho-Dy) may reflect the separation of fluoride phases or immiscible fluoride melts; microinclusions with positive Y anomalies are observed during ablation of diamondites. Despite significant variation from one deposit to another, nearly all monocrystalline diamonds show low LREE/HREE, Ba/MREE and Sr/MREE, as well as low Nb/Ta and Zr/Hf, suggesting that they have crystallised from the hydrous-silicate member of the proposed immiscible-liquid couple. Modelling of the conjugate Mg-rich “carbonatite” fluid shows it would have extremely high LREE/HREE and Sr. The reaction of this fractionated carbonatitic fluid with chromite + olivine + opx can produce subcalcic Cr-pyrope garnets with “sinuous” REE patterns and high Sr contents, which are a characteristic inclusion in diamonds of the peridotitic paragenesis. We therefore suggest that the development of immiscibility during the evolution of low-volume melts of the kimberlite–carbonatite spectrum produces conjugate fluids, one of which crystallises most monocrystalline diamonds, and the other of which interacts with mantle harzburgites to produce the most ubiquitous inclusions in peridotitic diamonds. Preliminary comparative studies show little difference in the trace-element patterns of peridotitic and eclogitic diamonds from single localities. This implies limited interaction between fluid and wall rock, which in turn suggests high fluid/rock ratios during diamond crystallisation. 2011-01-18T19:50:24.310Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:2968 We report on the power scaling to 103 W of a 1.1 μm continuous-wave Yb³⁺-doped silica fiber laser incorporating a point-by-point (PbP) fiber-Bragg grating inscribed directly into the active core using 800 nm femtosecond laser pulses. The spectrum of the laser exhibited a narrow linewidth that broadened to 260 pm at 103 W. The output was frequency doubled using an 11 mm long periodically poled MgO:LiNbO₃ crystal to generate 2.1 W of green with an internal conversion efficiency of 10% at high power and 0.81%/W at low power. 2011-01-17T05:58:19.444Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:2970 We report on a narrowband 5 W cw fiber laser incorporating a point-by-point fiber Bragg grating inscribed into the core of a Yb³⁺-doped double-clad fiber. The laser featured excellent long-term wavelength and power stability (0.3%), as well as a very narrow (15 pm) linewidth, when passive temperature stabilization of the grating was implemented. 2011-01-17T05:58:16.491Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:11252 CLIC1 belongs to a family of highly conserved and widely expressed intracellular chloride ion channel proteins existing in both soluble and membrane integrated forms. To study the physiological and biological role of CLIC1 in vivo, we undertook conditional gene targeting to engineer Clic1 gene knock-out mice. This represents creation of the first gene knock-out of a vertebrate CLIC protein family member. We first generated a Clic1 Knock-in (Clic1FN) allele, followed by Clic1 knock-out (Clic1−/−) mice by crossing Clic1FN allele with TNAP-cre mice, resulting in germline gene deletion through Cre-mediated recombination. Mice heterozygous or homozygous for these alleles are viable and fertile and appear normal. However, Clic1−/− mice show a mild platelet dysfunction characterized by prolonged bleeding times and decreased platelet activation in response to adenosine diphosphate stimulation linked to P2Y₁₂ receptor signaling. 2011-01-13T12:12:08.252Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:10646 5 page(s) 2010-11-19T08:50:41.022Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:10305 Major, trace, and rare earth element compositions of both tonalite–trondhjemite–granodiorite (TTG) and modern adakite-like magmas are typically used in conjunction with batch melting experiments and models to infer source rock composition, depth of melting and tectonic setting. However, batch melting does not capture the impact of melt segregation processes on magma geochemistry. We have used melting experiments in conjunction with numerical modelling to investigate the impact of melt segregation on TTG arc crust formation. Our melt segregation equilibrium (MSE) experiments are designed to reproduce the local changes in bulk composition that are predicted by the numerical model to occur as buoyant melt migrates upwards along grain boundaries and accumulates to form a magma that leaves the source region. The MSE experimental results show distinct differences in the melt and solid phase compositions and solid phase stability when compared with direct partial melting experiments. They yield a significant reduction in hornblende and plagioclase modal proportions at lower temperatures and partial melt compositions that are lower in An and have higher Mg-numbers. These results suggest that dynamic melt segregation and equilibrium processes may have a significant impact on modes, melt compositions and geochemical indicators such as Mg-numbers. Mantle wedge interaction may not be necessary to generate varying Mg-numbers in TTG and adakite magmas. Moreover, the use of batch melting models or experiments to interpret these geochemical signatures may not be appropriate. 2010-10-27T05:00:47.654Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:264 Sexual dimorphism is pronounced in Myrmarachne, a large genus of ant-like jumping spiders (Salticidae) and one of the major animal groups in which Batesian mimicry of ants has evolved. Although adult females and juveniles of both sexes are distinctly ant-like in appearance, Myrmarachne males have elongated chelicerae that might appear to detract from their resemblance to ants. Experimental findings suggest that the Myrmarachne male’s solution is to adopt compound mimicry (i.e. the male’s model seems to be not simply an ant worker but a combination of an ant and something carried in the ant’s mandibles: an ‘encumbered ant’). By becoming a mimic of a particular subset of worker ants, Myrmarachne males may have retained their Batesian-mimicry defence against ant-averse predators, but at the price of receiving the unwanted attention of predators for which encumbered ants are preferred prey. Two salticid species were used as predators in the experiments. Portia fimbriata is known to choose other salticids as preferred prey and to avoid unencumbered ants and their mimics (Myrmarachne females). In experiments reported here, P. fimbriata avoided encumbered ants and Myrmarachne males. Ants are the preferred prey of Chalcotropis gulosus. In our experiments, C. gulosus chose safer encumbered ants in preference to more dangerous unencumbered ants, chose Myrmarachne males more often than Myrmarachne females and showed no evidence of distinguishing between Myrmarachne males and encumbered ants. The cost of reconciling sexual dimorphism with Batesian mimicry appears to be that Myrmarachne males attract the unwanted attention of specialist predators of their compound model. 2010-10-18T03:50:12.084Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:2423 17 page(s) 2010-09-30T05:47:02.678Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:2126 Two populations of kimberlitic zircon are present in the Timber Creek kimberlites, Northern Territory. Laser-ablation ICP-MS U–Pb dating yields an age of 1483 ± 15 (2σ) Ma for the main group and an age of 179 ± 2 Ma for the other group. This distinction of two age groups is strongly supported by Hf isotope data on the same zircons. Although the trace-element patterns of both populations are typical of mantle-derived zircons, the ‘young’ population has slightly higher concentrations of most trace elements, but has lower Hf, Nb, Ta and Pb contents. The distinct differences in trace-element contents and Hf isotopic composition of the two zircon populations indicate that they were derived from different magma sources. The dating results indicate that the emplacement age of the Timber Creek kimberlites cannot be older than the age of the ‘young’ zircon population (i.e. 179 ± 2 Ma). This clarifies the inconsistency between the previously reported SHRIMP age of the Timber Creek zircons (1462 ± 53 Ma) and the much younger age (1200 Ma) of the sediments of the Victoria River Basin into which these kimberlites have intruded. The Timber Creek kimberlites are a newly recognised extension of the widespread Jurassic kimberlite activity known in Western Australia and South Australia (Wandagee, Orroroo, Cleve and Eurelia kimberlites). 2010-09-30T05:45:28.658Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:8823 Fiber lasers that utilize femtosecond (fs) laser inscribed type-II fiber Bragg gratings within the active medium are known to produce stable output powers in excess of 100 W during continuous-wave operation. However, here we show that the gratings undergo rapid annealing when employed as high reflectors in pulsed Q-switched fiber lasers operating at average power levels of less than 0.5 W. We demonstrate that a combination of a high population inversion and a high optical field seems to drive this annealing process and point out similarities to photodarkening. 2010-08-11T10:33:06.645Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:8858 20 page(s) 2010-07-06T07:40:28.918Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:251 A mimicry system was investigated in which the models were ants (Formicidae) and both the mimics and the predators were jumping spiders (Salticidae). By using motionless lures in simultaneous-presentation prey-choice tests, how the predators respond specifically to the static appearance of ants and ant mimics was determined. These findings suggest a rarely considered adaptive trade-off for Batesian mimics of ants. Mimicry may be advantageous when it deceives ant-averse potential predators, but disadvantageous in encounters with ant-eating specialists. Nine myrmecophagic (ant-eating) species (from Africa, Asia, Australia and North America) and one araneophagic (spider-eating) species (Portia fimbriata from Queensland) were tested with ants (five species), with myrmecomorphic (ant-like) salticids (six species of Myrmarachne) and with non-ant-like prey (dipterans and ordinary salticids). The araneophagic salticid chose an ordinary salticid and chose flies significantly more often than ants. Portia fimbriata also chose the ordinary salticid and chose flies significantly more often than myrmecomorphic salticids. However, there was no significant difference in how P. fimbriata responded to ants and to myrmecomorphic salticids. The myrmecophagic salticids chose ants and chose myrmecomorphic salticids significantly more often than ordinary salticids and significantly more often than flies, but myrmecophagic salticids did not respond significantly differently to myrmecomorphic salticids and ants. 2010-01-27T23:30:21.655Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:1920 A method has been developed for the in situ determination of Re-Os isotopes in single grains of sulfides in mantle-derived peridotites using a laser ablation microprobe attached to a multicollector-induced coupled plasma mass spectrometer (MC-ICPMS). High-precision Os isotope analysis by MC-ICPMS is demonstrated by the measurement of interlaboratory Os standards. Evaluation of mass bias correction procedures shows that the exponential law provides the best fit to the Os isotope data and that the ratio of the mass fractionation coefficients for Re and Os remains constant for the range of typical instrument operating conditions. This relationship enables the accurate and precise correction of the isobaric interference of ¹⁸⁷Re on ¹⁸⁷Os for ¹⁸⁷Re/¹⁸⁸Os values up to 1.6. Results are presented for single sulfide inclusions in olivine macrocryts from kimberlites in the Siberian and Slave Cratons, and sulfides enclosed in silicates and interstitial to silicates in peridotite xenoliths from the Slave Craton and Massif Central, France. Enclosed sulfides larger than 50 μm in diameter and with Os contents ≥40 ppm give ¹⁸⁷Os/¹⁸⁸Os ratios with a precision of 0.1% (2 SE), which is equivalent to N-TIMS whole-rock data. Interstitial sulfides typically have lower Os (10 to 30 ppm) and give analyses with lower precision (~1 to 2%) but still provide valuable information on the movement of Os within the lithosphere. The sulfide inclusions in silicates preserve significantly less radiogenic Os isotopic compositions than interstitial sulfides and accordingly produce significantly older and more realistic Re-Os age information. Whole-rock Os isotope compositions reflect the proportions of different generations of enclosed and interstitial sulfides; this calls into question the significance of many published “depletion ages.” 2010-01-27T23:10:31.344Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:2004 Coupling laser ablation sampling with MC-ICP-MS detection allows rapid, in situ determination of isotope ratios. However, measured isotope ratios can show large biases relative to the true ratio. We show that, at low laser pulse energies (3 J cm⁻²), the laser ablation aerosol of copper metal possessed a ⁶⁵Cu/⁶³Cu ratio that deviated by more than 12 ? units (12 parts per 10,000) from that of the sample. At high pulse energies (9 J cm⁻² and above), near isotopically stoichiometric ablation generally occurred. However, even at high pulse energies, on-line laser ablation-MC-ICP-MS Cu isotope ratios showed large biases (15–48 ? units) from the target sample. Filtering larger particles (>0.5 µm) from the ablation aerosol was accompanied by a reduction in signal that was generally much smaller than the associated reduction in volume transport (a factor of 2.8–84 for ablations in Ar), suggesting that volatilisation and ionisation of particles in the ICP was incomplete. Filtered aerosols always yielded isotopic values that were closer to the true value than unfiltered aerosols by an average of 18 ? units. These data suggest that, while significant isotopic fractionation occurred at the ablation site at low laser fluence, the dominant source of isotopic fractionation at high laser fluence was the preferential volatilisation of ⁶³Cu during incomplete vaporisation and ionisation in the ICP of particles greater than approximately 0.5 µm in diameter. 2010-01-27T23:09:22.855Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:2028 This paper reports new developments in in situ U–Pb zircon geochronology using 266 and 213 nm laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Standard spot ablation (spot diameters 40–80 μm) was employed, with no sampling strategies employed specifically to minimise elemental fractionation. Instead, He ablation gas and carefully replicated ablation conditions were employed to maintain constant ablation-related elemental fractionation of Pb and U between analyses. Combining these strategies with calibration on a new zircon standard (GJ-1) allows elemental fractionation and instrumental mass bias to be corrected efficiently, and accurate ²⁰⁶Pb/²³⁸U and ²⁰⁷Pb/²³⁵U ratios to be measured with short-term precision (2 r.s.d.) of 1.9% and 3.0%, respectively. Long-term precision (2 r.s.d.) of the technique (266 nm ablation), based on 355 analyses of the 91500 zircon (1065 Ma) standard over more than a year, was 3.8%, 4.0% and 1.4% for the ²⁰⁶Pb/²³⁸U, ²⁰⁷Pb/²³⁵U and ²⁰⁷Pb/²⁰⁶Pb ratios, respectively. Long-term precision (2 r.s.d.) for the ²⁰⁶Pb/²³⁸U, ²⁰⁷Pb/²³⁵U and ²⁰⁷Pb/²⁰⁶Pb ratios of the Mud Tank zircon (732 Ma) was 3.9%, 4.1% and 1.7%, respectively (359 analyses). Selective integration of time-resolved signals was used to minimise the effect of Pb loss and common Pb enrichments on the measured ages. The precision and accuracy of our data compare very favourably with those obtained using more involved procedures to correct or minimise ablation- and ICP-MS-induced biases. 213 nm laser ablation produced comparable precision to 266 nm ablation using generally smaller spot sizes (40–50 vs. 60–80 μm), and offered significant advantages in terms of ablation duration and stability, particularly for small zircons (<60 μm). For the 91500 zircon, but not the Mud Tank zircon, 213 nm ablation also produced significantly older and more accurate Pb/U ages. This suggests that shorter wavelength ablation may have reduced a matrix-dependent elemental fractionation difference between sample and standard. The accuracy and precision of the technique for young zircons are demonstrated by analysis of three zircon populations ranging in age from 417 to 7 Ma. In each case, the zircons have yielded concordant ages or common Pb discordia which give concordia intercept ages that are in agreement with independently determined ages for the same samples. Application of Tera–Wasserburg diagrams [Earth Planet. Sci. Lett. 14 (1972) 281] was found to be the most useful approach to handling common Pb contributions that were not removed by selective integration of signals. 2010-01-27T23:09:05.283Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:2029 ℇ⁶⁵Cu ([⁶⁵Cu/⁶³Cusample/⁶⁵Cu/⁶³CuNIST₋₉₇₆ -1]*10,000) in chalcopyrite from the 3 three igneous intrusions that make up the Grasberg Igneous Complex (GIC) and associated skarn deposits range from 0.2 to 13.4. Chalcopyrite grains from each intrusion have a specific range of ℇ⁶⁵Cu that is isotopically heavier in each successive intrusion. These variations may be interpreted in two ways: (1) isotope fractionation during distillation of Cu from the underlying source and establishment of hydrothermal cells associated with each intrusion; (2) isotope fractionation as the ore ore-bearing fluid moved outward from a central core. Within each sample, the smaller disseminated chalcopyrite grains yield consistently lower ℇ⁶⁵Cu values than larger disseminated grains, suggesting multiple mineralisation events. Chalcopyrite ℇ⁶⁵Cu from the Pyrite Shell, a sulfide-rich zone that surrounds the GIC, completely overlaps those from the three intrusions: suggesting that the source of Cu was the same. In contrast, while some chalcopyrite ℇ⁶⁵Cu values from the skarn deposits also overlap those from the GIC, a significant number are enriched in ⁶⁵Cu. These data may indicate that Cu within the skarns was derived from multiple sources or from multiple mineralisation events. ℇ⁵⁷Fe ([⁵⁷Fe/⁵⁴Fesample/⁵⁷Fe/⁵⁴FeIRMM₋₁₄ -1]*10,000) for pyrite and chalcopyrite range from -30.2 to 16.2. The ℇ⁵⁷Fe ranges of these two minerals do not overlap, suggesting that pyrite preferentially incorporated heavy Fe isotopes. ℇ⁵⁷Fe for GIC and skarn pyrite overlap, as do GIC and skarn chalcopyrite, suggesting genetic relationships. A large proportion of pyrite and chalcopyrite grains in the skarns also have low ℇ⁵⁷Fe values that do not overlap the igneous sulfides. This, coupled with the presence of pyrite grains with extremely low ℇ⁵⁷Fe values (ℇ⁵⁷Fe =-25), suggests that mixing between sedimentary and igneous Fe occurred during skarn replacement mineralisation. The chalcopyrite and pyrite Fe isotope data from the Pyrite Shell do not overlap those from the GIC, which indicates that Cu and Fe in the chalcopyrite were derived from different sources: the Cu is igneous, whereas the Fe is probably a mixture between sedimentary and igneous sources. The Cu and Fe isotope data from the Grasberg porphyry and skarn sulfides show that transition metal isotope variations occur within magmatic–hydrothermal systems, and that transition metal isotopes can become an important tool for interpretation of hydrothermal processes. 2010-01-27T23:09:04.165Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:2370 Laser ablation microprobe ICP-MS has been used to determine quantitatively the trace-element composition of diamond. Experiments with different synthetic multi-element carbon-based standards, various lasers and a range of instrument conditions have shown that a 266 nm UV laser at 10 Hz provided the best sensitivity, and synthetic oil and a doped cellulose proved most suitable as external standards; ¹³C was used as the internal standard. The precision and accuracy of the method, and the homogeneity of the cellulose multielement standard, were tested by multiple analyses. Artefacts resulting from polyatomic interferences were quantified by analysis of a pure synthetic diamond. Concentrations of 41 elements were determined for two fibrous diamonds from Jwaneng in Botswana (JWA 110 and JWA 115), which have been analysed previously by instrumental neutron-activation analysis (INAA) and proton microprobe (PIXE). A comparison of these three analytical techniques shows that the use of the cellulose standard produces accurate and precise data for most elements. Typical detection limits for the rare earth elements are 5–20 ppb, and for transition elements <500 ppb. Sodium and Fe have higher detection limits (2–3 ppm). The precision (expressed as % rsd) ranges through ~10% for concentrations between 1–100 ppm, ~15% for values between 0.1–1 ppm, ~30% for 0.01–0.1 ppm and ~25% for values <0.01 ppm, with the accuracy lying in the same range. The trace-element patterns obtained by this technique may be used for the characterisation of diamond in genetic studies. Further analyses are required to test whether reliable identification of the source locality of the diamonds is possible; if so this may have important forensic applications. 2010-01-27T23:05:19.217Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:2666 Isotopic fractionation during in-situ analysis of copper using laser ablation (LA) MC-ICP-MS has been investigated. Results show that particles <200 nm transported in the aerosol are isotopically lighter by up to 0.7 ⁰/₀₀ compared to the larger particles. The dependence of this isotopic fractionation on the ablation time, together with isotopic effects caused in the ICP during particle vaporisation, explains the variations of isotope ratios observed during LA-MC-ICP-MS. LA-MC-ICP-MS measurements of copper isotope ratios in metallic copper typically show large systematic within-run variations of up to several permil (⁰/₀₀) depending on the ablation time and, correspondingly, large offsets from solution data for the same sample when compared directly. Analysis of small particles generated by vapour condensation after the laser impact, and larger particles formed by ejection of liquid droplets from the crater, show that the laser impact results in isotopic fractionation of ⁶⁵Cu+/⁶³Cu⁺ between different aerosol particle size fractions of up to 0.7⁰/₀₀. This fractionation cannot be overcome by removal of large particles from the aerosol that are not completely vaporised and ionised in the ICP source. However, separation of the large particles is shown to significantly reduce within-run fractionation, as well as improving the accuracy relative to solution data, and is therefore recommended for the analysis of copper metal. Temporal variations in the isotopic composition of particulate vapour condensate are explained by a crater effect that influences the residence time of large particles in the laser-generated plasma plume, leading to preferential vaporisation of the lighter isotopes. 2010-01-27T23:01:55.334Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:3656 Fifty elements in NIST SRM 614 and 616 glass reference materials were determined by laser ablation microprobe-inductively coupled plasma-mass spectrometry (LAM-ICP-MS). The values determined for NIST SRM 614 agreed well with the NIST-certified and information values (mean relative difference ± 3.6%), except for B, Sc and Sb. The values determined for NIST SRM 616 agreed with the NIST-certified and information values within a mean relative difference of ± 1.5%, except for B, Sc and Ga. In addition, at an 80 μm sampling scale, NIST SRM 614 and 616 glass discs were homogeneous for trace elements within the observed precisions of 5 and 15% (mean), respectively. Detection limits were in the range 0.01 - 0.3 μg g⁻¹ for elements of lower mass numbers (amu < 80) and 1 - 10 ng g⁻¹ for heavy elements (amu > 80). Detection at the sub ng g⁻¹ level is possible for most of the heavy elements by using an ablation pit size larger than 10 0 μm. 2010-01-27T22:50:36.962Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:3710 The Pingtan and Tonglu igneous complexes in SE China are typical of the calc-alkaline series developed at active continental margins. These two complexes are dominated by felsic rocks, temporally and spatially associated with minor mafic rocks. Morphological and trace-element studies of zircon populations in rocks from each of these complexes show that the zircon populations may be divided into 3 - 4 distinct growth stages, characterized by different distributions of morphological indices (Ipr, Ipy and Iel), and different contents of the substituting elements (Hf, U, Th, Y and P). The four growth stages recognized in the zircons are believed to have formed successively in the magma chamber, during the emplacement, and in the early and later stages of magma consolidation, respectively. All four stages are recognized in the plutonic Pingtan complex, whereas the stages 3 and 4 are less developed in the volcanic/subvolcanic Tonglu complex. Based on the chemistry and morphology of the different zircon populations of the Pingtan and Tonglu complexes, it is suggested that basaltic magmas underplating at the boundary between crust and mantle caused partial melting of the mid-lower crust and produced granitoid magmas. Subsequently, mixing between magmas was important. 2010-01-27T22:50:00.219Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:3751 Field relations and whole-rock geochemistry indicate that magma mixing has been important in the genesis of the late Mesozoic I-type igneous complexes at Pingtan and Tonglu in SE China. Morphological and trace-element studies of zircon populations in rocks from each of these complexes have defined several distinct growth stages [Mineral. Mag. (2001)]. In-situ LAM-MC-ICPMS microanalysis shows large variations in ¹⁷⁶Hf/¹⁷⁷Hf (up to 15 εHf units) between zircons of different growth stages within a single rock, and between zones within single zircon grains (up to 9 εHfHf units). These variations suggest that each of the observed magmas in both complexes developed through hybridisation of ≥2 magmas with different sources. Although this mixing has produced similar Sr and Nd isotopic compositions in the different rock types of each complex, the zircons have functioned as “tape recorders” and have preserved details of the assembly of the different magmas. In the Tonglu complex the most primitive magma is a mafic monzonite (preserved as enclaves), whose isotopic composition suggests derivation from the lower crust; rhyodacites, rhyolites and quartz diorites reflect the mixing of the monzonite with ≥2 more felsic magmas, derived from older crustal materials. In the Pingtan complex, zircons in a quartz diorite enclave suggest mixing between a crustal magma and a more primitive mantle-derived component. Zircons from granites and granodiorite enclaves indicate mixing between the quartz diorite and more felsic melts with lower ¹⁷⁶Hf/¹⁷⁷Hf. Major changes in ¹⁷⁶Hf/¹⁷⁷Hf correlate with discontinuous changes in the trace-element composition and morphology of the zircons, in particular the development of sector zoning that suggests rapid disequilibrium crystallisation. We suggest that the magma mixing recorded by the changes in ¹⁷⁶Hf/¹⁷⁷Hf occurred during transport in magma conduits. The in-situ analysis of Hf-isotopic stratigraphy in zircons is a new and powerful tool for the detailed study of magma generation processes. 2010-01-27T22:49:29.631Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:4213 If reconstruction of major events in ancient orogenic belts is achieved in sufficient detail, the tectonic evolution of these belts can offer valuable information to widen our perspective of processes currently at work in modern orogens. Here, we illustrate this possibility taking the western European Cadomian–Avalonian belt as an example. This research is based mainly on the study and interpretation of U–Pb ages of more than 300 detrital zircons from Neoproterozoic and Early Paleozoic sedimentary rocks from Iberia and Brittany. Analyses have been performed using the laser ablation–ICP–MS technique. The U–Pb data record contrasting detrital zircon age spectra for various terranes of western Europe. The differences provide information on the processes involved in the genesis of the western European Precambrian terranes along the northern margin of Neoproterozoic Gondwana during arc construction and subduction, and their dispersal and re-amalgamation along the margin to form the Avalonia and Armorica microcontinents. The U–Pb ages reported here also support the alleged change from subduction to transform activity that led to the final break-up of the margin, the birth of the Rheic Ocean and the drift of Avalonia. We contend that the active northern margin of Gondwana evolved through several stages that match the different types of active margins recognised in modern settings. 2010-01-27T22:44:05.240Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:5746 Mid-Proterozoic calc-alkaline granitoids from southern Norway, and their extrusive equivalents have been dated by LAM-ICPMS U–Pb on zircons to ages ranging from 1.61 to 1.52 Ga; there are no systematic age differences across potential Precambrian terrane boundaries in the region. U–Pb and Lu–Hf data on detrital zircons from metasedimentary gneisses belonging to the arc association show that these were mainly derived from ca. 1.6 Ga arc-related rocks. They also contain a minor but significant fraction of material derived from (at least) two distinct older (1.7–1.8 Ga) sources; one has a clear continental signature, and the other represents juvenile, depleted mantle-derived material. The former component resided in granitoids of the Transscandinavian Igneous Belt, the other in mafic rocks related to these granites or to the earliest, subduction-related magmatism in the region. Together with published data from south Norway and southwest Sweden, these findings suggest that the western margin of the Baltic Shield was the site of continuous magmatic arc evolution from at least ca 1.66 to 1.50 Ga. Most of the calc-alkaline metaigneous rocks formed in this period show major- and trace-element characteristics of rocks formed in a normal continental margin magmatic arc. The exceptions are the Stora Le-Marstrand belt in Sweden and the Kongsberg complex of Norway, which have an arc-tholeiitic chemical affinity. The new data from south Norway do not justify a suggestion that the crust on the west side of the Oslo Rift had an early to mid-Proterozoic history different from the crust to the east. Instead, they indicate that the different parts of south Norway and southwest Sweden were situated at the margin of the Baltic Shield throughout the mid-Proterozoic. Changes from arc tholeitic to calc-alkaline magmatism reflect changes with time in the subduction zone system, or lateral differences in subduction zone geometry. The NW American Cordillera may be a useful present-day analogue for the tectonomagmatic evolution of the mid-Proterozoic Baltic margin. 2010-01-27T22:27:00.109Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:5844 Jumping spiders (Salticidae) are known for their elaborate vision-based display behaviour, and a sizeable minority of the species in this large family resemble ants. The display repertoire of two ant-like salticid species from the Philippines is investigated. Myrmarachne assimilis is a specialist ant mimic, closely matching the appearance of the weaver ant Oecophylla smaragdina. Myrmarachne bakeri is a generalist mimic, which, although ant-like, is not a close match to any sympatric ant species. Myrmarachne are sexually dimorphic, with males having enlarged chelicerae. The copulatory posture of Myrmarachne is unique among salticids, apparently as an adjustment for the male's elongated chelicerae. Details concerning the intraspecific behaviour of Myrmarachne appear to be adjustments to living in environments populated by numerous other animals with similar appearance (ants). However, the specialist and the generalist that were investigated have display repertoires that are broadly similar to each other and to those of more typical salticids. Generally, the display behaviour of Myrmarachne appears not to have necessitated dramatic deviation from typical salticid display and mating strategies. 2010-01-27T22:25:40.618Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:5855 Myrmarachne assimilis, an ant-like (myrmecomorphic) jumping spider (Araneae, Salticidae) from the Philippines, is a Batesian mimic of Oecophylla smaragdina, the Asian weaver ant. Salticids are well known for their acute eyesight and the elaborate vision-based display behaviour they adopt during encounters with conspecific individuals, but most salticids are not myrmecomorphic. Despite its unusual morphology, M. assimilis adopts display behaviour during intraspecific interactions that is similar to the display behaviour of more typical salticids. The specificity with which M. assimilis deploys display behaviour is investigated and provides insights into this mimic’s ability to differentiate, by sight alone, between models, conspecific individuals and prey. During each standardized test, an adult M. assimilis female was in a large cage along with a small transparent glass vial, a stimulus animal being enclosed in the vial such that potential optical cues, but not potential chemical cues, were available to the tested M. assimilis individual. Depending on the test, the stimulus animal was another adult M. assimilis female, a house fly (prey) or an ant (Camponotus sp. or O. smaragdina). Only the conspecific female consistently elicited display from M. assimilis, implying that M. assimilis is a Batesian mimic that can, when relying on vision alone, discriminate between conspecific individuals, models and prey. 2010-01-27T22:25:32.407Z ]]>