Recent publications in Science and Engineering
High-frequency stable isotope data are useful for validating atmospheric moisture circulation models and provide improved understanding of the mechanisms controlling isotopic compositions in tropical rainfall. Here, we present a near-continuous 6-month record of O- and H-isotope compositions in both water vapour and daily rainfall from Northeast Australia measured by laser spectroscopy. The data set spans both wet and dry seasons to help address a significant data and knowledge gap in the southern hemisphere tropics. We interpret the isotopic records for water vapour and rainfall in the context of contemporaneous meteorological observations. Surface air moisture provided near-continuous tracking of the links between isotopic variations and meteorological events on local to regional spatial scales. Power spectrum analysis of the isotopic variation showed a range of significant periodicities, from hourly to monthly scales, and cross-wavelet analysis identified significant regions of common power for hourly averaged water vapour isotopic composition and relative humidity, wind direction, and solar radiation. Relative humidity had the greatest subdiurnal influence on isotopic composition. On longer timescales (weeks to months), isotope variability was strongly correlated with both wind direction and relative humidity. The high-frequency records showed diurnal isotopic variations in O- and H-isotope compositions due to local dew formation and, for deuterium excess, as a result of evapotranspiration. Several significant negative isotope anomalies on a daily scale were associated with the activity of regional mesoscale convective systems and the occurrence of two tropical cyclones. Calculated air parcel back trajectories identified the predominant moisture transport paths from the Southwest Pacific Ocean, whereas moisture transport from northerly directions occurred mainly during the wet season monsoonal airflow. Water vapour isotope compositions reflected the same meteorological events as recorded in rainfall isotopes but provided much more detailed and continuous information on atmospheric moisture cycling than the intermittent isotopic record provided by rainfall. Improved global coverage of stable isotope data for atmospheric water vapour is likely to improve simulations of future changes to climate drivers of the hydrological cycle.
Noble, Tansyn N., Coman, Gregory J., Wade, Nicholas M., Thomson, Peter C., Raadsma, Herman W., Khatkar, Mehar S., Guppy, Jarrod L., and Jerry, Dean R. (2020) Genetic parameters for tolerance to gill-associated virus under challenge-test conditions in the black tiger shrimp (Penaeus monodon). Aquaculture, 516. 734428.
Diseases in shrimp aquaculture cause significant economic losses, particularly those caused by viruses. Genetic improvement of disease tolerance through selective breeding can be an important tool for managing the risk of disease in shrimp farming as long as the trait has a genetic basis (i.e. heritable) and is able to be accurately and reliably measured. This study presents the first estimates of genetic variation associated with tolerance to gill-associated virus (GAV) in Penaeus monodon using a unique controlled challenge test design. Shrimp families (n = 72) were communally spawned and reared prior to replicated communal challenge testing when they reached an average size of ~8 g. Pedigree determination was carried out using genotyping and shrimp were challenged by intramuscular injection with a weight standardised dose of GAV. Daily mortality data were collected over 15 days from 1717 individuals and GAV infection load was measured on the challenge test survivors (n = 963). Overall mortality after 15 days was 35.5% and ranged from 0 to 71% among families. Heritability estimates for mortality were 0.11 ± 0.03 using a binomial model and 0.14 (standard error not estimated) using Cox's proportional hazards model. The estimated heritability for GAV infection load was 0.21 ± 0.07. The genetic correlation between mortality and GAV infection load was not significantly different from zero, rg = 0.30 ± 0.23, suggesting that the two traits may be genetically independent, at least in the way they were measured in this study. Results from this study suggest a low but significant genetic basis for GAV tolerance in P. monodon and that selection may be a viable option to manage GAV-related disease. The study also demonstrated, for the first time in shrimp, communal-based spawning and rearing can be used for large-scale genetic analysis of disease tolerance, eliminating the need for single family rearing tanks and associated confounding environmental effects.
Humphreys, M.T., Ginger, J.D., and Henderson, D.J. (2020) Effect of opening size and wind speed on internal pressures in full-scale buildings. In: Lecture Notes in Civil Engineering (37) pp. 1061-1069. From: ACMSM25: 25th Australasian Conference on Mechanics of Structures and Materials, 4-7 December 2018, Brisbane, QLD, Australia.
Internal pressures contribute to a significant proportion of the net pressure across a building envelope, which needs to be accurately defined in wind loading standards to optimize structural design. Current quasi-steady criteria for internal pressures in AS/NZS1170.2(2011) is dependent on the ratio of open area on the windward wall to leeward and sidewalls, with no consideration of dynamic (i.e. inertial and damping) effects. This paper shows that the internal to external pressure fluctuation relationship is a function of the opening area to volume parameter, S*=(A^(3/2)/V)(as /U_h^2) and opening area to integral length scale of turbulence parameter, Φ5=(λu /√A). Simple quasi-steady analysis used in AS/NZS1170.2(2011) suggests internal pressure should be equal to the external pressure applied to the opening, however, results here show Cases where peak internal pressures are greater than, equal to and less than the peak external pressure. This is caused by internal pressure resonance and/or damping shown to be a function of S* and Φ_5.
Anderson, R Charles, Herrera, Miguel, Ilangakoon, Anoukchika D., Koya, K.M., Moazzam, M., Mustika, Putu L., and Sutaria, Dipani N. (2020) Cetacean bycatch in Indian Ocean tuna gillnet fisheries. Endangered Species Research, 41. pp. 39-53.
Pelagic gillnet (driftnet) fisheries account for some 34% of Indian Ocean tuna catches. We combined published results from 10 bycatch sampling programmes (1981−2016) in Australia, Sri Lanka, India and Pakistan to estimate bycatch rates for cetaceans across all Indian Ocean tuna gillnet fisheries. Estimated cetacean bycatch peaked at almost 100 000 ind. yr−1 during 2004−2006, but has declined by over 15% since then, despite an increase in tuna gillnet fishing effort. These fisheries caught an estimated cumulative total of 4.1 million small cetaceans between 1950 and 2018. These bycatch estimates take little or no account of cetaceans caught by gillnet but not landed, of delayed mortality or sub-lethal impacts on cetaceans (especially whales) that escape from gillnets, of mortality associated with ghost nets, of harpoon catches made from gillnetters, or of mortality from other tuna fisheries. Total cetacean mortality from Indian Ocean tuna fisheries may therefore be substantially higher than estimated here. Declining cetacean bycatch rates suggest that such levels of mortality are not sustainable. Indeed, mean small cetacean abundance may currently be 13% of pre-fishery levels. None of these estimates are precise, but they do demonstrate the likely order of magnitude of the issue. Countries with the largest current gillnet catches of tuna, and thus the ones likely to have the largest cetacean bycatch are (in order): Iran, Indonesia, India, Sri Lanka, Pakistan, Oman, Yemen, UAE and Tanzania. These 9 countries together may account for roughly 96% of all cetacean bycatch from tuna gillnet fisheries across the Indian Ocean.
Mbaru, Emmanuel K., Graham, Nicholas A.J., McClanahan, Timothy R., and Cinner, Joshua E. (2020) Functional traits illuminate the selective impacts of different fishing gears on coral reefs. Journal of Applied Ecology. (In Press)
Unsustainable fishing is a major driver of change in marine ecosystems. The ways that fishing gears target fishes with different ecological functions are unclear, particularly in complex multispecies fisheries. Here, we examine whether artisanal fishing gears selectively target fishes with unique combinations of ecological traits (diet, body size, depth, position in water column, period of activity, schooling behaviour) in a coral reef ecosystem. We use coral reef fish landing data from 25 sites along the Kenyan coast collected over a 7-year period. All fishing gears targeted a wide diversity of traits, but with some differentiation among gears. Fish assemblages captured by spearguns were significantly different from the other gear types, specializing on diurnal species that feed on sessile invertivores. Nets, including gillnets and beachseines, targeted the most functional diversity. Escape slot traps targeted the least functionally diverse assemblages. Basket traps and escape slot traps targeted the most functionally similar species of all two-gear combinations. There were 163 functional entities (unique combinations of traits) captured in the fishery; however, 50% of the catch by each gear was from only two to six functional entities. Most of the differences in gear selectivity were due to unique and rarely targeted functional entities, that made up only a small proportion of the catch. Synthesis and applications. Coral reef fisheries target a breadth of functional entities (unique combinations of traits), but catches are heavily skewed towards relatively few functional entities. While banning specific gears will benefit rare functional entities in the catch, effort reductions will be necessary to alleviate pressure on commonly targeted functional entities.
White, William T., Baje, Leontine, Appleyard, Sharon A., Chin, Andrew, Smart, Jonathan J., and Simpfendorfer, Colin A. (2020) Shark longline fishery of Papua New Guinea: size and species composition and spatial variation of the catches. Marine and Freshwater Research. (In Press)
This study provides the first detailed investigation of the catches of the shark longline fishery in Papua New Guinea. Fisheries observers collected data on shark catches from a total of 318 longline sets between May and June 2014, before its closure in July 2014. In all, 14 694 sharks were recorded with a total estimated biomass of 439 tonnes (Mg). Eighteen species of sharks were recorded in the observer data, with the most dominant species being Carcharhinus falciformis, which constituted more than 90% of the total catches by both weight and number of individuals. The level of observer misidentification was low (<10%), which reflected the use of region-specific identification guides by well-trained fisheries observers. The most diverse catches were in the Solomon Sea area, whereas catches in most other areas, particularly the Bismarck Sea areas, were less diverse and more strongly dominated by C. falciformis. Size and sex ratios varied by species, highlighting the importance of obtaining species-level information from the fishery being investigated. Any consideration by fisheries managers to reopen this fishery needs to consider the effect this will have on the species targeted and the livelihoods of coastal fishers who also rely on the same resources.
Henderson, Christopher J., Gilby, Ben L., Schlacher, Thomas A., Connolly, Rod M., Sheaves, Marcus, Maxwell, Paul S., Flint, Nicole, Borland, Hayden P., Martin, Tyson S.H., Gorissen, Bob, and Olds, Andrew D. (2020) Landscape transformation alters functional diversity in coastal seascapes. Ecography, 43 (1). pp. 138-148.
The ecological impacts of landscape modification and urbanisation have transformed the composition of plant and animal assemblages, and altered the condition of ecosystems globally. Landscape transformation influences the spatial distribution of species and ecological functions by selecting for generalist species with wide ecological niches, which can adapt to opportunities in highly-modified environments. These effects of landscape modification can shape functional diversity on land, but it is not clear whether they have similar functional consequences in the sea. We used estuaries as a model system to test how landscape transformation alters functional diversity in coastal seascapes, and measured how variation in level of urbanisation, catchment modification and habitat loss influenced fish diversity across thirty-nine estuaries in eastern Australia. Fish were surveyed with baited remote underwater video stations and functional diversity was indexed with three metrics that describe variation in the functional traits and niche space of assemblages. The extent of landscape transformation in the catchment of each estuary was associated with variation in the functional diversity of estuarine fish assemblages. These effects were, however, not what we expected as functional diversity was highest in modified estuaries that supported a large area of both urban and grazing land in their catchments, were bordered by a small area of natural terrestrial vegetation and that contained a moderate area of mangroves. Zoobenthivores and omnivores dominated assemblages in highly-modified estuaries, and piscivorous fishes were common in natural waterways. Our results demonstrate, that the modification and urbanisation of ecosystems on land can alter functional diversity in the sea. Intense landscape transformation appears to select for abundant generalists with wide trophic niches, and against species with specialised diets, and we suggest that these changes might have fundamental consequences for ecosystem functioning in estuaries, and other highly modified seascapes.
Armstrong, Amelia J., Armstrong, Asia O., Bennett, Michael B., McGregor, Frazer, Abrantes, Kátya G., Barnett, Adam, Richardson, Anthony J., Townsend, Kathy A., and Dudgeon, Christine L. (2020) The geographic distribution of reef and oceanic manta rays (Mobula alfredi and Mobula birostris) in Australian coastal waters. Journal of Fish Biology. (In Press)
The known distribution of manta rays in Australian waters is patchy, with records primarily centred around tourism hotspots. We collated 11,614 records of Mobula alfredi from photo-ID databases (n = 10,715), aerial surveys (n = 378) and online reports (n = 521). The study confirms an uninterrupted coastal distribution from north of 26 degrees S and 31 degrees S on the west and east coasts, respectively. More southerly M. alfredi records relate to warm-water events with a southernmost extent at 34 degrees S. Coastal sightings of Mobula birostris were rare (n = 32), likely reflecting a preference for offshore waters, but encompass a wider latitudinal extent than M. alfredi of 10-40 degrees S.
Buddle, Alice L., Otway, Nicholas M., Van Dyke, James U., Thompson, Michael B., Murphy, Christopher R., Dowland, Samson N., Simpfendorfer, Colin A., Ellis, Megan T., and Whittington, Camilla M. (2020) Structural changes to the uterus of the dwarf ornate wobbegong shark (Orectolobus ornatus) during pregnancy. Journal of Morphology. (In Press)
Embryos of the viviparous dwarf ornate wobbegong shark (Orectolobus ornatus) develop without a placenta, unattached to the uterine wall of their mother. Here, we present the first light microscopy study of the uterus of O. ornatus throughout pregnancy. At the beginning of pregnancy, the uterine luminal epithelium and underlying connective tissue become folded to form uterine ridges. By mid to late pregnancy, the luminal surface is extensively folded and long luminal uterine villi are abundant. Compared to the nonpregnant uterus, uterine vasculature is increased during pregnancy. Additionally, as pregnancy progresses the uterine epithelium is attenuated so that there is minimal uterine tissue separating large maternal blood vessels from the fluid that surrounds developing embryos. We conclude that the uterus of O. ornatus undergoes an extensive morphological transformation during pregnancy. These uterine modifications likely support developing embryos via embryonic respiratory gas exchange, waste removal, water balance, and mineral transfer.
Lei, Peng, Zhou, Ying, Zhu, Ruiqi, Liu, Yang, Dong, Chuan, and Shuang, Shaomin (2020) Novel strategy of electrochemical analysis of DNA bases with enhanced performance based on copper−nickel nanosphere decorated N,B−doped reduced graphene oxide. Biosensors and Bioelectronics, 147. 111735.
Design of suitable nanocomposites with tailored structures was significant in the fabrication of effective and reliable electrochemical sensors. Herein, the copper−nickel@nitrogen, boron−doped reduced graphene oxide (Cu–Ni@N,B−rGO) was successfully synthesized, which exhibited superior electrocatalytic performance towards guanine (G) and adenine (A) oxidation. The Cu–Ni NPs were sequentially decorated on N,B−rGO substrate via an environmentally friendly reduction strategy, which utilized glucose as reducer and stabilizing agent. The nanocomposites with large specific surface area, remarkable conductivity and high catalytic activity showed prominent synergistic effect owning to the uniform dispersion of Cu–Ni NPs on the surface of N,B−rGO. When applied to analysis of G and A using DPV, the wide linear ranges of 1.0–160.0 μM and 1.0–120.0 μM with the determination limits of 0.118 μM and 0.134 μM were obtained, respectively. The sensor was successfully applied to the detection of G and A in calf−thymus DNA with G/A ratio of 0.80. The facile preparation process and attractive sensing properties of the Cu–Ni@N,B−rGO nanocomposites made it a promising candidate for the development of advanced electrochemical sensor.
Zhu, Chengxi, Liu, Dong, Li, Yuye, Shen, Xiuli, Ma, Shuai, Liu, Yang, and You, Tianyan (2020) Ratiometric electrochemical aptasensor for ultrasensitive detection of Ochratoxin A based on a dual signal amplification strategy: engineering the binding of methylene blue to DNA. Biosensors and Bioelectronics, 150. 11814.
A novel ratiometric electrochemical aptasensor was developed for Ochratoxin A (OTA) detection based on the binding of methylene blue (MB) to DNA with a dual signal amplification strategy. The formation of dsDNA structures between ferrocene-labeled complementary DNA (Fc-cDNA), the OTA aptamer, and complementary helper DNA (hDNA) caused Fc away from the electrode, and allowed dsDNA to bind with a certain amount of MB. Here, a small oxidation current of Fc (IFc) and a large oxidation current of MB (IMB) were obtained. In the presence of OTA, its specific recognition with the aptamer induced the release of aptamer and hDNA from the electrode and subsequently the formation of hairpin structure for cDNA, which caused Fc close to the electrode and a weaker binding ability with MB. Then, an increased IFc and a decreased IMB were obtained. Based on this principle, OTA could be accurately quantified by measuring the ratiometric signal of IFc/IMB. Herein, the dual signal amplification strategy of the introduction of hDNA and the binding with MB after the OTA recognition was exploited to amplify the response signal. The obtained aptasensor showed a linear detection range from 10 pg mL1 to 10 ng mL1 and a detection limit of 3.3 pg mL1. The aptasensor was successfully applied to determine OTA in wheat, and the results were validated through HPLC-MS. Furthermore, by changing the target aptamers, this strategy could be universally used for the determination of various mycotoxins, showing prom-ising potential applications for mycotoxins monitoring in agricultural products and foods.
Li, Lin, Shi, Lihong, Jia, Jing, Jiao, Yuan, Gao, Yifang, Liu, Yang, Dong, Chuan, and Shuang, Shaomin (2020) “On-off-on” detection of Fe³⁺ and F⁻, biological imaging, and its logic gate operation based on excitation-independent blue-fluorescent carbon dots. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 227. 117716.
A fluorescent nanoprobe based on carbon dots (CDs) has been facilely synthesized by a one-step hydrothermal pyrolysis of salicylic acid and utilized for the sequential detection of Fe3+ and F− in vitro. The fluorescence of CDs can be extinguished dramatically by Fe3+ based on static quenching and subsequently recovery upon addition of F− due to the formation of stabler FeF3. The probe exhibits high selectivity and sensitivity toward Fe3+ and F− with a good linearity in the range of 10–300 μM and 0.1–200 μM, respectively, and a low detection limit of 52 nM and 8.5 nM, respectively. More importantly, as-prepared CDs with exceedingly fluorescence stability, negligible toxicity and superior biocompatibility have been expanded for detection Fe3+ and F− in living cell and Escherichia coli. Furthermore, an “AND” logic gate based on as-obtained CDs has been constructed.
Shen, Xiuli, Liu, Dong, Zhu, Chengxi, Li, Yuye, Liu, Yang, and You, Tianyan (2020) Photoelectrochemical and electrochemical ratiometric aptasensing: a case study of streptomycin. Electrochemistry Communications, 110. 106637.
There has been much interest in constructing ratiometric sensors using different sensing techniques because of their synergistic effect, although the simultaneous collection of the signals is challenging. Herein, we propose a ratiometric aptasensing strategy based on the dual-detection model with a photoelectrochemical (PEC) “signalon” and an electrochemical (EC) “signal-off”. As a proof-of-concept study, CdTe quantum dots (CdTe QDs) and a methylene blue-labeled aptamer (MB-Apt) were used to generate PEC and EC signals in the sensing system. The target-induced conformational change of MB-Apt pushed MB away from the electrode, thereby decreasing the EC signal; at the same time, the reduced steric hindrance favored the restoration of the PEC signal from the CdTe QDs. Thus, this PEC-EC strategy can achieve the PEC “signal-on” and EC “signal-off” states simultaneously, as well as allowing quantitative analysis of the target based on the ratio of the current intensities. As a model application, an aptasensor fabricated for streptomycin detection showed a wide linear range from 0.03 to 100 μM with a detection limit of 10 nM (S/N = 3). The proposed sensing platform displayed superior analytical properties compared with methods based on PEC or EC alone. Our work provides an efficient dual-detection modelbased ratiometric strategy for advanced analysis, and paves the way to the simultaneous acquisition of signals.
Li, Yuye, Liu, Dong, Zhu, Chengxi, Shen, Xiuli, Liu, Yang, and You, Tianyan (2020) Sensitivity programmable ratiometric electrochemical aptasensor based on signal engineering for the detection of aflatoxin B1 in peanut. Journal of Hazardous Materials, 387. 122001.
Accurately monitoring of aflatoxin B1 (AFB1), the most hazardous mycotoxin in agricultural products, is essential for the public health, but various testing demands (e.g. detection range, sensitivity) for different samples can be challenging for sensors. Here, we developed a sensitivity-programmable ratiometric electrochemical aptasensor for AFB1 analysis in peanut. Thionine functionalized reduced graphene oxide (THI-rGO) served as reference signal generator, ferrocene-labelled aptamer (Fc-apt) output the response signal. During analysis, the formation of Fc-apt-AFB1 complex led to its stripping from the electrode and faded the current intensity of Fc (IFc), while the current intensity of THI (ITHI) was enhanced. And ratiometric detection of AFB1 was achieved by using the current intensity ratio (ITHI/IFc) as quantitative signal. Compared with ratiometric strategies that highly rely on the labelled aptamers, the proposed strategy could regulate the value of ITHI/IFc by changing the modification of Fc-apt. And the detection sensitivity was found to be closely related to ITHI/IFc. Under the optimal conditions, the fabricated aptasensor with a dynamic range from 0.05–20 ng mL−1 and a detection limit of 0.016 ng mL−1 for AFB1 analysis. Besides, it exhibited excellent selectivity, reliability and reproducibility. The proposed sensitivity-programmable biosensor can be applied to detect various aptamer-recognized mycotoxins in agricultural sensing.
Chen, Fuchuan, Deng, Jun, Wang, Qingfei, Huizenga, Jan Marten, Li, Gongjian, and Gu, Youwei (2020) LA-ICP-MS trace element analysis of magnetite and pyrite from the Hetaoping Fe-Zn-Pb skarn deposit in Baoshan block, SW China: implications for ore-forming processes. Ore Geology Reviews, 117. 103309.
The Hetaoping deposit is one of the largest Fe-Zn-Pb skarn deposit in SW China, which is characterized by Zn-Pb mineralization in the upper part and the Fe mineralization in the deeper part. The Fe mineralization is dominated by magnetite and pyrite. Magnetite can be subdivided into four types: primary banded magnetite samples in clinopyroxene-actinolite skarn (Mt-1), primary disseminated magnetite in garnet skarn (Mt-2), primary disseminated magnetite in clinopyroxene-actinolite skarn (Mt-3), and altered magnetite in clinopyroxene-actinolite skarn (Mt-4). Pyrite can be subdivided into three types: pyrite in oxide-ore stage (Py-1), pyrite in early sulfide ore stage (Py-2), and pyrite in late sulfide-ore stage (Py-3). The flat time-resolved signals of laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) imply that trace elements exist mainly in the form of isomorphism in magnetite and pyrite with the exception some incompatible trace elements (e.g., Ca, K and Na in magnetite and Pb, Bi and Ag in pyrite). Trace element concentrations in magnetite and pyrite demonstrate that the ore-forming fluid in Hetaoping is of magmatic origin. Furthermore, compared to porphyry, IOCG, Kinuna and BIF type magnetite, the magnetite from Hetaoping has relatively low Ti, V and Ni concentrations but high Al, Mn and Ca concentrations, implying a typical skarn genesis. The variation of Ti concentrations in magnetite is an indication of the formation temperature and shows that banded magnetite (Mt-1) precipitated in a relatively high-temperature environment compared with disseminated magnetite (Mt-2 and Mt-3). Compared to Mt-1 and Mt-3, Mt-2 has a higher Si, Al, and W contents and a lower Mg and Mn contents. The Mn content increases from Py-1 to Py-2, and decreases from Py-2 to Py-3, suggesting that the fluid-rock interaction increased from the oxide-ore stage to the sulfide-ore stage, and decreased from sulfide-ore stage to post-ore stage. The variation of the V concentration in magnetite grains indicates a relatively higher oxygen fugacity of Mt-2 compared to Mt-1 and Mt-3, implying that the oxygen fugacity of the ore-forming fluid in the garnet skarn zone is higher than that in clinopyroxene-actinolite skarn zone. The variable oxygen fugacity probably caused spatial zoning of mineralization in Hetaoping Fe-Zn-Pb skarn deposit. The temperature and oxygen fugacity of the ore-forming fluid, and the extent of fluid-rock interaction, controlled the temporal order and spatial zonation of magnetite and sulfide precipitation, which led to the formation of the Hetaoping Fe-Zn-Pb skarn deposit.
Knutsen, Espen M., and Oerlemans, Emma (2020) The last dicynodont? Re-assessing the taxonomic and temporal relationships of a contentious Australian fossil. Gondwana Research, 77. pp. 184-203.
Dicynodonts, a lineage of non-mammalian therapsids, who's derived taxa evolved edentulous beaked jaws sporting a pair of caniniform tusks, dominated the herbivorous terrestrial vertebrate fauna for much of the Permian and Triassic periods. Long assumed to have met their demise during the end-Triassic extinction event, the discovery of a fragmentary possible dicynodont in Cretaceous rocks in Queensland Australia, potentially extended the longevity of the lineage by nearly 100 million years. This study reassesses the geological, anatomical and historical aspects of this specimen through museum archival research, detrital zircon geochronology, trace element analysis and x-ray synchrotron microtomography, and present new knowledge regarding its temporal, geographical and biological origins, supporting a late Cenozoic (Pliocene-Pleistocene) mammalian megafaunal affinity for the specimen, resulting in a lack of evidence for post-Triassic survival of dicynodonts.
Van Ryt, M.R., Sanislav, I.V., Dirks, P.H.G.M., and Huizenga, J. (2020) Trace element associations in magnetite and hydrothermal pyrite from the Geita Hill gold deposit, Tanzania. Journal of Geochemical Exploration, 209. 106418.
Gold mineralization in the Geita Hill deposit is associated with pyrite formed along microfracture networks and sulfidation fronts together with K-feldspar and biotite. The sulfidation fronts are best developed in magnetite-bearing ironstone. The gold is present mainly as electrum and gold tellurides along grain boundaries, and as inclusions in pyrite, quartz, biotite and K-feldspar. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of pyrite and magnetite grains reflect complex fluid-host rock interactions. Magnetite textures and chemistry change with alteration intensity, indicating the progression of the alteration front into the host rock. Pyrite textures are uniform across all rock types and reflect late-tectonic growth linked to multi-staged infiltration of hydrothermal fluids. Trace element distribution patterns in pyrite are locally complex and influenced by host rock chemistry. Gold distribution patterns in pyrite correlate closely with Te, Ag, Bi and Pb, indicating that gold occurs in micro- and nano-inclusions of telluride minerals. This is especially so for gold in quartz veins, whereas gold in ironstone and diorite also occurs as electrum with an average Au/Ag ratio of 0.41. As, Co and Ni in pyrite are lattice bound and occur in high concentrations in ironstone and diorite where they show characteristic growth zoning patterns. Pyrite in quartz veins has As, Co and Ni concentrations that are low and variable. Cr, Cu, Mo, Mn and Zn are present in all rock types in isolated inclusions in pyrite grains, whilst Pb, Bi and Sb occur in more dispersed patches of fine clustered inclusions. The Se content in pyrite is typical for Archean gold deposits, and reflects an average temperature of ~340 °C for the mineralizing fluid. The Co/Ni ratio of pyrite grains varies between 0 and 5.2 in ironstone and diorite, and most likely reflects the equilibration Co/Ni ratio of the host rock. The Co/Ni ratio of pyrite grains in quartz veins varies between 1 and 12, and is consistent with a magmatic-hydrothermal origin for the ore fluid. Trace element distribution patterns in magnetite and pyrite indicate that As, Ni, Co, Cr, Mn and Cu were mostly locally derived, and remobilised into the pyrite during sulfidation of the host rock. The concentrations of these elements are strongly lithologically controlled, and they are not consistently incorporated into the pyrite after initial stages of growth. Au, Ag, Te, Bi and Pb were externally derived, and closely correlate in all varieties of pyrite as well as strongly altered magnetite. The alteration footprint of the Geita Hill deposit is limited in extent, and does not involve As and Sb that are typically enriched in Archaean lode-gold systems. Instead, Te and Bi are most characteristic for the deposit and could be of use as path finder elements together with altered magnetite grains.
Puga-Bernabéu, Ángel, Webster, Jody Michael, Beaman, Robin Jordan, Thran, Amanda, López‐Cabrera, Javier, and Daniell, James (2020) Submarine landslides along the mixed siliciclastic-carbonate margin of the Great Barrier Reef (offshore Australia). In: Ogata, Kei, Festa, Andrea, and Pini, Gian Andrea, (eds.) Submarine Landslides: subaqueous mass transport deposits from outcrops to seismic profiles. Geophysical Monograph, 246 . Wiley, Washington, DC, USA, pp. 313-337.
Submarine landslides on modern mixed siliciclastic-carbonate margins are poorly understood compared to their counterparts in other settings. We present a synthesis of four representative submarine landslides types along the Great Barrier Reef margin, the largest extant mixed siliciclastic-carbonate province in the world. The investigated examples are 5–31 km in length, extend over 18–528 km2, and have remobilized an estimated 0.025–32 km3 of sediments. They display morphological features corresponding to debris avalanches and slides. The estimated timing of two dated landslides is coincident with deglaciations corresponding to the transitions MIS 12–11 and MIS 2–1. Large seismic events were the most likely triggering mechanism for the landslides, where high pore water pressure in examples close to paleo-deltaic systems could also have preconditioned the eventual failure. A potential preconditioning factor, yet to be confirmed, is the geologic control associated with alternating mixed siliciclastic and carbonate sediments in the failed lithologies. The Gloria Knolls Slide is large enough to have significant tsunamigenic potential. Tsunami simulations show that this landslide would produce a sizable tsunami under present-day sea level conditions, with coastal run-up heights of 0.5–2 m. We highlight a reef buffering effect due to broader-scale shelf bathymetry and the complex structure of coral reefs.
Bodhinayake, G.G., Ginger, J.D., and Henderson, D.J. (2020) Net cladding pressures on industrial building roofs. In: Lecture Notes in Civil Engineering (37) pp. 1077-1085. From: ACMSM25: 25th Australasian Conference on Mechanics of Structures and Materials, 4-7 December 2018, Brisbane, QLD, Australia.
The net wind pressure on roof cladding of metal clad buildings are critical for structural design. Large openings on the windward wall generate large positive internal pressure, which in combination with high external suction pressure produces large net negative pressure on the roof. Wind tunnel studies conducted on a 1:200 scale industrial building model and analytical methods were used to analyze combination effects of internal and external pressures on roof cladding. AS/NZS 1170.2 gives conservative net pressures on the windward roof edge of buildings, for quartering approach wind. The combination factor ( f_C= C_(p ̌,net)/(C_(p ̌e)- C_(p ̂i) )) varies depending on location of the cladding element and position and type of opening(s) in the envelope. The calculated f_C factors are 5% less than the combination factor in the AS/NZS 1170.2 for roof cladding of nominally sealed buildings while it is 5% to 10% less than the building with the large opening. Helmholtz resonance occurs in the building with large opening and internal pressure influences energy contained in the net pressure at the Helmholtz frequency. External suction pressures on windward roof edge and positive internal pressures in the building with large windward wall opening are negatively correlated whilst of external and internal pressures are positively correlated, in the nominally sealed building
Al Nahain, Abdullah, Ignjatovic, Vera, Monagle, Paul, Tsanaktsidis, John, Vamvounis, George, and Ferro, Vito (2020) Anticoagulant heparin mimetics via RAFT polymerization. Biomacromolecules. (In Press)
Heparin, a sulfated polysaccharide derivedfrom animal sources, is the most commonly used parenteralanticoagulant drug, but it suffers from significant safety andsupply issues. Herein, we describe the preparation of heparinmimetic homo- and copolymers via the reversible addition−fragmentation chain transfer (RAFT) polymerization in waterof commercially available (non-carbohydrate) sulfonated andcarboxylated monomers. The anticoagulant activities of thepolymers were assessed by activated partial thromboplastintime (APTT), thrombin clotting time (TCT), and for the more promising polymers, thrombin generation, antifactor Xa, andantifactor IIa assays. Sulfonated homopolymers studied herein displayed low cytotoxicity and significant anticoagulant activity inAPTT, TCT, and thrombin generation assays. In addition, copolymers of sodium styrenesulfonate and acrylic acid [poly(SSS-co-AA)] displayed unprecedented antifactor IIa activity. This study demonstrates the potential of RAFT polymers as lternativeanticoagulants for biomedical applications.
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