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Synchronous solid-state diffusion, dissolution-reprecipitation, and recrystallization leading to isotopic resetting: Insights from chalcopyrite replacement by copper sulfides
No full textReactions among minerals occur via solid-state diffusion or fluid-induced, interface-coupled dissolution-reprecipitation (ICDR). Both mechanisms can coexist under conditions where the rates of both processes are similar, depending mainly on the nature of the mineral, temperature, and fluid composition. To clarify the synergies between these reaction mechanisms, we investigated the replacement and recrystallization reactions of chalcopyrite in the presence of a 65Cu-enriched aqueous fluid. The replacement of chalcopyrite by secondary copper sulfides follows a paragenetic sequence, whereby chalcopyrite is initially replaced by covellite, and then by digenite, with some of the digenite replacing covellite in longer duration experiments. The replacement reactions proceed via ICDR along with solid-state diffusion of 65Cu from the fluid into product minerals, with both mechanisms occurring at similar rates. Over time, chalcopyrite is completely replaced, and the secondary copper sulfides attain isotopic equilibrium with the fluid. Depending on temperature, thermal history, and fluid-mineral ratio, the reaction products may preserve kinetic or equilibrium signatures. We have identified a new geochemical process of ‘porosity-aided recrystallization’, which may result in a re-equilibration or perturbation of mineral isotopic/trace element compositions due to exchanges between the mineral and fluid facilitated by extensive micro- to nano-scale porosity created by ICDR reactions. Porosity-aided recrystallization will affect any mineral-fluid system where mass transfers via solid-state diffusion and ICDR operate at similar rates, causing rapid (days-weeks) ‘resetting’ of the original isotopic abundances and trace element contents of the affected minerals. In copper sulfides, porosity-aided recrystallization occurs at lower temperatures (<300 °C) due to fast cation diffusion rates (log10D ≈ –13.6, 300 °C), but also takes place across other mineral systems where diffusion rates are faster at high temperatures. The open-system isotopic and trace element exchanges associated with porosity-aided recrystallization could lead to erroneous petrological interpretations, especially where these markers are used as a proxy for reconstructing geological evolution
Assessment of two types of passive sampler for the efficient recovery of SARS-CoV-2 and other viruses from wastewater
Get PDFWastewater-based epidemiology (WBE) has proven to be a useful surveillance tool during the ongoing SARS-CoV-2 pandemic, and has driven research into evaluating the most reliable and cost-effective techniques for obtaining a representative sample of wastewater. When liquid samples cannot be taken efficiently, passive sampling approaches have been used, however, insufficient data exists on their usefulness for multi-virus capture and recovery. In this study, we compared the virus-binding capacity of two passive samplers (cotton-based tampons and ion exchange filter papers) in two different water types (deionised water and wastewater). Here we focused on the capture of wastewater-associated viruses including Influenza A and B (Flu-A & B), SARS-CoV-2, human adenovirus (AdV), norovirus GII (NoVGII), measles virus (MeV), pepper mild mottle virus (PMMoV), the faecal marker crAssphage and the process control virus Pseudomonas virus phi6. After deployment, we evaluated four different methods to recover viruses from the passive samplers namely, (i) phosphate buffered saline (PBS) elution followed by polyethylene glycol (PEG) precipitation, (ii) beef extract (BE) elution followed by PEG precipitation, (iii) no-elution into PEG precipitation, and (iv) direct extraction. We found that the tampon-based passive samplers had higher viral recoveries in comparison to the filter paper. Overall, the preferred viral recovery method from the tampon passive samplers was the no-elution/PEG precipitation method. Furthermore, we evidenced that non-enveloped viruses had higher percent recoveries from the passive samplers than enveloped viruses. This is the first study of its kind to assess passive sampler and viral recovery methods amongst a plethora of viruses commonly found in wastewater or used as a viral surrogate in wastewater studies
Low-dose antenatal betamethasone treatment achieves preterm lung maturation equivalent to that of the WHO dexamethasone regimen but with reduced endocrine disruption in a sheep model of pregnancy
Get PDF[Introduction]
The intramuscular administration of antenatal steroids (ANS) to women at risk of preterm delivery achieves high maternal and fetal plasma steroid concentrations, which are associated with adverse effects and may reduce treatment efficacy. We have demonstrated that ANS efficacy is independent of peak materno-fetal steroid levels once exposure is maintained above a low threshold.
[Objectives]
We aimed to test, using a sheep model of pregnancy, whether the low-dose ANS regimen proposed as part of the ACTION III Trial would achieve preterm lung maturation equivalent to that of the existing WHO dexamethasone treatment regimen, but with reduced risk of adverse outcomes.
[Study Design]
Following ethical review and approval, date-mated ewes with single fetuses received intramuscular injections of either: i) four x 6mg maternal intramuscular injections of dexamethasone phosphate q12h (n=22); or ii) four x 2 mg maternal intramuscular injections of betamethasone phosphate q12h (n=21); or ⅲ) four x 2mL maternal intramuscular injections of saline q12h (n=16). Forty-eight hours after first injection, (124±1 d), lambs were delivered, ventilated for 30 minutes, and euthanised for sampling. Arterial blood gas, respiratory, haematological and biochemical data were analysed for between-group differences with ANOVA according to distribution and variance, with p<0.05 taken as significant.
[Results]
After 30 minutes ventilation, lambs from both steroid-treated groups had significant and equivalent improvements in lung function relative to saline control (p<0.05). There was no significant difference in arterial blood pH, pO2, pCO2, lung compliance, ventilator efficiency index or lung volume at necropsy with a static pressure of 40cmH2O. The mRNA expression of surfactant protein (Sp)a, Spb, Spc, Spd, aquaporin (Aqp)1, Aqp5 and sodium channel epithelial 1 subunit beta (Scnn1b) was equivalent between both steroid groups. Maternal and fetal plasma neutrophil, glucose and fetal plasma c-peptide levels were significantly elevated in the dexamethasone group, relative to the betamethasone group. Fetal plasma IGF-1 was significantly reduced in the dexamethasone group compared to the betamethasone group (p<0.05). Fetal ACTH (r=0.53), maternal glucose value (r=-0.52) and fetal glucose values (r=-0.42) were correlated with maternal weight in Betamethasone Group (p<0.05) while fetal pCO2 and pO2 were not correlated. There were no significant differences between male and female lamb outcomes in any groups for any of the items evaluated.
[Conclusions]
We report that, in preterm lambs, a low-dose treatment regimen of 8mg betamethasone achieves lung maturation equivalent to that of a 24mg dexamethasone-based regimen, but with smaller perturbations to the materno-fetal HPA axis. These data suggest that, given steroid pharmacokinetic differences between sheep and humans, a betamethasone dose of 2mg may remain above the minimum dose necessary for robust maturation of the preterm lung. Maternal weight-adjusted betamethasone doses might also be a key to reduce perturbations to the materno-fetal HPA axis
Abiotic and biotic responses to woody debris additions in restored old fields in a multi‐site Before‐After‐Control‐Impact experiment
Get PDFEcological restoration of former agricultural land can improve soil conditions, recover native vegetation, and provide fauna habitat. However, restoration benefits are often associated with time lags, as many attributes, such as leaf litter and coarse woody debris, need time to accumulate. Here, we experimentally tested whether adding mulch and logs to restoration sites in semi-arid Western Australia can accelerate restoration benefits. All sites had been cropped and then planted with native trees and shrubs (i.e., Eucalyptus, Melaleuca, and Acacia spp.) 10 years prior to our experiment, to re-establish the original temperate eucalypt woodland vegetation community. We used a Multi-site Before-After-Control-Impact (MBACI) design to test the effects on 30 abiotic and biotic response variables over a period of 2 years. Of the 30 response variables, a significant effect was found for just four variables: volumetric water content, decomposition, native herbaceous species cover and species richness of disturbance specialist ants. Mulch addition had a positive effect on soil moisture when compared to controls but suppressed growth of native (but not exotic) herbaceous plants. On plots with log additions, decomposition rates decreased, and species richness of disturbance specialist ants increased. However, we found no effect on total species richness and abundance of other ant species groups. The benefit of mulch to soil moisture was offset by its disbenefit to native herbs in our study. Given time, logs may also provide habitat for ant species that prefer concealed habitats. Indeed, benefits to other soil biophysical properties, vegetation, and ant fauna may require longer time frames to be detected. Further research is needed to determine whether the type, quantity, and context of mulch and log additions may improve their utility for old field restoration and whether effects on native herbs are correlated with idiosyncratic climatic conditions
Enumeration, antimicrobial resistance, and virulence genes screening of Enterococcus spp. Isolated from retail chicken carcasses in the United Arab Emirates
No full textEnterococci have recently emerged as nosocomial pathogens worldwide. Their ubiquitous nature determines their frequent finding in foods as contaminants. In this study, we aimed to determine the counts, species diversity, antimicrobial resistance profile, and to screen for a set of virulence genes among enterococci. Enterococcus were identified from 75.7% (125/165) of chilled chicken carcasses, belonging to seven companies, sampled from retail markets in Abu Dhabi Emirate, United Arab Emirates (U.A.E.). Overall, the samples, with a mean Enterococcus count of 2.58 log10 colony-forming unit (CFU)/g with a standard deviation of ±1.17 log10 CFU/g. Among the characterized Enterococcus isolates (n = 90), Enterococcus faecalis was the predominant species (51.1%), followed by Enterococcus faecium (37.8%). Using Vitek2 automated antimicrobial sensitivity panel, we found none of the E. faecalis nor E. faecium to be resistant to ampicillin, teicoplanin, vancomycin, or tigecycline. A third of the E. faecalis (28.3%) and E. faecium (35.3%) were resistant to high-level gentamicin. Over half of E. faecalis (54.3%) were resistant to ciprofloxacin, and the same was in about a third of E. faecium isolates (29.4%). Linezolid resistance was identified in 10 E. faecalis and 7 E. faecium isolates belonging to samples from three companies. All of the linezolid-resistant isolates harbored oxazolidinone resistance optrA gene. Virulence-associated genes (asa1 and gelE) were significantly (p < 0.05) more detected among E. faecalis compared to E. faecium isolates recovered in this study. Over half of the E. faecalis (25/46) and E. faecium (20/34) isolates were identified as multidrug-resistant. This study provides further insight into virulence genes and their association with the dissemination of multidrug-resistant E. faecalis and E. faecium in supermarket chicken meat in the U.A.E. This is probably the first description of the optrA gene in enterococci from supermarket chicken meat in the U.A.E. and from Arab countries. This study adds to the regional and global understanding of antimicrobial resistance spread in foods of animal origin
Using dietary additives to improve palatability of diets containing single‐cell protein from methanotrophic bacteria in yellowtail kingfish ( Seriola lalandi ) diets
Get PDFSingle-cell protein (SCP) derived from methanotrophic bacteria has significant potential as a fishmeal alternative in aquafeeds. However, SCP has known palatability issues, to overcome these issues tuna hydrolysate and garlic powder were tested as palatability enhancers against basal diets without these additives. This study tested the inclusion of SCP at four dietary levels of 0%, 10%, 20% and 30%, representing 0%, 25%, 50% and 75% fishmeal replacement in juvenile yellowtail kingfish (Seriola lalandi) (YTK) diets. YTK were fed these diets in triplicate over 35 days. Compared with the control diet, fish fed the SCP10% diet ate less feed, but had equal growth and subsequently an improved FCR. Feed intake decreased with increasing SCP inclusion, and the palatability enhancers were ineffective at improving intake. Despite the significant reduction in feed intake, FCR was equal across all SCP inclusion levels, demonstrating that the reduced growth performance at these higher inclusion levels was a function of only the reduced intake. Data showing equal protein retention efficiency and apparent digestibility coefficients across diets support this finding. This study showed that SCP derived from methanotrophic bacteria can replace 25% of fishmeal in a 400 g/kg FM diet and suggests if palatability issues can be overcome then higher inclusion of SCP could be achieved in YTK diets
Genome wide association study to map genetic loci underlying important agronomic traits of wild emmer wheat (Triticum dicoccoides)
Get PDFWild emmer (Triticum dicoccoides) is a progenitor of modern wheat that played the central role in wheat evolution. During the long process of evolution, rapid alteration and sporadic genomic changes occurred in wheat which resulted in gene modifications and some genes were lost in modern wheats. Thus, wild emmer contains a high number of novel genes which are absent in durum or bread wheat. Despite of huge diversity on morphological, grain quality and stress related traits, very few genes have been explored from wild emmer in the past. Particularly, only few shoots morphological trait related alleles have been well characterised. Likewise, root traits of wild emmer are almost unexplored. In this study, diversity of important shoot and root morphological traits across 263 wild emmer accessions were investigated and their genetics was studied. Accessions were collected from different parts of Israel, Turkey, Lebanon, and Syria. Shoot phenotyping was carried out on 19 traits by conducting three individual experiments, including two glasshouse experiments in 2019 and 2020 and one field trial in 2020. Root phenotyping was conducted on 10 traits in two independent glasshouse experiments in 2020 and 2021. All traits showed a wide range of variations, indicating a huge phenotypic diversity in wild emmer germplasm. The key traits identified with breeding potential include flowering time, tiller number, spike length, leaf area, shoot biomass, lateral root count, primary root count, and root biomass. Based on collection region, the germplasm was grouped into eight populations which demonstrated considerable variations for a few traits such as plant height, spike length and flag leaf area, but not for any root trait. Clustering based on shoot and root traits formed two broad groups where the Turkish germplasm grouped with that of Israeli, while the Lebanese and Syrian germplasm formed a separate group. Genotyping of the 263 wild emmer accessions was carried out using 90K SNP (Single Nucleotide Polymorphism) array. After quality checking, a total of 11,393 SNPs were selected for downstream analysis. A high level of diversity was observed, with an overall genetic diversity value of 0.4294 and a polymorphism information content (PIC) value of 0.3808. Structure analysis and phylogenetic analysis based on SNP markers divided the wild emmer germplasm into two sub-populations. GWAS (Genome Wide Association Study) was conducted using TASSEL (Trait Analysis by Association, Evolution and Linkage) software with the Mixed Linear Model (MLM). A total of 857 significant MTAs (Marker Trait Associations) were identified for shoot traits, among which 81 were highly significant. For root traits, 255 significant MTAs were identified, among which 31 were highly significant. Putative candidate genes and annotations were identified for all highly significant MTAs using specialized bioinformatics platform for wild emmer called ‘GrainGene’. The selected MTAs on phenotypes showed significant allelic effects among alternative alleles in most cases. However, the most promising MTAs belong to growth stage related traits, tiller number, shoot biomass, yield related traits, lateral and primary root count, and root biomass. Some of the novel alleles identified in the study include IWB19587 on 2A, IWB5392 on 4A, IWB58299 and IWB9063 on 7A for growth stage related traits; IWB3715 on 1B, IWA24354 and IWA4622 on 5B, IWB4154 on 7B for total tiller number; IWB64507 and IWB73323 on 4A for effective tiller number; IWB57171 on 7A for shoot biomass; IWB41324 and IWB57707 on 5A for yield; IWB44730 on 1B, IWB24094 and IWA1214 on 5A, IWA4622 on 5B, IWB67213 on 6B for lateral root count; IWB69753 and IWB32014 on 6B, IWB3235 on 7B for primary root count; and IWB70454 on 6A, IWA4249 on 7B for root biomass. The new alleles identified from this study have the potential to be incorporated into bread and durum wheat as wild emmer is easily crossable with both, which will ultimately accelerate wheat improvement
Required wound care content for nursing curricula in Australia: A Delphi Study
Get PDFBackground
There is evidence in the literature that there is a lack of knowledge related to wound care among entry to practice nursing students, which can influence nursing students’ confidence and competence. The research exploring the content and delivery of wound education is limited but does demonstrate that the nursing curricula between university programs internationally, and nationally within Australia, varies significantly. To reduce the inconsistencies and improve the quality of wound care education in undergraduate nursing curricula, it is important to identify what wound care content should be delivered and how this content should be scaffolded across the nursing program.
Aims
The central aims of the research were to ascertain what experts identify as important wound care curriculum content for a three year Bachelor of Nursing program and in which year students should first be introduced to each topic.
Methodology
A Delphi technique was used to establish consensus for a list of wound care topics (n=74) as to when they should be first introduced to nursing students. The wound care topics were taken from the Standards for Wound Prevention and Management (Wounds Australia, 2016) and divided into three categories: ‘anatomy and physiology’, ‘assessments’ and ‘treatments/therapies’ within the survey. Seventeen registered nurse wound care experts in Australia were recruited to take part in the three round Delphi survey and a response rate of 100% (n=17) was obtained in all three rounds. A consensus of >70% for the year that each topic should be first introduced was required.
Results
The Delphi process achieved consensus on the year that 65 wound care topics should be first introduced, with only nine topics not reaching above 70%. There were 19 topics nominated for year one and year two, 15 topics for year three and 12 topics that were nominated for post graduate study. There was a clear allocation of topics by the expert participants that enabled development of knowledge and skills over the three years across the conceptual areas of wound theory (includes anatomy and physiology, pathophysiology and pharmacology), physical assessment, psychosocial assessment, wound care skills, wound care planning, patient education and wound prevention.
Conclusion
Reducing the inconsistencies in wound care education and improving the standards of knowledge and skills in graduate nurses, is essential for the safe, effective and evidence-based care of individuals with wounds to improve their wound healing outcomes
An integrated bio- and hydrometallurgical approach for the extraction and recovery of metals from printed circuit boards
Get PDFElectronic waste (e-waste) is one of the fastest-growing waste streams globally. In 2019, 53.6 million tons of e-waste were generated globally. However, despite being projected to increase to 65.3 million tons by 2025, currently, only 17.4% of e-waste was recycled globally in 2019. In Oceania, the recycling rate is only 8.8%, despite generating 16.1 kg e-waste per capita. This is of environmental and economic concern. E-waste contains a range of heavy metals and other hazardous substances that can cause land, air and water contamination if improperly handled or sent to landfills, and thus risk to human and environmental health. Moreover, the value of raw materials in global e-waste was estimated to be USD 57 billion in 2019. Hence, there are significant environmental, economic, and social incentive to recycle e-waste. In fact, e-waste has been increasingly recognised as an urban mine. Given that the majority (3-6%) of value in e-waste is typically associated with end-of-life printed circuit boards (PCBs), which contain a range of valuable base and precious metals that can be recovered, the overarching goal of this PhD thesis was to develop new technology and knowledge useful for recovering valuable metals from PCBs.
The first objective of this thesis was to investigate an integrated biohydrometallurgical approach for the extraction of base metals from PCBs. Once the metals were extracted, the second objective of the thesis was to investigate the recovery of these metals using biogenic hydrogen sulfide. The third objective of this thesis was to develop a process flow sheet and conduct a techno-economic analysis (TEA) to determine the economic viability of the process.
The growing e-waste problem in Oceania is unique. Despite generating only 0.7 million tons of e-waste in 2019, it is one of the largest per capita generators of e-waste. A range of political, economic, legal, social, technological, and environmental factors affect the recycling of e-waste in this region. This thesis investigated these factors and identified various barriers and enablers for recycling e-waste in the region (Chapter 1). It also investigated the resource recovery technologies available that can be applied and identified the advantages and disadvantages associated with each of these technologies. This information is critical to understanding the incentives to recycling e-waste in the region and the challenges any future industrial process can face.
Due to their unique and highly heterogeneous composition, PCBs are challenging to be characterised. Currently, there is no standardised method for characterising the metal content of PCBs. Various analytical methods can have significantly different results, hindering the accurate tracking of metals throughout the value recovery process. To address this, various pre-treatment and analytical methods were compared to determine the most precise and accurate method for characterising base metals in PCBs (Chapter 2). Using a mixed metal standard, the proposed methods' accuracy was determined. Of these methods, microwave-assisted multi-acid digestion offered the most precision and accuracy. By determining the optimal method for quantifying base metals in PCBs, the accurate determination of base metal leaching efficiencies was greatly improved.
To facilitate base metals leaching from PCBs in biohydrometallurgical processing, a novel two-step biological lixiviant generation process was proposed and validated (Chapters 3 and 4). In the first step, crushed waste sulfur pastilles were biologically oxidised to produce biogenic H2SO4. The acidified effluent containing biogenic H2SO4 was then augmented with ferrous iron (20 g Fe L-1) in the second step, where it was biologically oxidised to produce ferric iron. The produced bio-lixiviant was then used for leaching base metals from PCBs.
The leaching of base metals from PCBs using the biogenic lixiviant was investigated at various experimental conditions to determine the effects of the process parameters on leaching efficiency. Leaching parameters tested in this study included temperature (25-45oC), aeration, PCB pulp density (PD, 1 and 5%), ferric iron concentration, solution pH, pH control, leaching reactor configuration, and pre-treatment of PCBs by ashing. Using optimised conditions, near-complete metal extraction was achieved for 1% PD. By controlling pH to a set point of pH 1.4 with feedback-dosing of 2 M H2SO4, high leaching efficiencies were also achieved at 5% PD compared to leaching without pH control.
By separating the unit processes for biogenic lixiviant generation from the leaching process, the optimisation of biogenic lixiviant production and PCB leaching parameters could be effectively achieved without compromising the growth and activity of the microorganisms.
Once in solution, the base metals from the leached PCBs were recovered through precipitation with biogenic hydrogen sulfide produced by sulfate-reducing bacteria (SRB) in an anaerobic fluidised bed reactor. The use of both lactate and glycerol as a carbon source for SRB was evaluated (Chapter 5). High metal precipitation efficiencies were achieved for base metals using biogenic sulfide and NaOH. This process facilitated the recovery of base metals as a high value mixed metal precipitate.
After the technical feasibility of the proposed biohydrometallurgical process was proven, a preliminary TEA was conducted to examine the potential capital and processing costs of establishing a plant capable of treating 1000 t/pa of PCBs in Australia (Chapter 6). The key factors that influence the economic feasibility were identified, and the effects of process efficiencies and market conditions on plant profitably were evaluated. The assessment provided insight into the economic aspects of the proposed process and helped to identify the critical research pathways for implementing the developed technology and opportunities for further optimisation in future work. Based on this analysis, the proposed process is profitable under optimised conditions.
Overall, a new biohydrometallurgical processing concept for extracting and recovery base metals from PCB waste was proposed and successfully validated in this thesis. The thesis also showed that the new process is an economically viable option that can potentially address some key challenges associated with e-waste processing in Australia
Nutrient (C, N and P) enrichment induces significant changes in the soil metabolite profile and microbial carbon partitioning
Get PDFThe cycling of soil organic matter (SOM) and carbon (C) within the soil is governed by the presence of key macronutrients, particularly nitrogen (N) and phosphorus (P). The relative ratio of these nutrients has a direct effect on the potential rates of microbial growth and nutrient processing in soil and thus is fundamental to ecosystem functioning. However, the effect of changing soil nutrient stoichiometry on the small organic molecule (i.e., metabolite) composition and cycling by the microbial community remains poorly understood. Here, we aimed to disentangle the effect of stoichiometrically balanced nutrient addition on the soil metabolomic profile and apparent microbial carbon use efficiency (CUE) by adding a labile C source (glucose) in combination with N and/or P. After incorporation of the added glucose into the microbial biomass (48 h), metabolite profiling was undertaken by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). 494 metabolites were identified across all treatments mainly consisting of lipids (n = 199), amino acids (n = 118) and carbohydrates (n = 43), >97% of which showed significant changes in concentration between at least one treatment. Overall, glucose-C addition generally increased the synthesis of other carbohydrates in soil, while addition of C and N together increased peptide synthesis, indicative of protein formation and turnover. The combination of C and P significantly increased the number of fatty acids synthesised. There was no significant change in the PLFA-derived microbial community structure or microbial biomass following C, N and P addition. Further, N addition led to an increase in glucose-C partitioning into anabolic processes (i.e., increased CUE), suggesting the microbial community was N, but not P limited. Based on the metabolomic profiles observed here, we conclude that inorganic nutrient enrichment causes substantial shifts in both primary and secondary metabolism within the microbial community, leading to changes in resource flow and thus soil functioning, however, the microbial community illustrated significant metabolic flexibility