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Groundwater releases CO2 to diverse global coastal ecosystems
Get PDFCoastal ecosystems play a major role in marine carbon budgets, but substantial uncertainties remain in the sources and fluxes of coastal carbon dioxide (CO2). Here, we assess when, where, and how submarine groundwater discharge (SGD) releases CO2 to shallow coastal ecosystems. Time-series observations of dissolved CO2 and radon (222Rn, a natural groundwater tracer) across 40 coastal systems from 14 countries revealed large SGD-derived CO2 fluxes. The mean groundwater partial pressure of CO2 was 35 times higher than surface seawater. The mean SGD-derived CO2 flux was 148 ± 226 millimoles per square meter per day (mmol m−2 day−1), resulting in a mean water-air CO2 flux of 80 ± 133 mmol m−2 day−1. Tidal rather than diel cycles drove CO2 enrichment in most ecosystems. Tidally driven SGD was the primary CO2 source in mangroves, salt marshes, tidal flats, estuaries, and canals. Overall, we expand current knowledge of marine carbon cycles by demonstrating SGD as an important source of CO2 that requires inclusion in coastal carbon budgets
Wellbeing after finalisation of a workers’ compensation claim: a cross-sectional survey
No full textObjective
Injured workers can be disadvantaged after a workers' compensation claims ends. This study investigated the association of a range of variables with well-being in injured workers who had finalized a workers' compensation claim >3 months prior.
Methods
On-line, cross-sectional survey (n = 129, 55.81% female). Well-being was measured using the Psychological Wellbeing 18-item (PWB) and the Personal Wellbeing Score (PWS).
Results
Multivariable quantile regression analysis controlling for education level demonstrated associations between the PWB and levels of psychological distress (−1.53; 95% CI, −2.11 to −0.94; P < 0.001) and resilience (6.51; 95% CI, 2.65 to 10.37; P = 0.001), and between the PWS and levels of psychological distress (−0.04; 95% CI, −0.51 to −0.29; P < 0.001) and resilience (1.2; 95% CI 0.47 to 1.93), P = 0.001.
Conclusions
Contemporaneous variables of resilience and psychological distress were stronger correlates with well-being than historic claim-related variables
Spreading across the continent: the Astronomical Society of Australia 1966-2023
No full textAustralian astronomy has undergone huge changes since the middle of the twentieth century, when astronomers generally only had access to the observing facilities of their own institution. In this paper, we look at the changes in the context of the membership of the Astronomical Society of Australia (ASA), since its formation in 1966. Initially, the dominant institutions were the Australian National University, the University of Sydney and the CSIRO, with each of these having more than twice the members of any other Australian institution. Access to world-class national facilities provided by the Anglo-Australian Telescope (AAT, an optical telescope) from 1975 and the Australia Telescope Compact Array (ATCA, a radio telescope) from 1991, led to increases in astronomer numbers at institutions other than the three dominant ones. More recently, to stay internationally competitive, astronomers need access to even larger observing facilities. One of these facilities is the Square Kilometre Array project (SKA). This radio telescope is to be split between Southern Africa and Australia with SKA-Low, observing in low frequency radio waves, to be sited at a remote location in Western Australia. That plan, and two new SKA precursor instruments, has boosted the number of astronomers in the state, making Western Australia one of the major centres of astrophysical research in Australia
Vertical kinematic response of monopiles subjected to vertically propagating seismic P-waves
No full textA rigorous mathematical model is developed to analyze the kinematic response of monopiles embedded in the seabed under vertically incident P-waves. The seabed is considered to consist of nearly saturated soil, in which the mixture of pore water and dissolved air bubbles is treated as a homogeneous fluid phase. The governing equations of soil and pile are formulated using the Biot's poroelastodynamic theory and one-dimensional bar vibration theory, respectively. The frictional forces between the inner and outer soil layers are derived, and a closed-form series solution for the monopile's vertical seismic response is obtained by applying the boundary conditions of the pile-soil system. The proposed solution is validated through comparisons with existing studies and is subsequently used to explore the effects of key parameters and the role of inner soil on the seismic behavior of the soil-pile system, leading to several significant conclusions
Mothers' duties and rights when positioned as remote education tutors in Australian distance schooling
No full textRemote Education Tutors (RETs) conduct the vital but undervalued work of delivering distance schooling to geographically isolated students in Australian rural and remote settings. Part of a broader research project, this paper reports the findings of extended, semi-structured interviews with four women who discharged dual roles as mothers and RETs of their child/ren. Conceptually and methodologically, the study draws on positioning theory (Davies & Harré, 1990, 1999) to construct dynamic storylines for the participants that explicated how each mother navigated her respective self-reported duties and rights with reference to distance education, as manifested in the particular ways that they positioned themselves and others and in how they were positioned by others. The findings demonstrated both continuities and divergences among the participants’ experiences and perceptions of their duties and rights, as well as diverse strategies and varied self-confidence in their work as RETs, all of which were framed and enacted in the specific contexts of their separate home-based schoolrooms. These findings affirm the crucial value of the mother RETs in facilitating their child/ren’s successful learning outcomes, and also underscore the importance of financial compensation if their work is to be equitable and sustainable in the long term
Aerodynamic Measurements of Hypersonic Free-Flight via Optical Tracking and Bayesian State Estimation
No full textOptical force and moment measurements of hypersonic free-flight can cover a range of attitudes during a single test and avoid difficulties encountered by alternative measurement techniques. However, the signal to noise ratio of image processing is often low, and results require significant smoothing for meaningful interpretation. This work presents a new method for such measurements in which a sigma-point Kalman filter and Rauch–Tung–Striebel smoother compute a state estimate at each time step using images from two or more high-speed camera images. Markers detected in each image are treated as individual system observations, so cameras need not be synchronized nor be viewing similar features. The benefits of this approach are demonstrated with experiments of a cube in Mach 6 flow in the University of Southern Queensland’s TUSQ wind tunnel. Measured aerodynamic coefficients show strong agreement to CFD simulations also conducted as part of this work; average differences are 1.7% and 7.8% of the maximum measured forces and moments, respectively. A discussion on factors influencing the accuracy, uncertainty, and resolution of the results provides guidance to further improve the method. Moreover, this method can be extended to more complex geometry representing space debris and hypersonic vehicles
Systematic Analysis of the Impact of Data Preprocessing Techniques on Machine-Learning Model Performance: A Case Study of a Compressive Strength Prediction Model for Geopolymer Concrete
No full textGeopolymer concrete (GPC) is emerging as a sustainable alternative to ordinary Portland cement (OPC) concrete. However, developing mix designs for GPC presents unique challenges due to the variability in fly ash properties and the selection of appropriate alkaline activators. Traditional experimental and statistical methods often fall short in predicting the compressive strength of GPC. Recently, machine
learning (ML) models have gained popularity in this area. This study evaluates the impact of various data preprocessing (DP) techniques namely missing data imputation, outlier detection, and normalization of the performance of an artificial neural network (ANN) model for predicting the compressive strength of GPC. The study also assessed the influence of feature selection using an ANN model considering
common input variables identified in the literature. Results indicate that the chemical oxide content of fly ash, NaOH solid content, and total water content are critical to accurate strength prediction. Furthermore, curing temperature and time significantly enhances model accuracy. The study found that removing missing data and using median outlier detection improved model performance, while proper hyperparameter tuning markedly enhanced prediction accuracy. Validation through laboratory experiments confirmed the model’s reliability, demonstrating its potential for advancing GPC mix design
ACARP 34018: Carbolt™: Pre-Commercial Fixed Length Carbolt Prototype
No full textThis project aimed to advance the carbon-fibre rock bolt, Carbolt™, prototype by refining its manufacturing process and enabling the testing of a full-length roof bolt. The development required specialized tools, including a braiding machine and a custom mould for resin curing, to ensure uniform diameter and create features such as ribs and threads. A standard nut and bolt locking mechanism was integrated to maintain compatibility with existing roof bolting systems.
Several design iterations were produced and tested against industry standards for steel rock bolts, evaluating shear strength, pull-out resistance, and tensile performance. The results indicated that, while comparing bolts of the same diameter, the direct tensile strength of the Carbolt was lower. However, after accounting for the reduced effective cross-sectional area due to the inclusion of the core, the Carbolt’s tensile strength is comparable, and in some cases higher, of both steel and fiberglass rock bolts. In addition, the Carbolt is significantly lighter—by approximately 80%—than steel rock bolts of equivalent tensile strength.
In shear tests, the Carbolt performed less than steel rock bolts. The braided carbon-fibre structure enhanced load-bearing capacity and energy absorption, making its single shear strength higher but its double shear strength was still lower than that of high-modulus fiberglass rock bolts, indicating room for improvement with higher-modulus carbon fibre. The ribbed design exhibited suboptimal pull-out performance, suggesting that further refinement is needed to improve grout adhesion and match the effectiveness of steel rock bolts.
A major advantage of the Carbolt is its corrosion resistance, making it well-suited for harsh mining environments where steel rock bolts are prone to rust and degradation. While flammability testing was not conducted, carbon fibre’s inherent inert properties suggest similar behaviour to fibreglass rock bolts in high-temperature conditions.
From a commercial perspective, the current braiding process speed may be sub-optimal for large-scale production. A more practical manufacturing approach would involve a wound or twisted fibre configuration, which would require collaboration with international partners due to Australia’s limited composite manufacturing capabilities.
Overall, the Carbolt shows strong potential as a lightweight, corrosion-resistant alternative to steel rock bolts. Further development in areas such as rib design, diameter optimization, underground field trials and scalable production methods is necessary before it can be commercially viable. With these refinements, the Carbolt could provide a practical, high-performance solution for mining operations, improving safety and durability while reducing maintenance costs in corrosive environments
Integrating Videoconferencing Therapist Guidance Into Stepped Care Internet-Delivered Cognitive Behavioral Therapy for Child and Adolescent Anxiety: Noninferiority Randomized Controlled Trial
Get PDFBackground:
Self-guided internet-delivered cognitive behavioral therapy (ICBT) achieves greater reach than ICBT delivered with therapist guidance, but demonstrates poorer engagement and fewer clinical benefits. Alternative models of care are required that promote engagement and are effective, accessible, and scalable.
Objective:
This randomized trial evaluated whether a stepped care approach to ICBT using therapist guidance via videoconferencing for the step-up component (ICBT-SC[VC]) is noninferior to ICBT with full therapist delivery by videoconferencing (ICBT-TG[VC]) for child and adolescent anxiety.
Methods:
Participants included 137 Australian children and adolescents aged 7 to 17 years (male: n=61, 44.5%) with a primary anxiety disorder who were recruited from participants presenting to the BRAVE Online website. This noninferiority randomized trial compared ICBT-SC[VC] to an ICBT-TG[VC] program, with assessments conducted at baseline, 12 weeks, and 9 months after treatment commencement. All ICBT-TG[VC] participants received therapist guidance (videoconferencing) after each session for all 10 sessions. All ICBT-SC[VC] participants completed the first 5 sessions online without therapist guidance. If they demonstrated response to treatment after 5 sessions (defined as reductions in anxiety symptoms to the nonclinical range), they continued sessions without therapist guidance. If they did not respond, participants were stepped up to receive supplemental therapist guidance (videoconferencing) for the remaining sessions. The measures included a clinical diagnostic interview (Anxiety Disorders Interview Schedule) with clinician-rated severity rating as the primary outcome and parent- and child-reported web-based surveys assessing anxiety and anxiety-related interference (secondary outcomes).
Results:
Although there were no substantial differences between the treatment conditions on primary and most secondary outcome measures, the noninferiority of ICBT-SC[VC] compared to ICBT-TG[VC] could not be determined. Significant clinical benefits were evident for participants in both treatments, although this was significantly higher for the ICBT-TG[VC] participants. Of the 89 participants (38 in ICBT-SC[VC] and 51 in ICBT-TG[VC]) who remained in the study, 26 (68%) in ICBT-SC[VC] and 45 (88%) in ICBT-TG[VC] were free of their primary anxiety diagnosis by the 9-month follow-up. For the intention-to-treat sample (N=137), 41% (27/66) ICBT-SC[VC], and 69% (49/71) ICBT-TG[VC] participants were free of their primary anxiety diagnosis. Therapy compliance was lower for the ICBT-SC[VC] participants (mean 7.39, SD 3.44 sessions) than for the ICBT-TG[VC] participants (mean 8.73, SD 3.08 sessions), although treatment satisfaction was moderate to high in both conditions.
Conclusions:
This study provided further support for the benefits of low-intensity ICBT for children and adolescents with a primary anxiety disorder and highlighted the excellent treatment outcomes that can be achieved through therapist-guided ICBT delivered via videoconferencing. Although noninferiority of the stepped care adaptive approach could not be determined, it was acceptable to families, produced good outcomes, and could assist in increasing access to evidence-based care.
Trial Registration:
Australian New Zealand Clinical Trials Registry (ANZCTR) ACTRN12618001418268; https://anzctr.org.au/Trial/Registration/TrialReview.aspx?ACTRN=1261800141826
Carbon Fiber Reinforced Thermoplastics: From Materials to Manufacturing and Applications
Get PDFCarbon fiber reinforced thermoplastics (CFRTs) have witnessed a resurgence in recent times since their first industrial use over five decades ago, with revitalized interest from aerospace companies and other key sectors including energy and automotive sectors. CFRTs are increasingly gaining footholds in high volume rapid manufacturing in aerospace and nonaerospace sectors owing to their inherent recyclability. However, there has been a lack of contemporary and critical review on this topic so far. This work aims to review the recent advances in CFRTs with emphasis on high performance thermoplastics. Both continuous and discontinuous fiber forms in tape, organosheet and short/long fiber architectures are discussed, their processing and postprocessing methods are reviewed, with emphasis on state-of-the-art welding techniques. Typical applications of CFRTs in industry are examined, including fuselage, pressure vessel, and automotive components. Finally, insights are provided into ongoing challenges, future development, and a roadmap for expediting the development of high-performance CFRTs