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Flame-Retardant and Smoke-Suppressive Epoxy Resins with Enhanced Storage and Thermal Stability via Curing with a Phosphorus-Containing Imidazole Derivative
No full textAddressing the flammability of epoxy resins and simplifying the production process remain huge challenges. In this work, an imidazole-derived phosphorus/nitrogen-containing latent curing agent (ATIM) was synthesized using nitrilotrimethylene triphosphonic acid (ATMP) and 1-methylimidazole as raw materials for fabricating a single-component flame-retardant epoxy (EP). The ATIM-cured EP (EP/ATIM) showed desired flame-retardant properties, and its UL-94 classification reached V-0 when ATIM content increased to 13 wt %. The limiting oxygen index (LOI) of EP/ATIM-15 (ATIM content: 15 wt %) reached 33.0%, and its peak heat release rate (PHRR) and peak smoke production rate (PSPR) were 51.9 and 41.4% lower than those of the imidazole (IM)-cured EP (EP/IM-7, IM content: 7 wt %), respectively, which demonstrated considerable progress in both flame resistance and smoke reduction properties. EP/ATIM exhibited a higher onset decomposition temperature and greater char residue compared with EP/IM-7, demonstrating superior thermal stability. The shelf life of EP/ATIM-15 could be up to 7 days, confirming that the introduction of P-containing acid endowed EP/ATIM with increased storage stability. Thus, this study offers a feasible strategy for enhancing the storage stability, fire retardant performance, and thermal properties of a single-component epoxy resin
Quantification of Microplastics in Agricultural Soils by total organic carbon-solid sample combustion analysis
Get PDFAccurate quantification of microplastics (MPs) in soils is a significant challenge due to the complex nature of the organo-mineral matrix. Fine mineral particles and organic matter often interfere with the efficiency of extraction, identification and quantification of MPs from soils. Here, an optimized MP extraction and quantification method is proposed, using total organic carbon analyser-solid sample combustion unit (TOC-SSM) analysis. The approach entails a field survey, digestion of organic matter by Piranha solution, density separation, and quantification. This method achieves a high total recovery rate of 97.39 ± 14.25 (SE) % for particles sized between 300 and 600 µm, and 94.80 ± 13.48 (SE) % for particles less than 300 µm with spiked soil as samples. The optimised method is then applied to strawberry farm soils that use plastic mulch films to quantify MP contamination levels. Our results indicate MP concentrations of 12.24 ± 3.65 (SE) mg kg−1 (for particles of 300–2000 µm in size) and 2.62 ± 0.66 (SE) mg kg−1 (for particles smaller than 300 µm). With improved simplicity and the ability to provide the actual weight of plastics for the extraction and quantification of MPs, this work offers a potential approach for assessing low-density plastics in the northeastern Australian agricultural soils with a dominant MP contamination, specifically polyethylene (PE)
Phosphorus-derived imidazolium salts with varied oxidation states: Tailoring latency, mechanical properties, and flame retardancy in single-component epoxy resins
No full textSingle-component epoxy resin (EP) is the premix of EP and latent curing agent, which is highly demanded in industries. However, current single-component EPs struggle to balance storage stability with mechanical properties and flame retardancy. To address this issue, three phosphorus-derived imidazolium salts (MPOx, x = 2, 3, 4) were synthesized using 2-ethyl-4-methylimidazole (EMI) and phosphorus-containing acids with different oxidation states (diphenylphosphinic acid, phenyl hydrogen phenylphosphonate, and diphenyl phosphate). The oxidation state of phosphorus significantly influenced thermal latency of MPOx, with higher oxidation states leading to improved latency. EP/MPO4 achieved the longest shelf life of 42 d at 25 °C. EP/MPO3 and EP/MPO4 exhibited enhanced tensile strength, modulus, and impact resistance compared to EP/EMI, but EP/MPO2 showed poor mechanical properties due to phase separation. All EP/MPOx achieved limiting oxygen index (LOI) exceeding 30 %, with EP/MPO3 showing the highest LOI of 34.0 % and significant reductions in heat release and smoke production. Flame-retardant mechanistic studies revealed a shift from gaseous-phase flame inhibition to condensed-phase promoting carbonization with increasing phosphorus oxidation state. Obviously, MPOx provides a tailored balance of latency, mechanical strength, and flame retardancy, making it a promising solution for advanced single-component EPs in aerospace, electronics, and optical applications
On the Recovery of the Environmental Pasts of Early Modern Plays
Get PDFThis article outlines initial findings from the “Playing Conditions” research project, which seeks to improve understanding of the role climate played in the rise of the Elizabethan playhouse industry. In the course of this research, it has been necessary to rethink prevailing assumptions about the English Little Ice Age. The primary source materials are being incorporated into the Weather Extremes in England’s Little Ice Age, 1500-1700 ArcGIS database. Examination of these materials reveals that the seasonal weather phenomena normally associated with Little Ice Age climate, including long frozen winters and cold, wet summers, did not fully develop in England until the first decade of the seventeenth century. During the sixteenth century, as the playhouse industry emerged, the English faced volatile seasonal variations with extremes of drought and severe storm weather and violent tidal surges. For theatre historians, accurate accounts of sixteenth-century climate in England are important in better understanding the rise of the playhouses and playing business. Yet this research has come up against some significant points of resistance both within and without the academy, which it is also helpful to document in the context of making a case for the continued value of historical research in relation to the impact of climate change as a driver of cultural innovation
Identifying unique integrated care competencies to inform health profession curriculum development.
No full textBackground
Integrated care can enhance health outcomes for patients, as well as improve healthcare efficiency for organisations. However, it is unclear what values and competencies health professionals need to develop at the pre-qualification stage to engage in integrated care practice upon graduation. Therefore, this review aimed to identify published integrated care competencies for professional entry health professional education programmes.
Methods
Guided by the systematic search methods of the Preferred Reporting Items for Systematic Review and Meta-Analyses, PubMed and CINAHL were searched for publications between January 2013 and December 2022. A two-stage screening process was used to determine eligibility of papers against the set inclusion criteria.
Findings
The initial search yielded 493 articles, with 35 articles eligible for full text screening. Of these, five articles addressed integrated care curriculum in a general sense and were included in the review. The focus of these articles was mainly educational activities and professional attributes deemed important for students to experience and develop if they are to work across sectors and systems. However, no studies described a specific set of integrated care competencies for students enrolled in any health discipline at professional entry level.
Discussion
Since our review, several frameworks covering a broad range of professional competency domains for integrated care have been recently published. A distillation of these frameworks is now needed to identify the unique capabilities required for new health professionals to deliver integrated care.
Conclusion
Educators now need specific integrated care competencies so they can create appropriate, learning, teaching and assessment experiences for pre-entry students
Performance Comparison of Solid Walls and Porous Fences in Protecting Structures from Firebrand Attack
Get PDFIn bushfire-prone regions, solid walls and porous fences are commonly employed as miti-gation measures against windblown embers (firebrands). This computational study eval-uates and compares the performance of a 2 m high solid wall and a 2 m porous fence (38% porosity) in protecting structures from firebrand showers. Using a numerical model sub-jected to free-stream velocities of up to 50 m/s, flow patterns and firebrand trajectories were analyzed. The findings indicate that impermeable walls offer superior protection for im-mediately adjacent structures by deflecting the incident flow upwards, creating a “jump board” effect. However, the deflected flow subsequently reattaches to the ground at a downstream distance, rendering structures further downwind vulnerable to ember attack. The porous fence also exhibits a similar, albeit less pronounced, upward deflection. The simulations reveal minimal flow descent downstream of the fence at lower free-stream ve-locities, suggesting extended downwind protection. In the immediate downstream vicinity of the porous fence, penetration by small firebrands is possible; however, prior studies have shown that the likelihood of ignition from these embers is minimal and decreases rapidly within a short downstream distance of several metres
Co-opted boards and bidder performance
Get PDFPurpose
Defining co-opted directors as those who join a company’s board after an incumbent chief executive officer assumes office, this study aims to investigate the influence of co-opted boards on bidder performance.
Design/methodology/approach
This study applies ordinary least squares regression analyses to a sample of 8,939 acquisition observations announced by US firms spanning the 1999–2019 period. Event study methodology was employed to capture the market response to acquisition announcements. Propensity score matching technique, a two-stage least squares instrumental variable approach and model selection through the Lasso method were performed for robustness and endogeneity correction purposes.
Findings
The results depict a significant negative relationship between a co-opted board and return to acquirers, suggesting that managers under co-opted boards make value-destructing Mergers and Acquisitions deals. We also show that the relationship between board co-option and acquisition performance is positively moderated by institutional ownership while being negatively moderated by an entrenched board. Our additional tests reveal that board co-option reduces acquisition efficiency and leads to worse financial performance.
Practical implications
This study offers important implications for regulators and policymakers by highlighting how poor monitoring of the board of directors can influence announcement returns.
Originality/value
To the best of the authors’ knowledge, this paper appears to be the first investigation that makes a link between board co-option and various dimensions of acquisition decision
EEG based over-complete rational dilation wavelet transform coupled with autoregressive for motor imagery classification
Get PDFMotor Imagery (MI) based Brain-Computer Interface (BCI) applications are designed to analyse how the brain interacts with the external environment from electroencephalograph (EEG) signals. Despite current models achieving promising results, developing an accurate classification of MI from EEG signals remains a significant challenge. In this paper, we designed an MI classification model named (ORDWT_AR) utilising an over-complete rational dilation wavelet transform (ORDWT) coupled with an autoregressive (AR) model. Firstly, EEG recordings are segmented into intervals using a sliding window method. Then, each EEG segment is passed through the ORDWT to analyse EEG signals. As a result, a series of stop bands is obtained from each segment. Then, the AR is adopted and integrated with ORDWT to extract representative features from each EEG interval. The selected features are sent into several classification models, including Weighted k-nearest Neighbour (WKNN), Decision Tree (DTree) and Boosted Trees (BST). Four benchmark EEG databases were used to evaluate the proposed model, three of which were collected from brain-computer interface (BCI) Competition III and one from the CHB-MIT. The results demonstrated that the proposed model ORDWT_AR coupled with the WKNN classifier achieved an average of 99.8% classification accuracy for the three BCI competition III datasets and 99.7% for the CHB-MIT dataset. The obtained results revealed that the proposed scheme is a promising tool for classifying EEG signals and has outstanding results. The proposed model can support experts in aiding disabled people to interact with their environment accurately and improve the quality of their lives
A novel closed-form solution for circular tunnels in cohesive-frictional soils using isogeometric analysis, upper bound limit analysis, and soft computing
No full textAn innovative method for deriving closed-form solutions to evaluate the stability of circular tunnels in cohesive-frictional soils under uniform surcharge loading is introduced in this study. By integrating isogeometric analysis (IGA) with upper bound limit analysis (UB) and advanced soft computing techniques, the approach simplifies complex geotechnical calculations for practical engineering applications. Utilizing Bézier extraction and non-uniform rational B-splines (NURBS) basis functions, the IGA framework ensures precise geometric representation and finite element analysis. A key innovation in this study is the automatic generation of a large dataset comprising 14,050 samples with varied parameters using IGA-UB. This dataset is used to train a deep neural network (DNN) and develop a multivariate adaptive regression splines (MARS) model. An importance-based sensitivity analysis and partial dependence plots (PDPs) are employed to evaluate and visualize the impact of various parameters on the stability outcomes, providing deeper insights into feature interactions and their effects. The resulting robust closed-form solution facilitates hand calculations, greatly aiding engineers in practical design and stability assessments. This approach enhances computational efficiency and accuracy, making it a valuable tool in geotechnical engineering
Two Earth-size Planets and an Earth-size Candidate Transiting the nearby Star HD 101581
Get PDFWe report the validation of multiple planets transiting the nearby (d = 12.8 pc) K5V dwarf HD 101581 (GJ 435, TOI– 6276, TIC 397362481). This system consists of at least two Earth-size planets whose orbits are near a mutual 4:3 meanmotion resonance, HD 101581 b ( = - + Rp 0.956 0.061 RÅ 0.063 , P = 4.47 days) and HD 101581c ( = - + Rp 0.990 0.070 RÅ 0.070 , P = 6.21 days). Both planets were discovered in Sectors 63 and 64 TESS observations and statistically validated withWe report the validation of multiple planets transiting the nearby (d = 12.8 pc) K5V dwarf HD 101581 (GJ 435, TOI– 6276, TIC 397362481). This system consists of at least two Earth-size planets whose orbits are near a mutual 4:3 meanmotion resonance, HD 101581 b ( = - + Rp 0.956 0.061 RÅ 0.063 , P = 4.47 days) and HD 101581c ( = - + Rp 0.990 0.070 RÅ 0.070 , P = 6.21 days). Both planets were discovered in Sectors 63 and 64 TESS observations and statistically validated with supporting ground-based follow-up. We also identify a signal that probably originates from a third transiting planet, TOI-6276.03 ( = - + Rp 0.982 0.098 RÅ 0.114 , P = 7.87 days). These planets are remarkably uniform in size and their orbits are evenly spaced, representing a prime example of the “peas-in-a-pod” architecture seen in other compact multiplanet systems. At V = 7.77, HD 101581 is the brightest star known to host multiple transiting planets smaller than 1.5 R⊕. HD 101581 is a promising system for atmospheric characterization and comparative planetology of small planets