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Nonlinear Effects of Ring Current Protons: Impacts of EMIC Wave Amplitude, Frequency, and Propagation Angle
No full textNonlinear cyclotron resonance is known to cause the scattering of ring current protons to deviate from the predictions of quasi-linear theory, when wave-induced motion dominates over adiabatic motion. This study employed a test-particle simulation to investigate the nonlinear processes of ring current protons and their dependence on the amplitude, frequency, and wave normal angle ψ of electromagnetic ion cyclotron (EMIC) waves. As the equatorial pitch angle αeq increases, proton motion becomes dominated by the wave's electromagnetic force and responds nonlinearly. When wave-induced motion and adiabatic motion become comparable, the superposition of nonlinear phase trapping and phase bunching leads to complex oscillations in both the test-particle advection and diffusion coefficients. The nonlinear behavior becomes pronounced when the wave amplitude increases significantly. As the wave frequency increases, EMIC waves can nonlinearly interact with lower energy protons (i.e., Ek < 10 keV). Furthermore, oblique EMIC waves tend to produce less significant nonlinear behavior compared to parallel EMIC waves. Increasing the wave normal angle causes the nonlinear regime (i.e., the number of protons responding nonlinearly) in the Ek−αeq plane to shrink, and the regime changes discontinuously with respect to αeq. We propose that the characteristics of EMIC waves significantly influence the nonlinear behavior of ring current protons and should be considered in the wave-particle interacting processes
A Key Fragment in Carbon Schwarzite Unit Cells and Its Triple [6]Helicene Precursor
No full textThis study explores two structurally related π-skeletons. The π-skeleton of compounds 1a–e containing three heptagons represents a key fragment in theoretical carbon schwarzites, while that of 2a–b is a triple [6]helicene. Compounds 1a–e were synthesized via Scholl reactions, and using a weaker acid allowed the reaction to stop at an intermediate stage, yielding 2a–b. X-ray crystallography revealed not only distinct stereochemistry of 1b and 2a but also unique supramolecular assemblies in the clathrate of 2a with chloroform. Compound 1b adopts a saddle-like geometry, while 2a exhibits a propeller-like structure with C3 symmetry, consistent with density functional theory (DFT) calculations. The π-skeleton of 1a–e is flexible, enabling rapid enantiomerization, whereas that of 2a–b is rigid, allowing resolution of 2b into optically pure forms with an absorption dissymmetry factor as high as 0.015. Comparative analysis shows that presence of seven-membered rings in 1a–e does not significantly alter the local aromaticity of the triple [6]helicene framework
Improving Efficiency in Healthcare: Lessons from Successful Health Policies in Chile
No full textBackground: Chile has made significant progress in recent decades in implementing policies to improve the efficiency of its health system with an impact on population health. Aim: To present five case studies of successful policies whose impact has been documented. Methods: Case study report. Results: First, we present a summary of the evidence supporting the policy that is changing the Chilean care model from a problem-based to a patient-centered care model. Second, we show how tele-nephrology and advanced renal care units have demonstrated significant impact on chronic kidney disease in Chile. This internationally recognized successful Chilean policy is contributing to address one of the conditions that explains the highest financial burden on the health system. Third, we present recent evidence on the effectiveness of teleoncology care in Chile. Fourth, we highlight the most recent system of epidemiological surveillance implemented in Chile, the EPIVIGILA system, which was essential to support decisions throughout the pandemic. Finally, we underline the health benefit plans implemented in recent decades to improve access to services and financial protection. Conclusions: Chile has successfully implemented policies in its health system that have an impact on efficiency and population health. These experiences can be replicated in countries facing similar challenges, using the Chilean experience as a benchmark.link_to_subscribed_fulltex
Extreme rainfall induced risk mapping for metro transit systems: Shanghai metro network as a case
No full textIn recent years, a changing climate has induced flood risk as a great threat to the safety and reliability of the metro transit network in mega-cities. A highly networked metro system can lead to a quick spread of this risk, and furthermore, the impact range of single-node accidents of a network is nonlinearly amplified through network connectedness defined by its topology. This study proposes a risk assessment framework integrating extreme rainfall simulation and network loss analysis. The methodology employs the Areal Reduction Factor (ARF) and Soil Conservation Service Curve Number (SCS-CN) to model rainfall-induced flooding, coupled with a multi-layer network-based approach that distinguishes topological interactions between stations and lines. Taking Shanghai metro as an example, this paper highlights its risk follows an exponential distribution to extreme rainfall events, characterized by the finding that nearly 50 % of extreme rainfall events result in 50 % network loss. When rainfall centers are located in the urban center where metro stations are densely distributed and intricately connected, or when the rainfall intensity and the spatial distribution uncertainty increases, it will pose a greater risk to the metro network
Accurate Prediction of Open-Circuit Voltages of Lithium-Ion Batteries via Delta Learning
No full textAccurate prediction of lithium-ion battery capacity before material synthesis is crucial for accelerating battery material discovery. The capacity can be theoretically determined by integrating open-circuit voltage vs state of charge (OCV-SoC) curves of electrode materials. OCV-SoC curves are traditionally computed using first-principles methods, either through geometry optimization (GO) with density functional theory (DFT) or molecular dynamics (MD) simulations of lithiation/delithiation processes using DFT or force fields. While MD simulations incorporate temperature effects that GO lacks, even DFT-based MD simulated OCV-SoC curves show systematic deviations from experimental results due to inherent approximations in DFT functionals. In this study, we performed MD simulations on 43 cathode materials to obtain their OCV-SoC curves. Initial results showed only moderate agreement with experimental data, yielding a coefficient of determination (R2) of 0.249 and a mean absolute error (MAE) of 1.561 V. Considering the scarcity of data, we implemented a delta learning approach to calibrate the MD results without substantial computational overhead, achieving an improved R2 of 0.933 and an MAE of 0.131 V on the testing set. This calibration method significantly enhanced the accuracy of energy density predictions, reducing the MAE from 106.0 to 10.7 Wh/kg. We also developed an automated delta learning platform to make this approach accessible to researchers without machine learning expertise.</p
Multifunctional Universal Additive for Stable and Efficient Inverted Perovskite Solar Cells
No full textThe performance of perovskite solar cells has significantly improved over the years in part due to defect passivation in the bulk and at the interfaces. While many additive molecules have been reported in the literature, they are commonly applicable only to one particular perovskite composition. Here we investigate a multifunctional additive, 4-amino-5-bromo nicotinic acid (ABrNA), for use in both methylammonium (MA)-free perovskites with different Br content (bandgaps ranging from 1.53 to 1.73 eV) as well as MA-containing perovskites. Significant performance improvements are obtained for all compositions, which can be attributed to the presence of multiple functional groups capable of modifying the crystallization of the perovskite as well as passivating defects. Exceptional features of ABrNA make it a promising universal passivator, which leads to a PCE increase from 23.9% to 25.0% for CsFAMA solar cells, and from 22.0% to 23.0% for MA-free solar cells. The ABrNA passivated MA-free devices also exhibit exceptional operational stability, with T90 exceeding 1000 h under ISOS-L-1 testing conditions. In addition, significant performance improvement is observed with ABrNA for modules in both conventional and inverted device architectures, further confirming the universality of ABrNA additive
Where on the Moon was the eruption that produced the recently reported ∼ 120 million year old volcanic glass beads?
No full textThree anomalously young, ∼120 Ma old lunar mare pyroclastic beads have recently been reported (Wang et al., 2024) from Chang'e-5 (CE-5 soils, particularly distinguished from impact melt beads by sulfur isotope (34S/32S) composition and correlations with sulfur concentration. We examine lunar pyroclastic eruption theory and candidate eruption conditions in order to locate the vent and assess its geological context, finding that the estimated maximum pyroclast dispersal range from a candidate source vent is likely to be ∼200 km, placing it within the area of the CE-5–2.0 Ga sampled Em4 unit. The greatest predicted dispersal distances are associated with an explosive eruption from a stalled dike several kilometers below the surface, creating an elongated, multi-km-scale pit crater potentially surrounded by a dark pyroclastic ring. We assessed the Chang'e-5 region for such candidates and found none. This raises the possibility that the ∼120 Ma pyroclastic beads might have been delivered to the site from an impact crater outside Em4, but the most likely candidates are sufficiently large and at such great distances that they are likely to have reset the ages of any young pyroclastic beads thus delivered. Lacking a clear source for extraordinarily young pyroclastic beads, we reassess the possibility that the ∼120 Ma beads may be of local impact melt origin. Evidence favoring this hypothesis includes the abundant CE-5 impact glass bead ages in the 100–200 Ma year range previously reported (Long et al., 2022), and the similarities in composition and characteristics of the three beads and those of local impact origin. To address these conundra, further regional searches for a source vent and continued geochemical characterization and dating of CE-5 regolith glass beads should be undertaken.link_to_subscribed_fulltex
Text as data: Narrative mining of non-collision injury incidents on public buses by structural topic modeling
Get PDF Introduction: Although numerous studies have investigated collisions involving public buses, there has been inadequate research on passenger injuries caused by non-collision incidents on public buses. One major obstacle is that the manual extraction of thematic information from massive document repositories is exceedingly labor intensive, cumbersome, and inaccurate. Our study thereby illustrated how to automatically characterize non-collision injury incidents on public buses by fusing advanced language processing techniques and large-scale incident reports. Methods: Based on the 12,823 textural narratives recorded by police during 2010–2019 in Hong Kong, the structural topic modeling was developed to uncover underlying themes, quantify topic prevalence, and portray complex interconnectedness. Results: Thirty-three topics were successfully labeled, with the topic stand and lost balance being the most prevalent. Non-collisions were more likely to result in serious consequences when incidents occurred because the bus skidded, when a passenger was boarding, and when a standing passenger lost the balance. Six unique patterns were uncovered, i.e., the failure to hold handrails accompanied by inappropriate behaviors of bus drivers when approaching bus stations, loss of balance among standing passengers due to the sharp braking of bus drivers in response to red traffic lights ahead, alighting passengers being hit by the door, passengers falling while climbing staircases, passengers being injured because of bus driver's emergency maneuvers to avoid collisions with nearside pedestrians, and passengers being injured due to the careless lane-changing of bus drivers when weaving through roundabouts. Conclusions: By leveraging the emerging text mining techniques, unstructured narratives written by the police can provide valuable and organized information for regular injury surveillance. Tailor-made countermeasures were proposed to prevent non-collision injury incidents on public buses. preprin
Benchmarking computer vision models for automated construction waste sorting
Get PDFWaste sorting is a critical process in construction waste management system. Computer vision (CV) offers waste sorting automation potential by recognizing waste composition and instructing robots or other mechanical devices accordingly. However, how the plethora of CV models developed perform relative to each other remains underexplored, making model selection challenging for researchers and practitioners. This study aims to benchmark existing CV models towards automated construction waste segregation. Seventeen models were selected and trained with unified configuration, and then their performance was evaluated on the aspect of accuracy, efficiency, and robustness, respectively. In experimental results, BEiT attained top accuracy (58.31 % MIoU) while FastFCN had the best efficiency (12.87 ms). SAN displayed the least standard deviation (4.41 %) for robustness evaluation. This research contributes a reliable reference for CV model selection, advancing automated construction waste sorting research and practices, and ultimately promoting efficient recycling while reducing the environmental impact of construction and demolition waste.preprin
Accelerating the momentum to achieve global elimination of hepatitis B infection: a scoping review of hepatitis B guidelines to reduce mother to child transmission
No full textProgress towards achieving global elimination of hepatitis B virus (HBV) by 2030 remains unsatisfactory. Prevention of mother to child transmission is crucial but current Clinical Practice Guidelines (CPGs) gave diverse recommendations, creating confusion and leading to significant challenges in the practical implementation across various regions owing to global inequity. We reviewed 47 CPGs on the management of hepatitis B during pregnancy against twelve important clinical questions. Of 47 guidelines, 80.9% (38/47) supported the universal approach to HBV screening. To select women for antiviral prophylaxis, 78.7% (37/47) recommended the use of HBV DNA levels, while 31.9% (15/47) recommended the use of HBeAg. Of 37 guidelines recommending HBV DNA levels, 94.6% (35/37) recommended a viral load threshold of >200,000 IU/mL to initiate antiviral prophylaxis. Of 16 guidelines addressing the mode of delivery, 87.5% (14/16) encouraged vaginal birth. Of 30 guidelines addressing breastfeeding, 60% (18/30) recommended breastfeeding. However, controversies were found in the optimal timing of HBV disease evaluation during pregnancy and the ideal timing to stop antiviral prophylaxis after delivery. Of 36 guidelines addressing the timing to initiate antiviral prophylaxis, 25% (9/36) advised starting prophylaxis between 24 and 28 weeks, while 75% (27/36) suggested other timings or provided vague descriptions. Of 38 guidelines addressing birth-dose vaccination, 42% (16/38) emphasized the importance of “vaccination as soon as possible after birth.” These deficiencies and discrepancies among CPGs could significantly impede global HBV elimination.</p