•The quality and quantity of street greenery are associated with increased recreational green physical activity.•Using Google Street View can accurately estimate residents’ daily exposure of street ...greenery.•The findings also help us recognize the impacts of environmental factors on residents’ physical activity.
Urban greenspaces have been demonstrated to have associations with physical activity and health. Yet empirical studies have almost exclusively focused on parks rather than street, although streets are among the most popular venues for physical activity and street greenery is an indispensable component of urban greenspaces. Even fewer greenspace-physical activity studies have objectively assessed eye-level street greenery. By using free Google Street View images, this study assessed both the quantity and quality of street greenery and associated them with the recreational physical activity occurring in green outdoor environments of 1390 participants in 24 housing estates in Hong Kong. After controlling for socio-demographic characteristics and other built environment factors, multilevel regression models revealed that the quality and quantity of street greenery were positively linked to recreational physical activity. Our finding is important for interpretations of the operational mechanisms between street greenery and health benefits because it demonstrates that physical activity is an intermediate health-related outcome. The findings also reveal the influences of eye-level street greenery on residents’ physical activity levels and hence contribute to the development and implementation of healthy cities to stimulate physical activity.
The 2019 Nobel Prize in Chemistry has been awarded to John B. Goodenough, M. Stanley Whittingham and Akira Yoshino for their contributions in the development of lithium-ion batteries, a technology ...that has revolutionized our way of life. Here we look back at the milestone discoveries that have shaped the modern lithium-ion batteries for inspirational insights to guide future breakthroughs.
Redox flow batteries (RFBs) are critical enablers for next‐generation grid‐scale energy‐storage systems, due to their scalability and flexibility in decoupling power and energy. Aqueous RFBs (ARFBs) ...using nonflammable electrolytes are intrinsically safe. However, their development has been limited by their low energy density and high cost. Developing ARFBs with higher energy density, lower cost, and longer lifespan than the current standard is of significant interest to academic and industrial research communities. Here, a critical review of the latest progress on advanced electrolyte material designs of ARFBs is presented, including a fundamental overview of their physicochemical properties, major challenges, and design strategies. Assessment methodologies and metrics for the evaluation of RFB stability are discussed. Finally, future directions for material design to realize practical applications and achieve the commercialization of ARFB energy‐storage systems are highlighted.
Aqueous redox flow batteries (ARFBs) are promising large‐scale energy storage technologies. The latest progress on advanced electrolyte design of ARFBs is reviewed, including a fundamental overview of their physicochemical properties, major challenges, and design strategies. Future directions for material design to realize practical applications and achieve the commercialization of ARFB energy‐storage systems are highlighted.
Developing low-cost and eco-friendly aqueous electrolytes with a wide voltage window is critical to achieve safe, high-energy and sustainable Li-ion batteries. Emerging approaches using highly ...concentrated salts (21-55 m (mol kg
)) create artificial solid-electrode interfaces and improve water stability; however, these approaches raise concerns about cost and toxicity. Molecular crowding is a common phenomenon in living cells where water activity is substantially suppressed by molecular crowding agents through altering the hydrogen-bonding structure. Here we demonstrate a 'molecular crowding' electrolyte using the water-miscible polymer poly(ethylene glycol) as the crowding agent to decrease water activity, thereby achieving a wide electrolyte operation window (3.2 V) with low salt concentration (2 m). Aqueous Li
Ti
O
/LiMn
O
full cells with stable specific energies between 75 and 110 W h kg
were demonstrated over 300 cycles. Online electrochemical mass spectroscopy revealed that common side reactions in aqueous Li-ion batteries (hydrogen/oxygen evolution reactions) are virtually eliminated. This work provides a path for designing high-voltage aqueous electrolytes for low-cost and sustainable energy storage.
Many studies have established that urban greenness is associated with better health outcomes. Yet most studies assess urban greenness with overhead-view measures, such as park area or tree count, ...which often differs from the amount of greenness perceived by a person at eye-level on the ground. Furthermore, those studies are often criticized for the limitation of residential self-selection bias. In this study, urban greenness was extracted and assessed from profile view of streetscape images by Google Street View (GSV), in conjunction with deep learning techniques. We also explored a unique research opportunity arising in a citywide residential reallocation scheme of Hong Kong to reduce residential self-selection bias. Two multilevel regression analyses were conducted to examine the relationships between urban greenness and (1) the odds of walking for 24,773 public housing residents in Hong Kong, (2) total walking time of 1994 residents, while controlling for potential confounders. The results suggested that eye-level greenness was significantly related to higher odds of walking and longer walking time in both 400 m and 800 m buffers. Distance to the closest Mass Transit Rail (MTR) station was also associated with higher odds of walking. Number of shops was related to higher odds of walking in the 800 m buffer, but not in 400 m. Eye-level greenness, assessed by GSV images and deep learning techniques, can effectively estimate residents' daily exposure to urban greenness, which is in turn associated with their walking behavior. Our findings apply to the entire public housing residents in Hong Kong, because of the large sample size.
Heteroatom doped atomically dispersed Fe1‐NC catalysts have been found to show excellent activity toward oxygen reduction reaction (ORR). However, the origin of the enhanced activity is still ...controversial because the structure‐function relationship governing the enhancement remains elusive. Herein, sulfur(S)‐doped Fe1‐NC catalyst was obtained as a model, which displays a superior activity for ORR towards the traditional Fe‐NC materials. 57Fe Mössbauer spectroscopy and electron paramagnetic resonance spectroscopy revealed that incorporation of S in the second coordination sphere of Fe1‐NC can induce the transition of spin polarization configuration. Operando 57Fe Mössbauer spectra definitively identified the low spin single‐Fe3+‐atom of C‐FeN4‐S moiety as the active site for ORR. Moreover, DFT calculations unveiled that lower spin state of the Fe center after the S doping promotes OH* desorption process. This work elucidates the underlying mechanisms towards S doping for enhancing ORR activity, and paves a way to investigate the function of broader heteroatom doped Fe1‐NC catalysts to offer a general guideline for spin‐state‐determined ORR.
The enhanced oxygen reduction reaction (ORR) activity of sulfur‐doped Fe‐N‐C single‐atom catalysts is studied from Fe spin‐state tuning. Operando 57Fe Mössbauer spectra monitoring further supported the low‐spin (LS) single‐Fe3+‐atom of the C‐FeN4‐S moiety as the active site for the ORR.
Glycans play important roles in all major kingdoms of organisms, such as archea, bacteria, fungi, plants, and animals. Cellulose, the most abundant polysaccharide on the Earth, plays a predominant ...role for mechanical stability in plants, and finds a plethora of applications by humans. Beyond traditional use, biomedical application of cellulose becomes feasible with advances of soluble cellulose derivatives with diverse functional moieties along the backbone and modified nanocellulose with versatile functional groups on the surface due to the native features of cellulose as both cellulose chains and supramolecular ordered domains as extractable nanocellulose. With the focus on ionic cellulose‐based compounds involving both these groups primarily for biomedical applications, a brief introduction about glycoscience and especially native biologically active glycosaminoglycans with specific biomedical application areas on humans is given, which inspires further development of bioactive compounds from glycans. Then, both polymeric cellulose derivatives and nanocellulose‐based compounds synthesized as versatile biomaterials for a large variety of biomedical applications, such as for wound dressings, controlled release, encapsulation of cells and enzymes, and tissue engineering, are separately described, regarding the diverse routes of synthesis and the established and suggested applications for these highly interesting materials.
Ionic cellulose‐based compounds as either polymeric cellulose derivatives or ionic nanocellulose have gained tremendous attention within the last years due to their remarkable properties, especially their biological properties. Recent advances about various ionic cellulose‐based compounds with diverse functional moieties either along the cellulose chains or on the surface of nanocellulose for biomedical applications are systematically summarized.
Redox mediators have been widely applied to reduce the charge overpotentials of lithium–oxygen (Li-O2) batteries. Here, we reveal the critical role of redox mediator in suppressing the charging ...instability of Li-O2 batteries. Using high temporal resolution online electrochemical mass spectrometry, we show that charging with redox mediators (using lithium bromide as a model system) significantly reduces parasitic gas evolution and improves oxygen recovery efficiency. Using redox mediator transforms the charge reactions from electrochemical pathways to chemical pathways, which unexpectedly bypasses the formation of highly reactive intermediates upon electro-oxidation of lithium peroxide (Li2O2). Such transformation reduces self-amplifying degradation reactions of electrode and electrolyte in Li-O2 cells. We further show that the improved stability associated with the redox mediator is much more pronounced at higher charging rates, owing to fast charge-transfer kinetics of the redox mediator. Together, we show that employing redox mediator not only reduces the charge overpotential but also suppresses side reactions of Li-O2 cells with improved charging rate. Our work demonstrates that transforming electro-oxidation of Li2O2 to chemical oxidation of Li2O2 is a promising strategy to simultaneously mitigate charging side reactions and achieve low overpotential for the Li-O2 batteries.
Monitoring dynamic balance during gait is critical for fall prevention in the elderly. The current study aimed to develop recurrent neural network models for extracting balance variables from a ...single inertial measurement unit (IMU) placed on the sacrum during walking. Thirteen healthy young and thirteen healthy older adults wore the IMU during walking and the ground truth of the inclination angles (IA) of the center of pressure to the center of mass vector and their rates of changes (RCIA) were measured simultaneously. The IA, RCIA, and IMU data were used to train four models (uni-LSTM, bi-LSTM, uni-GRU, and bi-GRU), with 10% of the data reserved to evaluate the model errors in terms of the root-mean-squared errors (RMSEs) and percentage relative RMSEs (rRMSEs). Independent t-tests were used for between-group comparisons. The sensitivity, specificity, and Pearson’s r for the effect sizes between the model-predicted data and experimental ground truth were also obtained. The bi-GRU with the weighted MSE model was found to have the highest prediction accuracy, computational efficiency, and the best ability in identifying statistical between-group differences when compared with the ground truth, which would be the best choice for the prolonged real-life monitoring of gait balance for fall risk management in the elderly.
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