Platinum is a much used catalyst that, in petrochemical processes, is often alloyed with other metals to improve catalytic activity, selectivity and longevity
. Such catalysts are usually prepared in ...the form of metallic nanoparticles supported on porous solids, and their production involves reducing metal precursor compounds under a H
flow at high temperatures
. The method works well when using easily reducible late transition metals, but Pt alloy formation with rare-earth elements through the H
reduction route is almost impossible owing to the low chemical potential of rare-earth element oxides
. Here we use as support a mesoporous zeolite that has pore walls with surface framework defects (called 'silanol nests') and show that the zeolite enables alloy formation between Pt and rare-earth elements. We find that the silanol nests enable the rare-earth elements to exist as single atomic species with a substantially higher chemical potential compared with that of the bulk oxide, making it possible for them to diffuse onto Pt. High-resolution transmission electron microscopy and hydrogen chemisorption measurements indicate that the resultant bimetallic nanoparticles supported on the mesoporous zeolite are intermetallic compounds, which we find to be stable, highly active and selective catalysts for the propane dehydrogenation reaction. When used with late transition metals, the same preparation strategy produces Pt alloy catalysts that incorporate an unusually large amount of the second metal and, in the case of the PtCo alloy, show high catalytic activity and selectivity in the preferential oxidation of carbon monoxide in H
.
It is important to understand the fragmentation processes and mechanisms of plastic litter to predict microplastic production in the marine environment. In this study, accelerated weathering ...experiments were performed in the laboratory, with ultraviolet (UV) exposure for up to 12 months followed by mechanical abrasion (MA) with sand for 2 months. Fragmentation of low-density polyethylene (PE), polypropylene (PP), and expanded polystyrene (EPS) was evaluated under conditions that simulated a beach environment. PE and PP were minimally fragmented by MA without photooxidation by UV (8.7 ± 2.5 and 10.7 ± 0.7 particles/pellet, respectively). The rate of fragmentation by UV exposure duration increased more for PP than PE. A 12-month UV exposure and 2-month MA of PP and PE produced 6084 ± 1061 and 20 ± 8.3 particles/pellet, respectively. EPS pellets were susceptible to MA alone (4220 ± 33 particles/pellet), while the combination of 6 months of UV exposure followed by 2 months of MA produced 12,152 ± 3276 particles/pellet. The number of fragmented polymer particles produced by UV exposure and mechanical abrasion increased with decreasing size in all polymer types. The size-normalized abundance of the fragmented PE, PP, and EPS particles according to particle size after UV exposure and MA was predictable. Up to 76.5% of the initial EPS volume was unaccounted for in the final volume of pellet produced particle fragments, indicating that a large proportion of the particles had fragmented into undetectable submicron particles.
Nitrogen-doped microporous carbons with various compositions of pyridinic, pyrrolic, and graphitic N species were synthesized by the pyrolysis of pyrrole using Ca 2+ ion-exchanged Y zeolite as a ...template. The Ca 2+ ions in zeolite pores served as a catalyst to lower the carbonization temperature, resolving the problems associated with high carbonization temperature, such as inhomogeneous carbon deposition, easy breakage of weak C–N bonds, and preferential formation of thermodynamically stable graphitic N species. The resultant carbons exhibited a 3D microporous structure with high surface area and uniform micropore diameters, as well as high N content (5–6 wt%). Taking advantage of the lowered carbonization temperature, the ratio of the N species was modulated by the carbonization temperature, while a similar pore structure of the carbons was maintained. These N-doped carbons were used to investigate the efficiency of each N species on the electrochemical oxygen reduction, without the influences from the porous structure of the carbons. The results of this electrochemical investigation indicate that the graphitic N was more effective in enhancing the oxygen-reduction performance of the 3D microporous carbons than pyridinic N.
Despite the excellent photoelectronic properties of the all‐inorganic cesium lead iodide (CsPbI3) perovskite, which does not contain volatile and hygroscopic organic components, only a few CsPbI3 ...devices are developed mainly owing to the frequent formation of an undesirable yellow δ‐phase at room temperature. Herein, it is demonstrated that a small quantity of poly(ethylene oxide) (PEO) added to the precursor solution effectively inhibits the formation of the yellow δ‐phase during film preparation, and promotes the development of a black α‐phase at a low crystallization temperature. A systematic study reveals that a thin, dense, pinhole‐free CsPbI3 film is produced in the α‐phase and is stabilized with PEO that effectively reduces the grain size during crystallization. A thin α‐phase CsPbI3 film with excellent photoluminescence is successfully employed in a light‐emitting diode with an inverted configuration of glass substrate/indium tin oxide/zinc oxide/poly(ethyleneimine)/α‐CsPbI3/poly(4‐butylphenyl‐diphenyl‐amine)/WO3/Al, yielding the characteristic red emission of the perovskite film at 695 nm with brightness, external quantum efficiency, and emission band width of ≈101 cd m−2, 1.12%, and 32 nm, respectively.
A small quantity of a poly(ethylene oxide) added in the precursor solution is beneficial for the development of all‐inorganic CsPbI3 perovskite in black α‐phase with significantly improved ambient stability. Dense, uniform, and pinhole‐free CsPbI3 thin films consisting of tens of nanometers black α‐phase crystals are successfully fabricated with excellent photophysical properties, leading to high performance light‐emitting diodes.
The human gut microbiome is closely linked to mental health and sleep. We aimed to verify the efficacy and safety of probiotic NVP-1704, a mixture of Lactobacillus reuteri NK33 and Bifidobacterium ...adolescentis NK98, in improving stress, depression, anxiety, and sleep disturbances, along with the measurement of some blood biomarkers. A total of 156 healthy adults with subclinical symptoms of depression, anxiety, and insomnia were retrospectively registered and randomly assigned to receive either NVP-1704 (n = 78) or a placebo (n = 78) for eight weeks. Participants completed the Stress Response Inventory, Beck’s Depression and Anxiety Inventory, Pittsburg Sleep Quality Index, and Insomnia Severity Index at baseline, at four and eight weeks of treatment. Pre- and post-treatment blood tests for biomarkers were conducted. After intervention, gut microbiota composition was quantified by pyrosequencing the bacterial 16S rRNA gene. The NVP-1704 group had a more significant reduction in depressive symptoms at four and eight weeks of treatment, and anxiety symptoms at four weeks compared to the placebo group. Those receiving NVP-1704 also experienced an improvement in sleep quality. NVP-1704 treatment led to a decrease in serum interleukin-6 levels. Furthermore, NVP-1704 increased Bifidobacteriaceae and Lactobacillacea, whereas it decreased Enterobacteriaceae in the gut microbiota composition. Our findings suggest that probiotic NVP-1704 could be beneficial for mental health and sleep.
Ventriculostomy is a common neurosurgery procedure performed for many purposes. Kocher’s point is most often used as the ventriculostomy entry point. But the accuracy of a cannula’s trajectory into ...the ventricles from entry at Kocher’s point is controversial. In this paper we attempt to evaluate the accuracy of the conventional sagittal trajectory, which uses Kocher’s point, and evaluate a new trajectory by creating virtual ventriculostomy simulations from computed tomography images of the brain. About 66 patients without brain and skull pathology in radiography were included. Three dimensional images were constructed using thin sliced brain computed tomography images, and a virtual ventriculostomy was performed toward the previous used surface landmark. And the path of ideal ventricular catheter was simulated. The anterior surface landmarks included the ipsilateral medial canthus, the contralateral medial canthus, and the midpoint between bilateral medial canthi. The lateral surface landmark was the external auditory canal. The sagittal trajectory of the three surface landmarks located in the frontal horn of ipsilateral ventricle was 0% for the ipsilateral medial canthus, 87.88% for the midpoint between bilateral medial canthi and 26.52% for the contralateral medial canthus. The anterior surface target of ideal sagittal trajectory, which connects the Kocher’s point with the central axis of ipsilateral ventricle, is contralaterally 6.7 mm away from midline. It was found that the conventional sagittal trajectory is inaccurate. The anterior target of surface landmark for the ideal sagittal trajectory is medial one third of the distance between the midline and the contralateral medial canthus.
Structural colors (SCs) of photonic crystals (PCs) arise from selective constructive interference of incident light. Here, an ink‐jet printable and rewritable block copolymer (BCP) SC display is ...demonstrated, which can be quickly written and erased over 50 times with resolution nearly equivalent to that obtained with a commercial office ink‐jet printer. Moreover, the writing process employs an easily modified printer for position‐ and concentration‐controlled deposition of a single, colorless, water‐based ink containing a reversible crosslinking agent, ammonium persulfate. Deposition of the ink onto a self‐assembled BCP PC film comprising a 1D stack of alternating layers enables differential swelling of the written BCP film and produces a full‐colored SC display of characters and images. Furthermore, the information can be readily erased and the system can be reset by application of hydrogen bromide. Subsequently, new information can be rewritten, resulting in a chemically rewritable BCP SC display.
An ink‐jet printable and rewritable full‐color structural color display is obtained by the position‐ and concentration‐controlled deposition of a single, colorless, water‐based ink containing a reversible crosslinking agent, ammonium persulfate, onto a self‐assembled block copolymer photonic‐crystal film. The information is quickly written and erased over 50 times with resolution nearly equivalent to a office ink‐jet printer.
Street trees play a crucial role in improving urban environments, and their management depends on the perceptions and preferences of urban residents. This study surveyed 884 urban residents’ ...preferences and perceptions towards street trees in a metropolitan area in Korea and proposed guidelines for their sustainable management. Urban residents were aware of the presence of street trees based on visual changes and were generally satisfied with their shape, size, and growth. They preferred trees that provide environmental and ecological services, such as offering shade, purifying the air, and preserving the ecosystem, while viewing the generation of debris from street trees as the most significant problem. Urban residents’ perspectives on street tree preference and issues varied based on age, income, and housing type. Although urban residents acknowledged the need for the maintenance and management of street trees, they believed that this was the responsibility of central and local governments, not local residents. Collectively, the residents had a positive view of urban street trees and believed that maintenance and management are necessary to address problems caused by their presence. Our research findings provide valuable information to help city and landscaping experts select street tree species and establish maintenance and management strategies.
Street trees are crucial for air pollutant reduction in urban areas. Herein, we used computational fluid dynamics (CFD) simulation to identify changes in airborne particulate matter (PM
) ...concentration based on wind characteristics (direction and velocity) and the green network of street trees. The green network was assessed based on composition of the green area of street trees in the central reserve area and between the motor and pedestrian roads. The PM
concentration varied according to the presence or absence of major reserve planting and the planting structure of the street trees, but not according to the wind direction or velocity. The concentration was lower when the wind direction was 45° (than when the wind direction was 0°), whereas it showed a more significant decrease as the wind velocity increased. Despite variation at each measurement site, the PM
reduction was generally higher when the central reserve and street trees had a multi-planting structure. Hence, to ensure an effective reduction in the PM
concentration on motor roads and reduce its negative impact on pedestrians, both arbors and shrubs should be planted in the central reserve area. The study results will serve as reference for managing the green area network and linear green infrastructure in terms of improving the atmospheric environment.
In this article, we propose a current-fed bidirectional resonant converter that has minimal switching loss over a wide voltage gain range. The proposed bidirectional resonant converter employs a ...double current-fed structure at the low-voltage side and an active voltage doubler with a bidirectional switch at the high-voltage side.The converter operates as a pulsewidth-modulation (PWM) double current-fed resonant converter in the forward mode and a PWM half-bridge resonant converter in the backward mode. By incorporating a bidirectional switch across center nodes of the active voltage doubler, the converter achieves almost zero-voltage switching at the turn-off instant, thereby, incurring little switching loss at all active switches. The proposed topology exhibits a high conversion ratio with low transformer turns-ratio and a low current ripple at the low-voltage side. The operating principles and theoretical derivations of the converter are discussed in detail. The performance of the proposed bidirectional converter are verified using a prototype that has 48-72-V low voltage, 380-V high voltage, and 1-kW output power.
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