Heteroarenes are structural motifs found in many bioactive compounds and functional materials. Dehydrogenative cross‐coupling of heteroarenes with aliphatic C−H bonds provides straightforward access ...to functionalized heteroarenes from readily available materials. Established methods employ stoichiometric chemical oxidants under conditions of heating or light irradiation. By merging electrochemistry and photochemistry, we have achieved efficient photoelectrochemical dehydrogenative cross‐coupling of heteroarenes and C(sp3)−H donors through H2 evolution, without the addition of metal catalysts or chemical oxidants. Mechanistically, the C(sp3)−H donor is converted to a nucleophilic carbon radical through H‐atom transfer with chlorine atom, which is produced by light irradiation of anodically generated Cl2 from Cl−. The carbon radical then undergoes radical substitution to the heteroarene to afford alkylated heteroarene products.
An efficient photoelectrochemical dehydrogenative cross‐coupling of heteroarenes with C(sp3)−H species is described. Chlorine atoms, which are produced by light irradiation of anodically generated Cl2 from Cl−, a hydrogen atom from C(sp3)−H bonds to afford carbon radicals. The latter undergo Minisci alkylation to afford the final functionalized heteroarene products.
Lithium metal batteries are considered a promising candidate for high‐energy‐density energy storage. However, the strong reducibility and high reactivity of lithium lead to low Coulombic efficiency ...when contacting oxidants, such as lithium polysulfide caused by the serious “shuttle effect” in lithium–sulfur batteries. Herein we design selectively permeable lithium‐ion channels on lithium metal surface, which allow lithium ions to pass through by electrochemical overpotential, while the polysulfides are effectively blocked due to the much larger steric hindrance than lithium ions. The selective permeation of lithium ions through the channels is further elucidated by the molecular simulation and visualization experiment. Consequently, a prolonged cycle life of 75 cycles and high Coulombic efficiency of 99 % are achieved in a practical Li–S pouch cell with limited amounts of lithium and electrolyte, confirming the unique role the selective ion permeation plays in protecting highly reactive alkali metal anodes in working batteries.
Selectively permeable lithium‐ion channels, which were created by aminopropyl‐terminated polydimethylsiloxanes anchored on the lithium metal surface, allow lithium ions to get through, while the polysulfides are effectively blocked due to their much larger volume. The selective lithium ion channels enable a prolonged cycle life and a high Coulombic efficiency of 99 % in a practical Li–S pouch cell.
Lithium‐sulfur (Li‐S) batteries are one of the most promising candidates for high energy density rechargeable batteries beyond current Li‐ion batteries. However, severe corrosion of Li metal anode ...and low Coulombic efficiency (CE) induced by the unremitting shuttle of Li polysulfides immensely hinder the practical applications of Li‐S batteries. Herein, a compact inorganic layer (CIL) formed by ex situ reactions between Li anode and ionic liquid emerged as an effective strategy to block Li polysulfides and suppress shuttle effect. A CE of 96.7% was achieved in Li‐S batteries with CIL protected Li anode in contrast to 82.4% for bare Li anode while no lithium nitrate was employed. Furthermore, the corrosion of Li during cycling was effectively inhibited. While applied to working batteries, 80.6% of the initial capacity after 100 cycles was retained in Li‐S batteries with CIL‐protected ultrathin (33 μm) Li anode compared with 58.5% for bare Li anode, further demonstrating the potential of this strategy for practical applications. This study presents a feasible interfacial regulation strategy to protect Li anode with the presence of Li polysulfides and opens avenues for Li anode protection in Li‐S batteries under practical conditions.
A compact inorganic layer (CIL) that can block lithium polysulfides and shuttle effect in lithium‐sulfur batteries is constructed on lithium metal anode. The CIL renders much improved Coulombic efficiency without LiNO3 additive and ensures superior cycling performance of lithium‐sulfur batteries with ultrathin lithium metal anodes.
Plasma accreted onto the surface of a neutron star can ignite due to unstable thermonuclear burning and produce a bright flash of X-ray emission called a Type-I X-ray burst. Such events are very ...common; thousands have been observed to date from over a hundred accreting neutron stars. The intense, often Eddington-limited, radiation generated in these thermonuclear explosions can have a discernible effect on the surrounding accretion flow that consists of an accretion disk and a hot electron corona. Type-I X-ray bursts can therefore serve as direct, repeating probes of the internal dynamics of the accretion process. In this work we review and interpret the observational evidence for the impact that Type-I X-ray bursts have on accretion disks and coronae. We also provide an outlook of how to make further progress in this research field with prospective experiments and analysis techniques, and by exploiting the technical capabilities of the new and concept X-ray missions
ASTROSAT
,
NICER
,
Insight-HXMT
,
eXTP
, and
STROBE-X
.
A Pervasive-computing-enriched smart home environment, which contains many embedded and tiny intelligent devices and sensors coordinated by service management mechanisms, is capable of anticipating ...intentions of occupants and providing appropriate services accordingly. Although there are a wealth of research achievements in recent years, the degree of market acceptance is still low. The main reason is that most of the devices and services in such environments depend on particular platform or technology, making it hard to develop an application by composing the devices or services. Meanwhile, the concept of Web of Things (WoT) is becoming popular recently. Based on WoT, the developers can build applications based on popular web tools or technologies. Consequently, the objective of this paper is to propose a set of novel WoT-driven plug-and-play service management schemes for a smart home called Resource-Oriented Service Administration (ROSA). We have implemented an application prototype, and experiments are performed to show the effectiveness of the proposed approach. The results of this research can be a foundation for realizing the vision of "end user programmable smart environments".
Lithium (Li) metal anodes have attracted considerable interest due to their ultrahigh theoretical gravimetric capacity and very low redox potential. However, the issues of nonuniform lithium deposits ...(dendritic Li) during cycling are hindering the practical applications of Li metal batteries. Herein, we propose a concept of ion redistributors to eliminate dendrites by redistributing Li ions with Al-doped Li
La
Zr
Ta
O
(LLZTO) coated polypropylene (PP) separators. The LLZTO with three-dimensional ion channels can act as a redistributor to regulate the movement of Li ions, delivering a uniform Li ion distribution for dendrite-free Li deposition. The standard deviation of ion concentration beneath the LLZTO composite separator is 13 times less than that beneath the routine PP separator. A Coulombic efficiency larger than 98% over 450 cycles is achieved in a Li | Cu cell with the LLZTO-coated separator. This approach enables a high specific capacity of 140 mAh g
for LiFePO
| Li pouch cells and prolonged cycle life span of 800 hours for Li | Li pouch cells, respectively. This strategy is facile and efficient in regulating Li-ion deposition by separator modifications and is a universal method to protect alkali metal anodes in rechargeable batteries.
Using results from 57 large‐scale physics‐based fault‐rupture and wave propagation simulations, this research aims to evaluate the seismic risk, loss, and resilience of more than 16,000 reinforced ...concrete buildings in the Zeytinburnu district of Istanbul, Turkey. For each building and under each earthquake scenario, the spatially varying site‐specific simulated ground motions were used for performing three‐dimensional nonlinear time‐history analyses. The resulting structural responses—such as peak story drift ratios (PSDR) and peak floor accelerations (PFAs)—were utilized to conduct three region‐scale tasks: (i) building‐ and site‐specific seismic fragility analysis for both structural and nonstructural components of each building; (ii) intensity‐based seismic loss assessment using the FEMA P58 methodology and Monte Carlo simulations; and (iii) resilience evaluation based on the expected time of recovery predicted through FEMA P58. Moreover, both inertial and kinematic soil–structure interaction (SSI) effects were considered using a substructuring method for all three tasks. Site‐specific soil properties were utilized to compute the coefficients of soil springs and dashpots, as well as the foundation input motions. The SSI effects were investigated by comparing the fragility, loss, and resilience indices obtained with and without considering SSI.
Physics‐based earthquake ground motion simulations (GMS) have acquired significant growth over the last two decades, mainly due to the explosive developments of high‐performance computing techniques ...and resources. These techniques benefit high/medium seismicity regions such as the city of Istanbul, which presents insufficient historical ground motion data to properly estimate seismic hazard and risk. We circumvent this reality with the aid of the Texas Advanced Computing Center (TACC) facilities to perform a suite of 57 high‐fidelity broadband (8–12 Hz) large‐scale physics‐based GMS for a region in Istanbul, Turkey. This paper focuses on the details of simulated GMS: (i) validation of the GMS approach against recorded ground motions produced by the 2019 Mw5.7$M_{w}\nobreakspace 5.7$ Silivri earthquake; (ii) characteristics of 57 different source models, which aim to consider the uncertainties of many fault rupture features, including the length and width, dip, strike, and rake angles of considered fault planes, as well as hypocenter locations and earthquake magnitudes ranging between Mw$M_{w}$ 6.5 and 7.2; (iii) high‐resolution topography and bathymetry and seismic data that are incorporated into all GMS; (iv) simulation results, such as PGAs and PGVs versus Vs30$V_{s30}$ and distances to fault ruptures (Rrup$R_{\text{rup}}$), of 2912 surface stations for all 57 GMS. More importantly, this research provides a massive database of displacement, velocity and acceleration time histories in all three directions over more than 20,000 stations at both surface and bedrock levels. Such site‐specific high‐density and ‐frequency simulated ground motions can notably contribute to the seismic risk assessment of this region and many other applications.
Frequent spontaneous facial self-touches, predominantly during outbreaks, have the theoretical potential to be a mechanism of contracting and transmitting diseases. Despite the recent advent of ...vaccines, behavioral approaches remain an integral part of reducing the spread of COVID-19 and other respiratory illnesses. The aim of this study was to utilize the functionality and the spread of smartwatches to develop a smartwatch application to identify motion signatures that are mapped accurately to face touching. Participants (n = 10, five women, aged 20–83) performed 10 physical activities classified into face touching (FT) and non-face touching (NFT) categories in a standardized laboratory setting. We developed a smartwatch application on Samsung Galaxy Watch to collect raw accelerometer data from participants. Data features were extracted from consecutive non-overlapping windows varying from 2 to 16 s. We examined the performance of state-of-the-art machine learning methods on face-touching movement recognition (FT vs. NFT) and individual activity recognition (IAR): logistic regression, support vector machine, decision trees, and random forest. While all machine learning models were accurate in recognizing FT categories, logistic regression achieved the best performance across all metrics (accuracy: 0.93 ± 0.08, recall: 0.89 ± 0.16, precision: 0.93 ± 0.08, F1-score: 0.90 ± 0.11, AUC: 0.95 ± 0.07) at the window size of 5 s. IAR models resulted in lower performance, where the random forest classifier achieved the best performance across all metrics (accuracy: 0.70 ± 0.14, recall: 0.70 ± 0.14, precision: 0.70 ± 0.16, F1-score: 0.67 ± 0.15) at the window size of 9 s. In conclusion, wearable devices, powered by machine learning, are effective in detecting facial touches. This is highly significant during respiratory infection outbreaks as it has the potential to limit face touching as a transmission vector.
Abstract
The detection of cyclotron resonance scattering features (CRSFs) is the only way to directly and reliably measure the magnetic field near the surface of a neutron star (NS). The broad energy ...coverage and large collection area of Insight-HXMT in the hard X-ray band allowed us to detect the CRSF with the highest energy known to date, reaching about 146 keV during the 2017 outburst of the first galactic pulsing ultraluminous X-ray source (pULX) Swift J0243.6+6124. During this outburst, the CRSF was only prominent close to the peak luminosity of ∼2 × 10
39
erg s
−1
, the highest to date in any of the Galactic pulsars. The CRSF is most significant in the spin-phase region corresponding to the main pulse of the pulse profile, and its centroid energy evolves with phase from 120 to 146 keV. We identify this feature as the fundamental CRSF because no spectral feature exists at 60–70 keV. This is the first unambiguous detection of an electron CRSF from an ULX. We also estimate a surface magnetic field of ∼1.6 × 10
13
G for Swift J0243.6+6124. Considering that the dipole magnetic field strengths, inferred from several independent estimates of magnetosphere radius, are at least an order of magnitude lower than our measurement, we argue that the detection of the highest-energy CRSF reported here unambiguously proves the presence of multipole field components close to the surface of the neutron star. Such a scenario has previously been suggested for several pulsating ULXs, including Swift J0243.6+6124, and our result represents the first direct confirmation of this scenario.
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