Psychological health problems, especially emotional disorders, are common among adolescents. The epidemiology of emotional disorders is greatly influenced by stressful events. This study sought to ...assess the prevalence rate and socio-demographic correlates of depressive and anxiety symptoms among Chinese adolescents affected by the outbreak of COVID-19. We conducted a cross-sectional study among Chinese students aged 12–18 years during the COVID-19 epidemic period. An online survey was used to conduct rapid assessment. A total of 8079 participants were involved in the study. An online survey was used to collect demographic data, assess students’ awareness of COVID-19, and assess depressive and anxiety symptoms with the Patient Health Questionnaire (PHQ-9) and the Generalized Anxiety Disorder (GAD-7) questionnaire, respectively. The prevalence of depressive symptoms, anxiety symptoms, and a combination of depressive and anxiety symptoms was 43.7%, 37.4%, and 31.3%, respectively, among Chinese high school students during the COVID-19 outbreak. Multivariable logistic regression analysis revealed that female gender was the higher risk factor for depressive and anxiety symptoms. In terms of grades, senior high school was a risk factor for depressive and anxiety symptoms; the higher the grade, the greater the prevalence of depressive and anxiety symptoms. Our findings show there is a high prevalence of psychological health problems among adolescents, which are negatively associated with the level of awareness of COVID-19. These findings suggest that the government needs to pay more attention to psychological health among adolescents while combating COVID-19.
The rapid progress of proton exchange membrane fuel cells (PEMFCs) and alkaline exchange membrane fuel cells (AMFCs) has boosted the hydrogen economy concept via diverse energy applications in the ...past decades. For a holistic understanding of the development status of PEMFCs and AMFCs, recent advancements in electrocatalyst design and catalyst layer optimization, along with cell performance in terms of activity and durability in PEMFCs and AMFCs, are summarized here. The activity, stability, and fuel cell performance of different types of electrocatalysts for both oxygen reduction reaction and hydrogen oxidation reaction are discussed and compared. Research directions on the further development of active, stable, and low‐cost electrocatalysts to meet the ultimate commercialization of PEMFCs and AMFCs are also discussed.
The development of fuel cells is of great significance for achieving a sustainable society. Recent progress in cathodic electrocatalysts for proton exchange membrane fuel cells and anodic and cathodic electrocatalysts for alkaline exchange membrane fuel cells is summarized. The rational design strategies, structure evolution, activities, fuel cell performance, and durability of noble‐metal‐ and non‐noble‐metal‐based electrocatalysts are discussed.
The lifespan of high‐energy‐density lithium metal batteries (LMBs) is hindered by heterogeneous solid electrolyte interphase (SEI). The rational design of electrolytes is strongly considered to ...obtain uniform SEI in working batteries. Herein, a modification of nitrate ion (NO3−) is proposed and validated to improve the homogeneity of the SEI in practical LMBs. NO3− is connected to an ether‐based moiety to form isosorbide dinitrate (ISDN) to break the resonance structure of NO3− and improve the reducibility. The decomposition of non‐resonant −NO3 in ISDN enriches SEI with abundant LiNxOy and induces uniform lithium deposition. Lithium–sulfur batteries with ISDN additives deliver a capacity retention of 83.7 % for 100 cycles compared with rapid decay with LiNO3 after 55 cycles. Moreover, lithium–sulfur pouch cells with ISDN additives provide a specific energy of 319 Wh kg−1 and undergo 20 cycles. This work provides a realistic reference in designing additives to modify the SEI for stabilizing LMBs.
The modification of NO3− is achieved by connecting NO3− to an ether‐based moiety. The broken resonance structure of −NO3 improves its reducibility compared with NO3−. The decomposition of −NO3 forms a LiNxOy‐rich solid electrolyte interphase (SEI) and induces uniform Li deposition.
Surface-supported isolated atoms in single-atom catalysts (SACs) are usually stabilized by diverse defects. The fabrication of high-metal-loading and thermally stable SACs remains a formidable ...challenge due to the difficulty of creating high densities of underpinning stable defects. Here we report that isolated Pt atoms can be stabilized through a strong covalent metal-support interaction (CMSI) that is not associated with support defects, yielding a high-loading and thermally stable SAC by trapping either the already deposited Pt atoms or the PtO
units vaporized from nanoparticles during high-temperature calcination. Experimental and computational modeling studies reveal that iron oxide reducibility is crucial to anchor isolated Pt atoms. The resulting high concentrations of single atoms enable specific activities far exceeding those of conventional nanoparticle catalysts. This non defect-stabilization strategy can be extended to non-reducible supports by simply doping with iron oxide, thus paving a new way for constructing high-loading SACs for diverse industrially important catalytic reactions.
The discovery of modern medicine relies on the sustainable development of synthetic methodologies to meet the needs associated with drug molecular design. Heterocycles containing difluoromethyl ...groups are an emerging but scarcely investigated class of organofluoro molecules with potential applications in pharmaceutical, agricultural and material science. Herein, we developed an organophotocatalytic direct difluoromethylation of heterocycles using O
as a green oxidant. The C-H oxidative difluoromethylation obviates the need for pre-functionalization of the substrates, metals and additives. The operationally straightforward method enriches the efficient synthesis of many difluoromethylated heterocycles in moderate to excellent yields. The direct difluoromethylation of pharmaceutical moleculars demonstrates the practicability of this methodology to late-stage drug development. Moreover, 2'-deoxy-5-difluoromethyluridine (F
TDR) exhibits promising activity against some cancer cell lines, indicating that the difluoromethylation methodology might provide assistance for drug discovery.
Lithium (Li)‐metal batteries promise energy density beyond 400 Wh kg−1, while their practical operation at an extreme temperature below −30 °C suffers severe capacity deterioration. Such battery ...failure highly relates to the remarkably increased kinetic barrier of interfacial processes, including interfacial desolvation, ion transportation, and charge transfer. In this work, the interfacial kinetics in three prototypical electrolytes are quantitatively probed by three‐electrode electrochemical techniques and molecular dynamics simulations. Desolvation as the limiting step of interfacial processes is validated to dominate the cell impedance and capacity at low temperature. 1,3‐Dioxolane‐based electrolyte with tamed solvent–solute interaction facilitates fast desolvation, enabling the practical Li|LiNi0.5Co0.2Mn0.3O2 cells at −40 °C to retain 66% of room‐temperature capacity and withstand remarkably fast charging rate (0.3 C). The barrier of desolvation dictated by solvent–solute interaction environments is quantitatively uncovered. Regulating the solvent–solute interaction by low‐affinity solvents emerges as a promising solution to low‐temperature batteries.
Desolvation is validated as the predominant contributor to energy loss at low temperatures, largely overwhelming the contributions from other interfacial ion transportation processes. A rational and original design by taming solvent–solute interaction with low‐affinity solvents like 1,3‐dioxolane is proposed to enable high capacity and durable operation of practical lithium‐metal batteries at −40 °C.
Microwave‐driven strategy shows many advantages including selective energization, uniform heating, and high penetration depth, which is a hot topic in wireless actuators. Understanding microwave ...stimulus‐response mechanisms is the key to developing universal construction strategies for advanced microwave‐driven actuators. Herein, reduced graphene oxide (rGO) with specified dielectric genes and thermal properties is implanted into the shape memory polymer, liquid crystal elastomer (LCE) as an example, to construct soft, reversible, and sensitive microwave actuators. Based on the analysis of microstructure and dielectric properties, LCE‐rGO composites exhibit excellent polarization relaxation‐dominated dielectric loss and electromagnetic (EM) energy conversion ability. The maximum dielectric loss factor (ε″) and loss tangent (tan δe) of LCE‐rGO are dramatically increased by 216% and 87.5% compared to pure LCE, respectively, and the optimum apparent energy harvest efficiency is 19.4 times higher than that of LCE. In addition, the implantation of rGO significantly lowers the microwave actuation threshold of LCE‐rGO composites and reinforces their stimulus‐response capacity. Response time under 750 W microwave irradiation of LCE‐rGO is shortened to <10s. These findings can provide a solid basis for the design and fabrication of highly efficient microwave stimuli‐responsive polymers and enlighten a new approach to wireless actuated smart devices.
Graphene‐implanted shape memory polymer (LCE‐rGO) is prepared, which can convert microwave energy into thermal energy through enhanced polarization genes dominated dielectric loss properties. Synergistic with excellent conduct heat capability of rGO, it triggers the inherent nematic‐isotropic phase transition of the LCE. As microwave‐driven composites, The LCE‐rGO is expected to act as kinetic components to provide mechanical energy for wireless drive equipment.
Abstract
As a major approach to looking for life beyond the Earth, the search for extraterrestrial intelligence (SETI) is committed to searching for technosignatures such as engineered radio signals ...that are indicative of technologically capable life. In this paper, we report a targeted SETI campaign employing an observation strategy named multibeam coincidence matching at the Five-hundred-meter Aperture Spherical radio Telescope toward 33 known exoplanet systems, searching for ETI narrowband drifting signals across 1.05–1.45 GHz in two orthogonal linear polarization directions separately. A signal at 1140.604 MHz detected from the observation toward Kepler-438 originally piqued our interest because its features are roughly consistent with assumed ETI technosignatures. However, evidences such as its polarization characteristics are able to eliminate the possibility of an extraterrestrial origin. Our observations achieve an unprecedented sensitivity because the minimum equivalent isotropic radiated power we are able to detect reaches 1.48 × 10
9
W.
Li‐CO2 batteries are regarded as next‐generation high‐energy‐density electrochemical devices. However, the greatest challenge arises from the formation of the discharge product, Li2CO3, which would ...accumulate and deactivate heterogenous catalysts to cause huge polarization. Herein, Ru(bpy)3Cl2 was employed as a solution‐phase catalyst for Li‐CO2 batteries and proved to be the most effective one screened so far. Spectroscopy and electrochemical analyses elucidate that the RuII center could interact with both CO2 and amorphous Li2C2O4 intermediate, thus promoting electroreduction process and delaying carbonate transformation. As a result, the charge potential is reduced to 3.86 V and over 60 discharge/charge cycles are achieved with a fixed capacity of 1000 mAh g−1 at a current density of 300 mA g−1. Our work provides a new avenue to improve the electrochemical performance of Li‐CO2 batteries with efficient mobile catalysts.
Ru(bpy)3Cl2 was applied as the first ruthenium‐based mobile catalyst to enhance the electrochemical performance of Li‐CO2 batteries. The RuII catalyst was discovered to interact with both CO2 molecules and amorphous Li2C2O4 intermediate, thus promoting CO2RR and delaying carbonate formation and consequently leading to lowered overpotential, enlarged capacity, and prolonged cyclability of the batteries.
The enantioselective ketimine–ene reaction is one of the most challenging stereocontrolled reaction types in organic synthesis. In this work, catalytic enantioselective ketimine–ene reactions of ...2‐aryl‐3H‐indol‐3‐ones with α‐methylstyrenes were achieved by utilizing a B(C6F5)3/chiral phosphoric acid (CPA) catalyst. These ketimine–ene reactions proceed well with low catalyst loading (B(C6F5)3/CPA=2 mol %/2 mol %) under mild conditions, providing rapid and facile access to a series of functionalized 2‐allyl‐indolin‐3‐ones with very good reactivity (up to 99 % yield) and excellent enantioselectivity (up to 99 % ee). Theoretical calculations reveal that enhancement of the acidity of the chiral phosphoric acid by B(C6F5)3 significantly reduces the activation free energy barrier. Furthermore, collective favorable hydrogen‐bonding interactions, especially the enhanced N−H⋅⋅⋅O hydrogen‐bonding interaction, differentiates the free energy of the transition states of CPA and B(C6F5)3/CPA, thereby inducing the improvement of stereoselectivity.
A highly efficient asymmetric ketimine–ene reaction of 2‐aryl‐3H‐indol‐3‐ones and alkenes was realized by using a B(C6F5)3/chiral phosphoric acid (CPA) catalyst system. The resulting 2‐allyl‐indolin‐3‐ones, which contain tetrasubstituted carbon stereocenters, were synthesized in high yields and very good enantioselectivity with low catalyst loading under mild conditions. Theoretical calculations were used to study the reaction mechanism.
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