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Developing high-performance electrocatalysts for alkaline hydrogen evolution reaction (HER) is crucial for producing green hydrogen, yet it remains challenging due to the sluggish kinetics in alkaline environments. Pt is located near the peak of HER volcano plot, owing to its exceptional performance in hydrogen adsorption and desorption, and Rh plays an important role in H2O dissociation. Lanthanides (Ln) are commonly used to modulate the electronic structure of materials and further influence the adsorption/desorption of reactants, intermediates, and products, and noble metal-Ln alloys are recognized as effective platforms where Ln elements regulate the catalytic properties of noble metals. Here Pt1.5Rh1.5Tm alloy is synthesized using the sodium vapor reduction method. This alloy demonstrates superior catalytic activity, being 4.4 and 6.6 times more effective than Pt/C and Rh/C, respectively. Density Functional Theory (DFT) calculations reveal that the upshift of d-band center and the charge transfer induced by alloying promote adsorption and dissociation of H2O, making Pt1.5Rh1.5Tm alloy more favorable for the alkaline HER reaction, both kinetically and thermodynamically.
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Mesocrystals (MCs) with high-index facets may have superior catalytic properties to those with low-index facets and their nanocrystal counterparts. However, synthesizing such mesocrystal materials is still very challenging because of the metastability of MCs and energetic high-index crystal facets. This work reports a successful solvothermal method followed by calcination for synthesizing copper oxide-based MCs possessing a core-shell structure (denoted as Cu2 O@CuO HIMCs). Furthermore, these MCs are predominantly bounded by the high-index facets such as {311} or {312} with a high-density of stepped atoms. When used as catalysts in Si hydrochlorination to produce trichlorosilane (TCS, the primary feedstock of high-purity crystalline Si), Cu2 O@CuO HIMCs exhibit significantly enhanced Si conversion and TCS selectivity compared to those with flat surfaces and their nanostructured counterparts. Theoretical calculations reveal that both the core-shell structure and the high-index surface contribute to the increased electron density of Cu sites in Cu2 O@CuO HIMCs, promoting the adsorption and dissociation of HCl and stabilizing the dissociated Cl* intermediate. This work provides a simple method for synthesizing high-index faceted MCs and offers a feasible strategy to enhance the catalytic performance of MCs.
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BACKGROUND: Cerebral small vessel injury, including loss of endothelial tight junctions, endothelial dysfunction, and blood-brain barrier breakdown, is an early and typical pathology for Alzheimer's disease, cerebral amyloid angiopathy, and hypertension-related cerebral small vessel disease. Whether there is a common mechanism contributing to these cerebrovascular alterations remains unclear. Studies have shown an elevation of BACE1 (ß-site amyloid precursor protein cleaving enzyme 1) in cerebral vessels from cerebral amyloid angiopathy or Alzheimer's disease patients, suggesting that vascular BACE1 may involve in cerebral small vessel injury. METHODS: To understand the contribution of vascular BACE1 to cerebrovascular impairments, we combined cellular and molecular techniques, mass spectrometry, immunostaining approaches, and functional testing to elucidate the potential pathological mechanisms. RESULTS: We observe a 3.71-fold increase in BACE1 expression in the cerebral microvessels from patients with hypertension. Importantly, we discover that an endothelial tight junction protein, occludin, is a completely new substrate for endothelial BACE1. BACE1 cleaves occludin with full-length occludin reductions and occludin fragment productions. An excessive cleavage by elevated BACE1 induces membranal accumulation of caveolin-1 and subsequent caveolin-1-mediated endocytosis, resulting in lysosomal degradation of other tight junction proteins. Meanwhile, membranal caveolin-1 increases the binding to eNOS (endothelial nitric oxide synthase), together with raised circulating Aß (ß-amyloid peptides) produced by elevated BACE1, leading to an attenuation of eNOS activity and resultant endothelial dysfunction. Furthermore, the initial endothelial damage provokes chronic reduction of cerebral blood flow, blood-brain barrier leakage, microbleeds, tau hyperphosphorylation, synaptic loss, and cognitive impairment in endothelial-specific BACE1 transgenic mice. Conversely, inhibition of aberrant BACE1 activity ameliorates tight junction loss, endothelial dysfunction, and memory deficits. CONCLUSIONS: Our findings establish a novel and direct relationship between endothelial BACE1 and cerebral small vessel damage, indicating that abnormal elevation of endothelial BACE1 is a new mechanism for cerebral small vessel disease pathogenesis.
Subject(s)
Alzheimer Disease , Cerebral Amyloid Angiopathy , Cerebral Small Vessel Diseases , Hypertension , Alzheimer Disease/metabolism , Amyloid Precursor Protein Secretases/metabolism , Amyloid beta-Peptides/metabolism , Amyloid beta-Protein Precursor , Animals , Aspartic Acid Endopeptidases/genetics , Aspartic Acid Endopeptidases/metabolism , Caveolin 1/genetics , Caveolin 1/metabolism , Cerebral Amyloid Angiopathy/complications , Cerebral Amyloid Angiopathy/metabolism , Humans , Hypertension/complications , Mice , Mice, Transgenic , Nitric Oxide Synthase Type III/metabolism , Occludin/metabolism , Tight Junction Proteins , Tight Junctions/metabolismABSTRACT
H2S is being detected in the atmospheres of ever more interstellar bodies, and photolysis is an important mechanism by which it is processed. Here, we report H Rydberg atom time-of-flight measurements following the excitation of H2S molecules to selected rotational (JKaKc') levels of the 1B1 Rydberg state associated with the strong absorption feature at wavelengths of λ â¼ 129.1 nm. Analysis of the total kinetic energy release spectra derived from these data reveals that all levels predissociate to yield H atoms in conjunction with both SH(A) and SH(X) partners and that the primary SH(A)/SH(X) product branching ratio increases steeply with ⟨Jb2⟩, the square of the rotational angular momentum about the b-inertial axis in the excited state. These products arise via competing homogeneous (vibronic) and heterogeneous (Coriolis-induced) predissociation pathways that involve coupling to dissociative potential energy surfaces (PES(s)) of, respectively, 1Aâ³ and 1A' symmetries. The present data also show H + SH(A) product formation when exciting the JKaKc' = 000 and 111 levels, for which ⟨Jb2⟩ = 0 and Coriolis coupling to the 1A' PES(s) is symmetry forbidden, implying the operation of another, hitherto unrecognized, route to forming H + SH(A) products following excitation of H2S at energies above â¼9 eV. These data can be expected to stimulate future ab initio molecular dynamic studies that test, refine, and define the currently inferred predissociation pathways available to photoexcited H2S molecules.
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Produced by both nature and human activities, sulfur dioxide (SO2) is an important species in the earth's atmosphere. SO2 has also been found in the atmospheres of other planets and satellites in the solar system. The photoabsorption cross sections and photodissociation of SO2 have been studied for several decades. In this paper, we reported the experimental results for photodissociation dynamics of SO2 via the GÌ1B1 state. By analyzing the images from the time-sliced velocity map ion imaging method, the vibrational state population distributions and anisotropy parameters were obtained for the O(1D2) + SO(X3Σ-, a1Δ, b1Σ+) and O(1S0) + SO(X3Σ-) channels, and the branching ratios for the channels O(1D2) + SO(X3Σ-), O(1D2) + SO(a1Δ), and O(1D2) + SO(b1Σ+) were determined to be â¼0.3, â¼0.6, and â¼0.1, respectively. The SO products were dominant in electronically and rovibrationally excited states, which may have yet unrecognized roles in the upper planetary atmosphere.
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Objective: To explore the recovery effect of acupuncture combined with rehabilitation therapy on muscle spasms in patients with spinal cord injury through a systematic review of meta-analysis methods. Methods: Use "acupuncture," "electronic-acupuncture," "spinal cord," "spasm," and "paraplegia" as keywords, CNKI, Google, Wanfang, VIP, sci-hub, Web of Science, PubMed, and other Chinese or English databases were searched. To collect the domestic and foreign research on acupuncture combined with rehabilitation for muscle spasms in patients with spinal cord injury. Preliminary screening was conducted, and data extraction and quality evaluation were carried out on the included literature, including publication time, sample size, treatment methods, recovery effects, etc. According to the literature, the influence of acupuncture combined with rehabilitation therapy on muscle spasms in patients with spinal cord injury and related indices was analyzed. The search period was from January 2018 to June 2023, and the selected research results were tested by RevMan5.3 software and data consolidation for consistency. The methodological quality of the included studies was assessed using the Newcastle-Ottawa Scale (NOS). Results: A preliminary literature search yielded 172 papers. 53 papers from sci-hub, 71 papers from HowNet, 36 papers from Wanfang, and 12 papers from VIP. Finally, 10 articles that met the criteria were included, including 594 patients. According to different treatment methods, the literature about acupuncture combined with rehabilitation therapy for muscle spasms in patients with spinal cord injury was analyzed for consistency, and data were merged. It was concluded that acupuncture combined with rehabilitation The clinical curative effect of the experimental group of patients is higher than that of the control group MD=5.31, 95%CI (2.94, 7.81), Z=5.64, P < .001; the clinical effective rate of the experimental group is higher than that of the control group. The improvement of the clinical spasticity index (CSI) score index of the patients in the experimental group was better than that of the control group MD = -3.09, 95%CI (-4.51, -1.67), Z =4.28, P < .001; the MAS score of the patients in the experimental group The improvement was better than that of the control group MD =-0.76, 95%CI (-1.16, -0.38), Z=8.13, P < .001; the improvement of Barthel index (BI) in the experimental group was better than that of the control group MD=9.81, 95%CI (7.84,11.71), Z=12.71, P < .001; no adverse events were reported in the experimental group and the control group. Conclusion: This study shows that acupuncture and rehabilitation are more effective than other therapeutic methods in the treatment of muscle spasms after spinal cord injury, and more randomized controlled trials are needed to verify this in the future.
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OBJECTIVES: To compare the efficacy of nadroparin and fondaparinux sodium for prevention of deep vein thromboembolism (DVT) in lower extremities after total hip arthroplasty (THA) and total knee arthroplasty (TKA). METHODS: A total of 592 patients were enrolled in the study. Clinical data of patients who underwent total hip arthroplasty (THA) and total knee arthroplasty (TKA) in our hospital from December 2021 to September 2022 were retrospectively collected, which mainly included patients' general information, surgery-related information, and DVT-related information. The patients were categorized into the nadroparin group(n = 278) and the fondaparinux sodium group(n = 314) according to the types of anticoagulants used. Anticoagulant therapy began 12-24 h after operation and continued until discharge. DVT prevalence between two groups was compared. The Statistical Package for Social Sciences (SPSS) software version 25 (SPSS, Armonk, NY, USA) was used for statistical analysis. RESULTS: The prevalence of DVT in the nadroparin group and the fondaparinux sodium group was 8.3% (23/278) and 15.0% (47/314), respectively(p = 0.012). Statistical analysis showed that nadroparin group showed a lower prevalence of thrombosis than fondaparinux group (OR = 1.952, P = 0.012). Subgroup analyses showed that nadroparin group had a lower prevalence of DVT than fondaparinux group in some special patients groups such as female patients (OR = 2.258, P = 0.007), patients who are 65-79 years old (OR = 2.796, P = 0.004), patients with hypertension (OR = 2.237, P = 0.042), patients who underwent TKA (OR = 2.091, P = 0.011), and patients who underwent combined spinal-epidural anesthesia (OR = 2.490, P = 0.003) (P < 0.05). CONCLUSION: Nadroparin may have an advantage over fondaparinux sodium in preventing DVT in lower extremities after THA and TKA.
Subject(s)
Anticoagulants , Arthroplasty, Replacement, Hip , Arthroplasty, Replacement, Knee , Fondaparinux , Nadroparin , Postoperative Complications , Venous Thromboembolism , Humans , Fondaparinux/therapeutic use , Female , Male , Retrospective Studies , Arthroplasty, Replacement, Hip/adverse effects , Arthroplasty, Replacement, Knee/adverse effects , Nadroparin/therapeutic use , Nadroparin/administration & dosage , Middle Aged , Venous Thromboembolism/prevention & control , Venous Thromboembolism/etiology , Venous Thromboembolism/epidemiology , Aged , Anticoagulants/therapeutic use , Anticoagulants/administration & dosage , Postoperative Complications/prevention & control , Postoperative Complications/epidemiology , Postoperative Complications/etiology , Lower Extremity/blood supply , Lower Extremity/surgery , Treatment OutcomeABSTRACT
The relationship between online self-disclosure and self-concept clarity has been previously examined through cross-sectional studies. This study examined causal connections between online self-disclosure and self-concept clarity among Chinese middle school students using longitudinal data collected over 18 months. Participants were 535 seventh-grade students aged 12-14 years (Mage = 12.93, SD = 0.54, 43.18% girls), assessed four times, six months apart. In a random intercept cross-lagged panel model, self-concept clarity significantly predicted online self-disclosure. Latent growth mixture modeling identified two distinct growth trajectories for both online self-disclosure (Rapid change, 7%; Slow change, 93%) and self-concept clarity (Rapid change, 8%; No change, 92%). Multiple logistic regression analysis suggested that changes in self-concept clarity influenced the developmental trajectory profile of online self-disclosure. Although male and female students differed in online self-disclosure and self-concept clarity, gender differences in the developmental trajectory profiles of online self-disclosure and self-concept clarity were not significant. Supporting adolescents in developing a clear self-concept to mitigate risks associated with excessive online self-disclosure is important.
Subject(s)
Self Concept , Self Disclosure , Students , Humans , Adolescent , Female , Male , Longitudinal Studies , China , Students/psychology , Child , Internet , Adolescent Behavior/psychology , East Asian PeopleABSTRACT
The cycloaddition reaction involving bicyclo[1.1.0]butanes (BCBs) offers a versatile and efficient synthetic platform for producing C(sp3)-rich rigid bridged ring scaffolds, which act as phenyl bioisosteres. However, there is a scarcity of catalytic asymmetric cycloadditions of BCBs to fulfill the need for enantioenriched saturated bicycles in drug design and development. In this study, an efficient synthesis of valuable azabicyclo[2.1.1]hexanes (aza-BCHs) by an enantioselective zinc-catalyzed (3+2) cycloadditions of BCBs with imines is reported. The reaction proceeds effectively with a novel type of BCB that incorporates a 2-acyl imidazole group and a diverse array of alkynyl- and aryl-substituted imines. The target aza-BCHs, which consist of α-chiral amine fragments and two quaternary carbon centers, are efficiently synthesized with up to 94% yield and 96.5:3.5 er under mild conditions. Experimental and computational studies reveal that the reaction follows a concerted nucleophilic ring-opening mechanism of BCBs with imines. This mechanism is distinct from previous studies on Lewis acid-catalyzed cycloadditions of BCBs.
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The copper-based (Cu-based) electrocatalytic materials effectively carry out the electrocatalytic carbon dioxide reduction reaction (CO2RR) toward C2+ products, yet the superiority and stability of the oxidation state of Cu are still worth studying. Herein, we designed and prepared three Cu-based electrocatalysts with different oxidation states to study the valence state-activity relationship. Among these Cu-based electrocatalysts, the Cu2O nanosheets with thickness of only 0.9 nm show an extremely high C2+ Faraday efficiency (FEC2+) of â¼81%, and the FEC2+ has an increase of 37% compared with the traditional CuOx phase. The ultrathin two-dimensional (2D) nanosheet structure with abundant oxygen vacancies can stabilize the oxidation state of Cu to improve the selectivity for C2+ products in CO2RR. In situ Raman spectroscopy and density functional theory calculations demonstrate that the rich Cu+ in the ultrathin 2D Cu2O nanosheets is the most suitable oxidation state for *CO adsorption and coverage on the catalyst surface, which promotes the C-C coupling reaction in CO2RR. This work provides an excellent catalyst for CO2RR toward C2+ products.
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Food allergies have emerged as a pressing health concern in recent years, largely due to food resources and environmental changes. Dairy products fermented by lactic acid bacteria play an essential role in mitigating allergic diseases. Lactic acid bacteria have been found to possess a distinctive proteolytic system comprising a cell envelope protease (CEP), transporter system, and intracellular peptidase. Studying the impact of different Lactobacillus proteolytic systems on the destruction of milk allergen epitopes and their potential to alleviate allergy symptoms by releasing peptides containing immune regulatory properties is a valuable and auspicious research approach. This paper summarizes the proteolytic systems of different species of lactic acid bacteria, especially the correlation between CEPs and the epitopes from milk allergens. Furthermore, the mechanism of immunomodulatory peptide release was also concluded. Finally, further research on the proteolytic system of lactic acid bacteria will provide additional clinical evidence for the possible treatment and/or prevention of allergic diseases with specific fermented milk/dairy products in the future.
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Seafoods are fashionable delicacies with high nutritional values and culinary properties, while seafood belongs to worldwide common food allergens. In recent years, many seafood allergens have been identified, while the diversity of various seafood species give a great challenge in identifying and characterizing seafood allergens, mapping IgE-binding epitopes and allergen immunotherapy development, which are critical for allergy diagnostics and immunotherapy treatments. This paper reviewed the recent progress on seafood (fish, crustacean, and mollusk) allergens, IgE-binding epitopes and allergen immunotherapy for seafood allergy. In recent years, many newly identified seafood allergens were reported, this work concluded the current situation of seafood allergen identification and designation by the World Health Organization (WHO)/International Union of Immunological Societies (IUIS) Allergen Nomenclature Sub-Committee. Moreover, this review represented the recent advances in identifying the IgE-binding epitopes of seafood allergens, which were helpful to the diagnosis, prevention and treatment for seafood allergy. Furthermore, the allergen immunotherapy could alleviate seafood allergy and provide promising approaches for seafood allergy treatment. This review represents the recent advances and future outlook on seafood allergen identification, IgE-binding epitope mapping and allergen immunotherapy strategies for seafood allergy prevention and treatment.
Subject(s)
Allergens , Food Hypersensitivity , Animals , Epitope Mapping , Epitopes/chemistry , Seafood , Immunotherapy , Immunoglobulin EABSTRACT
The combined molecular dynamics and coordinate driving (MD/CD) method is updated and generalized in this work to broaden its applications in automatically searching reaction pathways for complicated reactions. In this updated version, MD simulations are performed with the GFN's family of methods to systematically sample conformers for almost any systems with atomic numbers Z ≤ 86. The improved CD procedure is greatly accelerated by applying a pre-screening stage at the semiempirical GFN2-xTB level. An automatic module based on the Marcus theory and its improved version (the Wolynes theory) is designed to include single electron transfer (SET) processes into reaction pathways. The capabilities of this method are demonstrated by exploring the most possible reaction pathways of three experimentally reported reactions: the organophosphine-catalyzed trans phosphinoboration, the Fe(II) complex-mediated C(sp2)-H borylation reaction, and the SET-triggered deaminative radical cross-coupling reaction. Comprehensive reaction networks are obtained for all three reactions with reasonable computational costs. Detailed mechanisms for these reactions can account for the reported experimental facts.
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The state-resolved photodissociation of NO2via the 12B2 and 22B2 excited states has been investigated by using time-sliced velocity-mapped ion imaging technique. The images of the O(3PJ=2,1,0) products at a series of excitation wavelengths are measured by employing a 1 + 1' photoionization scheme. The total kinetic energy release (TKER) spectra, NO vibrational state distributions and anisotropy parameters (ß) are derived from the O(3PJ=2,1,0) images. For the 12B2 state photodissociation of NO2, the TKER spectra mainly present a non-statistical vibrational state distribution of the NO co-products, and the profiles of most vibrational peaks display a bimodal structure. The ß values show a gradual decrease with the photolysis wavelength increasing except for a sudden increase at 357.38 nm. The results suggest that the NO2 photodissociation via the 12B2 state proceeds via the non-adiabatic transition between the 12B2 and XÌ2A1 states, leading to the NO(X2Π) + O(3PJ) products with wavelength-dependent rovibrational distributions. As for photodissociation of NO2via the 22B2 state, the NO vibrational state distribution is relatively narrow with the main peak shifting from v = 1, 2 at 235.43-249.22 nm to v = 6 at 212.56 nm. The ß values exhibit two distinctly different angular distributions, i.e., near isotropic at 249.22 and 246.09 nm and anisotropic at the rest of the excitation wavelengths. These results are consistent with the fact that the 22B2 state potential energy surface has a barrier, and the dissociation process is fast when the initial populated level is above this barrier. A bimodal vibrational state distribution is clearly observed at 212.56 nm, in which the main distribution (peaking at v = 6) is ascribed to dissociation via an avoided crossing with the higher electronically excited state while the subsidiary distribution (peaking at v = 11) likely arises due to dissociation via the internal conversion to the 12B2 state or to the XÌ ground state.
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The nonadiabatic interactions between the CÌ state and neighboring electronic states of SO2 have attracted much attention; however, the predissociation mechanisms are not yet completely understood. In this work, the predissociation dynamics of SO2 via its CÌ state have been investigated at λ = 193-201 nm by using the time-sliced velocity map ion imaging technique. The translational energy distributions and the branching ratios of the O(3PJ=2,1,0) spin-orbit products at six photolysis wavelengths have been acquired. The SO(3Σ-) product population gradually decreases in v = 0 and increases in v = 2 as the photolysis wavelength decreases. The branching ratios of O(3P J=2,1,0) products are almost similar at most wavelengths, except at 194.8 nm. Our data suggest that the predissociation between 193 and 201 nm is via an avoided crossing between the CÌ state and the repulsive triplet 23A' state. The state-to-state dynamical pictures shown in this work provide a rigorous test of the potential energy surfaces (PESs) of the SO2 and the nonadiabatic couplings between these PESs.
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Organic frameworks (OFs) offer a novel strategy for assembling organic semiconductors into robust networks that facilitate transport, especially the covalent organic frameworks (COFs). However, poor electrical conductivity through covalent bonds and insolubility of COFs limit their practical applications in organic electronics. It is known that the two-dimensional intralayer πâââπ transfer dominates transport in organic semiconductors. However, because of extremely labile inherent features of noncovalent πâââπ interaction, direct construction of robust frameworks via noncovalent πâââπ interaction is a difficult task. Toward this goal, we report a robust noncovalent πâââπ interaction-stacked organic framework, namely πOF, consisting of a permanent three-dimensional porous structure that is held together by pure intralayer noncovalent πâââπ interactions. The elaborate porous structure, with a 1.69-nm supramaximal micropore, is composed of fully conjugated rigid aromatic tetragonal-disphenoid-shaped molecules with four identical platforms. πOF shows excellent thermostability and high recyclability and exhibits self-healing properties by which the parent porosity is recovered upon solvent annealing at room temperature. Taking advantage of the long-range πâââπ interaction, we demonstrate remarkable transport properties of πOF in an organic-field-effect transistor, and the mobility displays relative superiority over the traditional COFs. These promising results position πOF in a direction toward porous and yet conductive materials for high-performance organic electronics.
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BACKGROUND: Parvalbumin (PV) can be subdivided into two phylogenetic lineages, αPV and ßPV. The bony fish ßPV is considered a major fish allergen. However, there is no available report on the immunological property and epitope mapping of bony fish αPV. RESULTS: To characterize the allergenic property of bony fish αPV and investigate the difference in allergenic property of bony fish αPV and ßPV, turbot (Scophthalmus maximus) αPV and ßPV were identified by mass spectrometry and were expressed in Escherichia coli system in this study. Spectra analysis and three-dimensional (3D) modeling showed the similar structure between αPV and ßPV. However, αPV exhibited lower immunoglobulin E/immunoglobulin G (IgE/IgG) binding capacity than ßPV. Three identified ßPV epitopes possessed higher IgE reactivity and more hydrophobic residues than three identified αPV epitopes. In addition, less similarity in sequence homology of αPV epitopes was observed with allergen sequences in database. CONCLUSION: These finding expanded information on fish PV epitopes and substantiated the difference in allergenicity and epitope mapping between fish αPV and ßPV, which will improve the epitope-based detection tools of PV and diagnostic of PV induced fish allergy. © 2023 Society of Chemical Industry.
Subject(s)
Flatfishes , Food Hypersensitivity , Animals , Allergens , Epitopes/chemistry , Parvalbumins/chemistry , Phylogeny , Immunoglobulin EABSTRACT
Ruthenium-based materials are considered great promising candidates to replace Pt-based catalysts for hydrogen production in alkaline conditions. Herein, we adopt a facile method to rationally design a neoteric Schottky catalyst in which uniform ultrafine ruthenium nanoparticles featuring lattice compressive stress are supported on nitrogen-modified carbon nanosheets (Ru NPs/NC) for efficient hydrogen evolution reaction (HER). Lattice strain and Schottky junction dual regulation ensures that the Ru NPs/NC catalyst with an appropriate nitrogen content displays superb H2 evolution in alkaline media. Particularly, Ru NPs/NC-900 with 1.3% lattice compressive strain displays attractive activity and durability for the HER with a low overpotential of 19 mV at 10 mA cm-2 in 1.0 M KOH electrolyte. The in situ X-ray absorption fine structure measurements indicate that the low-valence Ru nanoparticle with shrinking Ru-Ru bond acts as catalytic active site during the HER process. Furthermore, multiple spectroscopy analysis and density functional theory calculations demonstrate that the lattice strain and Schottky junction dual regulation tunes the electron density and hydrogen adsorption of the active center, thus enhancing the HER activity. This strategy provides a novel concept for the design of advanced electrocatalysts for H2 production.
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Superoscillation is a kind of phenomenon which can generate oscillation faster than the fastest component of a band-limited function. For optics, superoscillation is generated by coherence of low spatial frequency waves. It can bring a localized region named "hot spot", which has a smaller size than the diffraction-limit, and this character has potential applicaions in super-resolution imaging. Using a high-order radially polarized Laguerre-Gaussian beam tightly focused by high-NA objective lens, we can easily obtain and control the superoscillation hot spot. Using a metasurface, which has compact volume and sub-wavelength pixel size, we can generate the high-order radially polarized Laguerre-Gaussian beam more simply than conventional methods like using a liquid crystal mode converter. We first analyze the properties of unit cells of the metasurface and simulate the performance of the metasurface. Then we analyze the property of the tightly focused high-order radially polarized Laguerre-Gaussian beam and design a super-resolution imaging system using our designed metasurface. Therefore, the 2-fold lateral resolution enhancement is realized in our approach. This method can be used to improve lateral resolution in conventional confocal imaging systems.
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Boron Lewis acid-catalyzed and catalyst-free hydroboration reactions of imines are attractive due to the mild reaction conditions. In this work, the mechanistic details of the hydroboration reactions of two different kinds of imines with pinacolborane (HBpin) are investigated by combining density functional theory calculations and some experimental studies. For the hydroboration reaction of N-(α-methylbenzylidene)aniline catalyzed by tris[3,5-bis(trifluoromethyl)phenyl]borane (BArF 3 ), our calculations show that the reaction proceeds through a boron Lewis acid-promoted hydride transfer mechanism rather than the classical Lewis acid activation mechanism. For the catalyst- and solvent-free hydroboration reaction of imine, N-benzylideneaniline, our calculations and experimental studies indicate that this reaction is difficult to occur under the reaction conditions reported previously. With a combination of computational and experimental studies, we have established that the commercially available BH3 â SMe2 can serve as an efficient catalyst for the hydroboration reactions of N-benzylideneaniline and similar imines. The hydroboration reactions catalyzed by BH3 â SMe2 are most likely to proceed through a hydroboration/B-H/B-N σ-bond metathesis pathway, which is very different from that of the reaction catalyzed by BArF 3 .