Two-dimensional (2D) crystal-to-crystal transition is an important method in crystal engineering because of its ability to directly create diverse crystal materials from one crystal. However, ...steering a 2D single-layer crystal-to-crystal transition on surfaces with high chemo- and stereoselectivity under ultra-high vacuum conditions is a great challenge because the transition is a complex dynamic process. Here, we report a highly chemoselective 2D crystal transition from radialene to cumulene with retention of stereoselectivity on Ag(111) via retro-2 + 1 cycloaddition of three-membered carbon rings and directly visualize the transition process involving a stepwise epitaxial growth mechanism by the combination of scanning tunneling microscopy and non-contact atomic force microscopy. Using progression annealing, we found that isocyanides on Ag(111) at a low annealing temperature underwent sequential 1 + 1 + 1 cycloaddition and enantioselective molecular recognition based on C–H···Cl hydrogen bonding interactions to form 2D triaza3radialene crystals. In contrast, a higher annealing temperature induced the transformation of triaza3radialenes to generate trans-diaza3cumulenes, which were further assembled into 2D cumulene-based crystals through twofold N–Ag–N coordination and C–H···Cl hydrogen bonding interactions. By combining the observed distinct transient intermediates and density functional theory calculations, we demonstrate that the retro-2 + 1 cycloaddition reaction proceeds via the ring opening of a three-membered carbon ring, sequential dechlorination/hydrogen passivation, and deisocyanation. Our findings provide new insights into the growth mechanism and dynamics of 2D crystals and have implications for controllable crystal engineering.
Abstract
In this paper, the hydrogen diffusion behavior and hydrogen induced delayed fracture (HIDF) of Q-P980 (Q-P: Quenching and Partitioning) and MS980 (MS: Martensitic steel) steels were ...investigated using hydrogen penetration, slow strain rate tensile (SSRT) tests, thermal desorption spectroscopy (TDS) tests, fracture analysis, and microstructural examination in this paper. The austenite in Q-P980 is massive retained-austenite (RA) with low stability. The TRIP (Transformation Induced Plasticity) effect will occur in the process of strain and change into high carbon martensite. HIDF is caused by a substantial amount of surplus hydrogen being enriched at the border and flaws. The fracture has a broad cleavage surface and is a typical quasi-cleavage fracture. MS980 has been sufficiently tempered, resulting in a substantial quantity of distributed spherical cementite (150nm) precipitating around the lath martensite. This size and form of cementite may successfully trap hydrogen while maintaining the material’s mechanical characteristics. And tempering can effectively reduce the local stress level of steel, so MS980 has a very low HE susceptibility. HIDF is related to local stress and hydrogen accumulation. We suppose that Z is a constant and
Z
C
is a critical value which associated to
σ
and
C
H
(the local stress and local hydrogen concentration), rising as
σ
and
C
H
rises. The atomic bonds at the crack tip, lattice position and the phase interface will fracture when
Z
C
reaches a particular value Z. Tempering to minimize local stress and carbide precipitation to capture hydrogen are two strategies for reducing hydrogen embrittlement (HE) susceptibility, particularly for dislocation strengthened steel. Microalloying elements can generate precipitates that function as hydrogen traps and obstruct the HELP (Hydrogen Enhanced Localized Plasticity) process, lowering local stress and hydrogen accumulation.
Tolypocladium, a diverse genus of fungicolous fungi belonging to Ophiocordycipitaceae, includes saprotrophic soil inhabitants, plant endophytes and pathogens of insects, nematodes, rotifers, and ...parasites of truffle-like fungi. Here, we review the research progress achieved for Tolypocladium regarding its taxonomy, species diversity, geographic distribution, host affiliations and ecological diversity. Furthermore, an undescribed taxon from China was established using morphology and multi-gene phylogeny. Tolypocladium inusitaticapitatum is introduced as a new species parasitizing ectomycorrhizal Elaphomyces species. It is diagnosed by its irregularly enlarged fertile heads and lemon, yellow-to-dark-brown, smooth and nearly cylindrical stipe. Phylogenetic analyses based on SSU, LSU, ITS, TEF1-α and RPB2 sequence data showed T. inusitaticapitatum to be an independent lineage separated from T. flavonigrum in the clade comprising T. capitatum, T. fractum and T. longisegmentatum. A key for identifying the sexual Tolypocladium species is also provided.
Recent geological survey has identified the Early Paleoproterozoic meta-mafic intrusions in the southwestern Yangtze Block. We present geochronological, whole-rock geochemical and Nd isotopic data ...for these meta-mafic rocks to better address the tectonic evolution of the Yangtze Block during the Early Paleoproterozoic Period. Geochronological data show that the meta-mafic rocks have zircon ages of 2 395-2 316 Ma. They have high TiO
2
contents of 1.40 wt.%3.66 wt.% and Nb concentrations of 13.7 ppm45.5 ppm, thus aregrouped as Nb-enriched mafic rocks. These mafic rocks are characterized by tholeiitic compositions with enrichment of LREEs and LILEs, and can be divided into two groups. Group 1 samples display E-MORB-like geochemical characteristics. Group 2 samples have positive ε
Nd
(
t
) values of 4.0–5.0. Geochemical data indicate that all meta-mafic rocks were likely derived from a depleted asthenospheric mantle. REE modeling indicates lower degree of partial melting for Group 2 samples (3%–10%) relative to Group 1 samples (15%–20%). Taking into account contemporaneous post-collisional granitoids in southwestern Yangtze Block, we propose that these meta-mafic rocks were formed in a post-collisional extension setting. These meta-mafic rocks can be compared with those in Africa, South America and Europe, and might be linked with the Arrowsmith orogenic belt. KEY WORDS: zircon dating, geochemistry, Early Paleoproterozoic, Nb-enriched rocks, Yangtze Block.
Discovery and identification of three bioactive compounds affecting endothelial function in
Extract (GBE) based on chromatogram-bioactivity correlation analysis. Three portions were separated from ...GBE via D101 macroporous resin and then re-combined to prepare nine GBE samples. 21 compounds in GBE samples were identified through UFLC-DAD-Q-TOF-MS/MS. Correlation analysis between compounds differences and endothelin-1 (ET-1) in vivo in nine GBE samples was conducted. The analysis results indicated that three bioactive compounds had close relevance to ET-1: Kaempferol-3-
-α-l-glucoside, 3-
-{2-
-{6-
-P-OH-trans-cinnamoyl-β-d-glucosyl}-α-rhamnosyl} Quercetin isomers, and 3-
-{2-
-{6-
-P-OH-trans-cinnamoyl-β-d-glucosyl}-α-rhamnosyl} Kaempferide. The discovery of bioactive compounds could provide references for the quality control and novel pharmaceuticals development of GRE. The present work proposes a feasible chromatogram-bioactivity correlation based approach to discover the compounds and define their bioactivities for the complex multi-component systems.
Background
Chronic subdural hematoma (CSDH) is a common illness in neurosurgical practice with a substantial recurrence rate. Previous studies found that serum lipids were associated with the risk of ...stroke and subarachnoid hemorrhage. In the current study, we aimed to identify the relationship between serum lipids and CSDH recurrence.
Methods
The medical records of 274 consecutive surgical patients with CSDH in our department were reviewed and analyzed. Patients were separated into recurrence and non-recurrence groups. Univariable and multivariable Cox proportional hazards regression analyses were performed to identify serum lipids (triglycerides, total cholesterol, LDL, HDL) and other potential predictors associated with CSDH recurrence, and the performance of predictors was assessed with receiver operating characteristic (ROC) curve.
Results
Of the 274 patients included in the study, 42 (15.3%) experienced at least 1 recurrence of CSDH. Univariate analysis showed that age, hypertension, diabetes mellitus, anticoagulant use, triglycerides, HDL, and midline shift were all significantly associated with CSDH recurrence. Multivariable Cox regression analysis found that only age, diabetes mellitus, midline shift, and HDL level were independent risk factors for CSDH recurrence. A higher HDL level (HR = 0.929, 95% CI 0.905–0.953) was significantly associated with a lower risk of recurrence, and ROC curve analysis revealed that the optimal HDL cut-off value as a predictor was 37.45 mg/dl.
Conclusions
Low level of high-density lipoprotein is significantly associated with recurrence of chronic subdural hematoma.
Homogeneous catalytic hydrogen evolution reaction (HER) by five‐coordinate Schiff base complexes with first‐row transition metals (Ni(II), Cu(II) and Zn(II)) were firstly investigated in organic ...medium. Both nickel and copper complexes revealed efficient electrocatalytic and photocatalytic HER activities. Cyclic voltammetry experiments and foot of wave analysis (FOWA) were applied to assess the electrocatalytic performance and to probe the catalytic mechanism. The Cu(II) and Ni(II) catalysts achieved maximum electrocatalytic HER turnover frequencies (TOFmax) of 70139.5 and 63827.5 s−1, respectively, in MeCN using acetic acid as a proton source. Photocatalytic HER investigation suggested a superior activity of the Cu(II) complex to the Ni(II) counterpart. In an aqueous three‐component system consisting of organic Eosin Y (EY2−) photosensitizer, trimethylamine (TEA) sacrificial donor, and the Cu(II) catalyst, a photocatalytic HER turnover number (TON) of 21 was obtained after 4 h irradiation under white LED light. Employing triethanolamine (TEOA) instead of TEA as a sacrificial donor substantially enhanced stability of the photocatalytic HER system, of which deactivation was not observed after 6 h photocatalysis. The photocatalytic HER reaction was monitored by time‐resolved UV‐vis spectra which suggested faster decomposition of EY2− in the presence of TEA than TEOA.
Electrocatalytic and photocatalytic hydrogen evolution by three five‐coordinate Schiff base complexes with first‐row transition metals (Ni, Cu, and Zn) is investigated. The Cu‐based complex shows superior catalytic activity compared to the Ni counterpart.
Dendronized polymers (DPs) consist of a linear polymeric backbone with dendritic side chains. Fine-tuning of the functional groups in the side chains enriches the structural versatility of the DPs ...and imparts a variety of novel physical properties. Herein, the first on-surface synthesis of DPs is achieved via the postfunctionalization of polymers on Au(111), in which the surface-confinement-induced planar conformation and chiral configurations were unambiguously characterized. While the dendronized monomer was synthesized in situ on Au(111), the subsequent polymerization afforded only short, cross-linked DP chains owing to multiple side reactions. The postfunctionalization approach selectively produced brominated polyphenylene backbone moieties by the deiodination polymerization of 4-bromo-4″-iodo-5′-(4-iodophenyl)-1,1′:3′,1″-terphenyl on Au(111), which smoothly underwent divergent cross-coupling reactions with two different isocyanides to form two types of DPs as individual long chains.
Zn2(ClQ)4(CH3OH)2 (1), Zn(BrQ)2(H2O)2 (2), Zn2(ClIQ)4 (3) and Cu(BrQ)2 (4) (H-ClQ = 5,7-dichloro-8-hydroxylquinoline, H-BrQ = 5,7-dibromo-8-hydroxylquinoline, and ...H-ClIQ = 5-chloro-7-iodo-8-hydroxylquinoline) were synthesized. Compounds 1–4 showed high anti-proliferative cytotoxicities against BEL-7404, SK-OV-3, NCI-H460 tumor cells, and HL-7702 normal cells in vitro, with IC50 values in the 1.4 nM to 32.13 μM range. Compounds 2–4 exhibited significantly enhanced cytotoxicity against BEL-7404 cell line, comparing with free 5,7-dihalo-8-quinolinol. Western blotting analysis showed that 2, 3 depleted mutant p53 protein in MDA-MB-231, and compound 2 decreased the ratio of Bcl-2/Bax in NCI-H460 significantly. The binding abilities of 1–4 to DNA were stronger than that of free quinolinol ligand. Intercalation is the probable binding mode for the complexes and free quinolinol ligands with DNA.
Display omitted Three zinc(II) and one copper(II) complexes with 5,7-dihalo-8-hydroxylquinoline were synthesized. They exhibited high antitumor activities and interacted with DNA mainly by intercalation.
•Three Zn(II) and Cu(II) complexes with 5,7-dihalo-8-quinolinolines were synthesized.•Theses complexes exhibited high antitumor activities against three human tumor cells.•Intercalation could be the most possible binding modes for these complexes to DNA.
PDF
