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Alcohols are the most commercially abundant, synthetically versatile and operationally convenient functional groups in organic chemistry. Therefore, a strategy that utilizes hydroxy-containing compounds to develop novel bond disconnection and formation process would achieve molecular diversity. Herein, a deconstructive strategy for the generation of quinoxalin-2(1H)-one derivatives has been developed from alcohol precursors via oxy-radical-induced ß-fragmentation. Additionally, 1,5-HAT and deoxygenation by P(III) along with oxy-radical were demonstrated as alternative pathways for this transformation. Furthermore, with the deep-seated reorganization of a few terpenes carbon framework, a unique activity with inhibition against the growth of pathogenic fungi was observed.
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An effective strategy to improve the proton conductivity of metal-organic frameworks (MOFs) is to regulate the pore size of composite materials. In this work, composite materials of MOF-808@MOG-808-X (X is the mass ratios of MOF-808 to MOG-808) was successfully prepared by grinding and blending. MOF-808@MOG-808-1:2 was optimal for its suitable pore structure, which facilitates the practical construction of hydrogen bonding networks, promotes rapid and stable proton conduction, and enables the proton conductivity, achieving a 1 + 1 > 2 effect. At 353 K and 93% relative humidity (RH), the maximum proton conductivity of MOF-808@MOG-808-1:2 reaches 1.08 × 10-1 S·cm-1. Next, MOF-808@MOG-808-1:2 was blended with chitosan (CS) to obtain composite proton exchange membranes (PEMs), namely, CS@MOF-808@MOG-808-1:2-Y (Y = 5%, 10%, or 15%) with the maximum proton conductivity reaching 1.19 × 10-2 S·cm-1 at 353 K and 93% RH for CS@MOF-808@MOG-808-1:2-10% with additional stability. The conductive mechanisms of the composite materials were revealed by activation energy calculation. This investigation not only proposes a simple grinding-blending method for the development of MOF-doped composite materials for proton conductivity but also provides a producting material basis for future applications of MOFs in proton exchange membrane fuel cells (PEMFCs).
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Chuandong Cave is an important Late Paleolithic site because it documents the early appearance of bone tools in southern China. We used the single-aliquot regenerative-dose protocol for optically stimulated luminescence dating to improve the precision of the chronology for the Chuandong Cave sedimentary sequence. The age of each layer was determined using a Bayesian modeling approach which combined optically stimulated luminescence ages with published AMS 14C dates. The results showed that Layer 10 began accumulating since 56 ± 14 ka and provides the upper age limit for all artifacts from the sequence. Bone awl tools from Layer 8, the earliest grinding bone tools in this site, were recovered within sediments between 40 ± 7 ka and 30 ± 4 ka. Layer 8 also indicates the appearance of modern humans in the Chuandong Cave sequence. Layers 4-2, ranging from 15 ± 3 ka until 11 ± 1 ka and including the Younger Dryas period, contain a few bone awls and an eyed bone needle. The shift from bone awls to eyed bone needles in the Chuandong Cave sequence indicates that modern humans adapted to the changing climate of southern China. We conclude that modern human behavior in bone tools appeared in southern China as early as 40 ± 7 ka, became more sophisticated during the Last Glacial Maximum, and spread more widely across southern China during the Younger Dryas.
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Hominidae , Animales , Humanos , Teorema de Bayes , Cuevas , Huesos , China , Datación Radiométrica , Arqueología , FósilesRESUMEN
We report the synthesis, characterization and reactivity of an air-stable, well-defined acenaphthoimidazolylidene palladium-BIAN-NHC chloro dimer complex, [Pd(BIAN-IPr)(µ-Cl)Cl]2. This rapidly activating catalyst merges the reactive properties of palladium chloro dimers, [Pd(NHC)(µ-Cl)Cl]2, with the attractive structural features of the BIAN framework. [Pd(BIAN-IPr)(µ-Cl)Cl]2 is the most reactive Pd(II)-NHC precatalyst discovered to date undergoing fast activation under both an inert atmosphere and aerobic conditions. The catalyst features bulky-yet-flexible sterics that render the C-H substituents closer to the metal center in combination with rapid dissociation to monomers and strong σ-donor properties. [Pd(BIAN-IPr)(µ-Cl)Cl]2 should be considered as a catalyst for reactions using well-defined Pd(II)-NHCs.
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Scans without evidence of dopaminergic deficit (SWEDD) patients are often misdiagnosed with Parkinson's disease (PD) but have normal dopamine transporter scans. We hypothesised that white matter tracts associated with motor and cognition functions may be affected differently by SWEDD and PD. Automatically annotated fibre clustering (AAFC) is a novel clustering method based on diffusion magnetic resonance imaging (dMRI) tractography that enables highly robust reconstruction of white matter tracts that are composed of corresponding clusters. This study aimed to investigate the white matter properties in the subdivisions of white matter tracts among SWEDD and PD groups. We applied AAFC to identify white matter tracts related to motion and cognition functions in the dataset consisting of SWEDD (nâ¯=â¯22), PD (nâ¯=â¯30) and normal control (NC) (nâ¯=â¯30). Then, we resampled 200 nodes along fibres of cluster, and the diffusion metric values corresponding to each node were calculated and used for comparison. Compared with NC, PD showed significant difference (pâ¯<â¯0.05) in two clusters in thalamo-frontal (TF), one cluster in thalamo-parietal (TP) and one cluster in thalamo-occipital (TO), whereas SWEDD presented no significant difference. Three clusters in cingulum bundle (CB) commonly exhibited significant differences in PD versus SWEDD and NC versus SWEDD. The support vector machine classifier achieved high accuracies in PD-NC, PD-SWEDD and NC-SWEDD classifications. This outcome validated these local white matter differences were useful to separate the three groups. These results suggest that PD exerts more significant effects on thalamo tracts than SWEDD, and unique microstructural changes occur in CB tract in SWEDD.