225 research outputs found

    Discovery and verification of two-dimensional organic–inorganic hybrid perovskites via diagrammatic machine learning model

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    Two-dimensional (2D) organic–inorganic hybrid perovskites (OIHPs) have drawn increased attention due to rich physical properties such as ferroelectricity and photovoltaic properties. Nevertheless, it is challenging to discover novel 2D OIHPs within the vast chemical composition space. Herein, a diagrammatic machine learning model was employed to improve this issue. We collected 179 OIHPs with a variety of organic cations and screened out 6 features from 10,622 descriptors. Subsequently, a decision tree model was created to predict the dimensionality of OIHPs, achieving a LOOCV accuracy of 0.94 and a test accuracy of 0.89, respectively. Then, one candidate from a virtual space with 8256 samples was successfully synthesized, which was consistent with the prediction of the model. Finally, three rules were produced by visualization of the tree structure to generally discriminate 2D from non-2D OIHPs. It is believed that the diagrammatic model has reliability in identifying 2D OIHPs and will serve further property studies of OIHPs in the future

    Efficient biosynthesis of (R)-mandelic acid from styrene oxide by an adaptive evolutionary Gluconobacter oxydans STA

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    Abstract Background (R)-mandelic acid (R-MA) is a highly valuable hydroxyl acid in the pharmaceutical industry. However, biosynthesis of optically pure R-MA remains significant challenges, including the lack of suitable catalysts and high toxicity to host strains. Adaptive laboratory evolution (ALE) was a promising and powerful strategy to obtain specially evolved strains. Results Herein, we report a new cell factory of the Gluconobacter oxydans to biocatalytic styrene oxide into R-MA by utilizing the G. oxydans endogenous efficiently incomplete oxidization and the epoxide hydrolase (SpEH) heterologous expressed in G. oxydans. With a new screened strong endogenous promoter P 12780 , the production of R-MA was improved to 10.26 g/L compared to 7.36 g/L of using P lac . As R-MA showed great inhibition for the reaction and toxicity to cell growth, adaptive laboratory evolution (ALE) strategy was introduced to improve the cellular R-MA tolerance. The adapted strain that can tolerate 6 g/L R-MA was isolated (named G. oxydans STA), while the wild-type strain cannot grow under this stress. The conversion rate was increased from 0.366 g/L/h of wild type to 0.703 g/L/h by the recombinant STA, and the final R-MA titer reached 14.06 g/L. Whole-genome sequencing revealed multiple gene-mutations in STA, in combination with transcriptome analysis under R-MA stress condition, we identified five critical genes that were associated with R-MA tolerance, among which AcrA overexpression could further improve R-MA titer to 15.70 g/L, the highest titer reported from bulk styrene oxide substrate. Conclusions The microbial engineering with systematic combination of static regulation, ALE, and transcriptome analysis strategy provides valuable solutions for high-efficient chemical biosynthesis, and our evolved G. oxydans would be better to serve as a chassis cell for hydroxyl acid production

    Phenanthrene-Incorporated Isoamethyrin: A Near-Planar Macrocycle That Display Enhanced Aromaticity via Protonation-Triggered Conformation Changes

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    Controlling the aromaticity in expanded porphyrins is a forefront research topic, and the strategy of using protonation-triggered conformational changes to fine-tune electronic properties and aromaticity has yet to be generalized in rigid and planar expanded porphyrins. Here, we synthesized phenanthrene-incorporated isoamethyrins that possess near-planar conformations and nonaromatic characters. However, when methanesulfonic acid (MSA) was added, geometric deformations occurred to minimize the unfavorable strain, resulting in macrocycles that were weakly aromatic as a whole

    Effect of Environmental Conditions on Strontium Adsorption by Red Soil Colloids in Southern China

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    The fate of radionuclides in the environment is attracting increased attention. The effect of various environmental effects on the adsorption behavior of the strontium ion (Sr2+) by red soil colloids in Southern China was studied by a series of batch experiments, and the adsorption mechanism was briefly investigated as well. With the increase in the solid–liquid ratio and the concentration of Sr2+, the adsorption efficiency increased gradually. The effect of pH and ionic strength on adsorption was strong, while temperature had little effect. The adsorption data fitted to the Langmuir model indicates that the process is monolayered and homogeneous. The thermodynamic parameters also show that the adsorption of Sr2+ on red soil colloids is a spontaneous and exothermic process. The aim of this work is to gain insight into the role of red soil colloids on the fate of radionuclides in the field

    Cancer cell employs a microenvironmental neural signal trans-activating nucleus-mitochondria coordination to acquire stemness

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    Abstract Cancer cell receives extracellular signal inputs to obtain a stem-like status, yet how tumor microenvironmental (TME) neural signals steer cancer stemness to establish the hierarchical tumor architectures remains elusive. Here, a pan-cancer transcriptomic screening for 10852 samples of 33 TCGA cancer types reveals that cAMP-responsive element (CRE) transcription factors are convergent activators for cancer stemness. Deconvolution of transcriptomic profiles, specification of neural markers and illustration of norepinephrine dynamics uncover a bond between TME neural signals and cancer-cell CRE activity. Specifically, neural signal norepinephrine potentiates the stemness of proximal cancer cells by activating cAMP-CRE axis, where ATF1 serves as a conserved hub. Upon activation by norepinephrine, ATF1 potentiates cancer stemness by coordinated trans-activation of both nuclear pluripotency factors MYC/NANOG and mitochondrial biogenesis regulators NRF1/TFAM, thereby orchestrating nuclear reprograming and mitochondrial rejuvenating. Accordingly, single-cell transcriptomes confirm the coordinated activation of nuclear pluripotency with mitochondrial biogenesis in cancer stem-like cells. These findings elucidate that cancer cell acquires stemness via a norepinephrine-ATF1 driven nucleus-mitochondria collaborated program, suggesting a spatialized stemness acquisition by hijacking microenvironmental neural signals

    An astronomical timescale for the Permian-Triassic mass extinction reveals a two-step, million-year-long terrestrial crisis in South China

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    The Permian-Triassic Mass Extinction (PTME) is the greatest biotic crisis of the Phanerozoic. In terrestrial settings, the PTME appears to have been diachronous and it has been suggested that losses initiated before the marine crisis. We examine organic carbon-isotope (δ13Corg) and geochemical proxies for environmental change in a palaeotropical wetland succession from southwest China. A newly constructed astronomical timescale provides a temporal framework for constraining the timing of the terrestrial PTME. Two major, negative carbon isotope excursions (CIEs) of 5.3‰ and 3.9‰ are observed between the top of the (Permian) Xuanwei Formation and the middle of the (Permian-Triassic) Kayitou Formation respectively. Our cyclostratigraphic model suggests that carbon cycle destabilization lasted ~0.6 ± 0.1 Myr. We calculate total erosion rates for basaltic landscapes as a proxy for volumes of bare soil resulting from deforestation. Two phases of accelerated erosion saw denudation rates rise over a ~1 Myr period from ~150 t/km2/yr in the upper Xuanwei Formation (Permian) to >2000 t/km2/yr at the base of the Dongchuan Formation (Triassic). Calibrating the collapse of terrestrial ecosystems indicates that although the equatorial terrestrial PTME initiated before the marine crisis, it was a protracted process with the final coup-de-grâce not until ~ 700ky later. This has a bearing on extinction scenarios in which the terrestrial PTME is a causal factor in marine losses via enhanced nutrient runoff, because the final devastation on land post-dates the much more abrupt marine PTME

    Palynological dynamics in the late Permian and the Permian-Triassic transition in southwestern China

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    The Permian-Triassic mass extinction (PTME) is regarded as the largest biotic crisis of the Phanerozoic. However, the influence of the terrestrial ecological disturbance on plants remains controversial. Here we study the late Permian to the Early Triassic palynological successions from three borehole sections drilled through the entire Lopingian (the late Permian) and the Permian–Triassic transitional strata in southwestern China. Analyses of palynomorph composition and relative abundance allow us to identify four distinct palynofloral assemblages, which include, in ascending order, the Tripartites cristatus var. minor - Torispora laevigata (ML) assemblage, the Crassispora orientalis - Anticapipollis tornatilis (OT) assemblage, the Lundbladispora communis - Aratrisporites yunnanensis (CY) assemblage, and the Pteruchipollenites reticorpus - Protopinus fuyuanensis (RF) assemblage. These palynological assemblages, together with recently updated age data, further improve our understanding of vegetation dynamics around the PTME. The ML and OT assemblages from the Xuanwei Formation are dominated by gigantopteris and fern peat-forming rainforest and reflect warm and humid paleoclimate conditions preceding the PTME. At the bottom of the overlying Kayitou Formation, the abrupt replacement of the diverse sporomorph assemblage by the assemblage containing herbaceous communities reveals a dramatic floral disruption. The CY assemblage from the bottom part of the Kayitou Formation marks the destruction of Gigantopteris peat-forming ecosystems, and only a few species of Gigantopteris were retained in this assemblage. Subsequently, in the Kayitou Formation notable quantities of gymnosperm pollen dominate the RF assemblage. Many gymnosperms from the RF assemblage were present in the older assemblages in low abundances but they persisted through the ecological disturbance interval and rebounded in the early Triassic RF assemblage. The drought-tolerant plants growing in uplands were likely the first batch of plants to adapt and recover after the extinction event. In the upper part of the Kayitou Formation and the overlying Dongchuan Formation, spore and pollen fossils are absent, which may suggest the collapse of the local terrestrial ecosystem and may also indicate unsuitable conditions for microfossil preservation. We conclude that the PTME caused a sharp decrease in plant species and changes in vegetation-community compositions, but it did not immediately eradicate the terrestrial ecosystem in southwestern China. More drought-tolerant plants persisted beyond the first stage of the terrestrial crisis, but with gradual environmental degradation, terrestrial vegetation eventually collapsed in the Early Triassic. This observation supports the hypothesis that the extinction process of terrestrial vegetation was a two-staged and longer-duration event in southwestern China

    The coal-forming environment during mass extinction in the latest permian: Evidence from geochemistry of rare Earth elements

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    The C1 coal of Latest Permian during mass extinction in eastern Yunnan was studied to reveal the terrestrial paleoenvironment and influence of geological events on coal-formation during mass extinction. An analysis of Rare Earth Elements (REEs) was conducted on the C1 coal from the Yantang Mine of Xuanwei, eastern Yunnan Province, which was deposited during the latest Permian. A total of 24 samples from coals, partings, roofs and floors from the C1 coal were taken from the fresh face in the underground mine. The results of the REEs analysis indicated that the total REE content (∑REE) in the C1 coal varies from 23.99 μg/g to 267.94 μg/g, averaged 122.69 μg/g. The C1 coal is enriched in light REE (LREE) relative to heavy REE (HREE), signifying the fractionation between LREE and HREE. Most samples of the coal seam C1 are depleted in Eu in various degrees and slightly depleted in Ce, especially two partings in sub-seams B1 and B3 which show the significant negative Eu anomalies. The geochemical characteristics of REE reveal that the C1 coal was deposited in a weak oxidation environment; the sedimentary environment was turbulent during the middle-later stage of coal-forming process; the C1 coal was affected by the basalt clastic materials from the Khangdian Oldland and acidic synsedimentary volcanic ash in the coal-forming period. The geochemical characteristics of Tonsteins in C1 coal are similar to those of marine Permian-Triassic boundary (PTB) volcanic ash layers in South China, which are both derived from the felsic volcanism caused by the closure of the Paleo-Tethys at the southwestern margin of the South China. Furthermore, the C1 coal was also affected by the eruption of Siberian large igneous province (SLIP) in the early stage

    Successful treatment of periungual warts with local hyperthermia: report of two cases

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    Periungual warts are common warts that grow on the periungual or nail margin, and it’s challenging to remove them due to their particular location, causing its high recurrence rate and brings difficulties to the treatments. We successfully cured two cases of stubborn periungual warts by local hyperthermia. A male with warts on his hands and knees and a girl with periungual warts on her fingers received local hyperthermia of 44 °C for 30 min a time. One month after the last treatment, their lesions disappeared entirely and did not relapse during the follow-up period. These two cases showed that local hyperthermia might be a safe and effective method for treating periungual warts in patients with poor traditional treatment

    Magneto-thermomechanically triggered active mechanical metamaterials -- untethered, reversible, reprogrammable transformations with shape locking

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    Future active metamaterials for reconfigurable structural applications require fast, untethered, reversible, and reprogrammable (multimodal) transformability with shape locking. Herein, we aim to construct and demonstrate a magneto-thermomechanical tool that enables a single material system to transform with untethered, reversible, low-powered reprogrammable deformations and shape locking via the application of magneto-thermomechanically triggered prestress on a shape memory polymer and structural instability with asymmetric magnetic torque. We demonstrate the mutual assistance of two physics concepts - magnetic control combined with the thermomechanical behavior of shape memory polymers, without requiring new materials synthesis and high-power energy for reprogramming. Our approach can open a new path of active metamaterials, flexible yet stiff soft robots, and multimodal morphing structures, where we can design them in reversible and reprogrammable ways
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