198 research outputs found

    Data_Sheet_1_Dynamic development of syntactic complexity in second language writing: A longitudinal case study of a young Chinese EFL learner.docx

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    The present study analyzes the English diaries written by a young Chinese English as a foreign language (EFL) learner over a 1-year period in an attempt to determine the developmental process of Chinese EFL young learners’ written language in terms of syntactic complexity. This study aimed to use a wide range of metrics to explore densely collected data based on Dynamic Systems Theory. The longitudinal study data were analyzed through eight large-grained measures related to sentential, clausal, and phrasal features by using L2 Syntactic Complexity Analyzer, as well as fine-grained measures related to seven modifiers, an adjective placed before a noun, ordinal numerals are indicated (ADJA), cardinal numeral (CARD), predicative adjective, adverbial adjective (ADJP), adverbs (ADV), prepositional phrases (PREP), subordinate (SUB), and relative clause (REL), through manual annotations. The results show that, first, the developmental process was not linear but spiral in terms of large-grained measures. The sentential level varied, and the development process of the young learner is different from Chinese English learners studying in colleges. Second, the dynamic features of fine-grained measures are also prominent in the seven indicators. ADJA, PREP, and REL showed a steady increase, ADJP showed an obvious decline, while ADV and SUB first increased and then declined. Third, the correlation analysis revealed a competitive interaction within fine-grained measures and between large-grained and fine-grained measures.</p

    Isotope Effects and the Nature of Enantioselectivity in the Shi Epoxidation. The Importance of Asynchronicity

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    The epoxidation of β-methylstyrene catalyzed by the Shi fructose-derived ketone is studied using experimental kinetic isotope effects and DFT calculations. The observation of a large β olefinic 13C isotope effect and small α carbon isotope effect is indicative of an asynchronous transition state with more advanced formation of the C−O bond to the β olefinic carbon. By varying the catalyst conformation and alkene orientation, diverse transition structure geometries were located calculationally, and the lowest-energy structure leads to an accurate prediction of the isotope effects. Given this support for the accuracy of the calculations employed, the nature of enantioselectivity in this and related epoxidations is considered. The lowest-energy transition structures are generally those in which the differential formation of the incipient C−O bonds, the “asynchronicity,” resembles that of an unhindered model, and the imposition of greater or less asynchronicity leads to higher barriers. In reactions of cis-disubstituted and terminal alkenes using Shi's oxazolidinone catalyst, the asynchronicity of the epoxidation transition state leads to increased steric interaction with the oxazolidinone when a π-conjugating substituent is distal to the oxazolidinone but decreased steric interaction when the π-conjugating substituent is proximal to the oxazolidinone. Overall, the asynchronicity of the transition state must be considered carefully to understand the enantioselectivity

    Mixed Matrix Membranes for Natural Gas Upgrading: Current Status and Opportunities

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    In the past few decades, natural gas has attracted worldwide attention as one of the most desired energy sources owing to its more efficient and cleaner combustion process compared to that of coal and crude oil. Due to the presence of impurities, raw natural gas needs to be upgraded to meet the pipeline specifications. Membrane-based separation is a promising alternative to conventional processes such as cryogenic distillation and pressure swing adsorption. Among the existing membranes for natural gas upgrading, polymeric membranes and inorganic membranes have been extensively explored, but each type has its own pros and cons. The development of mixed matrix membranes (MMMs) by incorporating organic/inorganic fillers into the polymer matrix provides a good strategy to combine the merits of each material and fabricate novel membranes with superior gas separation performance. In this review, we first discuss the recent advances in MMMs showing potentials in natural gas upgrading. Special attention is paid to a detailed evaluation on the polymer and filler choices for acidic gas removal. After that, we analyze factors that influence the membrane separation performance and summarize effective strategies reported in the open literature for the fabrication of high-performance MMMs. Finally, a perspective on future research directions in this field is presented

    Isolation of polyphenol compounds from olive waste and inhibition of their derivatives for <i>α</i>-glucosidase and <i>α</i>-amylase

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    Olive waste was used as a sustainable resource because it contained a variety of valuable compounds. The polyphenols active fraction from enrichment by microporous resin and extraction with ethyl acetate were analysed by different chromatographic methods. A total of 14 polyphenolic compounds were isolated and identified by structure elucidation. Based on the above obtained compounds, tyrosol was selected as a characteristic polyphenol and participated in transesterification reaction to synthesise β-ketoester using Yb(OTf)3. Then the Biginelli reaction with benzaldehyde, urea and ketoester (1:1.2:1.2) was performed at 90 °C for 3.0 h under the acidic condition. In addition, the β-ketoester prepared using tyrosol with benzyl had a greater inhibitory effect on α-glucosidase and α-amylase, and the inhibition of enzyme activity for 3, 4-dihydropyrimidinone derivatives prepared using abovementioned β-ketoester was improved significantly. Meanwhile, fluorine-containing dihydropyrimidinone derivatives were considerable inhibitors for both enzymes.</p

    Effects of bone marrow mesenchymal stem cells on ovarian and testicular function in aging Sprague-Dawley rats induced by D-galactose

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    To investigate the effect of bone marrow mesenchymal stem cells (MSCs) on ovarian and testicular function of aging Sprague-Dawley (SD) rats induced by D-galactose (D-gal) and try to clarify the underlying functional mechanism. Adherent culture was used to isolate and purify rat MSCs. The status, proliferation and differentiation of MSCs were detected by hematoxylin-eosin staining, MTT, colony formation, flow cytometry and directional differentiation. The aging rat model was established by subcutaneous injection of D-gal, and the homing of MSCs was detected by fluorescence microscope after infusion of GFP-labeled MSCs through caudal vein. ELISA was used to detect the content of sex hormone in serum, and HE staining was used to observe the structure and morphology of testis and ovary. The isolated and purified MSCs were in good condition, and most of the cells were in G1 phase, which had strong abilities of cell proliferation, colony formation and differentiation. After GFP-labeled MSCs were infused, MSCs could be homed into the testis and ovary of rats. MSCs infusion could significantly improve the morphology of testis and ovary, increase the contents of P and E2 while decrease the contents of LH and FSH in female rats, and increase the content of testosterone in male rats (P < 0.01). It also increased the activity of superoxide dismutase (SOD) in serum of ovary and testis and significantly decreased the content of malondialdehyde (MDA). MSCs affected the content of MDA and the activity of SOD by reducing the expression of cyclin-dependent kinase inhibitor 2A (p16) and increasing proliferating cell nuclear antigen (PCNA), consequently improving the aging and injury of reproductive organs.</p

    DataSheet_1_Causal effects of non-alcoholic fatty liver disease on osteoporosis: a Mendelian randomization study.zip

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    BackgroundOsteoporosis (OP) is a systemic skeletal disease characterized by compromised bone strength leading to an increased risk of fracture. There is an ongoing debate on whether non-alcoholic fatty liver disease (NAFLD) is an active contributor or an innocent bystander in the pathogenesis of OP. The aim of this study was to assess the causal association between NAFLD and OP.MethodsWe performed two‐sample Mendelian randomization (MR) analyses to investigate the causal association between genetically predicted NAFLD [i.e., imaging‐based liver fat content (LFC), chronically elevated serum alanine aminotransferase (cALT) and biopsy-confirmed NAFLD] and risk of OP. The inverse variant weighted method was performed as main analysis to obtain the causal estimates.ResultsImaging-based LFC and biopsy-confirmed NAFLD demonstrated a suggestive causal association with OP ([odds ratio (OR): 1.003, 95% CI: 1.001-1.004, P ConclusionThe two‐sample MR analyses suggest a causal association between genetically predicted NAFLD and OP.</p

    Associations between the frequency of foods intake and metabolic syndrome prevalence in women (n = 18559).

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    Associations between the frequency of foods intake and metabolic syndrome prevalence in women (n = 18559).</p

    Modeling Dynamics of Colloidal Fouling of RO/NF Membranes with A Novel Collision-Attachment Approach

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    We report a novel collision-attachment approach for modeling the dynamics of colloidal fouling. The model treats fouling as a two-step process: colloidal particles colliding with a membrane surface followed by their attachment onto the surface. An attachment coefficient is adopted to describe the probability of successful foulant attachment for any given collision event, the value of which can be determined by the classical Boltzmann distribution. Our model shows excellent agreement with experimental data in terms of both the kinetics of flux decline and foulant mass deposition. Modeling results reveal the critical roles of water flux and energy barrier in governing colloidal fouling. Greater water flux or lower energy barrier can lead to a collision-controlled condition, where severe fouling occurs and nearly all collision events lead to successful foulant attachment. On the contrary, fouling is increasingly controlled by the probability of successful attachment at lower water flux and/or greater energy barrier. Our model provides deep insights into the various mechanisms governing the dynamics of colloidal fouling (i.e., concentration polarization, collision, and attachment) and the self-limiting fouling behavior under constant-pressure mode

    The metabolic syndrome prevalence and its risk factors according to sex (n = 98042).

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    <p>The metabolic syndrome prevalence and its risk factors according to sex (n = 98042).</p
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