5 research outputs found

    Mechanically Robust Fluorinated Graphene/Poly(<i>p</i>‑Phenylene Benzobisoxazole) Nanofiber Films with Low Dielectric Constant and Enhanced Thermal Conductivity: Implications for Thermal Management Applications

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    Low-dielectric materials have found broad applications in microelectronics but are limited by poor mechanical properties and thermal conductivity. In this study, a class of nanocomposite films based on fluorinated graphene (FG) was developed by replacing the traditional polymer matrix with a 3D interconnected poly(p-phenylene benzobisoxazole) (PBO) nanofiber network. The FG nanosheets are uniformly distributed in the porous network of PBO nanofibers (PBONF) and stacked orderly to form a nacre-like layered structure while paving effective thermal conduction paths. Ultimately, the strong interfacial bonding and efficient synergy between FG and PBONF endow the composite films with unparalleled tensile properties (strength and modulus up to 295.4 MPa and 7.79 GPa, respectively) and folding endurance (no drop in tensile properties after 1000 folds), ultralow dielectric constant (as low as 1.71), and excellent thermal conductivity (12.13 W m–1 K–1). In addition, these FG/PBONF composite films also exhibit an ultrahigh thermal stability (5% weight loss temperature higher than 540 °C), which makes them promising for the heat dissipation of high-power electronic devices in extreme environments

    Crystallization and Rheology of Poly(ethylene oxide) in Imidazolium Ionic Liquids

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    Polymer and ionic liquid (IL) mixtures have attracted an increasing amount of attention due to their unique properties and potential applications. The interactions between poly­(ethylene oxide) (PEO) and imidazolium ILs of different cation alkyl lengths and anion structures have been investigated by measuring melting points (<i>T</i><sub>m</sub>), contact angles, and rheological properties. <i>T</i><sub>m</sub> of crystalline PEO dramatically decreased when it was blended with ILs. Similarly, the contact angles of different ILs on a PEO surface proportionally decreased. The interaction energy, as calculated from melting point depression using the Flory equation, increased with the length of imidazolium alkyl cations and the size of anions. The different anionic structures had a more significant influence on the interaction energy than the alkyl chain lengths of cations. These trends accorded with the solubility obtained by high-energy X-ray diffraction and swelling ratio measurements of PEO in different ILs [Asai Macromolecules 2013, 46, 2369−2375] and the solubility of poly­(methyl methacrylate) in different ILs [Ueno Langmuir 2014, 30, 3228−3235]. The rheological behavior of PEO in three different anionic ILs has also been studied to determine the effect of the anions on PEO conformations. The molecular weight dependence of the intrinsic viscosity of PEO in ILs revealed that the solvent quality of ILs (from poor solvents to good solvents) is highly influenced by anionic structures, which was consistent with the results of the melting point depression and contact angle

    Metabonomics Approach To Comparing the Antistress Effects of Four Panax ginseng Components in Rats

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    Different components of Panax ginseng have different properties and medicinal effects. Metabonomics was a prospective approach to analyze the global response of endogenous metabolites to physiological and pathological processes. In this study, an untargeted metabonomics method using GC/TOFMS combined with multivariate statistical techniques was applied to compare entire metabolite differences and the antistress variations among four components of P. ginseng, namely, total ginsenosides (TG), panaxadiol (PD), panaxatriol (PT), and ginseng polysaccharide (PS), in Wistar rats. The results of metabolite analysis showed that numerous urine metabolites involving neurotransmitters, amino acids, organic acids, and gut microbiota metabolites were changed after administration of the four components of P. ginseng, with TG having the least impact on urinary metabolites. The urinary metabolite profiling of these rats exposed to acute combined stress (forced swimming and behavior restriction) demonstrated that the four ginseng components attenuated urine metabolite changes involving gut microbiota metabolites, tricarboxylic acid (TCA) cycle and energy metabolites, and organic acids to different degrees, with TG improving most of the metabolites altered by stress

    Global and Targeted Metabolomics Evidence of the Protective Effect of Chinese Patent Medicine <i>Jinkui Shenqi</i> Pill on Adrenal Insufficiency after Acute Glucocorticoid Withdrawal in Rats

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    Glucocorticoids are commonly used in anti-inflammatory and immunomodulatory therapies, but glucocorticoid withdrawal can result in life-threatening risk of adrenal insufficiency. Chinese patented pharmaceutical product <i>Jinkui Shenqi</i> pill (JKSQ) has potent efficacy on clinical adrenal insufficiency resulting from glucocorticoid withdrawal. However, the underlying molecular mechanism remains unclear. We used an animal model to study JKSQ-induced metabolic changes under adrenal insufficiency and healthy conditions. Sprague–Dawley rats were treated with hydrocortisone for 7 days with or without 15 days of JKSQ pretreatment. Sera were collected after 72 h hydrocortisone withdrawal and used for global and free fatty acids (FFAs)-targeted metabolomics analyses using gas chromatography/time-of-flight mass spectrometry and ultraperformance liquid chromatography/quadruple time-of-flight mass spectrometry. Rats without hydrocortisone treatment were used as controls. JKSQ pretreatment normalized the significant changes of 13 serum metabolites in hydrocortisone-withdrawal rats, involving carbohydrates, lipids, and amino acids. The most prominent effect of JKSQ was on the changes of FFAs and some [product FFA]/[precursor FFA] ratios, which represent estimated desaturase and elongase activities. The opposite metabolic responses of JKSQ in adrenal insufficiency rats and normal rats highlighted the “<i>Bian Zheng Lun Zhi</i>” (treatment based on ZHENG differentiation) guideline of TCM and suggested that altered fatty acid metabolism was associated with adrenal insufficiency after glucocorticoid withdrawal and the protective effects of JKSQ

    Strategy for an Association Study of the Intestinal Microbiome and Brain Metabolome Across the Lifespan of Rats

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    There is increased appreciation for the diverse roles of the microbiome-gut-brain axis on mammalian growth and health throughout the lifespan. Numerous studies have demonstrated that the gut microbiome and their metabolites are extensively involved in the communication between brain and gut. Association study of brain metabolome and gut microbiome is an active field offering large amounts of information on the interaction of microbiome, brain and gut but data size and complicated hierarchical relationships were found to be major obstacles to the formation of significant, reproducible conclusions. This study addressed a two-level strategy of brain metabolome and gut microbiome association analysis of male Wistar rats in the process of growth, employing several analytical platforms and various bioinformatics methods. Trajectory analysis showed that the age-related brain metabolome and gut microbiome had similarity in overall alteration patterns. Four high taxonomical level correlated pairs of “metabolite type-bacterial phylum”, including “lipids-Spirochaetes”, “free fatty acids (FFAs)-Firmicutes”, “bile acids (BAs)-Firmicutes”, and “Neurotransmitters-Bacteroidetes”, were screened out based on unit- and multivariant correlation analysis and function analysis. Four groups of specific “metabolite-bacterium” association pairs from within the above high level key pairs were further identified. The key correlation pairs were validated by an independent animal study. This two-level strategy is effective in identifying principal correlations in big data sets obtained from the systematic multiomics study, furthering our understanding on the lifelong connection between brain and gut
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