Aurones and Flavonols from Coreopsis lanceolata L. Flowers and Their Anti-Oxidant,Pro-Inflammatory Inhibition Effects,and Recovery Effects on Alloxan-Induced Pancreatic Islets in Zebrafish

(1) Background: Many flavonoids have been reported to exhibit pharmacological activity; a preparatory study confirmed that Coreopsis lanceolata flowers (CLFs) contained high flavonoid structure content; (2) Methods: CLFs were extracted in aqueous methanol (MeOH:H₂O = 4:1) and fractionated into acetic ester (EtOAc), normal butanol (n-BuOH), and H₂O fractions. Repeated column chromatographies for two fractions led to the isolation of two aurones and two flavonols; (3) Results: Four flavonoids were identified based on a variety of spectroscopic data analyses to be leptosidin (1), leptosin (2), isoquercetin (3), and astragalin (4), respectively. This is the first report for isolation of 2–4 from CLFs. High-performance liquid chromatography (HPLC) analysis determined the content levels of compounds 1–4 in the MeOH extract to be 2.8 ± 0.3 mg/g (1), 17.9 ± 0.9 mg/g (2), 3.0 ± 0.2 mg/g (3), and 10.9 ± 0.9 mg/g (4), respectively. All isolated compounds showed radical scavenging activities and recovery activities in Caco-2, RAW264.7, PC-12, and HepG2 cells against reactive oxygen species. MeOH extract, EtOAc fraction, and 1–3 suppressed NO formation in LPS-stimulated RAW 264.7 cells and decreased iNOS and COX-2 expression. Furthermore, all compounds recovered the pancreatic islets damaged by alloxan treatment in zebrafish; (4) Conclusions: The outcome proposes 1–4 to serve as components of CLFs in standardizing anti-oxidant, pro-inflammatory inhibition, and potential anti-diabetic agents.     

Application of a kinematic hardening viscoplasticity model with thresholds to the residual stress relaxation

The life analysis of engine components needs to take into account the residual stress relaxation induced by cyclic service loads. The paper recalls a new class of constitutive equations for cyclic viscoplasticity, using a series of kinematic hardening models with thresholds. The equations are introduced within a recently enlarged thermodynamic framework. Some attention is focused to the relations with multisurface approaches and to a specific determination procedure of the model parameters. The new model is applied to the calculation of the near surface residual stress relaxation after shot peening, when the structure is submitted to cyclic service loads. The simulated stabilized residual stresses are in good accordance with experimental results obtained on an N18 disk alloy at 650°C. In comparison, the classical model without threshold predicts the complete vanishing of the residual stresses, which is not satisfactory.     

Synthesis of tailor‐made polyethylene through the control of polymerization conditions using selectively combined metallocene catalysts in a supported system

Tailoring of the molecular weight distribution (MWD) in ethylene polymerization was attempted by selectively combining different types of metallocene catalysts onto a single support. The catalyst produced by supporting Et[Ind]₂ZrCl₂ and Cp₂HfCl₂ onto a single MAO pretreated silica support was able to produce polymers with unimodal or bimodal MWD's. This approach permits the synthesis of polyethylene with different MWD's using the same catalyst as a function of the polymerization conditions. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 331–339, 1999     

Synthesis and characterization of a series of wholly aromatic copolyesters containing 2‐(α‐phenylisopropyl)hydroquinone moiety

Two series of new wholly aromatic thermotropic copolyesters containing the 2‐(α‐phenylisopropyl)hydroquinone (PIHQ) moiety have been synthesized and their basic properties such as glass transition temperature (T_g), melting temperature (T_m), thermal stability, crystallinity, and liquid crystallinity were studied by differential scanning calorimetry (DSC), thermogravimetry (TG), and wide‐angle X‐ray diffractometry (WAXD) and on a polarizing microscope. The first series was prepared from acetylated PIHQ, terephthalic acid (TPA), and 2,6‐naphthalenedicarboxylic acid (NDA), and the second series from acetylated PIHQ, TPA, and 1,1′‐biphenyl‐4,4′‐dicarboxylic acid (BDA). The T_g values (152–168°C) of the two series are not much different, although the values for the first series appear slightly higher. The T_m values (287–378°C) and the degree of crystallinity of the first series are appreciably greater than those of the second series. Such differences can be explained by the geometric structure of NDA and BDA moieties. All of the present polyesters are thermotropic and nematic. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 881–889, 1999     

Details of surface features in aromatic polyamide reverse osmosis membranes characterized by scanning electron and atomic force microscopy

In the present article, some new events on the surface morphology of the aromatic polyamide thin‐film‐composite (TFC) membranes were demonstrated in conjunction with their inherent chemical nature. In addition, the detailed, quantitative understanding of the microscopic surface features was shown to be essential in controlling the water permeability and eventually developing the high performance membranes. The surface roughness and the surface area were mainly affected by the existence or nonexistence of the crosslinking and/or the free amide groups not pertinent to the formation of the hydrogen bonding, which in turn contributed to the water permeability. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1429–1440, 1999     

Nucleic acid analogues: Synthesis and biomimetic reactions

Several nucleic acid analogues as shown in Scheme 1 were synthesized by alternating copolymerization of nucleoside analogues with maleic anhydride or acrylic anhydride. These polymers showed similar physicochemical properties to those of the natural polymers, such as base-pairing and base-stacking. Polymer 3U, for example, formed 1:1 complex with poly(adenylic acid) by base-pairing. Polymer 4A showed 33% of hypochromicity compared with the UV-absorption of adenosine due to the base-stacking. Polymer 5 catalyzed the cleavage of DNA and the hydrolysis of phosphodiester with a rate acceleration of 10³ compared with the uncatalyzed reaction.     

Mechanical spectroscopy study on biodegradable synthetic and biosynthetic aliphatic polyesters

Miscibility behavior and rheological properties with mechanical spectroscopy study of both poly(3-hydroxybutyrate) (PHB)/poly(ethylene oxide) (PEO) and biodegradable synthetic aliphatic polyester (BDP)/linear low density polyethylene (LLDPE) were investigated. Blends of BDP with LLDPE were immiscible, showing two separate T_g values in all compositions; whereas blends of PHB with PEO were miscible, showing a single T_g in the whole range of compositions. However, the shear viscosities of both synthetic and biosynthetic blend systems decrease with increasing shear rate. When a modified Cole-Cole plot of the blend system is further considered, the logG′-logG” plot shows little sensitivity to a variation in both LLDPE composition for synthetic BDP and PEO composition for biosynthetic PHB. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3HB-co-3HV)) random copolymers were also investigated.     

Recent Advances in Aerosol‐Assisted Spray Processes for the Design and Fabrication of Nanostructured Metal Chalcogenides for Sodium‐Ion Batteries

Increasing demand for sodium‐ion batteries (SIBs), one of the most feasible alternatives to lithium ion batteries (LIBs), has resulted because of their high energy density, low cost, and excellent cycling stability. Consequently, the design and fabrication of suitable electrode materials that govern the overall performance of SIBs are important. Aerosol‐assisted spray processes have gained recent prominence as feasible, scalable, and cost‐effective methods for preparing electrode materials. Herein, recent advances in aerosol‐assisted spray processes for the fabrication of nanostructured metal chalcogenides (e.g., metal sulfides, selenides, and tellurides) for SIBs, with a focus on improving the electrochemical performance of metal chalcogenides, are summarized. Finally, the improvements, limitations, and direction of future research into aerosol‐assisted spray processes for the fabrication of various electrode materials are presented.