Synthesis and characterization of 9,9‐bis(4‐hydroxyphenyl and 4‐aminophenyl)dibenzofluorenes: Novel fluorene‐based monomers

Two novel 9,9‐difunctionalized fluorene‐type monomers, 9,9‐bis(4‐hydroxyphenyl‐ and 4‐aminophenyl)‐2,3:6,7‐dibenzofluorenes, are synthesized by the reaction of dibenzenzofluorenone with phenol and aniline. These monomers are used for the preparation of polyester and polyimide as the typical polymers to evaluate the property change such as thermal stability caused by the benzene rings fused to the fluorene skeleton with keeping good solubility, in comparison with the polymers derived from simple fluorenone. In fact, these two new polymers have the fairly enhanced thermal stability and refractive index value along with satisfactory solubility in organic solvents, enough to emphasize the fusion effect. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2602–2605     

Optimization of high-performance liquid chromatographic parameters for the determination of capsaicinoid compounds using the simplex method.

A high-performance liquid chromatographic method was developed for the analysis of capsaicinoid compounds, the pungent principles of capsicum fruits. A sequential simplex method was applied to optimize the chromatographic response function used to assess the quality of separation by varying the chromatographic parameters. The separation was achieved in 11 min using a C-8 column of 15-cm length and 4.6 mm diameter using a UV detector. A flow rate of 1.15 ml min(-1) at a column temperature of 43.5 degrees C using 63.7% methanol in water gave the most efficient separation. The method was found to be suitable for the determination of the major capsaicinoid compounds in the capsicum samples.     

Quantitative analysis of a complex metal carbide formed during furnace cooling of cast duplex stainless steel using EELS and EDS in the TEM

In this work, a method to determine the atomic ratio of Mo and C within complex metal carbides using EELS in the TEM has been developed. The method is based on the determination of k-factors for given experimental conditions from the EEL spectra of Mo₂C and MoO₃ standards, which had been independently checked by XRD and EPMA. Factors affecting the k_Mo/C value of the Mo₂C standard were also investigated and the value was shown to be insensitive to background subtraction window width but sensitive to prolonged irradiation and specimen thicknesses above a critical value. The method and k-factor obtained from the Mo₂C standard was applied to spectra from a complex metal carbide precipitate formed during furnace cooling of a cast duplex stainless steel. Using EELS and EDS in the TEM, the composition was estimated to be (Cr_1.52Fe_2.33Mo_1.25Ni_0.17Si_0.46)C, which is close to M₆C stoichiometry, and the structure was confirmed by electron diffraction.     

New alkylamide from the stems of Zanthoxylum nitidum

A new alkylamide, named (2E,6E,8E)-N-(2-methylpropyl)-10-oxo-2,6,8-decatrienamide (1), together with 22 known compounds (2–23), were isolated from the stems of Zanthoxylum nitidum. Their structures were elucidated by spectroscopic methods, including 1D and 2D NMR spectroscopy. The isolated compounds exhibited slightly antioxidant activities through DPPH and ABTS radical scavenging assays but showed no antibacterial activity against Streptococcus mutans ATCC2517, a dental caries causing bacteria.     

Metallosurfactants: interfaces and micelles

Incorporating a metal cation as an integral component of the headgroup of a surfactant--a metallosurfactant--offers a route to concentrate these ions and their associated functionality at interfaces. To reduce the lability of the metal, various chelating or macrocyclic ligands may be employed leading to a family of homologous series of related metallosurfactants with a structural diversity that is arguably broader than is inherently possible with conventional surfactants. This review discusses the small number of key papers that are quantifying the physico-chemical properties of metallosurfactants and highlights their "classical" as well as "non-classical" surfactant behaviour, providing an insight into the structure of micelles and films formed from these novel materials.     

Synthesis of fluorene‐based high performance polymers. I. Poly(arylene thioether)s with excellent solubility and high refractive index

Several poly(arylene thioether)s ( PTEs ) containing a fluorene moiety were synthesized by the polycondensation of masked dithiols such as 9,9‐bis(4‐(N,N‐dimethyl‐S‐carbamoyl)phenyl)fluorene and various difluoroarenes. All PTEs were obtained in quantitative yields. The PTEs showed good thermal stability: the 10% weight loss temperature was over 480 °C under both nitrogen and air atmosphere by TGA, and glass temperature was within a range of 204–275 °C by DSC. Most PTEs exhibited remarkably high refractive index values in a range of 1.66–1.72 at 589 nm, whereas they had a very low degree of birefringence properties. Furthermore, the PTEs showed high solubility in ordinary organic solvents such as chloroform, N‐methylpyrrolidone, and tetrahydrofuran. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3073–3082, 2007     

Separation of some transition-metal ions on silica-immobilized 2-pyridinecarboxaldehyde phenylhydrazone

A metal-ion extractant, prepared by chemical binding of 2-pyridinecarboxaldehyde phenylhydrazone on a silica support, is described and shown to be effective for use in separation and determination of trace amounts of iron, cobalt, nickel, and copper. Metal-ion sorption conforms to the Langmuir isotherm. The relative orders of the Langmuir constants K and the column retention-capacity factors k' for the four transition-metal ions are the same as the natural order of the stabilities predicted for their metal chelates: Fe(II) < Co(II) < Ni(II) < Cu(II).     

Anti-Influenza with Green Tea Catechins: A Systematic Review and Meta-Analysis

Influenza is one of the most serious respiratory viral infections worldwide. Although several studies have reported that green tea catechins (GTCs) might prevent influenza virus infection, this remains controversial. We performed a systematic review and meta-analysis of eight studies with 5048 participants that examined the effect of GTC administration on influenza prevention. In a random-effects meta-analysis of five RCTs, 884 participants treated with GTCs showed statistically significant effects on the prevention of influenza infection compared to the control group (risk ratio (RR) 0.67, 95% CIs 0.51–0.89, p = 0.005) without evidence of heterogeneity (I² = 0%, p = 0.629). Similarly, in three cohort studies with 2223 participants treated with GTCs, there were also statistically significant effects (RR 0.52, 95% CIs 0.35–0.77, p = 0.001) with very low evidence of heterogeneity (I² = 3%, p = 0.358). Additionally, the overall effect in the subgroup analysis of gargling and orally ingested items (taking capsules and drinking) showed a pooled RR of 0.62 (95% CIs 0.49–0.77, p = 0.003) without heterogeneity (I² = 0%, p = 0.554). There were no obvious publication biases (Egger’s test (p = 0.138) and Begg’s test (p = 0.103)). Our analysis suggests that green tea consumption is effective in the prophylaxis of influenza infections. To confirm the findings before implementation, longitudinal clinical trials with specific doses of green tea consumption are warranted.     

Non-isothermal kinetics of the thermal decomposition of sodium oxalate Na<Subscript>2</Subscript>C<Subscript>2</Subscript>O<Subscript>4</Subscript>

The thermal transformation of Na₂C₂O₄ was studied in N₂ atmosphere using thermo gravimetric (TG) analysis and differential thermal analysis (DTA). Na₂C₂O₄ and its decomposed product were characterized using a scanning electron microscope (SEM) and the X-ray diffraction technique (XRD). The non-isothermal kinetic of the decomposition was studied by the mean of Ozawa and Kissinger–Akahira–Sunose (KAS) methods. The activation energies (E _α) of Na₂C₂O₄ decomposition were found to be consistent. Decreasing E _α at increased decomposition temperature indicated the multi-step nature of the process. The possible conversion function estimated through the Liqing–Donghua method was ‘cylindrical symmetry (R₂ or F_1/2)’ of the phase boundary mechanism. Thermodynamic functions (ΔH*, ΔG* and ΔS*), calculated by the Activated complex theory and kinetic parameters, indicated that the decomposition step is a high energy pathway and revealed a very hard mechanism.