The intramolecular capture of thermally generated merocyanine dyes derived from naphthopyrans: Photochromism of 5-(diarylhydroxymethyl)-2H-naphtho[1,2-b]pyrans

A series of 2H-naphtho[1,2-b]pyrans bearing a diarylmethanol unit at C-5 have been synthesised by the addition of an excess of an aryllithium reagent to alkyl 2H-naphtho[1,2-b]pyran-5-carboxylate precursors. These naphthopyrans show photochromism when exposed to ultraviolet irradiation and also generate intense colours at low pH through triarylmethine cation generation. However, photochromism of the triarylmethine cation derived from the naphthopyran unit could not be detected. An irreversible cascade process initiated by the thermally-induced ring-opening of the diarylmethanol substituted 2H-naphtho[1,2-b]pyrans in the presence of an acid catalyst afforded novel benzopentalenonaphthalenone dyes.     

Ab initio modelling of basal plane oxidation of graphenes and implications for modelling char combustion

Ab initio calculations have been performed to determine the energetics of oxygen atoms adsorbed onto graphene planes and the possible reaction path extracting carbon atoms in the form of carbon monoxide. From the energetics it is confirmed that this reaction path will not significantly contribute to the gasification of well ordered carbonaceous chars. Modelling results which explore this limit are presented.     

Stepwise-Graded Si3N4–SiC Ceramics with Improved Wear Properties

The processing of stepwise graded Si₃N₄/SiC ceramics by pressureless co-sintering is described. Here, SiC (high elastic modulus, high thermal expansion coefficient) forms the substrate and Si₃N₄ (low elastic modulus, low thermal expansion coefficient) forms the top contact surface, with a stepwise gradient in composition existing between the two over a depth of ∼1.7 mm. The resulting Si₃N₄ contact surface is fine-grained and dense, and it contains only 2 vol% yttrium aluminum garnet (YAG) additive. This graded ceramic shows resistance to cone-crack formation under Hertzian indentation, which is attributed to a combined effect of the elastic-modulus gradient and the compressive thermal-expansion-mismatch residual stress present at the contact surface. The presence of the residual stress is corroborated and quantified using Vickers indentation tests. The graded ceramic also possesses wear properties that are significantly improved compared with dense, monolithic Si₃N₄ containing 2 vol% YAG additive. The improved wear resistance is attributed solely to the large compressive stress present at the contact surface. A modification of the simple wear model by Lawn and co-workers is used to rationalize the wear results. Results from this work clearly show that the introduction of surface compressive residual stresses can significantly improve the wear resistance of polycrystalline ceramics, which may have important implications for the design of contact-damage-resistant ceramics.     

Size and morphology-controlled synthesis of mesoporous hydroxyapatite nanocrystals by microwave-assisted hydrothermal method

We report the rapid microwave-assisted hydrothermal synthesis of mesoporous hydroxyapatite (HAp) nanocrystals with controlled size, morphology, and surface area using various organic modifiers as regulators. The products were analyzed for their crystalline nature, phase purity, morphology, particle size and pore size distribution. Results indicated that ascorbic acid, cetyltrimethyl ammonium bromide (CTAB) and polyvinylpyrrolidone (PVP) play an important role to obtain needle like, rod like and fiber like mesoporous HAp nanocrystals with different specific surface area by controlling growth habit of HAp along c-axis. In addition, the prepared samples were B-type carbonated HAp similar to bone minerals. Therefore, the present approach can be a promising way to obtain precursor for making tissue engineering scaffolds, drug/protein delivery carriers and bone fillers with tunable characteristics.     

Investigation on La3+ and Dy3+ co-doped ceria ceramics with an optimized average atomic number of dopants for electrolytes in IT-SOFCs

In the present study, we investigate the fundamental properties of CeO₂ by selecting La³⁺ (57), and Dy³⁺ (66) as dopants with optimized average atomic number of 61.5, which lies in between Pm³⁺ (62) and Sm³⁺ (62) in accordance with the criteria for optimum doping. A system of co-doped ceria ceramics Ce_1–x–yLa_xDy_yO_2-δ ((x, y) = (0.00, 0.00), (0.025, 0.025), (0.05, 0.05), (0.075, 0.075), (0.10, 0.10), (0.00, 0.20) and (0.20, 0.00)) as electrolytes for intermediate temperature solid oxide fuel cells were successfully prepared by a well-known sol-gel auto-combustion route. In order to obtain dense samples, the prepared pellets were sintered in air at 1300 °C for 4 h using conventional furnace and relative densities of all the samples were found to be higher than 95%. Single phase cubic structure, microstructural density and elemental composition analysis of all the samples were studied by powder X-ray diffraction, scanning electron microscope and energy dispersive spectroscopy techniques, respectively. Raman spectroscopy analysis confirmed the formation of concentrated O^2-–vacancies in the co-doped ceria system. Impedance spectroscopy measurements revealed the high value of total ionic conductivity and low activation energy for the composition Ce_0.85La_0.075Dy_0.075O_2?δ i.e., 2.08 × 10^–2 S cm^–1 and 0.58 eV, respectively. Linear thermal expansion analyses of all the samples revealed the matched thermal expansion coefficients. Finally, these results recommend that the Ce_0.85La_0.075Dy_0.075O_2?δ sample can be useful as a solid electrolyte in IT-SOFC applications.     

Electrical,mechanical, structural,and thermal behaviors of polymeric gel electrolyte membranes of poly(vinylidene fluoride‐co‐hexafluoropropylene) with the ionic liquid 1‐butyl‐3‐methylimidazolium tetrafluoroborate plus lithium tetrafluoroborate

Polymeric gel electrolyte membranes based on the polymer poly(vinylidene fluoride‐co‐hexafluoropropylene) [P(VdF–HFP)] with different weight percentages of the ionic liquid (IL) 1‐butyl‐3‐methylimidazolium tetrafluoroborate plus 0.3M lithium tetrafluoroborate (LiBF₄) salt were prepared and characterized by scanning electron microscopy, X‐ray diffraction, differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared (FTIR) spectroscopy, complex impedance spectroscopy, pulse echo techniques, and Vickers hardness (H) testing. After the incorporation of the IL plus the salt solution in the P(VdF–HFP) polymer, the melting temperature, glass‐transition temperature (T_g), degree of crystallinity, thermal stability, elastic modulus (E), and hardness (H) gradually decreased with increasing content of the IL–salt solution as a result of complexation between the P(VdF–HFP) and IL. This was confirmed by FTIR spectroscopy. A part of the IL and LiBF₄ were found to remain uncomplexed as well. The ionic conductivity (σ) of the polymeric gel membranes was found to increase with increasing concentration of the IL–salt solution. The temperature‐dependent σs of these polymeric gel membranes followed an Arrhenius‐type thermally activated behavior. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41456.     

Heat Killed Lactobacillus reuteri GMNL-263 Reduces Fibrosis Effects on the Liver and Heart in High Fat Diet-Hamsters via TGF-β Suppression

Obesity is one of the major risk factors for nonalcoholic fatty liver disease (NAFLD), and NAFLD is highly associated with an increased risk of cardiovascular disease (CVD). Scholars have suggested that certain probiotics may significantly impact cardiovascular health, particularly certain Lactobacillus species, such as Lactobacillus reuteri GMNL-263 (Lr263) probiotics, which have been shown to reduce obesity and arteriosclerosis in vivo. In the present study, we examined the potential of heat-killed bacteria to attenuate high fat diet (HFD)-induced hepatic and cardiac damages and the possible underlying mechanism of the positive effects of heat-killed Lr263 oral supplements. Heat-killed Lr263 treatments (625 and 3125 mg/kg-hamster/day) were provided as a daily supplement by oral gavage to HFD-fed hamsters for eight weeks. The results show that heat-killed Lr263 treatments reduce fatty liver syndrome. Moreover, heat-killed Lactobacillus reuteri GMNL-263 supplementation in HFD hamsters also reduced fibrosis in the liver and heart by reducing transforming growth factor β (TGF-β) expression levels. In conclusion, heat-killed Lr263 can reduce lipid metabolic stress in HFD hamsters and decrease the risk of fatty liver and cardiovascular disease.     

Synthesis of Chlorinated and Non-chlorinated Polyols from Model Cross-Metathesis Modified Triacylglycerols

Three pure triacylglycerols (TAG) containing decenoic acid (D), and stearic acid (S), were hydroxylated into chlorinated and non-chlorinated polyols and studied in detail. D is a fatty moiety that can result from the cross metathesis of small olefins with common vegetable oils such as soybean oil. A fundamental understanding relating chemical composition and derived structure, particularly the number and position of the hydroxyl groups, to physical properties was established allowing us to add some perspective to the growing body of knowledge on industrially relevant polyol and polyurethane systems produced with metathesis-modified TAG (MTAG). The hydroxyl value, crystallization and melting behaviors, thermal degradation behavior of the polyols were directly related to their peculiar shortened and primary functionality inherited from the parent MTAG. The effect of regiochemistry on the physical properties of the polyols was investigated with the chromatography fractions of the trichlorinated polyol of propane-1,2,3-triyl tris(dec-9-enoate), giving an unhindered insight into the role of short and terminal functionality of MTAG polyols that will help select the optimal isomer composition for designer polyurethane materials.     

Parameters Influencing Third‐Phase Formation in the Extraction of Th(NO3)4 by some Trialkyl Phosphates

Third‐phase formation in the extraction of Th(IV) by trialkyl phosphates (TalP) such as tri‐n‐butyl phosphate (TBP), tri‐iso‐butyl phosphate (TiBP), tri‐sec‐butyl phosphate (TsBP), tri‐n‐amyl phosphate (TAP), tri‐2‐methylbutyl phosphate (T2MBP), tri‐iso‐amyl phosphate (TiAP), tri‐sec‐amyl phosphate (TsAP), and tri‐cyclo‐amyl phosphate (TcyAP) has been investigated under various conditions. Formation of a third phase in the extraction of Th(IV) by TBP/n‐dodecane as a function of TBP concentration at 303 K was studied. Measurements were also carried out on the extraction of Th(IV) from its solution with near‐zero free acidity by various phosphate/diluent binary solutions (1.1 M) as a function of temperature. Third‐phase formation in the extraction of Th(IV) by 1.1 M TalP in various diluents from nitric acid media has also been studied as a function of equilibrium aqueous‐phase acidity at 303 K. Empirical equations to predict limiting organic concentration with respect to various parameters for third‐phase formation in the extraction of Th(IV) by TBP and TAP from nitric acid media have been derived. Some of the above phosphates have been investigated for the distribution of Th(NO₃)₄ between the “diluent‐rich phase” (DP) and “third‐phase” (TP) in the extraction of Th(IV) by 1.1 M TalP in various diluents from its saturated solution with near‐zero free acidity at 303 K. Results of the above studies are presented in this paper. Based on these studies, the effects of extractant concentration, the temperature, the nature of the diluent, the equilibrium aqueous‐phase acidity, and the structure of the extractant on third‐phase formation behavior of trialkyl phosphates are described in this paper.