Synthesis of poly(α-thiophenediyl)benzylidene with high molecular weight and its thermal stability

Summary The synthesis of poly(-thiophenediyl)benzylidene (PTB) with high molecular weight is described. Number-average degrees of polymerization reached about 74. The characterizations of the polymer was investigated by ¹H-NMR, ¹³C-NMR, IR, and UV-VIS spectra. The polymer with well-defined structure and high molecular weight was obtained by polymerization at low temperature and in polar solvent. This polymer was thermally stable and a thermal decomposition took place at 391°C under nitrogen and at 370°C under air. The glass transformation temperature was 117°C and this PTB was nonfusible.     

Segmented conjugated polymer based on poly(α-thiophenediyl)benzylidine

Summary Segmented polymers with random sequences of conjugated and non-conjugated blocks are produced by partial dehydrogenation of poly(-thiophenediyl)benzylidene. The fraction of conjugated block was controlled by the elimination time. The polymers gave photoluminescence. Absorption coefficients of the polymers increased with the rate of dehydrogenation, and the highest fluorescence intensity were achieved around 9 % conjugation conversion. The polymers were characterized by ¹H- and ¹³C-n.m.r. and infrared spectra, and were soluble in common organic solvents, which suggests a good processability.     

Cooperative effect of crystallization temperature and NaF addition in the formation process and hydrothermal stability of MCM-48 mesoporous molecular sieve

The hydrothermal stability of MCM-48 was conveniently and effectively improved by increasing the crystallization temperature and directly adding NaF to the synthesis gel. The crystallization temperature varied from 373 K to 403 K. The influences of NaF addition, crystallization temperature and crystallization time on the formation process and hydrothermal stability of MCM-48 were systematically studied here to solve the problem of poor reproducibility. Results from XRD patterns indicated that the crystallization temperature and crystallization time were very critical factors for the improvement of the hydrothermal stability besides NaF addition. The formation process of MCM-48 was significantly accelerated and the pore structure ordering was also greatly improved by increasing the crystallization temperature and F⁻/Si ratio. A high hydrothermally stable MCM-48 mesoporous molecular sieve was obtained after being crystallized at 393 K for 36 h in the presence of NaF, which endured the hydrothermal treatment in boiling water at least for 4 days. However, only an amorphous product was obtained when the crystallization temperature was further increased to 403 K. Results from Si MAS NMR, N₂ adsorption isotherms, TEM, Raman spectra and XRD patterns manifested that the improved stability of MCM-48 was attributed to the high silicates condensation degree and the excellent pore structure ordering. The possible reason for the successful formation of hydrothermally stable MCM-48 sample by controlling the crystallization temperature, time and F⁻/Si ratio was explained here.     

Monitoring behaviour of catabolic genes and change of microbial community structures in seawater microcosms during aromatic compound degradation

The behaviour of microbial populations responsible for degradation of the aromatic compounds, phenol, benzoate, and salicylate, and changes of microbial community structures in seawater microcosms were analysed quantitatively and qualitatively using MPN–PCR and PCR–DGGE. The purpose of the study was to investigate the ecology of the entire microbial community during bioremediation. Bacterial populations possessing catechol 1,2-dioxygenase (C12O) DNA were evidently the primary degraders of phenol and benzoate, but others possessing catechol 2,3-dioxygenase (C23O) DNA increased to enhance substrate degradation under high-load conditions when the substrates were present for long periods. However, salicylate degradation was evidently facilitated by specific bacterial populations possessing C23O DNA. PCR–DGGE analyses suggested that bacterial populations already relatively dominant in the original microcosm contributed to phenol degradation. Bacteria composing a minor fraction of the original population apparently increased and contributed to benzoate degradation. Bacterial populations possessing C23O DNA were responsible for salicylate degradation, however, and different degrading bacteria were evidently selected for, depending on the initial salicylate concentration. Microbial community structure tended to be simplified by aromatic compound degradation. Thus, microbial monitoring can elucidate the behaviour of bacterial populations responsible for aromatic compound degradation and be used to assess the effects of bioremediation on intact microbial ecosystems.     

Zeta potential of alumina powders with different crystalline phases in simulated body fluids

The zeta potential of alumina (Al₂O₃) powder with different crystalline phases, prepared by heat treatment of boehmite, was measured in simulated body fluids in order to discuss the mechanism on in vivo formation of a calcium and phosphorus (CaP)-rich layer on bone cement containing δ-Al₂O₃-based bead powder. γ, δ, and θ-Al₂O₃ powders were obtained by heat treatment of boehmite powder at 600 °C, 900 °C, and 1025 °C, respectively. It was found that δ-Al₂O₃ gave a negative zeta potential in an acidic simulated body fluid, whereas γ-Al₂O₃ and θ-Al₂O₃ gave a positive potentials. During the bone fracture healing process, acidic conditions are maintained at the site of fracture for several days. Consequently, it is speculated that the negative surface potential of δ-Al₂O₃ in an acidic body fluid, similar to the fracture site, might be responsible for the in vivo formation of the CaP-rich layer on the overlying bone cement, given that the negatively charged surface of δ-Al₂O₃ would attract calcium ions from the surrounding body fluid, thereby facilitating the formation of the CaP-rich layer.     

Enhancing the Humidity Sensitivity of Ga2O3/SnO2 Core/Shell Microribbon by Applying Mechanical Strain and Its Application as a Flexible Strain Sensor

The humidity sensitivity of a single β‐Ga₂O₃/amorphous SnO₂ core/shell microribbon on a flexible substrate is enhanced by the application of tensile strain and increases linearly with the strain. The strain‐induced enhancement originates from the increase in the effective surface area where water molecules are adsorbed. This strain dependence of humidity sensitivity can be used to monitor the external strain. The strain sensing of the microribbon device under various amounts of mechanical loading shows excellent reliability and reproducibility with a gauge factor of ?41. The flexible device has high potential to detect both humidity and strain at room temperature. These findings and the mechanism involved are expected to pave the way for new flexible strain and multifunctional sensors.     

Processing of Al/SiC composites in continuous solid–liquid co-existent state by SPS and their thermal properties

Silicon carbide (SiC)-particle-dispersed-aluminum (Al) matrix composites were fabricated in a unique fabrication method, where the powder mixture of SiC, pure Al and Al–5mass% Si alloy was uniquely designed to form continuous solid–liquid co-existent state during spark plasma sintering (SPS) process. Composites fabricated in such a way can be well consolidated by heating during SPS processing in a temperature range between 798 K and 876 K for a heating duration of 1.56 ks. Microstructures of the composites thus fabricated were examined by scanning electron microscopy and no reaction was detected at the interface between the SiC particle and the Al matrix. The relative packing density of the Al–matrix composite containing SiC was higher than 99% in a volume fraction range of SiC between 40% and 55%. Thermal conductivity of the composite increased with increasing the SiC content in the composite at a SiC fraction range between 40 vol.% and 50 vol.%. The highest thermal conductivity was obtained for Al–50 vol.% SiC composite and reached 252 W/mK. The coefficient of thermal expansion of the composites falls in the upper line of Kerner’s model, indicating strong bonding between the SiC particle and the Al matrix in the composite.     

Improvement of thermal stability of nitrogen doped titania photocatalyst by addition of surfactants during solvothermal treatment

The TiO_2−x N _y nanocrystals with beige color were prepared by homogeneous precipitation-solvothermal process in TiCl₃-hexamethyleneamine-alcohol solutions with the addition of various surfactants, such as sodium dodecylbenzenesulfonate (SDBS), n-hexadecylamine (HAD), and n-hexadecyltrimethylammonium chloride (HTAC) at 190 °C for 10 h. The phase composition, crystallinity, microstructure, specific surface area, nitrogen doped amount, and photocatalytic activity of titania powders greatly changed depending on pH value and other reaction conditions. The TiO_2−x N _y powders prepared by solvothermal treatment with surfactant additives followed by calcination in air at 400 °C showed smaller particle size, larger BET specific surface area and higher photocatalytic activity than those without surfactant. The TiO_2−x N _y powders showed excellent visible-light absorption, thermal stability and photocatalytic activity for nitrogen monoxide destruction under irradiation of both visible-light and UV-light irradiation. About 40% and 60% nitrogen monoxide could be continuously removed with the residence time of 1.9 min by the TiO_2−x N _y photocatalyst under irradiation of visible-light (λ > 510 nm) and UV-light (λ > 290 nm), respectively.     

Analysis of locality of early-stage maturation in confluent state of human retinal pigment epithelial cells

Retinal pigment epithelial (RPE) cells were cultured on the laminin-coated and plain surfaces. The measurement of local nucleus density in non-stratified region, which correlated with formation of tight junction, is the indicator of the maturation, and the parameters can be applied to the evaluation of the early-stage maturation of RPE cells in culture.