Investigation on twisting distortion of thin plate stiffened structure under welding

The welding distortion of thin plate was selected as research subject, which causes loss of dimensional control, structural integrity and increases fabrication costs for straightening. To study the characteristic of the welding distortion on thin plate structures, experiments were conducted. The test model was a thin plate stiffened structure and a large twisting distortion was observed. The welding distortion of the same structure was analyzed as a large deformation problem using a thermal elastic plastic FEM and an elastic FEM based on the concept of inherent deformation. The computed results by both methods showed the twisting distortion which is a typical buckling type deformation and the magnitude of this distortion agreed well with the experimental measurement.     

Mechanical Properties of Alumina/Silicon Carbide Whisker Composites

The improvement of mechanical properties of Al₂O₃/SiC whisker composites has been studied with emphasis on the effects of the whisker content and of the hot-pressing temperature. Mechanical properties such as fracture toughness and fracture strength increased with increasing whisker content up to 40 wt%. In the case of the high SiC whisker content of 40 wt%, fracture toughness of the sample hot-pressed at 1900° decreased significantly, in spite of densification, compared with one hot-pressed at 1850°. Fracture toughness strongly depended on the microstructure, especially the distribution of SiC whiskers rather than the grain size of the Al₂O₃ matrix.     

Chemical dehydrofluorination and electrical conductivity of poly(vinylidene fluoride) films

The dehydrofluorination of poly(vinylidene fluoride) (PVDF) powder and films was studied using several kinds of base solution. Especially the reactivity of 1,8-diazabicyclo[5.4.0]-7-undecene (DBU) in ethanol, KOH in 2-propanol and aqueous NaOH solution with tetrabutylammonium bromide was investigated by the change in infrared (IR) and ultraviolet-visible (UV-VI) absorptions of PVDF films. The elimination reactions by DBU or KOH were considered to be accompanied by substitution reaction. The electrical conductivity of dehydrofluorinated PVDF films increased markedly by doping with iodine, and the activation energies of conduction were found to be between 0.4 and 0.5 eV. When a drawn PVDF film was dehydrofluorinated and doped with iodine, anisotropy in conductivity was observed.     

Effect of Surface Treatment on the Selective Photocatalytic Oxidation of Benzyl Alcohol into Benzaldehyde by O2 on TiO2 Under Visible Light

The photocatalytic oxidation of benzyl alcohol into benzaldehyde proceeded with high conversion and selectivity on a TiO₂ photocatalyst by O₂ under visible light irradiation. Surface complex formed by the interaction of benzyl alcohol with the Ti sites and/or surface OH groups of TiO₂ play an important role in the absorption of visible light and unique selective photocatalytic reaction.     

In utero exposure to a low concentration of diesel exhaust affects spontaneous locomotor activity and monoaminergic system in male mice

Background

Epidemiological studies suggest that inhalation of carbonaceous particulate matter from biomass combustion increases susceptibility to bacterial pneumonia. In vitro studies report that phagocytosis of carbon black by alveolar macrophages (AM) impairs killing of Streptococcus pneumoniae. We have previously reported high levels of black carbon in AM from biomass smoke-exposed children and adults. We therefore aimed to use a mouse model to test the hypothesis that high levels of carbon loading of AM in vivo increases susceptibility to pneumococcal pneumonia.

Methods

Female outbred mice were treated with either intranasal phosphate buffered saline (PBS) or ultrafine carbon black (UF-CB in PBS; 500 μg on day 1 and day 4), and then infected with S. pneumoniae strain D39 on day 5. Survival was assessed over 72 h. The effect of UF-CB on AM carbon loading, airway inflammation, and a urinary marker of pulmonary oxidative stress was assessed in uninfected animals.

Results

Instillation of UF-CB in mice resulted a pattern of AM carbon loading similar to that of biomass-smoke exposed humans. In uninfected animals, UF-CB treated animals had increased urinary 8-oxodG (P = 0.055), and an increased airway neutrophil differential count (P < 0.01). All PBS-treated mice died within 72 h after infection with S. pneumoniae, whereas morbidity and mortality after infection was reduced in UF-CB treated animals (median survival 48 h vs. 30 h, P < 0.001). At 24 hr post-infection, UF-CB treated mice had lower lung and the blood S. pneumoniae colony forming unit counts, and lower airway levels of keratinocyte-derived chemokine/growth-related oncogene (KC/GRO), and interferon gamma.

Conclusion

Acute high level loading of AM with ultrafine carbon black particles per se does not increase the susceptibility of mice to pneumococcal infection in vivo.     

Polymorph control of calcium carbonate by reactive crystallization using microbubble technique

In this study, we used the minute gas–liquid interfaces around CO₂/NH₃ microbubbles as new reaction fields where the crystal nucleation progresses and developed a crystallization technique to control the polymorphism of calcium carbonate (CaCO₃). In the regions around the gas–liquid interfaces of CO₂/NH₃ microbubbles, Ca²⁺ and CO₃²⁻ ion concentrations can be adjusted because of the characteristic of the electric charge on the bubble surface and the decrease in CO₂ concentration based on unit bubble caused by minimization of bubble size, and because of the pH difference between local pH at the gas–liquid interface and overall pH in the bulk liquid caused by mixing of NH₃ with CO₂; hence, the polymorph change of CaCO₃ is expected to occur. CaCO₃ was crystallized at 298 K by a semi-batch type reaction in which CO₂/NH₃/N₂ bubbles were continuously supplied to an aqueous Ca(NO₃)₂ solution using a self-supporting bubble generator. The solution pH during crystallization was maintained at a constant level of 6.9–12.0 by adding HNO₃ and NH₄OH solution. The average bubble size (d_bbl) was varied in the range of 40–1000 μm by controlling the N₂ flow rate, and the molar ratio of CO₂/NH₃ (αCO₂/NH₃${\alpha }_{\text{C}{\text{O}}_2\text{/N}{\text{H}}_3}$) was set at a specified value of 0.20–1.00 at a constant CO₂ flow rate. The following results were obtained by varying solution pH, d_bbl, and αCO₂/NH₃${\alpha }_{\text{C}{\text{O}}_2\text{/N}{\text{H}}_3}$: at a constant d_bbl of 40 μm and αCO₂/NH₃${\alpha }_{\text{C}{\text{O}}_2\text{/N}{\text{H}}_3}$ of 0.20, vaterite and calcite were major products at a solution pH lower than 9.0 and at a solution pH greater than 11.0, respectively, while aragonite was crystallized predominantly in the solution pH range of 9.7–10.5; at a constant solution pH of 9.7 the crystallization of aragonite was accelerated remarkably with a decrease in αCO₂/NH₃${\alpha }_{\text{C}{\text{O}}_2\text{/N}{\text{H}}_3}$ and d_bbl.     

The effect of the hydrothermal treatment with aqueous NaOH solution on the photocatalytic and photoelectrochemical properties of visible light-responsive TiO2 thin films

The effect of the hydrothermal treatment with aqueous NaOH solution on the photoelectrochemical and photocatalytic properties of visible light-responsive TiO₂ thin films prepared on Ti foil substrate (Vis-TiO₂/Ti) by a radio-frequency magnetron sputtering (RF-MS) deposition method has been investigated. The hydrothermally treated Vis-TiO₂/Ti electrodes exhibited a significant increase in their photocurrent under UV and visible light irradiation as compared to untreated Vis-TiO₂/Ti electrode. SEM investigations revealed that the surface morphology of Vis-TiO₂/Ti are drastically changed from the assembly of the TiO₂ crystallites to the stacking of nanowires with diameters of 30–50 nm with increasing hydrothermal treatment time (3–24 h), accompanying the increase in their surface area. The separate evolution of H₂ and O₂ from water under solar light irradiation was successfully achieved using the Vis-TiO₂/Ti/Pt which is hydrothermally treated for 5 h, while the H₂ evolution ratio was 15 μmol h⁻¹ in the early initial stage, corresponding to a solar energy conversion efficiency of 0.23%.     

Zirconium mesostructures immobilized in calcium alginate for phosphate removal

Eutrophication caused by the excessive supply of phosphate to water bodies has been considered as one of the most important environmental problems. In this study, the powder of zirconium mesostructure (ZM), which was prepared with the template of surfactant, was immobilized in calcium alginate for practical application and the resulting material was tested to evaluate the phosphate removal efficiency. Sorption isotherms and kinetic parameters were obtained by using the entrapped ZM beads with 30 to 60% of ZM. The maximum sorption capacity increased with the higher ZM content. Q _max in Langmuir isotherm was 51.74 mg/g for 60% of ZM with 7 mm of size. The smaller the particle size of the ZM beads, the faster the rate of phosphate removal, because the phosphate ions had less distance to reach the internal pores of the immobilized ZM beads. Chemical and electrochemical regeneration techniques were compared. Phosphates adsorbed on the ZM beads were effectively desorbed with NaCl, NaOH, and Na₂SO₄ solutions. An electrochemical regeneration system consisting of an anion exchange membrane between two platinum-coated titanium electrodes was successfully used to desorb and regenerate the phosphate-saturated ZM beads. Complete regeneration was reached under optimal experimental conditions. Chemical and electrochemical regeneration proved the reusability of the bead form of the entrapped ZM, and will enhance the economical performance of the phosphate treatment process.     

Fast and Almost Complete Nitridation of Mesoporous Silica MCM-41 with Ammonia in a Plug-Flow Reactor

The title reaction proceeded well to yield silicon (oxy)nitride at 973–1323 K using a plug-flow reactor. The degree of nitridation was studied as a function of temperature and time of nitridation, the sample weight, and the flow rate of ammonia. It was dependent on the reaction temperature and the amount of ammonia supplied per sample weight. The nitridation at 1273 K for 10–25 h yielded the oxynitride with 36–39 wt% nitrogen, which was very close to 40 wt% of Si₃N₄. Characterization with X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy measurements, and nitrogen adsorption revealed the conversion of MCM-41 to the corresponding oxynitride without essential loss of the mesoporous structure, the decrements of the lattice constant and the pore diameter by 20–35%, and the increments of the wall thickness by ca. 45%. Solid-state ²⁹Si nuclear magnetic resonance spectra during the nitridation clearly showed fast decrease in SiO₄ species and slow in SiO₃(OH). Various intermediate species, SiO _x N _y (NH₂ or NH) _z , were observed to be formed and finally, ca. 70% SiN₄ species, ca. 20% SiN₃(NH₂ or NH), and ca. 10% SiON₂(NH₂ or NH) were produced, being consistent with the results of the above mentioned elemental analysis.