Kinetic analysis of crystallization of zeolite beta synthesized by direct heating

To quantitatively investigate the initial crystallization of zeolite beta synthesized by direct heating, the extent of the reaction was precisely evaluated by X-ray diffraction measurements and Rietveld structural refinement, and a kinetic analysis of crystallization was performed using the Avrami-Erofe'ev equation. The activation energy for crystallization was lower than that for hydrothermal synthesis. Reaction and synthesis time curves revealed that the initial zeolite beta crystallization consisted of three stages. The first was an induction period with nucleation by the generation of building units and the formation of an initial coordinated structure. The second stage was crystal growth by a diffusion-controlled reaction, and the third stage involved slowing down of crystallization by the limitation of dehydrocondensation. These stages could be analyzed by calculation of the rate constant and Avrami exponent for each stage.     

Monolithiation of 5,5′‐Dibromo‐2,2′‐bithiophene Using Flow Microreactors: Mechanistic Implications and Synthetic Applications

The lithiation of 5,5′‐dibromo‐2,2′‐bithiophene with one equivalent of an alkyllithium such as n‐BuLi or s‐BuLi was studied by varying the residence time in flow microreactors. With a short residence time, the product 2,2′‐bithiophene (3) derived from dilithiation was obtained preferentially and a significant amount of the starting material 5,5′‐dibromo‐2,2′‐bithiophene remained unchanged. An increase in the residence time caused a higher yield of the product 5‐bromo‐2,2′‐bithiophene derived from monolithiation with expense in the yields of 2,2′‐bithiophene and 5,5′‐dibromo‐2,2′‐bithiophene. The lithiation using MeLi gave the product 5‐bromo‐2,2′‐bithiophene preferentially even with a very short residence time.     

Evaluation of effects of windows installed with near-infrared rays retro-reflective film on thermal environment in outdoor spaces using CFD analysis coupled with radiant computation

Recently, windows with low-e double-glazing or heat-shading films often have been installed to the exterior surfaces of buildings to reduce the cooling load of the buildings. These windows specularly reflect solar radiation into pedestrian spaces. It has been pointed out that the increase in the incident solar radiation reflected at the windows degrades the thermal comfort levels of pedestrians. The installation of near-infrared rays retro-reflective film to window surfaces may both reduce the cooling load of the building and reduce the impacts on the thermal environment in outdoor spaces. Hence, it is expected that the installation of this film will counteract this problem and have positive effects. To assess the feasibility of installing retro-reflective materials to the exterior surfaces of the building walls and ground forming part of a city block, for improving the thermal environment in outdoor spaces, computational methods could serve as a powerful tool for analyzing the radiant environment in urban and building spaces. In this paper, a computational method is outlined for considering the directional reflections from the exterior surfaces of building walls and windows. The method is used to estimate the effects on the outdoor thermal comfort of pedestrians in the summer season.     

In-situ immobilization of Sr radioactive isotope using nanocrystalline hydroxyapatite

Hydroxyapatite was used as the inert matrix for in-situ immobilization of strontium (Sr) radioactive isotopes at room temperature. A nano-emulsification method was applied to synthesize Sr-substituted calcium hydroxyapatite (Ca_1?xSr_x)₁₀(PO₄)₆(OH)₂. The concentration of incorporated Sr was in the range of 0 ≤ x ≤ 1. Immobilization of Sr was evaluated using a stable isotope instead of radioactive isotope. The effect of strontium concentration on the crystal structure was studied and the results have showed that in the whole concentration range, Sr forms solid solutions with the host hydroxyapatite crystal structure. Powders comprised of nanometre sized particles were obtained and their properties, such as crystallite and particle size, changes in lattice parameters as function of dopant content and thermal stability, were further examined. It was found that the crystal structure of obtained powders is thermally stable at high temperatures. No secondary phases were formed in as-prepared powders or during calcination. The results in this study showed that nano-emulsion strategy provides a simple pathway for synthesis of a single-phase Sr-substituted hydroxyapatite, which can be used for immobilization of Sr radioactive isotopes.     

Distribution of carbon contamination in MgAl2O4 spinel occurring during spark-plasma-sintering (SPS) processing: I – Effect of heating rate and post-annealing

Carbon contamination from the carbon paper/dies during spark-plasma-sintering (SPS) processing was examined in the MgAl₂O₄ spinel. The carbon contamination sensitively changes with the heating rate during the SPS processing. At the high heating rate of 100 °C/min, the carbon contamination having organized structures occurred over almost the entire area from the surface to deep inside the SPSed spinel disk. In contrast, at the slow heating rate of 10 °C/min, the carbon contamination having disordered structures occurred only around the surface area. The carbon phases transform into high pressure CO/CO₂ gases by post-annealing in air and lead to pore formation along the grain junctions. The pore formation significantly occurs at the high heating rate due to the large amount of the contaminant carbon phases. This suggests that if once the carbon contamination was formed in the materials, it is very difficult to remove the carbon phases from the materials.     

Short communication: Temporal changes in the skin morphology of dairy cows during the periparturient period

Management of dairy cow productivity requires monitoring of their nutritional status by visual observation. It has been suggested that changes in hair coat appearance are among the indicators of nutritional state in dairy cows. Temporal changes in the skin morphology in cows, however, have not been reported. In this study, we examined the changes in the skin of dairy cows that occur during the peripartum period. Seven pluriparous cows were used. Skin samples were collected at 28 d before the due date and 28 d and 56 d after calving for morphological examination. Hair follicle width was 108.8 ± 5.9 µm (±SD) in the dry period, 95.5 ± 5.5 µm at 28 d after calving, and 104.2 ± 5.3 µm at 56 d postpartum. The percentages of anagen hair follicles during these 3 periods were 41.4 ± 3.4, 18.5 ± 3.4, and 32.3 ± 3.3%, respectively. The corresponding sebaceous gland sizes were 8,362.0 ± 707.6, 7,800.0 ± 831.4, and 9,186.8 ± 962.6 µm², respectively. Hair follicle width was positively correlated with percentage of anagen hair follicles. The thickness of epidermal and proliferation rate of epidermal cell were also correlated. However, the hair follicle width, sebaceous gland size and cell proliferation rate, and thickness and proliferation rate of epidermal cells did not show any marked changes.