Preparation and properties of biodegradable network poly(ester-carbonate) elastomers

Biodegradable elastomeric network poly(ester-carbonate)s were prepared from multifunctional aliphatic carboxylic acids such as tricarballylic acid (Y_t) or trimesic acid (Y) and polycarbonate diols (PCD) with molecular weights of 1000 and 2000 g/mol. Prepolymers prepared by a melt polycondensation were cast from dimethylformamide solution and postpolymerized at 270 °C for 40-80 min to form a network. The resultant films were transparent, flexible and insoluble in organic solvents. WAXS exhibited the crystalline peaks due to polycarbonate segments for the network films from PCD₂₀₀₀, while those from PCD₁₀₀₀ were amorphous. The tensile properties were determined for these network films at the temperatures 22, 30, 40 and 50 °C. These films showed elastomeric properties at all temperatures measured. The elongation at break was much higher for the films from PCD₂₀₀₀ (208-434%) than those from PCD₁₀₀₀ (40-120%), and decreased with increasing temperatures. The weight losses of the network films degraded in the buffer solution of Rhizopus delemar lipase at 37 °C increased with time, suggesting that these network films are biodegradable. The degradation rate of the network films from Y_t is faster than that from Y. The GPC curves showed that the lipase hydrolyzed both the ester linkages between Y or Y_t and PCD as well as polycarbonate moiety in the network polymer.     

One‐Pot/Four‐Step/Palladium‐Catalyzed Synthesis of Indole Derivatives: The Combination of Heterogeneous and Homogeneous Systems

One‐pot, four‐step syntheses of indoles using both solid‐supported heterogeneous and homogeneous palladium catalysts and reagents were carried out. Such a combination of these two‐phase catalysts and reagents causes a dramatic increase in yield, and it is a simple process. The presented methodology is effective for four‐step reactions to provide various functionalized indoles.     

Formation of deagglomerated PLGA particles and PLGA-coated ultra fine powders by rapid expansion of supercritical solution with ethanol cosolvent

Rapid expansion of supercritical solution (RESS) was used for preparing polymer particles and polymer coating of ultra fine powders. The polymer of pharmaceutical interest was Poly(lactic-co-glycolic acid) (PLGA with PLA: PGA ratio of 85: 15 and MW of 50,000–75,000) and the simulated core particles were 1.4-μm SiO₂ and 70-nm TiO₂ particles. The supercritical solution was prepared by dissolving PLGA in supercritical carbon dioxide with ethanol as a cosolvent. Supercritical solution of CO₂-PLGA was sprayed through capillary nozzles to ambient conditions, resulting in formation of submicron PLGA particles. Similarly, rapid expansion of supercritical solution of CO₂-PLGA suspended with the core particles could provide solvent evaporation and deposition of submicron PLGA particles on the surface of the core particles, resulting in the formation of coating films on dispersed particles of SiO₂ and agglomerates of TiO₂. The influences of the core particle size, spray nozzle diameter as well as powder-to-polymer weight ratio were also investigated and discussed with respect to the coating performance.     

Development and characterization of a photoautotrophic cell line of pak-bung hairy roots

A cell line of photoautotrophic pak-bung hairy roots was established from photomixotrophic ones by acclimation cultivations with a stepwise change of sucrose concentration in a medium with 3.0% CO2-enriched air supplied under continuous light irradiation. The derived photoautotrophic hairy roots had high chlorophyll content and activity of 1,5-ribulose-bisphosphate carboxylase/oxygenase, the values of which were 4.1- and 2.0-fold more than those of the parent photomixotroph, respectively. Electron microscopic observation revealed that the photoautotrophic hairy root cells possessed well-developed chloroplasts. The activities of ascorbate peroxidase and guaiacoal peroxidase found in the hairy roots were comparable to those found in the leaves and roots of parent plants of pak-bung, respectively. The elongation rate of growing points of the hairy roots was maximum at 5.0% CO2 concentration in gas phase and an incident light intensity of 10 W/m2 under the photoautotrophic conditions examined. Although light was indispensable for ensuring photoautotrophy of the hairy roots, it was found that exposure of the roots to strong light resulted in the reduction in the number of viable growing points governing the overall growth rate of the hairy roots.     

Ferroelectric properties of ultrathin films of Nylon 11

Ferroelectric properties of ultrathin films of Nylon 11 were investigated. The thickness was in the range of 25 to 55 nm. Ferroelectric response was largely affected by thermal annealing and following cooling conditions. Thermal annealing at higher temperature followed by quenching in liquid nitrogen gave larger remanent polarization and smoother surface, whereas cooling down in an ambient atmosphere caused smaller remanent polarization and rough surface. Surface roughness strongly affected the polarization reversal and remanent polarization. Hydrogen bonding in crystal was also significantly related to the polarization reversal and thus remanent polarization.     

Effect of inorganic salts,amino acids and proteins on the degradation of pure magnesium in vitro

The possibility of magnesium and its alloys in medical applications is actively investigated in these days for the realization of biodegradable metallic devices. However, the degradation behavior and mechanisms of magnesium and its alloys in physiological environment such as inside the human body have not been elucidated. In this study, we performed 14-d long immersion tests of pure magnesium (3N) in 4 kinds of physiological solutions simulating the body fluids to examine the effects of the chemical components of the body fluids on the degradation of magnesium. The degradation rate of pure magnesium was strongly influenced by the kinds of the solution used. The highest degradation rate was obtained in NaCl, followed by E-MEM, Earle's solution, and E-MEM+FBS. The average degradation rate in NaCl for 8–14 d is about 100 times larger than that in E-MEM+FBS, which is the closest solution to human blood plasma. These results show that protein adsorption and insoluble salt formation retarded magnesium degradation, whereas organic compounds such as amino acids encourage the dissolution of magnesium. Buffering the solution also influenced the degradation rate; buffering NaCl with HEPES increased the degradation rate but buffering with NaHCO₃ decreased it. Based on these results, the use of appropriate solution such as E-MEM+FBS is important for in vitro evaluation of the magnesium degradation rate under the physiological environment simulating inside the human body.     

Quantum Effects on Hydrogen Isotopes Adsorption in Nanopores

We have investigated the applicability of simulations and theoretical techniques for exploring the selectivities of hydrogen isotopes. We have simulated the adsorption isotherms of H₂ in an idealized carbon slit pore at 77 K by using the grand canonical Monte Carlo simulations with the Feynman-Hibbs effective potential (FH-GCMC) and the rigorous path integral method (PI-GCMC), and we obtained good agreement between the isotherms from both simulations. This suggests that FH-GCMC, which uses the approximative Feynman-Hibbs treatment, is as useful as PI-GCMC for exploring H₂ adsorption at 77 K. Moreover, we show that the ideal adsorption solution theory (IAST) can predict the selectivity of D₂ over H₂ in the interstices of single-wall carbon nanotube (SWNT) bundles at 77 K (below 0.1 MPa) very well by comparing the obtained results with the mixture adsorption FH-GCMC simulations. This indicates that IAST is also applicable to the estimation of the selectivity of D₂ over H₂ at moderate pressures and at 77 K from experimental single-component adsorption isotherms. We also demonstrate that the FH-GCMC simulation can reproduce the experimental adsorption isotherms of H₂ and D₂ in aluminophosphate AlPO₄-5 at 77 K. Finally, we analyze the selectivity of D₂ over H₂ by IAST with the experimental single-component adsorption isotherms of H₂ and D₂ at 77 K for a variety of adsorbents: AlPO₄-5, activated carbon fibers (ACFs), HiPco SWNT, and SWNHs. The selectivities predicted by the experimental adsorption data based on the results from the FH-GCMC simulations are presented and discussed.     

Simple evaluation of aortic arch calcification by chest radiography in hemodialysis patients

Vascular calcification is associated with a poor prognosis in dialysis patients. It can be assessed with computed tomography but simple inoffice techniques may provide useful information. We compared the results obtained with a simple noninvasive technique with those obtained using multidetector computed tomography for aortic arch calcification volume (AoACV) in chronic hemodialysis (HD) patients. The enrolled study subjects were 63 (32 men and 31 women) maintenance HD patients. Calcification of the aortic arch was semiquantitatively estimated with a AoAC score (AoACS) on plain chest radiology. The AoACV was increased, with a mean value of 6.6 ranging from 0% to 36.5%. The coefficient of intraobserver variation was less than 2.5%. Aortic arch calcification score was highly correlated with AoACV (r=0.635, P<0.001). Multiple regression analysis showed age (F value=12.62, P<0.001) and pulse pressure (F value=4.54, P=0.037) to be significant independent determinants of AoACS. In conclusion, a simple measurement of AoACS may be useful for inoffice imaging to choose a therapeutic regimen in HD patients.     

Preparation of Cu2ZnSnS4 thin films by sulfurizing electroplated precursors

Cu₂ZnSnS₄ (CZTS) thin films were prepared by sulfurizing precursors deposited by electroplating. The precursors (Cu/Sn/Zn stacked layers) were deposited by electroplating sequentially onto Mo-coated glass substrates. Aqueous solutions containing copper sulfate for Cu plating, tin sulfate for Sn plating and zinc sulfate for Zn plating were used as the electrolytes. The precursors were sulfurized by annealing with sulfur at temperatures of 300, 400, 500 and 600 °C in an N₂ gas atmosphere. The X-ray diffraction peaks attributable to CZTS were detected in thin films sulfurized at temperatures above 400 °C. A photovoltaic cell using a CZTS thin film produced by sulfurizing an electroplated Sn-rich precursor at 600 °C exhibited an open-circuit voltage of 262 mV, a short-circuit current of 9.85 mA/cm² and an efficiency of 0.98%.