Preparation and characterization of stable dispersions of carbon black and nanodiamond in culture medium for in vitro toxicity assessment

Stable dispersions of carbon black and nanodiamond in culture medium were prepared by adding a pre-mixed dispersion of commercial carbon black or nanodiamond in aqueous bovine serum albumin (BSA) solution to culture medium. Dynamic light scattering revealed that carbon black and nanodiamond dispersions prepared in both NaCl solution and culture medium were highly stable. From DLVO theory and the results of zeta potential measurements, the theoretical effect of the electrostatic interactions between adsorbed BSA molecules was found to be minimal. The asymmetric flow field-flow fractionation measurements revealed that 0.05 or 0.56 mg/mL of BSA molecules were adsorbed on 0.11 or 1.09 mg/mL of carbon black, respectively, indicating 1:2 complexation of BSA with the colloidal particles. In the case of nanodiamond, 0.06 or 0.60 mg/mL of BSA molecules were adsorbed on 0.10 or 1.05 mg/mL of nanodiamond, respectively, indicating 1:2 complexation of BSA, which is the same ratio as in the case of carbon black. The adsorbed BSA molecules served as an effective stabilizing agent for the carbon black and nanodiamond, ensuring dispersion stability for at least 1 week. The preparation of the dispersions can be easily carried out by other researchers for toxicity studies.     

Prediction method of critical power by film flow rate measurement and subchannel analysis

This paper presents a method that can estimate the critical power of boiling water reactors, BWRs, with regard to spacer geometry. The current experimental method for estimating the critical power for BWR design requires many trained experts and expensive facilities to conduct the experiments. In the present method, the liquid film flow rate of adiabatic gas‐liquid two‐phase flow and a subchannel analysis of the actual BWR flow condition are measured experimentally and analyzed. In the experiment, deposition enhancement coefficients of three spacer geometries—a ferrule, an egg‐crate, and a ferrule spacer with twisted tape (CYCLONE spacer)—were estimated by measuring the liquid film flow rate of air‐water two‐phase flow flowing up in a vertical square (4 × 4) rod bundle that simulated the rod bundle of a BWR. Using these coefficients, the critical powers for bundles using each type of spacer geometry were calculated in the subchannel analysis. This method was validated using previous critical power data in the actual BWR flow condition. The critical powers predicted by this method agreed well with those of the experimental data. The result confirmed the effectiveness of this experiment‐simulation combined method, as well as the advantage over current experimental methods in terms of human and facility costs. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(5): 309–323, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20069     

Micro-flowers of poly(p-phenylene pyromelliteimide) crystals

Morphology control of poly(p-phenylene pyromelliteimide) (PPPI) crystals was examined using reaction-induced crystallization of oligomers during solution polymerization of self-polymerizable N-(4′-aminophenyl)-3-carboxyl-4-alkoxycarbonylphthalimide. Micro-flowers of the PPPI needle-like crystals were formed in which the needle-like crystals grew radially from the center part as petals. The molecules aligned regularly along the long axis of the needle-like crystal. The structure of alkoxy group in the monomer and the monomer concentration influenced the size of the needle-like crystals, and their average length and width were changeable from 640 nm to 1.69 μm and from 110 nm to 210 nm, respectively. The average thickness was 20 nm. The obtained micro-flowers possessed high crystallinity and exhibited excellent thermal stability.     

Shear-induced pre-crystallization structures of long chain branched polypropylene under steady shear flow near the melting temperature

Shear-induced crystallization of a long chain hyper-branched polypropylene (LCB-PP, denoted PP-3) was carried out at a relatively high temperature of 170 °C, close to its melting temperature of 158 °C. Small-angle X-ray scattering (SAXS) showed that the intensity ratio of the normal to the perpendicular to the shear (V/H) was always larger than 1 for PP-3, indicating that shish-like structures were predominately formed and further growth to kebab was suppressed in PP-3. The crystallization behavior of PP-3 can be explained by the nature of PP-3 that there were a large amount of crystallization nuclei due to their branching points, and the point-like precursors formed from these nuclei were arrayed linearly along the shear direction and transformed into thread-like precursors or premature shishs; however, owing to the large amount of branching, further progress in crystallization was suppressed.     

An electrochemical ionic liquid membrane reactor for NO x selective separation under excess oxygen conditions

A novel electrochemical ionic liquid membrane reactor capable of separating NO from a mixture of NO and oxygen with high current efficiency at low temperatures was designed and tested. This reactor consists of a combination of an ionic liquid and a thin film of anodised alumina with two platinum electrodes. During operation of the reactor, NO is electrically transported from the cathode side to the anode side.     

Screening the p53 status of human cell lines using a yeast functional assay

We have screened the p53 status of 156 human cell lines, including 142 tumor cell lines from 27 different tumor types and 14 cell lines from normal tissues by using functional analysis of separated alleles in yeast. This assay enables us to score wild-type p53 expression on the basis of the ability of expressed p53 to transactivate the reporter gene HIS3 via the p53-responsive GAL1 promotor in Saccharomyces cerevisiae. Of 142 tumor cell lines, at least 104 lines (73.2%) were found to express the mutated p53 gene: 94 lines (66.2%) were mutated in both alleles, three lines (2.1%) were heterozygous, and no p53 cDNA was amplified from seven lines (4.9%). Of the 14 cell lines originating from normal tissues, all the transformed or immortalized cell lines expressed mutant p53 only. Yeast cells expressing mutant p53 derived from 94 cell lines were analyzed for temperature-sensitive growth. p53 cDNA from eight cell lines showed p53-dependent temperature-sensitive growth, growing at 30 degrees C but not at 37 degrees C. Four temperature-sensitive p53 mutations were isolated: CAT-->CGT at codon 214 (H214R), TAC-->TGC at codon 234 (Y234C), GTG-->ATG at codon 272 (V272M), and GAG-->AAG (E285K). Functionally wild-type p53 was detected in 38 tumor cell lines (26.8%) and all of the diploid fibroblasts at early and late population doubling levels. These results strongly support the previous findings that p53 inactivation is one of the most frequent genetic events that occurs during carcinogenesis and immortalization.     

Effect of silver content on thermal fatigue life of Sn-xAg-0.5Cu flip-chip interconnects

The thermal fatigue properties of Sn-xAg-0.5Cu (x=1, 2, 3, and 4 in mass%) flip-chip interconnects were investigated to study the effect of silver content on thermal fatigue endurance. The solder joints with lower silver context (x=1 and 2) had a greater failure rate compared to those with higher silver content (x=3 and 4) in thermal fatigue testing. Cracks developed in the solders near the solder/chip interface for all joints tested. This crack propagation may be mainly governed by the nature of the solders themselves because the strain-concentrated area was similar for tested alloys independent of the silver content. From the microstructural observation, the fracture was a mixed mode, transgranular and intergranular, independent of the silver content. Higher silver content alloys (x=3 and 4) had finer Sn grains before thermal cycling according to the dispersion of the Ag₃Sn intermetallic compound, and even after the cycling, they suppressed microstructural coarsening, which degrades the fatigue resistance. The fatigue endurance of the solder joints was strongly correlated to the silver content, and solder joints with higher silver content had better fatigue resistance.     

Influence of γ Irradiation on the Mechanical Strength and In Vitro Biodegradation of Porous Hydroxyapatite/Collagen Composite

Gamma irradiation treatment (GIT) is the most widely used sterilization method for biomaterials in spite of the potential to degrade polymers. The adverse effects of GIT on the mechanical properties and biological stabilities of porous hydroxyapatite/collagen (HAp/Col) composites were investigated in this study. Those properties of a porous HAp/Col composite stabilized by dehydrothermal treatment (DHT) drastically decreased by GIT in the same manner as conventional pure Col materials. DHT after GIT could partially eliminate the adverse effects, due to the introduction of cross-linkage among the degraded Col molecules.     

Effect of metal cation type on the structure and properties of ethylene ionomers

Thermal properties by DSC, stiffness, melt viscosity, tensile properties, and dynamic mechanical properties were measured for the Na⁺, K⁺, Mg²⁺, Zn²⁺, Cu²⁺, Mn²⁺, and Co²⁺ salts of poly(ethylene-co-methacrylic acid) (EMAA). The changes in the structure and properties with increasing neutralization are larger in the alkaline and alkaline earth metal salts than in the transition metal salts. The stiffness shows a maximum at 33% neutralization in both the alkaline and alkaline earth metal salts, while no maxima are found up to 60% neutralization in the transition metal salts. The microphase separation of salt group aggregates is observed in both the alkaline and alkaline earth metal salts, but is not seen in the transition metal salts. These differences were attributed to both the stronger ionic interactions and the larger number of carboxyl groups associated with the alkaline and alkaline earth metal salts in the ordered structure of ionic salt groups (ionic crystallites). The mechanical properties measured at low strain, such as stiffness and yield stress, strongly depend on the degree of the crystalline order of the ionic crystallites. The high-strain properties, such as tensile strength and elongation at break, depend on the strength of the ionic interactions and the valence of the cation.