Use of structure-controlled polymers as high performance powder dispersants in the silicone oil phase

A novel polymer dispersant with a tri-block structure was designed. The tri-block polymer was composed of polyglycerin (PGL) with two dimethylpolysiloxane chains (DMPS) at both ends of the molecular structure. The high dispersibility of the dispersant was confirmed in both a model silica system and a sunscreen formulation. The apparent silica particle size was employed as an index for the dispensability for the dispersants. The novel dispersant showed 5 times more effective than conventional one. The flow properties of a sunscreen formulation containing titanium dioxide with the novel dispersant was Newtonian, indicating that the dispersibility of the dispersant was excellent. On the other hand, the formulation with conventional dispersant showed shear-thinning flow due to aggregation of the powder. These results mean that such a tri-block copolymer would make it possible to develop consumer demanded sunscreens.     

Percolation theory for flame propagation in non- or less-volatile fuel spray: A conceptual analysis to group combustion excitation mechanism

A percolation theory for flame propagation in non- or less-volatile fuel spray is developed based on a cubic lattice model representing a local spray state. The interdroplet flame propagation characteristics found from microgravity experiments on flame spread along a linear droplet array are applicable to describing interdroplet flame propagation between neighboring droplets in any distribution of droplets because the effect of heat conduction from the flame front is shielded by the nearest unburned droplet, which acts as a heat sink. Thus, once the method by which the unburned droplet nearest to the flame front is ignited is identified and formulated into a simple algorithm rule, we can examine by computer simulation the statistical flame propagation behavior in a non- or less-volatile fuel spray in the framework of the percolation theory. In non- or less-volatile fuel, an unburned droplet swallowed by an envelope diffusion flame of other droplets is heated and becomes a new supplier of fuel vapor to the flame front, allowing the flame front to advance. For randomly distributed droplets, the flame front selects the path that minimizes its propagation time. These two phenomena occur when the grid spacing of the cubic lattice model is equal to the maximum flame radius of an isolated droplet immersed in the same air conditions as the local spray state. Furthermore, physical considerations reveal that the lattice size that leads to statistically meaningful information can be rather small, i.e., 20×20×20 vertices. Therefore, the proposed percolation theory is tractable and useful in finding the probability that a flame front propagates across a spray element and for exploring the mechanism of the excitation of group combustion for non- or less-volatile fuel sprays.     

Prediction of vortex penetration depth at thermal stratification by cavity flow in a branch pipe with closed end (effect of heat radiation condition on temperature fluctuations)

In a branch pipe with one closed end, the cavity flow penetrates into the branch pipe from the main loop and a thermal boundary layer occurs because the cavity flow is a hot fluid, but heat removal causes a colder fluid in the branch pipe. This thermal stratification may affect the structural integrity. Therefore, a pipe design standard to suppress thermal fatigue should be established. The pipe design standard consists of the maximum penetration depth L_sv and the minimum penetration depth L_sh. In order to establish an evaluation method for L_sh, a visualization test and a temperature fluctuation test were carried out. A theoretical formula for thermal stratification was introduced from the heat balance model. Then the model was used to obtain an empirical equation from the map of fluid temperature fluctuation. This method can predict the vortex penetration depth by cavity flow in horizontal branch pipes. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(1):38–55, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20135     

Evaluation of geometric efficiency and radiation exposure in z-axis for volume scan

The International Electrotechnical Commission (IEC) recommended that a display be provided on the operating console of medical computed tomography (CT) scanners when the geometric efficiency (GE) in the z-axis is 70% or less. Taking into account the increase in the number of detector rows and the changes in the scanning method, the present study was conducted to review the GE and to evaluate the exposure dose in the z-axis direction. The GE for a single-rotation scan was calculated in accordance with IEC-606024 Ed. 2. The findings of the present study suggest that 320-row area detector computed tomography volume scan (single axial scan with no table movement in which it just happened to use a very large beam width) extends 18.8 mm beyond the nominal beam collimation, even when the GE is >70%. However, compared with the helical scan, which is the present mainstream of CT examinations, the dose beyond the scan length is narrower in volume scan for a limited scan length of 160 mm or less.     

Transport of carnitine and acetylcarnitine by carnitine/organic cation transporter (OCTN) 2 and OCTN3 into epididymal spermatozoa

Carnitine and acetylcarnitine are important for the acquisition of motility and maturation of spermatozoa in the epididymis. In this study, we examined the involvement of carnitine/organic cation transporter (OCTN) in carnitine and acetylcarnitine transport in epididymal spermatozoa of mice. Uptake of both compounds by epididymal spermatozoa was time-dependent and partially Na(+)-dependent. Kinetic analyses revealed the presence of a high-affinity transport system in the spermatozoa, with K(m) values of 23.6 and 6.57 muM for carnitine and acetylcarnitine respectively in the presence of Na(+). Expression of OCTN2 and OCTN3 in epididymal spermatozoa was confirmed by immunofluorescence analysis. The involvement of these two transporters in carnitine and acetylcarnitine transport was supported by a selective inhibition study. We conclude that both Na(+)-dependent and -independent carnitine transporters, OCTN2 and OCTN3, mediate the supply of carnitine and acetylcarnitine to epididymal spermatozoa in mice.     

PCR detection of DNA specific for Trichosporon species in serum of patients with disseminated trichosporonosis

Deep-seated trichosporonosis is a lethal opportunistic infection that disseminates rapidly and widely in immunocompromised patients, and early diagnosis is crucial for the treatment of this infection. We developed a novel nested-PCR assay that detects DNA specific for clinically important strains of Trichosporon in serum samples from patients with disseminated trichosporonosis. In this assay, two sets of oligonucleotide primers were derived from the sequence of 26S rRNA genes of Trichosporon asahii. The specific fragment was amplified from T. asahii and T. mucoides, but not from other microorganisms, including some other basidiomycetous fungi (Cryptococcus, Malassezia, Rhodotorula, and Sporobolomyces). Target DNA was detected by the nested PCR with as little as 5 fg of the extracted DNA of T. asahii. In a study using 11 clinical samples, the specific fragment was detected by the nested PCR in 64% (7 of 11) of sera from patients with histologically diagnosed disseminated trichosporonosis, while glucuronoxylomannan antigen was detected in only 54% (6 of 11) of the samples. Our new nested-PCR assay using serum samples can be performed repeatedly throughout the course of the disease. In addition, not only can it be used for early diagnosis of trichosporonosis, but it may also be beneficial for monitoring its progress or response to therapy.     

Synthesis of TiB2 by High-Dose Implantation of Boron Ions in Titanium Films

Boron ions were implanted at room temperature in Ti films at a high dose (7.1 × 10^I7 and 2.3 × 10¹⁸ ions/cm²), The formation of TiB₂ films was confirmed by X-ray diffraction. Boron concentration profiles in implanted films were studied by secondary-ion mass spectrometry.     

NMR study of adsorbed water on acrylic acid-grafted and methacrylic acid-grafted cellulose

The water-adsorbing properties of cellulose samples which had been graft copolymerized with hydrophilic vinyl monomers using ceric salt as an initiator were investigated by means of the width of the high-resolution NMR absorption spectrum, water retention, and moisture regain of the samples. In the change of the width at half-value of the spectrum with per cent grafting, a maximum value followed by a minimum value was observed on samples both grafted with acrylic acid and methacrylic acid. Thus, the effect of grafting on the water-adsorbing properties appeared not to be simple. Though no special change in the water retention by grafting was observed, the per cent grafting dependence on the moisture regain in high relative humidity showed a peculiar and definite relation. The per cent grafting giving maximum moisture regain was about 8% and 18% for acrylic acid and methacrylic acid, respectively, and this agreed very well with the minimum widths at half-value. The change in the glass transition temperature of the sample—water system caused by grafting is also described.     

Analysis on the fractionation of polyethylene–polypropylene blends

The hypothetical fractionation of polyethylene–polypropylene blends was carried out by assuming adequate molecular weight distribution and partition of polymer between two liquid phases for each hompolymer, and also by using the previously reported data of the molecular weight dependence on solubility. The experimental fractionation of blends was also carried out by the solvent gradient method, and the results were compared with those obtained by the hypothetical fractionation. Both results agreed fairly well in various distribution forms. Therefore, these results may provide valuable information for component or compositional analysis of unknown samples or copolymerization products.     

Treatment of Volatile Organic Compounds with a Pt/Co3O4‐CeO2 Catalyst

For emission control of volatile organic compounds (VOC), e.g., in the painting and printing industries, conventional Pt/Al₂O₃ and Co₃O₄‐CeO₂ catalysts are used. On the Pt/Al₂O₃ catalyst, aromatic hydrocarbons containing a benzene ring such as toluene can be oxidized at a lower complete oxidation temperature than on Co₃O₄‐CeO₂, under typical treatment conditions. However, ethyl acetate and isopropyl alcohol can be oxidized at a lower complete oxidation temperature on Co₃O₄‐CeO₂ than on Pt/Al₂O₃. In this study, platinum was directly supported on Co₃O₄‐CeO₂. Using chloroplatinic acid, the platinum cohered and the catalytic activity did not improve. But when the platinum was supported using platinum colloid coated with dispersant, high‐dispersion support of the platinum on the Co₃O₄‐CeO₂ surface was achieved, and toluene, ethyl acetate, and isopropyl alcohol could be oxidized at less than 250 °C.