Determination of Particle Size Distribution of Ultra-Fine Aerosols Using a Differential Mobility Analyzer

The size analysis of ultrafine aerosol particles using a differential mobility analyzer combined with a CNC is discussed from two standpoints: (1) particle loss caused by Brownian diffusion in the analyzer, and (2) data reduction procedure where Fuchs' charging theory is applied. As a result, it has been found that (1) particle loss becomes significant when particle size is smaller than about 15 nm, and (2) a simple and practical data reduction procedure may be used, where the stationary bipolar charge distribution given by Boltzmann's law is modified by using Fuchs' charge distribution in the smaller size range.     

Preparation of ZnO-TiO2 Composite Fine Particles Using the Ultrasonic Spray Pyrolysis Method and Their Characteristics on Ultraviolet Cutoff

ZnO-TiO₂ composite fine particles were prepared by ultrasonic spray pyrolysis of TiO₂ (anatase) particles suspended in Zn(NO₃)₂ aqueous solution. The morphology and the crystalline phases of fine particles were studied with varying nebulizing solution compositions, reactor temperature, and nitrogen carrier gas flow rate. The aggregate particles produced were spheres of ZnO (wurtzite structure) and TiO₂ (anatase), whose diameters ranged from 0.36 to 0.5μm. These particles were hollow or solid aggregate particles consisting of ultrafine primary particles with diameters ranging from 10 to 100 nm. The crystallinity of prepared particles was improved by increasing the reactor temperature and lowering the flow rate of nitrogen. The largest crystallites were obtained at a solution concentration ratio of C_Zn(NO3)2/C_TiO2 = 10:7. These composite particles showed a combined ultraviolet cutoff characteristic of ultraviolet light shielding in the wide range of wavelength ranging from 200 to 370 nm.     

Numerical Simulation and Experiment on the Transport of Fine Particles in a Ventilated Room

ABSTRACT

The change in concentration distribution of particulate contaminants emitted in a room was studied experimentally and theoretically to investigate whether the transport of contaminants in a room with a source of particles can be predicted by numerical simulation. Tracer contaminants, monodisperse latex particles, were introduced into a 3.3 m ×2.7 m ×2 m room with clean air for a given time, and the change in the contaminant concentrations with time was measured at various positions in the room. Calculations of the spatial and temporal distributions in the gas velocity and contaminant concentration were performed to predict the concentration change, with the Navier-Stokes and convection-diffusion equations solved numerically. The experimental results showed that the concentration distribution depends on the position of introduction of the contaminants. It was also indicated that the contaminants introduced near the room floor diffuse more than predicted. However, the calculated concentrations agreed almost quantitatively with the measured results, except near the floor and walls. The change in the concentration with time and the dependence of the concentration distribution on the position of the particle source were well reproduced by the calculation.     

Neurotrophic effect of citrus auraptene: neuritogenic activity in PC12 cells

The activation of extracellular signal-regulated kinases (ERK) leads to a number of cellular changes associated with the development of long-term memory. Using cultured cortical neurons, we previously showed that the n-hexane extract prepared from the peels of Citrus grandis (Kawachi bankan) induces the activation of ERK1/2 and that one of the compounds with this ability in the extract is 3,5,6,7,8,3',4'-heptamethoxyflavone (HMF), a Citrus polymethoxyflavone. In fact, we found that HMF has the ability to rescue mice from drug-induced learning impairment. This hexane extract contains auraptene (AUR), a coumarin derivative with a monoterpene unit, together with HMF. The present study was designed to investigate the effect of AUR in vitro. Our results show that 1) AUR had the ability to induce the activation of ERK1/2 in not only cortical neurons but also the rat pheochromocytoma cell line (PC12 cells), which is a model system for studies on neuronal proliferation and differentiation; and 2) AUR had the ability to promote neurite outgrowth from PC12 cells.     

Higher Serum EPA or DHA, and Lower ARA Compositions with Age Independent Fatty Acid Intake in Japanese Aged 40 to 79

Docosahexaenoic acid (DHA) and arachidonic acid (ARA) are the predominant long-chain polyunsaturated fatty acids (PUFA) among membrane phospholipids in the mammalian brain and neural tissues. This cross-sectional study examined age effects on serum eicosapentaenoic acid (EPA), DHA, and ARA compositions assessed with reference to dietary intakes among 1,014 Japanese men and 1,028 Japanese women aged 40–79 years. Venous blood was collected early in the morning after at least 12-h fasting. Serum fatty acid (FA) compositions were expressed as molar percentages of the total FA (mol% of total). Diet was assessed using a 3-day dietary record that included photographs. Participants were categorized into groups by sex and age (40–49, 50–59, 60–69, and 70–79 years). Intakes of fish, EPA, and DHA tended to increase with age. Significant positive correlations between serum FA composition and the corresponding weight percentage of total FA intake were observed for EPA and DHA in all sex and age groups, and for ARA among females in their 40s. Serum EPA and DHA compositions were higher, while ARA decreased with age, and these associations remained consistent even after adjusting for corresponding FA intake. These results suggest potential effects of age on differences in blood EPA, DHA, and ARA compositions, independent of corresponding FA intake among community-dwelling Japanese men and women.     

Functional Expression of Thyroid-Stimulating Hormone Receptor on Nano-Sized Bacterial Magnetic Particles in Magnetospirillum magneticum AMB-1

The measurement of autoantibodies to thyroid-stimulating hormone receptor (TSHR) is important for the diagnosis of autoimmune thyroid disease such as Graves’ disease (GD). Although TSHR from porcine thyroid membrane is commonly used for the measurement of TSHR autoantibodies (TRAb), recombinant human TSHR (hTSHR) remains ideal in terms of stable supply and species identity. Here we set out to express recombinant hTSHR on the lipid-bilayer surface of magnetic nanoparticles from a magnetotactic bacterium, Magnetospirillum magneticum AMB-1. Using a tetracycline-inducible expression system, we successfully overexpressed functional hTSHR on bacterial magnetic particles (BacMPs) in AMB-1 via an anchor protein specific for BacMPs. The overexpressed hTSHR was membrane integrated and possessed both ligand and autoantibody binding activity. Our data suggest that hTSHR-displayed BacMPs have potential as novel tools for ligand-receptor interaction analysis or for TRAb immunoassay in GD patients.     

The effect of electrically charged dielectric walls on the diffusive deposition of submicron aerosol particles

The effect of an electrical charge on a dielectric wall on the deposition of charged aerosol particles is investigated. The dielectric walls used in the deposition experiments, poly(vinyl chloride) or polytetrafluoroethylene disks, are prepared to have known uniform surface charge distributions by using a corona discharge procedure. This avoids any effects on deposition caused by nonuniformity of the surface charge. The surface charge densities are based on measurements of the surface voltage in the center of the sample. Deposition experiments using a turbulently-mixed stirred tank demonstrate that particle deposition rates to the wall decrease as the sample's thickness increases or its relative permittivity decreases, even at a constant surface voltage. The electric field over the sample wall is calculated using the surface charge density, and the convection-diffusion equations describing particle deposition by Brownian and turbulent diffusion and electric migration are solved numerically. The calculated deposition rates agree well with those measured, indicating that quantitative prediction of particle deposition is possible if the surface charge, material, thickness and the effect of adjacent walls are taken into account.     

Effects of poly(vinyl alcohol) suspension medium on critical current density of Ba2Y1Cu3 oxide superconducting filaments produced by suspension spinning method

Superconducting Ba₂Y₁Cu₃ oxide filament was produced by means of the suspension spinning method. The effects of poly(vinyl alcohol) (PVA) suspension medium on structure and critical current density (Jc) of the filament sintered were explored with PVA of various degrees of polymerization (DP) in dimethyl sufoxide (DMSO), hexamethylphosphoric triamide (HMTA) and the mixed solution of DMSO and HMTA (1 : 1). Although the PVA was removed as a volatile component by heating treatment of the filament, the dispersion behavior of the oxide powder in the filament was dependent on the suspension medium, hence the microstructure and superconducting properties of the filament obtained was affected by the suspension medium. The filament spun through the mixed solution of DMSO and HMTA had a high Jc of 77 K more than 100 A/cm² at the wide range of DP and powder content. The crystal grains of the oxide in the sintered filament grew finer with increasing the DP of PVA. On the other hand, the Jc of the filament produced by pure solution of DMSO and HMTA was not detected at DP of 3000 and 2450, respectively, due to the influence of entanglement of the molecular chains of PVA.     

LIQUID FLOW IN IMPELLER REGION OF AN UNBAFFLED AGITATED VESSEL WITH UNSTEADILY FORWARD-REVERSE ROTATING IMPELLER

For an unbaffled agitated vessel with an unsteadily forward-reverse rotating impeller whose rotation proceeds with repeated acceleration, deceleration, and stop-reverse processes, the liquid flow in the impeller region was studied based on photographs showing path lines of tracer particles. An image series taken during one cycle of the forward-reverse rotation was analyzed to characterize the internal stream inside the impeller rotational region and the discharge stream outside its region when a disk turbine impeller with six flat blades was rotated unsteadily. Because of the unsteady flow generated inside the impeller rotational region, the velocity vector of outflow from its region fluctuated periodically with the change of the impeller rotation rate. The circumferential velocity was almost in phase with the impeller rotation rate, oscillating periodically. The radial velocity exhibited larger values in the process for the impeller from decelerating to stopping and reversal. The radial flow, whose velocity decreased downstream outside the impeller rotational region, was clarified to be transformed into upward and downward axial flows that are almost uniform in the circumferential direction throughout the region near the vessel wall.     

Highly active methanol decomposition catalyst derived from Pd‐hydrotalcite dispersed on mesoporous silica

Pd‐hydrotalcite (abbreviated as Pd(HT)) was dispersed on HMS (hexagonal mesoporous silica) by synthesizing Pd(HT) in an HMS suspension, and the resultant product (Pd(HT)/HMS) was used as a catalyst precursor for methanol decomposition to synthesis gas. The IR spectra of Pd(HT)/HMS showed all the bands of Pd(HT) and HMS with little shift, which indicated that Pd(HT) was synthesized in the Pd(HT)/HMS. Pd(HT)/HMS did not show the XRD pattern of Pd(HT) when the mass ratio of Pd(HT) to HMS was from 2/1 to 1/2. This indicated that Pd(HT) was formed in very small particles in the Pd(HT)/HMS after dispersion. Two endothermic peaks of Pd(HT) in the DTA curve shifted to lower temperatures in the Pd(HT)/HMS because the small Pd(HT) particles formed in the Pd(HT)/HMS were easily collapsed by heat treatment. Pd(HT)/HMS was thermally decomposed and reduced to form a supported Pd catalyst (abbreviated Pd(Mg(Al)O)/HMS) for methanol decomposition. Pd(Mg(Al)O)/HMS at 3.6 wt% showed a 52.5% conversion which was much higher than those over 3.6 wt% Pd(Mg(Al)O) (34.7%) and 3.6 wt% Pd/HMS (13.7%) for methanol decomposition at 523 K. The conversions of methanol over Pd(Mg(Al)O) and Pd/HMS increased with the increase in Pd loadings from 3.6 to 15 wt% and decreased when the Pd loadings were over 15 wt%. In contrast, the conversion over Pd(Mg(Al)O)/HMS increased with the increase in Pd loading even when the Pd loading was up to 30%. 30 wt% Pd(Mg(Al)O)/HMS showed a 91.7% conversion which was about twice that over 15 wt% Pd(Mg(Al)O) (47.1%) at 523 K. The Pd(Mg(Al)O)/HMS catalyst showed a larger BET surface area and Pd metal surface area than those of Pd(Mg(Al)O). By characterization using XPS analyses, the metal–support interaction between small Pd and small Mg(Al)O became stronger in the Pd(Mg(Al)O)/HMS catalyst. Large surface area, high Pd dispersion and strong metal–support interaction caused the high catalytic activity for methanol decomposition to synthesis gas over the Pd(Mg(Al)O)/HMS catalyst. This revised version was published online in July 2006 with corrections to the Cover Date.