Biomedical subjects

A Onuki

Publications and source records attributed to A Onuki.

At least 19 recordsLinked to original sources

PubMed2005

Numerical simulation studies of the convective instability onset in a supercritical fluid.

Numerical simulation studies in 2D with the addition of noise are reported for the convection of a supercritical fluid, 3He , in a Rayleigh-Bénard cell. The noise addition is to accelerate the instability growth after starting the heat flow across the fluid, so as to bring simulations into better agreement with published experimental observations. Homogeneous temperature noise and spatial longitudinal periodic temperature variations in either top or bottom plates were programmed into the simulations. The second method was the most effective in speeding up the instability onset. For a small amplitude of the longitudinal perturbations, a semiquantitative agreement with the observations was obtained. The results are discussed in relation to predictions by El Khouri and Carlès.

Journal Article↗

PubMed2004

Indoor air pollution by alkylphenols in Tokyo.

UNLABELLED: The purposes of this study were to develop an analytical method for airborne alkylphenols (APs) using the gas chromatography/mass spectrometry (GC/MS)-SIM method and to investigate airborne C4-C9 APs pollution in houses, offices, and outdoor points in Tokyo. In addition, to identify APs emission sources in a newly built house, migration tests of APs from interior surfaces to solid extraction disks were performed. Air samples were collected from houses, offices, and outdoor points. The recovery of APs from air samples was increased by addition of ascorbic acid to the filters. 4-tert-butylphenol (4-t-BP), 4-tert-octylphenol (4-t-OP), and 4-nonylphenol (4-NP) were detected in both indoor and outdoor air. Their concentrations and detection frequencies were higher in indoor air than outdoor air. The maximum levels of 4-t-BP, 4-t-OP, and 4-NP in indoor were 387, 45.7, and 680 ng/m(3), respectively. 4-t-BP and 4-NP were detected with high frequencies (more than 97%) in indoor air samples. The concentrations of 4-t-BP, 4-t-OP, and 4-NP in indoor air were significantly correlated with room temperature (P < 0.01), and tended to be higher in newly built houses. The migration rates of APs from the floor, wall, and ceiling in the newly built house were higher in polyvinyl chloride coverings than in other materials. Practical Implications Alkylphenol ethoxylate (APE) are widely used surfactants in both industrial and domestic detergents. When these detergents are released into the environment, APE are biodegraded to the smaller chain ethoxylates and alkylphenols (APs). There are many reports about APs in aquatic environments because of their estrogenic effect on wildlife. In building materials, APs are used as antioxidant for polymer resins such as wall or floor coverings. Although APs has a lower vapor pressure, these agents are released into indoor air from the surface of polymer resins. This study surveyed concentrations of airborne AP in indoor air and outdoor air in Tokyo. In addition, to identify APs emission sources in a newly built house, migration tests of APs from interior surfaces to solid extraction disks were performed. PRACTICAL IMPLICATIONS: Alkylphenol ethoxylate (APE) are widely used surfactants in both industrial and domestic detergents. When these detergents are released into the environment, APE are biodegraded to the smaller chain ethoxylates and alkylphenols (APs). There are many reports about APs in aquatic environments because of their estrogenic effect on wildlife. In building materials, APs are used as antioxidant for polymer resins such as wall or floor coverings. Although APs has a lower vapor pressure, these agents are released into indoor air from the surface of polymer resins. This study surveyed concentrations of airborne AP in indoor air and outdoor air in Tokyo. In addition, to identify APs emission sources in a newly built house, migration tests of APs from interior surfaces to solid extraction disks were performed.

Air Pollution, Indoor↗

PubMed2003

Convection in a very compressible fluid: comparison of simulations with experiments.

The time profile DeltaT(t) of the temperature difference, measured across a very compressible fluid layer of supercritical 3He after the start of a heat flow, shows a damped oscillatory behavior before steady-state convection is reached. The results for DeltaT(t) obtained from numerical simulations and from laboratory experiments are compared over a temperature range where the compressibility varies by a factor of approximately 40. First the steady-state convective heat current j(conv) as a function of the Rayleigh number Ra is presented, and the agreement is found to be good. Second, the shape of the time profile and two characteristic times in the transient part of DeltaT(t) from simulations and experiments are compared, namely (1) t(osc), the oscillatory period, and (2) t(p), the time of the first peak after starting the heat flow. These times, scaled by the diffusive time tau(D) versus Ra, are presented. The agreement is good for t(osc)/tau(D), where the results collapse on a single curve showing a power-law behavior. The simulation hence confirms the universal scaling behavior found experimentally. However for t(p)/tau(D), where the experimental data also collapse on a single curve, the simulation results show systematic departures from such a behavior. A possible reason for some of the disagreements, both in the time profile and in t(p), is discussed.

Journal Article↗

PubMed2001

Thermal plumes and convection in highly compressible fluids.

We present simple hydrodynamic equations of supercritical fluids close to the gas-liquid critical point. We numerically solve them to examine plume generation and convection under gravity. These results are in good agreement with the experiment [A. B. Kogan and H. Meyer, Phys. Rev. E 63, 056310 (2001)]. This Letter is a first study of transient behavior of convection, which is unique in compressible fluids due to the piston effect.

Journal Article↗

PubMed2001

Phase transitions of binary alloys with elastic inhomogeneity.

In elastically inhomogeneous alloys, in which the shear modulus depends on the composition, coarsening in phase separation can be pinned even without quenched disorder. Here networks in the soft phase enclose the domains in the hard phase. Highly asymmetric strains in the two regions create large free energy barriers that prevent further coarsening. Thus a phase transition occurs between the one-phase and the glassy two-phase states. We numerically obtain the phase diagram and show that this transition is discontinuous at any composition. Therefore there is no critical point.

Journal Article↗

PubMed1999

Detection of porcine circovirus from lesions of a pig with wasting disease in Japan.

A wasting disease characterized by progressive weight loss and dyspnea has been observed in weaning pigs on a farm in Yamagata Prefecture in 1998. Histopathologic findings in an affected pig were bronchointerstitial pneumonia and intracytoplasmic clusters of basophilic inclusions in macrophages of lymph nodes, which were similar to those in pigs with postweaning multisystemic wasting syndrome (PMWS) recently reported in North America and Europe. Porcine circovirus (PCV)-like particles were observed in bronchial lymph node of the pig by electron microscopy, and PCV antigens were detected in the lesions by immunohistochemical staining. PCV DNA was also detected in the lung and tonsil by PCR, and restriction fragment length polymorphism analysis of the PCR products with HinfI showed the same type of the PCV associated with PMWS (pmws PCV). Homology of nucleotide sequences between the PCR product and corresponding regions of published pmws PCV genomes was very high. These results indicated that virus detected in this study was pmws PCV. To our knowledge, this is the first report on the presence of pmws PCV in Japan.

Amino Acid Sequence↗

PubMed1996