Measurement of surface dryout near heating surface at high heat fluxes in subcooled pool boiling

The authors have conducted measurements of liquid–vapor behavior in the vicinity of a heating surface for saturated and subcooled pool boiling on an upward-facing copper surface by using a conductance probe method. A previous paper [A. Ono, H. Sakashita, Liquid–vapor structure near heating surface at high heat flux in subcooled pool boiling, Int. J. Heat Mass Transfer 50 (2007) 3481–3489] reported that thicknesses of a liquid rich layer (a so-called macrolayer) forming in subcooled boiling are comparable to or thicker than those formed near the critical heat flux (CHF) in saturated boiling. This paper examines the dryout behavior of the heating surface by utilizing the feature that a thin conductance probe placed very close to the heating surface can detect the formation and dryout of the macrolayer. It was found that the dryout of the macrolayer formed beneath a vapor mass occurs in the latter half of the hovering period of the vapor mass. Two-dimensional measurements conducted at 121 grid points in a 1-mm × 1-mm area at the center of the heating surface showed that the dryout commences at specific areas and spreads over the heating surface as the heat flux approaches the CHF. Furthermore, transient measurements of wall void fractions from nucleate boiling to transition boiling were conducted under the transient heating mode, showing that the wall void fraction has small values (<10%) in the nucleate boiling region, and then steeply increases in the transition boiling region. These findings strongly suggest that the macrolayer dryout model is the most appropriate model of the CHF for saturated and subcooled pool boiling of water on upward facing copper surfaces.     

Temperature measurements near a heating surface at high heat fluxes in subcooled pool boiling

In previous papers (Int J Heat Mass Transfer, 2008;50:3481–3489, 2009;52: 814–821), the authors conducted measurements of liquid–vapor structures in the vicinity of a heating surface for subcooled pool boiling on an upward‐facing copper surface by using a conducting probe method. We reported that the macrolayer dryout model is the most appropriate model of the CHF and that the reason why the CHF increases with increasing subcooling is most likely that a thick macrolayer is able to form beneath large vapor masses and the lowest heat flux of the vapor mass region shifts towards the higher heat flux. To develop a mechanistic model of the CHF for subcooled boiling, therefore, it is necessary to elucidate the effects of local subcooling on boiling behaviors in the vicinity of a heating surface. This paper measured local temperatures close to a heating surface using a micro‐thermocouple at high heat fluxes for water boiling on an upward‐facing surface in the 0 to 40 K range of subcooling. A value for the effective subcooling, defined as the local subcooling during the period while vapor masses are being formed was estimated from the detected bottom peaks of the temperature fluctuations. It was established that the effective subcooling adjacent to the surface remains at considerably lower values than the bulk liquid subcooling. This suggests that, from nucleation to coalescence, the subcooling of a bulk liquid has a smaller effect on the behavior of primary bubbles than the extent of the subcooling would appear to suggest. An empirical correlation of the effective subcooling is proposed to provide a step towards quantitative modeling of the CHF for subcooled boiling. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20277     

Characterization of Dynamics in Materials Using Time-Resolved Electron Microscopy Incorporating Electron Counting and Electron Correlation Spectroscopy

Time-resolved electron microscopy incorporating electron counting and electron correlation spectroscopy can be used to quantify the dynamics in materials faster than the shot noise limit of the real-time observation in conventional transmission electron microscopy. An imaging electron beam current, temporally modulated by the dynamics of the specimen, is selected by the aperture in the image plane, and is measured by means of an electron counting technique. Applications of the method to the study of the dynamics of superconducting vortices and to the observation of nanovibrations of materials associated with elastic properties are discussed.     

Feasibility study of hydrogen production from wind power in the region of Ghardaia

A feasibility study on hydrogen production from wind power on the site of Ghardaia is carried out. This study is based on the estimation of the hydrogen rate produced by a 5 kW electrolyser fed by the electricity provided by a 10 kW wind turbine.Wind speed data were used to study the monthly variation of the wind power delivered and its variation according to the height of the wind turbine tower.The obtained results show that it is possible to improve the system output by increasing the height of the wind turbine tower. Indeed, it has been obtained 3200 Nm³ of hydrogen production for a 30 m wind turbine height and 4200 Nm³ at 60 m.In addition, it has been noticed that hydrogen production varies strongly with the months of the year. Thus, the production has reached a maximum of 395 Nm³ in May and a minimum of 187 Nm³ during November and October.     

Association of Ligamentum Flavum Hypertrophy with Adolescent Idiopathic Scoliosis Progression—Comparative Microarray Gene Expression Analysis

The role of the ligamentum flavum (LF) in the pathogenesis of adolescent idiopathic scoliosis (AIS) is not well understood. Using magnetic resonance imaging (MRI), we investigated the degrees of LF hypertrophy in 18 patients without scoliosis and on the convex and concave sides of the apex of the curvature in 22 patients with AIS. Next, gene expression was compared among neutral vertebral LF and LF on the convex and concave sides of the apex of the curvature in patients with AIS. Histological and microarray analyses of the LF were compared among neutral vertebrae (control) and the LF on the apex of the curvatures. The mean area of LF in the without scoliosis, apical concave, and convex with scoliosis groups was 10.5, 13.5, and 20.3 mm², respectively. There were significant differences among the three groups (p < 0.05). Histological analysis showed that the ratio of fibers (Collagen/Elastic) was significantly increased on the convex side compared to the concave side (p < 0.05). Microarray analysis showed that ERC2 and MAFB showed significantly increased gene expression on the convex side compared with those of the concave side and the neutral vertebral LF cells. These genes were significantly associated with increased expression of collagen by LF cells (p < 0.05). LF hypertrophy was identified in scoliosis patients, and the convex side was significantly more hypertrophic than that of the concave side. ERC2 and MAFB genes were associated with LF hypertrophy in patients with AIS. These phenomena are likely to be associated with the progression of scoliosis.     

A parallel method for large sparse generalized eigenvalue problems using a GridRPC system

In this paper we present a master–worker type parallel method for finding several eigenvalues and eigenvectors of a generalized eigenvalue problem , where A and B are large sparse matrices. A moment-based method that finds all of the eigenvalues that lie inside a given domain is used. In this method, a small matrix pencil that has only the desired eigenvalues is derived by solving large sparse systems of linear equations constructed from A and B. Since these equations can be solved independently, we solve them on remote servers in parallel. This approach is suitable for master–worker programming models. We have implemented and tested the proposed method in a grid environment using a grid RPC (remote procedure call) system called OmniRPC. The performance of the method on PC clusters that were used over a wide-area network was evaluated.     

A New Catalyst for Selective Oxidation of CO in H2: Part 1, Activation by Depositing a Large Amount of FeO x on Pt/Al2O3 and Pt/CeO2 Catalysts

1% Pt/Al₂O₃ and 1% Pt/CeO₂ are markedly activated by the deposition of a large quantity of FeO _x , about 100 wt% in Fe with respect to the supports. In contrast, the activity of a Ru/Al₂O₃ catalyst was completely suppressed by the deposition of FeO _x , but a Ru-Pt/Al₂O₃ was markedly activated by the FeO _x . The activation depends on the sequence of the deposition, that is, no pronounced activation was observed on the Pt supported on a FeO _x /Al₂O₃ as well as on the Pt codeposited with a small amount of Fe on Al₂O₃, that is, the activity was almost equal to that of the Pt/Al₂O₃. The XPS analysis of the Pt/CeO₂ and FeO _x /Pt/CeO₂ proved that the Pt is effectively covered with the FeO _x . Selectivity for the oxidation of CO in H₂ was also improved on the FeO _x /Pt/Al₂O₃ and FeO _x /Pt/CeO₂ catalysts and it is rather independent of the conversion. In conformity with the feature of the FeO _x /Pt/Al₂O₃ and FeO _x /Pt/CeO₂ catalysts, we deduced that the deposited FeO _x is activated by the Pt and the FeO _x is responsible for the selective oxidation of CO.     

Polyethylene glycol-modified pokeweed mitogen (PWM) as a potential non-immunogenic stimulator of lymphokine-activated killer cells

Among the various plant lectins, pokeweed mitoge (PWM) is most effective in enhancing the cytotoxicity of human lymphokine-activated killer (LAK) cells. However, the use of PWM in adoptive immunotherapy has been limited due to the strong immune response against the protein of plant origin. Amino groups in PWM was modified with 2,4-bis[O-methoxypoly(ethylene glycol)]-6-chioro-s-triazine, activated PEG2, to form PEG-PWM conjugates. Its immunoreactivity towards anti-PWM antibodies was reduced by increasing the degree of modification of amino groups in PWM. PEG-PWM, in which 54% of amino groups in PWM was modified with activated PEG2, had a nearly complete reduction of immunoreactivity. Intraperitoneal administration of PEG-PWM to mice did not produce substantial levels of anti-PWM antibodies. Nevertheless, PEG-PWM retained the ability to induce the maximum levels of cytotoxicity of human LAK cells in vitro.     

Usefulness of myeloperoxidase as a biomarker for the ranking of pulmonary toxicity of nanomaterials

Background

In order to examine whether myeloperoxidase (MPO) can be a useful marker for evaluating the pulmonary toxicity of nanomaterials, we analyzed MPO protein in bronchoalveolar lavage fluid (BALF) samples obtained from previous examinations of a rat model. In those examinations we performed intratracheal instillation exposures (dose: 0.2–1.0 mg) and inhalation exposures (exposure concentration: 0.32–10.4 mg/m³) using 9 and 4 nanomaterials with different toxicities, respectively. Based on those previous studies, we set Nickel oxide nanoparticles (NiO), cerium dioxide nanoparticles (CeO₂), multi wall carbon nanotubes with short or long length (MWCNT (S) and MWCNT (L)), and single wall carbon nanotube (SWCNT) as chemicals with high toxicity; and titanium dioxide nanoparticles (TiO₂ (P90) and TiO₂ (Rutile)), zinc oxide nanoparticles (ZnO), and toner with external additives including nanoparticles as chemicals with low toxicity. We measured the concentration of MPO in BALF samples from rats from 3 days to 6 months following a single intratracheal instillation, and from 3 days to 3 months after the end of inhalation exposure.

Results

Intratracheal instillation of high toxicity NiO, CeO_2, MWCNT (S), MWCNT (L), and SWCNT persistently increased the concentration of MPO, and inhalation of NiO and CeO₂ increased the MPO in BALF. By contrast, intratracheal instillation of low toxicity TiO₂ (P90), TiO₂ (Rutile), ZnO, and toner increased the concentration of MPO in BALF only transiently, and inhalation of TiO₂ (Rutile) and ZnO induced almost no increase of the MPO. The concentration of MPO correlated with the number of total cells and neutrophils, the concentration of chemokines for neutrophils (cytokine-induced neutrophil chemoattractant (CINC)-1 and heme oxygenase (HO)-1), and the activity of released lactate dehydrogenase (LDH) in BALF. The results from the receiver operating characteristics (ROC) for the toxicity of chemicals by the concentration of MPO proteins in the intratracheal instillation and inhalation exposures showed that the largest areas under the curves (AUC) s in both examinations occurred at 1 month after exposure.

Conclusion

These data suggest that MPO can be a useful biomarker for the ranking of the pulmonary toxicity of nanomaterials, especially at 1 month after exposure, in both intratracheal instillation and inhalation exposure.

     

Wettability of liquid caesium iodine and boron oxide on yttria-stabilized zirconia

During the Fukushima Daiichi Nuclear Power Plant accident occurred in 2011, volatile fission products (FPs) such as Cs and I had released and caused environmental contamination and public exposure, respectively. However, the release mechanism of these FPs from fuels under the accident is still not completely understood. In recent years, we have focused on the wettability of liquid FPs against solid fuels, because the interface between the fuel surface and the FPs becomes the migration pathway, which might have large influences on the release behaviour of the FPs. Here, we studied the wettability of liquid CsI and B₂O₃ on yttria-stabilized zirconia (YSZ) solid surface by the sessile drop test, where YSZ is a simulated material of the fuel. It was revealed that liquid CsI exhibited extremely high wettability against the YSZ surface with the contact angle of nearly zero. This high wettability may act to suppress the FPs release. Furthermore, it was confirmed that the crystal orientation and surface roughness of the YSZ solids have large influences on the wettability of liquid B₂O₃. The present results contribute for deep understanding of the release behaviour of the volatile FPs from fuels.