A New Process to Make a Porous PTFE Structure from Aqueous PTFE Dispersion with the Help of Hydrogel

A novel method to make a porous material having relatively large cell diameter (200–300 m), which consisted of mainly poly(tetrafluoroethylene) (PTFE), was developed from aqueous PTFE dispersion by using the characteristics of hydrogel with the addition of carbon nanofiber (CNF). The porous material was produced as follows: firstly, an aqueous agar gel containing PTFE and CNF was prepared; secondly, the gel was freeze-dried; thirdly, the dried gel was heat-treated at 400°C where the agar was almost decomposed and PTFE became molten. The porous material showed electric conductivity (about 50 ), high porosity (about 96 vol%), and relatively uniform cell structures without shrinkage during freeze drying and heat treatment. While the method without CNF resulted in large shrinkage during heat treatment, meaning that CNF prevented the shrinkage. It was explained by the idea that the existence of rigid CNF, which was dispersed in the cell wall, prohibited the shrinkage of PTFE during heat treatment. It was unexpectedly found by SEM analysis that the porous materials had another macro-porous structure inside the cell wall, suggesting that the developed materials had a double porous structure.     

Detection of light-absorbing iron oxide particles using a modified single-particle soot photometer

Copyright © 2016 American Association for Aerosol Research     

Effect of morphology on shear viscosity for binary blends of polycarbonate and polystyrene

The structure and rheological properties of binary blends of polycarbonate (PC) and polystyrene (PS) were investigated using various PS samples with different molecular weights, namely PS1k (M_w = 1,000), PS53k (M_w = 53,000), and PS240k (M_w = 240,000). The blends with PS53k and PS240k show phase-separated structures, whereas the blend with PS1k is miscible. The shear viscosity decreases greatly on addition of PS53k and PS240k, especially at high shear rates, which would be a great advantage at processing operations. Because the nonlinear response occurs in the small strain region for multilayered films of PC and PS240k, the origin of the significant viscosity drop for the phase-separated system is interfacial slippage at the phase boundary.     

Oxidation resistant ceramic foam from a silicone preceramic polymer/polyurethane blend

Silicon oxycarbide (SiOC) ceramic foams, produced by the pyrolysis of a foamed blend of a methylsilicone preceramic polymer and polyurethane (PU) in a 1/1 wt.% ratio, exhibit excellent physical and mechanical properties. The proposed process allows to easily modify the density and morphology of the foams, making them suitable for several engineering applications. However, it has been shown that, due to residual carbon present in the oxycarbide phase after pyrolysis, the foams are subjected to an oxidation process that reduces their strength after high temperature exposure to air (12 h 1200°C). A modified process, employing the same silicone resin preceramic polymer but a much lower PU content (silicone resin/PU=5.25/1 wt.% ratio), has been developed and is reported in this paper. Microstructural investigations showed that carbon rich regions deriving from the decomposition of the polyurethane template are still present in the SiOC foam, but have a much smaller dimension than those found in foams with a higher PU content. Thermal gravimetric studies performed in air or oxygen showed that the low-PU containing ceramic foams display an excellent oxidation resistance, because the carbon-rich areas are embedded inside the struts or cell walls and are thus protected by the dense silicon oxycarbide matrix surrounding them. SiOC foams obtained with the novel process are capable to maintain their mechanical strength after oxidation treatments at 800 and 1200°C (12 h), while SiOC foams obtained with a higher amount of PU show about a 30% strength decrease after oxidation at 1200°C (12 h).     

Simultaneous measurement of void fraction and fundamental bubble parameters in subcooled flow boiling

Visualization was performed for the vapor bubbles in water subcooled flow boiling in a vertical heated tube to measure simultaneously the void fraction and the four fundamental bubble parameters: nucleation site density, bubble release frequency, bubble lifetime and bubble size. Using the mass flowrate and liquid subcooling as the experimental parameters, the changes of void fraction and bubble parameters with the wall heat flux were measured. The results of image analysis showed that the vapor void fraction could be approximated by the function of nucleation site density and bubble lift-off diameter; the bubble lift-off diameter was more influential than the nucleation site density. It was hence concluded that the bubble lift-off diameter could be regarded as the key parameter to determine the vapor void fraction under the present experimental conditions. The strong relation of bubble lift-off diameter to superheated liquid layer thickness was indicated for the future model development studies of bubble lift-off diameter.     

A simple and fast method to disperse long single-walled carbon nanotubes introducing few defects

A simple and fast dispersion method that incorporates heating is used to disperse long (more than 10 μm) single-walled carbon nanotubes (SWCNTs) with minimal defects. The method enables a dispersed solution of SWCNTs to be produced in less than 10 min in only three steps: (1) addition of the dispersant, (2) heating, and (3) grinding. The dispersion method does not require sonication, which shortens the SWCNTs and can generate surface defects. SWCNT films were prepared from the dispersed solution, and the films exhibited a resistance of 380 Ω/sq at a transparency of 64.8%. This dispersion method can be easily scaled up, making it useful for the preparation of dispersed SWCNTs for commercial and industrial applications.     

Zeta potential measurement on the surface of blue-green algae particles for micro-bubble process.

Any kind of blue-green alga produces metabolites of musty substances and toxins. Therefore, it is necessary to remove the blue-green algae, and processing also including nutrient removal is desired for the water quality improvement of eutrophic lakes. The purpose of this study has been to investigate the possibility of a flotation system using a hybrid technique (chemical compounds and electrostatic bridge) applied to raw water containing phytoplankton with high pH of water, and to examine the zeta potential value of phytoplankton surface and the removal efficiency for phytoplankton, ammonia, nitrogen, and phosphoric acid.The results were as follows: firstly, zeta potential of M. aeruginosa particles was observed to achieve charge neutralization on their surface by adhesion of magnesium hydroxide precipitation with increasing pH. Secondly, maximum removal efficiency concerning chlorophyll-a was observed as 84%, and this efficiency was obtained in the condition of pH > 10, and magnesium hydroxide precipitation was observed. Thirdly, in the pH condition that the maximum removal efficiency of chlorophyll-a was obtained, the removal efficiency and the amount of decrease of NH(4)-N and PO(4)-P before and after the change of pH values were observed as 6.7% (0.04 mg-P/L) and 63.6% (0.07 mg-N/L), respectively.     

An experience of the modified Norwood's operation for hypoplastic left heart syndrome with aberrant origin of right subclavian artery and persistent left superior vena cava--the procedure without total circulatory arrest and cardiac arrest

We reported a successful case of the modified Norwood operation for a 21-day-old neonate with hypoplastic left heart syndrome (MS and AS) associated with an aberrant right subclavian artery and a persistent left superior vena cava. The modified Norwood operation was performed without total circulatory arrest and Cardiac arrest. A 4 mm Gore-Tex graft, which was anastomosed between the right carotid artery and the right pulmonary artery for systemic-pulmonary shunt, was used for cerebral perfusion during aortic arch reconstruction. Coronary perfusion was performed with a small cannula placed on the relatively large ascending aorta during anastomosis between the main pulmonary artery and the ascending aorta. Equine pericardial patch was used for aortic arch reconstruction and the ascending aorta was directly anastomosed to a part of the main PA. Postoperative course was uneventful and postoperative MRI revealed no stenosis of the aortic arch and the pulmonary artery.     

Novel system of electro-catalysts for methanol oxidation based on platinum and organic metal complexes

Novel system of electro-catalysts was developed for methanol oxidation reaction (MOR) in direct methanol fuel cells. Mixture of platinum tetraammine complex with cobalt quinolyldiamine complex with various mixing ratio was supported on graphite powder, and heat treated at 400-1000 °C in argon atmosphere. Powder thus obtained was put on a graphite disk electrode, and tested for electrochemical MOR in acid media. Although the cobalt complex itself showed almost no catalytic ability for MOR, it enhanced the activity of Pt more than several 10-fold when it was mixed with Pt. MOR performance was best exploited at about equal mixing ratio of platinum and cobalt complexes. Compared with platinum-ruthenium alloy catalysts, the new catalysts exhibited promising catalytic ability. The present investigation revealed good potentiality of organic complex catalysts in combination with metal catalysts for MOR, which opens the way to synthesize and develop a new class of electro-catalysts of low cost through wide range of molecular designing.     

Clinical and pathological significance of numerical aberrations of chromosomes 11 and 17 in colorectal neoplasms

Numerical chromosome aberrations by interphase cytogenetic analysis have been reported in a few samples of colorectal neoplasms. No studies have defined a distinct relationship between these aberrations and clinicopathological features. To investigate the chromosome aberrations as a marker of invasiveness or prognosis, we conducted an interphase cytogenetic study using fluorescence in situ hybridization and examined 142 colorectal neoplasms consisting of 15 adenomas and 127 cancers. The target chromosomes were chromosomes 11 and 17. We also evaluated the nuclear DNA content as detected by flow cytometry, analyzed the relationship between the frequency of aneusomy and clinicopathological features, and examined the survival rate in these patients. The loss of chromosome 11 was observed in 31% of adenomas, whereas in cancers DNA aneuploidy was observed in 63% of cases, a gain of chromosome 17 was observed in 63% of cases, and a gain of chromosome 11 was observed in 42% of cases. Numerical chromosome aberrations in diploid DNA were also observed. Increased depth of invasion (>/=T3) and advanced Dukes' stage (>/=B) of malignant tumors were associated with a higher frequency of a gain of chromosome 11 (P < 0.01 and P < 0.05, respectively). Increased depth of invasion (>/=T2) in cancers was associated with a higher frequency of a gain of chromosome 17 (P < 0.05). Multivariate analysis of postoperative survival showed that a loss or gain of chromosome 11 was independently associated with a poor prognosis (P < 0.05). Numerical chromosome aberrations appear prior to the alteration of nuclear DNA content as detected by flow cytometry and influence the progression of colorectal cancers. Aneusomy of chromosome 11 is associated with poor postoperative prognosis of primary colorectal cancers.