Improvement of the surface quality of foam injection molded products from a material property perspective

Microcellular injection molding is an attractive method. However, their surface imperfections have been a major problem hindering wide industrial applications. Several methods have been proposed to improve the surface appearance of foams. In this study, we proposed a method to improve the surface appearance of polypropylene (PP) foams from the material property perspective, especially with regard to crystallization and viscosity. The basic idea of the surface improvement is to reduce the size of bubbles generated at the flow front, delay the solidification behavior of the polymer at the mold interface, squeeze the bubbles existing at the mold–polymer interface, and redissolve the bubbles into the polymer by holding pressure. Blending a low-modulus PP delays the crystallization of the polymers at the skin layer and solidification, taking enough time to squeeze the bubbles smaller. A sorbitol-based gelling agent, bis-O-([4 methylphenyl]methylene)-D-Glucitol, was used to increase the viscosity at a low strain rate to reduce the size of the bubbles generated at the flow front during the filling stage. The foam injection molding experiments demonstrated that the proposed method effectively improved the surface appearance of the foams. In particular, the surface appearance of the foams became almost equivalent to that of solid samples using low-modulus PP.     

Relationship Between the B-Ring Hydroxylation Pattern of Condensed Tannins and their Protein-Precipitating Capacity

A series of condensed tannin derivatives with non-, mono-, di- and tri-hydroxylated B-rings were synthesized starting from phloroglucinol and benzaldehyde derivatives. The protein-precipitating capacity of these condensed tannin derivatives showed 1) A condensed tannin with only a 4′-hydroxylated B-ring has almost the same protein-precipitating capacity as that of a condensed tannin with 3′,4′-dihydroxylated or 3′,4′,5′-trihydroxylated B-rings. 2) The complexing ability of phenolic hydroxyl groups in the B-ring are effective in the order of p- > m- > o-positions.     

Neuroprotective Effects of Liraglutide for Stroke Model of Rats

The number of diabetes mellitus (DM) patients is increasing, and stroke is deeply associated with DM. Recently, neuroprotective effects of glucagon-like peptide-1 (GLP-1) are reported. In this study, we explored whether liraglutide, a GLP-1 analogue exerts therapeutic effects on a rat stroke model. Wistar rats received occlusion of the middle cerebral artery for 90 min. At one hour after reperfusion, liraglutide or saline was administered intraperitoneally. Modified Bederson’s test was performed at 1 and 24 h and, subsequently, rats were euthanized for histological investigation. Peripheral blood was obtained for measurement of blood glucose level and evaluation of oxidative stress. Brain tissues were collected to evaluate the level of vascular endothelial growth factor (VEGF). The behavioral scores of liraglutide-treated rats were significantly better than those of control rats. Infarct volumes of liraglutide-treated rats at were reduced, compared with those of control rats. The level of derivatives of reactive oxygen metabolite was lower in liraglutide-treated rats. VEGF level of liraglutide-treated rats in the cortex, but not in the striatum significantly increased, compared to that of control rats. In conclusion, this is the first study to demonstrate neuroprotective effects of liraglutide on cerebral ischemia through anti-oxidative effects and VEGF upregulation.     

Effect of the t–m transformation morphology and stress distribution around the crack path on the measured toughness of zirconia ceramics: A case study on Ce-TZP/alumina nanocomposite

The t–m transformation zone and related residual stress fields around two types of crack used for toughness measurements, i.e. SEVNB (arrested crack induced by a V-notch) and IF methods (indentation crack induced by a Vickers impression), are reported for a Ce-TZP/Al₂O₃ nanocomposite, in comparison with 3Y-TZP. The fact that Ce-TZP/Al₂O₃ exhibits significant high toughness value on occasions when evaluated by the IF method was determined to be clearly linked to the presence of wide ranged three-dimensional transformation configuration and resulting substantial compressive residual stress fields. In contrast, for 3Y-TZP, transformation behaviors around the two types of crack were quite similar, which proves that 3Y-TZP shows near toughness values for both SEVNB and IF methods.     

Novel CO2 Absorbents Using Lithium-Containing Oxide

We have discovered a series of lithium-containing oxides that immediately react with ambient carbon dioxide (CO₂) up to 700°C. The products react and return reversibly to the oxides at a temperatures higher than about 700°C. The absorption capacity surpasses that of other CO₂ absorbents by a factor of 10. Utilizing these absorbents, the possibility of a CO₂ separation system that operates at around 500°C is proposed. It is generally believed that a CO₂ separation process operable at temperatures higher than 500°C has the special benefit of a small energy penalty. Moreover, the absorption also proceeds at ambient temperature in the atmospheric environment. This property offers the possibility of many other applications, such as air cleaners or cartridges. Therefore, we think these materials have the potential to make a valuable contribution to the realization of CO₂ emission control.     

Polarization dependent optical absorption properties of single-walled carbon nanotubes and methodology for the evaluation of their morphology

Polarization dependence of the optical absorption properties of SWNTs is presented and investigated in detail for the energy range 0.5-6 eV. We found that the absorption peaks in the UV region at approximately 4.5 and 5.25 eV exhibit remarkable and different dependencies on the morphology of the SWNT film, or equivalently, on the incident light polarization relative to the SWNT axis. An analytical pathway to evaluate the physical degree of SWNT alignment for a vertically aligned SWNT film is developed with both transition dipoles parallel and perpendicular to the SWNT axis taken into account. This analytical procedure, coupled with polarized optical absorption measurements performed on the vertically aligned SWNT film grown on substrates, leads to the determination of the bare optical absorption cross-section of SWNTs for both parallel and perpendicular to SWNT axis. In the end, the proposed methodology for evaluating the SWNT film morphology is applied to investigate the transient change of the degree of alignment in the growth process of our vertically aligned SWNT films.     

Gas diffusion electrodes for polymer electrolyte fuel cells using novel organic/inorganic hybrid electrolytes: effect of carbon black addition in the catalyst layer

We have prepared novel gas diffusion electrodes for polymer electrolyte fuel cells (PEFC) using new organic/inorganic hybrid electrolytes. The catalyst layers were prepared by mixing 3-(trihydroxysilyl)-1-propanesulfonic acid [(THS)Pro-SO₃H], 1,8-bis(triethoxysilyl) octane (TES-Oct), Pt loaded carbon black (Pt-CB) and water, followed by a sol-gel reaction. It was found that addition of uncatalyzed carbon black (u-CB) into the cathode catalyst layer enhanced the performance at high current density region, due to an increase in the gas diffusion rate. The optimum volume ratio of u-CB/Pt-CB was found to be 0.1, at which the gas diffusivity and the catalyst utilization are well balanced.     

Synthesis and Reactions of Organometallic Polymers Containing Titanacyclobutene Units in the Main Chain

A new class of polymers containing titanacyclobutene units in the main chain were prepared by the reaction of organic dihalides (2) with a binuclear titanium propargyl complex (3) generated in situ from bis(pentamethylcyclopentadienyl)titanium chloride (Cp*₂TiCl, 1), SmI₂, and 1,4-bis(3-bromopropynyl)benzene (2a). The dark red colored polymers (4) thus obtained are soluble in organic solvents such as tetrahydrofuran and chloroform, and they are stable at ambient temperature under argon atmosphere. The reaction of the titanium-containing polymers (4) with hydrogen chloride was found to give organic polymers (7) containing unsaturated main chain.     

Strategies to Improve the Efficiency of Somatic Cell Nuclear Transfer

Mammalian oocytes can reprogram differentiated somatic cells into a totipotent state through somatic cell nuclear transfer (SCNT), which is known as cloning. Although many mammalian species have been successfully cloned, the majority of cloned embryos failed to develop to term, resulting in the overall cloning efficiency being still low. There are many factors contributing to the cloning success. Aberrant epigenetic reprogramming is a major cause for the developmental failure of cloned embryos and abnormalities in the cloned offspring. Numerous research groups attempted multiple strategies to technically improve each step of the SCNT procedure and rescue abnormal epigenetic reprogramming by modulating DNA methylation and histone modifications, overexpression or repression of embryonic-related genes, etc. Here, we review the recent approaches for technical SCNT improvement and ameliorating epigenetic modifications in donor cells, oocytes, and cloned embryos in order to enhance cloning efficiency.