Aging behavior of metal oxide aerogels

Aerogels of titania, zirconia, niobia, and silica were prepared by CO₂ supercritical drying of the corresponding alcogels. Their porous texture could be modified by further aging of the alcogels. This kind of textural modification was found to be different according to the nature of the metal precursor and sol-gel conditions. This paper was presented at the 8th APCChE (Asia Pacific Confederation of Chemical Engineering) Congress held at Seoul between August 16 and 19, 1999.     

Water‐soluble urethane acrylate ionomers: Effect of molecular structure on ultraviolet coating properties

Water‐soluble urethane acrylate ionomers containing dimethylolpropionic acid (DMPA) were synthesized, changing the molecular components, and their ultraviolet (UV) coating properties were studied. It was found that the UV coating properties of the urethane acrylate ionomer films were very dependent on the molecular weight of the soft segment, the type of the diisocyanate, and the amount of neutralization. In general observations, the cured films displayed much improved mechanical properties, compared with conventional urethane acrylate film not containing ionic groups. The main reason for the improved film properties seemed to be attributed to the presence of ionic groups in the network. In dynamic mechanical analysis, two distinct glass transition temperatures, corresponding to the ionic hard domains and soft domains, were detected at high content of ionic groups. This suggested that the urethane acrylate network be composed of two phases. Consequently, the ionic hard domains formed by the phase separation from crosslinked network could act as a reinforcing filler, which possibly explains the improved film properties of the urethane acrylate ionomer films. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1853–1860, 2000     

Effects of particle size of Al(OH)3 on electrical properties of EPDM compounds

Effects of particle size of Al(OH)₃ (ATH) filler on electrical properties of ethylene propylene diene terpolymer (EPDM)/ATH compounds were studied. It was found that tracking and erosion resistance of EPDM/ATH compounds decreased while dielectric properties and 90°C water resistance were improved with the increase of particle size. Homocharge accumulates in the compounds, which increases first and then decreases with the increase of particle size. This was explained by the change of particle‐to‐particle distance due to filler size.     

Neuroprotective and Anti-Inflammatory Effects of Evernic Acid in an MPTP-Induced Parkinson’s Disease Model

Oxidative stress, mitochondrial dysfunction, and neuroinflammation are strongly associated with the pathogenesis of Parkinson’s disease (PD), which suggests that anti-oxidative and anti-inflammatory compounds might provide an alternative treatment for PD. Here, we evaluated the neuroprotective effects of evernic aid (EA), which was screened from a lichen library provided by the Korean Lichen Research Institute at Sunchon National University. EA is a secondary metabolite generated by lichens, including Ramalina, Evernia, and Hypogymnia, and several studies have described its anticancer, antifungal, and antimicrobial effects. However, the neuroprotective effects of EA have not been studied. We found that EA protected primary cultured neurons against 1-methyl-4-phenylpyridium (MPP⁺)-induced cell death, mitochondrial dysfunction, and oxidative stress, and effectively reduced MPP⁺-induced astroglial activation by inhibiting the NF-κB pathway. In vivo, EA ameliorated MPTP-induced motor dysfunction, dopaminergic neuronal loss, and neuroinflammation in the nigrostriatal pathway in C57BL/6 mice. Taken together, our findings demonstrate that EA has neuroprotective and anti-inflammatory effects in PD models and suggest that EA is a potential therapeutic candidate for PD.     

Geometric error measurement of spiral bevel gears using a virtual gear model for STEP-NC

Geometric error measurement is required to evaluate the grade of the manufactured gears. Due to the complexity of the spiral bevel gear, direct measurement with the physical part has been conducted in a very limited way. In this paper, we present an indirect measurement based on the virtual gears model (VGM), obtained by NUBS fitting of the surface points measured by CMM (coordinate measuring machine). By comparing the VGM with CAD model (soft-master model), various errors such as tooth profile error and tooth trace error can be automatically measured. The developed method is simple and robust without requiring a special measuring device, and hence it can be applied for the industrial practice as a means for measuring the tooth profile and tooth trace errors which cannot be measured by the conventional method. Further, the model-based method can be incorporated on the advanced CNC controller based on the new CAM–CNC interface scheme of STEP-NC [STEP (standard for transfer and exchange of product model data) based data model for CAM and CNC interface] as an on-line inspection module. Algorithmic details together with experimental validation results are given.     

Korean Red Ginseng Improves Astrocytic Mitochondrial Function by Upregulating HO-1-Mediated AMPKα–PGC-1α–ERRα Circuit after Traumatic Brain Injury

Heme oxygenase-1 (HO-1) exerts beneficial effects, including angiogenesis and energy metabolism via the peroxisome proliferator-activating receptor-γ coactivator-1α (PGC-1α)–estrogen-related receptor α (ERRα) pathway in astrocytes. However, the role of Korean red ginseng extract (KRGE) in HO-1-mediated mitochondrial function in traumatic brain injury (TBI) is not well-elucidated. We found that HO-1 was upregulated in astrocytes located in peri-injured brain regions after a TBI, following exposure to KRGE. Experiments with pharmacological inhibitors and target-specific siRNAs revealed that HO-1 levels highly correlated with increased AMP-activated protein kinase α (AMPKα) activation, which led to the PGC-1α-ERRα axis-induced increases in mitochondrial functions (detected based on expression of cytochrome c oxidase subunit 2 (MTCO2) and cytochrome c as well as O₂ consumption and ATP production). Knockdown of ERRα significantly reduced the p-AMPKα/AMPKα ratio and PGC-1α expression, leading to AMPKα–PGC-1α–ERRα circuit formation. Inactivation of HO by injecting the HO inhibitor Sn(IV) protoporphyrin IX dichloride diminished the expression of p-AMPKα, PGC-1α, ERRα, MTCO2, and cytochrome c in the KRGE-administered peri-injured region of a brain subjected to TBI. These data suggest that KRGE enhanced astrocytic mitochondrial function via a HO-1-mediated AMPKα–PGC-1α–ERRα circuit and consequent oxidative phosphorylation, O₂ consumption, and ATP production. This circuit may play an important role in repairing neurovascular function after TBI in the peri-injured region by stimulating astrocytic mitochondrial biogenesis.     

Poly(methyl methacrylate) toughening with refractive index‐controlled core–shell composite particles

Poly(butylacrylate‐co‐styrene)/poly(methyl methacrylate) (PMMA) core–shell composite particles having different refractive indexes were prepared by a two‐stage consecutive emulsion polymerization. The refractive index of the core phase was controlled by varying the incorporated amount of divinylbenzene (DVB) which acted as a crosslinking agent as well as a refractive index enhancer. The blends of these core–shell composite particles with PMMA showed an impact strength increment of about three times compared with that of the pure PMMA. However, as the amount DVB increased, the impact strength showed a tendency toward decreasing. This was caused by the loss of the elastic property of the core phase. The toughened PMMA blended with core–shell composite particles having the core crosslinked with 1 wt % DVB showed the best transparency. However, the transparency was rather decreased, as the difference of the refractive index between the core phase and the pure PMMA increased. This suggested that in the case of using the core–shell composite particles as a toughening agent for PMMA the matching of the refractive index of the core phase with that of the pure PMMA was one of key factors in maintaining the transparency of the toughened PMMA. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1607–1614, 1999     

Graft copolymerization of mixtures of acrylic acid and acrylamide onto polypropylene film

Liquid phase ultraviolet irradiation in the presence of benzophenone as a photosensitizer and barium hydroxide as a pH controller were used to graft the mixtures of acrylic acid and acrylamide to a polypropylene surface. The surface of the grafted polypropylene samples were characterized by Fourier transform infrared spectroscopy‐attenuated total reflectance, electron spectroscopy for chemical analysis, scanning electron microscopy, and a contact angle meter. The pH value of the reaction medium that produced the graft with equal molar ratio was found to be ∼ 3.77. The optimal reaction condition was found at a monomer feed of 25%, a reaction time of 30 min, and a benzophenone concentration of 1%. Surface tension of the samples increased to a value of 40 dyn cm⁻¹ due to the graft of the hydrophilic monomers. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 251–256, 1999