Hitoshi Takagi

Bio: Hitoshi Takagi is an academic researcher from St. Marianna University School of Medicine. The author has contributed to research in topics: Ultimate tensile strength & Fiber. The author has an hindex of 35, co-authored 260 publications receiving 4465 citations. Previous affiliations of Hitoshi Takagi include University of Tokushima.

Erythropoietin as a Retinal Angiogenic Factor in Proliferative Diabetic Retinopathy

Abstract: background Although vascular endothelial growth factor (VEGF) is a primary mediator of retinal angiogenesis, VEGF inhibition alone is insufficient to prevent retinal neovascularization. Hence, it is postulated that there are other potent ischemia-induced angiogenic factors. Erythropoietin possesses angiogenic activity, but its potential role in ocular angiogenesis is not established. methods We measured both erythropoietin and VEGF levels in the vitreous fluid of 144 patients with the use of radioimmunoassay and enzyme-linked immunosorbent assay. Vitreous proliferative potential was measured according to the growth of retinal endothelial cells in vitro and with soluble erythropoietin receptor. In addition, a murine model of ischemia-induced retinal neovascularization was used to evaluate erythropoietin expression and regulation in vivo. results The median vitreous erythropoietin level in 73 patients with proliferative diabetic retinopathy was significantly higher than that in 71 patients without diabetes (464.0 vs. 36.5 mIU per milliliter, P<0.001). The median VEGF level in patients with retinopathy was also significantly higher than that in patients without diabetes (345.0 vs. 3.9 pg per milliliter, P<0.001). Multivariate logistic-regression analyses indicated that erythropoietin and VEGF were independently associated with proliferative diabetic retinopathy and that erythropoietin was more strongly associated with the presence of proliferative diabetic retinopathy than was VEGF. Erythropoietin and VEGF gene-expression levels are up-regulated in the murine ischemic retina, and the blockade of erythropoietin inhibits retinal neovascularization in vivo and endothelial-cell proliferation in the vitreous of patients with diabetic retinopathy in vitro. conclusions Our data suggest that erythropoietin is a potent ischemia-induced angiogenic factor that acts independently of VEGF during retinal angiogenesis in proliferative diabetic retinopathy.

Effect of alkali treatment on interfacial bonding in abaca fiber-reinforced composites

Abstract: Abaca fibers demonstrate enormous potential as reinforcing agents in composite materials. In this study, abaca fibers were immersed in 5, 10 or 15 wt.% NaOH solutions for 2 h, and the effects of the alkali treatments on the mechanical characteristics and interfacial adhesion of the fibers in a model abaca fiber/epoxy composite system systematically evaluated. After 5 wt.% NaOH treatment, abaca fibers showed increased crystallinity, tensile strength and Young’s modulus compared to untreated fibers, and also improved interfacial shear strength with an epoxy. Stronger alkali treatments negatively impacted fiber stiffness and suitability for composite applications. Results suggest that mild alkali treatments (e.g. 5 wt.% NaOH for 2 h) are highly beneficial for the manufacture of abaca fiber-reinforced polymer composites.

Polylactic acid (PLA) biocomposites reinforced with coir fibres: Evaluation of mechanical performance and multifunctional properties

Abstract: The effects of fibre content (5–30 wt%) and fibre treatment on surface morphology, tensile, flexural, thermal and biodegradable properties of polylactic acid (PLA)/coir fibre biocomposites were evaluated via scanning electron microscopy (SEM), mechanical testing, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and soil burial method. Similar decreasing trends were found for tensile and flexural strengths with higher strength values obtained for PLA/treated coir fibre biocomposites. 20 wt% treated coir fibres were determined to achieve optimum tensile and flexural strengths of biocomposites. Regardless of fibre treatment, the thermal stability of biocomposites is worsened with increasing the fibre content. The decreased cold crystallisation temperatures of biocomposites further confirms the effective nucleating agent role of coir fibres. The biocomposites undergo much faster degradation than PLA, with the maximum weight loss of 34.9% in treated fibre biocomposites relative to 18% in PLA after 18-day burial, arising from the hydrophilic nature of coir fibres.

Effect of Fiber Length on Mechanical Properties of "Green" Composites Using a Starch-Based Resin and Short Bamboo Fibers

Abstract: This paper describes a method to fabricate short bamboo fiber reinforced “green” composites (BFGC) and evaluate their mechanical properties. The composites were prepared by hot-pressing a mixture of starch-based resin and short bamboo fibers. Their tensile strength and flexural strength were characterized. The effects of fiber content and fiber length on the mechanical properties of BFGC were investigated in detail. Both tensile and flexural strengths of BFGC were strongly affected by fiber aspect ratio and fiber content. Bamboo fibers with a small aspect ratio of 20 do not act as reinforcement but as filler.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Microfibrillated cellulose and new nanocomposite materials: a review

Abstract: Due to their abundance, high strength and stiffness, low weight and biodegradability, nano-scale cellulose fiber materials (e.g., microfibrillated cellulose and bacterial cellulose) serve as promising candidates for bio-nanocomposite production. Such new high-value materials are the subject of continuing research and are commercially interesting in terms of new products from the pulp and paper industry and the agricultural sector. Cellulose nanofibers can be extracted from various plant sources and, although the mechanical separation of plant fibers into smaller elementary constituents has typically required high energy input, chemical and/or enzymatic fiber pre-treatments have been developed to overcome this problem. A challenge associated with using nanocellulose in composites is the lack of compatibility with hydrophobic polymers and various chemical modification methods have been explored in order to address this hurdle. This review summarizes progress in nanocellulose preparation with a particular focus on microfibrillated cellulose and also discusses recent developments in bio-nanocomposite fabrication based on nanocellulose.