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Linh, Nguyen Thuy Ba,Huyen, Nguyen Thi Dieu,Noh, Seok Kyun,Lyoo, Won Seok,Lee, Dong-Ho,Kim, Yongman Elsevier 2009 Journal of organometallic chemistry Vol.694 No.21
<P><B>Graphical abstract</B></P><P>Dinuclear half-titanocene bearing a xylene bridge, <I>ortho-</I> and <I>meta-</I>xylene, have been successfully synthesized and introduced for styrene polymerization. The activities of the catalysts with rigid <I>ortho</I>- and <I>meta</I>-xylene bridges were higher than those of catalysts with flexible pentamethylene bridges. Activity of the catalysts increased with higher temperature and [Al]:[Ti].</P><ce:figure></ce:figure> <P><B>Abstract</B></P><P>Half-titanocene is well-known as an excellent catalyst for the preparation of SPS (syndiotactic polystyrene) when activated with methylaluminoxane (MAO). Dinuclear half-sandwich complexes of titanium bearing a xylene bridge, <I>(Ti</I>Cl<SUB>2</SUB>L<I>)<SUB>2</SUB>{(μ-η<SUP>5</SUP>, η<SUP>5</SUP>-C<SUB>5</SUB>H<SUB>4</SUB>-ortho-(CH<SUB>2</SUB>–C<SUB>6</SUB>H<SUB>4</SUB>–CH<SUB>2</SUB>)C<SUB>5</SUB>H<SUB>4</SUB>}</I>, (<B>4</B> (L=Cl), <B>7</B> (L=O-2,6-<I>i</I>Pr<SUB>2</SUB>C<SUB>6</SUB>H<SUB>3</SUB>)) and <I>(Ti</I>Cl<SUB>2</SUB>L<I>)<SUB>2</SUB>{(μ-η<SUP>5</SUP>, η<SUP>5</SUP>-C<SUB>5</SUB>H<SUB>4</SUB>-meta-(CH<SUB>2</SUB>–C<SUB>6</SUB>H<SUB>4</SUB>–CH<SUB>2</SUB>)C<SUB>5</SUB>H<SUB>4</SUB>}</I> (<B>5</B> (L=Cl), <B>8</B>(L=O-2,6-<I>i</I>Pr<SUB>2</SUB>C<SUB>6</SUB>H<SUB>3</SUB>)), have been successfully synthesized and introduced for styrene polymerization. The catalysts were characterized by <SUP>1</SUP>H- and <SUP>13</SUP>C NMR, and elemental analysis. These catalysts were found to be effective in forming SPS in combination with MAO. The activities of the catalysts with rigid <I>ortho</I>- and <I>meta</I>-xylene bridges were higher than those of catalysts with flexible pentamethylene bridges. The catalytic activity of four dinuclear half-titanocenes increased in the order of <B>4</B><<B>5</B><<B>7</B><<B>8</B>. This result displays that the <I>meta</I>-xylene bridged catalyst is more active than the <I>ortho</I>-xylene bridged and that the aryloxo group at the titanium center is more effective at promoting catalyst activity compared to the chloride group at the titanium center. Temperature and ratio of [Al]:[Ti] had significant effects on catalytic activity. Polymerizations were conducted at three different temperatures (25, 40, and 70°C) with variation in the [Al]:[Ti] ratio from 2000 to 4000. It was observed that activity of the catalysts increased with increasing temperature, as well as higher [Al]:[Ti]. Different xylene linkage patterns (<I>ortho</I> and <I>meta</I>) were recognized to be a principal factor leading to the characteristics of the dinuclear catalyst due to its different spatial arrangement, causing dissimilar intramolecular interactions between the two active sites.</P>
Ba Linh, Nguyen Thuy,Lee, Kap‐,Ho,Lee, Byong‐,Taek Wiley Subscription Services, Inc., A Wiley Company 2013 Journal of biomedical materials research. Part A Vol.101 No.8
<P><B>Abstract</B></P><P>New biodegradable mats was successfully obtained by functional polyvinyl alcohol (PVA)/Gelatin (GE) blend fiber mats containing different BCP amounts (20, 40, and 50 w/v%) of biphasic calcium phosphate (BCP) nanoparticles for bone regeneration. BCP nanoparticles were loaded and dispersed successfully in the PVA/GE fibrous matrix. The addition of BCP was found to have increased fiber diameter, tensile strength, osteoblast cell adhesion, proliferation, and protein expression. Compared to the others, the 50% BCP‐loaded electrospun PVA/GE fibers had the most favorable mechanical properties, cell attachment and growth, and protein expression. <I>In vivo</I> bone formation was examined using rat models, and increased bone formation was observed for the 50% BCP‐loaded electrospun PVA/GE blends within 2 and 4 weeks. This result suggests that the 50% BCP‐PVA/GE composite nanofiber mat has high potential for use in the field of bone regeneration and tissue engineering. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013.</P>
Linh Ba Vu,정수호,배진희,박종민,김경태,손인준,조승기 한국분말재료학회 2024 한국분말재료학회지 (KPMI) Vol.31 No.2
The n-type Bi2-xSbxTe3 compounds have been of great interest due to its potential to achieve a high thermoelectric performance, comparable to that of p-type Bi2-xSbxTe3. However, a comprehensive understanding on the thermoelectric properties remains lacking. Here, we investigate the thermoelectric transport properties and band characteristics of n-type Bi2-xSbxTe3 (x = 0.1 – 1.1) based on experimental and theoretical considerations. We find that the higher power factor at lower Sb content results from the optimized balance between the density of state effective mass and nondegenerate mobility. Additionally, a higher carrier concentration at lower x suppresses bipolar conduction, thereby reducing thermal conductivity at elevated temperatures. Consequently, the highest zT of ~ 0.5 is observed at 450 K for x = 0.1 and, according to the single parabolic band model, it could be further improved by ~70 % through carrier concentration tuning. The n-type Bi2-xSbxTe3 compounds have been of great interest due to its potential to achieve a high thermoelectric performance, comparable to that of p-type Bi2-xSbxTe3. However, a comprehensive understanding on the thermoelectric properties remains lacking. Here, we investigate the thermoelectric transport properties and band characteristics of n-type Bi2-xSbxTe3 (x = 0.1 – 1.1) based on experimental and theoretical considerations. We find that the higher power factor at lower Sb content results from the optimized balance between the density of state effective mass and nondegenerate mobility. Additionally, a higher carrier concentration at lower x suppresses bipolar conduction, thereby reducing thermal conductivity at elevated temperatures. Consequently, the highest zT of ~ 0.5 is observed at 450 K for x = 0.1 and, according to the single parabolic band model, it could be further improved by ~70 % through carrier concentration tuning.
Linh, Nguyen Thuy Ba,Abueva, Celine D G,Lee, Byong-Taek IOP Publishing 2017 Biomedical materials Vol.12 No.1
<P>An injectable, in situ forming hydrogel system capable of co-delivering human adipose-derived stem cells (hADSC) and platelet-derived growth factor (PDGF) was investigated as a new system for tissue engineering, envisaged to support vascularization. The system consists of tyramine-conjugated gelatin and hydroxyphenyl acetamide chitosan derivative. Both are soluble and stable at physiologic conditions, which is a key factor for retaining viable cells and active growth factor. In situ gelation involved enzymatic crosslinking using horseradish peroxidase as a catalyst and hydrogen peroxide as an oxidant. Gel formation occurred within 30-90 s by controlling the concentration of polymers. PDGF release showed adequate release kinetics within the intended period of time and hADSC showed good compatibility with the hydrogel formulation based on the in vitro assay and subcutaneous implantation into BALB/c-nu/nu nude female mice. Immunohistochemical analysis confirmed viability of delivered hADSC. Histological analysis showed no immune reaction and confirmed blood vessel formation. The results implicate the hydrogel as a promising delivery vehicle or carrier of both cell and growth factor, which support vascularization for tissue engineering applications.</P>