The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

Chul B. Park - One of the best experts on this subject based on the ideXlab platform.

  • continuous processing of low density microCellular poly lactic acid foams with controlled Cell Morphology and crystallinity
    Chemical Engineering Science, 2012
    Co-Authors: Jing Wang, Hongtao Zhang, Chul B. Park
    Abstract:

    Abstract Poly(lactic acid) (PLA) represents perhaps the most viable environmentally-sustainable alternative to petrochemical-based plastics. This paper reports the continuous processing of PLA foams with a microCellular structure, a high expansion ratio, and varied microCell Morphology and crystallinity. The extrusion process, which can be easily scaled-up, takes advantage of the tailored physical properties of PLA and the plasticizing effect of the supercritical blowing agent. Three grades of PLA with different molecular weight and branching topology are used. The processing parameters are optimized based on the well-characterized thermal and rheological properties of PLAs and diffusion properties of PLA/CO2 mixture. In general, melt strength governs Cell Morphology, with Cell density, closed-Cell content, and expansion ratio increasing as a function of both molecular weight and branching density. Influences of shearing and dissolved-CO2 on crystallization of PLA are characterized and they are believed to induce crystallinity in the foams. In the case of branched PLA, crystallization allows high-expansion-ratio microCellular foams to be stably produced over a wide temperature window. By controlling crystallinity, foams with similar Cell Morphology but varied mechanical properties and surface gloss are also produced. X-ray diffraction of the foams confirms that crystallization is governed by shearing in the die, and the crystallites are mainly of α-form.

  • effects of nanoparticles on the density reduction and Cell Morphology of extruded metallocene polyethylene wood fiber nanocomposites
    Journal of Applied Polymer Science, 2007
    Co-Authors: Gangjian Guo, Chul B. Park, Ki Hyun Wang, Y S Kim
    Abstract:

    This article investigates the effects of nanoparticles on Cell Morphology and foam expansion in the extrusion foaming of metallocene polyethylene/wood fiber nanocomposites with a chemical blowing agent. The results indicate that the addition of clay generally reduces the Cell size, increases the Cell density, and facilitates foam expansion. Furthermore, the foam material with added clay shows good char formation when it is burned.

  • Cell Morphology and property relationships of microCellular foamed pvc wood fiber composites
    Polymer Engineering and Science, 1998
    Co-Authors: Laurent M Matuana, Chul B. Park, John J Balatinecz
    Abstract:

    Wood-fiber composites make use of Cellulose fibers as a reinforcing filler in the polymer matrix and are known to have a lower material cost and a higher stiffness than neat polymers. However, the lower material cost and enhanced stiffness of wood-fiber composites are achieved at the expense of other properties such as the ductility and impact strength. Since microCellular plastics exhibit a higher impact strength, higher toughness, and increased fatigue life compared to unfoamed plastics, microCellular foaming of wood-fiber composites will improve the mechanical properties of the composites and therefore increase the usefulness of the materials. In this paper, microCellular foamed PVC/wood-fiber composites with unique Cell Morphology and material composition are characterized. MicroCellular structures are produced in PVC/wood-fiber composites by first saturating the composite samples with CO2 under high pressure followed by rapidly decreasing the solubility of gas in the samples. The void fraction of the microCellular foamed PVC/wood-fiber composites is controlled by tailoring the composition of materials and the foaming process parameters. The results indicate that tensile and impact properties of microCellular foamed PVC/wood-fiber composites are most sensitive to changes in the Cell Morphology and the surface modification of fibers.

  • processing and Cell Morphology relationships for microCellular foamed pvc wood fiber composites
    Polymer Engineering and Science, 1997
    Co-Authors: Laurent M Matuana, Chul B. Park, John J Balatinecz
    Abstract:

    In this research, the effects of the materials and the processing conditions on the Cell Morphology of foamed PVC /wood-fiber composites were studied with a view to establishing their process-structure relationships. Each step of microCellular PVC / wood-fiber composites processing is addressed, including the surface treatment of the wood-fiber, mixing of polymer and wood-fiber, manufacture of the composites, the saturation of the composites with gas, microCellular foaming of the composites, and characterization of the Cell Morphology. The Cellular morphologies of the foamed PVC/wood-fiber composites are a strong function of the content of plasticizer and the surface treatment of wood-fiber as well as the gas saturation and foaming conditions.

Laurent M Matuana - One of the best experts on this subject based on the ideXlab platform.

  • Cell Morphology of extrusion foamed poly lactic acid using endothermic chemical foaming agent
    Bioresource Technology, 2009
    Co-Authors: Laurent M Matuana, Omar Faruk, Carlos A Diaz
    Abstract:

    Abstract Poly(lactic acid) (PLA) was foamed with an endothermic chemical foaming agent (CFA) through an extrusion process. The effects of polymer melt flow index, CFA content, and processing speed on the Cellular structures, void fraction, and Cell-population density of foamed PLA were investigated. The apparent melt viscosity of PLA was measured to understand the effect of melt index on the Cell Morphology of foamed PLA samples. The void fraction was strongly dependent on the PLA melt index. It increased with increasing melt index, reaching a maximum value, after which it decreased. Melt index showed no significant effect on the Cell-population density of foamed samples within the narrow range studied. A gas containment limit was observed in PLA foamed with CFA. Both the void fraction and Cell-population density increased with an initial increase in CFA content, reached a maximum value, and then decreased as CFA content continued to increase. The processing speed also affected the Morphology of PLA foams. The void fraction reached a maximum value as the extruder’s screw speed increased to 40 rpm and a further increase in the processing speed tended to reduce the void fraction of foamed samples. By contrast, Cell-population density increased one order of magnitude by increasing the screw speed from 20 to 120 rpm. The experimental results indicate that a homogeneous and finer Cellular Morphology could be successfully achieved in PLA foamed in an extrusion process with a proper combination of polymer melt flow index, CFA content, and processing speed.

  • Cell Morphology and property relationships of microCellular foamed pvc wood fiber composites
    Polymer Engineering and Science, 1998
    Co-Authors: Laurent M Matuana, Chul B. Park, John J Balatinecz
    Abstract:

    Wood-fiber composites make use of Cellulose fibers as a reinforcing filler in the polymer matrix and are known to have a lower material cost and a higher stiffness than neat polymers. However, the lower material cost and enhanced stiffness of wood-fiber composites are achieved at the expense of other properties such as the ductility and impact strength. Since microCellular plastics exhibit a higher impact strength, higher toughness, and increased fatigue life compared to unfoamed plastics, microCellular foaming of wood-fiber composites will improve the mechanical properties of the composites and therefore increase the usefulness of the materials. In this paper, microCellular foamed PVC/wood-fiber composites with unique Cell Morphology and material composition are characterized. MicroCellular structures are produced in PVC/wood-fiber composites by first saturating the composite samples with CO2 under high pressure followed by rapidly decreasing the solubility of gas in the samples. The void fraction of the microCellular foamed PVC/wood-fiber composites is controlled by tailoring the composition of materials and the foaming process parameters. The results indicate that tensile and impact properties of microCellular foamed PVC/wood-fiber composites are most sensitive to changes in the Cell Morphology and the surface modification of fibers.

  • processing and Cell Morphology relationships for microCellular foamed pvc wood fiber composites
    Polymer Engineering and Science, 1997
    Co-Authors: Laurent M Matuana, Chul B. Park, John J Balatinecz
    Abstract:

    In this research, the effects of the materials and the processing conditions on the Cell Morphology of foamed PVC /wood-fiber composites were studied with a view to establishing their process-structure relationships. Each step of microCellular PVC / wood-fiber composites processing is addressed, including the surface treatment of the wood-fiber, mixing of polymer and wood-fiber, manufacture of the composites, the saturation of the composites with gas, microCellular foaming of the composites, and characterization of the Cell Morphology. The Cellular morphologies of the foamed PVC/wood-fiber composites are a strong function of the content of plasticizer and the surface treatment of wood-fiber as well as the gas saturation and foaming conditions.

Ziyin Li - One of the best experts on this subject based on the ideXlab platform.

  • the cooperative roles of two kinetoplastid specific kinesins in cytokinesis and in maintaining Cell Morphology in bloodstream trypanosomes
    PLOS ONE, 2013
    Co-Authors: Huiqing Hu, Ziyin Li
    Abstract:

    The cytoskeleton of Trypanosoma brucei, a uniCellular eukaryote and a parasitic protozoan, is defined by the subpellicular microtubule corset that is arranged underneath the plasma membrane. We recently identified two orphan kinesins, TbKIN-C and TbKIN-D, that cooperate to regulate the organization of the subpellicular microtubule corset and thereby maintain Cell Morphology in the procyclic form of T. brucei. In this report, we characterize the function of TbKIN-C and TbKIN-D in the bloodstream form of T. brucei and investigate their functional cooperation in both the bloodstream and procyclic forms. TbKIN-C and TbKIN-D form a tight complex in vivo in the bloodstream form. TbKIN-C is strongly enriched at the posterior tip of the Cell, whereas TbKIN-D is distributed throughout the Cell body at all Cell cycle stages. RNAi of TbKIN-C or TbKIN-D in the bloodstream form inhibits Cell proliferation and leads to Cell death, due to cytokinesis defects. RNAi of TbKIN-C and TbKIN-D also results in defects in basal body segregation, but does not affect the synthesis and segregation of the flagellum and the flagellum attachment zone (FAZ) filament. Knockdown of TbKIN-C and TbKIN-D does not disrupt the organization of the subpellicular microtubule corset, but produces multinucleated Cells with an enlarged flagellar pocket and misplaced flagella. Interestingly, depletion of TbKIN-C results in rapid degradation of TbKIN-D and, similarly, knockdown of TbKIN-C destabilizes TbKIN-D, suggesting that formation of TbKIN-C/TbKIN-D complex stabilizes both kinesins and is required for the two kinesins to execute their essential Cellular functions. Altogether, our results demonstrate the essential role of the two kinesins in Cell morphogenesis and cytokinesis in the bloodstream form and the requirement of heteromeric complex formation for maintaining the stability of the two kinesins.

  • an orphan kinesin in trypanosomes cooperates with a kinetoplastid specific kinesin to maintain Cell Morphology by regulating subpellicular microtubules
    Journal of Cell Science, 2012
    Co-Authors: Huiqing Hu, Liu Hu, Zhonglian Yu, Amanda E Chasse, Ziyin Li
    Abstract:

    Microtubules are a vital part of the cytoskeleton of eukaryotic Cells and are involved in various Cellular processes. The cytoskeleton of Trypanosoma brucei is characterized by an array of subpellicular microtubules and is essential for maintenance of Cell shape and polarity, but little is known about the regulation of the assembly and organization of the subpellicular microtubule corset. Here, we report that the orphan kinesin TbKIN-D regulates the organization of subpellicular microtubules and is required for maintaining Cell Morphology. TbKIN-D possesses in vitro ATPase activity, associates with cytoskeletal microtubules and is distributed throughout the cytoskeleton at all Cell cycle stages. RNAi of TbKIN-D disrupts the organization of the subpellicular microtubule corset and distorts Cell Morphology, resulting in round Cells with an elongated posterior filled with newly assembled microtubules. Depletion of TbKIN-D also abolishes the segregation of organelles and cytoskeletal structures, suggesting that Cellular morphogenesis is essential for proper organelle segregation. Moreover, TbKIN-D deficiency impairs the attachment of the new flagellum without compromising the formation of the flagellum attachment zone. Finally, we identified TbKIN-C, a kinetoplastid-specific kinesin known to regulate subpellicular microtubules and Cell morphogenesis in T. brucei , as a partner of TbKIN-D. Further, we demonstrate that interaction between TbKIN-C and TbKIN-D requires the coiled-coil motifs in the C-termini of both proteins. Altogether, our results suggest that TbKIN-D cooperates with TbKIN-C to maintain Cell Morphology by regulating the organization of the subpellicular microtubule corset.

  • a kinetoplastid specific kinesin is required for cytokinesis and for maintenance of Cell Morphology in trypanosoma brucei
    Molecular Microbiology, 2012
    Co-Authors: Liu Hu, Huiqing Hu, Ziyin Li
    Abstract:

    Summary Kinesins are motor-based transport proteins that play diverse roles in various Cellular processes. The trypanosome genome lacks the homologues of many conserved mitotic kinesins, but encodes a number of trypanosome-specific kinesins with unknown function. Here, we report the biochemical and functional characterization of TbKIN-C, a trypanosome-specific kinesin, which was initially identified through an RNAi screen for cytokinesis genes in T. brucei. TbKIN-C possesses in vitro ATPase activity and associates with cytoskeletal tubulin microtubules in vivo. It is distributed throughout the cytoskeleton with a focal enrichment at the posterior end of the Cell during early Cell cycle stages. RNAi of TbKIN-C resulted in distorted Cell shape with an elongated posterior filled with tyrosinated tubulin microtubules. Silencing of TbKIN-C impaired the segregation of organelles and cytoskeletal structures and led to detachment of the new flagellum and a small portion of the cytoplasm. We also show that RNAi of TbKIN-C compromised cytokinesis and abolished the trans-localization of TbCPC1, a subunit of the chromosomal passenger complex, from the central spindle to the initiation site of cytokinesis. Our results suggest an essential role of TbKIN-C in maintaining Cell Morphology, likely through regulating microtubule dynamics at the posterior end of the Cell.

John J Balatinecz - One of the best experts on this subject based on the ideXlab platform.

  • Cell Morphology and property relationships of microCellular foamed pvc wood fiber composites
    Polymer Engineering and Science, 1998
    Co-Authors: Laurent M Matuana, Chul B. Park, John J Balatinecz
    Abstract:

    Wood-fiber composites make use of Cellulose fibers as a reinforcing filler in the polymer matrix and are known to have a lower material cost and a higher stiffness than neat polymers. However, the lower material cost and enhanced stiffness of wood-fiber composites are achieved at the expense of other properties such as the ductility and impact strength. Since microCellular plastics exhibit a higher impact strength, higher toughness, and increased fatigue life compared to unfoamed plastics, microCellular foaming of wood-fiber composites will improve the mechanical properties of the composites and therefore increase the usefulness of the materials. In this paper, microCellular foamed PVC/wood-fiber composites with unique Cell Morphology and material composition are characterized. MicroCellular structures are produced in PVC/wood-fiber composites by first saturating the composite samples with CO2 under high pressure followed by rapidly decreasing the solubility of gas in the samples. The void fraction of the microCellular foamed PVC/wood-fiber composites is controlled by tailoring the composition of materials and the foaming process parameters. The results indicate that tensile and impact properties of microCellular foamed PVC/wood-fiber composites are most sensitive to changes in the Cell Morphology and the surface modification of fibers.

  • processing and Cell Morphology relationships for microCellular foamed pvc wood fiber composites
    Polymer Engineering and Science, 1997
    Co-Authors: Laurent M Matuana, Chul B. Park, John J Balatinecz
    Abstract:

    In this research, the effects of the materials and the processing conditions on the Cell Morphology of foamed PVC /wood-fiber composites were studied with a view to establishing their process-structure relationships. Each step of microCellular PVC / wood-fiber composites processing is addressed, including the surface treatment of the wood-fiber, mixing of polymer and wood-fiber, manufacture of the composites, the saturation of the composites with gas, microCellular foaming of the composites, and characterization of the Cell Morphology. The Cellular morphologies of the foamed PVC/wood-fiber composites are a strong function of the content of plasticizer and the surface treatment of wood-fiber as well as the gas saturation and foaming conditions.

Huiqing Hu - One of the best experts on this subject based on the ideXlab platform.

  • the cooperative roles of two kinetoplastid specific kinesins in cytokinesis and in maintaining Cell Morphology in bloodstream trypanosomes
    PLOS ONE, 2013
    Co-Authors: Huiqing Hu, Ziyin Li
    Abstract:

    The cytoskeleton of Trypanosoma brucei, a uniCellular eukaryote and a parasitic protozoan, is defined by the subpellicular microtubule corset that is arranged underneath the plasma membrane. We recently identified two orphan kinesins, TbKIN-C and TbKIN-D, that cooperate to regulate the organization of the subpellicular microtubule corset and thereby maintain Cell Morphology in the procyclic form of T. brucei. In this report, we characterize the function of TbKIN-C and TbKIN-D in the bloodstream form of T. brucei and investigate their functional cooperation in both the bloodstream and procyclic forms. TbKIN-C and TbKIN-D form a tight complex in vivo in the bloodstream form. TbKIN-C is strongly enriched at the posterior tip of the Cell, whereas TbKIN-D is distributed throughout the Cell body at all Cell cycle stages. RNAi of TbKIN-C or TbKIN-D in the bloodstream form inhibits Cell proliferation and leads to Cell death, due to cytokinesis defects. RNAi of TbKIN-C and TbKIN-D also results in defects in basal body segregation, but does not affect the synthesis and segregation of the flagellum and the flagellum attachment zone (FAZ) filament. Knockdown of TbKIN-C and TbKIN-D does not disrupt the organization of the subpellicular microtubule corset, but produces multinucleated Cells with an enlarged flagellar pocket and misplaced flagella. Interestingly, depletion of TbKIN-C results in rapid degradation of TbKIN-D and, similarly, knockdown of TbKIN-C destabilizes TbKIN-D, suggesting that formation of TbKIN-C/TbKIN-D complex stabilizes both kinesins and is required for the two kinesins to execute their essential Cellular functions. Altogether, our results demonstrate the essential role of the two kinesins in Cell morphogenesis and cytokinesis in the bloodstream form and the requirement of heteromeric complex formation for maintaining the stability of the two kinesins.

  • an orphan kinesin in trypanosomes cooperates with a kinetoplastid specific kinesin to maintain Cell Morphology by regulating subpellicular microtubules
    Journal of Cell Science, 2012
    Co-Authors: Huiqing Hu, Liu Hu, Zhonglian Yu, Amanda E Chasse, Ziyin Li
    Abstract:

    Microtubules are a vital part of the cytoskeleton of eukaryotic Cells and are involved in various Cellular processes. The cytoskeleton of Trypanosoma brucei is characterized by an array of subpellicular microtubules and is essential for maintenance of Cell shape and polarity, but little is known about the regulation of the assembly and organization of the subpellicular microtubule corset. Here, we report that the orphan kinesin TbKIN-D regulates the organization of subpellicular microtubules and is required for maintaining Cell Morphology. TbKIN-D possesses in vitro ATPase activity, associates with cytoskeletal microtubules and is distributed throughout the cytoskeleton at all Cell cycle stages. RNAi of TbKIN-D disrupts the organization of the subpellicular microtubule corset and distorts Cell Morphology, resulting in round Cells with an elongated posterior filled with newly assembled microtubules. Depletion of TbKIN-D also abolishes the segregation of organelles and cytoskeletal structures, suggesting that Cellular morphogenesis is essential for proper organelle segregation. Moreover, TbKIN-D deficiency impairs the attachment of the new flagellum without compromising the formation of the flagellum attachment zone. Finally, we identified TbKIN-C, a kinetoplastid-specific kinesin known to regulate subpellicular microtubules and Cell morphogenesis in T. brucei , as a partner of TbKIN-D. Further, we demonstrate that interaction between TbKIN-C and TbKIN-D requires the coiled-coil motifs in the C-termini of both proteins. Altogether, our results suggest that TbKIN-D cooperates with TbKIN-C to maintain Cell Morphology by regulating the organization of the subpellicular microtubule corset.

  • a kinetoplastid specific kinesin is required for cytokinesis and for maintenance of Cell Morphology in trypanosoma brucei
    Molecular Microbiology, 2012
    Co-Authors: Liu Hu, Huiqing Hu, Ziyin Li
    Abstract:

    Summary Kinesins are motor-based transport proteins that play diverse roles in various Cellular processes. The trypanosome genome lacks the homologues of many conserved mitotic kinesins, but encodes a number of trypanosome-specific kinesins with unknown function. Here, we report the biochemical and functional characterization of TbKIN-C, a trypanosome-specific kinesin, which was initially identified through an RNAi screen for cytokinesis genes in T. brucei. TbKIN-C possesses in vitro ATPase activity and associates with cytoskeletal tubulin microtubules in vivo. It is distributed throughout the cytoskeleton with a focal enrichment at the posterior end of the Cell during early Cell cycle stages. RNAi of TbKIN-C resulted in distorted Cell shape with an elongated posterior filled with tyrosinated tubulin microtubules. Silencing of TbKIN-C impaired the segregation of organelles and cytoskeletal structures and led to detachment of the new flagellum and a small portion of the cytoplasm. We also show that RNAi of TbKIN-C compromised cytokinesis and abolished the trans-localization of TbCPC1, a subunit of the chromosomal passenger complex, from the central spindle to the initiation site of cytokinesis. Our results suggest an essential role of TbKIN-C in maintaining Cell Morphology, likely through regulating microtubule dynamics at the posterior end of the Cell.