The Experts below are selected from a list of 642 Experts worldwide ranked by ideXlab platform

Yuanchen Cui - One of the best experts on this subject based on the ideXlab platform.

  • Polyvinylidene Chloride supported l prolineamide as recoverable catalyst for asymmetric aldol reaction between ketone and aromatic aldehyde
    Journal of Applied Polymer Science, 2013
    Co-Authors: Xuan Zhang, Wenshan Zhao, Lili Yang, Yuanchen Cui
    Abstract:

    A series of prolineamide modified by Polyvinylidene Chloride (PVDC) was synthesized and used as green recoverable organocatalysts for the asymmetric Aldol reactions between various ketones and aromatic aldehydes. The effects of solvent and catalyst dosage on the catalytic performances of as-synthesized organocatalysts were investigated. It was found that as-synthesized PVDC-supported L-prolineamides possessed good catalytic performance for the asymmetric Aldol reactions between cyclohexanone and a variety of aromatic aldehydes, affording high yields of up to 99%, excellent diastereoselectivities of up to above 8 : 92 d.r. value, and high enantioselectivities of up to above 92.3% e.e. value. In general, the catalytic performance of as-synthesized organocatalysts closely depended on the catalyst dosage and solvent type as well. Particularly, as-synthesized organocatalyst 1c, at a dosage of 5 mol % in 10 μL of water, exhibited high catalytic activity and stereoselectivity for the asymmetric Aldol reaction between cyclohexanone and p-nitrobenzaldehyde at room temperature. In the meantime, it could be easily recovered and recycled, while the activity and enantioselectivity were nearly completely retained even after five cycles of recovery, showing promising application as an efficient green organocatalyst for the aforementioned asymmetric Aldol reactions. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

  • efficient asymmetric aldol reaction catalyzed by Polyvinylidene Chloride supported ionic liquid l proline catalyst system
    ChemInform, 2012
    Co-Authors: Xuan Zhang, Wenshan Zhao, Lili Yang, Yuanchen Cui
    Abstract:

    A novel PVC-supported ionic liquid—L-proline combined organocatalyst is successfully applied in the asymmetric aldol reaction of aromatic aldehydes with cyclic and acyclic ketones.

  • efficient asymmetric aldol reaction catalyzed by Polyvinylidene Chloride supported ionic liquid l proline catalyst system
    Tetrahedron-asymmetry, 2012
    Co-Authors: Xuan Zhang, Wenshan Zhao, Lili Yang, Yuanchen Cui
    Abstract:

    Abstract A series of Polyvinylidene Chloride (PVDC)-supported ionic liquids were derived from 4-dimethylaminopyridine and used together with l -proline in water as efficient asymmetric organocatalysts for direct asymmetric aldol reactions between cyclohexanone and a variety of aromatic aldehydes at room temperature. These PVDC-supported ionic liquids/ l -proline catalyst systems have been used as asymmetric organocatalysts to afford the corresponding aldol products with a moderate to high isolated yield of up to 99%, with diastereoselectivity of up to 6:94, and excellent enantioselectivity of up to 98%. Furthermore, they could be easily recycled and showed only a slight reduction in selectivity after seven recycles.

Yonghai Zhang - One of the best experts on this subject based on the ideXlab platform.

  • Multifractal analysis of the tensile fracture morphology of Polyvinylidene Chloride/glass fiber composite
    Applied Surface Science, 2011
    Co-Authors: Yonghai Zhang, Jingbo Chen, Jianqiang Li, Changyu Shen
    Abstract:

    In the present work, the building panel of glass fiber reinforced Polyvinylidene Chloride composite was prepared and the tensile fracture surfaces of the composites were investigated by the box-counting method of multifractal theory. It suggested that the tensile fracture surface of Polyvinylidene Chloride/glass fiber (PVDC/GF) composite exhibits multifractal features and the tensile fracture surface morphology of the composite have a strong dependence on the mechanical properties. The results showed that the variation of glass fiber content would lead to the change of mechanical properties, which were responsible for the tensile fracture morphology of PVDC/GF composite. Consequently, the gray value distribution characterizing the surface morphology on the tensile fracture surface would become more non-uniform or less due to this change. The multifractal spectrum could correspondingly mirror this variation according to multifractal methodology. It indicated that the width in multifractal spectrum is sensitive to the morphology of the tensile fractured surface. It is concluded that the multifractal spectrum is the result of the change in mechanical properties of the composites. Additionally, it also suggested that the tensile fracture of the composite is the result of the competition between ductile fracture and brittle fracture by comparing the multifractal spectra and the multifractal spectra would correspondingly change due to this competition. The more the percentage of ductile fracture is, the more rough the fracture surface, the larger the width in the multifractal spectrum. Therefore, it is thought that the multifractal spectrum could feature the rough morphology of the tensile fractured surface and the mechanical properties quantitatively. (C) 2010 Elsevier B.V. All rights reserved.

  • multifractal analysis of the tensile fracture morphology of Polyvinylidene Chloride glass fiber composite
    Applied Surface Science, 2011
    Co-Authors: Yonghai Zhang, Baofeng Bai, Jingbo Chen, Changyu Shen
    Abstract:

    In the present work, the building panel of glass fiber reinforced Polyvinylidene Chloride composite was prepared and the tensile fracture surfaces of the composites were investigated by the box-counting method of multifractal theory. It suggested that the tensile fracture surface of Polyvinylidene Chloride/glass fiber (PVDC/GF) composite exhibits multifractal features and the tensile fracture surface morphology of the composite have a strong dependence on the mechanical properties. The results showed that the variation of glass fiber content would lead to the change of mechanical properties, which were responsible for the tensile fracture morphology of PVDC/GF composite. Consequently, the gray value distribution characterizing the surface morphology on the tensile fracture surface would become more non-uniform or less due to this change. The multifractal spectrum could correspondingly mirror this variation according to multifractal methodology. It indicated that the width in multifractal spectrum is sensitive to the morphology of the tensile fractured surface. It is concluded that the multifractal spectrum is the result of the change in mechanical properties of the composites. Additionally, it also suggested that the tensile fracture of the composite is the result of the competition between ductile fracture and brittle fracture by comparing the multifractal spectra and the multifractal spectra would correspondingly change due to this competition. The more the percentage of ductile fracture is, the more rough the fracture surface, the larger the width in the multifractal spectrum. Therefore, it is thought that the multifractal spectrum could feature the rough morphology of the tensile fractured surface and the mechanical properties quantitatively. (C) 2010 Elsevier B.V. All rights reserved.

Changyu Shen - One of the best experts on this subject based on the ideXlab platform.

  • Multifractal analysis of the tensile fracture morphology of Polyvinylidene Chloride/glass fiber composite
    Applied Surface Science, 2011
    Co-Authors: Yonghai Zhang, Jingbo Chen, Jianqiang Li, Changyu Shen
    Abstract:

    In the present work, the building panel of glass fiber reinforced Polyvinylidene Chloride composite was prepared and the tensile fracture surfaces of the composites were investigated by the box-counting method of multifractal theory. It suggested that the tensile fracture surface of Polyvinylidene Chloride/glass fiber (PVDC/GF) composite exhibits multifractal features and the tensile fracture surface morphology of the composite have a strong dependence on the mechanical properties. The results showed that the variation of glass fiber content would lead to the change of mechanical properties, which were responsible for the tensile fracture morphology of PVDC/GF composite. Consequently, the gray value distribution characterizing the surface morphology on the tensile fracture surface would become more non-uniform or less due to this change. The multifractal spectrum could correspondingly mirror this variation according to multifractal methodology. It indicated that the width in multifractal spectrum is sensitive to the morphology of the tensile fractured surface. It is concluded that the multifractal spectrum is the result of the change in mechanical properties of the composites. Additionally, it also suggested that the tensile fracture of the composite is the result of the competition between ductile fracture and brittle fracture by comparing the multifractal spectra and the multifractal spectra would correspondingly change due to this competition. The more the percentage of ductile fracture is, the more rough the fracture surface, the larger the width in the multifractal spectrum. Therefore, it is thought that the multifractal spectrum could feature the rough morphology of the tensile fractured surface and the mechanical properties quantitatively. (C) 2010 Elsevier B.V. All rights reserved.

  • multifractal analysis of the tensile fracture morphology of Polyvinylidene Chloride glass fiber composite
    Applied Surface Science, 2011
    Co-Authors: Yonghai Zhang, Baofeng Bai, Jingbo Chen, Changyu Shen
    Abstract:

    In the present work, the building panel of glass fiber reinforced Polyvinylidene Chloride composite was prepared and the tensile fracture surfaces of the composites were investigated by the box-counting method of multifractal theory. It suggested that the tensile fracture surface of Polyvinylidene Chloride/glass fiber (PVDC/GF) composite exhibits multifractal features and the tensile fracture surface morphology of the composite have a strong dependence on the mechanical properties. The results showed that the variation of glass fiber content would lead to the change of mechanical properties, which were responsible for the tensile fracture morphology of PVDC/GF composite. Consequently, the gray value distribution characterizing the surface morphology on the tensile fracture surface would become more non-uniform or less due to this change. The multifractal spectrum could correspondingly mirror this variation according to multifractal methodology. It indicated that the width in multifractal spectrum is sensitive to the morphology of the tensile fractured surface. It is concluded that the multifractal spectrum is the result of the change in mechanical properties of the composites. Additionally, it also suggested that the tensile fracture of the composite is the result of the competition between ductile fracture and brittle fracture by comparing the multifractal spectra and the multifractal spectra would correspondingly change due to this competition. The more the percentage of ductile fracture is, the more rough the fracture surface, the larger the width in the multifractal spectrum. Therefore, it is thought that the multifractal spectrum could feature the rough morphology of the tensile fractured surface and the mechanical properties quantitatively. (C) 2010 Elsevier B.V. All rights reserved.

Xuan Zhang - One of the best experts on this subject based on the ideXlab platform.

  • Polyvinylidene Chloride supported l prolineamide as recoverable catalyst for asymmetric aldol reaction between ketone and aromatic aldehyde
    Journal of Applied Polymer Science, 2013
    Co-Authors: Xuan Zhang, Wenshan Zhao, Lili Yang, Yuanchen Cui
    Abstract:

    A series of prolineamide modified by Polyvinylidene Chloride (PVDC) was synthesized and used as green recoverable organocatalysts for the asymmetric Aldol reactions between various ketones and aromatic aldehydes. The effects of solvent and catalyst dosage on the catalytic performances of as-synthesized organocatalysts were investigated. It was found that as-synthesized PVDC-supported L-prolineamides possessed good catalytic performance for the asymmetric Aldol reactions between cyclohexanone and a variety of aromatic aldehydes, affording high yields of up to 99%, excellent diastereoselectivities of up to above 8 : 92 d.r. value, and high enantioselectivities of up to above 92.3% e.e. value. In general, the catalytic performance of as-synthesized organocatalysts closely depended on the catalyst dosage and solvent type as well. Particularly, as-synthesized organocatalyst 1c, at a dosage of 5 mol % in 10 μL of water, exhibited high catalytic activity and stereoselectivity for the asymmetric Aldol reaction between cyclohexanone and p-nitrobenzaldehyde at room temperature. In the meantime, it could be easily recovered and recycled, while the activity and enantioselectivity were nearly completely retained even after five cycles of recovery, showing promising application as an efficient green organocatalyst for the aforementioned asymmetric Aldol reactions. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

  • efficient asymmetric aldol reaction catalyzed by Polyvinylidene Chloride supported ionic liquid l proline catalyst system
    ChemInform, 2012
    Co-Authors: Xuan Zhang, Wenshan Zhao, Lili Yang, Yuanchen Cui
    Abstract:

    A novel PVC-supported ionic liquid—L-proline combined organocatalyst is successfully applied in the asymmetric aldol reaction of aromatic aldehydes with cyclic and acyclic ketones.

  • efficient asymmetric aldol reaction catalyzed by Polyvinylidene Chloride supported ionic liquid l proline catalyst system
    Tetrahedron-asymmetry, 2012
    Co-Authors: Xuan Zhang, Wenshan Zhao, Lili Yang, Yuanchen Cui
    Abstract:

    Abstract A series of Polyvinylidene Chloride (PVDC)-supported ionic liquids were derived from 4-dimethylaminopyridine and used together with l -proline in water as efficient asymmetric organocatalysts for direct asymmetric aldol reactions between cyclohexanone and a variety of aromatic aldehydes at room temperature. These PVDC-supported ionic liquids/ l -proline catalyst systems have been used as asymmetric organocatalysts to afford the corresponding aldol products with a moderate to high isolated yield of up to 99%, with diastereoselectivity of up to 6:94, and excellent enantioselectivity of up to 98%. Furthermore, they could be easily recycled and showed only a slight reduction in selectivity after seven recycles.

Antônio Paulino Da ,costa Netto - One of the best experts on this subject based on the ideXlab platform.

  • Avaliação da performance de diferentes plásticos usados para selar arranjos de cDNA em náilon
    Editora da Universidade Federal de Lavras, 2015
    Co-Authors: Antônio Paulino Da ,costa Netto, Drummond,rodrigo Duarte, Felix,juliana De Maria, Jorge,renato Atílio, Menossi Marcelo
    Abstract:

    cDNA arrays are a powerful tool for discovering gene expression patterns. Nylon arrays have the advantage that they can be re-used several times. A key issue in high throughput gene expression analysis is sensitivity. In the case of nylon arrays, signal detection can be affected by the plastic bags used to keep membranes humid. In this study, we evaluated the effect of five types of plastics on the radioactive transmittance, number of genes with a signal above the background, and data variability. A polyethylene plastic bag 69 μm thick had a strong shielding effect that blocked 68.7% of the radioactive signal. The shielding effect on transmittance decreased the number of detected genes and increased the data variability. Other plastics which were thinner gave better results. Although plastics made from Polyvinylidene Chloride, polyvinyl Chloride (both 13 μm thick) and polyethylene (29 and 7 μm thick) showed different levels of transmittance, they all gave similarly good performances. Polyvinylidene Chloride and polyethylene 29 mm thick were the plastics of choice because of their easy handling. For other types of plastics, it is advisable to run a simple check on their performance in order to obtain the maximum information from nylon cDNA arrays.Os arranjos de cDNA são uma poderosa ferramenta para o estudo de padrões de expressão gênica. Os arranjos em membranas de náilon apresentam ainda a vantagem de poderem ser reutilizados diversas vezes. Porém, um ponto bastante delicado em estudos de expressão gênica em larga escala é a sensibilidade. No caso de arranjos em membranas de náilon, a detecção dos sinais pode ser afetada pelo envoltório plástico utilizado para manter as membranas úmidas. Nesse estudo, nós avaliamos os efeitos de cinco tipos de plásticos na transmissão radioativa detectada, no número de genes com sinal acima da emissão de fundo e na variabilidade dos dados. O plástico produzido com polietileno com 69 μm de espessura apresentou uma forte interferência na emissão radioativa, bloqueando 68.7% do sinal detectado. Este bloqueio na transmitância diminuiu o numero de genes detectados e aumentou a variabilidade dos dados. Outros plásticos mais finos tiveram resultados melhores. Apesar de plásticos feitos de cloreto de polivinilideno e cloreto de polivinila (ambos com 13 μm de espessura) e polietileno (29 e 7 μm de espessura) terem diferentes níveis de transmitância, todos apresentaram performances semelhantes nos testes realizados. Cloreto de polivinilideno e polietileno com 29 μm de espessura foram os plásticos escolhidos devido à facilidade de manuseio. Para outros tipos de plásticos, é recomendável realizar um teste de suas performances antes de utilizá-los para envolver membranas de náilon, de forma a obter o máximo de informação dos experimentos com arranjos de cDNA

  • Avaliação da performance de diferentes plásticos usados para selar arranjos de cDNA em náilon
    'FapUNIFESP (SciELO)', 2015
    Co-Authors: Antônio Paulino Da ,costa Netto, Drummond,rodrigo Duarte, Felix,juliana De Maria, Jorge,renato Atílio, Menossi Marcelo
    Abstract:

    cDNA arrays are a powerful tool for discovering gene expression patterns. Nylon arrays have the advantage that they can be re-used several times. A key issue in high throughput gene expression analysis is sensitivity. In the case of nylon arrays, signal detection can be affected by the plastic bags used to keep membranes humid. In this study, we evaluated the effect of five types of plastics on the radioactive transmittance, number of genes with a signal above the background, and data variability. A polyethylene plastic bag 69 μm thick had a strong shielding effect that blocked 68.7% of the radioactive signal. The shielding effect on transmittance decreased the number of detected genes and increased the data variability. Other plastics which were thinner gave better results. Although plastics made from Polyvinylidene Chloride, polyvinyl Chloride (both 13 μm thick) and polyethylene (29 and 7 μm thick) showed different levels of transmittance, they all gave similarly good performances. Polyvinylidene Chloride and polyethylene 29 mm thick were the plastics of choice because of their easy handling. For other types of plastics, it is advisable to run a simple check on their performance in order to obtain the maximum information from nylon cDNA arrays.Os arranjos de cDNA são uma poderosa ferramenta para o estudo de padrões de expressão gênica. Os arranjos em membranas de náilon apresentam ainda a vantagem de poderem ser reutilizados diversas vezes. Porém, um ponto bastante delicado em estudos de expressão gênica em larga escala é a sensibilidade. No caso de arranjos em membranas de náilon, a detecção dos sinais pode ser afetada pelo envoltório plástico utilizado para manter as membranas úmidas. Nesse estudo, nós avaliamos os efeitos de cinco tipos de plásticos na transmissão radioativa detectada, no número de genes com sinal acima da emissão de fundo e na variabilidade dos dados. O plástico produzido com polietileno com 69 μm de espessura apresentou uma forte interferência na emissão radioativa, bloqueando 68.7% do sinal detectado. Este bloqueio na transmitância diminuiu o numero de genes detectados e aumentou a variabilidade dos dados. Outros plásticos mais finos tiveram resultados melhores. Apesar de plásticos feitos de cloreto de polivinilideno e cloreto de polivinila (ambos com 13 μm de espessura) e polietileno (29 e 7 μm de espessura) terem diferentes níveis de transmitância, todos apresentaram performances semelhantes nos testes realizados. Cloreto de polivinilideno e polietileno com 29 μm de espessura foram os plásticos escolhidos devido à facilidade de manuseio. Para outros tipos de plásticos, é recomendável realizar um teste de suas performances antes de utilizá-los para envolver membranas de náilon, de forma a obter o máximo de informação dos experimentos com arranjos de cDNA.18831887Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

  • Evaluation of the performance of different plastics used to seal nylon cDNA arrays
    Editora da Universidade Federal de Lavras, 2009
    Co-Authors: Antônio Paulino Da ,costa Netto, Drummond,rodrigo Duarte, Felix,juliana De Maria, Jorge,renato Atílio
    Abstract:

    cDNA arrays are a powerful tool for discovering gene expression patterns. Nylon arrays have the advantage that they can be re-used several times. A key issue in high throughput gene expression analysis is sensitivity. In the case of nylon arrays, signal detection can be affected by the plastic bags used to keep membranes humid. In this study, we evaluated the effect of five types of plastics on the radioactive transmittance, number of genes with a signal above the background, and data variability. A polyethylene plastic bag 69 μm thick had a strong shielding effect that blocked 68.7% of the radioactive signal. The shielding effect on transmittance decreased the number of detected genes and increased the data variability. Other plastics which were thinner gave better results. Although plastics made from Polyvinylidene Chloride, polyvinyl Chloride (both 13 μm thick) and polyethylene (29 and 7 μm thick) showed different levels of transmittance, they all gave similarly good performances. Polyvinylidene Chloride and polyethylene 29 mm thick were the plastics of choice because of their easy handling. For other types of plastics, it is advisable to run a simple check on their performance in order to obtain the maximum information from nylon cDNA arrays

  • Evaluation of the performance of different plastics used to seal nylon cDNA arrays Avaliação da performance de diferentes plásticos usados para selar arranjos de cDNA em náilon
    Universidade Federal de Lavras, 2009
    Co-Authors: Antônio Paulino Da ,costa Netto, Rodrigo Duarte Drummond, Juliana De Maria Felix, Renato Atílio Jorge, Marcelo Menossi
    Abstract:

    cDNA arrays are a powerful tool for discovering gene expression patterns. Nylon arrays have the advantage that they can be re-used several times. A key issue in high throughput gene expression analysis is sensitivity. In the case of nylon arrays, signal detection can be affected by the plastic bags used to keep membranes humid. In this study, we evaluated the effect of five types of plastics on the radioactive transmittance, number of genes with a signal above the background, and data variability. A polyethylene plastic bag 69 μm thick had a strong shielding effect that blocked 68.7% of the radioactive signal. The shielding effect on transmittance decreased the number of detected genes and increased the data variability. Other plastics which were thinner gave better results. Although plastics made from Polyvinylidene Chloride, polyvinyl Chloride (both 13 μm thick) and polyethylene (29 and 7 μm thick) showed different levels of transmittance, they all gave similarly good performances. Polyvinylidene Chloride and polyethylene 29 mm thick were the plastics of choice because of their easy handling. For other types of plastics, it is advisable to run a simple check on their performance in order to obtain the maximum information from nylon cDNA arrays.Os arranjos de cDNA são uma poderosa ferramenta para o estudo de padrões de expressão gênica. Os arranjos em membranas de náilon apresentam ainda a vantagem de poderem ser reutilizados diversas vezes. Porém, um ponto bastante delicado em estudos de expressão gênica em larga escala é a sensibilidade. No caso de arranjos em membranas de náilon, a detecção dos sinais pode ser afetada pelo envoltório plástico utilizado para manter as membranas úmidas. Nesse estudo, nós avaliamos os efeitos de cinco tipos de plásticos na transmissão radioativa detectada, no número de genes com sinal acima da emissão de fundo e na variabilidade dos dados. O plástico produzido com polietileno com 69 μm de espessura apresentou uma forte interferência na emissão radioativa, bloqueando 68.7% do sinal detectado. Este bloqueio na transmitância diminuiu o numero de genes detectados e aumentou a variabilidade dos dados. Outros plásticos mais finos tiveram resultados melhores. Apesar de plásticos feitos de cloreto de polivinilideno e cloreto de polivinila (ambos com 13 μm de espessura) e polietileno (29 e 7 μm de espessura) terem diferentes níveis de transmitância, todos apresentaram performances semelhantes nos testes realizados. Cloreto de polivinilideno e polietileno com 29 μm de espessura foram os plásticos escolhidos devido à facilidade de manuseio. Para outros tipos de plásticos, é recomendável realizar um teste de suas performances antes de utilizá-los para envolver membranas de náilon, de forma a obter o máximo de informação dos experimentos com arranjos de cDNA