Desde las primeras etapas de diseño de la superestructura de un autobús es necesario considerar s... more Desde las primeras etapas de diseño de la superestructura de un autobús es necesario considerar su influencia en el confort de los pasajeros de acuerdo con las directrices establecidas en la norma ISO 2631:1997. Por ello, en esta investigación se ha llevado a cabo un análisis modal experimental de la superestructura de un autobús urbano con el objeto de obtener las frecuencias y modos propios de vibración de dicha superestructura. A partir de dicho análisis se evaluará el confort de los pasajeros en función de su ubicación en el autobús, se identificarán las zonas del habitáculo que mayores aceleraciones verticales sufren y el modo de reducir dichas aceleraciones. Para ello, se ha excitado la carrocería mediante la técnica de impacto y se ha caracterizado la aceleración vertical de puntos estratégicos de la superestructura, obteniéndose las funciones de transferencia del sistema (FRF). Esto permite determinar las frecuencias y modos propios de vibración, tanto de flexión vertical como de torsión. Por último se proponen modificaciones en la superestructura del autobús con el objeto de reducir las aceleraciones a las que están sometidos los pasajeros, mejorando así el confort.
We report the synthesis, free-radical cyclization of precursors 1,2,7-trideoxy-7-iodo-3,4:5,6-di-... more We report the synthesis, free-radical cyclization of precursors 1,2,7-trideoxy-7-iodo-3,4:5,6-di-O-isopropylidene-d-gluco-hept-1-enitol (1), methyl 7-O-acetyl-6-O-benzyl-8-bromo-2,3,8-trideoxy-4,5-O-isopropylidene-d-gluco-oct-2-enonate (2) and 5-O-acetyl-4-O-benzyl-6-bromo-6-deoxy-2,3-O-isopropylidene-d-glucose-O-benzyloxime (3), readily prepared from d-glucose, and some selected transformations of the carbocycles obtained from these intermediates. In compound 1 we have installed a terminal double bond and an iodide as radical acceptor and leaving group, respectively. Compounds 2 and 3 are ε-bromo aldehydes substituted with α,β-unsaturated ester and oxime ether functions as radical traps, respectively. The tributyltin hydride mediated ring closure of these radical precursors have afforded a series of interesting, diverse and highly functionalized carbocycles which can be considered useful building blocks for the synthesis of branched-chain cyclitols, aminocyclitols and aminoconduritols. In these processes, a good chemical yield and high stereoselectivity has been found in the newly formed stereocenters. Particularly interesting has been the finding that the stereochemical outcome of the free-radical cyclization is independent of the ratio of isomers (E or Z) in oxime ether 3. These results show the power and the state of art of this strategy for the stereocontrolled synthesis of enantiomerically pure inositols from carbohydrates.Graphic
The composition of suberin and lignin in endodermal cell walls (ECWs) and in rhizodermal/hypoderm... more The composition of suberin and lignin in endodermal cell walls (ECWs) and in rhizodermal/hypodermal cell walls (RHCWs) of developing primary maize (Zea mays L.) roots was analysed after depolymerisation of enzymatically isolated cell wall material. Absolute suberin amounts related to root length significantly increased from primary ECWs (Casparian strips) to secondary ECWs (suberin lamella). During further maturation of the endodermis, reaching the final tertiary developmental state characterised by the deposition of lignified secondary cell walls (u-shaped cell wall deposits), suberin amounts remained constant. Absolute amounts of lignin related to root length constantly increased throughout the change from primary to tertiary ECWs. The suberin of Casparian strips contained high amounts of carboxylic and 2-hydroxy acids, and differed substantially from the suberin of secondary and tertiary ECWs, which was dominated by high contents of ω-hydroxycarboxylic and 1,ω-dicarboxylic acids. Furthermore, the chain-length distribution of suberin monomers in primary ECWs ranged from C16 to C24, whereas in secondary and tertiary ECWs a shift towards higher chain lengths (C16 to C28) was observed. The lignin composition of Casparian strips (primary ECWs) showed a high syringyl content and was similar to lignin in secondary cell walls of the tertiary ECWs, whereas lignin in secondary ECWs contained higher amounts of p-hydroxyphenyl units. The suberin and lignin compositions of RHCWs rarely changed with increasing root age. However, compared to the suberin in ECWs, where C16 and C18 were the most prominent chain lengths, the suberin of RHCWs was dominated by the higher chain lengths (C24 and C26). The composition of RHCW lignin was similar to that of secondary-ECW lignin. Using lignin-specific antibodies, lignin epitopes were indeed found to be located in the Casparian strip. Surprisingly, the mature suberin layers of tertiary ECWs contained comparable amounts of lignin-like epitopes.
Due to their low cytotoxicity, controllable size, and unique architecture, cyclodextrin (CD)-base... more Due to their low cytotoxicity, controllable size, and unique architecture, cyclodextrin (CD)-based polyrotaxanes and polypseudorotaxanes have inspired interesting exploitation as novel biomaterials. This review will update the recent progress in the studies on the structures of polyrotaxanes and polypseudorotaxanes based on different CDs and polymers, followed by summarizing their potential applications in life science and biotechnology, such as drug delivery, gene delivery, and tissue engineering. CD-based biodegradable polypseudorotaxane hydrogels could be used as promising injectable drug delivery systems for sustained and controlled drug release. Polyrotaxanes with drug or ligand-conjugated CDs threaded on polymer chain with biodegradable end group could be useful for controlled and multivalent targeting delivery. Cationic polyrotaxanes consisting of multiple oligoethylenimine-grafted CDs threaded on a block copolymer chain were attractive non-viral gene carries due to the strong DNA-binding ability, low cytotoxicity, and high gene transfection efficiency. Cytocleavable end caps were also introduced in the polyrotaxane systems in order to ensure efficient endosomal escape for intracellular trafficking of DNA. Finally, hydrolyzable polyrotaxane hydrogels with cross-linked α-CDs could be a desirable scaffold for cartilage and bone tissue engineering.
Desde las primeras etapas de diseño de la superestructura de un autobús es necesario considerar s... more Desde las primeras etapas de diseño de la superestructura de un autobús es necesario considerar su influencia en el confort de los pasajeros de acuerdo con las directrices establecidas en la norma ISO 2631:1997. Por ello, en esta investigación se ha llevado a cabo un análisis modal experimental de la superestructura de un autobús urbano con el objeto de obtener las frecuencias y modos propios de vibración de dicha superestructura. A partir de dicho análisis se evaluará el confort de los pasajeros en función de su ubicación en el autobús, se identificarán las zonas del habitáculo que mayores aceleraciones verticales sufren y el modo de reducir dichas aceleraciones. Para ello, se ha excitado la carrocería mediante la técnica de impacto y se ha caracterizado la aceleración vertical de puntos estratégicos de la superestructura, obteniéndose las funciones de transferencia del sistema (FRF). Esto permite determinar las frecuencias y modos propios de vibración, tanto de flexión vertical como de torsión. Por último se proponen modificaciones en la superestructura del autobús con el objeto de reducir las aceleraciones a las que están sometidos los pasajeros, mejorando así el confort.
We report the synthesis, free-radical cyclization of precursors 1,2,7-trideoxy-7-iodo-3,4:5,6-di-... more We report the synthesis, free-radical cyclization of precursors 1,2,7-trideoxy-7-iodo-3,4:5,6-di-O-isopropylidene-d-gluco-hept-1-enitol (1), methyl 7-O-acetyl-6-O-benzyl-8-bromo-2,3,8-trideoxy-4,5-O-isopropylidene-d-gluco-oct-2-enonate (2) and 5-O-acetyl-4-O-benzyl-6-bromo-6-deoxy-2,3-O-isopropylidene-d-glucose-O-benzyloxime (3), readily prepared from d-glucose, and some selected transformations of the carbocycles obtained from these intermediates. In compound 1 we have installed a terminal double bond and an iodide as radical acceptor and leaving group, respectively. Compounds 2 and 3 are ε-bromo aldehydes substituted with α,β-unsaturated ester and oxime ether functions as radical traps, respectively. The tributyltin hydride mediated ring closure of these radical precursors have afforded a series of interesting, diverse and highly functionalized carbocycles which can be considered useful building blocks for the synthesis of branched-chain cyclitols, aminocyclitols and aminoconduritols. In these processes, a good chemical yield and high stereoselectivity has been found in the newly formed stereocenters. Particularly interesting has been the finding that the stereochemical outcome of the free-radical cyclization is independent of the ratio of isomers (E or Z) in oxime ether 3. These results show the power and the state of art of this strategy for the stereocontrolled synthesis of enantiomerically pure inositols from carbohydrates.Graphic
The composition of suberin and lignin in endodermal cell walls (ECWs) and in rhizodermal/hypoderm... more The composition of suberin and lignin in endodermal cell walls (ECWs) and in rhizodermal/hypodermal cell walls (RHCWs) of developing primary maize (Zea mays L.) roots was analysed after depolymerisation of enzymatically isolated cell wall material. Absolute suberin amounts related to root length significantly increased from primary ECWs (Casparian strips) to secondary ECWs (suberin lamella). During further maturation of the endodermis, reaching the final tertiary developmental state characterised by the deposition of lignified secondary cell walls (u-shaped cell wall deposits), suberin amounts remained constant. Absolute amounts of lignin related to root length constantly increased throughout the change from primary to tertiary ECWs. The suberin of Casparian strips contained high amounts of carboxylic and 2-hydroxy acids, and differed substantially from the suberin of secondary and tertiary ECWs, which was dominated by high contents of ω-hydroxycarboxylic and 1,ω-dicarboxylic acids. Furthermore, the chain-length distribution of suberin monomers in primary ECWs ranged from C16 to C24, whereas in secondary and tertiary ECWs a shift towards higher chain lengths (C16 to C28) was observed. The lignin composition of Casparian strips (primary ECWs) showed a high syringyl content and was similar to lignin in secondary cell walls of the tertiary ECWs, whereas lignin in secondary ECWs contained higher amounts of p-hydroxyphenyl units. The suberin and lignin compositions of RHCWs rarely changed with increasing root age. However, compared to the suberin in ECWs, where C16 and C18 were the most prominent chain lengths, the suberin of RHCWs was dominated by the higher chain lengths (C24 and C26). The composition of RHCW lignin was similar to that of secondary-ECW lignin. Using lignin-specific antibodies, lignin epitopes were indeed found to be located in the Casparian strip. Surprisingly, the mature suberin layers of tertiary ECWs contained comparable amounts of lignin-like epitopes.
Due to their low cytotoxicity, controllable size, and unique architecture, cyclodextrin (CD)-base... more Due to their low cytotoxicity, controllable size, and unique architecture, cyclodextrin (CD)-based polyrotaxanes and polypseudorotaxanes have inspired interesting exploitation as novel biomaterials. This review will update the recent progress in the studies on the structures of polyrotaxanes and polypseudorotaxanes based on different CDs and polymers, followed by summarizing their potential applications in life science and biotechnology, such as drug delivery, gene delivery, and tissue engineering. CD-based biodegradable polypseudorotaxane hydrogels could be used as promising injectable drug delivery systems for sustained and controlled drug release. Polyrotaxanes with drug or ligand-conjugated CDs threaded on polymer chain with biodegradable end group could be useful for controlled and multivalent targeting delivery. Cationic polyrotaxanes consisting of multiple oligoethylenimine-grafted CDs threaded on a block copolymer chain were attractive non-viral gene carries due to the strong DNA-binding ability, low cytotoxicity, and high gene transfection efficiency. Cytocleavable end caps were also introduced in the polyrotaxane systems in order to ensure efficient endosomal escape for intracellular trafficking of DNA. Finally, hydrolyzable polyrotaxane hydrogels with cross-linked α-CDs could be a desirable scaffold for cartilage and bone tissue engineering.
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Papers by Ester Pozuelo