Fenómenos de resonancia asociados al transporte de mercancías líquidas por ferrocarril

Los vagones de mercancías se unen entre sí mediante acoplamientos UIC estándar. Aunque cada plataforma está equipada con un tensor de enganche en ambos extremos, sólo uno de ellos se utiliza, mientras que el otro descansa apoyado en un gancho. Debido a los efectos de oleaje del líquido contenido en las cisternas, este tensor en reposo puede entrar en resonancia con la frecuencia natural de algunos fluidos, llegando a oscilar de forma apreciable. En ocasiones llega a saltar fuera de su alojamiento, provocando ciertas molestias durante la circulación, aunque sin entrañar ningún riesgo para la seguridad de la marcha. Con el propósito de simular la influencia de diversos factores sobre el comportamiento dinámico asociado a estos fenómenos de oleaje, se ha desarrollado un modelo de la interacción fluido-vehículo, empleado técnicas de modelado de sistemas multicuerpo y de elementos finitos

Simulation of Freight Trains Equipped with Partially Filled Tank Containers and Related Resonance Phenomenon

To study the fluid motion-vehicle dynamics interaction, a model of four, liquid filled two-axle container freight wagons was set up. The railway vehicle has been modelled as a multi-body system (MBS). To include fluid sloshing, an equivalent mechanical model has been developed and incorporated. The influence of several factors has been studied in computer simulations, such as track defects, curve negotiation, train velocity, wheel wear, liquid and solid wagonload, and container baffles. SIMPACK has been used for MBS analysis, and ANSYS for liquid sloshing modelling and equivalent mechanical systems validation. Acceleration and braking manoeuvres of the freight train set the liquid cargo into motion. This longitudinal sloshing motion of the fluid cargo inside the tanks initiated a swinging motion of some components of the coupling gear. The coupling gear consists of UIC standard traction hooks and coupling screws that are located between buffers. One of the coupling screws is placed in the traction hook of the opposite wagon thus joining the two wagons, whereas the unused coupling screw rests on a hanger. Simulation results showed that, for certain combinations of type of liquid, filling level and container dimensions, the liquid cargo could provoke an undesirable, although not hazardous, release of the unused coupling screw from its hanger. The coupling screw's release was especially obtained when a period of acceleration was followed by an abrupt braking manoeuvre at 1 m/s2. It was shown that a resonance effect between the liquid's oscillation and the coupling screw's rotary motion could be the reason for the coupling screw's undesired release. Possible solutions to avoid the phenomenon are given.Acceleration and braking manoeuvres of the freight train set the liquid cargo into motion. This longitudinal sloshing motion of the fluid cargo inside the tanks initiated a swinging motion of some components of the coupling gear. The coupling gear consists of UIC standard traction hooks and coupling screws that are located between buffers. One of the coupling screws is placed in the traction hook of the opposite wagon thus joining the two wagons, whereas the unused coupling screw rests on a hanger. This paper reports on a study of the fluid motion-train vehicle dynamics interaction. In the study, a model of four, liquid-filled two-axle container freight wagons was developed. The railway vehicle has been modeled as a multi-body system (MBS). To include fluid sloshing, an equivalent mechanical model has been developed and incorporated. The influence of several factors has been studied in computer simulations, such as track defects, curve negotiation, train velocity, wheel wear, liquid and solid wagonload, and container baffles. A simulation program was used for MBS analysis, and a finite element analysis program was used for liquid sloshing modeling and equivalent mechanical systems validation. Acceleration and braking maneuvers of the freight train set the liquid cargo into motion. This longitudinal sloshing motion of the fluid cargo inside the tanks initiated a swinging motion of some components of the coupling gear. Simulation results showed that, for certain combinations of type of liquid, filling level and container dimensions, the liquid cargo could provoke an undesirable, although not hazardous, release of an unused coupling screw from its hanger. It was shown that a resonance effect between the liquid's oscillation and the coupling screw's rotary motion could be the reason for the coupling screw's undesired release. Solutions are suggested to avoid the resonance problem, and directions for future research are given

Chemical characterization of lignin and lipophilic fractions from leaf fibers of curaua (Ananas erectifolius)

E-mail: [email protected] (J.C. del Río)The chemical composition of leaf fibers of curaua (Ananas erectifolius), an herbaceous plant native of Amazonia, was studied. Special attention was paid to the content and composition of lignin and lipophilic compounds. The analysis of lignin in the curaua fibers was performed “in situ” by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and showed a lignin composition with a p-hydroxyphenyl:guaiacyl:syringyl units (H:G:S) molar proportion of 30:29:41 (S/G molar ratio of 1.4). The presence of p-hydroxycinnamic acids (p-coumaric and ferulic acids) in curaua fibers was revealed upon pyrolysis in the presence of tetramethylammonium hydroxide. On the other hand, the main lipophilic compounds, analysed by GC/MS, were series of long-chain n-fatty acids, n-fatty alcohols, α- and ω-hydroxyacids, monoglycerides, sterols and waxes. Other compounds, such as ω-hydroxy monoesters and ω-hydroxy acylesters of glycerol were also found in this fiber in high amounts.Peer reviewe

Oxidative modification of paper pulp lipophilic extractives by laccase-mediator system

Recently, we have shown the effectiveness of the laccase-mediator system in removing lipophilic extractives from pulp regardless the pulping process and the raw material used. This paper summarizes our research findings on the chemistry of the reactions of the main lipophilic extractives present in paper pulps with the laccase-mediator system. The results attained in reactions of several model lipids - including alkanes, fatty alcohols, fatty acids, resin acids, free sterols, sterol esters and triglycerides - with a fungal laccase in the presence of HBT as mediator, are discussed in the context of enzymatic control of pitch deposits, to explain the removal of complex lipid mixtures during laccase-mediator treatment of different pulp types, including eucalypt pulp.This study was funded by the BIORENEW EU-project (NMP2-CT-2006-026456) and the Spanish MICINN (AGL-2008-00709). Beldem (Andenne, Belgium) is acknowledged for laccase supply. S. Molina and J. Rencoret are acknowledged for their contribution to this work.Peer reviewe

Chemical composition of lipophilic extractives from non-woody plants used for manufacturing high-quality papers

The chemical composition of lipophilic extractives from fibers of three annual plants, namely hemp (Cannabis sativa), flax (Linum usitatissimum) and kenaf (Hibiscus cannabinus) that are commonly used for high quality paper pulp production was studied. The cloroform soluble fractions of the acetone extracts of the fibers were analyzed by gas chromatography-mass spectrometry. The main compounds identified were series of n-alkanes, n-fatty acids, n-aldehydes, n-fatty alcohols and waxes. On the other hand, free and esterified sterols and triterpenols, steroid hydrocarbons, steroid and triterpenoid ketones, as well as sterol glycosides were also found in the fibers studied here.A.G. acknowledges a "Ramón y Cajal" contract of the Spanish MCYT. We thank CELESA (Tortosa, Spain) for providing the raw materials.Peer reviewe

RELACIÓN DE LA DIVERSIDAD DE ANFIBIOS CON LAS VARIABLES ESTRUCTURALES DE SISTEMAS AGROFORESTALES DE CACAO ORGÁNICO

Se investigó como se relaciona la abundancia, riqueza y diversidad de anfibios de hojarasca con las variables de estructura vertical de la vegetación de 39 parcelas en diferentes tipologías de sistemas agroforestales con cacao orgánico y bosque en Valle de Risco, Palo Seco y Rio Oeste Arriba, Bosque Protector de Palo Seco (Panamá), durante los meses de mayo a julio de 2008. Se registraron un total de 2791 individuos pertenecientes a 34 especies de anfibios distribuidos en 11 familias. La abundancia, riqueza y diversidad de anfibios estuvo diferenciada en las tres tipologías de cacao orgánico y bosque (p<0,05). Existió correlación negativa entre la riqueza de anfibios y la cobertura de la vegetación de 0 a 2 m de altura (r = -0,38; p = 0,022), por otra parte la riqueza de anfibios estuvo relacionada positivamente con la cobertura de la vegetación de 2 a 9 m de altura (r = 0,26; p = 0,0121) y el porcentaje de luz en el dosel, este último con relación negativa (r = -0,37; p = 0,0274). También hubo correlación de la abundancia con la cantidad de hojarasca en la parcela (r = 0,40; p = 0,0133), en el caso de la diversidad de anfibios se correlacionó negativamente con la cantidad de hojarasca en la parcela (r = -0,42; p = 0,0105). Se observó que las tipologías de cacao orgánico con menor estructura vertical y mayor manejo, poseen los valores más bajos de riqueza y diversidad de anfibios; sin embargo, son las que poseen la mayor abundancia de individuos

Chemical composition of lipophilic extractives from sisal (Agave sisalana) fibers

Instituto de Recursos Naturales y Agrobiología de Sevilla, CSIC, PO Box 1052, E-41080 Seville, Spain. Corresponding author, E-mail: [email protected] (A. Gutiérrez)The chemical composition of lipophilic extractives from sisal (Agave sisalana) fibers, which are used for high-quality paper pulp production was studied. The lipophilic extract, which accounted for 0.5 % of total sisal fiber weight, was analyzed by gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS) using short- and medium-length high temperature capillary columns, respectively. For a more detailed characterization, the extract was fractionated by solid-phase extraction and the fractions obtained were analyzed by GC and GC/MS. The most predominant compounds identified were fatty acids (30% of total lipids) including α- and -hydroxyfatty acids, fatty alcohols (20%), free sterols (11%), alkanes (11%) and a series of ferulic acid esters of long chain alcohols and -hydroxyfatty acids (10%). Additionally, steroid hydrocarbons and ketones, monoglycerides, aldehydes, waxes, and sterol glycosides were also found together with minor amounts of diglycerides, and sterol esters.This study has been supported by the Spanish Ministerio de Ciencia y Tecnología (MCYT) (projects AGL2002-00393 and AGL2005-01748) and EU project (BIORENEW, NMP2-CT-2006-026456). We thank CELESA pulp mill (Tortosa, Spain) for providing the sisal fibers.Peer reviewe

Isolation and structural characterization of the acetylated heteroxylan from sisal (Agave sisalana) and its fate during alkaline pulping and TCF/ECF bleaching.

The heteroxylan from sisal, an O-acetyl-(4-O-methylglucurono)xylan with a molecular weight (Mw) of 18 kDa, was isolated by extraction of peracetic holocellulose with Me2SO and thoroughly characterized by wet chemistry, and NMR spectroscopy. The heteroxylan backbone is composed of (1→4)-linked β-D-xylopyranosyl units (Xylp) partially ramified with terminal (1→2)-linked 4-O-methyl-α-D-glucuronosyl (MeGlcpA) and a small proportion of α-D-glucuronosyl (GlcpA) residues. Roughly 61mol% of Xylp residues are acetylated (DS =0.70). During soda/AQ pulping, GlcpA and MeGlcA are partially removed or converted to 4-deoxy-β-L-threo-hex-4-enopyranosyluronic acid (HexA), though notable proportion of GlcpA maintained intact. The major part of acetyl groups was hydrolyzed during pulping. It was proposed that the predominantly low molecular weight xylan fraction was removed from pulp during bleaching. The profiles of uronosyl residues in xylans from TCF and ECF bleached sisal pulps were rather different.This study has been supported by the Spanish MEC (Project AGL2005-01748) and EU Contract NMP2-CT-2006-26456. We thank CELESA (Tortosa, Spain) for providing the samples. G.M. thanks the Spanish Ministry of Education for a FPI fellowship.Peer reviewe

Steroid hydroxylation by basidiomycete peroxygenases: A combined experimental and computational Study

13 páginas.-- 7 figuras.-- 4 tablas.-- 40 referencias.-- Supplemental material for this article may be found at http://dx.doi.org/10.1128/AEM.00660-15.The goal of this study is the selective oxyfunctionalization of steroids under mild and environmentally friendly conditions using fungal enzymes. With this purpose, peroxygenases from three basidiomycete species were tested for the hydroxylation of a variety of steroidal compounds, using H2O2 as the only cosubstrate. Two of them are wild-type enzymes from Agrocybe aegerita and Marasmius rotula, and the third one is a recombinant enzyme from Coprinopsis cinerea. The enzymatic reactions on free and esterified sterols, steroid hydrocarbons, and ketones were monitored by gas chromatography, and the products were identified by mass spectrometry. Hydroxylation at the side chain over the steroidal rings was preferred, with the 25-hydroxyderivativespredominating. Interestingly, antiviral and other biological activities of 25-hydroxycholesterol have been reported recently (M. Blanc et al., Immunity 38:106-118, 2013, http://dx.doi.org/10.1016/j.immuni.2012.11.004). However, hydroxylation in the ring moiety and terminal hydroxylation at the side chain also was observed in some steroids, the former favored by the absence of oxygenated groups at C-3 and by the presence of conjugated double bonds in the rings. To understand the yield and selectivity differences between the different steroids, a computational study was performed using Protein Energy Landscape Exploration (PELE) software for dynamic ligand diffusion. These simulations showed that the active-site geometry and hydrophobicity favors the entrance of the steroid side chain, while the entrance of the ring is energetically penalized. Also, a direct correlation between the conversion rate and the side chain entrance ratio could be established that explains the various reaction yields observed.This study was supported by the INDOX (KBBE-2013-7-613549), PEROXICATS (KBBE-2010-4-265397), and PELE (ERC-2009-Adg 25027) EU projects. We have no conflicts of interest to declare.Peer reviewe

Calidad de vida de los profesionales en el modelo de gestión clínica de Asturias

ResumenObjetivoAnalizar la calidad de vida profesional en el modelo de gestión clínica de Asturias y comprobar si hay diferencias en los centros donde el modelo lleva implantado más tiempo o en función del ámbito asistencial (atención primaria o especializada).MétodosSe aplicó el CVP-35 (35 preguntas), anónimo y autocumplimentado, con tres preguntas adicionales. Se realizó un análisis descriptivo, univariado y bivariado, de las preguntas por separado y según las subescalas «Apoyo directivo» (AD), «Cargas de trabajo» (CT) y «Motivación intrínseca» (MI), siendo las principales variables independientes el ámbito asistencial y el tiempo como unidad o área de gestión clínica.ResultadosDe la población de estudio, 2572 profesionales, respondieron 1395 (54%) (el 67% en primaria y 51% en especializada). El 87% llevaba 5 años o más en su puesto. Para el 33% era su primer año en gestión clínica. El ítem con mayor puntuación fue la capacitación para el trabajo (8,39±1,42) y el más bajo los conflictos con los compañeros (3,23±2,2). Primaria obtiene resultados más altos en AD y calidad de vida en el trabajo, y especializada en CT. Respecto a la gestión clínica, las mejores puntuaciones se obtienen en las de 3 años y las peores en las de primer año. Las diferencias son especialmente favorables a la gestión clínica en especializada: las que más tiempo llevan perciben menos CT y más MI y calidad de vida.ConclusionesLlevar más tiempo en el modelo de gestión clínica se asocia con mejores percepciones en la calidad de vida profesional, sobre todo en atención especializada.AbstractObjectiveTo evaluate professional quality of life in our clinical governance model by comparing differences according to the time since the model's implementation (1-3 years) and the setting (primary or hospital care).MethodsA cross-sectional descriptive study was performed. The 35-item, anonymous, self-administered Professional Quality of Life Questionnaire, with three additional questions, was applied. A minimum sample size for each clinical governance unit/area (CGU/CGA) was calculated. Descriptive, univariate and bivariate analyses were performed using the 35 items separately. The subscales of «management support», «workload» and «intrinsic motivation» were used as dependant variables, and the setting and time since implementation of the CGU/CGA as independent variables.ResultsOf the study population of 2572 professionals, 1395 (54%) responded (67% in primary care and 51% in hospital care). A total of 87% had been working for 5 years or more in their positions. Thirty-three percent had worked for less than a year in clinical governance. The item with the highest score was job training (8.39±1.42) and that with the lowest was conflicts with peers (3.23±2.2). Primary healthcare professionals showed better results in management support and quality of life at work and hospital professionals in workload. The clinical governance model obtained the best scores at 3 years and the worst at 1 year. These differences were especially favorable for clinical governance in hospitals: professionals working longer perceived a lower workload and more intrinsic motivation and quality of life.ConclusionsA longer time working in the clinical governance model was associated with better perception of professional quality of life, especially in hospital care