761 research outputs found

    Politiouretanos termoestables vitriméricos con propiedades mejoradas de reciclabilidad

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    En aquesta tesi s'ha avan√ßat en l'estudi de xarxes termoestables de politiouretan (PTU) reciclables, gr√†cies al bescanvi din√†mic entre grups tiouret√†. Els materials s'han preparat per reacci√≥ entre tiols i isocianats polifuncionals, tant en condicions √†cides com b√†siques. A m√©s, s'han estudiat les aplicacions d'aquests materials com a materials reciclables, autoreparables i com a matrius de materials compostos. Buscant una major sostenibilitat, s'ha estudiat l'activitat catal√≠tica d'alternatives als compostos d'estany (IV), els m√©s utilitzats a escala industrial. Tamb√© s'han preparat tiols a partir de derivats de la biomassa, i s'ha estudiat el seu paper com substitut de tiols derivats de combustibles f√≤ssils.En esta tesis se ha avanzado en el estudio de redes termoestables de politiouretano (PTU) reciclables, debido al intercambio din√°mico entre grupos tiouretano. Los materiales se han preparado por reacci√≥n entre tioles e isocianatos polifuncionales, tanto en condiciones √°cidas como b√°sicas. Adem√°s, se han estudiado las aplicaciones de estos materiales como materiales reciclables y autorreparables, y como matrices de composites. En b√ļsqueda de una mayor sostenibilidad, se ha estudiado la actividad catal√≠tica de alternativas a los compuestos de esta√Īo (IV), los m√°s empleados a nivel industrial. Tambi√©n se han preparado tioles a partir de derivados de la biomasa, y se ha estudiado su papel como sustituto de tioles derivados de combustibles f√≥siles.In this thesis, progress has been made in the study of recyclable polythiourethane (PTU) thermosetting networks, due to the dynamic exchange between thiourethane groups. The materials have been prepared by reaction between polyfunctional thiols and isocyanates, both under acidic and basic conditions. In addition, the applications of these materials as recyclable and self-healing materials and as matrix composite have been studied. In search of a greater sustainability, the catalytic activity of alternatives to tin (IV) compounds, the most widely used at an industrial level, has been studied. Different thiols have also been prepared from biomass derivatives, and their role as a substitute for thiols derived from fossil fuels has been studied

    Preparation and Characterization of a Series of Self-Healable Bio-Based Poly(thiourethane) Vitrimer-like Materials

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    A series of poly(thiourethanes) (PTUs) from biobased monomers have been synthesized. Limonene and squalene were transformed into polyfunctional thiols by thiol-ene reaction with thioacetic acid and further saponification. They were then reacted in different proportions with hexamethylene diisocyanate (HDI) in the presence of a catalyst to prepare bio-based poly(thiourethane) vitrimer-like materials. The different functionalities of squalene and limonene thiols (six and two, respectively) allow for changing the characteristics of the final material by only varying their relative proportions in the reactive mixture. The proportions of thiol and isocyanate groups were stoichiometric in all the formulations tested. An acidic and a basic catalyst were tested in the preparation of the networked polymers. As the acidic catalyst, we selected dibutyltin dilaurate (DBTDL), and as the basic catalyst, a tetraphenylborate salt of 1,8-diazabicyclo(5.4.0)undec-7-ene (BGDBU), which has the advantage of only releasing the base at high temperatures. The materials obtained were characterized by thermogravimetry and thermomechanical analysis. The vitrimeric-like behavior was evaluated, and we could see that higher proportions of the limonene derivative in the formulations led to faster stress relaxation of the material. The use of the base catalyst led to a much shorter relaxation time. The materials obtained demonstrated good self-healing efficiencyPeer ReviewedPostprint (published version

    The use of lanthanide triflates in the preparation of poly(thiourethane) covalent adaptable networks

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    Covalent adaptable networks (CANs) are new polymeric materials with the mechanical properties of thermosets and the possibility of being recycled like thermoplastics. Poly(thiourethane) networks have demonstrated vitrimeric-like behavior at high temperatures due to the trans-thiocarbamoylation process, which Lewis acids and bases can accelerate. In this study, we report the use of lanthanide triflates (La, Sm, Dy, Er, and Yb) as Lewis acid catalysts, a greener alternative to other metallic catalysts as dibutyltin dilaurate (DBTDL) widely used in poly (urethane) and poly(thiourethane) networks. Moreover, they are not as reactive as DBTDL, and the curing mixture can be manipulated for a longer time at room temperature. As monomers, trimethylolpropane tris(3- mercapto propionate) (S3), hexamethylene diisocyanate (HDI), and isophorone diisocyanate (IPDI) have been used. We have demonstrated that the materials prepared with lanthanum triflate present the lowest relaxation times than those prepared with other lanthanide triflates or DBTDL. Calorimetry (DSC) and infrared spectroscopy (FTIR) were applied to study the curing process. The materials obtained were fully characterized by thermog- ravimetric analysis (TGA) and thermomechanical tests (DMA).This work is part of the R&D projects PID2020-115102RB-C21 and PID2020-115102RB-C22 funded by MCNI/AEI/10.13039/ 501100011033. We acknowledge these grants and to the Generalitat de Catalunya (2021-SGR-00154 and BASE3D). F.G. thanks to MCNI/AEI for the grant PRE2018-084192.Postprint (published version

    Effectiveness hyperoxygenated fatt y acid with silicone in lo wer extremities with and without ulcerations

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    Introducci√≥n: Existen evidencias cient√≠ficas sobre los beneficios del uso de √°cidos grasos para la regeneraci√≥n epid√©rmica y la prevenci√≥n de las √ļlceras cr√≥nicas. Los √°cidos grasos hiperoxigenados (AGHO) son productos compuestos por √°cidos grasos esenciales (AGE) a los que se a√Īade oxigeno a la mol√©cula inicial a trav√©s de un proceso llamado hiperoxidaci√≥n. La formula a estudio presenta adem√°s ciclometicona (silicona). El objetivo de este estudio es comprobar la eficacia de los AGHO con silicona en extremidades inferiores, con y sin ulceraciones. Metodolog√≠a: Estudio observacional, longitudinal, por cohortes de car√°cter prospectivo y multic√©ntrico realizado desde octubre de 2010 hasta septiembre de 2011. En una muestra de pacientes se aplic√≥ AGHO con silicona en formato aceite, en extremidades inferiores con alteraciones vasculares venosas y AGHO con silicona en formato leche en extremidades inferiores isqu√©micas y/o neurop√°ticas. Se efect√ļo un seguimiento de 8 semanas, valorando a trav√©s de la escala Fedpalla la evoluci√≥n del grado de deterioro de la integridad cut√°nea. Resultados: En general la muestra evolucion√≥ tras 8 semanas de aplicaci√≥n de AGHO, desde un grado II (mal pron√≥stico de epitelizaci√≥n) a un grado IV (muy buen pron√≥stico) de la escala Fedpalla. En 9 pacientes se midi√≥ la presi√≥n transcut√°nea de ox√≠geno, al inicio y al final del estudio, elev√°ndose un 11.1%. Conclusi√≥n: Los AGHO con silicona utilizados han permitido la restauraci√≥n de la integridad cut√°nea en la mayor√≠a de los pacientes en un periodo de 56 d√≠as.Introduction: There is scientific evidence on the benefits of the use of fatty acids for epidermal regeneration and prevention of chronic ulcers. The hyperoxygenated fatty acids (HOFAs) are products composed for essential fatty acids (EFA) to which oxygen is added to molecule through a process called hyperoxidation. The formula to study presents addition cyclomethicone (silicone). The objective of this study is to test the efficacy of the HOFA with silicone in lower extremities, with or without ulcerations. Methodology: An observational study, longitudinal, cohort of character and prospective multicenter from October 2010 to September 2011. In a sample of patients were applied HOFA with silicone in oil format, in the lower extremities with vascular alterations venous and HOFA in milk format with silicone in lower extremities ischemic and/or neuropathic. There was a followup to 8 weeks, valuing through Fedpalla scale the evolution of the degree of deterioration of the skin integrity. Results: In general the sample evolved after 8 weeks of implementation of HOFA, since a grade II (poor prognosis of epithelization) to a grade IV (very good prognosis) of the scale Fedpalla. In 9 patients was measured the transcutaneous oxygen pressure at the beginning and the end of the study, rising 11.1 %. Conclusion: The HOFAs with silicone used have allowed the restoration of skin integrity in the majority of patients in a period of 56 days.Enfermer√≠

    Matching microscopic and macroscopic responses in glasses

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    Primero reproducimos en las computadoras Janus y Janus II un experimento importante que mide la longitud de la coherencia de los hilados de vidrio a trav√©s de la reducci√≥n de las barreras de energ√≠a libre inducidas por el efecto Zeeman. En segundo lugar, determinamos el comportamiento de escala que permite un an√°lisis cuantitativo de un nuevo experimento informado en la Carta complementaria [S. Guchhait y R. Orbach, Phys. Rev. Lett. 118, 157203 (2017)]. El valor de la longitud de coherencia estimada a trav√©s del an√°lisis de las funciones de correlaci√≥n microsc√≥picas resulta ser cuantitativamente consistente con su medici√≥n a trav√©s de las funciones de respuesta macrosc√≥pica. Adem√°s, las susceptibilidades no lineales, recientemente medidas en l√≠quidos formadores de vidrio, se escalan como potencias de la misma longitud microsc√≥pica.We first reproduce on the Janus and Janus II computers a milestone experiment that measures the spin glass coherence length through the lowering of free-energy barriers induced by the Zeeman effect. Secondly, we determine the scaling behavior that allows a quantitative analysis of a new experiment reported in the companion Letter [S. Guchhait and R. Orbach, Phys. Rev. Lett. 118, 157203 (2017)]. The value of the coherence length estimated through the analysis of microscopic correlation functions turns out to be quantitatively consistent with its measurement through macroscopic response functions. Further, nonlinear susceptibilities, recently measured in glass-forming liquids, scale as powers of the same microscopic length.‚ÄĘ European Research Council. Beca No. NPRGGLASS. Ayuda para Marco Baity Jesi ‚ÄĘ Uni√≥n Europea. Marie SkŇāodowska- Curie. Beca No. 654971 ‚ÄĘ Consejo Europeo de Investigaci√≥n (ERC). Subvenci√≥n 694925 ‚ÄĘ University of Syracuse. Beca No. NSF-DMR-305184, para David Yllanes Mosquera ‚ÄĘ Ministerio de Econom√≠a y Competitividad. No. FIS2012-35719-C02, No. FIS2013-42840-P (I+D+i), No. FIS2015-65078-C2, No. FIS2016-76359-P (I+D+i), y No. TEC2016-78358-R ‚ÄĘ Junta de Extremadura y Fondos FEDER. Contrato parcial GRU10158 ‚ÄĘ Dip√Ļtaci√≥n General de Arag√≥n y Fondos Social Europeo. AyudapeerReviewe

    The evolution of the ventilatory ratio is a prognostic factor in mechanically ventilated COVID-19 ARDS patients

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    Background: Mortality due to COVID-19 is high, especially in patients requiring mechanical ventilation. The purpose of the study is to investigate associations between mortality and variables measured during the first three days of mechanical ventilation in patients with COVID-19 intubated at ICU admission. Methods: Multicenter, observational, cohort study includes consecutive patients with COVID-19 admitted to 44 Spanish ICUs between February 25 and July 31, 2020, who required intubation at ICU admission and mechanical ventilation for more than three days. We collected demographic and clinical data prior to admission; information about clinical evolution at days 1 and 3 of mechanical ventilation; and outcomes. Results: Of the 2,095 patients with COVID-19 admitted to the ICU, 1,118 (53.3%) were intubated at day 1 and remained under mechanical ventilation at day three. From days 1 to 3, PaO2/FiO2 increased from 115.6 [80.0-171.2] to 180.0 [135.4-227.9] mmHg and the ventilatory ratio from 1.73 [1.33-2.25] to 1.96 [1.61-2.40]. In-hospital mortality was 38.7%. A higher increase between ICU admission and day 3 in the ventilatory ratio (OR 1.04 [CI 1.01-1.07], p = 0.030) and creatinine levels (OR 1.05 [CI 1.01-1.09], p = 0.005) and a lower increase in platelet counts (OR 0.96 [CI 0.93-1.00], p = 0.037) were independently associated with a higher risk of death. No association between mortality and the PaO2/FiO2 variation was observed (OR 0.99 [CI 0.95 to 1.02], p = 0.47). Conclusions: Higher ventilatory ratio and its increase at day 3 is associated with mortality in patients with COVID-19 receiving mechanical ventilation at ICU admission. No association was found in the PaO2/FiO2 variation

    MUSiC : a model-unspecific search for new physics in proton-proton collisions at root s=13TeV

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    Results of the Model Unspecific Search in CMS (MUSiC), using proton-proton collision data recorded at the LHC at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb(-1), are presented. The MUSiC analysis searches for anomalies that could be signatures of physics beyond the standard model. The analysis is based on the comparison of observed data with the standard model prediction, as determined from simulation, in several hundred final states and multiple kinematic distributions. Events containing at least one electron or muon are classified based on their final state topology, and an automated search algorithm surveys the observed data for deviations from the prediction. The sensitivity of the search is validated using multiple methods. No significant deviations from the predictions have been observed. For a wide range of final state topologies, agreement is found between the data and the standard model simulation. This analysis complements dedicated search analyses by significantly expanding the range of final states covered using a model independent approach with the largest data set to date to probe phase space regions beyond the reach of previous general searches.Peer reviewe

    Measurement of prompt open-charm production cross sections in proton-proton collisions at root s=13 TeV