Non-Markovian Methods in Glass Transition

[EN] A model for the heterogeneity of local dynamics in polymer and other glass-forming materials is provided here. The fundamental characteristics of the glass transition phenomenology emerge when simulating a condensed matter open cluster that has a strong interaction with its heterogeneous environment. General glass transition features, such as non-exponential structural relaxations, the slowing down of relaxation times with temperature and specific off-equilibrium glassy dynamics can be reproduced by non-Markovian dynamics simulations with the minimum computer resources. Non-Markovian models are shown to be useful tools for obtaining insights into the complex dynamics involved in the glass transition phenomenon, including whether or not there is a need for a growing correlation length or the relationship between the non-exponentiality of structural relaxations and dynamic heterogeneity.The APC was funded by the Spanish Ministry of Science, Innovations, and Universities through the RTI2018-097862-B-C21 Project (including the FEDER financial support). CIBER-BBN is an initiative funded by the VI National R&D&I Plan 2008¿2011, Iniciativa Ingenio 2010, Consolider Program. CIBER Actions are financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund.Torregrosa Cabanilles, C.; Molina Mateo, J.; Sabater I Serra, R.; Meseguer Dueñas, JM.; Gómez Ribelles, JL. (2020). Non-Markovian Methods in Glass Transition. Polymers. 12(9):1-14. https://doi.org/10.3390/polym12091997S11412

Fluctuations of conformational mobility of macromolecules around the glass transition

[EN] The heterogeneity of local dynamics in disordered systems is behind some key features of glass transition. In order to improve our understanding of the molecular dynamics in disordered systems in the vicinity of the glass transition, different parameters have been proposed to quantitatively describe dynamical heterogeneity. In the case of polymers, free volume models relate the macromolecular mobility to the free or accessible volume. The relationship between dynamic heterogeneity and fluctuations of accessible volume seems straightforward. In the present work, the heterogeneity of local dynamics in polymeric systems is analyzed by computer simulation with the bond fluctuation model. The value of the accessible volume around each polymer chain is evaluated from a snapshot or static structure at each system state, resulting in a distribution of accessible volume that reflects system heterogeneity. The relationship between the average value and the standard deviation of free volume distributions at different temperatures fits amaster curve for different systems, regardless of the specific inter- and intramolecular interaction potentials that define each material. The dynamic slowdown around the glass transition is accompanied by a clear evolution of the mean value and shape of the accessible free volume distribution. The relative fluctuation of the dynamically accessible volume has been used as a parameter to quantitatively describe heterogeneity. The fluctuation varies with temperature with remarkable differences between the liquid and glassy states of the systems studied, presenting a peak at the glass transition temperature, which can be interpreted as a reflection of the distribution of local glass transition temperatures.The support from the Ministry of Economy and Competitiveness (Spain) through Project No. MAT2016-76039-C4-1-R (including the FEDER financial support) is gratefully acknowledged. R.S.S. acknowledges the support of the Ministry of Education, Culture and Sports (Spain) through the program "Estancias de movilidad de profesores e investigadores seniores en centros extranjeros de ensenanza superior e investigacion 2016 under Grant No. PRX16/00208". CIBER-BBN is an initiative funded by the VI National R&D&I Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program. CIBER Actions are financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund.Torregrosa Cabanilles, C.; Molina Mateo, J.; Sabater I Serra, R.; Meseguer Dueñas, JM.; Gómez Ribelles, JL. (2018). Fluctuations of conformational mobility of macromolecules around the glass transition. Physical Review E. 97(6):062605-1-062605-7. https://doi.org/10.1103/PhysRevE.97.062605S062605-1062605-797

Computer simulation of the heterogeneity of segmental dynamics inamorphous polymers

The heterogeneity of local segmental dynamics in a polymer system is analyzed by computer simulation with the Bond Fluctuation Model. A different approach is proposed based on the concept of Dynamically Accessible Volume (DAV) due to the difficulties encountered in the characterization of this heterogeneity by means of the distribution of relaxation times. A DAV value is assigned to each polymer chain as the fraction of cells in its surroundings that could be occupied in one Monte Carlo Step. In this way it is possible to relate the mobility of a chain with the accessible volume around it, due to the relationship between DAV and diffusion coefficient. As temperature decreases in equilibrium the DAV distribution shifts towards lower values, its width decreases and the number of frozen molecules increases. The methodology proposed also provides a way of characterizing the evolution of segmental dynamics distribution in out of equilibrium states below glass transition temperatures.The authors would like to acknowledge the support provided by the Conselleria d'Educacio of the Generalitat Valenciana through the GV/2009/033 project. The translation of this paper was funded by the Universidad Politecnica de Valencia, Spain.Molina Mateo, J.; Torregrosa Cabanilles, C.; Sabater I Serra, R.; Meseguer Dueñas, JM.; Gómez Ribelles, JL. (2013). Computer simulation of the heterogeneity of segmental dynamics inamorphous polymers. Journal of Non-Crystalline Solids. 362:175-179. https://doi.org/10.1016/j.jnoncrysol.2012.11.034S17517936

Bio-Nanocomposite Hydrogel Based on Zinc Alginate/Graphene Oxide: Morphology, Structural Conformation, Thermal Behavior/Degradation, and Dielectric Properties

[EN] Bio-nanocomposite hydrogels based on sodium alginate (SA) as polymer matrix and graphene oxide (GO) nanosheets with zinc as crosslinking agent were synthesized with the aim of incorporating the intrinsic properties of their constituents (bioactivity and antimicrobial activity). Thus, stable and highly interconnected networks were obtained from GO nanosheets dispersed in SA matrices through interactions with low amounts of zinc. The GO nanosheets were successfully incorporated into the alginate matrix in the form of a complex nano-network involving different interactions: Bonds between alginate chains induced by Zn ions (egg box structure), interactions between GO nanosheets through Zn ions and hydrogen bonds between alginate chains, and GO nanosheets. The molecular interactions and morphology were confirmed by Fourier-transform infrared spectroscopy and transmission electron microscopy. The composite's structural organization showed enhanced thermal stability. The glass transition temperature shifted to a higher temperature due to the reduced mobility induced by additional crosslinking bonds after incorporating the GO nanosheets and Zn into the polymer matrix. Finally, the dielectric behavior revealed that charge carrier mobility was hampered by the compact structure of the nanonetwork, which reduced conductivity. The combined properties of these nanocomposite hydrogels make them attractive biomaterials in the field of regenerative medicine and wound care since both surface bioactivity and antibacterial behavior are two critical factors involved in the success of a biomaterial.This research was funded by the Spanish Ministry of Science, Innovations and Universities through the RTI2018-097862-B-C21 Project (including the FEDER financial support). A.S.-A. also acknowledges the Fundacion Universidad Catolica de Valencia San Vicente Martir though Grant No 2019-231-003UCV. CIBER-BBN (Centro de Investigacion Biomedica en Red, Bioingenieria, Biomateriales y Nanomedicina) is an initiative funded by the VI National R&D&I Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program. CIBER Actions are financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund.Sabater I Serra, R.; Molina Mateo, J.; Torregrosa Cabanilles, C.; Andrio-Balado, A.; Meseguer Dueñas, JM.; Serrano-Aroca, Á. (2020). Bio-Nanocomposite Hydrogel Based on Zinc Alginate/Graphene Oxide: Morphology, Structural Conformation, Thermal Behavior/Degradation, and Dielectric Properties. Polymers. 12(3):1-16. https://doi.org/10.3390/polym12030702S11612

Outcomes of COVID-19 Patients Admitted to the Intermediate Respiratory Care Unit: Non-Invasive Respiratory Therapy in a Sequential Protocol

The intermediate respiratory care units (IRCUs) have a pivotal role managing escalation and de-escalation between the general wards and the intensive care units (ICUs). Since the COVID-19 pandemic began, the early detection of patients that could improve on non-invasive respiratory therapies (NRTs) in IRCUs without invasive approaches is crucial to ensure proper medical management and optimize limiting ICU resources. The aim of this study was to assess factors associated with survival, ICU admission and intubation likelihood in COVID-19 patients admitted to IRCUs. Observational retrospective study in consecutive patients admitted to the IRCU of a tertiary hospital from March 2020 to April 2021. Inclusion criteria: hypoxemic respiratory failure (SpO(2) = 25 rpm with FiO(2) > 50% supplementary oxygen) due to acute COVID-19 infection. Demographic, comorbidities, clinical and analytical data, and medical and NRT data were collected at IRCU admission. Multivariate logistic regression models assessed factors associated with survival, ICU admission, and intubation. From 679 patients, 79 patients (12%) had an order to not do intubation. From the remaining 600 (88%), 81% survived, 41% needed ICU admission and 37% required intubation. In the IRCU, 51% required non-invasive ventilation (NIV group) and 49% did not (non-NIV group). Older age and lack of corticosteroid treatment were associated with higher mortality and intubation risk in the scheme, which could be more beneficial in severe forms. Initial NIV does not always mean worse outcomes

Percepción de los alumnos de enfermería de las unidades especiales a través de sus diarios

Conocer la experiencia clínica vivida por los alumnos de 4º curso de enfermería en las unidades de cuidados intensivos y reanimación. Potenciar el diario de prácticas clínicas como herramienta de reflexión durante los procesos de enseñanza aprendizaje clínico en las unidades de cuidados especiales. Introducir al alumno de prácticas clínicas en la rehumanización de los cuidados en unidades especiales (contextos clínicos cerrados y de alta incidencia tecnológica). Metodológicamente se emplearán, por una parte, los diarios de prácticas clínicas enfocados al problema planteado en esta investigación; por otra, se realizarán sesiones con grupos focales para debatir procesualmente, el problema de investigación a la luz de las narrativas vertidas en los diarios. Los principales resultados obtenidos ponen de manifiesto las siguientes categorías:-el miedo y la angustia vivido por los alumnos al comienzo en este tipo de unidades. La relevancia del tutor en este entorno. La importante labor desarrollada por un equipo multidisciplinar. La influencia de la tecnificación sin desatender los cuidados básicos. Ganan seguridad y confianza con el paso de los días siendo conscientes de sus limitaciones

El diario de prácticas clínicas en la unidad de cuidados intensivos

El objetivo de este trabajo se centra en conocer la experiencia clínica vivida por los alumnos de 4º curso de enfermería en las unidades de cuidados especiales. Para la obtención de los datos se empleará la utilización de una herramienta específica como es el diario de prácticas clínicas elaborado por los porpios alumnos donde se recojan las vivencias en las unidades especiales. Por otro lado se realizarán sesiones con grupos focales para debatir procesualmente, el problema de investigación a la luz de las narrativas vertidas en los diarios. Los resultados obtenidos ponen de manifiesto las siguientes categorías:-el miedo y la angustia vivido por los alumnos al comienzo en este tipo de unidades. La relevancia de la figura del tutor en este entorno. La labor desarrollada por un el equipo de soporte de la enseñanza clínica. La influencia de la tecnificación sin desatender los cuidados básicos y por último el aumento de la seguridad y confianza con el entorno con el paso de los día

Conformation and dynamics of a diluted chain in the presence of an adsorbing wall: A simulation with the bond fluctuation model

The bond fluctuation model has been used to simulate the adsorption process of a single long polymer chain on an adsorbing surface. Simulations start at high temperature with the chain in an equilibrium coil structure. The inter- and intra chain energy potential were selected in such a way that on cooling the polymer chain vitrifies without any indication of chain ordering or chain folding. The structure attained on cooling is analysed for arrange of values of the interaction potential between the surface and the polymer segments. Adsorption is measured by the fraction of polymer segments situated on the adsorbingwallwhilst crystalline ordering is characterized by the pair correlation function g(r), the bond order parameter P2(r) and the bond correlation functionM(j). Isothermal adsorption is followed as well as a function of temperature. The work shows that adsorbing surface nucleates crystalline order by suppressing one dimension in the segmental mobility of the polymer chain, along with factors as thermal treatment and inter and intra-potentials.RSS gratefully acknowledges the support of the Spanish Ministerio de Economia y Competitividad (MINECO) and FEDER funds under the project MAT2012-38359-C03-01.Sabater I Serra, R.; Torregrosa Cabanilles, C.; Meseguer Dueñas, JM.; Gómez Ribelles, JL.; Molina Mateo, J. (2014). Conformation and dynamics of a diluted chain in the presence of an adsorbing wall: A simulation with the bond fluctuation model. Journal of Non-Crystalline Solids. 402:7-15. https://doi.org/10.1016/j.jnoncrysol.2014.05.009S71540

Clinical Outcomes of Severe COVID-19 Patients Admitted to an Intermediate Respiratory Care Unit

Introduction: Many severe COVID-19 patients require respiratory support and monitoring. An intermediate respiratory care unit (IMCU) may be a valuable element for optimizing patient care and limited health-care resources management. We aim to assess the clinical outcomes of severe COVID-19 patients admitted to an IMCU. Methods: Observational, retrospective study including patients admitted to the IMCU due to COVID-19 pneumonia during the months of March and April 2020. Patients were stratified based on their requirement of transfer to the intensive care unit (ICU) and on survival status at the end of follow-up. A multivariable Cox proportional hazards method was used to assess risk factors associated with mortality. Results: A total of 253 patients were included. Of them, 68% were male and median age was 65 years (IQR 18 years). Ninety-two patients (36.4%) required ICU transfer. Patients transferred to the ICU had a higher mortality rate (44.6 vs. 24.2%; p < 0.001). Multivariable proportional hazards model showed that age ≥65 years (HR 4.14; 95%CI 2.31-7.42; p < 0.001); chronic respiratory conditions (HR 2.34; 95%CI 1.38-3.99; p = 0.002) and chronic kidney disease (HR 2.96; 95%CI 1.61-5.43; p < 0.001) were independently associated with mortality. High-dose systemic corticosteroids followed by progressive dose tapering showed a lower risk of death (HR 0.15; 95%CI 0.06-0.40; p < 0.001). Conclusions: IMCU may be a useful tool for the multidisciplinary management of severe COVID-19 patients requiring respiratory support and non-invasive monitoring, therefore reducing ICU burden. Older age and chronic respiratory or renal conditions are associated with worse clinical outcomes, while treatment with systemic corticosteroids may have a protective effect on mortality

Effect of the use of videos in the pre-class preparation of laboratory sessions taught by flip teaching

[EN] Nowadays, it is well stablished the effectiveness of flip teaching in different areas. Video is widely used as a pre-class learning material and it is progressively replacing text-document materials. The students, 70 in total, are enrolled in the laboratory practice of the subject of Physics (Bachelor¿s Degree: Industrial Electronics and Automation Engineering) at the Universitat Politècnica de València. Student¿s perception data were collected from the results of a survey. Students were asked about the usefulness of the videos and the in-class work, paying special attention to the roll of the instructor in relation to the flip teaching methodology and the pre-class material. The students were divided into two groups. In one of them, the videos were recorded by the same instructor present at the lab session, whereas the other group, the videos used were recorded by instructors different from the instructor present at the lab. The results indicate that students feel that the videos are very useful, rather than the written documents. They attribute a high value to the instructor in the lab session as they feel more confident with their work and they can ask for help when needed. They value positively the possibility of work autonomously. Small differences have been found in the opinion of both groups being the higher in the question that concerns the preference of the videos respect to the text.This work has been supported by the Universitat Politècnica de València through the Project of Innovation and Educational Improvement Program (Projects PIME/2018/B26 and PIME/2018/B25 Convocatoria de Proyectos de Innovación y Convergencia).Meseguer Dueñas, JM.; Quiles Casado, SDLS.; Sabater I Serra, R.; Serrano, M.; Gómez-Tejedor, J.; García-Sánchez, TM.; Tort-Ausina, I.... (2020). Effect of the use of videos in the pre-class preparation of laboratory sessions taught by flip teaching. Iated. 6107-6112. https://doi.org/10.21125/inted.2020.1654S6107611