Molecular mobility of n-ethylene glycol dimethacrylate glass formers upon free radical polymerization

Quando um líquido evita a cristalização durante o arrefecimento, diz-se que entra no estado sobrearrefecido. Se a temperatura continuar a diminuir, o consequente aumento da viscosidade reflecte-se na mobilidade molecular de tal maneira que os tempos característicos se tornam da mesma ordem de grandeza que os tempos acessíveis experimentalmente. Se o arrefecimento continuar, o líquido altamente viscoso acaba por vitrificar, i.e. entra no estado vítreo onde apenas os movimentos locais são permitidos. Os monómeros da família n -etileno glicol dimetacrilato ( n -EGDMA, para n = 1 até 4, que constituem o objecto deste estudo, facilmente evitam a cristalização, sendo pois bons candidatos para estudar a mobilidade molecular nos estados sobrearrefecido e vítreo. A Espectroscopia de Relaxação Dieléctrica (DRS) foi a técnica escolhida para obter informação detalhada sobre a sua dinâmica molecular (Capítulos 1 e 2). A primeira parte deste trabalho consistiu na caracterização dieléctrica dos processos de relaxação existentes acima e abaixo da temperatura de transição vítrea (g T ), a qual aumenta com o aumento do peso molecular (w M ), sendo este resultado confirmado por Calorimetria Diferencial de Varrimento (DSC). No que respeita ao processo cooperativo a , associado à transição vítrea, e ao processo secundário b, observa-se uma dependência com w M , enquanto que o outro processo secundário, g , aparenta ser independente deste factor (Capítulo 3). Nos capítulos seguintes, foram levadas a cabo diferentes estratégias com o objectivo de clarificar os mecanismos que estão na origem destas duas relaxações secundárias (b e g ), assim como conhecer a sua respectiva relação com a relaxação principal (a ). Do estudo, em tempo real, da polimerização isotérmica via radicais livres do TrEGDMA por Calorimetria de Varrimento Diferencial com Modulação de Temperatura (TMDSC), levado a cabo a temperaturas abaixo da g T do polímero final, concluem-se entre outros, dois importantes aspectos: i) que a vitrificação do polímero em formação conduz a graus de conversão relativamente baixos, e ii) que o monómero que está por reagir é expulso da rede polimérica que se forma, dando lugar a uma clara separação de fases (Capítulo 4). Com base nesta informação, o passo seguinte foi estudar separadamente a polimerização isotérmica do di-, tri- e tetra-EGDMA, dando especial atenção às alterações de mobilidade do monómero ainda por reagir. Com as restrições impostas pela formação de ligações químicas, as relaxações a e b detectadas no monómero tendem a desaparecer no novo polímero formado, enquanto que a relaxação g se mantém quase inalterada. Os diferentes comportamentos que aparecem durante a polimerização permitiram a atribuição da origem molecular dos processos secundários: o processo g foi associado ao movimento twisting das unidades etileno glicol, enquanto que a rotação dos grupos carboxilo foi relacionada com a relaxação b (Capítulo 5). No que respeita ao próprio polímero, um processo de relaxação adicional foi detectado, pol b , no poly-DEGDMA, poly-TrEGDMA e poly-TeEGDMA, com características similares ao encontrado nos poli(metacrilato de n -alquilo). Este processo foi confirmado e bem caracterizado aquando do estudo da copolimerização do TrEGDMA com acrilato de metilo (MA) para diferentes composições (Capítulo 6). Para finalizar, o EGDMA, o elemento mais pequeno da família de monómeros estudada, além de vitrificar apresenta uma marcada tendência para cristalizar quer a partir do estado líquido ou do estado vítreo. Durante a cristalização, a formação de uma fase rígida afecta principalmente o processo a , cuja intensidade diminui sem no entanto se observarem modificações significativas na dependência do tempo de relaxação característico com a temperatura. Por outro lado, o processo secundário b torna-se melhor definido e mais estreito, o que pode ser interpretado em termos de uma maior homogeneidade dos micro-ambientes associados aos movimentos locais(Capítulo 7)

Implicación de la isoforma H del factor de transcripción asociado a microftalmia (MITF-H) en la transición epitelio-mesénquina inducida por los factores de las familias Snail y bHLH

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Bioquímica. Departamento de Medicina. Fecha de lectura: 16-Octubre-200

Molecular dynamics in polymer networks containing caprolactone and ethylene glycol moieties studied by dielectric relaxation spectroscopy

Copolymer networks with methacrylate main chain and caprolactone and ethylene glycol side groups were obtained by free radical copolymerisation of caprolactone methacrylate (CLMA) and poly(ethylene glycol) methacrylate (PEGMA). Dielectric relaxation spectroscopy was used to analyse molecular mobility of the different groups in the system. Only one main dielectric relaxation process was found in CLMA/PEGMA copolymer networks, located between those of the corresponding homonetworks, indicating that the system does not present phase separation. The copolymers show a secondary relaxation process at temperatures below −50 °C, which can be assigned to the overlapping of the corresponding secondary processes for the homopolymer networks; one of them was related to the local mobility of caprolactone units in CLMA and the second one was assigned to the twisting motions within ethylene glycol moiety in PEGMA. Besides the relaxation processes, the mobility of space charges has been analysed by means of conductivity and electric modulus formalisms.The support from the Spanish Ministry of Economy and Competitiveness (MINECO) and FEDER funds under the project MAT2012-38359-C03-01 is gratefully acknowledged.Sabater I Serra, R.; Escobar Ivirico, JL.; Romero Colomer, FJ.; Andrio Balado, A.; Gómez Ribelles, JL. (2014). Molecular dynamics in polymer networks containing caprolactone and ethylene glycol moieties studied by dielectric relaxation spectroscopy. Journal of Non-Crystalline Solids. 404:109-115. https://doi.org/10.1016/j.jnoncrysol.2014.08.013S10911540

The government of Salvador Allende (1970-1973). An experience of the new latin american left of the 60's and 70's

RESUMEN: Salvador Allende a través de una coalición de partidos de izquierdas, la Unidad Popular, llegó al gobierno de Chile en 1970 para implementar la vía chilena al socialismo. Su objetivo era realizar una serie de reformas sociales para mejorar las condiciones de vida de las clases populares, varias reformas económicas centradas en la nacionalización de la minería y de las principales empresas del país, una reforma agraria y una reforma política que facilitara a esas clases populares el control de las instituciones del Estado. Se trató de una revolución respetuosa con la pluralidad política y la legalidad institucional democrática y esperaba que contara también con el apoyo de las Fuerzas Armadas. El proyecto de Allende se topó con la oposición de la oligarquía nacional y del gobierno de Estados Unidos, mientras que la extrema izquierda revolucionaria, que rechazaba la vía pacífica, obstaculizó la actuación de su gobierno. Tras una crisis social derivada de un bloqueo económico y una crisis política debida a la polarización del país, su gobierno fue derrocado por un golpe de Estado militar el 11 de septiembre de 1973.ABSTRACT: Salvador Allende, through a coalition of left-wing parties, the Popular Unity, came to the government of Chile in 1970 to implement the Chile’s Road to Socialism. Its objective was to carry out a series of social reforms to improve the conditions of the popular classes, several economic reforms focused on the nationalization of mining and the main companies in the country, an agrarian reform, and a political reform that would facilitate those popular classes control of state institutions. It was a revolution that was respectful of political plurality and democratic institutional legality, he also hoped that it would also have support of the Armed Forces. Allende's project ran into opposition from the national oligarchy and the US government, while the revolutionary extreme left, which rejected the peaceful route, obstructed the action of his government. After a national crisis derived from an economic blockade and a political crisis due to the polarization of the country, his government was overthrown by a military the coup d’état on September 11, 1973.Grado en Histori

Molecular motions in chitosan studied by dielectric Relaxation spectroscopy

Neutralized and nonneutralized chitosan films subject to different thermal treatments were studied by dielectric relaxation spectroscopy from -130 to +150 °C in the frequency range between 20 Hz and 1 MHz. Two main relaxation processes, both arrhenian type, were detected: process I at temperatures below 0 °C with a mean activation energy of 49 ( 1 kJ mol-1, which has the characteristics of a secondary relaxation process related with local chain dynamics, and process II observable at higher temperatures with an activation energy of 94 ( 2 kJ mol-1, correlated with dc conductivity, which is found in dried polysaccharides systems. Process I is always observed in neutralized chitosan, but it is strongly depleted in the wet nonneutralized form. Although the location of process I is independent of NH2/NH3 + side group, process II deviates to higher temperatures with dryness in both chitosan forms, being located at lower temperatures in nonneutralized chitosan.FCT, Foundation for Science and Technology, through the POCTI (POCTI/CTM/47363/2002) and FEDER programs

Reversible imine crosslinking in waterborne self-healing polymer coatings

Waterborne polymer coatings have the potential to address the environmental concerns associated with solvent based systems. To improve their performance without using volatile organic compounds, we propose a new approach based on reconfigurable covalent crosslinking that provides mechanical resistance and self-healing properties. The new waterborne polymer coatings are based on mixtures of aldehyde- and amine-functionalized polymer nanoparticles (PNPs) that take advantage of the reversibility of imine bonds in the presence of water. Different degrees of functional monomer incorporation (10 % to 40 %) allowed us to balance crosslinking and interdiffusion during film formation, to obtain mechanically robust and solvent resistant films. A clear structure-properties relation was assessed by following the formation of water resulting from amine-aldehyde condensation crosslinking, measured by differential scanning calorimetry. The resulting polymer coatings further show self-healing properties at room temperature, triggered with residual amounts of water and featuring high recovery rates of the mechanical properties. Our mechanically robust waterborne polymer coatings based in imine reversible crosslinking, featuring self-healing in mild conditions, offer excellent prospects for application in smart coating materials.publishe

Psychodynamic Psychotherapy for Postpartum Depression: A Systematic Review

Objectives: Postpartum depression estimated prevalence in women is between 5 and 26% and it has adverse effects both on the mother, infant and her partner. Psychological treatments have proved to be effective for women with mild-to-moderate symptoms. Whereas several systematic reviews have assessed the effects of different psychological interventions for postpartum depression, such as cognitive-behavioural therapy or interpersonal therapy, no review assessing psychodynamic therapy has been carried out. A systematic review was conducted to evaluate the efficacy of psychodynamic therapy for postpartum depression. Methods: Studies were identified using the following databases: PsycINFO, Psycarticles and Pubmed over January 2023. The requirements for the studies were the following: they had to be quantitative, available in English, including a psychodynamic intervention targeting treatment or prevention of postpartum depression which starts during pregnancy or within the first 12 months after giving birth. Case studies, qualitative studies or studies focused on improving parent-infant relationship or infant outcome were excluded from this research. Results: Seven trials including 521 women met the inclusion criteria. In summary, three randomized controlled trials and four longitudinal studies were found. The most frequently used assessment tool was EPDS, five were individual interventions and the other two were group interventions. Discussion: All studies reported the efficacy of psychodynamic interventions for postpartum depression, both in home and clinical settings and both in group and individual format. The limited number of trials, small sample sizes and lack of appropriate control groups were the main limitations. Conclusions for practice: Psychodynamic therapy is probably efficient intervention for postpartum depression. Future research with strong methodological designs is needed to confirm these findings. Significance: What is already known on this subject? Several systematic reviews have assessed the effects of different psychological interventions for postpartum depression, but no review assessing psychodynamic therapy has been carried out. What this study adds? A systematic review was conducted to evaluate the efficacy of psychodynamic therapy for postpartumdepression. This makes the systematic review a unique contribution to the literature

Influence of natural deep eutectic systems in water thermal behavior and their applications in cryopreservation

Natural deep eutectic systems (NADES), which have applications as solvents for both engineering and life sci-ences, are mainly composed of sugars, aminoacids or organic acids. In this work NADES composed by glucose,urea and proline (G:U:P in a molar ratio of 1:1:1) and proline and glucose (P:G 5:3) were prepared and addedin different mass fractions to water.By differential scanning calorimetry it was verified as the crystallization tendency of water is modified even forlow fraction of NADES added. This is also observed by polarized optical microscopy which allowed followingthe formation of crystals with different crystalline morphologies as bulk water. Calorimetric data also shown asthe crystallization temperature decreases for all P:G mixtures and this shift is more accentuated for weight frac-tion of NADES higher than 0.5. Crystallization is totally suppressed for NADES fraction higher than 0.7.NADES/water mixtures cytotoxicity was evaluated in vitro, revealing that they are less toxic as compared withthe commonly used cryoprotective additives as dimethyl sulfoxide (DMSO). Additionally, cell viability testswith cell lines cryopreserved using DMSO and both the prepared NADES showed comparable viability.This work combines thermophysical data on NADES and evaluates itâ s in vitro performance, providing cues fortheir use in cryopreservation applications.European Union Horizon 2020 Program under the agreement number ERC-2016-CoG 725034 (ERC Consolidator Grant Des.solve). This research was also funded by PTDC/EQU-EQU/29851/2017. A. Paiva acknowledges the financial support from project IF/01146/2015 attributed within the 2015 FCT researcher program. This work was supported by the Associate Laboratory for Green Chemistry - LAQV which is financed by national funds from FCT/MCTES (UIDB/50006/2020 and UIDP/50006/2020

Chitosan scaffolds with a shape memory effect induced by hydration

We demonstrate that chitosan-based porous scaffolds can present a shape memory effect triggered by hydration. The shape memory effect of non-crosslinked (CHT0) and genipin-crosslinked (CHT1) scaffolds was followed by innovative hydromechanical compressive tests and dynamic mechanical analysis (DMA), while the sample was immersed in varying compositions of water–ethanol mixtures. By dehydration with higher contents of ethanol, the vitreous-like nature of the amorphous component of chitosan allows the fixation of the temporary shape of the scaffold. The presence of water disrupts inter-molecular hydrogen bonds permitting large-scale segmental mobility of the chitosan chains upon the occurrence of glass transition and thus the recovery of the permanent shape of a pre-deformed scaffold. Results showed that chitosan possesses shape memory properties, characterized by a fixity ratio above 97.2% for CHT0 and above 99.2% for CHT1 and a recovery ratio above 70.5% for CHT0 and 98.5% for CHT1. In vitro drug delivery studies were also performed to demonstrate that such devices can also be loaded with molecules. We show that the developed chitosan scaffolds are candidates of biomaterials for applications in minimally invasive surgery for tissue regeneration or for drug delivery.This work was supported by the Portuguese Foundation for Science and Technology Foundation (FCT) through project PTDC/FIS/115048/2009. We acknowledge Dr Ana Rita Duarte for all the help during this project and Joana Marques Silva and So. a Caridade for their contribution to the DMA experiments

Evidence of Strong Guest–Host Interactions in Simvastatin Loaded in Mesoporous Silica MCM-41

Funding Information: This research was funded by the Associate Laboratory for Green Chemistry LAQV, which is financed by national funds from FCT/MEC (UID/QUI/50006/2019) and co-financed by the ERDF under the PT2020 Partnership Agreement (POCI-01-0145-FEDER—007265). This research was funded by the Interreg 2 Seas program 2014–2020, and co-funded by the European Regional Development Fund (FEDER) under subsidy contract 2S01-059_IMODE and 2S07-033_ Site Drug. This research was funded by the Program PHC PESSOA 2018 project nbr 4340/40868R. This research was funded by National Funds through FCT—Portuguese Foundation for Science and Technology, reference UIDB/00100/2020, UIDP/00100/2020, LA/P/0056/2020, UIDB/50025/2020-2023, and PTNMR (ROTEIRO/0031/2013; PINFRA/22161/2016), co-financed by ERDF through COMPETE 2020, Portugal, POCI and PORL and FCT through PIDDAC (POCI-01-0145-FEDER-007688). M.C.C. acknowledges PTNMR&i3N for the researcher contract. T. Cordeiro acknowledges Fundação para a Ciência e a Tecnologia (FCT) for the scholarship SFRH/BD/114653/2016. I. Matos acknowledges FCT for the Investigator FCT contract IF/01242/2014/CP1224/CT0008. Publisher Copyright: © 2023 by the authors.A rational design of drug delivery systems requires in-depth knowledge not only of the drug itself, in terms of physical state and molecular mobility, but also of how it is distributed among a carrier and its interactions with the host matrix. In this context, this work reports the behavior of simvastatin (SIM) loaded in mesoporous silica MCM-41 matrix (average pore diameter ~3.5 nm) accessed by a set of experimental techniques, evidencing that it exists in an amorphous state (X-ray diffraction, ssNMR, ATR-FTIR, and DSC). The most significant fraction of SIM molecules corresponds to a high thermal resistant population, as shown by thermogravimetry, and which interacts strongly with the MCM silanol groups, as revealed by ATR-FTIR analysis. These findings are supported by Molecular Dynamics (MD) simulations predicting that SIM molecules anchor to the inner pore wall through multiple hydrogen bonds. This anchored molecular fraction lacks a calorimetric and dielectric signature corresponding to a dynamically rigid population. Furthermore, differential scanning calorimetry showed a weak glass transition that is shifted to lower temperatures compared to bulk amorphous SIM. This accelerated molecular population is coherent with an in-pore fraction of molecules distinct from bulklike SIM, as highlighted by MD simulations. MCM-41 loading proved to be a suitable strategy for a long-term stabilization (at least three years) of simvastatin in the amorphous form, whose unanchored population releases at a much higher rate compared to the crystalline drug dissolution. Oppositely, the surface-attached molecules are kept entrapped inside pores even after long-term release assays.publishersversionpublishe