Kinetics of the thermal response of poly(N-isopropylacrylamide co methacrylic acid) hydrogel microparticles under different environmental stimuli: a time-lapse NMR study

Hypothesis: Hydrogels of N-isopropylacrylamide and methacrylic acid (P(NIPAm-co-MAA)) display pH sensitivity and complex positively charged molecules through carboxylate groups, while having a critical solution temperature at which they reduce in volume and dehydrate. We aimed to elucidate how the responsiveness of MAA to environmental changes alters PNIPAm hydrogels at the molecular level using nuclear magnetic resonance (NMR). Time-lapse NMR allows us to follow the evolution of NMR signal under a temperature stimulus, providing unique information on conformational freedom of the hydrogel polymers. Experiments: We used time-lapse NMR to follow the evolution of the NMR signal with time over a temperature change from 25 to 40 °C and to study the swelling/deswelling kinetics of P(NIPAm-co-MAA) microgels at different pH values and ionic strengths, and in the presence of positively charged molecules complexing carboxylate groups. Findings: At acid pH, hydrogel collapse is favored over neutral pH, and at basic pH the carboxylates remain steadily hydrated during temperature increase. Increasing ionic strength results in a faster, more effective collapse than decreasing pH. Complexation of medium-sized molecules with several charges (spermine, spermidine) causes a faster collapse than complexation with large molecular weight poly(allylamine) hydrochloride, but similar to the collapse effected by large poly(diallyldimethylammonium) chloride. This work opens new perspectives to using time-lapse NMR to study thermoresponsive systems that respond to multiple stimuli, with particular relevance in designing hydrogels for drug delivery.Fil: Martinez Moro, Marta. Basque Research and Technology Alliance; EspañaFil: Jenczyk, Jacek. Adam Mickiewicz University; PoloniaFil: Giussi, Juan Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Jurga, Stefan. Adam Mickiewicz University; PoloniaFil: Moya, Sergio E.. Basque Research and Technology Alliance; Españ

Enhanced antiadhesive properties of chitosan/hyaluronic acid polyelectrolyte multilayers driven by thermal annealing : Low adherence for mammalian cells and selective decrease in adhesion for Gram-positive bacteria

The development of antifouling coatings with restricted cell and bacteria adherence is fundamental for many biomedical applications. A strategy for the fabrication of antifouling coatings based on the layer-by-layer assembly and thermal annealing is presented. Polyelectrolyte multilayers (PEMs) assembled from chitosan and hyaluronic acid were thermally annealed in an oven at 37 °C for 72 h. The effect of annealing on the PEM properties and topography was studied by atomic force microscopy, ζ-potential, circular dichroism and contact angle measurements. Cell adherence on PEMs before and after annealing was evaluated by measuring the cell spreading area and aspect ratio for the A549 epithelial, BHK kidney fibroblast, C2C12 myoblast and MC-3T3-E1 osteoblast cell lines. Chitosan/hyaluronic acid PEMs show a low cell adherence that decreases with the thermal annealing, as observed from the reduction in the average cell spreading area and more rounded cell morphology. The adhesion of S. aureus (Gram-positive) and E. coli (Gram-negative) bacteria strains was quantified by optical microscopy, counting the number of colony-forming units and measuring the light scattering of bacteria suspension after detachment from the PEM surface. A 20% decrease in bacteria adhesion was selectively observed in the S. aureus strain after annealing. The changes in mammalian cell and bacteria adhesion correlate with the changes in topography of the chitosan/hyaluronic PEMs from a rough fibrillar 3D structure to a smoother and planar surface after thermal annealing.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Multiscale thermo-mechanical analysis of multi-layered coatings in solar thermal applications

Solar selective coatings can be multi-layered materials that optimize the solar absorption while reducing thermal radiation losses, granting the material long-term stability. These layers are deposited on structural materials (e.g., stainless steel, Inconel) in order to enhance the optical and thermal properties of the heat transfer system. However, interesting questions regarding their mechanical stability arise when operating at high temperatures. In this work, a full thermo-mechanical multiscale methodology is presented, covering the nano-, micro-, and macroscopic scales. In such methodology, fundamental material properties are determined by means of molecular dynamics simulations that are consequently implemented at the microstructural level by means of finite element analyses. On the other hand, the macroscale problem is solved while taking into account the effect of the microstructure via thermo-mechanical homogenization on a representative volume element (RVE). The methodology presented herein has been successfully implemented in a reference problem in concentrating solar power plants, namely the characterization of a carbon-based nanocomposite and the obtained results are in agreement with the expected theoretical values, demonstrating that it is now possible to apply successfully the concepts behind Integrated Computational Materials Engineering to design new coatings for complex realistic thermo-mechanical applications

Manifestaciones temporomandibulares en pacientes con síndrome de Ehlers-Danlos: una revisión sistemática

Introduction: Ehlers-Danlos Syndrome (EDS) consists of a group of diseases that imply a disorder among individual connective tissue due to an altered collagen production. Fibrocartilaginous structures, support ligaments, disc and retrodiscal from the temporomandibular joint are composed primarily of collagen. Objective: Identify TMJ manifestations in patients with different types of EDS. Materials and Methods: a systematic review of the literature was performed on PubMed, Scopus and Web of Science databases. Observational studies and case series reports published either in Spanish or not Spanish were included up until January 2023. Results: 12 articles met the inclusion criteria. The prevalence of temporomandibular disorders varies from 26.6% to 100%, being EDSh the most reported subtype, whereas disc displacement with or without reduction and joint hypermobility were the most reported joint disorders. Conclusion: Temporomandibular pathologies are common in patients with EDS, especially in those with the EDSh subtype.Introducción: El Síndrome de Ehlers-Danlos (SED) consiste en un grupo de enfermedades que implican un desorden de los tejidos conectivos de los individuos como producto de una alteración en la síntesis de colágeno. Las estructuras fibrocartilaginosas, los ligamentos de soporte, el disco y el tejido retrodiscal de la articulación temporomandibular (ATM) están compuestos por colágeno. Objetivo: Identificar las manifestaciones temporomandibulares en pacientes con diferentes subtipos de SED a través de una revisión sistemática. Materiales y métodos: Se realizó una revisión sistemática de la literatura incluyendo las bases de datos de PubMed, Scopus y Web of Science. Se incluyeron estudios observacionales y series de casos en idioma inglés o español publicados hasta enero de 2023. Resultados: Se seleccionó 12 artículos cumplieron con los criterios de inclusión. La prevalencia de desórdenes temporomandibulares varió entre el 26,6% y el 100%, con el subtipo SEDh como el más reportado. El desorden temporomandibular más identificado fue el desplazamiento del disco con o sin reducción e hipermovilidad articular. Conclusión: Las patologías temporomandibulares son habituales en pacientes con SED, especialmente en aquellos con el subtipo SEDh

Noninvasive assessment of patients undergoing percutaneous intervention in myocardial infarction

FUNDAMENTO: A reestenose pós-intervenção coronariana percutânea primária permanece um problema de relevância clínica, mesmo com o implante de stents. A capacidade das provas não invasivas para detecção de reestenose não foi totalmente demonstrada. OBJETIVO: Avaliar a habilidade do teste ergométrico (TE) e da cintilografia de perfusão miocárdica (CPM) no diagnóstico de reestenose em pacientes com infarto agudo do miocárdio, e supradenivelamento do segmento ST, submetidos à angioplastia coronariana percutânea primária (ACPP), com implante de stent nas primeiras 12 horas de evolução. MÉTODOS: De Ago/2003-Jan/2006, foram selecionados 64 pacientes (ps) (56,2 ± 10,2 anos, 53 homens) submetidos à ACPP. Apenas ps com fração de ejeção do ventrículo esquerdo > 40,0%, definida por ecocardiograma de repouso, foram incluídos. Teste ergométrico, com as 12 derivações do ECG associadas a precordiais direitas, e CPM foram realizados 6 semanas, 6 meses e um ano após o tratamento. Foi realizada cinecoronariografia no 6º mês. RESULTADOS: Doença uniarterial ocorreu em 46,9% dos ps, sendo a artéria descendente anterior tratada em 48,4%. Reestenose angiográfica ocorreu em 28,8%. Sensibilidade, especificidade, valor preditivo positivo (VPP), valor preditivo negativo (VPN) e acurácia do TE para detecção de reestenose não foram significativos. A adição de derivações precordiais direitas não proporcionou informações adicionais. Sensibilidade, especificidade, VPP, VPN e acurácia da CPM apresentaram correlação com reestenose apenas no 6º mês, considerando-se summed difference score > 2 (p = 0,006) e > 4 (p = 0,014). CONCLUSÃO: O TE não discriminou reestenose. A CPM realizada no 6º mês foi relacionada à reestenose e mostrou-se útil durante a evolução.BACKGROUND: Restenosis after primary percutaneous coronary intervention (PPCI) remains an important clinical problem, even with stent implantation. The ability of noninvasive testing to diagnose restenosis has had only inconsistent demonstration. OBJECTIVE: Our objective was to evaluate the ability of exercise treadmill testing (ETT) and myocardial perfusion imaging (MPI) to diagnose restenosis in patients treated by PPCI within 12 hours of ST-elevation myocardial infarction (STEMI). METHODS: From August 2003 to January 2006, 64 patients (mean age of 56.2±10.2 years, 53 males) were enrolled after PPCI. Only patients with left ventricular ejection fraction (LVEF) > 40%, as assessed by resting transthoracic echocardiography (TTE), were included. ETT with 12-lead ECG monitoring and right precordial leads, as also MPI were performed at 6 weeks, 6 months, and one year after intervention. Coronary angiography was performed at six months. RESULTS: Single-vessel disease was observed in 46.9% of the patients. The left anterior descending coronary artery was treated in 48.4% of the patients. Angiographic restenosis occurred in 28.8%. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of ETT in detecting restenosis were not significant. Right precordial leads did not add information. MPI sensitivity, specificity, PPV, NPV, and accuracy correlated with restenosis only in the 6-month follow-up, both when considering summed difference score >2 (p=0.006) and >4 (p=0.014). CONCLUSION: ETT did not discriminate restenosis in this population. MPI performed at 6 months correlated with restenosis and proved useful during follow-up

Video-Assisted Thoracoscopy For Penetrating Cardiac Box Injury in Stable Patients

Introduction: In high-volume trauma centers, especially in developing countries, penetrating cardiac box injuries are frequent. Although many aspects of penetrating chest injuries have been well established, video-assisted thoracoscopy is still finding its place in cardiac box trauma and algorithmic approaches are still lacking. The purpose of this manuscript is to provide a streamlined recommendation for penetrating cardiac box injury in stable patients. Methods: Literature review was carried out using PubMed/ MEDLINE and Google Scholar databases to identify articles describing the characteristics and concepts of penetrating cardiac box trauma, including the characteristics of tamponade, cardiac ultrasound, indications and techniques of pericardial windows and, especially, the role of video-assisted thoracoscopy in stable patients. Results: Penetrating cardiac box injuries, whether by stab or gunshot wounds, require rapid surgical consultation. Unstable patients require immediate open surgery, however, determining which stable patients should be taken to thoracoscopic surgery is still controversial. Here, the classification of penetrating cardiac box injury used in Colombia is detailed, as well as the algorithmic approach to these types of trauma. Conclusion: Although open surgery is mandatory in unstable patients with penetrating cardiac box injuries, a more conservative and minimally invasive approach may be undertaken in stable patients. As rapid decision-making is critical in the trauma bay, surgeons working in high-volume trauma centers should expose themselves to thoracoscopy and always consider this possibility in the setting of penetrating cardiac box injuries in stable patients, always in the context of an experienced trauma team

Scalar fields in an anisotropic closed universe

We study in this article a class of homogeneous, but anisotropic cosmological models in which shear viscosity is included. Within the matter content we consider a component (the quintessence component) determined by the barotropic equations of state, $p=\alpha \rho$, with $\alpha < 0$. We establish conditions under which a closed axisymmetrical cosmological model may look flat al low redshift.Comment: 6 pages, Latex, 2 figures, accepted in Phys. Rev.