Flexible Composite Films Made of EMAA-Na+ Ionomer: Evaluation of the Influence of Piezoelectric Particles on the Thermal and Mechanical Properties.

Studies that aim to produce flexible films of composite materials based on ionomers-PZT, and volume fractions lower than 10% PZT, in order to monitor damage in aeronautical structures are seldom investigated. The growing emphasis on the use of polymers capable of self-healing after damage or activation by heating has motivated the application of self-healing ionomers as polymeric matrices in composites with piezoelectric particles aiming to monitor damage. Flexible composite films were developed based on the self-healing polymer matrix Surlyn® 8940 ionomer (DuPontTM-Wilmington, DE, USA) and PZT particles (connectivity 2-3) in volume fractions of 1, 3, 5 and 7%, with thickness around 50-100 µm. The choice of PZT volume fractions followed the preliminary requirement that establishes a final density, which is lower or at least close to the density of the materials used in aeronautical structures. Since the application of composites based on epoxy resin/carbon fibers has been increasing in the aeronautical segment, this material (with density lower than 1500 kg/m3) was chosen as a reference for the present work. Thus, due to self-healing (a characteristic of the matrix Surlyn® 8940) combined with recyclability, high flexibility and low thickness, the flexible composite films showed advantages to be applied on aeronautical structures, which present complex geometries and low-density materials. The manufactured films were characterized by SEM, XRD, DMA and mechanical tensile tests. The results were discussed mainly in terms of the volume fraction of PZT. X-ray diffraction patterns showed coexistent rhombohedral and tetragonal phases in the PZT particles-dispersed composite, which can potentialize the alignment of ferroelectric domains during polarization under strong electrical field, enhancing dielectric and piezoelectric properties toward sensing applications. DMA and tensile testing results demonstrated that the addition of PZT particles did not impair either dynamic or quasi-static mechanical performance of the flexible composite films. It was concluded that the PZT volume fraction should be lower than 3% because, for higher values, the molecular mobility of the polymer would suffer significant reductions. These findings, combined with the high flexibility and low density of the ceramic particle-filled thermoplastic polymer, render the developed flexible composite film a very promising candidate for strain and damage sensing in aeronautical structures.

Hybrid dual-function thermal energy harvesting and storage technologies: towards self-chargeable flexible/wearable devices.

The worldwide energy scarcity arising from the massive consumption of nonrenewable energy sources raised a global awareness of the need for cleaner and affordable energy solutions to mitigate climate change and ensure the world sustainable development. The rise of the Internet of Things and the fast growth of the groundbreaking market of wearable electronics boosted a major quest for self-powered technologies merging energy harvesting and energy storage functionalities to meet the demands of a myriad of market segments, such as healthcare, transportation, defense and sports. Thermoelectric devices are a green energy harvesting solution for wearable electronics since they harness the low-grade waste heat from ubiquitous thermal energy sources and convert it into electrical energy. However, these systems generate electrical energy in an intermittent manner, depend on the local heat release availability and require an additional unit to store energy. Flexible and wearable supercapacitors are a safe and eco-friendly energy storage solution to power wearables, offering advantages of security, longer cycle life, higher power density and faster charging over batteries. However, an additional unit that generates energy or that is able to charge the storage device is required. More recently, a new class of all-in-one thermally-chargeable supercapacitors blossomed to meet the requirements of the next generation of autonomous wearable electronics and ensure an endurable energy supply. This self-chargeable hybrid technology combines the functionalities of thermal energy harvesting and supercapacitive energy storage in a single multitasking device. In this Perspective, the advances in the burgeoning field of all-in-one thermally-chargeable supercapacitors for flexible/wearable applications will be critically examined, ranging from their structure and working principle to the rational design of the composing materials and of tailor-made architectures. It will start by introducing the foundations of single flexible/wearable thermoelectric generators and supercapacitors and will evolve into the pioneering venture of fully-integrated thermal energy harvesting/storage systems. It will end by highlighting the current bottlenecks and future pathways for advancing the development of this sophisticated smart technology.

Graphene-based materials: the key for the successful application of pHEMA as a blood-contacting device.

Thrombosis and infection are the leading causes of blood-contacting device (BCD) failure, mainly due to the poor performance of existing biomaterials. Poly(2-hydroxyethyl methacrylate) (pHEMA) has excellent hemocompatibility but the weak mechanical properties impair its use as a bulk material for BCD. As such, pHEMA has been explored as a coating, despite the instability and difficulty of attachment to the underlying polymer compromise its success. This work describes the hydrogel composites made of pHEMA and graphene-based materials (GBM) that meet the biological and mechanical requirements for a stand-alone BCD. Five GBM differing in thickness, oxidation degree, and lateral size were incorporated in pHEMA, revealing that only oxidized-GBM can reinforce pHEMA. pHEMA/oxidized-GBM composites are cytocompatible and prevent the adhesion of endothelial cells, blood platelets, and bacteria (S. aureus), thus maintaining pHEMA's anti-adhesive properties. As a proof of concept, the thrombogenicity of the tubular prototypes of the best formulation (pHEMA/Graphene oxide (GO)) was evaluated in vivo, using a porcine arteriovenous-shunt model. pHEMA/GO conduits withstand the blood pressure and exhibit negligible adhesion of blood components, revealing better hemocompatibility than ePTFE, a commercial material for vascular access. Our findings reveal pHEMA/GO, a synthetic and off-the-shelf hydrogel, as a preeminent material for the design of blood-contacting devices that prevent thrombosis and bacterial adhesion.

Graphene Surfaces Interaction with Proteins, Bacteria, Mammalian Cells, and Blood Constituents: The Impact of Graphene Platelet Oxidation and Thickness.

Graphene-based materials (GBMs) have been increasingly explored for biomedical applications. However, interaction between GBMs-integrating surfaces and bacteria, mammalian cells, and blood components, that is, the major biological systems in our body, is still poorly understood. In this study, we systematically explore the features of GBMs that most strongly impact the interactions of GBMs films with plasma proteins and biological systems. Films produced by vacuum filtration of GBMs with different oxidation degree and thickness depict different surface features: graphene oxide (GO) and few-layer GO (FLGO) films are more oxidized, smoother, and hydrophilic, while reduced GO (rGO) and few-layer graphene (FLG) are less or nonoxidized, rougher, and more hydrophobic. All films promote glutathione oxidation, although in a lower extent by rGO, indicating their potential to induce oxidative stress in biological systems. Human plasma proteins, which mediate most of the biological interactions, adsorb less to oxidized films than to rGO and FLG. Similarly, clinically relevant bacteria, Staphylococcus epidermidis, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli, adhere less to GO and FLGO films, while rGO and FLG favor bacterial adhesion and viability. Surface features caused by the oxidation degree and thickness of the GBMs powders within the films have less influence toward human foreskin fibroblasts; all materials allow cell adhesion, proliferation and viability up to 14 days, despite less on rGO surfaces. Blood cells adhere to all films, with higher numbers in less or nonoxidized surfaces, despite none having caused hemolysis (<5%). Unlike thickness, oxidation degree of GBMs platelets strongly impact surface morphology/topography/chemistry of the films, consequently affecting protein adsorption and thus bacteria, fibroblasts and blood cells response. Overall, this study provides useful guidelines regarding the choice of the GBMs to use in the development of surfaces for an envisioned application. Oxidized materials appear as the most promising for biomedical applications that require low bacterial adhesion without being cytotoxic to mammalian cells.

Printed Flexible µ-Thermoelectric Device Based on Hybrid Bi2Te3/PVA Composites.

Inorganic-polymer composites have become promising materials to be processed by printing technologies because of their unique properties that allow the fabrication of flexible wearable electronics at reduced manufacturing costs. In the present work, a complete methodological process of assembling a flexible microthermoelectric generator based on inorganic-polymer materials is presented. The used microparticles were prepared by a top-down approach beginning with a previously prepared material by solid-state reaction and later scaled down through the use of ball milling. It was found that the necessity to proceed with a chemical treatment with HCl to reduce Bi2O3 present on the surface of the microparticle leads to a power factor (PF) of 2.29 µW K-2 m-1, which is two times higher than that of the untreated sample. On the fabrication of flexible inorganic-organic thermoelectric thick films based on Bi2Te3 microparticles (<50 µm) and the poly(vinyl alcohol) (PVA) polymer with different thicknesses ranging from 11 to 265 µm and with different Bi2Te3 weight percentages (wt %), we found that PVA allowed achieving a homogeneous dispersion of the parent inorganic thermoelectric materials, while still maintaining their high performance. The best produced ink was obtained with 25 wt % of PVA and 75 wt % of chemically treated Bi2Te3 micropowder with a Seebeck coefficient of -166 µV K-1 and a PF of 0.04 µW K-2 m-1. For this optimized concentration, a flexible thermoelectric device was fabricated using n-type thermoelectric inks, which constitutes a major advantage to be applied in printing techniques because of their low curing temperature. The device architecture was composed of 10 stripes with 0.2 × 2.5 cm2 each in a one-leg configuration. This prototype yielded a power output up to ∼9 µW cm-2 with a 46 K temperature gradient (Δ T), and the results were combined with numerical simulations showing a good match between the experimental and the numerical results. The thermoelectric devices studied in this work offer easy fabrication, flexibility, and an attractive thermoelectric output for specific power requirements such as for environmental health monitoring.

Stretch-induced compliance: a novel adaptive biological mechanism following acute cardiac load.

Aims: The heart is constantly challenged with acute bouts of stretching or overload. Systolic adaptations to these challenges are known but adaptations in diastolic stiffness remain unknown. We evaluated adaptations in myocardial stiffness due to acute stretching and characterized the underlying mechanisms. Methods and results: Left ventricles (LVs) of intact rat hearts, rabbit papillary muscles and myocardial strips from cardiac surgery patients were stretched. After stretching, there was a sustained >40% decrease in end-diastolic pressure (EDP) or passive tension (PT) for 15 min in all species and experimental preparations. Stretching by volume loading in volunteers and cardiac surgery patients resulted in E/E' and EDP decreases, respectively, after sustained stretching. Stretched samples had increased myocardial cGMP levels, increased phosphorylated vasodilator-stimulated phosphoprotein phosphorylation, as well as, increased titin phosphorylation, which was reduced by prior protein kinase G (PKG) inhibition (PKGi). Skinned cardiomyocytes from stretched and non-stretched myocardia were studied. Skinned cardiomyocytes from stretched hearts showed decreased PT, which was abrogated by protein phosphatase incubation; whereas those from non-stretched hearts decreased PT after PKG incubation. Pharmacological studies assessed the role of nitric oxide (NO) and natriuretic peptides (NPs). PT decay after stretching was significantly reduced by combined NP antagonism, NO synthase inhibition and NO scavenging, or by PKGi. Response to stretching was remarkably reduced in a rat model of LV hypertrophy, which also failed to increase titin phosphorylation. Conclusions: We describe and translate to human physiology a novel adaptive mechanism, partly mediated by titin phosphorylation through cGMP-PKG signalling, whereby myocardial compliance increases in response to acute stretching. This mechanism may not function in the hypertrophic heart.

Reinforcement of Thermoplastic Corn Starch with Crosslinked Starch/Chitosan Microparticles.

Microparticles of corn starch and chitosan crosslinked with glutaraldehyde, produced by the solvent exchange technique, are studied as reinforcement fillers for thermoplastic corn starch plasticized with glycerol. The presence of 10% w/w chitosan in the microparticles is shown to be essential to guaranteeing effective crosslinking, as demonstrated by water solubility assays. Crosslinked chitosan forms an interpenetrating polymer network with starch chains, producing microparticles with a very low solubility. The thermal stability of the microparticles is in agreement with their polysaccharide composition. An XRD analysis showed that they have crystalline fraction of 32% with Va-type structure, and have no tendency to undergo retrogradation. The tensile strength, Young's modulus, and toughness of thermoplastic starch increased by the incorporation of the crosslinked starch/chitosan microparticles by melt-mixing. Toughness increased 360% in relation to unfilled thermoplastic starch.

Nebulized lidocaine prevents airway inflammation, peribronchial fibrosis, and mucus production in a murine model of asthma.

BACKGROUND: Evidence suggests that nebulized lidocaine is beneficial in asthma therapy, but to what extent and the mechanisms underlying this effect remain poorly understood. The aim of this study was to assess the impact of lidocaine treatment using a murine model of allergic asthma characterized by expression of pivotal features of the disease: inflammation, mucus production, and lung remodeling. METHODS: A/J mice sensitized with ovalbumin were treated with inhaled lidocaine or vehicle immediately after ovalbumin intranasal challenges. Lung function, total and differential leukocytes in bronchoalveolar lavage fluid, peribronchial eosinophil density, interleukin (IL)-4, IL-5 and eotaxin-1 levels, epithelial mucus, collagen, extracellular-matrix deposition, matrix metalloproteinase-9 activity, and GATA-3 expression were evaluated. Between five and eight animals per group were used. RESULTS: Inhaled lidocaine inhibited ovalbumin-induced airway hyperreactivity to methacholine, and accumulation of lymphocytes, neutrophils, and eosinophils in bronchoalveolar lavage fluid 24 h after the last allergen provocation. Lidocaine administration also prevented other pathophysiological changes triggered by ovalbumin in lung tissue, including peribronchial eosinophil and neutrophil infiltration, subepithelial fibrosis, increased content of collagen and mucus, matrix metalloproteinase-9 activity, and increased levels of IL-4, IL-5, IL-13, and eotaxin-1. Furthermore, inhaled lidocaine inhibited lung tissue GATA-3 expression in ovalbumin-challenged mice. We also demonstrated that lidocaine inhibited the expression of GATA-3 in ovalbumin-stimulated T cells in vitro. CONCLUSIONS: Inhaled lidocaine prevents eosinophilic inflammation, overproduction of mucus, and peribronchial fibrosis in a murine model of asthma, and impaired airway hyperreactivity, possibly by inhibiting allergen-evoked GATA-3 expression and the subsequent up-regulation of proinflammatory cytokines and chemokines.

Macrophage migration inhibitory factor is essential for allergic asthma but not for Th2 differentiation.

Macrophage migration inhibitory factor (MIF) is increased in asthmatic patients and plays a critical role in the pathogenesis of asthma. We show here that mice lacking MIF failed to develop airway hyper-responsiveness (AHR), tissue eosinophilia, and mucus metaplasia. Analysis of the bronchoalveolar fluids revealed a substantial reduction of IL-13, eotaxin and cysteinyl-leukotrienes. The lack of these cardinal features of asthma in MIF(-/-) mice occurs regardless of high concentrations of IL-4 in the lung and OVA-specific IgE in the serum. Antigen-specific lymphocyte proliferation and IL-13 production were similarly increased in the draining lymph nodes of OVA-immunized and challenged MIF(-/-) mice compared to WT, but were reduced in the spleen of MIF(-/-), thus indicating differential roles of MIF in these compartments. Stimulation of naive CD4(+) cells with anti-CD3 antibody demonstrated that MIF(-/-) cells produced increased amounts of IFN-gamma and IL-4 compared to WT CD4(+) cells. Finally, treatment of sensitized BALB/c mice with neutralizing anti-MIF antibody abrogated the development of ARH and airway inflammation without affecting the production of Th2 cytokines or IgE. The present study demonstrates that MIF is required for allergic inflammation, adding important elements to our knowledge of asthma pathogenesis and suggesting that neutralization of MIF might be of therapeutic value in asthma.

Maus-tratos contra crianças e adolescentes: revisão da literatura para profissionais da saúde / Children and adolescents maltreatment: a literature review for health

A violência contra crianças e adolescentes é um grave problema de saúde, que deve ser identificado e abordado por profissionais que atuam na área. O objetivo deste estudo é apresentar uma revisão da literatura sobre maus-tratos na infância e adolescência. Método: publicações sobre o tema foram obtidas em bases de dados nacionais e internacionais (Lilacs; MedLine; Psycinfo) bancos de teses/dissertações, livros, legislação e sites de instituições reconhecidas na área. Resultados: a partir das publicações foi elaborado um breve histórico sobre este tipo de violência e seu reconhecimento; apresentados dados sobre o impacto dos maus-tratos sobre crianças e adolescentes vítimas do problema e dados epidemiológicos; definidos diferentes tipos de maus-tratos; apresentados fatores de risco e subsídios que auxiliam no diagnóstico ou suspeita de ocorrência do problema. Conclusões: A revisão permite uma compreensão global sobre maus-tratos na infância e adolescência, útil para o profissional que atua na saúde e que deve estar preparado para identificar e atuar adequadamente frente a casos de suspeita ou confirmação de maus-tratos...

[Digital morphometric and stereologic analysis of small intestinal mucosa in well-nourished and malnourished children with persistent diarrhea]. / Estudo morfométrico e estereológico digital da mucosa do intestino delgado de crianças eutróficas e desnutridas com diarréia persistente.

OBJECTIVE: To test the hypothesis that the proximal small intestines of children with persistent diarrhea present morphometric and stereologic changes proportional to their nutritional status, using microscope images stored in a computer. METHODS: Cross-sectional study with 65 pediatric patients, whose ages ranged from 4 months to 5 years, with persistent diarrhea for over 14 days. The nutritional assessment was performed according to the z-scores for weight/age (W/A), weight/height (W/H) and height/age (H/A) ratios, divided into: well-nourished = z > or =2SD and malnourished = z<2SD; well-nourished = z > or =2SD, nutritional risk = z<1SD and malnourished = z<-2SD; and continuously, in descending order, using the NCHS charts. After obtaining the computer images using the software Scion Image, villous height, crypt depth, mucosal thickness, total mucosal thickness, and villous/crypt ratio were measured in the fragments of the small intestinal mucosa, enlarged 100 times. When images were enlarged 500 times, enterocyte height, nuclear height and brush-border height were measured. Stereologic analysis was performed using cycloid arcs. RESULTS: For W/A, W/H and H/A z-scores, divided into two nutritional status categories, no statistically significant difference was observed in regard to villous height, crypt depth, mucosal thickness, total mucosal thickness and villous/crypt ratio. Enterocyte height presented the most significant difference between well-nourished and malnourished groups, for W/A and W/H ratios, with a 500x enlargement, although this difference was not statistically significant. When z-scores were subdivided into three nutritional status categories, a digital morphometric analysis showed a statistically significant difference for villous/crypt ratio between the well-nourished and slightly malnourished group and the well-nourished and mild to severe malnourished group (p=0.048). The villous/crypt ratio was higher among well-nourished children. Using the Spearman coefficient, the variables enterocyte height, height of enterocyte nucleus and brush-border height presented a clear association with the W/A ratio (r=0.25; p=0.038), W/H ratio (r=0.029; p=0.019). The height of the enterocyte and the brush-border height were associated with W/H ratio. CONCLUSION: The observed associations between nutritional status and the analyzed small intestinal mucosa variables showed a positive correlation with patients' weight. Although these associations were of a slight to moderate magnitude, we observed a tendency of enterocyte size reduction, as well as a reduction in the size of its nucleus and brush-border, as the level of malnutrition increases.

Estudo morfométrico e estereológico digital da mucosa do intestino delgado de crianças eutróficas e desnutridas com diarréia persistente / Digital morphometric and stereologic analysis of small intestinal mucosa in well-nourished and malnourished children with persistent diarrhea

OBJETIVOS: testar a hipótese de que a mucosa do intestino delgado proximal de crianças com diarréia persistente apresenta alterações morfométricas e estereológicas proporcionais ao estado nutricional, utilizando captura de imagens através de microscópio acoplado ao computador. MÉTODOS: estudo transversal incluindo 65 pacientes pediátricos, com idade entre quatro meses e cinco anos, com diarréia de mais de 14 dias de duraçäo, avaliados pelos escores z, divididos em eutróficos = z > 2 DP e desnutridos = z < -2DP; eutróficos = z > 2 DP, risco nutricional = z < -1DP e desnutridos = z < -2DP; e de maneira contínua em ordem decrescente, utilizando-se as tabelas do NCHS. Após a captura das imagens através do programa Scion Image, foram medidas a altura dos vilos, a profundidade das criptas, a espessura da mucosa, a espessura total da mucosa e a relaçäo vilo/cripta (100 aumentos) e a altura do enterócito, altura do núcleo e do bordo em escova (500 aumentos). A análise estereológica foi feita através de arcos ciclóides. RESULTADOS: para os escores z P/I, P/E e E/I, divididos em duas categorias de estado nutricional, näo houve diferença estatisticamente significante quanto às medidas da altura dos vilos, profundidade das criptas, espessura da mucosa, espessura total da mucosa e relaçäo vilo/cripta. A altura do enterócito foi a característica que apresentou maior diferença entre os grupos eutróficos e desnutridos, para os índices P/I e P/E, em 500 aumentos, sem atingir significância estatística. No entanto, para três categorias de estado nutricional, a análise morfométrica digitalizada mostrou diferença estatisticamente significante para a relaçäo vilo/cripta entre eutróficos e desnutridos leves e entre eutróficos e desnutridos moderados e graves (p=0,048). A relaçäo vilo/cripta foi maior nos eutróficos. Através do coeficiente de correlaçäo linear de Spearman, a altura do enterócito, a altura do núcleo do enterócito e a do bordo em escova mostraram clara associaçäo com os índices P/I (r=0,25;p=0,038) e P/E (r=0,029; p=0,019). A altura do núcleo do enterócito e a do bordo em escova mostraram, ainda, associaçäo com o índice P/E. CONCLUSÕES: as correlações encontradas entre o estado nutricional e a morfometria das variáveis da mucosa do intestino delgado relacionaram-se ao peso dos pacientes. Embora estas associações tenham sido de magnitude fraca a moderada, há uma tendência à diminuiçäo do tamanho do enterócito, do seu núcleo e do bordo em escova...