Caracterización mecánica de mezclas de caucho natural y residuos de celulosa originados en la industria automotriz con enfoque en el sector del calzado

Context: This publication shows a potential use for waste from the automotive industry, namely waste originating in the manufacturing process of gaskets and seals for motorcycles, which currently do not have a final use. In addition, due to their high-performance rubber surface layer, they imply an extensive degradation process, which constitutes a harmful factor for the environment and contributes to global warming. Method: First, the crushing of the residues was carried out, then their sieving and selection via granulometry, and finally a mixture with the natural rubber through chewing in open cylinders in order to obtain the master, which was vulcanized in a shoe sole mold. The final product was mechanically characterized via the techniques, tension-elongation, wear, hardness, bending, and tearing. Results: The obtained mixture opens a window to the design of products using residues from seals and gaskets for motors. It will be possible to design other proposals for functionalized rubbers, oriented towards the development of ecological footwear applications. Conclusions: The mixture of cellulose waste from the motor seal sector and natural rubber shows promise for the reduction of the negative impact caused by these wastes and proposes a circular economy –in this case, with the development of raw material in the footwear sector.Contexto: Esta publicación muestra un potencial uso para los residuos provenientes de la industria automotriz, en este caso residuos originados en el proceso de fabricación de empaques y sellos para motocicletas, que en la actualidad no tienen un uso final. Además, debido a la capa superficial de caucho de altas prestaciones, presentan un proceso de degradación extenso, lo cual constituye un factor perjudicial para el medio ambiente y contribuye al calentamiento global. Método: Primero se realizó la trituración de los residuos, posteriormente su tamizado y selección por granulometría, y por último se realizó una mezcla con el caucho natural a través del masticado en cilindros abiertos para obtener el máster, que fue vulcanizado en un molde de suela para zapatos. El producto final fue caracterizado mecánicamente con las técnicas tensión-elongación, desgaste, dureza, flexión y rasgadura. Resultados: La mezcla obtenida abre una ventana hacia el diseño de productos utilizando residuos de sellos y empaques para motor. Será posible diseñar otras propuestas para cauchos funcionalizados, orientados al desarrollo de aplicaciones de calzado ecológico. Conclusiones: La mezcla de residuos de celulosa provenientes del sector de sellos para motor con caucho natural proyecta la reducción del impacto negativo generado por estos residuos y propone una economía circular, en este caso con el desarrollo de materia prima para el sector del calzado

Electrosynthesis of Composites Consisting of FeOOH and Reduced Graphene Oxide in Graphite Electrodes

Carbon-based composite nanomaterials, such as graphene oxide, have demonstrated a great potential for applications in several areas. The present work sought to obtain, via electrosynthesis, a composite material based on graphene oxide and iron oxyhydroxide deposited onto graphite pencil surface. The electrodes modifications by electrosynthesis was performed using the cyclic voltammetry technique. The graphene oxide and the electrosynthesized FeOOH cuboids were characterized by SEM-FEG, EDX. The cyclic voltammetry was used to characterize the electrochemical behavior of the graphite pencil electrode (PEG). The composites electrodes of PEG modified with GO/FeOOH (PEG/GO/FeOOH) were formed in two stages. In the first stage, there was the formation of FeHCF in PEG/GO, and subsequently, there was the formation of PEG/GO/FeOOH in alkaline medium. DOI: http://dx.doi.org/10.17807/orbital.v12i3.147

Utility of a novel biofeedback device for within-breath modulation of heart rate in rats:a quantitative comparison of vagus nerve versus right atrial pacing

In an emerging bioelectronics era, there is a clinical need for physiological devices incorporating biofeedback that permits natural and demand-dependent control in real time. Here, we describe a novel device termed a central pattern generator (CPG) that uses cutting edge analogue circuitry producing temporally controlled, electrical stimulus outputs based on the real time integration of physiological feedback. Motivated by the fact that respiratory sinus arrhythmia (RSA), which is the cyclical changes in heart rate every breath, is an essential component of heart rate variability (an indicator of cardiac health), we have explored the versatility and efficiency of the CPG for producing respiratory modulation of heart rate in anaesthetised, spontaneously breathing rats. Diaphragmatic electromyographic activity was used as the input to the device and its output connected to either the right cervical vagus nerve or the right atrium for pacing heart rate. We found that the CPG could induce respiratory related heart rate modulation that closely mimicked RSA. Whether connected to the vagus nerve or right atrium, the versatility of the device was demonstrated by permitting: (i) heart rate modulation in any phase of the respiratory cycle, (ii) control of the magnitude of heart rate modulation and (iii) instant adaptation to changes in respiratory frequency. Vagal nerve pacing was only possible following transection of the nerve limiting its effective use chronically. Pacing via the right atrium permitted better flexibility and control of heart rate above its intrinsic level. This investigation now lays the foundation for future studies using this biofeedback technology permitting closer analysis of both the function and dysfunction of RSA

Enhancing respiratory sinus arrhythmia increases cardiac output in rats with left ventricular dysfunction

Key points: Respiratory sinus arrhythmia is physiological pacing of the heart that disappears in cardiovascular disease and is associated with poor cardiac prognosis. In heart failure, cardiac pacing has little, if any, variation in rate at rest. We proposed that reinstatement of respiratory sinus arrhythmia would improve cardiac function in rats with heart failure. Heart failure rats were paced daily for 2 weeks with either respiratory sinus arrhythmia or paced monotonically at a matched heart rate; cardiac function was measured using non-invasive echocardiography. Cardiac output and stroke volume were increased in rats paced with respiratory sinus arrhythmia compared to monotonic pacing, via improvement in systolic function that persisted beyond the pacing treatment period. We propose that respiratory sinus arrhythmia pacing reverse-remodels the heart in heart failure and is worth considering as a new form of cardiac pacemaking. Abstract: Natural pacing of the heart results in heart rate variability, an indicator of good health and cardiac function. A contributor to heart rate variability is respiratory sinus arrhythmia or RSA – an intrinsic respiratory modulated pacing of heart rate. The loss of RSA is associated with poor cardiac prognosis and sudden cardiac death. We tested if reinstatement of respiratory-modulated heart rate (RMH) would improve cardiac performance in heart failure. Heart failure was induced in Wistar rats by ligation of the left anterior descending coronary artery. Rats were unpaced, monotonically paced and RMH paced; the latter had the same average heart rate as the monotonically paced animals. Cardiac function was assessed non-invasively using echocardiography before and after 2 weeks of daily pacing at a time when pacing was turned off. RMH increased cardiac output by 20 ± 8% compared to monotonic pacing (−3 ± 5%; P &lt; 0.05). This improvement in cardiac output was associated with an increase in stroke volume compared to monotonic pacing (P = 0.03) and improvement in circumferential strain (P = 0.02). Improvements in ejection fraction (P = 0.08) and surrogate measures of left ventricle compliance did not reach significance. Increases in contractility (P &lt; 0.05) and coronary blood flow (P &lt; 0.05) were seen in vitro during variable pacing to mimic RMH. Thus, in rats with left ventricular dysfunction, chronic RMH pacing improved cardiac function through improvements in systolic function. As these improvements were made with pacing switched off, we propose the novel idea that RMH pacing causes reverse-remodelling.</p

Elastase-2, a tissue alternative pathway for angiotensin II generation, plays a role in circulatory sympathovagal balance in mice

In vitro and ex vivo experiments indicate that elastase-2 (ELA-2), a chymotrypsin-serine protease elastase family member 2A, is an alternative pathway for angiotensin II (Ang II) generation. However, the role played by ELA-2 in vivo is unclear. We examined ELA-2 knockout (ELA-2KO) mice compared to wild-type (WT) mice and determined whether ELA-2 played a role in hemodynamics [arterial pressure (AP) and heart rate (HR)], cardiocirculatory sympathovagal balance and baroreflex sensitivity. The variability of systolic arterial pressure (SAP) and pulse interval (PI) for evaluating autonomic modulation was examined for time and frequency domains (spectral analysis), whereas a symbolic analysis was also used to evaluate PI variability. In addition, baroreflex sensitivity was examined using the sequence method. Cardiac function was evaluated echocardiographically under anesthesia. The AP was normal whereas the HR was reduced in ELA-2KO mice (425 ± 17 vs. 512 ± 13 bpm from WT). SAP variability and baroreflex sensitivity were similar in both strains. The LF power from the PI spectrum (33.6 ± 5 vs. 51.8 ± 4.8 nu from WT) and the LF/HF ratio (0.60 ± 0.1 vs. 1.45 ± 0.3 from WT) were reduced, whereas the HF power was increased (66.4 ± 5 vs. 48.2 ± 4.8 nu from WT) in ELA-2KO mice, indicating a shift toward parasympathetic modulation of HR. Echocardiographic examination showed normal fractional shortening and an ejection fraction in ELA-2KO mice; however, the cardiac output, stroke volume, and ventricular size were reduced. These findings provide the first evidence that ELA-2 acts on the sympathovagal balance of the heart, as expressed by the reduced sympathetic modulation of HR in ELA-2KO mice

Analysis of the effects of body weight-supported gait training on the electromyographic activity of the lower limbs and motor irradiation to the upper limbs in spinal cord injured patients

Rehabilitation on the treadmill with partial body weight support (PBWS) in individuals with spinal cord injuries can passively reproduce gait, helping them with weight bearing on the lower limbs (LL) and orthostatic posture. The objective of the study was to assess motor irradiation from the lower limbs to the upper limbs during gait training with PBWS. The participants were three male individuals diagnosed with low spinal cord injury (T10 and L1), classified as ASIA A, with partial preservation of nerve roots. Subjects were submitted to gait training with PBWS and electromyographic assessment of the muscles Biceps brachii (BB), Rectus femoris (RF) and Lateral Gastrocnemius (LG) on both sides. Statistical analysis included Shapiro-Wilk and de Levene tests, One way ANOVA test and Tukey’s HSD post-hoc test. In the resting state, there was less activity of BB muscles on both sides when compared to the RF and LG, which can be explained by the secondary impairments arising from the individuals’ injury. The gait cycle (GC) was repeated three times; in GC1 there was greater electromyographic activity in the right LG muscle and lower activity of the right BB muscle and, statistically, right LG and left BB showed higher mean activity (statistically significant results). In GC2, the same pattern of activity of GC1 was observed, but the right RF muscle reduced its activation threshold. In GC3, the activity levels of the previous cycles were maintained, but the left RF muscle showed an increase in the thresholds of electromyographic activation when compared to the other muscles. Based on these results, the BB muscle presented quantitative variations in electromyographic activation, demonstrating the presence of motor irradiation from LL to upper limbs during the GC. The qualitative analysis showed “peaks” of activity in this muscle mainly during the support phases of the gait training.A reabilitação na esteira com suporte parcial de peso (ESPP) nos indivíduos lesados medulares pode reproduzir de modo passivo a marcha, proporcionando-lhes a descarga de peso em membros inferiores (MMII) e a manutenção da postura ortostática. O objetivo do estudo foi analisar se, durante a marcha passiva na ESPP, existe irradiação motora de MMII aos membros superiores. Foram selecionados três indivíduos do gênero masculino, com diagnóstico de Traumatismo Raquimedular baixo (T10 e L1), classificados como ASIA A com preservação parcial de raízes nervosas. Os indivíduos foram submetidos a uma avaliação passiva da marcha na ESSP, utilizando a avaliação eletromiográfica dos músculos: bíceps braquial (BB), reto femoral (RF) e gastrocnêmio lateral (GL) bilateralmente e a uma análise estatística, incluindo testes de Shapiro-Wilk e de Levene, One way ANOVA, post-hoc Tukey HSD. Na condição clínica de repouso, observou-se menor ativação dos músculos BB bilateralmente, quando comparado aos músculos RF e GL, fato justificado pelos comprometimentos secundários advindos da lesão dos indivíduos. As condições clínicas do ciclo da marcha (CM) repetiram-se três vezes; no CM1 observou-se uma maior ativação eletromiográfica do músculo GL direito e uma menor ativação do músculo BB direito, e estatisticamente, GL direito e BB esquerdo demonstraram maior atividade média (resultados estatisticamente significantes). No CM2 o mesmo padrão de ativação do CM1 foi observado, no entanto o músculo RF direito reduziu seu limiar de ativação. No CM3 os níveis de ativação das condições anteriores mantiveram-se, no entanto, o músculo RF esquerdo apresentou aumento nos limiares de ativação eletromiográfica, quando comparado aos demais músculos. Com base nestes resultados, o músculo BB apresentou variações quantitativas na ativação eletromiográfica, determinando a presença de irradiação motora de MMII para superiores durante o CM. Em uma análise qualitativa, foi observado que durante as fases de apoio da marcha houve “picos” de ativação deste músculo

Electrosynthesis of Composites Consisting of FeOOH and Reduced Graphene Oxide in Graphite Electrodes

Carbon-based composite nanomaterials, such as graphene oxide, have demonstrated a great potential for applications in several areas. The present work sought to obtain, via electrosynthesis, a composite material based on graphene oxide and iron oxyhydroxide deposited onto graphite pencil surface. The electrodes modifications by electrosynthesis was performed using the cyclic voltammetry technique. The graphene oxide and the electrosynthesized FeOOH cuboids were characterized by SEM-FEG, EDX. The cyclic voltammetry was used to characterize the electrochemical behavior of the graphite pencil electrode (PEG). The composites electrodes of PEG modified with GO/FeOOH (PEG/GO/FeOOH) were formed in two stages. In the first stage, there was the formation of FeHCF in PEG/GO, and subsequently, there was the formation of PEG/GO/FeOOH in alkaline medium. DOI: http://dx.doi.org/10.17807/orbital.v12i3.147

OBSTRUÇÃO INTRALUMINAL DE COLON MENOR POR FITOBENZOAR EM UMA RECEPTORA DE EMBRIÃO

A síndrome cólica é identificada como uma síndrome complexa e seu reconhecimento precoce e diferenciação apurada é muito importante para estabelecer a abordagem adequada. A síndrome cólica por compactação descreve uma obstrução luminal por massas desidratadas de ingesta, ocasionando uma obstrução simples do lúmen intestinal, que geralmente, não resulta em necrose ou isquemia, sendo apontada como a principal causa de cólica nos eqüinos. Vários agentes etiológicos estão envolvidos, mas a etiopatogenia da formação das compactações permanece incerta. Nem sempre a terapia clínica é eficaz nas obstruções intraluminais, sendo a correção cirúrgica necessária para a resolução do problema, como no caso a seguir, envolvendo uma receptora de embrião