Loss of myocardial LIF receptor in experimental heart failure reduces cardiotrophin-1 cytoprotection. A role for neurohumoral agonists?

OBJECTIVES: Cardiomyocyte loss is involved in the transition from compensatory left ventricular hypertrophy (LVH) to heart failure (HF). Our aim was to investigate the status of the leukaemia inhibitory factor receptor (LIFR)/gp130 survival pathway and its cytoprotective activity in intact cardiac tissue and in cardiomyocytes obtained from adult spontaneously hypertensive rats (SHR) with LVH (non-failing SHR) and from aged SHR with overt HF (failing SHR). METHODS: Cardiac morphometry was assayed by planimetry in an image analysis system. mRNA and protein expression were quantified by real time RT-PCR and Western blotting. Receptors were localized by immunocytochemistry. Trypan blue staining, TUNEL, and MTT cell viability assays were employed to study the cytoprotective activity of cardiotrophin-1 (CT-1) in isolated caridomyocytes. RESULTS: Compared to non-failing SHR, failing SHR exhibited enhanced myocardial cell death (p<0.01) demonstrated by the increase in Bax/Bcl-2 ratio, caspase-3 activation and poly (ADP-ribose) polymerase (PARP) fragmentation. Failing SHR had a 7-fold diminished expression (p<0.01) of LIFR, no changes in gp130, and 1.6-fold increased myocardial expression (p<0.01) of CT-1. In cardiomyocytes isolated from non-failing SHR, recombinant CT-1 inhibited apoptotic and non-apoptotic cell death induced by angiotensin II or hydrogen peroxide. LIFR protein was entirely absent in cardiomyocytes isolated from failing SHR, which were resistant to the cytoprotective effects of CT-1. Finally, stimulation of non-failing SHR cardiomyocytes with angiotensin II, aldosterone, norepinephrine or endothelin-1 significantly decreased (p<0.01) LIFR expression. CONCLUSIONS: These data suggest that loss of CT-1-dependent survival mechanisms may contribute to the increase of cell death associated with HF in SHR. Neurohumoral activation may contribute to this alteration via suppression of LIFR

Analysis of the Influence of Selective Contact Heterojunctions on the Performance of Perovskite Solar Cells

Knowledge of the mechanisms that take place at the selective contacts, located at the charge-transport-layer (CTL)/perovskite heterojunctions, is crucial for the optimization of perovskite solar cells. Anomalous high values of the low-frequency capacitance at open-circuit and short-circuit indicate a high accumulation of charge at the interfaces, which could hinder the extraction of charge and increase hysteresis in current-voltage curve. To investigate this issue, we develop a simulation model based on the drift diffusion differential equations with specific boundary conditions at the interfaces. We have simulated the CTL/perovskite structures as part of the entire perovskite solar cell, in order to establish the realistic energy profile across the interface. The energy profile allows to detect in which situations free charge accumulation at the interfaces exists, and to quantify this accumulation as a function of the device and material parameters. We discuss the role and the importance of each CTL/perovskite interface at open-circuit and short-circuit. We conclude that the accumulation of charge at the interfaces is strongly affected by the specific contact materials, and critically depends on a compromise between the presence of ions, the values of the carrier mobility, and the interfacial and bulk recombination parameters

Biochemical Diagnosis of Hypertensive Myocardial Fibrosis

A substantial increase in fibrillar collagen has been observed in the left cardiac ventricle of animals and humans with arterial hypertension. Hypertensive myocardial fibrosis is the result of both increased collagen types I and III due to the fact that its synthesis by fibroblasts and myofibroblasts is stimulated and its extracellular collagen degradation unchanged or decreased extracellular collagen degradation. Hemodynamic and non-hemodynamic factors may be involved in the disequilibrium between collagen synthesis and degradation that occurs in hypertension. As shown experimentally and clinically, an exaggerated rise in fibrilar collagen content promotes abnormalities of cardiac function, contributes to the decrease in coronary reserve and facilitates alterations in the electrical activity of the left ventricle. Although microscopic examination of cardiac biopsies is the most reliable method for documenting and measuring myocardial fibrosis, the development of non-invasive methods to indicate the presence of myocardial fibrosis in hypertensive patients would be useful. We have therefore applied a biochemical method based on the measurement of serum peptides derived from the tissue formation when synthesized and degradation of fibrillar collagens to monitor the turnover of these molecules in rats with spontaneous hypertension and patients with essential hypertension

Switching Off Hysteresis in Perovskite Solar Cells by Fine‐Tuning Energy Levels of Extraction Layers

Lead halide perovskites often suffer from a strong hysteretic behavior on their j–V response in photovoltaic devices that has been correlated with slow ion migration. The electron extraction layer has frequently been pointed to as the main culprit for the observed hysteretic behavior. In this work three hole transport layers are studied with well‐defined highest occupied molecular orbital (HOMO) levels and interestingly the hysteretic behavior is markedly different. Here it is shown that an adequate energy level alignment between the HOMO level of the extraction layer and the valence band of the perovskite, not only suppresses the hysteresis, avoiding charge accumulation at the interfaces, but also degradation of the hole transport layer is reduced. Numerical simulation suggests that formation of an injection barrier at the organic/perovskite heterointerface could be one mechanism causing hysteresis. The suppression of such barriers may require novel design rules for interface materials. Overall, this work highlights that both external contacts need to be carefully optimized in order to obtain hysteresis‐free perovskite devices

Device Physics of Hybrid Perovskite Solar cells: Theory and Experiment

Perovskite solar cells (PSCs) exhibit a series of distinctive features in their optoelectronic response which have a crucial influence on the performance, particularly for long-time response. Here, a survey of recent advances both in device simulation and optoelectronic and photovoltaic responses is provided, with the aim of comprehensively covering recent advances. Device simulations are included with clarifying discussions about the implications of classical drift-diffusion modeling and the inclusion of ionic charged layers near the outer carrier selective contacts. The outcomes of several transient techniques are summarized, along with the discussion of impedance and capacitive responses upon variation of bias voltage and irradiance level. In relation to the capacitive response, a discussion on the J-V curve hysteresis is also included. Although alternative models and explanations are included in the discussion, the review relies upon a key mechanism able to yield most of the rich experimental responses. Particularly for state-of-the-art solar cells exhibiting efficiencies around or exceeding 20%, outer interfaces play a determining role on the PSC's performance. The ionic and electronic kinetics in the vicinity of the interfaces, coupled to surface recombination and carrier extraction mechanisms, should be carefully explored to progress further in performance enhancement

Impacto da exposição académica no estado de saúde de estudantes universitários

OBJECTIVE: To assess the impact of academic life on health status of university students. METHODS: Longitudinal study including 154 undergraduate students from the Universidade de Aveiro, Portugal, with at least two years of follow-up observations. Sociodemographic and behavioral characteristics were collected using questionnaires. Students' weight, height, blood pressure, serum glucose, serum lipids and serum homocysteine levels were measured. Regression analysis was performed using linear mixed-effect models, allowing for random effects at the participant level. RESULTS: A higher rate of dyslipidemia (44.0% vs. 28.6%), overweight (16.3% vs. 12.5%) and smoking (19.3% vs. 0.0%) was found among students exposed to the academic life when compared to freshmen. Physical inactivity was about 80%. Total cholesterol, high density lipoprotein-cholesterol (HDL-C), triglycerides, systolic blood pressure, and physical activity levels were significantly associated with gender (p<0.001). Academic exposure was associated with increased low density lipoprotein-cholesterol (LDL-C) levels (about 1.12 times), and marginally with total cholesterol levels (p=0.041). CONCLUSIONS: High education level does not seem to have a protective effect favoring a healthier lifestyle and being enrolled in health-related areas does not seem either to positively affect students' behaviors. Increased risk factors for non-transmissible diseases in university students raise concerns about their well-being. These results should support the implementation of health promotion and prevention programs at universities.OBJETIVO: Avaliar a influência da vida académica na saúde de estudantes universitários. MÉTODOS: Estudo longitudinal envolvendo 154 estudantes de graduação da Universidade de Aveiro, Portugal, por pelo menos dois anos de acompanhamento. Características sociodemográfi cas e comportamentais foram recordados, por meio de questionários. Foram medidos peso, altura,pressão arterial, glicemia, perfil lipídico e os níveis séricos de homocisteína dos alunos. Foi realizada análise de regressão com modelos lineares mistos considerando as medidas repetidas de cada sujeito. RESULTADOS: Estudantes expostos à vida académica, quando comparados àqueles de ingresso recente à universidade apresentaram proporção mais elevada de dislipidemia (44,0% versus 28,6%), sobrepeso (16,3% versus 12,5%) e tabagismo (19,3% versus 0,0%). No geral, foi observada alta proporção de sedentarismo (cerca de 80%). O colesterol total, lipoproteína de alta densidade, triglicérides, pressão arterial sistólica e níveis de atividade física apresentaram associação signifi cativa com o género (p < 0,001). A exposição académica apresentou-se associada com o aumento dos níveis das lipoproteínas de baixa densidade (cerca de 1,12 vezes), e marginalmente com os níveis de colesterol total (p = 0,041). CONCLUSÕES: Nem o alto nível de instrução parece ter papel protetor na adoção de estilo de vida saudável, tampouco o envolvimento com áreas de saúde muda o comportamento dos estudantes. Altas proporções de fatores de risco para doenças não-transmissíveis em jovens universitários podem afetar seu bem-estar. Os resultados podem servir de apoio às universidades no desenvolvimento de programas de prevenção e promoção da saúde

Increasing efficiency and reducing bias in the sampling of seed-dispersal interactions based on mist-netted birds

Efficient and unbiased sampling of ecological interactions is essential to our understanding of the functions they mediate. Seed dispersal by frugivorous birds is a key mutualism for plant regeneration and community dynamics. Mist-netting is one of the most widely used methods to sample avian seed dispersal through the identification of seeds in droppings of captured birds kept inside cloth bags. However, birds may drop seeds on the ground before being extracted from the net, leading to a fraction of missing information due to ineffective sampling. Worryingly, this fraction could be unevenly distributed across bird and plant species, leading to sampling biases. Here, we assess the effectiveness of using a 1-m wide mesh below mist nets to sample seeds dropped by entangled birds. We used data from birds mist-netted during one-year-round. We sampled nearly 50% of interaction events and 75% of dispersed seeds on the mesh band below the mist nets (i.e. lost information without this optimization). The proportion of seeds sampled on the mesh bands was not evenly distributed among bird species but strongly related to bird size, ranging from 57–63% in warblers to 84–94% in thrushes. Moreover, the proportion of seeds sampled on the mesh was negatively related to seed size, although this relationship was weaker. We also evaluated accumulation curves of species and pairwise interactions with increasing sampling effort, both with and without using the mesh bands. The number of seed species sampled increased by 21% when using the mesh bands and the number of pairwise interactions by 36%. Our findings provide strong evidence on how inefficient and biased traditional mist-netting can be for sampling community-wide seed–dispersal interactions. We thus urge the use of mesh bands in future studies to increase sampling effectiveness and avoid biases, which will ultimately improve our understanding of the seed dispersal function

Boundary condition model for the simulation of organic solar cells

(c) 2017. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/http://www.sciencedirect.com/science/article/pii/S1566119917302434Organic solar cells (OSCs) are promising photovoltaic devices to convert solar energy into electrical energy. Their many advantages such as lightweight, flexibility and low manufacturing costs are intrinsic to the organic/polymeric technology. However, because the performance of OSCs is still not competitive with inorganic solar cells, there is urgent need to improve the device performance using better designs, technologies and models. In this work, we focus on the developing an accurate physics-based model that relates the charge carrier density at the metal-organic boundaries with the current density in OSCs using our previous studies on single-carrier and bipolar diodes. The model for the boundary condition of the charge carrier density at the interfaces of OSCs follows a power-law function with the current density, both in dark and under illumination, and simulated current-voltage characteristics are verified with experimental results. The numerical simulations of the current-voltage characteristics of OSCs consider well-established models for the main physical and optical processes that take place in the device: light absorption and generation of excitons, dissociation of excitons into free charge carriers, charge transport, recombination and injection-extraction of free carriers. Our analysis provides important insights on the influence of the metal-organic interfaces on the overall performance of OSCs. The model is also used to explain the anomalous S-shape current-voltage curves found in some experimental data.This work was supported by Ministerio de Educación y Ciencia under research Grant FPU12/02712 and MINECO/FEDER under research Project MAT2016-76892-C3-3-R, and the Canada Research Chair program, NSERC ResEau strategic network and the NCE IC-IMPACTS

On building physics-based AI models for the design and SHM of mooring systems

Expert systems in industrial processes are modelled using physics-based approaches, data-driven models or hybrid approaches in which however the underlying physical models generally constitute a separate block with respect to the Artificial Intelligence (AI) technique(s). This work applies the novel concept of “imbrication”-a physics-based AI approach-to the mooring system of offshore renewable energy devices to achieve a complete integration of both perspectives. This approach can reduce the size of the training dataset and computational time while delivering algorithms with higher generalization capability and explicability. We first undertake the design of the mooring system by developing a surrogate model coupled with a Bayesian optimiser. Then, we analyse the structural health monitoring of the mooring system by designing a supervised Deep Neural Network architecture. Herein, we describe the characteristics of the imbrication process, analyse preliminary results of our investigation and provide considerations for orienting further research work and sector applicability