In this work, the effect of fibre surface morphology on the effective thermal conductivity of the gas diffusion layer of a polymer electrolyte membrane fuel cell is presented. Atomic force microscopy ...was used to measure the fibre surface roughness and asperity height distributions for various fibres for Toray carbon paper. Hertzian contact mechanics was used to determine individual micro-contact areas and thermal resistances, and results were compared with the smooth cylinder approximation. The effective thermal contact resistance between rough fibres was determined using resistance network theory. The thermal contact resistance and total contact area were determined for various angles of fibre orientation and contact forces; results are presented as empirical formulations. It was found that the effective thermal contact resistance is significantly affected by fibre roughness features when compared to the smooth fibre case, which is often used in the literature. The analysis conducted provides an alternative to computationally expensive surface feature analyses by providing a tool which can be used to implement the nano-scale features of gas diffusion layer fibres into existing effective thermal conductivity models.
In this study, the microporous layer (MPL) of the polymer electrolyte membrane (PEM) fuel cell was analysed at the nano-scale. Atomic force microscopy (AFM) was utilized to image the top layer of MPL ...particles, and a curve fitting algorithm was used to determine the particle size and filling radius distributions for SGL-10BB and SGL-10BC. The particles in SGL-10BC (approximately 60 nm in diameter) have been found to be larger than those in SGL-10BB (approximately 40 nm in diameter), highlighting structural variability between the two materials. The impact of the MPL particle interactions on the effective thermal conductivity of the bulk MPL was analysed using a discretization of the Fourier equation with the Gauss-Seidel iterative method. It was found that the particle spacing and filling radius dominates the effective thermal conductivity, a result which provides valuable insight for future MPL design.
•Nano-scale characterization of MPL materials.•Atomic force microscopy used to analyse MPL particles and nano-features.•Numerical determination of thermal resistance between MPL particle structures.•Data presented for use in future stochastic MPL models.
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Chiral alkylidene-β-lactams and alkylidene-γ-lactams were synthesized and screened for their in vitro activity against four human cancer cell lines (melanoma, esophageal, lung and ...fibrosarcoma carcinoma). Alkylidene-β-lactams were synthesized via Wittig reaction of diverse phosphorus ylides with benzhydryl 6‐oxopenicillanate, derived from 6-aminopenicillanic acid. Moreover, novel chiral alkylidene-γ-lactams were synthesized through a multistep strategy starting from a chiral substrate (d-penicillamine). The in vitro assays allowed the identification of four compounds with IC50 values < 10 μM for A375 cell line, and three compounds with IC50 values < 10 μM for OE19 cell line. The effect of the most promising compounds on cell death mechanism, reactive oxygen species generation as well as the evaluation of their ability to act as MMP-9 inhibitors were studied. The reported results unveil the potential of alkylidene-β-lactams as anticancer agents.
•Carbon fibers were recovered from polymeric composite without comminution.•The physical and mechanical properties are important for recycled materials.•At 550 °C for 1 h, it is possible to obtain ...free carbon fibers.•Below 550 °C, polymeric matrix was not entirely removed.•Above 550 °C, the fibers were degraded reaching over 70% of mass losses.
The use of polymeric composite on transport applications as reinforcement material has been increased due to the low fuel consumption when replacing heavier materials. It is estimated that 170,000 tons of polymeric composites will be discarded by 2025, and recycling processing for carbon fibers recovery is required to save primary energy and reduce waste. Among the current techniques, pyrolysis processing has been most effective. On the other hand, innovation must maintain the structure for reuse since physical and mechanical properties are important for recycled materials. For this reason, the goal of the present study was the recycling of polymeric composite by pyrolysis. The recovered carbon fibers were analyzed in SEM and EDS to verify surface defects compared with virgin carbon fibers. The effect of temperature, time, and atmosphere were investigated. Results showed that at 550 °C for 1 h, it was possible to obtain free carbon fibers from the polymeric matrix. After the pyrolysis process in this condition, the fibers had no pores, material fracture, and carbonization. This paper contributes to the widening and systematizing knowledge on effectiveness and understanding polymeric composites recycling for carbon fiber recovery, maintaining its structure for reuse.
Actuators based on electroactive polymers are increasingly used in applications including microelectronic devices and artificial muscles, demanding low voltage operation and controllable switching ...response. This work reports on the preparation of electroactive actuators based on poly(vinylidene fluoride) (PVDF) composites with 10, 25, and 40 wt%
N,N,N
-trimethyl-
N
-(2-hydroxyethyl)ammonium bis(trifluoromethylsulfonyl)imide (N
1 1 1 2(OH)
NTf
2
) and 1-Ethyl-3-methylimidazolium Ethylsulfate (C
2
mimC
2
SO
4
) ionic liquids (ILs) prepared by solvent casting. Independent of the IL type, its presence leads to the crystallization of PVDF in the piezoelectric β-phase. The degree of crystallinity and electrical conductivity of the samples strongly depends on ILs type and content. The highest electrical conductivity was found for PVDF/IL composites with 40 wt% of N
1 1 1 2(OH)
NTf
2
. The strain displacement and bending of the PVDF/IL composites were evaluated as a function of IL type and content under applied peak voltages of 2.0, 5.0, and 10.0 V at a frequency of 10 mHz. Strain displacement of the actuators depends more on IL content than on IL type, and the best strain bending response was found for the PVDF/IL composite with 25 wt% of N
1 1 1 2(OH)
NTf
2
at 5.0 V. Further, it is shown that C
2
mim C
2
SO
4
/PVDF composites do not show cytotoxic behavior, being suitable for biomedical applications.
Group B streptococcus (GBS) is the main bacteria that infects pregnant women and can cause abortion and chorioamnionitis. The impact of GBS effects on human trophoblast cells remains largely elusive, ...and actions toward anti-inflammatory strategies in pregnancy are needed. A potent anti-inflammatory molecule, uvaol is a triterpene from olive oil and its functions in trophoblasts are unknown. We aimed to analyze biomechanical and functional effects of inactivated GBS in trophoblast cells, with the addition of uvaol to test potential benefits.
HTR-8/SVneo cells were treated with uvaol and incubated with inactivated GBS. Cell viability and death were analyzed. Cellular elasticity and topography were accessed by atomic force microscopy. Nitrite production was evaluated by Griess reaction. Nuclear translocation of NFkB p65 was detected by immunofluorescence and Th1/Th2 cytokines by bead-based multiplex assay.
GBS at 108 CFU increased cell death, which was partially prevented by uvaol. Cell stiffness, cytoskeleton organization and morphology were changed by GBS, and uvaol partially restored these alterations. Nuclear translocation of NFkB p65 began 15 min after GBS incubation and uvaol inhibited this process. GBS decreased IL-4 secretion and increased IL-1β, IFN-γ and IL-2, whereas uvaol reverted this.
The increased inflammation and cell death caused by GBS correlated with biomechanical and cytoskeleton changes found in trophoblast cells, while uvaol was effective its protective role.
Uvaol is a natural anti-inflammatory product efficient against GBS-induced inflammation and it has potential to be acquired through diet in order to prevent GBS deleterious effects in pregnancy.
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•GBS increased trophoblast cell death and altered their morphology•GBS induced changes in trophoblast cytoskeleton and reduced membrane stiffness•GBS induced NFkB translocation to the nuclei, nitrite and Th1 cytokines secretion•Uvaol prevented cell deatl and increased cell stiffness•Uvaol delayed GBS-induced NFkB translocation and reduced Th1 cytokines secretion
The introduction of oxygen moieties on a carbon-based material to enhance the electrode material activity for the oxygen reduction reaction (ORR) is a most unexplored experimental approach due to the ...risk of reducing the electron-transport ability of the electrode material. Herein, it is shown that carbon nanomaterials generated electrochemically from graphite can simultaneously show an anomalous high content of oxygen functionalities and a high heterogeneous electron transfer rate. This study was demonstrated with a set of four samples, prepared at different galvanostatic conditions. All the samples display a non-ordered carbon network dominated by aromatic rings, an O/C ratio greater than 0.4, but different amounts of various oxygen-containing functionalities. The electron-transport properties of the obtained films were appraised by cyclic voltammetry and electrochemical impedance spectroscopy.
The application of these metal-free electrode materials to the ORR in the alkaline medium has shown a direct correlation between the materials catalytic activity (potential onset, kinetic current and number of electrons transferred) and the CO amount, whereas a negative correlation was found for CO. Their excellent ability for the H2O2 reduction was also demonstrated. This work opens a new perspective on the use of highly oxidized carbon nanomaterials in electrocatalysis.
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•Approaches for the introduction of oxygen moieties on a carbon-based material•Surface characterization of oxygen-enriched nanomaterials (O/C > 0.4)•Electrode materials with a high electron-transport ability•Electrocatalytic activity towards oxygen and hydrogen peroxide reduction
•A review of scandium extraction by hydrometallurgical route is presented.•A discussion of factors affecting scandium extraction/recovery towards UN SDG.•A thorough review of current techniques for ...scandium extraction/recovery.•Analysis of each of the main scandium sources worldwide and opportunities.•Hydrometallurgical processing is the main route towards low CO2 emission.•The supply of Sc and REE in the following years will be from wastes.
Scandium is a critical metal in increasing demand for modern technologies, such as light-weight aluminum-scandium alloys. Evaluating current and identifying new sources of the element has become a pressing need in order to provide a reliable and cost effective future supply. As current resources are limited, new sources must be explored with due consideration for the environmental aspects of the mining and processing technologies. The present review considers scandium extraction from three different sources - primary, secondary and opportunities – focusing on clean technologies and eco-friendly processing to achieve goals 7, 8, 9, and 12 of the 17 sustainable development goals of the United Nations. The main scientific databases were explored using keyword combinations. The question “is it possible to have an ecofriendly process for scandium extraction?” - worldwide debated – was answered providing diversified opportunities for scandium extraction, demonstrating that the current development would achieve these goals. Several techniques were explored and compared. As important as technical studies, economic approaches must be deeply evaluated where both acid consumption and downstream refining are equally challenging.
Lectins are proteins that recognize specific carbohydrates, and the vasorelaxant effect of legume lectins has been previously reported, for example the Dioclea rostrata lectin (DRL). This study ...evaluated major pathways of DRL‐induced relaxation in different artery segments and the possible molecular interactions involved. Rat thoracic aorta, coronary and mesenteric resistance arteries were tested “in vitro” with concentration‐response curves to DRL (0.01‐100 µg/mL). L‐NAME, indomethacin and high KCl were used to evaluate nitric oxide, cyclooxygenase and hyperpolarization‐dependent effects. DRL promoted relaxation of all vessels throughout different mechanisms. L‐NAME blunted DRL‐induced effects only in the aorta and mesenteric resistance artery. By the use of depolarizing KCl solution, vasodilation was reduced in all arteries, while incubation with indomethacin indicated a role of cyclooxygenase‐derived factors for DRL effects in mesenteric and coronary arteries, but not in the aorta. Molecular docking results suggested interactions between DRL and heparan sulphate, CD31 and other glycans present on the membrane surface. These data indicate that the mechanisms involved in DRL‐mediated vasodilation vary between conductance and resistance arteries of different origins, and these effects may be related to the capacity of DRL to bind a diversity of glycans, especially heparan sulphate, a proposed mechanoreceptor for nitric oxide synthase and cyclooxygenase activation.
Biomarkers are needed to improve current diagnosis and surveillance strategies for patients with Barrett's oesophagus (BO) and oesophageal adenocarcinoma (OAC). Macrophage inhibitory cytokine ...1/growth differentiation factor 15 (MIC-1/GDF15) tissue and plasma levels have been shown to predict disease progression in other cancer types and was therefore evaluated in BO/OAC.
One hundred thirty-eight patients were studied: 45 normal oesophagus (NE), 37 BO, 16 BO with low-grade dysplasia (LGD) and 40 OAC.
Median tissue expression of MIC-1/GDF15 mRNA was ⩾25-fold higher in BO and LGD compared to NE (P<0.001); two-fold higher in OAC vs BO (P=0.039); and 47-fold higher in OAC vs NE (P<0.001). Relative MIC-1/GDF15 tissue expression >720 discriminated between the presence of either OAC or LGD vs NE with 94% sensitivity and 71% specificity (ROC AUC 0.86, 95% CI 0.73-0.96; P<0.001). Macrophage inhibitory cytokine 1/growth differentiation factor 15 plasma values were also elevated in patients with OAC vs NE (P<0.001) or BO (P=0.015).High MIC-1/GDF15 plasma levels (⩾1140 pg ml(-1)) were an independent predictor of poor survival for patients with OAC (HR 3.87, 95% CI 1.01-14.75; P=0.047).
Plasma and tissue levels of MIC-1/GDF15 are significantly elevated in patients with BO, LGD and OAC. Plasma MIC-1/GDF15 may have value in diagnosis and monitoring of Barrett's disease.
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