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Heliyon Jun 2024Modeling of proton exchange membrane (PEM) fuel cells is attracting more attention as fuel cell technology continues to develop. In this study, we considered a hybrid...
Using a three-dimensional computational fluid dynamics model and an agglomerate model to investigate the effect of varying agglomerate parameters and output voltages on proton exchange membrane fuel cell performance.
Modeling of proton exchange membrane (PEM) fuel cells is attracting more attention as fuel cell technology continues to develop. In this study, we considered a hybrid model that combines an agglomerate model based on the agglomeration of catalyst particles and the coverage-dependent kinetic equation of platinum oxide for ORR, and another 3D numerical model of a PEM fuel cell based on computational fluid dynamics (CFD). The obtained results from our developed models were validated with experimental results from literature. In fact, we investigated the effects of changing the agglomerate radius , the ionomer volume fraction within the agglomerate the effective agglomerate surface area , the distribution of the gases and the temperature on the cell performances. The results revealed that the cell performances are strongly influenced by changing and for medium and high current densities: The activation loss increases with increasing and decreasing . Also, increases with decreasing and increasing . In addition, the PEM fuel cell's power output is significantly enhanced when is decreased and is increased, the optimal power being obtained for values of and = 0.6. The numerical results also showed that decreasing the output voltage from 0.95V to 0.35V can accelerate the electrochemical reaction process.
PubMed: 38933966
DOI: 10.1016/j.heliyon.2024.e32277 -
Journal of Molecular and Cellular... Jun 2024Heart failure remains one of the largest clinical burdens globally, with little to no improvement in the development of disease-eradicating therapeutics. Integrin...
Heart failure remains one of the largest clinical burdens globally, with little to no improvement in the development of disease-eradicating therapeutics. Integrin targeting has been used in the treatment of ocular disease and cancer, but little is known about its utility in the treatment of heart failure. Here we sought to determine whether the second generation orally available, αvβ3-specific RGD-mimetic, , was cardioprotective. Male mice were subjected to transverse aortic constriction (TAC) and treated with 50 μg/kg or volume-matched saline as Vehicle control. At 3 weeks post-TAC, echocardiography showed that treatment significantly restored cardiac function and structure indicating the protective effect of treatment in this model of heart failure. Importantly, treatment improved cardiac function giving improved fractional shortening, ejection fraction, heart weight and lung weight to tibia length fractions, together with partial restoration of Ace and Mme levels, as markers of the TAC insult. At a tissue level, reduced cardiomyocyte hypertrophy and interstitial fibrosis, both of which are major clinical features of heart failure. RNA sequencing identified that, mechanistically, this occurred with concomitant alterations to genes involved molecular pathways associated with these processes such as metabolism, hypertrophy and basement membrane formation. Overall, targeting αvβ3 with provides a novel strategy to attenuate pressure-overload induced cardiac hypertrophy and fibrosis, providing a possible new approach to heart failure treatment.
PubMed: 38933087
DOI: 10.1016/j.jmccpl.2024.100069 -
Annals of Pediatric Cardiology 2024Echocardiographic quantification of left ventricular (LV) volume and ejection fraction (EF) is widely used in the pediatric population. However, there is no consensus on...
BACKGROUND
Echocardiographic quantification of left ventricular (LV) volume and ejection fraction (EF) is widely used in the pediatric population. However, there is no consensus on the most accurate method of quantifying ventricular volumes and systolic function.
PURPOSE
The purpose of this study is to compare two commonly used echocardiographic methods for the evaluation of LV volume and quantification of EF, the five-sixth area-length (5/6 AL) and the modified biplane Simpson (BS), to cardiac magnetic resonance (CMR) imaging in children.
METHODS
CMR studies were paired with echocardiograms and retrospectively analyzed in children 18 years of age and younger. Studies performed more than 3 months between modalities, patients with congenital heart disease, and patients who had changes in medication regimen between corresponding CMR and echocardiograms were excluded. LV volumes and EF were calculated using the 5/6 AL and BS methods and compared to volumes and EF measured on corresponding CMR studies. Subgroup analyses were conducted based on LV function, pathology, and weight.
RESULTS
We retrospectively analyzed 53 CMR and corresponding echocardiogram studies (23 studies for myocarditis and 30 studies for cardiomyopathy) in 46 patients. LVEF derived by both echocardiographic methods showed a good correlation to CMR (5/6 AL = 0.85 and BS = 0.82). However, both echocardiographic methods overestimated LVEF and underestimated LV volumes when compared to CMR.
CONCLUSION
Left ventricular volumes and EF, as measured by echocardiography, correlate well with CMR measurements. Echocardiography underestimates LV systolic and diastolic volumes and overestimates LVEF. While echocardiography is a good surrogate for estimating LVEF, CMR should be considered in patients for whom accurate measurements are needed for critical clinical decision-making.
PubMed: 38933052
DOI: 10.4103/apc.apc_199_23 -
Journal of Diabetes and Metabolic... Jun 2024Sodium glucose co-transporter2 (SGLT2) inhibitors have exhibited cardioprotective properties in diabetes patients. The aim of this study was to investigate the effect of...
Empagliflozin improves left ventricular ejection fraction and end systolic volume in patients with type 2 diabetes mellitus and coronary artery disease: a post-hoc analysis of EMPA-CARD trial.
BACKGROUND
Sodium glucose co-transporter2 (SGLT2) inhibitors have exhibited cardioprotective properties in diabetes patients. The aim of this study was to investigate the effect of Empagliflozin on changes in echocardiographic parameters.
METHODS
This was a post hoc analysis of the EMPA-CARD trial which was a multicenter, triple-blind randomized controlled trial. Type 2 diabetes mellitus patients with concomitant history of coronary artery disease were randomized on a 1:1 ratio into two groups receiving either 10 mg/day Empagliflozin or placebo. Patients with a history of heart failure (NYHA class 3-4) and ejection fraction (EF) < 40% were excluded. Trans-thoracic echocardiography was performed at baseline and at 26 weeks of intervention.
RESULTS
A total of 69 (Empagliflozin = 39 and placebo = 30) patients underwent echocardiography. Significant changes were observed for left ventricular ejection fraction [standard error (SE) = 0.76; beta (95% correlation interval (CrI)] = -5.558 (-7.25; -4.18) and left ventricular end-systolic volume (SE = 1.38; beta (95% CrI) = 3.915 (1.2; 0.66). Other echocardiographic parameters relating to right ventricular or atrial function did not change significantly.
CONCLUSION
Empagliflozin can have cardioprotective benefits in subjects without HF. Further studies are required to determine the effect of Empagliflozin in non-HF patients.
TRIAL REGISTRATION
The original EMPA-CARD study has been registered in Iranian Registry of Clinical Trials. www.IRCT.ir, Identifier: IRCT20190412043247N2. Registration Date: 6/13/2020. Registration timing: prospective.
PubMed: 38932825
DOI: 10.1007/s40200-024-01393-8 -
Materials Horizons Jun 2024Extrusion-based 3D printing methods with in-nozzle impregnation mechanisms have been extensively employed in the fabrication of continuous fiber composites. This study...
Extrusion-based 3D printing methods with in-nozzle impregnation mechanisms have been extensively employed in the fabrication of continuous fiber composites. This study presents an innovative embedded 3D printing technique that addresses significant challenges associated with existing methods. The technique utilizes a deposition nozzle to precisely write continuous fibers below the resin. A laser beam is directed onto the resin surface, which simultaneously cures the resin around the fiber bundle. The printing method demonstrates its advantages in producing high-quality composite samples with well-aligned fibers, minimized void density, and outstanding mechanical properties. More importantly, it introduces several capabilities that are highly desirable in the fabrication of contemporary composites, but unattainable with existing methods, including the dynamic control of fiber volume fractions and the ability to change matrix materials during printing. Furthermore, it enables the printing of filaments along curved pathways and printing of overhanging filaments for hollow features without support materials. The developed printing method exhibits versatility in working with different commercially available feedstock resins and reinforcement fibers. It is anticipated to be an impactful approach for the future development of thermosetting composites with diverse structural or multifunctional applications.
PubMed: 38932627
DOI: 10.1039/d4mh00705k -
Journal of Neuroimaging : Official... Jun 2024In acute ischemic stroke (AIS) due to large-vessel occlusion (LVO), the relationship between cerebral oxygen extraction fraction (OEF) as the hallmark of the ischemic...
BACKGROUND AND PURPOSE
In acute ischemic stroke (AIS) due to large-vessel occlusion (LVO), the relationship between cerebral oxygen extraction fraction (OEF) as the hallmark of the ischemic penumbra and leptomeningeal collateral supply is not well established. We aimed to investigate the relationship between pial collateralization and tissue oxygen extraction in patients with LVO using magnetic resonance imaging (MRI).
METHODS
Data from 14 patients with anterior circulation LVO who underwent MRI before acute stroke treatment were analyzed. In addition to diffusion-weighted imaging and perfusion-weighted imaging (PWI), the protocol comprised sequences for multiparametric quantitative blood-oxygen-level-dependent imaging for the calculation of relative OEF (rOEF). Pial collateral supply was quantitatively assessed by analyzing the signal variance in T2*-weighted PWI time series. Relationships between collateral supply, infarct volume, rOEF in peri-infarct hypoperfused tissue, and clinical stroke severity were assessed.
RESULTS
The PWI-based parameter quantifying collateral supply was negatively correlated with baseline ischemic core volume and rOEF in the hypoperfused peri-infarct area (p < .01). Both reduced collateral supply and increased rOEF correlated significantly with higher scores on the National Institutes of Health Stroke Scale (p < .05). Increased rOEF within hypoperfused tissue was associated with higher baseline (p = .043) and follow-up infarct volume (p = .009).
CONCLUSIONS
Signal variance-based mapping of collaterals with PWI depicts pial collateral supply, which is closely tied to tissue pathophysiology and clinical and imaging outcomes. Magnetic-resonance-derived mapping of cerebral rOEF reveals penumbral characteristics of hypoperfused tissue and might provide a promising imaging biomarker in AIS.
PubMed: 38932469
DOI: 10.1111/jon.13220 -
Polymers Jun 2024Pultrusion is a highly efficient continuous process to manufacture advanced fiber-reinforced composites. The injection pultrusion variant permits a higher control of the...
Pultrusion is a highly efficient continuous process to manufacture advanced fiber-reinforced composites. The injection pultrusion variant permits a higher control of the resin flow, enabling the manufacturing of a high reinforcement volume fraction. Moreover, it reduces the emission of volatile compounds that are dangerous for the operators and for the working environment. The present study proposes an experimental analysis of injection pultrusion in three different operative conditions. In particular, the activity focused on the effects of the temperature setup on the thermochemical and rheological behaviors of the resin system and on the interaction between the processed materials and the pultrusion die wall. The setup of the parameters was selected to evidence the behavior of the viscous interaction during the thermoset transition to the solid state, which is particularly challenging due to the localization of high adhesive forces related to the sharp increase in resin viscosity. Microscope observations of the cross-sections were performed to discuss the effects of the process parameters.
PubMed: 38931992
DOI: 10.3390/polym16121642 -
Polymers Jun 2024Additive manufacturing (AM) has arisen as a transformative technology for manufacturing complex geometries with enhanced mechanical properties, particularly in the realm... (Review)
Review
Additive manufacturing (AM) has arisen as a transformative technology for manufacturing complex geometries with enhanced mechanical properties, particularly in the realm of continuous fiber-reinforced polymer composites (CFRPCs). Among various AM techniques, fused deposition modeling (FDM) stands out as a promising method for the fabrication of CFRPCs due to its versatility, ease of use, flexibility, and cost-effectiveness. Several research papers on the AM of CFRPs via FDM were summarized and therefore this review paper provides a critical examination of the process-printing parameters influencing the AM process, with a focus on their impact on mechanical properties. This review covers details of factors such as fiber orientation, layer thickness, nozzle diameter, fiber volume fraction, printing temperature, and infill design, extracted from the existing literature. Through a visual representation of the process parameters (printing and material) and properties (mechanical, physical, and thermal), this paper aims to separate out the optimal processing parameters that have been inferred from various research studies. Furthermore, this analysis critically evaluates the current state-of-the-art research, highlighting advancements, applications, filament production methods, challenges, and opportunities for further development in this field. In comparison to short fibers, continuous fiber filaments can render better strength; however, delamination issues persist. Various parameters affect the printing process differently, resulting in several limitations that need to be addressed. Signifying the relationship between printing parameters and mechanical properties is vital for optimizing CFRPC fabrication via FDM, enabling the realization of lightweight, high-strength components for various industrial applications.
PubMed: 38931971
DOI: 10.3390/polym16121622 -
Nutrients Jun 2024Diabetes mellitus (DM) is a major risk and prognostic factor for heart failure (HF). Insulin resistance (IR) is an important component of DM, but the relationship...
Diabetes mellitus (DM) is a major risk and prognostic factor for heart failure (HF). Insulin resistance (IR) is an important component of DM, but the relationship between IR and HF prognosis has not yet been established across a wide variety of HF populations. We retrospectively evaluated the relationship between IR and clinical outcomes of HF patients at our hospital between 2017 and 2021. IR was defined as a homeostatic model assessment of IR (HOMA-IR) index ≥ 2.5, calculated from fasting blood glucose and insulin concentrations. The primary outcome was a composite of all-cause death and hospitalisation for HF (HHF). Among 682 patients included in the analyses, 337 (49.4%) had IR. The median age was 70 [interquartile range (IQR): 59-77] years old, and 66% of the patients were men. Among the patients, 41% had a left ventricular ejection fraction below 40%, and 32% had DM. The median follow-up period was 16.5 [IQR: 4.4-37.3] months. IR was independently associated with the primary outcome (HR: 1.91, 95% CI: 1.39-2.62, < 0.0001), death (hazard ratio [HR]: 1.86, 95% confidence interval [CI]: 1.28-2.83, < 0.01), and HHF (HR: 1.91, 95% CI: 1.28-2.83, < 0.01). HOMA-IR is an independent prognostic factor of HF in a wide variety of HF populations.
Topics: Humans; Insulin Resistance; Heart Failure; Male; Female; Aged; Middle Aged; Prognosis; Japan; Retrospective Studies; Blood Glucose; Hospitalization; Insulin; Risk Factors; Stroke Volume
PubMed: 38931242
DOI: 10.3390/nu16121888 -
The Grafting of Hydroxyaromatic Organics within Layered Perovskites via a Microwave-Assisted Method.Molecules (Basel, Switzerland) Jun 2024A new series of inorganic-organic hybrid perovskite materials were prepared by microwave-assisted grafting reactions. Simple carboxylic acids, acetic acid, and propionic...
A new series of inorganic-organic hybrid perovskite materials were prepared by microwave-assisted grafting reactions. Simple carboxylic acids, acetic acid, and propionic acid, as well as hydroxyaromatic carboxylic acids, 3,5-dihydroxy benzoic acid (DBA), 5-hydroxyisophthalic acid (HPA), 4-hydroxybenzoic acid (HBA), and 4-hydroxy-4-biphenyl carboxylic acid (HBCA), were reacted with the Dion-Jacobson double-layered perovskite, HLaNbO and its alcoxy derivatives. Grafting was found to not occur with simple carboxylic acids, while those molecules with hydroxyls were all attached to the perovskite interlayers. Reactivity of the hydroxyaromatic carboxylic acids varied with the different layered perovskite hosts where reactions with HLaNbO did not occur, and those with n-propoxy-LaNbO were limited; the greatest extent of reactivity was seen with n-decoxy-LaNbO. This is attributed to the larger interlayer spacing available for the insertion of the various hydroxyaromatic carboxylic acid compounds. The loading exhibited by the grafting species was less than that seen with well-known long-chain alkoxy grafting groups. It is expected that the width of the molecules contributes to this where, due to the benzyl groups, the interlayer volume of the grafted moieties occupies a larger horizontal fraction, therefore minimizing the loading to the below half. X-ray powder diffraction and transmission electron microscopy studies found that grafting of the n-decoxy-LaNbO intermediates with the series of hydroxyaromatics resulted in a reduction in crystallinity along with a disruption of the layer structure. Raman data on the series show little variation in local structure except for HBCA, where there appears to be a lengthening of the Nb-O apical linkage and a possible reduction in the distortion of inner-layer NbO octahedra. The optical properties of the hydroxyaromatic carboxylic acid grafted perovskites were also investigated using diffuse-reflectance UV-Vis spectroscopy. The band gaps of DBA, HPA, and HBA were found to be similar to the parent (E ≈ 3.4 eV), while the HBCA was significantly less by ca. 0.6 eV. This difference is attributed to electron withdrawal from the perovskite block to the HBCA ligand, leading to a lower band gap for the HBCA compound. The methods described herein allow for the formation of a new series of inorganic-organic hybrid materials where the products are of interest as precursors to more complex architectures as well as models for band gap modification of metal oxide photocatalysts.
PubMed: 38930953
DOI: 10.3390/molecules29122888