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Open AccessFeature PaperArticle
The Effect of CeO2 Preparation Method on the Carbon Pathways in the Dry Reforming of Methane on Ni/CeO2 Studied by Transient Techniques
Catalysts 2019, 9(7), 621; https://doi.org/10.3390/catal9070621 (registering DOI) -
Abstract
The present work discusses the effect of CeO2 synthesis method (thermal decomposition (TD), precipitation (PT), hydrothermal (HT), and sol-gel (SG)) on the carbon pathways of dry reforming of methane with carbon dioxide (DRM) applied at 750 °C over 5 wt% Ni/CeO2 [...] Read more.
The present work discusses the effect of CeO2 synthesis method (thermal decomposition (TD), precipitation (PT), hydrothermal (HT), and sol-gel (SG)) on the carbon pathways of dry reforming of methane with carbon dioxide (DRM) applied at 750 °C over 5 wt% Ni/CeO2. In particular, specific transient and isotopic experiments (use of 13CO, 13CO2, and 18O2) were designed and conducted in an attempt at providing insights about the effect of support’s preparation method on the concentration (mg gcat−1), reactivity towards oxygen, and transient evolution rates (μmol gcat−1 s−1) of the inactive carbon formed under (i) CH4/He (methane decomposition), (ii) CO/He (reverse Boudouard reaction), and (iii) the copresence of the two (CH4/CO/He, use of 13CO). Moreover, important information regarding the relative contribution of CH4 and CO2 activation routes towards carbon formation under DRM reaction conditions was derived by using isotopically labelled 13CO2 in the feed gas stream. Of interest was also the amount, and the transient rate, of carbon removal via the participation of support’s labile active oxygen species. Full article
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Open AccessArticle
Modification Mechanism of Spinel Inclusions in Medium Manganese Steel with Rare Earth Treatment
Metals 2019, 9(7), 804; https://doi.org/10.3390/met9070804 (registering DOI) -
Abstract
In aluminum deoxidized medium manganese steel, spinel inclusions are easily to form during refining, and such inclusions will deteriorate the toughness of the medium manganese steel. Rare earth inclusions have a smaller hardness, and their thermal expansion coefficients are similar to that of [...] Read more.
In aluminum deoxidized medium manganese steel, spinel inclusions are easily to form during refining, and such inclusions will deteriorate the toughness of the medium manganese steel. Rare earth inclusions have a smaller hardness, and their thermal expansion coefficients are similar to that of steel. They can avoid large stress concentrations around inclusions during the heat treatment of steel, which is beneficial for improving the toughness of steel. Therefore, rare earth Ce is usually used to modify spinel inclusions in steel. In order to clarify the modification mechanism of spinel inclusions in medium manganese steel with Ce treatment, high-temperature simulation experiments were carried out. Samples were taken step by step during the experimental steel smelting process, and the inclusions in the samples were analyzed by SEM-EDS. Finally, the experimental results were discussed and analyzed in combination with thermodynamic calculations. The results show that after Ce treatment, the amount of inclusions decrease, the inclusion size is basically less than 5 μm, and the spinel inclusions are transformed into rare earth inclusions. After Ce addition, Mn and Mg in the spinel inclusions are first replaced by Ce, and the spinel structure is destroyed to form CeAlO3. When the O content in the steel is low, S in the steel will replace the O in the inclusion, and CeAlO3 and spinel inclusions will be transformed into Ce2O2S. By measuring the total oxygen content of the steel, the total Ce content required for complete modification of spinel inclusions can be obtained. Finally, the critical conditions for the formation and transformation of inclusions in the Fe-Mn-Al-Mg-Ce-O-S system at 1873K were obtained according to thermodynamic calculations. Full article
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Open AccessArticle
Efficient Photocatalytic Hydrogen Peroxide Production over TiO2 Passivated by SnO2
Catalysts 2019, 9(7), 623; https://doi.org/10.3390/catal9070623 (registering DOI) -
Abstract
Photocatalysis provides an attractive strategy for synthesizing H2O2 at ambient condition. However, the photocatalytic synthesis of H2O2 is still limited due to the inefficiency of photocatalysts and decomposition of H2O2 during formation. Here, we [...] Read more.
Photocatalysis provides an attractive strategy for synthesizing H2O2 at ambient condition. However, the photocatalytic synthesis of H2O2 is still limited due to the inefficiency of photocatalysts and decomposition of H2O2 during formation. Here, we report SnO2-TiO2 heterojunction photocatalysts for synthesizing H2O2 directly in aqueous solution. The SnO2 passivation suppresses the complexation and decomposition of H2O2 on TiO2. In addition, loading of Au cocatalyst on SnO2-TiO2 heterojunction further improves the production of H2O2. The in situ electron spin resonance study revealed that the formation of H2O2 is a stepwise single electron oxygen reduction reaction (ORR) for Au and SnO2 modified TiO2 photocatalysts. We demonstrate that it is feasible to enhance H2O2 formation and suppress H2O2 decomposition by surface passivation of the H2O2-decomposition-sensitive photocatalysts. Full article
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Open AccessFeature PaperArticle
One-Point Optimal Family of Multiple Root Solvers of Second-Order
Mathematics 2019, 7(7), 655; https://doi.org/10.3390/math7070655 (registering DOI) -
Abstract
This manuscript contains the development of a one-point family of iterative functions. The family has optimal convergence of a second-order according to the Kung-Traub conjecture. This family is used to approximate the multiple zeros of nonlinear equations, and is based on the procedure [...] Read more.
This manuscript contains the development of a one-point family of iterative functions. The family has optimal convergence of a second-order according to the Kung-Traub conjecture. This family is used to approximate the multiple zeros of nonlinear equations, and is based on the procedure of weight functions. The convergence behavior is discussed by showing some essential conditions of the weight function. The well-known modified Newton method is a member of the proposed family for particular choices of the weight function. The dynamical nature of different members is presented by using a technique called the “basin of attraction”. Several practical problems are given to compare different methods of the presented family. Full article
Open AccessArticle
Molecular Dynamics Simulation on Mechanical and Piezoelectric Properties of Boron Nitride Honeycomb Structures
Nanomaterials 2019, 9(7), 1044; https://doi.org/10.3390/nano9071044 (registering DOI) -
Abstract
Boron nitride honeycomb structure is a new three-dimensional material similar to carbon honeycomb, which has attracted a great deal of attention due to its special structure and properties. In this paper, the tensile mechanical properties of boron nitride honeycomb structures in the zigzag, [...] Read more.
Boron nitride honeycomb structure is a new three-dimensional material similar to carbon honeycomb, which has attracted a great deal of attention due to its special structure and properties. In this paper, the tensile mechanical properties of boron nitride honeycomb structures in the zigzag, armchair and axial directions are studied at room temperature by using molecular dynamics simulations. Effects of temperature and strain rate on mechanical properties are also discussed. According to the observed tensile mechanical properties, the piezoelectric effect in the zigzag direction was analyzed for boron nitride honeycomb structures. The obtained results showed that the failure strains of boron nitride honeycomb structures under tensile loading were up to 0.83, 0.78 and 0.55 in the armchair, zigzag and axial directions, respectively, at room temperature. These findings indicated that boron nitride honeycomb structures have excellent ductility at room temperature. Moreover, temperature had a significant effect on the mechanical and tensile mechanical properties of boron nitride honeycomb structures, which can be improved by lowering the temperature within a certain range. In addition, strain rate affected the maximum tensile strength and failure strain of boron nitride honeycomb structures. Furthermore, due to the unique polarization of boron nitride honeycomb structures, they possessed an excellent piezoelectric effect. The piezoelectric coefficient e obtained from molecular dynamics was 0.702 C/m2, which was lower than that of the monolayer boron nitride honeycomb structures, e=0.79 C/m2. Such excellent piezoelectric properties and failure strain detected in boron nitride honeycomb structures suggest a broad prospect for the application of these new materials in novel nanodevices with ultrahigh tensile mechanical properties and ultralight-weight materials. Full article
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Open AccessArticle
Ethanol- and Methanol-Coordinated and Solvent-Free Dodecahydro closo-Dodecaborates of 3d Transition Metals and of Magnesium
Crystals 2019, 9(7), 372; https://doi.org/10.3390/cryst9070372 (registering DOI) -
Abstract
Magnesium and 3d transition metals closo-borates were prepared by mechanosynthesis (ball milling) of the mixtures Na2B12H12 + MCl2 (M = Mn, Fe, Co, Ni, Mg), followed by addition of ethanol or methanol and drying under [...] Read more.
Magnesium and 3d transition metals closo-borates were prepared by mechanosynthesis (ball milling) of the mixtures Na2B12H12 + MCl2 (M = Mn, Fe, Co, Ni, Mg), followed by addition of ethanol or methanol and drying under dynamic vacuum. The dead mass of NaCl is partly removed by filtration. The crystal structures of solvent-coordinated and solvent-free closo-borates have been characterized by temperature dependent synchrotron radiation X-ray powder diffraction, ab initio calculations, thermal analysis and infrared spectroscopy. Various solvated complexes containing six, four, three, two or one solvent molecules were obtained by successive removal of the solvent until in most case the solvent-free metal closo-borates were obtained with the exception of Mg whose hypothetical crystal structure, however, could have its prototype in MnB12H12. The 3d transition metal closo-borates were studied in the view of their potential use as Na- or Li-ion battery electrodes in combination with Na or Li closo-borate solid electrolytes. The metal oxidation state (II) obtained in compounds presented here does not allow such application. Full article
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Open AccessArticle
Nutrition Quality Parameters of Almonds as Affected by Deficit Irrigation Strategies
Molecules 2019, 24(14), 2646; https://doi.org/10.3390/molecules24142646 (registering DOI) -
Abstract
The influence of full irrigation, double-regulated (RDI) and sustained deficit irrigation (SDI) treatments on almond quality was assessed by analyzing different parameters: sugars, organic acids, antioxidant activity, total phenolic content (TPC), and volatile compounds. Almond quality studies for plants submitted to water stress [...] Read more.
The influence of full irrigation, double-regulated (RDI) and sustained deficit irrigation (SDI) treatments on almond quality was assessed by analyzing different parameters: sugars, organic acids, antioxidant activity, total phenolic content (TPC), and volatile compounds. Almond quality studies for plants submitted to water stress are scarce, and it is essential to understand the biochemical responses of plants to water stress in maintaining fruit yield and quality. Citric acid, sucrose, antioxidant activity, and TPC were not affected by the application of studied deficit irrigation strategies (DI). An increase in malic acid and a decrease in glucose was observed for stressed samples (T3 and T4), while a higher number of total volatiles compounds was found for moderate RDI (T2). Using deficit irrigation strategies, the almond yield and quality was not changed, and in fact, some parameters, such as glucose and key volatile compounds, slightly increased under moderate RDI. This finding might encourage farmers to implement these strategies and contribute to sustainable agriculture. Full article
Open AccessArticle
Molecular Structure and Antioxidant Properties of Alkali Metal Salts of Rosmarinic Acid. Experimental and DFT Studies
Molecules 2019, 24(14), 2645; https://doi.org/10.3390/molecules24142645 (registering DOI) -
Abstract
The molecular structure of alkali metal rosmarinates was studied in comparison to rosmarinic acid using FT-IR, FT-Raman, 1H and 13C NMR spectroscopy, as well as density functional theory (DFT) calculations. The B3LYP/6-311+G(d,p) method was used to calculate optimized geometrical structures of [...] Read more.
The molecular structure of alkali metal rosmarinates was studied in comparison to rosmarinic acid using FT-IR, FT-Raman, 1H and 13C NMR spectroscopy, as well as density functional theory (DFT) calculations. The B3LYP/6-311+G(d,p) method was used to calculate optimized geometrical structures of studied compounds, atomic charges, dipole moments, energies, as well as the wavenumbers and intensities of the bands in vibrational and NMR spectra. Theoretical parameters were compared to experimental data. Antioxidant activity was determined using two spectrophotometric methods: (i) Assessing the ability to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) stable radical and (ii) assay of antioxidant power of ferric ions reducing (FRAP). The linear correlations were found between HOMO–LUMO (highest occupied molecular orbital–lowest unoccupied molecular orbital) energy gap and the reducing power expressed as FRAP (R = 0.77) as well as between IC50 values (the ability of quenching DPPH radicals) and Δνas-s(COO) in IR spectra (differences between asymmetric and symmetric stretching vibrations bands) (R = 0.99). Photochemical properties of studied compounds were also evaluated. The influence of alkali metal on the electronic system of the rosmarinic acid molecule was discussed. Full article
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Open AccessArticle
Cold Plasma Treatment for Efficient Control over Algal Bloom Products in Surface Water
Water 2019, 11(7), 1513; https://doi.org/10.3390/w11071513 (registering DOI) -
Abstract
Algal bloom significantly alters the physicochemical properties of water due to drastic pH change, dissolved oxygen depletion/super-saturation, and toxicity, which lead to ecosystem destruction. To prevent this, this study evaluated the reduction performance of algal biomass by applying a non-thermal or cold plasma [...] Read more.
Algal bloom significantly alters the physicochemical properties of water due to drastic pH change, dissolved oxygen depletion/super-saturation, and toxicity, which lead to ecosystem destruction. To prevent this, this study evaluated the reduction performance of algal biomass by applying a non-thermal or cold plasma process. We used chlorophyll-a (chl-a), suspended solids (SS), and turbidity as indicators of the biomass. Results demonstrated that their removal efficiencies were in the ranges 88–98%, 70%–90%, and 53%–91%, respectively. Field emission scanning electron microscopy indicated how the cell wall of microalgae was destroyed by cold plasma. Also, the removal kinetics of cold plasma confirmed the enhanced removal rate constants. The estimated required times for 99% removal were 0.4–1.2 d (chl-a), 1.3–3.4 d (SS), and 1.6–6.2 d (turbidity), respectively. Overall, cold plasma could be a useful option to effectively treat pollution associated with algal bloom in surface water. Full article
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Open AccessArticle
Understanding the Global Sensory Landscape for Facial Cleansing/Makeup Remover Wipes
Cosmetics 2019, 6(3), 44; https://doi.org/10.3390/cosmetics6030044 (registering DOI) -
Abstract
Makeup chemistries have evolved over the recent years and have become more long-wearing, waterproof and difficult to remove. Thus, many changes have occurred among products designed to remove makeup. Specifically, the facial cleansing/makeup remover wipes category is challenged to establish new strategies and [...] Read more.
Makeup chemistries have evolved over the recent years and have become more long-wearing, waterproof and difficult to remove. Thus, many changes have occurred among products designed to remove makeup. Specifically, the facial cleansing/makeup remover wipes category is challenged to establish new strategies and adapt to the changing consumer needs and the evolving competitive landscape. A global product category review can provide the upfront understanding necessary to establish fundamental knowledge. That knowledge can in turn be leveraged when developing future products. A customized descriptive analysis method was applied to address the unique challenges of the category. The method leveraged existing methods and was augmented with new descriptive modalities, specific to the unique developments in the category. A total of seventy-one attributes were identified that spanned visual and tactile cues of the wipes, cleansing performance cues during use, as well as skin look and feel attributes after use. Thirteen facial cleansing/makeup remover wipes from global markets were selected for testing based on commercial and historical insights. Three sensorial perceptual maps were generated displaying the profiles of the thirteen products in three areas of product properties—visual and tactile, cleaning performance, and skin look and feel. These study results combined with existing consumer insights helped the R&D team to establish strategies to guide product development for this category. Full article
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Open AccessArticle
Residual Stress, Microstructure and Mechanical Properties in Thick 6005A-T6 Aluminium Alloy Friction Stir Welds
Metals 2019, 9(7), 803; https://doi.org/10.3390/met9070803 (registering DOI) -
Abstract
Plates (37 mm thick) of 6005A-T6 aluminum alloy were butt joined by a single-sided and double-sided friction stir welding (FSW). The 3D residual stresses in the joints were determined using neutron diffraction. The microstructures were characterized by a transmission electron microscope (TEM) and [...] Read more.
Plates (37 mm thick) of 6005A-T6 aluminum alloy were butt joined by a single-sided and double-sided friction stir welding (FSW). The 3D residual stresses in the joints were determined using neutron diffraction. The microstructures were characterized by a transmission electron microscope (TEM) and electron backscatter diffraction (EBSD). In the single-sided FSW specimen, there were acceptable mechanical properties with a tensile strength of 74.4% of base metal (BM) and low residual stresses with peak magnitudes of approximately 37.5% yield strength of BM were achieved. The hardness is related to the grain size of the nugget zone (NZ), and in this study, precipitations were dissolved due to the high heat input. In the double-sided FSW specimen, there were good mechanical properties with a tensile strength of 80.8% of BM, but high residual stresses with peak magnitudes of approximately 70% yield strength of BM were obtained. The heat input by the second pass provided an aging environment for the first-pass weld zone where the dissolved phases were precipitated and residual stresses were relaxed. Full article
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Open AccessArticle
Neurological Enhancement Effects of Melatonin against Brain Injury-Induced Oxidative Stress, Neuroinflammation, and Neurodegeneration via AMPK/CREB Signaling
Cells 2019, 8(7), 760; https://doi.org/10.3390/cells8070760 (registering DOI) -
Abstract
Oxidative stress and energy imbalance strongly correlate in neurodegenerative diseases. Repeated concussion is becoming a serious public health issue with uncontrollable adverse effects in the human population, which involve cognitive dysfunction and even permanent disability. Here, we demonstrate that traumatic brain injury (TBI) [...] Read more.
Oxidative stress and energy imbalance strongly correlate in neurodegenerative diseases. Repeated concussion is becoming a serious public health issue with uncontrollable adverse effects in the human population, which involve cognitive dysfunction and even permanent disability. Here, we demonstrate that traumatic brain injury (TBI) evokes oxidative stress, disrupts brain energy homeostasis, and boosts neuroinflammation, which further contributes to neuronal degeneration and cognitive dysfunction in the mouse brain. We also demonstrate that melatonin (an anti-oxidant agent) treatment exerts neuroprotective effects, while overcoming oxidative stress and energy depletion and reducing neuroinflammation and neurodegeneration. Male C57BL/6N mice were used as a model for repetitive mild traumatic brain injury (rmTBI) and were treated with melatonin. Protein expressions were examined via Western blot analysis, immunofluorescence, and ELISA; meanwhile, behavior analysis was performed through a Morris water maze test, and Y-maze and beam-walking tests. We found elevated oxidative stress, depressed phospho-5′AMP-activated protein kinase (p-AMPK) and phospho- CAMP-response element-binding (p-CREB) levels, and elevated p-NF-κB in rmTBI mouse brains, while melatonin treatment significantly regulated p-AMPK, p-CREB, and p-NF-κB in the rmTBI mouse brain. Furthermore, rmTBI mouse brains showed a deregulated mitochondrial system, abnormal amyloidogenic pathway activation, and cognitive functions which were significantly regulated by melatonin treatment in the mice. These findings provide evidence, for the first time, that rmTBI induces brain energy imbalance and reduces neuronal cell survival, and that melatonin treatment overcomes energy depletion and protects against brain damage via the regulation of p-AMPK/p-CREB signaling pathways in the mouse brain. Full article
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