Presence Of MgO Research Articles

Methylglyoxal potentiates thrombin and collagen‐induced human platelet aggregation.

ObjectivesMethylglyoxal (MGO), a metabolite of the glycolysis pathway, is a precursor of advanced glycation end products (AGE). Levels of MGO are elevated in pre‐diabetic and diabetic patients (Dornadula 2015 et al. Chem Res Toxicol. 2015;28:1666–74). Because increased AGE formation has been proposed as one mechanism involved in vascular complications and platelet activation of diabetes (Hadas K et al, Plos One, 8:e74401; 2013), this study aimed to evaluate the effects of MGO on the human washed platelet aggregation induced by thrombin and collagen.MethodsThe study was approved by the local Ethics Committee (Protocol No. 66299817.4.0000.5137). Platelets were isolated from peripheral blood of human healthy volunteers (7 men and 10 women, aged 27.8±1.9 y.o.). Platelet samples (200 μL) were incubated with MGO (0.08–0.64 mM), and subsequently activated with either thrombin (0.01 to 1.0 U/ml) or collagen (0.2 to 20 μg/ml). Platelet aggregation was performed with an optical aggregometer (PAP‐8E Platelet Aggregation Profiler, PA, USA).ResultsThrombin produced concentration‐dependent platelet aggregation, achieving a maximum response at 0.3 and 1 U/ml (0.8 ± 0.5, 15.7±4.7, 27.8±5.5, 59.6±5.4 and 63.9±3.3% for 0.01, 0.03, 0.1, 0.3 and 1 U/ml, respectively). Pre‐incubation with MGO (0.08 mM) markedly increased (p<0.001) the thrombininduced platelet aggregation (14.0±13.5, 50.6±4.7, 72.4±4.2, 79.4±4.4 and 77.2±2.7%, respectively). Similar data were observed using higher concentrations of MGO (0.16 and 0.64 mM). In separate samples, addition of collagen induced concentration‐dependent platelet aggregation (0.2±0.2, 8.6±3.7, 14.4±4.4, 41.4±4.9 and 53.2±5.3 for 0.2, 1.0, 2.0, 10.0 and 20.0ug respectively). Pre‐incubation with MGO (0.08 mM) significantly increased (p<0.001) the collagen‐induced aggregation (0.5±0.3, 38.7±11.5, 38.3±6.8, 56.8±4.9 and 57.1±4.9 respectively). Higher concentrations of MGO (0.16 and 0.64 mM) also significantly potentiated collagen‐induced aggregation. MGO incubated had no effect in the absence of thrombin or collagen. Next, we evaluated if the potentiation of thrombin‐ and collagen‐induced platelet aggregation by MGO was due to inactivation of nitric oxide (NO) – cyclic GMP signaling Incubation of the NO donor sodium nitroprusside (3uM) inhibited by 32,7% a 60,9% (p<0.05) the thrombin‐ and collagen‐induced aggregation, respectively. However, MGO (0.08 e 0.16 mM) had no effect on the inhibitory effect of SNP on thrombin‐ and collagen‐induced aggregation. We also evaluated the protein expression by western blotting of both α1 and β1 subunits of soluble guanylate cyclase in the absence and presence of MGO. However, MGO did not significantly modify the expression of either subunits.ConclusionMGO enhances human platelet aggregation induced by thrombin and collagen by mechanisms independent of inactivation of NO‐cGMP signaling.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Análisis de la bioactividad de Mg AZ31 recubierta por PEO (Plasma Electrolytic Oxidation)

El Magnesio es un material que presenta propiedades favorables para su selección como biomaterial; sin embargo, su aplicación se ve restringida por la rápida corrosión. En esta investigación se evaluó la modificación superficial de magnesio AZ31 mediante PEO y su efecto sobre las propiedades protectoras y bioactivas. La microestructura, composición de la fase y la distribución de los elementos en el recubrimiento fue caracterizada mediante MEB, DRX y EDX. La estabilidad química, la resistencia a la corrosión, la bioactividad y las propiedades electrónicas se evaluaron usando EIE y Mott-Schottky en solución de fluido corporal simulado. El análisis de DRX y EDX índico la presencia de MgO, MgSiO4 en los recubrimientos. Un análisis de la sección transversal presento un recubrimiento compacto cerca al sustrato seguido por un estrato poroso en la superficie. Del análisis de EIE se mostró que el tratamiento incrementa la protección del sustrato en un medio fisiológico simulado.

COMBINED STEAM AND CO2 REFORMING OF CH4 OVER NICKEL CATALYSTS BASED ON Al2O3–MO (M= Mg, Ca, Ba)

A series of 10 wt% Ni/Al2O3–MO (M = Mg, Ca, Ba) catalyst was prepared by impregnation method for applying in the combined steam and carbon dioxide reforming of methane (CSCRM). In this study, five supported nickel catalysts were impregnated on different supports. All of the supports have been obtained by co–precipitation method and also have been investigated. Several techniques, including N2 physisorption measurements, X–ray powder diffraction (XRD), temperature–programmed reduction using H2 (H2–TPR), and transmission electron microscopy (TEM) were used to investigate catalysts’ physicochemical properties. The results showed that MgO was the most suitable promoter comparing with CaO and BaO in CSCRM. The presence of MgO in Ni/Al2O3 changed catalysts’ characteristics leading to an increase in the catalytic activity and stability with time on stream (TOS). It was found that the suitable catalyst was Ni–based on Al2O3–MgO of mass ratio 2:1 which showed a high metal dispersion as well as dominated spinel structure. The CH4 and CO2 conversion at 800 °C reached 99.8 % and 51.7 %, respectively. Catalytic stability of this catalyst with TOS at 800 °C could reach to more than 20 hours until it started decreasing.

Ozonation inactivation of Escherichia coli in aqueous solution over MgO nanocrystals: modelling and mechanism

AbstractBACKGROUNDThis study aims to reveal the potential of using heterogeneous catalytic ozonation processes (HCOP) in water disinfection and provide a direction to tailor the catalytic activity by crystal facet engineering. Four kinds of MgO nanocrystals individually with exposure of (111), (200), (110) and (100) facets were prepared and used.RESULTSIt is found that MgO functions as a bactericide as well as a catalyst for ozonation. The catalytic activity of MgO nanocrystals decreases in the order MgO(111) > MgO(200) > MgO(110) > MgO(100). The apparent first‐order inactivation rate (kap) fitted by the Hom model of MgO(111)/O3 is 2.56 min‐1, which is 32.0 and 3.5 times that of single ozonation and classic MgO(100)/O3. It is confirmed by scavenger studies that •OH mainly works in MgO(111)/O3 while more direct ozonation occurs in other cases. Some O2•− are also detected in the presence of MgO. With the attack of these reactive oxidation species, cell membranes were damaged and intracellular components were released, leading to the death of Escherichia coli.CONCLUSIONThese results indicate that HCOP is a promising technology for water disinfection, and crystal facet engineering is an effective strategy to enhance the catalytic performance. © 2017 Society of Chemical Industry

Thermoelectric Properties and Transport Mechanism of Pure and Bi‐Doped SiNWs‐Mg2Si

Through the use of nano‐Si wires as additive, a significant improvement in the thermoelectric (TE) properties of Mg2Si is achieved. SiNWs‐Mg2Si materials are prepared by a wet etching method followed by field activated pressure assisted synthesis (FAPAS). The results show that the presence of SiNWs successfully decouples the relationship between the electrical resistivity and the Seebeck coefficient of Mg2Si. The effect of doping with Bi is also investigated. The results show that the addition of Bi changed the scattering mechanism, and a zT value of 0.47 is determined at 800 K for Mg2Si0.99Bi0.01‐0.005SiNWs. The presence of MgO as an impurity and its effect on zT are discussed.

Physicochemical properties and methane adsorption performance of activated carbon nanofibers with different types of metal oxides

In this study, composite PAN-based ACNFs embedded with MgO and MnO2 were prepared by the electrospinning method. The resultant pristine ACNFs, ACNF/MgO and ACNF/MnO2 were characterized in terms of their morphological changes, SSA, crystallinity and functional group with FESEM-EDX, the BET method, XRD and FTIR analysis, respectively. Results from this study showed that the SSA of the ACNF/MgO composite (1893 m2 g–1) is significantly higher than that of the pristine ACNFs and ACNF/MnO2 which is 478 and 430 m2 g–1, respectively. FTIR analysis showed peaks of 476 and 547 cm–1, indicating the presence of MgO and MnO2, respectively. The FESEM micrographs analysis showed a smooth but coarser structure in all the ACNFs. Meanwhile, the ACNF/MgO has the smallest fiber diameter (314.38±62.42 nm) compared to other ACNFs. The presence of MgO and MnO2 inside the ACNFs was also confirmed with EDX analysis as well as XRD. The adsorption capacities of each ACNF toward CH4 were tested with the volumetric adsorption method in which the ACNF/MgO exhibited the highest CH4 adsorption up to 2.39 mmol g–1. Meanwhile, all the ACNF samples followed the pseudo-second order kinetic model with a R2 up to 0.9996.

Effect of MgO on WO3/SiO2-catalyzed light olefin metathesis using different feedstocks

Different feedstocks were adopted to undergo reactions catalyzed by WO3/SiO2 and WO3/SiO2-MgO catalysts to better understand the effect of MgO on the process. The results of 1-butene self-metathesis show that, although the isomerization of 1-butene was clearly enhanced by MgO, the propylene selectivity was not improved because of insufficient 1-butene or ethylene. The main route to produce propylene in this system is through cross-metathesis of 1-butene and 2-butene. When propylene was used as the feed, more 2-butene, which was produced from propylene self-metathesis, was transformed into 1-butene by the addition of MgO, resulting in an improved metathesis performance between 1-butene and propylene. The cross-metathesis of 2-butene and ethylene, however, did not show an significant enhancement by MgO. In addition, the analysis on n-butene isomers distribution reveals that the presence of MgO is helpful in keeping the isomers at their theoretical values, leading to the good stability of the reactions. Lastly, a further comparison for the reactions between trans-2-butene and cis-2-butene demonstrates that there is little difference in their metathesis reactivity.

Réduction de volume dans l’emphysème pulmonaire: Lung volume reduction in pulmonary emphysema

The carbothermic reduction of Panzhihua ilmenite with activated carbon in vacuum was investigated by isothermal experiments over the temperature range of 1473–1773 K. The reaction mechanism of the impurity elements in vacuum was investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and thermodynamic calculation. It was found that when the reaction temperature was higher than 1673 K and the reaction time was longer than 4 h, the main phases of the final products obtained at 10 Pa were Fe and TiC, without the presence of MgO and MgAl2O4 which existed when roasting at 1 atm in argon atmosphere. The contents of Mg and Mn in the products decreased with increasing the reaction temperature or lowering the pressure. After the carbothermic reduction process, the main impurity elements of Si and Al were dissolved in the iron.

Effects of MgO and SiO2 on Plasma-Sprayed Hydroxyapatite Coating: An in Vivo Study in Rat Distal Femoral Defects.

Plasma-sprayed hydroxyapatite (HA)-coated titanium implants have been widely used in orthopedic applications due to their inheritance of an excellent mechanical property from titanium and great osteoconductivity from HA. However, the lack of osteoinductivity limits their further applications. In this study, 1 wt % MgO and 0.5 wt % SiO2 were mixed with HA for making plasma-sprayed coatings on titanium implants. Plasma-sprayed HA- and MgO/SiO2-HA-coated titanium implants showed adhesive bond strengths of 25.73 ± 1.92 and 23.44 ± 2.89 MPa, respectively. The presence of MgO and SiO2 significantly increased the osteogenesis, osseointegration, and bone mineralization of HA-coated titanium implants by the evaluation of their histomorphology after 6, 10, and 14 weeks of implantation in rat distal femoral defects. Implant pushout tests also showed a shear modulus of 149.83 ± 3.69 MPa for MgO/SiO2-HA-coated implants after 14 weeks of implantation, compared to 52.68 ± 10.41 MPa for uncoated implants and 83.92 ± 3.68 MPa for pure HA-coated implants; These are differences in the shear modulus of 96% and 56.4%, respectively. This study assesses for the first time the quality of the bone-implant interface of induction plasma-sprayed MgO and SiO2 binary-doped HA coatings on load-bearing implants compared to bare titanium and pure HA coatings in a quantitative manner. Relating the osseointegration and interface shear modulus to the quality of implant fixation is critical to the advancement and implementation of HA-coated orthopedic implants.

STUDY OF BEACHROCKS IN EAST ATTICA

Sea level indicators, such as tidal notches and beachrocks, may provide valuable information for the relative sea level changes of an area. Beachrocks in particular have received various arguments concerning their use as reliable sea level indicators and their formation environment. This work focuses on the coasts of East Attica in order to trace the palaeoshorelines of the Upper Holocene through the study of beachrocks. The coastal zone was surveyed in detail by snorkelling and diving, in order to locate, map and sample beachrocks. The samples were studied under a SEM, which showed that the beachrocks are mainly composed of quartz grains, a few calcites and feldspars, while the carbonate cement is characterized with the presence of MgO at percentages between 5 and 7.8%. Based on correlations with published drillings in the study area, the studied beachrocks should not be older than 2000 years BP.

Deep study of MgCl2 as activator in CdS/CdTe solar cells

Abstract The activation process using chlorine compounds is considered an important issue in CdTe solar cells technology. For a long time researchers have tried to replace the most successful CdCl 2 activator with a non-toxic compound more suitable for industrial production. In the last years many alternatives were presented, among them the most promising is the MgCl 2 . In this work we study the CdTe activated using MgCl 2 solution. Its chemical, physical and electrical transformations were deeply investigated. FESEM, EDS, XRD, and XPS characterization bring out the presence of MgO and residues of another’s oxides on the CdTe surface. The impact of these oxides on the solar cell performance was studied by EQE, J-V , C-V and DLCP . The solar cell activated with MgCl 2 had an efficiency of 12.5%; the V oc , J sc and FF were 831 mV, 23.3 mA/cm 2 and 64.5%, respectively, in a device with an area of 0.5 cm 2 .

Carbothermic reduction of Panzhihua ilmenite in vacuum

The carbothermic reduction of Panzhihua ilmenite with activated carbon in vacuum was investigated by isothermal experiments over the temperature range of 1473–1773 K. The reaction mechanism of the impurity elements in vacuum was investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and thermodynamic calculation. It was found that when the reaction temperature was higher than 1673 K and the reaction time was longer than 4 h, the main phases of the final products obtained at 10 Pa were Fe and TiC, without the presence of MgO and MgAl2O4 which existed when roasting at 1 atm in argon atmosphere. The contents of Mg and Mn in the products decreased with increasing the reaction temperature or lowering the pressure. After the carbothermic reduction process, the main impurity elements of Si and Al were dissolved in the iron.

Effect of magnesium on calcium silicate hydrate (C-S-H)

The addition of MgCl2 to synthetic calcium silicate hydrate (C-S-H) with Ca/Si=0.8 lowers the pH values below 10. Experimental observations and thermodynamic calculations show the destabilization of C-S-H and the precipitation of magnesium silicate hydrate (M-S-H). In contrast, the addition of MgO to C-S-H increases the pH values up to 11.5 and the Ca/Si in C-S-H from 0.8 to ~1.0. At high pH, the formation of M-S-H and brucite is observed experimentally. Less brucite is present at 50 than at 20°C indicating a slow dissolution kinetic of brucite at 20°C. Thermodynamic modelling is in good agreement with the changes in C-S-H and M-S-H formation in the presence of MgO although no brucite is predicted.M-S-H is observed in the presence of both MgCl2 and MgO, is stable from pH7.5 to 11.5 and has a structure comparable to the structure of M-S-H prepared from MgO and SiO2 only.

Effect of the addition of different sintering aids on the densification behavior of zirconia-toughened alumina nanocomposite powder

AbstractIn the present study, Al2O3-5 wt.% ZrO2 nanocomposite powder was fabricated via the sol–gel method, and then the sintering behavior was investigated using various sintering aids (MgO, TiO2 and MgO/TiO2) at different temperatures. In this regard, the size and structure of fabricated powder, and hardness, fracture toughness and density of sintered samples were studied. The results of X-ray diffraction indicated the presence of α-alumina and tetragonal zirconia. Scanning electron micrographs revealed agglomerated nanometer-sized spherical particles ranging in size from 60 to 150 nm. Energy-dispersive X-ray mapping micrographs also demonstrated the homogeneous dispersion of zirconia in alumina. Moreover, density results indicated that using 0.5 wt.% MgO/0.5 wt.% TiO2 produced the best results, as the relative density reached 95 % at 1 500 °C. Finally, it was observed that the presence of MgO and TiO2 induces higher hardness and lower fracture toughness.

Phase and microstructural evolution based on Al, Si and TiO2 reactions with a MgO-C resin-bonded refractory

Adding carbon to refractory products (i.e. MgO-C) usually results in unique properties that allow these materials to attain the performance level required for the steel-making process. Nevertheless, C oxidation is still a big concern and using antioxidant additives has become an important alternative to prevent carbon loss and induce the generation of further compounds (carbides, nitrides, etc.) in the fired microstructure, which will affect the overall thermo-mechanical behavior of the refractories. Aiming to better understand the main phase transformations derived from the interaction of polymeric binders with antioxidants and other refractory components in the MgO-C system, this work addresses the evaluation of mixtures containing novolak resin + antioxidants (Al, Si, and/or TiO2) and: (i) fine MgO, (ii) ferrocene (catalyst for carbon graphitization), and (iii) coal-tar-based binder. X-ray diffraction, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses were carried out in order to identify the main phases comprising the fired samples (kept at 1000°C and 1400°C for 5h in a reducing environment) and observe their morphology and distribution in the resultant microstructure. Based on the attained results, a great variety of whiskers with different shapes, dimensions and distributions were also observed on the fractured surface of the prepared samples containing antioxidants. Furthermore, not only the carbon graphitization, but also the presence of MgO and other binders (Carbores® P) affected the phase evolution at a high temperature, which highlights the complexity of phase transformations and the many likely interactions derived from the combination of various raw materials.

Theory of perpendicular magnetocrystalline anisotropy in Fe/MgO (001)

The origin of large perpendicular magnetocrystalline anisotropy (PMCA) in Fe/MgO (001) is revealed by comparing Fe layers with and without the MgO. Although Fe-O p-d hybridization is weakly present, it cannot be the main origin of the large PMCA as claimed in previous study. Instead, perfect epitaxy of Fe on the MgO is more important to achieve such large PMCA. As an evidence, we show that the surface layer in a clean free-standing Fe (001) dominantly contributes to EMCA, while in the Fe/MgO, those by the surface and the interface Fe layers contribute almost equally. The presence of MgO does not change positive contribution from 〈xz|ℓZ|yz〉, wherease it reduces negative contribution from 〈z2|ℓX|yz〉 and 〈xy|ℓX|xz,yz〉.

Development of low-carbon cementitious materials via carbonating Portland cement–fly ash–magnesia blends under various curing scenarios: a comparative study

This study investigates a potential approach to produce low-carbon cementitious materials via using fly ash and reactive MgO as cement replacements, exposed to a pressurized CO2 curing regime. Pressurized CO2 with a concentration of 99.9% and pressures ranging from 0.1 MPa to 1.0 MPa were employed to accelerate the carbonation of MgO–fly ash–PC (Portland cement) blends in which up to 60% of PC was replaced with reactive MgO and fly ash. The carbon footprint of each cementitious material produced under various curing scenarios is evaluated based on life cycle assessment. Results indicate that after exposure to pressurized CO2, the cement pastes exhibited fast CO2 uptake, rapid compressive strength gain and microstructure densification due to the formation of carbonate products in terms of CaCO3 and/or (Ca, Mg)CO3 due to the incorporation of Mg2+ at the presence of MgO. The addition of fly ash facilitated carbonation, as it produced a more permeable microstructure for the ingress of CO2. A more rapid CO2 uptake and compressive strength development of the cement pastes was obtained as higher-pressure CO2 was used. In comparison to moist curing, pressurized CO2 curing yielded less carbon emissions. The CO2 emissions of the cement pastes decreased with increasing fly ash content as cement replacement but increased with the increase of MgO content from 20 to 40% by mass.

A facile, novel and low-temperature synthesis of MgO nanorods via thermal decomposition using new starting reagent and its photocatalytic activity evaluation

Herein, the MgO nanorods were successfully synthesized via a facile, novel and solvent-free thermal decomposition route at low temperature using Mg–MOF as a new starting reagent for the first time. The Mg–MOF was prepared via fast microwave-based method using 2,6-pyridinedicarboxylic acid ammonium and Mg(NO3)2·2H2O. Furthermore, the efficiency of MgO nanostructures as a photocatalyst for decolorization of methylene blue (MB) under visible light irradiation has been evaluated. The synthesized MgO nanostructures exhibited appreciable photocatalytic activity and in presence of MgO, 90% degradation of MB was obtained after 180min.

Direct synthesis of dimethyl ether from syngas over Cu-based catalysts: Enhanced selectivity in the presence of MgO

Direct synthesis of dimethyl ether (DME) from syngas was investigated over a series of hybrid catalytic systems containing a Cu-based methanol synthesis component with varying amounts of ZnO and MgO, and γ-Al2O3 as a methanol dehydration component. Methanol synthesis and methanol dehydration components were homogeneously mixed in a 2:1 weight ratio to prepare the hybrid catalysts, which were characterized by transmission electron microscopy, scanning electron microscopy, BET surface area analysis, powder X-ray diffraction, NH3 temperature-programmed desorption, and H2 temperature-programmed reduction methods. The syngas-to-DME (STD) reaction was studied in an isothermal fixed bed reactor at 30bar and 260°C. The catalysis results revealed improved effectiveness of the catalyst in the presence of 20mol% MgO, enabling a significant enhancement in CO conversion from 19% to 37% and in DME selectivity from 36% to 83%, as compared with the activity of a catalyst without MgO. By-product CO2 and C1 and C2 hydrocarbon selectivity was also decreased from 48% to 14% for CO2 and from 8% to 2.5% for hydrocarbons. Catalyst performance, CO conversions and DME selectivity were evaluated by varying the reaction temperature, pressure, space velocity and H2/CO ratio in syngas. XRD data revealed the formation of a good crystalline malachite structure for the catalysts containing up to 20mol% MgO, but the crystallinity in the structure was lost when 30% MgO was added, resulting in decreased catalytic activity.

Vapour phase transfer hydrogenation of α,β-unsaturated carbonyl compounds. Thermodynamic and experimental studies

This paper presents the first systematic thermodynamic study of the vapour phase transfer hydrogenation of α,β-unsaturated carbonyl compounds at temperatures: 423.15–723.15K. Calculations were made for four compounds, namely: acrolein, α-methylacrolein, β-methylacrolein and methyl vinyl ketone. The Gibbs free energies and equilibrium mole fractions (EMFs) were calculated for transfer hydrogenation with ethanol and 2-propanol as hydrogen donors. It was noted that for transfer hydrogenation and hydrogenation with hydrogen the formation of the unsaturated alcohol (UOL) is the least thermodynamically favoured reaction and that saturated alcohol (SOL) and saturated aldehyde or ketone (SAL or SON) are the main products.A set of eight carbonyl compounds have been transfer hydrogenated with ethanol and 2-propanol in the presence of MgO as the catalyst. The main conclusions are that: (a) the reduction of a carbonyl group into a carbinol group occurs with a very high selectivity, (b) for almost all carbonyl compounds, except acrolein, the reactivity of 2-propanol highly exceeded that shown by ethanol and (c) the high chemoselectivity of transfer hydrogenation of acrolein with alcohols resulted from the kinetic control caused by the presence of magnesium oxide.