Range Of Mg Concentrations Research Articles

High Magnesium Corrosion Rate has an Effect on Osteoclast and Mesenchymal Stem Cell Role During Bone Remodelling

The aim of this study was to gain an understanding on the collective cellular effects of magnesium (Mg) corrosion products on the behaviour of cells responsible for bone formation and remodelling. The response of mesenchymal stem cells (MSCs) and osteoclast cells to both soluble (Mg ions) and insoluble (granule) corrosion products were recapitulated in vitro by controlling the concentration of the corrosion products. Clearance of corrosion granules by MSCs was also inspected by TEM analysis at sub-cellular level. The effect of Mg corrosion products varied depending on the state of differentiation of cells, concentration and length of exposure. The presence of the corrosion products significantly altered the cells’ metabolic and proliferative activities, which further affected cell fusion/differentiation. While cells tolerated higher than physiological range of Mg concentration (16 mM), concentrations below 10 mM were beneficial for cell growth. Furthermore, MSCs were shown to contribute to the clearance of intercellular corrosion granules, whilst high concentrations of corrosion products negatively impacted on osteoclast progenitor cell number and mature osteoclast cell function.

Structural, optical and photocatalytic properties of MgO/ZnO nanocomposites prepared by a hydrothermal method

MgO/ZnO nanocomposites were synthesized by a hydrothermal method at 180°C for 15h. The XRD results showed that MgO phase occurred over the whole range of Mg concentration used. The MgO induced a growth of crystallite size of ZnO. The particle shape of ZnO altered from an agglomerated nanosheet to a hexagonal platelet when loading with MgO and MgO was shaped in small rod structures. The optical band gap was increased from 3.190 to 3.225eV. The photocatalytic degradation depended upon the irradiation time and MgO loading contents. In this study, the 5mol% MgO/ZnO nanocomposite exhibited the best photocatalytic degradation of 98.3% during irradiation by blacklight for 90min.

Effect of Magnesium on the Crystal Transformation and Electrochemical Properties of A2B7-Type Metal Hydride Alloys

The effect of Mg content on crystal transformation and electrochemical characteristics of La2-xMgxNi7 (x = 0.40–0.60) alloys has been studied. It is found that alloys with allotropic structures Ce2Ni7-type (2H) and Gd2Co7-type (3R) phases exist in a range of Mg concentration from 0.48 to 0.50. Beyond that range, further increasing Mg to 0.60 is favorable for the formation of PuNi3-type phase due to the rising ratio of [A2B4] to [AB5] slabs in regard to the demand of La and Ni atoms for Mg to assemble [A2B4] slabs. Conversely, the surplus of La and Ni atoms for Mg to assemble [A2B4] slabs lowers the ratio of [A2B4] to [AB5] slabs, which helps the formation of CaCu5-type phase as Mg decreases to 0.40. Electrochemical studies show that the electrochemical properties of the alloy electrodes with allotropic phases are superior in discharge capacity (388 mAh g−1) and cycling stability (78% capacity retaining rate at 100th cycle). Appearance of PuNi3-type or CaCu5-type phase reduces the cycling stability, while CaCu5-type phase can significantly improve the high rate dischargeablity (HRD) of the alloy electrode.

Magnesium Impacts Myosin V Motor Activity by Altering Key Conformational Changes in the Mechanochemical Cycle

We investigated how magnesium (Mg) impacts key conformational changes during the ADP binding/release steps in myosin V and how these alterations impact the actomyosin mechanochemical cycle. The conformation of the nucleotide binding pocket was examined with our established FRET system in which myosin V labeled with FlAsH in the upper 50 kDa domain participates in energy transfer with mant labeled nucleotides. We examined the maximum actin-activated ATPase activity of MV FlAsH at a range of free Mg concentrations (0.1-9 mM) and found that the highest activity occurs at low Mg (0.1-0.3 mM), while there is a 50-60% reduction in activity at high Mg (3-9 mM). The motor activity examined with the in vitro motility assay followed a similar Mg-dependence, and the trend was similar with dimeric myosin V. Transient kinetic FRET studies of mantdADP binding/release from actomyosin V FlAsH demonstrate that the transition between the weak and strong actomyosin.ADP states is coupled to movement of the upper 50 kDa domain and is dependent on Mg with the strong state stabilized by Mg. We find that the kinetics of the upper 50 kDa conformational change monitored by FRET correlates well with the ATPase and motility results over a wide range of Mg concentrations. Our results suggest the conformation of the upper 50 kDa domain is highly dynamic in the Mg free actomyosin.ADP state, which is in agreement with ADP binding being entropy driven in the absence of Mg. Overall, our results demonstrate that Mg is a key factor in coupling the nucleotide- and actin-binding regions. In addition, Mg concentrations in the physiological range can alter the structural transition that limits ADP dissociation from actomyosin V, which explains the impact of Mg on actin-activated ATPase activity and in vitro motility.

Self-assembled MgxZn1−xO quantum dots (0 ≤ x ≤ 1) on different substrates using spray pyrolysis methodology

By using the spray pyrolysis methodology in its classical configuration we have grown self-assembled MgxZn1−xO quantum dots (size ∼4–6 nm) in the overall range of compositions 0 ≤ x ≤ 1 on c-sapphire, Si (100) and quartz substrates. Composition of the quantum dots was determined by means of transmission electron microscopy-energy dispersive X-ray analysis (TEM-EDAX) and X-ray photoelectron spectroscopy. Selected area electron diffraction reveals the growth of single phase hexagonal MgxZn1−xO quantum dots with composition 0 ≤ x ≤ 0.32 by using a nominal concentration of Mg in the range 0 to 45%. Onset of Mg concentration about 50% (nominal) forces the hexagonal lattice to undergo a phase transition from hexagonal to a cubic structure which resulted in the growth of hexagonal and cubic phases of MgxZn1−xO in the intermediate range of Mg concentrations 50 to 85% (0.39 ≤ x ≤ 0.77), whereas higher nominal concentration of Mg ≥ 90% (0.81 ≤ x ≤ 1) leads to the growth of single phase cubic MgxZn1−xO quantum dots. High resolution transmission electron microscopy and fast Fourier transform confirm the results and show clearly distinguishable hexagonal and cubic crystal structures of the respective quantum dots. A difference of 0.24 eV was detected between the core levels (Zn 2p and Mg 1s) measured in quantum dots with hexagonal and cubic structures by X-ray photoemission. The shift of these core levels can be explained in the frame of the different coordination of cations in the hexagonal and cubic configurations. Finally, the optical absorption measurements performed on single phase hexagonal MgxZn1−xO QDs exhibited a clear shift in optical energy gap on increasing the Mg concentration from 0 to 40%, which is explained as an effect of substitution of Zn2+ by Mg2+ in the ZnO lattice.

Effect of phase transition on the optoelectronic properties of Zn1−xMgxS

Density functional calculations are performed to investigate the structural, electronic, and optical properties of Zn1−xMgxS (0 ≤ x ≤ 1). In the present DFT calculations, we used modified Becke-Johnson potential in the exchange and correlation energy, which is effective for the treatment of the d-orbitals. A structural phase transition from zinc-blende to rock-salt is observed at 73% magnesium, which is consistent with the experimental results. Furthermore, the alloy has direct band gap nature for the whole range of Mg concentration in the zinc-blende structure, while the band gap nature for the rock-salt phase is indirect. The zinc-blende crystal structure has many established applications in the UV optoelectronic devices, and therefore the maintenance of the compound in zinc-blende crystal structure for the maximum range of Mg-composition is highly desirable which is dependent on the composition rate, external environment, and thickness of the film. Keeping in view the importance of ZnMgS in UV optical devices, its optical properties like dielectric functions, refractive indices, reflectivity, and energy loss function are also investigated.

The absence of a metallic phase in magnesium fullerides [formula omitted

Magnesium fullerides Mg x C 60 ( 1 < x ≤ 6 ) were prepared by a solid-state reaction. Mg 3.9C 60 was assigned a rhombohedral structure with a = 0.999 nm, α=55.1°. All Mg x C 60 fullerides were found to have almost the same rhombohedral structure. Mg 4.9C 60 did not show metallicity based on the electrical resistivity and electron spin resonance measurements. Mg x C 60 appears to form polymers over a wide range of Mg concentrations and behaves as a non-magnetic insulator.

Structural phase transitions and fundamental band gaps ofMgxZn1−xOalloys from first principles

The structural phase transitions and the fundamental band gaps of ${\text{Mg}}_{x}{\text{Zn}}_{1\ensuremath{-}x}\text{O}$ alloys are investigated by detailed first-principles calculations in the entire range of Mg concentrations $x$, applying a multiple-scattering theoretical approach (Korringa-Kohn-Rostoker method). Disordered alloys are treated within the coherent-potential approximation. The calculations for various crystal phases have given rise to a phase diagram in good agreement with experiments and other theoretical approaches. The phase transition from the wurtzite to the rock-salt structure is predicted at the Mg concentration of $x=0.33$, which is close to the experimental value of 0.33--0.40. The size of the fundamental band gap, typically underestimated by the local-density approximation, is considerably improved by the self-interaction correction. The increase in the gap upon alloying ZnO with Mg corroborates experimental trends. Our findings are relevant for applications in optical, electrical, and, in particular, in magnetoelectric devices.

Temperature‐dependent current‐voltage and lightsoaking measurements on Cu(In,Ga)Se2 solar cells with ALD‐Zn1‐xMgxO buffer layers

AbstractIn this paper, lightsoaking and temperature‐dependent current‐voltage (JVT) measurements on Cu(In,Ga)Se2 solar cells with atomic layer deposited Zn1‐xMgxO buffer layers are presented. A range of Mg concentrations are used, from pure ZnO (x=0) to 26% Mg (x=0·26). Since this kind of solar cells exhibit strong metastable behaviour, lightsoaking is needed prior to the JVT‐measurements to enable fitting of these to the one‐diode model. The most prominent effect of lightsoaking cells with Mg‐rich buffer layers is an increased fill factor, while the effect on cells with pure ZnO buffer is mainly to increase Voc·. The activation energy is extracted from JVT‐measurement data by applying three different methods and the ideality factors are fitted to two different models of temperature‐dependence. A buffer layer consisting either of ZnO or Zn1‐xMgxO with a minor Mg content gives solar cells dominated by interface recombination, which probably can be related to a negative conduction band offset. A relatively high Mg content in the buffer layer (x=0·21) leads to solar cells dominated by recombination in the space charge region. The recombination is interpreted as being tunnelling‐enhanced. The situation in between these Mg concentrations is less clear. Before lightsoaking, the sample with x=0·12 has the highest efficiency of 15·3%, while after lightsoaking the sample with x=0·21 holds the best efficiency, 16·1%, exceeding the value for the CdS reference. The Jsc values of the Zn1‐xMgxO cells surpass that of the reference due to the larger bandgap of Zn1‐xMgxO compared to CdS. Copyright © 2009 John Wiley &amp; Sons, Ltd.

Determination of the content and localization of magnesium in bioapatite of bone

Using x-ray diffraction, electrothermal atomization atomic absorption spectroscopy, and scanning electron microscopy with an x-ray microanalysis, we have studied the phase decomposition of biogenic and synthetic Mg-containing apatite at 900°C with formation of β-tricalcium-magnesium phosphate (β-TCMP). Employing simplified model representations, we obtained a relation that couples the initial Mg concentration with the degree of transformation of apatite into β-TCMP. It is shown that for the β-TCMP contents measured in bioapatite samples and on replacement of calcium by magnesium to about 8% in this phase the calculated range of Mg concentrations coincides with that available in literature sources (0.2–0.6 wt. %). A comparative investigation of the products of decomposition of biogenic and synthetic apatite by the methods of analysis of the composition and structure has established that the formation of β-TCMP is limited by both the insufficient concentration of magnesium and the small sizes of the crystals. The results of the investigations carried out together with the experimental data known from the literature are indicative of the nonuniform distribution of magnesium in the bulk of crystals of biogenic and synthetic apatite, with its predominant localization at the surface sites of the lattice.

Screening broad beans (Vicia faba) for magnesium deficiency. I. Growth characteristics, visual deficiency symptoms and plant nutritional status.

We used broad beans (Vicia faba L.) as a case study to characterise the development of magnesium (Mg) deficiency symptoms in plants and make a comparative evaluation of the suitability of various physiological characteristics as prospective tools for early diagnosis of Mg deficiency. Growth characteristics were measured at monthly intervals from plants grown in soil solution with a wide range of Mg concentrations (from 1 to 200 ppm). The data were then correlated with plant yield responses, pigment composition and nutrient content in leaves, as well as with visual deficiency symptoms. At the age of 4 weeks, no visual symptoms of deficiency were evident even for plants grown at 1 ppm (severe Mg deficiency). Shoot growth characteristics were very similar for a wide range of treatments, although a pronounced difference in plant yield was observed at the end of the experiment. It appears that neither plant biomass nor leaf area are good indicators for use as diagnostic tools for detection of Mg deficiency in broad beans. Although pigment analysis revealed some difference between treatments, at no age was it possible to distinguish between moderately Mg-deficient (10 or 20 ppm) and sufficient (50-80 ppm) treatments. Leaf elemental analysis for Mg content remained the most sensitive and accurate indicator of Mg deficiency in broad beans. However, it is unsuitable for screening purposes as it is both costly and time-consuming. There is a need for less expensive but effective, rapid screening tools of Mg deficiency in crops at early stages of plant ontogeny.

Polarity control during molecular beam epitaxy growth of Mg-doped GaN

Mg doping has been found in some situations to invert growth on Ga-face GaN to N-face. In this study, we clarified the role the Ga wetting layer plays in rf plasma molecular beam epitaxy of GaN when Mg doping, for [Mg] from ∼2×1019 to ∼1×1020 cm−3 corresponding to the useful, accessible range of hole concentrations of p∼1017–1018 cm−3. Structures were grown in the N-rich and Ga-rich growth regime for single Mg doping layers and for multilayer structures with a range of Mg concentrations. Samples were characterized in situ by reflection high-energy electron diffraction and ex situ by atomic force microscopy, transmission electron microscopy, convergent beam electron diffraction, and secondary ion mass spectroscopy. Growth on “dry” surfaces (without a Ga wetting layer) in the N-rich regime completely inverted to N-face upon exposure to Mg. No reinversion to Ga-face was detected for subsequent layers. Additionally, Mg was seen to serve as a surfactant during this N-rich growth, as has been reported by others. Growth initiated in the Ga-rich regime contained inversion domains that nucleated with the initiation of Mg doping. No new inversion domains were found as the Mg concentration was increased through the useful doping levels. Thus the Ga wetting layer was found to inhibit nucleation of N-face GaN, though a complete wetting layer took time to develop. Finally, by establishing a complete Ga wetting layer on the surface prior to growth, we confirmed this finding and demonstrated Mg-doped GaN completely free from inversion domains to a doping level of [Mg]∼2×1020.

Laser flow measurements of scattering and fluorescence from cell nuclei in the presence of increasing Mg++ concentrations

The effects of Mg++ on the spatial organization of nuclei from rat hepatocytes are analyzed in the range 0-60 mM, in the presence of suitable concentrations of KCl to reproduce physiological conditions. It is shown that the scatter-signal distribution measured by means of a flow microfluorimeter is greatly affected by this range of Mg concentrations. By coupling this result to phase-contrast-automated image analysis, it is possible to identify a shrinking process induced by Mg++ in the range 0-2.5 mM, which reaches a plateau in the range 5-20 mM and is followed by a swelling process in the range 30-60 mM. The same Mg ranges are shown to affect the intercalation of the fluorochrome acridine orange into chromatin, suggesting that the shrinking-swelling phenomenon has also a molecular correspondence at the genome level. Possible implications in terms of the influence of Mg++ on the organization of chromatin inside intact cells are briefly discussed.