Magnesium Substitution Research Articles

Heat treatment-induced phase transformations of materials in a system of calcium phosphates and magnesium phosphates with (Ca + Mg)/P = 2

We have studied the effect of heat treatment in a wide temperature range (from 300 to 1500°C) on the phase composition, heat effects and weight loss of powder materials in a system of calcium phosphates and magnesium phosphates with (Ca + Mg)/P = 2. The results demonstrate that crystalline magnesium-substituted whitlockite phases begin to form at temperatures above 600°C. Raising the heat treatment temperature reduces the degree of magnesium substitution for calcium in the structure of the magnesium-substituted whitlockite. Tetracalcium phosphate, a high-temperature phase, is formed through apatite phase recrystallization.

Impact of a Potassium-enriched, Chloride-depleted 5% Glucose Solution on Gastrointestinal Function after Major Abdominopelvic Surgery: Results of a Randomized Controlled Trial.

Gastrointestinal (GI) complications often delay recovery after radical cystectomy with urinary diversion. The authors investigated if perioperative administration of a potassium-enriched, chloride-depleted 5% glucose solution (G5K) accelerates recovery of GI function. This randomized, parallel-group, single-center double-blind trial included 44 consecutive patients undergoing radical cystectomy and pelvic lymph node dissection with urinary diversion. Patients were randomized to receive either a G5K (G5K group) solution or a Ringer's maleate solution (control group). Fluid management aimed for a zero fluid balance. Primary endpoint was time to first defecation. Secondary endpoints were time to normal GI function, need for electrolyte substitution, and renal dysfunction. Time to first defecation was not significantly different between groups (G5K group, 93 h [19 to 168 h] and control group, 120 h [43 to 241 h]); estimator of the group difference, -16 (95% CI, -38 to 6); P = 0.173. Return of normal GI function occurred faster in the G5K group than in the control group (median, 138 h [range, 54 to 262 h] vs. 169 h [108 to 318 h]); estimator of the group difference, -38 (95% CI, -74 to -12); P = 0.004. Potassium and magnesium were less frequently substituted in the G5K group (13.6 vs. 54.5% [P = 0.010] and 18.2 vs. 77.3% [P < 0.001]), respectively. The incidence of renal dysfunction (Risk, Injury, Failure, Loss and End-stage kidney disease stage "risk") at discharge was 9.1% in the G5K group and 4.5% in the control group; P = 1.000. Perioperative administration of a G5K did not enhance first defecation, but may accelerate recovery of normal GI function, and reduces potassium and magnesium substitution after radical cystectomy and urinary diversion.

Magnesium substitution to improve the electrochemical performance of layered Li2MnO3 positive-electrode material

Li2MnO3 has received lots of attention due to its large theoretical capacity. However, its application is obstructed by low practical capacity and poor cycling stability. Here, a new tactic of magnesium substitution for partial lithium to improve the electrochemical performance of Li2MnO3 by a traditional solid state reaction is presented. Sample with only 1% magnesium content delivers a large initial discharge capacity of 307.5 mAh g−1 which is much superior than the 241.9 mAh g−1 of pristine Li2MnO3. The cycling performance also get improved that the capacity retention is 84.5% for Li1.98Mg0.01MnO3 but only 77.7% for pristine counterpart after 30 cycles at 0.1 C. Moreover, the effective suppression of voltage decay has been achieved because of improved kinetic properties and leads to a tremendous progress in the energy density which is as much as 944 Wh kg−1 for Li1.98Mg0.01MnO3 compared with 747.1 Wh kg−1 of Li2MnO3. These achievements attained by Mg-doping make Li2MnO3 a promising positive-electrode material for the next generation of lithium ion batteries.

Synthesis and Electrochemical Properties of Li2MnO3 Li4Mn5O12 Binary System As Positive Electrode Materials for Lithium Ion Battery

Synthesis and Electrochemical Properties of Li2MnO3―Li4Mn5O12 Binary System as Positive Electrode Materials for Lithium Ion Battery Masaki Okada and Yuya Sakaguchi Inorganic Materials Research Laboratory, TOSOH CORPORATION Lithium ion batteries are their high energy density compared with other batteries, progressed recently applied to applications requiring large capacity like for electric power storage system and electric vehicle. The positive electrode materials for a lithium ion battery, lithium metal oxide containing a large amount of rare metallic element such as cobalt or nickel are mainly investigated. Positive electrode material containing a large amount of these rare elements is very difficult to achieve both high energy density and low cost. As a positive electrode material that does not contain a rare metallic element, it is being studied of Li2MnO3 with a layered rock-salt structure. Li2MnO3 shows a large discharge capacity of more than 250mAh/g in the first cycle, but the capacity decreases with charge and discharge cycles. [1-3] In this work, we studied the Li2MnO3―Li4Mn5O12 binary system (Li4/3-4X/5Mn2/3O2-2X/5, 0<X<1) of the positive electrode materials based on Li2MnO3. Li4/3-4X/5Mn2/3O2-2X/5 can be suppressed capacity fading as compared with the conventional Li2MnO3. It may be able to achieve both low cost and high energy density. Li4/3-4X/5Mn2/3O2-2X/5 was prepared by reacting of mixture of MnCO3･0.5H2O and LiOH･H2O as raw material. The mixture was fired at 400～600ºC for 32h in air stream. Crystal structure and multilayered particle structure were investigated through TEM and N2adsorption-desorption isotherm analysis, respectively. The electrochemical characterization of positive electrode material was performed on CR2032 coin type cells. From the TEM images of the prepared samples, the presence of two crystal phases was observed. In addition, the electron diffraction pattern is attributed to the rock salt and the spinel phase, the possibility of a two-phase coexistence structure of Li2MnO3 and Li4Mn5O12 having a twin structure has been suggested. The initial charge and discharge capacity of Li4/3-4X/5Mn2/3O2-2X/5 was reduced as compared with Li2MnO3, but cycle stability was improved (X=0.36, 170mAh/g@50th, 50mA/g, RT). In additionally, capacity fading is suppressed by magnesium substitution of a part of manganese, the substituted sample showed stable cycling at about 200mAh/g (X=0.36, Mg 8mol %). In the viewpoint of the crystal structure and multilayered particle structure, the effect of the characters on capacity and cycle ability will be discussed. [1] Denis Y.W. Yu et.al., J. Electrochem. Soc. 2009 156(6) A417-A424 [2] Denis Y.W. Yu et.al. J. Electrochem. Soc. 2010 157(11) A1177-A1182 [3] Denis Y.W. Yu et.al., J. Electrochem. Soc. 2011 158(9) A1015-A1022

The Effects of High Level Magnesium Dialysis/Substitution Fluid on Magnesium Homeostasis under Regional Citrate Anticoagulation in Critically Ill.

BackgroundThe requirements for magnesium (Mg) supplementation increase under regional citrate anticoagulation (RCA) because citrate acts by chelation of bivalent cations within the blood circuit. The level of magnesium in commercially available fluids for continuous renal replacement therapy (CRRT) may not be sufficient to prevent hypomagnesemia.MethodsPatients (n = 45) on CRRT (2,000 ml/h, blood flow (Qb) 100 ml/min) with RCA modality (4% trisodium citrate) using calcium free fluid with 0.75 mmol/l of Mg with additional magnesium substitution were observed after switch to the calcium-free fluid with magnesium concentration of 1.50 mmol/l (n = 42) and no extra magnesium replenishment. All patients had renal indications for CRRT, were treated with the same devices, filters and the same postfilter ionized calcium endpoint (<0.4 mmol/l) of prefilter citrate dosage. Under the high level Mg fluid the Qb, dosages of citrate and CRRT were consequently escalated in 9h steps to test various settings.ResultsMedian balance of Mg was -0.91 (-1.18 to -0.53) mmol/h with Mg 0.75 mmol/l and 0.2 (0.06–0.35) mmol/h when fluid with Mg 1.50 mmol/l was used. It was close to zero (0.02 (-0.12–0.18) mmol/h) with higher blood flow and dosage of citrate, increased again to 0.15 (-0.11–0.25) mmol/h with 3,000 ml/h of high magnesium containing fluid (p<0.001). The arterial levels of Mg were mildly increased after the change for high level magnesium containing fluid (p<0.01).ConclusionsCompared to ordinary dialysis fluid the mildly hypermagnesemic fluid provided even balances and adequate levels within ordinary configurations of CRRT with RCA and without a need for extra magnesium replenishment.Trial RegistrationClinicalTrials.gov Identifier: NCT01361581

136 - A Member of Solute Carrier Family SLC41 Regulates the Interaction of Magnesium and Mesenchymal Stromal Cells During Osteogenic Differentiation

As the second most abundant intracellular cation, magnesium exists mostly in bone and the amount of magnesium is dynamically regulated by skeletal remodeling. Previous studies showed that accelerating bone mass loss occurs in post-menopause animals when their magnesium intake is insufficient and increased magnesium intake alleviates the osteoporotic symptoms. However, high magnesium status has been reported to lead to mineralization defects possibly due to the magnesium substitution for calcium in hydroxyapatite structure. In the present study, we used murine and human mesenchymal stromal cells (MSCs) to investigate the effect of high extracellular magnesium concentration on osteogenic differentiation and the role of magnesium transporters in the mineralization process. We verified the differentiation efficiency by observing cell morphology, expression profiling of osteogenic marker genes, and performing alizarin red staining (Fig. 1) . The results showed that high concentration of extracellular magnesium ion inhibited mineralization during osteogenic differentiation of MSCs. Gene expressions of osterix, type I collagen alpha 1, and alkaline phosphatase were downregulated, as well as osteopontin and osteocalcin were upregulated in MSCs treated with high concentration of magnesium. siRNA treatment targeting the specific magnesium transporter, which is also a member of solute carrier family SLC41, accelerated the mineralization process and ameliorated the inhibition of mineralization caused by high concentration of magnesium. The sensitivity to extracellular magnesium was also diminished after the knockdown. Pathway analysis of differentially expressed genes indicated that Wnt signaling is involved in the regulation mediated by the magnesium transporter. The study suggests that caution should be taken when magnesium supplement used as a therapy for bone mass loss and provide insights into the design of magnesium alloys for implantation.

The effect of magnesium alloy wires and tricalcium phosphate particles on apatite mineralization on polylactide-based composites

Biodegradable magnesium alloy wires and tricalcium phosphate nanoparticles were used as a modifying phase of novel polylactide based composite system. The aim of this study was to determine the effect of those two components on apatite mineralization and thus potential bioactivity of the composite material. Studied samples were incubated in Simulated Body Fluid and Phosphate Buffer Saline to simulate biological environment. It was revealed that coexisting modification of polymer matrix with Mg and TCP resulted in formation of apatites with magnesium substitutions that have superior biological properties. Results of the study confirmed that chemical composition of the incubation medium affects composition of the precipitates. Designed multiphase composite can be potentially used for bioactive bone implants.

Suppressing the P2-O2 Phase Transition of Na0.67 Mn0.67 Ni0.33 O2 by Magnesium Substitution for Improved Sodium-Ion Batteries.

Room-temperature sodium-ion batteries (SIBs) have shown great promise in grid-scale energy storage, portable electronics, and electric vehicles because of the abundance of low-cost sodium. Sodium-based layered oxides with a P2-type layered framework have been considered as one of the most promising cathode materials for SIBs. However, they suffer from the undesired P2-O2 phase transition, which leads to rapid capacity decay and limited reversible capacities. Herein, we show that this problem can be significantly mitigated by substituting some of the nickel ions with magnesium to obtain Na0.67 Mn0.67 Ni0.33-x Mgx O2 (0≤x≤0.33). Both the reversible capacity and the capacity retention of the P2-type cathode material were remarkably improved as the P2-O2 phase transition was thus suppressed during cycling. This strategy might also be applicable to the modulation of the physical and chemical properties of layered oxides and provides new insight into the rational design of high-capacity and highly stable cathode materials for SIBs.

Magnetic and Electrical Properties of Magnesium-Substituted Ni–Zn Ferrites

The effect of magnesium substitution in Ni–Zn ferrites (Ni0.80−x Mg x Zn0.20Fe2 O 4, where x = 0, 0.10–0.50) was studied on its electrical and magnetic properties. Ni–Mg–Zn ferrites were synthesized by novel combustion method, followed by calcination at 900 ∘C. The X-ray diffraction (XRD) pattern shows that the prepared sample was a single-phase spinel cubic structure, and the calculated crystallite sizes were found to be in the range 44–48 nm. Fourier transform infrared spectroscopy (FTIR) spectra confirm the tetrahedral and octahedral modes of vibrations. The observed saturation magnetization values range from 37 to 63 emu/g for magnesium-added Ni–Zn ferrites. The increase in resistivity was observed with the addition of magnesium ions except for the concentration of x = 0.50. The change in dielectric behavior with respect to composition and frequency were studied.

Effect of Mg Substitution in the Structural and Electrochemical Properties of Li2MnO3

The revolutionary concept of energy storage is constantly changing due to the increasing demand of high energy density devices. However, issues such as safety, high temperature performance, cost, and environmental concerns need to be addressed, especially for the high power applications. Among the cathode materials investigated, lithium manganese oxides have been exploited due to the abundance of Mn in earth, low toxicity and safety. In this family of oxides, Li2MnO3 possess monoclinic structure having c2/m space group symmetry with a layered arrangement of Li[Li1/3Mn2/3]O2, thus resembling the ideal layered structure of LiCoO2. Li2MnO3 is known to be electrochemically inactive due to the presence of Mn in tetravalent oxidation state. Substitutions of ions in the structure allow possible reduction of the valance state of manganese and electrochemically activating the material. In the present study, we investigated the electrochemical and structural properties of Li2MnO3at room temperature by partially substituting lithium with magnesium using the Pechini synthesis method. Li2MnO3, Li1.5Mg0.25MnO3, Li1.0Mg0.50MnO3 and Li0.5Mg0.75MnO3 compositions were prepared by the Pechini synthesis method. These substitutions were chosen balancing the charge of the cations. For the individual compounds the synthesis was carried out using lithium nitrate [LiNO3], manganese nitrate [Mn(NO3)2], magnesium nitrate [Mg(NO3)2•6H2O], ethylene glycol [C2H6O2] and citric acid [H3C6H5O7] as precursors materials.The molar ratio of M:CA:EG used was 1:1.2:1.2, where M is the sum of all metal ions. Stoichiometric ratios of the metals corresponding to each composition were measured and dissolved in deionized water (H2O) along with citric acid (CA), which behaves as a chelating reagent. The resulting compound was placed in an oven at 130oC for 24 h to complete the drying process, followed by annealing of the powder at 750oC for 8h in air to obtain desire phase. The final heat treated powder samples were mixed with polyvinylidenefloride (PVDF) and carbon black in the wt % ratio of 80:1010, respectively. A slurry paste was prepared using 1-methyl 2-pyrolidone as solvent and was coated on Al foil substrates to form a homogeneous layer. Electrodes were punched out for the fabrication of 2032 coin cells. Metallic Li was used as the counter electrode along with 1.2M LiPF6in EC:DMC (1:1) as electrolyte. The charge and discharge analysis was performed at 10mAh/g within a potential window of 2.0V- 4.8V. The structural phase formation of the materials and presence of any crystalline impurities in the compounds were studied with X-ray diffraction (XRD). Figure 1 shows XRD patterns for Li2MnO3, Li1.5Mg0.25MnO3, Li1.0Mg0.50MnO3 and Li0.5Mg0.75MnO3 synthesized at 7500C for 8h. The formation of single phase material was confirmed for Li2MnO3 and a combination of monoclinic/spinel phases (Li2-xMn1-yMgx+yO3+z) was observed for the Mg-substituted compounds. X-ray photoelectron spectroscopy (XPS) was used to study the valance state of the manganese ion after magnesium substitution. Figure 2 shows XPS pattern for Mn 2p of pristine and partially Mg-substituted samples. A shift to a lower binding energy is observed for Li1.0Mg0.50MnO3 and Li0.5Mg0.75MnO3, indicating a decrease in the tetravalent state of manganese. Therefore, an improvement in electrochemical cycling performance is expected. Preliminary results shown in Figure 3 indicate that partial Mg-substitution enhances the cycleability of Li2MnO3 and increase the capacity to ~90mAh/g. All the electrochemical performance of Li2MnO3, Li1.5Mg0.25MnO3, Li1.0Mg0.50MnO3 and Li0.5Mg0.75MnO3 cathodes will be presented in detail. Figure 1

PD12-11 GASTROINTESTINAL RECOVERY IS ACCELERATED AND ELECTROLYTE DISTURBANCES ARE REDUCED AFTER RADICAL CYSTECTOMY BY PERIOPERATIVE USE OF A NEW CRYSTALLOID SOLUTION: RESULTS OF A RANDOMIZED CLINICAL TRIAL.

You have accessJournal of UrologyTrauma/Reconstruction/Diversion: Ureter (including Pyeloplasty) and Bladder Reconstruction (including fistula), Augmentation, Substitution, Diversion I1 Apr 2016PD12-11 GASTROINTESTINAL RECOVERY IS ACCELERATED AND ELECTROLYTE DISTURBANCES ARE REDUCED AFTER RADICAL CYSTECTOMY BY PERIOPERATIVE USE OF A NEW CRYSTALLOID SOLUTION: RESULTS OF A RANDOMIZED CLINICAL TRIAL. Lukas M. Löffel, Fiona C. Burkhard, and Patrick Y. Wuethrich Lukas M. LöffelLukas M. Löffel More articles by this author , Fiona C. BurkhardFiona C. Burkhard More articles by this author , and Patrick Y. WuethrichPatrick Y. Wuethrich More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2016.02.906AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Open radical cystectomy (ORC) is associated with a high complication rate and has a high risk of delayed return of normal gastrointestinal (GI) function postoperatively. The objective of this study is to determine if perioperative administration of a chloride-depleted glucose (Glc) and potassium based crystalloid solution accelerates GI recovery. METHODS Randomized, parallel-group single-center trial including 44 consecutive patients undergoing ORC with urinary diversion receiving either a glucose 5% potassium based crystalloid solution (G5K group) or a balanced crystalloid solution (Ringerfundin® control group) perioperatively. The setting was a fluid management aiming for a zero balance. The primary endpoint was the return to normal defecation. Data were analyzed using non-parametric statistical models and multiple linear regression analysis was conducted. RESULTS The groups were comparable regarding surgical characteristics, length of stay, intraoperative parameters and fluid administration (G5K group: 750ml [500-1700ml] vs. control group 975ml [400-1600ml], P=0.185) and amount of fluid administered postopera-tively (G5K group: 4750ml [4000-6000ml] vs. control group 4750ml [4000-6000ml], P=0.941). Normal defecation occurred significantly faster in the G5K group (5.8d [2.3-10.9]) than in the control group (7.0d [4.5-13.3]); P<0.001. This was confirmed by multiple linear regres-sion analysis (regression coefficient: -47.25 SE: 15.35; P=0.004). Time to first flatus and first defecation were similar (G5K group 1.8d [0.6-4.9] and 3.9d [0.8-7.0]; and control group 2.0d [0.9-4.8] and 5.0d [1.8-10.0]; P=0.716 and P=0.173, respectively). As a safety endpoint, the incidence of renal dysfunction at discharge was similar for the G5K (9.1%) and control group (4.0%) staged as RIFLE »risk«; P=1.000, while the need for substitution of magnesium and potassium was significantly lower in the G5K group (13.6% and 18.2%, respectively) than in the control group (54.6% and 77.3%, respectively; P=0.010 and P<0.001). The limitation of this study is performance in a high case-load center, whether the results are reproducible in other centers needs to be shown. CONCLUSIONS Perioperative administration of a G5K based crystalloid solution accelerates recovery of bowel function after open RC with superior safety as the need for potassium or magnesium substitution was reduced with no difference in renal function. © 2016FiguresReferencesRelatedDetails Volume 195Issue 4SApril 2016Page: e297 Advertisement Copyright & Permissions© 2016MetricsAuthor Information Lukas M. Löffel More articles by this author Fiona C. Burkhard More articles by this author Patrick Y. Wuethrich More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Structure and dielectric properties of zinc borate glass–ceramics modified by magnesium

The effects of magnesium substitution for zinc in zinc borate glass–ceramics [xMgO–(3 − x)ZnO–2B2O3 where x = 0, 0.1, 0.2, 0.3] prepared by conventional solid state on structure, crystallized temperature and dielectric properties were investigated. Fourier transform infrared spectrometer was used to investigate the variations of the glass structure. With increasing magnesium amount, the non-bridge oxygen amount increased, lowering the crystallized temperature. Surplus substitution leaded to the formation of boroxol rings and [MgO4] groups in the glass structure, strengthening the glass structure. Thus, the crystallized temperature increased. Two main crystalline phases of α-Zn(BO2)2 and Zn3B2O6 were found at the x level of 0 and 0.1 for the sintered samples, while Mg3B2O6 appeared when the magnesium substitution achieved to 0.2 and 0.3. Further, the magnesium-substitution lowered the dielectric constant slightly due to its relatively low ionic polarizability and low magnesium content. When the 0.2 mol magnesium amounts was substituted for zinc, the specimens showed the optimal dielectric properties, with a dielectric constant of 6.7 and a dielectric loss of 1 × 10−3 after sintering at 640 °C for 30 min, which demonstrated a good potential for use in low temperature co-fired ceramic technology.

Magnesium-substituted calcium phosphate cements with (Ca + Mg)/P = 2

The introduction of magnesium ions into bone calcium phosphate cements (CPCs) increases the strength and biodegradation rate of the materials. Cement powders with the (Ca + Mg)/P ratio of 2 and the degree of magnesium substitution for calcium of 0, 10, 20, and 40 wt % were used in the study. Sodium phosphate-based solutions were used as the cement fluids. Depending on the magnesium content, CPCs based on magnesium-substituted apatite and whitlockite phases were obtained. The phase composition, setting time, strength, and microstructure of the cements were determined. An increase in the acidity of the cement liquid was found to give cements with a greater content of amorphous phase and more homogeneous structure, resulting in higher strength.

Effect of synthesis conditions on hydrothermal crystallization, textural characteristics and morphology of aluminum-magnesium montmorillonite

Studied was the effect of synthesis conditions on the process of hydrothermal crystallization, porosity and textural characteristics of aluminum-magnesium montmorillonite Na2x(Al2(1−x),Mg2x)Si4O10(OH)2·nH2O (0 < x < 1), with varying degrees of isomorphous substitution of magnesium for aluminum in the octahedral layers. Hydrothermal synthesis was carried out at temperatures from 200 to 350 °С, autogenous pressure from 20 to 70 MPa, and duration of synthesis from 5 to 288 h. Samples were examined by X-ray diffraction, scanning and transmission electron microscopy, and by low-temperature nitrogen adsorption. The crystallization of montmorillonite is affected to the greatest extent by the temperature and the duration of synthesis. Pressure has no effect within in the studied value range. The particle size of the samples in a plane perpendicular to axis c is 20 ± 3 nm, and does not depend on the synthesis conditions and the chemical composition of the samples. Depending on the synthesis conditions, both delaminated samples in the form of nanolayers, in some cases, twisted into tubes, and package structure samples can be obtained. In addition, the specific surface area values may range from 80 to 680 m2/g. Thus, the samples with specified characteristics can be obtained by directed hydrothermal synthesis, which can enhance the potential uses of montmorillonite in areas (medicine, catalysis, nanocomposites) where there are special requirements to the physicochemical properties and morphology of the materials used.

Magnesium substitution in carbonated hydroxyapatite: Structural and microstructural characterization by Rietveld's refinement

Four stoichiometric compositions of nanocrystalline Mg doped carbonated hydroxyapatite (cHAp) powders are synthesized by mechanical alloying (ball milling) the powder mixtures of CaCO3, CaHPO4.2H2O and MgO in open air at room temperature. FTIR analysis confirms the A-type carbonation in all milled HAp powder samples (A-cHAp). Microstructure characterization in terms of lattice imperfections and phase quantification of ball milled samples are made by analyzing XRD patterns employing Rietveld's structure refinement method. Transmission electron microscopy (TEM) study of 15 mol % Mg doped A-cHAp sample reveals microstructure similar to that obtained from XRD pattern analysis. Cumulative effect of Mg substitution and mechanical alloying results in amorphization of a major part of crystalline A-cHAp, analogous to native bone mineral. Rietveld analysis reveals that the Ca2 vacancy site is energetically more favorable for occupation of Mg substitution. MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay test reveals sufficiently high percentage cell viability confirming the cytocompatibility of the sample.

Effect of magnesium substitution into Fe-based La-hexaaluminates on the activity for CH4 catalytic combustion

The introduction of Mg2+ into Fe-based La-hexaaluminates significantly enhanced the activity for CH4 catalytic combustion and the resistance to deactivation after calcination at 1300 °C.

Phoxilium(®) reduces hypophosphataemia and magnesium supplementation during continuous renal replacement therapy.

BackgroundAlthough associated with severe clinical complications, phosphate remains a neglected ion. Additionally, phosphate balance during continuous renal replacement therapy (CRRT) is complex and multifunctional. The present retrospective study investigated the effects of phosphate-containing CRRT fluid on phosphate homeostasis.MethodsWe retrospectively analysed 112 patients treated with CRRT at Skåne University Hospital, Sweden. The control group was treated with Hemosol® B0 (no phosphate; n = 36) as dialysis and replacement fluid, while the study group received Phoxilium® (phosphate; n = 76) as dialysis fluid and Hemosol® B0 as replacement fluid.ResultsHypophosphataemia (<0.7 mM) occurred in 15% of the treatment days in the control group compared with 7% in the study group (P = 0.027). Magnesium substitution was reduced by 40% in the study group (P < 0.001). No differences in acid–base parameters were detected between the groups.ConclusionsIn this larger cohort, we could confirm that Phoxilium® reduced the episodes of hypophosphataemia during CRRT. A beneficial effect on magnesium balance could also be observed.

Rod-shaped and substituted hydroxyapatite nanoparticles stimulating type 1 and 2 cytokine secretion

A Th1 immune response is required for modern vaccines as the most commonly used alum adjuvant has weak capacity for inducing Th1 immune response. Herein, rod-shaped hydroxyapatite (HA), magnesium-substituted HA (MgHA) and zinc-substituted HA (ZnHA) nanoparticles with irregular nanopores were synthesized and used as immunoadjuvants. Magnesium and zinc substitution in HA showed no influence on morphology, particle size, zeta potential and surface area of the nanoparticles. The rod-shaped MgHA and ZnHA nanoparticles promoted the cellular uptake of a molecular immunopotentiator, stimulated both type 1 and 2 cytokine secretion in vitro that relate to Th1 and Th2 immunity of bone marrow dentritic cells, respectively. The MgHA and ZnHA nanoparticles may be useful as immunoadjuvants for human.

Structural and dielectric studies of Mg2+ substituted Ni–Zn ferrite

AbstractPolycrystalline ferrites having the chemical formula Ni0.65−xZn0.35MgxFe2O4 (0 ⩽ x ⩽ 0.2) were prepared by solid state reaction route in steps of x = 0.04. The effect of incorporation of diamagnetic divalent magnesium at expense of nickel on the structural properties of these ferrites has been studied. The proposed cation distribution was derived from theoretical X-ray diffraction intensity calculations. These intensity calculations were done by varying the concentration of magnesium ions over two sites in the lattice. For a certain amount of magnesium concentration, the calculated and observed X-ray diffraction intensities were found to be in good agreement. Site occupancy of divalent diamagnetic magnesium was established from this cation distribution. The octahedral environment facilitates magnesium to enter the B-site at about 95 % and the remaining 5 % occupy tetrahedral sites (A-sites). The movements of cations between tetrahedral and octahedral sites as a result of magnesium substitution were discussed in the view of structural parameters, such as tetrahedral and octahedral bond lengths, cation-cation and cation-anion distances, bond angles and hopping lengths, which were calculated using experimental lattice constants and oxygen parameters. All structural parameters showed slight deviations from ideal values. Among all magnesium substituted samples, the ones with x = 0.12 exhibited insignificant variation in view of structural properties. Dielectric measurements were conducted at a standard frequency of 1 kHz. Large values of the recorded dielectric constants displayed typical characteristics of bulk ferrites. Both dielectric constant and loss values showed mixed variations, attributed to the loss of zinc ions during the sintering process.

Magnesium substitution in brushite cements: Efficacy of a new biomaterial loaded with vancomycin for the treatment of Staphylococcus aureus infections

Staphylococcus aureus is the most relevant pathogen associated with bone infection that sometimes appears after implant surgery, thus compromising a successful treatment. The aim of this work was to assess the effectiveness of brushite cements, doped with magnesium, as a new vancomycin carrier system against S.aureus infections.We performed an “in vitro” study to evaluate vancomycin release from the cements by measuring its antimicrobial activity against a strain of S.aureus. We have used two methods to load the cements with vancomycin: i) adsorption from a solution and ii) incorporation of the antibiotic into the solid phase during the cement synthesis. Furthermore, the compression strength of the loaded samples was measured to detect changes in the mechanical properties of the system.The “in vitro” study showed that the sustained release of vancomycin depends on the concentration of magnesium in the cement matrix. In addition, the standardized antibacterial assay revealed that the release of vancomycin from the cements may be helpful to prevent infections in bone regeneration procedures.