Bio-cementation for tidal erosion resistance improvement of foreshore slopes based on microbially induced magnesium and calcium precipitation

In most coastal and estuarine areas,tides easily cause surface erosion and even slope failure,resulting in severe land losses,deterioration of coastal infrastructure,and increased floods.The bio-cementation technique has been previously demonstrated to effectively improve the erosion resistance of slopes.Seawater contains magnesium ions(Mg^(2+))with a higher concentration than calcium ions(Ca^(2+));therefore,Mg^(2+)and Ca^(2+)were used together for bio-cementation in this study at various Mg^(2+)/Ca^(2+)ratios as the microbially induced magnesium and calcium precipitation(MIMCP)treatment.Slope angles,surface strengths,precipitation contents,major phases,and microscopic characteristics of precipitation were used to evaluate the treatment effects.Results showed that the MIMCP treatment markedly enhanced the erosion resistance of slopes.Decreased Mg^(2+)/Ca^(2+)ratios resulted in a smaller change in angles and fewer soil losses,especially the Mg^(2+)concentration below 0.2 M.The decreased Mg^(2+)/Ca^(2+)ratio achieved increased precipitation contents,which contributed to better erosion resistance and higher surface strengths.Additionally,the production of aragonite would benefit from elevated Mg^(2+)concentrations and a higher Ca^(2+)concentration led to more nesquehonite in magnesium precipitation crystals.The slopes with an initial angle of 53°had worse erosion resistance than the slopes with an initial angle of 35°,but the Mg^(2+)/Ca^(2+)ratios of 0.2:0.8,0.1:0.9,and 0:1.0 were effective for both slope stabilization and erosion mitigation to a great extent.The results are of great significance for the application of MIMCP to improve erosion resistance of foreshore slopes and the MIMCP technique has promising application potential in marine engineering.

Structure, Formation, Properties, and Application of Calcium and Magnesium Silicate Hydrates System—A Review

In order to expand the advantages of strong durability and high compressive strength of calcium silicate hydrates(C-S-H),at the same time to make up for the poor early mechanical strength of magnesium silicate hydrates (M-S-H),we present the features and advantages of C-S-H and M-S-H and a comprehensive review of the progress on CaO-MgO-SiO_(2)-H_(2)O.Moreover,we systematically describe natural calcium and magnesium silicate minerals and thermodynamic properties of CaO-MgO-SiO_(2)-H_(2)O.The effect of magnesium on C-S-H and calcium on M-S-H is summarized deeply;the formation and structural feature of CaO-MgO-SiO_(2)-H_(2)O is also explained in detail.Finally,the development of calcium and magnesium silicate hydrates in the future is pointed out,and the further research is discussed and estimated.

Novel mechanism for the modification of Al_2O_3-based inclusions in ultra-low carbon Al-killed steel considering the effects of magnesium and calcium

Many researchers have explored the inclusion modification mechanism to improve non-metallic inclusion modifications in steelmaking. In this study, two types of industrial trials on inclusion modifications in liquid steel were conducted using ultra-low-carbon Al-killed steel with different Mg and Ca contents to verify the effects of Ca and Mg contents on the modification mechanism of Al_2O_3-based inclusions during secondary refining. The results showed that Al_2O_3-based inclusions can be modified into liquid calcium aluminate or a multi-component inclusion with the addition of a suitable amount of Ca. In addition, [Mg] in liquid steel can further reduce CaO in liquid calcium aluminate to drive its evolution into CaO–MgO–Al_2O_3 multi-component inclusions. Thermodynamic analysis confirmed that the reaction between [Mg] and CaO in liquid calcium aluminate occurs when the MgO content of liquid calcium aluminate is less than 3 wt% and the temperature is higher than 1843 K.

Recent advances in hydrothermal modification of calcium phosphorus coating on magnesium alloy

Magnesium(Mg) and its alloys have emerged as a favored candidate for bio-regenerative medical implants due to their superior biocompatibility, biodegradability and the elastic modulus close to that of human bone. Unfortunately, the rapid and uncontrollable degradation rate of Mg alloys in chloride-rich body microenvironments limits their clinical orthopedic applications. Recently, Calcium Phosphate(Ca-P)biomaterials, especially Hydroxyapatite(HA), have been broadly applied in the surface functional modification of metal-based biomaterials attributed to their excellent bioactivity and biocompatibility. Hydrothermal modification of Ca-P coatings on Mg alloys has been extensively exploited by researchers for its significant superiorities in controlling coating structure and improving interfacial bonding strength for better osseointegration and corrosion resistance. This work focuses on the up-to-the-minute advances in Ca-P coatings on the surface of Mg and its alloys via hydrothermal methods, including the strategies and mechanisms of hydrothermal modification. Herein, we are inclined to share some feasible and attractive hydrothermal surface modification strategies. From the perspectives of hydrothermal manufacturing technique innovation and coating structure optimization, we evaluate how to foster the corrosion resistance, coating bonding strength, osseointegration and antibacterial properties of Mg alloys with Ca-P coatings synthesized by hydrothermal method. The challenges and future perspectives on the follow-up exploration of Mg alloys for orthopedic applications are also elaborately proposed.

Refinement Role of Electromagnetic Stirring and Calcium in AZ91 Magnesium Alloy

Effects of calcium addition and electromagnetic stirring on the microstructure of AZ91 magnesium alloy and refinement mechanism were investigated. The results show that calcium addition ranging from 0.1wt% to 0.3 wt% does not lead to formation of any new phases but cause the refinement of ascast microstructure.However, combined calcium alloying and electromagnetic stirring significantly decrease the grain size, change the morphologies of the β-Mg17Al12 phases,and reduce their volume percentage. The minimum grain size of AZ91 alloy is obtained in the case of the addition of 0.2 wt%Ca with exciting voltage of 100 V. The microstructural refinement is attributed to the increase of the degree of undercooling and nucleation temperature of primary α-Mg phases on the basis of DTA analysis results.

The Role of Calcium in Microstructural Refinement of AZ91 Magnesium Alloy

The effect of calcium addition on the microstructures of AZ91 magnesium alloy was investigated. It was found that a small amount of calcium in AZ91 allay produced a large decrease in the α- Mg grain size and the dispersed fine β-Mgt7 Alt2 phases. In addition, some Al4Ca particles were found to exist in the AZ91 alloy containing 0.5wt% Ca. EDS analysis and water-quenched technique revealed that the grain-refining mechanism of calcium for the AZ91 alloys was mainly attributed to the role of restricting growth of calcium in the primary α-Mg crystals.

Pedogenic and Anthropogenic Influence on Calcium and Magnesium Behaviors in Stagnic Anthrosols

The formation of Stagnic Anthrosols is closely related to rice planting and parent materials. Six representative pedons, two from each of three Stagnic Anthrosol subgroups, Vertic Haplic-, Vertic Gleyic-, and Sulfic Gleyic-Stagnic Anthrosols, from different parent materials and soil formation processes, from Liaoning Province, China, were selected and used along with additional supporting data to assess the potential impact in each soil subgroup combination of both pedogenic and anthropogenic factors on the migration and geochemical characteristics of calcium (Ca) and magnesium (Mg) and their relations to soil particle-size composition. Results revealed that exchangeable Mg was correlated positively with clay and silt content, but negatively with sand content, suggesting that clay and silt could retain more exchangeable Mg than sand. Also, in the six pedons exchangeable Ca/Mg ratios generally decreased with depth, which was most likely due to the preferential retention of Mg below the Apl horizon and the effects of bio-cycling in rice-soil systems. The pedons with high pH had smaller exchangeable Ca/Mg ratios than those with low pH. Thus, it was concluded that exchangeable Ca/Mg ratios could be helpful in classification of Stagnic Anthrosols.

Effects of Paper Mill Sludge on Potassium, Sodium, Calcium, and Magnesium Concentrations in Different Soybean Cultivars

A field experiment was conducted on a sandy loam soil at an Experimental Farm in Taejon, South Korea, to determine the effects of paper mill sludge compost application rates on K, Na, Ca and Mg concentrations of soybean (Glycine max(L.) Merr.) aboveground tissues and the genotypic effects on the concentrations of these elements. Sludge compost treatments of 0, 75, and 150 t ha-1 were applied to 30 diverse soybean cultivars. Concentrations of K, Na, Ca, and Mg in aboveground tissues harvested 69 days after planting (DAP) varied with the genotype and the application rate of paper-mill sludge compost, with the sludge compost application rate exerting stronger influence on these concentrations than the genotype. The magnitude of variation caused by both genotype and sludge compost application was in the order of Mg ＞ K ＞ Ca ＞ Na. Significantly positive correlations were observed between K and Na (P ＜ 0.01), Na and Ca(P ＜ 0.05), and Ca and Mg (P ＜ 0.01). Also, the lower the sludge compost application rate, the larger the variation in the concentrations of K, Na, and Ca. From this several cultivars were identified for use as an accumulator for one or more of these elements.

Calcium and Magnesium Levels Are down Regulated in Nigerian Children with Autism Spectrum Disorder and Cerebral Palsy

Autism Spectrum Disorders (ASDs) and Cerebral Palsy (CP) are amongst the leading neurodevelopmental disorders in children worldwide causing diminished quality of life. Unlike CP caused by brain damage affecting muscle tone, movement and motor skills, equivocal report of different genes with varying loci as genetic malformation and genetic modulation by environmental factors have been the focus of attention in the aetiology of ASD. This study investigated levels of toxic metal (Pb) and macro elements (Ca and Mg) in blood of children with ASD and CP in Nigeria. 8 and 18 Children (aged 2 - 12 years) clinically screened for features of ASD and CP respectively by pediatric neurologist using DMS-IV classification along with 15 age-matched neurologically healthy ones as controls were recruited. Plasma levels of Ca, Mg and Pb were determined in the children using Induction Coupled Plasma Mass Spectroscopy (ICP-MS). Results were analyzed using students t-test. The gender difference was not significant in the children (P = 0.216) while developmental milestones’ abnormalities (stable neck, sitting, crawling and walking) was significantly prevalent among CP children relative to ASD and normal children (P= 0.003, 0.003, 0.003 and 0.000 respectively);however, abnormality in talking was common in ASD and CP relative to normal children (P = 0.000). There was significant difference in educational background of ASD and CP parents relative to those of normal children (P = 0.025). Mean plasma calcium and magnesium levels was significantly reduced in children with ASD (7.90 ± 0.17 mg/dl, 2.44 ± 0.07 mg/dl) and CP (7.26 ± 0.31 mg/dl, 2.42 ± 0.08 mg/dl) in comparison to the controls (8.97 ± 0.20 mg/dl and 3.26 ± 0.16 mg/dl);(P < 0.001;P < 0.000 and P < 0.002;P < 0.000) respectively. However, mean lead levels in children with CP (10.38 ± 1.45 μg/dl) were significantly greater than in ASD (7.92 ± 1.30 μg/dl) and normal children (6.83 ± 0.72 μg/dl) (P < 0.433;P < 0.047). Hypocalcaemia and hypomagnesaemia with concurrent plumbism (more pronounced in CP) was observed in children with ASD and CP in this study).

Synthesis of cation exchange resin-supported iron and magnesium oxides/hydroxides composite for nitrate removal in water

In this study,we reported on the concept and practical use of cation exchange resin(CER)for removing anions in water via pretreating the CER with metal salts.The cation exchange resinsupported iron and magnesium oxides/hydroxides composite(FeMg/CER)was synthesized and introduced as a new and potential adsorbent for selective removal of nitrate ion in the water environment.Characteristics of FeMg/CER were determined by techniques such as Fouriertransform infrared spectroscopy,scanning electron microscopy,and Xray diffraction.The results showed that FeMg/CER material had a high nitrate adsorption capacity of 200 mg NO_(3)^()·g^(1)with a fast equilibrium adsorption time of 30 min at pH 5.In addition,it had good durability of at least 10 times of regeneration,which could be applied to practical water and wastewater treatment.

Tribological Properties of Magnesium Ion-exchanged α-Zirconium Phosphate as a Solid Lubricant Additive in Lithium Grease

Magnesium ion-exchanged a-zirconium phosphates(Mg-α-ZrP) with particle sizes of 600 and 80 nm were prepared through the sealed ion-exchange and one-step hydrothermal synthesis methods, respectively. It was found that larger particles of Mg-α-ZrP had a higher load-carrying capacity than that of smaller particles, whereas smaller Mg-α-ZrP particles had better anti-wear properties than that of larger Mg-α-ZrP particles under mild loads. The correlation between the particle size of the sample and the surface roughness of the friction pair thus seems to be a key factor influencing the performance.

Synthesis of Environmentally Friendly Multifunctional Metal (Calcium,Magnesium) Oleate Detergent with Antioxidation Property

This article covers a method for synthesizing environmentally friendly multifunctional metal (calcium,magnesium) oleate detergents with antioxidation property.These multifunctional metal (calcium,magnesium) oleate detergents with antioxidation property were synthesized using oil-soluble liquid antioxidants (PPIBP,PPIBTSTBP,and PPIBPDA) as reactive functional materials.These oil-soluble liquid antioxidants have the potential to be used as functional materials for application in synthesizing other kinds of substrate detergents.

Simultaneous Determination of Calcium and Magnesium in Water Using Artificial Neural Network Spectro-Photometric Method

A new analytical method using Back-Propagation(BP) artificial neural networks and spectrophotometry for simultaneous determination of calcium and magnesium in tap water,the Yellow River water and seawater is established.By condition experiment,the optimum analytical conditions for calcium,magnesium and Arsenazo(Ⅲ) color reactions are obtained.Levenberg-Marquart(L-M) algorithm is used for calculation in BP neural network.The topological structure of three-layer BP ANN network architecture is chosen as 11-10-2(nodes).The initial value of gradient coefficient μ is fixed at 0.001 and the increase factor and reduction factor of μ take the default values of the system.The data are processed by computers with our own programs written in MATLAB 7.0.The relative standard deviations of the calculated results for calcium and magnesium are 2.31% and 2.14%,respectively.The results of standard addition method show that the recoveries of calcium and magnesium are 103.6% and 100.8% in the tap water,103.2% and 96.6% in the Yellow River water(Lijin district of Shandong Province),and 98.8%-103.3% and 98.43%-103.4% in seawater from Jiaozhou Bay of Qingdao.It is found that 14 common cations and anions do not interfere with the determination of calcium and magnesium under the optimum experimental conditions.The comparative experiments do not show any obvious difference between the results obtained by this new method and those obtained by the classical complexometric titration method in seawater medium.This method exhibits good reproducibility and high accuracy in the determination of calcium and magnesium and can be used for the simultaneous determination of Ca2+ and Mg2+ in tap water and natural water.

Vapor-Liquid Equilibria for Water+Hydrochloric Acid+Magnesium Chloride and Water+Hydrochloric Acid+Calcium Chloride Systems at Atmospheric Pressure

Vapor-liquid equilibria for water+hydrochloric acid+magnesium chloride and water+hydrochloric acid+calcium chloride systems at atmospheric pressure were measured using a Othmer-type equilibrium still. The experimental data are correlated using a modified Meissner’s method. Satisfactory agreements are obtained between the experimental and the calculated results.

Microstructure and mechanical properties of ZA62 based magnesium alloys with calcium addition

As-cast microstructure and mechanical properties of Mg-6Zn-2Al-0.3Mn (ZA62) alloys with calcium addition were investigated.The as-cast microstructure of the base alloy ZA62 consists of the α-Mg matrix and eutectic phase Mg51Zn20.The Mg51Zn20 eutectic was gradually replaced by MgZn phase and Mg32(Al,Zn)49 phase when calcium is added into the base alloy.Further addition of calcium leads to the increase of grain boundary phases and formation of a new quaternary Mg-Zn-Al-Ca eutectic compound.In comparison with the base alloy,the increase of calcium addition to the base alloy results in the reduction of both strength and ductility at ambient temperature,but increase at elevated temperatures due to the thermal stability of Ca-containing phases.At elevated temperatures,the creep resistance of ZA62 based alloys containing calcium is significantly higher than that of AZ91 which is the most commonly used magnesium alloy.

Dissolution behavior of calcium-magnesium-silicate glass fiber

The dissolution behavior of CaO-MgO-SiO2 glass fiber was investigated by scanning electron microscopy (SEM), Fourier-transform infrared spectrometer (FTIR) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) using in-vitro tests. The results show that the soaked fiber is surrounded by an outer calcium-magnesium silicate hydrated layer, and there exists a balancing function between the formation and abscission of the hydrated layer during the dissolution process. The concentrations of leached ions increase constantly, and the mass loss of the fibers and pH changes of the solution are found to rise rapidly during the initial dissolution process, then their increasing rates are controlled by the balancing function of the hydrated layer at the subsequent dissolution stages. The dissolution rate constant and time for complete dissolution are estimated to be 274 ng/(cm2·h) and 15.2 d, respectively, presenting preferable biosolubilities.

Destructive effect of magnesium and calcium atoms on TEX

The interaction of TEX(an explosive recently attracts attention) with Mg and Ca atom(s) has been investigated within the limitations of density functional theory at the level of B3 LYP/6-311 ++G(d,p). The effect of Mg in 1:1 mol ratio is very drastic on TEX and one of the NO_2 moieties is expelled as preform of nitrite ion. The second Mg atom in the composite(1:2 mol ratio of TEX:Mg) shows balancing effect of the first Mg atom, thus no bond cleavage occurs but some distortions happen. As for the effect of calcium, in1:1 and 1:2(TEX:Ca) ratios nitramine bond cleavage(s) occur(s) drastically. Some structural and quantum chemical data are presented.

THE STUDY ON THE CHANGES OF ZINC, COPPER, CALCIUM AND MAGNESIUM IN PLASMA AND ERYTHROCYTES DURING CARDIOPULMONARY BYPASS

Objective To study the changes and their influence factors involved of zinc, copper, calcium and magnesium in plasma and erythrocytes during cardiopulmonary bypass(CPB). Methods Zinc, copper, calcium and magnesium values in plasma and erythrocytes were measured by atomic absorption spectrophotometer during CPB. Results Zinc and copper levels in plasma were significantly elevated above preinduction level before perfusion, but calcium and magnesium levels did not change significantly; zinc, copper and calcium levels in plasma were significantly below preoperation level during CPB, but magnesium level in plasma was significantly increased above preoperation; zinc level in plasma was increased to preoperation level after CPB and began to decrease again at 8 hours after CPB, copper level in plasma was increased to preoperation level at 20 hours after CPB, calcium in plasma was increased significantly from beginning to 8 hours after CPB, magnesium level in plasma was decreased to preoperation level at 8 hours afterCPB. Concentration of zinc , copper, calcium and magnesium in erythrocytes did not change significantly. Conclusion During CPB, the changes of zinc, copper, calcium and magnesium had relation to hemodilution, operative wound, carrier protein, stress and component of priming solution and cardioplegic solution, but no relation to transfer from plasma erythrocytes. The results indicate that it is beneficial to patient's recovery to supplement zinc, copper, calcium and magnesium properly by different ways during cardiac perioperation.

Rapid Inhibition of the Glutamate-induced Increase of Intracellular Free Calcium by Magnesium in Rat Hippocampal Neurons

By using Fura-2/AM, the effects of magnesium (Mg 2+) on the glutamate-induced increase of intracellular free calcium ([Ca 2+]i) in the cultured hippocampal neurons and the features were investigated by integrated photoelectric detecting system. The experiments were designed to three groups (The drug was spit to the cells for 20 s): Group A receiving 1×10 —5 mol/L glutamate; Group B receiving 1×10 —5 mol/L glutamate and1×10 —5 mol/L Mg 2+ simultaneously; Group C receiving 1×10 —5 mol/L glutamate again after [Ca 2+]i in group B back to the baseline. The results showed that in group A, [Ca 2+]i was obviously increased. In group B, the changes in [Ca 2+]i and the peak value were significantly decreased. Moreover, the elevation of Phase 1 was slowed down and Phase 2 was shortened to some extent, and the plateau phase between them was relatively prolonged. In group C, calcium oscillation similar to that in group A occurred, but both the Phase 1 and Phase 2 were shortened and the △[Ca 2+]i was slightly decreased. It was suggested that Mg 2+ could quickly inhibit the rise of [Ca 2+]i induced by glutamate in the cultured hippocampal neurons in rats.

Pharmacological evaluation of catalepsy in low calcium and/or magnesium deficient feeding mice

Populations from the Kii peninsula of Japan and Guam present a high incidence of amyotrophic lateral sclerosis and parkinsonism-dementia complex. It is thought that the low levels of calcium (Ca) and magnesium (Mg) in the drinking water are involved in the pathogenesis of these diseases. The present study aimed to test the hypothesis that catalepsy, a behavioral immobility and one of the Parkinsonian symptoms, may result from functionally impaired dopaminergic neurons in low Ca and Mg (LCa/Mg) fed mice. A group of mice fed with an LCa/Mg diet for 6 weeks was compared to a control group on a standard diet. Cataleptic symptoms such as akinesia and rigidity were measured using the bar test. The antiparkinsonian drugs dopamine (DA) precursor L-3, 4-dihydroxy phenylamine (L-DOPA), the selective DA receptor D2 agonist bromocriptine and the DA releaser amantadine were tested for their effects on the induced catalepsy. Mice developped catalepsy after 3 weeks on the LCa/Mg diet. LCa/Mg diet-induced catalepsy was improved by the administration of either L-DOPA (50 - 200 mg/kg i.p.) in combination with benserazide (25 mg/kg i.p.), bromo- criptine (0.25 - 4 mg/kg i.p.) or amantadine (5 - 20 mg/kg i.p.). These results suggest that catalepsy in LCa/Mg mice might result from a hypofunction of dopaminergic neurons. Moreover, our results support the hypothesis that LCa/Mg in-take may be one etiological factor in neurodegenerative disorders including Parkinson’s disease.