Addition Of Calcium Research Articles

Effect of Calcium Addition on Fluidized Bed Agglomeration Caused by Potassium Phosphates

Effect of Calcium Addition on Fluidized Bed Agglomeration Caused by Potassium Phosphates

Impact of calcium-reinforcement on stability, bioavailability, and bioactivity of quercetin-loaded zein/alginate-pectin nanoparticles.

Cationic calcium ions can crosslink anionic alginate and pectin molecules. It was hypothesized that calcium crosslinking would improve the stability and functionality of biopolymer nanoparticles consisting of zein cores coated by alginate-pectin shells. The effects of calcium ion addition on the structural, physicochemical, and gastrointestinal properties of quercetin-loaded zein/alginate-pectin nanoparticles were therefore investigated. The nanoparticles remained stable to aggregation at calcium ion concentrations of 9 mmol/L or less but aggregated and sedimented at higher concentrations. Calcium ion reinforcement increased the particle dispersion stability even at NaCl concentrations up to 1.4 molL-1. The presence of the calcium ions also reduced quercetin release during the early stages of simulated gastrointestinal digestion but increased its release during the later stages. The relatively high release (56.1%) of quercetin from the calcium-reinforced nanoparticles after digestion resulted in higher intracellular antioxidant activities. The pharmacokinetics of the encapsulated quercetin was measured after its oral administration to rats. The maximal concentration (Cmax) of quercetin in rat plasma for calcium-reinforced nanoparticles was 6.1% higher than non-reinforced nanoparticles; the half-life (t1/2) increased by 17.5%, and the mean retention time (MRT) was 10.0% higher (P < 0.05). These results suggest that calcium ion addition improved the performance and bioavailability of nutraceutical-loaded biopolymer nanoparticles. This might find application in the food and beverage industry. © 2024 Society of Chemical Industry.

The selective adsorption mechanism of calcium ions/pullulan in the flotation separation of chalcopyrite from talc

The flotation separation of chalcopyrite from talc by use of pullulan and sodium butyl xanthate (SBX) under calcium ions was investigated in this study. The single mineral flotation shows that SBX collector had a good collecting ability for chalcopyrite while talc had a good natural floatability. The talc flotation was observably depressed while that of chalcopyrite was not affected in the presence of pullulan alone. With the addition of calcium ions. The depression of talc could be achieved with a small amount of pullulan. The artificial chalcopyrite/talc mixture flotation tests reveal that the addition of pullulan could realize the separation of chalcopyrite from talc in the absence and presence of calcium ions, and the dosage of pullulan with calcium ions was lower than that in the absence of calcium ions. Zeta potential measurements suggest pullulan was easily adsorbed onto the calcium ions treated talc surface, and the XPS tests further confirm that calcium ions could selectively adsorb onto the talc surface and increase its activated sites for hydrogen bonding with pullulan molecules. This study is expect to provide a novel polysaccharide depressant for the beneficiation of chalcopyrite from talc.

Effect of Ca addition on structure, phase composition and hardness of Al–6 %Cu–2 %Mn sheet alloy

The Al–Cu–Mn–Ca system was proposed as a bases for the design of new group of heat-resistant alloys which can be used for high-temperature applications instead of the 2219 types industrial alloys. Unlike the latter ones, the new alloys also do not require a full cycle of strengthening heat treatment including solid solution treatment, quenching and aging. The effect of calcium addition in the 1–4 wt% range on the structure, phase composition and hardness after high temperature annealing of the Al–6 %Cu–2 %Mn base sheet alloy has been studied. It has been shown that calcium addition leads to the formation of high-temperature eutectics (614–617 °С) with the participation of the Al27Ca3Cu7 and (Al,Cu)4Ca phases that are capable of spheroidization at high temperature annealing. The ingots of Ca-containing alloys do not require homogenization but have sufficient deformation plasticity at both hot and cold rolling. The structure of the previously unstudied quaternary Al–Cu–Mn–Ca phase diagram in the region of the aluminum corner has been also proposed, according to which it can contain 5 four-phase fields in the solid state with the participation of (Al), binary (Al2Cu, Al4Ca, Al6Mn) and ternary (Al8CaCu4, Al27Ca3Cu7, Al10CaMn2 and Al20Cu2Mn3) phases. Based on the obtained data, the composition Al–6 %Cu–2 %Mn–1 %Ca has been proposed as a basis for the development of a new heat-resistant alloy. It is shown that this alloy superior to industrial 2219 alloy in terms of heat resistance, especially after annealing at 400 °C, when the difference in hardness reaches 32 HV. The high heat resistance of the new wrought alloy originates from the formation of a specific microstructure consisting of fine Ca-containing eutectic inclusions and Al20Cu2Mn3 phase dispersoids with a size of about 100 nm which prevent recrystallization and allow maintaining the fine sub-grained structure.

Behaviors and Mechanism of Volatiles Producing during Coal Pyrolysis with Calcium Oxide Loading: Insights from Model Compounds Analysis

Calcium is a highly effective catalyst for controlling the tar compounds produced during the pyrolysis of low-rank coal, forming valuable end products. However, the exact catalytic mechanism of calcium in coal pyrolysis remains unclear due to the complex nature of coal. In this study, the pyrolysis process and tar composition of lignite, both with and without the addition of calcium, were investigated across three distinct temperature intervals. The addition of calcium oxide increased the hydrocarbon content of tar by 16.39% in the low-temperature range and 26.53% in the intermediate-temperature range. Four model compounds containing different coal-related functional groups were selected to investigate the effects of calcium on pyrolysis performance and tar composition using thermogravimetric analysis, fixed bed reactor experiments, gas chromatography/mass spectrometry, in situ Fourier transform infrared spectroscopy, X-ray diffractometer, and X-ray photoelectron spectroscopy. The addition of calcium did not affect the thermal decomposition of polystyrene or polyethylene terephthalate; however, the primary pyrolysates underwent secondary reactions on the surface of calcium, which affected the composition of the liquid pyrolysis product. Meanwhile, calcium interacted with the carboxyl and phenolic hydroxyl groups in trimeric acid and phenolic resin to form carboxylates and phenates, which affected the thermal reaction and distribution of liquid products. The influence of calcium on the transformation mechanism of coal-related functional groups provides a theoretical basis for understanding the mechanism of calcium-catalyzed coal pyrolysis.

Comparative Effects of Calcium, Boron, and Zinc Inhibiting Physiological Disorders, Improving Yield and Quality of Solanum lycopersicum.

Localized calcium deficiency at the tomato flower end causes a physiological disorder called blossom end rot, resulting in yield losses of up to 50 percent. Fruit cracking is another physiological disorder of tomatoes that most often occurs when the movement of water and solutes to the tomato is protracted or rapid, but the underlying cause of fruit cracking is, again, calcium deficiency. Therefore, the present field experiment was conducted with the aim of increasing yield and reducing physiological disorders in tomatoes with a foliar application of calcium and micronutrients (zinc and boron). Four levels of calcium (0, 0.3, 0.6, and 0.9%), three levels of boron (0, 0.25, and 0.5%), and three levels of Zinc (0, 0.25, and 0.5%) were applied foliarly three times (starting at flowering, the 2nd application was repeated when the fruits set, and the 3rd after a period of 15 days from the fruits set). An addition of 0.6% calcium increased yield and associated traits with a decreased flower drop. Likewise, a 0.9% calcium addition increased fruit Ca content and decreased blossom end rot, fruit cracking, and Zn content. Foliar spraying with 0.25% boron (compound B) improved flowering and production while reducing flower drop and tomato fruit cracking. Similarly, an application of 0.5% B significantly increased Ca and B content with minimal blossom end rot and Zn content. Likewise, a 0.5% Zn application resulted in yield and yield-related traits with increased fruit B and Zn contents while blossom end rot, fruit cracking, and fruit Ca content were lower when 0.5% of foliar Zn was applied. Therefore, it is concluded that a foliar application of Ca, B, and Zn can be used alone or in combination to minimize the physiological disorders, increase production, and improve tomato fruit quality.

Calcium-Poison-Resistant Cu/YCeO2-TiO2 Catalyst for the Selective Catalytic Reduction of NO with CO and Naphthalene in the Presence of Oxygen.

The pollution from industrial processes based on biomass combustion is still an ongoing problem. In the present contribution, the selective catalytic reduction of NO with CO and naphthalene is carried out in the presence of 10% oxygen. The accumulation of alkaline and alkaline earth metals during biomass combustion is here simulated by the addition of calcium to a Cu-impregnated YCeO2-TiO2 support. The results show that a high dispersion of copper is obtained, which is resistant to the accumulation of calcium. Full conversion of CO and naphthalene is achieved above 200 °C, whereas NO conversions of 80, 90, and 87% are obtained for the catalysts with Ca loadings of 2.6, 5.2, and 13%, respectively, at 350 °C. It is proposed that the high activity of the catalysts is ascribed to the formation of Cu-Ox-Ce species and that the accumulation of Ca acts as a barrier to avoid copper sintering. It was found that different forms of carbonate and nitrite/nitrate species form during reaction, coexisting as adsorbed species during the SCR reaction. The selectivity to N2 was almost 100% in all cases, due to the small presence of NO2 in the reactor outlet (no N2O was detected in any conditions).

Effects of electrokinetic stabilization combined with addition of calcium ions on soil shear strength characteristics in the hilly granitic region of southern China

Enhancing soil shear strength is of great importance in preventing soil collapse and erosion in the hilly granitic region of southern China. However, limited studies have been conducted on improving soil shear strength in collapsing gullies. Electrokinetic stabilization (EKS) involves applying an electrical current through a soil mass to promote the migration of chemicals from injection points, thereby altering the chemical composition of the treated soil to improve its physical properties. In this study, the effects of calcium chloride (CaCl 2 ) addition and EKS techniques on the soil shear characteristics (shear strength, and its two components: cohesion and internal friction angle) of three different soil layers in collapsing gullies were investigated. The results showed that the EKS techniques significantly increased the migration of calcium ions from the anode to the cathode region of the power supply device used in the soils. Using EKS process alone did not increase or even decrease the soil shear strength, but combining EKS with CaCl 2 injection (Ca-EKS) increased the soil shear strength, and this increase was mainly due to the increasing the soil cohesion. The soil cohesion after Ca-EKS treatment increased on average by 49.84%, 83.11%, and 100.36% compared with the soil without treatments (CK) for the red soil, sandy soil, and detritus, respectively. However, soil amended by sole CaCl 2 addition, Water-EKS or Ca-EKS all can not increase soil internal friction angles compared with the CK. These results demonstrated that the application of Ca-EKS can be applied to improve the soil shear strength and stability of gully walls in hilly granitic regions.

The role of calcium addition through powder sintering process in microstructure and mechanical behavior of a microalloyed magnesium

Calcium effectively strengthens magnesium through grain refinement when added in small quantities using the ingot metallurgy process. The extremely low solubility of calcium in magnesium restricts its addition using traditional powder metallurgy processes. However, the powder metallurgy process provides advantages like reduced material loss, properties control, and net-shape products. Hence, in this study, a diluted magnesium-calcium alloy was processed using the traditional blend-press-sinter (BPS) powder metallurgy process. Commercially pure magnesium was microalloyed with 0.4 wt% calcium. The sintered magnesium-calcium alloy was subjected to high-temperature extrusion. Microstructural characterization of the microalloyed Mg0.4Ca alloy revealed that the elemental calcium diffused into the magnesium particles during the sintering process and developed a gradient granular microstructure. The added initial calcium nanoparticles also acted as nucleation sites for magnesium during the sintering process. The gradient microstructure recrystallized and grew into equiaxed grains during the subsequent extrusion process. Mechanical properties characterization revealed that the addition of calcium as solute atoms increased the hardness, compressive strength, and ductility of magnesium, which was further enhanced by the extrusion process. The presence of calcium as solute atoms increased the tensile strength of extruded magnesium by a reasonable amount, while ductility remained almost unchanged.

Simultaneous hydroxyapatite-based phosphorus recovery and partial denitrification-anammox-based nitrogen removal during sludge leachate treatment

Anammox has been widely applied for treating high ammonia‑nitrogen leachate, but challenges remain due to the phosphorus in the wastewater and by-products nitrate (NO3−). Therefore, we combined partial denitrification-anammox and hydroxyapatite crystallization within a single UASB reactor. This method achieved an effluent with a 4.27 ± 0.45 mg TN/L and a maximum PO43− removal efficiency of 68.31 ± 5.42 %. The addition of excess calcium led to an increase in phenylalanine-like substances, the humification index (HIX) of extracellular polymeric substances (EPS), and the MLVSS/MLSS ratio. These changes indicated that hydroxyapatite coated the initial granular sludge, causing it to crack and re-granulate, but the MLVSS didn't decrease significantly. Therefore, calcium addition didn't significantly impact the function of biomass. Metagenomic analysis revealed that by-products NO3− was removed through partial denitrification using in-situ refractory dissolved organic matters in SL. The formation of hydroxyapatite crystals is the main pathway for PO43− removal, and biological process also contributed to some PO43− removal. Overall, our study provided a viable solution for the simultaneous removal of nitrogen and recovery of phosphorus from high ammonia‑nitrogen wastewater.

Commercially available carrageenans show broad variation in their structure, composition, and functionality

Carrageenans are polysaccharides from red algae which are widely used as food additives and in other applications. Their structure is often described by different disaccharide repeating units, although it was already demonstrated that reality is more complex. In many studies, commercial carrageenans were used to establish structure function relationships, but a structural and compositional analysis was rarely conducted. Therefore, the aim of our study was to systematically and comprehensively characterize a broad collection of commercial carrageenans with different specifications from different manufacturers. For a more detailed characterization, an analytical approach based on partial enzymatic hydrolysis in combination with HPLC–MS and HPSEC-RI was developed and applied. Furthermore, rheology was used to gain detailed insights into the functionality of selected samples. Our results demonstrate that significant structural variation can be observed for commercial carrageenans. The samples contained different cations and the carrageenan type specified by the manufacturer did not always represent the structure of the corresponding polysaccharides. This was especially true for λ-carrageenans: Of the six commercial samples analyzed, none contained structural elements from the λ-type. Instead, the corresponding carrageenans contained κ-, ι- and ν-units. The application of the developed enzymatic-chromatographic approach showed that different hybrid carrageenans are present. In addition, the rheological analysis of the commercial carrageenan samples showed clear differences in the gelling properties upon calcium addition which could influence their behavior in different applications. Our results demonstrate that before an investigation of structure–function relationships, commercial carrageenan samples should be analyzed for their structure and composition. We also showed that the enzymatic-chromatographic approach described in this study is well suited for this purpose.

Underestimation of calcium carbonate saturation state in marginal seas due to the disregard of calcium ion addition: A case study of the Bohai sea, China

Seawater calcium ion (Ca2+) concentration was investigated based on the potentiometric titration method during the summer of 2018 in the Bohai Sea, China. The measured Ca2+ concentration ranged from 7760 to 9739 μmol kg−1 and deviated from the theoretical Ca2+ values, which were estimated from the calcium/salinity ratio. The excess calcium (Ca2+excess) ranged from 186 to 1229 μmol kg−1, showing a decreasing trend from the estuary to the nearshore, and then the offshore areas. Riverine input was an important source of seawater Ca2+excess in the Bohai Sea. Biological activity was another factor in regulating seawater Ca2+excess by precipitation in the Yellow River estuary and dissolution in other area of the Bohai Sea. Furthermore, the aragonite saturation state (Ωarag) values calculated from the measured Ca2+ concentrations showed a significant deviation from the values calculated from the theoretical Ca2+ concentrations, especially in the estuarine area with a maximum difference of 18.5%. Therefore, the disregard of the calcium addition would lead to an underestimation of the calcium carbonate saturation state and a deviation in the assessment of ocean acidification in marginal seas.

Synthesis of nanoscale zirconium carbide powders via a two-step process

Herein, ZrC powders with the average particle sizes of 100–300 nm were synthesized via a method composed of vacuum carbothermal reduction followed by calcium treatment. The effects of carbon and calcium addition amounts as well as temperature on the micromorphology of obtained products had been studied, and the involved mechanisms were described. Due to the dissolution-transportation-precipitation mechanism, ZrC grains would grow during the calcium treatment process. The finest ZrC with the average particle size of 126.2 nm could be obtained by the combination of vacuum carbothermal reduction at 1773 K for 4 h and calcium treatment at 1173 K for 4 h, with the carbon addition amount of 1.2 times the theoretical value. Furthermore, carbon defect was found in the final products and the lattice spacing was in good agreement with those calculated by proposed formula.

Practical Implications of Using an Online Data-Driven Optimizer for Calcium-Treated Steels

Calcium (Ca) additions during secondary steelmaking are a well-adopted practice to transform solid oxide non-metallic inclusions (NMIs) into globular-shaped liquid oxides. The claimed hypothesis that liquid NMIs reduce SEN clogging has been proven in the past by researchers. However, the exact quantity of Ca needed to transform the physical state of NMIs during steelmaking remains uncertain. Operators in the steel plant use a consistent quantity of Ca additions for specific steel grades, but this approach does not account for the varying physical states and evolving dynamics of NMIs characteristics in each ‘heat’. To overcome this, a study was conducted to explore the impact of varying Ca additions on the transformation and behavior of NMIs in low-alloyed Ca-treated steel grades. The aim was to establish a more reliable and responsive approach to Ca treatment, potentially leading to more effective control in preventing submerged entry nozzle (SEN) clogging. The proposed methodology involved online monitoring of NMIs state coupled with controlled variations in Ca addition, deviating from fixed quantity, to observe its effects on NMIs state transformations. Through careful analysis of collected data and the implementation of a data-driven optimizer, this study reports the practical implications of using optimal amounts of Ca during secondary steelmaking. The resulting change due to dynamic calcium silicide (CaSi)-cored wire additions and their impact on SEN clogging were evaluated. The findings reveal the significant role of optimal CaSi wire additions, leading to improved steel castability and a notable 30 pct reduction in SEN clogging tendencies. The results obtained after the implementation of the data-driven optimizer ‘ClogCalc’ have significant implications for steel manufacturers, offering new insights into enhancing Ca treatment efficiency.

Abstract Mo042: Poison Peptides May Contribute to Dysregulation of SERCA in Heart Failure

Proteolysis increases in heart disease, resulting in an accumulation of degraded membrane protein fragments in heart cells. Previous studies have shown that diverse hydrophobic alpha helices can bind and non-specifically inhibit the cardiac calcium pump SERCA. Thus, we hypothesized that partially degraded fragments of transmembrane proteins may directly inhibit SERCA or compete with native peptide regulators of the pump, like such as phospholamban. The resulting dysregulation of SERCA may contribute to calcium mishandling in heart failure. To test these hypotheses, purified cell membranes from non-failing or dilated cardiomyopathy human hearts were subjected to SDS-PAGE and mass spectrometry to identify protein fragments smaller than 26 kD. 1800 proteins were detected, of which 92 were upregulated &gt;3 fold in the failing heart samples, consistent with increased production of small fragments from these membrane proteins. 9 of the upregulated fragments containing transmembrane segments were selected for further analysis based on sequence hydrophobicity and structural similarity to endogenous micropeptide regulators of SERCA. Of these 9 fragments, 6 showed ER localization, suggesting potential for a toxic interaction with SERCA. The relative binding of these candidates to SERCA was quantified with FRET microscopy. Fragments of three membrane proteins (SEC61B, VAMP3, VAMP8) showed an avid interaction with SERCA. To measure SERCA inhibition, we utilized a calcium activity assay was performed usingin which HEK293T cells were transfected with SERCA, ryanodine receptor, candidate peptides and rCepia as an ER calcium indicator. ER-calcium level was normalized to minimum fluorescence after caffeine addition and an ionomycin induced maximum fluorescence after addition of ionomycin and calcium and caffeine induced minimum. Unregulated Candidate poison peptides were compared to SERCA alone and SERCA-PLB phospholamban controls were also performed. . SEC61B demonstrated the a strongest inhibition, most (similar to phospholamban, ) while VAMP3 and VAMP8’s effect was more modest. This type of non-nativeThus, we propose accumulation of toxic transmembrane peptide fragments may inhibition could be contributinginhibit SERCA and contribute to the calcium mishandling seen in heart failure. Future experiments will be performed to quantify the relative abundance of the fragments compared to endogenous regulatory micropeptides.

Ageing Characteristics of Stir Cast AZ 61 Alloy with Minor Additions

Background: Knowing that magnesium (Mg) alloys and its composites bear the potential of being used simultaneously for light structural as well as biomedical applications, it appears prudent to look for developing a novel Mg alloy; the concurrent demand is to monitor recent trend in development of functional Mg-alloy and its composite materials through extensive patent search. Review of recent patents in the related field makes it relevant to investigate this aspect. Objective: The authors aim to study the evolution of structure and properties in stir cast of AZ- 61 alloy with minor additions of scandium, calcium and manganese. This paper reports the results of this investigation. Methods: The castings are prepared by stirring the molten alloy at 600 rpm for 10 minutes, followed by pouring into a preheated metal mould. The solidified alloys are homogenized at 550°C for 12 hours. The homogenized alloys are then subjected to solutionising treatment at 500°C for 5 hours; subsequently, the alloys are quenched in iced water. The quenched alloys are subjected to ageing treatment at different temperatures between 100°C to 400°C at an interval of 100°C. Similar experiments are conducted with its statically cast counterparts. The structure and properties of all the samples have been characterized by optical and scanning electron microscopy, and XRD analysis; DSC heating run is conducted to study the kinetics of phase transformation. Mechanical behaviour of castings is studied with the aid of tensile testing and fractography. Moreover, tribological behaviour of alloys is assessed by wear testing with the help of pin on disc method. Results: The results show that the stir cast alloy produces a homogeneous structure with significant improvement in properties. The precipitates of Mg17Al12, Al Mn, Mg Zn2, Al2 Ca and Mg2 Ca are formed due to the ageing of both stir cast and statically cast alloy. It is found that the diffusion of Al in magnesium controls the precipitation process. The tribological properties are found to be satisfactory for the stir cast alloy. Conclusion: The modified AZ61 alloy with minor additives, achieves excellent structural homogeneity and mechanical properties after stir casting followed by quench ageing.

The effect of pH shifting on the calcium-fortified milk analogue with chickpea protein

Milk alternative attracts more attention due to nutrition benefits, but the low solubility and the calcium deficiency of plant protein hinder the development of milk alternatives. Therefore, pH shifting was optimized to improve chickpea protein solubility and calcium fortification while ensuring good digestibility. The results showed that pH shifting reduced the particle size from 2197.67 ± 178.2 nm to 80.2 ± 2 nm, and increased the net ζ potential from −0.48 ± 0.24 to −21.27 ± 0.65 due to the unfolding of secondary protein structure, by which chickpea protein bring better solution stability. Additionally, the whiteness of the solution with chickpea protein increased. The calcium addition kept the solution stable with small particle size despite a slight increase. The microstructure of chickpea protein during digestion was well disrupted even with fortifying calcium. This study provides proof of the positive effect of pH shifting on chickpea protein stability and calcium fortification

Improving foam stability: Calcium addition, high hydrostatic pressure, and their combinations on soybean protein isolates

Various combinations of high hydrostatic pressure treatment (HHPT, 0.1 or 600 MPa), calcium addition (0, 0.50, or 0.75 mmol CaCl2/g protein), and protein content ([Prot.], 1, 5, or 10 g/L) were applied to soybean protein isolate (SPI) dispersions to analyze their effects on the formation and stability of foams. The significant interactions between these factors led to several combinations that improved foam stability via different mechanisms that involved different solubilities, aggregate sizes, and molecular structures of proteins. Thirty min after foam formation, calcium combined with HHPT improved volume of foam (VF30) and volume of liquid retained (VLr30), by the formation of strong interfacial films owing to the increased cross-linking ability of soluble and intermediate-sized aggregates. Calcium without HHPT had a greater effect on VLr30 than on VF30, which could be owing to the insoluble and large aggregates that blocked Plateau borders. HHPT without calcium led to small denatured aggregates that were soluble and improved the VLr30 when [Prot.] was lower. Industrial relevanceCalcium enriched plant proteins with good techno-functional properties is a prevailing need, considering the current cultural, economic and environmental changes that occur. The findings of this study could serve as an input for the incorporation of high biological value proteins and calcium into aerated foods, and would contribute to develop innovative products. Treatment with high hydrostatic pressure could be advantageous on account of modifying the protein structure and thereby improving the stability of the foams. Under certain conditions, such as those of aerosol whipping creams, high hydrostatic pressure would simultaneously improve techno-functional properties of proteins and pasteurize the dispersions, which would then have to be safely canned.

Calcium ions do not influence the Aβ(25–35) triggered morphological changes of lipid membranes

We have studied the effect of calcium ions (Ca2+) at various concentrations on the structure of lipid vesicles in the presence of amyloid-beta peptide Aβ(25–35). In particular, we have investigated the influence of calcium ions on the formation of recently documented bicelle-like structures (BLSs) emerged as a result of Aβ(25–35) triggered membrane disintegration. First, we have shown by using small-angle X-ray and neutron scattering that peptide molecules rigidify the lipid bilayer of gel phase DPPC unilamellar vesicles (ULVs), while addition of the calcium ions to the system hinders this effect of Aβ(25–35). Secondly, the Aβ(25–35) demonstrates a critical peptide concentration at which the BLSs reorganize from ULVs due to heating and cooling the samples through the lipid main phase transition temperature (Tm). However, addition of calcium ions does not affect noticeably the Aβ-induced formation of BLSs and their structural parameters, though the changes in peptide's secondary structure, e.g. the increased α-helix fraction, has been registered by circular dichroism spectroscopy. Finally, according to 31P nuclear magnetic resonance (NMR) measurements, calcium ions do not affect the lipid-peptide arrangement in BLSs and their ability to align in the magnetic field of NMR spectrometer. The influences of various concentrations of calcium ions on the lipid-peptide interactions may prove biologically important because their local concentrations vary widely in in-vivo conditions. In the present work, calcium ions were investigated as a possible tool aimed at regulating the lipid-peptide interactions that demonstrated the disruptive effect of Aβ(25–35) on lipid membranes.

Experimental evidence reveals the mobilization and mineralization processes of rare earth elements in carbonatites.

Whereas the genesis of carbonatitic rare earth element (REE) deposits has long been a focus of study, the controls on mobilization and mineralization of REEs during magmatic-hydrothermal processes still remain open to debate. Here, we present our investigation of the dissolution and crystallization of REE (fluor)carbonate minerals in alkaline carbonate brine-melts up to 850°C and 11.6 kbar. Our results show that REEs are soluble in Na2CO3 brine-melts, achieving concentrations exceeding 8 weight % at temperatures above 650°C. The addition of calcium and/or fluoride has minimal impact on REE mobilization, whereas introduction of silica suppresses REE solubilities by half, due to britholite formation above 550°C. Upon cooling, sodium and REEs combine to crystallize in burbankite or carbocernaite in sodium-enriched brine-melts, even at fluoride saturation. However, while the brine-melts contain substantial ferro- or aluminosilicate, REE mineralization in fluorcarbonates occurs after sufficient sodium precipitation in alkaline silicate minerals, hence revealing how silicate and sodium carbonate govern REE mineralization.