Increase In Ca Concentration Research Articles

A chloroplast localized heavy metal-associated domain containing protein regulates grain calcium accumulation in rice

Calcium (Ca) is an essential mineral nutrient and plays a crucial signaling role in all living organisms. Increasing Ca content in staple foods such as rice is vital for improving Ca nutrition of humans. Here we map a quantitative trait locus that controls Ca concentration in rice grains and identify the causal gene as GCSC1 (Grain Ca and Sr Concentrations 1), which encodes a chloroplast vesicle localized homo-oligomeric protein. GCSC1 exhibits Ca2+ transport activity in heterologous assays in yeast and Xenopus laevis oocytes and is involved in the efflux of Ca2+ from the chloroplast to the cytosol. Knockout of GCSC1 results in increased chloroplast Ca concentration, lower stomatal conductance in leaves and enhanced Ca allocation to grains. Natural variation in grain Ca concentration is attributed to the variable expression of GCSC1 resulting from its promoter sequence variation. Our study identifies a chloroplast localized heavy metal-associated domain containing protein that regulates chloroplast Ca2+ efflux and provides a way to biofortify Ca in rice to benefit human nutrition.

Mechanisms of calcium-mediated As(V) immobilization by undissolved and dissolved biochar in saline-alkali environments

The environmental impact of arsenic (As) pollution has been a focal point within environmental science. In arsenic-polluted saline-alkali environment, the addition of exogenous biochar can affect the morphological transformation of As both through direct and indirect mechanisms, with calcium ions (Ca(II)) playing a crucial role. This study investigates the immobilization mechanisms of undissolved biochar (UOB) and dissolved biochar (DOB) on As(V) in the absence and presence of Ca(II) under alkaline conditions and aerobic atmosphere. While UOB and DOB alone are insufficient for As(V) immobilization, their combined action in the presence of Ca(II) achieves remarkable immobilization rates of 91.9% and 98.1%, respectively. Precipitation of calcium arsenate is identified as the primary immobilization pathway in both the UOB-Ca(II)-As(V) and DOB-Ca(II)-As(V) systems. Furthermore, Ca(II) acts as a mediator for As(V) immobilization through the formation of ternary UOB/DOB-Ca-As complexes, which are corroborated by Density Functional Theory (DFT) analysis from a microscopic perspective. Notably, the synergistic immobilization of As by DOB and newly generated CaCO3 in DOB-Ca(II)-As(V) system is highlighted. Additionally, the increase in Ca(II) concentration (0–100 mM) and solution pH (9.0–12.0) both significantly enhance the immobilization of As(V). An increase in the dosage of UOB (0.4–4 g/L) reduces the immobilization of As(V), while effect of the DOB concentration is insignificant. This study provides new insights into how the release of two biochar fractions into a typical Ca(II)-rich saline-alkali environment may alter the fate and transport of As species.

Oxygen vacancy induced electrical conductivity enhancement in Ca-doped BiFeO3 thin films

Bismuth ferrite, recognized for its exceptional physical properties as a multiferroic material, has recently attracted considerable attention due to its high domain wall conduction. However, challenges in further improving domain wall conductivity and magnetoelectric coupling hamper the practical application of pure-phase BFO thin films. Addressing these limitations, we successfully synthesized Bi1-xCaxFeO3 thin films on LaAlO₃ (001) substrates with varied calcium (Ca) doping levels (x = 0–0.3) through pulsed laser deposition. Our experimental data demonstrate a direct relationship between the films' electrical conductivity and the prevalence of oxygen vacancies (OV). An upward trend in both OV density and electrical conductivity emerges with incremental Ca doping, peaking at x = 0.2. Beyond this doping threshold, a further increase in Ca concentration inversely affects OV density and electrical conductivity. These insights suggest that fine-tuning OV concentration in Ca-doped BFO thin films can significantly modulate their electrical properties, paving the way for the advancement of bismuth ferrite-based electronic devices.

STOP1 regulates CCX1-mediated Ca2+ homeostasis for plant adaptation to Ca2+ deprivation.

Calcium (Ca) is essential for plant growth and stress adaptation, yet its availability is often limited in acidic soils, posing a major threat to crop production. Understanding the intricate mechanisms orchestrating plant adaptation to Ca deficiency remains elusive. Here, we show that the Ca deficiency-enhanced nuclear accumulation of the transcription factor SENSITIVE TO PROTON RHIZOTOXICITY 1 (STOP1) in Arabidopsis thaliana confers tolerance to Ca deprivation, with the global transcriptional responses triggered by Ca deprivation largely impaired in the stop1 mutant. Notably, STOP1 activates the Ca deprivation-induced expression of CATION/Ca2+ EXCHANGER 1 (CCX1) by directly binding to its promoter region, which facilitates Ca2+ efflux from endoplasmic reticulum to cytosol to maintain Ca homeostasis. Consequently, the constitutive expression of CCX1 in the stop1 mutant partially rescues the Ca deficiency phenotype by increasing Ca content in the shoots. These findings uncover the pivotal role of the STOP1-CCX1 axis in plant adaptation to low Ca, offering alternative manipulating strategies to improve plant Ca nutrition in acidic soils and extending our understanding of the multifaceted role of STOP1.

The effect of various Sn and Ca equal proportional addition on the microstructure, mechanical behavior and corrosion performance of Mg alloys

In the present study, the effects of various Sn and Ca equal proportional addition (0.3:0.1, 0.6:0.2, 1.2:0.4, wt%) on the microstructure, mechanical properties and corrosion behavior of Mg-Sn-Ca alloys were systematically investigated. With the increase of Sn and Ca content, microstructure uniformity of the Mg-Sn-Ca alloy was improved, the average grain size was refined (from 34.4 μm to 21.62 μm, 13.47 μm), and more CaMgSn phases were generated (from 0.39 % to 1.64 %, 4.53 %). With increasing Sn and Ca content, the tensile yield strength (TYS) and ultimate tensile strength (UTS) of Mg-Sn-Ca alloys were gradually increased (TYS: from 91.8 MPa to 98.24 and 125.05 MPa; UTS: from 187.48 MPa to 190.73 and 214.58 MPa), mainly due to the contribution of grain refinement. The electrochemical tests revealed that the corrosion resistance of the Mg-Sn-Ca alloy initially decreases and then increases with the increase of Sn and Ca contents. The hydrogen evolution volume of Mg-0.3Sn-0.1Ca alloy was 41.91 mL cm−2, and the corrosion current density was −1.54 × 10−3 A/cm2. As for Mg-0.6Sn-0.2Ca alloy, deteriorated corrosion resistance compared to the Mg-0.3Sn-0.1Ca alloy was mainly ascribed to the micro-galvanic corrosion between the CaMgSn phase and Mg-matrix. The Mg-1.2Sn-0.4Ca alloy had the best corrosion resistance, with the lowest hydrogen evolution volume of 34.09 mL cm−2 and a minimum current density of −1.15×10−3 mA cm−2, its high corrosion resistance could be attributed to the grain refinement and homogenous distributed CaMgSn phase and more generated Ca(OH)2 product film with dense-structure.

Engineering Corrosion Resistance in Magnesium Alloys for Biomedical Applications: A Synergy of Zn/Ca Atomic Ratio and Texture-Based Approach

Magnesium (Mg) and Magnesium-Zinc-Calcium alloys present a compelling option for biodegradable implant materials. Utilizing Vacuum Induction Casting, Mg–2.5Zn-xCa (with x = 0.3, 0.5, 0.9, 1.15 wt%) alloys were fabricated and subjected to hot-rolling for thermo-mechanical processing. The hot-rolled Mg–2.5Zn-0.3Ca alloy exhibits the lowest corrosion rate along with the highest basal texture. Increasing the Zn/Ca atomic ratio intensifies the basal texture and enhances corrosion resistance. Elevated Zn concentration improves corrosion resistance via Ca2Mg6Zn3 phase formation, while increased Ca content diminishes corrosion resistance due to the Mg2Ca phase. Advancement of this alloy is poised to extend Mg alloy use in innovative biomedical bone implants.

Improved ferroelectricity and endurance in Ca doped Hf0.5Zr0.5O2 films

Doped Hf0.5Zr0.5O2 materials have drawn increasing attention due to the excellent ferroelectric properties, but the relevant research is just in the preliminary stage and the reported doped systems are rare. In this work, Ca doped Hf0.5Zr0.5O2 (Ca:HZO) ferroelectric films were successfully fabricated via chemical solution deposition and investigated for the first time. It is observed that Ca doping induces a phase transformation from monoclinic to orthorhombic/tetragonal and then to monoclinic/tetragonal. The highest orthorhombic phase fraction is achieved in 2.5 mol% Ca doped HZO film, contributing to the optimum ferroelectric property with the largest remnant polarization of 14.00 μC/cm2 after 105 cycles. Additionally, the leakage current density is observed to decrease with increasing Ca content, which is mainly associated with the changes of grain size and surface roughness. As a result, the endurance is significantly improved in the Ca doped films, and an excellent endurance of 1010 cycles is achieved in the 2.5 mol% Ca doped film. These results suggest that Ca doping can enhance the ferroelectric and endurance properties of HZO films by optimizing the phase and morphological structure.

Milk component ratios and their associations with energy balance indicators and serum calcium concentration in early-lactation spring-calving pasture-based dairy cows

Indirect assessment of metabolic status using milk samples provides a non-invasive and objective tool for cow-level health monitoring. Milk fat-to-protein ratio (FPR) has been commonly evaluated as an indirect measure for negative energy balance (EB) in confined dairy cows. However, milk component ratios have not been explored for their association with pasture-based cows' metabolic status. The objectives of this observational study were to 1) describe milk component ratios from 0 to 45 d postpartum, 2) evaluate the associations between milk component ratios [FPR, fat-to-lactose (FLR), protein-to-lactose (PLR)] and indicators of EB (serum β-hydroxybutyrate (BHB) concentration at 5-45 d postpartum and body condition score (BCS) change during the transition period), and 3) evaluate the associations between milk component ratios and serum Ca concentration 0-4 d postpartum in spring-calving dairy cows from pasture-based commercial farms. Milk component ratios were determined on samples collected before AM or PM milkings from 548 cows at 0-45 d postpartum (n = 970). Serum BHB and Ca determinations were performed in blood samples collected at the time of milk sample collection at 5-45 d postpartum (n = 918) and 0-4 d postpartum (n = 50), respectively; and BCS change was calculated using BCS assigned between 29 d prepartum and 45 d postpartum (n = 851). Cows' calving date, parity (1st, 2nd-3rd or ≥ 4th) and breed (Holstein-Friesian or dairy crossbred) information was obtained from the farm records. Data was analyzed by multiple linear regression. Average milk FPR, FLR and PLR were 0.70, 0.53 and 0.72, respectively. Milk FPR linearly increased while milk FLR linearly decreased postpartum both at a rate of 0.004 units per day; milk PLR decreased 0.05 units per day for the first 30 d postpartum and moderately increased afterward. Milk FPR and FLR were 0.71 and 0.52 units lower before AM than PM milking, respectively; while milk PLR was similar before AM and PM milking. Milk FPR and FLR were 0.07 to 0.10 units higher for 2nd-3rd compared with 1st and ≥ 4th parity cows. Milk PLR was 0.03 units greater for ≥ 4th compared with 2nd-3rd and 1st parity cows. Further, crossbred cows had 0.07, 0.08 and 0.03 higher milk FPR, FLR and PLR than Holstein-Friesian cows, respectively. Moderate to high P-values along with moderate to small estimated slopes and wide 95% confidence intervals were observed for the associations between milk component ratios and indicators of EB. A positive linear association was observed between milk FPR and serum Ca concentration within 4 d postpartum; milk FPR increased 0.31 units per each mmol/L increase in serum Ca concentration. Cows with low serum Ca concentration within 4 d postpartum had 0.27 units lower milk FPR compared with cows at or above the threshold (2.12 mmol/L), and tended to have 0.15 units lower milk FPR compared with cows at or above the threshold (2.00 mmol/L). In conclusion, further research is needed to reach conclusions on the association between milk component ratios determined before milking and EB indicators. The potential of milk FPR for monitoring blood Ca status warrants further investigation in early-lactation pasture-based dairy cows.

Calcium fertilization on the Phalaenopsis ssp. cultivation (Orchidaceae)

The cultivation efficiency and quality improvement of Phalaenopsis sp. production through mineral nutrition has been widely studied. The objective of this study was to evaluate the effects of different concentrations of calcium (Ca) in the nutrient solution on the growth, nutrient uptake, and overall health of Phalaenopsis sp. Seedlings obtained from in vitro propagation at 6 months of age were fed biweekly with a nutrient solution suggested by Hoagland and Arnon with modified Ca concentrations of 0 mM, 1.25 mM, 2.5 mM, 5 mM, 7.5 mM, and 10 mM. After 24 months, characteristics such as number of leaves, width and length of the largest leaf, total leaf area, dry mass of leaves and roots, leaf texture, and number and dry mass of flowers were evaluated. Macronutrient content was determined from leaf dry mass. Substrate pH and electrical conductivity were also measured. Increasing Ca concentrations up to 6.25 mM improved leaf length, total leaf area, number of flowers and flower dry mass. Leaf texture and electrical conductivity of the substrate increased up to a Ca concentration of about 2.5 mM. Leaf nitrogen and phosphorus contents increased with higher Ca concentrations. Optimal Ca fertilization at 6.25 mM had positive effects on both vegetative and reproductive growth, with no visual symptoms of Ca deficiency observed during vegetative development. These results emphasize the importance of precise and tailored nutrient management, not only to avoid hidden deficiencies, but also to maximize the quality and commercial value of Phalaenopsis sp. plants.

The efficiency of Ca and K nitrate on the control of SERB damage in 'Thomson’ orange by modification of peel physical and chemical characteristics

One of the most severe peel physiological disorders of orange fruits is Stem End Rind Breakdown (SERB), a severe postharvest physiological disorder. We expected foliar Ca and K application to reduce orange SERB by modifying several peel biochemical and physical characteristics. Therefore, one experiment (2018–2020) was designed in complete randomized blocks in four treatments with three replicates. Experimental treatments included foliar spray of (1) K nitrate; (2) Ca nitrate; (3) Ca, and K nitrate separately, with a time interval (Ca + K; combination of treatments 1 and 2); (4) control. The effects of treatments were evaluated on several parameters underlying fruit peel quality at harvest and intensity of SERB damage after 12 wk of fruit storage at 5 ◦C and 85% RH. The results showed that K-treated fruits had higher TSS and TSS/TA than other fruits. Also, the Ca treatments (including Ca and Ca + K treatments) increased Ca content in fruit peels and significantly decreased SERB damage and weight loss by 70% and 30%, respectively. In addition, Thomson orange peel obtained from Ca-treated trees (including Ca and Ca + K treatments) displayed elevated levels of pectin than other fruits. In contrast, the peels of fruits picked from trees sprayed with Ca, especially those treated with Ca + K, exhibited lower levels of total phenolic, antioxidant, and electrolyte leakage than other fruits. This study suggests that foliar application of Ca(NO3)2 and KNO3 during the fruit growth cycle while improving the internal quality of the fruit is an effective agronomical strategy that prolongs Thomson orange shelf life.

Changes in calcium accumulation and utilization efficiency and their impact on recycling, immobilization, and export across the oil palm cycle

Effective calcium (Ca) management is crucial for optimizing oil palm cultivation and enhancing crop yield. This study aimed to gain insights into the dynamics of Ca concentration, accumulation, exportation, immobilization, and recycling in various oil palm organs relative to plant age. The experiment was conducted at the Agropalma enterprise site in the northeastern region of Pará State, Brazil, evaluating seven plant age treatments: 2, 3, 4, 5, 6, 7, and 8 years old. Employing a completely randomized design with four replications. The results demonstrated an age-related increase in Ca concentration in petioles, rachis, arrows, male inflorescences, peduncles, and fruits. Furthermore, Ca accumulation exhibited an upward trend in all organs with progressing plant age. Notably, the study revealed an enhanced Ca use efficiency across all plant organs in correlation with the age of oil palm cultivation. These findings underscore the dynamic nutritional demands of oil palm, influencing Ca immobilization, cycling, and export throughout its developmental stages.

VALUE OF BONE REMODELLING MARKERS IN MANDIBULAR FRACTURE PATIENTS BY GENDER AND BONE MINERAL DENSITY

Numerous studies have shown that fractures of the mandible are the most common injuries of the facial skeleton. The high incidence of such fractures is due to the anatomical and physiological characteristics of the mandible, as well as a variety of local and general causes. Disturbances in the structural-functional properties of bone tissue can occur as a result of internal and external influences and provide a favorable background for the development of fractures in various locations, including the mandible. A large number of regulatory factors of a nervous, humoral and immune nature, the presence of inflammation as an obligatory (first) phase of reparative regeneration after bone damage, dictate the need for an in-depth study of the structuralfunctional state of bone tissue in patients with traumatic injuries of the mandible, through the improvement of diagnostic and therapeutic methods. The aim of the study is to analyze the levels of bone remodeling markers in the oral fluid of patients with traumatic lesions of the mandible according to sex and BMD status compared with those of practically healthy control subjects (without general somatic and dental diseases). Materials and methods. The study is based on the results of laboratory tests on 151 people (main group) with mandibular fractures and 30 people (control group) without general somatic and dental diseases. The study included patients of both sexes aged 18-44 years: 92 (60,93%) male and 59 (39,07%) female patients. The levels of total calcium (Ca) and inorganic phosphorus (P) in the oral fluid were determined by photometric methods using commercial kits from «Filisit-Diagnostics» (Ukraine). The activity of alkaline phosphatase and acid phosphatase in oral fluid was determined by the kinetic method with n-nitrophenol phosphate. Oxyproline excretion was determined in daily urine using the Cobas test system (Roshe Diagnostics, Germany). Statistical processing of the study results was performed using Microsoft Excel and Statistics software packages for the statistical analysis of biomedical research data. Results and discussion. As a result of the studies, it was found that in men with osteoporosis, the levels of P in oral fluid were not significantly different from those in the control group, p>0,05. At the same time, the remaining values of bone remodeling markers in biological fluids were characterized by a pronounced imbalance, namely an increase in Ca content by 92,85%, p<0,01, p1<0,05, Ca/P ratio by 2,8 times, p, p1<0,01, AP activity by 89,48%, p<0,01, p1>0,05, ALP by 56,34%, p<0,05, p1>0,05, and urinary hydroxyproline level by 54,09%, p, p1<0,01, compared with the same data in the control group. In women with osteoporotic mandibular fractures, the values of all the parameters studied were significantly different from those of the control group. Thus, we found an increase in the oral fluid content of Ca – by 102,38%, p, p1<0,05, Ca/P ratio – by 3,5 times, p, p1<0,01, AP activity – by 99,06%, p, p1<0,01, ALP – by 65,15%, p, p1<0,01 against a decrease in the value of P – by 42,31%, p, p1<0,05, compared to the data of the control group. At the same time, in this subgroup of women there was an increase in urinary hydroxyproline by 58,26%, p, p1<0,01, compared to the data in the control group. Conclusions. Thus, analysis of bone remodeling marker levels showed that in patients with mandibular fractures due to destruction of the bone matrix as a result of trauma, there was an increase in osteoresorption activity that depended on the structural-functional state of the patients' bone tissue and was more pronounced in women.

Effect of Calcium Addition on Oxide and Sulfide Inclusions in Heavy Steel Ingot Simulated by Lab Experiments

The effect of calcium addition on inclusions (oxides and sulfides) in heavy steel ingot is investigated via lab experiments and thermodynamic calculation. The characteristics (chemistry, size, morphology, and number) of inclusions in the steel samples are investigated by scanning electron microscope with an energy‐dispersive spectrometer. The three‐dimensional morphology of inclusions is investigated by the nonaqueous solution electrolysis method. Inclusions in the fast‐quenched steel are changed from Al2O3 to Al2O3–CaO, Al2O3–CaO–CaS, and CaS after Ca addition. After slow cooling, inclusions in the solid steels are changed from Al2O3, single MnS, and Al2O3–MnS complex inclusions to Al2O3–CaO–CaS–MnS and CaS–MnS. The evolution trajectory of inclusions is Al2O3→Al2O3–CaO→Al2O3–CaO–CaS→Al2O3–CaO–CaS–MnS. With increasing Ca content in the steel, the number density and proportion of single MnS inclusions decrease. The formation mechanism of inclusions after Ca addition is explained by thermodynamic calculation.

Role of Ca content on microstructure, mechanical properties and strain evolution of as-rolled Mg-Al-Ca-Zn-Mn alloy

The role of Ca content (0.5, 1.0, 2.0 wt.%) on microstructure, mechanical properties and strain evolution of as-rolled Mg-Al-Ca-Zn-Mn alloy was thoroughly investigated in this work. The results indicate that the primary second phase transformed from the Mg17Al12 phase to the Al2Ca phase after homogenization, and the amount of Al2Ca phase increased significantly with increasing Ca content. After hot rolling, the alloys exhibited the typical bimodal microstructure composed of fine dynamic recrystallized (DRXed) grains and coarse elongated un-DRXed grains, the area fraction of the DRXed regions increased with increasing Ca content. Besides, a large number of submicron-sized as well as nano-scaled spherical Mg17Al12 phases dynamically precipitated along the DRXed grain boundaries in all alloys, which promoted the DRX and restricted the grain growth. During rolling deformation, DRX preferentially occurred near the primary second phases and shear bands by the particle stimulated nucleation (PSN) and shear band induced nucleation (SBIN) mechanism in the alloys. The ultimate tensile strength (UTS), yield strength (YS), and elongation to failure (EF) along the rolling direction (RD) of the Mg-8.0Al-1.0Ca-1.0Zn-0.4Mn (wt.%) sheet were 393 MPa, 334 MPa and 8.7 %, respectively. Such high strength was mainly attributed to fine DRXed grains, high number density of dynamically precipitated Mg17Al12 phases and strongly textured un-DRXed grains with numerous sub-structures. The reasonable DRX ratio moderated strain localization and thus stabilized tensile deformation, leading to moderate plasticity of the alloy.

Age and composition of perovskite in ultramafic lamprophyres from the Zima alkaline-ultramafic carbonatite complex, the southern margin of the Siberian craton: Petrogenetic implications

This paper presents data on the age and trace element composition of perovskites from dykes of ultramafic lamprophyres (aillikites) of the Zima alkaline-ultramafic carbonatite complex (Bolshaya Tagna and Bushkanay) located within the Urik-Iya graben, Eastern Sayan region, southern margin of the Siberian craton. The studied samples exhibit similar textural and structural features but differ slightly in the mineral composition of the groundmass. They have a porphyritic structure, a massive texture, and consist of olivine macrocrystals embedded in a fully crystallized groundmass composed of perovskite, apatite, spinel, phlogopite, garnet, carbonates, clinopyroxene and other minerals. The macrocrystals quantity varies between 40 and 50 vol%. With the exception of a single sample from the Bushkanay dyke, olivine is entirely replaced by serpentine and/or talc.Perovskites from aillikites of the Bolshaya Tagna intrusion exhibit crystals with normal zoning showing a decrease in Na, REE, and Nb contents with center-to-rim increasing Ca content. In contrast, minerals from the aillikites of the Bushkanay dyke demonstrate reverse zoning, with an increase in Na, REE, and Sr and decrease in Ca contents from the center to the rim. We suggest that during crystallization of perovskites, the magma parental to the aillikites of the Bolshaya Tagna intrusion and the Bushkanay dyke had nearly similar trace element composition, but after crystallization of the cores of perovskite crystals each melt portion evolved independently. The samples from the Bushkanay dyke show an increase in fO2 and the residual magma enrichment in REE, Na, and Sr as evidenced by their elevated contents at the rims of perovskite grains. In the Bolshaya Tagna aillikites after crystallization of perovskite cores, the melt was depleted in REE, Na, and Nb.Based on U-Pb dating of perovskites, the age of aillikites from the Bolshaya Tagna intrusion is 583–654 Ma. Perovskite from aillikites of the Bushkanay dyke is relatively young, with an age of 575 ± 39 Ma. The obtained ages are consistent with the age of formation of Neoproterozoic alkaline-ultramafic carbonatite complexes of the Siberian craton and other occurrences of aillikites in a response to extension of the Rodinia lithosphere.

Dynamics of micro and macronutrients in a hydroponic nutrient film technique system under lettuce cultivation

While hydroponics is considered an efficient vegetable production system, there is a compelling need to investigate the efficiency of the current generic nutrient dosing recommendation primarily based on electrical conductivity (EC) measurements. Such information is critical to fine-tune and optimize the current hydroponic management practices for improved nutrient uptake efficiency. This study investigated the dynamics of some micro and macronutrients (N, P, Ca, Mg, K, Fe, and Mn) in a recirculating nutrient film technique (NFT) hydroponic system under lettuce cultivation. The research was conducted in an indoor controlled environment growth chamber with lettuce grown in different EC levels (1.2 and 1.6 dS m−1). Each treatment had four hydroponic cultivation units, each one with 24 plants. Nutrient solution and tissue samples were collected two to three times per week. Nutrient dynamics, including nutrient uptake efficiencies and environmental losses, were calculated using a mass balance approach. The effects of EC level on fresh and dry lettuce biomass and nutrient uptake were insignificant. Observed variations in nutrient solution composition during lettuce cultivation included the almost complete removal of ammonia nitrogen, nitrate decreases towards the end of the experiment, consistent increases in aqueous Ca concentration, and corresponding decreases in K and Mn. Average N losses ranged between 27 and 40 %, presumably through denitrification, while 10–14 % of N was assimilated into the plant biomass. The remaining N in the recirculating nutrient solution was estimated to be between 50 and 59 %. The average P loss was 11–35 %, likely due to precipitation, while 52–77 % remained in the nutrient solution. Nutrient uptake efficiencies averaged 19–31 % K, 12–21 % P, 9–16 % Mn, 4–6 % Ca, 3–4 % Mg, and 2–4 % Fe. These results suggest that elevated nutrient concentrations in recirculating nutrient solutions led to losses and underutilization. Findings from this study provide a comprehensive dataset critical to improving hydroponic nutrient management beyond N and P. Hydroponic nutrient management should target providing essential nutrients needed by plants at the correct proportions considering the plant growth stage.

Evolution of 3D microstructure and correlation with deformation behavior of as-cast Mg-4Zn-[formula omitted]Ca alloys

In this study, X-ray microtomography results aided with fractography have been utilised to elucidate the effect of distribution of the secondary phases on the damage mechanism of the Mg-4Zn-xCa (x = 0, 0.2, 0.4, 0.6, 1.0 wt%) alloys. The alloy Mg-4Zn exhibited 2-phase microstructure comprising of α-Mg matrix and second phase (MgZn), which converted to interconnected network of Ca2Mg6Zn3 phase along grain boundaries with increase in Ca content. The compressive strength increased with the increase in Ca content up to 0.4 wt% due to the formation of Ca2Mg6Zn3 phase. However, it further decreased due to easier crack propagation through the 3D network of Ca2Mg6Zn3 at grain boundaries.

The microstructure and corrosion resistance of Mg–Zn-0.5Ag-xCa (x=0, 0.5, 1.0, 1.5 wt%) alloys in Hank's solution

Due to the excellent biocompatibility of Zn, Ag, and Ca, these elements were chosen for the development of a Mg–Zn–Ag–Ca alloy system for biomedical applications. This study studied the effect of Ca on the microstructure and corrosion behavior of as-cast Mg–Zn-0.5Ag-xCa alloy. The composition and microstructure of the alloys were analyzed using metallographic microscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffractometry. The alloys were immersed in Hank's solution for weight loss experiments to analyze the corrosion rate and micro-corrosion morphology of alloys with different Ca contents. It was observed that with the increase of Ca content, grain refinement and the amount of the second phase increased. Corrosion tests in Hank's solution demonstrated that a minor addition of Ca could reduce the corrosion rate, but the rate increased sharply once the Ca content exceeded 1.0 wt%. Considering corrosion performance, the optimal range of Ca concentration was determined to be 1.0 wt% to 1.5 wt%.

Impacts of Various Calcium Concentrations on the Biochemical Characteristics of Corn (Zea mays L.) Seedlings in Drought Conditions

ABSTRACT In recent years, there has been a significant decrease in corn production and quality due to drought. Ca applications are thought to be effective in eliminating this negative effect of drought. The research was conducted in a climatic chamber using a completely randomized experimental design. Four Ca doses were used in this study as research factors. In the study, increases in malondialdehyde, catalase activity, and superoxide dismutase levels, as well as leaf proportional water content, membrane damage index, Ca, and potassium contents, were examined. As a result of the research; leaf proportional water content was 55.633–72.103%, membrane damage index 44.540–71.643%, K content 1.967–2.733%, Ca content 0.243–0.497%, malondialdehyde activity 0.090–0.114 nmol g−1 FW, catalase activity 0.015–0.043 nmol g−1 FW and superoxide dismutase varied between 0.011 and 0.027 unit g−1 FW. Drought stress has negative effects on yield and quality properties in crop production. It has been determined that these negative impacts vary depending on the genetic structure of the plants as well as the presence of regulatory elements such as Ca. In this research, it was determined that Ca fertilization under drought stress caused a decrease in K content and some enzymatic activities such as MDI, MDA, CAT, and SOD, and an increase in LWC and Ca contents in corn seedlings. As a result, it is concluded that the applied Ca doses reduced the negative effects of drought. In conclusion, the 400 mg L−1 Ca application is recommended for reducing the negative effects of drought stress.

Enhanced strength and ductility of aluminum alloy laser welded joints through Ca micro˗alloyed welding materials

Aluminum alloy is widely used in high˗speed train bodies. However, compared with the base material, the tensile strength and elongation of its laser welded joints are significantly reduced, which limits the lightweight application of the next generation of high˗speed trains. The research in this article indicates that laser welding with Ca micro˗alloyed 5356 filler metal has changed the mechanical properties and microstructure of the weld seam. Without the Ca in the filler metal, the strength and elongation of the laser welded joint are only 215.5 MPa and 3.1 %. When the Ca content in the filler metal reaches 0.04 wt%, the laser welded joint has high tensile strength and maximum elongation, which are 251.5 MPa and 9.7 %, respectively. As the Ca content increases, the grain size of the welded joint gradually decreases, and the limiting effect of Ca element on the growth of α˗Al grains is the main reason for grain refinement. In addition, the addition of Ca transforms the coarse Fe˗rich phase in the weld into a fine˗grained second phase, while promoting the formation of deformable nanoparticles γ˗Al12Mg17, leading to the accumulation of dislocations and successfully improving the strength and plasticity of laser welded joints. When the Ca content further increases, the second phase grows, and the tensile strength and plasticity of the joint slightly decrease, but are still higher than that of the joint without Ca.