Addition Of Ca Ions Research Articles

Structural and electrical properties of Ca-doped Co1.5−xCaxMn1.2Ni0.3O4 (0 ≤ x ≤ 0.8) NTC ceramics

The influence of Ca content on the morphology and related electrical properties of Co1.5−xCaxMn1.2Ni0.3O4 (x = 0, 0.2, 0.4, 0.8) ceramics was studied. Appropriate addition of Ca will reduce the grain size, but when the content of Ca is 0.4, the holes will appear on the surface. As the Ca content of Co1.5−xCaxMn1.2Ni0.3O4 increases from 0 to 0.8, the temperature-dependent resistivity (ρ25) decreases from 1291.5 to 180.8 Ω cm, and the value of B25/50 decreases from 3860 to 3077 K. This is because the addition of Ca ions promotes the valence conversion of Mn3+ ions to Mn4+ ions, reduces the ratio of Mn3+/Mn4+, and thereby reduces the resistivity. The results show that when the Ca content is 0.4, the material has small grain size, low resistivity, and B value. It can be used as a NTC thermistor potential candidate materials in the temperature range of 223 K to 323 K.

Enhanced structural and magnetic ordering in as-synthesized Ca doped bismuth iron oxide nanoceramics

Calcium (Ca) added bismuth iron oxide (Bi1-xCaxFeO3) nanoparticles are synthesized using sol-gel method and studied under as-synthesized conditions. Calcium (Ca) concentration (x) is varied as 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5. XRD results verify the formation of phase pure BiFeO3 at dopant concentration x = 0.0–0.3. Raman analysis and EDX spectrum also confirm the formation and incorporation of Ca in the lattice. At x = 0.4 and 0.5 peaks corresponding to calcium oxide are observed. With addition of Ca ions in the lattice, strain is induced, resulting in reduced symmetry and increased inhomogeneity in the crystal structure. XPS analysis indicates small number of Fe2+ cations whereas no change in oxygen stoichiometry is observed. Size distribution and surface morphology of nanoparticles is observed using SEM and TEM images. Ca added bismuth iron oxide nanoparticles demonstrate ferromagnetic behavior where saturation magnetization increases from 9.202 emu/g to 21.097 emu/g as x increases from 0.0 to 0.3. This increase in saturation magnetization is accompanied by reduced magnetocrystalline anisotropy. High temperature magnetization curves indicate increase in magnetic ordering temperature from 643.7 K to 697 K. Field-cooled and zero field-cooled curves exhibit magnetic ordering with blocking temperature of ∼89 K under applied field of 500 Oe. P-E loops show high saturation polarization of 3.58 × 10−4 μC/cm2 for Ca concentration of x = 0.3. It is important to mention here that nanoparticles are synthesized without the use of any post thermal treatment.

Electronic and Magnetic Properties of Ca-Doped Mn-Ferrite

Spinel ferrite structures have vast applications, from microwave to radio frequencies. In order to acquire new electronic and optical behavior, divalent cations can be added to normal spinel ferrite structure. This way it is possible to facilitate its usage in material and science technology. In this work we have analyzed the impact of Ca addition to normal spinel manganese ferrite on electronic and magnetic properties by the first-principles calculations. For the exchange-correlation functional, Wu-Cohen, generalized gradient approximation method was used for electron-electron interactions. The calculation of electronic band structures is based on full potential linear augmented plane wave method. The calculated density of states shows that the addition of Ca ions has a significant impacts on the electronic and magnetic structure.

Surface modification of pure titanium by hydroxyapatite-containing composite coatings

Micro-arc oxidation (MAO) is commonly applied to modify the surface of titanium (Ti)-based medical implants with a bioactive and porous Ti oxide (TiO2) coating. The study reports a new method of incorporating hydroxyapatite (HA) within the TiO2 coating by MAO and alkali heat treatment (AHT) in the solution containing Ca ion and P ion. The morphology, composition and phase composition of the coatings were analyzed with scanning electron microscopy with energy-dispersive X-ray spectrometer and X-ray diffraction. Surface topography and roughness of the coatings were investigated by atomic force microscopy operated in the tapping mode. The results showed that TiO2-based coatings were obtained on pure Ti by MAO with an electrolyte containing Ca ion and P ion; the prepared MAO coatings were mainly composed of Ca, P, O and Ti. AHT transformed Ca and P to HA crystals. In conclusion, the TiO2/HA composite coatings can be obtained on the surface of pure Ti by MAO and AHT, and the addition of Ca ion and P ion to the AHT solution contributed to the formation of HA.

Study on structural and compositional transitions of coal ash by using NMR

Structural and compositional transitions of Datong coal ash and its CaCO3 additional effects were carefully examined at a temperature range of 300 to 1 600 °C by using XRD and solid state NMR. The quantitative estimation of amorphous structures of ashes can be successfully obtained through the analyses of solid state NMR spectra. Viscosity of molten ash and its changes with CaCO3 addition were also evaluated up to 1 700 °C by using a rotary type viscometer. Glasses with poor crystalline and amorphous phase were continuously formed through the eutectic reaction of silica above fusing temperature (FT>1 500 °C) that caused broadening and shift of 29Si and 27Al peaks in NMR results. With the additional amount of CaCO3 increasing, the peaks shifted to downfield obviously; the fraction of Si(OAl)0(OSi)4 decreased, while that of Si(OAl)1(OSi)1 at −84.3×10−6 increased apparently. These transitions indicated the destruction of large alumina-silicate framework into small segments by the addition of Ca ion.

Current Status of Bi-Based Precursors for Integrated Ferroelectrics

Two typical precursors for Bi4Ti3O12 thin films were analyzed spectroscopic methods and the local structure of those were chemically distinguished. Bi═Ti double alkoxide precursor containing Bi═O═Ti bonds promoted the homogeneous crystallization and was applicable to a series of Ca═Bi═Ti layer-structured ferroelectric thin films by addition of Ca ions. A hybrid precursor composed of Bi-triethylhexanoate and Ti-alkoxide needed the additional glass phase to suppress Bi2O3 segregation and resultantly, thinner Bi4Ti3O12 films with a thickness of 40 nm could be synthesized at 500°C and showed ferroelectricity.

Magnetic After-Effect in Polycrystalline Ca-Doped Gadolinium Iron Garnets

Magnetic after-effect phenomena in polycrystalline Gadolinium Iron Garnets (GdIG) doped with calcium are analyzed by means of magnetic disaccommodation techniques. The results are presented as isochronal spectra in which the relative variation of the initial magnetic permeability after specimen demagnetization is plotted at different time windows. These results reveal that the addition of Ca ions in the garnet lattice changes drastically the spectra, appearing three positive peaks at temperatures around 150, 240 and 350 K. The features of these processes are strongly influenced by the amount of Ca doping and the presence of the compensation temperature around 280 K, which, on the contrary, depends just slightly on doping. These phenomena seem to be related with the formation of Fe4+ ions in the crystal lattice by electronic hopping. Some reasonable speculations about the mechanisms responsible for these behaviours are pointed out.

Degradation of Enamel Matrix Proteins in Porcine Secretory Enamel

To elucidate the progressive disappearance of 25 kDa amelogenin occurring in a narrow space near the surface of enamel, the alkaline soluble fraction which contained 80% of the total proteins was extracted from a newly formed porcine enamel. When this fraction was incubated with the addition of Ca ions in an in vitro system, the degradation of the coexisting amelogenin and enamelin occurred without activation during the incubation period. Although the fraction contained mainly two kinds of metalloproteinases, 56 kDa and 61 kDa gelatinolytic, and 41 kDa and 46 kDa caseinolytic activities, it was demonstrated on amelogenin enzymography that the caseinolytic one was concerned with the conversion of the 25 kDa amelogenin into the 20 kDa amelogenin. The protein distribution of the newly formed enamel indicated that the metalloproteinases degraded the coexisting enamelin and amelogenin imperfectly. Nevertheless, during the next developing stage they demonstrated their full activities. It is suspected that these activities are regulated by Ca ions, which may be increased by a cascade system.

Insulin pumps and insulin quality--requirements and problems.

In developing insulin solution suitable for delivery devices the chemical and biological stability, as well as the physical stability, must be taken into consideration. Addition of certain mono- and disaccharides increases the physical stability of neutral insulin solutions, but concurrently the chemical and biological stability decrease to an unacceptable degree. Addition of Ca-ions in low concentrations offers a physiologically acceptable method for stabilizing neutral insulin solutions against heat precipitation without affecting the quality, including the chemical and biological stability.

Variability of the molecular size of extracellular amylase produced by intact cells and protoplasts of Bacillus caldolyticus.

One of the typical properties of the extracellular amylase produced by Bacillus caldolyticus is the tendency to disintegrate into subunits with a molecular weight (MW) of less than 10,000, when the enzyme is subjected to ultrafiltration. Disintegration is due to a loss of Ca-ions, leading to nonactive subunits. Activity can be fully restroed by addition of Ca-ions. Reactivation occurs also spontaneously if the low MW fraction is stored in glassware. Comparative ultrafiltration experiments with the subunit fraction with or without a supply of Ca revealed that in presence of this divalent cation the subunits reaggregated to the active enzyme. The different distribution patterns obtained in absence or presence of Ca showed that reactivation is directly linked to the formation of a high MW form of the protein. Substitution of Ca by other divalent cations also led to reaggregation. These aggregates are, however, inactive. The enzyme was found to be formed intracellularly in its low MW form. Experiments with protoplasts revealed that these are capable to produce and release the amylase. When the production of the enzyme by protoplasts declined, full restoration could be achieved by a recovery treatment. Normally, the enzyme released by the protoplasts consisted of equal portions of the high, medium, and low MW form of the amylase. If the cells were, however, depleted as a result of continued incubations, the extruded enzyme consisted increasingly of the low MW form, which could finally represent more than 80%. This trend could be completely reversed by the supply of carbon and nitrogen sources during the recovery treatment, whereafter the enzyme consisted again of the intially observed equal amounts of the three MW forms. Vesicles prepared from the protoplasts were also found to release amylase, but on a lower level, and only for a very limited time, with no possibility to regain activity by a recovery treatment. Subunit formation was also observed during column chromatography, which could be counteracted by a sufficient supply with Ca-ions.

微生物が生産する凝乳酵素について(第7報)

(1) When the rennin, rennin-like enzymes and other proteases were incubated on the each casein agar gel plate, the formation of white turbid zone were observed. And patterns of white turbid zones on each plates by each enzymes were compared. The diameters of white turbid zones on κ-casein gel plates formed by the rennin-like enzymes (animal rennin crystal, Pfizer microbial rennin, Hansens cheese rennet and Mucor-rennin (isolated from Mucor pusillus LINDT)) were larger than those Hammarsten-casein agar gel plates. In the case of other proteases, the patterns of formation of turbid zones observed on κ-casein and Hammarsten-casein agar gel plates did not exhibit remarkable differences. (2) When Mucor-rennin solution was incubated on κ-casein agar gel plates, the following points were observed: i) the turbid zone area was increased by addition of Ca ion, ii) the layer of the distinct turbid and clear zone was easily formed at higher level of enzyme concentration and at lower incubation temperature, iii) logarithms of milk clotting activity (U) were proportional to the values of the white turbid zone area formed (A). A=κlogU+A0

Isolation of Lactobacillus phage and its biological character

On the materials gathered from sewages, salivas, dental plaques, and feces of sucklings which may contain lactobucillus, isolation of phage was done. A phage “N-1” was isolated from a material of the sewage.N-1 phage should have biological characters as followed when examined with L. casei, strain L-10 in L-broth: adsorption rate 73 % at 37°C for 10 minutes, latent period 150 minutes, average but size 46 per cell.Plaque formation of N-1 phage disturbed by addition of citrate-ion to L-A media as formed less than 1/5 of plaque number of the control. Addition of Ca-ion is essential to have better efficiency of plating.Survival of N-1 phage in L-broth should decreased to less than 0.1 per cent at 60°C for 5 minutes. Of 40 lactobacillus strains, sensitivity were examined against N-1 phage and J-1 phage which was donated from the Yakuruto Institute. A few strains were detected as sensitive ones against either one of N-1 or J-1 phages respectively.

The role of phosphocreatine and adenosinetriphosphate in muscular contraction.

In the presence of 20 mM PC a strong contraction is produced in glycerol-extracted muscle fibers by ATP and AMP in concentrations as low as 10(-6)M per liter. At low concentrations of nucleotide tension rises very slowly. This rise is interpreted as being due to absorption of nucleotide by the contractile elements. AMP gives an S-shaped tension curve, indicating that the conversion of AMP into ATP is an autocatalytic process. Tension is maintained in a contracted muscle even in PC solutions free of ATP. PC alone produces a contraction if applied within 5 minutes after ATP has been washed out from a contracting muscle. It is concluded from these results that PC is the substrate for the enzymatic activity of the contractile elements and that this activity depends on the presence of bound nucleotide which acts as an energy transfer mechanism. PC accelerates relaxation which is caused by ATP under certain conditions. In the presence of PC even very low concentrations of ATP can produce relaxation. A strong contraction can be produced under these conditions by the addition of Ca ions. These observations support the conclusion that relaxation depends on the rephosphorylation of nucleotide bound by the contractile elements.