Effect Of Alkaline Earth Ions Research Articles

Spectroscopic study of the role of alkaline earth oxides in mixed borate glasses - site basicity, polarizability and glass structure

The effect of alkaline earth ions on the structure and properties of borate glasses near the metaborate composition was studied for two glass series, 30MO-10Li2O-10Al2O3-50B2O3 with M=Mg, Ca, Sr or Ba and xMgO-(30-x)BaO-10Li2O-10Al2O3-50B2O3 series, for undoped and doped (0.5 mol% MnO or CuO) glasses. Thermal and optical properties, including the optical basicity, were correlated with structural variations. IR and Raman spectra showed the highest N4 fraction for the high basicity glasses, decreasing for higher field strength ions (Ba>Sr>Ca>Mg). As determined from far IR bands the mixing of dissimilar cations affects M-O interactions. The glass transition temperature Tg correlates well to the average bond strength of the compared alkaline earth ions. The redox ratio of Mn2+/Mn3+ or Cu2+/Cu+ shifted to lower valences in low basicity glasses. The optical basicity probe ion Mn2+ gives consistently higher values compared to the average optical basicity, suggesting that Mn2+ ions seek out high basicity ligands.

The Effects of Alkaline‐Earth Counterions on the Architectures, Band‐Gap Energies, and Proton Transfer of Triazole‐Based Coordination Polymers

The effects of alkaline-earth ions on the architectures, band-gap energies, and proton transfer of triazole-based coordination polymers are investigated.

Effects of alkaline earth ions on the broadband near infrared emissions of Bi doped aluminophosphsilicate glasses

The effects of alkaline earth ions as network modifiers on the broad near infrared (NIR) emission from bismuth doped aluminophosphsilicate glasses were investigated. The results showed the intensity of NIR emission peaked at 1300 nm increased with increase in the radius of alkaline earth ions, while those of NIR emission peaked at 1100 nm and red emission from Bi2+ vary in an opposite tendency. We propose that particular emission performance of Bi result from the abnormal reduction phenomenon of Bi ions by SiO2–P2O5–Al2O3–RO (R = Mg, Ca, Sr, Ba, SPAR) glass hosts, which became effective with the order of MgO–CaO–SrO–BaO. Then the origins of infrared-emitting bismuth centers were discussed according to the effect of alkaline earth ions on the conversion of Bi ions.

The structural role of alkaline earth ions in oxyfluoride aluminosilicate glasses—Infrared spectroscopy study

The effect of alkaline earth ions as a function of composition of oxyfluoride aluminosilicate glass has been explored with FTIR spectroscopy. Glasses have been prepared for Al 2O 3/(Na 2O + MeO + 3La 2F 6) ratio from 0.4 to 0.8 in Na 2O–MeO–Al 2O 3–SiO 2–LaF 3 systems with CaO, MgO and BaO substitution, respectively. The influence of Me 2+ ions on the network structure of melts has been studied. The role of F − replacing O 2− ions in the glassy network has been described as well. Spectroscopic results have been compared with thermal stability of glass and tendency to LaF 3 ceramization. Finally, the effect of crystallization of LaF 3 as a phase of low phonon energy (∼350 cm −1) for introduction of alkaline earth ions to the glass has been considered.

Effect of alkaline-earth ions on the dynamics of alkali ions in bismuthate glasses

The effect of alkaline earth ions on the dynamics of ${\mathrm{Li}}^{+}$ ions in bismuthate glasses has been studied in the temperature range $353--503\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and in the frequency range $10\phantom{\rule{0.3em}{0ex}}\mathrm{Hz}--2\phantom{\rule{0.3em}{0ex}}\mathrm{MHz}$. The dc conductivity increases and activation energy decreases with the increase of a particular alkaline earth content for the glasses with a fixed alkali content. The increased modification of the network due to the increase in alkaline earth content in the compositions is responsible for the increasing conductivity. Also the compositions with smaller alkaline earth ions were found to exhibit higher conductivity. Although the conductivity increases with the decrease of ionic radii of alkaline earth ions, the activation energy shows a maximum for the Sr ion. The electric modulus and the conductivity formalisms have been employed to study the relaxation dynamics of charge carriers in these glasses. The alkali ions were observed to change their dynamics with the change of the alkaline earth ions. The same anomalous trend for activation energy for the conductivity relaxation frequency and the hopping frequency was also observed for glasses containing SrO. It was also observed that the mobile lithium ion concentrations are independent of nature of alkaline earth ions in these glasses.

The addition effects of alkaline earth ions in the chemical synthesis of ε-Fe2O3 nanocrystals that exhibit a huge coercive field

An iron oxide/silica composite material, which was prepared by combining reverse-micelle and sol-gel techniques, exhibited a huge coercive field Hc of 20kOe (1.6×105Am−1) in our previous work. The key of this synthetic procedure was the added Ba2+ ions that created a single phase of ε-Fe2O3. In the present work, the addition effect of Ca2+ ions to this procedure was investigated. Consequently, rod-shape ε-Fe2O3 nanocrystals (40–120nm×15–20nm) were obtained and a Hc value of 20kOe was observed. Thermodynamical analysis that considered the surface energy of nanoparticle suggested that a single ε-Fe2O3 phase was generated by retarding the crystal growth of Fe2O3 particles under the presence of alkaline earth ions.

An ion-gate response of the cysteine-containing dipeptide monolayers formed on a gold electrode. The effects of alkaline earth ions

An ion-gate response of the cysteine-containing dipeptide monolayers formed on a gold electrode. The effects of alkaline earth ions

Strontium and barium induce exocytosis in electropermeabilized neutrophils

Calcium, strontium and barium induced an exocytotic response in electropermeabilized rabbit neutrophils while magnesium was without any effect. The extent of enzyme release was found to depend upon the concentration of these cations. For all cations, an optimum concentration was found with the same maximum enzyme release. At concentrations higher than optimum a decrease in lysozyme release was observed. Efficiency to induce enzyme release was in the order: Ca 2+>Sr 2+>Ba 2+. Enzyme release was significantly enhanced by guanosine-5′-[γ-thio]triphosphate (GTPγS) resulting in a shift to the left of the dose/response curve. The enhancement by GTPγS was strongest with Ca 2+, was less with Sr 2+, and was very little with Ba 2+. The time course of lysozyme release was the same for Ca 2+, Sr 2+, and Ba 2+ in the presence and absence of GTPγS when suboptimal cation concentrations were used. A decrease in responsiveness to the effectors after electropermeabilization was observed with Ca 2+, Sr 2+ and Ba 2+ in the presence and absence of GTPγS. The lysozyme release induced by the different cations was not inhibited by the protein kinase C inhibitor staurosporine and was slightly affected by pertussis toxin. Ca 2+ and Sr 2+, but not Ba 2+, potentiated formyl-methionyl-leucyl-phenylalanine (fMet-Leu-Phe) induced enzyme release in intact neutrophils. The divalent cation ionophore A23187 induced enzyme release in the presence of Ca 2+ and Sr 2+ but not in the presence of Ba 2+. The results obtained with electropermeabilized neutrophils indicate that Sr 2+ and Ba 2+ can act as substitutes for Ca 2+ in activating exocytosis, and that permeabilized neutrophils provide the best tool to investigate the effects of alkaline earth ions in exocytosis.

An ion-gate response of the glutathione monolayer assembly formed on a gold electrode: Part 2. The effect of alkaline earth ions

Glutathione (y-L-glutamyl-L-cysteinyl-glycine) (GSH) is a well-known biologically active tripeptide which participates in the various functions of biological processes [ll. For example, GSH has been reported to act as a coenzyrne for ion-channel proteins and to participate in the biological redox systems 121. Longchain molecules containing thiol terminals, like n-alkanethiols, are known to form a well-ordered, densely packed and electron-insulating self-assembled monolayer film on a gold surface [3,4]. Furthermore, the ion-selective and ion-gate responses of such a monolayer assembly have also been reported by several authors [5,6]. The novel electrochemical characteristics of a GSH monolayer assembly formed on a gold surface, i.e. the ion-gate response which is controlled by the pH and the concentration of Ca*+ ion, have been reported previously [7]. In this communication we report electrochemical investigations of the effect of alkaline earth ions M*+ on the ion-gate response of the GSH monolayer assembly formed on a gold surface. The redox signal of the Fe(CN)zion was used as the marker of the ion-gate response of the GSH monolayer assembly.

Effect of alkaline earth ions on the movement of mobile charges in Valonia utricularis

An attempt was made to further characterise the pressure-dependent translocation of mobile charges which are probably linked to the pressure-dependent K + transport system in the membranes of the giant marine alga Valonia utricularis. It could be shown that concentrations of 10 mM BaCl 2 added to the external sea water specifically and reversibly reduce the pressure dependence of the translocation rate of the mobile charges, leaving their total concentration unaffected. No such effect could be observed with other alkaline earth ions. The results are discussed on the basis that either Ba 2+ decreases membrane compressibility or that the transport system may consist of a pressure-independent and a pressure-dependent part and that Ba 2+ competes with K + for specific sites on the latter.

Effect of Alkaline Earth Ions on Alkaline Durability of High TiO<sub>2</sub> Content Glasses

多量のTiO2を含むSrO-BaO-SiO2-TiO2系のガラスが優れた耐アルカリ性を示す原因を明らかにするために, TiO2微粒子を分散させたNaOH水溶液にSrCl2及びBaCl2を添加したときに起こる現象を観察した. これらの塩化物はごく少量でTiO2を沈殿させ, 水溶液を濁らせることが分った. このことから, SrO-BaO-SiO2-TiO2系のガラスの耐アルカリ性を次のように推定した. すなわち, ガラス中のSr2+及びBa2+イオンは, NaOH水溶液中でいったんガラスから溶出した後, ガラス表面に形成されるTiO2に富む層に選択的に吸着されるため, 表面におけるこれらイオンの濃度が高くなり, また表面層がち密化されてガラス内部からのSrO及びBaO成分ばかりでなく, SiO2成分の溶出も抑制されると推定した. なお, MgCl2及びCaCl2を添加した場合にもTiO2の沈殿を生じたことから, Mg2+及びCa2+イオンもSr2+及びBa2+イオンと同様TiO2含有ガラスの耐アルカリ性を高める効果があることが確かめられた.

The effect of alkaline earth ions on the co-operativity of the oxygenation of Helix pomatia haemocyanin

1. 1. The most pronounced sigmoidal oxygenation curve is obtained for Helix pomatia haemocyanin, in the absence of buffer, at pH 7·9 in the presence of 6 mM Ca 2+ or 10 mM Sr 2+. Mg 2+ and Ba 2+, on the contrary, have no effect on the co-operativity of the oxygenation. 2. 2. The influence of alkaline earth ions on the stabilization of H. pomatia haemocyanin at pH 7·9 follows a different order: Ca 2+>Mg 2+>Sr 2+ = Ba 2+, suggesting two types of binding sites. The type with the higher affinity could be responsible for the stabilization, the type with the lower affinity for the co-operativity of the oxygen binding. 3. 3. An interpretation is suggested for the co-operative oxygen binding of H. pomatia haemocyanin by postulating a deoxy and an oxy structure in a relaxed and in a tense state. In the relaxed state the transition between the two structures is easy and the oxygen affinity high, in the tense state, stabilized at pH 7·9 by Ca 2+ or Sr 2+, the transition is difficult and the oxygen affinity low.