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1.
《Solid State Communications》1986,57(10):799-803
The EPR spectra of Mn2+ ions embedded into precipitated phases of Mg2+, Cd2+, Fe2+ and Ca2+ in NaCl single crystals have been investigated. The spectrum from samples whose major impurity is Mg, Cd or Fe corresponds to Mn2+ substituting some divalent cation inside the Suzuki phase (6NaCl.MCl2). The existence of such a phase has been ascertained by means of Raman spectroscopy. On the other hand, the EPR spectrum of Ca2+ doped samples has been attributed to Mn2+ inside various CaCl2 precipitates. 相似文献
2.
D. A. Kuznetsov A. L. Buchachenko 《Russian Journal of Physical Chemistry B, Focus on Physics》2018,12(4):690-694
Magnetic isotope effect controls enzymatic DNA synthesis and strongly, by 2–3 times, suppresses catalytic activity of polymerases and increases even more strongly, by 20–50 times, the mortality of cancer cells. Catalyzing ions 25Mg2+, 43Ca2+, and 67Zn2+ carrying magnetic nuclei are shown to efficiently kill cancer cells. The advantage of these ions for practical medicine is that being injected in blood they are captured selectively and almost exclusively by cancer cells inducing their death. The healthy cells capture these ions much less efficiently (perhaps due to the lower penetrability of their membranes) and are not vulnerable to these ions in comparison with cancer cells. Of course, penetrability of cells is identical for magnetic and nonmagnetic ions, but only the former kill cancer cells. 相似文献
3.
The effect of thermal processing on the mobility of dislocations is investigated in NaCl crystals doped with impurities of
various types—high-solubility impurities (Ca2+) and low-solubility impurities (Pb2+). The results obtained after aging and thermal processing indicate that the type of impurity and its state (e.g., level of
aggregation) in the crystal have a strong effect on the relative mobility of edge and screw dislocations, and also on the
parameters of double transverse slip.
Fiz. Tverd. Tela (St. Petersburg) 41, 1041–1043 (June 1999) 相似文献
4.
Yongfu Liu Xia Zhang Zhendong Hao Yongshi Luo XiaoJun Wang Jiahua Zhang 《Journal of luminescence》2012,132(5):1257-1260
The yellow-emitting phosphor [Ca3?(x+0.06)LuxCe0.06](Sc2?yMgy)Si3O12 obtained from Lu3+ and Mg2+ co-modified green-emitting silicate garnet Ca3Sc2Si3O12:Ce3+ (CSS:Ce3+) exhibits promising applications for white LEDs. In this paper, we discuss the effect of charge balance on the garnet structure formation. The changes of bond length and covalence caused by the replacement of Lu3+ and Mg2+ for Ca2+ and Sc3+ are analyzed. The shift of the Ce3+ emission and excitation can be attributed to the combined results from crystal field splitting effect and centroid shift of Ce3+ 5d levels. Thermal stability is analyzed according to configurational coordinate diagram. 相似文献
5.
Alberto Pérez‐Huerta Maggie Cusack Markus Janousch Adrian A. Finch 《Journal of synchrotron radiation》2008,15(6):572-575
Micro X‐ray absorption near‐edge spectroscopy at the Mg K‐edge is a useful technique for acquiring information about the environment of Mg2+ in biogenic calcite. These analyses can be applied to shell powders or intact shell structures. The advantage of the latter is that the XANES analyses can be applied to specific areas, at high (e.g. micrometre) spatial resolution, to determine the environment of Mg2+ in a biomineral context. Such in situ synchrotron analysis has to take into account the potential effect of crystallographic orientation given the anisotropy of calcite crystals and the polarized nature of X‐rays. Brachiopod shells of species with different crystallographic orientations are used to assess this crystallographic effect on in situ synchrotron measurements at the Mg K‐edge. Results show that, owing to the anisotropy of calcite, in situ X‐ray absorption spectra (XAS) are influenced by the crystallographic orientation of calcite crystals with a subsequent potentially erroneous interpretation of Mg2+ data. Thus, this study demonstrates the importance of crystallography for XAS analyses and, therefore, the necessity to obtain crystallographic information at high spatial resolution prior to spectroscopic analysis. 相似文献
6.
The hardening effect of Mg2+, Ca2+, Sr2+, Cd2+ and Ba2+ impurities in polycrystalline AgCl was investigated. With exception of Mg2+ the hardening effect of the impurities decreases with increasing atomic number (atomic weight). The hardening effects of Mg2+ and Ca2+ are expressively stronger than those of the three remaining impurities. Approximately linear dependence of the stress at the beginning of plastic deformation on the impurity concentration was found. Possible causes of the different hardening effects of the divalent impurities are discussed. 相似文献
7.
Hydration characteristics of Ca2+ and Mg2+: a density functional theory,polarized continuum model and molecular dynamics investigation 总被引:1,自引:0,他引:1
In this work, density functional theory, Møller–Plesset second-order perturbation theory, and ab initio molecular dynamics (AIMD) were used to investigate hydrated characteristics of Mg2+ and Ca2+ as a function of coordination number in the first hydration shell (CN) and cluster size. It is generally accepted that the CNs of Mg2+ and Ca2+ are both six. Calculations show that the hydration of Mg2+ generally prefers six-coordinated structures, whereas the CN value of Ca2+ varies from 6 to 8 as the hydration proceeds. Moreover, the first hydration of Ca2+ is found to be more flexible than that of Mg2+, as indicated by the results of transition state calculations and AIMD simulations. In addition, the constraint of Mg2+ on the first hydration shell is obviously stronger than that of Ca2+, while the constraint on the inner hydration shells fades slightly faster for Mg2+ than Ca2+. It is also found that the charge transfer from central cation to water molecules is affected only by the first hydration shell for Mg2+, whereas by the first and second hydration shells for Ca2+. Based on hydration characteristics, approximatively saturated ion hydration shells for the hydration of Mg2+ and Ca2+ were proposed. 相似文献
8.
Christelle Nguyen Hang Korng Ea Dominique Thiaudiere Solenn Reguer Didier Hannouche Michel Daudon Frédéric Lioté Dominique Bazin 《Journal of synchrotron radiation》2011,18(3):475-480
Calcium (Ca2+)‐containing crystals (CCs), including basic Ca2+ phosphate (BCP) and Ca2+ pyrophosphate dihydrate (CPPD) crystals, are associated with severe forms of osteoarthritis (OA). Growing evidence supports a role for abnormal articular cartilage mineralization in the pathogenesis of OA. However, the role of Ca2+ compounds in this mineralization process remains poorly understood. Six patients, who underwent total knee joint replacement for primary OA, have been considered in this study. Cartilage from femoral condyles and tibial plateaus in the medial and lateral compartments was collected as 1 mm‐thick slices cut tangentially to the articular surface. First, CCs presence and biochemical composition were assessed using Fourier transform infrared spectroscopy (FT‐IR). Next, Ca2+ compound biochemical form was further assessed using X‐ray absorption spectroscopy (XAS) performed at the Ca2+K‐absorption edge. Overall, 12 cartilage samples were assessed. Using FT‐IR, BCP and CPPD crystals were detected in four and three out of 12 samples, respectively. Ca2+ compound biochemical forms differed between areas with versus without CCs, when compared using XAS. The complete set of data shows that XANES spectroscopy can be used to accurately characterize sparse CCs in human OA cartilage. It is found that Ca2+ compounds differ between calcified and non‐calcified cartilage areas. In calcified areas they appear to be mainly involved in calcifications, namely Ca2+ crystals. 相似文献
9.
The effect of divalent cation substitution on the structure and magnetic properties of La1.2Sr1.8-xCaxMn2O7 (x = 0-0.900) is investigated in this paper. Partly replacing divalent cation Sr2+ by Ca2+ ions results in the weakening and then disappearance of long-range ferromagnetic ordering, and the formation of spin canting and low-temperature spin-glass. Based on structural analysis by Rietveld profile fitting, we suggest that this variation of magnetic property be related to a Jahn-Teller-type attice distortion of MnO6 octahedra due to the introduction of the smaller sized Ca2+ ions. 相似文献
10.
At SIMS XIV, we reported SIMS evidence of specific Mg2+ binding to the AT-rich regions of human metaphase chromosomes represented by G-bands. Subsequent Mg2+-depletion experiments supported a direct role for Mg2+ in promoting and maintaining the higher order chromatin structure originating G-bands, possibly due to both Mg2+-DNA and Mg2+-protein interactions. An in-depth study, reported elsewhere, implicated also Ca2+ in the maintenance of chromatin ultrastructure in the scaffold of mammalian chromosomes, in association with topoisomerase II.We examine here the association of Mg2+ with AT-rich regions of chromatin in the chromosomes of the Indian muntjac deer (IMD), leading to conclusions similar to the above. To answer the question whether the presumed divalent cation role in the chromosomes of advanced eukaryotes had an evolutionary history to be traced back to earlier evolutionary stages, we have SIMS-mapped Ca2+ and Mg2+ in BrdU-labeled polytene chromosomes from the salivary gland of the Dipteran Drosophila melanogaster. Striking Ca2+ and Mg2+ SIMS banding patterns correlating with those of the Br label (a thymidine analogue) implicate unequivocally a close association of both these cations with the AT-rich regions of DNA for these primitive eukaryotes. 相似文献
11.
Using the Raman scattering spectra, we investigated the ordering of the structural units in the cation sublattice and the
photorefractive properties of lithium niobate single crystals of variable composition, i.e., nominally pure ones with different
Li/Nb ratios and those doped with the nonphotorefractive cations Mg2+, Gd3+, and Y3+. It is shown that at low concentrations of Mg2+, Gd3+, and Y3+ the magnitude of the photorefractive effect is substantially determined by the ordering of the structural units of the cation
sublattice. It has been found for the first time that the intensity of the line corresponding to the bridge valence vibrations
of oxygen atoms in the octahedrons of NbO6 is sensitive to the dipole ordering of the cation sublattice of the crystal.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 5, pp. 611–614, September–October, 2005. 相似文献
12.
R. B. Morgunov 《JETP Letters》2010,92(3):156-160
A photocontrolled resonance decrease in microhardness, which is due to the application of mutually perpendicular static and
microwave fields, in γ-irradiated KCl:Fe crystals has been revealed. It has been found that the magnetic plasticity of unirradiated
γ-KCl:Fe crystals is due to the resonance effect of magnetic fields on two types of impurity centers: first, centers containing
Fe2+-ν
c
ion-vacancy pairs and, second, centers containing Fe+ ions. The illumination of γ-KCl:Fe crystals with F-light (with a wavelength of λ = 500–600 nm) is accompanied by rearrangement of the spectrum of electron paramagnetic resonance
detected by a change in microhardness. The effect of F-light on the spectrum of magnetic resonance plasticity is manifested as the suppression of the spectra of Fe2+-ν
c
ions with effective g-factors of 7.0 and 3.5 due to their recombination with F-electrons and reconstruction to Fe+ centers with g-factors of 2.2 and 4.1. 相似文献
13.
Yunjie JiaYuejuan Zhang Runwei WangFaying Fan Qinghong Xu 《Applied Surface Science》2012,258(7):2551-2561
A new adsorbent named zirconium glyphosate [Zr(O3PCH2NHCH2COOH)2·0.5H2O, denoted as ZrGP] and its selective adsorptions to Pb2+, Cd2+, Mg2+ and Ca2+ ions in water were reported in this paper. Compared to other zirconium adsorbents, such as zirconium phosphate [Zr(HPO4)2], ZrGP exhibited highly selective adsorption to Pb2+ in solution which contained Pb2+, Cd2+, Mg2+ and Ca2+ ions. The loaded ZrGP with metallic ions can be efficaciously regenerated by aqueous solution of HCl (1.0 M) without any noticeable capacity loss, and almost all of it can be reused and recycled. The memory effect on structural regeneration of ZrGP was also found when Mg2+ and Ca2+ were adsorbed. To be specific, the structure of ZrGP was destroyed due to adsorbing these two ions, but it could be regenerated after the loaded materials were dipped in HCl solution (1.0 M) for several minutes to remove metallic ions. 相似文献
14.
A conducting polymer-based advanced nanocomposite ion exchanger was synthesized by incorporating polyaniline (PANI) into the inorganic counterpart zirconium(IV) selenotungstophosphate (ZSWP). The nanocomposite exhibited an excellent ion exchange capacity of 1.20 meq g?1 in addition to high thermal stability. The polymeric–inorganic nanocomposite ion exchanger was characterized by Fourier transform infrared (FTIR), XRD, SEM, and TEM studies. The DC conductivity of PANI/ZSWP was also investigated. The nanocomposite ion exchanger was found to be highly selective for Cu2+ ions with a distribution coefficient value of 650 mL/g. The analytical applications of the material were explored by achieving selective separations of Cu2+ and Ca2+ ions from a synthetic mixture of Cu2+, Pb2+, Zn2+, Ni2+, Fe3+, Mg2+, and Al3+ and Ca2+, Pb2+, Zn2+, Ni2+, Al3+, Mg2+, and Ba2+. 相似文献
15.
Nora A Cavara Angela Orth Gordon Hicking Guiscard Seebohm Michael Hollmann 《BMC neuroscience》2010,11(1):133
Background
Members of the complex N-methyl-D-aspartate receptor (NMDAR) subfamily of ionotropic glutamate receptors (iGluRs) conventionally assemble from NR1 and NR2 subunits, the composition of which determines receptor properties. Hallmark features of conventional NMDARs include the requirement for a coagonist, voltage-dependent block by Mg2+, and high permeability for Ca2+. Both Mg2+ sensitivity and Ca2+ permeability are critically dependent on the amino acids at the N and N+1 positions of NR1 and NR2. The recently discovered NR3 subunits feature an unprecedented glycine-arginine combination at those critical sites within the pore. Diheteromers assembled from NR1 and NR3 are not blocked by Mg2+ and are not permeable for Ca2+. 相似文献16.
The effect of electric field E on the magnetoplastic effect (MPE) has been investigated in NaCl crystals with different impurities, which provide either the plasticization of the samples in the magnetic field (positive MPE) or their magnetic hardening (negative MPE). The mobility of individual dislocations under the joint action of the magnetic and electric fields and the mechanical load on the crystals has been studied. The sharp electric stimulation of the MPE of both signs has been revealed, i.e., an increase or a decrease in the mean free path of dislocations that is roughly proportional to exp(±E/E 0) at E ? E 0 ~ 1–10 kV/m. In particular, in the negative-MPE NaCl(Pb) crystals, the accompanying electric field enhances the magnetic suppression of plasticity. The results are attributed to the electrically induced transformation of the additional part of the pinning impurity ions Me++ to the magnetically active state of Me+ on the dislocations. The subsequent magnetic transformation of the structure of these pinning centers should lead to a sharper variation of the dislocation pinning force (either an increase or a decrease, depending on the MPE sign). 相似文献
17.
A. A. Konovalov D. A. Lis B. Z. Malkin S. I. Nikitin K. A. Subbotin V. F. Tarasov E. N. Vorobieva E. V. Zharikov D. G. Zverev 《Applied magnetic resonance》2005,28(3-4):267-280
Electron paramagnetic resonance (EPR) of Ho3+ single ions and Ho3+?Mg2+-vacancy-Ho3+ associates in holmium-doped forsterite single crystals are studied at 9.4, 37.3 and 65–250 GHz. Crystals were grown from melt by the Czochralski technique in slightly oxidizing atmosphere. For both centers, directions of the principal magnetic axes and parameters of the effective spin Hamiltonians describing dependences of electron-nuclear levels on applied magnetic field are obtained. For Ho3+ substituting Mg2+ in the M2 site as the single ion and for Ho3+ ions in dimer centers, values of crystal field parameters related to a real crystal lattice structure are estimated in the framework of the exchange charge model. The calculated crystal field energies, values of theg-factors of the ground Ho3+ quasi-doublet and the directions of the corresponding magnetic moments agree satisfactorily with the data obtained from measurements of EPR and optical absorption and site-selective luminescence spectra. 相似文献
18.
Dielectric losses were measured in the following crystals NaCl+ (Mg2+, Co2+, Ni2+, Sr2+, Ca2+, Mn2+, Zn2+, Cd2+, Ba2+, Pb2+), KCl + (Ca2+, Sr2+, Ba2+, 2+, Pb2+) and KBr + (Sr2+, Ba2+) in the frequency region 5–500 kHz. It was found that when the divalent cation impurity has an electronic configuration similar to the inert gases (1) no observable deviation from simple Debye theory exists (2) the activation energy Φ increases linearly with the ionic radius of the impurity.The above observations (1) and (2) do not hold when the divalent cation impurity has d-electrons in the outer subshell. 相似文献
19.
S. V. Verkhovskii A. Yu. Yakubovskii A. Trokiner B. Z. Malkin S. K. Saikin V. I. Ozhogin A. V. Tikhomirov A. V. Ananyev A. P. Gerashenko Yu. V. Piskunov 《Applied magnetic resonance》1999,17(4):557-576
We have studied the influence of isotopic disorder on the local deformations in Ge single crystals from both experimental and calculation points of view. The nuclear magnetic resonance (NMR) spectra of73Ge nuclei (the nuclear spin equals 9/2) in perfect single crystals of germanium with different isotopic content were measured at temperatures 80, 300 and 450 K. Abnormal broadening of the spectrum was found to occur when the magnetic field was aligned along the [111] axis of a crystal. The observed specific angular dependence of the quadrupole broadening was attributed to isotopic disorder among atoms of germanium sited around the73Ge NMR probe. Local lattice deformations in germanium crystal lattice due to isotopic impurity atoms were calculated in the framework of the adiabatic bond charge model. The results obtained were applied to study random noncubic crystal field interactions with the nuclear quadrupole moments and corresponding effects in NMR spectra. Simulated second and fourth moments of resonance frequency distributions caused by the magnetic dipole-dipole and electric quadrupole interactions are used to analyze the lineshapes, theoretical predictions agree qualitatively with the experimental data. 相似文献
20.
Improvement for electrochemical luminescence (ECL) property of MgIn2O4 is attempted by partial exchange of Mg2+ ion in MgIn2O4 to Ca2+ ion. Mg1−xCaxIn2O4 solid solution was obtained in the region 0<x<0.4. Efficiency for ECL per unit current for Mg1−xCaxIn2O4:Er3+ increased with the increase in the ratio of Ca2+ ion, and showed a peak at x=0.25 and then decreased steeply. ECL efficiency for other rare-earth ion-(RE:Sm, Eu, Ho) doped Mg1−xCaxIn2O4 also increased comparing with those for MgIn2O4:RE. This Ca2+ addition effect on the ECL efficiency seems to be caused by the improvement of the efficiency for the impact activation. 相似文献