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1.
Summary A study was made of soluble manganese silicates prepared by adding a solution of manganese sulfate to different concentrations of sodium silicate in alkaline medium. The solubility of manganese increased with increasing amounts of sodium silicate and reached its maximum at a molar Na2SiO3/MnSO4 ratio between 10 and 15. At molar Na2SiO3/MnSO4 ratios of 5 and more a red-brown coloured manganese silicate is formed, which is stable in the pH range of 4 to 12. Gel chromatographic analysis indicated that this compound contains 1 molecule Mn per 15 molecules SiO2. At a molar Na2SiO3/MnSO4 ratio of 15 the yield of soluble manganese could be raised to 98.5% of the theoretical amount by preventing the rapid oxidation of the Mn2+-ions in the alkaline solution. A pot experiment with oats was conducted to evaluate the effectiveness of the red-brown manganese silicate in controlling manganese deficiency. The effect of the Mn-carrier on Mn-content and yield of grain and on the colour scores was compared with that of Mn-EDTA, Mn-DTPA and MnSO4·4H2O. The manganese silicate was found to be a more effective manganese source than Mn-EDTA, Mn-DTPA or MnSO4·4H2O.  相似文献   

2.
Applegate , Howard G., Donald F. Adams , and Roy C. Carriker . (Washington State U., Pullman.) Effect of aqueous fluoride solutions on respiration of intact bush bean seedlings. I. Inhibition and stimulation of oxygen uptake. Amer. Jour. Bot. 47(5): 339—345. Illus. 1960.–Intact bush bean seedlings were infiltrated with 1 × 10–1, 1 × 10–2, 1 × 10–3, and 1 × 10–4 M fluoride. A linear relationship was found to exist between the fluoride concentrations of the infiltrating solutions and tissue fluoride. The higher fluoride concentrations inhibited oxygen uptake, whereas lower fluoride concentrations accelerated oxygen uptake. Both the inhibition and acceleration of oxygen uptake by fluoride were modified by light, CO2, and presence or absence of chlorophyll.  相似文献   

3.
This study investigated neurotoxicity of chronic fluorosis in the rat hippocampus. Newly weaning, male, Sprague-Dawley (SD) rats were administered 15, 30, and 60 mg/L sodium fluoride (NaF) solution (fluorine ion concentration 8.25, 16.50, and 33.00 mg/L, respectively), and tap water, for 18 months. The neurotoxicological mechanism was examined with a focus on intracellular calcium overload. Results showed that as the fluoride concentration increased, calcium ion concentration [Ca2+], the expression of calcium/calmodulin-dependent protein kinase II α (CaMKIIα), and the expression of catus proto-oncogene protein c-fos (c-fos) all tend to increase. Compared to the control group, Ca2+, CaMKIIα, and c-fos significantly increased (P < 0.05) in the moderate-fluoride and the high-fluoride groups. These results indicate that Ca2+/CaMKIIα/c-fos channel signal may be the molecular mechanism of central nervous system damage caused by chronic fluoride intoxication. Moreover, elevated Ca2+ concentration in the hippocampus may be the initiating factor of neuronal apoptosis induced by fluoride.  相似文献   

4.
Hu Y  Yang JP  Liu JS 《Luminescence》2012,27(5):437-440
Mn‐doped willemite (Zn2SiO4:Mn) green phosphor were synthesized by sol–gel technology. The effect of the addition of sodium, as in the composition Zn(1.92 – X) NaXMn0.08SiO4, on the emission behavior was studied. FT–IR and EPR results revealed that sodium ion is incorporated into the lattice and results in the formation of isolated Mn2+ and Mn–Mn pairs. The maximum emission intensity of the sample under ultraviolet (UV) excitation occurred at the sodium concentration of x = ~0.03. The green emission at about 525 nm is assigned to Mn2+–Mn2+ pair centres on nearest neighbour Zn sites. The highest intensity of the green emission for x = ~0.03 is well close to the highest concentration of the Mn2+–Mn2+ pair. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

5.
Eu2+‐doped Sr2SiO4 phosphor with Ca2+/Zn2+ substitution, (Sr1–xMx)2SiO4:Eu2+ (M = Ca, Zn), was prepared using a high‐temperature solid‐state reaction method. The structure and luminescence properties of Ca2+/Zn2+ partially substituted Sr2SiO4:Eu2+ phosphors were investigated in detail. With Ca2+ or Zn2+ added to the silicate host, the crystal phase could be transformed between the α‐form and the β‐form of the Sr2SiO4 structure. Under UV excitation at 367 nm, all samples exhibit a broad band emission from 420 to 680 nm due to the 4f65d1 → 4f7 transition of Eu2+ ions. The broad emission band consists of two peaks at 482 and 547 nm, which correspond to Eu2+ ions occupying the ten‐fold oxygen‐coordinated Sr.(I) site and the nine‐fold oxygen‐coordinated Sr.(II) site, respectively. The luminescence properties, including the intensity and lifetime of Sr2SiO4:Eu2+ phosphors, improved remarkably on Ca2+/Zn2+ addition, and promote its application in white light‐emitting diodes. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

6.
The transparent thermoluminescent aluminum oxide‐based glass of 15Al2O3–35P2O5–25CaO–25Na2CO3, abbreviated as APCN (all in mol%) doped with different concentrations of SiO2 from 0.0–500 ppm was prepared using a conventional melt‐quenching technique. The TL sensitivities of the prepared glasses were investigated at 3 Gy γ‐dose using a 60Co source and measured at a heating rate 10 C/sec. The highest TL intensity of the material doped with SiO2 was found at a concentration of 500 ppm (APCNSi5). Deconvolution of the glow curve from APCNSi5 resulted in four peaks at about 161, 194, 237 and 293 C with a Figure Of Merit (FOM) of 1.28%. The APCNSi5 specimen had the best dosimetric properties when compared with the other samples. Reproducibility, repeatability, dose–response curve and fading effect were checked for peak 3, which appeared at about 237 C. The results displayed that the APCNSi5 glass system was a low‐Z material (Zeff ≈ 10), and had good reproducibility and good repeatability. Peak 3 showed good linearity over a dose range up to 20 Gy (R2 = 0.999) and sublinearity behaviour was found. The signal from APCNSi5 faded by about 11% after 2 days post irradiation, therefore it showed almost no significant loss. Such properties make the newly prepared glasses suitable for and highly recommended for use in γ‐dosimeters. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

7.
The present endeavor has demonstrated the impacts of different sources of silicon (Si) such as potassium silicate (K2SiO3) and calcium silicate (CaSiO3) during the in vitro axillary shoot multiplication of carnation. For the Si treatments, nodal explants were cultured onto the Murashige and Skoog’s medium fortified with 1.0 mg L?1 of 6-benzyladenine and 0.5 mg L?1 indole-3-acetic acid with or without K2SiO3 and CaSiO3 in three different concentrations (0, 1.8, or 3.6 mM). After six weeks, the shoot induction ratio, number of shoots produced per explant, expression of photosystem (PS) I and II core proteins, and activities of antioxidant enzymes were examined. Among the Si sources, K2SiO3 application enhanced the axillary shoot multiplication and the uptake of Si on comparison with CaSiO3. Both forms of Si resulted in the enhancement of stomatal density, and PS-related protein such as PsaA and PsbA illustrating the apparent involvement of Si on the photosynthetic process. Nevertheless, addition of Si improved the antioxidant capacity during the in vitro shoot multiplication. Overall, the outcomes of the present study suggested that Si can be utilized as a supplementary source during the in vitro propagation of carnation.  相似文献   

8.
Solid oxide electrolysis cells (SOECs) can efficiently convert the greenhouse‐gas CO2 to valuable fuel CO at the cathodes. Herein, fluorine is doped into mixed ionic–electronic conducting Sr2Fe1.5Mo0.5O6‐δ (SFM), to evaluate its potential use as a cathode for CO2 reduction reaction (CO2‐RR). SFM retains its cubic structure after doped with fluorine, forming perovskite oxyfluoride Sr2Fe1.5Mo0.5O6‐δF0.1 (F‐SFM). The substitution of oxygen by fluorine increases CO2 adsorption by a factor of ≈2, bulk oxygen vacancy concentration by 35–37% at 800 °C, and consequently enhances the surface reaction rate constant for CO2‐RR and chemical bulk diffusion coefficient by factors of 2–3. The faster kinetics are also reflected by a lower polarization resistance of 0.656 Ω cm2 for F‐SFM than 1.130 Ω cm2 for SFM at 800 °C in symmetrical cells. Furthermore, the single cell with F‐SFM cathode exhibits the best CO2 electrolysis performance among the reported perovskite electrodes, achieving current density of 1.36 A cm?2 at 1.5 V and excellent stability over 120 h at 800 °C under harsh conditions. The theoretical computations confirm that fluorine doping is energetically favorable to CO2 adsorption and dissociation. The present work provides a promising strategy for the design of robust cathodes for direct CO2 electrolysis in SOECs.  相似文献   

9.
Bioactive glasses such as Hench's 45S5 (Bioglass®) have applications to tissue engineering as well as bone repair, and the insertion of fluoride in their composition has been proposed to enhance their bioactivity. In view of a potential clinical application, we investigated whether fluoride-containing glasses exert toxic effects on human MG-63 osteoblasts, and whether and how fluoride, which is released in the cell culture medium, might play a role in such cytotoxicity. A 24 h incubation with 50 μg/ml (12.5 μg/cm2) of fluoride-containing bioactive glasses termed HCaCaF2 (F content: 5, 10 and 15 mol.%) caused the release of lactate dehydrogenase in the extracellular medium (index of cytotoxicity), the accumulation of intracellular malonyldialdehyde (index of lipoperoxidation), and the increase of glutathione consumption. Furthermore, fluoride-containing glasses inhibited the pentose phosphate oxidative pathway and the glucose 6-phosphate dehydrogenase activity. These effects are ascribable to the fluoride content/release of glass powders, since they were mimicked by NaF solutions and were prevented by dimethyl sulfoxide and tempol (two radical scavengers), by superoxide dismutase (a superoxide scavenger), and by glutathione (the most important intracellular antioxidant molecule), but not by apocynin (an inhibitor of NADPH oxidase). The presence of fluoride-containing glasses and NaF caused also the generation of reactive oxygen species, which was prevented by superoxide dismutase and catalase. The data suggest that fluoride released from glasses is the cause of MG-63 cell oxidative damage and is independent of NADPH oxidase activation. Our data provide a new mechanism to explain F? ions toxicity: fluoride could trigger, at least in part, an oxidative stress via inhibition of the pentose phosphate oxidative pathway and, in particular, through the oxidative inhibition of glucose 6-phosphate dehydrogenase.  相似文献   

10.
Ag ions are known for their antibacterial effects. Ag containing silicate glasses have been extended to create bioactive glasses that exhibit inhibitory effects on bacterial growth using different techniques. In this work, calcium and calcium/silver silicophosphate glasses were synthesized from the sol-gel process and their physicochemical and in vitro biological properties were studied and compared. The effect of silver concentration on in vitro bioactivity and antibacterial properties of the glasses was investigated. Ag2O was substituted for CaO in the glass formula up to 2 mol% and in vitro bioactivity of the samples was evaluated by soaking them in simulated body fluid followed by structural characterization using XRD, FTIR and SEM techniques. The results showed that both glasses favored precipitation of the calcium phosphate layer when they were soaked in simulated body fluid; however, the morphology of apatite crystals changed for the 2% mol silver containing sample. Substitution of 2% mol Ag2O for CaO seemed to slightly stimulate the rate of precipitation. The in vitro biodegradation rate of the silver/ calcium silicophosphate glasses was lower than that of the silver-free one (control). Also, the antibacterial properties of the samples indicated that these effects were improved by increasing silver concentration in bioactive glass composition.  相似文献   

11.
One-pot reaction of cobalt(II) nitrate hexahydrate Co(NO3)2 · 6H2O with H2salpn (N,N′-bis(salicylidene)-1,3-diaminopropane) in presence of a large excess of sodium azide (NaN3) gives the new Co(III) compound {Na[CoIII(μ-salpn)(μ1,1-N3)2]}n (1), which was characterized by single crystal X-ray diffraction analysis. The crystal structure shows polymeric 1D complex generated by the hexadentate Schiff base salpn2− and two crystallographically different azide ligands. The two nitrogen atoms of the salpn ligand are bonded to the cobalt(III) ion while each phenoxo oxygen atom is bonded to the same Co(III) ion and to two equivalent sodium ions. Each azide ligand acts with the end-on bridging coordination mode between Co(III) and Na(I) ions. The Co(III) ion adopts a distorted octahedral geometry arising from two oxygen and two nitrogen atoms of the salpn ligand and from two nitrogen atoms of the two crystallographically different azide ligands in trans positions. Such [Co(salpn)(N3)2] entities are connected each other by sodium ions through four oxygen atoms of two equivalent Schiff base ligands and two nitrogen atom of the two different azide ligands to generate the 1D structure of 1.  相似文献   

12.
Ning Liu  Ping Yang 《Luminescence》2013,28(4):542-550
Novel hybrid SiO2‐coated CdTe quantum dots (QDs) were created using CdTe QDs coated with a hybrid SiO2 shell containing Cd2+ ions and a sulfur source via a sol–gel process in aqueous solution. Aqueous CdTe QDs with tunable emitting color created through a reaction between cadmium chloride and sodium hydrogen telluride was used as cores for the preparation of hybrid SiO2‐coated CdTe QDs. In our experiments we found that the surface state of the cores and preparation conditions that affect the formation of the hybrid SiO2 shell also greatly affect photoluminescence of the hybrid SiO2‐coated CdTe QDs. The generation of CdS‐like clusters in the vicinity of the CdTe QDs, caused the quantum size effect of the QDs to be greatly reduced, which changes photoluminescence properties of the hybrid QDs fundamentally. Namely, the novel hybrid SiO2 shell played an important role in generating a series of specific optical properties. In addition, the novel hybrid SiO2 shell can be created if no CdTe QD is added. In order to gain an insight into the inter structure of the hybrid shell, we characterized the hybrid SiO2‐coated CdTe QDs using X‐ray diffraction analysis and discuss the formation mechanism of such a hybrid structure. This work is significant because the novel hybrid SiO2‐coated CdTe QDs with its excellent properties can be used in many applications, such as biolabeling and optoelectronic devices. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

13.
We have evaluated the effects of oxygen partial pressure (pO2), combined nitrogen, and the availability of organic substrates on nitrogen fixation (acetylene reduction) by bacteria associated with the roots of intact maize and sorghum plants. We also investigated the possibility of enhancing associative nitrogen-fixation by inoculating the soil in which the plants were grown withAzospirillum. Acetylene reduction (AR) activity was greatest when roots of intact plants were exposed to pO2 between 1.3 and 2.1 kPa. Field-grown and greenhouse-grown plants supported similar levels of activity. Respiration inhibitors (2,4-dinitrophenol and sodium azide) eliminated AR activity at 2 kPa O2, whereas a fermentation inhibitor (sodium fluoride) only partially reduced the activity. Acetylene reduction activity was rapidly (1–3 h) inhibited by NH 4 + , NO 3 , and NO 2 at concentrations of 4–20 mg Nl–1. Rates of AR varied substantially among individual plants in each experiment and between experiments. Amendment with any of several organic substrates greatly increased AR activity when rates were low, suggesting that the lack of activity was caused by a shortage of available carbon in the rhizosphere. Inoculation withAzospirillum failed to increase rates of AR associated with maize plants. In several experiments the indigenous bacteria associated with uninoculated plants exhibited greater activity than the bacteria associated with inoculated plants.  相似文献   

14.
The MgO–Ga2O3–SiO2 glasses and glass‐ceramics samples doped with Eu2+/Mn2+/Er3+ and heated in reductive atmosphere were prepared by the sol–gel method. The structure, morphology and the luminescence properties were studied using X‐ray diffraction, high‐resolution transmission electron microscope, fluorescence spectra, and up‐conversion emission. The luminescence characteristics of doped ions could be influenced by temperature and matrix component. The characteristic emission of Mn2+, Eu2+ and Er3+ were seen and the energy transfer efficiency from Eu2+ to Mn2+ was enhanced as Mn2+ concentration was increased. In addition, the two‐photon process was determined for the Er3+‐doped samples.  相似文献   

15.
This article reports on the optical properties of Er3+ ions doped CdO–Bi2O3–B2O3 (CdBiB) glasses. The materials were characterized by optical absorption and emission spectra. By using Judd–Ofelt theory, the intensity parameters Ωλ (λ = 2, 4, 6) and also oscillatory strengths were calculated from the absorption spectra. The results were used to compute the radiative properties of Er3+:CdBiB glasses. The concentration quenching and energy transfer from Yb3+–Er3+ were explained. The stimulated emission cross‐section, full width at half maximum (FWHM) and FWHM × values are also calculated for all the Er3+:CdBiB glasses. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

16.
Summary We investigated the influence of Mg2+ and Mn2+ on the effects of adenosine and some derivatives on basal adenylate cyclase activity in rat fat cell membranes as well as on enzyme activity stimulated by isoprenaline or sodium fluoride. Adenosine and derivatives modified in the ribose function were inhibitory, irrespective of the stimulant used, both in the presence of MgCl2 or MnCl2. Inhibition of basal and sodium fluoride stimulated adenylate cyclase activity was more pronounced in the presence of MnCl2 than in the presence of MgCl2. N6-substituted adenosine analogs proved to be inhibitory in the presence of 5 MM MgCl2, but in the presence of 1 mM MnCl2 the fluoride stimulated adenylate cyclase activity was potentiated, while basal and isoprenaline stimulated activity were not significantly inhibited. These effects of adenosine and derivatives could not be blocked by theophylline with or without guanyl nucleotides.The potentiating effect of N6-substituted adenosine derivatives on sodium fluoride activated adenylate cyclase is dependent on the structure of the N6-substitutent and consists of an enhancement of Vrnax in combination with a small decrease of the Km for MnATP2–, indicative of an allosteric effect on adenylate cyclase. No potentiation by N6-phenylisopropyladeno sine of sodium fluoride stimulated cyclase was found on digitonin solubilized cyclase, while the inhibitory effect of adenosine was retained. The relevance of these findings is discussed in connection with the current hypothesis concerning the presence of two adenosinesensitive sites on rat fat cell membranes.  相似文献   

17.
Calcium boro fluoro zinc phosphate glasses modified using alkali oxide and doped with Nd3+ and Er3+ ions with the chemical composition of 69.5 (B2O3) + 10 (P2O5) + 10 (CaF2) + 5 (ZnO) + 5 (Na2O/Li2O/K2O) + 0.5 (Er2O3/Nd2O3) were prepared using a conventional melt quenching technique. The results of X-ray diffraction patterns indicated the amorphous nature of all the prepared glasses. The visible–near-infrared red (NIR) absorption spectra of these glasses were analyzed systematically. The NIR emission spectra of Er3+ and Nd3+:calcium boro fluoro zinc phosphate glasses showed prominent emission bands at 1536 nm (4I13/24I15/2) and 1069 nm (4F3/24I11/2) respectively with λexci = 514.5 nm (Ar+ laser) as the excitation source.  相似文献   

18.
The recent discovery of Li‐excess cation‐disordered rock salt cathodes has greatly enlarged the design space of Li‐ion cathode materials. Evidence of facile lattice fluorine substitution for oxygen has further provided an important strategy to enhance the cycling performance of this class of materials. Here, a group of Mn3+–Nb5+‐based cation‐disordered oxyfluorides, Li1.2Mn3+0.6+0.5xNb5+0.2?0.5xO2?xFx (x = 0, 0.05, 0.1, 0.15, 0.2) is investigated and it is found that fluorination improves capacity retention in a very significant way. Combining spectroscopic methods and ab initio calculations, it is demonstrated that the increased transition‐metal redox (Mn3+/Mn4+) capacity that can be accommodated upon fluorination reduces reliance on oxygen redox and leads to less oxygen loss, as evidenced by differential electrochemical mass spectroscopy measurements. Furthermore, it is found that fluorine substitution also decreases the Mn3+‐induced Jahn–Teller distortion, leading to an orbital rearrangement that further increases the contribution of Mn‐redox capacity to the overall capacity.  相似文献   

19.
Summary The interrelationships between sodium ion, calcium transport and oxygen utilization have been investigated in the chick chorioallantoic membrane. The oxygen uptakes of the two surface layers of the tissue, the ectoderm and the endoderm, were separated into their basal, Na+ dependent and Ca++ dependent components. The endoderm has a basal rate of respiration of 3.6 liters O2/cm2/hr and a Na+ dependent component of 1.4 liters O2/cm2/hr. The ectoderm has a basal rate of respiration of about 3.5 liters O2/cm2/hr, and Na+ and Ca++ dependent components of 1.1 and 3.6 liters O2/cm2/hr, respectively. The rate of ectodermal calcium transport and calcium-stimulated oxygen uptake is strictly dependent on the presence of sodium in the bathing medium, and complex kinetics are observed as a function of sodium concentration. On the other hand, in 140mm Na+ the rate of calcium transport exhibits simple saturation kinetics as a function of calcium concentration. Ca++/O2 ratios determined for many different rates of transport give a ratio of about 0.5, a value much lower than similar ratios determined for other transport mechanisms. The calcium transport mechanism in the ectoderm responds to changes in transport rate very sluggishly, taking 30 to 50 min to give a maximum response. The differences between the calcium transport mechanism in this membrane and other known transport systems are discussed and it is suggested that these differences may represent the adaptations necessary for transcellular calcium transport.  相似文献   

20.
Novel erbium(III) ion-doped borate-based glasses (Er3+:BCNF) by conventional melt-quenching technique were designed and synthesized. The glasses were characterized for their structural, vibrational and spectroscopic properties. The nephelauxetic ratio, bonding parameters, and Judd–Ofelt (JO) intensity parameters (Ωλ λ = 2, 4 and 6) were determined by using absorption spectrum of 1 mol% Er2O3 doped glass. These JO parameters were utilized to derive radiative properties for various excited states of erbium(III) ions. Emission cross-section for 4I13/24I15/2 transition of erbium(III) ions was computed through McCumber theory. The decay curves for (2H11/2, 4S3/2) and 4I13/2 levels were recorded and analysed. All the results of Er3+:BCNF glasses revealed that the studied glasses are efficient and thermally stable and could be suitable for display devices, optical amplification and green laser applications.  相似文献   

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