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排序方式: 共有122条查询结果,搜索用时 62 毫秒
61.
B. P. Chandra S. Tiwari Meera Ramrakhiani M. H. Ansari 《Crystal Research and Technology》1991,26(6):767-781
The paper reports that the mechanoluminescence (ML) is not an inherent property of only the non-centrosymmetric crystals. The ML may appear in number of centrosymmetric crystals due to variety of processes. The ML of 82 centrosymmetric crystals are reported and different models are proposed for the ML excitation. The models proposed are: space charge electrification model, triboelectrification model, phase transformation model, gas adsorption model, chemical reaction model, thermal population model, molecular deformation model, cleavage electrification model, defective piezoelectric phase model, dislocation defect stripping model, dislocation unpinning model, dislocation annihilation model, charged dislocation model and incandecent light emission model. It is shown that on the basis of the proposed model, intense mechanoluminescent materials with desired nature and characteristics may be prepared. 相似文献
62.
Moydeen Meera Kumar Radhakrishnan Surendra Idhayadhulla Akbar Manilal Aseer 《Molecular diversity》2019,23(1):35-53
Molecular Diversity - Novel pyrazolidine-3,5-dione derivatives (2a–g, 4a–g, and 6a–g) were synthesized by an easy-to-perform Mg(II) acetylacetonate-catalyzed reaction with high... 相似文献
63.
Bono van IJzendoorn Dr. Inigo J. Vitorica-Yrezabal Dr. George F. S. Whitehead Dr. Meera Mehta 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(6):e202103737
Despite being known for decades the chemical reactivity of homoatomic seven-atom phosphorus clusters towards small molecules remains largely unexplored. Here, we report that neutral tris(silyl) functionalised heptaphosphane (P7(SiR3)3) cages are capable of heteroallene capture between the P−Si bonds of the cluster. A range of isocyanates and an isothiocyanate were investigated. In the case of isocyanates, silyl bonding at oxygen or nitrogen is regioselectively directed by the functional group on the isocyanate and substituents on the silyl moiety. Above all, we find that captured isothiocyanate molecules can be exchanged for isocyanate molecules, indicative of small molecule catch and release. Small molecule catch and release at these Zintl-derived clusters reveals their potential application as chemical storage materials or as reusable probes. 相似文献
64.
Nidhi Adhlakha K.L. YadavAmit Kumar Piyush Kumar PatelJyoti Rani Meera Rawat 《Physica B: Condensed Matter》2012,407(17):3427-3433
We report the study of structural, optical and magnetic properties of (1−x)ZnO–xMgO (x=0.35, 0.40, 0.45 and 0.50) composites prepared by solid state reaction method. X-ray diffraction pattern confirms the presence of both the phases associated with ZnO (hexagonal) and MgO (cubic), which is revealed through the existence of (1 1 1) and (2 0 0) peaks in addition to ZnO peaks. The lattice parameter c as calculated using X-ray analysis undergoes shrinkage with increasing content of MgO. Microstructural analysis suggests that there is no variation in spherical elongated shape of grains with increasing concentration of MgO, where the average grain size is found to be ∼600 nm. The band gap as calculated from optical absorption spectra obtained by diffuse reflectance method recorded at room temperature is tuned from 3.16 to 3.55 eV. Photoluminescence spectra consist of near band edge UV emission (389 nm) and defect level emission (503 nm). The increase of MgO concentration leads to blue shift of UV emission peaks. The magnetic measurements conducted using SQUID at 5 K temperature reveals ferromagnetism along with paramagnetic and superparamagnetic components. Saturation magnetisation (Ms) is observed to be enhanced with MgO doping. 相似文献
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Chloroperoxidase from Musa paradisiaca stem juice has been purified to homogeneity using a concentration obtained by ultrafiltration and anion exchange chromatography on diethylaminoethyl (DEAE) cellulose. The purified enzyme gave a single protein band in SDS‐PAGE analysis corresponding to molecular mass of 43 kDa. The native PAGE analysis result has also given a single protein band, confirming the purity of the enzyme. The purified enzyme was chlorinated and brominated with monochlorodimedone, the substrate used for measuring the halogenating activity of chloroperoxidases. The Km and kcat values using monochlorodimedone as the substrate were 20 μM and 1.64 s?1, respectively, giving a kcat/Km value of 8.2 × 104 M?1 s?1. The pH and temperature optima of the chlorinating activity were 3.0 and 25°C, respectively. The Km values for the peroxidase activity using pyragallol and H2O2 as the variable substrates were 89 and 120 μM, respectively. The pH and temperature optima of the peroxidase activity using pyrogalllol as the substrate were the same as the pH and temperature optima of the halogenating activity. The peroxidase activity of the enzyme is competitively inhibited by sodium azide, indicating that it is a hemeperoxidase different from nonheme peroxidases. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 45: 92–100, 2013 相似文献
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69.
Drishty Satpati Archana Mukherjee Meera Venkatesh Sharmila Banerjee 《Journal of Radioanalytical and Nuclear Chemistry》2011,290(1):89-93
The over-expression of folate receptors in variety of neoplastic tissues makes radiolabeled folate conjugates potential agents
for imaging and therapy of such cancers. With the aim of preparing an imaging agent for targeting folate receptors, folic
acid has been conjugated with homocysteine for complexation with [99mTc(CO)3(H2O)3]+ core. The radiolabeled complex of the homocysteine-folate could be obtained in >95% radiochemical yield as observed by HPLC.
Stability of complex in saline was studied and challenge studies with histidine and cysteine revealed kinetic stability of
the complex. Lipophilicity of the radiolabeled complex (log P) was found to be 0.45. In vitro uptake of 99mTc(CO)3-labeled folic acid derivative was studied in KB cells and inhibition studies were carried out using 3H-folic acid and cold homocysteine–folate conjugate. The in vitro studies indicated loss of binding affinity of the derivative
towards folate receptors. 相似文献
70.
Rubel Chakravarty Ramu Ram K. C. Jagdeesan Meera Venkatesh Ashutosh Dash 《Chromatographia》2011,74(7-8):531-540
The present work demonstrates the utility of polymer embedded nanocrystalline titania (TiP) as a new, accessible and viable solid sorbent for the chromatographic separation of high specific activity 77As from neutron irradiated natural GeO2. Experimental parameters such as distribution ratios (K d), equilibrium sorption capacity, breakthrough capacity and separation yields were determined. A two-step ion-exchange procedure was developed to avail 77As, from irradiated Ge in alkaline medium. The first step involved removal of the bulk Ge from 77As by selective sorption of Ge ions on a TiP column at pH 13. Subsequently, the effluent solution containing 77As was further purified and concentrated by sorption on a small TiP column at pH 10. 77As could be eluted from the second column in 2?C3?mL of 0.1?M NaOH solution with >80% radiochemical yield. The 77As obtained by this method was found to have insignificantly small level of radiocontaminants. 相似文献