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91.
Grubišic Sonja Gruden-Pavlović Maja Niketić Svetozar R. Sakagami-Yoshida Narumi Kaizaki Sumio 《Transition Metal Chemistry》2003,28(1):37-42
The structure of trans-equatorial [Cr(edtrp)(H2O)] · 3H2O (edtrp3– is the anion of ethylenediamine-N,N,N-tripropionic acid) was determined by single crystal X-ray diffraction. The chromium(III) ion is surrounded octahedrally by the two nitrogen and three oxygen atoms of the quinquedentate edtrp3–, forming a five-membered diamine ring and the three six-membered -propionato chelate rings. The remaining coordination position is occupied by the H2O ligand. The crystal structure conformation is compared to the result of recent molecular mechanics analysis. The ring strain of R and G chelate rings was found to be in agreement with the previously proposed mechanisms for the C—N bond cleavage and recombination. 相似文献
92.
Interpretation of the results of determinations of free fluoride (Ff−) and total fluoride (Ft−) obtained with fluoride ISE while conducting elemental chemical analysis of bulk material of newly synthesized inorganic fluoride compounds is of crucial importance for the purpose of determination of purity and stoichiometry of these compounds. Knowledge of the properties and behavior of these compounds in aqueous media is therefore essential. Observations are presented on the determinations of the amounts of Ft− and Ff− in fluorinated compounds, in the particular hexafluoropnictate salts (PnF6−, Pn = P, As, Sb, Bi) as found in aqueous media and in some compounds with XeF2, AsF3 ligands. A critical look at the determined amounts of Ff−, Ft−and calculated amounts of bound fluoride (Fb−) is provided. 相似文献
93.
Tatiana V. Shubina Maja Remkar Valery Yu. Davydov Kirill G. Belyaev Alexey A. Toropov Bernard Gil 《Annalen der Physik》2019,531(6)
Nanotubes (NTs) of transition metal dichalcogenides (TMDs), were first synthesized more than a quarter of a century ago; nevertheless, many of their optical properties have so far remained basically unknown. Herein, the state of the art in the knowledge of the optical properties of TMD NTs is presented. First, general properties of multilayered crystals are evaluated, and available data on related NTs are analyzed. Then, the technology for the formation and the structural characteristics of NTs are represented, focusing on the structures synthesized by chemical transport reaction. The core of this work is the presentation of the ability of synthesized TMD NTs to emit bright photoluminescence (PL), which has been discovered recently. By means of micro‐PL spectroscopy of individual tubes, we show that excitonic transitions relevant to both direct and indirect band gaps contribute to the emission spectra of the NTs despite having the dozens of monolayers in their walls. The performance of the tubes as efficient optical resonators is highlighted, where confined optical modes strongly affect the emission. Finally, a brief conclusion is presented, along with an outlook of the future studies of this novel radiative member of the NTs family, which have unique potential for different nanophotonics applications. 相似文献
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Rodolphe Leforestier Anna Fleury François Mariette Guylaine Collewet Sylvain Challois Maja Musse 《Magnetic resonance in chemistry : MRC》2022,60(7):637-650
A quantitative magnetic resonance imaging (MRI) analysis at 1.5T of the effects of different dehydration regimes on transverse relaxation parameters measured in tomato tissue is presented. Multi-exponential T2 maps have been estimated for the first time, providing access to spatialized microstructural information at voxel scale. The objective was to provide a better understanding of the changes in the multi-exponential transverse relaxation parameters induced by dehydration in tomato tissues and to unravel the effects of microstructure and composition on relaxation parameters. The results led to the hypothesis that the multi-exponential relaxation signal reflects cell compartmentation and tissue heterogeneity, even at the voxel scale. Multi-exponential relaxation times provided information about water loss from specific cell compartments and seem to indicate that the dehydration process mainly affects large cells. By contrast, total signal intensity showed no sensitivity to variations in water content in the range investigated in the present study (between 95% [fresh tissue] and 90% [after dehydration]). The variation in relaxation times resulting from water loss was due to both changes in solute concentration and compartment size. The comparative analysis of the two contrasted tissues in terms of microporosity demonstrated that magnetic susceptibility effects, caused by the presence of air in the placenta tissue, significantly impact the effective relaxation and might be the dominant effect in the variations observed in relaxation times in this tissue. 相似文献
97.
Dragica M. Minić Maja T. Šumar-Ristović Đenana U. Miodragović Katarina K. Anđelković Dejan Poleti 《Journal of Thermal Analysis and Calorimetry》2012,107(3):1167-1176
The kinetics of multi-step thermal degradation of Co(II) complex with N-benzyloxycarbonyl glycinato ligand [Co(N-Boc-gly)2(H2O)4]·2H2O, in non-isothermal conditions was studied using isoconversional and non-isoconversional methods. The degradation of complex
occurs in three well-separated steps involving the loss of water molecules in first step followed by two degradation steps
of dehydrated complex. The dependence of Arrhenius parameters on conversion degree showed that all observed steps of thermal
degradation are very complex, involving more than one elementary step, as can be expected for most solid-state heterogeneous
reactions with solid reactants and solid and gaseous products. It was shown that step 1, corresponding to the dehydration,
involves a series of competitive dehydration steps of differently bound water molecules complicated by diffusion. Second step
involves two parallel reactions related to the loss of two identical C6H5CH2O– ligand fragments complicated by the presence of products in gaseous state. Further degradation in step 3 corresponds to
complex process with a change in the limiting stage, in this case from the kinetic to the diffusion regime, connected with
the presence of gaseous products diffusing through the solid product. 相似文献
98.
Eva Marguí PhD Rogerta Dalipi PhD Emanuele Sangiorgi PhD Maja Bival Štefan PhD Katarina Sladonja Vanessa Rogga Jasna Jablan PhD 《X射线光谱测定》2022,51(3):204-213
The aim of this study was the comparison of the results obtained in the determination of the content of essential elements such as Mn, Fe, Cu and Zn in vegetation samples using different analytical approaches, including suspension preparation and total reflection X-ray fluorescence ( TXRF) analysis as well as most commonly used spectroscopic methods in the field of vegetal analysis such as acid digestion in combination with atomic emission (AES) and atomic absorption spectrometry (AAS). In the case of TXRF analysis, two instruments equipped with different X-ray tubes anodes (W and Mo) were used to better evaluate the potential of TXRF for vegetal samples analysis. Analytical figures of merit for the considered methods were determined by the analysis of plant reference materials. The one-way analysis of variance (ANOVA) applied to the analysed and certified values showed that the results were not statistically different at the significance level of p-values <0.05. Therefore, suspension preparation and TXRF analysis proved to be a sustainable and fast analytical alternative to the most commonly used ones involving a previous digestion of the sample and inductively coupled plasma optical emission spectrometry (ICP-OES) or flame atomic absorption spectrometry (FAAS) analysis. Finally, the different analytical approaches were applied to the determination of Mn, Fe, Cu and Zn in a set of herbal teas used for medical purposes. 相似文献
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