A review of ^(17)O isotopic labeling techniques for solid-state NMR structural studies of metal oxides in lithium-ion batteries

Recent advances in utilizing ^(17)O isotopic labeling methods for solid-state nuclear magnetic resonance(NMR)investigations of metal oxides for lithium-ion batteries have yielded extensive insights into their structural and dynamic details.Herein,we commence with a brief introduction to recent research on lithium-ion battery oxide materials studied using ^(17)O solid-state NMR spectroscopy.Then we delve into a review of ^(17)O isotopic labeling methods for tagging oxygen sites in both the bulk and surfaces of metal oxides.At last,the unresolved problems and the future research directions for advancing the ^(17)O labeling technique are discussed.

Revealing the catalytic mechanism of an ionic liquid with an isotope exchange method

The alkylation mechanism catalyzed by an ionic liquid （as a Lewis acid） may be different from the traditional alkylation mechanism catalyzed by Br nsted acid,especially as their initiation steps are still not clear.In this paper,an isotope exchange method is used to investigate the catalytic mechanism of AlCl 3 /butyl-methyl-imidazolium chloride ionic liquid in the alkylation of benzene with 1-dodecene.The proposed catalytic mechanism was confirmed by analysis of ionic liquid before and after reaction and of the alkylation products of deuterated benzene （C 6 D 6） with 1-dodecene.The proposed mechanism consists of the equilibrium reaction between [Al 2 Cl 7 ] ＋H ＋ and [AlHCl 3 ] ＋ ＋[AlCl 4 ],in which the Br nsted acid [AlHCl 3 ] ＋ is supplied by the reaction of 2-H on the imidazolium ring and [Al 2 Cl 7 ].The alkylation reaction is initiated by the Br nsted acid [AlHCl 3 ] ＋ which reacts with 1-dodecene to form a carbonium ion,then the carbonium ion reacts with benzene to form an unstable σ complex,leading to the formation of 2-phenyldodecane.

Separating component parts of soil respiration under Robinia pseudoacacia plantation in the Taihang Mountains,China

Partitioning the respiratory components of soil surface CO2 efflux is important in understanding carbon turnover and in identifying the soil carbon sink/source function in response to land-use change. The sensitivities of soil respiration components on changing climate patterns are currently not fully understood. We used trench and isotopic methods to separate total soil respiration into autotrophic （RA） and heterotrophic components （RH）. This study was undertaken on a Robinia pseudoacacia L. plantation in the southern Taihang Mountains, China. The fractionation of soil ^13CO2 was analyzed by comparing the δ^13C of soil CO2 extracted from buried steel tubes with results from Gas Vapor Probe Kits at a depth of 50 cm.at the preliminary test （2.03‰）. The results showed that the contribution of autotrophic respiration （fRA） increased with increasing soil depth.The contribution of heterotrophic respiration （fR/4） declined with increasing soil depth. The contribution of autotrophic respiration was similar whether estimated by the trench method （fRA, 23.50%） or by the isotopic method in which a difference in value of ^13C between soil and plant prevailed in the natural state （RC, 21.03%）. The experimental error produced by the trench method was insignificant as compared with that produced by the isotopic method, providing a technical basis for further investigations.

Estimation of N_2 Fixation by Some Legumes Using ^（15）N－Labelled Soil in Greenhouse Experiment

Pot experimeats were carried out to estimate N2 fixation by vetch, milk vetch, sickle alfalfa and broadbean in pure stand using a 15N-labelled soil. Winter wheat was used as the non-fixing control. The 15N-labelled soil used was prepared by growing corn-wheat-corn successively on a nearly organic-matter-free Xiashu loess supplemented with adequate amounts of (15NH4)aSO4, P, K and micronutrients, then incorporating these 15N-labelled plant msterials into the soil after each harvest, and allowing the plant materials to be decomposed aerobically for 410 d after incorporation of the plant material of the third crop. The 15N enrichment of wheat plant-N varied slightly with organs,with a maximum difference of 9.8%. Based on 15N enrichment of soil N inferred from the mean value of the 15N enrichment in different organs of wheat 79%-91% of total N in the tops and 67%-74% of total N in the roots of legumes studied were derived from atmosphere. Estimate by isotope dilution method was in good agreement with that by the conventional difference method provided values obtained by the latter were corrected for seed N, and also with that from the measurement of N accumulated in the tops of the legumes.

Uncertainty evaluation of the isotope shift factors for 2s2p^(3,1)P_1~o–2s^2 ~1S_0 transitions in B Ⅱ

Accurate isotope shift factors of the 2s2p^（3,1）P_1~o–2s^2 ~1S_0 transitions in B II, obtained with the multi-configuration Dirac–Hartree–Fock and the relativistic configuration interaction methods, are reported. We found a linear correlation relation between the mass shift factors and the energies for the transitions concerned, considering all-order electron correlations. This relation is important for estimating the uncertainty in the calculation of isotope shift factors. These atomic data can be used to extract the nuclear mean-square charge radii of the boron isotopes with halo structures or to resolve the high precise spectroscopy of B II in astronomical observation.

Using isotope methods to study alpine headwater regions in the Northern Caucasus and Tien Shan

High mountain areas provide water resources for a large share of the world＇s population. The ongoing deglaciation of these areas is resulting in great instability of mountainous headwater regions, which could significantly affect water supply and intensify dangerous hydrological processes. The hydrological processes in mountains are still poorly understood due to the complexity of the natural conditions, great spatial variation and a lack of observation. A knowledge of flow-forming processes in alpine areas is essential to predict future possible trends in hydrological conditions and to calculate river runoff characteristics. The goal of this study is to gain detailed field data on various components of natural hydrological processes in the alpine areas of the North Caucasus and Central Tien Shan, and to investigate the possibility that the isotopic method can reveal important regularities of river flow formation in these regions. The study is based on field observations in representative alpine river basins in the North Caucasus （the Dzhankuat river basin） and the Central Tien Shan （the Chon-Kyzyl-Suu river basin） during 2013-2015. A mixing-model approach was used to conduct river hydrograph separation. Isotope methods were used to estimate the contribution of different nourishment sources in total runoff and its regime. ~80, ~D and mineralization were used as indicators. Two equation systems for the study sites were derived： in terms of water routing and runoff genesis. The Dzhankuat and Chon-Kyzyl-Suu river hydrographs were separated into 4 components： liquid precipitation/meltwaters, surface routed/subsurface routed waters.

Inherited disturbances of phenylalanine metabolic kinetics in essential hypert ension

Objective To clarify whether the disturbances in metabolic kinetics of the essential aminoacid, phenylalanine (phe), are implicated in the genetic pathogenesis of essential hypertension (EH).Methods 1. L-(2, 3D3)-leucine, L-(2, 3D3)-isoleucine, L-15N-lysine, L-(2, 3D3)-valine and L-(2, 3D3)-phe were used for simultaneously studying comparative metabolic kinetics using stable isotope tracer methods with a GC-MS system. Study groups were the offspring with both parents suffering EH (n=10, FH+), 2 or more than 2 parents and grand-parents with EH and stroke (n=12, FS+) and those without genetic predisposition of EH and stroke (n=12, F) groups. 2. By comparing the radioactive counts of ［3H］-phe, and their weight transformation in blood after 1.5?Ci/kg i.v. administration at defined intervals and in tissues obtained after being sacrified among spontaneously hypertensive rats (SHR), 2 kidney-1 clip hypertensive rats (2K1C) and their normotensive controls (WKY). 3. The time transport and concentration transport of ［3H］-L-phe in cpm between the cultured vascular smooth muscle cell of 5th generation in SHR and WKY were compared.Results A single and unique disturbance of metabolic kinetics in phe were found in FH+, FS+ and SHR. The plasma pool or apparent volume of distribution was enlarged, and the turnover rate constants between plasma and cell tended to show a decrease. The pharmacokinetics of phe in 2K1C was not changed. Only phe content in heart and aorta, the vital organs for predicting BP, were higher in SHR than in WKY tissues studied. Both the time and concentration transport were higher in SHR, e.g., an increment in the net-uptake of L-phe by vascular tissue.Conclusion A unique aberrant of metabolic kinetics of phe might be implicated in the inherited pathogenesis of EH and stroke both from clinical and animal studies.