共查询到20条相似文献,搜索用时 312 毫秒
1.
Y. B. Xu S. D. Zhang H. J. Ding X. T. Lu W. F. Yang S. G. Yuan Y. H. Xiao Y. N. Niu 《Journal of Radioanalytical and Nuclear Chemistry》2007,272(2):227-230
The neutron-rich target-like isotope 236Th has been produced in the 238U-2p multinucleon transfer reaction between a 60 MeV/u 18O beam and natural 238U targets. The activities of thorium were determined after radiochemical separation of Th from the mixture of uranium and
reaction products. The 236Th isotope was identified by the characteristic γ-rays of 642.2, 687.6 and 229.6 keV. The production cross section of 236Th was determined to be 250±50 μb. 相似文献
2.
Christine Johnson Justin D. Lowrey Mark L. Rockhold Scott R. Waichler 《Journal of Radioanalytical and Nuclear Chemistry》2018,317(1):131-144
Analyses of stable (D and 18O) and radioactive (T) isotopes of different waters were applied to obtain the hydrological information in watersheds with different frozen ground types in the Source Area of the Yellow River, northeastern of Qinghai–Tibet Plateau in 2014 and 2016. Variations of oxygen and hydrogen isotope ratios, statistically higher tritium concentrations and lower water yields in thaw lakes confirm disparate sources of recharges to thaw lakes and other lakes. Thaw lakes at various stages of evolution influence the surface and subsurface water systems differently. 相似文献
3.
A. V. Belyaev S. N. Vorob’eva M. A. Fedotov 《Russian Journal of Inorganic Chemistry》2012,57(2):231-236
Rhodium(III) complex formation with phosphoric acid in strong acidic solutions has been studied by 103Rh, 17O, and 31P NMR. Phosphoric acid is mainly coordinated to rhodium as a monodentate terminal HPO42− ion, while the coordinated phosphate ion accounts for no more than 7%. 相似文献
4.
5.
Gao X Hu X Zhu J Zeng Z Han D Tang G Huang X Xu P Zhao Y 《Journal of the American Society for Mass Spectrometry》2011,22(4):689-702
Cationic metal ion-coordinated N-diisopropyloxyphosphoryl dipeptides (DIPP-dipeptides) were analyzed by electrospray ionization multistage tandem mass spectrometry
(ESI-MS
n
). Two novel rearrangement reactions with hydroxyl oxygen or carbonyl oxygen migrations were observed in ESI-MS/MS of the
metallic adducts of DIPP-dipeptides, but not for the corresponding protonated DIPP-dipeptides. The possible oxygen migration
mechanisms were elucidated through a combination of MS/MS experiments, isotope (18O, 15N, and 2H) labeling, accurate mass measurements, and density functional theory (DFT) calculations at the B3LYP/6-31 G(d) level. It
was found that lithium and sodium cations catalyze the carbonyl oxygen migration more efficiently than does potassium and
participation through a cyclic phosphoryl intermediate. In addition, dipeptides having a C-terminal hydroxyl or aromatic amino
acid residue show a more favorable rearrangement through carbonyl oxygen migration, which may be due to metal cation stabilization
by the donation of lone pair of the hydroxyl oxygen or aromatic π-electrons of the C-terminal amino acid residue, respectively.
It was further shown that the metal ions, namely lithium, sodium, and potassium cations, could play a novel directing role
for the migration of hydroxyl or carbonyl oxygen in the gas phase. This discovery suggests that interactions between phosphorylated
biomolecules and proteins might involve the assistance of metal ions to coordinate the phosphoryl oxygen and protein side
chains to achieve molecular recognition. 相似文献
6.
E. M. Sadovskaya A. P. Suknev A. V. Toktarev L. G. Simonova E. A. Paukshtis B. S. Bals’zhinimaev 《Kinetics and Catalysis》2006,47(1):131-137
The dynamics of 18O isotope exchange between NO or H2O and a catalyst and the dynamics of 18O label transfer from NO to H2O have been studied under conditions of sorption-desorption equilibrium. The occurrence of a reaction of oxygen exchange between NO and water sorbed in the bulk of the catalyst was detected. This reaction occurs at platinum sites with the participation of acid sites of the glass matrix. The rate constants of the reaction of NO with platinum sites and the diffusion coefficients of water in the bulk of the glass matrix are evaluated. 相似文献
7.
I. A. Grigor'ev M. A. Voinov M. A. Fedotov 《Chemistry of Heterocyclic Compounds》2005,41(9):1134-1138
Derivatives of 3-imidazoline 3-oxide have been studied by 14N and 17O NMR methods. Regularities of the influence of substituents and of a hydrogen bond on chemical shifts have been made apparent.
The range of changes of the chemical shifts of the nitrogen and oxygen nuclei of the nitrone group has been determined. Both
in the 17O and in the 14N NMR spectra the signals of the amino derivatives are the highest field signals for the nitrone group, and the lowest field
signals are the signals of the cyano derivatives in the series of derivatives investigated. Depending on the substituent (from
amino to cyano group) the 17O chemical shifts varied over a range ∼155 ppm, but the interval of change of the 14N chemical shifts for the same substituents was ∼110 ppm.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1336–1341. September, 2005. 相似文献
8.
Nizam M. El-Ashgar Issa M. El-Nahhal Mohamed M. Chehimi Michel Delamar Florence Babonneau Jacques Livage 《Journal of Sol-Gel Science and Technology》2007,41(1):3-10
A new insoluble solid functionalized ligand system bearing chelating ligand group of the general formula P-(CH2)3-N[CH2CONH(C6H4)NH2]2, where P represents [Si–O]
n
polysiloxane network, was prepared by the reaction of the immobilized diethyliminodiacetate polysiloxane ligand system, P-(CH2)3N(CH2CO2Et)2 with 1,2-diaminobenzene in toluene. 13C CP-MAS NMR, XPS and FTIR results showed that most ethylacetate groups (–COOEt) were converted into the amide groups (–N–C=O).
The new functionalized ligand system exhibits high capacity for extraction and removal of the metal ions (Fe3+, Co2+, Ni2+, Cu2+ and Zn2+) with efficiency of 95–97% after recovery from its primary metal complexes. This functionalized ligand system formed 1:1
metal to ligand complexes. 相似文献
9.
The local and medium-range structure of the 20CaO·20Al2O3·60SiO2 glass generated by classical molecular dynamics simulations has been compared to NMR experiments by computing the 27Al and 17O NMR parameters and NMR spectra from first-principles simulations. The calculation of the NMR parameters (chemical shielding
and quadrupolar parameters), which are then used to simulate solid-state MAS and 3QMAS NMR spectra, is achieved by the gauge
including projector augmented-wave and the projector augmented-wave methods on the DFT-PBE relaxed structure. The NMR spectra
calculated with the present approach are found to be in excellent agreement with the experimental data, providing an unambiguous
view of the local and medium-range structure of aluminosilicate glasses. 相似文献
10.
Jiaoyun Xia Shu Long Junfeng Yu Yongxian Wang Zhong Cao 《Journal of Radioanalytical and Nuclear Chemistry》2009,281(3):493-499
The purpose of this work was to indirect label IgG with fac-[188Re(CO)3(H2O)3]+ and to check the radiochemical behavior of the labeled product. The compound of (bis(2-pyridylmethyl)-amino)-acetic acid
(L2H) was synthesized and labeled with fac-[188Re(CO)3(H2O)3]+. The labeling yield of 188Re(CO)3–L2H was more than 90%. The effects of protein concentration, reaction time, pH and reaction temperature of labeling of IgG with
188Re(CO)3–L2H were investigated. The conjugation conditions were optimized. The labeled product was analyzed by size exclusion HPLC and
TLC. The stability of 188Re(CO)3–L2H–IgG in vitro was high. The results of this study may be useful for [188Re(CO)3(H2O)3]+ labeling of protein for radioimmunotherapy. 相似文献
11.
Potassium persulfate oxidizes triphenylphosphine to triphenylphosphine oxide in 60% aqueous acetonitrile. It has been suggested that the oxygen of the product, triphenylphosphine oxide, might originate from solvent water, following nucleophilic attack on an intermediate phosphonium ion. We have investigated the origin of the oxygen in the oxidation of triphenylphosphine by potassium persulfate in 60% aqueous acetonitrile containing 20% [18O]water. The product was analyzed by using the 18O isotope effect in 31P NMR spectroscopy. The magnitude of the 18O isotope-induced shift was determined by synthesizing triphenylphosphine [18O]oxide and was found to be 0.038 ppm upfield. The product of the oxidation reaction in 20% [18O]water displayed no 18O isotope effect. The origin of the oxygen in the oxidation reaction is the persulfate ion, consistent with an alternative mechanism involving nucleophilic attack by water at the sulfur atom of a phosphonium peroxysulfate intermediate. 相似文献
12.
A new molybdophosphate (NH4)8{Mo2VO4[(Mo2VIO6)CH3C(O)(PO3)2]2}·14H2O (1), has been synthesized by the reaction of {Mo2VO4(H2O)6}2+ fragments with 1-hydroxyethylidenediphosphonate (hedp HOC(CH3)(PO3H2)2), and it is characterized by 31P NMR, IR, UV, element analysis, TG and single-crystal X-ray analysis. The structure analysis reveals that the polyoxoanion
can be described as two {(Mo2VIO6)(CH3C(O)(PO3)2} units connected by a {Mo2VO4}2+ moiety. In the structure, the six Mo atoms are arranged into a new “W-shaped” structure, which represents a new kind of molybdophosphate. 相似文献
13.
The complex formation in the system GaCl3-ROH-MNCS-18K6 is considered (ROH = MeOH, EtOH; M = Na, K; 18C6 is 1,4,7,10,13,16-hexaoxocyclooctadecane). Two modifications of [Na(18C6)][GaCl4], namely, aggregates [Na(18C6)][GaCl4](MeOH)0.9(EtOH)1.1 and [Ga(H2O)3(NCS)3] · 18C6, are synthesized and identified. The 71Ga NMR (solutions) and X-ray diffraction studies showed that the compositions and structures of the title compounds are determined by the ratio of the competing acido ligands (Cl? and NCS?) in the reaction solution. 相似文献
14.
A. G. Nozad S. Meftah M. H. Ghasemi M. Aghazadeh 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(13):2270-2277
DFT calculations of electric field gradient (EFG) tensors at the sites of 14N, 17O, and 2H nuclei are carried out to characterize the hydrogen bond (HB) interactions in the sulfapyridine crystal structure. One-molecule
(monomer) and hydrogen-bonded hexameric cluster models of sulfapyridine are constructed according to available X-ray coordinates
where the proton positions are optimized. Then, EFG tensors are calculated for both monomer and target molecule in the hexameric
cluster of sulfapyridine to show the effect of HB interactions on the tensors. The calculated EFG tensors are converted to
the experimentally measurable nuclear quadrupole resonance (NQR) parameters: quadrupole coupling constant (C
Q
) and asymmetry parameter (η
Q
). The results reveal different contribution of various nuclei to N-H⋯N and N-H⋯O HB interactions in the cluster where the
N2 and O1 have major contributions. The computations are performed with B3LYP and B3PW91 functionals DFT method and 6-311+G*
and 6-311++G** standard basis sets using the Gaussian 98 package. 相似文献
15.
J. H. Park K. B. Lee C. S. Lee Y. K. Kwon J. H. Lee J. Y. Kim W. Hong 《Journal of Radioanalytical and Nuclear Chemistry》2008,275(3):627-631
A (D3C)2O (d6-acetone) target was irradiated with semi-monoenergetic neutrons generated from 9Be(p,n)9B reaction with 20 MeV protons to convert 13C and oxygen nuclides in the target into 14C. With both liquid scintillation counting (LSC) and accelerator mass spectrometry (AMS) we measured the (D3C)2O (d6-acetone) liquid targets, which were combustible and easy to afford CO2 for the AMS measurements. The 14C yield measured by the LSC method turned out to be 80 times larger than that by the AMS method. This large discrepancy may
be attributed to the loss of 14C atoms during the sample pretreatment in the AMS method such as combustion and cryogenic trapping of CO2. It means that 14C newly produced by nuclear reactions can exist in various chemical forms, i.e., C3D6O, CO, CO2, hydrocarbons, etc., and a simple sample pretreatment right after production can cause serious isotopic fractionation. Therefore,
using the AMS method, extreme caution in sample pretreatment should be exercised when the 14C yield produced immediately by nuclear reaction is measured. 相似文献
16.
A.L. Buchachenko A.V. Fedorov L.L. Yasina E.M. Galimov 《Chemical physics letters》1984,103(5):405-407
Experimental evidence based on the dependence of molecular oxygen isotope enrichment on the oxygen conversion, temperature and kinetic chain length indicate that, in chain processes of polymer oxidation, the elementary, reactions (recombination or disproportionation) of peroxy radicals are responsible for the selection of both 17O and 18O isotopes. The 17O selection is induced by a magnetic isotope effect and is sensitive to the molecular dynamics, while 18O selection is due to a classical mass-dependent isotope effect and is much less effective. 相似文献
17.
The analysis of 226Ra in natural waters can be tedious and time-consuming. For the determination and differentiation of activities of 226Ra and 222Rn in drinking water by γ-ray spectrometry a simple and fast method is presented. Activities of 226Ra > 0.5 Bq L−1 can be determined according to stabilization of the sample without further procedures. For a more sensitive detection sample
volumes of up to 5 litres are applicable by a rapid precipitation procedure without large expenditure. Further laborious enrichment
methods are not necessary. Thus, detection limits of 0.1 Bq L−1 can be obtained when using sample volumes of 5 litres. Therefore the method is suitable for the monitoring of radioactivity
in drinking water samples in accordance with the legal guidance of the European Union. 相似文献
18.
A. N. Kozachkova N. V. Tsaryk V. V. Trachevskii A. B. Rozhenko V. I. Pekhnyo 《Russian Journal of Coordination Chemistry》2009,35(9):674-680
The complex formation in the K2PdCl4-nitrilotrimethylenephosphonic acid (NTMP) system with a metal to ligand molar ratio of 1: 1 and 1: 2 was studied by 31P and 1H NMR spectroscopy. The formation of equimolar complexes with NTMP coordinated in the bidentate ([N,O]) and tridentate ([N,O,O])
fashions depending on the reactant and chloride ion concentrations and solution pH was observed. 相似文献
19.
Mónika Kéri László Palcsu Marianna Túri Enikő Heim Andrea Czébely Levente Novák István Bányai 《Cellulose (London, England)》2015,22(4):2211-2220
Alpha-cellulose is a part of the wooden material that preserves isotopic composition during tree-growth, and therefore provides important indirect data for paleoclimatological studies. For this reason, it is exceptionally important to extract the alpha-cellulose component from plants, e.g. from tree rings of wood. Since the cell wall of plant cells consists of multicomponent polysaccharides, the extraction of cellulose from wood is not an obvious task. In this paper, we describe, evaluate and compare nine methods, based on the literature and experimental observations, for obtaining cellulose from tree rings of wood. We show that the distortionless enhancement by polarization transfer (DEPT-135) variant of liquid-state 13C NMR spectroscopy is a powerful analytical method for monitoring the preparation process. Trifluoroacetic acid was applied as solvent for the NMR analysis. We proved that all the preparation methods give pure cellulose samples without hemicellulose and lignin content, and we propose methods resulting in non-fragmented cellulose. 13C and 18O isotope ratio measurements have shown that all the applied extraction methods result in similar isotope ratios, thus they are suitable for paleoclimatological studies. 相似文献
20.
Gholam Hossein Rounaghi Mohammad Hossein Arbab Zavvar Kataneh Badiee 《Russian Journal of Inorganic Chemistry》2008,53(4):660-664
The equilibrium constants and thermodynamic parameters for complex formation of 18-Crown-6 (18C6) with Tl+, Pb2+, Hg2+, and Zn2+ metal cations have been determined by conductivity measurements in methanol (MeOH)-water (H2O) binary solutions. 18-Crown-6 forms 1:1 complexes with Hg2+ and Zn2+ cations, but in the case of Tl+ and Pb2+ cations, in addition to 1:1 stoichiometry, 1:2 (ML2) complexes are formed in some binary solvents. The thermodynamic parameters (ΔH
c0 and ΔS
c0), which were obtained from the temperature dependences of equilibrium constants, show that in most cases the complexes are
enthalpy destabilized but entropy stabilized. Non-linear behavior is observed between the equilibrium constants (log K
f
) of complexes and the composition of the mixed solvent. The selectivity of the ligand for these metal cations is sensitive
to the solvent composition, and, in some cases, the selectivity order is reversed in certain compositions of the mixed solvent.
The results also show that the mechanism of complexation reactions and the stoichiometry of complexes of some metal cations
change with the nature and even with the composition of the mixed solvent.
The article was submitted by the authors in English. 相似文献