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951.
Li P Coleman DW Spaulding KM McClennen WH Stafford PR Fife DJ 《Journal of chromatography. A》2001,914(1-2):147-159
HPLC and gel permeation chromatographic (GPC) characterization of complex phenol-formaldehyde resins is described. Reversed-phase HPLC fingerprints the phenolic monomers, dimers and some oligomers. The molecular masses of these phenolic compounds were determined using an ion trap mass spectrometer. GPC analyzes tetrahydrofuran-soluble phenolic polymers beyond HPLC capability. The molecular mass distribution and structural information of the phenolics was determined by both conventional and laser light-scattering calibration methods. GPC with both UV and refractive index detection provides weight concentration of phenolic resin and the molar concentration of the phenol unit in the oligomers or polymers. 相似文献
952.
Jerry L. Atwood Anthony W. Coleman Hongming Zhang Simon G. Bott 《Journal of inclusion phenomena and macrocyclic chemistry》1989,7(2):203-211
The title calixarenes all exist in the solid state as bilayers of anionic calixarenes in the cone configuration. These layers alternate with inorganic regions which contain the cations and the water molecules. The overall structures bear a close resemblance to those found for clay minerals. The sodium salt crystallizes in the triclinic space groupP witha = 10.998(6),b = 13.582(5),c = 14.472(5) Å, = 74.01(3), = 89.09(4), = 86.50(4)°, andZ = 2 forD
calc
= 1.72 g cm–3. Refinement based on 4727 observed reflections led to a conventionalR = 0.050. The potassium salt crystallizes in the triclinic space groupP witha = 11.815(9),b = 13.636(6),c = 14.040(9) Å, = 100.24(5), = 111.86(9), = 95,14(9)°, andZ = 2 forD
calc
= 1.77 g cm–3. Refinement based on 2977 observed reflections led toR = 0.15. The rubidium and cesium salts are isostructural and crystallize in the monoclinic space groupP21/n with parameters for Rb[Cs]a = 11.603(5) [11.704(3)],b = 28.607(8) [29.747(9)],c = 12.512(5) [12.604(4)] Å, = 91.70(4) [91.63(2)°], andZ = 4 forD
calc
= 2.01 [2.24] g cm–3. Refinement based on 1750 [4257] observed reflections led toR = 0.108 [0.075]. Disorder of the cations was observed for the rubidium and cesium salts.
Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82074 (95 pages). 相似文献
953.
A decomposition of an N-particle operator as a sum of N + 1 components is defined such that, in the case of a model system employing a finite one-particle basis set, the decomposition is invariant under unitary transformations of the basis set. Applied to a two-particle Hamiltonian, this decomposition gives rise to the distinction between the independent-particle energy and the coupling energy defined in previous papers. Applied to the reduced density operator for a quantum state, the decomposition corresponds to partitioning the density into irreducible components. This partitioning is illustrated by graphs of electron density for the water molecule. 相似文献
954.
Roqueline Rodrigues Silva de Miranda Grácia Divina de Fátima Silva Lucienir Pains Duarte Sidney Augusto Vieira Filho 《Helvetica chimica acta》2007,90(4):652-658
The triterpene ester (3β)‐olean‐18‐en‐3‐yl stearate ( 1 ), together with (3β)‐urs‐12‐en‐3‐yl stearate ( 2 ), and (3β)‐lup‐20(29)‐en‐3‐yl stearate ( 3 ) were isolated from leaves of Maytenus salicifolia Reissek (Celastraceae). The structure of 1 , a new compound, including its configuration, was established by 1H, 13C, and DEPT‐135 NMR data, including 2D experiments (HSQC, HMBC, COSY, and NOESY). The molecular mass (692 Da) was confirmed by gas chromatography coupled with mass spectrometry (CG/MS). 相似文献
955.
The synthesis of a mono-galactosylated amphiphilic β-cyclodextrin, in five steps from mono-6-azido-6-deoxy-β-cyclodextrin, via coupling to a N-β-d-galactopyranosylamino-antenna is described. Both characterization by electrospray mass spectrometry and NMR show the presence of only the mono-substituted product. The Langmuir isotherms of the final product and intermediates are described. 相似文献
956.
Fumio Hamada Simon G. Bott G. William Orr Anthony W. Coleman Hongming Zhang Jerry L. Atwood 《Journal of inclusion phenomena and macrocyclic chemistry》1990,9(3):195-206
Bromocalix[4]arene methyl ether serves as a precursor in the synthesis of the title thiocalixarene via the reagent CuSEt. Ethylthiocalix[4]arene methyl ether crystallizes in the monoclinic space groupP21/c witha = 20.577(9),b, = 10.722(5),c = 20.315(9) Å, = 120.46(4)°, andD
c = 1.24 g cm–3 forZ = 4. Refinement based on 1441 observed reflections led toR = 0.080. The configuration of the calixarene lies between the partial cone and the 1,3-altemate conformations. Bromocalix[4]arene methyl ether crystallizes in the triclinic space groupPI witha = 12.283(7),b = 17.658(9),c = 18.118(6) Å, = 90.25(6), = 105.95(4), = 105.11(6)°, andD
c = 1.68 g cm–3 forZ = 4. Refinement based on 3028 observed reflections led toR = 0.083. The unit cell also contains four CHCl3 molecules which exist pairwise enclathrated by six calixarenes. The partial cone conformation of the bromocalixarene is identical to that of ethylthiocalix[4]arene methyl ether. 相似文献
957.
Radiochemical analyses for the defense waste processing facility startup at the Savannah River Site 总被引:1,自引:0,他引:1
W. F. Kinard N. E. Bibler C. J. Coleman R. A. Dewberry 《Journal of Radioanalytical and Nuclear Chemistry》1997,219(2):197-201
Highly radioactive waste from defense-related activities at the Savannah River Site in South Carolina are to be incorporated into a borosilicate glass in the Defense Waste Processing Facility (DWPF) for long-tem geological isolation. Processing and repository safety considerations require the determination of 24 radioisotopes that meet the reporting criteria. These isotopes include fission products, activation products, and daughter nuclei that grow into the waste. Four isotopes,137Cs,90Sr,238Pu and238U will be routinely measured in the DWPF operation for process control. This work shows that the concentrations of the other 20 reportable radioisotopes in the final glass product can be predicted from a thorough characterization of the high level waste (HLW) tanks and a knowledge of the concentrations of the major non-radioactive components in the vitrification process. 相似文献
958.
959.
Vikram Kestens Gert Roebben Jan Herrmann Åsa Jämting Victoria Coleman Caterina Minelli Charles Clifford Pieter-Jan De Temmerman Jan Mast Liu Junjie Frank Babick Helmut Cölfen Hendrik Emons 《Journal of nanoparticle research》2016,18(6):171
A new certified reference material for quality control of nanoparticle size analysis methods has been developed and produced by the Institute for Reference Materials and Measurements of the European Commission’s Joint Research Centre. The material, ERM-FD102, consists of an aqueous suspension of a mixture of silica nanoparticle populations of distinct particle size and origin. The characterisation relied on an interlaboratory comparison study in which 30 laboratories of demonstrated competence participated with a variety of techniques for particle size analysis. After scrutinising the received datasets, certified and indicative values for different method-defined equivalent diameters that are specific for dynamic light scattering (DLS), centrifugal liquid sedimentation (CLS), scanning and transmission electron microscopy (SEM and TEM), atomic force microscopy (AFM), particle tracking analysis (PTA) and asymmetrical-flow field-flow fractionation (AF4) were assigned. The value assignment was a particular challenge because metrological concepts were not always interpreted uniformly across all participating laboratories. This paper presents the main elements and results of the ERM-FD102 characterisation study and discusses in particular the key issues of measurand definition and the estimation of measurement uncertainty. 相似文献
960.
Dr. Rajendra Kurapati Dr. Claudia Backes Dr. Cécilia Ménard‐Moyon Prof. Jonathan N. Coleman Dr. Alberto Bianco 《Angewandte Chemie (International ed. in English)》2016,55(18):5506-5511
Hexagonal boron nitride (hBN) nanosheets are emerging as promising 2D materials for different types of applications. However, biodegradation of hBN materials is poorly explored owing to their high chemical inertness and strong oxidation resistance. The assessment of oxidation/biodegradation of hBN is important in developing biomedical tools. Herein, we report the first study on the biodegradability of hBN nanosheets comparing the enzymatic catalysis of two different peroxidases, horseradish peroxidase (HRP) and human myeloperoxidase (MPO), with the photo‐Fenton (P.F.) reaction. The results show that degradation of hBN nanosheets is different to that of graphene and graphene oxide, since partial oxidation was found using MPO after 35 h, while HRP failed to degrade hBN up to 60 days. Nearly complete oxidation/degradation was occurred by P.F. reaction in 100 h. These results are helpful in designing advanced conjugates for biomedical uses of hBN. 相似文献