排序方式: 共有75条查询结果,搜索用时 15 毫秒
1.
2.
The conformation in solution of derivatives of methyl hexopyranosides has been studied by n.m.r. The esters of methyl 2,3-O-isopropylidene-α-D-manno- and -talopyranosides as well as their 4-deoxy-4-C-methyl analog having a manno configuration exist mainly in a flattened (4,0F) chair conformation (4C1). The presence in the talo epimer of the 4-deoxy-4-C-methyl analog of the bulky methyl group on the endo side of the bicyclic system results in a skew form (3S1). The methyl 4-deoxy-2,3-O-isopropylidene-4-C-methylene-α-D-lyxo-hexopyranosides monosubstituted at C-4′ adopt, in solution, a conformation close to 3S1, whichever their configuration (cis or trans) at the double bond, as indicated by their allylic coupling constants. 相似文献
3.
Treatment of 2,5-anhydro-1-bromo-1-deoxy-2,3-O-isopropylidene-1-p-nitrophenylhydrazono-d-ribose with methyl acetylenecarboxylate gave methyl 3-(2,3-O-isopropylidene-β-d-erythrofuranosyl)-1-p-nitrophenylpyrazole- (8) and 5-carboxylate (9). Amidification at C-5 of 8 was easier than at C-4 of 9. Similarly, dimethyl 3-(2,3-O-isopropylidene-β-d-erythrofuranosyl)- 1 - p-nitrophenylpyrazole-4,5-dicarboxylate gave specifically a 5-carbamoyl derivative, the structure of which was established by comparison of the 13C-n.m.r.spectrum with those of a series of glycosylpyrazoles. The correlation between the experimental values of the chemical shifts of the carbon atoms of the pyrazole ring and the values calculated by addition of the contributions of the various groups linked to the ring was better (R 0.98) than the correlations obtained by calculation by the CNDO/2 method of the total electron population (R 0.92) or of the π-electron population of each carbon atom (R 0.85). 相似文献
4.
5.
6.
7.
8.
G. Bonardel C. Barrau M. Soussan E. D’Estanque B. Erra C. Etard N. Fayard M.O. Habert S. Hapdey E. Hindie F. Hyafil C. Labriolle Vaylet O. Lairez P.Y. Leroux P. Olivier M. Queneau E. Rust R. Seban M. Wartski 《Médecine Nucléaire》2018,42(5):295-297
Nuclear medicine hybrid imaging is a technological evolution of gamma camera scintigraphy or positron emission tomography imaging methods that are now often coupled with an anatomical imaging device, essentially a CT scanner. Following a large demand from the nuclear physicians themselves, but also from the French Nuclear Safety Authority, this guide is intended for the entire nuclear medicine community to integrate both the aspects of radiation protection related to coupled CT and those related to the quality of the CT images according to the clinical context. 相似文献
9.
G. Bonardel C. Barrau M. Soussan E. D’Estanque B. Erra C. Etard N. Fayard M.O. Habert S. Hapdey E. Hindie F. Hyafil C. Labriolle Vaylet O. Lairez P.Y. Leroux P. Olivier M. Queneau E. Rust R. Seban M. Wartski 《Médecine Nucléaire》2018,42(5):298-313
Many parameters can affect the patient's dose and the CT image quality. It is therefore essential, in order to optimize the patient's dosimetry, to know the influence of these parameters as well as their link with the dose modulation tools. 相似文献
10.
G. Bonardel C. Barrau M. Soussan E. D’Estanque B. Erra C. Etard N. Fayard M.O. Habert S. Hapdey E. Hindie F. Hyafil C. Labriolle Vaylet O. Lairez P.Y. Leroux P. Olivier M. Queneau E. Rust R. Seban M. Wartski 《Médecine Nucléaire》2018,42(5):359-366
The examples and clinical cases presented in this section are not intended to be considered as absolute models in terms of image quality or device parameter settings. They must initiate an individual analysis according to CT parameters and image quality. Nevertheless, they present practically different CT levels, which can be used according to the clinical context and the type of device. 相似文献