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41.
Nicolas Sbirrazzuoli Alice Mititelu-Mija Luc Vincent Camille Alzina 《Thermochimica Acta》2006,447(2):167-177
The curing reaction of stoichiometric and off-stoichiometric diglycidyl ether of bisphenol A (DGEBA) and 1,3-phenylene diamine (m-PDA) mixtures was studied by differential scanning calorimetry, thermogravimetric analysis and rheological measurements. In order to highlight the side reactions such as etherification and homopolymerization, the neat DGEBA and DGEBA/DMBA (N,N-dimethylbenzylamine) mixture were examined. The classical model-fitting and the advanced isoconversional methods were used to determine the activation energy of the different reactions. The advanced isoconversional method leads to a good agreement between isothermal, nonisothermal and rheological results. The effective activation energies of primary amine epoxy reaction, etherification and homopolymerization were estimated to about 55-60, 104 and 170 kJ mol−1, respectively. 相似文献
42.
Recently, clinicians have observed an increase in the incidence of laryngeal papilloma coincident with the rising incidence of venereal warts. The lesions occur in young adults of professional singing age. Different types of human papillomavirus (HPV) are presented. Gynecologic exam revealed cervical tumors, involving 18 HPV in benign and malignant lesions. Thirty patients with the following pathologic conditions were studied: 10 papillomas, 10 severe dysplasias, and 10 invasive cancers. All the lesions were located on the free edge of the vocal folds or the anterior commissure involving the epithelium. The results are as follows: 11 patients (33%) had virus infection, of which four had HPV 6 or HPV 11 on laryngeal papilloma, three had HPV 16 or HPV 18 on severe dysplasia, four had HPV 16 or HPV 18 on carcinoma; and 19 (66%) had no virus infection. Gynecologic research in this field is more advanced. However, this preliminary report raises interesting research questions in laryngology. 相似文献
43.
44.
A new synthesis of wurtzitane (13) is described starting from 2-oxo-protoadamant-4-ene (2). The key intermediate ketone 7 was obtained by regiospecific ring expansion of the β-amino alcohol 6. Entry to the wurtzitane system involved solvolysis of the tricyclic unsaturated mesylate 10 (→11). 相似文献
45.
A synthesis of twista-4,9-diene ( 17 ) from tricyclo[4.3.1.03,8]dec-4-en-10-one ( 2 ) is described. 相似文献
46.
An easy approach to the novel adamantane isomer 1,2endo-trimethylenenorbornane (2) is described. Starting from a mixture of pent-4-ynylcyclopentadienes 3 the tricyclic monosaturated key intermediate 5 was prepared by intramolecular cycloaddition (→ 4 ) and subsequent regioselective reduction of the C(5), C(6) double bond. The title hydrocarbon 2 was obtained from 5 upon stereoselective hydrogenation by diimide. In addition specifically deuteriated analogues of 2 were prepared applying dideuteriodiimide. Compound 2 rearranged to 2endo, 6endo-trimethylenenorbornane (4-homobrendane, 10 ) in sulfuric acid as well as with aluminium bromide in carbon disulfide. 相似文献
47.
48.
A further synthetic approach to 2, 5-trimethylenenorbornane ( 1 ; tricycle [5.3.0.03,9]decane, 4-homotwistbrendane), a member of the «adamantaneland», is described starting from methyl 5-oxo-2endo-norbornanecarboxylate ( 5 ). The required C2-chain was introduced by a Wittig-Horner reaction and the ring closure of the trimethylene bridge achieved by an acyloin condensation. 相似文献
49.
Camille Laurent-Gengoux Abdenacer Makhlouf Joana Teles 《Journal of Pure and Applied Algebra》2018,222(5):1139-1163
We construct the universal enveloping algebra of a Hom-Lie algebra and endow it with a Hom-Hopf algebra structure. We discuss group-like elements that we see as a Hom-group integrating the initial Hom-Lie algebra. 相似文献
50.
A magnetic tweezers setup is used to control both the stretching force and the relative linking number DeltaLk of a palindromic DNA molecule. We show here, in absence of divalent ions, that twisting negatively the molecule while stretching it at approximately 1 pN induces the formation of a cruciform DNA structure. Furthermore, once the cruciform DNA structure is formed, the extrusion of several kilo-base pairs of palindromic DNA sequence is directly and reversibly controlled by varying DeltaLk. Indeed the branch point behaves as a nanomechanical gear that links rotation with translation, a feature related to the helicity of DNA. We obtain experimentally a very good linear relationship between the extension of the molecule and DeltaLk. We use then this experiment to obtain a precise measurement of the pitch of B-DNA in solution: 3.61 +/- 0.03 nm/turn. 相似文献