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51.
52.
The thermal excitation of artificial brushite in dried air and normal atmosphere generates the following reactions: We could not register the monotropic γ→β and β→χ transformations by DTA. At low pH2O values unstable inordinate intermediates are formed until the exothermic transformation, at high pH2O value and in water a stable, secondary hydrogen phosphate of ordinate crystal lattice and γ-pyrophosphate originate. The amorphous intermediate compounds are pseudomorphous with the initial brushite. The lack of H2O hinders, whereas the excess of H2O promotes the formation of nuclei and crystallization of monetite and as a result of this its thermal existence region is expanded. Accordingly, during the dehydratation process in dry air the decrease of the 相似文献
53.
54.
Gisela Peters 《Fresenius' Journal of Analytical Chemistry》1964,202(1):75
Ohne Zusammenfassung 相似文献
55.
Gisela Peters 《Fresenius' Journal of Analytical Chemistry》1965,209(3):463
Ohne Zusammenfassung 相似文献
56.
Jia G Strange W Collado J Guan Q 《The Journal of the Acoustical Society of America》2006,119(2):1118-1130
In this study we assessed age-related differences in the perception and production of American English (AE) vowels by native Mandarin speakers as a function of the amount of exposure to the target language. Participants included three groups of native Mandarin speakers: 87 children, adolescents and young adults living in China, 77 recent arrivals who had lived in the U.S. for two years or less, and 54 past arrivals who had lived in the U.S. between three and five years. The latter two groups arrived in the U.S. between the ages of 7 and 44 years. Discrimination of six AE vowel pairs /i-i/, /i-e(I)/, /e-ae/, /ae-a/, /a-(symbol see text)/, and /u-a/ was assessed with a categorial AXB task. Production of the eight vowels /i, i, e(I), e, ae, (symbol see text), a, u/ was assessed with an immediate imitation task. Age-related differences in performance accuracy changed from an older-learner advantage among participants in China, to no age differences among recent arrivals, and to a younger-learner advantage among past arrivals. Performance on individual vowels and vowel contrasts indicated the influence of the Mandarin phonetic/phonological system. These findings support a combined environmental and L1 interference/transfer theory as an explanation of the long-term younger-learner advantage in mastering L2 phonology. 相似文献
57.
Peter Krumbiegel Irina Lehmann Albin Alfreider Gisela J. Fritz David Boeckler Ulrike Rolle-Kampczyk 《Isotopes in environmental and health studies》2013,49(1):75-80
Background.?Studies conducted in Europe as well as in North and South America have tried to link Helicobacter pylori colonization with the drinking water supply, especially since H. pylori is known to survive quite well in water. Methods.?In 2000, a cohort of 1884 grade-two children from two rural counties surrounding the city of Leipzig, Germany (77.4% of the 1991/1992 birth cohort) were tested for H. pylori colonization using the [13C]urea breath test. A parent-completed questionnaire elicited details on living conditions and lifestyle habits including questions on the children's drinking water from sources other than public water supplies, swimming in natural waters, etc. In a second independent study, samples of well water, taken from 157 private wells still used in the two counties, were being tested for the presence of H. pylori, using polymerase chain reaction (PCR) method to determine relevant target DNA fragments of H. pylori. Results.?In county I, 5.7% of the children and in county II 6.6% tested H. pylori-positive. Cluster analyses of the questionnaire data in both counties pointed to ‘drinking water from other than municipal sources’, as the closest H. pylori-associated cluster variable. The cluster estimations were supported by odds ratio (OR) calculations with an OR?=?16.4 (95% confidence interval (CI) 3.1,…,88.5) for county I and OR?=?4.0 (95% CI 1.3,…,12.4) for county II. The PCR analyses showed H. pylori DNA fragments in 10.8% of the wells in county I and 9.2% in county II. The detection limit was set at 10 DNA copies corresponding to 125?bacteria/L, the average infestation of these wells was 931?bacteria/L. Conclusion.?Despite the fact that the microbiological and epidemiological data do not correspond except that both studies were conducted in the same geographical areas, the independent findings of H. pylori in well water in the same general areas where children do seem to drink water other than from the public water supply suggests that water may be an important source of H. pylori infection. 相似文献
58.
Takai-Utimoto reactions with secondary and tertiary aliphatic halides usually failed according to previous reports. Now, significant improvements could be achieved, and especially secondary aliphatic halides can be coupled to aromatic aldehydes in yields of up to >95%. A variety of processes are competing with the desired one, and thus conditions must be adapted to the nature of the aldehyde as well as the aliphatic halide used, as the outcome of these reactions is strongly affected by the putative radical intermediates. 相似文献
59.
A new oleanane-type saponin lactone was isolated from the ethanolic extract of the aerial parts of Astragalus corniculatus Bieb. The structure of the saponin was elucidated as 19-hydroxyolean-12-ene-28, 21beta-olide 3beta-D-xylopyranoside (1) by chemical and spectral methods. 相似文献
60.
Gisela Boeck 《Nachrichten aus der Chemie》2004,52(5):584-585