Thermoanalytische untersuchung von sekundärem calciumphosphatdihydrat

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 p_H2O values unstable inordinate intermediates are formed until the exothermic transformation, at high p_H2O 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     

Die Bestimmung von ?thylendiamin in 2-Methylpiperazin

Ohne Zusammenfassung     

Versuche zur Trennung von Gemischen des n-Butans, der n-Butene und des Butadiens

Ohne Zusammenfassung     

Perception and production of English vowels by Mandarin speakers: age-related differences vary with amount of L2 exposure

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.     

Helicobacter pylori determination in non-municipal drinking water and epidemiological findings

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.     

Die quantitative chemische Bestimmung von Vitamin D

Zusammenfassung Die zur Vitamin D₂-Bestimmung bekannten spezifischen Farbreaktionen nachHalden und H.Brockmann werden durch die Unbeständigkeit des erhaltenen Farbtones und dieser durch Fettbegleitsubstanzen empfindlich gestört. Es gelingt, eine für Vitamin D spezifische, im Farbton beständige Reaktion bei Verwendung einer 20%igen Antimontrichloridund 5%igen Guajakol-Lösung in Chloroform. Die Empfindlichkeit der Reaktion ist 1200000. Es können quantitativ 15 in 2,8 ml Chloroform nachgewiesen werden bei tunlichster Einhaltung der beschriebenen Versuchsbedingungen.Der Einfluß der Sterine auf die Reaktion ist sehr gering, doch werden die Empfindlichkeit und die Spezifität dann vermindert, wenn sehr große Mengen dieser Begleitstoffe vorhanden sind. Mit Hilfe der Adsorption an frisch behandeltes, bei 120 erhitztes Aluminiumoxyd können störende Begleitstoffe abgetrennt werden. Das Vitamin D₂ wird dabei in einer scharf umrissenen Zone festgehalten, die im UV.-Licht weiß aufleuchtet.Die vorliegende Methode ist geeignet zur mengenmäßigen Bestimmung von Vitamin D in tierischen und pflanzlichen Fetten, in Milch und Milcherzeugnissen, in Kindernährmitteln, bestrahlten Hefen und pharmazeutischen Präparaten. Um die hier auftretenden, störenden Begleitstoffe auszuschalten, werden die Präparate nach der Extraktion des Vitamins D verseift, und der unverseifbare Anteil wird an Aluminiumoxyd adsorbiert. Dabei wird das Vitamin D bei Einhaltung der Arbeitsvorschrift immer in einer charakteristischen schmalen Zone festgehalten, die im Tageslicht gelb bis rosafarben erscheint. Durch die Anwesenheit von Vitamin A, Provitamin A und anderen. Carotinoiden kann die Reaktion gestört werden, so daß auch hier eine chromatographische Auftrennung erforderlich ist, die sich aber leicht durchführen läßt.     

Reaction of secondary and tertiary aliphatic halides with aromatic aldehydes mediated by chromium(II): a selective cross-coupling of alkyl and ketyl radicals

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.