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Spatio-temporal patterns of throughfall and solute deposition in an open tropical rain forest
(2008)
A series of 9,10-diarylanthracenes with various substituents at the ortho positions have been synthesised by palladium-catalysed cross-coupling reactions. Such compounds exhibit interesting physical properties and can be applied as molecular switches. Despite the high steric demand of the substituents, products were formed in moderate-to-good yields. In some cases, microwave conditions further improved yields. Bis-coupling afforded two isomers (syn and anti) that do not interconvert at room temperature. These products were easily separated and their relative stereochemistries were unequivocally assigned by NMR spectroscopy and X-ray analysis. The syn and anti isomers exhibit different physical properties (e.g., melting points and solubilities) and interconversion by rotation around the aryl-aryl axis commences at <100 °C for fluoro-substituted diarylanthracenes and at >300 °C for alkyl- or alkoxy-substituted diarylanthracenes. The reactions with singlet oxygen were studied separately and revealed different reactivities and reaction pathways. The yields and reactivities depend on the size and electronic nature of the substituents. The anti isomers form the same 9,10-endoperoxides as the syn species, occasionally accompanied by unexpected 1,4-endoperoxides as byproducts. Thermolysis of the endoperoxides exclusively yielded the syn isomers. The interesting rotation around the aryl-aryl axis allows the application of 9,10-diarylanthracenes as molecular switches, which are triggered by light and air under mild conditions. Finally, the oxygenation and thermolysis sequence provides a simple, synthetic access to a single stereoisomer (syn) from an unselective coupling step.
This study presents an application of an innovative sampling strategy to assess soil moisture dynamics in a headwater of the Weißeritz in the German eastern Ore Mountains. A grassland site and a forested site were instrumented with two Spatial TDR clusters (STDR) that consist of 39 and 32 coated TDR probes of 60 cm length. Distributed time series of vertically averaged soil moisture data from both sites/ensembles were analyzed by statistical and geostatistical methods. Spatial variability and the spatial mean at the forested site were larger than at the grassland site. Furthermore, clustering of TDR probes in combination with long-term monitoring allowed identification of average spatial covariance structures at the small field scale for different wetness states. The correlation length of soil water content as well as the sill to nugget ratio at the grassland site increased with increasing average wetness and but, in contrast, were constant at the forested site. As soil properties at both the forested and grassland sites are extremely variable, this suggests that the correlation structure at the forested site is dominated by the pattern of throughfall and interception. We also found a strong correlation between average soil moisture dynamics and runoff coefficients of rainfall-runoff events observed at gauge Rehefeld, which explains almost as much variability in the runoff coefficients as pre-event discharge. By combining these results with a recession analysis we derived a first conceptual model of the dominant runoff mechanisms operating in this catchment. Finally, long term simulations with a physically based hydrological model were in good/acceptable accordance with the time series of spatial average soil water content observed at the forested site and the grassland site, respectively. Both simulations used a homogeneous soil setup that closely reproduces observed average soil conditions observed at the field sites. This corroborates the proposed sampling strategy of clustering TDR probes in typical functional units is a promising technique to explore the soil moisture control on runoff generation. Long term monitoring of such sites could maybe yield valuable information for flood warning. The sampling strategy helps furthermore to unravel different types of soil moisture variability.
Tuning of the excited-state properties and photovoltaic performance in PPV-based polymer blends
(2008)
Enuresis
(2008)
Die meisten Kinder werden mit 2 bis 4 Jahren am Tage und in der Nacht trocken. Gemäß den klinisch- diagnostischen Leitlinien der ICD-10 (WHO 1993) spricht man von einer Enuresis, wenn es am Tag oder in der Nacht zu einem Entleeren der Blase in die Kleidung bzw. das Bett kommt, die relativ zum geistigen Entwicklungsstand der Person abnorm ist und nicht auf organische Ursachen zurückgeführt werden kann. Die Störungen der Blasenkontrolle dürfen nicht als Folge einer neurologischen Erkrankung, epileptischer Anfälle oder einer strukturellen Anomalie der ableitenden Harnwege auftreten. Gemäß den Forschungskriterien der ICD-10 (WHO 1994) muss das einnässende Kind nach seinem Lebens- und geistigen Alter mindestens 5 Jahre alt sein, um von einer nichtorganischen Enuresis (F 98.0) zu sprechen (in den klinisch-diagnostischen Leitlinien wird ein geistiger Entwicklungsstand gefordert, der mindestens dem eines Vierjährigen entspricht). Um die Diagnose zu erhalten, müssen Kinder unter 7 Jahren zumindest 2mal monatlich, 7-jährige oder ältere Kinder wenigstens einmal im Monat einnässen. Die Symptomdauer sollte mindestens 3 Monate betragen. In der Literatur wird synonym zum Begriff der "nichtorganischen Enuresis" häufig die Bezeichnung "funktionelle Enuresis" verwendet. Auch nach dem DSM-IV (Saß et al. 1996) sollten die Kinder für die Diagnose einer Enuresis (307.6) zumindest ein Entwicklungsalter von 5 Jahren aufweisen und die Symptomatik muss wenigstens seit 3 Monaten bestehen. Im Unterschied zur ICD-10 wird das Einnässen erst dann als klinisch bedeutsam beurteilt, wenn es mindestens 2mal wöchentlich auftritt. Ist dies nicht gegeben, kann die Diagnose dennoch gestellt werden, wenn durch das Einnässen klinisch bedeutsames Leiden hervorgerufen wird oder Beeintraechtigungen in sozialen, schulischen (beruflichen) oder anderen wichtigen Funktionsbereichen entstehen. Die Forderung eines 2mal wöchentlichen Einnässens erscheint deutlich zu streng, während das ein- bzw. 2malige Einnässen pro Monat ein sehr weiches Kriterium darstellt. V. Gontard (1998b) empfiehlt, Einnässen dann als klinisch bedeutsam einzuschätzen, wenn dies mindestens einmal wöchentlich auftritt.