Speleothems in 6 sandstone caves in the Bohemian Paradise (Český ráj) were dated by means of 14C and U-series methods. Stable isotopes of C and O, FAAS, IR, XRD, XRF and SEM were used to characterize the carbonate material and its source. Stable isotopes (C and O) composition of speleothems in two caves corresponds to values characteristic for cave speleothems in Central Europe. In other caves they indicate evaporation and fast carbon dioxide escape during carbonate precipitation. The speleothems from the Krtola Cave were deposited between 8 and 13 kyr BP. Speleothems were deposited 5-8 kyr BP in the Sintrová, Mrtvé Údolí and U Studánky caves. Calcite coatings on smooth sandstone surfaces in studied caves demonstrate that cave walls did not retreat even a few mm in the last 5-8 kyr since speleothem deposition and are thus not evolving under recent climatic conditions. Most of the cave ceilings and walls are at present time indurated by hardened surfaces, which protect the sandstone from erosion. Sandstone caves probably intensively evolved either during or at the end of the Last Glacial period. There are two different erosion mechanisms which might have formed/reshaped the caves at that time: A) In the case of permafrost conditions: Repeated freeze/melt cycles affecting sandstone pore space followed by the transport of fallen sand grains by minor temporary trickles. We expect that heat was transmitted by air circulating between the cave and the surface; B) Seepage erosion of sandstone during the melting of permafrost, prior forming of case hardening., Jiří Bruthans, Jana Schweigstillová, Petr Jenč, Zdeňka Churáčková and Petr Bezdička., and Obsahuje bibliografii
Basis der vorgelegten Untersuchung war die Seriation von Keramik aus ungestörten Inventaren der Siedlungen von Neckenmarkt und Strögen, Ostösterreich. Bei dieser Seriation war es erstmals gelungen, Phasen innerhalb des altbandkeramischen Fundgutes zu erarbeiten. Die drei derart erfaßten Siedlungsphasen erlaubten die Beobachtung der feintypologischen Entwicklung der Keramik ebenso wie die Erschließung von Bauabfolgen an den beiden Plätzen. Für die absolute Datierung der drei Siedlungsphasen wurden 10 Holzkohleproben im Rahmen eines eigenen Forschungsprojektes gemessen, die durch drei Daten aus früheren 14C-Messungen an Getreide ergänzt wurden. Die Meßergebnisse der Proben sowie deren Einzel– und Gruppenkalibrationen zeigten, daß die erwartete Gesamtdauer von etwa 75–150 Jahren für alle drei Siedlungsphasen trotz Hochpräzisionsmessungen derzeit noch zu kurz ist, um eine absolute Datierung der einzelnen Phasen zu erlauben. Durch die neue Datenserie und deren Gesamtgruppenkalibration ist aber nunmehr der Zeitrahmen für die altbandkeramische Besiedlung der beiden Fundstellen zwischen 5380– –5200 BC mit 53,6 % Wahrscheinlichkeit gesichert. and 14C-DATES AND SERIATION OF EARLY LINEAR POTTERY–CULTURE INVENTORIES. The investigation presented in this paper is based upon the seriation of ceramics from undisturbed inventories of the settlements Neckenmarkt and Strögen, eastern Austria. The result of this seriation was the first successful attempt to define settlement phases within the earlier Linear Pottery culture. The three occupation phases deduced that way permitted to see the development of the pottery as well as the succession of the buildings on both places. With the aid of an own investigation project 10 charcoal samples of the three settlement phases were analysed, which were completed by three previous measurements of grain. The dates obtained by all these samples, their calibration one by one and in groups showed the expected time span of around 75 to 150 years for all three settlement phases together is too short at the moment to date each phase, even when using high precision measuring like AMS. According to the new dataset of 14C-dates and their calibration as a group the time span for the occupation of the two places during the earlier Linear Pottery culture can be fixed between 5380–5200 BC with 53,6% probability.
Chlorophyll and nitrogen contents were highest in leaves of middle position, similarly as photosynthetic efficiency represented by 14C fixation (maxima in leaf 5 from the top). All the leaves lost 14C after 2 weeks of 14CO2 exposure. However, the reduction in radioactivity was less in young upper leaves than in the mature lower leaves. Leaves exported 14C-photosynthates to stem both above and below the exposed leaf. Very little radioactivity was recovered from the seeds of plants in which only first or second leaves were exposed to 14CO2 implying thereby that the carbon contribution of first two leaves to seed filling was negligible. The contribution of leaves to seed filling increased with the leaf position up to the sixth leaf from the top and after the seventh leaf their contribution to seed filling declined gradually. and Desiraju Subrahmanyam, V. S. Rathore.
Our own study as well as others have previously reported that hypoxia activates 15-lipoxygenase (15-LO) in the brain, causing a series of chain reactions, which exacerbates ischemic stroke. 15-hydroxyeicosatetraenoic acid (15-HETE) and 15-oxoeicosatetraenoic acid (15-oxo-ETE/15-KETE) are 15-LO-specific metabolites of arachidonic acid (AA). 15-HETE was found to be rapidly converted into 15-oxo-ETE by 15-hydroxyprostaglandin dehydrogenase (15-PGDH) in some circumstances. We have demonstrated that 15-HETE promotes cerebral vasoconstriction during hypoxia. However, the effect of 15-oxo-ETE upon the contraction of cerebral vasculature remains unclear. To investigate this effect and to clarify the underlying mechanism, we performed immunohistochemistry and Western blot to test the expression of 15-PGDH in rat cerebral tissue, examined internal carotid artery (ICA) tension in isolated rat ICA rings. Western blot and reverse transcription polymerase chain reaction (RT-PCR) were used to analyze the expression of voltage-gated potassium (Kv) channels (Kv2.1, Kv1.5, and Kv1.1) in cultured cerebral arterial smooth muscle cells (CASMCs). The results showed that the levels of 15-PGDH expression were drastically elevated in the cerebral of rats with hypoxia, and 15-oxo-ETE enhanced ICA contraction in a dose-dependent manner. This effect was more significant in the hypoxic rats than in the normoxic rats. We also found that 15-oxo-ETE significantly attenuated the expression of Kv2.1 and Kv1.5, but not Kv1.1. In conclusion, these results suggest that 15-oxo-ETE leads to the contraction of the ICA, especially under hypoxic conditions and that specific Kv channels may play an important role in 15-oxo- ETE-induced ICA constriction., Di Wang, Yu Liu, Ping Lu, Daling Zhu, Yulan Zhu., and Obsahuje bibliografii