Search results for "PELE"
showing 10 items of 139 documents
In-situ high spatial resolution LA-MC-ICPMS 230Th/U dating enables detection of small-scale age inversions in speleothems
2017
Abstract We present an in-situ method for Th and U isotope measurements by laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICPMS) to determine possible age inversions of stalagmites, using a 213 nm Nd:YAG laser connected to an MC-ICPMS. Due to the low ion beam intensity of 230 Th (20–120 counts per second, cps), we carefully optimized the operating parameters to get highest possible ion beam intensities, i.e., laser fluence (25 J cm −2 ), spot size (110 μm), pulse repetition rate (20 Hz), scan speed (4 μm s −1 ), integration time (1000 s), and He and Ar gas flow (∼0.9 L min −1 and ∼0.6 L min −1 respectively). A precision (2 relative standard error, 2RSE) o…
Monitoring of Cueva Larga, Puerto Rico—A First Step to Decode Speleothem Climate Records
2017
This study presents results of an ongoing cave monitoring program at Cueva Larga, Puerto Rico. The monitoring includes monthly analyses of stable isotope ratios of rain and drip water, and trace element ratios of drip water and cave air parameters. Drip sites are above growing speleothems offering the unique chance to calibrate geochemical variations in speleothems in order to reconstruct past climate conditions. Seasonal rainfall patterns above Cueva Larga show characteristic stable isotope values. The wet season is characterized by more negative δ18O and δD values and a maritime deuterium excess (+10‰). The dry season has more positive δ18O and δD values and elevated deuterium excess (>15…
Abnormalities caused by chloroform and ether in the spermatogenesis of mammals [Chloroforma un ētera radītie traucējumi zīdītāju spermatogenezē]
1937
Teksts angļu valodā, kopsavilkums latviešu valodā.
Dermal histology of the Latvian "naked mouse"
1937
Über die Hauthistologie der haarlosen Lettländischen Maus [Par Latvijas kailās peles ādas histoloģiju]
1937
Teksts vācu valodā, kopsavilkums latviešu valodā.
Atrichosis und ihre Vererbung bei der albinotischen Hausmaus
1927
Izvilkums no: Biologischen Zentralblatt, 47. Bd., Heft 12., 1927.
Investigation of marine and continental layers in a stalactite older than 1 million years (Custonaci, north-western sector of Sicily)
2012
Questo lavoro si basa sul ritrovamento, in una grotta carsica, a 100 metri di quota a Custonaci in provincia di Trapani, di una stalattite di notevole interesse paleo climatico, ricoperta da coralli marini, la cui sezione rivela la presenza di 3 Iatus che denotano una interruzione della deposizione di carbonato continentale presumibilmente in seguito a trasgressioni marine. Il carbonato, datato attraverso la metodologia 230Th/U MC-ICPMS (NeptunePlus), ha fornito una età più antica del limite temporale massimo di applicabilità del metodo ( 600 ka). I coralli, che ricoprono il livello continentale più giovane, analizzati usando il rapporto 87Sr/86Sr, hanno fornito una età di 1.1±0.2 Myrs. Al…
Effects of organic matter complexation on partitioning of transition metals into calcite: Cave-analogue crystal growth experiments
2022
We highlight the potential for first row transition metals to carry paleohydrological signals in speleothems, and argue that these metals constitute valuable proxies for climate reconstructions. Metal availability to speleothems is hypothesised to be restricted by organic complexation, which strongly limits the free ion activity of transition metals (Co2+, Ni2+ and Cu2+) in dripwater, thereby creating a kinetic overprint on metal concentrations and isotope ratios in speleothem calcite. This study presents the results of the first cave-analogue experiments of transition metal partitioning into calcite in the absence and presence of organic ligands. The Geological Microclimate (GeoMic) system…
2018
Abstract. Here we present a sensitive method to analyze lignin oxidation products (LOPs) in speleothems and cave drip water to provide a new tool for paleo-vegetation reconstruction. Speleothems are valuable climate archives. However, compared to other terrestrial climate archives, such as lake sediments, speleothems contain very little organic matter. Therefore, very few studies on organic biomarkers in speleothems are available. Our new sensitive method allows us to use LOPs as vegetation biomarkers in speleothems. Our method consists of acid digestion of the speleothem sample followed by solid-phase extraction (SPE) of the organic matter. The extracted polymeric lignin is degraded in a m…