Sedimentary ancient DNA insights into foraminiferal diversity near the grounding line in the western Ross Sea, Antarctica

Foraminifera are important marine environmental indicators widely used in paleoceanography and paleoclimate studies. They are a dominant component of meiobenthic communities around the Antarctic continental shelf, including rarely studied locations below the ice shelves, close to the grounding line. In this study, we use high-throughput sequencing of sedimentary ancient DNA (sedaDNA) targeting foraminifera with two molecular markers, including an ultrashort marker newly designed for this study, in five cores from the western Ross Sea, containing sediments up to 30 000 years old. No foraminiferal DNA is detected in the tills, suggesting a lack of preservation of sedaDNA during glacially induced sediment reworking and transport. We reconstruct diverse foraminiferal communities in the open-marine settings and significantly less diverse communities in sediments from the slopes of the sub-ice-shelf grounding-zone wedges, deposited proximal to the grounding line. Both assemblages are rich in soft-walled monothalamids not preserved in the fossil record and complement the results of earlier micropaleontological studies, allowing for a more complete reconstruction of past biodiversity. The newly designed minibarcode marker provides higher foraminiferal diversity in surface and subsurface samples than the standard barcode and allows for better differentiation between foraminiferal communities in different sediment types. It appears to have great potential for future paleoenvironmental studies, although its taxonomic resolution needs to be evaluated.</p

Applications of sedimentary ancient DNA analyses in geological Quaternary research

During the past few decades genetic research has been developed in parallel with paleogenetics. A dynamic progress in this field of studies is possible due to the advance in laboratory and computer technologies. Today, scientists have the Next Generation Sequencing methods at their disposal, which enable them to read millions ofsequences at the same time, thus furthermore significantly reducing time needed for laboratory procedures. Concurrently, costs of analysis and equipment have been decreasing, which makes paleogenetical analyses widely available. They are commonly used in medicine, biotechnology, genetic engineering, food industry and forensics, as well as in life sciences like biology, paleobiology, archeology, geology and environmental protection sciences. This paper presents seda DNA (sedimentary ancient DNA) analyses and their use in Quaternary research, as well as describes sources of DNA in sediments and main processes contributing to its degradation or preservation

High-magnetic-field EPR of Cr-based diluted magnetic semiconductors

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High-Field EPR of Zn1−x\text{}_{1-x}Crx\text{}_{x}Te

High magnetic field electron paramagnetic resonance experiments have been performed on Zn$\text{}_{1-x}$Cr$\text{}_{x}$Te covering the energy range 1-7 cm$\text{}^{-1}$ in fields up to 20 T at T = 1.2 K. The static magnetic field was oriented along the (100), (110) and (111) crystallographic axes of the sample. Pronounced absorption lines for intra-chromium transitions have been observed for these different orientations, revealing a strong anisotropy due to a static Jahn-Teller distortion. The measured low energy level structure of the Cr$\text{}^{++}$ ion can be described by a cubic crystal field model including this distortion of the Cr centers