Surface nitrate utilization in the Bering Sea since 180 ka BP : insight from sedimentary nitrogen isotopes

We present high-resolution records of sedimentary nitrogen (δ15Nbulk) and carbon isotope ratios (δ13Cbulk) from piston core SO201-2-85KL located in the western Bering Sea. The records reflect changes in surface nitrate utilization and terrestrial organic matter contribution in submillennial resolution that span the last 180 kyr. The δ15Nbulk record is characterized by a minimum during the penultimate interglacial indicating low nitrate utilization (~62–80%) despite the relatively high export production inferred from opal concentrations along with a significant reduction in the terrestrial organic matter fraction (mterr). This suggests that the consumption of the nitrate pool at our site was incomplete and even more reduced than today (~84%). δ15Nbulk increases from Marine Isotope Stage (MIS) 5.4 and culminates during the Last Glacial Maximum, which indicates that nitrate utilization in the Bering Sea was raised during cold intervals (MIS 5.4, 5.2, 4) and almost complete during MIS 3 and 2 (~93–100%). This is in agreement with previous hypotheses suggesting that stronger glacial stratification reduced the nutrient supply from the subeuphotic zone, thereby increasing the iron-to-nutrient ratio and therefore the nitrate utilization in the mixed surface layer. Large variations in δ15Nbulk were also recorded from 180 to 130 ka BP (MIS 6), indicating a potential link to insolation and sea-level forcing and its related feedbacks. Millennial-scale oscillations were observed in δ15Nbulk and δ13Cbulk that might be related to Greenland interstadials

Decadal-centennial scale monsoon variations in the Arabian Sea during the Early Holocene

An essential prerequisite for the prediction of future climate change due to anthropogenic input is an understanding of the natural processes that control Earth's climate on timescales comparable to human-lifespan. The Early Holocene period was chosen to study the natural climate variability in a warm interval when solar insolation was at its maximum. The monsoonal system of the Tropics is highly sensitive to seasonal variations in solar insolation, and consequently marine sediments from the region are a potential monitor of past climate change. Here we show that during the Early Holocene period rapid

Low Temperature Deposition of High-k/Metal Gate Stacks on High-Sn Content (Si)GeSn-Alloys

(Si)GeSn is an emerging group IV alloy system offering new exciting properties, with great potential for low power electronics due to the fundamental direct band gap and prospects as high mobility material. In this Article, we present a systematic study of HfO2/TaN high-k/metal gate stacks on (Si)GeSn ternary alloys and low temperature processes for large scale integration of Sn based alloys. Our investigations indicate that SiGeSn ternaries show enhanced thermal stability compared to GeSn binaries, allowing the use of the existing Si technology. Despite the multielemental interface and large Sn content of up to 14 atom %, the HfO2/(Si)GeSn capacitors show small frequency dispersion and stretch-out. The formed TaN/HfO2/(Si)GeSn capacitors present a low leakage current of 2 × 10(-8) A/cm(2) at -1 V and a high breakdown field of ∼8 MV/cm. For large Sn content SiGeSn/GeSn direct band gap heterostructures, process temperatures below 350 °C are required for integration. We developed an atomic vapor deposition process for TaN metal gate on HfO2 high-k dielectric and validated it by resistivity as well as temperature and frequency dependent capacitance-voltage measurements of capacitors on SiGeSn and GeSn. The densities of interface traps are deduced to be in the low 10(12) cm(-2) eV(-1) range and do not depend on the Sn-concentration. The new processes developed here are compatible with (Si)GeSn integration in large scale applications

Biomechanics for inclusive urban design : effects of tactile paving on older adults’ gait when crossing the street

In light of our ageing population it is important that the urban environment is easily accessible and hence supports older adults’ independence. Tactile ‘blister’ paving was originally designed to provide guidance for visually impaired people at pedestrian crossings. However, as research links irregular surfaces to falls in older adults, such paving may have an adverse effect on older people. We investigated the effects of tactile paving on older adults’ gait in a scenario closely resembling “crossing the street”. Gait analysis of 32 healthy older adults showed that tactile, as compared to smooth, paving increases the variability in timing of foot placement by 20%, thereby indicating a disturbance of the rhythmic gait pattern. Moreover, toe-clearance during the swing phase increased by 7% on tactile paving, and the ability to stop upon cue from the traffic light was compromised. These results need to be viewed under consideration of the limitations associated with laboratory studies and real world analysis is needed to fully understand their implications for urban design

Distinct and overlapping control of 5-methylcytosine and 5-hydroxymethylcytosine by the TET proteins in human cancer cells

BACKGROUND: The TET family of dioxygenases catalyze conversion of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), but their involvement in establishing normal 5mC patterns during mammalian development and their contributions to aberrant control of 5mC during cellular transformation remain largely unknown. We depleted TET1, TET2, and TET3 in a pluripotent embryonic carcinoma cell model and examined the impact on genome-wide 5mC, 5hmC, and transcriptional patterns. RESULTS: TET1 depletion yields widespread reduction of 5hmC, while depletion of TET2 and TET3 reduces 5hmC at a subset of TET1 targets suggesting functional co-dependence. TET2 or TET3 depletion also causes increased 5hmC, suggesting these proteins play a major role in 5hmC removal. All TETs prevent hypermethylation throughout the genome, a finding dramatically illustrated in CpG island shores, where TET depletion results in prolific hypermethylation. Surprisingly, TETs also promote methylation, as hypomethylation was associated with 5hmC reduction. TET function is highly specific to chromatin environment: 5hmC maintenance by all TETs occurs at polycomb-marked chromatin and genes expressed at moderate levels; 5hmC removal by TET2 is associated with highly transcribed genes enriched for H3K4me3 and H3K36me3. Importantly, genes prone to hypermethylation in cancer become depleted of 5hmC with TET deficiency, suggesting that TETs normally promote 5hmC at these loci. Finally, all three TETs, but especially TET2, are required for 5hmC enrichment at enhancers, a condition necessary for expression of adjacent genes. CONCLUSIONS: These results provide novel insight into the division of labor among TET proteins and reveal important connections between TET activity, the chromatin landscape, and gene expression

Memorials to the victims of Nazism: the impact on tourists in Berlin

This qualitative study explores tourist responses to memorials to the victims of Nazism in Berlin and the impact they have on the tourist experience. The findings are located in the field of study known as dark tourism, of which visiting memorials is a part. The analysis shows that tourists increased their knowledge of the crimes committed by the Nazis, thus fulfilling the educational function of memorials. Tourists were also overwhelmed by their experience; they attested to feelings of sadness, shock, anger, despair and incomprehension. These feelings made it hard for them to resume the role of tourist after their exposure to a memorial. There was acknowledgement of the extent of commemoration practised in Germany

Late pleistocene sedimentation history of the Shirshov Ridge, Bering Sea

The analysis of the lithology, grain-size distribution, clay minerals, and geochemistry of Upper Pleistocene sediments from the submarine Shirshov Ridge (Bering Sea) showed that the main source area was the Yukon–Tanana terrane of Central Alaska. The sedimentary materials were transported by the Yukon River through Beringia up to the shelf break, where they were entrained by a strong northwestward-flowing sea current. The lithological data revealed several pulses of ice-rafted debris deposition, roughly synchronous with Heinrich events, and periods of weaker bottom-current intensity. Based on the geochemical results, we distinguished intervals of an increase in paleoproductivity and extension of the oxygen minimum zone. The results suggest that there were three stages of deposition driven by glacioeustatic sea-level fluctuations and glacial cycles in Alaska