Late Quaternary terrigenous sediment supply in the Drake Passage in response to Patagonian and Antarctic ice dynamics

The Drake Passage, as the narrowest passage around Antarctica, exerts significant influences on the physical, chemical, and biological interactions between the Pacific and Atlantic Ocean. Here, we identify terrigenous sediment sources and transport pathways in the Drake Passage region over the past 140 ka BP (thousand years before present), based on grain size, clay mineral assemblages, geochemistry and mass-specific magnetic susceptibility records. Terrigenous sediment supply in the Drake Passage is mainly derived from the southeast Pacific, southern South America and the Antarctic Peninsula. Our results provide robust evidence that the Antarctic Circumpolar Current (ACC) has served as the key driver for sediment dispersal in the Drake Passage. High glacial mass accumulation rates indicate enhanced detrital input, which was closely linked to a large expansion of ice sheets in southern South America and on the Antarctic Peninsula during the glacial maximum, as significantly advanced glaciers eroded more glaciogenic sediments from the continental hinterlands into the Drake Passage. Moreover, lower glacial sea levels exposed large continental shelves, which together with weakened ACC strength likely amplified the efficiency of sediment supply and deposition in the deep ocean. In contrast, significant glaciers' shrinkage during interglacials, together with higher sea-level conditions and storage of sediment in nearby fjords reduced terrigenous sediment inputs. Furthermore, a stronger ACC may have induced winnowing effects and further lowered the mass accumulation rates. Evolution of ice sheets, sea level changes and climate related ACC dynamic have thus exerted critical influences on the terrigenous sediment supply and deposition in the Drake Passage region over the last glacial-interglacial cycle

Flight mechanics model for spanwise lift and rolling moment distributions of a segmented active high-lift wing

In this study, the aerodynamics of wings using an active high-lift system are investigated. The target is the flight mechanical description of the spanwise forces and resulting moments and the influence of the active high-lift system to their distribution. The high-lift system is a blown flap system divided into six segments per wing. Each segment is assumed to be individually controlled, so the system shall be used for aircraft control and system failure management. This work presents a flight mechanical sub-model for the simulation of flight dynamics, which has been derived from high-fidelity CFD results. An assessment of single-segment blowing system failures will be presented including recommendations for compensation of either lift or rolling moment loss. For this investigation, the compensation is required to act at the same wing side on which the failure appears. Thus, the potential for an increase of system reliability shall be proven. The results show that less performance investment in terms of pressurized air is necessary to compensate the rolling moment of a failing segment instead of its lift. However, large blowing performance increases for the remaining wing segments that occur for some of the failure cases

Soluble Receptor for Advanced Glycation End Products (sRAGE) Is a Sensitive Biomarker in Human Pulmonary Arterial Hypertension.

Pulmonary arterial hypertension (PAH) is a progressive condition with an unmet need for early diagnosis, better monitoring, and risk stratification. The receptor for advanced glycation end products (RAGE) is activated in response to hypoxia and vascular injury, and is associated with inflammation, cell proliferation and migration in PAH. For the adult cohort, we recruited 120 patients with PAH, 83 with idiopathic PAH (IPAH) and 37 with connective tissue disease-associated PAH (CTD-PAH), and 48 controls, and determined potential plasma biomarkers by enzyme-linked immunoassay. The established heart failure marker NTproBNP and IL-6 plasma levels were several-fold higher in both adult IPAH and CTD-PAH patients versus controls. Plasma soluble RAGE (sRAGE) was elevated in IPAH patients (3044 ± 215.2 pg/mL) and was even higher in CTD-PAH patients (3332 ± 321.6 pg/mL) versus controls (1766 ± 121.9 pg/mL; p < 0.01). All three markers were increased in WHO functional class II+III PAH versus controls (p < 0.001). Receiver-operating characteristic analysis revealed that sRAGE has diagnostic accuracy comparable to prognostic NTproBNP, and even outperforms NTproBNP in the distinction of PAH FC I from controls. Lung tissue RAGE expression was increased in IPAH versus controls (mRNA) and was located predominantly in the PA intima, media, and inflammatory cells in the perivascular space (immunohistochemistry). In the pediatric cohort, plasma sRAGE concentrations were higher than in adults, but were similar in PH (n = 10) and non-PH controls (n = 10). Taken together, in the largest adult sRAGE PAH study to date, we identify plasma sRAGE as a sensitive and accurate PAH biomarker with better performance than NTproBNP in the distinction of mild PAH from controls

Deglacial Land-Ocean Linkages at the Alaskan Continental Margin in the Bering Sea

A marine sediment record from the central Bering Sea, spanning the last 20 thousand years (ka), was studied to unravel the depositional history with regard to terrigenous sediment supply and biogenic sedimentation. Methodic approaches comprised the inference of accumulation rates of siliciclastic and biogenic components, grain-size analysis, and (clay) mineralogy, as well as paleoclimatic modelling. Changes in the depositional history provides insight into land-ocean linkages of paleoenvironmental changes. During the finale of the Last Glacial Maximum, the depositional environment was characterized by hemipelagic background sedimentation. A marked change in the terrigenous sediment provenance during the late Heinrich 1 Stadial (15.7–14.5 ka), indicated by increases in kaolinite and a high glaciofluvial influx of clay, gives evidence of the deglaciation of the Brooks Range in the hinterland of Alaska. This meltwater pulse also stimulated the postglacial onset of biological productivity. Glacial melt implies regional climate warming during a time of widespread cooling on the northern hemisphere. Our simulation experiment with a coupled climate model suggests atmospheric teleconnections to the North Atlantic, with impacts on the dynamics of the Aleutian Low system that gave rise to warmer winters and an early onset of spring during that time. The late deglacial period between 14.5 and 11.0 ka was characterized by enhanced fluvial runoff and biological productivity in the course of climate amelioration, sea-level rise, seasonal sea-ice retreat, and permafrost thaw in the hinterland. The latter processes temporarily stalled during the Younger Dryas stadial (12.9-11.7 ka) and commenced again during the Preboreal (earliest Holocene), after 11.7 ka. High river runoff might have fertilized the Bering Sea and contributed to enhanced upper ocean stratification. Since 11.0 ka, advanced transgression has shifted the coast line and fluvial influence of the Yukon River away from the study site. The opening of the Bering Strait strengthened contour currents along the continental slope, leaving behind winnowed sand-rich sediments through the early to mid-Holocene, with non-deposition occurring since about 6.0 ka

Heuristics for Domain Decomposition

The domain decomposition method embodies large potentials for a parallelization of FEM methods. In this data-parallel approach, the domain of interest is partitioned into smaller subdomains, either before the mesh generation or afterwards (mesh partitioning). The subdomains are assigned to processors that calculate the corresponding part of the approximation. The mesh decomposition and assignments of subdomains to processors can be modeled as graph embedding problem where a large graph (the mesh) has to be mapped onto a smaller one (the processor network). Unfortunately, this mapping problem is NP-complete and there exist almost no efficient sequential or parallel heuristics that solve this problem sufficiently [1]. With growing performance of interconnection networks and especially with the establishment of independent routing networks, it is appropriate to reduce the mapping problem to the task of partitioning the graph (the FEM-mesh) into as many equal sized (or weighted) clusters a..

A Local Graph Partitioning Heuristic Meeting Bisection Bounds (Extended Abstract)

The problem of graph partitioning is of major importance for a broad range of applications. VLSI-Layout and parallel programming are only two examples where large graphs have to be cut into pieces. The partitioning of a graph into several clusters is often done by recursive bisection. Bisection heuristics are usually divided into global and local methods. Popular global methods are inertial or spectral partitioning. For a long time, the KernighanLin algorithm (KL) was the only efficient local heuristic and is still widely used in several applications. Based on the idea of so called Helpful Sets, we recently proposed a new local graph bisection heuristic [3]. Helpful Sets can be used to prove upper bounds on the bisection width of regular graphs. Thus, we are able to give upper bounds on the quality of the bisections found by HS. In this paper, we will present the HS-idea, the bisection heuristic, ideas of the proofs of upper bounds, and, finally, discuss the performance of th..

On the Communication Throughput of Buffered Multistage Interconnection Networks

Multistage networks (MIN) are used as interconnection structure in a large number of applications. Their performance is mainly determined by their communication throughput which, in most cases, has to be investigated by time-consuming simulations or approximated by simple models. In this paper, we investigate the steady state throughput of single buffered multistage interconnection networks using the so called relaxed blocking model, where a message is deleted, if the receiving buffer is occupied. We derive upper and lower bounds on the throughput of MINs of arbitrary height and show that the throughput of singlebuffered networks is an order of magnitude higher than the throughput of non-buffered MINs. In detail we show, that the throughput is \Theta(n= p log n) if n is the size of the network. Because the time-dynamic of finite buffered MINs defies each marcov- or semi-marcov approach, we analyze the the equilibrium-situation of the network and give tight upper and lower bounds on t..