Formation of Vacancies in Si- and Ge-based Clathrates: Role of Electron Localization and Symmetry Breaking

The formation of framework vacancies in Si- and Ge-based type-I clathrates is studied as function of filling the cages with K and Ba atoms using density-functional theory. Our analysis reveals the relevance of structural disorder, geometric relaxation, electronic saturation, as well as vibrational and configurational entropy. In the Si clathrates we find that vacancies are unstable, but very differently, in Ge clathrates up to three vacancies per unit cell can be stabilized. This contrasting behavior is largely driven by the different energy gain on populating the electronic vacancy states, which originates from the different degree of localization of the valence orbitals of Si and Ge. This also actuates a qualitatively different atomic relaxation of the framework.Comment: 5 pages, 6 figures, submitted to a journa

Functional and self-rated health mediate the association between physical indicators of diabetes and depressive symptoms

Background Depression is common among persons with diabetes and associated with adverse health outcomes. To date, little is known about the causal mechanisms that lead to depression in diabetes. The aim of the present study was to examine to which extent functional and self-rated health mediate the association between physical health and depressive symptoms in diabetes. Methods Data of n = 3222 individuals with type 2 diabetes were analyzed cross- sectionally and longitudinally at three measurement occasions using path analysis. Indicators of physical health were glycemic control, number of comorbid somatic diseases, BMI, and insulin dependence. Furthermore, functional health, self-rated health and depressive symptoms were assessed. Results The effects of physical health on depressive symptoms were largely mediated by functional health and self-rated health. There was only a weak indirect effect of physical health on depressive symptoms. In contrast, self- rated health was a strong direct predictor of depressive symptoms. Self-rated health in turn depended strongly on patients’ functional health. Conclusions The way individuals perceive their health appears to have a stronger effect on their depressive symptoms than objective physical indicators of diabetes. Therefore practitioners should be trained to pay more attention to their patients’ subjective health perceptions

Interactive and Urgent HPC: Challenges and Opportunities

As a broader set of applications from simulations to data analysis and machine learning require more parallel computational capability, the demand for interactive and urgent high performance computing (HPC) continues to increase. This paper overviews the progress made so far and elucidates the challenges and opportunities for greater integration of interactive and urgent HPC policies, techniques, and technologies into HPC ecosystems.Comment: 10 pages, submitted to IEEE CiSE journa

Seasonal variability of the warm Atlantic Water layer in the vicinity of the Greenland shelf break

The warmest water reaching the east and west coast of Greenland is found between 200?m and 600?m. Whilst important for melting Greenland's outlet glaciers, limited winter observations of this layer prohibit determination of its seasonality. To address this, temperature data from Argo profiling floats, a range of sources within the World Ocean Database and unprecedented coverage from marine-mammal borne sensors have been analysed for the period 2002-2011. A significant seasonal range in temperature (~1-2?°C) is found in the warm layer, in contrast to most of the surrounding ocean. The phase of the seasonal cycle exhibits considerable spatial variability, with the warmest water found near the eastern and southwestern shelf-break towards the end of the calendar year. High-resolution ocean model trajectory analysis suggest the timing of the arrival of the year's warmest water is a function of advection time from the subduction site in the Irminger Basin

Siegener Beiträge zur Geschichte und Philosophie der Mathematik 2022

Die im nunmehr vorliegenden sechzehnten Band von SieB - Siegener Beiträge zur Geschichte und Philosophie der Mathematik - vereinten Aufsätze dokumentieren jene Pluralität von Themen, Perspektiven und Methoden das große Oberthema Geschichte und Philosophie der Mathematik betreffend, die in den vorangehenden Bänden bereits ein Anliegen der Reihe war. Die Siegener Beiträge bieten ein Forum für den Diskurs im Bereich von Philosophie und Geschichte der Mathematik. Dabei stehen die folgenden inhaltlichen Aspekte im Zentrum: 1. Philosophie und Geschichte der Mathematik sollen einander wechselseitig fruchtbar irritieren: Ohne Bezug auf die real existierende Mathematik und ihre Geschichte läuft das philosophische Fragen nach der Mathematik leer, ohne Bezug auf die systematische Reflexion über Mathematik wird ein Bemühen um die Mathematikgeschichte blind. 2. Geschichte ermöglicht ein Kontingenzbewusstsein, philosophische Reflexion fordert Kontextualisierungen heraus. Damit stellen sich u. a. Fragen nach der Rolle der Mathematik für die Wissenschaftsgeschichte, aber auch nach einer gesellschaftlichen Rolle der Mathematik und deren historischer Bedingtheit.Inhaltsverzeichnis: Harald Boehme: Von Theodoros bis Speusippos. Zur Entdeckung des Inkommensurablen sowie der Seiten- und Diagonalzahlen Jasmin Özel: Diagrammatisches Denken bei Euklid Christian Hugo Hoffmann: Der Hauptsatz in der Ars conjectandi: Interpretationen von Bernoullis Beiträgen zu den Anfängen der mathematischen Wahrscheinlichkeitstheorie Jens Lemanski: Schopenhauers Logikdiagramme in den Mathematiklehrbüchern Adolph Diesterwegs Dolf Rami: Frege über Merkmale von Begriffen Daniel Koenig: Der Raum als Reihenbegriff – Ernst Cassirers Deutung der Geometrieentwicklung des 19. Jahrhunderts Renate Tobies: Zum 100-jährigen Jubiläum des Ernst Abbe-Gedächtnispreises Štefan Porubský: Štefan Schwarz und die Entstehung der Halbgruppentheorie Stephan Berendonk: Ein dialektischer Weg zur Summe der Kubikzahlen Felicitas Pielsticker & Ingo Witzke: Devilish prime factorization – fundamental theorem of arithmeti

Subglacial discharge plume behaviour revealed by CTD-instrumented ringed seals

This research was supported by the Norwegian Polar Institute’s Centre for Ice, Climate and Ecosystems (ICE) and the Research Council of Norway. Some of this financial support was derived from the TIGRIF (RCN project number 243808/E40) and TW-ICE research programmes. AP was also funded by The Ministry of Earth Sciences, India, Grant/Award number: MoES/16/22/12-RDEAS (PhD fellowship-NPI).Subglacial discharge plumes increase submarine melting of marine-terminating glaciers significantly; however, in-situ data on their properties and behaviour are limited. We present oceanographic data collected by ringed seals (Pusa hispida) instrumented with GPS-equipped conductivity-temperature-depth satellite relay data loggers (GPS-CTD-SRDLs) in Kongsfjorden, Svalbard, during 2012. The seals foraged just outside the plumes and collected hydrographic data from within the plumes’ upwelling cores as they returned to the surface. The seals encountered water with fractions of subglacial discharge as high as 27% at 60 m below the ocean surface. The ringed seals responded rapidly to spatial and temporal variations in subglacial discharge at the glacier terminus, suggesting that prey becomes available quickly following the appearance of plumes. The seals’ dive locations were used to monitor the presence of plumes over a four-month period. High surface runoff from Kronebreen catchment created strong plumes, but weak plumes were present even during periods of low surface runoff. The continued retreat of Kronebreen, and other tidewater glaciers, will lead to the loss of these marine-termini as the glaciers retreat onto land. The techniques presented here improve our understanding of the drivers of glacial retreat and the implications of future habitat loss for glacier-associated birds and mammals.Publisher PDFPeer reviewe

What Research Is Needed to Stop TB? Introducing the TB Research Movement

Christian Lienhardt and colleagues describe the development of the TB Research Movement, which aims to create a framework for concrete actions to harmonize and synergize TB research efforts globally

Circumpolar habitat use in the southern elephant seal : implications for foraging success and population trajectories

In the Southern Ocean, wide-ranging predators offer the opportunity to quantify how animals respond to differences in the environment because their behavior and population trends are an integrated signal of prevailing conditions within multiple marine habitats. Southern elephant seals in particular, can provide useful insights due to their circumpolar distribution, their long and distant migrations and their performance of extended bouts of deep diving. Furthermore, across their range, elephant seal populations have very different population trends. In this study, we present a data set from the International Polar Year project; Marine Mammals Exploring the Oceans Pole to Pole for southern elephant seals, in which a large number of instruments (N = 287) deployed on animals, encompassing a broad circum-Antarctic geographic extent, collected in situ ocean data and at-sea foraging metrics that explicitly link foraging behavior and habitat structure in time and space. Broadly speaking, the seals foraged in two habitats, the relatively shallow waters of the Antarctic continental shelf and the Kerguelen Plateau and deep open water regions. Animals of both sexes were more likely to exhibit area-restricted search (ARS) behavior rather than transit in shelf habitats. While Antarctic shelf waters can be regarded as prime habitat for both sexes, female seals tend to move northwards with the advance of sea ice in the late autumn or early winter. The water masses used by the seals also influenced their behavioral mode, with female ARS behavior being most likely in modified Circumpolar Deepwater or northerly Modified Shelf Water, both of which tend to be associated with the outer reaches of the Antarctic Continental Shelf. The combined effects of (1) the differing habitat quality, (2) differing responses to encroaching ice as the winter progresses among colonies, (3) differing distances between breeding and haul-out sites and high quality habitats, and (4) differing long-term regional trends in sea ice extent can explain the differing population trends observed among elephant seal colonies.Publisher PDFPeer reviewe

In-situ observations using tagged animals

Marine mammals help gather information on some of the harshest environments on the planet, through the use of miniaturized ocean sensors glued on their fur. Since 2004, hundreds of diving marine animals, mainly Antarctic and Arctic seals, have been fitted with a new generation of Argos tags developed by the Sea Mammal Research Unit of the University of St Andrews in Scotland, UK. These tags investigate the at-sea ecology of these animals while simultaneously collecting valuable oceanographic data. Some of the study species travel thousands of kilometres continuously diving to great depths (up to 2100 m). The resulting data are now freely available to the global scientific community at http://www.meop.net. Despite great progress in their reliability and data accuracy, the current generation of loggers while approaching standard ARGO quality specifications have yet to match them. Yet, improvements are underway; they involve updating the technology, implementing a more systematic phase of calibration and taking benefit of the recently acquired knowledge on the dynamical response of sensors. Together these efforts are rapidly transforming animal tagging into one of the most important sources of oceanographic data in polar regions and in many coastal areas.Publisher PDFNon peer reviewe