University of Potsdam

About: University of Potsdam is a education organization based out in Potsdam, Germany. It is known for research contribution in the topics: Population & Computer science. The organization has 9629 authors who have published 26740 publications receiving 759745 citations. The organization is also known as: Universität Potsdam.

Manganese metabolism in humans.

Abstract: Manganese (Mn) is an essential nutrient for intracellular activities; it functions as a cofactor for a variety of enzymes, including arginase, glutamine synthetase (GS), pyruvate carboxylase and Mn superoxide dismutase (Mn-SOD). Through these metalloproteins, Mn plays critically important roles in development, digestion, reproduction, antioxidant defense, energy production, immune response and regulation of neuronal activities. Mn deficiency is rare. In contrast Mn poisoning may be encountered upon overexposure to this metal. Excessive Mn tends to accumulate in the liver, pancreas, bone, kidney and brain, with the latter being the major target of Mn intoxication. Hepatic cirrhosis, polycythemia, hypermanganesemia, dystonia and Parkinsonism-like symptoms have been reported in patients with Mn poisoning. In recent years, Mn has come to the forefront of environmental concerns due to its neurotoxicity. Molecular mechanisms of Mn toxicity include oxidative stress, mitochondrial dysfunction, protein misfolding, endoplasmic reticulum (ER) stress, autophagy dysregulation, apoptosis, and disruption of other metal homeostasis. The mechanisms of Mn homeostasis are not fully understood. Here, we will address recent progress in Mn absorption, distribution and elimination across different tissues, as well as the intracellular regulation of Mn homeostasis in cells. We will conclude with recommendations for future research areas on Mn metabolism.

Structure-property relationships of a biological mesocrystal in the adult sea urchin spine

Abstract: Structuring over many length scales is a design strategy widely used in Nature to create materials with unique functional properties. We here present a comprehensive analysis of an adult sea urchin spine, and in revealing a complex, hierarchical structure, show how Nature fabricates a material which diffracts as a single crystal of calcite and yet fractures as a glassy material. Each spine comprises a highly oriented array of Mg-calcite nanocrystals in which amorphous regions and macromolecules are embedded. It is postulated that this mesocrystalline structure forms via the crystallization of a dense array of amorphous calcium carbonate (ACC) precursor particles. A residual surface layer of ACC and/or macromolecules remains around the nanoparticle units which creates the mesocrystal structure and contributes to the conchoidal fracture behavior. Nature’s demonstration of how crystallization of an amorphous precursor phase can create a crystalline material with remarkable properties therefore provides inspiration for a novel approach to the design and synthesis of synthetic composite materials.

The weakening summer circulation in the Northern Hemisphere mid-latitudes

Abstract: Rapid warming in the Arctic could influence mid-latitude circulation by reducing the poleward temperature gradient. The largest changes are generally expected in autumn or winter, but whether significant changes have occurred is debated. Here we report significant weakening of summer circulation detected in three key dynamical quantities: (i) the zonal-mean zonal wind, (ii) the eddy kinetic energy (EKE), and (iii) the amplitude of fast-moving Rossby waves. Weakening of the zonal wind is explained by a reduction in the poleward temperature gradient. Changes in Rossby waves and EKE are consistent with regression analyses of climate model projections and changes over the seasonal cycle. Monthly heat extremes are associated with low EKE, and thus the observed weakening might have contributed to more persistent heat waves in recent summers.

Self-disclosure and Privacy Calculus on Social Networking Sites: The Role of Culture - Intercultural Dynamics of Privacy Calculus

Abstract: Social Network Sites (SNSs) rely exclusively on user-generated content to offer engaging and rewarding experience to its members As a result, stimulating user communication and self-disclosure is vital for the sustainability of SNSs However, considering that the SNS users are increasingly culturally diverse, motivating this audience to self-disclose requires understanding of their cultural intricacies Yet existing research offers only limited insights into the role of culture behind the motivation of SNS users to self-disclose Building on the privacy calculus framework, this study explores the role of two cultural dimensions – individualism and uncertainty avoidance – in self-disclosure decisions of SNS users Survey responses of US and German Facebook members are used as the basis for our analysis Structural equation modeling and multi-group analysis results reveal the distinct role of culture in the cognitive patterns of SNS users The authors find that trusting beliefs play a key role in the self-disclosure decisions of users from individualistic cultures At the same time, uncertainty avoidance determines the impact of privacy concerns This paper contributes to the theory by rejecting the universal nature of privacy calculus processes The findings provide for an array of managerial implications for SNS providers as they strive to encourage content creation and sharing by their heterogeneous members

Ocean-generated microseismic noise located with the Gräfenberg array

Abstract: The main cause for mid-period seismic ground distortions are ocean waves generated by atmospheric disturbances. These act upon the earth through different mechanisms. The microseismic wavefield can be divided into primary (T =12–18 s) and secondary (T = 6–9 s) noise. Classical theory tells that the origin of these induced ground distortions depends on the location and the intensity of the low pressure region. A considerable part of the microseismic wave field reaches the GRF-array in southern Germany with high coherency and almost constant amplitudes. Thus it is possible to locate the generating areas using frequency-wavenumber analysis. Five discrete generating areas for secondary microseisms and three generating areas for primary microseisms could be determined in the Atlantic Ocean, the Arctic Sea and the Mediterranean Sea by investigating broadband continuous recordings over four months in winter 1995/96. An essential result is the long-time constancy of the backazimuths of the coherent part of the microseismic wavefield with respect to the origin areas, independent of the location of the moving low pressure zone. Results from a triangulation using additionally broadband data from the NORSAR-array and an independent estimation of the distance of the source region with water wave dispersion data indicate an origin of the secondary microseismic wavefield near the north-Norwegian coast for the strongest source. The array analysis of a temporary network of ten three-component broadband stations in south-east Germany shows that the ratio of energy between coherent Love and Rayleigh waves is much higher for the primary than for the secondary microseismic noise wavefield. This indicates differences in the source mechanisms.