University of Göttingen

About: University of Göttingen is a education organization based out in Göttingen, Germany. It is known for research contribution in the topics: Population & Gene. The organization has 43851 authors who have published 86318 publications receiving 3010295 citations. The organization is also known as: Georg-August-Universität Göttingen & Universität Göttingen.

Emission of N2O, N2 and CO2 from soil fertilized with nitrate: effect of compaction, soil moisture and rewetting

Abstract: Soil compaction and soil moisture are important factors influencing denitrification and N2O emission from fertilized soils. We analyzed the combined effects of these factors on the emission of N2O, N2 and CO2 from undisturbed soil cores fertilized with N 15 O 3 − (150 kg N ha−1) in a laboratory experiment. The soil cores were collected from differently compacted areas in a potato field, i.e. the ridges (ρD=1.03 g cm−3), the interrow area (ρD=1.24 g cm−3), and the tractor compacted interrow area (ρD=1.64 g cm−3), and adjusted to constant soil moisture levels between 40 and 98% water-filled pore space (WFPS). High N2O emissions were a result of denitrification and occurred at a WFPS≥70% in all compaction treatments. N2 production occurred only at the highest soil moisture level (≥90% WFPS) but it was considerably smaller than the N2O–N emission in most cases. There was no soil moisture effect on CO2 emission from the differently compacted soils with the exception of the highest soil moisture level (98% WFPS) of the tractor-compacted soil in which soil respiration was significantly reduced. The maximum N2O emission rates from all treatments occurred after rewetting of dry soil. This rewetting effect increased with the amount of water added. The results show the importance of increased carbon availability and associated respiratory O2 consumption induced by soil drying and rewetting for the emissions of N2O.

Phase retrieval, error reduction algorithm, and Fienup variants: a view from convex optimization.

Abstract: The phase retrieval problem is of paramount importance in various areas of applied physics and engineering. The state of the art for solving this problem in two dimensions relies heavily on the pioneering work of Gerchberg, Saxton, and Fienup. Despite the widespread use of the algorithms proposed by these three researchers, current mathematical theory cannot explain their remarkable success. Nevertheless, great insight can be gained into the behavior, the shortcomings, and the performance of these algorithms from their possible counterparts in convex optimization theory. An important step in this direction was made two decades ago when the error reduction algorithm was identified as a nonconvex alternating projection algorithm. Our purpose is to formulate the phase retrieval problem with mathematical care and to establish new connections between well-established numerical phase retrieval schemes and classical convex optimization methods. Specifically, it is shown that Fienup’s basic input–output algorithm corresponds to Dykstra’s algorithm and that Fienup’s hybrid input–output algorithm can be viewed as an instance of the Douglas–Rachford algorithm. We provide a theoretical framework to better understand and, potentially, to improve existing phase recovery algorithms.

Role of microglia and host prion protein in neurotoxicity of a prion protein fragment

Abstract: THE prion protein PrPc is a glycoprotein of unknown function1 normally found in neurons2 and glia3. It is involved in diseases such as bovine spongiform encephalopathy (BSE), scrapie and Creutzfeldt–Jakob disease4. PrPSc, an altered isoform of PrPc that is associated with disease, shows greater protease resistance and is part of the infectious agent, the prion5,6. Prion diseases are characterized by neuronal degeneration, gliosis and accumulation of PrPSc (ref. 7). Mice devoid of PrPc are resistant to scrapie8. A fragment of human PrP consisting of amino acids 106–126 that forms fibrils in vitro is toxic to cultured neurons9–11. Here we show that this toxic effect requires the presence of microglia which respond to PrP106–126 by increasing their oxygen radical production. The combined direct and microglia-mediated effects of PrP106–126 are toxic to normal neurons but are insufficient to destroy neurons from mice not expressing PrPc.

Carbon input by roots into the soil: Quantification of rhizodeposition from root to ecosystem scale

Abstract: Despite its fundamental role for carbon (C) and nutrient cycling, rhizodeposition remains ‘the hidden half of the hidden half’: it is highly dynamic and rhizodeposits are rapidly incorporated into microorganisms, soil organic matter, and decomposed to CO2. Therefore, rhizodeposition is rarely quantified and remains the most uncertain part of the soil C cycle and of C fluxes in terrestrial ecosystems. This review synthesizes and generalizes the literature on C inputs by rhizodeposition under crops and grasslands (281 data sets). The allocation dynamics of assimilated C (after 13C-CO2 or 14C-CO2 labeling of plants) were quantified within shoots, shoot respiration, roots, net rhizodeposition (i.e., C remaining in soil for longer periods), root-derived CO2, and microorganisms. Partitioning of C pools and fluxes were used to extrapolate belowground C inputs via rhizodeposition to ecosystem level. Allocation from shoots to roots reaches a maximum within the first day after C assimilation. Annual crops retained more C (45% of assimilated 13C or 14C) in shoots than grasses (34%), mainly perennials, and allocated 1.5 times less C belowground. For crops, belowground C allocation was maximal during the first 1-2 months of growth and decreased very fast thereafter. For grasses, it peaked after 2-4 months and remained very high within the second year causing much longer allocation periods. Despite higher belowground C allocation by grasses (33%) than crops (21%), its distribution between various belowground pools remain very similar. Hence, the total C allocated belowground depends on the plant species, but its further fate is species independent. This review demonstrates that C partitioning can be used in various approaches, e.g. root sampling, CO2 flux measurements, to assess rhizodeposits’ pools and fluxes at pot, plot, field and ecosystem scale and so, to close the most uncertain gap of the terrestrial C cycle. This article is protected by copyright. All rights reserved.