University of Kiel

About: University of Kiel is a education organization based out in Kiel, Germany. It is known for research contribution in the topics: Population & Crystal structure. The organization has 27816 authors who have published 57114 publications receiving 2061802 citations. The organization is also known as: Christian Albrechts University & Christian-Albrechts-Universität zu Kiel.

Is the Pollution Effect of the FEM Avoidable for the Helmholtz Equation Considering High Wave Numbers

Abstract: The development of numerical methods for solving the Helmholtz equation, which behaves robustly with respect to the wave number, is a topic of vivid research. It was observed that the solution of the Galerkin finite element method (FEM) differs significantly from the best approximation with increasing wave number. Many attempts have been presented in the literature to eliminate this lack of robustness by various modifications of the classical Galerkin FEM. However, we will prove that, in two and more space dimensions, it is impossible to eliminate this so-called pollution effect. Furthermore, we will present a generalized FEM in one dimension which behaves robustly with respect to the wave number.

How relevant is recalcitrance for the stabilization of organic matter in soils

Abstract: Traditionally, the selective preservation of certain recalcitrant organic compounds and the formation of recalcitrant humic substances have been regarded as an important mechanism for soil organic matter (SOM) stabilization. Based on a critical overview of available methods and on results from a cooperative research program, this paper evaluates how relevant recalcitrance is for the long-term stabilization of SOM or its fractions. Methodologically, recalcitrance is difficult to assess, since the persistence of certain SOM fractions or specific compounds may also be caused by other stabilization mechanisms, such as physical protection or chemical interactions with mineral surfaces. If only free particulate SOM obtained from density fractionation is considered, it rarely reaches ages exceeding 50 y. Older light particles have often been identified as charred plant residues or as fossil C. The degradability of the readily bioavailable dissolved or water-extractable OM fraction is often negatively correlated with its content in aromatic compounds, which therefore has been associated with recalcitrance. But in subsoils, dissolved organic matter aromaticity and biodegradability both are very low, indicating that other factors or compounds limit its degradation. Among the investigated specific compounds, lignin, lipids, and their derivatives have mean turnover times faster or similar as that of bulk SOM. Only a small fraction of the lignin inputs seems to persist in soils and is mainly found in the fine textural size fraction ( 40–50 y, unless fossil C was present in substantial amounts, as at a site exposed to lignite inputs in the past. Here, turnover of pyrolysis products seemed to be much longer, even for those attributed to carbohydrates or proteins. Apparently, fossil C from lignite coal is also utilized by soil organisms, which is further evidenced by low 14C concentrations in microbial phospholipid fatty acids from this site. Also, black C from charred plant materials was susceptible to microbial degradation in a short-term (60 d) and a long-term (2 y) incubation experiment. This degradation was enhanced, when glucose was supplied as an easily available microbial substrate. Similarly, SOM mineralization in many soils generally increased after addition of carbohydrates, amino acids, or simple organic acids, thus indicating that stability may also be caused by substrate limitations. It is concluded that the presented results do not provide much evidence that the selective preservation of recalcitrant primary biogenic compounds is a major SOM-stabilization mechanism. Old SOM fractions with slow turnover rates were generally only found in association with soil minerals. The only not mineral-associated SOM components that may be persistent in soils appear to be black and fossil C.

Genome-wide association scan identifies a colorectal cancer susceptibility locus on 11q23 and replicates risk loci at 8q24 and 18q21.

Abstract: In a genome-wide association study to identify loci associated with colorectal cancer (CRC) risk, we genotyped 555,510 SNPs in 1,012 early-onset Scottish CRC cases and 1,012 controls (phase 1). In phase 2, we genotyped the 15,008 highest-ranked SNPs in 2,057 Scottish cases and 2,111 controls. We then genotyped the five highest-ranked SNPs from the joint phase 1 and 2 analysis in 14,500 cases and 13,294 controls from seven populations, and identified a previously unreported association, rs3802842 on 11q23 (OR = 1.1; P = 5.8 x 10(-10)), showing population differences in risk. We also replicated and fine-mapped associations at 8q24 (rs7014346; OR = 1.19; P = 8.6 x 10(-26)) and 18q21 (rs4939827; OR = 1.2; P = 7.8 x 10(-28)). Risk was greater for rectal than for colon cancer for rs3802842 (P < 0.008) and rs4939827 (P < 0.009). Carrying all six possible risk alleles yielded OR = 2.6 (95% CI = 1.75-3.89) for CRC. These findings extend our understanding of the role of common genetic variation in CRC etiology.