Radboud University Nijmegen

About: Radboud University Nijmegen is a education organization based out in Nijmegen, Gelderland, Netherlands. It is known for research contribution in the topics: Population & Randomized controlled trial. The organization has 35417 authors who have published 83035 publications receiving 3285064 citations. The organization is also known as: Catholic University of Nijmegen & Radboud University.

Biochemistry and molecular biology of anammox bacteria

Abstract: Anaerobic ammonium-oxidizing (anammox) bacteria are one of the latest additions to the biogeochemical nitrogen cycle. These bacteria derive their energy for growth from the conversion of ammonium and nitrite into dinitrogen gas in the complete absence of oxygen. These slowly growing microorganisms belong to the order Brocadiales and are affiliated to the Planctomycetes. Anammox bacteria are characterized by a compartmentalized cell architecture featuring a central cell compartment, the "anammoxosome". Thus far unique "ladderane" lipid molecules have been identified as part of their membrane systems surrounding the different cellular compartments. Nitrogen formation seems to involve the intermediary formation of hydrazine, a very reactive and toxic compound. The genome of the anammox bacterium Kuenenia stuttgartiensis was assembled from a complex microbial community grown in a sequencing batch reactor (74% enriched in this bacterium) using a metagenomics approach. The assembled genome allowed the in silico reconstruction of the anammox metabolism and identification of genes most likely involved in the process. The present anammox pathway is the only one consistent with the available experimental data, thermodynamically and biochemically feasible, and consistent with Ockham's razor: it invokes minimum biochemical novelty and requires the fewest number of biochemical reactions. The worldwide presence of anammox bacteria has now been established in many oxygen-limited marine and freshwater systems, including oceans, seas, estuaries, marshes, rivers and large lakes. In the marine environment over 50% of the N(2) gas released may be produced by anammox bacteria. Application of the anammox process offers an attractive alternative to current wastewater treatment systems for the removal of ammonia-nitrogen. Currently, at least five full scale reactor systems are operational.

Online video game addiction: identification of addicted adolescent gamers.

Abstract: Aims To provide empirical data-driven identification of a group of addicted online gamers. Design Repeated cross-sectional survey study, comprising a longitudinal cohort, conducted in 2008 and 2009. Setting Secondary schools in the Netherlands. Participants Two large samples of Dutch schoolchildren (aged 13-16 years). Measurements Compulsive internet use scale, weekly hours of online gaming and psychosocial variables. Findings Thisstudyconfirmstheexistenceof asmallgroupof addictedonlinegamers(3%),representingabout1.5% of all children aged 13-16 years in the Netherlands. Although these gamers report addiction-like problems, relation- ships with decreased psychosocial health were less evident. Conclusions The identification of a small group of addicted online gamers supports efforts to develop and validate questionnaire scales aimed at measuring the phenom- enon of online video game addiction. The findings contribute to the discussion on the inclusion of non-substance addictions in the proposed unified concept of 'Addiction and Related Disorders' for the DSM-V by providing indirect identification and validation of a group of suspected online video game addicts.

Organocatalysed asymmetric Mannich reactions.

Abstract: The asymmetric Mannich reaction ranks among the most potent enantioselective and diastereoselective C–C-bond forming reactions. In recent years, organocatalysed versions of asymmetric Mannich processes have been increasingly reported and used in a rapidly growing number of applications. This tutorial review provides an overview of the recent history of the asymmetric organocatalysed Mannich reaction, including scope and limitations, and application of different catalyst systems.

Planck 2013 results. XXIV. Constraints on primordial non-Gaussianity

Abstract: The Planck nominal mission cosmic microwave background (CMB) maps yield unprecedented constraints on primordial non-Gaussianity (NG). Using three optimal bispectrum estimators, separable template-fitting (KSW), binned, and modal, we obtain consistent values for the primordial local, equilateral, and orthogonal bispectrum amplitudes, quoting as our final result fNLlocal = 2.7 ± 5.8, fNLequil = -42 ± 75, and fNLorth = -25 ± 39 (68% CL statistical). Non-Gaussianity is detected in the data; using skew-Cl statistics we find a nonzero bispectrum from residual point sources, and the integrated-Sachs-Wolfe-lensing bispectrum at a level expected in the ΛCDM scenario. The results are based on comprehensive cross-validation of these estimators on Gaussian and non-Gaussian simulations, are stable across component separation techniques, pass an extensive suite of tests, and are confirmed by skew-Cl, wavelet bispectrum and Minkowski functional estimators. Beyond estimates of individual shape amplitudes, we present model-independent, three-dimensional reconstructions of the Planck CMB bispectrum and thus derive constraints on early-Universe scenarios that generate primordial NG, including general single-field models of inflation, excited initial states (non-Bunch-Davies vacua), and directionally-dependent vector models. We provide an initial survey of scale-dependent feature and resonance models. These results bound both general single-field and multi-field model parameter ranges, such as the speed of sound, cs ≥ 0.02 (95% CL), in an effective field theory parametrization, and the curvaton decay fraction rD ≥ 0.15 (95% CL). The Planck data significantly limit the viable parameter space of the ekpyrotic/cyclic scenarios. The amplitude of the four-point function in the local model τNL< 2800 (95% CL). Taken together, these constraints represent the highest precision tests to date of physical mechanisms for the origin of cosmic structure.