Microbial dormancy improves development and experimental validation of ecosystem model

Climate feedbacks from soils can result from environmental change followed by response of plant and microbial communities, and/or associated changes in nutrient cycling. Explicit consideration of microbial life-history traits and functions may be necessary to predict climate feedbacks owing to changes in the physiology and community composition of microbes and their associated effect on carbon cycling. Here we developed the microbial enzyme-mediated decomposition (MEND) model by incorporating microbial dormancy and the ability to track multiple isotopes of carbon. We tested two versions of MEND, that is, MEND with dormancy (MEND) and MEND without dormancy (MEND_wod), against long-term (270 days) carbon decomposition data from laboratory incubations of four soils with isotopically labeled substrates. MEND_wod adequately fitted multiple observations (total C–CO₂ and ¹⁴C–CO₂ respiration, and dissolved organic carbon), but at the cost of significantly underestimating the total microbial biomass. MEND improved estimates of microbial biomass by 20–71% over MEND_wod. We also quantified uncertainties in parameters and model simulations using the Critical Objective Function Index method, which is based on a global stochastic optimization algorithm, as well as model complexity and observational data availability. Together our model extrapolations of the incubation study show that long-term soil incubations with experimental data for multiple carbon pools are conducive to estimate both decomposition and microbial parameters. These efforts should provide essential support to future field- and global-scale simulations, and enable more confident predictions of feedbacks between environmental change and carbon cycling.     

Zur Ökonomie des Bostrychietum

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Cardiac magnetic resonance imaging in daily practice in a peripheral medical centre: description of the first 383 patients

Background. Cardiac magnetic resonance (CMR) imaging has evolved over the last decade into an indispensable diagnostic instrument. CMR imaging noninvasively provides structural, functional and morphological information with high spatial resolution and an unlimited field of view. Since October 2006 the VieCuri Medical Centre in Venlo has a CMR scanner at its disposal.Objectives. The goal of this study was to analyse the impact of CMR imaging on diagnosis and treatment in daily practice in the setting of a medium-volume peripheral hospital.Methods. All patients who underwent CMR imaging between October 2006 and November 2008 were included in this analysis. The medical history before and after the CMR scan, the application form for CMR imaging and the outcome of the scans were reviewed. CMR images, obtained using a 1.5-T magnetic resonance imaging system, were reviewed by a multidisciplinary team.Results. In 235 patients CMR imaging demonstrated one or more abnormalities, whereas CMR imaging did not identify any abnormalities in 148 patients. CMR imaging confirmed an expected finding in 166 cases, identified an unexpected condition in 69 cases, ruled out an expected finding in 59 cases and ruled out a suspected condition in 89 cases. Due to better insight into diagnosis, CMR imaging resulted in a change of treatment in 166 of the total of 383 CMR scans (43%).Conclusion. In a relevant number of cases CMR imaging leads to a change in the treatment of a patient, proving the value of CMR imaging as a diagnostic modality. Therefore, CMR imaging is an excellent opportunity for peripheral medical centres to improve efficiency and the standard of patient care. (Neth Heart J 2010;18:524–30.)     

A Monte-Carlo estimate of DNA loop formation

The ends of rather short double-helical DNA segments (approximately two persistence lengths) can be enzymatically joined to form closed circles. Such covalent closure into circles is a measure of the likelihood of the two ends of the DNA coming into close contact. There is a length of DNA for which loop formation is most likely to occur. We have determined the chain-length dependence of loop formation for stiff chains using computer-generated chains of cylinders. The distribution from which the values for the angles between cylinders were chosen relates the chain parameters to a given chain persistence. Our results are compared with those of other theories, including a statistical wormlike chain model, and with the experimental measurements for ring closure of DNA restriction fragments.     

Chromosome numbers in Onchocerca dukei and O. tarsicola

Testicular examination of male Onchocerca dukei and German O. tarsicola revealed five pairs of chromosomes, which is typical of most filariae. In contrast to German O. tarsicola, specimens from Sweden had only three pairs of chromosomes.