Improved modelling of atmospheric ammonia over Denmark using the coupled modelling system DAMOS

A local-scale Gaussian dispersion-deposition model (OML-DEP) has been coupled to a regional chemistry-transport model (DEHM with a resolution of approximately 6 km × 6 km over Denmark) in the Danish Ammonia Modelling System, DAMOS. Thereby, it has been possible to model the distribution of ammonia concentrations and depositions on a spatial resolution down to 400 m × 400 m for selected areas in Denmark. DAMOS has been validated against measured concentrations from the dense measuring network covering Denmark. Here measured data from 21 sites are included and the validation period covers 2–5 years within the period 2005–2009. A standard time series analysis (using statistic parameters like correlation and bias) shows that the coupled model system captures the measured time series better than the regional- scale model alone. However, our study also shows that about 50% of the modelled concentration level at a given location originates from non-local emission sources. The local-scale model covers a domain of 16 km × 16 km, and of the locally released ammonia (NH<sub>3</sub>) within this domain, our simulations at five sites show that 14–27% of the locally (within 16 km × 16 km) emitted NH<sub>3</sub> also deposits locally. These results underline the importance of including both high-resolution local-scale modelling of NH<sub>3</sub> as well as the regional-scale component described by the regional model. The DAMOS system can be used as a tool in environmental management in relation to assessments of total nitrogen load of sensitive nature areas in intense agricultural regions. However, high spatio-temporal resolution in input parameters like NH<sub>3</sub> emissions and land-use data is required

Population-based study of diagnostic assays for Borrelia infection: comparison of purified flagella antigen assay (Ideia™, Dako Cytomation) and recombinant antigen assay (Liaison®, DiaSorin)

<p>Abstract</p> <p>Background</p> <p>Testing for <it>Borrelia</it>-specific IgM and IgG-antibodies are often performed on a variety of poorly defined symptoms, and isolated IgM results are a frequent finding, which results in diagnostic uncertainty and further testing. We wanted to test the hypothesis that Borrelia-specific assays using recombinant antigens perform differently from assays based on purified flagella antigen.</p> <p>Methods</p> <p>We compared the use of recombinant antigens (LIAISON^®DiaSorin, Saluggia, Italy) and purified flagella antigen (IDEIA™ Borrelia, DakoCytomation, Glostrup, Denmark) in the assay for <it>Borrelia</it>-specific IgM and IgG-antibodies. The assays were tested on an unselected population of serum samples submitted from general practice. A total of 357 consecutive samples for analysis of <it>Borrelia </it>IgM and IgG antibodies. Furthermore, we analysed 540 samples for <it>Borrelia</it>-specific IgM or IgG antibodies first by the IDEIA™ and, if they were positive, the samples were further analysed using the LIAISON^®assay. To verify the correctness of the patient's serological status, discrepant samples were analysed by line blots (EcoLine, Virotech).</p> <p>Results</p> <p>In the consecutive series of 357 samples, the IgM assays detected 308 negative and 3 positive samples with concordant results. Compared with the line blot, the IDEIA™ system produced 21 false-positive IgM results, whereas the LIAISON^®system produced only one false-positive IgM result. The IgG assays showed 1 positive and 328 negative concordant results. The LIAISON^®system produced 9 true IgG-positive samples that were not detected by the IDEIA™ system, but the former produced 4 positive IgG results that were negative by line blot.</p> <p>Conclusion</p> <p>Diagnostic assays based on flagella antigen seem to show more false-positive IgM and false-negative IgG results than assays based on recombinant antigens. The latter may reduce the number of presumably false-positive IgM results and identify more IgG-positive subjects, but this system also produces more false-positive IgG results.</p

Geometric and Electronic Structures of the NiI and Methyl−NiIII Intermediates of Methyl-Coenzyme M Reductase†

ABSTRACT: Methyl-coenzyme M reductase (MCR) catalyzes the terminal step in the formation of biological methane from methyl-coenzyme M (Me-SCoM) and coenzyme B (CoBSH). The active site in MCR contains a Ni-F430 cofactor, which can exist in different oxidation states. The catalytic mechanism of methane formation has remained elusive despite intense spectroscopic and theoretical investigations. On the basis of spectroscopic and crystallographic data, the first step of the mechanism is proposed to involve a nucleophilic attack of the NiI active state (MCRred1) on Me-SCoM to form a NiIII-methyl intermediate, while computational studies indicate that the first step involves the attack of NiI on the sulfur of Me-SCoM, forming a CH3 radical and a NiII-thiolate species. In this study, a combination of Ni K-edge X-ray absorption spectroscopic (XAS) studies and density functional theory (DFT) calculations have been performed on the NiI (MCRred1), NiII (MCRred1-silent), and NiIII-methyl (MCRMe) states of MCR to elucidate the geometric and electronic structures of the different redox states. Ni K-edge EXAFS data are used to reveal a five-coordinate active site with an open upper axial coordination site in MCRred1. Ni K-pre-edge and EXAFS data and time-dependent DFT calculations unambiguously demonstrate the presence of a long Ni-C bond (∼2.04 Å) in the NiIII-methyl state of MCR. The formation and stability of this species support mechanism I, and the Ni-C bond length suggests a homolytic cleavage of the NiIII-methyl bon

Entry of Herpes Simplex Virus Type 1 (HSV-1) into the Distal Axons of Trigeminal Neurons Favors the Onset of Nonproductive, Silent Infection

Following productive, lytic infection in epithelia, herpes simplex virus type 1 (HSV-1) establishes a lifelong latent infection in sensory neurons that is interrupted by episodes of reactivation. In order to better understand what triggers this lytic/latent decision in neurons, we set up an organotypic model based on chicken embryonic trigeminal ganglia explants (TGEs) in a double chamber system. Adding HSV-1 to the ganglion compartment (GC) resulted in a productive infection in the explants. By contrast, selective application of the virus to distal axons led to a largely nonproductive infection that was characterized by the poor expression of lytic genes and the presence of high levels of the 2.0-kb major latency-associated transcript (LAT) RNA. Treatment of the explants with the immediate-early (IE) gene transcriptional inducer hexamethylene bisacetamide, and simultaneous co-infection of the GC with HSV-1, herpes simplex virus type 2 (HSV-2) or pseudorabies virus (PrV) helper virus significantly enhanced the ability of HSV-1 to productively infect sensory neurons upon axonal entry. Helper-virus-induced transactivation of HSV-1 IE gene expression in axonally-infected TGEs in the absence of de novo protein synthesis was dependent on the presence of functional tegument protein VP16 in HSV-1 helper virus particles. After the establishment of a LAT-positive silent infection in TGEs, HSV-1 was refractory to transactivation by superinfection of the GC with HSV-1 but not with HSV-2 and PrV helper virus. In conclusion, the site of entry appears to be a critical determinant in the lytic/latent decision in sensory neurons. HSV-1 entry into distal axons results in an insufficient transactivation of IE gene expression and favors the establishment of a nonproductive, silent infection in trigeminal neurons