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Search Results: 1 - 10 of 34 matches for " Tage; Thamdrup "
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Nitrogen cycling in sub-oxic water colmns
Dalsgaard,Tage; Thamdrup,Bo; Mark Jensen,Marlene;
Gayana (Concepción) , 2006, DOI: 10.4067/S0717-65382006000300004
Abstract: the current knowledge about nitrogen removal processes in suboxic water columns will be reviewed. the most recent development in the understanding of these processes is the documentation of anaerobic ammonium oxidation with nitrite (anammox) in these areas, and the balance between the traditional denitrification and anammox will be in focus.
Nitrogen cycling in sub-oxic water colmns Ciclamiento del nitrógeno en columnas de agua sub-oxicas
Tage Dalsgaard,Bo Thamdrup,Marlene Mark Jensen
Gayana (Concepción) , 2006,
Abstract: The current knowledge about nitrogen removal processes in suboxic water columns will be reviewed. The most recent development in the understanding of these processes is the documentation of anaerobic ammonium oxidation with nitrite (anammox) in these areas, and the balance between the traditional denitrification and anammox will be in focus. Se revisa el conocimiento actual sobre los procesos de remoción del nitrógeno en columnas de agua subóxicas. En estas áreas el más reciente desarrollo en la comprensión de estos procesos es la documentación sobre la oxidación anaeróbica del amonio con nitrato (anammox). Además enfocaremos el balance entre la tradicional denitrificación y el anammox.
Experimental Incubations Elicit Profound Changes in Community Transcription in OMZ Bacterioplankton
Frank J. Stewart, Tage Dalsgaard, Curtis R. Young, Bo Thamdrup, Niels Peter Revsbech, Osvaldo Ulloa, Don E. Canfield, Edward F. DeLong
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0037118
Abstract: Sequencing of microbial community RNA (metatranscriptome) is a useful approach for assessing gene expression in microorganisms from the natural environment. This method has revealed transcriptional patterns in situ, but can also be used to detect transcriptional cascades in microcosms following experimental perturbation. Unambiguously identifying differential transcription between control and experimental treatments requires constraining effects that are simply due to sampling and bottle enclosure. These effects remain largely uncharacterized for “challenging” microbial samples, such as those from anoxic regions that require special handling to maintain in situ conditions. Here, we demonstrate substantial changes in microbial transcription induced by sample collection and incubation in experimental bioreactors. Microbial communities were sampled from the water column of a marine oxygen minimum zone by a pump system that introduced minimal oxygen contamination and subsequently incubated in bioreactors under near in situ oxygen and temperature conditions. Relative to the source water, experimental samples became dominated by transcripts suggestive of cell stress, including chaperone, protease, and RNA degradation genes from diverse taxa, with strong representation from SAR11-like alphaproteobacteria. In tandem, transcripts matching facultative anaerobic gammaproteobacteria of the Alteromonadales (e.g., Colwellia) increased 4–13 fold up to 43% of coding transcripts, and encoded a diverse gene set suggestive of protein synthesis and cell growth. We interpret these patterns as taxon-specific responses to combined environmental changes in the bioreactors, including shifts in substrate or oxygen availability, and minor temperature and pressure changes during sampling with the pump system. Whether such changes confound analysis of transcriptional patterns may vary based on the design of the experiment, the taxonomic composition of the source community, and on the metabolic linkages between community members. These data highlight the impressive capacity for transcriptional changes within complex microbial communities, underscoring the need for caution when inferring in situ metabolism based on transcript abundances in experimental incubations.
Nitrogen isotope dynamics and fractionation during sedimentary denitrification in Boknis Eck, Baltic Sea
K. D?hnke,B. Thamdrup
Biogeosciences Discussions , 2013, DOI: 10.5194/bgd-10-681-2013
Abstract: The global marine nitrogen cycle is constrained by nitrogen fixation as a source of reactive nitrogen, and denitrification or anammox on the sink side. These processes with their respective isotope effects set the marine nitrate 15N-isotope value (δ15N) to a relatively constant average of 5‰. This value can be used to better assess the magnitude of these sources and sink terms, but the underlying assumption is that sedimentary denitrification and anammox, processes responsible for approximately one third of global nitrogen removal, have little to no isotope effect on nitrate in the water column. We investigated the isotope fractionation in sediment incubations, measuring net denitrification and nitrogen and oxygen stable isotope fractionation in surface sediments from the coastal Baltic Sea (Boknis Eck, Northern Germany), a site with seasonal hypoxia and dynamic nitrogen turnover. We found tremendously high denitrification rates, and regardless of current paradigms assuming little fractionation during sediment denitrification, we measured fractionation factors of 18.9‰ for nitrogen and 15.8‰ for oxygen in nitrate. While the input of nitrate to the water column remains speculative, these results challenge the current view of fractionation during sedimentary denitrification and imply that nitrogen budget calculations may need to consider this variability, as both preferential uptake of light nitrate and release of the remaining heavy fraction can significantly alter water column nitrate isotope vales at the sediment-water interface.
Solution of the spherically symmetric linear thermoviscoelastic problem in the inertia-free limit
Tage Christensen,Jeppe C. Dyre
Physics , 2008, DOI: 10.1103/PhysRevE.78.021501
Abstract: The coupling between mechanical and thermal properties due to thermal expansion complicates the problem of measuring frequency-dependent thermoviscoelastic properties, in particular for highly viscous liquids. A simplification arises if there is spherical symmetry where - as detailed in the present paper - the thermoviscoelastic problem may be solved analytically in the inertia-free limit, i.e., the limit where the sample is much smaller than the wavelength of sound waves at the frequencies of interest. As for the one-dimensional thermoviscoelastic problem [Christensen et al., Phys. Rev. E 75, 041502 (2007)], the solution is conveniently formulated in terms of the so-called transfer matrix, which directly links to the boundary conditions that can be experimentally controlled. Once the transfer matrix has been calculated, it is fairly easy to deduce the equations describing various experimentally relevant special cases (boundary conditions that are adiabatic, isothermal, isochoric, etc.). In most situations the relevant frequency-dependent specific heat is the longitudinal specific heat, a quantity that is in between the isochoric and isobaric frequency-dependent specific heats.
Cytokine responses in infants infected with respiratory syncytial virus  [PDF]
Morten Breindahl, Klaus Rieneck, Claus Nielsen, Tage Justesen, Klaus Bendtzen, Klaus Müller
Open Journal of Immunology (OJI) , 2012, DOI: 10.4236/oji.2012.21005
Abstract: Introduction: Variability in severity of Respiratory Syncytial Virus (RSV) infection is reportedly due to differences in inflammatory response. Objective: To characterize the cytokine response in RSV+ infants aged 0 - 36 months and to relate their responses to disease severity. Methods: Nasopharyngeal aspirations (NPAs) were analyzed for RSV and IL-1β, IL-2, IL-4, IL-5, IL-6, IL-10, IL-12, IL-1RA, IL-4R, IFN-γ, sTNFR1, sTNFR2, and TNF-α. Clinical data were collected from the medical records. Results: We included 331 infants of whom 214 were RSV+. In comparison to RSV- infants, they had significantly higher levels of TNF-α, IL-6, IL-1β, and IFN-γ (p < 0.05). This also applied to anti-inflammatory cytokine IL-10 levels, but these levels were remarkably lower than levels of TNF-α, IL-6, and IL-1β. sTNFR1/2 were significantly increased in RSV+ infants. Hospitalized patients had significantly higher levels of TNF-α, sTNFR2, and IL-10 (p < 0.05) than non-hospitalized patients. The cytokine response could not be related to disease severity. We found no evidence of a skewed Th1/Th2 immune profile. Conclusion: In acute RSV disease, infected infants’ NPAs contain a significant amount of pro-inflammatory cytokines. Whether this response is beneficial or deleterious remains unanswered. Interpersonal variations in cytokine responses might be linked to an inherited tendency to variations in disease severity.
Frequency Dependent Specific Heat from Thermal Effusion in Spherical Geometry
Bo Jakobsen,Niels Boye Olsen,Tage Christensen
Physics , 2008, DOI: 10.1103/PhysRevE.81.061505
Abstract: We present a novel method of measuring the frequency dependent specific heat at the glass transition applied to 5-polyphenyl-4-ether. The method employs thermal waves effusing radially out from the surface of a spherical thermistor that acts as both a heat generator and thermometer. It is a merit of the method compared to planar effusion methods that the influence of the mechanical boundary conditions are analytically known. This implies that it is the longitudinal rather than the isobaric specific heat that is measured. As another merit the thermal conductivity and specific heat can be found independently. The method has highest sensitivity at a frequency where the thermal diffusion length is comparable to the radius of the heat generator. This limits in practise the frequency range to 2-3 decades. An account of the 3omega-technique used including higher order terms in the temperature dependency of the thermistor and in the power generated is furthermore given.
Anticoagulant treatment at a specialized outpatient anticoagulant therapy unit, a descriptive study
Kim Ekblom, Johan Hultdin, Bo Carlberg, Tage Strand
Thrombosis Journal , 2005, DOI: 10.1186/1477-9560-3-20
Abstract: Patients on continuous oral anticoagulant treatment at the Outpatient Anticoagulant Clinic at Ume? University Hospital in 2002 were included in a descriptive study (n = 900). 263 of those had a mechanical heart valve prosthesis. Only patient records for patients with other indications than mechanical heart valve prosthesis were examined. 582 of those records were found. In the 55 remaining patients some clinical information was retrieved from the computerised warfarin dosage database. These latter, more unsure clinical data, are presented separately. Anticoagulant treatment was discontinued if lack of proper indication or presence of too high risk for hemorrhagic complications were found.The prevalence of continuous oral anticoagulant treatment in the uptake area was 0.65%. The most common target interval was INR 2.1–3.0, but patients with a mechanical heart valve prosthesis were often treated more aggressively, i.e. with a higher INR target interval. Of the patients on continuous treatment, 26.6% of the INR values were outside 2.0–3.0. The most common reasons for oral anticoagulant treatment were atrial fibrillation or mechanical heart valve prosthesis, in contrast to earlier findings in studies of our population in 1987 and 1990. We found 90 patients (10.0%) without proper indication for oral anticoagulant treatment or too high risk, and their treatment was discontinued.In patients on oral anticoagulant therapy, re-evaluation of indications and risks resulted in a substantial number of treatment withdrawals. There have been major changes in treatment indications during the last decade, possibly due to rapid development of knowledge in the field of thrombosis risk factors. Treatment should be re-considered once a year.Treatment with warfarin or other coumarin derivatives is an established method of secondary prevention after venous or arterial thromboembolic events, as well as for primary prevention. In 1997 the prevalence of oral anticoagulant treatment in Sweden
Is the demand-control model still a usefull tool to assess work-related psychosocial risk for ischemic heart disease? Results from 14 year follow up in the Copenhagen City Heart study
Bo Netterstr m, Tage S. Kristensen, Gorm Jensen, Peter Schnor
International Journal of Occupational Medicine and Environmental Health , 2010, DOI: 10.2478/v10001-010-0031-6
Abstract: Objectives: To test the usefulness of the Demand-Control Model as predictor for ischemic heart disease (IHD). Materials and Methods: One thousand one hundred forty six actively employed men and women from the general population of Copenhagen participated at baseline in 1993-1994. They filled in questionnaires on the Demand-Control Model, job title, work place, civil status, family income, leisure time activity, smoking, medication, social support, social relations, conflicts, job responsibility, satisfaction, and insecurity and went through a medical examination, including measurements of coronary risk factors. All deaths and hospital admissions due to IHD, including first myocardial infarction (MI) in the cohort were traced in the Danish registries of deaths and hospital admissions to June 2007. Results: 104 cases of first time hospitalisation or death due to IHD including 49 cases of MI occurred during 14 years follow up. Odds ratio (OR) compared to the relaxed group was 1.1 (0.1-3.1) among women and 1.6 (0.4-4.9) among men after confounder adjustment. Neither demands nor control were significantly associated with IHD. Among men 50 years of age or more, the risk for IHD was, however, elevated in the job strain group and the active group (OR = 3.5 and 3.2 respectively). Job insecurity was, however, strongly associated with IHD in men (OR = 2.7 (1.1-5.6)) after all adjustments. The risk was increased for MI too (OR = 2.7 (1.2-6.1)). Among women, the only significant association with IHD was for job dissatisfaction (OR = 3.0 (1.2-7.6)). Conclusion: In this population and in a period and society characterized by relative wealth and increasing employment rates, the Demand-control Model did not predict IHD. However, the feeling of job insecurity predicted both IHD and MI among men and job dissatisfaction predicted IHD among women.
Investigation of the shear-mechanical and dielectric relaxation processes in two mono-alcohols close to the glass transition
Bo Jakobsen,Claudio Maggi,Tage Christensen,Jeppe C. Dyre
Physics , 2008, DOI: 10.1063/1.3007988
Abstract: Shear-mechanical and dielectric measurements on the two monohydroxy (mono-alcohol) molecular glass formers 2-ethyl-1-hexanol and 2-butanol close to the glass transition temperature are presented. The shear-mechanical data are obtained using the piezoelectric shear-modulus gauge method covering frequencies from 1mHz to 10kHz. The shear-mechanical relaxation spectra show two processes, which follow the typical scenario of a structural (alpha) relaxation and an additional (Johari-Goldstein) beta relaxation. The dielectric relaxation spectra are dominated by a Debye-type peak with an additional non-Debye peak visible. This Debye-type relaxation is a common feature peculiar to mono-alcohols. The time scale of the non-Debye dielectric relaxation process is shown to correspond to the mechanical structural (alpha) relaxation. Glass-transition temperatures and fragilities are reported based on the mechanical alpha relaxation and the dielectric Debye-type process, showing that the two glass-transition temperatures differ by approximately 10K and that the fragility based on the Debye-type process is a factor of two smaller than the structural fragility. If a mechanical signature of the Debye-type relaxation exists in these liquids, its relaxation strength is at most 1% and 3% of the full relaxation strength of 2-butanol and 2-ethyl-1-hexanol respectively. These findings support the notion that it is the non-Debye dielectric relaxation process that corresponds to the structural alpha relaxation in the liquid.
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