Search results for "ISOTOPE"

Activity and kinetics of DNA dependent DNA and RNA polymerases n xeroderma pigmentosum and in normal human skin.

1971

1. DNA dependent DNA polymerase (E.C.2.7.7.7) was prepared from human normal and from Xeroderma pigmentosum skin. 2. DNA polymerase from normal skin has the same Michaelis constant with native and denatured DNA as templateKm= 120 ± 11 µg DNA/ml, with differing maximum reaction velocities. 3. The enzyme from Xeroderma pigmentosum has the same Michaelis constant for denatured DNA as the enzyme from normal skin, but with native DNA as template, theKmvalue is lower (97.2 ± 9.8). The maximum reaction velocities of the Xeroderma pigmentosum enzyme with native resp. denatured DNA as template are the same. 4. DNA dependent RNA polymerases (E.C.2.7.7.6) from normal and Xeroderma pigmentosum skin wer…

Study of the origin and fate of organic matter in a tropical bay using elemental, isotopic and fatty acid biomarkers.

2014

Organic matter (OM) exchanges between adjacent coastal ecosystems affect the role of the different primary producers as energy and nutrient sources in food webs. Elemental and isotope parameters (C/N ratios, δ13C) and fatty acid (FA) biomarkers were used to assess the origin and distribution of OM in both surface sediment and water along a strongly tidally-influenced tropical area, Gazi Bay (Kenya), in two climatic seasons (dry and rainy). Dominant primary producers (i.e. mangroves, macroalgae and seagrasses) were also characterized through the same combined approach. Export of the mangrove-derived OM, highly depleted, to the adjacent bay was evident from a gradual 13C-enrichment of primary…

Invasive crayfish increase habitat connectivity

2012

Several studies have shown that distinct compartments of lake ecosystems are coupled via transportation of organic matter, nutrients and energy across habitat boundaries. Here we evaluate the potential of the invasive signal crayfish (Pacifastacus leniusculus (Dana)) to modify energy pathways in large boreal lakes. Using a stable isotope mixing model and calculation of the isotopic niches we estimated the contribution of different food sources to the diets of crayfish captured from different habitats, and from that inferred their potential to transport energy across the littoral-profundal gradient. The crayfish caught from the littoral area utilized mainly littoral food sources, whereas the…

Réponses de la plante et des microorganismes du sol aux changements environnementaux

2015

Denitrifying microbial communities along a boreal stream with varying land-use

2019

Streams have an important role in regulating nitrogen (N) transportation from terrestrial ecosystems to downstream waters. Here, we examined how catchment land-use affects potential denitrification rates and the function and composition of denitrifier communities in boreal stream sediments, using stable isotope incubations and qPCR and 454-pyrosequencing targeted on nirS, nirK and nosZ genes. Although land-use influenced the water chemistry as higher nitrite + nitrate (NO x − ) concentration at the agriculture-affected sampling point, sediment organic matter content was found to be the key factor in regulating potential denitrification rates. However, the abundance as well as the diversity …

Keurusselän denitrifikaatioaktiivisuuden ajallinen ja paikallinen vaihtelu

2015

Vesien rehevöityminen on maailmanlaajuinen ongelma. Ihmisen toiminnan takia ravinteita, kuten typpeä ja fosforia, kulkeutuu vesiin paljon aiheuttaen mm. massiivisia leväkukintoja ja happikatoa orgaanisen aineen hajotessa. Tämä vähentää mm. vesien virkistysarvoa sekä kaupallista arvoa. Merissä typpi on rajoittava ravinne ja suurin osa typestä päätyy meriin jokivesien mukana. Järvissä tapahtuvassa denitrifikaatiossa typpi muuttuu kaasumaiseen muotoon, mikä vähentää merien typpikuormaa. Tutkimuksessamme mittasimme denitrifikaationopeutta kolmella eri mittauspisteellä Keuruunselällä vuosien 2013 ja 2014 aikana viitenä kertana. Jaoimme aineiston vuodenajan mukaan kesään, syksyyn ja talveen. Hypo…

Nitrogen removal by microbial processes in aquatic systems

2012

A study of VUV emission and the extracted electron-ion ratio in hydrogen and deuterium plasmas of a filament-driven H−/D− ion source

2019

Vacuum ultraviolet (VUV) emission diagnostics for studying differences of electron impact processes in hydrogen and deuterium plasmas are presented. The method is applied to study a filament driven multicusp arc discharge negative ion source by comparing the VUV-emission intensities of different emission bands and extracted currents of H−/D− ions and electrons. It was found that the ratio of coextracted electrons to extracted ions is four times higher for deuterium than for hydrogen. No significant differences of the VUV-spectra or volumetric rates of ionization, excitation, production of high vibrational states, and dissociation were found between the plasmas of the two isotopes. The volum…

Identification of a dipole band above the Iπ = 31/2- isomeric state in 189Pb

2015

A dipole band of six transitions built upon a firmly established I π = 31/2− isomeric state has been identified in 189Pb using recoil-isomer tagging. This is the lightest odd-mass Pb nucleus in which a dipole band is known. The dipole nature of the new transitions has been confirmed through angular-intensity arguments. The evolution of the excitation energy and the aligned-angular momentum of the states in the new dipole band are compared with those of dipole bands in heavier, odd-mass lead isotopes. This comparison suggests that the new band in 189Pb is based upon a π[s−2 1/2h9/2i13/2]11− ⊗ ν[i −1 13/2+ ]13/2+ configuration. However, the increased aligned-angular momentum in 189Pb may sugg…

A no-carrier-added 72Se/72As radionuclide generator based on distillation

2004

Abstract Arsenic-72 is a positron emitting isotope with promising properties for syntheses of 72As-labelled radiopharmaceuticals for future application in positron emission tomography. This work describes the radiochemical separation of no-carrier-added 72Se from cyclotron irradiated germanium targets and the development of a 72Se/72As radionuclide generator, avoiding the addition of any selenium carrier. Using a vertical quartz tube device, no-carrier-added 72As is nearly quantitatively released from various chloride salt solutions containing 72Se within 10 min at a temperature of 100 °C in an HCl gas flow. The kinetics of the 72Se/72As isotope generator has been studied in relation to tem…