Temperature sensitivity of soil respiration is dependent on readily decomposable C substrate concentration

International audienceTemperature acclimation of soil organic matter (SOM) decomposition is one of the major uncertainties in predicting soil CO2 efflux by the increase in global mean temperature. A reasonable explanation for an apparent acclimation proposed by Davidson and colleagues (2006) based on Michaelis-Menten kinetics suggests that temperature sensitivity decreases when both maximal activity of respiratory enzymes (Vmax) and half- saturation constant (Ks) cancel each other upon temperature increase. We tested the hypothesis of the canceling effect by the mathematical simulation of the data obtained in the incubation experiments with forest and arable soils. Our data confirm the hypothesis and suggest that concentration of readily decomposable C substrate as glucose equivalent is an important factor controlling temperature sensitivity. The highest temperature sensitivity was observed when C substrate concentration was much lower than Ks. Increase of substrate content to the half-saturation constant resulted in temperature acclimation associated with the canceling effect. Addition of the substrate to the level providing respiration at a maximal rate Vmax leads to the acclimation of the whole microbial community as such. However, growing microbial biomass was more sensitive to the temperature alterations. This study improves our understanding of the instability of temperature sensitivity of soil respiration under field conditions, explaining this phenomenon by changes in concentration of readily decomposable C substrate. It is worth noting that this pattern works regardless of the origin of C substrate: production by SOM decomposition, release into the soil by rhizodeposition, litter fall or drying-rewetting events

ОПРЕДЕЛЕНИЕ ПРИМЕСЕЙ В ОСОБО ЧИСТЫХ НАНОПОРОШКАХ ОКСИДА ИТТРИЯ, ЛЕГИРОВАННОГО НЕОДИМОМ, МЕТОДОМ АТОМНО-ЭМИССИОННОЙ СПЕКТРОМЕТРИИ С ИНДУКТИВНО СВЯЗАННОЙ ПЛАЗМОЙ

The technique of inductively coupled plasma atomic-emission spectrometry determination of Al, Ba, Be, Ca, Cd, Co, Cr, Fe, K, Li, Mg, Mn, Na, Ni, Pb, Sb, V and Zn in neodymium doped yttrium oxide nanopowders was developed. The limits of quantitation raged in diapason 10-5-10-4 % mass. Matrix effects were minimized using the standards and blank solutions with the same content of matrix (≈ 1 %mass.) as the samples solutions.Keywords: inductively coupled plasma atomic emission spectrometry, yttrium oxide, determination of impurities(Russian)DOI: http://dx.doi.org/10.15826/analitika.2013.17.2.006I.I. Yevdokimov, V.G. PimenovG.G. Devyatykh Institute of Chemistry of High-Purity Substances of the Russian Academy of Sciences, Nizhny Novgorod, Russian FederationРазработана методика атомно-эмиссионного с индуктивно связанной плазмой анализа особо чистых нанопорошков оксида иттрия, легированного неодимом, – прекурсоров оптической керамики – с пределами определения примесей Al, Ba, Be, Ca, Cd, Co, Cr, Fe, K, Li, Mg, Mn, Na, Ni, Pb, Sb, V и Zn на уровне 10-5-10-4 % мас. Матричные помехи при анализе 1 %-х растворов проб учитывали применением близких по матричному составу градуировочных растворов и растворов холостого опыта.Ключевые слова: атомно-эмиссионная спектрометрия с индуктивно связанной плазмой, оксид иттрия, определение примесейDOI: http://dx.doi.org/10.15826/analitika.2013.17.2.00

Temperature response of soil respiration is dependent on concentration of readily decomposable C

International audienceTemperature acclimation of soil organic matter (SOM) decomposition is one of the major uncertainties in predicting soil CO2 efflux associated with the increase in global mean temperature. A reasonable explanation for an apparent acclimation proposed by Davidson and colleagues (2006) based on Michaelis-Menten kinetics suggests that temperature sensitivity decreases when both maximal activity of respiratory enzymes (Vmax) and half-saturation constant (Ks) cancel each other upon temperature increase. We tested the hypothesis of the canceling effect by the mathematical simulation of data obtained in incubation experiments with forest and arable soils. Our data support the hypothesis and suggest that concentration of readily decomposable C substrate (as glucose equivalents) and temperature dependent substrate release are the important factors controlling temperature sensitivity of soil respiration. The highest temperature sensitivity of soil respiration was observed when substrate release was temperature dependent and C substrate concentration was much lower than Ks. Increase of substrate content to the half-saturation constant by glucose addition resulted in temperature acclimation associated with the canceling effect. Addition of the substrate to the level providing respiration at a maximal rate Vmax leads to the acclimation of the whole microbial community as such. However, growing microbial biomass was more sensitive to the temperature alterations. This study improves our understanding of the instability of temperature sensitivity of soil respiration under field conditions, attributing this phenomenon to changes in concentration of readily decomposable C substrate

Two modes of longe-range orientation of DNA bases realized upon compaction.

Formation of compact particles from linear DNA-anthracycline complexes is accompanied by appearance of intense bands in the CD spectra in the region of absorption of DNA bases (UV-region) and in the region of absorption of anthracycline chromophores (visible region). The intense (positive or negative) bands in the region of anthracycline absorption demonstrate an ordered helical location of anthracycline molecules on the DNA template. This fact, in its turn, is related to formation of the DNA superstructure in PEG-containing water-salt solutions with a long-range orientation of nitrogen bases. Possible types of DNA superstructures and the relation between the local- and the long-range order of bases in the DNA superstructure are discussed

RESPIRATORY SYNCYTIAL VIRUS INFECTION IN INFANTS

The review focuses on respiratory syncytial virus infection (RSVI) and, based on the literature and authors' own observations, highlights epidemiological aspects and risk factors for RSVI (including severe forms of the infection), the specific clinical manifestations, challenges of laboratory diagnostics, and the benefits of various methods and their relevance in clinical practice. The available types of RSVI therapies are discussed based on meta-analyses of the data. The authors emphasize the importance of palivizumab in the specific passive prevention of respiratory syncytial virus infection in children from risk groups