Product and rate determinations with chemically activated nucleotides in the presence of various prebiotic materials, including other mono- and polynucleotides

We are investigating the reactions of ImpN's in the presence of a number of prebiotically plausible materials, such as metal ions, phosphate, amines and other nucleotides and hope to learn more about the stability/reactivity of ImpN's in a prebiotic aqueous environment. We find that, in the presence of phosphate, ImpN's form substantial amounts of diphosphate nucleotides. These diphosphate nucleotides are not very good substrates for template directed reactions, but are chemically activated and are known to revert to the phosphoimidazolides in the presence of imidazole under solid state conditions. With respect to our studies of the oligomerization reaction, the determination of the dimerization rate constant of a specific ImpN (guanosine 5'-phospho 2 methylimidazolide) both in the absence and the presence of the template leads to the conclusion that at 37 C the dimerization is not template directed, although the subsequent polymerization steps are. In other words, this specific polynucleotide synthesizing system favors the elongation of oligonucleotides as compared with the formation of dimers and trimers. This favoring of the synthesis of long as opposed to short oligonucleotides may be regarded as a rudimentary example of natural selection at the molecular level

Travailleurs étrangers et travail irrégulier en Italie: évidences sur la base de la régularisation de 2002

Objectif de ce travail est de montrer en quelle mesure la régularisation 2002 reproduit une géographie spécifique de l’insertion des immigrés dans l’économie souterraine au niveau local. Notamment, en utilisant les données des étrangers régularisés par province de présentation des demandes on cherchera à mettre en évidence l’homogénéité ou hétérogénéité des différentes régions du pays par rapport à la typologie de régularisation et aux caractéristiques socioprofessionnelles des régularisés. De plus, on montrera l’existence de liens entre l’emploi de travailleurs étrangers en condition d’irrégularité et certaines caractéristiques des marchés du travail et des systèmes productifs locaux. On se servira de cartogrammes et de technique statistiques telles que l’analyse factorielle et cluster et la régression linéaire multiple

A dual isotopic approach using radioactive phosphorus and the isotopic composition of oxygen associated to phosphorus to understand plant reaction to a change in P nutrition

Abstract Background Changing the phosphorus (P) nutrition leads to changes in plant metabolism. The aim of this study was to investigate how these changes are reflected in the distribution of 33P and the isotopic composition of oxygen associated to P (δ18OP) in different plant parts of soybean (Glycine max cv. Toliman). Two P pools were extracted sequentially with 0.3 M trichloroacetic acid (TCA P) and 10 M nitric acid (HNO3; residual P). Results The δ18OP of TCA P in the old leaves of the − P plants (23.8‰) significantly decreased compared to the + P plants (27.4‰). The 33P data point to an enhanced mobilisation of P from residual P in the old leaves of the − P plants compared to the + P plants. Conclusions Omitting P for 10 days lead to a translocation of P from source to sink organs in soybeans. This was accompanied by a significant lowering of the δ18OP of TCA P in the source organs due to the enzymatic hydrolysis of organic P. Combining 33P and δ18OP can provide useful insights in plant responses to P omission at an early stage

Electron-phonon interaction in the solid form of the smallest fullerene C20_{20}

The electron-phonon coupling of a theoretically devised carbon phase made by assembling the smallest fullerenes C$_{20}$ is calculated from first principles. The structure consists of C$_{20}$ cages in an {\it fcc} lattice interlinked by two bridging carbon atoms in the interstitial tetrahedral sites ({\it fcc}-C$_{22}$). The crystal is insulating but can be made metallic by doping with interstitial alkali atoms. In the compound NaC$_{22}$ the calculated coupling constant $\lambda/N(0)$ is 0.28 eV, a value much larger than in C$_{60}$, as expected from the larger curvature of C$_{20}$. On the basis of the McMillan's formula, the calculated $\lambda$=1.12 and a $\mu^*$ assumed in the range 0.3-0.1 a superconducting T$_c$ in the range 15-55 K is predicted.Comment: 7 page

Report on advances for pediatricians in 2018: allergy, cardiology, critical care, endocrinology, hereditary metabolic diseases, gastroenterology, infectious diseases, neonatology, nutrition, respiratory tract disorders and surgery.

This review reported notable advances in pediatrics that have been published in 2018. We have highlighted progresses in allergy, cardiology, critical care, endocrinology, hereditary metabolic diseases, gastroenterology, infectious diseases, neonatology, nutrition, respiratory tract disorders and surgery. Many studies have informed on epidemiologic observations. Promising outcomes in prevention, diagnosis and treatment have been reported. We think that advances realized in 2018 can now be utilized to ameliorate patient car

Nitrate leaching from short-hydroperiod floodplain soils

Numerous studies have shown the importance of riparian zones to reduce nitrate (NO<sub>3</sub><sup>−</sup>) contamination coming from adjacent agricultural land. Much less is known about nitrogen (N) transformations and nitrate fluxes in riparian soils with short hydroperiods (1–3 days of inundation) and there is no study that could show whether these soils are a N sink or source. Within a restored section of the Thur River in NE Switzerland, we measured nitrate concentrations in soil solutions as an indicator of the net nitrate production. Samples were collected along a quasi-successional gradient from frequently inundated gravel bars to an alluvial forest, at three different depths (10, 50 and 100 cm) over a one-year period. Along this gradient we quantified N input (atmospheric deposition and sedimentation) and N output (leaching) to create a nitrogen balance and assess the risk of nitrate leaching from the unsaturated soil to the groundwater. Overall, the main factor explaining the differences in nitrate concentrations was the field capacity (FC). In subsoils with high FCs and VWC near FC, high nitrate concentrations were observed, often exceeding the Swiss and EU groundwater quality criterions of 400 and 800 μmol L<sup>−1</sup>, respectively. High sedimentation rates of river-derived nitrogen led to apparent N retention up to 200 kg N ha<sup>−1</sup> yr<sup>−1</sup> in the frequently inundated zones. By contrast, in the mature alluvial forest, nitrate leaching exceeded total N input most of the time. As a result of the large soil N pools, high amounts of nitrate were produced by nitrification and up to 94 kg N-NO<sub>3</sub><sup>−</sup> ha<sup>−1</sup> yr<sup>−1</sup> were leached into the groundwater. Thus, during flooding when water fluxes are high, nitrate from soils can contribute up to 11% to the total nitrate load in groundwater

Isotopic (δ13C, Δ14C) Analysis of Organic Acids in Marine Samples Using Wet Chemical Oxidation

We present a method for the isolation and off-line isotope analysis of formate and acetate in marine samples. Organic acids are separated by high performance liquid chromatography and collected in glass Exetainer® screw-capped vials that have been prespiked with an oxidant and flushed with helium. The vials are subsequently heated to convert the organic compounds to CO2 for radiocarbon and δ13C analysis. Small aliquots are sampled for measurement of δ13C by isotope ratio mass spectrometry, whereas the majority of the CO2 is saved for radiocarbon analysis by accelerator mass spectrometry using a gas ion source. Accurate δ13C and radiocarbon values were obtained for formate and acetate standards spiked into deep seawater and saline Milli-Q water at concentrations of 25 to 1000 µM C. The process blank associated with the isolation of formate for radiocarbon analysis was ~1.5 µg C and stable over time. Accurate results could be obtained for marine samples with only 25 µM formate. The radiocarbon analysis of acetate showed significantly higher and more variable extraneous carbon contributions, particularly for samples spiked into seawater. Potential improvements that may make the method appropriate for the radiocarbon analysis of acetate in seawater are discussed. The blanks associated with the wet chemical oxidation were assessed independently and found to be small and consistent (\u3c0.3 µg C), potentially making this approach feasible for a broader set of compounds separated by HPLC for radiocarbon analysis