Search results for "δ"
showing 10 items of 315 documents
Meson retardation in deuteron electrodisintegration
2004
The effect of meson retardation in $NN$-interaction and exchange currents on deuteron electrodisintegration is studied in a coupled channel approach including $NN$-, $N \Delta$- and $\pi d$-channels. It is shown that the influence of retardation depends on the energy regime: Whereas below $\pi$-threshold calculations with static and retarded operators yield almost identical results, they differ significantly in the $\Delta$-region. Especially, the longitudinal and the longitudinal-transverse interference structure functions are strongly affected.
(Table 1) Stable oxygen and carbon isotopic ratios of tree rings, and tree ring width of white spruce (Picea glauca), Ennadai Lake
2012
Stable isotope ratios from tree rings and peatland mosses have become important proxies of past climate variations. We here compare recent stable carbon and oxygen isotope ratios in cellulose of tree rings from white spruce (Picea glauca), growing near the arctic tree line; and cellulose of Sphagnum fuscum stems, growing in a hummock of a subarctic peatland, in west-central Canada. Results show that carbon isotopes in S. fuscum correlate significantly with July temperatures over the past ~20 yr. The oxygen isotopes correlate with both summer temperature and precipitation. Analyses of the tree-ring isotopes revealed summer temperatures to be the main controlling factor for carbon isotope var…
Climate Sensitivity and Parameter Coherency in Annually Resolved δ13C and δ18O from Pinus uncinata Tree-Ring Data in the Spanish Pyrenees
2014
We explore the 20th century climate sensitivity of annually resolved carbon and oxygen isotope ratios in five Pinus uncinata individuals from the upper treeline in similar to 2400 m asl of the Span ...
An evaluation of inoceramid single-prism sclerochronology
2020
Abstract Inoceramid prisms are among the most common microfossils that can be found in Late Cretaceous strata. Since these biomineral units were formed by sequential accretion in the outer shell layer of the bivalves, they potentially serve as archives of short-term (circa-annual) paleowater temperature fluctuations. In the present study, we tested to what extent intra-prismatic stable isotope variations of individual inoceramid prisms reflect sub-annual δ13C and the δ18O patterns. We obtained multiple carbonate samples from prisms recovered from the sediment and from a cross-sectioned inoceramid shell fragment and compared data from these samples to data from classical sclerochronological …
13C/12C composition, a novel parameter to study the downward migration of paper sludge in soils
2002
δ13C values of crop and forest soils were measured 8 years after disposal of paper sewage sludge. The carbon transfer from paper sludge downward to the first humic layer is evidenced by a 13C-enrichnient of up to + 5.6‰ due to the input of 13C-enriched sludge carbonates. 13C/12C composition is thus a novel, sensitive parameter to follow the downward transfer of paper sludge carbon.
Carbon and nitrogen stabile isotope ratio and heavy metals in Leccinum aurantiacum in a hybrid aspen plantation in agricultural land
2020
Edible mycorrhizal fungi can be harvested in the fourth year after establishment of a hybrid aspen plantation in previous agricultural land at hemiboreal conditions. It is important to understand the role of fungi in element cycling at the ecosystem level as well as the amounts of elements, including heavy metals, that are accumulated in fruitbodies of edible fungi in the context of food safety. Therefore we evaluated the carbon and nitrogen stable isotope ratio and content of heavy metals (Cr, Pb, Mn, Ni, Cd, Cu and Zn) in Leccinum aurantiacum (Bull.) Gray in a juvenile hybrid aspen (Populus tremuloides Michx. × Populus tremula L.) plantation in agricultural land initially fertilised with …
Conformational investigation of alpha,beta-dehydropeptides. VIII. N-acetyl-alpha,beta-dehydroamino acid N'-methylamides: conformation and electron de…
2009
The Fourier transform infrared spectra are analyzed in the regions of Vs(N-H), amide I, amide II and Vs(C alpha = C beta) bands for a series of Ac-delta Xaa-NHMe, where delta Xaa = delta Ala, (Z)-delta Abu, (Z)-delta Leu, (Z)-delta Phe and delta Val, to determine the predominant solution conformation of these alpha,beta-dehydropeptide-related molecules and the electron distribution perturbation in their amide bonds. The measurements were performed in dichloromethane (DCM). To confirm and rationalize the assignments, the spectra of the respective series of saturated Ac-Xaa-NHMe, recorded in DCM, and the spectra of these two series of unsaturated and saturated compounds, recorded in acetonitr…
An overview on chemical structures as ΔF508-CFTR correctors
2019
Deletion of phenylalanine at position 508 (F508del) in the CFTR protein, is the most common mutation causing cystic fibrosis (CF). F508del causes misfolding and rapid degradation of CFTR protein a defect that can be targeted with pharmacological agents termed “correctors”. Correctors belong to various chemical classes but are generally small molecules based on nitrogen sulfur or oxygen heterocycles. The mechanism of action of correctors is generally unknown but there is experimental evidence that some of them can directly act on mutant CFTR improving folding and stability. Here we overview the characteristics of the various F508del correctors described so far to obtain indications on key ch…
Stable isotope composition and rare earth element content of vertebrate remains from the Late Cretaceous of northern Spain (Laño): did the environmen…
2003
Abstract Oxygen and carbon isotope measurements have been performed on phosphatic remains from faunal associations (dinosaurs, crocodiles, turtles and fish) of the Late Cretaceous continental and marine sediments from northern Spain (Basque Country). The environmental meaning of the oxygen isotope record in fossil reptiles is discussed on the basis of known paleoecology, modern fauna analogs, and apatite chemistry (rare earth elements (REE), CO32− and PO43− contents). Fossil remains in sandstones and argillites from two localities (Urria and Cuezva) have low (down to 16‰) and scattered δ18O(PO4,CO3) and δ13C values with REE patterns characterized by strong middle REE enrichments. These geoc…
Oxygen isotope and salinity measurements of coastal surface waters in the Gulf of Maine
2020
These data include salinity and oxygen isotope measurements of water samples collected from coastal sites along the Gulf of Maine between 2003 and 2015. In particular, a suite of samples were collected along the coast of Maine, east of Penobscot Bay, on a monthly basis between April 2014 and March 2015. These data also include several freshwater samples collected from the Kennebec and Penobscot Rivers on a semi-monthly basis in 2014 and 2015. For the water samples with sample IDs starting with DSW, JSW, NSW, or OSW: The water samples were collected by hand from shore or boat using French square glass bottles with phenolic polycone lined caps. Salinity was measured using a Oakton SALT 6+ han…