Search results for "ISOTOPES"
showing 10 items of 1216 documents
Effect of L-Histidine on the Survival of a T-Strain of Mycoplasma
1975
The addition of L-histidine to the growth medium prolongs the stationary phase and the survival of a T-strain of mycoplasma. Results of an experiment performed with 14 C-labeled urea demonstrate that the action of L-histidine is based on the retardation of the rise of pH.
Strontium/lithium ratio in aragonitic shells of Cerastoderma edule (Bivalvia) — A new potential temperature proxy for brackish environments
2015
Abstract Quantitative reconstruction of water temperature from shells of bivalve mollusks is still a very challenging task. For example, in highly variable environments such as intertidal zones, shell oxygen isotope values can only provide reliable temperature estimates if the δ18Owater signature during the time of growth is known. Furthermore, trace element-to-calcium ratios such as Sr/Ca or Mg/Ca often do not serve as reliable paleothermometers, because their incorporation into bivalve shells is known to be strongly biologically controlled. Here, we present a potential novel temperature proxy which is based on the Sr/Lishell ratio of the intertidal bivalve Cerastoderma edule. Up to 81% of…
Fourier-transform spectroscopy of (4)1Σ+→A 1Σ+−b 3Π,A 1Σ+−b 3Π →X1Σ+, and (1)3Δ1→bΠ0±3 transitions in KCs and deperturbation treatment ofA 1Σ+andb 3Π…
2013
High resolution Fourier-transform spectroscopy data of term values in the spin-orbit (SO) coupled first excited A 1Σ+ and b 3Π states in KCs were obtained from (4)1Σ+ → A 1Σ+ − b 3Π, A 1Σ+ − b 3Π → X1Σ+, and (1)3Δ1→bΠ0±3 spectra of laser-induced fluorescence (LIF). About 3000 new rovibronic term values of the A 1Σ+ and b3ΠΩ states were obtained with an uncertainty about 0.01 cm−1 and added to the previously obtained 3439 term values in Kruzins et al. [Phys. Rev. A 81, 042509 (2010)] and 30 term values of the b3Π0+ state levels below the A 1Σ+ state in Tamanis et al. [Phys. Rev. A 82, 032506 (2010)]. The data field was extended considerably, going down to vibrational level vb = 0 and up in e…
The conductance of lithium-7 fluoride in dioxane-water mixtures at 25�C
1990
Conductance data for lithium-7 fluoride in dioxane-water mixtures covering the range 78.35>D>36 in dielectric constant are presented. These data and other previous data on lithium-7 chloride and lithium-7 iodide were analyzed by the Fuoss 1980 conductance equation in order to find the limiting conductance Δo, the pairing distance R and the conductometric association constant Kλ. Setting Ka=Kλ/VM (where VM is the molar volume of the solvent), the thermodynamic pairing constant and the corresponding change of the free energy Δg were calculated. Correlation among the values found for R and Δg=Δh−TΔs and the properties characteristic of the ions and solvents are discussed.
Assessment of a single-acquisition imaging sequence for oxygen-sensitive (3)He-MRI.
2001
MRI of the lungs using hyperpolarized helium-3 (3He) allows the determination of intrapulmonary oxygen partial pressures (pO2). The need to separate competing processes of signal loss has hitherto required two different imaging series during two different breathing maneuvers. In this work, a new imaging strategy to measure pO2 by a single series of consecutive scans is presented. The feasibility of the method is demonstrated in three healthy human volunteers. Maps and histograms of intrapulmonary pO2 are calculated. Changes in the oxygen concentration of the inhaled gas mixture are well reproduced in the histograms. Monte Carlo (MC) simulations of the temporal evolution of 3He hyperpolariza…
Tracing anthropogenic thallium in soil using stable isotope compositions.
2014
Thallium stable isotope data are used in this study, for the first time, to apportion Tl contamination in soils. In the late 1970s, a cement plant near Lengerich, Germany, emitted cement kiln dust (CKD) with high Tl contents, due to cocombustion of Tl-enriched pyrite roasting waste. Locally contaminated soil profiles were obtained down to 1 m depth and the samples are in accord with a binary mixing relationship in a diagram of Tl isotope compositions (expressed as e(205)Tl, the deviation of the (205)Tl/(203)Tl ratio of a sample from the NIST SRM 997 Tl isotope standard in parts per 10(4)) versus 1/[Tl]. The inferred mixing endmembers are the geogenic background, as defined by isotopically l…
Organic matter quantity and quality, metals availability and foraminiferal assemblages as environmental proxy applied to the Bizerte Lagoon (Tunisia)
2016
International audience; This study analyzes the benthic trophic state of Bizerte Lagoon (Tunisia) based on the total organic matter and the bioavailability of biopolymeric carbon including proteins (PTN), carbohydrates (CHO), lipids (LIP), chlorophyll a, as well as bacteria counts. The overall simultaneously extracted metals (SEM), and acid volatile sulfides (AVS) as well as the SEM/AVS ratio indicative of the toxicity of the sediments also were analyzed aiming to study their impact in the dimension, composition and structure of both dead and living benthic foraminiferal assemblages.In the studied sites TOC content is relatively high and the PTN/CHO values indicate that they can be consider…
Organic carbon and nitrogen stable isotopes in the intertidal sediments from the Yangtze Estuary, China
2005
The natural isotopic compositions and C/N elemental ratios of sedimentary organic matter were determined in the intertidal flat of the Yangtze Estuary. The results showed that the ratios of carbon and nitrogen stable isotopes were respectively -29.8 per thousand to -26.0 per thousand and 1.6 per thousand-5.5 per thousand in the flood season (July), while they were -27.3 per thousand to -25.6 per thousand and 1.7 per thousand-7.8 per thousand in the dry season (February), respectively. The delta(13)C signatures were remarkably higher in July than in February, and gradually increased from the freshwater areas to the brackish areas. In contrast, there were relatively complex seasonal and spati…
A Method to Quantitatively Trap Volatilized Organoselenides for Stable Selenium Isotope Analysis
2011
If volatile organoselenides are to be analyzed for their stable Se isotope composition to elucidate sources and formation processes, organoselenides need to be trapped quantitatively to avoid artificial Se isotope fractionation. We developed an efficient trap of organoselenides to be used in microcosms designed to determine the Se isotope fractionation by microbial transformation of inorganic Se to volatile organoselenides. The recoveries of volatilized dimethyldiselenide (DMDSe) from aqueous standard solutions by activated charcoal and alkaline peroxide solution with subsequent freeze-drying and purification via a cation exchange resin were tested. Microcosm experiments with the Se-methyla…
Processing of Generator-Produced 68Ga for Medical Application
2007
The (68)Ge/(68)Ga generator provides an excellent source of positron-emitting (68)Ga. However, newly available "ionic" (68)Ge/(68)Ga radionuclide generators are not necessarily optimized for the synthesis of (68)Ga-labeled radiopharmaceuticals. The eluates have rather large volumes, a high concentration of H(+) (pH of 1), a breakthrough of (68)Ge, increasing with time or frequency of use, and impurities such as stable Zn(II) generated by the decay of (68)Ga, Ti(IV) as a constituent of the column material, and Fe(III) as a general impurity.We have developed an efficient route for the processing of generator-derived (68)Ga eluates, including the labeling and purification of biomolecules. Prec…