Search results for "Coupled"
showing 10 items of 742 documents
Assessment of Five Monazite Reference Materials for U-Th/Pb Dating Using Laser-Ablation ICP-MS
2019
Monazite is a common accessory phosphate mineral that occurs under a wide range of pressure and temperature conditions in sedimentary, metamorphic and igneous rocks. Monazite contains high amounts of Th and U, rendering single monazite grains suitable for in-situ U-Th/Pb dating using laser ablation inductively-coupled mass spectrometry (LA-ICP-MS). Two key aspects of monazite dating that are critical for accurate age data with maximum precision are (i) optimized instrumental conditions to minimize analytical scatter and (ii) a well characterized reference material to ensure the accuracy of the obtained aged. Here, we analyzed five monazite reference materials (USGS 44069, 94-222, MAdel, Moa…
Comparative LA-ICP-IDMS determinations of trace elements in powdered samples using laser ablation systems with low and high ablation rates
2004
The results of laser ablation inductively coupled plasma isotope dilution mass spectrometry (LA-ICP-IDMS) with a special laser ablation system with high ablation rates (LINA-Spark-Atomiser), which was constructed for bulk analyses of solid samples, are compared with those obtained by one of the commonly used LA systems (UP213). Using different reference materials for validation it was demonstrated that the accuracy of LA-ICP-IDMS determinations of elements like Fe, Cu, Pb, and Zn by both systems is comparable in the concentration range of 10−2–10−6 g g−1, but the LINA-Spark-Atomiser also provides accurate results in the sub-μg g−1 range. IDMS enables accurate calibration of LA-ICP-MS determ…
(Table 1) Geochemistry of ODP Site 160-963 sediments
2010
The Mediterranean Sea acts as a miniature ocean with the development of its own conveyor belt. It constitutes an ideal location to study and forecast how the marine environment responds to rapid climatic change. Here we present a palaeoenvironmental study carried out on the sediments of ODP Site 963, recovered in the Sicily Channel, the sill which divides the western from the eastern Mediterranean basin. We focused on the transition between the penultimate glacial (MIS 6) and the last interglacial (MIS 5), between approximately 130 and 115 kyr BP. A novel approach is proposed, taking into account centennial-scale geochemical data on major elements, selected trace elements, and yttrium and R…
(Table 1) Trace element/Ca ratios of Orbulina universa shells from late Neogene Mediterranean samples
2008
A Mediterranean composite sedimentary record was analyzed for Ba/Ca ratios on carbonate shells of Orbulina universa planktonic foraminifer (Ba/Ca)carb providing the opportunity to study and assess the extent of freshwater inputs on the basin and possible impacts on its dynamics during the Tortonian to Recent period. A number of scanning electron microscope analyses and auxiliary trace element measurements (Mn, Sr, and Mg), obtained from the same samples, exclude important diagenetic effects on the studied biogenic carbonates and corroborate the reliability of (Ba/Ca)carb ratios in foraminifera calcite as indicators of seawater source components during the studied interval. A long-term trend…
Predictive First-Principles Modeling of a Photosynthetic Antenna Protein: The Fenna–Matthews–Olson Complex
2020
High efficiency of light harvesting in photosynthetic pigment–protein complexes is governed by evolutionary-perfected protein-assisted tuning of individual pigment properties and interpigment interactions. Due to the large number of spectrally overlapping pigments in a typical photosynthetic complex, experimental methods often fail to unambiguously identify individual chromophore properties. Here, we report a first-principles-based modeling protocol capable of predicting properties of pigments in protein environment to a high precision. The technique was applied to successfully uncover electronic properties of the Fenna–Matthews–Olson (FMO) pigment–protein complex. Each of the three subunit…
Mitochondrial G protein coupled receptor kinase 2 regulates proinflammatory responses in macrophages.
2013
G-protein-coupled receptor kinase 2 (GRK2) levels are elevated in inflammation but its role is not clear yet. Here we show that GRK2 expression is dependent on NFκB transcriptional activity. In macrophages, LPS induces GRK2 accumulation in mitochondria increasing biogenesis. The overexpression of the carboxy-terminal domain of GRK2 (βARK-ct), known to displace GRK2 from plasma membranes, in macrophages induces earlier localization of GRK2 in mitochondria in response to LPS leading to increased mt-DNA transcription, reduced ROS production and cytokines expression. Our study shows the relevance of GRK2 subcellular localization in macrophage’s biology and its potential therapeutic properties i…
Sphingosine-1-phosphate increases human alveolar epithelial IL-8 secretion, proliferation and neutrophil chemotaxis
2009
Sphingosine-1-phosphate (S1P) has been presented recently as a pro-inflammatory agent in the airway epithelium since S1P levels are increased in bronchoalveolar lavage fluid of human asthmatics. However, the effects of S1P over the alveolar epithelium and neutrophil interactions are poorly understood. Here, we show that S1P increased interleukin 8 (IL-8) gene expression and protein secretion and proliferation in alveolar epithelial cells A549 at physiological concentrations (1 microM). At the same time, S1P increased intracellular Ca2+ concentration (potency 17.91 microM, measured by epifluorescence microscopy), phospholipase D (PLD) activity (measured by chemiluminiscence method) and extra…
Global stability of coupled Markovian switching reaction–diffusion systems on networks
2014
Abstract In this paper, we investigate the stability problem for some Markovian switching reaction–diffusion coupled systems on networks (MSRDCSNs). By using the Lyapunov function, we establish some novel stability principles for stochastic stability, asymptotically stochastic stability, globally asymptotically stochastic stability and almost surely exponential stability of the MSRDCSNs. These stability principles have a close relation to the topology property of the network. We also provide a systematic method for constructing global Lyapunov function for these MSRDCSNs by using graph theory. The new method can help analyze the dynamics of complex networks.
Calcium Carbonate and Phosphate Reference Materials for Monitoring Bulk and Microanalytical Determination of Sr Isotopes
2017
In situ laser ablation analyses rely on the microanalytical homogeneity of reference materials (RMs) and a similar matrix and mass fraction between unknown samples and RMs to obtain reliable results. Suitable carbonate and phosphate RMs for determination of Sr isotope ratios in such materials are limited. Thus, we determined Sr-87/Sr-86 ratios of several carbonate (JCt-1, JCp-1, MACS-1, MACS-3) and phosphate (MAPS-4, MAPS-5, NIST SRM 1400, NIST SRM 1486) international RMs using dissolved samples and two different multi-collector inductively coupled plasma-mass spectrometers (MC-ICP-MS). Our Sr isotope data are in agreement with published data and have an improved measurement precision for s…
The neuropeptide PACAP promotes ?‐secretase pathway for processing Alzheimer amyloid precursor protein
2006
SPECIFIC AIMSProteolytic cleavage of the amyloid precursor protein (APP) by α-secretase within the Aβ sequence precludes formation of amyloidogenic peptides and leads to a release of soluble APPsα,...