Search results for "trol"
showing 10 items of 16682 documents
A New LA ‐ ICP ‐ MS Method for Ti in Quartz: Implications and Application to High Pressure Rutile‐Quartz Veins from the Czech Erzgebirge
2016
Experimental determination of the pressure and temperature controls on Ti solubility in quartz provides a calibration of the Ti-in-quartz (TitaniQ) geothermometer applicable to geological conditions up to ~ 20 kbar. We present a new method for determining 48Ti mass fractions in quartz by LA-ICP-MS at the 1 μg g−1 level, relevant to quartz in HP-LT terranes. We suggest that natural quartz such as the low-CL rims of the Bishop Tuff quartz (determined by EPMA; 41 ± 2 μg g−1 Ti, 2s) is more suitable than NIST reference glasses as a reference material for low Ti mass fractions because matrix effects are limited, Ca isobaric interferences are avoided, and polyatomic interferences at mass 48 are i…
A solvent-directed stereoselective and electrocatalytic synthesis of diisoeugenol.
2018
A stereoselective and electrocatalytic coupling reaction of isoeugenol has been reported for the first time in a 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP)/boron-doped diamond (BDD) electrode system. This particular C-C bond formation and diastereoselectivity is driven by a solvate interaction between the radical species and another isoeugenol molecule. Due to an electrocatalytic cycle, only understoichiometric amounts of charge are necessary. Since electric current is directly employed as the oxidant, the reaction is metal and reagent-free. In addition, the electrolysis can be conducted in a very simple undivided beaker-type cell under constant current conditions. Therefore, the protocol is …
Nature of (C5Me5)2Mo2O5in water–methanol at pH 0–14. On the existence of (C5Me5)MoO2(OH) and (C5Me5)MoO2+: a stopped-flow kinetic analysis
2002
A stopped-flow analysis of compound Cp*2Mo2O5 (Cp* = η5-C5Me5) in 20% MeOH–H2O over the pH range 0–14 has provided the speciation of this molecule as well as the rate and mechanism of interconversion between the various species that are present in solution. The compound is a strong electrolyte in this solvent combination, producing the Cp*MoO2+ and Cp*MoO3− ions in equilibrium with a small amount of Cp*MoO2(OH), the latter attaining ca. 15% relative amount at pH 4. At low pH ( 6. The acid dissociation constant of Cp*MoO2(OH) has been measured directly (pK = 3.65 ± 0.02) while the pK for the protonation equilibrium leading to Cp*MoO3H2+ is estimated as 5. The prevalent pathway at high pH i…
Structural and metallo selectivity in the assembly of [2 × 2] grid-type metallosupramolecular species: Mechanisms and kinetic control
2011
An unsymmetrical bis(tridentate) ligand LH in which one binding site can be readily deprotonated forms a kinetically inert [Co(III)L(2)](+) complex which can be used as a "corner" species for the "Coupe du Roi" assembly of trans,trans-[Co(2)M(2)L(4)](6+) metallogrids (M = Fe(II), Co(II), Cu(II), Zn(II)). In the mixed Co(III)/Co(II) species, the oxidation states appear to be localised. In solution, the ligand LH forms octacationic, homometallic [2 × 2] grids with the individual labile metal ions Fe(II), Co(II), Cu(II), Zn(II), seemingly as mixtures of all possible isomers arising from the unsymmetrical nature of the ligand. In the solid state, however, [Zn(4)L(4)](CF(3)SO(3))(8)·4CH(3)CN cry…
Electrochemical and spectroelectrochemical studies of β-phosphorylated Zn porphyrins
2013
The electrochemical and spectroelectrochemical properties of two β-phosphorylated Zn porphyrins, [2-diethoxyphosphoryl-5,10,15,20-tetraphenylporphyrinato]zinc (1) and [2-diisopropoxyphosphoryl-5,10,15,20-tetraphenylporphyrinato]zinc (2), are reported in CH 2 Cl 2 and PhCN containing tetrabutylammonium perchlorate (TBAP) or tetrabutylammonium hexafluorophosphate (TBAPF6) as supporting electrolyte. Under certain solution conditions, three one-electron reductions are observed, with the last process being attributed to the product of a chemical reaction following formation of the porphyrin dianion. Two or three oxidations are observed for the same compounds, again depending upon the solution c…
Diabetes and renin-angiotensin-aldosterone system: Implications for covid-19 patients with diabetes treatment management
2020
In the context of the COVID-19 continuous spreading, this paper focuses on the increased risk of diabetic patients regarding the metabolic control and the uncertainties related to SARS-CoV-2 infection. Chronic hyperglycaemia negatively affects the immune system, which triggers an increase of morbidity and mortality for viral infections. A key aspect of COVID-19 resides in the involvement of renin-angiotensin-aldosterone (RAAS) system that causes a cascade of reactions mediated by vasoactive peptides with implications in vasoconstriction, vascular permeability, oxidative stress remodelling and tissue injuries. Activation of RAAS at pulmonary level, is responsible for the local damage. Many q…
Optimal Dynamic Portfolio Risk Management
2016
Numerous econometric studies report that financial asset volatilities and correlations are time-varying and predictable. Over the past decade, this knowledge has stimulated increasing interest in various dynamic portfolio risk control techniques. The two basic types of risk control techniques are: risk control across assets and risk control over time. At present, the two types of risk control techniques are not implemented simultaneously. There has been surprisingly little theoretical study of optimal dynamic portfolio risk management. In this paper, the author fills this gap in the literature by formulating and solving the multi-period portfolio choice problem. In terms of dynamic portfoli…
Global trends in NDVI-derived parameters obtained from GIMMS data
2011
The Normalized Difference Vegetation Index (NDVI) has been proven to be useful to assess vegetation changes around the world, in spite of limitations such as sensitivity to cloud or snow contamination. In order to map vegetation changes at global scale, this study uses NDVI time series provided by the GIMMS (Global Inventory Modeling and Mapping Studies) group, which were fitted annually to a double logistic function. This fitting procedure allowed for retrieval of NDVI-derived parameters which were tested for trends using Mann-Kendall statistics. These trends were validated by comparison at 73 ground control points documented as change hotspots. The obtained trends for NDVI-derived paramet…
A Global Sensitivity Analysis Toolbox to Quantify Drivers of Vegetation Radiative Transfer Models
2017
Abstract Global sensitivity analysis (GSA) enables to gain insight into the functioning of radiative transfer models (RTMs) by identifying the driving input variables of RTM spectral outputs such as reflectance, fluorescence, or radiance. This contribution introduces automated radiative transfer models operator's (ARTMO’s) new GSA toolbox. With the GSA toolbox the majority of ARTMO’s available RTMs can be decomposed into its driving variables. For a selected RTM output, a GSA identifies the most influential and noninfluential input variables according to Sobol' first-order and total-order indices. The toolbox can process RTM spectral outputs for any kind of optical sensor setting within the…
Generation of global vegetation products from EUMETSAT AVHRR/METOP satellites
2020
We describe the methodology applied for the retrieval of global LAI, FAPAR and FVC from Advanced Very High Resolution Radiometer (AVHRR) onboard the Meteorological-Operational (MetOp) polar orbiting satellites also known as EUMETSAT Polar System (EPS). A novel approach has been developed for the joint retrieval of three parameters (LAI, FVC, and FAPAR) instead of training one model per parameter. The method relies on multi-output Gaussian Processes Regression (GPR) trained over PROSAIL EPS simulations. A sensitivity analysis is performed to assess several sources of uncertainties in retrievals and maximize the positive impact of modeling the noise in training simulations. We describe the ma…