Search results for "RATIO"
showing 10 items of 33258 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…
High-resolution rovibrational spectroscopy of c-C3H2+: The ν7 C–H antisymmetric stretching band
2020
Abstract The ν 7 antisymmetric C–H stretching fundamental of c- C 3 H 2 + has been characterized in a cryogenic 22-pole ion trap by a novel type of action spectroscopy, in which the rovibrational excitation of c- C 3 H 2 + is detected as a slowing down of the low-temperature reaction c- C 3 H 2 + + H2 → C 3 H 3 + + H. Ninety-one rovibrational transitions with partly resolved fine structure doublets were measured in high resolution. Supported by high-level quantum chemical calculations, spectroscopic parameters were determined by fitting the observed lines with an effective Hamiltonian for an asymmetric rotor in a doublet electronic ground state, X ˜ A 1 2 , yielding a band origin at 3113.6…
Thorough evaluation of OECD principles in modelling of 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine derivatives using QSARINS.
2020
The human immunodeficiency virus is a lethal pathology considered as a worldwide problem. The search for new strategies for the treatment of this disease continues to be a great challenge in the scientific community. In this study, a series of 107 derivatives of 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine, previously evaluated experimentally against HIV-I reverse transcriptase, was used to model antiretroviral activity. A model of linear regression, implemented in the QSARINS software, was developed with a genetic algorithm for variable selection. The fit of its parameters was good and exhaustive validation, according to the OECD regulatory principles, was performed. Also, the applica…
Localization of alkali metal ions in sodium-promoted palladium catalysts as studied by low energy ion scattering and transmission electron microscopy
1996
Three series of palladium-based catalysts have been studied by Low Energy Ion Scattering (LEIS) and Transmission Electron Microscopy (TEM). The first series is comprised of Na-Pd/SiO{sub 2} catalysts, obtained by addition of palladium to a silica support and by further addition of sodium ions with a Na/Pd atomic ratio (R) equal to 0,6.4 and 25.6. The second series consists of palladium catalysts supported on natural pumice, in which, due to a different loading of supported palladium, R{prime}, the (Na+K)/Pd atomic ratio, is equal to 17.0 and 39.4. The third series is represented by two palladium-based catalysts supported on {open_quotes}model pumices,{close_quotes} synthetic silico-aluminat…
Encapsulation and solid state sequestration of gases by calix[6]arene-based molecular containers
2017
Two calix[6]arene-based molecular containers were synthesized in high yields. These containers can encapsulate small guests through a unique "rotating door" complexation process. The sequestration of greenhouse gases is clearly demonstrated. They can be stored in the solid state for long periods and released via dissolution of the inclusion complex.
Synthesis of substituted piperidines by enantioselective desymmetrizing intramolecular aza-Michael reactions.
2018
An organocatalytic enantioselective intramolecular aza-Michael reaction has been described for the first time in a desymmetrization process employing substrates different from cyclohexadienones. By using 9-amino-9-deoxy-epi-hydroquinine as the catalyst and trifluoroacetic acid as a co-catalyst, a series of enantiomerically enriched 2,5-and 2,6-disubstituted piperidines have been obtained in good yields and with moderate diastereoselectivity. Depending on the catalyst/co-catalyst loading ratio, either the major or the minor diastereoisomer of the final piperidine products was achieved with high levels of enantioselectivity. Finally, some mechanistic insights have been considered by means of …
Protonation and Electrochemical Properties of Pyridyl- and Sulfonatophenyl-Substituted Porphyrins in Nonaqueous Media
2017
International audience; The protonation and electrochemical properties of positively charged and negatively charged porphyrins are reported in up to five different nonaqueous solvents. The positively charged porphyrins are represented by mono- and di-pyridyl derivatives having the formula Pyx(PhMe)4-xPM, where P=the dianion of the porphyrin macrocycle, PhMe is a meso-tolyl group, Py a meso-pyridyl group, x=1 or 2, and M=H2, NiII, CuII, ZnII, or CoII. The negatively charged porphyrins are comprised of meso-tetrasulfonato derivatives having the formula [(R)4(TPPS)H2]4−(X+)4, where [(TPPS)H2]4− represents the porphyrin with four SO3− groups on the meso-phenyl substituents of the macrocycle, R=…
Fluorine-Containing Drugs Approved by the FDA in 2018
2019
Over the last two decades, fluorine substitution has become one of the essential structural traits in modern pharmaceuticals. Thus, about half of the most successful drugs (blockbuster drugs) contain fluorine atoms. In this review, we profile 17 fluorine-containing drugs approved by the food and drug administration (FDA) in 2018. The newly approved pharmaceuticals feature several types of aromatic F and CF3 , as well as aliphatic (CF2 ) substitution, offering advances in the treatment of various diseases, including cancer, HIV, malarial and smallpox infections.
A Generalized Semiempirical Approach to the Modeling of the Optical Band Gap of Ternary Al-(Ga, Nb, Ta, W) Oxides Containing Different Alumina Polymo…
2021
A generalization of the modeling equation of optical band gap values for ternary oxides, as a function of cationic ratio composition, is carried out based on the semiempirical correlation between the differences in the electronegativity of oxygen and the average cationic electronegativity proposed some years ago. In this work, a novel approach is suggested to account for the differences in the band gap values of the different polymorphs of binary oxides as well as for ternary oxides existing in different crystalline structures. A preliminary test on the validity of the proposed modeling equations has been carried out by using the numerous experimental data pertaining to alumina and gallia p…
Linking PO43− and HAsO42− anions with a dinuclear [ZnII2] complex: Formation and stabilization of novel decanuclear metallomacrocyclic [ZnII10] and t…
2017
The linkage of PO43- and HAsO42--anions with a newly synthesized five-coordinate dinuclear zinc complex, Zn-2(cpdp)(H2O)(2)]Cl (1) H(3)cpdp =N,N'-bis2-carboxybenzomethyl]-N,N'-bis2-pyridylmethyl]-1,3diamino propan-2-ol], has been explored. In methanol-water, the reaction of 1 with Na2HPO4 center dot 2H(2)O and Na2HAsO4 center dot 7H(2)O/NaBr separately, at ambient temperature, yielded the novel phosphate-bridged decanuclear zinc cluster, (H3O)(4)Zn-10(cPdP)(4)(mu(5)-PO4)(2)(H2O)(6)](6 center dot Cl)center dot 53H(2)O (2) and hydrogen arsenate bridged tetranuclear zinc cluster, Na-2Zn-4(cpdp)(2)(mu(4)-HAsO4)]ClBr center dot 13H(2)O (3), respectively. Analysis of the single crystal X-ray stru…