Search results for " SPECT"
showing 10 items of 11464 documents
A coincidence-point problem of Perov type on rectangular cone metric spaces
2017
We consider a coincidence-point problem in the setting of rectangular cone metric spaces. Using alpha-admissible mappings and following Perov's approach, we establish some existence and uniqueness results for two self-mappings. Under a compatibility assumption, we also solve a common fixed-point problem.
The essential spectrum of AM-compact operators
1991
Homoleptic heavy alkaline Earth and europium triazenides.
2009
The sigma-bond metathesis reaction between PhSiH(3) and the heteroleptic metal pentafluorophenyl compounds [Dmp(Tph)N(3)MC(6)F(5)(thf)(n)] (Dmp = 2,6-Mes(2)C(6)H(3) with Mes = 2,4,6-Me(3)C(6)H(2); Tph = 2-TripC(6)H(4) with Trip = 2,4,6-(i)Pr(3)C(6)H(2); n = 1, 2; M = Sr, Ba, Eu) supported by sterically crowded, biphenyl- and terphenyl-substituented triazenido ligands afforded the first homoleptic stontium, barium, and europium triazenides [M{N(3)Dmp(Tph)}(2)] {M = Sr (2), Ba (4), Eu (5)}. Crystallization of 2 from an n-heptane/1,2-dimethoxyethane mixture gave the complex [Sr{N(3)Dmp(Tph)}(2)(dme)] (3). All new compounds have been characterized by (1)H and (13)C NMR spectroscopy (not 5), ele…
An improved cathode for alkaline fuel cells
2010
Abstract The use of nickel foam as an electrode substrate in alkaline fuel cells (AFCs) has been investigated for bipolar cells incorporating an electrically conducting gas diffusion layer (GDL). Improved performance, compared to a previous design, was obtained by adding an extra active layer (AL) composed of manganese (IV) oxide (MnO2) deposited onto carbon black. This new cathode design performed significantly better (130 mA cm−2 at 0.8 V and 25 °C) than the previous design (35 mA cm−2 under the same condition), especially at higher potential. It has been shown that the GDL is a key component of the gas diffusion electrode for both performance and durability, especially with liquid electr…
Cytotoxic Activity and Composition of Petroleum Ether Extract from Magydaris tomentosa (Desf.) W. D. J. Koch (Apiaceae)
2015
The petroleum ether extract of Magydaris tomentosa flowers (Desf.) W. D. J. Koch has been analyzed by GC-MS. It is mainly constituted by furanocoumarins such as xanthotoxin, xanthotoxol, isopimpinellin, and bergaptene. Other coumarins such as 7-methoxy-8-(2-formyl-2-methylpropyl) coumarin and osthole also occurred. The antiproliferative activity of Magydaris tomentosa flower extract has been evaluated in vitro on murine monocye/macrophages (J774A.1), human melanoma (A375) and human breast cancer (MCF-7) tumor cell lines, showing a major activity against the latter.
Reaction products and pathways in the selective oxidation of C-2-C-4 alkanes on MoVTeNb mixed oxide catalysts
2010
[EN] The catalytic properties of MoVTeNbO catalysts during the selective oxidation of short chain alkanes and olefins (C-2-C-4) have been comparatively studied The main reaction products have been ethylene from ethane acrylic acid from propane maim anhydride from n-butane and methacrolein from isobutane FTIR studies of the adsorption of the main reaction products i e olefins and aldehydes over MoVTeNbO catalyst has been carried out Accordingly the reaction pathway is explained on the basis of the characteristics of the alkane fed the stability and reactivity of both the intermediates and the reaction products and the nature of the catalytic sites involved in each reaction (C) 2010 Elsevier …
Catalytic cracking of n-alkane naphtha: The impact of olefin addition and active sites differentiation
2015
An extended dual kinetic model allows to fit the n-heptane cracking results working in a wide range of reaction conditions. The duality of the model is provided by the contribution of monomolecular and bimolecular cracking mechanisms. It takes into account the role played by the olefins formed on the global cracking or added within the feed. Furthermore by means of this model and the kinetic parameters obtained when cracking n-heptane on ZSM-5, it has been observed that, while some characterization techniques show a homogeneous zeolite surface from the point of view of the active sites, rigorous kinetic experiments point to the possibility that the reactant sees a heterogeneous surface with…
Supramolecular Aggregates in Vacuum: Positively Mono-Charged Sodium Alkanesulfonate Clusters
2010
The formation and structural features of positively mono-charged aggregates of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and sodium methane—(MetS), butane—(ButS) and octane—(OctS) sulfonate molecules in the gas phase have been investigated by electrospray ionization mass spectrometry, energy-resolved mass spectrometry and density functional theory (DFT) calculations. The experimental results show that the center-of-mass collision energy required to dissociate 50% of these mono-charged aggregates scantly depends on the length of the alkyl chain as well as on the aggregation number. This, together with the large predominance of mono-charged species in the mass spectra, was rationalized i…
A multifunctional bioconjugate module for versatile photoaffinity labeling and click chemistry of RNA
2011
A multifunctional reagent based on a coumarin scaffold was developed for derivatization of naive RNA. The alkylating agent N3BC [7-azido-4-(bromomethyl)coumarin], obtained by Pechmann condensation, is selective for uridine. N3BC and its RNA conjugates are pre-fluorophores which permits controlled modular and stepwise RNA derivatization. The success of RNA alkylation by N3BC can be monitored by photolysis of the azido moiety, which generates a coumarin fluorophore that can be excited with UV light of 320 nm. The azidocoumarin-modified RNA can be flexibly employed in structure-function studies. Versatile applications include direct use in photo-crosslinking studies to cognate proteins, as dem…
A Combination of Visible-Light Organophotoredox Catalysis and Asymmetric Organocatalysis for the Enantioselective Mannich Reaction of Dihydroquinoxal…
2019
[EN] An enantioselective photooxidative Mannich reaction of dihydroquinoxalinones with ketones by the merger of organophotoredox and asymmetric organocatalysis is described. This protocol features very mild reaction conditions using simple and cheap catalysts (Eosin Y and (S)-Proline) for the synthesis of chiral quinoxaline derivatives with good to high yields (up to 94%) and excellent enantioselectivities (up to 99% ee).