Heavy Atom Effect
Mostrando 1-12 de 14 artigos, teses e dissertações.
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1. Nonperturbative treatment of the screened-Coulomb contribution of projectile-electron loss
The electron-loss cross section of He+ ions impinging upon noble-gas targets (2≤Z2≤36) is calculated by using the coupled-channel method for the active projectile electron in the static screened field of the target atom. The calculations show a saturation of the projectile-electron-loss cross section with increasing target atomic number. This saturation
Publicado em: 2011
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2. SELECTIVE DETERMINATION OF FLUORQUINOLONES FOR CELLULOSE SURFACE ROOMTEMPERATURE PHOSPHORIMETRY WHITH THORIUM NITRATE / DETERMINAÇÃO SELETIVA DE FLUOROQUINOLONAS POR FOSFORIMETRIA NA TEMPERATURA AMBIENTE SUPORTADA EM SUBSTRATO DE CELULOSE COM NITRATO DE TÓRIO
In this work, analytical methods based on solid surface room-temperature phosphorimetry were developed aiming the selective determination of fluorquinolones. More spectilly, thorium nitrate was evaluated as phosphorescence inducer aiming the sequential determination of norfloxacin (NOR) and levofloxacin (LEV), selective determination of NOR in presence of ci
Publicado em: 2007
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3. SOLID SURFACE ROOMTEMPERATURE PHOSPHORIMETRY FOR THE SELETIVE DETERMINATION OF NITROGENATED AND SULPHURATED POLYCICLIC AROMATIC COMPOUNDS INGASOLINE AND SEDIMENT SAMPLE / UTILIZAÇÃO DA FOSFORIMETRIA NA TEMPERATURA AMBIENTE SUPORTADA EM SUBSTRATO SÓLIDO PARA A DETERMINAÇÃO SELETIVA DE COMPOSTOS POLICÍCLICOS AROMÁTICOS NITROGENADOS E SULFURADOS EM GASOLINA E EM SEDIMENTO
Neste trabalho, métodos analíticos baseados na fosforimetria na temperatura ambiente foram desenvolvidos para a determinação de sete compostos policíclicos aromáticos (CPA) sulfurados e nitrogenados presentes do petróleo. Mais especificamente, o objetivo foi o de fornecer ferramentas analíticas que permitissem avaliar e quantificar estes CPA em gasol
Publicado em: 2007
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4. DESENVOLVIMENTO E VALIDAÇÃO DE MÉTODO FOSFORIMÉTRICO EM SUBSTRATO DE CELULOSE PARA DETERMINAÇÃO DE PIRENO E CRISENO / DEVELOPMENT AND VALIDATION OF THE PHOSPHORIMETRIC METHOD IN CELLULOSE SUBSTRATE TO DETERMINATION OF PYRENE AND CHRYSENE
In this work, solid surface room-temperature phosphorimetry (SSRTP) was used to develop ultra-trace and selective methods for determination of chrysene and pyrene in complex samples containing several other polycyclic aromatic hydrocarbons (PAHs). Both chrysene and pyrene were selected because they are classificated by the U.S. Environmental Protection Agenc
Publicado em: 2007
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5. FOSFORIMETRIA NA TEMPERATURA AMBIENTE E EM SUBSTRATO SÓLIDO (FTASS) PARA A DETERMINAÇÃO DE DOIS DERIVADOS DA BETA-CARBOLINA (HARMANE E HARMINE) / SOLID SURFACE ROOM-TEMPERATURE PHOSPHORIMETRY (SSRTP) FOR THE DETERMINATION OF TWO BETA-CARBOLINES DERIVATIVES (HARMANE E HARMINE)
Neste trabalho foi avaliado o uso da Fosforimetria na Temperatura Ambiente em Substrato Sólido (FTASS) como técnica analítica aplicável na determinação de dois derivados da ¿-carbolina (harmane e harmine). Como suporte sólido foi utilizado o papel de filtro de baixo sinal de fundo. As características fosforescentes dos analitos foram estudadas em fu
Publicado em: 2005
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6. Estudos espectroscopicos das propriedades de luminescencia da cumarina a 77K
The luminescence spectra and polarization spectra of coumarin (1,2-benzopyrone), obtained from Tonka Bean (Cumarú) which exist widely in Amazonia, have been investigated in polar and non-polar solvents at 77 K. The emission of coumarin in ethanol (~10M) gives the intensity ratio of phosphorescence and fluorescence as (Irel P/F = 1,29). The emission spectra
Publicado em: 1984
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7. Alguns aspectos de reatividade nucleofilica nas reações de substituição nucleofilica aromatica
In extension of earlier research on the strength of nucleophiles in SNAr reactions, studies have been made of: (i) the reactivity in MeOH of the more important pseudohalide ions, using methoxide ion as reference nucleophile; (ii) the scope of the occurrence of the a-effect, and its magnitude; (iii) the quantitative effects of solvent changes. Thermochemical
Publicado em: 1976
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8. Ligands containing heavy atoms: Perturbation of phosphorescence of a tryptophan residue in the binding site of wheat germ agglutinin
Information on the structure of binding sites of wheat germ agglutinin was obtained on the basis of fluorescence and phosphorescence changes of tryptophan residues induced by the binding of several thiomercuribenzoate derivatives of glycosides. The thiomercuribenzoate derivatives bind selectively to wheat germ agglutinin in the same way as the corresponding
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9. A spectroscopic probe of stacking interactions between nucleic acid bases and tryptophan residues of proteins.
The external heavy atom effect of mercury on the spectroscopic properties of the indole ring has been used to investigate stacking interactions of tryptophan with mercurinucleotides in mixed aggregates formed in frozen aqueous solutions as well as in oligopeptide-polynucleotide complexes. This effect is characterized at 77 K by a quenching of the tryptophan
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10. Effect of Xenon on the Excited States of Phototropic Receptor Flavin in Corn Seedlings 1
The chemically inert, water-soluble heavy atom gas, xenon, at millimolar concentrations specifically quenches the triplet excited state of flavin in solution without quenching the flavin singlet excited state. The preferential quenching of the flavin triplet over the singlet excited state by Xe has been established by showing that the flavin triplet-sensitiz
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11. Photosnesitization of DNA by gold.
Au (III) reacts with DNA at pH 5.6 to form a complex which is sensitive to mid-UV radiation. Cyclobutane pyrimidine dimers are produced at some 15 to 30 times the rate that they are in untreated DNA. The mechanism of photosensitization appears to involve energy absorption by Au-urine and Au-cytosine adducts which can then transfer energy to thymine residues.
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12. Influence of Mercuric Ions on the Phosphorescence and Photochemistry of DNA*
Partial mercuration of DNA, such that roughly one mercuric ion is bound for every two thymine residues, results in an enhancement of the phosphorescence by a factor of ten and a small enhancement of the photosteady thymine dimer yield. Complete mercuration of DNA [one Hg(II) added per momoner unit] results in quenching of the phosphorescence intensity and an