Metal To Non Metal To Metal Transition
Mostrando 13-24 de 24 artigos, teses e dissertações.
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13. Síntese e espectroscopia de sistemas envolvendo tungstatos e íons de terras raras / Synthesis and spectroscopy of system envolving tungstates and rare earth ions
The studies about the photoluminescent properties of the rare earth tungstates Eu2(WO4)3 and Gd2(WO4)3:RE3+ (RE3+ = Eu, Sm and Tb) obtained via three different methods of preparation were reported: i) ceramic method, which is the older one and uses high temperatures (>1000 ºC) and long periods of heating, with the physical mixture of the reagents in the pow
Publicado em: 2003
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14. Estudo do efeito da substituição quimica nas propriedades de compostos intermetalicos de Yb e U
In the present work we studied the effect of the chemical substitution on the properties of Yb and U systems through the series Yl-xYbxCuAl, YbNi1-xCuxAl, YbInNi4-xCux, Y1-xYbxInNi4, U(Gel-xSnx)2, U(Gel-xNix)2 e Yl-xUxGe2. The results of resistivity, speci:fic heat and magnetization showed that the chemical substitution leads to modi:fication on the ground s
Publicado em: 2002
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15. Participação do oxido nitrico no desenvolvimento da encefalomielite alergica experimental em ratos
Nitric oxide (NO) is a free radical endogenously synthetised by oxidation of one of the guanidinum nitrogen atoms of the aminoacid L-arginine by molecular oxygen. This biosynthesis is catalised by a family of enzimes generically known as nitric oxide synthases (NOS), which can be inhibited by structural analogs of L-arginine having substituent groups at the
Publicado em: 2001
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16. Heteroestruturas de semicondutores na presença de campos AC intensos
The study of coupling of the electronic structure of a semiconductor heterostructure with strong AC fields, is the main purpose of the present work. The interaction of the electronic structure of a heterostructure with an AC field of determined frequency is given by a time-independent Hamiltonian which replaces a semiclassic time- dependent Hamiltonian. The
Publicado em: 1998
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17. Propriedades eletrônicas do monocalcogenetos de Sm e de ligas do tipo Sm1-xMxS
We present a theoretical model to explain the valence transitions of Sm in Sm1-xMxS alloys, where M is a transition metal (e.g. Y or La) as a function of the concentration x. The system is described by a two-band model: a zero width band of energy E0 (the 4f-level of Sm) and a conduction band, which is treated in the coherent potencial approximation (CPA). T
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 1981
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18. Compostos de coordenação de trimorfolino fosfonoxido com alguns metais de transição
Adducts between Trimorpholinophosphine oxide (MORPO) and hydratated bromides, perchlorates and hexafluorophosphates of some divalents transition metals were obtained the compounds of the bromides presented the general formulas MBr2.2MORPO in which M = Mn, Co, Cu and Zn and NiBr2.2(MORPO).2H2O. The compounds of the perchlorates presented the general formula M
Publicado em: 1977
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19. Structure of the complex of active site metal-depleted horse liver alcohol dehydrogenase and NADH.
The complex between active site-specific metal-depleted horse liver alcohol dehydrogenase and NADH has been studied with X-ray crystallographic methods to 2.9 A resolution. The electron density maps revealed that only the catalytic zinc ions are removed, whereas the non-catalytic zinc sites ae fully occupied. A gross conformational change in the protein indu
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20. Divalent transition metal cations counteract potassium-induced quadruplex assembly of oligo(dG) sequences.
Nucleic acids containing tracts of contiguous guanines tend to self-associate into four-stranded (quadruplex) structures, based on reciprocal non-Watson-Crick (G*G*G*G) hydrogen bonds. The quadruplex structure is induced/stabilized by monovalent cations, particularly potassium. Using circular dichroism, we have determined that the induction/stabilization of
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21. Five-fold symmetry in crystalline quasicrystal lattices
To demonstrate that crystallographic methods can be applied to index and interpret diffraction patterns from well-ordered quasicrystals that display non-crystallographic 5-fold symmetry, we have characterized the properties of a series of periodic two-dimensional lattices built from pentagons, called Fibonacci pentilings, which resemble aperiodic Penros
The National Academy of Sciences of the USA.
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22. X-ray structures of a novel acid phosphatase from Escherichia blattae and its complex with the transition-state analog molybdate
The structure of Escherichia blattae non-specific acid phosphatase (EB-NSAP) has been determined at 1.9 Å resolution with a bound sulfate marking the phosphate-binding site. The enzyme is a 150 kDa homohexamer. EB-NSAP shares a conserved sequence motif not only with several lipid phosphatases and the mammalian glucose-6-phosphatases, but also with the vana
Oxford University Press.
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23. Conformational lability of poly(dG-m5dC):poly(dG-m5dC).
The remarkable conformational lability of poly(dG-m5dC):poly(dG-m5dC) is demonstrated by the observation of an acid-mediated conformational hysteresis. An acid-mediated Z conformation that exists in solutions containing low sodium concentrations that would normally favor the B conformation is described in this report. This Z conformation is reached by an aci
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24. Modulation of GABA-mediated synaptic transmission by endogenous zinc in the immature rat hippocampus in vitro.
1. Intracellular recordings from postnatal 2- to 12-day-old (P2-12) rat hippocampal CA3 pyramidal neurones exhibited spontaneous synaptic potentials mediated by GABAA receptors. These potentials can be separated on the basis of amplitude into two classes which are referred to as small and large. 2. The large depolarizing potentials were reversibly inhibited