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Papers by Voicu Grecu

Research paper thumbnail of EPR study of complex formation between copper (II) ions and sympathomimetic amines in aqueous solution

Il Nuovo Cimento D, 1997

The complex formation between sympathomimetic amines (SA): adrenaline (AD), noradrenaline (NA), d... more The complex formation between sympathomimetic amines (SA): adrenaline (AD), noradrenaline (NA), dopamine (DA), ephedrine (ED) and p-tyramine (pTA), and Cu(II) ion in aqueous solution has been studied by X-band EPR at room temperature. Excepting pTA, all investigated SA yielded two types of complexes in different pH domains. All complexes presented a g ll D g » relationship, consistent with a ligand field having a distorted octahedral symmetry, i.e. hexacoordination of Cu(II). The covalence coefficient calculated from the isotropic g and A values has shown strong ionic sigma-type ligand bonds. A structural model with the Cu(II) ion bound by four catecholic O(hydroxy) atoms for the low pH complexes of AD, NA, and DA is proposed. For the high pH complexes of the former compounds as well as for both ED complexes, we suppose Cu(II) bound by two N (amino) and two O (hydroxy) atoms. The spectra are consistent to water binding on the longitudinal octahedron axis in all compounds excepting the high pH complex of ED, where OH 2 ions are bound. Possible implications for the SA-cell receptors interactions are discussed.

Research paper thumbnail of Hydrogen saturator effects on silicon cluster Model calculations

Romanian Journal of Physics

Research paper thumbnail of Modificari in spectrul electronilor transmisi datorate dezordonarii unui lant finit de bariere

Research paper thumbnail of Longitudinal Elastic Waves in Deformed Carbon Nanotubes

Romanian Journal of Information Science and Technology

This study investigates the exciting of the elastic waves in single walled carbon nanotubes (SWCN... more This study investigates the exciting of the elastic waves in single walled carbon nanotubes (SWCNT) during their deformations according to the conditions of mechanical treatments. The assumed procedures for longitudinal deformation are related to a short time extension at different velocities and to a harmonic oscillation impose to the atoms placed at one end of the nanotube. We analyse the responses of SWCNT to the external mechanical actions by using a large atomistic model of 2200 atoms simulating a carbon nanotubes of 27.3 nm in the conditions of rigid couplings at its both ends using modified Morse inter-atomic potentials. The simulation models provides details about reversible and irreversible disruption of SWCNT manifested by local transitions to carbon nanowire and self healing processes, being related to the conditions of the mechanical treatments.

Research paper thumbnail of Elastic waves propagation in stressed SWCNT

CAS 2011 Proceedings (2011 International Semiconductor Conference), 2011

This paper presents the study on the behaviour of deformed singe wall carbon nanotubes associated... more This paper presents the study on the behaviour of deformed singe wall carbon nanotubes associated to the conditions of mechanical treatments. We investigate the time evolution of the deformation wave, propagating along the carbon nanotube, and reflected at both clamped ends by using large atomistic models based on molecular dynamics calculation. The system is turned into a non-homogeneous one by

Research paper thumbnail of EPR and TEM Characterization of Electroluminescent Alq<sub>3</sub>

Materials Science Forum, 2006

Research paper thumbnail of Stable oxygen and hydrogen isotopes measurement by CF-IRMS with applications in hydrology studies

Journal of Physics: Conference Series, 2009

... CF-IRMS with applications in hydrology studies Diana Costinel1, Voicu V Grecu2, Raluca Vremer... more ... CF-IRMS with applications in hydrology studies Diana Costinel1, Voicu V Grecu2, Raluca Vremera1 and Stela Cuna3 1 National Research and Development Institute for Cryogenics and Isotopic Technologies, 4 Uzinei, POBox Raureni 7, 240050 Râmnicu Vâlcea, Romania ...

Research paper thumbnail of EPR study of complex formation between copper (II) ions and sympathomimetic amines in aqueous solution

Il Nuovo Cimento D, 1997

The complex formation between sympathomimetic amines (SA): adrenaline (AD), noradrenaline (NA), d... more The complex formation between sympathomimetic amines (SA): adrenaline (AD), noradrenaline (NA), dopamine (DA), ephedrine (ED) and p-tyramine (pTA), and Cu(II) ion in aqueous solution has been studied by X-band EPR at room temperature. Excepting pTA, all investigated SA yielded two types of complexes in different pH domains. All complexes presented a g ll D g » relationship, consistent with a ligand field having a distorted octahedral symmetry, i.e. hexacoordination of Cu(II). The covalence coefficient calculated from the isotropic g and A values has shown strong ionic sigma-type ligand bonds. A structural model with the Cu(II) ion bound by four catecholic O(hydroxy) atoms for the low pH complexes of AD, NA, and DA is proposed. For the high pH complexes of the former compounds as well as for both ED complexes, we suppose Cu(II) bound by two N (amino) and two O (hydroxy) atoms. The spectra are consistent to water binding on the longitudinal octahedron axis in all compounds excepting the high pH complex of ED, where OH 2 ions are bound. Possible implications for the SA-cell receptors interactions are discussed.

Research paper thumbnail of Hydrogen saturator effects on silicon cluster Model calculations

Romanian Journal of Physics

Research paper thumbnail of Modificari in spectrul electronilor transmisi datorate dezordonarii unui lant finit de bariere

Research paper thumbnail of Longitudinal Elastic Waves in Deformed Carbon Nanotubes

Romanian Journal of Information Science and Technology

This study investigates the exciting of the elastic waves in single walled carbon nanotubes (SWCN... more This study investigates the exciting of the elastic waves in single walled carbon nanotubes (SWCNT) during their deformations according to the conditions of mechanical treatments. The assumed procedures for longitudinal deformation are related to a short time extension at different velocities and to a harmonic oscillation impose to the atoms placed at one end of the nanotube. We analyse the responses of SWCNT to the external mechanical actions by using a large atomistic model of 2200 atoms simulating a carbon nanotubes of 27.3 nm in the conditions of rigid couplings at its both ends using modified Morse inter-atomic potentials. The simulation models provides details about reversible and irreversible disruption of SWCNT manifested by local transitions to carbon nanowire and self healing processes, being related to the conditions of the mechanical treatments.

Research paper thumbnail of Elastic waves propagation in stressed SWCNT

CAS 2011 Proceedings (2011 International Semiconductor Conference), 2011

This paper presents the study on the behaviour of deformed singe wall carbon nanotubes associated... more This paper presents the study on the behaviour of deformed singe wall carbon nanotubes associated to the conditions of mechanical treatments. We investigate the time evolution of the deformation wave, propagating along the carbon nanotube, and reflected at both clamped ends by using large atomistic models based on molecular dynamics calculation. The system is turned into a non-homogeneous one by

Research paper thumbnail of EPR and TEM Characterization of Electroluminescent Alq<sub>3</sub>

Materials Science Forum, 2006

Research paper thumbnail of Stable oxygen and hydrogen isotopes measurement by CF-IRMS with applications in hydrology studies

Journal of Physics: Conference Series, 2009

... CF-IRMS with applications in hydrology studies Diana Costinel1, Voicu V Grecu2, Raluca Vremer... more ... CF-IRMS with applications in hydrology studies Diana Costinel1, Voicu V Grecu2, Raluca Vremera1 and Stela Cuna3 1 National Research and Development Institute for Cryogenics and Isotopic Technologies, 4 Uzinei, POBox Raureni 7, 240050 Râmnicu Vâlcea, Romania ...

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