Search results for "Spectroscopy"

Effect of thermal annealing on the luminescence of defective ZnO nanoparticles synthesized by pulsed laser ablation in water

2016

This work concerns ZnO nanoparticles (NPs), with sizes of tens of nm, produced by ablation with a pulsed Nd:YAG laser of a Zn plate in H2O. TEM images evidence the formation of nanoparticles with sizes of tens of nm. Moreover, HRTEM images and Raman spectra show that the distance between the crystalline planes and the vibrational modes are consistent with ZnO nanocrystal in wurtzite structure. Their optical properties are characterized by two emission bands both excited above the energy gap (3.4 eV): the first at 3.3 eV is associated with excitons recombination, the second at 2.2 eV is proposed to originate from a singly ionized oxygen vacancy. The green emission is independent of water pH,…

Study of the curing of a DGEBA based system through structural investigation

2011

Protein tyrosine nitration and thiol oxidation by peroxynitrite-strategies to prevent these oxidative modifications.

2013

The reaction product of nitric oxide and superoxide, peroxynitrite, is a potent biological oxidant. The most important oxidative protein modifications described for peroxynitrite are cysteine-thiol oxidation and tyrosine nitration. We have previously demonstrated that intrinsic heme-thiolate (P450)-dependent enzymatic catalysis increases the nitration of tyrosine 430 in prostacyclin synthase and results in loss of activity which contributes to endothelial dysfunction. We here report the sensitive peroxynitrite-dependent nitration of an over-expressed and partially purified human prostacyclin synthase (3.3 μM) with an EC50 value of 5 μM. Microsomal thiols in these preparations effectively co…

Structural distortions in homoleptic (RE)4A (E = O, S, Se; A = C, Si, Ge, Sn): Implications for the CVD of tin sulfides

2001

The structures of Sn(SBut)4 and Sn(SCy)4 have been determined and adopt S4 and D2 conformations respectively; the anion [(PhS)Sn3]−, as its Ph4P+ salt, has a structure approaching Cs symmetry. In all three compounds, there are large variations in the ∠S–Sn–S within the same molecule, which have been rationalised in terms of the C–S–Sn–S–C conformations. For Sn(SR)4, the ∠S–Sn–S increases as the conformations change from trans, trans to trans, gauche and gauche, gauche, as the number of eclipsed lone pairs decreases and this rationale is shown to be applicable to a variety of A(ER)4 (A = C, Si, Ge, Sn; E = O, S, Se) and related [Mo(SR)4, Ga(SR)4−] systems. AM1 calculations have been used to …

Deposition of tin sulfide thin films from tin(iv) thiolate precursors

2001

AACVD (aerosol-assisted chemical vapour deposition) using (PhS)(4)Sn as precursor leads to the deposition of Sn3O4 in the absence of H2S and tin sulfides when H2S is used as co-reactant. At 450 degreesC the film deposited consists of mainly SnS2 while at 500 degreesC SnS is the dominant component. The mechanism of decomposition of (PhS)(4)Sn is discussed and the structure of the precursor presented.

Calcium mediated polyelectrolyte adsorption on like-charged surfaces.

2011

International audience; Monte Carlo simulations within the primitive model of calcium-mediated adsorption of linear and comb polyelectrolytes onto like-charged surfaces are described, focusing on the effect of calcium and polyion concentrations as well as on the ion pairing between polymers and calcium ions. We use a combination of Monte Carlo simulations and experimental data from titration and calcium binding to quantify the ion pairing. The polymer adsorption is shown to occur as a result of surface overcharging by Ca2+ and ion pairing between charged monomers and Ca2+. In agreement with experimental observations, the simulations predict that the polymer adsorption isotherm goes through …

Experimental study of 100Tc β decay with total absorption γ -ray spectroscopy

2017

The β decay of 100Tc has been studied by using the total absorption γ -ray spectroscopy technique at the Ion Guide Isotope Separator On-Line facility in Jyväskylä. In this work the new Decay Total Absorption γ -ray Spectrometer in coincidence with a cylindrical plastic β detector has been employed. The β intensity to the ground state obtained from the analysis is in good agreement with previous high-resolution measurements. However, differences in the feeding to the first-excited state as well as weak feeding to a new level at high excitation energy have been deduced from this experiment. Theoretical calculations performed in the quasiparticle random-phase approximation framework are also r…

r Process (n, γ) Rate Constraints from the γ Emission of Neutron Unbound States in β decay

2017

Total absorption gamma-ray spectroscopy is used to measure accurately the intensity of γγ emission from neutron-unbound states populated in the ββ-decay of delayed-neutron emitters. From the comparison of this intensity with the intensity of neutron emission a constraint on the (n, γγ) cross section for highly unstable neutron-rich nuclei can be deduced. A surprisingly large γγ branching was observed for a number of isotopes which might indicate the need to increase by a large factor the Hauser-Feshbach (n, γγ) cross-section estimates that impact on r process abundance calculations. peerReviewed

Total absorption spectroscopy study of the β decay of 86Br and 91Rb

2017

The beta decays of 86Br and 91Rb have been studied using the total absorption spectroscopy technique. The radioactive nuclei were produced at the Ion Guide Isotope Separator On-Line facility in Jyväskylä and further purified using the JYFLTRAP. 86Br and 91Rb are considered to be major contributors to the decay heat in reactors. In addition, 91Rb was used as a normalization point in direct measurements of mean gamma energies released in the beta decay of fission products by Rudstam et al. assuming that this decay was well known from high-resolution measurements. Our results show that both decays were suffering from the Pandemonium effect and that the results of Rudstam et al. should be renor…

Total absorption γ-ray spectroscopy of the β-delayed neutron emitters 87Br, 88Br, and 94Rb

2017

We investigate the decay of 87,88Br and 94Rb using total absorption γ -ray spectroscopy. These important fission products are β-delayed neutron emitters. Our data show considerable βγ intensity, so far unobserved in high-resolution γ -ray spectroscopy, from states at high excitation energy. We also find significant differences with the β intensity that can be deduced from existing measurements of the β spectrum. We evaluate the impact of the present data on reactor decay heat using summation calculations. Although the effect is relatively small it helps to reduce the discrepancy between calculations and integral measurements of the photon component for 235U fission at cooling times in the r…