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Theresa Hague Andrea Petroczi Paul LR Andrews James Barker Declan P Naughton 《Chemistry Central journal》2010,4(1):2
This is a correction to the following paper: Hague T, Petroczi A, Andrews PR, Barker J, Naughton DP: Determination of metal
ion content of beverages and estimation of target hazard quotients: a comparative study. Chem Central J 2008, 2:13. 相似文献
3.
A. Nucara F. Miletto Granozio M. Radovic F. M. Vitucci P. Maselli R. Fittipaldi A. Vecchione P. Calvani 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,79(4):435-441
We measure the transmittance of LaMnO3 (LMO) thin films in the spectral range from 10 000 to 38 000 cm-1 as a function of temperature. The optical conductivity obtained from the transmittance data is decomposed into five Drude-Lorentz
contributions: three of them show evident changes below the Néel temperature T
N
@\simeq 140 K. We discuss the band assignment in the framework of the tight-binding and of the orbitally degenerate Hubbard models.
Our results ascribe the overall low-frequency spectrum of LMO to charge-transfer mechanisms involving the t
2g
and e
g
electrons of the Mn ions, without invoking the presence of excitonic contributions. This finding definitely promotes a Mott-Hubbard
scenario for LMO and provides an estimate of the Hamiltonian parameters. 相似文献
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This study examines the elastic and dielectric properties of active composites consisting of barium titanate (BaTiO3) and silver (Ag) constituents using experimental and numerical approaches. The elastic constants including Young’s modulus, shear modulus and Poisson’s ratio were measured by resonant ultrasound spectroscopy (RUS), a nondestructive dynamic technique, while a dielectric (impedance) spectroscopy was used to measure the relative permittivity and dielectric loss at different frequencies. The dielectric tests were also conducted at temperature ranges from ?50 to 200 °C where the two phase transformations of barium titanate at around 0 °C and 120 °C were examined. The experimental results in this study were compared to data available in the literature. In addition to the experimental work, a numerical method is also considered in order to study the effects of blending silver into barium titanate on the effective elastic and dielectric properties of the composite and the local field fluctuations. For this purpose, two micromechanics models describing the detailed composite microstructures were constructed. The first model is based on two dimensional (2D) images of realistic microstructures obtained by the scanning electronic microscopy (SEM), while the second model is based on randomly generated three-dimensional (3D) microstructures with spherical particles. The effects of loading direction, porosity, particle shape and dispersion were examined using the micromechanics models. Numerical predictions of the effective elastic and dielectric constants were compared to the experiment results. 相似文献
5.
Ezddin Ali Farag Hutli Milos S. Nedeljkovic Nenad A. Radovic 《Archive of Applied Mechanics (Ingenieur Archiv)》2008,78(5):329-341
Experimental setup with a submerged cavitating jet has been used for the study of influences of material, exposure time and
working fluid temperature on the erosion process. Each of the parameters has been varied separately, and the results of erosion
are analyzed in detail. Additionally, comparison of experiments with nitrated and non-nitrated material has been made in order
to study the enhancement (mostly reflected as the prolonged incubation time) of erosion resistance achieved by nitrating the
specimen surface. 相似文献
6.
Alon Zaida Ezra Bar-Ziv Ljubisa R. Radovic Young-Jae Lee 《Proceedings of the Combustion Institute》2007,31(2):1881-1887
The effect of heat treatment on reactivity of cellulose char was investigated, using two methods: (1) Raman Microprobe spectroscopy analysis (RMA) and (2) thermogravimetric analysis (TGA). The heat-treatment was in the temperature range of 600–2600 °C, temperature prevailing in combustion of coal-chars. In the RMA, first- and second-order Raman spectra in the range of 800–2000 and 2000–3600 cm−1, respectively, were measured for all samples. In the first-order Raman spectra, the following bands have been observed: D band and G (at 1350 and 1590 cm−1 respectively), 1150 and 1450 cm−1. In the second-order Raman spectra, four bands have been observed at 2450, 2700, 2940 and 3250 cm−1. Both first- and second-order Raman spectra were fitted by Lorentzian functions. The Lorentzian parameters (bandwidth and intensity ratio) showed significant changes with heat treatment, which is consistent with structural modification. Also, from TGA experiments we observed the expected significant influence of heat treatment on char reactivity. Attempts were made to correlate the Lorentzian parameters with char reactivity. A good correlation was found between the 2940 cm−1 bandwidth in the second-order Raman spectrum and char reactivity, confirming the strong connection between char structure and its reactivity, and illustrating the usefulness of RMA in such studies. 相似文献
7.
An assessment is offered regarding the progress made, and the remaining challenges, in the field of carbocatalysis. The fundamental principles that govern the preparation and performance of sp2-hybridized carbon materials in heterogeneous catalysis have been known for decades, and the level of understanding of key issues – especially the importance of textural and ion-exchange properties (i.e., surface area, pore size distribution, and proton transfer) – remains quite satisfactory. The opportunities for novel catalytic materials – especially graphene nanosheets and carbon nanotubes– are tremendous, especially when it comes to taking advantage of their structural order, such that electron transfer can be both better understood and controlled to enhance catalytic activity and selectivity. 相似文献
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We analyze the diffusion of oxygen atoms on graphene and its dependence on the carrier density controlled by a gate voltage. We use density functional theory to determine the equilibrium adsorption sites, the transition state, and the attempt frequency for different carrier densities. The ease of diffusion is strongly dependent on carrier density. For neutral graphene, we calculate a barrier of 0.73 eV; however, upon electron doping the barrier decreases almost linearly to reach values as low as 0.15 eV for densities of -7.6×10(13) cm(-2). This implies an increase of more than 9 orders of magnitude in the diffusion coefficient at room temperature. This dramatic change is due to a combined effect of bonding reduction in the equilibrium state and bonding increase at the transition state and can be used to control the patterning of oxidized regions by an adequate variation of the gate voltage. 相似文献
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Theresa Hague Andrea Petroczi Paul LR Andrews James Barker Declan P Naughton 《Chemistry Central journal》2008,2(1):13
Background
Considerable research has been directed towards the roles of metal ions in nutrition with metal ion toxicity attracting particular attention. The aim of this study is to measure the levels of metal ions found in selected beverages (red wine, stout and apple juice) and to determine their potential detrimental effects via calculation of the Target Hazard Quotients (THQ) for 250 mL daily consumption. 相似文献10.