Thin Notched Beams

The three-dimensional elasticity energy for a notched rod under axial loads is shown to converge in a variational sense to a class of one-dimensional models with a localized compliance when the beam becomes very slender and when the ratio between the depth and the width of each notch vanishes in a suitable way. Also the case of notched thermal conductors is considered, in a parallel treatment, because it falls in a similar but simpler framework.     

Lactate determination in human vitreous humour by capillary electrophoresis and time of death investigation

Forensic inquests, particularly, in assessing time since death currently recognize the importance of the analysis of vitreous humour (VH) biomarkers. Present research, studies, and validates the determination of lactate (La) in VH by CZE with indirect UV detection. The BGE (pH 8.9) consisted of Tris buffer (37 mM) containing 4-methoxybenzoic acid (4 mM) and alkyl-trimethyl-ammonium bromide (1.2 mM). Each VH specimen was diluted with a butyric acid solution (internal standard 0.057 mM) and La and butyrate were separated within 3–5 min (30 kV). The La LOQ and LOD were 4 and 2 mM, respectively. The calibration curve linearity ranged from 4 to 80 mM; intra- and interruns precisions were less than 10% for standard as well as for VH specimen, respectively. To investigate postmortem interval (PMI) and VH lactate level correlation, human VH specimens were collected during autopsy (n = 40) and stored at −20°C until assay. La levels ranged from 16 to 42 mM; PMI values ranged from 10 to 141 h. La (mM) and PMI (h) correlation was statistically significant (r² = 0.527; p < 0.05). In conclusion, the present CZE analysis is efficacious to determine VH La as a biomarker for PMI investigation.     

Structural and spectroscopic characterization of Mo1−xWxO3−δ mixed oxides

Mo_1−xW_xO₃ oxides with different cationic fraction (x=0.2, 0.5 and 0.8) and, for comparison purposes, pure MoO₃ and WO₃ were prepared. Along with textural and structural characterizations, absorbance FT-IR, diffuse reflectance UV-vis-NIR and EPR spectroscopies were employed to study the changes in the electronic properties of these materials passing from Mo_1−xW_xO₃ in oxidizing atmosphere to Mo_1−xW_xO_3−δ in reducing conditions. XRD analysis showed that the Mo-W mixed oxides are constituted by two or three crystalline phases, whose abundance and composition are well characterized by structural refinement with the Rietveld method. Only the sample with the highest Mo content (x=0.2) shows a predominant mixed phase and also a superior ability to lose oxygen with respect to the other mixed oxides. The oxygen loss in the reduced oxides induces the formation of defects with electronic levels in the band gap of the material, in particular, electrons trapped in oxygen vacancies and/or at cationic sites (polarons). While the nature of defect sites induced in the mixed and in the pure oxides is similar, the photo-ionization energies, the ratio between surface and bulk defects and the stability of the defects in oxygen at increasing temperature are peculiar of each mixed oxide.     

Heats and kinetics of oxidation of small copper particles in copper-containing catalysts

The r.t. interaction of oxygen with finely-divided copper in Cu/ZnO catalysts has been studied by gas-solid microcalorimetry. The oxidation is accompanied by the presence of a pseudo-equilibrium pressure, which increases as the reaction proceeds. Surface and several subsurface layers are involved, but a metallic core is always left. The heat of reaction is the same for all samples and does not vary with the extent of reaction (ΔH=181 kJ mol (1/20₂)^?1). The rate of reaction depends upon the pressure, and decreases dramatically to a point where oxidation stps and molecular oxygen is weakly chemisorbed. The overall process is interpreted by assuming that the rate-determining step is the surface dissociation of a molecular precursor onto Cu atoms.