Upgrading of gas oils: the HDS kinetics of dibenzothiophene and its derivatives in real gas oil

The hydrodesulphurization (HDS) of dibenzothiophene (DBT), 4-methyl dibenzothiophene (4 M-DBT), 4,6-dimethyl dibenzothiophene (4,6 DM-DBT) and 4,6-diethyl dibenzothiophene (4,6 DE-DBT) as real gas oil components on NiMo/Al₂O₃ catalyst was investigated. On the basis of the first order rate constants of HDS of the individual sulphur compounds reactivities of the investigated compounds decreased in the order DBT ≫ 4 M-DBT > 4,6 DE-DBT ≈ 4,6 DM-DBT. Apparent activation energies of HDS of above sulphur compounds increased from 80.0 to 120.5 kJ/mol.     

Equilibrium and dynamics of acetylene sorption in multiwalled carbon nanotubes

Multiwalled carbon nanotubes (MWCNT) were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and by adsorption of N₂ and acetylene. The dynamics of acetylene sorption was studied by frequency response spectroscopy. The average tube dimension and the shell number were determined from a statistical evaluation of the TEM images. This value agreed with that obtained from XRD via the Scherrer equation only if a shape factor of 0.49 was used. The diffusion of acetylene in the nanotubes of the MWCNT sample was found to be the rate-controlling step of the sorption process. Relationships between the tube dimensions and the equilibrium and dynamic sorption properties were demonstrated.     

Comparison of Two Analytical Methods for Assessing Antioxidant Capacity of Rapeseed and Olive Oils

The oxygen radical absorbance capacity (ORAC) and the ferric reducing antioxidant power (FRAP) methods were used for the determination of antioxidant capacities (AC) of rapeseed oils at different steps of technological process and olive oils. The mean ORAC and FRAP results obtained for rapeseed oils (1,106–160 and 552–95.6 μmol TE/100 g) were higher than for olive oils (949–123 and 167–32.1 μmol TE/100 g). Although, FRAP values were lower than ORAC values for all studied oils, there is a linear and significant correlation between these two analytical methods (r = 0.9665 and 0.9298, P < 0.0005) for rapeseed and olive oils, respectively). Also, total phenolic compounds in rapeseed oils and olives correlated with antioxidant capacities (correlation coefficient ranged between 0.9470 and 0.8049). The refining process of rapeseed oils decreased the total phenolics content and antioxidant capacities by about 80%.     

Investigation of impact materials around Barringer Meteor Crater by SEM-EDX and micro-PIXE techniques

Impact materials collected at the Barringer Meteor Crater have been characterized by SEM-EDX and micro-PIXE techniques. Fine textural and true elemental images were created. As a main feature silica-bearing shell and an S–Fe–Ni–Cu core could be distinguished. Three different types of S–Fe–Ni–Cu systems were identified such as chalcopyrite, pentlandite and pyrrhotite.     

SEM and EDS investigation of a pyrolytic carbon covered C/C composite maxillofacial implant retrieved from the human body after 8 years

The long term effect of the human body on a pyrolytic carbon covered C/C composite maxillofacial implant (CarBulat^Tm) was investigated by comparing the structure, the surface morphology and composition of an implant retrieved after 8 years to a sterilized, but not implanted one. Although the thickness of the carbon fibres constituting the implants did not change during the 8 year period, the surface of the implant retrieved was covered with a thin surface layer not present on the unimplanted implant. The composition of this layer is identical to the composition of the underlying carbon fibres. Calcium can only be detected on the surface as a trace element implying that the new layer is not formed by bone tissue. Residual soft tissue penetrating the bulk material between the carbon fibre bunches was found on the retrieved implant indicating the importance of the surface morphology in tissue growth and adhering to implants.     

Investigation of the combined effect of argon addition and substrate bias on the growth of ultrananocrystalline diamond layers

In our recent project the combined effect of argon addition and substrate bias was investigated in the microwave plasma assisted chemical vapor deposition of diamond, focused on the ultrananocrystalline phase. Over the conventional qualifying techniques, i.e., Raman and SEM studies, we have led a special in-situ mass spectrometry investigation to explore the growth mechanism of UNCD, analysing the gas composition close to the surface. To achieve this aim, ion beam mass spectrometry (IBMS) was used for in-situ, real time, mass-selective analysis of the incoming species playing an important role in the MWPECVD (Microwave Plasma Enhanced Chemical Vapor Deposition) of the ultrananocrystalline diamond. In our experiments Ar, CH₄, and H₂ gases were used as source gases in a wide range of concentrations applying different values of substrate bias to deposit different phases of diamond. By the IBMS technique we can measure the fluxes of different species: C_xH_y (x = 1–2, y = 0–2) during the phases of deposition, either under the conditions of microcrystalline diamond (MCD), nanocrystalline diamond (NCD) and ultrananocrystalline diamond (UNCD) synthesis. As a result of it, we can compare the different mechanisms of layer formation: i.e.: whether C₁ species or C₂ mediated growth method takes place, or probably both C₁ and C₂ species propagate the diamond lattice. Based on the given tendency by comparing the IBMS data (i.e.: fluxes of surface species) with the growth rate, morphology, and Raman spectra of the layers we propose, that in the case of UNCD a similar (but not exactly the same) growth mechanism can be found as in the case of MCD i.e.: C₁ species are the most likely precursors.     

Exploiting direct and indirect methods for the estimation of the total carotenoid concentration in dried pastas

The total carotenoid concentration (TCC) of several commercially available dried pastas prepared with or without eggs was assessed by means of the two well-established destructive approaches [spectrophotometry (SP) and high-performance liquid chromatography (HPLC)] and three non-destructive, direct (i.e., no sample preparation required) methods (resonance Raman spectroscopy, photoacoustic (PA) spectroscopy and colorimetry). The results obtained by the three direct methods correlate well with the TCC of investigated dried pastas assessed by SP and HPLC. The best linear correlation and detection limit were achieved for the PA method at 470 nm.