University of Patras

About: University of Patras is a education organization based out in Pátrai, Greece. It is known for research contribution in the topics: Population & Catalysis. The organization has 13372 authors who have published 31263 publications receiving 677159 citations. The organization is also known as: Panepistímio Patrón.

Calcium carbonate phase analysis using XRD and FT-Raman spectroscopy

Abstract: There is a need for the quantitative determination of the ternary mixtures of calcium carbonate polymorphs (calcite, aragonite and vaterite), which are present in a number of materials including limestones, industrial scale formation and several pathological cases Application of infrared spectroscopy proved to be inadequate, due to band overlapping, while use of Raman spectroscopy and X-ray powder diffraction (XRD) has been reported only for the calcite–aragonite mixture In order to address the problem, a comprehensive non-destructive methodology for the simultaneous quantitative determination of the calcium carbonate crystal phases in their ternary mixtures based on the use of Fourier transform Raman spectroscopy (FT-RS) was developed Binary mixtures were used to construct the calibration graphs using the Raman bands at 711 cm−1 for calcite, 700 cm−1 for aragonite and 750 cm−1 for vaterite Detection limits were found to be 013, 018 and 13 mol-% for calcite, aragonite and vaterite, respectively, while the relative errors in determining the mol-% of a known ternary mixture of calcium carbonate polymorphs were 16% for calcite, 03% for aragonite and 11% for vaterite A similar methodology was developed using XRD XRD calibration graphs were constructed using the 104 reflection of calcite, the 221 reflection of aragonite and the 110 reflection of vaterite Detection limits for calcite, aragonite and vaterite were found to be 090, 290 and 690 mol-%, respectively, while the relative errors in determining the mol-% of the same ternary mixture used for testing the FT-RS methodology were 25, 18 and 06%, for calcite, aragonite and vaterite, respectively

Electronic structure and Slater–Pauling behaviour in half-metallic Heusler alloys calculated from first principles

Abstract: Intermetallic Heusler alloys are amongst the most attractive half-metallic systems due to their high Curie temperatures and their structural similarity to binary semiconductors. In this review we present an overview of the basic electronic and magnetic properties of both Heusler families: the so-called half-Heusler alloys like NiMnSb and the full-Heusler alloys like Co2MnGe. Ab initio results suggest that both the electronic and magnetic properties in these compounds are intrinsically related to the appearance of the minority-spin gap. The total spin magnetic moment Mt scales linearly with the number of the valence electrons Zt, such that Mt = Zt − 24 for the full-Heusler and Mt = Zt − 18 for the half-Heusler alloys, thus opening the way to engineer new half-metallic alloys with the desired magnetic properties.

Syntactic Change: A Minimalist Approach to Grammaticalization

Abstract: The phenomenon of grammaticalization - the historical process whereby new grammatical material is created - has attracted a great deal of attention within linguistics. This is an attempt to provide a general account of this phenomenon in terms of a formal theory of syntax. Using Chomsky's Minimalist Program for linguistic theory, Roberts and Roussou show how this approach gives rise to a number of important conceptual and theoretical issues concerning the nature of functional categories and the form of parameters, as well as the relation of both of these to language change. Drawing on examples from a wide range of languages, they construct a general account of grammaticalization with implications for linguistic theory and language acquisition.

VOC oxidation over CuO–CeO2 catalysts prepared by a combustion method

Abstract: CuO–CeO 2 catalysts were prepared via a urea combustion method and their performance in the oxidation of ethanol, ethyl acetate and toluene was evaluated. XRD, H 2 -TPR and N 2 physisorption were employed in catalyst characterization. The specific surface area of mixed materials was higher than the one of single oxides. In ceria-rich materials, crystalline copper oxide phases are absent and segregation of a CuO phase takes place at atomic Cu/(Cu + Ce) ratios higher than 0.25. The mixed oxides get reduced by H 2 at lower temperatures than the corresponding single oxides and copper ions promote reduction of ceria. Ethanol gets more easily oxidized than ethyl acetate, which in turn gets more easily oxidized than toluene. CuO–CeO 2 catalysts of low copper content produce very low amounts of acetaldehyde during ethanol and ethyl acetate oxidation at all conversion levels. This is augmented by the presence of water in the feed. The specific activity of Cu x Ce 1− x catalysts in the oxidation of ethanol, ethylacetate and toluene (specific rate of volatile organic compound (VOC) consumption) is lower than the one of pure CuO and CeO 2 , i.e. combination of the two phases leads to suppression of intrinsic activity. On the other hand, the specific rate of CO 2 production during ethanol and ethyl acetate oxidation is also lower over CuO–CeO 2 than over CeO 2 , but higher than over CuO. The larger surface area of CuO–CeO 2 catalysts counterbalances their smaller specific activity allowing complete VOC conversion at lower temperatures compared to the single oxides.