In recent years, the upgrading of lignocellulose bio-oils from fast-pyrolysis by means of ketonization has emerged as a frontier research domain to produce a new generation of biofuels. Propionic acid (PA) ketonization is extensively investigated as a model reaction over metal oxides, but the activity of other materials, such as metal phosphates, is mostly unknown. Therefore, PA ketonization was preliminarily investigated in the gas phase over both phosphates and oxides of Al, Zr, and La. Their catalytic activity was correlated to the physicochemical properties of the materials characterized by means of XRD, XRF, BET N2 porosimetry, and CO2- and NH3-TPD. Noteworthy, monoclinic ZrO2 proved to be the most promising candidate for the target reaction, leading to a 3-pentanone productivity as high as 5.6 h−1 in the optimized conditions. This value is higher than most of those reported for the same reaction in both the academic and patent literature.
I discuss and try to evaluate the argument about constructible sets made by Putnam in Ô'Models and Reality'Õ, and some of the counterarguments directed against it in the literature. I shall conclude that Putnam's argument, while correct in substance, nevertheless has no direct bearing on the philosophical question of unintended models of set theory.Erkenntnis (2005) 62: 395-409 Ó Springer 2005
I make an attempt at the description of the delicate role of the standard model of arithmetic for the syntax of formal systems. I try to assess whether the possible instability in the notion of finiteness deriving from the nonstandard interpretability of arithmetic affects the very notions of syntactic metatheory and of formal system. I maintain that the crucial point of the whole question lies in the evaluation of the phenomenon of formalization. The ideas of Skolem, Zermelo, Beth and Carnap (among others) on the problem are discussed.'A tries to explain to B the meaning of negation. Finally A gives up, saying: "You don't understand what I mean, and I am not going to explain any longer," to which B replies: "Yes, I see what you mean, and I am glad you are willing to continue your explanations"'.
We consider the consistency proof for a weak fragment of arithmetic published by von Neumann in 1927. This proof is rather neglected in the literature on the history of consistency proofs in the Hilbert school. We explain von Neumann’s proof and argue that it fills a gap between Hilbert’s consistency proofs for the so-called elementary calculus of free variables with a successor and a predecessor function and Ackermann’s consistency proof for second-order primitive recursive arithmetic. In particular, von Neumann’s proof is the first rigorous proof of the consistency of an axiomatization of the first-order theory of a successor function.
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