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Revisiting esters hydrolysis in young white wines
No full textEsters play an essential role in the young white wines’ fruity expression, particularly the groups of ethyl esters of fatty acids (EEFAs) and higher alcohol acetates (HAAs) [1]. However, generally, these groups of esters decrease relatively fast during the first two years of ageing [1, 2]. Ester hydrolysis naturally occurs during wine maturation and bottle ageing [3]. Some authors suggested that the rate of esters hydrolysis could be affected by other factors such as the presence of metal ions or antioxidants [4, 5]. However, in wine, this has been poorly reported.
Thirty-three one-year-old commercial white wines, made from Chardonnay and Welschriesling varieties from different Eastern European countries, were subjected to accelerated ageing, all the samples in triplicate. Basic wine parameters were characterised and 17 esters were quantified by HS-SPME-GCMS before and after the forced ageing process. Additionally, the metal ion content (K, Ca, Na, Mg, Cr, Mn, Fe, Co, Ni, Cu and Zn) was measured using ICP-MS. EEFAs and HAAs concentration decreased with ageing as reported in the literature [1, 2]. However, an important matrix effect on the hydrolysis rate was observed between wines, particularly in the case of HAAs. Contrary to our expectations, there was no link between the hydrolysis rate and the initial concentration of esters. Interestingly, iron concentration was positively correlated (Spearman’s correlation) with the loss of HAAs and EEFAs with the longest carbon chains (C10 and C12), suggesting that in real wine conditions metal ions could potentially favour ester hydrolysis. Additionally, K and Mg have shown an impact on HAAs of these wines through a PLS-R model. In parallel, a previous study performed on white wines artificially spiked with metal ions and esters showed that iron, manganese and copper increased the loss of esters during forced ageing irrespective of oxygen level [6]. The difference between both studies suggests that the role of metal ions in ester hydrolysis is matrix-specific. The present work demonstrated that ester hydrolysis is significantly affected by wine chemical components that differ from initial ester concentration and pH which were so far known as the most influential chemical factors on ester hydrolysis. Metal ions particularly iron can potentially favour faster ester hydrolysis but the important matrix effect on the ester hydrolysis rate observed in this study is overall driven by other factors, excluding pH, that still need to be investigated
Coexisting attractors in a non-ideal mechanical system
No full textThe present study delves into the chaotic behavior of a non-ideal, vibrating system. The system is a mechanical setup, composed of a mass-spring-damper structure with cubic stiffness and an external excitation from a power-limited CD electric motor, driven by an unbalanced rotating mass causing the non-ideal excitation [1-3]. The dynamical behavior of the system is studied using a range of techniques, including phase portraits, bifurcation diagrams, back and forward continuation diagrams. Numerical simulations illustrate the qualitative behavior of the system and distinguish the phenomenon of coexisting attractors, present for a range of parameter values
An ARM-FPGA-based co-design for implementing chaotic systems
No full textAn ARM-FPGA-based interface for implementing nonlinear systems through project-based learning for undergraduate students is presented in this work. This setup has a low cost and can be utilized in courses (post-graduate and under-graduate) related to dynamical systems to show the complex behaviors such as chaos, bi-stability, hidden attractors, etc. It consists of a Python-based program in the ARM processor to control the implementation on the FPGA board. As examples, the physical implementation of Lorenz system, as well as the realization of a hidden chaotic system are given
Ferrante, Augusto: The geometry of the generalized algebraic Riccati equation and of the singular Hamiltonian system. (English). Linear Multilinear Algebra 67, No. 1, 158-174 (2019).
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Prosodic analysis of idiomatic and non-idiomatic sentences in Slovenian
No full textThe main aim of the study is to observe whether and how prosody changes in Slovenian sentences with minimal idioms versus their respective literal interpretations. Minimal idioms describe syntactic constructions made up of a lexical and function word (Kržišnik, 2005Babič, 2008), where the idiomatic meaning is conveyed as a sum of both parts and does not have a direct relationship to the meaning of the lexical word. In particular, the observed structure in the study is the verb + clitic pronoun construction, such as popihati jo (literally ‘to blow her’, idiomatically ‘to flee’). Previous studies have found that idiomatic context might have an influence on the sentence prosody, focusing in particular on L2 teaching and learning. Hence, the pitch changes within sentences with minimal idioms were observed. More specifically, the same verb + clitic pronoun structure have been used in a literal context and in two idiomatic contexts, one where the clitic pronoun might have been a potential referent to the subject and the second where the pronoun could not refer to the subject. The results have shown differences in pitch during production, which however are strongly dependent on the speaker. Such findings might shed light on how prosody works in minimal idioms in Slovenian, as well as observing how clitics in the minimal idioms are addressed. Such research might provide a ground for further research on clitics and no how idioms
are processed in the brain
