The relaxation dynamics of the conductive process present in PbNb 2 O 6 piezoelectric ceramics was investigated. A relaxation function in the time domain, (t), was found from the frequency dependence of the dielectric modulus (imaginary component, M ) by using a relaxation function in the frequency domain, F * (ω). The best relaxation function, F * (ω), was found to be a Cole-Cole distribution function, in which relaxation characteristic parameters, such as α and τ CC , are involved. On the other hand, the relaxation function, (t), obtained by the time domain method, was found to be a Kohlrausch-Williams-Watts (KWW) function type. The thermal evolution of the characteristics parameters of the KWW function (β and τ * ) was analysed. The values of the activation energy (E a ), obtained in the whole investigated temperature interval, suggest the existence of a relaxation mechanism (a conductive process), which may be interpreted by an ion hopping between neighbouring sites within the crystalline lattice. The results are corroborated with the formalism of the AC conductivity.

Aromatic plants and essential oils are important agents as complementary and alternative medicines in many cultures and geographical locations. In this review, a literature search on essential oils from Cuba, their chemical compositions, and their pharmacological properties was carried out. Out of 171 published scientific articles on essential oils of Cuban plants, a total of 31 documents, focused on both chemical composition and pharmacological properties, were considered for this review. In general, an increase in articles published in the last decade was noted, particularly in recognized international journals in English. Myrtaceae and Piperaceae were the most representative families collected in the occidental area of the country. Leaves and aerial parts were predominantly used, while a wide and variable number of components were identified, including terpenes, aliphatic derivatives, sulfur-containing compounds, phenylpropanoids, alkaloids and amine-type compounds. Finally, different biological activities were reported such as antiprotozoal, antibacterial, antifungal, cytotoxic, anthelmintic, larvicidal and insecticidal. In conclusion, we encourage further studies that would promote the use of essential oils from Cuban plants in new pharmaceutical products.

Essential oils (EOs) are a mixture of chemical compounds with a long history of use in food, cosmetics, perfumes, agricultural and pharmaceuticals industries. The main object of this study was to find chemical patterns between 45 EOs and antiprotozoal activity (antiplasmodial, antileishmanial and antitrypanosomal), using different machine learning algorithms. In the analyses, 45 samples of EOs were included, using unsupervised Self-Organizing Maps (SOM) and supervised Random Forest (RF) methodologies. In the generated map, the hit rate was higher than 70% and the results demonstrate that it is possible find chemical patterns using a supervised and unsupervised machine learning approach. A total of 20 compounds were identified (19 are terpenes and one sulfur-containing compound), which was compared with literature reports. These models can be used to investigate and screen for bioactivity of EOs that have antiprotozoal activity more effectively and with less time and financial cost.