The crystallization kinetics of poly(l-lactide), PLLA, is slow enough to allow a quasi-amorphous polymer to be obtained at low temperature simply by quenching from the melt. The PLLA crystallization process was followed by differential scanning calorimetry and optical microscopy after nucleation isothermal treatments at temperatures just below (53 degrees C) and just above (73 degrees C) the glass transition temperature. The crystallization exotherm shown in the heating thermograms shifts toward lower temperatures as the annealing time at 73 degrees C increases. The same effect is shown to a lesser extent when the sample nucleates at 53 degrees C, showing the ability to nucleate in the glassy state, already shown in other polymers. The shape of the DSC thermograms is modeled by using Avrami's theory and allows an estimation of the number of crystallization germs formed. The results of optical microscopy are converted to thermograms by evaluating the average gray level of the image recorded in transmission mode as a function of temperature and calculating its temperature derivative. The shape of such optical thermograms is quite similar to that of the DSC traces but shows some peculiarities after long nucleation treatments. Atomic force microscopy was used to analyze the crystal morphology and is an additional proof of the effect of nucleation in the glassy state. The crystalline morphology observed in samples crystallized after nucleation in the glassy state is qualitatively different from that of samples nucleated above the glass transition temperature, and the number of crystals seems to be much greater than what could be expected from the crystallization kinetics.

Bio-nanocomposite hydrogels based on sodium alginate (SA) as polymer matrix and graphene oxide (GO) nanosheets with zinc as crosslinking agent were synthesized with the aim of incorporating the intrinsic properties of their constituents (bioactivity and antimicrobial activity). Thus, stable and highly interconnected networks were obtained from GO nanosheets dispersed in SA matrices through interactions with low amounts of zinc. The GO nanosheets were successfully incorporated into the alginate matrix in the form of a complex nano-network involving different interactions: Bonds between alginate chains induced by Zn ions (egg box structure), interactions between GO nanosheets through Zn ions and hydrogen bonds between alginate chains, and GO nanosheets. The molecular interactions and morphology were confirmed by Fourier-transform infrared spectroscopy and transmission electron microscopy. The composite’s structural organization showed enhanced thermal stability. The glass transition temperature shifted to a higher temperature due to the reduced mobility induced by additional crosslinking bonds after incorporating the GO nanosheets and Zn into the polymer matrix. Finally, the dielectric behavior revealed that charge carrier mobility was hampered by the compact structure of the nanonetwork, which reduced conductivity. The combined properties of these nanocomposite hydrogels make them attractive biomaterials in the field of regenerative medicine and wound care since both surface bioactivity and antibacterial behavior are two critical factors involved in the success of a biomaterial.

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This paper reports the preparation and characterization of semi-interpenetrating polymer networks (semi-IPN) of poly(3-hydroxybutirate-co-3-hydroxyvalerate), PHBV, and poly (vinyl alcohol), PVA, with conductive polypirrole (PPy) nanoparticles. Stable hybrid semi-IPN (PHBV/PVA 30/70 ratio) hydrogels were produced by solvent casting, dissolving each polymer in chloroform and 1-methyl-2-pyrrolidone respectively, and subsequent glutaraldehyde crosslinking of the PVA chains. The microstructure and physical properties of this novel polymeric system were analysed, including thermal behaviour and degradation, water sorption, wettability and electrical conductivity. The conductivity of these advanced networks rose significantly at higher PPy nanoparticles content. Fourier transform infrared spectroscopy (FTIR) and calorimetry characterization indicated good miscibility and compatibility between all the constituents, with no phase separation and strong interactions between phases. A single glass transition was observed between those of pure PHBV and PVA, although PVA was dominant in its contribution to the glass transition process. Incorporating PPy nanoparticles significantly reduced the hydrogel swelling, even at low concentrations, indicating molecular interactions between the PPy nanoparticles and the hydrogel matrix. The PHBV/PVA semi-IPN showed higher thermal stability than the neat polymers and PHBV/PVA blend, which also remained in the tertiary systems.

Graphical abstractHighlights:• Lab results for Flip and Traditional Methodologies are analysed and compared.• Flip Teaching in the lab sessions improves students' academic performance.• Since students spend more time thinking, they write better lab reports.• Definition of the "analogous students" enables a more detailed statistical study. José A. Gómez-Tejedor et al., Computers AbstractThe progressive introduction of the flip teaching (FT) instructional model into higher education has accelerated in recent years. The FT methodology seems to be especially suitable for laboratory practice sessions: before the lab session the students are given documents and videos that explain the theoretical contents and the experimental procedure. When this material is studied in advance, the practice session can be devoted to the discussion, clarification and practical application of the acquired knowledge. This paper describes the effect of the FT methodology on the students' academic performance when it was applied to the laboratory practice in two subjects, Physics and Electricity, of a technical degree. The laboratory and final grades of these subjects were compared in four consecutive years. The characteristics of all four years were quite similar, except that the traditional teaching method (TM) was used in two, while FT was applied in the other two. The statistical analysis shows that the academic results of the students were better in both subjects under FT than those obtained using TM, and that the difference was statistically significant.

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Auditory hallucinations (AH) are the most frequent positive symptoms in patients with schizophrenia. Hallucinations have been related to emotional processing disturbances, altered functional connectivity and effective connectivity deficits. Previously, we observed that, compared to healthy controls, the limbic network responses of patients with auditory hallucinations differed when the subjects were listening to emotionally charged words. We aimed to compare the synchrony patterns and effective connectivity of task-related networks between schizophrenia patients with and without AH and healthy controls.Schizophrenia patients with AH (n = 27) and without AH (n = 14) were compared with healthy participants (n = 31). We examined functional connectivity by analyzing correlations and cross-correlations among previously detected independent component analysis time courses. Granger causality was used to infer the information flow direction in the brain regions.The results demonstrate that the patterns of cortico-cortical functional synchrony differentiated the patients with AH from the patients without AH and from the healthy participants. Additionally, Granger-causal relationships between the networks clearly differentiated the groups. In the patients with AH, the principal causal source was an occipital–cerebellar component, versus a temporal component in the patients without AH and the healthy controls.These data indicate that an anomalous process of neural connectivity exists when patients with AH process emotional auditory stimuli. Additionally, a central role is suggested for the cerebellum in processing emotional stimuli in patients with persistent AH.

Summary: The glass transition and physical aging processes of a polymeric material have been simulated using the bond fluctuation model. Two potentials that represent intra‐ and inter‐molecular interactions have been employed. Simulations of different thermal histories that include cooling from equilibrium have been performed. The evolution of the system and the structure attained at low temperature are analyzed as a function of the assumed weight of inter‐ and intra‐molecular potentials in the total energy of the system. A new way of characterizing the free volume of the system and its evolution with the temperature or time is proposed. It is based on the concept of dynamically accessible volume but modified in the sense of considering the probability of an empty site to be accessed according to a Metropolis criterion. The results obtained show that the thermal redefinition of the dynamically accessible volume, TDAV, offers a better representation of the real mobility of the polymeric systems. The use of information on the structure of the system coming from the pair‐correlation function and the molecular mobility in the glassy state characterized by the time evolution of TDAV allows to reach the conclusion that a combination of inter‐ and intra‐molecular potentials produces the vitrification of the polymer system on cooling.