Experimental Study on the Transport of Light Gas Molecules through Low-Density Polyethylene Films

An original experimental procedure for the study of gas permeation process through thin polymer films is presented. Employing mass spectroscopy techniques, this procedure allows the detection of the permeation flux with a signal-to-noise ratio large enough to obtain accurate measurements of the gas diffusivity also in processes with transient transport conditions lasting for short-interval times (~few seconds). The procedure is validated using as test material a thin low-density polyethylene (LDPE) film: the transport of four test gases with different molecular sizes and condensation properties (CO2, N2, D2, and He) is studied in the 295 to 350 K temperature interval. The CO2 diffusivity values well compare with values previously obtained studying the same LDPE film samples by integral permeation technique measuring the time lag value. Original data on the diffusivity of the He and D2 penetrant molecules are reported: in the examined temperature range, the diffusivity values of these small-size penetrants are in the 10−6 cm2/s range and follow an Arrhenius behavior with temperature. The activation energy values for diffusion are 18.8 ± 0.4 and 10.0 ± 0.4 kJ/mol for D2 and He, respectively

Mitochondrial Kv1.3: a New Target in Cancer Biology?

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Exploring the membrane-based separation of CO2/CO mixtures for CO2 capture and utilisation processes: Challenges and opportunities

The separation and removal of CO2 from its mixtures with CO2 is gaining increasing interest due to the novel processes in which these two gases are mixed, such as the non-thermal plasma activated reaction of CO2 splitting, a promising CO2 utilisation route that could be performed using renewable energy. The aim of this review is to propose a novel database suitable for membrane scientists to evaluate the feasibility of membrane-based separation processes involving such gas mixture, not included in the original Robeson’s works on the upper bound, nor in later developments. For this reason, we reviewed the data on the permeation, diffusion and sorption of these two gases in different classes of polymers, from polyolefins to polyimides and green polymers, spanning over a wide range of permeability values. Furthermore, we propose an upper bound for this separation, and provide a theoretical explanation for it. The separation mechanism is solubility-driven, and all polymeric membranes inspected in the literature show a CO2-selective behaviour, despite a very limited, or unfavourable, diffusion selectivity for CO2, which is consistent with empirical correlations. Consequently, the observed selectivity values are determined by the solubility-selectivity and are comprised mainly in the range 7–20, in agreement with known empirical correlations between the solubility and the critical temperature of the penetrants. Temperature has a detrimental effect onCO2/CO selectivity, as the activation energy for permeation of CO2 is always lower than that of CO. In general, while the permeability can vary over several orders of magnitude depending on the polymer nature, selectivity mostly ranges between 7 and 20, which makes the trade-off mechanism between permeability and selectivity rather weak in the case of this mixture. Such an effect provides a wider variety of design choices, and makes this separation attractive for polymeric membranes, if carried out at low temperatures and with CO2-philic materials. A preliminary calculation of the separation obtainable with single-stage membrane unit for a binary mixture is carried out for some representative polymers

Colmare le distanze: strategie traduttive per giovani segnanti emergenti

Young emergent signers are intended as Deaf children, born into hearing non-signing families, who have not yet developed a full linguistic competence in sign language. Our research goal is to investigate how a text translated into Italian Sign Language (LIS) can be adapted in order to help these lower-proficiency signers access informative contents. We present an analytical comparison between translated texts designed for Deaf adults, fluent in LIS, and adapted texts designed for Deaf children whose sign language is still at a developing stage. Data annotation has been conducted with the software ELAN. The comparative analysis shows that the texts for young non-native signers contain specific translation strategies and adaptations aiming at bridging the linguistic, cognitive, and cultural gap due both to the young age of children and their limited linguistic competence in sign language. In support of these findings, both quantitative and qualitative data are shown and discussed

Recombinant Human Voltage Dependent Anion Selective Channel Isoform 3 (hVDAC3) Forms Pores with a Very Small Conductance

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Polylactic acid-lauryl functionalized nanocellulose nanocomposites: Microstructural, thermo-mechanical and gas transport properties

Thermo-mechanical and gas transport properties of polylactic acid (PLA) matrix containing various amounts (from 1 to 20 wt%) of nanocellulose esterified with lauryl chains (LNC) were investigated on solvent cast film of about 50 micron. Scanning electron microscopy indicated that, up to a filler content of 6.5 wt%, LNC was well dispersed or formed small, sub-micrometric clusters. At higher filler contents, oval aggregates in the micrometric range were detected. The addition of LNC did not change the matrix glass transition temperature and melting temperature. Concurrently, as LNC content increased, both elastic and storage moduli at room temperature exhibited a sharp decrease up to 5 wt% of filler, and a lower reduction for LCN concentration of 10\u201320 wt.%. Nanocomposites with 3 and 5 wt% of LNC showed the highest strain at break and a large amount of plastic deformation due to a strong interfacial adhesion between the PLA and filler particles. For higher LNC fractions the presence of aggregates weakened the nanocomposite leading to lower values of maximum stress and strain at break. With the addition of LNC particles, gas barrier properties of the PLA film versus deuterium, nitrogen and carbon dioxide were improved up to a critical LNC concentration of 6.5 wt%, where the gas permeability of the nanocomposite resulted to be 70% lower than that of the PLA matrix. At higher filler contents, large LNC aggregates increased the gas permeability of the nanocomposites

Electrophysiological Characterization of the Activity and Regulation of the Mitochondrial Calcium Uniporter

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The language instinct in extreme circumstances: The transition to tactile Italian Sign Language (LISt) by Deafblind signers

Tactile sign languages used by Deafblind signers are most often acquired by signers competent in a visual sign language who can no longer rely on the grammatical system of the visual language as it is, since some of its features are lost due to the loss of vision. A natural question is which repair strategies are adopted to compensate for the loss of the grammatical features of the visual language that can no longer be perceived. We argue that the transformation of LIS (Italian Sign Language) into tactile Italian Sign Language (LISt) is constrained by grammatical principles, rather than reflecting communication strategies that in principle might compensate for the visual loss equally well. Certain innovations are introduced to carry over the grammatical features of LIS to LISt. Even when LISt undergoes processes that make it diverge from LIS, these processes are attested in other natural languages. For example, among the innovations unconsciously introduced by LISt signers we found an instance of cross-modal grammaticalization. Our research suggests that tactile languages have the potential of becoming complete grammatical systems, at least when they build on previous knowledge of a visual sign language