2,521 research outputs found

    Exploring the social representations of vulnerable populations being helped

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    Resorting to Social Representation Theory, the aim of this study was to investigate the perceptions of help recipients about Help, namely in terms of the shared representations about Helping Institutions, the self-perceptions of aid recipients and the potential Social Status Distance with regard to their helpers. Twenty-five members of vulnerable groups that benefited from help programs offered by Non-Profit Institutions/Organizations, aged between 18 and 70-years-old, responded to semi-structured interviews. Following the theoretical-methodological orientation of the structural approach of Social Representation Theory (Abric, 1984), the 800 free evocations and 149 words produced during the interviews, underwent a prototypical analysis with open-EVOC software (2000). In addition to contributing to Social Representation Theory by considering the theme of helping relations, the results of the present study showed – in contrast to the literature on orientations toward help (Nadler, 1997; 1998; 2002; 2015) – the importance, at different levels, of both autonomy and dependency orientations (and not just the latter). This study showed the importance, for the recipients of help, of being protagonists, active and autonomous in the process of improving their psychological and material situation; together with the importance of enjoying material goods, even if it means depending on an institution. Results are discussed as a potential contribution to designing help programs that might provide greater benefits and well-being to help recipients.info:eu-repo/semantics/publishedVersio

    Low temperature dielectric relaxation in ordinary perovskite ferroelectrics: enlightenment from high-energy x-ray diffraction

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    Ordinary ferroelectrics exhibit a second order phase transition that is characterized by a sharp peak in the dielectric permittivity at a frequency-independent temperature. Furthermore, these materials show a low temperature dielectric relaxation that appears to be a common behavior of perovskite systems. Tetragonal lead zirconate titanate is used here as a model system in order to explore the origin of such an anomaly, since there is no consensus about the physical phenomenon involved in it. Crystallographic and domain structure studies are performed from temperature dependent synchrotron x-ray diffraction measurement. Results indicate that the dielectric relaxation cannot be associated with crystallographic or domain configuration changes. The relaxation process is then parameterized by using the Vogel–Fulcher–Tammann phenomenological equation. Results allow us to hypothesize that the observed phenomenon is due to changes in the dynamic behavior of the ferroelectric domains related to the fluctuation of the local polarization.Postprint (author's final draft

    Stacking effect via solvent polarity differences in micellar electrokinetic chromatography with aqueous-organic background electrolyte

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    In this manuscript, a new stacking mode for micellar electrokinetic chromatography with anionic micelles and neutral analytes was investigated. The variation in the velocity of the analytes between the sample and the separation zones, needed for stacking effects, was obtained by using solvents with different polarities, the concentration of salts and micelles being identical between the two zones. Whereas a pure aqueous solvent was used in the injection zone, up to 30% ACN was used in the separation zone. In such conditions, higher interactions between the analyte and the micelles are obtained in the sample zone than in the separation zone, this due to the presence of the organic solvent. As the velocity of neutral analyte depends on its interactions with the moving micelles, its speed will drop when crossing two distinct zones where in the second zone its interactions with the micelles are lower than in the outgoing zone. This will induce a stacking effect. This approach was validated using a background electrolyte in the separation zone made with 10 mM disodium hydrogen phosphate, 15 mM sodium dodecyl sulphate and 15% ACN. The three triazines (simazine, atrazine, and terbuthylazine), used as test analytes, were dissolved in 10 mM disodium hydrogen phosphate, 15 mM sodium dodecyl sulphate and either 15 or 0% ACN. A stacking factor of around 2 was obtained injecting the sample in 0% ACN rather than 15% ACN. This was in accordance with the theoretical values predicted measuring the effective mobilities in both zonesCOMPETE/QREN/UE and PTDC/QUI-QUI/116156/2009 and SFRH / BPD / 30548 / 200

    Carbon Materials Derived from Cyano-Based IL@ZIF-8 Composites for CO2 Sorption Separation Systems

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    Additionally, this work was partially supported by the Asso- ciate Laboratory for Green Chemistry, LAQV, which is funded by national funds from FCT/MCTES (LA/P/00 08/2020) .The sorption capacity and selectivity of pre- and post-carbonized cyano-based metal-organic framework (MOF) composite materials (cyano-based IL@ZIF-8) were investigated for the first time. The influence of the ionic liquid (IL) loading and number of cyano groups in the IL anion on a materials gas sorption separation performance was studied. Sorption-desorption equilibrium isotherms of CO2, CH4, and N2 were measured at 303 K in the ZIF-8, cyano-based IL@ZIF-8 composites and their derived carbon materials. The IL loading did not significantly affect the gas uptake of the carbon materials, while for the composites its main contribution was on the increase of the selectivity. The number of cyano groups in the anion played a key role in the sorption capacity and selectivity performance as it directly affects the N content and textural properties. The carbon material obtained from ZIF-8 (C_ZIF-8) precursor showed the best sorption capacity for all gases, just being surpassed by the C_15%[C6MIM][B(CN)4]@ZIF-8 carbon up to 1 bar. In terms of selectivity performance, carbons based on [C6MIM][B(CN)4]@ZIF-8 composites revealed to be equally or more selective than C_ZIF-8, increasing up to 65% between 0 and 1 bar depending on the mixture. The composites produced and their respective carbons demonstrated a promising application as sorbents for post-combustion CO2 separation systems.publishersversionpublishe

    Produção de bovinos de corte em manejo intensivo de pastagem.

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    Estacionalidade de produção; Desempenho animal a pasto; Manejo do sistema; Resultados de produção e viabilidade economica.Resumo expandido

    Identification of carbonium and carbenium ions by QTAIM

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    The Gassman-Fentiman tool of increasing electron demand was used to identify carbonium and carbenium ions. Nonetheless, due to its ambiguous understanding, it was pivot of a historical dispute. We applied the Quantum Theory of Atoms in Molecules (QTAIM) metodology to characterize the carbonium and carbenium ions on an easier and more effective way. By comparing selected topological information of reference carbenium ions the QTAIM metodology can be used to evaluate whether a carbocation is classical or not. In addition, it is possible to rank a set of carbonium ions in order of their corresponding σ or π delocalization. There are few differences between our QTAIM-based model and Gassman-Fentiman tool. Unlike Gassman-Fentiman tool results, 7-anisyl-7-norbornenyl and 2-anisyl-2-norbornyl cations are non-classical, although they are the least nonclassical ions in their corresponding set of studied cations

    Electronic nature of the aromatic adamantanediyl ions and its analogues

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    The relative stability of the 1,3-dehydro-5,7-adamantanediyl dication is ascribed to its tridimensional aromaticity. However, its electronic nature is not well known. In order to improve its understanding, dicationic and monocationic adamantanedyil species and some key analogues were studied by atoms in molecules (AIM) theory. They were compared to non-aromatic adamantane analogues. AIM results indicate that the density in center of the cage structure and the average of all delocalization indexes involving its bridged atoms are higher in aromatic than in non-aromatic compounds. Degeneracy in energy of the bridged atoms, uniformity and magnitude of their shared charge distinguish the dications 1,3-adamantyl and the 1,3-dehydro-5,7-adamantanediyl. However, both are aromatic as well as the 1,3-dehydro-5,7-diboroadamantane. The 1,3-dehydro-7-adamantyl cation has a characteristic planar homoaromaticity
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