Experimental and Theoretical Study of SbPO4 under Compression.

SbPO4 is a complex monoclinic layered material characterized by a strong activity of the nonbonding lone electron pair (LEP) of Sb. The strong cation LEP leads to the formation of layers piled up along the a axis and linked by weak Sb-O electrostatic interactions. In fact, Sb has 4-fold coordination with O similarly to what occurs with the P-O coordination, despite the large difference in ionic radii and electronegativity between both elements. Here we report a joint experimental and theoretical study of the structural and vibrational properties of SbPO4 at high pressure. We show that SbPO4 is not only one of the most compressible phosphates but also one of the most compressible compounds of the ABO4 family. Moreover, it has a considerable anisotropic compression behavior, with the largest compression occurring along a direction close to the a axis and governed by the compression of the LEP and the weak interlayer Sb-O bonds. The strong compression along the a axis leads to a subtle modification of the monoclinic crystal structure above 3 GPa, leading from a 2D to a 3D material. Moreover, the onset of a reversible pressure-induced phase transition is observed above 9 GPa, which is completed above 20 GPa. We propose that the high-pressure phase is a triclinic distortion of the original monoclinic phase. The understanding of the compression mechanism of SbPO4 can aid to improve the ion intercalation and catalytic properties of this layered compound.

Zein films with unoxidized or oxidized tannic acid.

BACKGROUND: Corn zein is a predominatly hydrophobic protein, forming films with relatively good water resistance. Tannic acid, especially in its oxidized form, is supposed to cross-link proteins including zein, which may be explored to further enhance the water resistance of zein films. The effects of different contents (0-8 wt%) of unoxidized and oxidized tannic acid (uTA and oTA, respectively) on the properties of zein films at different pH values (4-9) were studied, according to central composite designs. RESULTS: Increasing tannic acid contents and pH values resulted in decreased water solubility and increased tensile strength and modulus of films. The presence of tannic acid provided the films with a yellowish color and increased opacity. Paired t-tests indicated that oTA films presented higher tensile strength, lower water vapor permeability and lower water solubility than uTA films. CONCLUSION: Higher tannic acid contents and pH values resulted in films with better overall physical properties, which might be ascribed to cross-linking, although the films were still not water resistant. The resulting films have potential to be used for food packaging and coating applications. © 2017 Society of Chemical Industry.

Size-Dependent High-Pressure Behavior of Pure and Eu3+-Doped Y2O3 Nanoparticles: Insights from Experimental and Theoretical Investigations.

We report a joint high-pressure experimental and theoretical study of the structural, vibrational, and photoluminescent properties of pure and Eu3+-doped cubic Y2O3 nanoparticles with two very different average particle sizes. We compare the results of synchrotron X-ray diffraction, Raman scattering, and photoluminescence measurements in nanoparticles with ab initio density-functional simulations in bulk material with the aim to understand the influence of the average particle size on the properties of pure and doped Y2O3 nanoparticles under compression. We observe that the high-pressure phase behavior of Y2O3 nanoparticles depends on the average particle size, but in a different way to that previously reported. Nanoparticles with an average particle size of ~37 nm show the same pressure-induced phase transition sequence on upstroke and downstroke as the bulk sample; however, nanoparticles with an average particle size of ~6 nm undergo an irreversible pressure-induced amorphization above 16 GPa that is completed above 24 GPa. On downstroke, 6 nm nanoparticles likely consist of an amorphous phase.

Unveiling the role of the lone electron pair in sesquioxides at high pressure: compressibility of ß-Sb2O3.

The structural, vibrational and electronic properties of the compressed ß-Sb2O3 polymorph, a.k.a. mineral valentinite, have been investigated in a joint experimental and theoretical study up to 23 GPa. The compressibility of the lattice parameters, unit-cell volume and polyhedral unit volume as well as the behaviour of its Raman- and IR-active modes under compression have been interpreted on the basis of ab initio theoretical simulations. Valentinite shows an unusual compressibility up to 15 GPa with four different pressure ranges, whose critical pressures are 2, 4, and 10 GPa. The pressure dependence of the main structural units, the lack of soft phonons, and the electronic density charge topology address the changes at those critical pressures to isostructural phase transitions of degree higher than 2. In particular, the transitions at 2 and 4 GPa can be ascribed to the changes in the interaction between the stereochemically-active lone electron pairs of Sb atoms under compression. The changes observed above 10 GPa, characterized by a general softening of several Raman- and IR-active modes, point to a structural instability prior to the 1st-order transition occurring above 15 GPa. Above this pressure, a tentative new high-pressure phase (s.g. Pcc2) has been assigned by single-crystal and powder X-ray diffraction measurements.

Bacterial cellulose aerogels: Influence of oxidation and silanization on mechanical and absorption properties.

Biodegradable aerogels may help to develop eco-friendly technological pathways to increase the efficiency of chemical processes. In the present work, we describe the preparation of a novel bacterial cellulose aerogel oxidized by TEMPO, nanofibrillated in a blender, and silanized with methyltrimethoxysilane, resulting in four different types of aerogel. The aerogels produced from the double-functionalized cellulose suspension (BCOXNS) were compared to other non-oxidized (BCN and BCNS) and non-silanized (BCOXN) aerogels All aerogels were very light (density 10-14 kg.m-3) and very porous (porosity >99 %). The aerogels of BCOXNS showed better mechanical properties (tension of 13.0 kPa, modulus of elasticity of 39.4 kPa) and hydrophobicity, and could absorb organic solvents of different polarities. The BCOXNS could be recycled at least 7 times after absorbing organic solvents while retaining an absorption capacity of 83 %. This material can be used as a standard for the further development of aerogels based on bacterial biopolymers.

Improvement of polyvinyl alcohol properties by adding nanocrystalline cellulose isolated from banana pseudostems.

Cellulose nanocrystals (CNCs) isolated from banana pseudostems fibers (BPF) of the Pacovan variety were used as fillers in a polyvinyl alcohol (PVOH) matrix to yield a nanocomposite. The fibers from the external fractions of the BPF were alkaline bleached and hydrolyzed under acidic conditions (H2SO4 62% w/w, 70 min, 45 °C) to obtain CNCs with a length (L) of 135.0 ± 12.0 nm and a diameter (D) of 7.2 ± 1.9 nm to yield an aspect ratio (L/D) of 21.2. The CNCs were applied to PVOH films at different concentrations (0%, 1%, 3%, and 5% w/w, dry basis). With higher concentrations of CNCs, the water-vapor barrier of the films increased, while the optical properties changed very little. Increasing the concentration of the CNCs up to 3% significantly improved the mechanical properties of the nanocomposite.

Para além do pensamento social hegemônico: Abdias do Nascimento e a condição afro-brasileira

A importância dos intelectuais militantes, nos diversos movimentos sociais contemporâneos, não pode ser medida apenas por sua atuação frente às organizações ou instituições concebidas pela sociedade civil. Muitos deles tendem a estabelecer novas formas de percepção e análise da realidade social em que estão inseridos. Tais formas de percepção propiciam análises que se encontram a margem do espaço acadêmico sobre os fenômenos sociais, os quais merecem um tratamento sociológico que busque contemplar a lacuna deixada no debate sobre o pensamento social brasileiro. Este é o caso de Abdias do Nascimento, considerado internacionalmente como um dos principais pensadores pan-africanistas. Sua obra representa um aporte central para a análise da natureza orgânica e estrutural do racismo latino-americano, especialmente a partir da perspectiva da política regional. O que este trabalho propõe é que se pense produção para além do militantismo, já bastante analisado por diversos autores, localizando sua contribuição analítica ao pensamento social brasileiro. O que se pretende evidenciar ao longo do texto é a forma como esse modelo analítico é produzido. (AU)

The importance of intellectual activists, in various contemporary social movements, can not be measured only by its performance in the face oforganizations or institutions designed by civil society. Many of them tend toestablish new forms of perception and analysis of social reality in which theylive. Such forms of analysis provide insight - that are the edge of the academic space - on social phenomena, which deserve a sociological treatment that seeks to address the gap left in the debate on Brazilian social thought. This is the case of Abdias do Nascimento, regarded internationally as a leading pan-Africanist thinkers. His work represents a central contribution to the analysis of organic and structural nature of racism in Latin America, especially from the perspective of regional policy. What this paper proposes is to think beyond the production militancy, already well studied by several authors, locating its analytical contribution to the Brazilian social thought. What if you want to highlight in the text is how this analytical model is produced. (AU)

Mobilização política, resistência cultural e religiões afrobrasileiras sob o olhar de Abdias do Nascimento / Political mobilization cultural resistance and african-Brazilian religions under the gaze of Abdias do Nascimento

O presente trabalho visa aduzir a discussão proposta por Abdias do Nascimento acerca das condições sociais de possibilidades de existência e prática das religiões afrobrasileiras no Brasil. Um dos principais espaços onde se buscou a eliminação do referencial cultural africano foi a religião. No entanto, o que o texto evidenciará é que, justamente, na manutenção das práticas religiosas afrobrasileiras que se verificará a resistência às diversas formas de opressão a que foram submetidos os afrodescendentes no Brasil. (AU)

Estudo da relação anatômica do nervo ulnar com os fiod de Kirschner aplicados percutaneamente no côndilo medial do cotovelo / Anatomical relation of ulnar nerve with percutaneously applied K-wires at the elbow medial condyle

Foi realizado um estudo anatômico em 20 membros su periores de 10 cadáveres esqueleticamente maduros. Dois fios de Kirschner de 2,0mm, lisos, foram introduzidos no epicôndilo medial, sendo um no terço superior e outro no terço inferior. Os espécimes foram dissecados para determinar: a) o trajeto do nervo ulnar no túnel cubital; b) as distâncias entre os pinos superior e inferior, no epicôndilo medial, e entre estes e o nervo ulnar. Os resultados foram analisados estatisticamente através do teste t de Student. Não houve transfixação do nervo ulnar por nenhum pino. Os resultados deste estudo experimental controlado indicam que, quando o pino é corretamente introduzido através do terço superior do epicôndilo medial, o nervo ulnar corre menor risco de ser transfixado.