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A first‐principles‐based effective Hamiltonian is developed and employed to investigate finite‐temperature structural properties of a prototype of perovskite halides, that is CsPbI3. Such simulations, when using first‐principles‐extracted coefficients, successfully reproduce the existence of an orthorhombic Pnma state and its iodine octahedral tilting angles around room temperature. However, they also yield a direct transformation from Pnma to cubic upon heating, unlike measurements that reported the occurrence of an intermediate long‐range‐tilted tetragonal P4/mbm phase in‐between the orthorhombic and cubic phases. Such disagreement, which may cast some doubts about the extent to which first‐principle methods can be trusted to mimic hybrid perovskites, can be resolved by “only” changing one short‐range tilting parameter in the whole set of effective Hamiltonian coefficients. In such a case, some reasonable values of this specific parameter result in the predictions that i) the intermediate P4/mbm state originates from fluctuations over many different tilted states; and ii) the cubic phase is highly locally distorted and develops strong transverse antiphase correlation between first‐nearest neighbor iodine octahedral tiltings, before undergoing a phase transition to P4/mbm under cooling. 相似文献
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Two proprietary biocides were compounded and extruded at three concentrations, respectively, into high density polyethylene-maple wood flour lumber (HDPE-MWL) and evaluated for their efficacy to control fungal colonization and discoloration using the ASTM Standard G 21-96. Although the silver biocide used in this study did not control fungal colonization and discoloration of HDPE-MWL, statistically significant difference was observed between the highest silver biocide concentration and those of the two lower silver biocide concentrations. The latter exhibited no significant difference with the controls. In contrast, the three levels of zinc biocides showed significant difference from each other with respect to their efficacy against fungal colonization and discoloration of HDPE-MWL. Overall, only the zinc biocide was efficacious against fungal colonization and discoloration. The biocide containing zinc as an active biocidal agent was most efficacious at 1% (by weight) concentration. 相似文献
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Cristiane Vieira Helm Alicia de Francisco Salete Aparecida Gaziola Ricardo Francisco Fornazier Georgia Bertoni Pompeu Ricardo Antunes Azevedo 《Food Biotechnology》2005,18(3):327-341
Barley (Hordeum vulgare L.) has had an important impact on human nutrition. Hull-less barley is a genetically improved type that has been widely used in recent years. Six Brazilian hull-less barley varieties (IAC-IBON 214-82; IAC 8612-421; IAC 8501-31; IAC 8501-12; IAPAR 39-ACUMAI; IAC 8501-22) were analyzed for storage protein constituents, amino acid contents, and similarity among the hull-less barley varieties. Albumins, globulins, prolamins I and II, and glutelins were extracted and separated by SDS-PAGE. The total protein amino acid contents of the flour were also determined for each variety by TLC and HPLC. Variations in intensity and appearance and disappearance of protein bands were observed among the varieties suggesting genetic variability. However, the amino acid profile did not indicate any major variations in the amino acid concentrations. The high lysine and threonine total concentrations detected in the seeds of the hull-less barley varieties encouraged an investigation into the regulation of amino acid metabolism and storage protein synthesis. 相似文献
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Auguste Commeyras Hlne Collet Laurent Boiteau Jacques Taillades Odile Vandenabeele‐Trambouze Herv Cottet Jean‐Philippe Biron Raphaël Plasson Louis Mion Olivier Lagrille Herv Martin Franck Selsis Michel Dobrijevic 《Polymer International》2002,51(7):661-665
Addressing the still open question of the prebiotic origin of sequential macromolecules (peptides, nucleic acids) on the primitive Earth, we describe a molecular engine (the primary pump), which works at ambient temperature and continuously generates, elongates and complexifies sequential peptides. This new scenario is based on a cyclic reaction sequence, whose keystep is the activation of amino acids into their N‐carboxyanhydrides (NCA) through nitrosation by NOx. This process could have taken place on tidal beaches; it requires a buffered ocean, emerged land and a nitrosating atmosphere. With the help of geochemical studies and computer simulations of atmosphere photochemistry, we show that the primitive Earth during the Hadean may have satisfied all these requirements. © 2001 Society of Chemical Industry. 相似文献
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An optical nondestructive strain measurement technique was performed to analyze the mechanical deformation induced by an electrical field within the insulating materials. Poly(ethylene naphthalene 2,6‐dicarboxylate) (PEN) films were then subjected to constant electrical fields right up to their electrical breakdown. The experimental technique made it possible to follow the various stages of the mechanical behavior of PEN in real time. The final breakdown occurred in the observation zone and the related mechanical deformation was captured. A “margarita” structure was observed with a hole at the center. The experimental results indicated that the level of the induced‐mechanical deformations depended on the local environment. We defined two different zones representing the inside and the outside of the damaged area. The induced‐deformations were larger in the damaged zone. It was also observed that deformations increased when the sample had a lower degree of crystallinity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
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