Parasitic phases at the origin of magnetic moment in BiFeO3 thin films grown by low deposition rate RF sputtering

FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQA series of epitaxial BiFeO3 thin films has been grown under high partial pressure in a pure O-2 atmosphere, which leads to a low deposition rate. The samples grown under these conditions have presented an evolution of the quality of the epitaxy as the deposition temperature increases, however, spurious beta-Bi2O3 and supertetragonal BiFeO3 phases are present in the films grown at higher temperatures. The presence of gamma-Fe2O3 is reported in one growing condition, and has been attributed to the origin of hysteretic ferromagnetic behavior. A second kind of magnetism, with higher magnetic moment and anhysteretic behaviour, is attributed to the presence of mixed phases of BiFeO3.1221215FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ2012/18397-12012/51198-2309354/2015-3This work was supported by FAPESP (Project No. 2012/51198-2). Some of the XRD measurements were performed at the XRD2 beamline of the LNLS/CNPEM under Project Nos. 20150162 and 20160908. The authors thank the LNNano/CNPEM for XRD/XRR, AFM and sputtering facilities, the LIEC/UFSCar for the SQUID measurements, and M. M. Soares for important discussions regarding the structural characterization. P.S. thanks FAPESP for financial support (Project No. 2012/18397-1). J.C.C. acknowledges support from CNPq (Project No. 309354/2015-3)

Energy and Environmental Performance Comparison of Heat Pump Systems Working with Alternative Refrigerants

Featured Application: An energy and environmental performance analysis of air-source and ground-source heat pump systems able to operate with traditional (R-410A) and alternative low-GWP (R-454B) refrigerants is conducted. The case study is composed of an existing residential single-family house, and the coupled HVAC system is modeled by means of the commercial software TRNSYS. The TEWI index is considered to evaluate the environmental impact of the heat pump systems. The results of the numerical simulations show a significant reduction in the overall greenhouse emissions of those systems in which R-454B is employed as a refrigerant. The European Parliament has imposed to reduce by 2030 whole HFC emissions by at least two-thirds with respect to 2014 levels. With the aim of contributing to determine the energy and environmental advantages of refrigerants alternative to R-410A, this paper reports the results of a numerical study focused on an HVAC system coupled to a residential building and based on a reversible electric heat pump. In particular, two heat pump typologies are considered: an air-source and a ground-source heat pump, both operating with the two refrigerants R-410A and R-454B. The environmental performance of the studied system is assessed by means of the TEWI (total equivalent warming impact) index. The adoption of R-454B involves a slight decrease (2–3%) in the overall annual energy performance of the system with respect to the use of R-410A. On the other hand, the working fluid R-454B guarantees a marked decrease in the TEWI indicator. Indeed, considering the current Italian emission factor of electricity taken from the grid, the total emissions over the entire heat pump operating life drop by about 25% and can decrease by up to 89% in perspective, following the current reduction trend of the emission factor

Conservation of Nickel Ion Single-Active Site Character in a Bottom-Up Constructed π-Conjugated Molecular Network

On-surface chemistry holds the potential for ultimate miniaturization of functional devices. Porphyrins are promising building-blocks in exploring advanced nanoarchitecture concepts. More stable molecular materials of practical interest with improved charge transfer properties can be achieved by covalently interconnecting molecular units. On-surface synthesis allows to construct extended covalent nanostructures at interfaces not conventionally available. Here, we address the synthesis and properties of covalent molecular network composed of interconnected constituents derived from halogenated nickel tetraphenylporphyrin on Au(111). We report that the π-extended two-dimensional material exhibits dispersive electronic features. Concomitantly, the functional Ni cores retain the same single-active site character of their single-molecule counterparts. This opens new pathways when exploiting the high robustness of transition metal cores provided by bottom-up constructed covalent nanomeshes

Características de carcaça e do couro de bovinos precoces e superprecoces.

Objetivou-se avaliar o efeito do sistema de produção sobre características produtivas e do couro de bovinos cruzados precoces e superprecoces. Foram utilizados 36 animais, sendo 16 provenientes do sistema superprecoce (10 machos castrados e seis fêmeas), terminados em confinamento e 20 animais do sistema precoce (10 machos castrados e 10 fêmeas), terminados em pastagens, recebendo suplementação protéico energética (1 kg/dia/animal). Após o abate os couros foram processados até a etapa de couro semi-acabado, onde foram retiradas as amostras da região do dorsolombar para os ensaios físico-mecânicos de tração e rasgamento. Houve efeito do sistema de produção para ganho de peso total (GPT), ganho médio diário (GMD), área de olho de lombo (AOL), espessura de gordura subcutânea (EGS), marmoreio, peso da pele ao abate (PPe1) e perdas com a padronização, com menores médias para animais precoces. As perdas apresentadas pelas fêmeas foram 14,48 e 6,88 kg, e para os machos castrados 9,32 e 4,84 kg, respectivamente para superprecoces e precoces. As médias de PA, peso da pele padronizada e área do couro Wet-blue dos machos castrados foram 473,60 kg, 40,60 kg e 4,52 m², respectivamente, para superprecoces e 462,83 kg, 29,77 kg e 4,31 m², respectivamente, para precoces. Não houve efeito de sexo e de sistema de produção para as características avaliadas nos ensaios físicos mecânicos no couro de bovinos precoces e superprecoces

Photoionization Dynamics of the Tetraoxo Complexes OsO4 and RuO4

The photoionization dynamics of OsO4 and RuO4, chosen as model systems of small-size mononuclear heavy-metal complexes, has been theoretically studied by the time-dependent density functional theory (TDDFT). Accurate experimental measurements of photoionization dynamics as a benchmarking test for the theory are reported for the photoelectron asymmetry parameters of outer valence ionizations of OsO4, measured in the 17-90 eV photon energy range. The theoretical results are in good agreement with the available experimental data. The observed dynamical behavior of partial cross sections and asymmetry parameters has been related to both the coupling to the continuum of discrete excited states, giving strong modulations in the photon energy dependency, and the atomic composition of the initial ionized states, which determines the rate of decay of ionization probability for increasing excitation energies. Overall, an extensive analysis of the photoionization dynamics for valence and core orbitals is presented, showing good agreement with all the available experimental data. This provides confidence for the validity of the TDDFT approach in describing photoionization of heavy transition element compounds, with the perspective of being used for larger systems. Further experimental work is suggested for RuO4 to gather evidence of the sensitivity of the theoretical method to the nature of the metal atom