Excess free volume and structural properties of inert gas condensation synthesized nanoparticles based CuZr nanoglasses

Nanoglass (NG) as a new structure-tunable material has been investigated using both experiments and computational modeling. Experimentally, inert gas condensation (IGC) is commonly employed to prepare metallic glass (MG) nanoparticles that are consolidated using cold compression to generate an NG. In computational modeling, various methods have been used to generate NGs. However, due to the high computational cost involved, heretofore modeling investigations have not followed the experimental synthesis route. In this work, we use molecular dynamics simulations to generate an NG model by consolidating IGC-prepared Cu(64)Zr(36) nanoparticles following a workflow similar to that of experiments. The resulting structure is compared with those of NGs produced following two alternative procedures previously used: direct generation employing Voronoi tessellation and consolidation of spherical nanoparticles carved from an MG sample. We focus on the characterization of the excess free volume and the Voronoi polyhedral statistics in order to identify and quantify contrasting features of the glass-glass interfaces in the three NG samples prepared using distinct methods. Results indicate that glass-glass interfaces in IGC-based NGs are thicker and display higher structural contrast with their parent MG structure. Nanoparticle-based methods display excess free volume exceeding 4%, in agreement with experiments. IGC-prepared nanoparticles, which display Cu segregation to their surfaces, generate the highest glass-glass interface excess free volume levels and the largest relative interface volume with excess free volume higher than 3%. Voronoi polyhedral analysis indicates a sharp drop in the full icosahedral motif fraction in the glass-glass interfaces in nanoparticle-based NG as compared to their parent MG

A importância da preparação física para atletas de rodeio de montaria em touros

Monografia (graduação)—Universidade de Brasília, Universidade Aberta do Brasil, Faculdade de Educação Física, Licenciatura em Educação Física a Distância, 2012.O rodeio é hoje o esporte que mais cresce no país e com isto aumenta também a quantidade de atletas envolvidos nestes eventos, desta forma foi feito uma pesquisa visando levantar o tema: “à importância da preparação física dos atletas de rodeio de montarias em touro”. O trabalho foi realizado através de uma pesquisa qualitativa usando questionário, analisando dois atletas de alto nível tidos como experientes e mais dois atletas em inicio de carreira. A pesquisa foi realizada no parque do peão durante a 57ª Festa do peão de Barretos-SP no período de 16 a 26 de agosto de 2012 e no Brahma Super Bull PBR de Olímpia-SP de 14 a 17 de novembro de 2012. Pesquisei ainda um líder sindical dos atletas e um organizador de rodeio. Fiz ainda um estudo sobre obras similares e encontrei poucas infelizmente, denotando necessidade de mais trabalhos científicos sobre este tema. No final ficaram claro algumas tendências: 100% dos entrevistados fazem preparação física, porém apenas 50% deles alegaram que utilizam profissionais formados, ou seja, alguns fazem a preparação por conta própria ou com pessoas despreparadas. Os custos de contratação destes profissionais segundo 75% dos entrevistados deveriam ser pago pelos próprios atletas e exatamente 75% alegaram também terem condições de pagar um personal trainer, porém, outros 25% que disseram não, mostram que nem todos têm condições, principalmente os novatos e o ideal seria algum clube ou associação fazer o pagamento destes educadores físicos. Só que hoje são poucas as associações nesta área como a PBR Brasil. Outra solução segundo os entrevistados seria a criação de centros de treinamento nas cidades que promovem este tipo de evento. Ficou latente a criação de um novo campo de atividade para a Educação Física. É necessário mais estudos sobre o assunto, mas pelo que diz os entrevistados e a literatura, à tendência maior é que a Educação Física é de fato importante na preparação Física dos atletas de rodeio. _____________________________________________________________________________ ABSTRACTThe rodeo is now the fastest growing sport in the country with an increasing number of athletes becoming involved in these events. That motivated the development of this research which has as subject "the importance of physical training of rodeo bull rider athletes". The study was conducted assessing qualitatively the feedback from the athletes in the field through a questionnaire, analyzing two top bull riders, taken as experienced athletes, and two other athletes in early career. The research was conducted at “Parque do Peão” during the 57th Rodeo Festival of Barretos-SP, which occurred from 16 to 26 August 2012, and the Brahma Super Bull PBR Olimpia-SP, which occurred from 14 to 17 November 2012. Research data was also acquired from interviews with a rodeo union leader and a rodeo organizer. An extensive literature review on the topic showed a lack of similar research and evidenced the need to develop more scientific studies on this important field. Results from this research show clear trends. 100% of the athletes who participated in the research in fact do physical preparation. However, only 50% of them claimed to have utilized certified professionals. The other 50 % do their physical preparation by themselves or use non-certified professionals. According to 75% of the athletes consulted the cost of hiring these professionals should be covered by the athletes themselves. 75% of the athletes in fact claimed to be able to afford a personal trainer. However, the other 25% of the athletes, including mostly those in early career, who cannot afford a personal trainer, show that ideally some professional club or association should provide these physical educators. However, today there are few organizations in this area such as the PBR Brazil, which could provide such training. Another solution according to the interviewees would be the creation of training centers in cities that promote this type of event. This research indicated the development of a new field of activity in Physical Education. Additional work is needed to better clarify this field and the actual physical training needs of the rodeo bull rider athletes. However, this preliminary assessment of the topic based on the interviews and the literature review indicates that in fact Physical Education is of key importance for the physical preparation of rodeo bull rider athletes

Differences in Sb2Te3 growth by pulsed laser and sputter deposition

High quality Van der Waals chalcogenides are important for phase change data storage, thermoelectrics, and spintronics. Using a combination of statistical design of experiments and density functional theory, we clarify how the out-of-equilibrium van der Waals epitaxial deposition methods can improve the crystal quality of Sb2Te3 films. We compare films grown by radio frequency sputtering and pulsed laser deposition (PLD). The growth factors that influence the crystal quality for each method are different. For PLD grown films a thin amorphous Sb2Te3 seed layer most significantly influences the crystal quality. In contrast, the crystalline quality of films grown by sputtering is rather sensitive to the deposition temperature and less affected by the presence of a seed layer. This difference is somewhat surprising as both methods are out-of-thermal-equilibrium plasma-based methods. Non-adiabatic quantum molecular dynamics simulations show that this difference originates from the density of excited atoms in the plasma. The PLD plasma is more intense and with higher energy than that used in sputtering, and this increases the electronic temperature of the deposited atoms, which concomitantly increases the adatom diffusion lengths in PLD. In contrast, the adatom diffusivity is dominated by the thermal temperature for sputter grown films. These results explain the wide range of Sb2Te3 and superlattice crystal qualities observed in the literature. These results indicate that, contrary to popular belief, plasma-based deposition methods are suitable for growing high quality crystalline chalcogenides.Comment: 24 pages, 8 fig

Suppression of Phase Separation in LiFePO4 Nanoparticles During Battery Discharge

Using a novel electrochemical phase-field model, we question the common belief that LixFePO4 nanoparticles separate into Li-rich and Li-poor phases during battery discharge. For small currents, spinodal decomposition or nucleation leads to moving phase boundaries. Above a critical current density (in the Tafel regime), the spinodal disappears, and particles fill homogeneously, which may explain the superior rate capability and long cycle life of nano-LiFePO4 cathodes.Comment: 27 pages, 8 figure

Atomic-scale structure and properties of highly stable antiphase boundary defects in Fe3O4

The complex and intriguing properties of the ferrimagnetic half metal magnetite (Fe3O4) are of continuing fundamental interest as well as being important for practical applications in spintronics, magnetism, catalysis and medicine. There is considerable speculation concerning the role of the ubiquitous antiphase boundary (APB) defects in magnetite, however, direct information on their structure and properties has remained challenging to obtain. Here we combine predictive first principles modelling with high-resolution transmission electron microscopy to unambiguously determine the three-dimensional structure of APBs in magnetite. We demonstrate that APB defects on the {110} planes are unusually stable and induce antiferromagnetic coupling between adjacent domains providing an explanation for the magnetoresistance and reduced spin polarization often observed. We also demonstrate how the high stability of the {110} APB defects is connected to the existence of a metastable bulk phase of Fe3O4, which could be stabilized by strain in films or nanostructures

Suppression of Shear Banding and Transition to Necking and Homogeneous Flow in Nanoglass Nanopillars

10.1038/srep15611Scientific Reports51561