SAFT-γ force field for the simulation of molecular fluids: 8. hetero-group coarse-grained models of perfluoroalkylalkanes assessed with new vapour-liquid interfacial tension data

The air-liquid interfacial behaviour of linear perfluoroalkylalkanes (PFAAs) is reported through a combined experimental and computer simulation study. The surface tensions of seven liquid PFAAs (perfluorobutylethane, F4H2; perfluorobutylpentane, F4H5; perfluorobutylhexane, F4H6, perfluorobutyloctane, F4H8; perfluorohexylethane, F6H2; perfluorohexylhexane, F6H6; and perfluorohexyloctane, F6H8) are experimentally determined over a wide temperature range (276 to 350 K). The corresponding surface thermodynamic properties and the critical temperatures of the studied compounds are estimated from the temperature dependence of the surface tension. Experimental density and vapour pressure data are employed to parameterize a generic heteronuclear coarse-grained intermolecular potential of the SAFT- γ family for PFAAs. The resulting force field is used in direct molecular dynamics simulations to predict with quantitative agreement the experimental tensions and to explore the conformations of the molecules in the interfacial region revealing a preferential alignment of the PFAA molecules towards the interface and an enrichment of the perfluoro-groups at the outer interface region

Exact Nonequilibrium Work Generating Function for a Small Classical System

We obtain the exact nonequilibrium work generating function (NEWGF), for a small system consisting of a massive Brownian particle connected to internal and external springs. The external work is provided to the system for a finite time interval. The Jarzynski equality (JE), obtained in this case directly from the NEWGF, is shown to be valid for the present model, in an exact way regardless of the rate of external work

Lamellae Stability in Confined Systems with Gravity

The microphase separation of a diblock copolymer melt confined by hard walls and in the presence of a gravitational field is simulated by means of a cell dynamical system model. It is found that the presence of hard walls normal to the gravitational field are key ingredients to the formation of well ordered lamellae in BCP melts. To this effect the currents in the directions normal and parallel to the field are calculated along the interface of a lamellar domain, showing that the formation of lamellae parallel to the hard boundaries and normal to the field correspond to the stable configuration. Also, it is found thet the field increases the interface width.Comment: 4 pages, 2 figures, submitted to Physical Review

Ecologia da polinização do feijão-caupi (Vigna ungulculata (L.) walp.) em área de sequeiro no municipio de Petrolina-PE.

o feijão-caupi é uma leguminosa de origem africana de importante papel como fonte alimentarpara as regiõestropicais e subtropicaisdo mundo

Critical scaling in standard biased random walks

The spatial coverage produced by a single discrete-time random walk, with asymmetric jump probability $p\neq 1/2$ and non-uniform steps, moving on an infinite one-dimensional lattice is investigated. Analytical calculations are complemented with Monte Carlo simulations. We show that, for appropriate step sizes, the model displays a critical phenomenon, at $p=p_c$. Its scaling properties as well as the main features of the fragmented coverage occurring in the vicinity of the critical point are shown. In particular, in the limit $p\to p_c$, the distribution of fragment lengths is scale-free, with nontrivial exponents. Moreover, the spatial distribution of cracks (unvisited sites) defines a fractal set over the spanned interval. Thus, from the perspective of the covered territory, a very rich critical phenomenology is revealed in a simple one-dimensional standard model.Comment: 4 pages, 4 figure

TRIZ and lean philosophies applied together in management activities

Purpose: In the current market, the Portuguese industry faces strong competition from countries with substantially lower operating costs. The agri-food industry is also subject to increasing competition, both nationally and internationally. The utilization of methodologies that, in addition to continuous improvement, provide the development of creative and innovative solutions may be relevant for highlighting and differentiating between organizations. In this work, Teoriya Resheniya Izobretatelskikh Zadach and Lean Philosophies have been implemented together. Methodologies as Matrix of Ideality Matrix of Contradiction, Single Minute Exchange of Die, 5S and the Substance-Field analyses were used as complementary tools to improve the production management activities of agri-food sector. Strongly focused on the issues of time wastage and the organization and management of the filling line, the implementation of these methodologies led to a reduction of setup times, of the operators’ movement and an improvement in the line’s management and organization, and improve the results of 5S audits, depending on the work station. The aims of this study is the implementation of diferent methodologies, philosophies and tools to improve management activities. Methodology/Approach: The methodology presented in this work involves using Lean and TRIZ methodologies together. Namely Matrix of Ideality, the Matrix of Contradictions, SMED, 5S and the Substance-Field Analysis, were used to optimize the management activities, in agro-food industrial sector. The methodology strongly focused on the issues of time wastage, organization and management of an filling line. Findings: The implementation of methodologies led to a reduction of setup times by 60% to 70%, a reduction of the operators’ movement during format changes by 26.2%, and an improvement in the line’s management and organization by 9% to 12%, depending on the work station. Research Limitation/implication: In the management activities, the results are not universal. Therefore, the same methodology applied in another industrial sector will present differents results. Nevertheless, the application of this methodology and the tools choosen only make sense if it facilitates the management of improvements. Originality/Value of paper: There is a need and demand for innovative solutions that lead to continuous improvement, production processes optimization and resource saving. The combination of different validated methologies, with new concrete studies, is always in scientific and technical interest and continuously sought-after (demanded, welcome) by academic and industrial sectors.publishersversionpublishe

Avaliação do potencial de estirpes de rizóbio em fixar nitrogênio associadas ao feijão-caupi em Petrolina-PE.

O feijão-caupi é uma cultura leguminosa de grande importância para a alimentação humana, constituindo-se em uma fonte de proteína para a maioria da população rural. A eficiência de diferentes estirpes de rizóbio em fixar o nitrogênio atmosférico em associação com o feijão-caupi foi testada ao nível de campo na Estação Experimental da Caatinga, da Embrapa Semi-Árido, localizada no município de Petrolina-PE (09o23'S e 40o30'W, altitude: 350 m). O experimento foi implantado em condições de sequeiro, com delineamento de blocos ao acaso e seis repetições, constando de seis tratamentos, sendo quatro estirpes de rizóbio - BR 3267, BR 3299, BR 33o1 e BR 3302, uma dose de nitrogênio mineral - 50 kg ha-1 e uma testemunha. Aos trinta dias após o plantio, o número e peso seco de nódulos, peso de matéria seca e concentração de nitrogênio na parte aérea da planta foram determinados. Todas as estirpes superaram significativamente o tratamento testemunha, tanto em número como em peso seco de nódulos, denotando uma alta eficiência em nodular as raízes de feijão-caupi em relação às estirpes de rizóbio existentes no solo da área experimental

Probing the Structure of Liquids with 129Xe NMR Spectroscopy: n-Alkanes, Cycloalkanes, and Branched Alkanes

The liquid organization of linear, branched, and cyclic alkanes was studied using atomic 129Xe as a NMR probe. 129Xe chemical shifts have been experimentally determined for xenon dissolved in a total of 21 alkanes. In order to allow the comparison of the different solvents at similar thermodynamic conditions, the measurements were performed over a wide range of temperatures, from the melting point of the solvent up to 350 K. The results were rationalized in terms of the density, nature, and organization of the chemical groups within xenon’s coordination sphere. Additionally, molecular dynamics simulations were performed using established atomistic force fields to interpret and clarify the conclusions suggested by the experimental results. The analysis is able to interpret previous results in the literature for ethane and propane at very different experimental conditions