Browsing by Issue Date, starting with "2008-01"
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- Three-Dimensional CFD modelling and analysis of the thermal entrainment in open refrigerated display cabinetsPublication . Gaspar, Pedro Dinis; Gonçalves, Luís Carlos Carrilho; Pitarma, Rui A.This study presents a three-dimensional Computational Fluid Dynamics (CFD) simulation of the air flow pattern and the temperature distribution in a refrigerated display cabinet. The thermal entrainment is evaluated by the variations of the mass flow rate and thermal power along and across the air curtain considering the numerical predictions of abovementioned properties. The evaluation on the ambient air velocity for the three-dimensional (3D) effects in the pattern of this type of turbulent air flow is obtained. Additionally, it is verified that the longitudinal air flow oscillations and the length extremity effects have a considerable influence in the overall thermal performance of the equipment. The non uniform distribution of the air temperature and velocity throughout the re-circulated air curtain determine the temperature differences in the linear display space and inside the food products, affecting the refrigeration power of display cabinets. The numerical predictions have been validated by comparison with experimental tests performed in accordance with the climatic class n.º 3 of EN 441 Standard (Tamb = 25 ºC,φamb = 60%; vamb = 0,2 m s-1). These tests were conducted using the point measuring technique for the air temperature, air relative humidity and air velocity throughout the air curtain, the display area of conservation of food products and nearby the inlets/outlets of the air mass flow.
- Monoteísmo, Trindade e Teologia PolíticaPublication . Rosa, José Maria SilvaÉ sabido que Erik Peterson (1890-1960) inicia a sua obra mais famosa, «O Monoteísmo como Problema Politico: uma Contribuiçãoo para a História da Teologia Política no Imperio Romano», precisamente com o verso da Íliada com que Aristóteles terrnina o livro XII da Metafísica (1076a), o seu texto teológico por excelência. Reza assim a palavra que Homero põe na boca de Agamémnon: «ouk agathon polykoiranie: eis koiranos esto.« / «Non bonum pluralitas principatum: unus ergo princeps.« / «Não é boa coisa o governo de muitos: que haja apenas um só soberano!»
- Separation of different forms of proteose peptone 3 by hydrophobic interaction chromatography with a dual salt systemPublication . Sousa, Ângela Maria Almeida de; Passarinha, Luís António Paulino; Rodrigues, L.R.; Teixeira, José; Mendonça, António; Queiroz, JoãoA panel of four hydrophobic adsorbents (butyl-, octyl-, phenyl- and epoxy-Sepharose) was used to examine the selectivity and fractionation of several proteose peptone 3 (PP3) forms from a freeze-dried extract of whey bovine milk. In particular, the effects of altering the ligand type and salt were investigated. The chromatographic studies suggest that PP3 strongly interacts among the three commercial hydrophobic resins leading to a drop off in selectivity, while a complete binding was achieved at low salt concentrations (below 0.5 M) and total elution only with phosphate buffer and/or water stepwise conditions. Only in epoxy–Sepharose was an appreciably selectivity of the several fractions of PP3 present in the initial feedstock attained. Despite the high salt concentration for a complete binding of PP3 (above 1.5 M ammonium sulfate) onto this support, the dual salt system (ammonium sulfate 1 M and sodium citrate 0.8 M) led to a high separation degree of high and low molecular weight forms of PP3.