Browsing by Author "Gutierrez, G"

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    Can an ideal gas feel the shape of its container?
    (1997) Gutierrez, G; Yanez, JM
    Thermodynamic quantities of an ideal gas enclosed in a finite container are examined. We use an asymptotic expansion for high temperatures to obtain the partition function of an ideal gas, both in two and three dimensions, showing the leading corrections to the internal energy due to a finite container. In the three-dimensional case, the first correction term depends only on the area-volume ratio, but higher order terms depend also on other geometric properties of the container. However, according to recent results, we show that the answer to the question posed in the title is negative. (C) 1997 American Association of Physics Teachers.
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    Gibbs' phase rule revisited
    (1996) Gutierrez, G
    Gibbs' phrase rule and related properties of phase diagrams are obtained using the simple combinatorial methods of associating a graph to each thermodynamic system. We think this approach allows a deeper understanding of the geometric roots of this rule.
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    Microstructural changes of potato cells and starch granules heated in oil
    (ELSEVIER SCIENCE BV, 2001) Aguilera, JM; Cadoche, L; Lopez, C; Gutierrez, G
    A method that mimics the frying operation was implemented to observe microstructural changes in potato cells and starch. Isolated cells were obtained by successive treatments of potato tissue with acid and alkali solutions. Potato cells were heated in oil at a rate of 40 degreesC/min or directly in hot oil (180 degreesC) using a hot stage attached to a light microscope and studied by video-microscopy. Starch granules in cells underwent rapid gelatinization, deformation and compaction into one mass that occupied the whole volume of the cell. After dehydration cells showed a distinctive outer zone and a homogeneous core. Cell walls showed no signs of disruption but at temperatures > 100 degreesC a reduction in cell area occurred. Immersion of cells in hot oil resulted in rapid swelling of starch. Relative projected area increased by 12% after 45 s of heating. Wet isolated starch granules began to expand and gelatinize at 65 degreesC and became disrupted at 120 degreesC. No changes were observed in dry starch granules subjected to a similar treatment. (C) 2001 Elsevier Science Ltd. All rights reserved.