Analytical solution for a strong free-surface water vortex describing flow in a full-scale gravitational vortex hydropower system

Strong free-surface water vortices are found throughout industrial hydraulic systems used for water treatment, flow regulation, and energy generation. Previous models using the volumetric flow rate as a model input have generally been semi-empirical, and have tended to have some limitations in terms of the design of practical hydropower systems. In this study, an analytical model of a strong free-surface water vortex was developed. This model only requires the water head and geometric parameters as its inputs and calculates the maximum volumetric flow rate, aircore diameter, and rotational constant. Detailed experimental depthedischarge data from a full-scale gravitational vortex hydropower system,unavailable in the relevant literature, were obtained, and the simulated results showed excellent agreement with the experimental observations.These data could be used to verify similar models using laboratory-scale physical models in order to investigate the scaling effects. In contrast to previous models, this model does not assume a constant average velocity across the vortex radius and allows precise calculation of the resultant velocity vectors. Therefore, this model presents advantages in turbine design for energy generation systems.     

Water Sorption Characteristics of Sugar Impregnated Strawberries

ABSTRACT

Sorption behaviour of fresh and sucrose or glucose impreqnated strawberries in the a, ranqe 0.11-0.90 was determined at 28°C. For both- fresh and osmosed strawberries, the sorption isotherms displaved hysteresis Osmotic treatment produced a complex influence on the fruit behaviour that might be explained in terms of the chemical complexity of the systems, sucrose hydrolysis, sugar supersaturation, kinetic impediment to solute dissolution and crystallization of sugar.     

Synthesis and optical behavior of PLED devices based on (PMMA)/(PAA)/Er(AP)6Cl3 complex and N,N′-didodecyl-3,4,9,10-perylene tetracarboxylic diimide composites

The realization of efficient polymeric light emitting diode (PLEDs) in a double-layered configuration was investigated. The devices are composed by transparent conductive oxide (ITO)/MoO₃/organic layers/aluminum/selenium, conformed by thin film sandwich structures obtained by vacuum evaporation. Two organic layers were developed. First a n-type organic layer of composite based on polymethylmethacrylate (PMMA)/polyacrilic acid (PAA)/Er(AP)₆Cl₃ complex and second a n-type organic semiconductor, N,N′-didodecyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI-C₁₂H₂₅). The rare earth complex composites and the perilenic compound were synthesized and characterized using UV–Visible absorption, XPS, and NMR techniques, respectively. Driving voltage of devices was lowered by applying MoO₃ thin film as buffer layer and high current intensity efficiency was obtained applying a perilenic film. The effect of MoO₃ and PTCDI-C₁₂H₂₅ thin films, on the optical and the physical properties of the electroluminescent devices were discussed. I–V measurements have shown that the structures exhibit diode characteristics and the electroluminescent signal increases when PTCDI-C₁₂H₂₅ thin layer is introduced between the anode and the holes transporting layer. The morphology of the thin films with and without buffer layer indicates that introduction of this layer allows to obtain a homogeneous surface morphology. The results indicate that carrier injection ability and optimized charge balance is obtained to the lowest driving voltage and highest intensities efficiency among the referenced devices.     

Mild Thermal Process Combined with Vanillin Plus Citral to Help Shorten the Inactivation Time for <Emphasis Type=Italic>Listeria innocua</Emphasis> in Orange Juice

The response of Listeria innocua (surrogate for Listeria monocytogenes) to combined treatments involving moderate temperatures (57 to 61 °C) and the addition of different levels of citral (0 to 75 ppm) was assessed to obtain a minimally processed orange juice. The presence of citral notoriously increased the bactericidal effect of mild heating treatment. This effect did not depend on the amount of added citral at all assayed temperatures. In a second stage, combinations of two natural antimicrobials (vanillin and citral) were assessed in order to find the most effective inactivation treatment in orange juice. Vanillin (900–1,100 ppm) and citral (25 ppm) combined with mild heating treatment (52 or 57 °C) were tested against L. innocua in orange juice. The addition of 900 ppm vanillin and 25 ppm citral halved or more the time required to achieve five logarithmic cycles of reduction at both temperatures with respect to thermal treatment without antimicrobial addition. The increase in the maximum growth rate calculated from the modified Gompertz model properly correlated with the increasing vanillin level for a given citral concentration. Complementary information was obtained from successfully fitting a Weibullian model to the nonlinear semilogarithmic survival curves: The addition of vanillin and citral significantly increased the bactericidal effect of mild thermal treatment, changing the distribution of inactivation times and obtaining narrower frequency shapes with lower variance and mode values. The combination of vanillin and citral with mild heating treatment resulted in an innovative alternative to minimize detrimental effects caused by thermal processing of fruit juices. In addition, a consumer panel evaluated them with an acceptable overall pleasantness.     

Kinetics of Escherichia coli inactivation employing hydrogen peroxide at varying temperatures,pH and concentrations

The effectiveness of hydrogen peroxide on the destruction of planktonic cells of Escherichia coli at different temperatures, pH and sanitizer concentrations was studied. Inactivation kinetics of E. coli exhibited a clear dependence on hydrogen peroxide concentration, pH and temperature. A Weibullian mathematical model successfully described the inactivation curves. Quantitative kinetic results obtained allowed to identify various combinations H₂O₂ concentration–pH–temperature for 5-log cycles reduction of E. coli. Flow cytometry analysis revealed induced H₂O₂ cytoplasm membrane damage. TEM observations indicated that H₂O₂ treatment resulted in rupture of outer and cytoplasm membranes and a more uniform granularity.     

Turgor Pressure Effects on Textural Behavior of Honeydew Melon

ABSTRACT: Melon samples were equilibrated with solutions of increasing mannitol concentration in the range 0.00 to 0.80 M for the purpose of evaluating turgor pressure through volume change measurement. Melon compression and relaxation behaviors were evaluated with an Instron Testing machine, and structural characteristics were observed through microscopy. Immersion in mannitol solutions affected tissue firmness, reducing its value in all studied cases. After plasmolysis and plasmotypsis, samples became less elastic and more viscous, and firmness reduced more than 50%. Textural parameters obtained and microscopy results indicated that, in general, fracture might be associated with cell-wall integrity, and residual relaxation force might be associated with tissue turgor pressure.     

Osmotic dehydration of apple: Influence of sugar and water activity on tissue structure,rheological properties and water mobility

Osmotic dehydration of apple tissue (Malus pumila, Granny Smith cultivar) to water activity (a_w) 0.97 or 0.94 with maltose or maltose syrup solutions was studied and compared with previous results using glucose or trehalose as humectants. Structure (optical and transmission electronic microscopy observations), rheological properties (small scale dynamic oscillatory and creep/recovery measurements and large scale compression force-deformation testing), and water mobility (¹H NMR spectra) of parenchymatous apple tissue were significantly affected by osmotic treatments. Osmotically dehydrated apples became soft and extensible and lost crispness and hardness, while the behavior of the moduli G′ and G″ indicated weaker gels after osmosis. Compression properties of the tissues abruptly changed after osmotic dehydration to a_w 0.97, while reduction to a_w 0.94 led to a compression response more similar to that of untreated apples. Compression behavior and state and distribution of water in apple tissues were influenced by the osmotic agent employed and the a_w level, while in general mechanical spectra and creep analysis were not able for distinguishing physical differences between osmotic treatments assayed.     

Inactivation kinetics of peroxidase and polyphenol oxidase in peach juice treated with gaseous ozone

The effectiveness of gaseous ozone for inactivating peroxidase (POD) and polyphenoloxidase (PPO) in peach juice was investigated. The suitability of first‐order and Weibull models to describe inactivation kinetics was also analysed. Peach juice was exposed to ozone (0.11 and 0.20 mg O₃ min^?1 mL^?1) in a bubble column up to 12 min at 20 ± 1 °C. Enzyme activities were reduced due to treatments. The magnitude of the inactivation increased with ozone level and exposure time. Reductions in activity after 12 min of treatment ranged between 99.5% and 99.8% for POD and between 93.9% and 97.3% for PPO, depending on ozone concentration. Inactivation curves were successfully fitted with the first‐order and Weibull models; although, based on the root‐mean‐square error, the corrected Akaike and the Bayesian Schwarz criterion, the Weibull model showed stronger capability in all cases.     

Study of Pulsed Light-Induced Damage on Saccharomyces cerevisiae in Apple Juice by Flow Cytometry and Transmission Electron Microscopy

This work analyzed the pulsed light (PL) (0.0–71.6 J/cm²)-induced damage on Saccharomyces cerevisiae KE162 cells in peptone water (pH 3.5 or 5.6) and apple juice (pH 3.5) by applying flow cytometry (FCM) and transmission electronic microscopy. Cells were labeled with fluorescein diacetate (FDA) for detecting membrane integrity and esterase activity and with propidium iodide (PI) for monitoring membrane integrity. S. cerevisiae inactivation curves reached 6–7 log reductions (peptone water systems) and 3.9 log reductions (apple juice) after 60 s (71.6 J/cm²) of PL exposure. FCM revealed the same damage pattern (although at different doses) in all media: at low doses, there was an increase in population in PI⁺?FDA⁺ quadrant, while at high doses, most of the population was located at quadrant PI⁺–FDA^?, indicating that PL provoked rupture of the cytoplasm membrane allowing PI to penetrate cells and there was progressive loss of esterase activity. Comparison of conventional culture technique with FCM revealed the occurrence of certain cell subpopulations in peptone water with pH 3.5 which were stressed and lost their ability to grow in agar but still showed metabolic activity. Transmission electron microphotographs of PL-treated cells clearly indicated that various cell structures other than plasma membranes were altered and/or destroyed in a different degree depending on exposure time and type of medium.