Changes in Phenolic Compounds During Storage of Pasteurized Strawberry

This study aimed to establish mathematical models to describe changes in phenolics of pasteurized strawberry (Fragaria?×?ananassa Duch.) during storage at 23 °C for 90 days. Freshly cut strawberries cubes were pasteurized for 5 min in a water bath at 90 °C following a heating time of 15 min. Antioxidant activity, total phenolics, total anthocyanins, and individual phenolic compounds were assessed immediately before or after pasteurization and at regular time intervals during storage. The results indicated that (1) pasteurization did not affect (P?<?0.05) the concentrations of total phenolics or total anthocyanins, but significantly reduced the concentrations of quercetin-3-rutinoside, kaempferol, and cyanidin-3-glucoside, and increased the concentrations of (+)-catechin, (?)-epicatechin, epigallocatechin gallate, quercetin-3-galactoside, and ellagic acid; (2) changes in antioxidant capacity, total anthocyanin, and individual compounds during storage were described by a pseudo-first-order model with the exception of total phenolic and specifically kaempferol and ellagic acid which followed zero-order kinetic models. Pelargonidin-3-glucoside degraded at the highest rate (k?=?0.07 day^?1), followed by ellagic acid (k?=?0.004 day^?1) and kaempferol (k?=?0.003 day^?1). The rate constants can be used to predict phytochemical changes in strawberry products during storage.     

Soft computing systems applied to PWR''s xenon

The present work intends to introduce a soft computing technique as an effective and robust tool available to deal with nuclear engineering problems. This goal is reached by the presentation of an application: a genetic programming system (GP) able to automatically design a controller for the axial xenon oscillations in a pressurized water reactors (PWRs). The axial xenon oscillations control methodology is based on three axial offsets: the xenon axial offset (AOx), the iodine axial offset (AOi) and the neutron flux axial offset (AOf), effectively used in former work. Simulations were made using a two-point xenon oscillation model which employs the non-linear xenon and iodine balance equations and the one group, one-dimensional neutron diffusion equation, with non-linear power reactivity feedback, also proposed in the literature. Obtained results showed the ability of the GP in finding a strategy which can effectively control the axial xenon oscillations.     

An exact algorithm for optimal MAE stack filter design.

We propose a new algorithm for optimal MAE stack filter design. It is based on three main ingredients. First, we show that the dual of the integer programming formulation of the filter design problem is a minimum cost network flow problem. Next, we present a decomposition principle that can be used to break this dual problem into smaller subproblems. Finally, we propose a specialization of the network Simplex algorithm based on column generation to solve these smaller subproblems. Using our method, we were able to efficiently solve instances of the filter problem with window size up to 25 pixels. To the best of our knowledge, this is the largest dimension for which this problem was ever solved exactly.     

Reactions and emissivity of cerium oxide with phosphate binder coating on basic refractory brick

High emissivity coatings which aim to help the cement industry reduce heat loss in its production process have been developed with different CeO₂ and AlH₆O₁₂P₃ ratios (1:3, 1:5, and 1:12 by volume). The coating slurries were shear thinning and after heat treatment in air at 1300°C, 1°C/min, dwell 3 hours, XRD revealed that CePO₄ forms more easily as the Ce/P ratio decreases. The composition with a 1:5 ratio of CeO₂:AlH₆O₁₂P₃ was gun sprayed on basic refractory bricks, then heat treated under the same conditions as the slurries. SEM, (S)TEM and EDX were used to study thickness, microstructure, and chemical composition of the coatings which revealed that the coating was composed of pores, CeO₂ grains, CePO₄ grains, and M-P-O glass. SEM images show that CePO₄ was nucleated from a reaction between CeO₂ and AlH₆O₁₂P₃. Consequently, CePO₄ grains (~2 µm diameter) were smaller than CeO₂ (~10 µm diameter). The emissivities of un-coated and coated basic refractory bricks were measured at 1100 and 1300°C over the wave number range of 700-12 000 cm⁻¹. At both temperatures, the emissivity of the coated bricks was higher than the uncoated bricks and the emissivity was measured to be higher at a higher temperature for both samples. The coated bricks gave the highest emissivity of 0.81 from 1050 to 11 000 cm⁻¹ which is about twice the un-coated bricks for the same conditions. This demonstrates that the developed high emissivity coating has potential to be used with basic refractory brick.     

ZnO semiconductors obtained by slip casting: Application and reuse in photocatalysis

This work described the acquisition of immobilized ZnO semiconductors using the slip casting technique, for application as reusable photocatalysts in the degradation of Rhodamine B. The influence of the heat treatment temperature (800°C, 900°C, and 1000°C) on the physical, thermal, microstructural, and photocatalytic properties was investigated. All samples presented the wurtzite crystal structure, and the surface was completely absent of organic matter residues. The samples presented band gap values around 3.2 eV. The ones heat treated at 800°C showed lower density (3.40 g/cm³, corresponding to 60% of the ZnO theoretical density), smaller average grain size, in addition to higher apparent porosity (around 40%). These characteristics provide better photocatalytic activity to the sample heat treated at 800°C, since it promoted 92.2% dye degradation, while samples heat treated at 900°C and 1000°C promoted 81.8% and 54.2% dye degradation, respectively. The integrity of all samples was maintained after the photocatalytic tests. Thus, the reuse capability of the sample with the best photocatalytic performance, that is, the sample heat treated at 800°C, was evaluated in six cycles of photocatalysis. The sample proved to be reusable, promoting degradation of practically 100% of the dye after the third cycle of reuse.     

Optical indices and transport scattering coefficient of pyrolytic boron nitride: a natural thermal barrier coating for solar shields

Absorption and scattering properties of pyrolytic boron nitride (pBN) have been characterized by infrared spectroscopy. The strong dielectric anisotropy predicted by first principles calculations is confirmed by measurements performed on a highly oriented pBN sample. Optical properties of textured samples elaborated by chemical vapor deposition were identified from normal hemispherical reflectance and transmittance spectra by applying modified two-flux and four-flux transport models. It is also shown that coating carbon–carbon composites used to build solar shields with a pBN layer having an optimal thickness could improve the protection performance.