Spray Drying of Green Corn Pulp

Maize (Zea mays) is a cereal grown in Brazil, and its availability is limited to the harvest season. An alternative processing route is based on the production of green corn powder, which has a longer shelf-life and increased versatility. This study aimed to evaluate the influence of drying conditions on the physical characteristics, size, and morphology of green corn powder. Drying experiments were performed on a spray dryer according to a central composite rotational design to evaluate inlet air temperature, feed flow rate, and pulp concentration. The yield of dried pulp corn had an average value of 36.19%. The following mean values for the physical properties of the powder were measured: solubility of 94.37 g/100 g, wettability of 128.05 seconds, moisture content of 1.97%, water activity of 0.13, density of 0.79 g/mL, and a particle diameter of 31.02 µm. The powder was also yellow with less intensity, and the particle surface was smooth at higher temperatures and had a tendency to form agglomerates. The estimated optimal conditions for spray drying were 48% (w/w) pulp concentration, 172°C inlet air temperature, and feed flow rate of 0.56 L/h.     

Structure, microstructure and electrical conductivity of 8YSZ containing NiO

The effects of NiO addition on the structure and microstructure of yttria-stabilized zirconia were investigated to clarify the role of the additive in the microstructure-related electrical conductivity of the solid electrolyte. Specimens of 8 mol% yttria-stabilized zirconia with NiO contents up to 5.0 mol% were prepared using nickel oxide and trihydroxi nickel carbonate as precursors. The specimens were sintered at 1350 °C for several holding times. The evolution of the lattice parameter with NiO content was evaluated by X-ray diffraction and the microstructural features by scanning electron microscopy. Electrical conductivity was evaluated by impedance spectroscopy measurements. The solubility limit of NiO at 1350 °C was found to be 1.5 mol% by X-ray diffraction. Energy dispersive spectroscopy results revealed Ni segregation for large holding times at 1350 °C. The grain boundary conductivity was found to be influenced by Ni segregation and to decrease with increasing holding times at high temperature.     

High-temperature electrical properties of lanthanum beta-alumina solid electrolytes

Impedance spectroscopy measurements were carried out in the 10 Hz to 10 MHz frequency range from 500 to 1200 °C in LaAl₁₁O₁₈ pellets sintered at 1600 °C. The powders were obtained by the polymeric precursor technique. The sintered pellets were nearly single phase LaAl₁₁O₁₈. The bulk electrical resistivity was evaluated from the [−Z″(ω) × Z′(ω)] impedance diagrams. The value of the activation energy for the ionic conduction, 0.89 eV, was determined from the Arrhenius plot of the bulk conductivity. An yttria-stabilized zirconia (YSZ) oxygen pump and an YSZ oxygen sensor were used for providing 10–1500 ppm of partial pressure of oxygen (pO₂) at 1000 °C for determining the electromotive force (emf) in a Pt/LaAl₁₁O₁₈/Cr₂O₃ + Cr electrochemical cell. The results follow the Nernst law. The high signal-to-noise ratio of the emf at low pO₂ values shows that the LaAl₁₁O₁₈ specimens may be used in sensors for detection of oxygen at high temperatures.     

Effects of natural antioxidants on the lipid profile of electron beam‐irradiated beef burgers

The purpose of this study was to assess the efficacy of rosemary and oregano extracts in avoiding oxidative changes in beef burgers, and to evaluate the fatty acid profile of these products after electron beam exposition. Extracts, individually or in combination, were added to beef burgers and compared to synthetic antioxidants commonly used in food (butylated hydroxytoluene, butylated hydroxyanisole). The ground beef were submitted to electron beam irradiation at doses of 0, 3.5 and 7 kGy, and stored for 90 days. At regular time intervals, lipid oxidation and fatty acid composition were evaluated through measurement of thiobarbituric acid‐reactive substances (TBARS) and gas chromatography, respectively. The results indicate that, although the irradiation process triggers an increase in the lipid oxidation ratio expressed by TBARS values, great changes in the fatty acid profiles were not observed; instead, they continued to present characteristics very similar to that of non‐irradiated beef. Thus, as irradiation doses of up to 7 kGy for frozen meat can make foods safe from foodborne pathogens, natural antioxidants derived from spices are able to reduce and avoid lipid changes that may cause a deterioration of the sensory quality of these foods, and these natural extracts offer a good choice for replacing synthetic additives.     

Investigating the cutting phenomena in free-form milling using a ball-end cutting tool for die and mold manufacturing

This paper presents an investigation of nonplanar tool-workpiece interactions in free-form milling using a ball-end cutting tool, a technique that is widely applied in the manufacturing of dies and molds. The influence of the cutting speed on the cutting forces, surface quality of the workpiece, and chip formation was evaluated by considering the specific alterations of the contact between tool-surface along the cutting time. A trigonometric equation was developed for identifying the tool-workpiece contact along the toolpath and the point where the tool tip leaves the contact with the workpiece. The experimental validation was carried out in a machining center using a carbide ball-end cutting tool and a workpiece of AISI P20 steel. The experimental results demonstrated the negative effect of the engagement of the tool tip into the cut on machining performance. The length of this engagement depends on the tool and workpiece curvature radii and stock material. When the tool tip center is in the cut region, the material is removed by shearing together with plastic deformation. Such conditions increase the cutting force and surface roughness and lead to an unstable machining process, what was also confirmed by the chips collected.     

An experimental setup for shrinkage evaluation during electric field-assisted flash sintering: Application to yttria-stabilized zirconia

Analyses of electrochemical impedance spectroscopy plots and dilatometric curves of ZrO₂:Y₂O₃ (YSZ) green compacts upon sintering show the possibility of choosing the shrinkage level of the green pellet by passing a current flash through the interparticle regions. The experiments consisted on inserting a YSZ green compact in a dilatometer sample holder, connecting either to a power supply or to an impedance analyzer, and monitoring the shrinkage upon sintering with and without applying an ac voltage in the 800–1000 °C temperature range. This procedure allows taking the sample from the first to the second sintering stage in few seconds without the occurrence of significant grain growth.     

Thermoelectret properties of BeO

Thermoelectret properties of beryllium oxide have been studied in the temperature range RT-600°C. Depolarisation currents detected during the thermal destruction of the thermoelectret state have been measured under different polarization conditions. The induced polarization has been found to be a uniform volume effect. Two peaks of depolarization current have been detected and their corresponding thermal activation energies measured to be 0.47 eV and 0.56 eV. Electric field enhanced migration of ions with trapping as well as dipolar orientation are proposed to be the contributors to the induced polarization in the formation of the thermoelectret state in BeO.     

Hydroconversion kinetics of Marlim vacuum residue

A kinetic model was obtained for the Marlim crude vacuum residue (VR) hydroconversion. Marlim VR mixed with FCC decant oil in an 80%/20% weight basis was put in contact with a commercial NiMo on γ-alumina catalyst in a stirred batch reactor. Several temperatures and oil/catalyst ratios were used over different times (0–240 min), at a 110 bar pressure and constant hydrogen flow. The analysis of the collected product showed residua conversions of up to 70%. Hydroconversion kinetics involving thermal and catalytic cracking contributions was proposed to represent the obtained data. The resulting system of differential equations of the kinetic model was solved within reaction time, taking into account the experimental temperature profile. The chi-square objective function was minimized to adjust model parameters. A proposed effective hybrid minimization method was used, by applying a Newton-type method between certain simulated annealing minimization steps. The proposed kinetic model allowed the representation of thermal and catalytic cracking effects, in order to take into account different catalyst concentrations. Therefore it is possible to consider distinct reactor hydrodynamics, such as expanded or bubble column reactors.     

Morphological and biochemical changes of the heart in experimental hypochromic anemia in rats

The effect of iron deficiency anemia on the catecholamine levels and morphology of the heart was studied in young male Wistar rats. The iron-deficient rats showed mild restriction of body weight gain and a striking lowering of blood hemoglobin concentration. In addition the present study demonstrated that the experimental iron deficiency anemia induces cardiac hypertrophy, as revealed by increased heart weight associated with increased size of cardiac muscle cells, as well as decreased myocardium catecholamine levels. The possible meaning of the neurohormonal change in the pathogenesis of the hypertrophic heart is discussed.