On the methodology of the thyroid epithelial cell thickness determination

The average thickness of the thyroid epithelial cells may be determined either directly or indirectly. By the direct or caliper method, this thickness is overestimated as a result of which its empirical value must be divided by a correction factor K_d. By the indirect method, on the other hand, the thickness of the thyroid gland epithelium is calculated as the ratio of the double volume density of the epithelium to the sum of the inner and the outer surface density of the epithelium; in this case the sought for thickness value is underestimated and must consequently be multiplied by a factor K_i. Both correction factors are algebraically defined. Their values are calculated and graphically represented as a function of the thyroid activation index (the ratio between the volume density of the epithelium and the colloid) for the range from 0·1 to 100. The validity of the theoretical interpretation of the discrepancy between the values obtained for the average thickness of the thyroid epithelium by the direct and the corresponding values obtained by the indirect method, is empirically tested. It is shown that by the introduction of appropriate correction factors the difference between the results obtained by each method can be reduced. These improved direct and indirect methods for determining the wall thickness of a hollow sphere seem to lend themselves to being used in the stereological analysis of other biological, perhaps even non-biological materials of similar structure.     

Optimal design of periodic surface texture for thin‐film a‐Si:H solar cells

Optical analysis of hydrogenated amorphous silicon (a‐Si:H) solar cells with a periodic texture applied to the interfaces was carried out by two‐dimensional optical simulator. The optical simulator solves the electromagnetic wave equations by means of finite element method using triangular elements for the discretization of space. The periodic texture with rectangular‐like shape acts as a diffraction grating which scatters light into selective angles and thus gives a potential for significant prolongation of optical paths in thin absorber layers of the cells. Optimization of the geometrical parameters (period, height and duty‐cycle) of the periodic texture was carried out in order to obtain the highest photocurrent from a‐Si:H solar cells. The a‐Si:H solar cell with the optimal periodic texture parameters (period of 300 nm, height of 300 nm and duty cycle of 50%) and the absorber layer thickness of 300 nm generates up to 35% more photocurrent in comparison to the cell with flat interfaces. The optical analysis demonstrates that the optimal periodic texture in the a‐Si:H solar cell results in the best trade‐off between the antireflection effect at front interfaces, light scattering efficiency and the absorption losses at realistic metal back contact. Copyright © 2010 John Wiley & Sons, Ltd.     

Influence Of Trehalose Addition On Instrumental Textural Properties Of Strawberry Pastes

Objective of this study was investigation of influence of trehalose addition (3, 5 and 10%) on instrumental textural properties of evaporated and freeze-dried strawberry pastes. As a control, strawberry paste without addition of trehalose was used. Addition of trehalose had influence on both, hardness and stickiness of the samples, but it is very important to define the amount of trehalose in order to achieve desirable properties. With addition of trehalose hardness of both, evaporated and freeze-dried samples decreased, from 29.89 N to 14.72 N for evaporated samples and from 184.83 N to 44.95 N in freeze-dried samples. Also, from those results it could be seen that freeze-dried samples were much harder than evaporated ones, regardless of trehalose addition. While hardness of samples decreased with addition of trehalose, stickiness increased. Stickiness values were from 0.016 N to 0.0102 N for evaporated samples, and from 0.066 N to 0.018 N for freeze-dried samples. Since evaporated samples had lower values for stickiness they were stickier than freeze-dried ones.     

Automated detection of surface defects on power transmission belts

Development of a new method for an automated detection of surface defects on synchronous belts is presented and demonstrated on a group of samples with typical surface defects. Three-dimensional shape of the belt teeth is initially measured by a laser scanning system and further processed using a novel approach based on deviation map analysis. A deviation map shows deviations between the measured surface and a predefined reference surface of the tooth. Defects are detected and classified on the base of the deviation parameters calculated from the deviation map. The developed method produces results that correspond well with the results of the visual inspection.     

Hydrogenation of CO2 and CO in a high temperature gradient field between catalyst surface and opposite inert cool plate

Methanol synthesis was carried out at 25 bar in slit formed by two parallel plates 5 mm apart. Upper plate was covered by catalyst layer and heated up to 250°C, whereas lower one was kept at about 30°C. Reaction stream in laminar flow consisted of H_2, CO₂, and CO in concentration range usually encountered in industrial processes. Catalyst layer was prepared by spraying CuO/ZnO/Al₂O₃/V₂O₃ slurry on SS‐plate. Continuous removal of methanol and water by condensation on the cool surface shifted equilibrium toward products formation. At isothermal conditions with no temperature gradient in slit, total carbon conversion approached the thermodynamic equilibrium when residence time was long enough. Experiments with high temperature difference showed total carbon conversion much larger compared to the thermodynamic one calculated at plate‐catalyst temperature. Three‐dimensional model predicted total carbon conversion for both isothermal and high temperature gradient operation reasonably well. © 2013 American Institute of Chemical Engineers AIChE J 60: 613–622, 2014     

Formation of 0.65 Pb(Mg1/3Nb2/3)O3–0.35 PbTiO3 Using a High-Energy Milling Process

We have investigated the synthesis of lead-magnesium-niobate–lead-titanate perovskite powder using high-energy milling of the constituent oxides. The compositions of the crystalline and amorphous phases as a function of milling time were determined with X-ray powder diffraction using a Rietveld refinement. The perovskite can be formed by two reaction routes. In the initial stage of milling, it is formed directly from the highly activated nano-sized constituent oxides, and after a certain milling time it is mainly formed from a pyrochlore phase. The obtained as-milled powder consists of crystalline perovskite and an amorphous phase that crystallizes into the perovskite after heating at 800°C.     

Morphology and Crystallization Behavior of Sol-Gel-Derived Titania

TiO₂ sols were prepared by hydrolysis of titanium ethoxide. The sols were exposed for several days at room temperature to atmospheres of different humidity in order to study its influence during aging of sols on rutile formation, morphology, and crystal structure. Exposure of sols to high relative humidity resulted in nonagglomerated TiO₂ powders with a rutile structure. TiO₂ gels obtained from sols aged at low relative humidity were composed of gel fragments with a poorly crystallized anatase structure.     

Void fraction distribution in a bisectional bubble column reactor

This article presents the distribution of the local void fraction (α) in a mock-up bisectional bubble column with a diameter of 0.63 m. Owing to the lack of such data in the literature, α was investigated experimentally using a microresistivity (R) probe and a phase discrimination procedure based on the probe signal. The two-phase mixture that consisted of air and tap water was measured at 342 nodes in the vertical half-section plane of the column. Relatively small differences between the volume-integrated local values of α and the measured total gas holdups showed reasonably good agreement under all conditions. Experimental data were used for validation of a bubble column numerical model for a low hydrodynamic regime with commercial computational fluid dynamics (CFD) code. The difference between the CFD calculated total gas holdup and the experimentally measured mean value is 8.8%, while some differences in the local void fraction distributions were found in the lower part of the column. © 2019 American Institute of Chemical Engineers AIChE J, 65: 1186–1197, 2019