MATHEMATICAL FUNDAMENTALS TO DETERMINE THE KINETIC CONSTANTS OF FIRST-ORDER CONSECUTIVE REACTIONS

An accurate mathematical analysis of the trend of experimental data to determine the kinetic constants of consecutive reactions is important for further design and optimization studies. For this purpose, the kinetics of the consecutive reactions was evaluated for different cases, and an unconstrained minimization (optimization) problem was defined to determine the kinetic constants. Minimization of least square analysis was used with the Newton's multivariable optimization procedure. The solution method for the defined optimization problem and the effect of initial guess parameters were discussed in detail. The applied optimization algorithm was then tested with simulated and literature‐reported kinetic data. The algorithm was shown to converge under different situations, and it was concluded that knowing the mathematical fundamentals and using them through different optimization techniques would be a useful tool in the evaluation of experimental data.     

COMPLEX METHOD FOR NONLINEAR CONSTRAINED MULTI-CRITERIA (MULTI-OBJECTIVE FUNCTION) OPTIMIZATION of THERMAL PROCESSING

The goal in a multi‐objective function optimization problem is to optimize the several objective functions simultaneously. the complex method is a powerful algorithm to find the optimum of a general nonlinear function within a constrained region. the objective of this study was to apply the complex method to two different shapes (a sphere and a finite cylinder) subjected to the same thermal processing boundary conditions to find a variable process temperature profile (decision variable) to maximize the volume‐average retention of thiamine. A process temperature range of 5 to 150C was used as an explicit constraint. Implicit constraints were center temperature and accumulated center lethality of the sphere and the finite cylinder. the objective functions for both shapes were combined into a single one using a weighting method. Then, the previously developed complex algorithm was applied using Lexicographic Ordering to order the objective functions with respect to their significance. the results were reported as optimum variable process temperature profiles using the given geometries and objective functions. the thiamine retentions were also compared with a constant process temperature process, and 3.0% increase was obtained in the combined objective function. the results showed that the complex method can be successfully used to predict the optimum variable process temperature profiles in multi‐criteria thermal processing problems.     

EXPERIMENTAL DETERMINATION OF MASS TRANSFER COEFFICIENT: MOISTURE CONTENT AND HUMIDITY RATIO DRIVING FORCE APPROACHES DURING BAKING

Moisture distribution in baked products at the end of baking is important because it directly affects the product's quality. In fact, nonhomogeneous moisture distribution may result in quality defects such as cracking, checking etc. Diffusion inside and convective mass transfer outside the product are important factors affecting the quality. Therefore, accurate values of mass transfer parameters should be known for optimization of the baking process to obtain a product of higher quality. For this objective, infinite mass transfer and constant diffusion coefficient simplifying approximations have been applied in the literature numerous times to develop mass transfer models. However, the infinite mass transfer coefficient approximation may not hold true, especially under natural convection conditions. To evaluate the mass transfer coefficient, baking experiments were carried out to obtain the moisture content changes of cookies during baking at 190, 200 and 210C under natural and forced convection conditions. Then, mass transfer coefficient was determined using the moisture content difference and the humidity ratio difference as the driving force for mass transfer. The results of these two approaches were compared, and the use of humidity ratio difference seemed to be a better approach in terms of reflecting actual process conditions because it is based on the surface changes.     

Short term protective effect of digitoxin in sepsis-induced acute lung injury

Purpose: Digitoxin is a cardiac glycoside used in the treatment of heart failure. Inspired by its known anti-inflammatory effect, this study aims to investigate the effect of digoxin in a sepsis model and to bring to light its effect and underlying mechanism in acute lung injury (ALI). Method: 28 wistar albino rats were divided into 4 groups. Sepsis model is performed by the feces intraperitoneal-injection procedure (FIP). Results: TNF-a, CRP, IL-6, IL 1-Beta, lactic acid, and MDA values were significantly decreased in the FIP+digitoxin group compared to the FIP+Saline group. When the same groups were examined, histological improvements such as decrease in alveolar inflammation and decrease in septal thickening in the digitoxin group and thorax CT were found to be significantly higher in the Hounsfield unit digitoxin group compared to the Saline group. Conclusion: Digitoxin has shown biochemical improvement in sepsis with all known mechanisms of action, and healing effects in both computerized tomography and histology in the lung.     

Investigation of optical,structural and morphological properties of nanostructured boron doped TiO 2 thin films

Pure and different ratios (1, 3, 5, 7 and 10%) of boron doped TiO₂ thin films were grown on the glass substrate by using sol–gel dip coating method having some benefits such as basic and easy applicability compared to other thin film production methods. To investigate the effect of boron doped on the physical properties of TiO₂, structural, morphological and optical properties of growth thin films were examined. 1% boron-doping has no effect on optical properties of TiO₂ thin film; however, optical properties vary with > 1%. From X-ray diffraction spectra, it is seen that TiO₂ thin films together with doping of boron were formed along with TiB₂ hexagonal structure having (111) orientation, B₂O₃ cubic structure having (310) orientation, TiB_0·024O ₂ tetragonal structure having rutile phase (110) orientation and polycrystalline structures. From SEM images, it is seen that particles together with doping of boron have homogeneously distributed and held onto surface.     

EXPERIMENTAL COMPARISON OF NATURAL CONVECTION AND CONDUCTION HEAT TRANSFER

Magnitude of fluid motion is significant in convective heat transfer (the faster the fluid motion, the greater the heat transfer), while in conductive heat transfer, there is no physical movement of objects undergoing heat transfer. Due to this statement, it is a real fact that convection can be many times faster than conduction. The objective of this research was to compare natural convection and conduction by creating both heat transfer mechanisms in the same product. For this purpose, canned water and 1% agar-gelled water were used in the experimental and further computational fluid dynamics studies. Experiments were conducted at 70C and in boiling water, and ANSYS V.10 (Ansys Inc., Canonsburg, PA) was used in the numerical simulations. The results showed that addition of agar prevented the natural convection phenomena in the gels resulting in pure conduction while the effect of natural convection, which occurred due to thermal buoyancy effects in the given gravitational force field, was obvious in the case of water. Creation of both natural convection and conduction heat transfer mechanisms in the same medium is an important contribution as the effect of natural convection over the conduction heat transfer can directly be emphasized.

PRACTICAL APPLICATIONS

Creation of both natural convection and conduction heat transfer mechanisms in the same medium would be an important contribution as the effect of natural convection over the conduction heat transfer can experimentally be emphasized. The results of this study are significant to show the significant difference between these heat transfer modes as both mechanisms were created in the same medium, and these results will be useful especially for teaching heat transfer purposes.     

NONLINEAR CONSTRAINED OPTIMIZATION OF THERMAL PROCESSING: I. DEVELOPMENT OF A MODIFIED ALGORITHM OF COMPLEX METHOD

The complex method, a general and flexible optimization algorithm, was used to determine the optimum process temperature profiles during thermal processing to maximize (optimize) the objective function of volume average retention of thiamine in conduction heated foods with restrictive explicit and implicit constraints. Implicit constraints were the target lethality at the coldest point, and a threshold below which the center temperature must reach at the end of the process. A process temperature range of 5–150C was used as an explicit constraint. Another explicit constraint was that the process temperature had to reach 5C at the end of the process. Control variable for the optimization was process temperature profile discretized at equidistant time steps throughout the process. All calculations were performed using a computer program written in Microsoft Visual Basic V. 6.0. This Windows‐based software calculated the optimum temperature profiles with resulting objective functions and implicit constraints. The developed algorithm for the Complex Method was found to be satisfactorily usable for the optimization of thermal processing of conduction heated foods.     

OPTIMIZATION OF GLYCEROL EFFECT ON THE MECHANICAL PROPERTIES AND WATER VAPOR PERMEABILITY OF WHEY PROTEIN-METHYLCELLULOSE FILMS

Biopolymer films and coatings are generally designed using biological materials such as proteins, polysaccharides, lipids and their derivatives. The use of plasticizers is also required to improve the mechanical properties (tensile strength and elongation) of the films. For application of films to food systems, it is important for the developed films to possess favorable mechanical and permeability characteristics. Therefore, knowledge of optimum conditions where the water vapor permeability (WVP) is minimized while the mechanical properties are enhanced would be significant depending on the application of the edible films. In this study, the effects of glycerol, as a plasticizer, and methylcellulose (MC) ratios on WVP and mechanical properties of the whey protein films were investigated. Optimum properties of edible films were obtained by applying the complex method optimization algorithm to this multiobjective function problem, and glycerol to total polymer ratio (MC and whey protein concentrate [WPC]) of 0.356 and 0.45 was found for the films with MC : WPC ratios of 0.3 and 0.8, respectively. With respect to the results of this study, it might be concluded that optimum conditions for different edible film‐forming agents can be determined via the use of a good experimental design.