Polyelectrolyte complex formation between alginate and chitosan as a function of pH

Chitosan and alginate are two polyelectrolytes that can be used as thickening agents in the food industry, in drug‐release systems in pharmaceutical applications as biomaterials in wound healing, and cell culture applications, or as ion exchange material for the removal of heavy metal ions from industrial wastewaters. These two polysaccharides can also be used together to form a polyelectrolyte complex, especially to encapsulate proteins, cells, and enzymes. Although there are many applications of these polyions, few publications explain the interaction between their functional groups. This is mostly because of the difficulty of following ionic interaction in an interface of macromolecules, especially since they alter much with the reaction conditions such as pH. The present study reveals the interaction between chitosan and alginate at different pH values by means of a particular method for Fourier transform infrared (FTIR) studies. A previously reported disagreement between the yield of the complexes in weight and density of the interacting functional groups is explained through this method. The obtained results are supported with the morphological studies of the polyelectrolyte beads prepared at different pH values. Freeze‐dried beads of both alginate and chitosan‐coated alginate beads could be viewed after hexamethyl disilazane (HMDS) treatment. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 346–351, 2003     

Fatty acid composition of wild and cultivated gilthead seabream (Sparus aurata) and sea bass (Dicentrarchus labrax)

Total lipid content and fatty acid composition were determined for wild and cultivated gilthead seabream and sea bass. Fatty acid analyses were carried out by gas chromatography‐ mass spectrometry. Respective total lipid content of flesh in cultivated gilthead seabream and sea bass were 1.7‐5.0‐times those of wild samples. Palmitic acid (C16:0) and oleic acid (C18:1n‐9) were the major fatty acids respectively among the saturated fatty acids and monounsaturated fatty acids of each fish species. It is noteworthy that both linoleic acid (C18:2n‐6) and arachidonic acid (C20:4n‐6) were predominant in total n‐6 polyunsaturated fatty acids in the respective cultivated and wild types. Eicosapentaenoic acid (C20:5n‐3) and docosahexaenoic acid (C22:6n‐3) amounts were significantly higher in flesh of cultivated fish than in wild fish.     

Identification of materials with magnetic characteristics by neural networks

In industry, there is a need for remote sensing and autonomous method for the identification of the ferromagnetic materials used. The system is desired to have the characteristics of improved accuracy and low power consumption. It must also autonomous and fast enough for the decision. In this work, the details of inaccurate and low power remote sensing mechanism and autonomous identification system are given. The remote sensing mechanism utilizes KMZ51 anisotropic magneto-resistive sensor with high sensitivity and low power consumption. The images and most appropriate mathematical curves and formulas for the magnetic anomalies created by the magnetic materials are obtained by 2-D motion of the sensor over the material. The contribution of the paper is the use of the images obtained by the measurement of the perpendicular component of the Earth magnetic field that is a new method for the purpose of identification of an unknown magnetic material. The identification system is based on two kinds of neural network structures. The MultiLayer Perceptron (MLP) and the Radial Basis Function (RBF) network types are used for training of the neural networks. In this work, 23 different materials such as SAE/AISI 1030, 1035, 1040, 1060, 4140 and 8260 are identified. Besides the ferromagnetic materials, three objects are also successfully identified. Two of them are anti-personal and anti-tank mines and one is an empty can box. It is shown that the identification system can also be used as a buried mine identification system. The neural networks are trained with images which are originally obtained by the remote sensing system and the system is operated by images with added Gaussian white noises.     

Analysis of variable-base heating and cooling degree-days for Turkey

The degree-day method is one of the well-known and the simplest methods used in the Heating, Ventilating and Air-Conditioning industry to estimate heating and cooling energy requirements. In this study, the heating and cooling degree-days for Turkey are determined by using long-term recent measured data. Five different base temperatures ranging from 14 to 22°C are chosen in the calculation of heating degree-days. In the case of cooling degree-days, 6 different base temperatures in the range 18 to 28°C are used. Yearly heating and cooling degree-days are given both in tabular form and as counter maps for all the provinces of Turkey (78 weather stations).     

Design of Regenerative Heat Exchangers

Rotary regenerators are used widely for energy recovery, both in industrial and air-conditioning applications, because of the advantages they have over other types of heat exchangers. In this study, a mathematical model for the design of rotary regenerators is presented. The method is valid for all kinds of channel geometries that form the matrix of a rotary regenerator and can be used for all rotational speeds. The validity of the method is tested with the experimental and numerical results available for rotational speeds between 0.05 and 7 rev/min. A good agreement between the model and the experimental numerical results is obtained. The method presented can therefore be recommended for the safe design of rotary regenerators.     

Optimizing a submerged Monascus cultivation for production of red pigment with bug damaged wheat using artificial neural networks

The combined effect of temperature, agitation speed, and light on red pigment production by Monascus purpureus (M. purpureus) Went DSM 1604 using bug damaged wheat was studied using an artificial neural network (ANN). Information retrieved from the ANN was used to determine the optimal operating conditions for pigment production by M. purpureus using bug damaged wheat meal. The developed ANN had R ² values for training, validation, and testing data sets of 0.993, 0.961, and 0.944, respectively. According to the model, the highest pigment production of 1.874 absorbance units at 510 nm (A_{510 nm}) would be achieved at 29°C and 150 rpm under light conditions. The mean value of the experimental results obtained under these optimum conditions was 1.787±0.072 A_{510 nm}, corresponding to a pigment yield of 35.740 A_{510 nm}/g. The study showed that bug damaged wheat can be used as a substrate for red pigment production by M. purpureus.     

Comparison of Polyphenol Oxidases Prepared From Different Parts of Artichoke (Cynara Scolymus L.)

Artichoke polyphenol oxidases (PPOs) were obtained by (NH₄)₂SO₄ precipitation using ascorbic acid, polyvinylpyrrolidone, and Triton X-100. The PPO content of artichoke head (AHPPO) was 8820 units (mg protein)^?1 as compared with 3370 units (mg protein)^?1 in artichoke leaves-and-stem (ALSPPO) by using catechol as a substrate. The substrates of both AHPPO and ALSPPO are o-diphenols, such as catechol, pyrogallol, and L-DOPA. Optimum pH and temperature of both PPOs were determined. AHPPO had higher thermal stability than ALSPPO. Also, T_m (the midpoint of thermal inactivation) and t_1/2 (half-life) values were determined. K_m and V_max of both PPOs were observed to be similar. Twelve inhibitors were tested and their I₅₀ values were determined. The most effective inhibitors were found to be potassium cyanide, ascorbic acid, L-cysteine, and thiourea. Sodiumdodecylsulfate, urea, and cupric sulfate caused an increase about 20–30% in the PPO activity.