Experimental and Analytical Research of the Heat Transfer Process in the Package of Perforated Plates

The need for compact heat exchangers has led to the development of many types of surfaces that enhance the rate of heat transfer, among them the perforated plate heat exchangers, also known as matrix heat exchangers. The perforated plate heat exchangers consist of a series of perforated plates that are separated by a series of spacers. The present study investigates the heat transfer characteristics of the package of perforated plates. Perforated plates were 2 mm thick, with holes with 2 mm in diameter and porosity of 25.6%. The package of one, two, and three perforated plates was set in the channel of the experimental chamber at which entrance was a thrust fan with the ability to control the flow rate. The fluid flow rates, the temperatures of the fluids at the inlet and outlet of the chamber and the temperature of the air between the plates, were measured at the pre-defined locations in the package and the experimental chamber. Based on the measurements, heat transfer coefficients for the individual plates, as well as for the packages of perforated plates were determined. In further research, an iterative analytical procedure for investigation of the heat transfer process and the overall heat transfer coefficient for the package of perforated plates were developed. Based on these analytical and experimental results, conclusions were drawn about the heat transfer in a package of perforated plates.17th Symposium of the Society-of-Thermal-Engineers-of-Serbia (SIMTERM), Oct 20-23, 2015, Sokobanja, Serbi

Statistička zavisnost sekundarne strukture proteina od frekvencije digrama aminokiselina

The statistical dependence of protein secondary structure on amino acid bigram frequencies was studied. Proteins in the PDBSELECT subset of the Protein Data Bank database were investigated. Protein secondary structures were determined using DSSP software. The conditional probabilities of protein secondary structures were calculated and presented. The results on bigrams show the frequencies of all the possible bigrams in all secondary structure types. These results elucidate some factors important for the prediction of the secondary structures of proteins based on the amino acid sequence. © 2017, CI and CEQ. All rights reserved.U radu je opisana statistička zavisnost sekundarne strukture proteina od bigrama aminokiselina. Istraživanje je urađeno na proteinima koji se nalaze u podskupu PDBSELECT baze podataka o proteinima Protein Data Bank (PDB). Sekundarne strukture proteina su određene primenom programa DSSP. Izračunate su i prikazane uslovne verovatnoće pojavljivanja različitih sekundarnih struktura. Rezultati za bigrame su prikazani za sve tipove sekundarnih struktura. Rezultati ukazuju na faktore koji su značajni za predviđanje sekundarne strukture proteina koje je zasnovano na redosledu aminokiselina u proteinu

Environmental Education in Serbian Primary Schools: Challenges and Changes in Curriculum, Pedagogy, and Teacher Training

The protection of human health and the preservation of the environment are topics that form anintegral part of the primary school curriculum in Serbia. However, research studies have shown thatstudents do not have enough knowledge to contribute to the development of a healthy lifestyle andenvironmental awareness. The latest changes in school policy and curricula confirm that the relevanceof environmental education has been recognized, but changes in school practice are yet to come. Thisarticle discusses the challenges encountered in the implementation of the intended curriculum andoffers suggestions for changes to the curriculum, pedagogy, and teacher training in order to enhanceenvironmental educationThis is the peer-reviewd version of the artivle: Stanišić, Jelena, и Slavica Maksić. 2014. „Environmental Education in Serbian Primary Schools: Challenges and Changes in Curriculum, Pedagogy, and Teacher Training“. Journal of Environmental Education 45(2):118–31. doi: 10.1080/00958964.2013.829019.Related to published version: [ http://ipir.ipisr.org.rs/handle/123456789/240

The influence of Ce-based coatings as pretreatments on corrosion stability of top powder polyester coating on AA6060

Cerium-based conversion coatings (CeCCs) are one of the most prospective alternatives to the widely used chromate conversion coatings (CCCs) due to their anticorrosion efficiency, environmentally friendly nature and low cost. In this work, the CeCCs on AA6060 were prepared by immersion into aqueous cerium salt solutions at room temperature, and subsequently post-treated in heated phosphate solution. The effect of counter ion (nitrate and chloride) on the coating properties was studied testing CeCCs as sole or conversion layers for the top polyester coating. Since the 60 mu m thick polyester coating was applied, an artificial defect of 0.8 mm hole was introduced to faster assess the differences between pretreatments. The system with CCC pretreatment was used as reference. Corrosion properties were investigated in 0.5 M NaCl solution by electrochemical impedance spectroscopy while the adhesion strength was measured by NMPR (N-methyl-2-pyrrolidone) and pull-off tests. As shown, the post-treated chloride-based CeCC offered better protection than crack-free thin nitrate-based CeCC, when used as sole coatings. On the other hand, it was brought to evidence that in combination with top powder polyester coating, the CeCC deposited from nitrate solution exhibited better protection compared to protective system pretreated with chloride-based one. Excellent polyester coating adhesion was found independently on aluminium surface pretreatment. (C) 2013 Elsevier B.V. All rights reserved

Osteogenic effect of inflammatory macrophages loaded onto mineral bone substitute in subcutaneous implants

We analyzed the influence of inflammatory macrophages on the osteogenic process in subcutaneous implants composed of mineral bone substitute. Thioglycollate-elicited peritoneal macrophages (TEPMs) were characterized as inflammatory. This was confirmed microscopically by the nitroblue tetrazolium (NBT) test and the production of tumor necrosis factor α (TNF-α). The implants (M-type) were made of mineral bone substitute (Bio-Oss®) mixed with TEPMs and blood clot. Implants without macrophages served as the control (C-type). Subcutaneous implantation in the interscapular area was performed on BALB/c mice. Implants were extracted after 2 and 8 weeks. In M-type implants, phagocytosis and angiogenesis were more pronounced, and osteoblast-like cells aligned onto granules of implanted material and osteoid structures can be seen. The observed higher osteocalcin and lower osteopontin immunoexpression in M-type implants when compared to the control after 8 weeks suggest a more advanced osteogenic process. Our results indicate that the presence of inflammatory macrophages in the composition of an implant may have a beneficial effect on the osteogenic process. [Projekat Ministarstva nauke Republike Srbije, br. III41017

Effect of irregular interproximal dental restorations on periodontal status

Introduction. Research of effects that irregular interproximal dental restoration have on supporting structures of the teeth and examination of evolution and course of changes in tissue structure is quite a poorly studied topic. Aim of this study is to examine and assess clinical and radiological changes in periodontal tissue caused by irregular interproximal dental restoration in particular group of patients with different age and sex. Methods. Irregularities which were assesed in this study are divided into two groups: a) gap (cracks) occurring between dental restorations and the gingival walls in Class II cavities, b) prominence of dental fillings out of the teeth anatomical sphere, resulting with the positive step in gum third of tooth in Class II cavities. The study was based on whether in the particular forms of irregularities of the dental restorations are differences in the degree of change in the periodontal tissue, depending on the material from which the restoration is made, and the materials used were composite fillings and amalgams. Results of this study show that irregular dental fillings significantly affect the inflammatory response in periodontal tissue. Irregularities in the form of unfilled space cause major changes in periodontal tissue. Composite fillings cause a higher degree of inflammation in relation to amalgam fillings. Conclusion. Improper tooth fillings cause periodontal tissue damages

Statistical Dependence of Protein Secondary Structure on Amino Acid Bigrams

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TYROSINASE INHIBITORY AND ANTIOXIDANT ACTIVITY OF WILD ROSA CANINA L. AND SORBUS AUCUPARIA L. FRUIT EXTRACTS

In the present work, fruits from two plant species, Rosa canina L. and Sorbus aucuparia L., popular in traditional folk medicine in Serbia, were studied. The aim was to examine and compare the efficiency of the ultrasonic extraction with different solvents regarding physicochemical properties, polyphenolic profile of extracts, as well as their tyrosinase inhibitory and antioxidant activity. The polyphenols evaluation indicated that water was the best solvent for a thorough extraction of bioactive compounds from the R. canina fruits, while propylene glycol-water (45:55, v/v) was the most efficient regarding S. aucuparia fruits, followed by ethanol-water (7:3, v/v). Only flavonoids were more abundant in S. aucuparia fruit extracts. R. canina water extracts showed a higher antioxidant activity, using several in vitro tests with different working principles. However, S. aucuparia ultrasonic extracts with propylene glycol-water (45:55, v/v) demonstrated a higher potential concerning tyrosinase inhibitory and chelating activity. Therefore, these ultrasonic extracts, being great sources of natural anti-tyrosinase inhibitors and antioxidants, can be considered as promising candidates suitable for pharmaceutical application, as great sources of natural anti-tyrosinase inhibitors and antioxidants

Experimental and analytical research of the heat transfer process in the package of perforated plates

The need for compact heat exchangers has led to the development of many types of surfaces that enhance the rate of heat transfer, among them the perforated plate heat exchangers, also known as matrix heat exchangers. The perforated plate heat exchangers consist of a series of perforated plates that are separated by a series of spacers. The present study investigates the heat transfer characteristics of the package of perforated plates. Perforated plates were 2 mm thick, with holes with 2 mm in diameter and porosity of 25.6%. The package of one, two, and three perforated plates was set in the channel of the experimental chamber at which entrance was a thrust fan with the ability to control the flow rate. The fluid flow rates, the temperatures of the fluids at the inlet and outlet of the chamber and the temperature of the air between the plates, were measured at the predefined locations in the package and the experimental chamber. Based on the measurements, heat transfer coefficients for the individual plates, as well as for the packages of perforated plates were determined. In further research, an iterative analytical procedure for investigation of the heat transfer process and the overall heat transfer coefficient for the package of perforated plates were developed. Based on these analytical and experimental results, conclusions were drawn about the heat transfer in a package of perforated plates. [Projekat Ministarstva nauke Republike Srbije, br. III 42008

Effect of degree of crystallinity and the contents of aluminium oxide and sodium oxide on water sorption capacity in NaY zeolite

The paper presents mathematical models which describe the dependence between water sorption capacity, on one hand, and the degree of crystallinity and the content of Na2O and Al2O3 in NaY zeolite, on the other. NaY was synthesized from sodium aluminate solution, water glass and sulfuric acid under different conditions of crystallization. The obtained zeolite powders underwent chemical analysis (Na2O, Al2O3), water sorption capacity (WSC), as well as diffraction analysis which served to determine the degree of crystallinity (CD). Zeolite powder samples had the following values: for the content of Na2O from 13.81 to 16.14%, for Al2O3 from 21.58 to 27.17%, degree of crystallinity from 58.70 to 114.00 and WSC from 21.32 to 36.59%, and regression analysis lead to the conclusion that there is a significant correlation between water sorption capacity and the degree of crystallinity, unlike the contents of Na2O and Al2O3 in the zeolite powder, whose correlation with water sorption capacity was neglibile. The mathematical model obtained by linear regression analysis had a high R2= 0.796, where as non-linear regressional analysis produced a better mathematical model R2= 0.912, where water sorption capacity was expressed through a quadratic model