Influence of temperature on behavior of the interfacial crack between the two layers

In this paper is considered a problem of the semi-infinite crack at the interface between the two elastic isotropic layers in conditions of the environmental temperature change. The energy release rate needed for the crack growth along the interface was determined, for the case when the two-layered sample is cooled from the temperature of the layers joining down to the room temperature. It was noticed that the energy release rate increases with the temperature difference increase. In the paper is also presented the distribution of stresses in layers as a function of the temperature and the layers' thickness variations. Analysis is limited to the case when the bimaterial sample is exposed to uniform temperature

R&D Product Development KPIs and Performance of Companies in Serbia

The main intent of the article is to explore whether assumed research and development (R&D) product development key performance indicators (KPIs) are in relationship with a company’s performance, as well as to determine the impact of R&D product development KPIs to predicting company performance. The presented research was carried out on a sample of 196 manufacturing food companies in the Republic of Serbia. Statistical techniques of correlation and multiple regression analysis were applied. Results show that all analysed R&D product development KPIs have significant impact on company performance displayed by ROA, ROE and EBITDA margin

Impregnacija želatin-hitozan filmova etarskim uljem karanfilića pomoću natkritičnog co2 i njihova karakterizacija

Supercritical CO2 impregnation process was used for the first time to fabricate biodegradable gelatin-chitosan (G/Ch) films containing clove oil (CO) for potential use in active food packaging. All the impregnations were carried out at moderately low temperature (40 °C). Aiming to maximize CO loading in the films with acceptable morphological, structural and thermal properties, CO2 pressure, impregnation time and G:Ch mass ratio were varied. Gelatin fraction in the films of 25-50 wt.%, scCO2 pressures of 10-20 MPa and impregnation time of 2-6 h impregnation favoured the CO loading. Processing of the film with equal gelatin to chitosan mass ratio (G/Ch50:50) at 10 MPa for 2 h yielded sufficiently high loading (56 mg CO/gfilm) without an adverse effect on morphological properties. The G/Ch50:50 film was therefore chosen for structural and thermal analyses. ATR-FTIR analysis confirmed successful CO incorporation into the G/Ch50:50 and its interaction with the film. Plasticizing effect of scCO2 and CO on the film was evidenced by DSC. Incorporation of 56 mg CO/gfilm into the G/Ch50:50 didn't affect thermal stability of the film. Beside environmental benefits, supercritical impregnation process enables fast fabrication of G/Ch bio-composite films containing CO, thermally stable to 110 °C, which is suitable for most of food packaging applications. © 2019, CI and CEQ. All rights reserved

Development of macroporous bioceramic materials based on multi-ion doped calcium-hydroxyapatite coated with chitosan

In recent years, scientists have been working on developing biocompatible materials that closely mimic the structure and properties of natural biological tissues for their application in hard tissue regeneration and controlled drug release. Human bones and teeth primarily consist of calcium-phosphate crystals with small amounts of various ions incorporated into their crystal structure. The aim of this study was to examine the possibility of processing macroporous bioceramic scaffolds based on calcium-hydroxyapatite (HAp) doped with magnesium (Mg), strontium (Sr) and fluorine (F) ions, subsequently coated with polymer chitosan. In this study, the doped HAp powder was synthesized by a hydrothermal process, and scaffolds were made using the sponge replica method, sintered and then coated with the chitosan. The influence of dopant ions and chitosan on the scaffold's microstructure, mechanical properties, bioactivity, cytotoxicity and drug release properties was examined. Energy dispersive spectroscopy confirmed that Mg and Sr are incorporated in all powder samples, while the presence of F was confirmed in samples synthesized with 1 and 2 mol.% F in the precursor solution. The phase composition of powders and scaffolds determined by X-ray analysis showed the presence of HAp and β-tricalcium phosphate phase (β-TCP) in scaffolds. In the compressive strength (CS) test, coated scaffolds showed significantly higher CS compared to uncoated scaffolds. Scanning electron microscopy was used to examine the morphology of nanostructured powders, microstructure, and the bioactivity of the scaffolds. The uncoated scaffolds showed satisfactory bioactivity after being immersed in simulated body fluid for 28 days, while lower bioactivity was observed in the coated scaffolds due to the slow degradation of chitosan. The synthesized scaffolds also demonstrated to have a positive impact on cell viability, even slightly stimulating the cell proliferation. Additionally, scaffolds were shown to successfully release drug. In concusion, the addition of ions and chitosan polymer significantly improved the properties of the obtained scaffolds, which indicates their potential application in tissue engineering and controlled drug release.Twenty-First Young Researchers’ Conference - Materials Science and Engineering: Program and the Book of Abstracts; November 29 – December 1, 2023, Belgrade, Serbi

Consumer behaviour: the influence of age and family structure on the choice of activities in a tourist destination

Changes in the structure of consumers’(tourists’) needs that shape tourism in accordance with the modern way of life attribute greater importance to different types of consumers/tourists. Understanding consumer behaviour (tourists as consumers) is significant in terms of tourism destination management. This paper presents the results of a research conducted with the aim of identifying activities (visiting cultural and historical attractions, sport and recreation, health, fun, gastronomy, shopping, cultural entertainment events) that consumers/tourists prefer in a tourist destination depending on their age and family structure. Two hypotheses were set in this paper: H 1 : There is a statistically significant difference between the age of tourists and the activity preferences in a tourist destination; and H 2 : There is a statistically significant difference between the family structure of tourists and the activity preferences in a tourist destination. The sample included 1117 respondents from the area of the Autonomous Province of Vojvodina. A survey was conducted from January to March 2017. In accordance with the defined hypotheses, descriptive statistics and a statistical test of multivariate analysis of variance (MANOVA) were used

Oral praxis and stutterling

Mucanje predstavlja višedimenzionalni problem kako u dijagnostici tako i u terapiji. To je poremećaj fluentnosti govora koji pogađa približno 5% dece i 1% odraslih. Različiti faktori utiču na smanjenje učestalosti i težine mucanja, često tako što smanjuju zahteve za motornom kontrolom govora i jezičkom formulacijom iskaza. Postoji veća verovatnoća za spontani oporavak ako su u pitanju osobe ženskog pola, osobe koje imaju dobre fonološke, jezičke i neverbalne sposobnosti, desnoruke su, imaju stabilniji motorni govorni sistem i adekvatno porodično okruženje. Tokom višegodišnjeg rada sa decom i odraslima koji mucaju zapazili smo da veliki broj dece, ali i starijih pacijenata koji nam se obrate zbog problema mucanja pokazuju i druge govorne i/ili jezičke probleme. Zato smo želeli da ispitamo jedan od važnih segmenata govornog funkcionisanja, a to je oralna praksija, odnosno kinestetska i motorna kontrola pokreta mišića orofacijalne regije koji se, kombinovani, koriste i pri govoru. Subjekti su bili grupa od 10 pacijenata Zavoda za psihofiziološke poremećaje i govornu patologiju ’’Prof. Dr Cvetko Brajović’’, na tretmanu zbog mucanja, uzrasta 9-12 godina, i kontrolna grupa od 10-oro dece istog uzrasta i pola, koja ne mucaju niti imaju druge govorne ili jezičke probleme. Korišćen je Test oralne praksije autora Radičević i Stevanković. Rezultati ukazuju na značajnu razliku u sposobnosti izvođenja zadatih pokreta, u korist kontrolne grupe. S obzirom na mali uzorak planirano je opsežnije istraživanje na većem uzorku, kako bi se isključila slučajnost u dobijanju ovakvih rezultata. Međutim, imajući u vidu već pomenute nalaze različitih istraživanja koji potkrepljuju naše rezultate, smatramo da je i ovaj nalaz dovoljan da bi se u tretman mucanja dece ovog uzrasta uključile i vežbe za poboljšanje sposobnosti oralne praksije.Stuttering is a multidimensional problem in diagnostics and in therapy. It is fluency disorder that affects aproximatelly 5% of children and 1% of adults. Different factors influence decrease in stuttering frequency and severity by reducing demands for motoric-speech control and language formulation. There is higher posibillity for spontaneous recovery amnog female individuals, individuals with adequate family environment, righthanded, who have good phonological, linguistic and non verbal skills, and have more stable motoric speech sistem. During years of working with children and adults who stutter, we noticed that large number of children, but also older patients who come to us for teatment of stuttering, show other speech and/or language problems as well. This was the reason for us to investigate status of oral praxia, as one of important segments of speech functioning, showing level of kinestetic and motor control of movements of orofacial muscles, wich are used during speech as well. Subjects were a group of 10 patients, aged 9-11, on therapy treatment for stuttering at the Institute for Psychophysiological Disorders and Speech Pathology “Prof. Dr Cvetko Brajovic” in Belgrade. Control group consisted of 10 children, age and gender matched, without stuttering or other speech or language disorder. We used the Test of oral praxia, by Radičević&Stevanković. Results show signifficant diference in performing in favour of non-stuttering children. Since we used small group in our research, we plan to repead it on considerably larger number of subjects, in order to exclude statistical coincidence/ incidental results. However, considering already mentioned results of other researches, we belive that even this finding is enough to include oral motor excercises into the treatment of stuttering among this age group

Oral praxis and stutterling

Mucanje predstavlja višedimenzionalni problem kako u dijagnostici tako i u terapiji. To je poremećaj fluentnosti govora koji pogađa približno 5% dece i 1% odraslih. Različiti faktori utiču na smanjenje učestalosti i težine mucanja, često tako što smanjuju zahteve za motornom kontrolom govora i jezičkom formulacijom iskaza. Postoji veća verovatnoća za spontani oporavak ako su u pitanju osobe ženskog pola, osobe koje imaju dobre fonološke, jezičke i neverbalne sposobnosti, desnoruke su, imaju stabilniji motorni govorni sistem i adekvatno porodično okruženje. Tokom višegodišnjeg rada sa decom i odraslima koji mucaju zapazili smo da veliki broj dece, ali i starijih pacijenata koji nam se obrate zbog problema mucanja pokazuju i druge govorne i/ili jezičke probleme. Zato smo želeli da ispitamo jedan od važnih segmenata govornog funkcionisanja, a to je oralna praksija, odnosno kinestetska i motorna kontrola pokreta mišića orofacijalne regije koji se, kombinovani, koriste i pri govoru. Subjekti su bili grupa od 10 pacijenata Zavoda za psihofiziološke poremećaje i govornu patologiju ’’Prof. Dr Cvetko Brajović’’, na tretmanu zbog mucanja, uzrasta 9-12 godina, i kontrolna grupa od 10-oro dece istog uzrasta i pola, koja ne mucaju niti imaju druge govorne ili jezičke probleme. Korišćen je Test oralne praksije autora Radičević i Stevanković. Rezultati ukazuju na značajnu razliku u sposobnosti izvođenja zadatih pokreta, u korist kontrolne grupe. S obzirom na mali uzorak planirano je opsežnije istraživanje na većem uzorku, kako bi se isključila slučajnost u dobijanju ovakvih rezultata. Međutim, imajući u vidu već pomenute nalaze različitih istraživanja koji potkrepljuju naše rezultate, smatramo da je i ovaj nalaz dovoljan da bi se u tretman mucanja dece ovog uzrasta uključile i vežbe za poboljšanje sposobnosti oralne praksije.Stuttering is a multidimensional problem in diagnostics and in therapy. It is fluency disorder that affects aproximatelly 5% of children and 1% of adults. Different factors influence decrease in stuttering frequency and severity by reducing demands for motoric-speech control and language formulation. There is higher posibillity for spontaneous recovery amnog female individuals, individuals with adequate family environment, righthanded, who have good phonological, linguistic and non verbal skills, and have more stable motoric speech sistem. During years of working with children and adults who stutter, we noticed that large number of children, but also older patients who come to us for teatment of stuttering, show other speech and/or language problems as well. This was the reason for us to investigate status of oral praxia, as one of important segments of speech functioning, showing level of kinestetic and motor control of movements of orofacial muscles, wich are used during speech as well. Subjects were a group of 10 patients, aged 9-11, on therapy treatment for stuttering at the Institute for Psychophysiological Disorders and Speech Pathology “Prof. Dr Cvetko Brajovic” in Belgrade. Control group consisted of 10 children, age and gender matched, without stuttering or other speech or language disorder. We used the Test of oral praxia, by Radičević&Stevanković. Results show signifficant diference in performing in favour of non-stuttering children. Since we used small group in our research, we plan to repead it on considerably larger number of subjects, in order to exclude statistical coincidence/ incidental results. However, considering already mentioned results of other researches, we belive that even this finding is enough to include oral motor excercises into the treatment of stuttering among this age group

The effect of pH on visible-light photocatalytic properties of pseudobrookite nanoparticles

In this study, pseudobrookite (Fe2TiO5) nanoparticles were fabricated by a modified sol-gel method using Fe(NO3)39H2O and Ti(OC3H7)4 as starting reagents and ethanol as solvent. Oxalic acid was used as a chelating agent while cetyltrimethyammonium bromide (CTAB) and citric monohydrate were used as surfactants. Structral and morphological characterization using X-Ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM) analysis confirmed the formation of pseudobrookite nanoparticles. As synthetized Fe2TiO5 nanoparticles were utilized as photocatalysts for decolorisation of Methylene blue (MB) under visible light irradiation. It was observed that the adsorption of MB onto Fe2TiO5 nanoparticles is strongly dependent on the solution pH. Maximum decolorozation was observed for Fe2TiO5 nanoparticles prepared with CTAB under alcaline conditions (pH=10.5)

Nanocrystalline iron-manganite (FeMnO3) applied for humidity sensing

Nanocrystalline iron manganite was synthesized using a sol-gel self-combustion method with glycine as fuel, followed by calcination at 900 °C for 8 hours. Structural characterization was performed using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). It confirmed the formation of nanocrystalline iron-manganite with a perovskite structure. Humidity sensing properties of bulk and thick film samples of the obtained nanocrystalline iron manganite powder were analyzed. Organic vehicles were added to the powder to form a thick film paste that was screen printed on alumina substrate with test PdAg interdigitated electrodes. Impedance response of bulk and thick film samples was analyzed in a humidity chamber in the relative humidity range 30-90% in the frequency range 42 Hz to 1 MHz in view of applying iron-manganite for humidity sensing applications

Supercritical Fluid Extraction of Celery and Parsley Fruit-Chemical Composition and Antibacterial Activity

Supercritical fluid extraction as an environmentally friendly technology was applied to isolate biologically active extracts from celery and parsley fruits for potential applications in the food industry. The extractions were performed under mild temperature conditions of 39.85 °C and at pressures of 10 and 30 MPa. The extracts were analyzed regarding their chemical composition, antibacterial activity, and cytotoxic effect. Sedanolide was the dominant component of the celery fruit extracts, comprising more than 70% of the obtained fraction, while the content of apiole in the parsley fruit SC CO2 extracts exceeded 85%. The celery fruit extracts showed strong and moderately strong antibacterial activity against tested Staphylococcus aureus, Bacillus (B.) cereus, B. subtilis, B. circulans, Listeria (L.) greyi, L. seeligeri and L. welshimeri, with minimal inhibitory concentration (MIC) values between 160 and 640 µg/mL, and weak activity against the selected Salmonella isolates with a MIC of 2560 µg/mL. The parsley extract obtained at 10 MPa showed strong and moderately strong antibacterial effects against Bacillus strains with obtained MICs of 160-640 µg/mL, and weak activity against Staphylococcus, Listeria, and Salmonella with a MIC of 2560 µg/mL. Cytotoxicity investigation showed that the extracts with proven antibacterial activity had no cytotoxic effect on rabbit kidney cells at concentrations of up to 640 µg/mL