Application of polylactide (PLA) biomaterial in various fields of medicine

Polylactide (PLA) or polylactic acid is a biodegradable and biocompatible biomaterial obtained from lactic acid, extracted from sugar cane or corn starch. Due to its biocompatibility, after application, it will cause a minimal reaction of the organism, and by virtue of its biodegradability, it will facilitate postoperative recovery because there is no need for its removal. It is often in combination with other compounds to fulfill the requirement about properties which implant need to have. In this review, this will be described in which areas of medicine apply this biomaterial and in which forms. We will see that this material can be made various implants such as surgical sutures, tiles, screws, coatings, capsules and tissue matrices and that this application is especially important in surgical branches of medicine.Twenty-First Young Researchers’ Conference - Materials Science and Engineering: Program and the Book of Abstracts; November 29 – December 1, 2023, Belgrade, Serbi

q-Karamatine funkcije i asimptotska svojstva rešenja nelinearnih q-diferencnih jednačina

The purpose of the doctoral dissertation is to determine the conditions for the existence and to examine in detail the asymptotic properties of solutions of the second order nonlinear q-difference equations, with an application of the theory of q-regular variation. The half-linear q-difference equation was analyzed in the framework of q-regular variation. Necessary and sufficient conditions for the existence of q-regularly varying solutions of the half-linear q- difference equation were obtained. Moreover, sufficient conditions for all eventually positive solutions to be q-regularly varying were examined. In cases where this is possible, the application of q-Karamata’s integration theorem and properties of q-regularly varying functions have been used to determine the precise asymptotic formula of different types of solutions, which accurately describes the behavior of these solutions in long time intervals, which is of special importance from the point of view of application. The obtained results in the q-calculus were compared with the known results in the continuous and the discrete case, but also, they were used to obtain new results in the discrete asymptotic theory. The sublinear second order q-difference equation of Emden-Fowler type was also analyzed in the framework of q-regularly varying functions. Assuming that the coefficients of this equation are q-regularly varying functions, necessary and sufficient conditions for the existence of strongly increasing and strongly decreasing solutions, as well as their asymptotic representations at infinity, have been determined. Moreover, it was shown that all q-regularly varying solutions of the same regularity index have the same asymptotic representation at infinity. The obtained results enabled the complete structure of the set of q-regularly varying solutions to be presented

Sintering of fly ash based composites with zeolite and bentonite addition for application in construction materials

Due to pozzolanic characteristics, fly ash is commonly used as a cement replacement in construction composites. Addition of natural clays with sorption ability (i.e. zeolite and bentonite) in to the fly ash based construction materials is of both scientific and industrial interest. Namely, due to the application of sorptive clay minerals, it is possible to immobilize toxic heavy metals from the composite structure. The thermal compatibility of fly ash and zeolite, as well as fly ash and bentonite, within the composite was observed during sintering procedure. The starting components were used in 1:1 ratio and they were applied without additional mechanical treatment. The used compaction pressure for the tablets was 2 t•cm-2. The sintering process was conducted at 1000ºC and 1200ºC for two hours in the air atmosphere. The mineralogical phase composition of the non-treated and sintered samples was analyzed using X-ray diffraction method. Scanning electron microscopy was applied in the analysis of the microstructure of starting and sintered samples. The thermal behavior was observed via DTA method. The influence of temperature on the properties of fly ash-zeolite and fly ash-bentonite composites was investigate

The photogenerated excess carriers influence on the photoacoustic signal of a narrow bandgap semiconductor

In this work, the influence of photogenerated excess carriers on thermodiffusion and thermoelastic mechanisms in the total photoacoustic signal is analyzed. Optically excited ntype silicon with light periodically modulated in the audio range from 20 to 20kHz showed that photogenerated excess carriers, with bulk and surface carrier recombination, lead to creation of slow thermal source (compared to fast source caused by photo-excited phonon) that have effects on thermodiffusion and thermoelastic mechanisms of the total photoacoustic signal at frequencies up to 1kHz, but also cause additional, plasmaelastic bending of semiconductor, which has an influence on the total photoacoustic signal at frequencies greater than 10kHz.Twenty-First Young Researchers’ Conference - Materials Science and Engineering: Program and the Book of Abstracts; November 29 – December 1, 2023, Belgrade, Serbi

Education for democratic citizenship in Europe

U članku se analiziraju primeri dobre prakse u oblasti obrazovanja za demokratiju i građansko društvo (u tekstu: demokratsko građanstvo) u Evropi. Socijalni i politički život Evropljana je sve kompleksniji. Intenzivne političke promene formiraju specifične društvene okolnosti u kojima stari obrasci ponašanja više nisu adekvatni, pa je potrebno usvajati nova znanja kako bi se razumeli novi društveno-politički procesi i uzelo aktivno učešće u njima. Obrazovanje odraslih u ovom kontekstu dobija širi smisao i značenje. Javlja se potreba za novim područjima obrazovanja, poput obrazovanja za demokratsko građanstvo, koje ima za cilj da doprinese razvoju kritičkog mišljenja i građanske odgovornosti kod odraslih i da podstakne na participaciju u rešavanju problema u svom okruženju i šire.The article analyzes the examples of good practice in the field of education for democratic citizenship in Europe. The social and political life of Europeans is increasingly complex. Intensive political changes shape specific social circumstances and the old models of behavior are no longer adequate. Consequently, it is necessary to acquire new knowledge in order to understand new political processes and take active part in them. In this context, the adult education assumes broader sense and meaning. A need for new fields of education arises, such as education for democratic citizenship which has as its goal to contribute to developing of critical thinking and citizen responsibility among adults and to encourage them to participate in solving of the problems in their community and broader environment

HAAR WAVELET OPERATIONAL MATRIX BASED NUMERICAL INVERSION OF LAPLACE TRANSFORM FOR IRRATIONAL AND TRANSCENDENTAL TRANSFER FUNCTIONS

Irrational and transcendental functions can often be seen in signal processing or physical phenomena analysis as consequences of fractional-order and distributed-order models that result in fractional or partial differential equations. In cases when finding solution in analytical form tends to be difficult or impossible, numerical calculations such as Haar wavelet operational matrix method can be used.  Haar wavelet establishes a direct procedure for transfer function inversion using the wavelet operational matrix for orthogonal function set integration. In this paper an inverse Laplace transform of irrational and transcendental transfer functions using Haar wavelet operational matrix is proposed. Results for a number inverse Laplace transforms are numerically solved and compared with the analytical solutions and solutions provided by commonly used Invlap and NILT algorithms. This approach is useful when the original cannot be represented by an analytical formula and validity of the obtained result needs to be crosschecked and error estimated

Hranidbeno ponašanje pasa lutalica u javnom prihvatilištu

Feeding time of stray dogs on the first, second, third, fifth and seventh day of captivity in a municipal shelter was studied. The average value of the feeding time of dogs decreased from the first day (429.07±107.08 seconds) to the third day in captivity when it reached the lowest average value (229.53±95.18 seconds). The feeding time of dogs on the third day in captivity differs significantly from the same parameter on the first (429.07±107.08 seconds) and second day (372.73±100.58 seconds) in captivity (p lt 0.01). The highest average value of feeding time of stray dogs in the shelter was recorded on the first day. On the fifth and seventh day the feeding time of dogs increased compared to the third day. However, there were no significant differences of the average value of feeding time on the third day comparing with the fifth day (260.8±111.06 seconds) or the seventh day (301.33±119.89 seconds). Dogs ate their food more slowly on the fifth and the seventh day than on the third day, but more quickly than on the first and the second day (372.73±100.58 seconds). Significant differences were estimated comparing the feeding time of dogs on the first day with the third (p lt 0.01), fifth (p lt 0.01), and seventh day (p lt 0.05) of housing in the municipal shelter. Also, the feeding time of dogs on the second day differed significantly from the third (p lt 0.01) and the fifth day (p lt 0.05).U radu su prikazani rezultati proučavanja brzine unošenja hrane kod pasa lutalica u javnom prihvatilištu u Beogradu prvog, drugog, trećeg, petog i sedmog dana boravka. Prosečna brzina unošenja hrane je opadala počev od prvog dana (429,07±107,08 sekundi) do trećeg dana boravka pasa u zatočeništvu kada je ovaj pokazatelj dostigao najnižu vrednost (229,53±95,18 sec). Brzina unošenja hrane trećeg dana se statistički značajno razlikovala u poređenju sa prvim danom (429,07±107,08 sec) i drugim danom (372,73±100,58 sec) boravka pasa u prihvatilištu (p lt 0,01). Najveća prosečna vrednost brzine unošenja hrane zabeležena je prvog dana boravka u prihvatilištu. Petog i sedmog dana boravka u prihvatilištu brzina unošenja hrane se povećala u poređenju sa trećim danom. Međutim, nisu uočene statistički značajne razlike u poređenju brzine unošenja hrane između trećeg i petog (260,8±111,06 sec) i trećeg I sedmog dana (301,33±119,89 sec). Psi su mnogo sporije unosili hranu petog i sedmog dana nego trećeg dana, ali brže nego prvog i drugog dana boravka u prihvatilištu (372,73±100,58 seconds). Značajne razlike su utvrđene u brzini unošenja hrane između prvog i trećeg (p lt 0,01), petog (p lt 0,01), sedmog dana (p lt 0,05) boravka pasa u prihvatilištu. Takođe, brzina unošenja hrane se značajno razlikovala i drugog dana u poređenju sa trećim (p lt 0,01) i petim danom (p lt 0,05)

Numerical analysis of stress distribution in total hip replacement implant

Total hip replacement implants represent permanent implants and require large bone and cartilage removal during implantation. Revision would affect joint capability to sustain load, which makes this procedure irreversible. During exploitation, i.e. everyday activities, implants are subjected to dynamic loading. Thereby, these structures are prone to failure by fatigue. Highest stress states on total hip replacement implants are present in the neck area of the implant, which is a position of crack initiation. Under loading the implant neck exhibits tension and compression zones. Crack initiation in the neck side under tension would lead to crack opening and certain fracture. Implants are examined by experimental and numerical methods. The most common numerical method is finite element method (FEM) used to simulate different loading conditions. In this paper numerical analysis of stress distribution in the neck area is performed on a specific implant. Four numerical models are created in order to show how certain design solutions influence the stress distribution in the neck area

Numerical analysis of stress distribution in total hip replacement implant

Total hip replacement implants represent permanent implants and require large bone and cartilage removal during implantation. Revision would affect joint capability to sustain load, which makes this procedure irreversible. During exploitation, i.e. everyday activities, implants are subjected to dynamic loading. Thereby, these structures are prone to failure by fatigue. Highest stress states on total hip replacement implants are present in the neck area of the implant, which is a position of crack initiation. Under loading the implant neck exhibits tension and compression zones. Crack initiation in the neck side under tension would lead to crack opening and certain fracture. Implants are examined by experimental and numerical methods. The most common numerical method is finite element method (FEM) used to simulate different loading conditions. In this paper numerical analysis of stress distribution in the neck area is performed on a specific implant. Four numerical models are created in order to show how certain design solutions influence the stress distribution in the neck area

Potential genomic biomarkers of obesity and its comorbidities for phthalates and bisphenol A mixture: In silico toxicogenomic approach

This in silico toxicogenomic study aims to explore the relationship between phthalates and bisphenol A (BPA) co-exposure and obesity, as well as its comorbid conditions, in order to construct a possible set of genomic biomarkers. The Comparative Toxicogenomics Database (CTD; http://ctd.mdibl.org) was used as the main data mining tool, along with GeneMania (https://genemania.org), ToppGene Suite (https://toppgene.cchmc.org) and DisGeNET (http://www. disgenet.org). Among the phthalates, bis(2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP) were chosen as the most frequently curated phthalates in CTD, which also share similar mechanisms of toxicity. DEHP, DBP and BPA interacted with 84, 90 and 194 obesity-related genes/proteins, involved in 67, 65 and 116 pathways, respectively. Among these, 53 genes/proteins and 42 pathways were common to all three substances. 31 genes/proteins had matching interactions for all three investigated substances, while more than half of these genes/proteins (56.49%) were in co-expression. 7 of the common genes/proteins (6 relevant to humans: CCL2, IL6, LPL, PPARG, SERPINE1, and TNF) were identified in all the investigated obesity comorbidities, while PPARG and LPL were most closely linked to obesity. These genes/proteins could serve as a target for further in vitro and in vivo studies of molecular mechanisms of DEHP, DBP and BPA mixture obesogenic properties. Analysis reported here should be applicable to any mixture of environmental chemicals and any disease present in CTD