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This research was focused on the influence of manganese (Mn) incorporation at Sr and/or Ti sites on the microstructure, relative dielectric permittivity and specific magnetization of strontium titanate (SrTiO3) ceramics. A solid-state method was used for the preparation of mechanically activated (10, 30 and 120 min) Mn-doped SrTiO3 ceramics with various manganese dioxide (MnO2) weight percentages (1.5, 3 and 6 wt%). Rietveld's analysis showed that the mean crystallite size in doped-activated SrTiO3 ceramics is smaller than in undoped ceramics, which is a consequence of additional crystal structure distortion due to ion substitution. Changes in the Raman spectra indicated dopant incorporation in the SrTiO3 lattice. The microstructural analysis pointed out a decrease in the mean grain size with increasing dopant concentration and time of activation. The highest values of permittivity and magnetization were observed for Mn-doped SrTiO3 ceramic mechanically activated for 120 min. Based on all the above, the optimal electrical and magnetic properties of SrTiO3 ceramics can be achieved by the appropriate choice of mechanical activation time and dopant concentration.

Mechanically activated strontium titanate (SrTiO3) powders with various manganese dioxide (MnO2) doping levels (1.5, 3 and 6 wt%) were prepared by solid state method. Due to the possibility of manganese ion incorporation in SrTiO3 at Ti4+ and/or Sr2+ sites a detailed analysis of the influence of dopants on the microstructure, morphology and optical properties of perovskite oxide was conducted. The investigation showed that manganese was incorporated into the lattice and surface layers of SrTiO3 particles with the presence of manganese segregation and inhomogeneities. Optical measurements indicated a shift of the absorption edge to higher values of wavelengths where the lowest value of the band gap (3.10 eV) was for the longest activation time (120 min) and the highest weight percentage of dopant (6 wt%). In the case of lower concentration (1.5 wt%), there was a significant relative contribution of the substitution of Sr2+ ions by Mn2+ ions, while the substitution of Ti4+ ions by Mn4+ ions dominated samples with an increased concentration.

Iron-doped strontium-titanate (SrTiO3) powders with various iron(III) oxide (Fe2O3) weight percentages (1.5, 3 and 6 wt%) were prepared by a solid-state method in the presence of mechanical activation (10, 30 and 120 min). A systematic investigation by XRD, SEM and Raman spectroscopy has been undertaken to evaluate the role of dopant on the microstructural and morphological study of the perovskite oxide obtained. The optical properties of the different iron-doped and activated Fe-SrTiO3 powders have been also evaluated. The results demonstrated that Fe has been substituted into the lattice and surface layers of particles of SrTiO3 powders and the absorption edge shifted to higher wavelength values with increasing activation time and dopant weight percentage. The lowest value of the band gap (Eg=3.20 eV) was registered for the longest activation (120 min) and the highest weight percentage of dopant (6 wt%). Combining doping with mechanical activation, led to lower values of Eg and that fact could be used in subsequent studies to make Fe-SrTiO3 more suitable photocatalysts.

In this study, microstructure evolution and dielectric properties of SrTiO3 ceramic have been investigated, whereby mechanical activation of SrTiO3 powders was used to modify the functional properties of ceramic materials. Microstructural SEM analysis of SrTiO3 ceramics showed that the increase in mechanical activation time results in less porous samples. Raman spectroscopy indicated changes in the broadening and asymmetry of the TO2 mode with a change in the time of mechanical activation. TO2 mode showed a Fano asymmetry due to its interaction with polarization fluctuations in polar micro-regions, which are a consequence of the presence of oxygen vacancies caused by activation. The maximum value of dielectric permittivity was observed in the sample activated for 10 min. Also, the sample activated for 10 min exhibits relatively low values of loss tangent, compared to the other mechanically activated samples, providing the best overall dielectric performance compared to other samples. © 2022 Authors. Published by association for ETRAN Society.

Manganese doped SrTiO3 powders with various manganese dioxide weight percentages in the range of 1.5, 3 and 6 wp% were prepared by a solid-state method in the presence of mechanical activation (10, 30 and 120 minutes). A systematic investigation by X-ray diffraction (XRD), scanning electron microscopy (SEM), particle size analisys (PSA), Brunauer-Emmett-Teller (BET) methods and Raman spectroscopy has been undertaken to evaluate the role of dopants on the microstructural and morphological study of the perovskite oxide obtained. The optical properties of the different manganese doped and activated SrTiO3 powders have been also evaluated. Mn insertion in SrTiO3 is discussed considering the possibility for Mn ions to occupy both Ti4+ and Sr2+ sites as well as manganese segregation and Mn incorporation-related non-homogeneities. The results demonstrated that Mn has substituted into the lattice and surface layers of the particles of SrTiO3 powders and the absorption onset shifted to higher values of wavelengths with increasing time of activation and dopant concentration. The lowest value of the band gap (Eg=3.10 eV) was registered with the longest activation for 120 minutes and the highest concentration of dopant (6 wp%). Combining doping with mechanical activation lower values of band gap can be achieved and that fact could be used in subsequent studies to make Mn-SrTiO3 more suitable visible-light photocatalysts.

The influence of Mn incorporation into the Sr and Ti sites of SrTiO3 ceramics on the structure, microstructure and dielectric tunability was studied. Manganese doped SrTiO3 ceramics with various manganese dioxide weight percentages (1.5, 3 and 6 wt %) were prepared by a solid-state method in the presence of mechanical activation (10, 30 and 120 minutes). According to Ritveld's analysis it was found that the size of the crystallite in doped activated SrTiO3 ceramics is smaller than the size of the crystallite in undoped ceramics. This lower degree of crystallinity is a consequence of additional distortion of the crystal structure due to ion substitution. SEM analysis showed that with increasing dopant concentration in the sample, at the same time as a time of mechanical activation, the grain size decreases, which is explained by the increasingly dominant incorporation of Mn4+ ions at sites of Ti4+ ions. On the Raman spectra of doped ceramic samples, the appearance of a peak at 750 cm-1 was observed, its change in intensity with the increase of dopant concentration indicates the incorporation of dopant in the SrTiO3 lattice. It was stated that mechanical activation leads to a more pronounced increase in the intensity of the mentioned peak, i.e. that activation leads to effectively higher incorporation of dopant into the strontium-titanate lattice. Higher values of relative dielectric permittivity of doped SrTiO3 ceramics were observed for 1.5 wt %, in relation to inactivated and activated undoped ceramics. Based on all previous analysis, it is estimated that this can be related not only to higher sample densities but also to the contribution of Mn2+ ion incorporation at Sr2+ ion positions in the lattice. Based on all the above, the optimal electrical properties of SrTiO3 ceramics can be achieved by the appropriate choice of mechanical activation time and dopant concentration.

Magnesium aluminate spinel (MgAl2O4) is a material with good mechanical, chemical, and thermal properties, low dielectric permeability and loss tangent. Based on those properties, MgAl2O4 has found a significant application in refractory ceramics, ceramics windows, integrated electronic devices, etc. Also, it possesses a high chemical and radiation resistance. In this research, MgO was calcined at 1000ºC for an hour, with a step of 10ºC/min to avoid presence of hydroxide or carbonate. MgO and Al2O3 powders were mixed in a one-to-one molar ratio afterwards. The powders were mechanically activated for 15, 30, and 60 minutes. The mass ratio of powder and balls was 1:40. The mechanically activated powders are pressed in the tablets, under the pressure of 0.5 t. The pressed powders were heated up to 1300 ºC with a step of 10 ºC/min and held for 1 h for the reaction. Reacted pellets were crushed and sieved. Obtained spinel powders were sintered at 1450 ºC for 2 h. Both sintered and non-sintered samples were investigated by XRD and SEM. The particle size distribution of the reacted powders was investigated by laser diffraction analysis. Raman spectroscopy was used to determine the lattice vibration in the sintered samples. All results are in accordance with our previous results, and the pure dense spinel phase is obtained.

Mechanical activation represents a very useful technique for powder processing prior to sintering process. First of all, it makes powders homogenized, leads to attrition of powder particles, and makes powder mixtures more reactive. Secondly, it can lead to mechano-chemical reaction, and finally, lowering of sintering time and temperature. Mixtures of ZrO2 and C were mechanically activated by high-energy ball milling. Powders were milled for times from 0 to 120 minutes in air atmosphere. Mechanically activated powder mixtures were characterized by various techniques, such as particle size analysis (PSA), X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, and diffraction scanning calorimetry along with thermo gravimetry (DSC-TGA). As milling time increased, surface area of powders increased, indicating significant particle size reduction. Mechanical activation for 15 minutes provides the best balance between particle size reduction and reactivity for the powders.

In recent years, a lot of interest has been shown in obtaining materials with predetermined properties. The aim is to establish a functional dependence between the synthesis parameters, structural characteristics, and properties of the material. Ceramic materials based on strontium titanate (SrTiO3) are of special interest due to their unique physical-chemical properties. Having in mind the importance of examining the influence of synthesis parameters on the process of obtaining and properties of functional electroceramic materials, and the importance of SrTiO3 as a perovskite material, the motive was to analyze and consider the influence of mechanical activation. It has been established that the time of mechanical activation (0, 10, 30, 60, 90, and 120 minutes) of SrTiO3 powders indirectly affects on electrical properties of SrTiO3 ceramics. It was noticed that in SrTiO3 ceramics the values of relative dielectric permittivity in the radio frequency range (0,3 MHz-3 GHz) are stable, which is important for the fabrication of electronic components. Microstructural SEM analysis showed that the increase in mechanical activation time results in less porous samples. It was found that the value of the relative dielectric permittivity of ceramic samples at room temperature changes following the combined effect of changes in sample density, grain size, as well as changes in the grain boundary region. The maximum value of dielectric permittivity was observed in the sample activated for 10 minutes. Also, the sample activated for 10 min exhibits relatively low values of loss tangent, compared to the other mechanically activated samples, providing the best overall dielectric performance compared to other samples.

Cilj ove doktorske disertacije je bio da se analizira i sagleda uticaj mehaničke aktivacije nastrukturu i svojstva nedopiranog i dopiranog SrTiO3 praha, kao i uticaj na strukturu i svojstvakeramike dobijene sinterovanjem ispresaka pomenutih prahova. U slučaju sinterovanih nedopiranihSrTiO3 uzoraka dodatno su razmatrane promene u brzini densifikacije i kinetici sinterovanja. Uticajmehaničke aktivacije i dopanta na električna svojstva stroncijum-titanatne keramike je analiziranmerenjem frekventne zavisnosti relativne dielektrične permitivnosti i tangensa ugla dielektričnihgubitaka na sobnoj temperaturi. Magnetnim merenjima, kod dopiranih SrTiO3 uzoraka dobijenihdodavanjem mangan(IV)-oksida, praćen je uticaj mehaničke aktivacije, koncentracije dopanta ijačine magnetnog polja na vrednost specifične magnetizacije.Mehanička aktivacija SrTiO3 praha je vršena u visoko-energetskom planetarnom mlinu sakuglama, pri čemu je vreme aktivacije nedopiranog praha iznosilo: 5, 10, 30, 60, 90 i 120 minuta,dok je efekat dopiranja razmatran za aktivaciju od 10, 30 i 120 minuta. U cilju dobijanja SrTiO3:Mnsistema, tipa Sr1-xMnxTiO3 (SMnT) ili SrTi1-xMnxO3 (STMn), u polazni SrTiO3 prah je dodatmangan(IV)-oksid (MnO2), pri čemu su izabrane vrednosti za x bile: 0,03, 0,06 i 0,12. Raspodelaveličina čestica je ukazala da je mehanička aktivacija dovela do usitnjavanja čestica polaznog praha,uz istovremenu pojavu šire raspodele veličina čestica pri dužim vremenima aktivacije.Skenirajućom i transmisionom elektronskom mikroskopijom (SEM i TEM) analizirana jemikrostruktura i morfologija polaznog i mehanički aktiviranih prahova. BET metodom je utvrđenoda se najviša vrednost specifične površine kod nedopiranih prahova postiže pri aktivaciji u trajanjuod 60 minuta, dok pri daljoj aktivaciji specifična površina ostaje približno konstantne vrednosti,usled povećane sekundarne aglomerizacije. Pokazano je da je gustina ispreska kod prahaaktiviranog tokom 10-30 minuta najveća. Zapaženo je sniženje intenzit, The aim of this doctoral dissertation is to analyze and evaluate the effect of mechanicalactivation on the structure and properties of undoped and doped SrTiO3 powders, as well as theeffect on the structure and properties of the ceramics obtained by sintering these powders. For thesintered undoped SrTiO3 samples, changes in the densification rate were also analyzed. The effectof mechanical activation and dopant on the electrical properties of strontium titanate ceramics wasanalyzed by measuring the frequency-dependent relative dielectric permittivity and the loss tangentat room temperature. Magnetic measurements performed on the doped SrTiO3 samples obtained bythe addition of manganese(IV) oxide were used to monitor the influence of mechanical activation,dopant concentration and magnetic field strength on magnetization.The mechanical activation of the SrTiO3 powder was performed in a high-energy planetaryball mill; the activation times of the undoped powder were: 5, 10, 30, 60, 90, and 120 minutes,while the doping effect was analyzed for the activation periods of 10, 30, and 120 minutes. In orderto obtain SrTiO3:Mn systems belonging to Sr1-xMnxTiO3 (SMnT) or SrTi1-xMnxO3 (STMn)compound types, manganese(IV) oxide (MnO2) was added to the starting SrTiO3 powder, where thevalues selected for x were: 0.03, 0.06 and 0.12. The particle size distribution indicated thatmechanical activation resulted in the comminution of the starting powder particles, accompaniedwith a wider particle size distribution at longer activation times. The microstructural andmorphological analysis of the starting and mechanically activated powders was performed usingscanning and transmission electron microscopy (SEM and TEM). The BET method revealed that60-minute activation resulted in the highest specific surface area in undoped powders, while furtheractivation led to a relatively constant specific surface due to increased secondary agglomeration.The density of the powder activated for 10-30 minut

Introduction/Objective Knowledge and practical skills in medical waste (MW) management are of equal importance for medical and dental doctors. The first comparative study on the knowledge and skills in the field of MW management among Belgrade students was conducted with the goal of examining whether students of medicine and dentistry are equally familiar with this extremely important field. Methods a cross-sectional study included 558 students of the sixth year of studies (430 medical and 128 dental students) who completed an anonymous semi-structured questionnaire to determine attitudes and knowledge on MW management. Results the majority of medical and dental students had no training in MW management (79.5% and 74.6%, respectively). Dental students use protective equipment more frequently than medical students (94.5% vs. 42%, p lt 0.001). However, full vaccinal protection against hepatitis B is better among medical students compared to dental students (57.7% vs. 39.1%, p lt 0.001). Complete knowledge on postexposal prophylaxis is better among medical students compared to dental students (44.5% vs. 13.3%, p lt 0.001). However, dental students are more disciplined in reporting injuries (63.1% vs. 52.4%, p = 0.038). The students' knowledge on primary separation of infectious waste (93% vs. 77.8%, p lt 0.001) and used needles (80.3% vs. 70.4%, p = 0.007) is better among dental students compared to medical students' correct answers. Conclusion Dental students show better knowledge on MW management and are more disciplined in using personal infection protection compared to medical students. The students support continued training on MW management and investigations on this topic., Uvod/Cilj Znanje i praktične veštine upravljanja medicinskim otpadom su od posebnog značaja za doktore medicine i stomatologije. Komparativna studija o znanju i veštinama iz oblasti upravljanja medicinskim otpadom sprovedena je među beogradskim studentima prvi put, u cilju ispitivanja da li ovom izuzetno važnom oblašću studenti medicine i stomatologije vladaju podjednako dobro. Metode Ova studija preseka obuhvatila je 558 studenata šeste godine studija na Beogradskom univerzitetu (430 studenata medicine i 128 studenata stomatologije), koji su popunili anonimni upitnik o znanju i stavovima o upravljanju medicinskim otpadom. Rezultati Većina studenata stomatologije i medicine nisu imali nikakvu posebnu obuku iz upravljanja medicinskim otpadom (79,5% i 74,6%). Studenti stomatologije su češće koristili zaštitnu opremu (94,5% prema 42%, p lt 0,001). Vakcinalna zaštita od hepatitisa B je kompletnija među studentima medicine u odnosu na studente stomatologije (57,7% prema 39,1%, p lt 0,001). Znanje o profilaksi posle izloženosti bolja je među studentima medicine (44,5% prema 13,3%, p lt 0,001). Međutim, studenti stomatologije su ažurniji u pogledu prijavljivanja povreda na radnom mestu (63,1% prema 52,4%, p = 0,038). Znanje studenata o primarnoj separaciji infektivnog otpada i korišćenih igala je bolje među budućim stomatolozima (tačni odgovori 93% nasuprot 77,8%; p lt 0,001 i 80,3% prema 70,4%; p = 0,007). Zaključak Studenti stomatologije imaju bolje znanje o upravljanju medicinskim otpadom i disciplinovaniji su u pogledu korišćenja zaštitne opreme na radu u odnosu na studente medicine. Studenti podržavaju kontinuiranu edukaciju o upravljanju medicinskim otpadom i dalja istraživanja o ovoj temi.

The initial-stage of sintering plays a significant role in determining the final microstructure that defines the main characteristics of electroceramics materials such as functional properties. In this article non-isothermal sintering of non-activated and mechanically activated SrTiO3 samples was investigated up to 1300 °C. Dilatometric curves indicate that mechanical activation leads to an earlier onset of sintering, suggesting that it should lead to a more homogenous and denser sintered product. Analysis of the initial stage of sintering reveals that the sintering process of all examinated samples consists of two or three overlapping single-step processes, with a change in the dominant mass transport mechanism. The values of apparent activation energy of the considered single-step process exhibit a significant decrease with an increase in mechanical activation time. The values of the density of samples after isothermal sintering indicate that the final stage of sintering has not been reached by 1300 °C. © 2018 Authors.

Cilj ove doktorske disertacije je bio da se analizira i sagleda uticaj mehaničke aktivacije na strukturu i svojstva nedopiranog i dopiranog SrTiO3 praha, kao i uticaj na strukturu i svojstva keramike dobijene sinterovanjem ispresaka pomenutih prahova. U slučaju sinterovanih nedopiranih SrTiO3 uzoraka dodatno su razmatrane promene u brzini densifikacije i kinetici sinterovanja. Uticaj mehaničke aktivacije i dopanta na električna svojstva stroncijum-titanatne keramike je analiziran merenjem frekventne zavisnosti relativne dielektrične permitivnosti i tangensa ugla dielektričnih gubitaka na sobnoj temperaturi. Magnetnim merenjima, kod dopiranih SrTiO3 uzoraka dobijenih dodavanjem mangan(IV)-oksida, praćen je uticaj mehaničke aktivacije, koncentracije dopanta i jačine magnetnog polja na vrednost specifične magnetizacije. Mehanička aktivacija SrTiO3 praha je vršena u visoko-energetskom planetarnom mlinu sa kuglama, pri čemu je vreme aktivacije nedopiranog praha iznosilo: 5, 10, 30, 60, 90 i 120 minuta, dok je efekat dopiranja razmatran za aktivaciju od 10, 30 i 120 minuta. U cilju dobijanja SrTiO3:Mn sistema, tipa Sr1-xMnxTiO3 (SMnT) ili SrTi1-xMnxO3 (STMn), u polazni SrTiO3 prah je dodat mangan(IV)-oksid (MnO2), pri čemu su izabrane vrednosti za x bile: 0,03, 0,06 i 0,12. Raspodela veličina čestica je ukazala da je mehanička aktivacija dovela do usitnjavanja čestica polaznog praha, uz istovremenu pojavu šire raspodele veličina čestica pri dužim vremenima aktivacije. Skenirajućom i transmisionom elektronskom mikroskopijom (SEM i TEM) analizirana je mikrostruktura i morfologija polaznog i mehanički aktiviranih prahova. BET metodom je utvrđeno da se najviša vrednost specifične površine kod nedopiranih prahova postiže pri aktivaciji u trajanju od 60 minuta, dok pri daljoj aktivaciji specifična površina ostaje približno konstantne vrednosti, usled povećane sekundarne aglomerizacije. Pokazano je da je gustina ispreska kod praha aktiviranog tokom 10-30 minuta najveća. Zapaženo, The aim of this doctoral dissertation is to analyze and evaluate the effect of mechanical activation on the structure and properties of undoped and doped SrTiO3 powders, as well as the effect on the structure and properties of the ceramics obtained by sintering these powders. For the sintered undoped SrTiO3 samples, changes in the densification rate were also analyzed. The effect of mechanical activation and dopant on the electrical properties of strontium titanate ceramics was analyzed by measuring the frequency-dependent relative dielectric permittivity and the loss tangent at room temperature. Magnetic measurements performed on the doped SrTiO3 samples obtained by the addition of manganese(IV) oxide were used to monitor the influence of mechanical activation, dopant concentration and magnetic field strength on magnetization. The mechanical activation of the SrTiO3 powder was performed in a high-energy planetary ball mill; the activation times of the undoped powder were: 5, 10, 30, 60, 90, and 120 minutes, while the doping effect was analyzed for the activation periods of 10, 30, and 120 minutes. In order to obtain SrTiO3:Mn systems belonging to Sr1-xMnxTiO3 (SMnT) or SrTi1-xMnxO3 (STMn) compound types, manganese(IV) oxide (MnO2) was added to the starting SrTiO3 powder, where the values selected for x were: 0.03, 0.06 and 0.12. The particle size distribution indicated that mechanical activation resulted in the comminution of the starting powder particles, accompanied with a wider particle size distribution at longer activation times. The microstructural and morphological analysis of the starting and mechanically activated powders was performed using scanning and transmission electron microscopy (SEM and TEM). The BET method revealed that 60-minute activation resulted in the highest specific surface area in undoped powders, while further activation led to a relatively constant specific surface due to increased secondary agglomeration. The density of the powder acti

The influence of mechanical activation on the formation, sintering kinetics and morphology was investigated in sintered barium strontium titanate (BST) ceramics with different Ba-to-Sr ratios. Initial powders were mechanically activated for 20 and 120 min, leading to mechano-chemical reaction and formation of BaxSr1-xTiO3 phases. Agglomeration was found to represent an important factor in the process of formation of BaxSr1-xTiO3 phases around 800 oC and during sintering. It reduces the effectiveness of mechanical activation on formation of BaxSr1-xTiO3 phases beyond the short period (20 min), while in the process of sintering, prolonged mechanical activation (120 min) leads to a significant reduction in sintering temperature and the corresponding value of activation energy. In addition, all three systems show a phase transformation around 1100 oC, attributed to the hexagonal-to-cubic phase transition. Morphology of the final sintered ceramics can be correlated primarily with the state of the pre-sintered powder, where mechanically activated powders with smaller particle size produced more compact and less porous final product.

Mechanical activation leads to the creation of new surfaces and decrease in particle size of the initial powder particles, which affects the crystallization of PVDF matrix. In addition, prolonged mechanical activation leads to agglomeration of nanoparticles agglomerates of different sizes. Microstructural changes due to mechanical activation in ZnO, BaTiO3, SrTiO3 and TiO2 powders were investigated using electron microscopy (TEM and SEM), x-ray diffraction (XRD) and particle size analysis (PSA). These were correlated with molecular simulations of mechanical properties of PVDF-nanocluster composites with different oxide nanocluster sizes (1, 1.5 and 2 nm) Each system was simulated using a periodic system of metal oxide nanocrystal inside β-PVDF matrix. β-PVDF was chosen for its superior properties over α- and γ- phases. Geometry of each system was optimized prior to the calculation of mechanical properties using GULP v4.3 software package. Molecular simulations show that, in general, mechanical properties (Young modulus as an indication of elasticity, Shear modulus as an indication of hardness) for all systems improve with decrease in nanocluster size. This suggests that mechanical activation of fillers in PVDF-metal oxide nanoparticle composites should have a positive effect on the mechanical properties of composite systems. This suggests mechanical activation as an easy an inexpensive method of improving mechanical properties of polymer-nanocrystal composite materials.

Polni hormoni igraju značajnu ulogu u regulaciji laringealne funkcije. Ciklične hormonalne promene estrogena i progesterona utiču na akustič- ke karakteristike glasa žena, tokom redovnog menstrualnog ciklusa. Taj uticaj se u periodu ovulacije ogleda u većoj atraktivnosti glasa, dok u pre- menstrualnom periodu uslovljava pojavu premenstrualnog vokalnog sindro- ma. Cilj ovog rada bio je da se analizira veza između akustičkih karakte- ristika glasa i nivoa polnih hormona tokom ovulativne i premenstrualne faze redovnog menstrualnog ciklusa. Ispitivanje je obuhvatilo 30 ispita- nica, starosti od 25 do 30 godina, koje imaju redovan menstrualni ciklus i ne koriste kontracepciju. Analiza glasa vršena je procenom akustičkih parametara glasa, tokom foniranja vokala „a“, primenom kompjuterske la- baratorije za glas „Kay Elemetrics“. Obrađivani su sledeći parametri: prosečna fundamentalna frekvencija (Fo); varijacije u visini fundamen- talne frekvencije – Jitt (%); parametar kratkotrajnih i dugotrajnih po- remećaja amplitude – Shim (%); parametar procene šuma (NHR). Za ocenu statističke značajnosti razlika u zabeleženim vrednostima akustičkih parametara glasa u dve faze menstrualnog ciklusa primenjen je t-test po- novljenih merenja, dok je za procenu normalnosti raspodele korišćen Kolgo- morov-Smirnovljev test. Za ispitivanje razlika među starosnim kategori- jama korišćena je jednofaktorska analiza varijanse (ANOVA). Rezultati akustičke analize nisu pokazali statistički značajnu razliku ni jednog od ispitivanih akustičkih parametara glasa, između perioda ovulacije i premenstrualnog perioda. Iako brojni nalazi u literaturi ukazuju na uti- caj polnih hormona na funkciju larinksa, rezultati našeg istraživanja, bazirani na proceni četiri akustička parametra glasa, takav uticaj ne potvrđuju. S obzirom da je glas multidimenzionalan fenomen, sasvim je verovatno da neki drugi parametri, koje naše istraživanje nije obuhvatilo, mogu biti nosioci tih hormonalnih uticaja, te bi buduća istr, Sex hormones play an important role in the regulation of laryngeal function. Cyclical hormonal changes in estrogen and progesterone affect the acoustic characteristics of the voice of women during the normal menstrual cycle. This influence is reflected in the period of ovulation in a voice more attractive, while the premenstrual period influences the development of vocal premenstrual syndrome. The aim of this study was to analyze the relationship between the acoustic characteristics of voice and levels of sex hormones during the premenstrual phase ovulativne and regular menstrual cycles. The study enrolled 30 patients, aged 25 to 30 years, with regular menstrual cycles and not using contraception. Voice analysis was performed by the evaluation of acoustic parameters of voice over foniranja vowel “a”, using the computerized laboratory “Kay Elemetrics.” The following parameters were analyzed: average fundamental frequency (Fo) variation in the fundamental frequency - Jitte (%) setting short-term and long-term disturbance amplitude - Shim (%) parameter estimates forests (NHR). To evaluate the statistical significance of differences in the recorded values of the acoustic parameters of voice in two phases of menstrual cycle, we used the t-test of repeated measurements, and to assess the normality of the distribution used Kolgomor-Smirnov test. For testing differences among age groups were used factor analysis of variance (ANOVA). The results of the acoustic analysis showed no statistically significant difference in any of the studied acoustic parameters of voice, between ovulation and premenstrual period. Although numerous findings in the literature describing the influence of sex hormones on the function of the larynx, the results of our study, based on an estimate of four acoustic parameters of voice, such an effect is not confirmed. As the voice of a multi-dimensional phenomenon, it is likely that some other parameters that our research did not, they can be carriers o

Strontium-titanate powder was mechanically activated in a planetary ball mill for 0, 5, 10, 30, 60, 90 and 120 minutes. Non-isothermal sintering of non-activated and activated SrTiO3 powder samples in the temperature interval from 50 to 1300 0C with three different heating rates (10, 15 and 20 0C/min) was investigated on a dilatometer. X-ray powder diffraction and scanning electron microscopy (SEM) were used to determine the phase composition, lattice microstrains and microstructure morphology of the samples. XRD results showed the presence of new phases: SrCO3 (strontuim-carbonate) and TiO2 (anatase) after 30 minutes of mechanical activation.

Cilj: Mnogobrojni negativni faktori okruženja i psihosocijalni stresori, kao što su konstantni pritisak za uspehom, preopterećenost akademskim obavezama i nedostatak slobodnog vremena, a u današnje vreme i teška socijalno ekonomska situacija, doprinose nastanku sve češćih poremećaja psihofizičkog zdravlja univerzitetskih studenata, te je zdravlje ove populacije postalo fokus istraživanja poslednjih godina. Glavni ciljevi rada sastoje se u ispitivanju specifičnosti zdravstvenog stanja studenata Medicinskog fakulteta, Ekonomskog fakulteta i Fakulteta veterinarske medicine Univerziteta u Beogradu iz podataka sistematskih pregleda Zavoda za zdravstvenu zaštitu studenata Beograd sa posebnim osvrtom na mentalno zdravlje i analiza njihovog uspeha na studijama. Cilj rada je i procena uticaja socio-ekoloških faktora na psihofizičko zdravlje studenata tri ispitivana fakulteta, sa prospektivnim praćenjem uticaja ovih faktora kod studenata medicine. Kao cilj je navedena i analiza stanja psihičkog distresa, analiza rezultata pojave sindroma izgaranja (emocionalne iscrpljenosti, depersonalizacije i umanjenog samopostignuća) za studente sva tri ispitivana fakulteta, kao i analiza prevalencije faktora rizika za nastanak akademskog distresa i sindroma izgaranja na predkliničkim i kliničkim godinama studija Medicinskog fakulteta u Beogradu. Metodologija: Ovo istraživanje je dizajnirano kao kombinacija dve studije – studije preseka, koja predstavlja istraživanje prevalencije akademskog distresa i sindroma izgaranja kod studenata ispitivana tri fakulteta u Beogradu i prospektivne studije, kojom su obuhvaćeni studenti I i III godine Medicinskog fakulteta i tokom naredne II i IV godina studija sa ciljem da se ispitaju promene u rezultatima pojave akademskog distresa i sindroma izgaranja na predkliničkim i kliničkim godinama studija..., Objective: Numerous negative environmental factors and psychosocial stressors, such as constant pressure to succeed, excessive academic obligations and lack of free time, and in the present time the difficult socioeconomic situation, contribute to the emergence of increasingly frequent mental and physical health disorders in university students, making the health of this population the focus of the recent research. The main objectives of this work include the analysis of the specifics of the health status of students of the School of Medicine, Faculty of Economics and the Faculty of Veterinary Medicine, University of Belgrade based on the data of physical examinations conducted at the Institute for Student Health Care Belgrade, with special emphasis on their mental health and academic achievement. The aim is to estimate the impact of socio-environmental factors on psychological and physical health of students of these three faculties, with the prospective monitoring of the impact these factors have on medical students. Another goal is the analysis of the mental distress, the analysis of the results of the occurrence of burnout syndrome (emotional exhaustion, depersonalization and reduced personal accomplishment) for students of all three faculties, as well as the analysis of the prevalence of risk factors for academic distress and burnout syndrome in preclinical and clinical years of studies at the School of Medicine in Belgrade. Methodology: This study was designed as a combination of two studies - cross section, which is a survey on the prevalence of academic distress and burnout syndrome among students studied at three universities in Belgrade and prospective studies, which included students first and third year of the School of Medicine, and over the next two and four years of study in order to examine the changes in the results of the occurrence of academic distress and burnout syndrome in preclinical and clinical years of study...