Merenje raspodele veličina čestica metodom difrakcije laserske svetlosti

U ovom tekstu opisan je princip rada instrumenta za merenje raspodele veličina čestica Mastersizer 2000, Malvern Instruments Ltd., UK, koji radi na principu analize difraktovane svetlosti. Na konkretnim primerima, pokazali smo da metoda nije rutinska, da se ne svodi na unošenje uzorka u uređaj i pritiskanje dugmeta. Pokazali smo da način pripreme uzoraka za merenje i tačnost rezultata zavise od fizičkih i hemijskih karakteristika analiziranog materijala.The paper deals with the main principles of determination of particle size distribution using Mastersizer 2000, Malvern Instruments Ltd., UK. On the example of several problems we have demonstrated that the method is not a routine one and that the measurement procedure is not limited to entering a sample into the dispersion unit and pressing the button. Furthermore, we have shown that the sample preparation method and, therefore, the accuracy of results conclusively depend on physical and chemical properties of the analyzed materials

Proučavanje procesa sinteze i svojstava višefaznih oksidnih prahova dobijenih hidrotermalnim procesiranjem

PhD defence presentation. The thesis "The Study of Synthesis Processes and Properties of Multiphase Oxide Powders Obtained by Hydrothermal Processing" was defended at the University of Belgrade, Faculty of Technology and Metallurgy, in 2014.Prezentacija prikazana na odbrani doktorske teze "Proučavanje procesa sinteze i svojstava višefaznih oksidnih prahova dobijenih hidrotermalnim procesiranjem". Teza je odbranjena na Tehnološko-metalurškom fakultetu Univerziteta u Beogradu 2014. godine

Directional relays based on digital phase comparator

U ovoj doktorskoj disertaciji predstavljen je nov algoritam za usmereni relej baziran na digitalnoj faznoj komparaciji. Za realizaciju digitalnog faznog komparatora pošlo se od ideje da se ne računa fazni pomeraj između struje i referentnog napona, već energija odnosno integral trenutne snage signala na intervalu dužine polovine osnovne periode napona ili struje. Interval integracije je polovina osnovne periode jer je frekvencija trenutne snage dva puta veća u odnosu na frekvenciju ulaznih signala. Algoritam usmerenog releja koji se bazira na integralu trenutne snage signala ima osobine faznog komparatora. Podešavanje maksimalne osetljivosti releja vrši se direktno iz naponskog ili strujnog registra. U odnosu na dosadašnja rešenja, ovakvim pristupom eliminisana je potreba za impedansom modela voda Zm. Izlaz koji generiše usmereni relej ograničen je na intervalu ±1, deljenjem srednje snage signala prividnom snagom. Na taj način omogućeno je jednostavno zadavanje praga reagovanja ili blokiranja releja, koji je različit od nule. Opisani postupak u proračunima koristi samo jednostavne matematičke operacije (sabiranje, množenje i deljenje) zbog čega u maloj meri koristi procesorsko vreme. Zbog postojanja viših harmonika i jednosmerne komponente u ulaznim signalima algoritam je u nastavku proširen digitalnim Fourierovim filtrom. To je otvorilo mogućnost regulacije osetljivosti releja korišćenjem sinusne i kosinusne komponente Fourierovog reda. Brzina reagovanja releja zavisi od režima koji je prethodio kvaru i podešenog praga reagovanja. Kreće se od trenutnog dejstva do 10 ms, što relej svrstava u one sa brzim odzivom. Opisani algoritam može umesto trenutnih vrednosti signala da koristi njihove priraštaje čime se dobija ultrabrzi usmereni relej. Vreme odziva ovog releja je manje od 5 ms i nema zonu neosetljivosti. U nastavku disertacije izloženo je nekoliko specifičnih primena digitalnog faznog komparatora na realnim problemima. Svaki od algoritama detaljno je testiran serijom računarski generisanih signala...In this doctorial dissertation, a new algorithm for directional relay based on digital phase comparison is presented. The basic idea for realization of digital phase comparator is as follows: instead of calculating phase shift between the reference voltage and current, this algorithm calculates energy i.e. integral of the instantaneous power over one half-period of the voltage or current signal. The integration interval is the half-period because the frequency of the instantaneous power is two times higher than the frequency of the input signals. The algorithm for the directional element based on the integral of instantaneous power possesses the features of the phase comparator. The adjustment of relay sensitivity is performed directly from voltage or current register. In comparison to existing solutions, this approach eliminates the necessity for the line or network model impedance Zm. The output signal, generated by the directional element is limited to interval ±1, by division of the average signal power with the apparent power. This way, the tripping or blocking threshold setting different than zero is enabled. The described procedure uses only simple mathematical operations (addition, multiplication and division) for calculations resulting in small CPU time occupation. Due to existence of higher harmonics and/or direct component in input signals, the algorithm is extended by Fourier filter. This opened a possibility for rough regulation of the relay sensitivity by using only sine or cosine component of the Fourier series. The relay tripping time depends upon the regime before the fault occurrence and the adjusted tripping threshold. It varies from the instantaneous tripping to 10 ms so the relay is characterized by high speed of response. Instead of instantaneous values of the input signals, the described algorithm can use their increments and therefore further increase the speed of response. The tripping time of this relay is less than 5 ms and operates without dead tripping zone. In the following chapters of dissertation, several specific applications of digital phase comparator on practical problems are investigated. Each algorithm is tested in detail with the series of computer-generated signals..

Effects of use of riboflavin and ultraviolet light for pathogen inactivation on quality of platelet concentrates

Background/Aim. Pathogen inactivation in blood and blood products is one of the major means to achieve a zero risk blood supply and improve transfusion safety. Riboflavin (vitamin B2) activated by ultraviolet (UV) light, produces active oxygen which damages cell membrane and prevents replication of the carrier of diseases (viruses, bacteria, protozoa) in all blood products. The aim of this study was to establish the influence of the process of pathogens photoinactivation using riboflavin and UV rays on the biochemical and functional characteristics of platelet concentrates prepared from “buffy coat”. Methods. The examination included 80 platelet concentrates prepared from “buffy coat”, which was separated from whole blood donated by voluntary blood donors around 6 hours from the moment of collection. Concentrates were pooled, filtered and separated unton two groups: one consisted of 10 control units and the other of 10 examined units (pooled platelet concentrates). Examined units of the platelets were treated by riboflavin (35 mL) and UV rays (6.24 J/mL, 265-370 nm) on Mirasol aparature (Caridian BCT Biotechnologies, USA) in approximate duration of 6 min. A total of 35 mL of saline solution was added to the control units. The samples for examining were taken from the control and examined units initially (K0, I0), after the addition of saline (K1) and riboflavin (I1), after illumination (I2), first day of storage (K3, I3) and the fifth day of storage (K4, I4). The following parameters were measured: platelet count and platelet yield, residual erythrocyte and leukocyte count, pH, pO2, pCO2 and bacterial contamination. Results. All the measured parameters showed a statistically significant decrease comparing to K0 and I0; all the results of the first day of platelet storage showed statistically significant decrease comparing to K1 and I1, and all the results of the fifth day of platelet storage (K4, I4) showed a statistically significant decrease comparing to K1 and K3 and to I1 and I3. There was no the mentioned difference in the measured parameters between K4 and I4 (the end of storage - the fifth day). All the platelet units were sterile till the seventh day, when the investigation ended. Conclusion. Platelet concentrates inactivated by riboflavin and UV rays (Mirasol PRT sistem, Caridian BCT, USA) keep all the characteristics assessed by the Guide to the preparation, use and quality assurance of blood components (Council of Europe), during the whole storage period (five days). The obtained data were correlated with existing up to date literature and demonstrated that Mirasol treated platelets were safe and could be incorporated effectively in the routine blood bank and transfusion setting

Hydrothermal synthesis of LiFePO4

Poster presented at the 11th Conference of the Materials Research Society of Serbia - YUCOMAT 2009, Herceg Novi, Montenegro, August 31 – September 4, 2009

Semiintensive capr (Cyprinus carpio, L) production: Type of sustainable fishery

Semiintensive carp production is based on two sources of food for fish proteins that are present in live food and carbohydrates that are provided from additional feeds. By consumption of secondary producers (zooplankton and bottom fauna) nutrients, main causer of water ecosystem eutrophication (phosphorus and nitrogen) is utilized. Unused nutrients (inorganic or organic compounds) are settled at the pond's bottom and through application of agrotechnical measures (natural drainage, winter killing, disking) fertility of the pond's bottom is increased. Semiintensive carp production based on live food as the main protein source fits into the concept of sustainable agriculture

Pittcon 2016 experience in Atlanta – firsthand conference impressions from ACS delegate

In this informal presentation and chat about my Pittcon 2016 experience held in Atlanta, US, I will attempt to give you an insight of this extraordinary event which is held annually and is considered as a leading conference and exposition on laboratory science. I will also try to give you a guidelines how to apply for travel grants which are sponsored by Pittcon organizers in collaboration with ACS Committee on International Activities (IAC). These grants are available to early career analytical chemists from all around the globe, and are given for a different region annually. Beside great lectures provided by eminent scientists from all around the world, updating with latest achievements in instrumentation from all companies in the field of analytical and lab equipment, possibility to meet and make collaborations with participating scientists and companies, you will certainly enjoy hanging around with other ACS delegates from your part of the world

Hydrothermal Synthesis of LiFePO4 Powders as Cathode Material for Li-Ion Batteries

Poster presented at the 11th Conference of the Materials Research Society of Serbia - YUCOMAT 2009, Herceg Novi, Montenegro, August 31 – September 4, 2009

Acute Toxicity Assessment of Orally Administered Microplastic Particles in Adult Male Wistar Rats

While the effects of chronic exposure to microplastic particles (MPs) are extensively studied, the outcomes of a single treatment have received relatively less attention. To investigate MPs’ potential acute toxicity, including their impact on general health status (victual consumption, sensorimotor deficits, and clinical toxicity signs) and serum biochemical parameters (markers of organ/tissue function and oxidative stress indicators), we administered thoroughly characterized MPs (1.4, 35, or 125 mg/kg), generated from polyethylene terephthalate (PET) bottles, to adult male Wistar rats via oral gavage. The MPs’ short-term effects were assessed with well-established tests and methods. The results point to the absence of sensorimotor deficits and clinical toxicity signs, while levels of markers of liver, heart, and kidney function were altered in all MP groups. Decreased victual consumption and increased levels of oxidative stress indicators were evident following treatment with the two higher MP doses. Presented data indicate that examined MPs are able to initiate the development of local changes in tissues and organs within a short time frame, potentially leading to their damage and dysfunction. This study may increase the awareness of the detrimental effects of plastic contamination, as even a single exposure to MPs may provoke adverse health outcomes

Hydrothermal Synthesis of Cathode Materials for Lithium-ion Batteries

Poster presented at the 9th Conference of the Yugoslav Materials Research Society - YUCOMAT 2007, Herceg Novi, Montenegro, September 10-14, 2007