Assessment of the Trophic Status by Monitoring of Reservoir’s Water Quality

Continuous long-term monitoring of aquatic systems is important for understanding their complete evolution in order to monitor changes in the trophic status and water quality. The continuous monitoring during a period of 20 years, by sampling once a month at two locations, the water quality of reservoir “Grlište”, which is used for the water supplying town Zaječar (Eastern Serbia), is observed and developmental stages in the life of the reservoir were determinated. It should be noted that the obtained results were used also in the purpose of finding a cause of cyanobacteria bloom, as a consequence of algal production. Limiting factors of algal production usually were nitrogen and phosphorus, however, in this study, obtained results of subtraction between trophic state index, calculated through total chlorophyll a (TSIChl-a) and trophic state index, calculated through total phosphorus (TSITP), indicated that limiting factor of algal production was light. On the basis of the concentrations of dissolved oxygen (DO), total phosphorus (TP) and chlorophyll a (Chl-a) in the surface and in the bottom, it was concluded that the reservoir passed through four development phases during the examined period. Results of long-term monitoring showed that in the first years after the formation of the reservoir, the highest trophicity was detected (hypereutrophic status), but later the reservoir mostly maintained eutrophic status

Kontaminacija polimera teškim metalima

The contamination of important synthetic (surface unmodified) polymers by various heavy metal compounds (such as copper, manganese and lead) in aqueous medium was investigated in this study. The influence of the pH of the aqueous medium, temperature and metal type on contamination was investigated during a 10 day period. It was found that increasing pH contributed to higher polymer contamination (at higher pH 100 times for copper and up to 400 times for lead), as well as contact with easily penetrable substances. Increasing temperature decreased contamination by the metal compound for PELD and PET which was not the case for PEHD and PR.U radu je praćena kontaminacija najznačajnijih sintetskih (površinski nemodifikovanih) polimera teškim metalima (prevashodno bakrom, manganom i olovom) u vodenoj sredini. Praćen je uticaj više faktora (pH vrednost rastvora, temperatura i tip metala) tokom perioda od 10 dana. Utvrđeno je da porast pH vrednosti uzrokuje porast kontaminacije metalima (kod bakra 100 a kod olova i do 400 puta), kao i kontakt polimera sa supstancama koje lakše prodiru u polimer od vode. Zapaženo je smanjenje kontaminacije teškim metalima samo kod polletllena niske gustine (PENG) i poli(etilen tereftalata) (PET) usled rasta temperature, a ne i kod polietilena visoke gustine (PEVG) i polipropilena (PP)

Optical Properties of Acupunctural Points as Diagnostic Method

The goal of this work was to establish a connection between the optical parameters of the skin in which the acupuncture points have been settled and the pathological state of the organism. For the first time a connection between the optical characteristics of the specific skin parts (acupuncture points) and the state of the organism has been demonstrated. The optical parameter of the acupuncture point optical parameter (on surface of the reflectance curve between 470 nm and 660 nm) conduct in accordance with the traditional Chinese medicine theories (balance disturbance within the organism, time change). Acquired results point to the possibility of using acupuncture point optical parameter measuring as a method to determine the number of therapeutical treatments during the traditional Chinese medical treatments

Freedom deprivation in prisons of Serbia

The subject of this research is the deprivation of freedom at two time points. A total of 490 convicts from open, semi-open, and closed prisons participated in the research. Freedom deprivation intensity was determined by using the freedom deprivation scale (alpha = .93). The results of the research indicate that almost all the participants reported freedom deprivation. The prison type had an impact on freedom deprivation intensity, whereas an influence of the ward type on deprivation was not demonstrated. Freedom deprivation intensity was consistent from the turn of the century to the present day

Laser-PMMA Interaction and Mechanical Stresses

The polymethylmetacrylate samples were exposed to laser beams of various types of lasers. The modifications of the surfaces of the samples were analyzed by light microscopy and scanning electron microscopy. Numerical approach to thermal distribution for specified power ranges of selected lasers was obtained. The results of polymethylmetacrylate drilling and cutting performed by laser and non-laser means were compared by photoelastic methods

Kinetics of specific surface area change using the Boltzmann model

During sintering of the 2MgO-2Al2O3-5SiO2 system, cordierite, an attractive ceramic material because of its properties, is obtained. Effects of mechanochemical activation of stoichiometric mixtures, performed to investigate possibilities of lowering cordierite formation temperature during sintering, were monitored by thermogravimetric and differential thermal analyses. Specific surface areas of the mechanically activated powder mixtures were determined by the BET method. Kinetics of the specific surface area increase was analyzed using the Boltzmann model. It was confirmed that with activation time increase, temperatures of phase transformations were shifted to lower values and, according to FTIR analysis no significant changes occurred during material aging. According to the obtained results, it may be concluded that since mechanochemical activation has an influence on the treated powder mixture, lowering of the cordierite formation temperature during the sintering process is expected

High pressure effect on optical properties, fluorescence spectra and lifetime τ for 5D0→ 7F2 transition, in L-GdBO3:Eu3+ crystal

This paper presents an experiment on the effects of high hydrostatic pressure on optical properties (the line position) and fluorescence lifetime τ for 5D0 → 7F2 transitions in L-GdBO3: Eu3+ crystals. In all the considered lines of this material, the high pressure induced red-shifts towards longer wavelengths with different rates. Additionally, results show that the fluorescence lifetime τ (5D0 → 7F2 transitions) rapidly decreases with increase of pressure. We have explained the obtained results with a simple theoretical model, which gives a satisfactory agreement between the measured and theoretically predicted values of τ. In addition, the proposed theoretical model gives more accurate results comparing to other models available in the literature

Analysis of the possibility of obtaining super-paramagnetic powders based on Ferro oxides as precursor by MR contrast material synthesis

Contrast materials have very great role in many medical areas. Considering modern medical diagnostic techniques and the significance of the solution to the therapy (or surgery) tasks, the questions on precise medical images of high resolution are very important. The high resolution (especially if the image serves further for the numerical processing and analysis is certainly of significances as well as the material for recording or other assisting tasks. The contrasts material for the processes of magnetic resonance (or NMR) and analysis of their performances in the form of initial powder material with super paramagnetic performances are presented in this paper

Durability of sulfur concrete in various aggressive environments

Durability of sulfur concrete with different fillers, as well as Portland cement concrete, was tested in the solutions of HCl, H(2)SO(4), and NaCl. Regarding mass changes, in the solutions of HCl and H(2)SO(4) sulfur concrete with talc and fly ash exhibited higher durability, while in NaCl samples with alumina and microsilica were better. The type of filler did not affect durability regarding compressive strength. Strength loss was higher in the solution of HCl comparing to H(2)SO(4), while negligible in NaCl which is in accordance with apparent porosity increase. Portland cement concrete after two months lost 20% of mass