Separation of rhenium (VIII) from tungsten (VI)

Examined were the conditions for an effective separation of tungsten(VI) and rhenium(VII) on alumina if the solution of 0.20 mol dm-3 NaCl, pH=2-6, is used as the aqueous phase. Under the given experimental conditions alumina was found to be much better adsorbent for tungsten than for rhenium. The breakthrough and saturation capacities of alumina at pH = 2 are 24 and 78 mg W/g Al2O3, respectively. With the increase of pH these values decrease. So, at pH = 6 they are only 4 and 13 mg W/g Al2O3, respectively. The elution volume for rhenium for the given column dimensions and the quantity of the adsorbent, is about 16 ml. These results were confirmed by the experiments of the radiochemical separations. Tungsten-187 remains firmly bound to alumina. The radionuclidic purity of the eluted 186,188 Re at pH = 2 is very high.Physical chemistry 2004 : 7th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 21-23 September 200

Chronic Kidney Disease and Nonalcoholic Fatty Liver Disease—Is There a Link?

Research in recent years has led to the recognition of the importance of nonalcoholic fatty liver disease (NAFLD) and its relationship to the metabolic syndrome (MS). This has led to a growing interest in the potential prognostic value of NAFLD for adverse cardiovascular disease (CVD) outcome. On the other hand, searching for new risk factors for chronic kidney disease (CKD) development and progression is very important. Growing evidence suggests that the MS is an important factor in the pathogenesis of CKD. The best confirmation of this pathogenic link is hypertensive and diabetic nephropathy as the main causes of CKD. Furthermore, the possible link between NAFLD and CKD has also attracted research interest and recent data suggest an association between these two conditions. These findings have fuelled concerns that NAFLD may be a new and added risk factor for the development and progression of CKD. NAFLD and CKD share some important cardiometabolic risk factors and possible common pathophysiological mechanisms, and both are linked to an increased risk of incident CVD events. Therefore, common factors underlying the pathogenesis of NAFLD and CKD may be insulin resistance, oxidative stress, activation of rennin-angiotensin system, and inappropriate secretion of inflammatory cytokines by steatotic and inflamed liver

Effect of Sample Preparation on Portable X-Ray Fluorescence Spectrometry Analysis of Contaminated Soils

Toxic metals in soil are routinely determined by several analytical spectroscopic techniques (Atomic Absorption Spectrometry AAS, Inductively Coupled Plasma Optical Emission Spectrometry ICP-OES,and Inductively Coupled Plasma Mass Spectrometry ICPMS)[1]. Those techniques measure metals from aqueous samples. Procedures of sample dissolution or extraction typically involve a lengthy process which requires the use of harsh conditions. Sample preparation procedures make these routinely used techniques generally time-consuming and too expensive [2]. On the other side, the need for reliable, economical, and environmental friendly technique for soil composition measuring has been growing in the environmental field, so has the demand for time and cost-efficient analytical methods for soil analysis [3]. X-ray fluorescence spectrometry (XRF) is a multi-element analytical technique for direct, non-destructive analysis of various materials (including soils) with minimal sample preparation. The most attractive advantage of XRF is the wide dynamic range (from mg kg-1 to 100%). A portable X-ray fluorescence spectrometer (PXRF) is also capable of in-situ analysis in a short time (30–120 s) [4]. In situ PXRF analysis provides flexibility and allows rapid collection of data for a large number of samples, andproduces real-time data that can be used for rapid decision making. It is well-known that the physical characteristics of the sample play an important role in obtaining accurate results when it comes to XRF methods. Therefore it is important to determine how reliable in situ PXRF results are. Analytical accuracy and precision could be generally improved if adequate sample preparation procedure is applied compared to in situ measurements. The aim of this research was to determinate in what extent sample preparation procedure changes measured concentrations of elements and is that change the same for all investigated elements. Does soil sample homogenization or further pressing into the compact pellet systematically affect measured concentrations? Soil samples from 32 industrial, potentially contaminated sites were collected from a depth of 10 cm, 30 cm, and 50 cm. Such soils provide wide concentration range of different elements. Samples were first directly analyzed in the field, without any sample preparation using the Thermo Scientific™ Niton™ XL3t GOLDD+ PXRF Analyzer. The second PXRF analysis was performed in the laboratory on the dry,ground, and homogenized soil powder sample. One aliquot of soil powder was digested for AAS analysis, while another aliquot was pressed into a 32 mm diameter pellet and analyzed using PXRF. The quality control program involves comparison of the results with AAS reference technique. Additionally, certified reference materials of stream sediment (STSD-3) and soil (NCS DC 77301) are analyzed with different sample preparation procedures

Toxic Metals in 3 Fractions (d<63µm, d63-250µm and d250-1000µm) of Dust Collected on Roads of Industrial Town Kostolac, Serbia

Kostolac is a town exposed to several serious sources of toxic metals and other inorganic pollutants. They arrive from sources typical for urban environments such as traffic, but also from various heavy industry sources: coal mining, burning of coal in power plants, ash landfills, and steel factory. Toxic metals in the air are concentrated in particulate matter. Their transport and health risks depend strongly on the size of dust particles. Goals of the research were to estimate: 1. how much does traffic contributes to the total pollution load compared to the natural sources and the industry; 2. how is pollution distributed in different fractions of the dust; 3. are there any spatial trends present and is there any correlation between vicinity of pollution sources and concentrations of toxic elements in different fractions of the dust. Samples of dust were collected from 10 locations in July and in September. Each location had one sampling site on a major road with intensive traffic and the other site on auxiliary road with much less traffic, located 10- 20 m away from the major road. The dust was dried, sieved through sieves with 3 different apertures (d=63µm, 250µm and 1000µm) and pressed into 32 mm diameter pellets. The samples were analysed by WD-XRF standardless method. The results showed that Al, P, K, V, Mn, Fe, Co, Zr, Rb and Ti have the highest concentrations in the smallest fraction (d<63µm) and the lowest concentrations in the most coarse fraction with stat. significant differences among concentrations. Concentrations of: Mg, S, Zn and Cu have the same trend as previous group of elements but no stat. significant differences, wile conc. of Si and Ca have the opposite trend. Neither the time of the year nor the intensity of the traffic have had any significant effect to the concentrations, therefore it can be concluded that industrial sources of pollution have significantly higher attribution to the total pollution load than traffic. The trend that toxic elements are more concentrated in the smallest fraction of the dust indicates that the source of the pollution is rather anthropogenic than natural. Concentrations of elements in dust collected on sites from our research were compared to concentrations of the same elements in the soil collected by SEPA (Serbian Environmental Protection Agency). Although locations from both researches were in close proximity, no significant correlation between concentrations was observed. The lack of correlation can be explained by several hypotheses which should be further investigated in future researches

Analiza korelacionih osobina pseudoslučajnih sekvenci dužine 255 za zaštitu upravljačkog signala bespilotne letelice / Analysis of correlation properties of pseudorandom sequences of length 255 for the UAV control signal protection

Tehnike prenosa signala u proširenom spektru sa direktnom sekvencom predstavlja efikasan metod zaštite upravljačkog signala bespilotne letelice (BL). Zaštita signala se ostvaruje primenom pseudoslučajnih (PS) sekvenci u predajniku, koje su poznate prijemniku, ali ne i neovlašćenom korisniku. Da bi se ostvario pouzdan prenos signala, PS sekvence treba da imaju dobre autokorelacione osobine. Ukoliko je prenos signala realizovan primenom nekoliko PS sekvenci, tada su od velike važnosti i njihove međukorelacione karakteristike. U radu su analizirane autokorelacione i međukorelacione osobine PS sekvenci dužine 255. Razmatrane su tri najčešće korišćene klase PS sekvenci: linearne sekvence maksimalne dužine, Goldove sekvence i Kasamijeve sekvence. Predložen je optimalan skup PS sekvenci za zaštitu upravljačkog signala BL. / The Direct Sequence Spread Spectrum technique represents an effective method for unmanned aerial vehicle (UAV) control signal protection. Signal protection is obtained by applying pseudorandom (PR) sequences within a transmitter, known by a receiver, but unknown to an unauthorized user. In order to achieve reliable signal transmission, PR sequences ought to have good autocorrelation properties. If the signal transmission is realized by using several PR sequences, their crosscorrelation properties are of high importance as well. In this paper autocorrelation and crosscorrelation properties of PR sequences of length 255 are analyzed. Three most frequently used classes of PR sequences: linear maximum length, Gold and Kasami sequences are considered. An optimal set of PR sequences for UAV control signal protection is recommended

A solution for the over-the-horizon-radar simulator

Introduction/purpose: The OTHR simulator presented in this paper is developed and used in practice, with the aim of emulating radar signal environment, but also optimizing the radar parameters in real applications such as: radiated power, antenna array gain, path loss, radar cross section, external interference, and noises. Methods: In this paper, the methodology of mathematical modeling is used as well as simulations . Results: Based on the performed analysis, the output data from the OTHR simulator is presented and discussed. Conclusion: The usage of the presented OTHR simulator makes assessing the reliability of a potential radar at predetermined locations automated, controllable and efficient, with results closely matching radar behavior in real operation