Jelena Nikolić

Leaves of higher plants as biomonitors of radionuclides (137Cs, 40K, 210Pb and 7Be) in urban air

Leaves of linden (Tilia tomentosa L. and Tilia cordata Mill.) and horse chestnut (Aesculus hippocastanum L.) were analysed as biomonitors of radionuclides in urban air. Samples of soils, leaves and aerosols were collected in Belgrade, Serbia. Activities of 137Cs, 40K, 210Pb and 7Be in the samples were measured on an HPGe detector by standard gamma spectrometry. “Soil-to-leaves” transfer factors were calculated. Student’s t test and linear Pearson correlation coefficients were used for statistical analysis. Differences in local conditions at the sampling sites were not significant, and the mechanisms of the radionuclides’ accumulation in both plant species are similar. Ceasium-137 was detected in some of the leaf samples only. Transfer factors for 137Cs and 40K were (0.03–0.08) and 1.3, respectively. The concentrations of 210Pb and 7Be in leaves were higher in autumn than in spring, and there were some similarities in their seasonal patterns in leaves and in air. Weak to medium correlation was obtained for the 210Pb and 7Be activities in leaves and aerosols. Large positive correlation was obtained for the 210Pb activities in linden leaves and the mean activity in aerosols for the preceding months. Different primary modes of radionuclides accumulation in leaves were observed. Since large positive correlation was obtained for the 210Pb activity in linden leaves and the mean in aerosols for the preceding months, mature linden leaves could be used as biomonitors of recent 210Pb activity in air.

Clostridium difficile infection: a Serbian single-center experience

INTRODUCTION Clostridium difficile infection (CDI) is the most common cause of hospital-acquired diarrhea. Severity of CDI is associated with advanced age and co-morbidities. The clinical spectrum varies from mild watery diarrhea to severe fulminant pseudomembranous colitis with complications. METHODOLOGY This study conducted over a six-year period (2008 to 2013) included 510 patients treated at the University Hospital for Infectious and Tropical Diseases in Belgrade, Serbia. In patients with a history of previous hospitalization and/or treatment with antimicrobial agents who developed diarrhea, the diagnosis was established with rapid tests for C. difficile toxin A and B and by stool culture for C. difficile (454 patients) or by endoscopic examination and histological analyses of the biopsy samples taken from the colonic mucosa (56 patients). RESULTS The mean age of patients was 67.71±13.34 years. A total of 67.8% patients were older than 65 years. Over half (58.7%) of the patients were female. 93% had been previously hospitalized and/or had surgical interventions, during which they had been treated with antibiotics. In the clinical presentation spectrum, pseudomembranous colitis occurred in 51.0%. The mean duration of illness after the introduction of specific antibiotic therapy was 7.10 ± 4.88 days. Complications developed in 14 patients. The disease relapsed in 43 (8.4%). Thirty-two (6.3%) patients died, mostly due to co-morbidities. CONCLUSIONS CDI is the most important cause of hospital-acquired diarrhea in Serbia. The disease mainly affects elderly patients with co-morbidities. The incidence of complications is low and prognosis is age dependent and related to pre-existing diseases.

Application of GEANT4 simulation on calibration of HPGe detectors for cylindrical environmental samples

The determination of radionuclide activity concentration requires a prior knowledge of the full-energy peak (FEP) efficiency at all photon energies for a given measuring geometry. This problem has been partially solved by using procedures based on Monte Carlo simulations, developed in order to complement the experimental calibration procedures used in gamma-ray measurements of environmental samples. The aim of this article is to apply GEANT4 simulation for calibration of two HPGe detectors, for measurement of liquid and soil-like samples in cylindrical geometry. The efficiencies obtained using a simulation were compared with experimental results, and applied to a realistic measurement. Measurement uncertainties for both simulation and experimental values were estimated in order to see whether the results of the realistic measurement fall within acceptable limits. The trueness of the result was checked using the known activity of the measured samples provided by IAEA.

Clinical and Immunologic Outcomes of HAART-Treated HIV-Infected Women in Resource Constrain Settings: The Belgrade Study

We performed a study to identify factors related to favorable response to highly active-antiretroviral therapy (HAART) in HIV-infected women. A retrospective study was performed on 216 women who had initiated HAART from January 1, 1998 to December 31, 2012, at the HIV/AIDS Center, Belgrade, Serbia. Participants were followed-up for 8.2 ± 3.4 years. The mean age was 37 ± 9.7 years. During follow-up, it was found that 26 patients had died. Clinical AIDS at initiation of HAART was observed in 43.9% patients, while 64.8% had a CD4+ T-cell count below 200 cells/μL. Multivariate analyses revealed that the single factor independently related to a favorable response to HAART was good compliance (odds [OR] ratio for survival = 2.9, 95% confidence intervals [CI] = 1.0–8.6, p = 0.03), while a baseline CD4+ T-cell count below 100 cells/μL, hepatitis C virus coinfection, and aged 40 years and older were all associated with an unfavorable response to HAART (OR = 0.28, 95% CI = 0.15–0.52, p < 0.001; OR = 0.49, 95% CI = 0.22–0.8, p = 0.008; OR = 0.41, 95% CI = 0.21–0.79, p = 0.008, respectively). The estimated 14-year-survival was 100% in patients with sustained viral suppression, regardless of the CD4+ counts achieved (p = 0.6, log-rank). If women with advanced HIV-related immunodeficiency reach and maintain optimal viral suppression during HAART, regardless of the level of immune recovery, and if they continue to maintain this suppression for up to a mean 8 years of treatment, their prognosis may be fairly good, even in resource-limited settings.

Uncertainty evaluation in radon concentration measurement using charcoal canister.

Active charcoal detectors are used for testing the concentration of radon in dwellings. The method of measurement is based on radon adsorption on coal and measurement of gamma radiation of radon daughters. The contributions to the final measurement uncertainty are identified, based on the equation for radon activity concentration calculation. Different methods for setting the region of interest for gamma spectrometry of canisters were discussed and evaluated. The obtained radon activity concentration and uncertainties do not depend on peak area determination method.