Vladimir M. Nikolic

Synthesis and characterization of a new type of levan-graft-polystyrene copolymer.

Novel macromolecular graft copolymers were synthesized by reaction of the hydroxyl groups of the microbial polysaccharide levan, produced using Bacillus licheniformis, with polystyrene (Lev-g-PS). Synthesis was performed by the free radical reaction using potassium persulfate (PPS) as initiator. The prepared copolymer was characterized by FTIR, SEM, TG/DTA, XRD and (13)C NMR. The influence of the different conditions (reaction temperature, air or nitrogen atmosphere, reaction time, type of amines and ascorbic acid (AA) concentration) on the grafting reaction was investigated. Results showed that maximum percentage of grafting (58.1%) was achieved at a reaction temperature 70°C, in a nitrogen atmosphere and using dimethylethanolamine (DMEA) as the amine activator. On the basis of the obtained results, the likely reaction mechanism was proposed. Synthesized copolymers have better thermal stability in comparison with their initial components. Copolymers such as Lev-g-PS could potentially have many applications, such as compatibilizers and material for membranes.

Translation and validation of the Serbian primary biliary cholangitis-40 questionnaire

Background and aims To translate into Serbian and validate the Primary Biliary Cholangitis–40 (PBC-40) and PBC-27 questionnaires. Materials and methods Ninety-four consecutive outpatients with the diagnosis of PBC from three departments across two tertiary care institutions in Belgrade were enrolled from February to October 2016. Standard methodology for cultural adaption of healthcare related quality of life questionnaires was used, and included: a forward translation, backward translation and a pilot test of the Serbian PBC-40 on five patients who gave suggestions and comments. For evaluation of the questionnaires, acceptance was shown by the proportion of missing items and the internal consistency was assessed using Cronbach’s α coefficient. The PBC-40 was self-administered under the supervision of an experienced hepatologist. The PBC-27 is a shorter version of the PBC-40. Results A total of 92 (97.9%) of the patients were females. The mean age was 59.26 ± 1.05 years and the average length of disease was 60.45 ± 48.314 months. The average PBC-40 score was 85.62 ± 30.46. The total time needed to complete the questionnaire ranged from 7 to 16 minutes. The proportion of missing items was 5.45% (205/3760). Cronbach’s α for the entire scale was 0.93. Reliability for all of the domains of the PBC-40 was above 0.70, except for the domain “Symptoms” (α = 0.52). Overall reliability of the PBC-27 was α = 0.90. Domains “Dryness”, “Symptoms” and “Fatigue” demonstrated reliability below α = 0.70. Conclusions The Serbian PBC-40 is a valid and reasonably adequate for use in Serbian PBC patients. The PBC-40 is preferred over the PBC-27.

Poly(methyl methacrylate) denture base materials modified with ditetrahydrofurfuryl itaconate: Significant applicative properties

The aim of this work was to examine the possibility of modification of commercial denture base materials with itaconic acid esters, in order to obtain materials with lower toxicity and higher biocompatibility. Despite their relatively higher price compared to methacrylates, itaconic acid and itaconates are materials of choice for environmentally friendly applications, because they are not produced from petrochemical sources, but from plant products. A commercial system based on poly(methyl methacrylate) was modified using ditetrahydrofurfuryl itaconate (DTHFI), whereby the ratio of DTHFI was varied from 2.5 to 10 % by weight. Copolymerization was confirmed using FTIR spectroscopy, while SEM analysis showed the absence of micro defects and pores in the structure. The effects of the itaconate content on the absorption of fluids, the residual monomer content, thermal, dynamic-mechanical and mechanical properties (hardness, toughness, stress and elongation at break) were investigated. It was found that the addition of DTHFI significantly reduced the amount of residual methyl methacrylate, which made these materials less toxic. It was shown that increasing the DTHFI content resulted in materials with decreased glass transition temperatures, as well as with decreased storage mod ulus, ultimate tensile strength and impact fracture resistance; however the mech anical properties were in the rang prescribed by ADA standards, and the materials could be used in practice. The deterioration in mechanical properties was therefore worthwhile in order to gain lower toxicity of the leached monomer.

Validation and uncertainty estimation of UPLC-PDA method for the analysis of polycyclic aromatic hydrocarbons in concrete

Human exposure to persistent organic contaminants, from building materials, negatively affects peoples health and overall quality of life. This paper presents the validation and uncertainty assessment of the analytical method, developed for the simultaneous determination of 16 EPA polycyclic aromatic hydrocarbons (PAHs) in solid-solid concrete by ultra-performance liquid chromatography with photo diode-array detector. Linearity of calibration curves was good over the whole range of calibration. Limits of detection varied between 0.2 and 2.9μgkg-1. The accuracy in terms of recovery of the validated method is within the range from 54 to 106%. The developed method proved to be appropriate for analysis of PAHs and can be used for the quality control testing of concrete during the construction of new buildings, the old residences and related buildings associated with sick-building syndrome. In addition, this is the first reported method described for the evaluation of PAHs in solid-solid concrete.

Eritropoetin u procjeni ishoda liječenja kod bolesnika s politraumom

Polytrauma is a term describing patients with injuries involving multiple body regions that compromises function of the body and/or organ involved. The aim of the study was to evaluate the potential role of erythropoietin in predicting poorer outcome in trauma patients. This prospective study included 86 patients admitted to the Emergency Center of Serbia due to polytrauma assigned according to Injury Severity Score (ISS). The patients were further evaluated using the Acute Physiology and Chronic Health Evaluation II and Sequential Organ Failure Assessment scores and erythropoietin levels. There was a significant difference among erythropoietin levels at admission, after 48 and 72 hours, and on day 7 of hospital stay, with significantly higher levels in patients with ISS values 49-75. Based on the results, ROC curves were used to identify cut-off levels to predict ISS score with critical clinical course. It was concluded that erythropoietin could be a good marker of injury severity. Further research has to be performed to determine the cut-off values of erythropoietin that are significant for injury severity.