Изогеметријска анализа утицаја покрентог оптерећења на просторној криволинијској Бернули-Ојлеровој греди

Dynamic analysis of a spatially curved Bernoulli-Euler beam subjected to the moving load is considered in this paper. The isogeometric approach is used for the spatial discretization of the weak form of the equation of motion. Both the reference geometry and the solution space are represented using the same NURBS basis functions that guarantee an accurate description of beam’s centerline. The time integration is done by the explicit technique. The presented formulation is validated by the comparison with the existing results from the literature for the curved beam subjected to the constant load moving with the constant velocity.У овом раду је приказана динамичка анализа просторне криволинијске Бернули-Ојлерове греде под утицајем покретног оптерећења. Изогеометријски приступ је примењен у циљу просторне дискретизације слабе форме једначина кретања греде. Овај приступ се базира на примени истих базних NURBS функцијa за описивање геометрије и кинематике криволинијске греде, чиме је омогућен тачан приказ системне линије греде. Временска интеграција једначина је извршена применом експлицитне методе. Приказана формулација је валидирана поређењем са резултатима из литературе за случај криволинијске греде оптерећене покретном силом константног интензитета и брзине

Линеарна динамичка анализа утицаја покретног оптерећења на просторној криволинијској Бернули-Ојлеровој греди

This paper considers the dynamic analysis of a spatially curved Bernoulli-Euler beam subjected to a moving load. The isogeometric approach is used for the spatial discretization of the weak form of the equation of motion. Both the reference geometry and the solution space are represented using the same NURBS basis functions that guarantee an accurate description of the beam centerline. The time integration is done by the explicit technique. The presented formulation is validated by the comparison with the existing results from the literature for the curved beam subjected to a constant load moving with a constant velocity. In addition, the influence of the moving load velocity on the dynamic response of a spatially curved beam has been investigated.У овом раду је приказана динамичка анализа просторне криволинијске Бернули-Ојлерове греде под утицајем покретног оптерећења. Изогеометријски приступ је примењен у циљу просторне дискретизације слабе форме једначина кретања греде. Овај приступ се базира на примени истих базних NURBS функцијa за описивање геометрије и кинематике криволинијске греде, чиме је омогућен тачан приказ системне линије греде. Временска интеграција једначина је извршена применом експлицитне методе. Приказана формулација је валидирана поређењем са резултатима из литературе за случај криволинијске греде оптерећене покретном силом константног интензитета и брзине. Такође је извршена и анализа утицаја брзине кретања покрене силе на динамички одговор просторне криволинијске греде

Association between oxidative stress biomarkers and concentrations of some metal ions in the blood of patients with brain tumors and hydrocephalus

Introduction Any substance that induces production of free radicals can be a potential cause of brain damage. The aim of our study was to investigate the relationship between some metal ions and oxidative stress biomarkers in the blood of patients with brain tumor and hydrocephalus. Material and methods Our study included 27 control subjects, 24 patients with brain tumor and 21 patients with hydrocephalus. The activities of superoxide dismutase (CuZn SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR), glutathione S-transferase (GST) and acetyl cholinesterase (AChE), as well as concentrations of reduced glutathione (GSH), lipid peroxides (TBARS) and sulfhydryl groups (SH) were analyzed in the plasma and red blood cells (RBCs) of patients. We also determined the concentrations of Mn, Ni, Co, Cu, Zn, As, Se, Cd, Hg and Fe. Results The higher activity of SOD and concentration of GSH in both investigated groups could indicate higher oxidative stress. We also observed decreased levels of SH groups in both groups of patients. In both groups of patients we detected decreased concentrations of Ni, Co, Zn and Fe (and Mn in brain tumor patients) and increased concentrations of As, Se and Cd in the blood. Interestingly, we observed a higher concentration of Cd in both plasma and RBCs of hydrocephalus patients compared to the patients with brain tumor. Conclusions There are strong correlations between some metal ion concentrations and certain oxidative stress biomarkers in the blood of patients, which supports our hypothesis, but the observed trend needs to be further investigated

Assessment of trace metal alterations in the blood, cerebrospinal fluid and tissue samples of patients with malignant brain tumors

The pathogenesis of malignant brain tumors (MBTs) should be better understood due to the evident association between prolonged exposure to metals and increased risk of MBTs. The present research aimed to find trace metals that could contribute to the pathogenesis of MBTs. Essential trace elements (Mn, Co, Zn, Cu, Se) and relevant toxic metals (Al, Ni, As, Sr, Cd, Ce, Pt, Pb, U) in the serum, cell fraction (CF), cerebrospinal fluid (CSF) and cancerous tissue (CT) samples of MBT patients were analyzed. The results were compared with sex- and age-matched control groups. For the first time, this research showed that elemental profiles of serum, CF, CSF and CT samples in MBT patients were significantly altered compared to the appropriate controls, as well as that higher contents of trace elements (particularly Mn, Se, and Pb) could be involved in the pathogenesis of MBTs. However, the most noticeable change found was the elevated U content, indicating its considerable role as a major cerebral discriminator of the presence/absence of MBTs. The U/Se ratio could be considered as an appropriate blood marker in diagnostic MBT evaluation. The reported results could contribute to better understanding of the poorly understood pathogenesis of MBTs. Furthermore, the reported results could highlight a molecular basis for the pathophysiological changes caused by the hazardous effects of trace metals on brain homeostasis

A first record of the antioxidant defense and selected trace elements in Salamandra salamandra larvae on Mt. Avala and Mt. Vršački Breg (Serbia)

We investigated the activities of superoxide dismutase (SOD), catalase (CAT), glutathioneperoxidase (GSH-Px), glutathione reductase (GR) and the phase II biotransformation enzyme glutathioneS-transferase (GST) in the whole body of fire salamander larvae (Salamandra salamandra) from twolocalities on Mt. Avala (AVS and ABP) and one locality on Mt. Vršački Breg (VSB), Serbia. We alsodetermined the total glutathione (GSH) and sulfhydryl group (SH) contents, as well as the concentrations ofmanganese (Mn), copper (Cu), zinc (Zn), selenium (Se), arsenic (As), cadmium (Cd), lead (Pb) and uranium(U). The obtained results show that animals from VSB had significantly lower weights and lengths thananimals from AVS and ABP. The activities of all investigated enzymes were significantly higher, while theSH content was significantly lower in animals from VSB compared to those from AVS and ABP. Nocorrelations between trace-element concentrations in water and animal tissue were observed. We concludedthat the obtained results were more likely a consequence of the combination of developmental differencesand the effects of different habitat conditions, environmental and anthropogenic influences than ofconcentrations of trace elements in the water alone

EXPERIMENTAL AND NUMERICAL IDENTIFICATION OF STRUCTURAL MODES FOR ENGINEERING EDUCATION

Abstract. Development of simple classroom demonstration device and software for visualization of structural normal modes is presented. Device is made of parts of old speaker, controlled with personal computer, where the harmonic motion of solenoid is used as an excitation for beam and plate models. Simple code for finite element free vibration analysis of plates is written in Wolfram Mathematica. Good agreement of results and attractive visual patterns of normal modes attracted attention of students. Results are confirmed using modern modal testing methods. Presented approach is complementary to standard teaching of structural dynamics. Key words: engineering education, normal modes, Chladni plate, modal testing, finite element metho

The Effects of BSA-Stabilized Selenium Nanoparticles and Sodium Selenite Supplementation on the Structure, Oxidative Stress Parameters and Selenium Redox Biology in Rat Placenta

The chemical element selenium (Se) is a nonmetal that is in trace amounts indispensable for normal cellular functioning. During pregnancy, a low Se status can increase the risk of oxidative stress. However, elevated concentrations of Se in the body can also cause oxidative stress. This study aimed to compare the effects of BSA-stabilized Se nanoparticles (SeNPs, Se0) (BSA-bovine serum albumin) and inorganic sodium selenite (NaSe, Se+4) supplementation on the histological structure of the placenta, oxidative stress parameters and the total placental Se concentration of Wistar rats during pregnancy. Pregnant females were randomized into four groups: (i) intact controls; (ii) controls that were dosed by daily oral gavage with 8.6% bovine serum albumin (BSA) and 0.125 M vit C; (iii) the SeNP group that was administered 0.5 mg of SeNPs stabilized with 8.6% BSA and 0.125 M vit C/kg bw/day by oral gavage dosing; (iv) the NaSe group, gavage dosed with 0.5 mg Na2SeO3/kg bw/day. The treatment of pregnant females started on gestational day one, lasted until day 20, and on day 21 of gestation, the fetuses with the placenta were removed from the uterus. Our findings show that the mode of action of equivalent concentrations of Se in SeNPs and NaSe depended on its redox state and chemical structure. Administration of SeNPs (Se0) increased fetal lethality and induced changes in the antioxidative defense parameters in the placenta. The accumulation of Se in the placenta was highest in SeNP-treated animals. All obtained data indicate an increased bioavailability of Se in its organic nano form and Se0 redox state in comparison to its inorganic sodium selenite form and Se+4 redox state

Supplementary data for the article: Stojsavljević, A.; Rovčanin, B.; Krstić, Đ.; Borković-Mitić, S.; Paunović, I.; Kodranov, I.; Gavrović-Jankulović, M.; Manojlović, D. Evaluation of Trace Metals in Thyroid Tissues: Comparative Analysis with Benign and Malignant Thyroid Diseases. Ecotoxicology and Environmental Safety 2019, 183. https://doi.org/10.1016/j.ecoenv.2019.109479

Supplementary material for: [10.1016/j.ecoenv.2019.109479]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/3285

Metal and metalloid bioaccumulation in three centipedes (Chilopoda)

Three centipede species (Clinopodes flavidus, Cryptops anomalans and Eupolybothrus transsylvanicus) were used as bioindicators of trace metal and metalloid pollution in Belgrade, Serbia. The concentrations of 13 elements (the metals Mn, Co, Ni, Cu, Zn, Rb, Sr, Cd, Tl, Pb and U and metalloids As, Se) in whole animals and soil were measured by inductively coupled plasma mass spectrometry (ICP-MS). Differences in the concentrations of some elements in the analyzed species were observed, both in response to the sites and between species. In most cases, the trace element concentrations were higher in centipedes from a polluted site (an industrial area near a busy street with heavy traffic) but C. anomalans and E. transsylvanicus had higher Mn concentrations at an unpolluted site (a deciduous woodland on Mt. Avala). C. flavidus was a good bioindicator for detecting differences between Zn, Se and Cd. C. flavidus and C. anomalans were more efficient in accumulating Zn than E. transsylvanicus. It appears that C. anomalans poorly accumulated Cd, unlike C. flavidus and E. transsylvanicus, which accumulated Cd according to the high bioaccumulation factor (BAF) values. We conclude that the centipedes C. flavidus, C. anomalans and E. transsylvanicus can be used as suitable bioindicators of trace element exposure. Their ability to accumulate trace elements was different and depends on their physiology and lifestyle as well as the route of exposure.Supplementary material: [https://cherry.chem.bg.ac.rs/handle/123456789/5673

Supplementary material for the article: Stojsavljević, A.; Rovčanin, B.; Krstić; Jagodić, J.; Borković-Mitić, S.; Paunović, I.; Živaljević, V.; Mitić, B.; Gavrović-Jankulović, M.; Manojlović, D. Cadmium as Main Endocrine Disruptor in Papillary Thyroid Carcinoma and the Significance of Cd/Se Ratio for Thyroid Tissue Pathophysiology. Journal of Trace Elements in Medicine and Biology 2019, 55, 190–195. https://doi.org/10.1016/j.jtemb.2019.06.009

Supplementary material for: [https://doi.org/10.1016/j.jtemb.2019.06.009]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/3293