Hydrochemistry of groundwater contaminated by petroleum hydrocarbons: the impact of biodegradation (Vitanovac, Serbia).

Aquifer contamination by petroleum hydrocarbons leads to measurable changes of groundwater hydrochemistry, primarily due to the microbiological activity. This study analyzes this phenomenon at an historical kerosene-contaminated site in Vitanovac (central Serbia). Due to the long-term hydrocarbon contamination and exposure to aerobic and anaerobic biodegradation mechanisms, the lowest concentrations of O2, NO3-, and SO42- (electron acceptors) and the highest concentrations of Mn and Fe (products of microbial metabolic activity) overlap. The terminal redox-accepting processes in groundwater ranged from oxygen reduction to sulfate reduction. The most anoxic processes were registered in piezometers closest to the source of contamination, as was also confirmed by the redox potential (Eh) measurements. High electrical conductivity values and the highest TOC, SiO2, and Al concentrations also overlap in the contaminated zone close to the source of contamination. Scanning electron microscopy study of quartz grains from the zone undergoing the impact of biodegradation confirmed the occurrence of weathering microscale processes on mineral surfaces. Taking all these factors together, it seems reasonable to assume that microbiological activity has caused the enhanced weathering of silicate minerals.

Accuracy of three electronic apex locators in determining the apical foramen in multi-rooted teeth: Randomised clinical and laboratory study.

This study aimed to compare the accuracy of three electronic apex locators (EALs), Raypex 5, Apex NRG and ProPex II, in locating the apical foramen (AF) in vivo. Thirty multi-rooted teeth were included in the study. Distances from the file tip to the radiographic apex from the buccal (R1) and mesial (R2) aspect were measured after extraction. The distance from the file tip to the AF (L) was measured microscopically. Raypex 5, Apex NRG and ProPex II were accurate to within ± 0.5 mm in 84.6%, 78.6% and 66.7% of cases, respectively. R1, R2 and L measurements between the EALs were not statistically different (P > 0.05). R1 and L correlated positively (r(2) = 0.817; P < 0.001). There were no significant differences in all measurements between vital and non-vital root canals (P > 0.05). There was no statistically significant difference between the EALs. There was a positive correlation between electronic and radiographic measurements when locating the AF.

The influence of bisoprolol dose on ADP-induced platelet aggregability in patients on dual antiplatelet therapy.

PURPOSE: Dual antiplatelet therapy is recommended after acute coronary syndrome or after percutaneous coronary intervention with coronary stent implantation. Many of the patients on dual antiplatelet therapy receive ß-blockers; some of them could have antiaggregatory effect. Bisoprolol is a highly selective adrenoceptor-blocker, which is often used in the settings of percutaneous coronary intervention or acute coronary syndrome in patients on dual antiplatelet therapy. Its antiaggregative effect has not been extensively studied. Therefore, the aim of this study is to investigate the effect of bisoprolol on ADP-induced platelet aggregation in patients on dual antiplatelet therapy. METHODS: Platelet aggregability has been measured in 100 patients on dual antiplatelet therapy with multiplate analyzer using ADP test in blood samples anticoagulated with heparin. ADP test values have been expressed by arbitrary units/minute. In univariate and multivariate regression analyses, we have investigated the influence of bisoprolol and its dose and also different factors, such as risk factors, concomitant drugs and their dosage, laboratory findings, on ADP test values. RESULTS: Univariate regression analysis showed significant correlation between the bisoprolol dose and the ADP test value (P=0.046, B=52.55, 95% confidence interval 0.87-104.23), which was also shown in the multivariate regression analysis (P=0.018; B=57.011; 95% confidence interval 10.455-103.567). CONCLUSION: We have identified a positive correlation between bisoprolol dose and ADP-induced platelet aggregability in patients on dual antiplatelet therapy.

[Comparative analysis of audiometric and impedancemetric findings in workers exposed to the effects of various duration industrial noise].

BACKGROUND/AIM: Industrial noise is produced in workshops due to factory machinery and tools used in technological processes. It has detrimental effect to primarily the organ of the sense of hearing, thus damaging hearing in oversensitive subjects. The aim of the study was to perform a detailed analysis of audiometric and, especially, impedancemetric parameters in workers exposed to the effects of industrial noise of various duration, as well as to determine similarities and differences in workers with differences in sensitivity to damaging effects of noise. METHODS: The study included a homogenous group of 173 industrial workers involved in the same department of a huge workshop named "Kovacica" exposed to noise level above a threshold intensity, and divided into three groups: the group I of 116 workers (232 ears) exposed to noise for 8 h in the workshop "Kovacica", the group II of 41 workers (82 ears) exposed to noise only half of the working time, and the group III of 16 workers (32 ears) exposed to the same conditions and having the normal hearing sense. The group III served as a control group. Prior to the study any workers went through a thorough anamnesis and complete ORL examination, and then they were submitted to audiometric testing. The study included only the workers with no hearing damage due to diseases, injuries nor other detrimental factors in order to be sure that the hearing findings had been caused by industrial noise. RESULTS: The results obtained by audiometric testing showed that 90.75% of the workers had hearing damage of various degrees, while 9.25% of the workers had regular hearing although had been exposed to the same conditions. More severe hearing damage was revealed in the workers of the group I. Tympanometricly, in most ears of the group I workers (65.52%) a compliance value was found to be more than 0.9 cm3, while in the majority of those of the group II (59.75%) a compliance value was in the range from 0.5 to 0.9 cm3. In the workers of the group III with no hearing damage, a compliance value for any ears was in the range from 0.1 to 0.9 cm3. Mean value of threshold reflex (98.56 dB) at 500 Hz and 1 000 Hz in the group I was increased as compared with the group II (95.6 dB) and the group III (84.38 dB). At higher frequences, 2 000 and 4 000 Hz, threshold reflex was increased in the group I (99.05 dB), and in the group II (97.6 dB) as compared with the group III (86.4 dB). The amplitude of stapedic reflex was lowest in the group I, while mean values of amplitude at 500, 1 000, 2 000 and at 4 000 Hz were 2.31, 1.38, 1 and 0.3, respectively. In the group II mean values of amplitude at 500, 1 000, 2 000 and 4 000 Hz were 2.52, 1.80, 1.30 and 0.5, respectively. In the group III mean values of amplitude at 500, 1 000, 2 000 and at 4 000 Hz were 2.36, 2.45, 2.5 and 2.08, respectively. By measuring input (rising) and output angles it was revealed that most ears of the workers in the groups I and II had rising angle ranging from 41 to 50 degrees, and in the workers with no hearing loss from 31 to 50 degrees. In the majority of the ears of the groups I and II outlet angle was in the range from 16 to 35 degrees, and in the workers with no hearing damage from 26 to 35 degrees. CONCLUSION: By audiometric and impedancemetric examinations it was determined that for the sense of hearing it is significant not only a threshold hearing expressed in the audiometric curve at various frequences, but also a threshold of unpleasantness and pain under higher intensities shown by the occurrence of stapedic reflex. The less hearing field between threshold hearing and threshold acustic reflex is, the less capabilities of hearing perception due to the occurrence of recrutment.