Si₃N₄ceramics show excellent characteristics of mechanical and chemical resistance in combination with good biocompatibility, antibacterial property and radiolucency. Therefore, they are intensively studied as structural materials in skeletal implant applications. Despite their attractive properties, there are limited data in the field about in vitro studies of cellular growth on ceramic implant materials. In this study, the growth of bone cells was investigated on porous silicon nitride (Si₃N₄) ceramic implant by using electrochemical impedance spectroscopy (EIS). Partial sintering was performed at 1700 °C with limited amount of sintering additive for the production of porous Si₃N₄scaffolds. All samples were then sterilized by using ethylene oxide followed by culturing MG-63 osteosarcoma cells on the substrates for in vitro assays. At 20 and 36 h, EIS was performed and results demonstrated that magnitude of the impedance as a result of the changes in the culture medium increased after incubation with osteosarcoma cells. The changes are attributed to the cellular uptake of charged molecules from the medium. Si₃N₄samples appear to show large impedance magnitude changes, especially between 100 and 1 Hz. Impedance changes were also correlated with WST-1 measurements (36 h) and DAPI results.

Objective: To investigate thiol/disulfide homeostasis in patients with stable angina pectoris.Materials and Methods: The study population consisted of 85 stable angina pectoris patients and 31 healthy volunteers. To compare the thiol/disulfide values of the patients and controls, the newly developed analysis method was used by Erel and Neselioglu. Disulfide/total thiol, free thiol/total thiol and disulfide/free thiol values were calculated for both groups.Results: Disulfide, free thiol and total thiol values obtained in the study were; 18.00 µmol/L, 365.08 µmol/L, 401.10 µmol/L for the patient group and 9.67 µmol/L for the control group, 372.51 µmol/L, 391.85 µmol/L for the control group. It is the first time thiol/disulphide homeostasis in plasma was examined by new developed method in stable angina pectoris patients with this study. Disulfide, disulfide/free thiol and disulfide/total thiol values were significantly higher in the patient group compared to the control group. free thiol/total thiol levels were significantly lower in patients (p<0.001).Conclusion: Thiol and disulfide values can be seen at high levels in patients with stable angina pectoris, so thiol/disulfide homeostasis may be an indicator for this disease.

Objective: Preanalytical errors account for the vast majority of preanalytical incidents and remain a fundamental threat to the reliability of test results. Although the types and frequencies of these errors have been extensively studied in the literature, their time-dependent variability has received comparatively little attention. This study aimed to evaluate how preanalytical specimen rejection rates vary across intraday time intervals and to assess the independent influence of time on preanalytical quality. Methods: This retrospective observational study included a total of 579,845 specimens accepted by the central laboratory of Istanbul Atlas University Hospital between January 2024 and December 2025. Specimens were analyzed with respect to preanalytical rejection reasons, the distribution and rate of these reasons across clinical units, and time of day. Each day was divided into six equal four-hour intervals: Z1 (00:00–04:00), Z2 (04:00–08:00), Z3 (08:00–12:00), Z4 (12:00–16:00), Z5 (16:00–20:00), and Z6 (20:00–24:00). Statistical analyses were performed using the Pearson chi-square test, and effect sizes were quantified using Cramér’s V coefficient. Results: Of the 579,845 specimens examined, 4365 were rejected, yielding an overall rejection rate of 0.79%. Rejection rates were found to be non-uniformly distributed across the day (p < 0.001). The highest rejection rate was observed during the Z2 interval (04:00–08:00) at 1.98%, whereas the lowest was recorded during Z3 (08:00–12:00) at 0.45%. Negative binomial regression analysis identified the Z2 interval as the only time period independently associated with an increased rejection risk Incidence Rate Ratio (IRR) = 1.63; 95% Confidence Interval (CI): 1.22–2.19. Among clinical units, the highest rejection rate was recorded in the emergency department (1.92%). Analysis of error types revealed that the majority of rejections were attributable to hemolysis (47.5%) and clotted specimens (26.3%). Hemolysis rates peaked in the emergency department, while clotted specimens occurred more frequently within intensive care units. Analysis of time and error interactions revealed that clotted specimens peaked during Z1 and Z2, whereas hemolysis became the primary cause of rejection during Z3 and Z4. Conclusions: Preanalytical specimen rejection rates exhibited significant variation according to time of day, clinical unit, and error type, with time emerging as a factor independently associated with preanalytical quality. The coexistence of elevated rejection risk during Z2 (04:00–08:00) and markedly low rejection rates during Z3 (08:00–12:00) indicates that the relationship between workload and error frequency is not linear. Although hemolysis and clotted specimens constituted the dominant error types, their distribution followed distinct patterns depending on the clinical unit and time interval. These results underscore the necessity of time-based monitoring to pinpoint unit-specific risks, providing a clear roadmap for targeted quality improvement interventions.