This study investigated the improvement in the electrical conductivity and mechanical properties obtained by adjusting the amount of the Sr addition to the Al-Zn-Mg-Mn alloy. The addition of Sr formed an intermetallic compounds, and the volume fraction of the intermetallic compounds increased with increasing Sr content. As the amount of Sr added increased from 0 to 1.0 wt%, the electrical conductivity of the extruded alloy decreased to 48.9, 45.2 and 42.5% IACS. As the addition amount of Sr increased, the average grain size of the rolled alloy decreased to 55.5, 53.1 and 42.3 μm. And, the ultimate tensile strength increased to 195, 212 and 216 MPa.

Introduction: Acute subdural hematoma (aSDH) removal is one of the most commonly performed procedure in neurosurgery. Complications of those surgeries which require reoperation are associated with higher risk of poor treatment outcome. Th erefore we decided to analyse potential factors which might be associated with risk of early reoperation among patients who underwent aSDH surgery. Material and methods: We retrospectively analysed 328 patients treated due to aSDH. From their medical records we obtained detailed medical history. Early reoperation was defi ned as reoperation during the same hospital stay. To determine the potential predictors of early reoperation we used univariate and multivariate logistic regression analyses. Results: A total of 20 (6.09%) patients required early reoperation. Th ose patients had signifi cantly higher International Normalized Ratio (INR) upon admission (1.96 ± 2.55 vs. 1.26 ± 0.50; p <0.01) and signifi cantly higher Prothrombin Time (PT) upon admission (21.84 ± 27.10 vs. 13.40 ± 3.45; p <0.01). In multivariate logistic regression analysis aft er adjustment for all possible confounders higher INR (OR: 1.762; 95% CI: 1.017–22.840; p = 0.045) remained independently associated with higher risk of early reoperation among patients with aSDH. Conclusions: Patients with higher INR and PT upon admission are at higher risk of early reoperation. Higher INR is independently associated with higher risk of early reoperation among patients with aSDH.