Mechanic strengh measurements in concrete

107 σ.Το σκυρόδεμα είναι το υλικό που παρουσιάζει την ευρύτερη χρήση από όλα τα άλλα δομικά υλικά τόσο στη χώρα μας όσο και διεθνώς, με παγκόσμια κατανάλωση που κυμαίνεται γύρω στα 5.5 δισεκατομμύρια τόνους ετησίως. Το σκυρόδεμα παρουσιάζει πολύ υψηλή αντοχή στη θλίψη, αλλά η εφελκυστική του αντοχή είναι χαμηλή. Για την ενίσχυσή του συνεπώς χρησιμοποιείται ο χάλυβας, και έτσι προκύπτει ο όρος οπλισμένο σκυρόδεμα. Ο χάλυβας όμως με την πάροδο του χρόνου διαβρώνεται προκαλώντας σοβαρές ζημιές στις κατασκευές με αποτέλεσμα να χρειάζονται επισκευές, κάτι το οποίο κοστίζει αρκετά. Κάτι το οποίο ενισχύει την διάβρωση του χάλυβα, είναι το NaCl το οποίο μπορεί να περιέχεται μέσα στο νερό ανάμιξης του σκυροδέματος. Για τον λόγο αυτό γίνονται έρευνες για να βρεθεί ποια είναι η ποσότητα NaCl που μπορεί να περιέχεται μέσα στο νερό και δεν θα προκαλέσει προβλήματα στην κατασκευή. Σκοπός της παρούσας μεταπτυχιακής εργασίας είναι να γίνει εξέταση της θλιπτικής αντοχής σε σχέση με τα συστατικά του σκυροδέματος, και να εξεταστεί η επίδραση στις μηχανικές αντοχές του, που έχει η χρήση NaCl και ΜgSO4 στο νερό ανάμειξης του σκυροδέματος.Concrete is a material that is widely used among other building materials in Greece, as well as internationally, and its worldwide annual consumption reaches the number of 5,5 billion tones. Concrete shows very high durability in compression, but its tensile strength is low. Steel is used for the reinforcing of concrete, and that is how the term reinforced concrete results. After a considerable lapse of time, steel tends to show corrosion and serious damages in constructions take place, as a result all the necessary repairs cost a considerable amount of money. NaCl can reinforce the corrosion of steel and it is usually a part of the water that is used for the mixture of concrete. For these reasons, academic research is taking place to calculate the quantity of NaCl allowed in the water, so that there will be no significant problems with the construction. The aim of this dissertation is to examine the compression strength of concrete in comparison with the ingredients of concrete as well as to examine the effect of NaCl and ΜgSO4 usage in the water that is used for the mixture of the concrete.Ιωάννα Ι. Σουκούλ

The Evolution of Living Donor Nephrectomy Program at A Hellenic Transplant Center. Laparoscopic vs. Open Donor Nephrectomy: Single-Center Experience

Since its introduction in 1995, laparoscopic nephrectomy has emerged as the preferred surgical approach for living donor nephrectomy. Given the ubiquity of the surgical procedure and the need for favorable outcomes, as it is an elective operation on otherwise healthy individuals, it is imperative to ensure appropriate preoperative risk stratification and anticipate intraoperative challenges. The aim of the present study was to compare peri-and postoperative outcomes of living kidney donors (LD), who had undergone laparoscopic nephrectomy (LDN), with a control group of those who had undergone open nephrectomy (ODN). Health-related quality of life (QoL) was also assessed using the validated SF-36 questionnaire. Data from 252 LD from a single transplant center from March 2015 to December 2020 were analyzed retrospectively. In total, 117 donors in the LDN and 135 in the ODN groups were assessed. Demographics, type of transplantation, BMI, duration of surgery, length of hospital stay, peri- and postoperative complications, renal function at discharge and QoL were recorded and compared between the two groups using Stata 13.0 software. There was no difference in baseline characteristics, nor in the prevalence of peri-and postoperative complications, with a total complication rate of 16% (mostly minor, Clavien–Dindo grade II) in both groups, while a different pattern of surgical complications was noticed between them. Duration of surgery was significantly longer in the ODN group (median 240 min vs. 160 min in LDN, p < 0.01), warm ischemia time was longer in the LDN group (median 6 min vs.2 min in ODN, p < 0.01) and length of hospital stay shorter in the LDN group (median 3 days vs. 7 days in ODN). Conversion rate from laparoscopic to open surgery was 2.5%. There was a drop in estimated glomerular filtration rate (eGFR) at discharge of 36 mL/min in the LDN and 32 mL/min in the ODN groups, respectively (p = 0.03). No death, readmission or reoperation were recorded. There was a significant difference in favor of LDN group for each one of the eight items of the questionnaire (SF1–SF8). As for the two summary scores, while the total physical component summary (PCS) score was comparable between the two groups (57.87 in the LDN group and 57.07 in the ODN group), the mental component summary (MCS) score was significantly higher (62.14 vs. 45.22, p < 0.001) in the LDN group. This study provides evidence that minimally invasive surgery can be performed safely, with very good short-term outcomes, providing several benefits for the living kidney donor, thereby contributing to expanding the living donor pool, which is essential, especially in countries with deceased-donor organ shortage