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    The fate of patent stents in patients undergoing coronary artery bypass grafting
    (Galenos Yayınevi, 2023) Başgöze, Serdar; Şen, Onur; Güner, Yeşim; Duman, Mert Zihni; Karaçalılar, Mehmet; Demirel, Aylin; Bayram, Muhammed; Aydın, Ünal
    Objectives: Bypassing a patently stented coronary artery has a risk of flow competition, and leaving it ungrafted has a high risk of stent restenosis. This study determines the fate of patently stented coronary arteries bypassed and left ungrafted. Materials and Methods: Patients undergoing isolated coronary artery bypass grafting (CABG) with previous percutaneous coronary intervention (PCI) were retrospectively scanned between January 1, 2015, and January 1, 2020. Patients undergoing surgery with a patently stented coronary artery were identified. Postoperative coronary angiography was performed in 52 of these patients. Results: There were 24 patients whose patently stented coronary artery was bypassed and 28 whose patently stented coronary artery was not bypassed. The median follow-up time was 49 months in the non-bypass group and 53.5 months in the bypass group. Twenty (71.4%) patently stented coronary arteries remained open in the non-bypass group, and 23 (95.8%) vessels were open in the bypass group (p=0.02). The estimated open rate of vessels was 56% in the non-bypass group and 95% in the bypass group at five years (log-rank p=0.01). Major adverse cardiac events were developed in 12 (42.8%) patients in the non-bypass group and 6 (25%) patients in the bypass group. Conclusion: Patients with an open stented vessel that was not bypassed during CABG have a risk of in-stent restenosis and major adverse cardiac events during the mid-and long-term periods. It may not be safe to leave patently stented coronary arteries ungrafted, particularly those with bare metal stents.
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    Thermal energy saving and physico-mechanical properties of foam concrete incorporating form-stabilized basalt powder/capric acid based composite phase change material
    (Elsevier Ltd., 2023) Koçyiğit, Fatih; Bayram, Muhammed; Hekimoğlu, Gökhan; Çay, Vedat Veli; Gencel, Osman; Ustaoğlu, Abid
    The incorporation of phase change materials (PCM) in construction materials for the purpose of thermal energy storage (TES) can prevent temperature fluctuations and enable the conservation of thermal energy in buildings. Accordingly, this study aims to create a novel, environmentally friendly foam concrete incorporating a composite PCM composed of capric acid saturated waste basalt powder. Basalt powder, a byproduct of the grinding or crushing of basalt volcanic rock, was selected as a carrier material due to its high porosity resulting from its lightweight and porous nature. This allowed for the creation of a leak-free composite PCM, which was then integrated with foam concrete made of CEM I 42.5R cement, water, quartz sand, and a foaming agent. BasaltPCM was substituted into the mixture at 50% and 100% by weight of quartz aggregate. Comprehensive evaluations were conducted on the novel foam concretes with regard to their morphological, mechanical, physical, thermal, and TES properties. The results indicate that the incorporation of basalt-PCM causes a minor reduction in the dry unit weight of the mixtures and a reduction in compressive and flexural strength. However, the leakproof basalt powder/capric acid composite displayed a phase transition behavior, melting at 28.5 ◦C with a latent heat of fusion (47.9 J/g), which retained 99.5% capacity after 500 melting-solidification cycles. The specimen with 100 wt% basalt-PCM exhibited a melting temperature and latent heat of 27.8 ◦C and 17.4 J/g, respectively. Additionally, the basalt powder/capric composite exhibited high thermal stability up to 156 ◦C, far above its normal operating temperature. The foam concretes incorporating the basalt-PCM demonstrated solar thermoregulation properties, maintaining a more stable and comfortable indoor temperature. These results suggest that the form-stable PCM-incorporating foam concretes developed in this study can be considered as environmentally friendly building materials for thermoregulation and energy conservation.