Recep Tayyip Erdoğan Üniversitesi Kurumsal Akademik Arşivi
DSpace@RTEÜ, Recep Tayyip Erdoğan Üniversitesi tarafından doğrudan ve dolaylı olarak yayınlanan; kitap, makale, tez, bildiri, rapor, araştırma verisi gibi tüm akademik kaynakları uluslararası standartlarda dijital ortamda depolar, Üniversitenin akademik performansını izlemeye aracılık eder, kaynakları uzun süreli saklar ve yayınların etkisini artırmak için telif haklarına uygun olarak Açık Erişime sunar.
Güncel Gönderiler
Strength evolution and carbonation behavior of red mud–fly ash geopolymers under varying pre-curing conditions
(Elsevier, 2025) Wu, Guowei; Bai, Jinwen; Yılmaz, Erol; Feng, Guorui; Han, Yanna; Li, Jian
Harnessing red mud (RM) and fly ash (FA) on a large scale could transform these industrial byproducts into valuable resources, driving greener, low-carbon advancements in the aluminum industry. Mastering mechanical and carbon sequestration behaviors of RM-FA based geopolymer grouting materials will provide theoretical support for achieving this goal. The carbonation characteristics, including depth, area, and CO₂ absorption rate, were evaluated for specimens with different precuring durations via phenolphthalein titration and gravimetric methods. The mechanical features of carbonation-cured materials were then tested. Through wide-ranging microstructural characterization systems (XRD, FTIR, SEM-EDS, TG-DTG, and LF NMR), evolution of phase composition, microstructure, and pore-fracture features during both carbonation and geopolymerization processes was systematically explored under varying precuring conditions. Results demonstrate that extending pre-curing duration significantly mitigates NaHCO3-induced obstruction of CO2 diffusion channels, increasing carbonation depth from 1.01 ± 0.05 mm to 5.07 ± 0.11 mm (RSD＜5.0 %). In specimens with shorter pre-curing periods, elevated free alkali content enhances CO₂ absorption to 2.29 ± 0.07 % (RSD＜5.0 %) (C1P). Notably, C14P specimens achieve maximum CO2 sequestration of 30.9 kg/ton through CaCO3 formation, benefiting from both unimpeded CO2 diffusion (absence of excessive NaHCO3 blockage) and sufficient Ca2 + availability. The 40.58 % strength deterioration in C1P specimens stems from the competition between early-stage geopolymerization and carbonation reactions. Subsequent standard curing promotes the growth of Na2CO3/CaCO2 crystals and further drives geopolymerization, thereby significantly reducing the final strength degradation rate of the specimens. Microstructural analysis confirms that carbonation-induced suppression of N(C)-A-S-H gel/ettringite formation increases total pore volume, constituting the primary reason for strength degradation. These findings systematically elucidate the interaction mechanisms between geopolymerization and carbonation reactions under varying pre-curing conditions, providing a theoretical basis for synergistically optimizing the CO₂ sequestration capacity and mechanical performance of RM-FA based geopolymer materials.
Spontaneous reverse seroconversion in resolved hepatitis B infection
(Elsevier, 2025) Özşahin, Aybegüm; İlgar, Tuba
Dear Editor;
We read with great interest the article by Çerik and Aldemir
reporting a rare case of spontaneous reactivation of resolved hepatitis B
virus (HBV) infection in the absence of immunosuppression [1]. In
accordance with their findings, we would like to share a case in which
reverse seroconversion (HBV-RS) occurred despite the absence of
ongoing immunosuppressive therapy.
Assessing microplastic contamination and health risks in infant formula: A case study from Turkey
(Elsevier, 2025) Şirin, Murat; Mutlu, Tanju; Eryaşar, Ahmet Raif; Gedik, Kenan
Microplastic (MP) contamination is an emerging concern for food safety and infant health. This study provides the first systematic assessment of MPs in infant formulas marketed in Turkey. A total of 36 samples from 12 commercial brands were analyzed using stereomicroscopy and micro-Raman spectroscopy. Analyses were performed with 532 and 785×nm lasers, 50 × magnification, 10 s exposure, a 300–3200 cm−1 spectral range, and gratings of 600/1200 l/mm. Suspected particles were compared against the ST-Japan MP library, with a ≥70 % spectral match threshold applied for polymer identification. MPs were detected in 100 % of samples (n = 36), with 97 % of particles successfully characterized. Concentrations ranged from 14 to 52 MPs/100 g (mean 31.3 MPs/100 g). Fibers were the dominant form (58 %), followed by fragments and films. Nine polymers were identified, with polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), and polyamide (PA) most abundant. Packaging materials, manufacturing processes, and feeding equipment were identified as likely contamination sources. Estimated daily intake for infants aged 0–6 months averaged 5.64 MP/kg bw/day (∼15,400 MPs annually). This annual exposure estimate was calculated based on an assumed body weight of 7.5 kg for a 6-month–old infant and a daily formula consumption of 135 g, as recommended in previous nutritional intake assessments. To enhance toxicological relevance, mass- and surface–area–based exposures were also calculated, averaging 326.77 μg/kg bw/day and 0.009 cm2/kg bw/day, respectively. The polymeric risk index (pRi) ranged from 8.27 to 1647.65 (mean 472.12), classifying 50 % of samples as low risk, 33.3 % as high risk, and 8.3 % as very high risk. These findings confirm infant formulas as a consistent source of MP exposure and highlight the need for stricter production and packaging controls to reduce early–life risks.
Usefulness of endoscopic ultrasound strain elastography for measuring liver stiffness and the role of blood cytokeratin 18 levels as a surrogate marker of fibrosis
(2025) Duman, Deniz Güney; Alahdab, Yesim Özen; Demirtaş, Coşkun Özer; Yılmaz, Yusuf; Dilber, Feyza; Keklikkıran, Çağlayan; Özdoğan, Osman Cavit
Background/Aims: The role of semi-quantitative strain ratio (SR) using real-time endoscopic ultrasound strain elastography (EUS-E) in chronic liver disease (CLD) and cirrhosis is yet to be determined. Herein, the aim was to assess the usefulness of EUS-E to detect CLD and cirrhosis. Materials and Methods: Patients with cirrhosis and non-cirrhotic CLD were enrolled prospectively. Patients without liver disease and undergoing EUS examinations for non-hepatic indications were taken as control group. Strain ratio was calculated from strains of hepatic vein and liver parenchyma. Fibrosis-4 (FIB-4) and aspartate aminotransferase (AST)-to-Platelet Ratio Index (APRI) scores were recorded, and blood cytokeratin-18 (CK-18) levels were measured to assess hepatic fibrosis. A clinical evaluation was also conducted. Results: One hundred participants (control: 49, CLD: 33, cirrhotic: 18) were included. The SR and liver parenchyma strains in cirrhotics were significantly higher than those in the CLD (P < .001) and control (P < .001) groups. Strain ratio threshold set at 5.67 had a sensitivity of 94.4% and a specificity of 95.9% to differentiate cirrhotics from control patients. An SR threshold of 10.65 had a sensitivity of 94.4% and a specificity of 84.8% in differentiating cirrhotics from CLD patients. The SR showed a strong positive correlation with FIB-4 and APRI scores, but not with CK-18 levels. Conclusions: Strain ratio thresholds of 5.67 and 10.65 obtained by EUS-E are useful to differentiate cirrhotics from non-cirrhotic CLD patients and liver-disease-free subjects, respectively. This pilot study is the first one evaluating the role of EUS-E in liver diseases, and future studies involving patients having CLD of specific etiologies are warranted.
Relationship between meteorological variability and pollen sensitization over the past 10 years
(Bangkok Medical Publishers, 2025) Akkuş, Fatma Arzu; Çölkesen, Fatih; Gerek, Mehmet Emin; Önalan, Tuğba; Evcen, Recep; Sadi Aykan, Filiz; Arslan, Şevket
Introduction
Allergic diseases are hypersensitivity disorders of
the immune system induced by an allergen-specific
immunoglobulin E (IgE)-mediated response. Aero-allergens
play a significant role in the pathogenesis of allergic
diseases. The increasing prevalence of allergic diseases over
time highlights the importance of environmental factors.1
The atmospheric content of aero-allergens varies across
different regions, depending on climate type, geography,
and vegetation. Pollen, molds, house dust mites, and pets
are the most common aero-allergens.2
