İstinye Üniversitesi Kurumsal Akademik Arşivi
DSpace@İstinye, İstinye 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 telif haklarına uygun olarak Açık Erişime sunar.
Güncel Gönderiler
Modification of flame etched carbon-fiber microelectrode (FE-CFME) by single walled carbon nanotube/pyreneacetic acid (SWCNT/PAA) nanocomposite for sensitive and selective detection of dopamine
(Elsevier B.V., 2025) Alizadeh, Vali; Mahmoudi, Ghodrat; Hosseinifard, Mojtaba; Jamali Moghadam, Ahmad; Servati Gargari, Masoumeh
An inexpensive, simple and fast methode of sensor construction as well as negligible sensor surface fouling, along with the high sensitivity and selectivity has always been a challenge in the fabrication of electrochemical sensors. In this study, to achieve this goal, carbon fiber microelectrode (CFME) was pretreated by applying fast flame etching and then simply modifed by pyrene acetic acid (PAA) decorated single walled carbon nanotube (SWCNT) nanocomposite for highly sensitive and selective dopamine (DA) detection. The results show that, although the CFME became active upon flame etching due to introduces nanometer-scale roughness features on it, surface modification by SWCNT-PAA further increases its sensitivity due to synergistic effects. Attaching PAA onto SWCNTs can effectively inhibit the π-stacking of the SWCNTs to prevent their agglomeration and offer a large surface area of electrode, as well as enhancing the diffusion of positively charged DA by its anionic carboxylate moieties. This is the first report on applying PAA/SWCNT nanocomposite for surface modification of flame etched carbon fiber microelectrode (FE-CFME). The surface morphology of the Bare-CFME, FE-CFME, and FE-CFME/SWCNT-PAA electrodes were evaluated using Field-emission scanning electron microscopy (FE-SEM), being correlated with the electrochemical characteristics observed by cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) techniques. As expected, the fabricated sensor showed improved electrochemical response with high sensitivity and selectivity. Under optimum conditions, this sensor exhibited high performance toward DA determination with good linearity in a broad linear range of 0.5 to 22 μM with the detection limit of 12.9 nM, and excellent reproducibility and repeatability. The practical applicability of the fabricated sensor has been successfully tested for the determination of DA in human serum and injection ampoule samples with recovery rates ranging from 98 % to 105 % and relative standard deviations below 3.1 %. © 2025 Elsevier B.V.
Amantadine’s Neuroprotective Effects in Rabbit Spinal Cord Ischemia/Reperfusion Model
(Turkish Neurosurgical Society, 2024) Ünlüler, Caner; Kuru Bektaşoğlu, Pınar; Ergüder, Berrin İmge; Arıok, Ata Türker; Ermutlu, İlçim; Gürer, Bora; Kertmen, Hayri
AIM: To examine the effects of amantadine, a drug with neuroprotective and anti-inflammatory activities on oxidative stress, tissue necrosis, apoptosis, and neurological recovery in an experimental rabbit spinal cord ischemia-reperfusion injury (SCIRI) model. MATERIAL and METHODS: A total of 32 rabbits were randomized into five groups: control, ischemia, vehicle, methylprednisolone (MP), and amantadine (AMT) (n=8/each). At 24th-hour neurological examination was performed, spinal cord tissues were collected, and biochemical and histopathological examinations were performed. RESULTS: When ischemia and vehicle groups were compared with control group, significant increase was seen in serum and tissue caspase-3, malondialdehyde (MDA), and myeloperoxidase (MPO) levels (p<0.001); significant decrease was seen in serum and tissue catalase (CAT) levels (p<0.001); and significant increase was seen in serum xanthine oxidase (XO) levels (p<0.001). When the ischemia group and the MP and AMT groups were compared, low serum and tissue caspase-3 levels (p<0.001), high serum and tissue CAT levels (p<0.001), significantly low serum XO levels (p<0.001), low serum and tissue MDA levels (p<0.05) and tissue MPO levels (p<0.001) were found. Both AMT and MP groups showed decreased histopathological score and higher number of normal neurons (p<0.001) compared to ischemia group. Both AMT and MP showed better modified Tarlov scores compared to the ischemia group (p<0.001). CONCLUSION: Our study found that AMT had antioxidant, anti-inflammatory, anti-apoptotic, and neuroprotective effects on SCIRI. We used biochemical, microscopic, and ultrastructural approaches to demonstrate these effects. AMT might be a candidate medication for SCIRI prophylaxis and treatment. © (2024), (Turkish Neurosurgical Society). All rights reserved.
Analysis of Complications of a Neglected Disease: 13 Years of Experience with Liver Hydatid Cysts in a High-Volume Hospital
(Multidisciplinary Digital Publishing Institute (MDPI), 2024) Azizoğlu, Mustafa; Aydoğdu, Bahattin; Kamçı, Tahsin Onat; Arslan, Serkan; Başuguy, Erol; Bilici, Salim; Okur, Mehmet Hanifi
Background and Objectives: The aim of this study was to evaluate the clinical presentation, treatment outcomes, and complications associated with hepatic hydatid cysts in a pediatric population. Materials and Methods: This retrospective study analyzed 214 pediatric patients with liver hydatid cysts, focusing on clinical presentation, treatment outcomes, and associated complications. Patients were classified based on treatment modality, including non-operative management with albendazole, PAIR, and surgical intervention. This study compared cyst characteristics, recurrence rates, and complications such as cysto-biliary fistulas. Results: Among the patients, 68% (n = 145) had a single cyst and 86% (n = 184) were found to have isolated liver cysts. No significant statistical difference was observed between Group 1 and Group 2 in terms of age, gender, and basic laboratory values and general characteristics of the cysts, such as the lobe where the cyst was located, involvement of multiple organs, number of cysts, the state of cyst rupture, and recurrence; no statistically significant difference was found between the groups (p > 0.05 for each comparison). Cyst rupture incidence was 6%, and the average incidence of recurrence was 2%, with a surgical recurrence incidence of 3%. A total of 37 patients had a laparotomy, while 7 had laparoscopic surgery. In total, capitonnage was performed in 68 patients, omentopexy in 4, and cystostomy in 6. Consequently, among the treated patients (PAIR + surgery), the incidence of cysto-biliary fistula was 11%, anaphylaxis was 2%, surgical recurrence was 3%, and the incidence of reoperation (Clavien–Dindo ≥ 3) was 6%. The average follow-up period was 72 months, during which no mortality was observed. Conclusions: We identified key clinical outcomes related to both non-surgical treatments (cyst rupture and recurrence) and surgical groups (cysto-biliary fistulas, anaphylaxis, the need for reoperation, rupture, and recurrence). © 2024 by the authors.
Androgen receptor CAG repeat polymorphism might be a possible cause of familial constitutional delay of growth and puberty
(Springer Science and Business Media Deutschland GmbH, 2024) Kağızmanlı, Gözde Akın; Sevim, Reyhan Deveci; Manyas, Hayrullah; Paketçi, Ahu; Demir, Korcan; Böber, Ece; Çatlı, Gönül; Anık, Ahmet; Abacı, Ayhan
Background: Induction of puberty in boys with constitutional delay of growth and puberty (CDGP) through a short course of low-dose testosterone therapy indicates the critical interaction between testosterone and the androgen receptor (AR) during the activation and maturation of the hypothalamic-pituitary-gonadal axis at puberty onset. Previous studies have shown an inverse relationship between the CAG repeat length and the transactivation function or expression level of the AR gene. Objective: We aimed to investigate whether the AR CAG repeat polymorphism has any implications on pubertal delay. Subjects and methods: Thirty-three male patients with CDGP were enrolled in the study group, while 53 age-matched healthy individuals who had entered puberty on time were included in the control group. The CAG repeat length was determined through direct DNA sequencing analysis. Results: The median chronological age of boys with CDGP was 14.2 (14.1–14.6) years, compared to 14.2 (13.65–14.8) years for healthy subjects (p = 0.5). In the CDGP group, 22 (66.7%) children had a family history of the condition. There was no significant difference between the groups in terms of AR CAG repeat length (median AR CAG repeat length: 21 (20–24.5) and 20 (20–24), respectively, p = 0.1). However, in boys with CDGP with a similar family history (n = 22), a significantly longer AR CAG repeat length was found compared to the control group (n = 53) (median AR CAG repeat length: 22 (20–25) and 20 (20–24), respectively, p = 0.03). The median AR CAG repeat length in boys without a family history was 21 (20–22) triplets. Although boys with a family history had a slightly longer AR CAG repeat length than those without, the difference was not statistically significant (p = 0.07). Additionally, no significant differences were observed between boys with non-familial CDGP and control subjects (p = 0.8). Furthermore, no significant differences in anthropometric characteristics or hormonal parameters were found when patients with CDGP were categorized by AR CAG repeat length quartiles. Conclusion: This is the first study to investigate the role of AR CAG polymorphism in the etiopathogenesis of CDGP. Our findings suggest that the AR CAG repeat length may be associated with familial CDGP. © The Author(s), under exclusive licence to Italian Society of Endocrinology (SIE) 2024.
Antenna Selection With Beam Squint Compensation for Integrated Sensing and Communications
(Institute of Electrical and Electronics Engineers Inc., 2024) Elbir, Ahmet Mete; Abdallah, Asmaa; Çelik, Abdülkadir; Eltawil, Ahmed M.
Next-generation wireless networks strive for higher communication rates, ultra-low latency, seamless connectivity, and high-resolution sensing capabilities. To meet these demands, terahertz (THz) band signal processing is envisioned as a key technology offering wide bandwidth and sub-millimeter wavelength. Furthermore, THz integrated sensing and communications (ISAC) paradigm has emerged to jointly access the spectrum and reduce the hardware costs through a unified platform. To address the challenges in THz propagation, THz-ISAC systems employ extremely large antenna arrays to improve the beamforming gain for communications with high data rates and sensing with high resolution. However, the cost and power consumption of implementing fully digital beamformers are prohibitive. While hybrid analog/digital beamforming can be a potential solution, the use of subcarrier-independent analog beamformers leads to the beam-squint phenomenon where different subcarriers observe distinct directions because of adopting the same analog beamformer across all subcarriers. In this paper, we develop a sparse array architecture for THz-ISAC with hybrid beamforming to provide a cost-effective solution. We analyze the antenna selection problem under beam-squint influence and introduce a manifold optimization approach for hybrid beamforming design. To reduce computational and memory costs, we propose novel algorithms leveraging grouped subarrays, quantized performance metrics, and sequential optimization. These approaches yield a significant reduction in the number of possible subarray configurations, which enables us to devise a neural network with classification model to accurately perform antenna selection. Numerical simulations show that the proposed approach exhibits up to 95% lower complexity for large antenna arrays while maintaining satisfactory communications with approximately 6% loss in the achievable rate. © 2024 IEEE.
