Hacettepe Üniversitesi Açık Erişim Sistemi (HÜAES)
- HÜAES, Hacettepe Üniversitesi bünyesinde üretilen kitap, makale, tez, bildiri, rapor gibi tüm akademik kaynakları uluslararası standartlarda dijital ortamda depolar, etkisini artırmak için telif haklarına uygun olarak Açık Erişime sunar.
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Recent Submissions
SYNTHETIC APERTURE RADAR (SAR) GUIDED RECONSTRUCTION AND CLOUD REMOVAL IN OPTICAL SATELLITE IMAGES
(Fen Bilimleri Enstitüsü, 2026-05) KARATATAR ALİHAN; Bilgisayar Mühendisliği
Cloud cover affects approximately 60–67% of the Earth’s surface at any given moment,
creating systematic gaps in optical satellite imagery that disrupt land monitoring, agricultural
assessment, and disaster response workflows. Existing deep learning approaches to cloud
removal share a fundamental deficiency: they process every pixel through the generative
network indiscriminately, modifying cloud-free observations that require no reconstruction
and occasionally hallucinating surface features that do not exist.
This thesis proposes CMSRNet (Cloud-Aware Multi-Scale SAR-Guided Reconstruction
Network), a lightweight deterministic architecture that addresses these deficiencies using
co-registered Sentinel-1 SAR data as a structural prior for Sentinel-2 optical reconstruction.
The architecture consists of three principal components. First, a dual-encoder design
processes optical and SAR inputs through separate convolutional pathways before fusion,
preventing the lower-information SAR signal from diluting optical feature representations.
Second, MultiScaleSARFusion blocks integrate the two modalities at three encoder
scales using channel-wise gating and spatial attention, allowing SAR features to guide
optical reconstruction at both coarse structural and fine textural levels. Third, a
CloudAwareRefinement module produces an explicit cloud importance map as a direct
network output and applies a hard-replacement constraint: pixels identified as cloud-free
are copied exactly from the input to the output, providing a strict mathematical guarantee
that valid surface observations are never modified.
CMSRNet is trained on the ROIs1158 spring subset of the SEN12MS-CR benchmark using
a cloud-aware loss function that concentrates reconstruction penalties on cloud-affected
regions. The network contains 3.26 million parameters and runs in a single forward pass,
avoiding the iterative sampling cost of diffusion-based alternatives such as DiffCR. Ablation
experiments validate the individual contribution of each architectural component. The
results demonstrate that a deterministic, mask-aware architecture can achieve reasonable
reconstruction quality within the operational constraints of large-scale satellite data
processing.
Türk Kadın Yazar Gözüyle Atatürk, Cumhuriyet ve Türk Devrimi
(Atatürk İlkeleri ve İnkılap Tarihi Enstitüsü, 2026-08-12) Serap Yeşiltuna Arısoy; Atatürk İlke ve İnkılapları Tarihi
This study aims to analyse the perspectives of Turkish women writers, who emerged as intellectual voices in the late Ottoman period, on Atatürk, the Republic, and the Turkish Revolution, by focusing on their literary and political contributions. To this end, the study examines the cases of Nezihe Muhiddin (1889-1958), Sabiha Sertel (1895-1968), Şükûfe Nihal (1896-1973) and Suat Derviş (1905-1972) who experienced and wrote, the social transformation brought about by the successive revolutions introduced especially between 1920 and 1938. A comparative analysis was conducted drawing on written sources produced by the writers themselves, including articles, interviews, surveys, novels short stories, memoirs and autobiographies. Beginning with these women writers’ views on the Second Constitutional Era and the National Struggle, the study examines their perspectives on the Republic itself and Republican revolutions that transformed social life such as the Civil Code, the Surname Law, and the Alphabet and Language Reforms. It further examines their views on the revolutions that enabled women to participate in education, working life, and political life, as well as the ways in which they accepted and embraced these revolutions. The study also explores their approaches to the concept of feminism, whether they identified themselves as feminists, and their views and criticisms regarding the economic structure and development, social class and status relations, as well as religion, religious communities and religious orders (tariqa) are analysed. Their views on Atatürk and their ways of embracing him as a liberator and leader are also discussed in detail. This research adopts a comparative textual and discourse analysis methodology, enriched through a close examination of Turkish and foreign archival documents and periodicals. Considering the diverse viewpoints-both affirmative and critical-in women’s studies addressing the Atatürk era, this study seeks to analyse how Atatürk’s revolutions were perceived by women writers from a historical perspective.
Girişimsel radyoloji ders
(Tıp Fakültesi, 2024-04-27) Ünal Emre; Radyoloji
interventional radiology in surgery
ROTATOR MANȘET TENDON HASARLARI İÇİN GDF-5 YÜKLÜ VE HİZALI NANOFİBERLERLE KATKILANDIRILMIŞ POLİ(BÜTİLEN ADİPAT-KO-TEREFTALAT) YAMALARIN GELİŞTİRİLMESİ: IN VİTRO ÇALIŞMALAR
(Fen Bilimleri Enstitüsü, 2027) Akbulut, Serdar Onat; Biyomühendislik
Injuries to the supraspinatus tendon of the rotator cuff are unable to heal spontaneously because of the limited intrinsic regenerative capacity of the affected tissue. Depending on the severity of the injury, physical therapy or surgical repair is recommended. However, current treatment approaches are unable to fully recapitulate the anisotropic architecture and biochemical composition of the native tendon. Tissue engineering has therefore emerged as a promising strategy for the repair and regeneration of tendon injuries. The aim of the present thesis was to develop growth/differentiation factor-5 (GDF-5)-incorporated bilayer anisotropic nanofibrous poly(butylene adipate-co-terephthalate) (PBAT) matrices for use as supraspinatus tendon patches and to evaluate their effects on the tenogenic differentiation of adipose-derived mesenchymal stem cells (ADMSCs) under dynamic culture conditions.
In the first part of the thesis, a random nanofibrous matrix was initially fabricated by electrospinning a PBAT solution prepared using hexafluoroisopropanol (HFIP). Subsequently, aligned nanofibers were electrospun onto the random layer to produce bilayer PBAT matrices with different thicknesses. The collection times for both the random and aligned fiber layers were maintained equally at 4, 6, and 8 h, and the resulting matrices were designated as 4S, 6S, and 8S, respectively. Following physicochemical characterization, the mechanical properties of the matrices were evaluated before and after degradation. Based on cell viability, morphological, and gene expression analyses conducted under static culture conditions, the 4S group was identified as the most effective scaffold for promoting the tenogenic differentiation of ADMSCs, and all subsequent experiments were therefore performed using this group.
In the second part of the thesis, the optimal dose of GDF-5 for inducing the tenogenic differentiation of ADMSCs was first determined. This dose was subsequently incorporated into the aligned fiber layer of the 4S scaffold during the electrospinning process to fabricate G-PBAT matrices. The G-PBAT matrices exhibited enhanced nanofiber alignment, reduced fiber diameter, and improved mechanical properties. The release profile of GDF-5 was evaluated by enzyme-linked immunosorbent assay (ELISA), demonstrating an initial burst release on the first day followed by a controlled and sustained release over a period of 20 days. Comprehensive evaluation of cell viability, tenocyte-like morphology, tendon-like mechanical properties, and tenogenic marker expression at both the gene and protein levels demonstrated that the G-PBAT matrix most effectively supported the tenogenic differentiation of ADMSCs.
In the third part of the thesis, an experimental design based on response surface methodology was established by considering the 2–4% strain range accepted for the physiological stress–strain behavior of native tendon tissue, together with the loading frequencies and loading–rest durations reported in the literature for mechanically stimulated dynamic bioreactor studies. According to the determined parameters, preliminary experiments were conducted using a mechanically active dynamic bioreactor system capable of applying both uniaxial and biaxial tensile loading. Following mechanical stimulation, the morphological and mechanical properties of the samples were evaluated, and the elastic modulus values obtained from the mechanical analyses were defined as the response variable of the response surface model. The model analysis demonstrated that the embryonic-stage mechanical stimulation parameters were within the safe operating range, and these parameters were subsequently employed in the cell culture experiments.
The embryonic-stage mechanical stimulation protocol was developed to mimic the biomechanical microenvironment present during embryonic tendon development, whereas the physical therapy-mimicking mechanical stimulation protocol was designed to model the mechanical loading applied during the non-surgical treatment of supraspinatus tendon injuries. Accordingly, the embryonic-stage mechanical stimulation protocol consisted of tensile loading at 1 Hz frequency and 3% strain for 4 h, followed by a 20 h resting period. In contrast, the physical therapy-mimicking mechanical stimulation protocol consisted of tensile loading at 0.1 Hz frequency and 4% strain, applied for 30 s per stimulation, nine times daily in three sessions with three repetitions per session. Cell culture studies performed using ADMSCs included cell viability, morphological, mechanical, gene expression, and protein expression analyses. The findings demonstrated that the synergistic effect of the controlled release of GDF-5 from the matrix and mechanical stimulation markedly enhanced the tenogenic differentiation and tendon maturation of ADMSCs. In the G-PBAT/P group, approximately 700-fold, 14-fold, and 300-fold increases were observed in the expression levels of tenomodulin (TNMD), collagen type III (COL3A1), and tenascin-C (TNC), respectively. Collectively, the findings obtained under dynamic culture conditions demonstrated that the combined application of G-PBAT matrices and physical therapy-mimicking mechanical stimulation effectively promoted the tenogenic differentiation and tendon maturation of ADMSCs.
Within the scope of the present thesis, a bilayer anisotropic tendon patch was successfully developed to simultaneously mimic the structural organization, biochemical cues, and mechanical microenvironment of the posterior region of the supraspinatus tendon. Furthermore, the physical therapy-mimicking mechanical stimulation applied to the matrices was shown to establish a favorable microenvironment that supports functional tendon tissue formation. The findings of this study indicate that the developed tendon patch represents a promising tissue engineering strategy for supraspinatus tendon repair. Nevertheless, further in vivo studies are required to validate its clinical translation potential.
H. varium subsp. varium Willd. Bitkisi Toprak Üstü Sulu Ekstresi Üzerinde Fitokimyasal ve Biyolojik Etki Çalışmaları
(Sağlık Bilimleri Enstitüsü, 2026) Hatice Nazlı Gümüş; Farmakognozi
Hedysarum species have traditionally been used for their antidiabetic, wound-healing, antiarrhythmic, antihypercholesterolemic, laxative, and diuretic effects. Phytochemical studies have identified a wide variety of metabolites, predominantly flavonoids, which are considered responsible for their antioxidant and anti-inflammatory activities. In the present thesis, fractions (Fr. A–E2) obtained by polyamide column chromatography of the aqueous fraction (HSF) derived from the 80% ethanol extract of the aerial parts of Hedysarum varium subsp. varium were investigated. The HSF and its fractions were evaluated for their total phenolic and flavonoid contents, antioxidant, cytotoxic, anti-inflammatory, and neuroprotective activities. Antioxidant activity was assessed by DPPH and superoxide (SO) radical scavenging assays, cytotoxicity by the MTT assay, anti-inflammatory activity by NO quantification in LPS-stimulated RAW 264.7 cells, and neuroprotective activity using an H₂O₂-induced neurotoxicity model in SH-SY5Y cells. Among the fractions, Fr. E1 showed the strongest antioxidant activity, with IC₅₀ values of 26.3 and 82.9 µg/ml in the DPPH and SO assays, respectively, while all tested fractions exhibited significant anti-inflammatory and neuroprotective effects at 100 and 200 µg/ml compared with the control group. Rutin, nicotiflorin, and vestitol were isolated and structurally characterized. These phytochemical and biological findings indicate that H. varium subsp. varium is a promising natural source of pharmaceutically valuable bioactive compounds.