Browsing by Subject "Topography"

Now showing 1 - 5 of 5

Open Access
Chemical and topographical modification of PHBV surface to promote osteoblast alignment and confinement
(John Wiley & Sons, Inc., 2008) Kenar, H.; Kocabas, A.; Aydınlı, Atilla; Hasirci, V.
Proper cell attachment and distribution, and thus stronger association in vivo between a bone implant and native tissue will improve the success of the implant. In this study, the aim was to achieve promotion of attachment and uniform distribution of rat mesenchymal stem cell-derived osteoblasts by introducing chemical and topographical cues on poly(3-hydroxybutyrate-co-3- hydroxyvalerate) (PHBV) film surfaces. As the chemical cues, either alkaline phosphatase was covalently immobilized on the film surface to induce deposition of calcium phosphate minerals or fibrinogen was adsorbed to improve cell adhesion. Microgrooves and micropits were introduced on the film surface by negative replication of micropatterned Si wafers. Both chemical cues improved cell attachment and even distribution on the PHBV films, but Fb was more effective especially when combined with the micropatterns. Cell alignment (<10° deviation angle) parallel to chemically modified microgrooves (1, 3, or 8 μm groove width) and on 10 μm-thick Fb lines printed on the unpatterned films was achieved. The cells on unpatterned and 5 μm-deep micropitted films were distributed and oriented randomly. Results of this study proved that microtopographies on PHBV can improve osseointegration when combined with chemical cues, and that microgrooves and cell adhesive protein lines on PHBV can guide selective osteoblast adhesion and alignment.
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Harita Genel Müdürlüğü tarihi
(Bilkent University, 2020) Mirza, İrem; Avcı, Bora; Yalçın, Hatice Şeyma; İkizlioğlu, İzel; Koçak, İrem
Günümüzdeki adıyla Harita Genel Müdürlüğü 1880 yılında Genelkurmay Başkanlığı’na bağlı Harita ve Fen şubesinde Harita Komisyonu olarak kuruldu. Fransa’dan getirilen uzmanlarla komisyon ilk çalışmalarına başladı. Komisyonun asıl amacı Osmanlı haritasını hazırlamaktı. Takip eden yıllarda Birinci Dünya Savaşı’nın patlak vermesiyle, savaş sırasında ihtiyaç duyulabilecek askeri amaçlı haritalara hiç olmadığı kadar ihtiyaç duyuldu ve ülkenin bu ihtiyacını karşılamak için Harita Şubesi kurulmasıyla bu bölüm ülkenin dört bir yanında çeşitli faaliyetler sürdürdü ve farklı ölçekte birçok farklı bölgenin haritası çizdi. Kurtuluş Savaşı döneminde herhangi bir saldırıya her an hazırlıklı olup ordunun ihtiyaçlarını en iyi şekilde karşıladı. Cumhuriyetin ilanından sonra Harita Umum Müdürlüğü ismini alan kurum inkılaplar döneminde pek çok yenilik yaptı. Yapılan bu inkılaplar sadece askeri alanlarda değil, kamusal ve bilimsel alanlarda da ilerlemeyi sağladı ve Türkiye’yi haritacılık bakımından uluslararası standartlara taşıdı. Günümüzdeki ismiyle Harita Genel Müdürlüğü, ulusal haritacılık kurumu olarak, TSK birimleri tarafından iç güvenlik harekâtlarında ve sınır dışı operasyonlarda ihtiyaç duyulan haritaların ve coğrafi verilerin temininin yanı sıra sivil amaçlı haritacılık ve diğer coğrafi faaliyetler de yürütmekte, diğer projelere destek sağlamaktadır. GPS ve dijital haritacılık teknolojisini takiben kurumun alt birimleri son halini aldı ve haritacılık alanındaki son teknolojiler günümüzde kullanılmaya başlandı.
Open Access
MDM2 T309G polymorphism is associated with bladder cancer
(International Institute of Anticancer Research, 2006) Onat, O. E.; Tez, M.; Özçelik, T.; Törüner, G. A.
Recently, a functional T to G polymorphism at nucleotide 309 in the promoter region of the MDM2 gene (rs: 2279744, SNP 309) has been identified. This polymorphism has an impact on the expression of the MDM2 gene, which is a key negative regulator of the tumor suppressor molecule p53. The effect of T309G polymorphism of the MDM2 gene on bladder cancer susceptibility was investigated in a case-control study of 75 bladder cancer patients and 103 controls from Turkey. The G/G genotype exhibited an increased risk of 2.68 (95% CI, 1.34-5.40) for bladder cancer compared with the combination of low-risk genotypes T/T and T/G at this locus. These results show an association between MDM2 T309G polymorphism and bladder cancer in our study group. To the best of our knowledge, this is the first study reporting that MDM2 T309G polymorphism may be a potential genetic susceptibility factor for bladder cancer.
Open Access
Retinal proteins as model systems for membrane protein folding
(Elsevier BV, 2014) Tastan, O.; Dutta, A.; Booth, P.; Klein-Seetharaman, J.
Experimental folding studies of membrane proteins are more challenging than water-soluble proteins because of the higher hydrophobicity content of membrane embedded sequences and the need to provide a hydrophobic milieu for the transmembrane regions. The first challenge is their denaturation: due to the thermodynamic instability of polar groups in the membrane, secondary structures in membrane proteins are more difficult to disrupt than in soluble proteins. The second challenge is to refold from the denatured states. Successful refolding of membrane proteins has almost always been from very subtly denatured states. Therefore, it can be useful to analyze membrane protein folding using computational methods, and we will provide results obtained with simulated unfolding of membrane protein structures using the Floppy Inclusions and Rigid Substructure Topography (FIRST) method. Computational methods have the advantage that they allow a direct comparison between diverse membrane proteins. We will review here both, experimental and FIRST studies of the retinal binding proteins bacteriorhodopsin and mammalian rhodopsin, and discuss the extension of the findings to deriving hypotheses on the mechanisms of folding of membrane proteins in general. This article is part of a Special Issue entitled: Retinal Proteins - You can teach an old dog new tricks.
Open Access
The Lower Danube in Late Antiquity: The case of Histria
(2023-08) Batum, Sercan
This thesis analyses the nature of Histria in Late Antiquity between the 3rd and the 7th century AD. Histria is chosen as a case study as it is the most comprehensively studied city in Scythia Minor for the period. The thesis has two focal points. Firstly, it investigates the evolution of the site in Late Antiquity. Secondly, it re-assesses the nature of Histria in terms of the divergent claims as proposed by Constantin Scorpan in 1980 and by Andrew Poulter in 1992 regarding the nature of the place and other cities in the region in Late Antiquity. To achieve both aims, the thesis examines Histria in terms of its urban change and the transformation of both ecclesiastical and civic buildings and street networks in Late Antiquity. This is done within a chronological framework to assess the possible reasons for such change, such as Christianity, invasion, and urban reconstruction. In particular, the thesis concentrates on the Christianization of urban topography, and the inter-relationship between the extra- and intra-mural basilica churches there and Histria’s residential areas, in the context of the rise of Christianity in the Roman Empire during Late Antiquity. By examining the effect of Christianity on the development of urbanism in the region, the thesis will favour the idea that the classical urban amenities lost their function of earlier periods as Christianity transformed the urban areas with significant landmarks, most especially the basilicas.