2316 results
Search Results
Now showing 1 - 10 of 2316
Article Citation - Scopus: 1An Investigation on the Dna Binding Activities of Melamine, Cyanuric Acid and Uric Acid(Editura Acad Romane, 2021) Senol, Ali; Devrim, Alparslan Kadir; Sudagidan, Mert; Ozalp, Veli CengizMelamine can be added to various foods such as milk, milk powder, baby food, pet, and livestock feed for cheating purposes due to its high nitrogen content. Regarding its usage in food products, there is a need to investigate its possible interactions with DNA. Thus, this study aimed to investigate the interactions of melamine and its metabolized products, cyanuric acid and uric acid with genomic DNA, isolated from eukaryotic (calf thymus) and prokaryotic (Staphylococcus aureus) sources. UV-absorbance spectrophotometry, fluorescence spectrophotometry, and agarose gel electrophoresis techniques were used to evaluate these interactions. The five different concentrations of melamine, cyanuric acid, and uric acid were incubated with fixed DNA concentration and it was determined that the test compounds interacted with the DNA molecules. The data obtained by UV-absorbance and fluorescence spectrophotometry techniques revealed an increase in wave peaks observed with the increasing substance concentration. After the obtained data of the aforementioned techniques were evaluated together, it was concluded that melamine, cyanuric acid, and uric acid bonded to the eukaryotic and prokaryotic genomic DNA materials via groove binding.Article Citation - WoS: 6A Light Bulb in Every House the Istanbul General Electric Factory and American Technology Transfer To Turkey(Johns Hopkins Univ Press, 2022) Tunc, Tanfer Emin; Tunc, GokhanIn 1946, Turkish entrepreneur Vehbi Koc signed an agreement with the U.S. firm General Electric to build and operate its first light bulb factory in the Near/Middle East, in Istanbul. This private joint venture introduced new manufacturing techniques, business practices, and consumer habits to Turkey, opening channels of postwar technological exchange. Closer examination of the GE-Koc partnership reveals that during the early Cold War, the transfer and embedding of American technologies in Turkey was a politically complicated process of innovation that required constant adaptation. Fraught with unforeseeable obstacles, it also required cautious negotiation with multiple transnational actors. The story of the GE-Koc partnership thus adds a new dimension to historical understandings of the Turkish Cold War experience and the Americanization of the region. It illustrates how transferring a nonmilitary, soft-power, domestic technologythe light bulb-played a significant role in Turkish-American relations and therefore contributes to studies of U.S. Cold War diplomacy through transnational investment in innovation.Article Citation - WoS: 1Citation - Scopus: 1The Effect of Group Behavior on the Pull-Out Capacity of Model Soil Nails in High Plasticity Clay(Springer int Publ Ag, 2024) Akis, Ebru; Bakir, Bahadir Sadik; Yilmaz, Mustafa TolgaSoil nailing technique is widely used in stabilizing roadway and tunnel portal cut excavations. The key parameter in the design of soil nail systems is the pull-out capacity. The pull-out capacity of soil nails can be estimated either from the studies involving similar soil conditions or from the empirical formulas available in the literature. Particularly, it has been documented placing nails closer than a certain minimum distance results in a reduction in the pull-out resistance of a nail placed in sand. However, this requirement has not been discussed for the nail groups located within clay formations. In order to investigate the influence of nail spacing on the pull-out resistance of nails, a series of laboratory pull-out experiments were performed in clay of high plasticity. The results of these experiments showed a remarkable trend. Specifically, there was a significant reduction in the pull-out capacity of a nail when the spacing between nails two times the nail diameter (2 & Oslash;). In contrast, the pull-out capacity of a nail embedded in clay remained unaffected by neighboring nails, provided the spacing was maintained at six times the nail diameter (6 & Oslash;). In addition, during the conducted pull-out tests, it was observed that the failure mode of a single nail and 6 & Oslash; spaced group nails near the surface results as heaving around the single nail. However, in the case of closely positioned (2 & Oslash; spaced) nails, the affected area following nail failure exhibits distinct characteristics, which operate as a group. This leads to the occurrence of failure in the form of heaving around the group of nails.Article Covid-19 Salgınının Bölgesel Borsa Turizm Endekslerine Etkilerinin Araştırılması(2023) Tümer, Tolga; Tengilimoğlu, DilaverBu çalışmada, bölgesel borsa turizm endekslerinin COVID-19’dan etkilenme düzeyleri araştırılmıştır. Bu amaçla çalışmada, Kuzey Amerika, Avrupa ve Asya Pasifik bölgelerini kapsayan borsa turizm endeksleri kullanılarak istatistiki analizler yapılmıştır. Çalışmanın kapsamı COVID-19’un dünyaya yayılmaya başladığı dönemden itibaren 22 Ocak 2020-22 Ocak 2022 tarihleri arasındaki iki yıllık süreci kapsamaktadır ve çalışmada bu süreç çeyrek dilimlere ayrılarak sekiz dönem kapsamında analiz edilmektedir. Günlük veriler kullanılan araştırmada hem dünyadaki hem de kullanılan endekslerin kapsadığı bölgelerdeki COVID-19 verileri dikkate alınmıştır. COVID-19 verileri olarak günlük vaka, günlük ölüm, toplam vaka ve toplam ölüm sayıları toplanmıştır. Araştırmanın sonucunda, borsa turizm endekslerini negatif yönde en fazla COVID-19 kaynaklı bölgesel günlük ölümlerin etkilediği bulunmuştur. Bu çalışma, geniş kapsamı, bölgesel ve dönemsel karşılaştırma sunan bulguları ile alanyazına katkı sunmaktadır.Article Alzheimer hastalığında Kallikrein-6, 7 ve potasyum kanal proteinlerinin olası rolü(2021) Bulduk, Erkut; Yıldırım, Filiz; Yıldırım, ZuhalAmaç: Alzheimer hastalığının (AH) oluşum mekanizması kesin olarak bilinmemekle birlikte AH’dan sorumlu başlıca iki protein, senile plakların yapısındaki beta amiloid ve nörofibriler yumakların yapısındaki tau proteinidir. Hastalığa yol açan en önemli etmenlerden biri çözünür olmayan amiloid çökeltilerin oluşumu, diğeri ise artmış tau fosforillenmesidir. Kallikreinler, nöronal hasar ve işlev kaybı ile belirgin AH’nın etiyolojisinde rol oynayan, serin proteazların bir alt familyasıdır. Kallikrein (KLK)-6 ve KLK-7’nin merkezi sinir sisteminde (MSS) yüksek seviyelerde bulunan yaşa bağlı proteaz olduğu bilinmektedir. Daha once AH’ı gibi nörodejeneratif hastalıklarda yer alan hücre dışı proteinlerin proteolizine karıştığı gösterilmiştir. Bu çalışmada KLK-6 ve KLK-7’nin AH patogenezindeki olası rolünü ve potasyum kanal proteinleri arasındaki ilişkiyi araştırmayı amaçladık. Yöntem: Çalışmaya Polatlı Duatepe Devlet Hastanesinde takip edilen yaşları 65’in üzerinde olan 35 AH ve rutin tarama amacıyla nöroloji polikliniğine başvuran kognitif durumu normal olarak değerlendirilen 35 sağlıklı birey (control grubu) dahil edildi. 12 saat açlığı takiben antekübital venden alınan kan örnekleri 4°C’de 2500xg’de 10 dakika santrifüj edilerek, serum örneklerinde KLK-6 ve KLK-7 ile içeri doğru düzeltici potasyum kanalı (KCNJ3) ve iki gözenekli potasyum kanalı (KCNK9) protein düzeyleri enzim-bağımlı immunosorbent assay (ELISA) ile ölçüldü. Gruplar arasındaki fark T-test ile incelendi. p<0.05 istatistiksel olarak anlamlı kabul edildi. Bulgular: Gruplar arasında yaş ve cinsiyet açısından bir fark saptanmadı (p>0.05). Alzheimer grubu control grubu ile karşılaştırıldığında serum KLK-6 ve KLK-7 düzeyleri anlamlı olarak artarken (p<0.05), KCNJ3 ve KCNK9 protein düzeylerinde bir fark saptanmadı (p>0.05). Sonuç: Beyinde anormal protein katlanmasının ve birikmesinin önüne geçilememesinin AH’ye yol açtığı düşünülmektedir. Bu araştırmanın bulgularına göre KLK- 6 ve KLK-7 düzeyleri ile AH’nın patolojisi arasında bir ilişki saptandı.Article Citation - WoS: 13Citation - Scopus: 13Evaluation of procedural and clinical outcomes of transcatheter aortic valve implantation: A single-center experience(Kare Publ, 2020) Karaduman, Bilge Duran; Kayaoğlu, Hüseyin Ayhan; Keleş, Telat; Bozkurt, EnginObjective: Transcatheter aortic valve implantation (TAVI) is an established alternative to surgical aortic valve replacement. Our study aimed to evaluate the implementation of TAVI at our large-volume center, having an all-comer patient population with short and long-term follow-ups. Methods: This retrospective, single-center analysis included 556 consecutive patients with symptomatic severe aortic stenosis (AS) who underwent TAVI between July 2011 and December 2019. Results: The mean age of the entire population was 77.6±7.9 years, and 54.9% were women. The Society of Thoracic Surgeons (STS) mean score of the cohort was 6.0%±3.5%. The balloon-expandable valve (Sapien XT, Sapien 3; Edwards Lifesciences, Irvine, California) was the most frequently used valves in this cohort (94.6%). Transfemoral access was used in 96.3% of patients. Implantation success was achieved in 96.6% of cases. During the TAVI procedure, 7.2% of patients required permanent pacemaker implantation, with 37.5% in the Lotus valve group needing the most permanent pacemakers. The mean length of hospital stay for the entire cohort was 4.5±2.3 days. Overall, 22 (3.9%) in-hospital deaths occurred before hospital discharge. The mean follow-up period was 15.1±14.9 months for all patients, and a significant improvement was noted in all echocardiographic parameters and functional capacity. Paravalvular leak (PVL) was documented in 18.9% patients, mild in 17.9%, and moderate in 1% at discharge. No cases with severe PVL, necessitating additional procedures. The multiple logistic regression analysis revealed that sex, STS score, baseline SYNTAX score, bicuspid valve morphology, common femoral artery diameter, and post-TAVI PVL were independent predictors of overall mortality. Conclusion: To our knowledge, this study, which is the largest single-center real-world experience of TAVI in Turkey, demonstrated low complication rates with favorable short- and mid-term THV performance in patients undergoing TAVI.Article Citation - WoS: 24Citation - Scopus: 27The Pimpled Gold Nanosphere: a Superior Candidate for Plasmonic Photothermal Therapy(Dove Medical Press Ltd, 2020) Nasseri, Behzad; Turk, Mustafa; Kosemehmetoglu, Kemal; Kaya, Murat; Piskin, Erhan; Rabiee, Navid; Webster, Thomas J.Background: The development of highly efficient nanoparticles to convert light to heat for anti-cancer applications is quite a challenging field of research. Methods: In this study, we synthesized unique pimpled gold nanospheres (PGNSs) for plasmonic photothermal therapy (PPTT). The light-to-heat conversion capability of PGNSs and PPTT damage at the cellular level were investigated using a tissue phantom model. The ability of PGNSs to induce robust cellular damage was studied during cytotoxicity tests on colorectal adenocarcinoma (DLD-1) and fibroblast cell lines. Further, a numerical model of plasmonic (COMSOL Multiphysics) properties was used with the PPTT experimental assays. Results: A low cytotoxic effect of thiolated polyethylene glycol (SH-PEG400-SH-) was observed which improved the biocompatibility of PGNSs to maintain 89.4% cell viability during cytometry assays (in terms of fibroblast cells for 24 hrs at a concentration of 300 mu g/mL). The heat generated from the nanoparticle-mediated phantom models resulted in Delta T=30 degrees C, Delta T=23.1 degrees C and Delta T=21 degrees C for the PGNSs, AuNRs, and AuNPs, respectively (at a 300 mu g/mL concentration and for 325 sec). For the in vitro assays of PPTT on cancer cells, the PGNS group induced a 68.78% lethality (apoptosis) on DLD-1 cells. Fluorescence microscopy results showed the destruction of cell membranes and nuclei for the PPTT group. Experiments further revealed a penetration depth of sufficient PPTT damage in a physical tumor model after hematoxylin and eosin (H&E) staining through pathological studies (at depths of 2, 3 and 4 cm). Severe structural damages were observed in the tissue model through an 808-nm laser exposed to the PGNSs. Conclusion: Collectively, such results show much promise for the use of the present PGNSs and photothermal therapy for numerous anti-cancer applications.Article Investigating of Dynamic Compressive Response of Plain and Fiber-Reinforced Concrete Structures at Various Strain Rates(SAGE Publications Ltd, 2025) Gunay, A.R.; Hafizoglu, H.; Akdeniz, E.; Kaya, C.Across the world, studies on building design are conducted at various scales. The behavior of structures under static loading has been the subject of various studies in the modern era, leading to the development of significant standards and application techniques. However, studies on the behavior of structures under dynamic loading have remained limited. This study investigated the dynamic compressive behavior of plain and fiber-reinforced C60 and C80 concrete samples through experimental studies at room temperature. In addition, this study also investigated dynamic deformation and fracture behavior of plain concrete samples by numerical studies. For this purpose, plain and fiber-reinforced C60 and C80 concrete samples were produced. Experimental studies covered both static and dynamic compression tests. Following the static tests, dynamic test samples with a diameter and length of 10 mm were produced from the static test samples by water jet cutting method and were dynamically compressed in the Split Hopkinson Pressure Bar (SHPB) test setup. Dynamic compression test results showed that the strength of plain and fiber-reinforced C60 and C80 concretes were obtained in the range of 74–162 MPa at an average strain rate of between 139 and 650 s−1. Experimental results also showed that the fiber addition affected the dynamic increase factor (DIF) and impact toughness of both C60 and C80 concretes in a good manner. To compare experimental and numerical results, a dynamic compression test condition was visualized with a high-speed camera and simulated with the Ls-Dyna software using the finite-element method. Numerical studies indicated a good correlation with dynamic compression results in terms of crack formation and fracture progress. © IMechE 2025.Article Citation - WoS: 19Citation - Scopus: 19A Study on the Dark and Illuminated Operation of Al/Si3< Schottky Photodiodes: Optoelectronic Insights(Springer Heidelberg, 2024) Surucu, Ozge; Yildiz, Dilber Esra; Yildirim, MuratThis work extensively investigates the operation of an Al/ Si3N4/p-Si Schottky-type photodiode under dark and varying illumination intensities. The photodiode is fabricated by employing the metal-organic chemical vapor deposition (MOCVD) method. A thorough electrical characterization is performed at room temperature, encompassing measurements of current-voltage (I-V), current-time (I-t), capacitance-time (C-t), and conductance time (G-t). The photodiode's rectification factor and reverse bias area increased under illumination. The relationship between light power density, barrier height, and diode ideality factor is found. The study also found a strong correlation between light intensity and applied voltage on series resistance (R-s) and shunt resistance (R-sh). R-s values are calculated using Cheung's functions, revealing the diode's resistance behavior. The study also examines the photodiode's photoconductivity and photoconductance, finding a non-linear relationship between photocurrent and illumination intensity, suggesting bimolecular recombination. Calculated photosensitivity (K), responsivity (R), and detectivity (D*) values show the device's light response effectiveness, but efficiency decreases at higher illumination intensities. Transient experiments indicate stable and reproducible photocurrent characteristics, revealing photogenerated charge temporal evolution. This study provides a complete understanding of the Al/Si3N4/p-Si Schottky photodiode's behavior under different illumination intensities. The findings advance optoelectronic device knowledge and enable their use in advanced technologies.Article Geç Kapitalizmin İdeolojik Söylemi Olarak Yeni Materyalizm: Metalaşmış ‘şeylerin’ Egemenliği(2020) Yalvaç, Faruk; Erçandırlı, YeldaBu makale yeni materyalizmin tarihsel materyalist bir eleştirisini yapmaktadır. Yenikapitalizmi geç kapitalizmin ideolojik bir söylemi olarak nitelendirmektedir. Yenimateryalizm meta üretiminin hâkimiyet kazandığı bir sosyo-politik ortamı yansıtanbir söylem olarak tanımlanmakta, tarihsel materyalist anlayışla olan farklılıkları ortayakoyulmaktadır. Hem yeni materyalizm hem de tarihsel materyalizm maddenin öneminevurgu yapmakla birlikte, aralarında önemli farklılıklar vardır. Yeni materyalizmingenişletilmiş madde anlayışı, metalaşmış bir dünyanın söylemi ve savunusunadönüşmekte, insanın madde ve doğa ile olan ilişkisinin özgürleştirici niteliği göz ardıedilmektedir. Bu çerçevede, yazının ilk kısmında önce yeni materyalizm tanıtılacaktır.İkinci bölümde madde kavramının tarihsel materyalist anlayışta nasıl incelendiğiirdelenecektir. Üçüncü kısımda yeni materyalizmin Marx’ın meta fetişizmi anlayışıçerçevesinde bir değerlendirilmesi yapılarak, yeni materyalizmin ideolojik niteliğinevurgu yapılacaktır. Makale yeni materyalizmin laissez-faire kapitalizminin günümüzdekibir görüntüsü olduğu görüşüyle sona ermektedir.
