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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/6
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Publication Open Access Liver transplantation in hepatic myelopathy(Kare Yayıncılık, 2022) Acar, Sencan; Dinçkan, Ayhan; Akyıldız, Murat; Faculty Member; School of Medicine; 123080Hepatic myelopathy (HMy) is a rare neurological complication of liver cirrhosis that involves spastic paraplegia caused by lateral cord demyelination especially due to the accumulation of some metabolites such as ammonia and manganese. We report a young adult woman presenting with spasticity and paraparesis in extremities after intrahepatic portosystemic shunting (TIPS) application and underwent deceased liver transplantation (LT). A 39-year-old woman underwent deceased LT because of cryptogenic liver cirrhosis. She underwent a TIPS procedure 5 years ago. After that, hepatic encephalopathy and spasticity appeared. She was on the waiting list for 3 years. Neurological findings after LT significantly decreased, but did not return to normal. After the emergence of neurological findings, the earlier LT can provide improvement in neurological findings.Publication Open Access Early/fast VLF events produced by the quiescent heating of the lower ionosphere by thunderstorms(American Geophysical Union (AGU), 2017) Kabirzadeh, R.; Marshall, R. A.; Department of Electrical and Electronics Engineering; İnan, Umran Savaş; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 177880Large and easily distinguishable perturbations of the VLF transmitter signals due to interactions with thundercloud-driven ionospheric modifications have been observed and studied for about three decades. These events are called "early/fast VLF" or "early VLF" events due to their immediate detection (similar to 20 ms) after the causative lightning flash on the ground and the fast rise time of the perturbed signal. Despite many years of study, the physical mechanisms responsible for these perturbations are still under investigation. Modifications of the sustained heating level of the ionosphere due to a lightning flash has been previously proposed as the causative mechanism of early/fast VLF events. The perturbations predicted by this mechanism, however, have been much smaller than experimental observations of 0.2-1 dB or higher. In this study, by using an improved 3-D thundercloud electrostatic upward coupling model which uses a realistic geomagnetic field, we find that the sustained heating model can predict perturbations that are consistent with reported experimental observations. Modifications in the quiescent heating of the lower ionosphere by thundercloud fields by individual lightning flashes may thus account for some observations of early/fast VLF events. Large and easily distinguishable perturbations of the VLF transmitter signals due to interactions with thundercloud-driven ionospheric modifications have been observed and studied for about three decades. These events are called "early/fast VLF" or "early VLF" events due to their immediate detection (similar to 20 ms) after the causative lightning flash on the ground and the fast rise time of the perturbed signal. Despite many years of study, the physical mechanisms responsible for these perturbations are still under investigation. Modifications of the sustained heating level of the ionosphere due to a lightning flash has been previously proposed as the causative mechanism of early/fast VLF events. The perturbations predicted by this mechanism, however, have been much smaller than experimental observations of 0.2-1 dB or higher. In this study, by using an improved 3-D thundercloud electrostatic upward coupling model which uses a realistic geomagnetic field, we find that the sustained heating model can predict perturbations that are consistent with reported experimental observations. Modifications in the quiescent heating of the lower ionosphere by thundercloud fields by individual lightning flashes may thus account for some observations of early/fast VLF events.Publication Open Access Generation of transgene-free iPSC lines from three patients with Friedreich's ataxia (FRDA) carrying GAA triplet expansions in the first intron of FXN gene(Elsevier, 2021) Kelekçi, Simge; Uğurlu Çimen, Deniz; Demir, Ata Berk; Özçimen, Burcu; Yıldız, Abdullah Burak; Karakuş, Mehmet Batuhan; Börklü Yücel, Esra; Önder, Tamer Tevfik; PhD Student; Undergraduate Student; Other; Faculty Member; Graduate School of Health Sciences; School of Medicine; Koç University Hospital; N/A; N/A; N/A; N/A; N/A; N/A; N/A; 42946Friedreich's ataxia (FRDA) is a rare neurodegenerative disorder which is caused by triplet repeat expansion (GAA) in the first intron of FXN gene. In this present study, we generated induced pluripotent stem cells (iPSC) lines from fibroblasts of three unrelated FRDA patients using integration-free episomal vectors. All iPSC lines express the pluripotency markers such as OCT4 and SSEA4, display normal karyotypes and can differentiate into all three germ layers via in vivo teratoma formation assay.Publication Open Access Turk Cardiology Association completion report: COVID-19 pandemic and things to know about cardiovascular diseases (25 Mart 2020)(Turkish Society of Cardiology, 2020) Aktoz, Meryem; Altay, Hakan; Aslanger, Emre; Atalar, Enver; Baykan, Ahmet Oytun; Barçın, Cem; Barış, Nezihi; Boyacı, Asiye Ayça; Çavuşoğlu, Yüksel; Çelik, Ahmet; Cinier, Göksel; Değertekin, Muzaffer; Ertürk, Mehmet; Erol, M. Kemal; Görenek, Bülent; Gürsoy, Mustafa Ozan; Hunuk, Burak; Kahveci, Gökhan; Karabay, Can Yücel; Karaca, Ilgın; Kayıkcıoğlu, Meral; Keskin, Muhammed; Kılıç, Teoman; Kırma, Cevat; Kocabaş, Umut; Küçükoğlu, Serdar; Mutlu, Bülent; Nalbantgil, Sanem; Okuyan, Ertuğrul; Okyay, Kaan; Özen, Deniz Kaptan; Özgül, Sami; Özpelit, Ebru; Pirat, Bahar; Sert, Sena; Sinan, Ümit Yaşar; Şener, Yusuf Ziya; Tatlı, Ersan; Tekkesin, Ahmet İlker; Tutar, Eralp; Yıldırımtürk, Özlem; Aytekin, Vedat; Ural, Dilek; Ergönül, Önder; Faculty Member; Faculty Member; Faculty Member; School of Medicine; N/A; 1057; 110398In December 2019, in the city of Wuhan, in the Hubei province of China, treatment-resistant cases of pneumonia emerged and spread rapidly for reasons unknown. A new strain of coronavirus (severe acute respiratory syndrome coronavirus-2 [SARS-CoV-2]) was identified and caused the first pandemic of the 21st century. The virus was officially detected in our country on March 11, 2020, and the number of cases increased rapidly; the virus was isolated in 670 patients within 10 days. The rapid increase in the number of patients has required our physicians to learn to protect both the public and themselves when treating patients with this highly infectious disease. The group most affected by the outbreak and with the highest mortality rate is elderly patients with known cardiovascular disease. Therefore, it is necessary for cardiology specialists to take an active role in combating the epidemic. The aim of this article is to make a brief assessment of current information regarding the management of cardiovascular patients affected by COVID-19 and to provide practical suggestions to cardiology specialists about problems and questions they have frequently encountered. / Aralık 2019’da, Çin’in Hubei eyaletindeki Wuhan şehrinde, nedeni bilinmeyen, tedaviye dirençli pnömoni olguları ile ortaya çıkan ve devamında hızla yayılarak XXI. yüzyılın ilk pandemisine neden olan yeni koronavirüsün (severe acute respiratory syndrome koranavirüs-2 [SARS-CoV-2]) 11 Mart 2020 tarihinde ülkemizde de resmi olarak saptanmasının ardından olgu sayısı hızla artmış ve 10 gün içerisinde 670 hastada virüs izole edilmiştir. Hasta sayısındaki hızlı artış, hekimlerimizin bir yandan etkilenen hastalara müdahale ederken diğer yandan toplumu ve kendilerini korumayı öğrenmelerini gerektirmektedir. Salgından en çok etkilenen ve ölüm oranı en yüksek seyreden grup, bilinen kalp ve damar hastalıkları olan yaşlılardır. Bu nedenle, kardiyoloji uzmanlarının salgınla mücadelede aktif görev almaları kaçınılmazdır. Bu makale, COVID-19’dan etkilenen kalp-damar hastalarının yönetiminde güncel bilgilerin kısa bir değerlendirmesini yapmayı ve kardiyoloji uzmanlarına sık karşılaştıkları sorunlar ve sorular hakkında pratik öneriler sunmayı amaçlamaktadır.Publication Open Access Pneumonia in HIV-infected patients(Aves, 2016) Önür, Seda Tural; Dalar, Levent; Yalçın, Arzu Didem; İliaz, Sinem; Doctor; Koç University Hospital; 168584Acquired immune deficiency syndrome (AIDS) is an immune system disease caused by the human immunodeficiency virus (HIV). The purpose of this review is to investigate the correlation between an immune system destroyed by HIV and the frequency of pneumonia. Observational studies show that respiratory diseases are among the most common infections observed in HIV-infected patients. In addition, pneumonia is the leading cause of morbidity and mortality in HIV-infected patients. According to articles in literature, in addition to antiretroviral therapy (ART) or highly active antiretroviral therapy (HAART), the use of prophylaxis provides favorable results for the treatment of pneumonia. Here we conduct a systematic literature review to determine the pathogenesis and causative agents of bacterial pneumonia, tuberculosis (TB), nontuberculous mycobacterial disease, fungal pneumonia, Pneumocystis pneumonia, viral pneumonia and parasitic infections and the prophylaxis in addition to ART and HAART for treatment. Pneumococcus-based polysaccharide vaccine is recommended to avoid some type of specific bacterial pneumonia.Publication Open Access An information theoretical analysis of broadcast networks and channel routing for FRET-based nanoscale communications(Institute of Electrical and Electronics Engineers (IEEE), 2012) Kuşcu, Murat; Malak, Derya; Akan, Özgür Barış; Faculty Member; College of EngineeringNanoscale communication based on Forster Resonance Energy Transfer (FRET) enables nanomachines to communicate with each other using the excited state of the fluorescent molecules as the information conveyer. In this study, FRET-based nanoscale communication is further extended to realize FRET-based nanoscale broadcast communication with one transmitter and many receiver nanomachines, and the performance of the broadcast channel is analyzed information theoretically. Furthermore, an electrically controllable routing mechanism is proposed exploiting the Quantum Confined Stark Effect (QCSE) observed in quantum dots. It is shown that by appropriately selecting the employed molecules on the communicating nanomachines, it is possible to control the route of the information flow by externally applying electric field in FRET-based nanonetworks.Publication Open Access Ultraslow optical modes in Bose-Einstein condensates(Society of Photo-optical Instrumentation Engineers (SPIE), 2007) Tarhan, Devrim; Postacıoğlu, Nazmi; Department of Physics; Müstecaplıoğlu, Özgür Esat; Faculty Member; Department of Physics; College of Sciences; 1674Light can be slowed down to ultraslow speeds via electromagnetically induced transparency in atomic Bose-Einstein condensates. This is thought to be useful for storage of quantum information for weak probe pulses. We investigate the effects of inhomogeneous density profile of-the condensate on propagation of such ultraslow pulses. We find that spatial density of an atomic condensate leads to a graded refractive index profile, for an off-resonant probe pulse when condensate parameters are suitably chosen. Within the window of negligible absorption, conditions for degenerate multiple waveguide modes are determined. Both analytical and numerical studies are presented to reveal the effects of experimentally controllable parameters, such as temperature and interatomic interaction strength on the number of modes. Group velocity dispersion and modal dispersion are discussed. The effect of waveguide dispersion, in addition to usual material dispersion, on ultraslow pulses is pointed out.Publication Open Access How do mega-bank merger policy and regulations contribute to financial stability? Evidence from Australia and Canada(Taylor _ Francis, 2017) Department of International Relations; Bakır, Caner; Faculty Member; Department of International Relations; College of Administrative Sciences and Economics; 108141Although the role of financial regulatory failures in the global financial crisis (GFC) has been explored extensively in the post-GFC literature, our knowledge of the role of bank merger and takeover policy and regulation in reinforcing financial stability is limited. Based on an exploratory case study of Australia, which is examined in comparison to Canada, this article argues that competition policy and regulation contributed to financial stability by insulating the largest Australian and Canadian banks from domestic or foreign hostile takeover threats, and by limiting their asset size, and thus their internationalization and interconnections with the global banking community.Publication Open Access On the capacity of diffusion-based molecular communications with SiNW FET-based receiver(Institute of Electrical and Electronics Engineers (IEEE), 2016) Department of Electrical and Electronics Engineering; Kuşcu, Murat; Akan, Özgür Barış; Faculty Member; Department of Electrical and Electronics Engineering; College of EngineeringMolecular communication (MC) is a bio-inspired communication method based on the exchange of molecules for information transfer among nanoscale devices. Although MC has been extensively studied from various aspects, limitations imposed by the physical design of transceiving units have been largely neglected in the literature. Recently, we have proposed a nanobioelectronic MC receiver architecture based on the nanoscale field effect transistor-based biosensor (bioFET) technology, providing noninvasive and sensitive molecular detection at nanoscale while producing electrical signals at the output. In this paper, we derive analytical closed-form expressions for the capacity and capacity-achieving input distribution for a memoryless MC channel with a silicon nanowire (SiNW) FET-based MC receiver. The resulting expressions could be used to optimize the information flow in MC systems equipped with nanobioelectronic receivers.Publication Open Access HF beam parameters in ELF/VLF wave generation via modulated heating of the ionosphere(American Geophysical Union (AGU), 2012) Cohen, M. B.; Golkowski, M.; Lehtinen, N. G.; McCarrick, M. J.; Department of Electrical and Electronics Engineering; İnan, Umran Savaş; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 177880ELF/VLF (0.3–30 kHz) wave generation is achievable via modulated HF (3–30 MHz) heating of the lower ionosphere in the presence of natural currents such as the auroral electrojet. Using the 3.6 MW High Frequency Active Auroral Research Program (HAARP) facility near Gakona, AK, we investigate the effect of HF frequency and beam size on the generated ELF/VLF amplitudes, as a function of modulation frequency, and find that generation in the Earth-ionosphere waveguide generally decreases with increasing HF frequency between 2.75–9.50 MHz. HAARP is also capable of spreading the HF power over a wider area, and we find that a larger beam area yields larger generated amplitudes on the ground. Measurements are shown to generally agree with a theoretical model, which is then applied to also predict the effect of HF beam parameters on magnetospheric injection with HAARP.