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Original Article

A change in the coronary sinus (CS) activation pattern from an eccentric to a concentric pattern during the ablation of an orthodromic reciprocating tachycardia might falsely suggest the presence of a second (septal) accessory pathway (AP) during tachycardia or the successful ablation of the left lateral AP under ventricular pacing despite persistent and unaffected AP conduction. Complete or partial intra-atrial block should be suspected when an abrupt change in the atrial activation sequence is noted during catheter ablation at the posterolateral and lateral aspects of the mitral annulus. The correct anatomical position of the CS catheter plays a vital role in the differential diagnosis of this situation.

A 58-year-old man with previous inferior myocardial infarction (MI) was referred for cardiac resynchronization therapy pacemaker (CRT-P) for decreased left ventricular ejection fraction (LVEF; 45%) and left bundle branch block (LBBB) (Figure 1). He had New York Heart Association Class I functional classification but palpitation for 3 months. General physical and cardiac examinations were normal. On the admission day, the electrocardiogram showed a narrow QRS rhythm with and without tachycardia (Figures 2 and 3). Would you recommend or consider a CRT-P device or a CRT defibrillator or only an implantable cardioverter defibrillator (ICD) based on these clinical and electrocardiographic findings, or ablation or medical therapy only.

A 78-year-old man suffering from gastric cancer with ischemic cardiomyopathy and recurrent ICD shocks consented to ventricular tachycardia (VT) ablation. He had a previous endocardial VT ablation 1 year ago, and a stereotactic radioablation for his recurrent VT 4 months ago. We planned again left ventricular endocardial mapping for his incessant slow VT suggesting an apical exit site (Figure 1A). However, the activation mapping of LV did not cover the whole VT cycle length, and we decide to map the right ventricular septal side instead of the epicardial access due to the patient's poor frailty. Fortunately, the mid-diastolic potential (MDP) was acquired in an unusual position (Figures 1A and 1B); however, the pericardial location of the mapping catheter was confirmed fluoroscopically (Figures 1C and 1D). An urgent surgical consultation was called for, and operative preparations were initiated. However, since no pericardial tamponade occurred and blood pressure remained stable, we continued the endo-epicardial ablation by ablating the MDP (Video 1).

Günümüzde fosil yakıtlar, petrol ürünleri ve benzeri sistemler, özellikle soğutucu gazlar, ozon tabakasına ciddi zararlar vermekte ve küresel ısınmaya neden olmaktadır. Özellikle Küresel Isınma Katsayısı (GWP) ve ozon tabakası hasar potansiyel katsayısı (ODP) günümüzün en önemli konuları arasında yer almaya devam etmektedir. Bilim adamları ve öncü devletler çözüm olarak güneş enerjisi, rüzgâr enerjisi ve nükleer enerji gibi yenilenebilir kaynaklara yönelik çalışmalar yapsa da, küresel ısınma ve ozon tabakası riski hala önemli bir problem olarak karşımıza çıkmaktadır.Genel olarak soğutucu akışkanların bu olumsuz etki üzerinde çarpan etkisi yaratması araştırmacıları farklı alternatif gazları araştırmaya itmiştir. Bu zararlı gazların başında R22, R12, R11, R134A vb. gelir. Bu tür gazlar ozon tabakasına ciddi şekilde zarar verir. Bu nedenle, kullanımları kademeli olarak kısıtlanır veya yasaklanır. Araştırmalar sonucunda, amonyak ve CO2 gibi geçmişte bilinen ve halen üzerinde çalışılan gazlardan yararlanma fikri ortaya çıkmıştır. CO2, ucuzdur, doğada bol miktarda bulunur, toksik değildir ve sıvı olarak taşınabilir. Birçok yönden alternatiflerinden daha iyi performans gösterir. En önemlisi GWP değerinin 1 ve ODP değerinin 0 olmasıdır. Konvansiyonel gazlı soğutmalı akışkanlara göre bu oran çok düşüktür. Diğer avantajlı yönlerinden bir tanesi de kullanım alanı olarak öne çıkmaktadır. Özellikle hassas elektronik cihazların soğutulması gibi uygulamalarda kullanılmaya başlanmıştır. Örneğin, İsviçre'deki CERN projesinde yüksek hassasiyetli soğutma gerektiren cihazlarda CO2’li soğutma uygulamalarına başlanmıştır. Ayrıca İngiltere'de yaygın olarak kullanılan gaz soğutmalı reaktörlerde de yoğun olarak kullanılmaktadır. Birçok araştırmacının CO2 üzerinde yaptığı çalışmaların sonucunda CO2’nin çift fazlı kaynamalı akış durumunda çekirdekli kaynama (nükleotit) bölgesinde veriminin en yüksek olduğu kanıtlanmıştır. CO2’nin nükleoit bölgesinde birçok faz ortaya çıkmaktadır. Örneğin, kuru fazlı akış, dairesel fazlı akış, kesikli-dalga fazlı akış, kabarcık fazlı akış vb. birçok faz vardır. Araştırmacılar, CO2’nin hangi faz aralığında daha verimli çalıştığını anlamak için deneysel ve teorik olarak farklı yöntemler geliştirmiş ve farklı korelasyonlar ortaya koymuş veya mevcut korelasyonları daha da geliştirerek en yüksek doğrulukta ısı transfer katsayısını veren korelasyonu bulmaya çalışmışlardır. Ancak, 90%'ın üzerinde doğruluk oranına sahip bir çalışma henüz elde edilememiştir. Araştırmacılar, neredeyse benzer test koşulları altında bile meydana gelen mantıksız sapmaların nedenini açıklayamamıştır. Farklı çalışmalarda elde edilen deneysel veriler, farklı ısı transfer katsayıları ortaya çıkarmıştır. Yüksek doğrulukta bir korelasyon ortaya koymak ve bunu klasik matematiksel veya nümerik yöntemlerle ispatlamak çok zordur. Tez çalışması CO2 için yeni bir ısı transfer katsayısı korelasyonu ortaya koyma amacı taşımaktadır. Bu çalışmada yapay zekâ kullanılarak 80%'in üzerinde doğrulukla bir ısı transfer katsayı modeli çıkarılmaya çalışılacaktır. Modelde kullanılan veriler daha önce laboratuvar ortamlarında elde edilmiş deneysel veriler olacaktır. Modelde, nükleotid bölgesinde ortaya çıkan tüm fazları kapsayan ortak bir korelasyon geliştirilecektir. Bu korelasyon genel olarak tüm fazları kapsayacağından, her aşama için ayrı ayrı oluşturulmaya çalışılan mevcut korelasyonlara alternatif olarak araştırmacılara kolaylık sağlayacaktır. Çok katmanlı algılama yöntemi (MLP), Genetik algoritma (GA) ve faktör analizi sırayla kullanılacaktır.Böylelikle, mevcut klasik korelasyonlara alternatif bir korelasyon ortaya çıkarılmış olacaktır. Today, fossil fuels, petroleum products, and similar systems, especially refrigerant gases, cause severe damage to the ozone layer and cause global warming. Especially the Global Warming Coefficient (GWP) and ozone layer damage potential coefficient (ODP) continue to be among today's most critical issues. Although scientists and pioneering states work on renewable resources such as solar, wind, and nuclear energy as a solution, the risk of global warming and the ozone layer is still a significant problem.In general, the fact that refrigerants have a multiplier effect on this adverse effect has pushed researchers to investigate different alternative gases. Some of these harmful gases are R22, R12, R11, R134A, etc. Such gases seriously damage the ozone layer. Therefore, their use is gradually restricted or banned. As a result of the research, the idea of utilizing gases such as ammonia and CO2, known in the past and still being studied, emerged. CO2 is inexpensive, abundant in nature, non-toxic and, transportable. In many ways, it outperforms its alternatives. The most important is that the GWP value is unity, and the ODP value is 0. This ratio is very low compared to conventional gas-cooled fluids.One of its other advantageous aspects is its usage area. It has started to be used in applications such as cooling-sensitive electronic devices. For example, in the CERN project in Switzerland, CO2 cooling applications have been started in devices that require high-precision cooling. It is also used extensively in gas-cooled reactors, which are widely used in the UK.As a result of the studies carried out by many researchers on CO2, it has been proven that the efficiency of CO2 is highest in the nucleate boiling region in the case of two-phase boiling flow. Many phases emerge in the nucleate boiling region of CO2. For example, dry phase flow, annular phase flow, pulsed-wave phase flow, bubbly phase flow, etc. There are many phases. Researchers have developed different experimental and theoretical methods to understand which phase range CO2 works more efficiently. They have revealed different correlations or tried to find the correlation that gives the highest accuracy heat transfer coefficient by further improving the existing correlations. However, a study with an accuracy rate above 90% has yet to be obtained. Experimental data obtained in different studies revealed different heat transfer coefficients. The researchers could not explain why the unreasonable deviations occurred even under similar test conditions. Establishing a highly accurate correlation and proving it using classical mathematical or numerical methods is almost impossible.The thesis study aims at developing a new heat transfer coefficient correlation for CO2. In this study, a heat transfer coefficient model is worked out, which yields an accuracy of over 80%. The data used in the model will be experimental data previously obtained in laboratory environments. A common correlation in the model is developed, covering all phases in the nucleate boiling region. Since this correlation will cover all stages in general, it will provide convenience to researchers as an alternative to existing correlations that are tried to be created separately for each stage. Multi-layered detection method (MLP), Genetic Algorithm (GA), and factor analysis are going to be used in order. Thus, an alternative correlation will be proposed and substituted with the existing correlations.

Tachycardia-induced tachycardia, or so-called double tachycardia, appears to be a relatively rare condition. The underlying mechanism for stable beat-to-beat cycle length variability (alternans) in atrial tachycardia has been sparsely reported.

The present study was conducted to group some paddy cultivars in terms of their zinc nutritional capabilities and to identify the best zinc nutrition traits of these cultivars. Present experiments were conducted with 5 different paddy cultivars (Oryza sativa L. cv Biga İncisi, Osmancık 97, Hamzadere, Ronaldo, Edirne). In the experiment, a complete nutrient solution containing 0 and 2.0 µM Zn in the form of zinc sulphate heptahydrate was applied to lime-free (0 % CaCO3) and lime-added (4 % CaCO3) quartz sand media. Experiments were conducted in 5×2×2 factorial design with 3 replications. At the end of the experiments, zinc nutrition traits of paddy cultivars were determined. Both in lime-free and lime-added sand media, Biga İncisi paddy cultivar was identified as tolerant to zinc deficiency. Ronaldo paddy cultivar was identified as the most sensitive cultivar to zinc deficiency. It was observed that in terms of investigated 15 zinc nutrition traits, 5 different paddy cultivars grown under zinc deficiency (Zn0) conditions were gathered under 2 main groups. Biga İncisi and Edirne cultivars constituted the first group; Osmancık-97 and Hamzadere cultivars constituted the second group. On the other hand, Ronaldo cultivar was found to be closer to the second group including Osmancık-97 and Hamzadere cultivars. The closest paddy cultivars grown under zinc deficiency conditions in terms of investigated traits were identified as Biga İncisi and Edirne cultivars; on the other hand, the furthest cultivars were identified as Biga İncisi and Osmancık-97 cultivars. For Osmancık-97 and Biga İncisi paddy cultivars, SPAD readings in lime-added sand media were identified as the best zinc nutrition traits. For Edirne cultivar, zinc ratio transported to shoot and shoot relative dry matter content in lime-added media were identified as the best zinc nutrition traits. For Hamzadere cultivar, relative chlorophyll content in lime-free media was identified as the best zinc nutrition.