Hüseyin Altuğ Çakmak

Metalorganic chemical vapor deposition growth and thermal stability of the AlInN/GaN high electron mobility transistor structure

The AlxIn1−xN barrier high electron mobility transistor (HEMT) structure has been optimized with varied barrier composition and thickness grown by metalorganic chemical vapor deposition. After optimization, a transistor structure comprising a 7 nm thick nearly lattice-matched Al0.83In0.17 N barrier exhibits a sheet electron density of 2.0 × 10 13 cm −2 with a high electron mobility of 1540 cm 2 V −1 s −1 .A n Al0.83In0.17N barrier HEMT device with 1 μm gate length provides a current density of 1.0 A mm −1 at VGS = 0 V and an extrinsic transconductance of 242 mS mm −1 , which are remarkably improved compared to that of a conventional Al0.3Ga0.7N barrier HEMT. To investigate the thermal stability of the HEMT epi-structures, post-growth annealing experiments up to 800 ◦ C have been applied to Al0.83In0.17N and Al0.3Ga0.7N barrier heterostructures. As expected, the electrical properties of an Al0.83In0.17N barrier HEMT structure showed less stability than that of an Al0.3Ga0.7N barrier HEMT to the thermal annealing. The structural properties of Al0.83In0.17N/GaN also showed more evidence for decomposition than that of the Al0.3Ga0.7N/GaN structure after 800 ◦ C post-annealing. (Some figures in this article are in colour only in the electronic version)

Evolution of the mosaic structure in InGaN layer grown on a thick GaN template and sapphire substrate

The InxGa1−xN epitaxial layers, with indium (x) concentration changes between 0.16 and 1.00 (InN), were grown on GaN template/(0001) Al2O3 substrate by metal organic chemical vapour deposition. The indium content (x), lattice parameters and strain values in the InGaN layers were calculated from the reciprocal lattice mapping around symmetric (0002) and asymmetric (10–15) reflection of the GaN and InGaN layers. The characteristics of mosaic structures, such as lateral and vertical coherence lengths, tilt and twist angle and heterogeneous strain and dislocation densities (edge and screw dislocations) of the InGaN epilayers and GaN template layers were investigated by using high-resolution X-ray diffraction (HR-XRD) measurements. With a combination of Williamson–Hall (W-H) measurements and the fitting of twist angles, it was found that the indium content in the InGaN epilayers did not strongly effect the mosaic structures’ parameters, lateral and vertical coherence lengths, tilt and twist angle, or heterogeneous strain of the InGaN epilayers.

Prognostic value of CHA2DS2-VASc score in patients with ST-segment elevation myocardial infarction who underwent primary percutaneous coronary intervention

Objectives The aim of the study was to investigate the relationship between CHA2DS2-VASc score and in-hospital and long-term all-cause and cardiovascular mortality in patients with STEMI who underwent primary PCI. Methods In this retrospective study, 604 patients, admitted to the emergency department with a diagnosis of STEMI, were included. The study patients were divided into three risk groups according to CHA2DS2-VASc score: low-risk group (1 point), moderate-risk group (2 points), and high-risk group (3 points and higher), respectively. Results The mean follow-up time was 680 ± 286 days. In the high-risk group, the rates of in-hospital and long-term all-cause and cardiovascular mortality were higher than in the other groups. The Kaplan-Meier curves for the group with CHA2DS2-VASc scores > 2 indicated a significantly shorter long-term survival (P <0.001). In the receiver operating characteristic curve analysis, CHA2DS2-VASc scores > 2 were identified as an effective predictive cut-off point for all-cause mortality in STEMI (area under curve = 0.850, 95% confidence interval: 0.819–0.878, P< 0.001). CHA2DS2-VASc score > 2 yielded a sensitivity of 70.18% and a specificity of 83%. Conclusion The CHA2DS2-VASc is a simple and easily calculated score that provides an additional level of risk stratification beyond that provided by conventional risk scores in predicting in-hospital and long-term all-cause and cardiovascular mortality in STEMI.

Assessment of relationships between novel inflammatory markers and presence and severity of preeclampsia: Epicardial fat thickness, pentraxin-3, and neutrophil-to-lymphocyte ratio

ABSTRACT Objective: The aim of this study was to evaluate the relation of three new inflammatory markers with presence and severity of preeclampsia and to compare the predictive values of all markers for presence of this setting. Methods: In this study, a total of 100 consecutive pregnants with a diagnosis of preeclampsia and 40 healthy pregnants between October 2014 and April 2015 were included. Epicardial fat tissue was calculated by two-dimensional transthoracic echocardiography, and pentraxin-3 and neutrophil-to-lymphocyte ratio were measured by using an enzyme-linked immunosorbent assay method and routine blood count analysis, respectively. Results: Epicardial fat thickness (p < 0.001), pentraxin-3 (p < 0.001), and neutrophil-to-lymphocyte ratio (p < 0.001) were found to be significantly increased in the preeclampsia as compared to the healthy pregnants. Furthermore, epicardial fat thickness (p = 0.002), pentraxin-3 (p < 0.001), and neutrophil-to-lymphocyte ratio (p < 0.001) were significantly elevated in the severe preeclampsia compared to mild preeclampsia. In the multivariate analysis, epicardial fat thickness (p = 0.013), pentraxin-3 (p = 0.04), and neutrophil-to-lymphocyte ratio (p < 0.001) were found as significant independent predictors of presence of preeclampsia after adjusting for other risk factors. Conclusion: Epicardial fat thickness, neutrophil-to-lymphocyte ratio, and pentraxin-3 are important markers that provide an additional information beyond that provided by conventional methods in predicting presence and severity of preeclampsia.

Mosaic Structure Characterization of the AlInN Layer Grown on Sapphire Substrate

The 150 nm thick, (0001) orientated wurtzite-phase Al1−xInxN epitaxial layers were grown by metal organic chemical vapor deposition on GaN (2.3 µm) template/(0001) sapphire substrate. The indium (x) concentration of the Al1−xInxN epitaxial layers was changed as 0.04, 0.18, 0.20, 0.47, and 0.48. The Indium content (x), lattice parameters, and strain values in the AlInN layers were calculated from the reciprocal lattice mapping around symmetric (0002) and asymmetric (10–15) reflection of the AlInN and GaN layers. The mosaic structure characteristics of the AlInN layers, such as lateral and vertical coherence lengths, tilt and twist angle, heterogeneous strain, and dislocation densities (edge and screw type dislocations) of the AlInN epilayers, were investigated by using high-resolution X-ray diffraction measurements and with a combination of Williamson-Hall plot and the fitting of twist angles.

[EUROASPIRE-IV: European Society of Cardiology study of lifestyle, risk factors, and treatment approaches in patients with coronary artery disease: Data from Turkey].

Sexual activity is an important component of patient and partner quality of life for men and women with cardiovascular disease, including many elderly patients. Older adults desire sexual intimacy when there is a partner and a health status that allows sexual relationships. Older individuals desire to love and enjoy sexual activity in relation to personal circumstances, and when health status allows them to experience close relations, most often within marriage especially in our country. Normal changes occur in the phases of sexual cycle with aging, male erectile dysfunction and female sexual dysfunction increase with age. Elderly patients are often affected by multiple organic diseases which can interfere with sexual function especially cardiovascular disease. Treating those disorders or modifying lifestyle-related risk factors may help prevent sexual dysfunction in the elderly. Sexuality is important for older adults and physicians should give their patients opportunity to voice their concerns with sexual function and offer them alternatives for evaluation and treatment. Asking about sexual health remains difficult or embarrassing for many physicians; in addition, many patients find it difficult to raise sexual issues with their doctor.

Localization of Accessory Pathway Using Tissue Doppler Echocardiography Prior Radiofrequency Ablation in Patients with Wolff-Parkinson-White Syndrome

Objective: We sought to examine the diagnostic accuracy of tissue Doppler imaging (TDI) for the localization of the accessory pathways (APs) in Wolff-Parkinson-White (WPW) syndrome. Material and Methods: We prospectively studied 35 patients with evidence of pre-excitation on electrocardiography. Patients were categorized into three groups according to the site of the AP: left ventricular free wall; septal; and right ventricular free wall. The recordings obtained using TDI from the lateral mitral annulus, septal annulus, and lateral tricuspid annulus were respectively compared with the electrophysiological study (EPS) results for the location of the AP. Electromechanical interval (p-Sm) was defined as the time difference between the onset of the p wave and the onset of regional myocardial contraction (Sm) on echocardiography. Results: In patients with left free access in EPS, electromechanical interval (pre-p-Sm) in the lateral mitral annulus was significantly shorter in the other two regions (septal annulus, and lateral tricuspid annulus) in TDI before treatment (p=0.0001). In patients with septal AP and right free AP detected at EPS, the pre-p-Sm interval was shorter, respectively, at the septal annulus and lateral tricuspid annulus, but was not statistically significant, due to the small numbers of patients in both regions. Conclusion: The p-Sm interval in TDI before the ablation procedure, specifically in patients having a left free AP, was found to be short due to early stimulus. This was especially detected without using a free electrocardiogram (ECG) algorithm. The prediction of AP in TDI may play an important role in planning and performing the radiofrequency catheter ablation (RFCA).

Usefulness of the platelet-to-lymphocyte ratio in predicting long-term cardiovascular mortality in patients with peripheral arterial occlusive disease

Introduction Inflammation and increased platelet activation play a crucial role in the initiation and progression of atherosclerosis. Platelet-to-lymphocyte ratio (PLR) has recently been reported as a new independent predictor for major adverse cardiovascular events in cardiovascular diseases. Aim To investigate the relation between PLR and cardiovascular mortality in patients with intermittent claudication or critical limb ischemia (CLI) or both. Material and methods In our retrospective study, 602 consecutive patients who were admitted to a large tertiary hospital with the diagnosis of symptomatic peripheral arterial occlusive disease (PAOD) were included. Patients were divided into two groups according to their PLR as follows: high PLR (PLR > 142) and low PLR (PLR ≤ 142) groups. Results During the follow-up period (median: 33.8 months (interquartile range: 21–45)), 131 deaths occurred out of 602 (21.8%) patients. Cardiovascular mortality was found to be significantly higher in the high PLR group compared to the low PLR group (31.6% vs. 17.2 %; p < 0.001). Even after adjustment for various risk factors, PLR > 142 and age were found to be independent predictors of long-term cardiovascular mortality in Cox regression analysis (hazard ratios (95% confidence interval): 1.03 (1.01–1.04) and 1.04 (1.02–1.06), p < 0.001 and p < 0.001, respectively). Conclusions Platelet-to-lymphocyte ratio, which is one of the parameters of routine complete blood count, reflects increased inflammatory status, platelet activation and aggregation. PLR is a cheap and readily available marker that has the ability to improve risk stratification provided by conventional risk scores in predicting long-term cardiovascular mortality in PAOD.

Extensively Looped Temporary Pacemaker Lead in Pulmonary Artery and Right Heart Chambers: Original Image

pacemaker can be a lifesaving procedure in the emergency setting. The temporary pacemaker lead was inserted to 64 years old male for syncope attacks due to marked pauses. Procedure was performed in emergency setting without floroscopy. During dual chamber permanent pacemaker implantation, temporary pacemaker lead was found as extensive loop in right heart chamber and pulmonary artery trunk and ended in right atrium (Figure 1). Because of the pacemaker dependence, permanent pacemaker active fixation ventricle lead was implanted from left subclavian vein at first. Afterward, temporary pacemaker lead pulled back and active fixation atrial lead was implanted (Figure 2). If this patient had an atrioventricular complete block, than the temporary pacemaker in the atrium would be ineffective. The sinusoidal arrest provided an effective pacemaker activity from atrium. Temporary pacemaker should be implanted under floroscopy. Especially, if temporary pa-