Computerized ionospheric tomography with the IRI model

Computerized ionospheric tomography (CIT) is a method to estimate ionospheric electron density distribution by using the global positioning system (GPS) signals recorded by the GPS receivers. Ionospheric electron density is a function of latitude, longitude, height and time. A general approach in CIT is to represent the ionosphere as a linear combination of basis functions. In this study, the model of the ionosphere is obtained from the IRI in latitude and height only. The goal is to determine the best representing basis function from the set of Squeezed Legendre polynomials, truncated Legendre polynomials, Haar Wavelets and singular value decomposition (SVD). The reconstruction algorithms used in this study can be listed as total least squares (TLS), regularized least squares, algebraic reconstruction technique (ART) and a hybrid algorithm where the reconstruction from the TLS algorithm is used as the initial estimate for the ART. The error performance of the reconstruction algorithms are compared with respect to the electron density generated by the IRI-2001 model. In the investigated scenario, the measurements are obtained from the IRI-2001 as the line integral of the electron density profiles, imitating the total electron content estimated from GPS measurements. It has been observed that the minimum error between the reconstructed and model ionospheres depends on both the reconstruction algorithm and the basis functions where the best results have been obtained for the basis functions from the model itself through SVD. © 2007 COSPAR

Algorithms and basis functions in tomographic reconstruction of ionospheric electron density

Computerized ionospheric tomography (CIT) is a method to investigate ionosphere electron density in two or three dimensions. This method provides a flexible tool for studying ionosphere. Earth based receivers record signals transmitted from the GPS satellites and the computed pseudorange and phase values are used to calculate Total Electron Content (TEC). Computed TEC data and the tomographic reconstruction algorithms are used together to obtain tomographic images of electron density. In this study, a set of basis functions and reconstruction algorithms are used to investigate best fitting two dimensional tomographic images of ionosphere electron density in height and latitude for one satellite and one receiver pair. Results are compared to IRI-95 ionosphere model and both receiver and model errors are neglected

Ionospheric total electron content estimation using IONOLAB method [IONOLAB tekniǧi ile i̇yonosfer toplam elektron i̇çerigi kestirimi]

Ionosphere which is an important atmospheric layer for HF and satellite communications, can be investigated through Total Electron Content (TEC). Global Positioning System provides cost-effective means for TEC estimation. Regularized TEC estimation method (D-TEI) is developed to estimate high resolution, robust TEC values. The method combines measurements of GPS satellites above 10° elevation limit and estimates can be obtained with 30 s time resolution. In this paper, parameters that are used in D-TEI method such as ionospheric height, weighting function, and satellite receiver biases are studied. It is found that TEC estimation results of D-TEI method is almost independent of ionospheric height. Different weighting functions are tried and the weighting function that minimizes non-ionospheric effects is selected. By using satellite and receiver biases in the correct form consistent TEC estimation results are obtained with IGS analysis centers. In this paper, the method is improved to include phase measurements. Taking either pseudorange or phase measurements as input, high resolution, robust TEC estimates are obtained using D-TEI method

Baseline clinical characteristics and patient profile of the TURKMI registry: Results of a nation-wide acute myocardial infarction registry in Turkey

PubMed: 32628144Objective: The TURKMI registry is designed to provide insight into the characteristics, management from symptom onset to hospital discharge, and outcome of patients with acute myocardial infarction (MI) in Turkey. We report the baseline and clinical characteristics of the TURKMI population. Methods: The TURKMI study is a nation-wide registry that was conducted in 50 centers capable of percutaneous coronary intervention selected from each EuroStat NUTS region in Turkey according to population sampling weight, prioritized by the number of hospitals in each region. All consecutive patients with acute MI admitted to coronary care units within 48 hours of symptom onset were prospectively enrolled during a predefined 2-week period between November 1, 2018 and November 16, 2018. Results: A total of 1930 consecutive patients (mean age, 62.0±13.2 years; 26.1% female) with a diagnosis of acute MI were prospectively enrolled. More than half of the patients were diagnosed with non-ST elevation MI (61.9%), and 38.1% were diagnosed with ST elevation MI. Coronary angiography was performed in 93.7% and, percutaneous coronary intervention was performed in 73.2% of the study population. Fibrinolytic therapy was administered to 13 patients (0.018%). Aspirin was prescribed in 99.3% of the patients, and 94% were on dual antiplatelet therapy at the time of discharge. Beta blockers were prescribed in 85.0%, anti-lipid drugs in 96.3%, angiotensin converting enzyme inhibitors in 58.4%, and angiotensin receptor blockers in 7.9%. Comparison with European countries revealed that TURKMI patients experienced MI at younger ages compared with patients in France, Switzerland, and the United Kingdom. The most prevalent risk factors in the TURKMI population were hypercholesterolemia (60.2%), hypertension (49.5%), smoking (48.8%), and diabetes (37.9%). Conclusion: The nation-wide TURKMI registry revealed that hypercholesterolemia, hypertension, and smoking were the most prevalent risk factors. TURKMI patients were younger compared with patients in European Countries. The TURKMI registry also confirmed that current treatment guidelines are largely adopted into clinical cardiology practice in Turkey in terms of antiplatelet, anti-ischemic, and anti-lipid therapy. ©Copyright 2020 by Turkish Society of CardiologyAcknowledgments: TURKMI is an investigator-initiated study sponsored by the Turkish Society of Cardiology that receives major funding from Astra-Zeneca Company for this project

Response to letter regarding article, "Efficacy and Safety of Apixaban Compared With Warfarin at Different Levels of Predicted International Normalized Ratio Control for Stroke Prevention in Atrial Fibrillation"

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