Near Vertical Incidence Skywave (NVIS) Antenna and Propagation Research in The Netherlands

Near Vertical Incidence Skywave (NVIS) propagation can be used to realize radio communication without the need for an intermediate network. NVIS uses the ionosphere as a reflector to cover a large area (200 × 200 km) around the transmitter, on frequencies ranging from 3 to 10 MHz. NVIS is therefore used for telecommunication in areas that lack a telecommunication infrastructure, or in areas where the existing infrastructure is destroyed by a large scale disaster, such as the 2005 flooding of New Orleans. We will give an overview of the NVIS research performed in The Netherlands

Assessment of mitral valve regurgitation by cardiovascular magnetic resonance imaging

Mitral regurgitation (MR) is a common valvular heart disease and is the second most frequent indication for heart valve surgery in Western countries. Echocardiography is the recommended first-line test for the assessment of valvular heart disease, but cardiovascular magnetic resonance imaging (CMR) provides complementary information, especially for assessing MR severity and to plan the timing of intervention. As new CMR techniques for the assessment of MR have arisen, standardizing CMR protocols for research and clinical studies has become important in order to optimize diagnostic utility and support the wider use of CMR for the clinical assessment of MR. In this Consensus Statement, we provide a detailed description of the current evidence on the use of CMR for MR assessment, highlight its current clinical utility, and recommend a standardized CMR protocol and report for MR assessment

Intracardiac 4D flow MRI in congenital heart disease : recommendations on behalf of the ISMRM flow & motion study group

Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2019.Cardiovascular Aspects of Radiolog

Reproducibility of left ventricular blood flow kinetic energy measured by four-dimensional flow CMR

Objectives Four-dimensional flow CMR allows for a comprehensive assessment of the blood flow kinetic energy of the ventricles of the heart. In comparison to standard two-dimensional image acquisition, 4D flow CMR is felt to offer superior reproducibility, which is important when repeated examinations may be required. The objective was to evaluate the inter-observer and intra-observer reproducibility of blood flow kinetic energy assessment using 4D flow of the left ventricle in 20 healthy volunteers across two centres in the United Kingdom and the Netherlands. Data description This dataset contains 4D flow CMR blood flow kinetic energy data for 20 healthy volunteers with no known cardiovascular disease. Presented is kinetic energy data for the entire cardiac cycle (global), the systolic and diastolic components, in addition to blood flow kinetic energy for both early and late diastolic filling. This data is available for reuse and would be valuable in supporting other research, such as allowing for larger sample sizes with more statistical power for further analysis of these variables

Normal and reference values for cardiovascular magnetic resonance-based pulse wave velocity in the middle-aged general population

Background Aortic stiffness, assessed through pulse wave velocity (PWV), is an independent predictor for cardiovascular disease risk. However, the scarce availability of normal and reference values for cardiovascular magnetic resonance imaging (CMR) based PWV is limiting clinical implementation. The aim of this study was to determine normal and reference values for CMR assessed PWV in the general population. Methods From the 2,484 participants of the Netherlands Epidemiology of Obesity (NEO) study that have available CMR-PWV data, 1,394 participants free from cardiovasculard disease, smokers or treatment for diabetes, hypertension or dyslipidaemia were selected (45-65 years, 51% female). Participants were divided into sex, age and blood pressure (BP) subgroups. Normal values were specified for participants with a BP = 130/80 and = 140/90 mmHg). Differences between groups were tested with independent samples t-test or ANOVA. Due to an oversampling of obese individuals in this study, PWV values are based on a weighted analysis making them representative of the general population. Results Normal mean PWV was 6.0 m/s [95% CI 5.8-6.1]. PWV increased with advancing age and BP categories (both p 140/90 mmHg women had a higher PWV (p = 0.005). The interpercentile ranges were smaller for participants = 55 years, indicating an increasing variability of PWV with age. PWV upper limits were particularly elevated in participants >= 55 years old in the high blood pressure subgroups. Conclusion This study provides normal and reference values for CMR-assessed PWV per sex, age and blood pressure category in the general population.Clinical epidemiolog

Estimated pulse wave velocity (ePWV) as a potential gatekeeper for MRI-assessed PWV: a linear and deep neural network based approach in 2254 participants of the Netherlands Epidemiology of Obesity study

Pulse wave velocity (PWV) assessed by magnetic resonance imaging (MRI) is a prognostic marker for cardiovascular events. Prediction modelling could enable indirect PWV assessment based on clinical and anthropometric data. The aim was to calculate estimated-PWV (ePWV) based on clinical and anthropometric measures using linear ridge regression as well as a Deep Neural Network (DNN) and to determine the cut-off which provides optimal discriminative performance between lower and higher PWV values. In total 2254 participants from the Netherlands Epidemiology of Obesity study were included (age 45-65 years, 51% male). Both a basic and expanded prediction model were developed. PWV was estimated using linear ridge regression and DNN. External validation was performed in 114 participants (age 30-70 years, 54% female). Performance was compared between models and estimation accuracy was evaluated by ROC-curves. A cut-off for optimal discriminative performance was determined using Youden's index. The basic ridge regression model provided an adjusted R-2 of 0.33 and bias of < 0.001, the expanded model did not add predictive performance. Basic and expanded DNN models showed similar model performance. Optimal discriminative performance was found for PWV < 6.7 m/s. In external validation expanded ridge regression provided the best performance of the four models (adjusted R-2: 0.29). All models showed good discriminative performance for PWV < 6.7 m/s (AUC range 0.81-0.89). ePWV showed good discriminative performance with regard to differentiating individuals with lower PWV values (< 6.7 m/s) from those with higher values, and could function as gatekeeper in selecting patients who benefit from further MRI-based PWV assessment.Clinical epidemiolog

Partitioning the Heritability of Tourette Syndrome and Obsessive Compulsive Disorder Reveals Differences in Genetic Architecture

The direct estimation of heritability from genome-wide common variant data as implemented in the program Genome-wide Complex Trait Analysis (GCTA) has provided a means to quantify heritability attributable to all interrogated variants. We have quantified the variance in liability to disease explained

Elevation angle measurements during a local contest

In Holland two national contests are held on a yearly basis. One is the PACC contest in February, aimed at contacts with other countries. The other is the PA Trophy contest, where only traffic between Dutch stations is allowed on the 75 meters and 40 meters bands. Holland measures only 130 x 200 miles, so in some other countries this would probably be considered a ‘local contest’. Out of sheer curiousity some radioamateurs of the Radioclub of the Dutch Radio Agency participated in a very special way in the PA Trophy contest. Using a professional shortwave direction finding installation elevation angles of as many participants as possible were measured. The results are presented here

Impact of a solar X-Flare on NVIS propagation: daytime characteristic wave refraction and nighttime scattering.

An experiment to investigate several characteristics of near vertical incidence skywave (NVIS) propagation (polarization, characteristic waves and their isolation, elevation angles, and radio noise) over a distance of 105 km and at 7 MHz was performed in The Netherlands. Daytime characteristic wave propagation with almost perfectly circular polarization and high isolation values had been expected from our earlier work and could now be demonstrated. Simultaneous elevation angle measurements showed pure single-hop F2-layer reflection and no ground wave component. Nighttime scattering with loss of polarization was observed when the critical frequency (fxF2) dropped below the operating frequency. The "Happy Hour" propagation, shown in our previous work [2], was confirmed with new measurements. The occurrence of a solar X-ray flare during the measurements provided a unique opportunity to compare the observations in a quiet ionosphere with those during a short wave fadeout (SWF). During the SWF, the signal strength of the ordinary wave dropped 35 dB and that of the extraordinary wave 45 dB. This lasted 15 min; recovery to normal signal levels took 35 min. The radio noise level, which was already low in the quiet rural measurement location, dropped another 12 dB during the SWF, with the remainder being generated locally. This proves that in a quiet rural location the major part of the radio noise arrives via the ionosphere

Ascending aorta curvature and flow displacement are associated with accelerated aortic growth at long-term follow-up: a MRI study in Marfan and thoracic aortic aneurysm patients

Background: Aortic aneurysm formation is associated with increased risk of aortic dissection. Current diagnostic strategies are focused on diameter growth, the predictive value of aortic morphology and function remains underinvestigated. We aimed to assess the long-term prognostic value of ascending aorta (AA) curvature radius, regional pulse wave velocity (PWV) and flow displacement (FD) on aortic dilatation/elongation and evaluated adverse outcomes (proximal aortic surgery, dissection/rupture, death) in Marfan and non-syndromic thoracic aortic aneurysm (NTAA) patients.Methods: Long-term magnetic resonance imaging (MRI) and clinical follow-up of two previous studies consisting of 21 Marfan and 40 NTAA patients were collected. Baseline regional PWV, AA curvature radius and normalized FD were assessed as well as diameter and length growth rate at follow-up. Multivariate linear regression was performed to evaluate whether baseline predictors were associated with aortic growth.=.Results: Of the 61 patients, 49 patients were included with MRI follow-up (n = 44) and/or adverse aortic events (n = 7). Six had undergone aortic surgery, no dissection/rupture occurred and one patient died during follow-up. During 8.0 [7.3-10.7] years of follow-up, AA growth rate was 0.40 +/- 0.31 mm/year. After correction for confounders, AA curvature radius (p = 0.01), but not FD or PWV, was a predictor of AA dilatation. Only FD was associated with AA elongation (p = 0.01).Conclusion: In Marfan and non-syndromic thoracic aortic aneurysm patients, ascending aorta curvature radius and flow displacement are associated with accelerated aortic growth at long-term follow-up. These markers may aid in the risk stratification of ascending aorta elongation and aneurysm formation.</p