Echocardiography in myocardial infarction : aspects on diastolic function and evaluation by cardiovascular magnetic resonance imaging

Background Echocardiography is routinely used to evaluate patients with known or suspected myocardial infarction (MI). Cardiovascular magnetic resonance imaging (CMR) provides the ability to quantify myocardial infarction size (IS), and to establish an underlying diagnosis in MI cases with nonobstructive coronary arteries (MINOCA). While echocardiography provides valuable information regarding cardiac function, the relationships between how pathology is manifested on CMR, and the information gleaned from echocardiography are not fully explored. The focus of this thesis was 1) to assess diastolic function and mechanics in MI, and 2) to assess the ability of echocardiography to identify patients needing further evaluation by CMR in MINOCA. Methods and results In Study I, a software application was developed for the purpose of facilitating the analysis of diastolic function using the parameterized diastolic filling (PDF) method. Inter- and intraobserver variability was studied using patients from Study III and Study IV. The software was successfully developed and made publicly available at www.echoewaves.org, and inter- and intraobserver reliability was good or excellent for most PDF measures (intraclass correlation coefficient 0.80-0.99). In Study II, an available clinical database of patients undergoing resting and stress echocardiography was used to identify a cohort of patients with normal echocardiographic findings. PDF analysis was performed in 138 patients for the establishment of normal reference values for the method, and presented as sex-specific 95% reference intervals. In Study III, a pre-planned substudy of the RECOND trial, the association between myocardial infarction size (IS) and parameters of diastolic function, and whether the peri-infarction edema of the myocardium at risk (MaR) influenced these relationships was investigated. Weak associations were found between IS and deceleration time (R² = 0.24, p < 0.001), left atrial volume index (R² = 0.13, p = 0.01), and the PDF stiffness parameter k (R² = 0.21, p < 0.001). The only parameter influenced by the addition of MaR was e′ (increase in adjusted R² = 0.08, p = 0.02). The PDF damping parameter c was the only parameter associated with final IS at 6 months follow-up (R² = 0.22, p = 0.001). In Study IV, a pre-planned substudy of the SMINC2 study, the value of normal vs pathological echocardiography, as well as the blood biomarkers hs-TnT and NT-pro-BNP, for selecting patients presenting with MINOCA for further evaluation with CMR was investigated. Pathological echocardiography identified patients with a CMR diagnosis with sensitivity 77%, specificity 38%, positive predictive value 82%, and negative predictive value 30%. At low levels of hs-TnT and NT-pro-BNP, the probability of obtaining a diagnosis by CMR was still substantial (> 25%). Conclusions and summary In summary, a freely available and reliable software application for the application of the PDF method was developed (Study I), and normal reference limits were provided, for use in further clinical research (Study II). IS as measured by CMR does not seem to be a major determinant of diastolic dysfunction after MI, and other factors are likely to be more important (Study III). CMR is a valuable diagnostic tool for the evaluation of patients with MINOCA, even when echocardiographic examinations are normal, and levels of hs-TnT and NT-pro-BNP are low (Study IV)

Mg I emission lines at 12 and 18 micrometer in K giants

The solar Mg I emission lines at 12 micrometer have already been observed and analyzed well. Previous modeling attempts for other stars have, however, been made only for Procyon and two cool evolved stars, with unsatisfactory results for the latter. We present high-resolution observational spectra for the K giants Pollux, Arcturus, and Aldebaran, which show strong Mg I emission lines at 12 micrometer as compared to the Sun. We also present the first observed stellar emission lines from Mg I at 18 micrometer and from Al I, Si I, and presumably Ca I at 12 micrometer. To produce synthetic line spectra, we employ standard non-LTE modeling for trace elements in cool stellar photospheres. We compute model atmospheres with the MARCS code, apply a comprehensive magnesium model atom, and use the radiative transfer code MULTI to solve for the magnesium occupation numbers in statistical equilibrium. We successfully reproduce the observed Mg I emission lines simultaneously in the giants and in the Sun, but show how the computed line profiles depend critically on atomic input data and how the inclusion of energy levels with n > 9 and collisions with neutral hydrogen are necessary to obtain reasonable fits.Comment: 9 pages, 6 figures, accepted for publication in Astronomy & Astrophysic

Investigating the origin of cyclical wind variability in hot, massive stars - II. Hydrodynamical simulations of co-rotating interaction regions using realistic spot parameters for the O giant ξ\xi Persei

OB stars exhibit various types of spectral variability historically associated with wind structures, including the apparently ubiquitous discrete absorption components (DACs). These features have been proposed to be caused either by magnetic fields or non-radial pulsations. In this second paper of this series, we revisit the canonical phenomenological hydrodynamical modelling used to explain the formation of DACs by taking into account modern observations and more realistic theoretical predictions. Using constraints on putative bright spots located on the surface of the O giant $\xi$ Persei derived from high precision space-based broadband optical photometry obtained with the Microvariability and Oscillations of STars (MOST) space telescope, we generate two-dimensional hydrodynamical simulations of co-rotating interaction regions in its wind. We then compute synthetic ultraviolet (UV) resonance line profiles using Sobolev Exact Integration and compare them with historical timeseries obtained by the International Ultraviolet Explorer (IUE) to evaluate if the observed behaviour of $\xi$ Persei's DACs is reproduced. Testing three different models of spot size and strength, we find that the classical pattern of variability can be successfully reproduced for two of them: the model with the smallest spots yields absorption features that are incompatible with observations. Furthermore, we test the effect of the radial dependence of ionization levels on line driving, but cannot conclusively assess the importance of this factor. In conclusion, this study self-consistently links optical photometry and UV spectroscopy, paving the way to a better understanding of cyclical wind variability in massive stars in the context of the bright spot paradigm.Comment: 16 pages, 10 figures, accepted for publication by MNRA

Public R&D Innovation: The Case of Wind Energy in Denmark, Germany and the United Kingdom

This paper examines the impact of public research and development (R&D) support on cost reducing innovation for wind turbine farms in Denmark, Germany and the United Kingdom (UK). First we survey the literature in this field. The literature indicates that in Denmark R&D policy has been more successful than in Germany or the UK in promoting innovation of wind turbines. Furthermore, such studies point out that (subsidy-induced) capacity expansions were more effective in the UK and Denmark in promoting cost-reducing innovation than in Germany. The second part of the paper describes the quantitative analysis of the impact of R&D and the capacity expansion on innovation. This is calculated using the two-factor learning curve (2FLC) model, in which investment cost reductions are explained by cumulative capacity and the R&D based knowledge stock. Time-series data were collected for the three countries and organized as a panel data set. The parameters of the 2FLC model were estimated, focusing on the heterogeneity of the parameters across countries. We arrive at robust estimations of a learning-by-doing rate of 5.4% and a learning-by-searching rate of 12.6%. The analysis underlies the homogeneity of the learning parameters, enhancing the validity of the 2FLC formulation

The effect of O2 impurities on the low temperature radial thermal expansion of bundles of closed single-walled carbon nanotubes

The effect of oxygen impurities upon the radial thermal expansion (ar) of bundles of closed single-walled carbon nanotubes has been investigated in the temperature interval 2.2-48 K by the dilatometric method. Saturation of bundles of nanotubes with oxygen caused an increase in the positive ar-values in the whole interval of temperatures used. Also, several peaks appeared in the temperature dependence ar(T) above 20 K. The low temperature desorption of oxygen from powders consisting of bundles of single-walled nanotubes with open and closed ends has been investigatedComment: 7 pages, 3 figure