The sounds associated with the five classical Korotkoff phases are clinically important for measuring systolic and diastolic blood pressures. The frequency ranges of the sounds have already been described simply using the overall peak frequencies within each phase by Fourier methods. However, such analysis may be missing potentially useful clinical information. The aim of this study was to compare features associated with the different phases of the Korotkoff sounds obtained during blood pressure measurement using a joint time-frequency analysis (JTFA) technique. A single operator recorded Korotkoff sounds from 25 healthy subjects using a measurement system comprising cardiology stethoscope, microphone, amplifier and recording system for computer sound digitization, and a MiniDisc system for playback to the cardiologist for Korotkoff phase classification. We have shown that using this system the phase classification by the cardiologist is repeatable, with no significant differences found in the number of sounds allocated to phases on two separate recording assessments. The digitized sounds were processed using a MATLAB-based short-time Fourier transform JTFA technique and differences in time, frequency and amplitude characteristics between the phases compared. It was found that on average, phase III had the largest overall amplitude and high frequency energy. Phase II had the greatest high frequency component and longest murmur, and was visibly the most complex phase in terms of time and frequency content. In contrast, phases IV and V had the lowest amplitude and frequency components. Overall, the statistically significant transitions between phases were: phase I to II with increases in high frequency (224 to 275 Hz) (p < 0.01) and sound duration (49 to 98 ms) (p < 0.0001), II to III with a significant decrease in sound duration (to 37 ms) (p < 0.0001), III to IV with decreases in maximum amplitude (0.95 to 0.25), highest frequency (262 to 95 Hz), and relative high frequency energy of the sounds (0.61 to 0.10) (all p < 0.0001), and IV to V with decreases in the maximum amplitude (0.25 to 0.13) (p < 0.0002) and high frequency energy (0.10 to 0.03) (p < 0.005). This study has demonstrated that joint time-frequency analysis of Korotkoff sounds was able to identify characteristic differences associated with the different phases classified by the expert cardiologist. Ultimately, exploiting the joint time and frequency characteristics of the sounds may improve blood pressure measurement and help to assess the stiffness of the peripheral arteries.

The EU’s new trade strategy promises to advance open strategic autonomy that is to balance the benefits of economic interdependence with growing demands to manage Europe’s exposure to the risks it entails. What explains these shifting priorities? This article situates open strategic autonomy in the theoretical debates of International Political Economy (IPE) literature on economic interdependence and geoeconomics to aid our understanding of the debates ensnaring economic strategy in the EU, but also related debates in the United States, China and elsewhere. This framework, the article argues, helps us understand changing strategic priorities in economic policy by reference to wider structural shifts engulfing the global economy. It then identifies four priority targets of EU economic policy in which (new) autonomous policies are forthcoming: (i) tackle economic distortions; (ii) defend against economic coercion; (iii) link with values and sustainability; and (iv) protect critical assets and supply chains. These observations build towards addressing the main research question: Has open strategic autonomy turned a corner on EU principles of openness, liberalization and international cooperation? trade and investment, European Union, geoeconomics, International Political Economy

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Abstract. Pulse-echo ultrasound signal formation can be simulated by numerical emulation of the process chain: emit signal -electromechanical emit transformation -wave propagation and scattering -electromechanical receive transformation -receive signal. The simulation software Field II is indented for simulation of linear ultrasound systems. We present an extension to Field II that enables the inclusion of nonlinear oscillations of ultrasound contrast agent bubbles into the simulation. An example is given for contrast agent enhanced imaging of a virtual vessel phantom probed by a linear array transducer.