Danube University Krems

About: Danube University Krems is a education organization based out in Krems, Niederösterreich, Austria. It is known for research contribution in the topics: Stroke & Population. The organization has 498 authors who have published 1572 publications receiving 68797 citations.

Direct-digital time-domain oscillator stability measurement

Abstract: Oscillators are the pacemaker of digital logic as well as communication systems. For the cooperation of systems equipped with different oscillators, the oscillator stability is of great interest, for instance to parametrize phase tracking loops, or to synchronize carrier frequencies for modulations using phase-shift keying. In most cases the Allan variance is used to describe the stability of oscillators which is measured using a heterodyne measurement system creating a low-frequency beat signal. This paper proposes a direct-digital time-domain oscillator stability measurement method. After capturing the oscillator's signal using a sampling instrument, it is converted into its analytical representation using the Hilbert transform. The low-pass filtered analytical signal is then used to determine the phase of the signal and the exact instants of its zero crossings. Finally, measurements show the feasibility of the proposed approach and analyze its limitations.

The long-term effects of an implantable drop foot stimulator on gait in hemiparetic patients.

Abstract: Drop foot is a frequent abnormality in gait after central nervous system lesions. Different treatment strategies are available to functionally restore dorsal extension during swing phase in gait. Orthoses as well as surface and implantable devices for electrical stimulation of the peroneal nerve may be used in patients who do not regain good dorsal extension. While several studies investigated the effects of implanted systems on walking speed and gait endurance, only a few studies have focussed on the system’s impact on kinematics and long-term outcomes. Therefore, our aim was to further investigate the effects of the implanted system ActiGait on gait kinematics and spatiotemporal parameters for the first time with a 1-year follow-up period. 10 patients were implanted with an ActiGait stimulator, with 8 patients completing baseline and follow-up assessments. Assessments included a 10-m walking test, video-based gait analysis and a Visual Analogue Scale (VAS) for health status. At baseline, gait analysis was performed without any assistive device as well as with surface electrical stimulation. At follow-up patients walked with the ActiGait system switched off and on. The maximum dorsal extension of the ankle at initial contact increased significantly between baseline without stimulation and follow-up with ActiGait (p = 0.018). While the spatio-temporal parameters did not seem to change much with the use of ActiGait in convenient walking speed, patients did walk faster when using surface stimulation or ActiGait compared to no stimulation at the 10-m walking test at their fastest possible walking speed. Patients rated their health better at the 1-year follow-up. In summary, a global improvement in gait kinematics compared to no stimulation was observed and the long-term safety of the device could be confirmed.

Disentangling the migration-development nexus using QCA

Abstract: Under what circumstances does human development facilitate or constrain emigration? Moreover, under what conditions is migration a driver for rather than an obstacle for development? Empirical evid...

Development of a Multidimensional App-Quality Assessment Tool for Health-Related Apps (AQUA)

Abstract: Background A multitude of health-related mobile applications is available to the public in app stores. Many of these apps were not developed by health professionals and do not keep what they promise. To facilitate a safe handling and use of such apps, it is important to assess their quality in a standardized way. Some instruments for app quality assessment exist, although they have some limitations, which we want to improve on with this new assessment tool. Objectives The objective of this paper is to introduce a new multidimensional criteria-based tool for the quality assessment of health-related apps. Method Based on existing app-quality assessment tools and guidelines for evaluating health-related app-quality, items were constructed to assess objective and subjective app-quality. A pretest in form of cognitive testing was conducted with six participants and some items were optimized. Results An expert and a user version of AQUA were developed in English and German language. The expert version consists of 31 items in the seven dimensions Usability, User Engagement, Content, Visual Design, Therapeutic Quality, Security and Information. The user version consists of 34 items and additionally includes the dimension Impact. Conclusion AQUA is a brief multidimensional app-quality assessment tool that can be used for the quality assessment of health-related and mental health-related apps by experts and app-users.