Tallinn University of Technology

About: Tallinn University of Technology is a education organization based out in Tallinn, Estonia. It is known for research contribution in the topics: European union & Computer science. The organization has 3688 authors who have published 10313 publications receiving 145058 citations. The organization is also known as: Tallinn Technical University & Tallinna Tehnikaülikool.

Spectral Asymmetry and Higuchi’s Fractal Dimension Measures of Depression Electroencephalogram

Abstract: This study was aimed to compare two electroencephalogram (EEG) analysis methods, spectral asymmetry index (SASI) and Higuchi's fractal dimension (HFD), for detection of depression. Linear SASI method is based on evaluation of the balance of powers in two EEG frequency bands in one channel selected higher and lower than the alpha band spectrum maximum. Nonlinear HFD method calculates fractal dimension directly in the time domain. The resting EEG signals of 17 depressive patients and 17 control subjects were used as a database for calculations. SASI values were positive for depressive and negative for control group (P 0.05). The results indicated that the linear EEG analysis method SASI and the nonlinear HFD method both demonstrated a good sensitivity for detection of characteristic features of depression in a single-channel EEG.

Fundamentals, Recent Advances, and Future Challenges in Bioimpedance Devices for Healthcare Applications

Abstract: This work develops a thorough review of bioimpedance systems for healthcare applications. The basis and fundamentals of bioimpedance measurements are described covering issues ranging from the hardware diagrams to the configurations and designs of the electrodes and from the mathematical models that describe the frequency behavior of the bioimpedance to the sources of noise and artifacts. Bioimpedance applications such as body composition assessment, impedance cardiography (ICG), transthoracic impedance pneumography, electrical impedance tomography (EIT), and skin conductance are described and analyzed. A breakdown of recent advances and future challenges of bioimpedance is also performed, addressing topics such as transducers for biosensors and Lab-on-Chip technology, measurements in implantable systems, characterization of new parameters and substances, and novel bioimpedance applications.

Evolution of bacterial consortia in spontaneously started rye sourdoughs during two months of daily propagation.

Abstract: The evolution of bacterial consortia was studied in six semi-solid rye sourdoughs during long-term backslopping at different temperatures. Each rye sourdough was started spontaneously in a laboratory (dough yield 200), propagated at either 20°C or 30°C, and renewed daily at an inoculation rate of 1∶10 for 56 days. The changes in bacterial diversity over time were followed by both DGGE coupled with partial 16S rRNA gene sequencing and pyrosequencing of bar-coded 16S rRNA gene amplicons. Four species from the genus Lactobacillus (brevis, crustorum, plantarum, and paralimentarius) were detected in different combinations in all sourdoughs after 56 propagation cycles. Facultative heterofermentative lactic acid bacteria dominated in sourdoughs fermented at 30°C, while both obligate and facultative heterofermentative LAB were found to dominate in sourdoughs fermented at 20°C. After 56 propagation cycles, Kazachstania unispora (formerly Saccharomyces unisporus) was identified as the only yeast species that dominated in sourdoughs fermented at 20°C, while different combinations of strains from four yeast species (Kazachstania unispora, Saccharomyces cerevisiae, Candida krusei and Candida glabrata) were detected in sourdoughs propagated at 30°C. The evolution of bacterial communities in sourdoughs fermented at the same temperature did not follow the same time course and changes in the composition of dominant and subdominant bacterial communities occurred even after six weeks of backslopping.

Selective laser manufacturing of Ti-based alloys and composites: impact of process parameters, application trends, and future prospects

Abstract: Aviation and automobile industries demand high strength, fatigue resistant, and wear-resistant materials in combination with lightweight, especially for structural applications. On the other hand, biomedical applications demand materials with low modulus and stiffness for optimized implants better matching the modulus of human bone combined with enhanced strength and wear resistance. For all the aforementioned applications in various fields, the fabrication of parts with desired size and shape without the need for joining or welding operations is desired while simultaneously reaching improved mechanical properties and more resistance to environmental attack, which are stringent requirements for almost all the applications. To achieve all these demands, both material developments, as well as modification of process conditions and parameters, are essential. Along these lines, a lot of research work focusses on advanced or even disruptive manufacturing routes and proper alloy development (e.g. Ti, Al, steels, and so on) applying additive manufacturing (AM) techniques for various applications. Among different AM methods, selective laser melting (SLM) is in high demand and preferred for achieving fully dense products in the required dimensions. Titanium alloys designed for AM have replaced a variety of other alloys due to their superior properties such as lightweight or good fatigue and corrosion resistance, achievable through modified microstructures gained by the faster heating and cooling rates realized upon laser printing. Ti alloys with a single (α) or dual (α+β) microstructure are mostly implemented in the aviation and automobile industries, whereas β alloys with exceptionally low modulus close to that of human bone are intensively studied for bio and dental implants but have not been commercialized yet. The modification of microstructure and properties in Ti-based materials with the addition of suitable reinforcement is also a reliable method. In this article, critical aspects for the optimization of processing parameters affecting the properties of SLM manufactured Ti alloys and titanium matrix composites (TMCs) will be presented, and future prospects of such materials will be critically assessed. This work is expected to be helpful for future studies on Ti alloys and composites with enhanced properties processed by laser manufacturing.