1. Motor unit discharge rate modulation during isometric contractions to failure is intensity- and modality-dependentTamara Valenčič, Paul Ansdell, Callum G. Brownstein, Padraig M. Spillane, Aleš Holobar, Jakob Škarabot, 2024, original scientific article Abstract: The physiological mechanisms determining the progressive decline in the maximal muscle torque production capacity during isometric contractions to task failure are known to depend on task demands. Task-specificity of the associated adjustments in motor unit discharge rate (MUDR), however, remains unclear. This study examined MUDR adjustments during different submaximal isometric knee extension tasks to failure. Participants performed a sustained and an intermittent task at 20% and 50% of maximal voluntary torque (MVT), respectively (Experiment 1). High-density surface EMG signals were recorded from vastus lateralis (VL) and medialis (VM) and decomposed into individual MU discharge timings, with the identified MUs tracked from recruitment to task failure. MUDR was quantified and normalised to intervals of 10% of contraction time (CT). MUDR of both muscles exhibited distinct modulation patterns in each task. During the 20% MVT sustained task, MUDR decreased until ∼50% CT, after which it gradually returned to baseline. Conversely, during the 50% MVT intermittent task, MUDR remained stable until ∼40–50% CT, after which it started to continually increase until task failure. To explore the effect of contraction intensity on the observed patterns, VL and VM MUDR was quantified during sustained contractions at 30% and 50% MVT (Experiment 2). During the 30% MVT sustained task, MUDR remained stable until ∼80–90% CT in both muscles, after which it continually increased until task failure. During the 50% MVT sustained task the increase in MUDR occurred earlier, after ∼70–80% CT. Our results suggest that adjustments in MUDR during submaximal isometric contractions to failure are contraction modality- and intensity-dependent.
Keywords: muscle contractions, high-density EMG signals, electromyiograms
Published in DKUM: 23.08.2024; Views: 110; Downloads: 3
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2. Traffic density-related black carbon distribution : impact of wind in a basin townBorut Jereb, Brigita Gajšek, Gregor Šipek, Špela Kovše, Matevž Obrecht, 2021, original scientific article Abstract: Black carbon is one of the riskiest particle matter pollutants that is harmful to human health. Although it has been increasingly investigated, factors that depend on black carbon distribution and concentration are still insufficiently researched. Variables, such as traffic density, wind speeds, and ground levels can lead to substantial variations of black carbon concentrations and potential exposure, which is even riskier for people living in less-airy sites. Therefore, this paper "fills the gaps" by studying black carbon distribution variations, concentrations, and oscillations, with special emphasis on traffic density and road segments, at multiple locations, in a small city located in a basin, with frequent temperature inversions and infrequent low wind speeds. As wind speed has a significant impact on black carbon concentration trends, it is critical to present how low wind speeds influence black carbon dispersion in a basin city, and how black carbon is dependent on traffic density. Our results revealed that when the wind reached speeds of 1 ms-1 , black carbon concentrations actually increased. In lengthy wind periods, when wind speeds reached 2 or 3 ms-1 , black carbon concentrations decreased during rush hour and in the time of severe winter biomass burning. By observing the results, it could be concluded that black carbon persists longer in higher altitudes than near ground level. Black carbon concentration oscillations were also seen as more pronounced on main roads with higher traffic density. The more the traffic decreases and becomes steady, the more black carbon concentrations oscillate.
Keywords: black carbon, black carbon concentration, traffic pollution, air pollution, wind, traffic density, logistics, basin city
Published in DKUM: 20.08.2024; Views: 39; Downloads: 3
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3. Investigation of the best manufacturing orientation of Co-Cr-W-Si dental prosthetic elements in the selective laser melting processSnehashis Pal, Janez Gotlih, Igor Drstvenšek, 2022, original scientific article Abstract: It is well known that Selective Laser Melting (SLM) does not provide the same mechanical
properties in all directions of the part. This is due to the microstructural grain orientation and
pore shape in SLM products. Therefore, depending on the direction of the pressure applied to the
SLM product, a different manufacturing orientation is required to achieve the best mechanical
properties. Changing the microstructural grain orientation is difficult through SLM, but a process
to reduce the size and number of the pores can be discovered through different combinations
of manufacturing parameters. In prosthodontics, pressure is usually applied in the vertical
direction, which leads to compression and bending of crowns with bridges. The compressive
load can be easily absorbed in the crowns, but the bending force has a significant effect here.
Therefore, a product with high tensile strength and high ductility is needed to survive longer.
Considering these requirements, this study determined the best parameters for laser processing
by SLM method to reduce porosity and improve mechanical strength and ductility of Co-CrW-Si alloy products. The result is a relative product density of 100% for cubic specimens and a
yield strength, ultimate tensile strength, and elongation at break of the tensile specimens of 900
MPa, 1200 MPa, and 15%, respectively, obtained in specimen build-up in the Z direction with a
laser power of 60 W and a scanning speed of 450 mm/s. Eventually, the best orientation for the
production of dental prosthetic elements using the SLM process was determined.
Keywords: cobalt-chromium alloy, dental implant, density, tensile strength, ductility, selective laser melting
Published in DKUM: 03.07.2024; Views: 64; Downloads: 7
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4. Motor unit identification in the M waves recorded by high-density electromyMiloš Kalc, Jakob Škarabot, Matjaž Divjak, Filip Urh, Matej Kramberger, Matjaž Vogrin, Aleš Holobar, 2023, original scientific article Keywords: M wave, high-density surface EMG, firing identification, motor unit
Published in DKUM: 13.06.2024; Views: 131; Downloads: 8
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5. Identification of motor unit firings in H-reflex of soleus muscle recorded by high-density surface electromyographyMiloš Kalc, Jakob Škarabot, Matjaž Divjak, Filip Urh, Matej Kramberger, Matjaž Vogrin, Aleš Holobar, 2023, original scientific article Keywords: motor units identification, high-density surface EMG, decomposition, H-reflex
Published in DKUM: 13.06.2024; Views: 125; Downloads: 8
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6. Materials for HybridNeuro webinar titled "Validation of results: statistical models and MU identification accuracy"Aleš Holobar, Nina Murks, 2024, complete scientific database of research data Abstract: This dataset contains a collection of teaching materials that were used in the HybridNeuro project webinar titled "Validation of results: statistical models and MU identification accuracy". The webinar was presented by Aleš Holobar and covered the complexities of motor unit (MU) identification accuracy, regression analysis and Bayesian models. The primary aim of the webinar was to spark a robust discussion within the scientific community, particularly focusing on the application and implications of linear mixed models and Bayesian regression in the realm of MU identification. The teaching materials include Matlab and R source code for statistical analysis of the included data, as well as three examples of MU identification results in CSV format (from both synthetic and experimental HDEMG signals). The presentation slides in PDF format are also included. The dataset is approximately 9 MB in size.
Keywords: HybridNeuro, webinar, teaching materials, statistical models, regression analysis, motor unit identification, matlab, rstudio, statistics, surface high density electromyogram (HDEMG), tibialis anterior, dataset
Published in DKUM: 30.05.2024; Views: 216; Downloads: 15
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7. Simulated and experimental HDEMG signals of biceps brachii muscle for analysis of motor unit mergingAleš Holobar, Jakob Škarabot, Dario Farina, 2024, complete scientific database of research data Abstract: This dataset contains a collection of simulated and experimental surface HDEMG recordings of the biceps brachii muscle during the isometric elbow flexion. Simulated data contains 50 recordings: 5 subjects and 5 excitation levels, each with and without added noise. Experimental data contains 16 recordings: 2 subjects with 4 excitation levels and 2 repetitions of each level. Synthetic data was simulated using the cylindrical volume conductor model [1] and the motor unit recruitment and firing modulation model proposed in [2]. Each recording is 20 seconds in length with 90 HDEMG channels sampled at 2048 Hz and is stored as a 2D matrix of raw EMG values in Matlab’s MAT format. Experimental surface EMG data was recorded on two volunteers during isometric contractions at constant force level. Each recording is 25 seconds in length with 64 HDEMG channels sampled at 2048 Hz and is also stored as a 2D matrix of raw EMG values in Matlab’s MAT format. The dataset is approximately 1.5 GB in size.
Keywords: surface high density electromyogram (HDEMG), motor unit, spike train, motor unit merging, simulated data, experimental data, biceps brachii, dataset
Published in DKUM: 30.05.2024; Views: 162; Downloads: 5
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