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Sand as a medium for transmission of vibratory signals of prey in antlions Euroleon nostras (Neuroptera: Myrmeleontidae)
Dušan Devetak, Bojana Mencinger Vračko, Miha Devetak, Marko Marhl, Andreja Špernjak, 2007, izvirni znanstveni članek

Opis: European pit-building antlions (Euroleon nostras/ Geoffroy in Fourcroy/) detect their prey by sensing the vibrations that prey generate during locomotory activity. The behavioural reactions and some of the physical properties of substrate vibrations in sand are measured to observe signal transmission through the substrate. The frequency range of the signals of four arthropod species (Tenebrio molitor, Pyrrhocoris apterus, Formica sp. and Trachelipus rathkei) is 0.1-4.5 kHz and acceleration values are in the range ▫$400 {mu}m s^{-2} to 1.5 mm s^{-2}$▫. Substrate particle size and the frequency of prey signals both influence the propagation properties of vibratory signals. The damping coefficient at a frequency 300 Hz varies from 0.26 to 2.61 dB ▫$cm^{-1}$▫ and is inversely proportional to the size of the sand particle. The damping coefficient is positively correlated with the frequency of the pulses. Vibrations in finer sand are attenuated more strongly than in coarser sand and, consequently, an antlion detects its prey only at a short distance. The reaction distance is defined as the distance of the prey from the centre of the pit when the antlion begins tossing sand as a reaction to the presence of prey. The mean reaction distance is 3.3 cm in the finest sand (particle size ▫$le 0.23 mm$▫) and 12.3 cm in coarser sand (particle size 1-1.54 mm). The most convenient sands for prey detection are considered to be medium particle-sized sands.
Ključne besede: biology, zoology, receptors, chordotonal organs, vibrations, vibratory signals, transmission of vibrations, reception of vibrations, electrophysiology, substrate vibration, antlions, Myrmeleontidae, sand, substrate vibration, particle size
Objavljeno: 07.06.2012; Ogledov: 1671; Prenosov: 88
URL Povezava na celotno besedilo

Analysis of neuromuscular disorders using statistical and entropy metrics on surface EMG
Rok Istenič, Prodromos A. Kaplanis, Constantinos S. Pattichis, Damjan Zazula, 2008, izvirni znanstveni članek

Opis: This paper introduces the surface electromyogram (EMG) classification system based on statistical and entropy metrics. The system is intended for diagnostic use and enables classification of examined subject as normal, myopathic or neuropathic, regarding to the acquired EMG signals. 39 subjects in total participated in the experiment, 19 normal, 11 myopathic and 9 neuropathic. Surface EMG was recorded using 4-channel surface electrodes on the biceps brachii muscle at isometric voluntary contractions. The recording time was only 5 seconds long to avoid muscle fatigue, and contractions at fiveforce levels were performed, i.e. 10, 30, 50, 70 and 100 % of maximal voluntary contraction. The feature extraction routine deployed the wavelet transform and calculation of the Shannon entropy across all the scales in order to obtain a feature set for each subject. Subjects were classified regarding the extracted features using three machine learning techniques, i.e. decision trees, support vector machines and ensembles of support vector machines. Four 2-class classifications and a 3-class classification were performed. The scored classification rates were the following: 64+-11% for normal/abnormal, 74+-7% for normal/myopathic, 79+-8% for normal/neuropathic, 49+-20% for myopathic/neuropathic, and 63+-8% for normal/myopathic/neuropathic.
Ključne besede: surface electromyography, neuromuscular disorders, neuropathy, myopathy, EMG signals, signal processing, wavelet transform, metrics
Objavljeno: 31.05.2012; Ogledov: 1281; Prenosov: 27
URL Povezava na celotno besedilo

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