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Wavelet analysis

Andrei-Emil Briciu
The orthotidal rivers are a new concept referring to inland rivers influenced by gravitational tides through the groundwater tides. "Orthotidal signals" is intended to describe tidal signals found in inland streamwaters (with no oceanic input); these tidal signals were locally generated and then exported into streamwaters. Here, we show that orthotidal signals can be found in proglacial rivers due to the gravitational tides affecting the glaciers and their surrounding areas. The gravitational tides act on glacier through earth and atmospheric tides, while the subglacial water is affected in a manner similar to the groundwater tides...
February 22, 2018: Environmental Monitoring and Assessment
Maria Gabriella Chiariello, Nadia Rega
Advances in time resolved vibrational spectroscopy techniques provided a new stimulus for understanding the transient molecular dynamics triggered by the electronic excitation. The detailed interpretation of such time dependent spectroscopic signals is a challenging task from both experimental and theoretical points of view. We simulated and analyzed the transient photorelaxation of the pyranine photoacid in aqueous solution, with special focus on structural parameters and low frequency skeleton modes that are possibly preparatory for the photoreaction occurring at later time, as suggested by experimental spectroscopic studies...
February 21, 2018: Journal of Physical Chemistry. A
Marcin Gruszecki, Gemma Lancaster, Aneta Stefanovska, J Patrick Neary, Ryan T Dech, Wojciech Guminski, Andrzej F Frydrychowski, Jacek Kot, Pawel J Winklewski
Abnormal cerebrospinal fluid (CSF) pulsatility has been implicated in patients suffering from various diseases, including multiple sclerosis and hypertension. CSF pulsatility results in subarachnoid space (SAS) width changes, which can be measured with near-infrared transillumination backscattering sounding (NIR-T/BSS). The aim of this study was to combine NIR-T/BSS and wavelet analysis methods to characterise the dynamics of the SAS width within a wide range of frequencies from 0.005 to 2 Hz, with low frequencies studied in detail for the first time...
February 15, 2018: Scientific Reports
Shin-Yi Chiou, Ermis Koutsos, Pantelis Georgiou, Paul H Strutton
OBJECTIVES: Characteristics of muscle activity, represented by surface electromyography (EMG), have revealed differences between patients with low back pain (LBP) and healthy adults; how they relate to functional and clinical parameters remains unclear. The purpose of the current study was to examine the correlation between frequency characteristics of EMG (analysed using continuous wavelet transform (CWT) analysis) and patients' self-rated score of disability. DESIGN AND SETTING: This is a case-control study with 15 patients with mechanical LBP without radicular symptoms...
February 14, 2018: BMJ Open
Abdullah Al Kafee, Aydin Akan
Electrogastrogram is used for the abdominal surface measurement of the gastric electrical activity of the human stomach. The electrogastrogram technique has significant value as a clinical tool because careful electrogastrogram signal recordings and analyses play a major role in determining the propagation and coordination of gastric myoelectric abnormalities. The aim of this article is to evaluate electrogastrogram features calculated by line length features based on the discrete wavelet transform method to differentiate healthy control subjects from patients with functional dyspepsia and diabetic gastroparesis...
February 1, 2018: Proceedings of the Institution of Mechanical Engineers. Part H, Journal of Engineering in Medicine
Daniel García Iglesias, Nieves Roqueñi Gutiérrez, Francisco Javier De Cos, David Calvo
BACKGROUND: Fragmentation and delayed potentials in the QRS signal of patients have been postulated as risk markers for Sudden Cardiac Death (SCD). The analysis of the high-frequency spectral content may be useful for quantification. METHODS: Forty-two consecutive patients with prior history of SCD or malignant arrhythmias (patients) where compared with 120 healthy individuals (controls). The QRS complexes were extracted with a modified Pan-Tompkins algorithm and processed with the Continuous Wavelet Transform to analyze the high-frequency content (85-130 Hz)...
February 12, 2018: Sensors
Gregory W McGarr, Gary J Hodges, Matthew M Mallette, Stephen S Cheung
BACKGROUND: Ischemia-reperfusion (IR) injury impairs microcirculatory function by reducing nitric oxide (NO) bioavailability and increasing sympathetic tone. This study non-invasively examined the effects of acute upper limb IR injury on local thermal hyperemia (LTH) in glabrous and non-glabrous finger skin. MATERIALS AND METHODS: In ten healthy males, LTH was examined twice (~7-10 d apart) for each skin type on the index finger using laser-Doppler flowmetry in a counterbalanced design with either 1) 20 min ischemia, followed by reperfusion (ISCH) or 2) time-matched control (SHAM)...
February 10, 2018: Microvascular Research
Fulong Jing, Chunjie Zhang, Weijian Si, Yu Wang, Shuhong Jiao
Polynomial phase signals (PPSs) have numerous applications in many fields including radar, sonar, geophysics, and radio communication systems. Therefore, estimation of PPS coefficients is very important. In this paper, a novel approach for PPS parameters estimation based on adaptive short-time Fourier transform (ASTFT), called the PPS-ASTFT estimator, is proposed. Using the PPS-ASTFT estimator, both one-dimensional and multi-dimensional searches and error propagation problems, which widely exist in PPSs field, are avoided...
February 13, 2018: Sensors
Atefeh Goshvarpour, Ataollah Abbasi, Ateke Goshvarpour
BACKGROUND: The purpose of the current study was to examine the effectiveness of Matching Pursuit (MP) algorithm in emotion recognition. METHODS: Electrocardiogram (ECG) and galvanic skin responses (GSR) of 11 healthy students were collected while subjects were listening to emotional music clips. Applying three dictionaries, including two wavelet packet dictionaries (Coiflet, and Daubechies) and discrete cosine transform, MP coefficients were extracted from ECG and GSR signals...
December 2017: Biomedical Journal
Sahar Jahani, Seyed K Setarehdan, David A Boas, Meryem A Yücel
Motion artifact contamination in near-infrared spectroscopy (NIRS) data has become an important challenge in realizing the full potential of NIRS for real-life applications. Various motion correction algorithms have been used to alleviate the effect of motion artifacts on the estimation of the hemodynamic response function. While smoothing methods, such as wavelet filtering, are excellent in removing motion-induced sharp spikes, the baseline shifts in the signal remain after this type of filtering. Methods, such as spline interpolation, on the other hand, can properly correct baseline shifts; however, they leave residual high-frequency spikes...
January 2018: Neurophotonics
Kevin J Verdière, Raphaëlle N Roy, Frédéric Dehais
Monitoring pilot's mental states is a relevant approach to mitigate human error and enhance human machine interaction. A promising brain imaging technique to perform such a continuous measure of human mental state under ecological settings is Functional Near-InfraRed Spectroscopy (fNIRS). However, to our knowledge no study has yet assessed the potential of fNIRS connectivity metrics as long as passive Brain Computer Interfaces (BCI) are concerned. Therefore, we designed an experimental scenario in a realistic simulator in which 12 pilots had to perform landings under two contrasted levels of engagement (manual vs...
2018: Frontiers in Human Neuroscience
Hong Tran, Hongxiao Zhu, Xiaowei Wu, Gunjune Kim, Christopher R Clarke, Hailey Larose, David C Haak, Shawn D Askew, Jacob N Barney, James H Westwood, Liqing Zhang
Deoxyribonucleic acid (DNA) methylation is an epigenetic alteration crucial for regulating stress responses. Identifying large-scale DNA methylation at single nucleotide resolution is made possible by whole genome bisulfite sequencing. An essential task following the generation of bisulfite sequencing data is to detect differentially methylated cytosines (DMCs) among treatments. Most statistical methods for DMC detection do not consider the dependency of methylation patterns across the genome, thus possibly inflating type I error...
February 8, 2018: Genes
Xinrui Huang, Sha Li, Song Gao
Cryo-electron tomography (cryo-ET) is one of the most advanced technologies for the in situ visualization of molecular machines by producing three-dimensional (3D) biological structures. However, cryo-ET imaging has two serious disadvantages-low dose and low image contrast-which result in high-resolution information being obscured by noise and image quality being degraded, and this causes errors in biological interpretation. The purpose of this research is to explore an optimal wavelet denoising technique to reduce noise in cryo-ET images...
February 7, 2018: Scientific Reports
Xiao-Wei Ye, You-Hua Su, Pei-Sen Xi
In this paper, a fiber Bragg grating (FBG)-based stress monitoring system instrumented on an orthotropic steel deck arch bridge is demonstrated. The FBG sensors are installed at two types of critical fatigue-prone welded joints to measure the strain and temperature signals. A total of 64 FBG sensors are deployed around the rib-to-deck and rib-to-diagram areas at the mid-span and quarter-span of the investigated orthotropic steel bridge. The local stress behaviors caused by the highway loading and temperature effect during the construction and operation periods are presented with the aid of a wavelet multi-resolution analysis approach...
February 7, 2018: Sensors
M Ghofrani Jahromi, H Parsaei, A Zamani, M Dehbozorgi
Background: Electromyographic (EMG) signal decomposition is the process by which an EMG signal is decomposed into its constituent motor unit potential trains (MUPTs). A major step in EMG decomposition is feature extraction in which each detected motor unit potential (MUP) is represented by a feature vector. As with any other pattern recognition system, feature extraction has a significant impact on the performance of a decomposition system. EMG decomposition has been studied well and several systems were proposed, but feature extraction step has not been investigated in detail...
December 2017: Journal of Biomedical Physics & Engineering
Chu Zhang, Fei Liu, Yong He
Hyperspectral imaging was used to identify and to visualize the coffee bean varieties. Spectral preprocessing of pixel-wise spectra was conducted by different methods, including moving average smoothing (MA), wavelet transform (WT) and empirical mode decomposition (EMD). Meanwhile, spatial preprocessing of the gray-scale image at each wavelength was conducted by median filter (MF). Support vector machine (SVM) models using full sample average spectra and pixel-wise spectra, and the selected optimal wavelengths by second derivative spectra all achieved classification accuracy over 80%...
February 1, 2018: Scientific Reports
A N Pavlov, O N Pavlova, A S Abdurashitov, O A Sindeeva, O V Semyachkina-Glushkovskaya, J Kurths
The scaling properties of complex processes may be highly influenced by the presence of various artifacts in experimental recordings. Their removal produces changes in the singularity spectra and the Hölder exponents as compared with the original artifacts-free data, and these changes are significantly different for positively correlated and anti-correlated signals. While signals with power-law correlations are nearly insensitive to the loss of significant parts of data, the removal of fragments of anti-correlated signals is more crucial for further data analysis...
January 2018: Chaos
Akira Kimata, Yasuhiro Yokoyama, Satoshi Aita, Hiroaki Nakamura, Koji Higuchi, Yasuaki Tanaka, Akihiko Nogami, Kenzo Hirao, Kazutaka Aonuma
INTRODUCTION: Dominant frequency (DF) derived from fast Fourier transform (FFT) analysis has failed to guide atrial fibrillation (AF) ablation since it cannot guarantee temporal stability. Continuous wavelet transform (CWT) analysis is another frequency analysis that can show the temporal stability of a frequency. METHODS AND RESULTS: Forty-four consecutive patients with persistent AF (PeAF) underwent pulmonary vein (PV) isolation (PVI) as the first-time catheter ablation...
January 25, 2018: Journal of Cardiovascular Electrophysiology
H M Fahad, M Usman Ghani Khan, Tanzila Saba, Amjad Rehman, Sajid Iqbal
Auscultation of heart dispenses identification of the cardiac valves. An electronic stethoscope is used for the acquisition of heart murmurs that is further classified into normal or abnormal murmurs. The process of heart sound segmentation involves discrete wavelet transform to obtain individual components of the heart signal and its separation into systole and diastole intervals. This research presents a novel scheme to develop a semi-automatic cardiac valve disorder diagnosis system. Accordingly, features are extracted using wavelet transform and spectral analysis of input signals...
January 23, 2018: Microscopy Research and Technique
Wenjing Du, Huihui Li, Olatunji Mumini Omisore, Lei Wang, Wenmin Chen, Xiangjun Sun
BACKGROUND: Muscular performance is an important factor for the mechanical stability of lumbar spine in humans, in which, the co-contraction of lumbar muscles plays a key role. We hypothesized that when executing different daily living motions, the performance of the lumbar muscle co-contraction stabilization mechanism varies between patients with lumbar disc herniation (LDH) and healthy controls. Hence, in this study, co-contraction performance of lumbar muscles between patients with LDH and healthy subjects was explored to check if there are significant differences between the two groups when performing four representative movements...
January 24, 2018: Biomedical Engineering Online
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