Relating the spectrum of cardiac signals to the spatiotemporal dynamics of cardiac sources

An increasing number of studies use the spectrum of cardiac signals for analyzing the spatiotemporal dynamics of complex cardiac arrhythmias. However, the relationship between the spectrum of cardiac signals and the spatiotemporal dynamics of the underlying cardiac sources remains to date unclear. In this paper, by following a multivariate signal analysis approach we identify the relationship between the spectrum of cardiac signals, the spatiotemporal dynamics of cardiac sources, and the measurement characteristics of the lead systems. Then, by using analytical methods and computer simulations we analyze the spectrum of cardiac signals measured by idealized lead systems during correlated and uncorrelated spatiotemporal dynamics. Our results show that lead systems can have distorting effects on the spectral envelope of cardiac signals, which depend on the spatial resolution of the lead systems and on the degree of spatiotemporal correlation of the underlying cardiac sources. In addition to this, our results indicate that the spectral features that do not depend on the spectral envelope behave robustly against different choices of lead systems.     

Infarct-related chronic total coronary occlusion and the risk of ventricular tachyarrhythmic events in out-of-hospital cardiac arrest survivors

IntroductionChronic total coronary occlusion (CTO) has been identified as a risk factor for ventricular arrhythmias, especially a CTO in an infarct-related artery (IRA). This study aimed to evaluate the effect of an IRA-CTO on the occurrence of ventricular tachyarrhythmic events (VTEs) in out-of-hospital cardiac arrest survivors without ST-segment elevation.MethodsWe conducted a post hoc analysis of the COACT trial, a multicentre randomised controlled trial. Patients were included when they survived index hospitalisation after cardiac arrest and demonstrated coronary artery disease on coronary angiography. The primary endpoint was the occurrence of a VTE, defined as appropriate implantable cardioverter-defibrillator (ICD) therapy, sustained ventricular tachyarrhythmia or sudden cardiac death.ResultsA total of 163 patients from ten centres were included. Unrevascularised IRA-CTO in a main vessel was present in 43 patients (26%). Overall, 61% of the study population received an ICD for secondary prevention. During a follow-up of 1 year, 12 patients (7.4%) experienced at least one VTE. The cumulative incidence rate of VTEs was higher in patients with an IRA-CTO compared to patients without an IRA-CTO (17.4% vs 5.6%, log-rank p = 0.03). However, multivariable analysis only identified left ventricular ejection fraction < 35% as an independent factor associated with VTEs (adjusted hazard ratio 8.7, 95% confidence interval 2.2–35.4). A subanalysis focusing on CTO, with or without an infarct in the CTO territory, did not change the results.ConclusionIn out-of-hospital cardiac arrest survivors with coronary artery disease without ST-segment elevation, an IRA-CTO was not an independent factor associated with VTEs in the 1st year after the index event.Supplementary InformationThe online version of this article (10.1007/s12471-021-01578-3) contains supplementary material, which is available to authorized users.     

基于滤除R波的主导频率算法的房颤心内信号分析

为了进一步探究房颤患者心内不同位置信号的主导频率(Dominant frequency,简称DF)的关联性,本文对传统的Botteron’s算法进行了改进。当信号中含有较大幅值的室波时,该改进算法可以更好地提取DF。利用该算法对20例临床房颤消融手术的冠状静脉窦(Coronary sinus,简称CS)导管、环肺静脉(Pulmonary veins,简称PV)导管采集的信号进行了观察和分析。在大部分病例中都能观察到其CS和PV的信号里都存在相同频率的DF;同时发现CS的DF并不仅仅来自当前标测的PV。实验结果表明:房颤的潜在病灶区域不仅仅具有较高频率的DF,且其DF的频率应当与心房采集的DF频率存在对应关系。这或许可以为寻找房颤的潜在病灶区域提供参考。     

Unusual presentation of supraventricular tachycardia degenerating into ventricular fibrillation during pregnancy: Aortocaval compression the probable culprit

Cardiac arrhythmias are common and often benign in pregnancy. However, haemodynamic instability can occur when tachyarrhythmias are accompanied by aortocaval compression, which can lead to loss of cardiac output. We present an atypical case of a pregnant woman with a supraventricular tachyarrhythmia, which degenerated into ventricular fibrillation arrest while supine due to aortocaval compression. Inducible atypical atrioventricular nodal re-entry tachycardia was subsequently detected on electrophysiological study and presumed to be the most likely initial supraventricular tachyarrhythmia.     

Analysis of spectral shape in the barn owl auditory system

In a behavioral experiment, we investigated how efficiently barn owls (Tyto alba) could detect changes in the spectral profile of multi-component auditory signals with stochastic envelope patterns. Signals consisted of one or five bands of noise (bandwidth 4, 16, or 64 Hz each; center frequencies 1.02, 1.43, 2.0, 2.8, 3.92 kHz). We determined increment thresholds for the 2 kHz component for three conditions: single-band condition (only the 2 kHz component), all five noise bands with the envelope fluctuations of the bands being either correlated or uncorrelated. Noise bandwidth had no significant effect on increment detection. Increment thresholds for the different conditions, however, differed significantly. Thresholds in correlated conditions were generally the lowest of all conditions, whereas, thresholds in uncorrelated conditions mostly resulted in the highest thresholds. This can be interpreted as evidence for comodulation masking release in barn owls. If the increment in the 2 kHz component is balanced by decrementing the four flanking bands in amplitude, increment detection thresholds are not affected. The data suggest that the barn owls used information from simultaneous spectral comparison across different frequency channels to detect spectral changes in multi-component noise signals rather than sequential comparison of overall stimulus levels.     

泥炭藓群落的光谱特征及遥感识别研究

以中位泥炭藓(Sphagnum magellanicum Brid.)为研究对象,分别从实测冠层光谱和遥感传感器模拟光谱层面分析其群落的光谱特征。研究结果显示,中位泥炭藓与北方针叶林光谱差异明显,最佳光谱识别区间为740～1140 nm和1230～1412 nm。在可见光波段上,中位泥炭藓与云杉(Picea engelmannii Parry ex Engelmann)和黑松(Pinus contorta Douglas ex Loudon)的绿峰位置有所差异。水竹(Phyllostachys heteroclada Oliver)和中位泥炭藓的光谱识别特征波段集中在可见光-近红外波段,分别为400～550、560～696、1025～1143 nm。中位泥炭藓与北方针叶林以及水竹的特征光谱区间存在细微差异,且与水竹在可见光波段有较好的可分性,因此不同纬度带上中位泥炭藓群落的特征谱宽有所差异。红外波段是中位泥炭藓识别的最佳光谱区间。在多光谱遥感水平上,中位泥炭藓识别效果较好,传感器的识别能力依次为:MSI> ALI> OLI> ASTER。在2个中位泥炭藓群落的光谱特征分析中,导数、对数、包络线去除法的光谱降维能力有所差异,其中包络线去除法效果最好。     

泥炭藓群落的光谱特征及遥感识别研究

以中位泥炭藓（Sphagnum magellanicum Brid.）为研究对象,分别从实测冠层光谱和遥感传感器模拟光谱层面分析其群落的光谱特征。研究结果显示,中位泥炭藓与北方针叶林光谱差异明显,最佳光谱识别区间为740~1140 nm和1230~1412 nm。在可见光波段上,中位泥炭藓与云杉（Picea engelmannii Parry ex Engelmann）和黑松（Pinus contorta Douglas ex Loudon）的绿峰位置有所差异。水竹（Phyllostachys heteroclada Oliver）和中位泥炭藓的光谱识别特征波段集中在可见光-近红外波段,分别为400~550、560~696、1025~1143 nm。中位泥炭藓与北方针叶林以及水竹的特征光谱区间存在细微差异,且与水竹在可见光波段有较好的可分性,因此不同纬度带上中位泥炭藓群落的特征谱宽有所差异。红外波段是中位泥炭藓识别的最佳光谱区间。在多光谱遥感水平上,中位泥炭藓识别效果较好,传感器的识别能力依次为：MSI > ALI > OLI > ASTER。在2个中位泥炭藓群落的光谱特征分析中,导数、对数、包络线去除法的光谱降维能力有所差异,其中包络线去除法效果最好。     

The spectral content of postural sway during quiet stance: Influences of age, vision and somatosensory inputs

Maintenance of human upright stance requires the acquisition and integration of sensory inputs. Conventional measures of sway have had success in identifying age- and some disease-related changes, but remain unable to address the complexities and dynamics associated with postural control. We investigated the effects of vision, surface compliance, age, and gender on the spectral content of center of pressure (COP) time series. Sixteen healthy young (age 18-24) and older participants (age 55-65) performed trials of quiet, upright stance under different vision (eyes open vs. closed) and surface (hard vs. compliant) conditions. Spectral analyses were conducted to describe COP mean normalized power in discretized bands. Effects of the two sensory modalities and age were distinct in the antero-posterior and medio-lateral directions, and a reorganization of spectral content was evident with increasing task difficulty (eyes open vs. closed and hard vs. compliant surface) and among older adults. These results indicate that vision and surface compliance are predominantly associated with responses from musculature associated with antero-posterior and medio-lateral directions of sway, respectively. Finally, distinguishing between the contributions of different afferent systems to the postural control system using the spectral content of sway bi-directionally may help in diagnosing individuals with balance impairments.     

Analysis of the relationship between the spectral characteristics of maize canopy and leaf area index under drought stress

Maize is one of the most widespread grain crops in the world; however, more than 70% of corn in China suffers some degree of drought disaster every year. Leaf area index (LAI) is an important biophysical parameter of the vegetation canopy and has important significance for crop yield estimation. Using the data of canopy spectral reflectance and leaf area index (LAI) for maize plants experiencing different levels of soil moisture from 2011 to 2012, the characteristics of the canopy reflective spectrum and its first derivative, and their relationships to leaf area index, were analyzed. Soil moisture of the control group was about 75% while that of the drought stress treatment was about 45%. In addition, LAI retrieval models for maize were established using vegetation indices (VIs) and principal component analysis (PCA) and the models were tested using independent datasets representing different soil water contents and different developmental stages of maize. The results showed that canopy spectral reflectances were in accordance with the characteristics of green plants, under both drought stress and at different developmental stages. In the visible band, canopy reflectance for both healthy and damaged vegetation had a green-wavelength peak and a red-wavelength valley; reflectance under drought stress, especially in the green peak (about 550 nm) and the red valley (about 676 nm) was higher than in the control group. In the near-infrared band, the canopy spectral reflectance decreased substantially between 780 and 1350 nm under drought stress. Moreover, the red edge of the spectrum was shifted toward blue wavelengths. The first derivative spectrum showed a double peak phenomenon at the edge of the red band at different developmental stages: the main peak appeared between 728 and 732 nm and the minor peak at about 718 nm. The double peaks become more obvious through the growth and development of the maize, with the most notable effect during the silking and milk stages, after which it gradually decreased. During maize growth, the LAI of all plants, regardless of soil moisture conditions, increased, and the largest LAI also occurred during the silking and milk stages. During those stages, the LAI of plants under different drought stress levels was significantly lower (by 20% or more) than in normal plants with sufficient water supplies. The LAI was highly significantly correlated with canopy spectral reflectance in the bands from 350 nm to 510 nm, from 571 nm to 716 nm, and from 1450 nm to 1575 nm. Also, the LAI was significantly correlated with red edge parameters and several VIs. The Perpendicular Vegetation Index (PVI) had the best correlation with LAI, with a coefficient of determination (R²) of 0.726 for the exponential correlation. Using dependent data, a LAI monitoring model for the maize canopy was constructed using PCA and VI methods. The test results showed that both the VI and PCA methods of monitoring maize LAI could provide robust estimates, with the predicted values of LAI being significantly correlated with the measured values. The model based on PVI showed higher precision under the drought stresses, with a correlation coefficient of 0.893 (n = 27), while the model based on PCA was more precise under conditions of adequate soil moisture, with a correlation coefficient of 0.877 (n = 32). Therefore, a synthesis of the models based on both VI and PCA could be more reliable for precisely predicting LAI under different levels of drought stresses in maize.     

Analysis of heart rate variability during exercise stress testing using respiratory information

This paper presents a novel method for the analysis of heart rate variability (HRV) during exercise stress testing enhanced with respiratory information. The instantaneous frequency and power of the low frequency (LF) and high frequency (HF) bands of the HRV are estimated by parametric decomposition of the instantaneous autocorrelation function (ACF) as a sum of damped sinusoids. The instantaneous ACF is first windowed and filtered to reduce the cross terms. The inclusion of respiratory information is proposed at different stages of the analysis, namely, the design of the filter applied to the instantaneous ACF, the parametric decomposition, and the definition of a dynamic HF band. The performance of the method is evaluated on simulated data as well as on a stress testing database. The simulation results show that the inclusion of respiratory information reduces the estimation error of the amplitude of the HF component from 3.5% to 2.4% in mean and related SD from 3.0% to 1.7% when a tuned time smoothing window is used at an SNR of 15 dB. Results from the stress testing database show that information on respiratory frequency produces HF power estimates which closely resemble those from the simulations which exhibited lower SD. The mean SD of these estimates with respect to their mean trends is reduced by 84% (from 0.74×10⁻³ s⁻² to 0.12×10⁻³ s⁻²). The analysis of HRV in the stress testing database reveals a significant decrease in the power of both the LF and HF components around peak stress.     

A technique for the measurement of synchronised feeding in miniature pigs: determination by means of Walsh - Fourier spectral analysis

In order to investigate feeding synchronization in miniature pigs, a computer-controlled laboratory setup has been developed, recording the feeding behavior of two pigs at a time for weeks. Since, this setup delivers time series with a binary data structure, and thus Fourier-Spectral analysis is difficult to perform, Walsh - Fourier Spectral analysis for ordinal or binary data was utilized. Synchronicity between pigs housed together was estimated by coherency values, determined for the highest sequences of the Walsh - Fourier power spectra. Feeding behavior was recorded in 12 pigs (26 - 50 kg) housed in pairs, in separate, but adjacent pens. Pigs were conditioned to operate feeders and feeding was recorded for two weeks. Pigs housed adjacent to one another showed an overlap in the dominant sequencies which was confirmed by high corresponding coherency values. Furthermore, pairs of pigs were matched according to age, weight and gender, and combined by chance. Compared to these pairings, coherencies were higher and more consistent in pigs housed in adjacent pens. If the data structure is binary, Walsh - Fourier Spectral analysis utilizing coherencies as a measure of correlation between the spectra has been shown to be a useful tool in the investigation of behavioral synchronization.     

Testing the phylogeny of swordtail fishes using split decomposition and spectral analysis

We examine ways of testing for the reliability of inference from biological sequence data using sequences from Xiphophorus fishes and newly implemented methodology for sequence analysis. The approach we take provides one means to examine the fit between model and data for different sequences and hence to evaluate heterogeneity between data sets. In the case of the present study we show D-loop sequences to be a better molecule for studying the phylogeny of Xiphophorus fishes than cytochrome b sequences. The results of the split decomposition and spectral analysis confirm an earlier phylogenetic hypothesis which had been based on maximum parsimony, neighbor-joining, maximum likelihood analyses. Correspondence to: A. Meyer     

Spectral composition of photosynthetically active radiation penetrating into a Norway spruce canopy: the opposite dynamics of the blue/red spectral ratio during clear and overcast days

The spectral composition of photosynthetically active radiation (PAR) during clear and overcast days was studied above the canopy (U) and at two layers of a dense Norway spruce stand [Picea abies (L.) Karst.] characterized with an average LAI = 7.3 ± 0.8 (middle layer: M) and 12.3 ± 0.7 (lower layer: L). Whereas the spectral composition of PAR incoming on the canopy surface during cloudy days (characterized by diffuse index DI > 0.7) was almost independent of the solar elevation angle, the proportion of the blue-green spectral region of PAR was significantly reduced at low elevation angles during days with prevailing direct radiation (DI < 0.3). The PAR spectrum at both M and L levels was only slightly enriched in the green spectral region (more pronounced for DI < 0.3). The penetration of diffuse radiation into the canopy resulted in a slight (approx. 5%) reduction of the blue region proportion that remained stable during the day. On the contrary, under clear sky conditions the penetration of blue and red radiation was dependent on the solar elevation in an opposite manner in comparison with the spectral composition of PAR incident on canopy, giving almost twofold proportion of the blue part of the spectrum at a low elevation angle at M layer. We suggest that the blue enhancement of the spectrum within the Norway spruce canopy during clear days is due to a specific spatial arrangement of the assimilatory apparatus of a coniferous stand. Further, the possible consequences of the observed dynamics of the PAR spectrum inside the canopy during clear days on the efficiency of PAR absorption of the needles located within the canopy are discussed.     

北京地区植被景观中斑块形状的指数分析

选取４个斑块形状指数（斑块的击长面积比ＳＩ１、斑块周长与等面积的圆周长之比ＳＩ２和身份个斑块分维ＳＩ３和ＳＩ４）并借助ＧＩＳ软件ＡＲＣ／ＩＮＦＯ对北京地区植被景观中的斑块形状进行分析,又地这四个形状指数进行 ｅａｒｓｏｎ相关分析和Ｓｐｅａｒｍａｎ秋相关分析,结果表明,ＳＩ１与ＳＩ４,ＳＩ２与ＳＩ３两两之间均呈显著的正的秩相关,ＳＩ１与ＳＩ２,ＳＩ２与ＳＩ４,ＳＩ３与ＳＩ４两两之间于垢负和秩相关。因     

Analysis of the tennis racket vibrations during forehand drives: Selection of the mother wavelet

The time–frequency analysis of the tennis racket and hand vibrations is of great interest for discomfort and pathology prevention. This study aimed to (i) to assess the stationarity of the vibratory signal of the racket and hand and (ii) to identify the best mother wavelet to perform future time–frequency analysis, (iii) to determine if the stroke spin, racket characteristics and impact zone can influence the selection of the best mother wavelet. A total of 2364 topspin and flat forehand drives were performed by fourteen male competitive tennis players with six different rackets. One tri-axial and one mono-axial accelerometer were taped on the racket throat and dominant hand respectively. The signal stationarity was tested through the wavelet spectrum test. Eighty-nine mother wavelet were tested to select the best mother wavelet based on continuous and discrete transforms. On average only 25 ± 17%, 2 ± 5%, 5 ± 7% and 27 ± 27% of the signal tested respected the hypothesis of stationarity for the three axes of the racket and the hand respectively. Regarding the two methods for the detection of the best mother wavelet, the Daubechy 45 wavelet presented the highest average ranking. No effect of the stroke spin, racket characteristics and impact zone was observed for the selection of the best mother wavelet. It was concluded that alternative approach to Fast Fourier Transform should be used to interpret tennis vibration signals. In the case where wavelet transform is chosen, the Daubechy 45 mother wavelet appeared to be the most suitable.     

A new parameter for quantifying the variability of surface electromyographic signals during gait: The occurrence frequency

Natural variability of myoelectric activity during walking was recently analyzed considering hundreds of strides. This allowed assessing a parameter seldom considered in classic surface EMG (sEMG) studies: the occurrence frequency, defined as the frequency each muscle activation occurs with, quantified by the number of strides when a muscle is recruited with that specific activation modality. Aim of present study was to propose the occurrence frequency as a new parameter for assessing sEMG-signal variability during walking. Aim was addressed by processing sEMG signals acquired from Gastrocnemius Lateralis, Tibialis Anterior, Rectus Femoris and Biceps femoris in 40 healthy subjects in order to: (1) show that occurrence frequency is not correlated with ON/OFF instants (R_mean = 0.11 ± 0.07; P > 0.05) and total time of activation (R_mean = 0.15 ± 0.08; P > 0.05); (2) confirm the above results by two handy examples of application (analysis of gender and age) which highlighted that significant (P < 0.05) gender-related and age-related differences within population were detected in occurrence frequency, but not in temporal sEMG parameters. In conclusion, present study demonstrated that occurrence frequency is able to provide further information, besides those supplied by classical temporal sEMG parameters and thus it is suitable to complement them in the evaluation of variability of myoelectric activity during walking.     

4株SARS冠状病毒基因组5’端序列的分析与比较

利用5′RACE试剂盒对从中国不同地区、不同SARS患者体中分离的SARS-CoV基因组5′端序列进行RT-PCR扩增,并将扩增产物克隆至T easy vector。扩增片段的序列测定结果表明:所分离的4株SARS-CoV基因组5′端非编码区的核苷酸序列和其他国家和地区报道的序列基本一致,而且所形成二级结构也完全相同,但与已知普通冠状病毒的差别较大。同时发现在依赖于RNA的RNA聚合酶起始密码子上游-197 nt处有冠状病毒典型的转录调控核心保守序列5′-CUAAAC-3′。     

Analysis of the Neuronal Background Impulse Activity in the Rat Locus Coeruleus

Using several techniques of statistical analysis, we studied in detail the extracellularly recorded background impulse activity (BA) of neuronal elements of the rat locus coeruleus (LC). Impulse trains generated by most LC neurons were stationary and demonstrated different levels of regularity; a nonstationary type of BA was observed in 17% of the neurons under study. Statistical parameters of the BA generated by LC neurons showed a wide variability. Distributions of the BA interspike intervals (ISI) of most LC neurons were characterized by more or less expressed bimodality or polymodality. Serial correlation analysis of the ISI durations both in stationary and nonstationary spike trains allowed us to differentiate five main types of the dynamics of ISI successions in the BA of LC neurons.     

Analysis of the cell kinetics during planarian regeneration by means of SAMBA 200 cell image processor

Summary The relationships between cell kinetics and nuclear transformations in regeneration were investigated in the planarianPolycelis nigra by means of image analysis. A SAMBA 200 cell image processor was used to compute densitometric, textural and morphological parameters on Feulgen-stained nuclei in the blastema and near the cut 2–96 h after decapitation. On the basis of these parameters, the phase of the cell cycle (G₁–G₀, S, G₂ and M) was identified and the variations in the percentage of cells in the various phases as well as the blastema cell number were computed against time after decapitation. It was demonstrated that the transection is followed by the sequential wasting of the M, G₂, S and G₁–G₀ compartments. The depletion of a compartment was interpreted as being responsible for the subsequent recovery observed in the next one. The results show that cell proliferation at the section level is not sufficient to account for the increase of the blastema cell number during the first 48 h of regeneration, since the doubling time is about 12 h while the average cycle time is 48 h. It is thus suggested that G₁–G₀ cells migrate toward the section level, at least during the first 2 days of regeneration. Analysis of the nuclear profiles demonstrated that there are two different classes of G₁–G₀ cells: one corresponding to mature cells with a lot of condensed chromatin distributed in clumps within the nucleus, the other to immature cells with chromatin regularly distributed according to a rather homogeneous pattern. About one G₁–G₀ cell out of five is immature at the section level before decapitation while four cells out of five are immature as early as 8 h after the cut. This early inversion of the ratio between mature and immature cells argues in favour of an immigration of immature G₁–G₀ cells to the young blastema, where they are expected to accomplish only one cell cycle, and thus gives rise to mature cells.