Position difference regularity of corresponding R-wave peaks for maternal ECG components from different abdominal points

We collected 343 groups of abdominal electrocardiogram(ECG) data from 78 pregnant women and deleted the channels unable for experts to determine R-wave peaks from them; then, based on these filtered data, the statistics of position difference of corresponding R-wave peaks for different maternal ECG components from different points were studied. The resultant statistics showed the regularity that the position difference of corresponding maternal R-wave peaks between different abdominal points does not exceed the range of 30 ms. The regularity was also proved using the fECG data from MIT–BIH PhysioBank. Additionally, the paper applied the obtained regularity, the range of position differences of the corresponding maternal R-wave peaks, to accomplish the automatic detection of maternal R-wave peaks in the recorded all initial 343 groups of abdominal signals, including the ones with the largest fetal ECG components, and all 55 groups of ECG data from MIT–BIH PhysioBank, achieving the successful separation of the maternal ECGs.     

Wavelet optimization for applying continuous wavelet transform to maternal electrocardiogram component enhancing

In the procedure of non-invasive fetal electrocardiogram(ECG) extraction, high-quality maternal R wave peak detection demands enhancing the maternal ECG component firstly. Among all the enhancing algorithms, the one based on the continuous wavelet transform(CWT) is very important and its effectiveness depends on the optimization of the used wavelet. However, up to now, there is still no clear conclusion on the optimal wavelet(including type and scale) for CWT to enhance the maternal ECG component of an abdominal ECG signal. To solve this problem, in this paper, we select several common used types of wavelets to carry out our research on what the optimal wavelets are. We first establish big-enough training datasets with different sampling rates and make a maternal QRS template for each signal in the training datasets.Second, for each type of selected wavelets, we find its optimal scale corresponding to each QRS template in a training dataset based on the principle of maximal correlation. Then calculating the average of all optimized wavelet scales results in the mean optimal wavelet of this type for the dataset. We use two original abdominal ECG databases to train and test the optimized mean optimal wavelets. The test results show that, as a whole, the mean optimal wavelets obtained are superior to the wavelets used in other publications for applying CWT to maternal ECG component enhancing.     

Wireless retrospective gating: Application to cine cardiac imaging

A new “wireless” method of cardiac imaging is introduced, which, unlike ECG triggering, allows imaging the heart at end-diastole, and greatly reduces smearing artifacts in the phase-encoding direction. It is an improvement over ECG-driven retrospective gating, in that patients with poor ECGs can be imaged. This method extends the applicability of cardiac imaging, and since it requires no physiological monitoring hardware, can be implemented easily on any MR imager. The images produced by this method are superior to those from ECG triggering, especially when viewed in a “cine” loop. The technique described herein is, furthermore, extendable to any area where periodic or quasi-periodic motion is a problem.     

Clifford Wavelet Entropy for Fetal ECG Extraction

Analysis of the fetal heart rate during pregnancy is essential for monitoring the proper development of the fetus. Current fetal heart monitoring techniques lack the accuracy in fetal heart rate monitoring and features acquisition, resulting in diagnostic medical issues. The challenge lies in the extraction of the fetal ECG from the mother ECG during pregnancy. This approach has the advantage of being a reliable and non-invasive technique. In the present paper, a wavelet/multiwavelet method is proposed to perfectly extract the fetal ECG parameters from the abdominal mother ECG. In a first step, due to the wavelet/mutiwavelet processing, a denoising procedure is applied to separate the noised parts from the denoised ones. The denoised signal is assumed to be a mixture of both the MECG and the FECG. One of the well-known measures of accuracy in information processing is the concept of entropy. In the present work, a wavelet/multiwavelet Shannon-type entropy is constructed and applied to evaluate the order/disorder of the extracted FECG signal. The experimental results apply to a recent class of Clifford wavelets constructed in Arfaoui, et al. J. Math. Imaging Vis. 2020, 62, 73–97, and Arfaoui, et al. Acta Appl. Math. 2020, 170, 1–35. Additionally, classical Haar–Faber–Schauder wavelets are applied for the purpose of comparison. Two main well-known databases have been applied, the DAISY database and the CinC Challenge 2013 database. The achieved accuracy over the test databases resulted in Se = 100%, PPV = 100% for FECG extraction and peak detection.     

The measurement of fetal liver T(*)(2) in utero before and after maternal oxygen breathing: progress towards a non-invasive measurement of fetal oxygenation and placental function

Utero-placental insufficiency is thought to be a major cause of growth retardation in utero and an important risk factor in the perinatal period. The purpose of this study was to investigate whether MRI could detect changes of fetal oxygenation, based on the blood oxygenation level dependence (BOLD) of the MRI tissue signal. Nine third trimester women (34-38 weeks) with normal pregnancies underwent abdominal MRI examinations. Following localization of the fetal liver using T(2)-weighted single-shot HASTE scans, up to 7 breath-held transaxial single-slice gradient-echo image sets were obtained through the fetal liver. The mother then commenced oxygen breathing with the imaging procedure repeated after 20 minutes of O(2) breathing. For each image set, T(*)(2) values are calculated using linear regression of log (signal) versus TE for a region of interest within the fetal liver selected by the attending radiologist. Fetal liver T(*)(2) values were calculated before and after O(2) breathing for each multi-echo image acquisition set. A signed rank test was used to test for a significant change in fetal liver T(*)(2) between the pre-O(2) and post-O(2) image sets. A significant increase in T*(2) (alpha < 0.05) was seen in 5 of the 9 fetal livers, a smaller increase (of borderline statistical significance, alpha = 0.057) in 2 livers, and no significant change (alpha > 0.05) in 2 livers. Our study indicates that T(*)(2) measurement of the fetal liver may detect alteration in fetal oxygen level following maternal oxygenation using the BOLD effect. This technique may potentially be applied to the identification and understanding of placental dysfunction in intra-uterine growth retardation.     

The biosonar field around an Atlantic bottlenose dolphin (Tursiops truncatus)

The use of remote autonomous passive acoustic recorders (PAR) to determine the distribution of dolphins at a given locations has become very popular. Some investigators are using echolocation clicks to gather information on the presence of dolphins and to identify species. However, in all of these cases, the PAR probably recorded mainly off-axis clicks, even some from behind the animals. Yet there is a very poor understanding of the beam pattern and the click waveform and spectrum from different azimuths around the animal's body. The beam pattern completely around an echo locating dolphin was measured at 16 different but equally spaced angles in the horizontal plane using an 8-hydrophone array in sequence. Eight channels of data were digitized simultaneously at a sampling rate of 500 kHz. The resulting beam patterns in both planes showed a continuous drop off in sound pressure with azimuth around the animal and reached levels below -50 dB relative to the signal recorded on the beam axis. The signals began to break up into two components at angles greater than ± 45° in the horizontal plane. The center frequency dropped off from its maximum at 0° in a non-uniform matter.     

混响室吸声测量中旋转扩散体角度状态及顶角测点位置的影响

通过对3个吸声构件进行了多测点的混响室吸声测量的实验结果进行分析,发现旋转扩散体静止在不同角度状态对测量结果有显著影响,进而提出同一测点在多个旋转扩散体的角度状态下进行测量的测量方法。并使用这一测量方法,比较了混响室顶角测点位置和与按照ISO标准和国标要求选择的空间测点位置所得的测量结果,分析得出顶角测点和空间测点的平均结果是一致的,且顶角位置处的测量结果拥有更小的离散度。因此可以在矩形混响室角落设置少量测点,通过改变旋转扩散体角度状态进行混响室吸声测量。      

Forward masking patterns produced by intracochlear electrical stimulation of one and two electrode pairs in the human cochlea

Three psychophysical forward masking studies were conducted on a multichannel cochlear implant patient. The first study investigated the masking pattern produced by a bipolar electrode pair at different stimulus currents. It was found that the masking pattern for a single-masker bipolar electrode pair had a maximum located at an electrode position where the masker and probe coincided. The spread of the masking pattern was not symmetrical about the maximum. The amount of masking decreased very rapidly toward the apical direction and less rapidly toward the basal direction from the position of the maximum. As the stimulus current increased, the amount of masking at the maximum increased and the masking pattern broadened toward the base. The second study investigated the masking pattern produced by the activation of single bipolar electrode pairs with different spatial extents. The spatial extent of a bipolar electrode pair is defined as the distance between the apical and basal electrode members of the bipolar pair. With a small spatial extent (1.5 mm), the more basal electrode pairs (higher threshold and smaller dynamic range) produced broader masking patterns than the more apical electrode pairs (lower threshold and wider dynamic range), suggesting that there was more current spread at the basal region. With a larger spatial extent (4.5 mm), an additional secondary masking maximum was observed in the vicinity of the apical electrode member of the masker; this was observed only when the apical electrode member lay within the low-threshold apical region. The third study investigated the masking patterns produced by two loudness balanced bipolar masker electrode pairs activated within a stimulus period (inverse of the pulse repetition rate). The biphasic current pulses delivered to the two electrode pairs were nonoverlapping in time. It was found that, at any probe electrode position, the amount of masking produced by the two combined bipolar electrode pairs approximately followed the greater of the two maskings produced respectively by the two individual bipolar masker electrode pairs.     

Identification of mechanisms responsible for fetal weight reduction in mice following ultrasound exposure

This study challenges existing interpretations of the effects of ultrasound on fetal development. The results demonstrated that a lower mean fetal weight in mice observed after intrauterine exposure to 2 MHz ultrasound resulted from maternal distress, and was not simply a direct effect of ultrasound interaction with the fetuses. At day 8 of gestation continuous wave ultrasound was applied to different regions of the maternal abdomen at spatial average intensities between 0.5 and 5.5 W cm-2 for 3 min. Insonating the uterus directly resulted in resorptions, abortions and gross developmental abnormalities, with rare instances of fetal weight reduction which were apparently associated with maternal distended bladder syndrome (DBS). When the ultrasound beam deliberately avoided the uterus, by a dorsal approach centred on the vertebral column, mean fetal weight at day 18 was significantly lower in all mothers showing DBS. Fetuses of insonated mothers not affected by DBS were not significantly different from the sham-insonated group whether the uterus was directly exposed or not. The fetal weight reduction endpoint was therefore found to be more closely correlated with maternal damage (DBS) than with ultrasound intensity.     

Modulation effects in non-drilling NMR in the Earth’s field

The paper describes the variant of nuclear magnetic resonance (NMR) in the Earth’s field using no prepolarization. This method can be employed to record the NMR signal of underground proton-containing liquids, such as water, located at the depth of more than 100 m without drilling. The non-drilling NMR in the Earth’s field is recorded by locating on the surface the circular wire with a diameter of about 100 m. This wire serves as an antenna for the exciting field source and the NMR signal receiver. The radiofrequency pulse with the carrier frequency equal to that of proton resonance in the Earth’s field is passed through the wire. When the exciting pulse is switched off, the induction e.m.f. signal caused by the free Larmor nuclear precession in the geomagnetic fields is observed. An important case when in the non-drilling NMR in the Earth’s field the signal is excited and observed at different frequencies is studied both from theoretical and practical viewpoints. The resulting modulation effects are considered. Such situations arise e.g. either in magnetic rocks or upon magnetic storms.     

Mapping charge-mosaic surfaces in electrolyte solutions using surface charge microscopy

A significant limitation of electrokinetic measurements is that only an average value of the zeta potential/streaming potential is measured—regardless of whether the surface charge distribution is homogeneous or otherwise. However, in real-world situations, nearly all solids (and liquids) of technological significance exhibit surface heterogeneities. To detect heterogeneities in surface charge, analytical tools which provide accurate and spatially resolved information about material surface potential—particularly at microscopic and sub-microscopic resolutions—are needed.A novel AFM-based technique for mapping surface charge domains on heterogeneous surfaces, which we call Surface Charge Microscopy (SCM), was recently introduced by our research team. It relies on recording colloidal force curves over multiple locations on the substrate surface using small probes. The surface charge characteristics of the heterogeneous substrate are determined from the recorded colloidal force curves, allowing for the surface charge variation to be mapped. In this communication, we briefly review the SCM technique. Examples of results of measurements of the surface interaction forces that were recorded between a silicon nitride AFM cantilever and a multi-phase volcanic rock and heterogeneous surface of bitumen are also given.     

2,5-二乙基吡嗪的SERS光谱中电荷转移增强机制的贡献(英文)

SERSspectraof2,5-dimethylpyrazinehave beenrecordedonsilversurfaceatdifferentelec trodepotentials.TherelativeSERSintensitiesare comparedwiththoseoftheRamanspectrumofan aqueoussolutionandtheselectiveSERSenhance menthasbeenexplainedaccordingtoacharge trans…     

惯性约束聚变装置中靶面光场特性的统计表征方法

在激光驱动的惯性约束聚变装置中,常采用多种束匀滑手段对焦斑的时空特性进行调控.光传输链路中涉及的光学元件众多、传输变换复杂,往往导致光传输模型复杂,且在运用衍射光学方法分析焦斑形态和特征时面临大量的数据处理和计算,致使出现计算量大、计算效率低等问题,亟需寻求快速而简便的新方法来描述焦斑的统计特征.本文利用光场特性的统计表征方法对靶面光场进行表征,采用圆型复数高斯随机变量直接描述靶面光场的统计特征,并基于典型焦斑评价参数对衍射光学方法和统计表征方法得到的远场焦斑进行了对比和分析.结果表明,采用衍射光学方法和统计表征方法获得的焦斑的瞬时特征基本一致,其时间积分的远场焦斑有所不同,但仍可进一步采用相关系数来表征其远场焦斑的时间变化特征.     

Effect of dielectric barrier discharge on semiconductor Si electrode surface

Electrode materials and shapes affected the discharge modes. Meanwhile, the discharge has influence upon electrode surface. In order to study the effect of discharge on semiconductor electrode, the experiments were carried out using single crystal Si wafer as high voltage electrode of atmospheric pressure dielectric barrier discharge in air. The effects of dielectric barrier discharge on Si electrode surface are analyzed by means of field emission scanning electron microscope (FESEM) and X-ray photoelectron spectroscopy (XPS). The results show that surface roughness and oxidation increase with discharge time, while surface nitridation is not observed on Si electrode surface. It is different from Cu electrode. The difference is due to different chemical reactions between electrode surface and air plasma but could also be ascribed to the different analysis techniques used.     

When Langmuir is too simple: H2 dissociation on Pd(111) at high coverage

Recent experiments of H2 adsorption on Pd(111) [Nature (London) 422, 705 (2003)]] have questioned the classical Langmuir picture of second order adsorption kinetics at high surface coverage requiring pairs of empty sites for the dissociative chemisorption. Experiments find that at least three empty sites are needed. Through density functional theory, we find that H2 dissociation is favored on ensembles of sites that involve a Pd atom with no direct interaction with adsorbed hydrogen. Such active sites are formed by aggregation of at least 3 H-free sites revealing the complex structure of the "active sites."     

Geometry of locating sounds from differences in travel time: isodiachrons

Calling animals may be located from measurements of the differences in acoustic travel time at pairs of receivers. For inhomogeneous fields of speed, locations can be made with better accuracy when the location algorithm allows the speed to vary from path to path. A new geometrical shape, called an isodiachron, is described. It is the locus of points corresponding to a constant difference in travel time along straight paths between the animal and two receivers. Its properties allow an interpretation for locations when the speed differs from path to path. An algorithm has been developed for finding the location of calling animals by intersecting isodiachrons from data collected at pairs of receivers. When the sound speed field is spatially homogeneous, isodiachrons become hyperboloids. Unlike a hyperboloid that extends to infinity, an isodiachron is confined to a finite region of space when the speeds differ between the animal and each of two receivers. Its shape is significantly different than a hyperboloid for cases of practical interest. Isodiachrons can be used to better understand locations of calling animals and other sounds in the sea, Earth, and air.     

总体经验模态分解能量向量用于ECG能量分布的研究

总体经验模态分解(EEMD)改进了经验模态分解(EMD)存在的模态混叠问题, 依据信号自身的波动特点将信号分解, 特别适合非线性非平稳信号的分析处理. ECG信号能量分布有一定的规律, 疾病会引起能量分布的变化, 研究ECG能量分布的改变对心脏疾病的研究和临床诊断有重要意义. 本文将ECG信号通过EEMD方法分解为多个本征模态函数(IMF)分量, 观察IMF分量的波动规律, 指出了ECG信号在不同时间尺度上的波动特点和物理意义. 将IMF分量分别计算能量, 得到ECG的能量向量, 并对健康人和三种心脏疾病患者能量向量进行对比分析. 结果表明心脏疾病导致EEMD能量向量的高频分量显著降低, 尤其是p₁分量具有较好的区分度, 可以作为心脏疾病诊断的参考依据. 相比较传统的频域分析方法单纯关注频率而忽略信号自身特点和信号成分之间的相互作用, EEMD的分解结果依赖于ECG信号本身, 因此更能够反映ECG信号的真实情况, 揭示年龄和疾病对ECG能量分布的影响.     

电极熔蚀导致的气体开关绝缘子性能劣化

气体开关导通时,电极材料熔融或汽化并从电极表面移出,导致开关绝缘子被染污,并可能诱发开关内绝缘闪络事故,直接影响气体开关寿命和脉冲功率系统稳定性。在开关内嵌入有机玻璃圆环,收集黄铜电极熔蚀产物,并研究其对开关绝缘子表面形貌和沿面绝缘强度的影响。实验结果表明,电极熔蚀会产生大量金属蒸汽和溅射液滴,且熔蚀产物具有明显的轴向分布特性,其中,金属蒸汽冷凝并附着在绝缘子表面,形成细微的金属粉末;溅射液滴轰击绝缘子表面,在局部区域形成密集的表面裂纹和金属颗粒嵌入物。在两种电极熔蚀产物的共同作用下,开关绝缘子表面绝缘电阻下降,闪络场强降低;同时,绝缘子表面轴向不同区域的绝缘电阻差别很大,引起绝缘子表面电压分布不均和局部电场增强,最终导致开关绝缘子闪络电压降低,闪络概率增大。     

Perception of multiple electrode stimulus patterns: implications for design of an electrotactile speech processor

Identification of multiple-electrode stimulus patterns was evaluated in nine adult subjects, to assess the feasibility of providing additional speech information through the tactual display of an electrotactile speech processor. Absolute identification scores decreased from 97.8% for single electrodes, to 61.9% for electrode pairs, and, to 31.8% for electrode triplets. Although input information increased with paired-and triple-electrode stimuli, information transmission scores were not significantly increased for either electrode pairs (2.99 bits) or triplets (2.84 bits) as compared with single electrodes (2.84 bits). These results suggest that speech coding strategies using stimulus patterns of electrode pairs or triplets would provide little improvement beyond that found for the present single-electrode scheme. However, higher absolute identification scores (73.6%), and an increase in information transmission to 3.88 bits, were recorded for test stimuli containing all combinations of paired and single electrodes. Based on this finding, two stimulus sets using a restricted number of combinations of paired and single electrodes were evaluated. The two stimulus sets simulated the spatial patterns of paired and single electrodes arising from use of alternative speech coding schemes to increase consonant voicing information. Results for the two stimulus sets showed higher electrode identification scores (79.7% and 90.4%), as compared with paired-electrode stimuli. Although electrode identification score was not as high as for single electrodes, information transmission was increased to 3.31 bits for the VF2 stimulus set. Analysis of the responses also showed that scores for identification of simulated voicing information conveyed by the two stimulus sets were 99.4 and 90.4% correct.(ABSTRACT TRUNCATED AT 250 WORDS)     

Heat transfer and cold cathode erosion in electric arc heaters

A simple thermophysical model is proposed for cold electrode erosion in electric arc heaters. The model regards erosion as characterized by an effective enthalpy of electrode material ablation, resulting in heat unbalance between heat supply and heat removal by conduction. Replacing the arc spot by a moving surface heat source, the space-time evolution of the electrode surface temperature is studied in coordinates coupled to the source. Applying heat diffusion equations, we show that the erosion problem can be represented by a system of three simple equations. An experimental coaxial setup, with a magnetically driven arc, has been used for the erosion measurements in copper electrodes. Special thermal experiments were carried out for measuring needed arc spot parameters. A comparison of the model with our own and other experimental data demonstrates a reasonable agreement. The present model reveals the relative significance of the different parameters in the erosion process, and permits us to predict the erosion behavior in cold electrode electric arc heaters in a wide range of parameters