多层生物介质传感器的特性研究（英文）

目的 多层生物介质的生物传感器被广泛应用于各大领域,其检测特性对于传感器优劣的评估尤为重要。本文目的在于量化表征多层生物介质的电学特征。方法 基于生物电阻抗谱技术来探究多层生物介质的电化学阻抗谱特性,并结合保角映射的方法来量化表征多层生物介质,阐明其对阻抗的影响规律,继而为生物传感器的研制与开发提供理论基础。有效提取各生物介质层修饰后电阻抗参数(Z^*),从而量化表征多层生物介质层的电阻抗谱特性。结果 对多层模型进行了理论计算并构建了相关试验测试系统,研究结果表明,随着生物介质层的逐步修饰,检测区域电阻抗参数(Z^*)在f=0.1～50 MHz下持续上升,理论计算结果趋势与试验结果趋势较好吻合,论证了此理论计算方法的正确性。结论 本文证实了可根据生物电阻抗谱和保角映射方法量化表征多层生物介质的电阻抗谱特性,对生物传感器的研制与开发有一定的实用价值。     

一种高阶插值边界单元法及其在人体生物电场计算中的应用

在人体生物电分析方面,人们熟悉的方法是由体表测取人体生物电信号直接分析处理,如常规心电图(ECG)和脑电图(EEG)。这种由体表电信号测量加上临床医生经验推断,就构成了目前生物电分析的主要手段。近年虽然在生物电测量与显示方面应用了一些新技术,如多点同步采集电信号与插值平滑技术结合获得包含一定空间信息的体表电位图与脑地形图。测量分析体表功率谱以及压缩谱阵等。但这些方法终究仅能反应一种源     

基于MIMIC数据库的多参数数据D/A回放系统

文中分析了MIMIC多参数智能监护数据库存储文件的识读方法,该数据库公开发表于PhysioNET,还研究及基于STM32和DAC8568的多参数数据D/A回放系统,包括系统硬件工作原理和系统软件工作原理。MIMIC多参数智能监护数据库的数据文件对于变异性较大的生理参数采用连续采样的方式,而对于相对稳定的生理参数采用周期采样的方式,因此,多参数数据各信号的抽样频率不同。系统首先通过VC++编程读取一个多抽样频率数据并在PC机上显示其波形,然后经过D/A硬件设备进行D/A转换后使用示波器输出其波形,实现输出的波形与原始的波形能同时回放。系统可作为模拟信号源,为远程多参数生理监护仪的研制奠定了基础。     

电阻抗断层成像技术进展

电阻抗断层成像技术分为:静态EIT(以电阻抗分布的绝对值为成像目标)和动态EIT(以电阻抗分布的相对值为成像目标),它是近年来国内外生物医学工程研究的比较热门的一种成像技术。因为与已有的X射线成像、计算机断层扫描成像(CT)、核磁共振成像(MRI)及超声成像相比,这种新的成像技术不仅具有解剖学的特征信息,还有功能性成像的性质。又因为它的无创、简单、便宜、容易应用等特点,在临床有着很好的应用前景。本文通过数学、物理以及应用上的论述并结合了最新的国内外科研动态。介绍了电阻抗断层成像技术的数学计算(包括算法和算法分析),物理基础(激励方式,激励频率,驱动模式),揭示了电阻抗断层成像技术的基本原理,并展示了此项技术的临床应用情况。     

一类信号转导通路模型参数辨识中最小应测量状态的确定

建立信号转导通路的数学模型是系统生物学的一个重要目标．但是信号转导通路本身的复杂结构及其所表现出的强非线性特征,使得对该类模型的参数辨识十分困难．参数辨识所需要的测量数据的选择对于辨识结果有重要影响．本文研究了一类信号转导通路模型参数辨识中最小应测量状态的计算问题．给出了用于确定该最小应测量状态的目标函数,通过对目标函数进行简单的运算,确定了用来估计未知参数的最小应测量状态的数量,同时给出了一种计算系统状态对应于未知参数的敏感性系统曲线的新方法．以TNFα诱导的NF-κB信号转导通路为例进行了仿真研究,并给出了仿真结果．     

阻抗心动图生理基础及其临床意义

阻抗心动图是近十余年来国际上新发展起来的一种反映血流动力学变化的无创伤检查方法。本文概括论述了方法学上一些有关问题和阻抗心动图△Z 波及其一阶导数 dz/dt 波的组成。着重讨论胸腔内血流动力学、血液理化特性等若干因素对阻抗动、静态变化的作用;阻抗心动图在反映病理生理状态下心输出量可信度;以及测量参数及各波形的临床意义。对于方法学理论上的不同学术观点和阻抗波形的一些非特异性病理生理现象,本文亦同时予以评述。     

射击过程中主要生理特征的研究

八名射击运动员(手枪2人,步枪6人),在实弹射击训练中,连续同步地记录了脑电、心电、心率、阻抗呼吸波。同时记录了受试者持枪稳定的程度。 分析表明,射击环数是五项独立无关的指标综合作用的结果。本文首次对射击时生理指标和射击环数进行系统辨识建模分析,求出每个人的系统参数_i值。找出了每人射击时最佳生理参数,为指导射击练习和反馈训练,提供了客观生理依据。 本文设计的激光光点录相方法,可反映持枪稳定的程度,简单、方便,可在射击训练中采用。     

基于GIS的梭梭年轮测量方法

年轮信息对重建气候和预测环境的动态变化有重要意义。为准确测量梭梭年轮间距等各项参数,研究基于GIS对扫描后的梭梭圆盘PS图像赋予坐标系统,通过ENVI图像分类软件结合GIS测量工具,完成梭梭年轮间距测量;利用WinDENDRO年轮分析系统验证测量结果的准确性。结果表明: 两种方法测量结果差异不显著(P=0.63),配对平均值差值为0.87 μm,测量结果准确可信。研究构建的方法可以用于梭梭年轮间距测量,并为面积、周长等年轮参数的自动化测量奠定了基础。该方法也可替代现有专业树木年轮分析系统用于部分年轮参数测量。研究结果有助于梭梭树轮气候学分析和种群年龄结构调查。     

神经冲动积分仪

本文主要介绍一种新的神经冲动积分仪结构原理。由于在仪器设计中,采用了线性的模数转换和十二位(BIN)的数模转换电路,配合其它数字逻辑之后,使仪器除了具有置零积分,平均值电路功能外,还具有频率直方图和幅度直方图处理功能,并同时有六位数字显示和声音监听,尤其更适合于用来描绘变化较慢而又需长时间观察的各种生物电的实验信息。线路中由于设置了去除电刺激伪迹装置和阈值电平调节,使仪器能有效地抑制各种干扰信号。     

多导联在线阻抗检测的实现与分析

目的：提出了一种基于多导联生理信号采集装置平台的快速、稳定、低功耗的在线阻抗测量方法。方法：在线阻抗测量的实现主要有两个关键技术：正弦信号恒流源和数字带通滤波器,都主要是采用软件的方式实现的。结果：单极性和双极性两种模式四组测量阻值的变异系数均不超过10%,测量值的稳定性较高,可以通过多次测量求平均值的办法来修正测量误差,修正后的误差明显优于修正之前的误差。结论：由单极性和双极性两种模式实际阻抗测量值可知,测量值能够准确反映电极与人体表皮的接触情况,此种方法稳定可靠。     

Detection of viable Salmonella typhimurium by impedance measurement of electrode capacitance and medium resistance

Three-electrode electrochemical impedance technique was investigated for detection of Salmonella typhimurium by monitoring the growth of bacteria in selenite cystine (SC) broth supplemented with trimethylamine oxide hydrochloride (TMAO.HCl) and mannitol (M). The change in the system impedance during the growth of bacteria was studied using frequency spectral scanning. It was found that the impedance at low frequencies (<10 kHz) mainly came from the double-charged layer capacitance, reflecting the changes at the electrode interface and the adsorption on the electrode surface. While at high frequencies (>10 kHz), the system impedance mainly depended on the medium resistance. The adsorption of bacteria on the electrode surface was detected by measuring low frequency impedance, and verified with Faradic impedance spectroscopy. Enumeration of S. typhimurium using a low frequency (1 Hz) capacitance measurement and a high frequency (1 MHz) resistance measurement were compared. The detection times were determined for quantitative analysis based on the growth curves of bacteria referring to either the medium resistance or electrode capacitance. The regression equations for the detection times (t(d), h) and the initial cell number (N, cells.ml(-1)) were t(d)=-1.24logN+13.4 with R(2)=0.98 and t(d)=-1.40logN+14.46 with R(2)=0.97 for the medium resistance and electrode capacitance methods, respectively.     

The Modulation Transfer Function for Speech Intelligibility

We systematically determined which spectrotemporal modulations in speech are necessary for comprehension by human listeners. Speech comprehension has been shown to be robust to spectral and temporal degradations, but the specific relevance of particular degradations is arguable due to the complexity of the joint spectral and temporal information in the speech signal. We applied a novel modulation filtering technique to recorded sentences to restrict acoustic information quantitatively and to obtain a joint spectrotemporal modulation transfer function for speech comprehension, the speech MTF. For American English, the speech MTF showed the criticality of low modulation frequencies in both time and frequency. Comprehension was significantly impaired when temporal modulations <12 Hz or spectral modulations <4 cycles/kHz were removed. More specifically, the MTF was bandpass in temporal modulations and low-pass in spectral modulations: temporal modulations from 1 to 7 Hz and spectral modulations <1 cycles/kHz were the most important. We evaluated the importance of spectrotemporal modulations for vocal gender identification and found a different region of interest: removing spectral modulations between 3 and 7 cycles/kHz significantly increases gender misidentifications of female speakers. The determination of the speech MTF furnishes an additional method for producing speech signals with reduced bandwidth but high intelligibility. Such compression could be used for audio applications such as file compression or noise removal and for clinical applications such as signal processing for cochlear implants.     

Female phonotaxis and frequency discrimination in the bushcricket Requena verticalis

ABSTRACT. The male bushcricket, Requena verticalis , calls with a signal containing two predominant frequencies, 16 kHz and 28 kHz. A synthesized call, made from a template of the natural call, was played to females under conditions of a two-speaker trial on a flat arena. Orientation pathways to a speaker emitting only a 16 kHz signal were more circuitous than the pathways made by females orientating to a speaker emitting only a 28 kHz signal. Females preferred a signal with both carrier frequency peaks present within the song to a signal with only a 16 kHz or 28 kHz carrier frequency, when the signal containing a double peak was kept at equivalent absolute intensity to that with a single peak. Females chose signals containing a more powerful high frequency peak over a signal in which both peaks were balanced. For the higher peak, they were able to differentiate between frequencies with a separation of 8 kHz but not of 4 kHz. They were unable to differentiate between frequencies with a separation up to 8 kHz in the lower peak when one frequency was held at 16 kHz; however, when this frequency was held at 18 kHz, females were able to distinguish between frequencies with a difference of 4 kHz. ( N.B. 18 kHz is 2 kHz above the mean value for this frequency within the natural population.) We conclude that females are choosing males on the amount of power in the higher frequency range of their song and that this may be equivalent to a close calling male in the field.     

Effects of Sound Frequency on Audiovisual Integration: An Event-Related Potential Study

A combination of signals across modalities can facilitate sensory perception. The audiovisual facilitative effect strongly depends on the features of the stimulus. Here, we investigated how sound frequency, which is one of basic features of an auditory signal, modulates audiovisual integration. In this study, the task of the participant was to respond to a visual target stimulus by pressing a key while ignoring auditory stimuli, comprising of tones of different frequencies (0.5, 1, 2.5 and 5 kHz). A significant facilitation of reaction times was obtained following audiovisual stimulation, irrespective of whether the task-irrelevant sounds were low or high frequency. Using event-related potential (ERP), audiovisual integration was found over the occipital area for 0.5 kHz auditory stimuli from 190–210 ms, for 1 kHz stimuli from 170–200 ms, for 2.5 kHz stimuli from 140–200 ms, 5 kHz stimuli from 100–200 ms. These findings suggest that a higher frequency sound signal paired with visual stimuli might be early processed or integrated despite the auditory stimuli being task-irrelevant information. Furthermore, audiovisual integration in late latency (300–340 ms) ERPs with fronto-central topography was found for auditory stimuli of lower frequencies (0.5, 1 and 2.5 kHz). Our results confirmed that audiovisual integration is affected by the frequency of an auditory stimulus. Taken together, the neurophysiological results provide unique insight into how the brain processes a multisensory visual signal and auditory stimuli of different frequencies.     

Dolphins Adjust Species-Specific Frequency Parameters to Compensate for Increasing Background Noise

An increase in ocean noise levels could interfere with acoustic communication of marine mammals. In this study we explored the effects of anthropogenic and natural noise on the acoustic properties of a dolphin communication signal, the whistle. A towed array with four elements was used to record environmental background noise and whistles of short-beaked common-, Atlantic spotted- and striped-dolphins in the Canaries archipelago. Four frequency parameters were measured from each whistle, while Sound Pressure Levels (SPL) of the background noise were measured at the central frequencies of seven one-third octave bands, from 5 to 20 kHz. Results show that dolphins increase the whistles’ frequency parameters with lower variability in the presence of anthropogenic noise, and increase the end frequency of their whistles when confronted with increasing natural noise. This study provides the first evidence that the synergy among SPLs has a role in shaping the whistles'' structure of these three species, with respect to both natural and anthropogenic noise.     

Measurement of total respiratory impedance in infants by the forced oscillation technique

The forced oscillation technique according to Làndsér et al. (J. Appl. Physiol. 41:101-106, 1976) was modified for use in infants. Adaptations, including a flexible tube to connect the infant to the measuring system and a bias flow to avoid rebreathing, did not influence impedance values. The linearity of the respiratory system was assessed and confirmed by 1) applying pseudo-random noise oscillations at three different amplitudes to 7 infants and 2) comparing in 12 infants impedance values obtained with pseudo-random noise and with sinusoidal oscillations at 12 and 32 Hz. Intersubject variability, averaged for all frequencies, was 6%. In 17 infants the relative error (+/- SD) between two series of five measurements within a time interval of 15 min was 0.5 +/- 5.7%. No statistically significant difference was found between impedance values before and after repositioning of the infant's head, whereas rotation resulted in a decrease in resistance and no effect on reactance. Our results indicate that the infant-adapted forced pseudo-random noise oscillation technique has the potential to give valuable information about ventilatory lung function in infants.     

In Vivo Impedance of the Gerbil Cochlear Partition at Auditory Frequencies

The specific acoustic impedance of the cochlear partition was measured from 4 to 20 kHz in the basal turn of the gerbil cochlea, where the best frequency is ∼40 kHz. The acoustic impedance was found as the ratio of driving pressure to velocity response. It is the physical attribute that governs cochlear mechanics and has never before been directly measured, to our knowledge. The basilar membrane velocity was measured through the transparent round window membrane. Simultaneously, the intracochlear pressure was measured close to the stapes and quite close to the cochlear partition. The impedance phase was close to −90° and the magnitude decreased with frequency, consistent with stiffness-dominated impedance. The resistive component of the impedance was relatively small. Usually the resistance was negative at frequencies below 8 kHz; this unexpected finding might be due to other vibration modes within the cochlear partition.     

长江和畅洲江段大型船舶的噪声特征及其对长江江豚的潜在影响

长江航运业的快速发展导致长江中船舶数量激增,相应的水体噪声污染可能对同水域的长江江豚（Neophocaena asiaeorientalis asiaeorientalis）产生一定的负面影响,本研究采用宽频录音设备对长江和畅洲北汊非正式通航江段的各类常见大型船舶（长>15m且宽>5m）的航行噪声进行了记录,并分析其峰值-峰值声压级强度（SPLp-p）和功率谱密度（PSD）等。结果表明,大型船舶的航行噪声能量分布频率范围较广（>100kHz）,但主要集中于中低频（<10kHz）部分,各频率（20Hz~144kHz）处的均方根声压级（SPLrms）对环境背景噪声在该频率处的噪声增量范围为3.7~66.5dB。接收到的1/3倍频程声压级（TOL）在各频率处都大于70dB,在8~140kHz频段内都高于长江江豚的听觉阈值。说明大型船舶的航行噪声可能会对长江江豚个体间的声通讯及听觉带来不利影响,如听觉掩盖。     

Why longer song elements are easier to detect: threshold level-duration functions in the Great Tit and comparison with human data

Our study estimates detection thresholds for tones of different durations and frequencies in Great Tits (Parus major) with operant procedures. We employ signals covering the duration and frequency range of communication signals of this species (40–1,010 ms; 2, 4, 6.3 kHz), and we measure threshold level-duration (TLD) function (relating threshold level to signal duration) in silence as well as under behaviorally relevant environmental noise conditions (urban noise, woodland noise). Detection thresholds decreased with increasing signal duration. Thresholds at any given duration were a function of signal frequency and were elevated in background noise, but the shape of Great Tit TLD functions was independent of signal frequency and background condition. To enable comparisons of our Great Tit data to those from other species, TLD functions were first fitted with a traditional leaky-integrator model. We then applied a probabilistic model to interpret the trade-off between signal amplitude and duration at threshold. Great Tit TLD functions exhibit features that are similar across species. The current results, however, cannot explain why Great Tits in noisy urban environments produce shorter song elements or faster songs than those in quieter woodland environments, as detection thresholds are lower for longer elements also under noisy conditions.     

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.