便携式双通道脑电遥测系统的研制

目的 研制一套便携式的双通道脑电遥测系统.方法 1）脑电放大器,AD8221仪用放大器为前置放大端,精密放大器AD824完成放大、滤波以及电平调整;2）无线传输,采用两片nRF24E1作为无线收发主芯片,该芯片集成8051内核、8通道A/D转换器,通过软件编程实现双通道脑电信号的采集和数据打包.3）电源设计,系统采用锂电池供电,并有电源充放电管理和监测报警电路.结果 经测试性能达到要求,可用于便携式脑电信号的采集. 结论 这套研制便携式脑电遥测系统的方法是可行的,进一步改进后可做成头戴式遥测系统.     

Amplification of biosignals by body potential driving. Analysis of the circuit performance

A method for amplification of biosignals with asymmetrical amplifiers in the presence of mains interference is described. The common mode body potential is reduced by a body potential driver (BPD) circuit. A detailed model of the BPD circuit is analysed. A new quantity, residual impedance Z_r, which estimates the BPD performance is introduced. The influence of the BPD circuit parameters on the stability and Z_r are estimated so that optimal performance can be reached. Practical recommendations for the circuit design are given because controversial conditions must be satisfied to reach both the stability and minimum Z_r. The main advantage of the method is its simplicity, which leads to significant reduction of the number of elements as well as precision requirements in multichannel amplifier design.     

Development of digital stethoscope for telemedicine

The stethoscope is a medical acoustic device which is used to auscultate internal body sounds, mainly the heart and lungs. A digital stethoscope overcomes the limitations of a conventional stethoscope as the sound data is transformed into electrical signals which can be amplified, stored, replayed and, more importantly, sent for an expert opinion, making it very useful in telemedicine. With the above in view, a low cost digital stethoscope has been developed which is interfaceble with mobile communication devices. In this instrument sounds from various locations can be captured with the help of an electret condenser microphone. Captured sound is filtered, amplified and processed digitally using an adaptive line enhancement technique to obtain audible and distinct heart sounds.     

Identification of limited regions of genetic aberrations in patients affected with Wilms' tumor using a tiling-path chromosome 22 array

Wilms' tumor (WT) is one of the most common solid tumors of childhood. The genetics of this disorder is complex and few studies have suggested allelic loss of chromosome 22 as a frequent aberration. To assess tumor- and possible germline-specific regions affected with gene copy number variations on this chromosome, we applied a high-resolution genomic clone-based chromosome 22 array to a series of 28 WT samples and the paired blood-derived DNA of the patients. The group of tumors was enriched for cases with metastases, relapse or fatal outcome, criteria that were expected to yield a higher number of alterations on chromosome 22. Overall, the array-based form of comparative genomic hybridization (array-CGH) analysis revealed genomic changes in 53% (15 out of 28) of cases. We identified hemizygous deletion of the whole arm of 22q in 3 tumors (11%). Furthermore, a complex amplifier genotype was detected in 8 samples, presenting regions of gain along the chromosome, which defined 7 distinct minimal overlapping segments. The distribution of aberrations in 4 additional cases displaying regional genomic imbalances delimited 2 tumor suppressor/oncogene candidate loci, 1 in the proximal and the other in the terminal part of 22q. Analysis of these regions revealed the presence of several candidate genes that may play a role in the development of WT. These findings demonstrate the power of array-CGH in the determination of DNA copy number alterations and further strength the notion that WT-associated genes exist on this chromosome.     

Characterization of human peripheral blood T lymphocytes bearing receptors for autologous erythrocytes and T lymphocytes lacking these receptors

When human T cells were treated with neuraminidase fromVibrio cholerae, the capacity of T cells to form rosettes with autologous erythrocytes was markedly enhanced. The neuraminidase-treated T cells were separated with autologous erythrocytes into autorosetting and nonrosetting cell populations, and these two populations examined for their reactivity to mitogens and B cells and for their regulatory activities. Autorosetting T cells proliferated poorly in response to mitogens and autologous and allogeneic B cells; these cells were particularly enriched for cells capable of becoming concanavalin A-induced suppressor cells. Nonrosetting T cells capable of most actively proliferating in response to the mitogens and the B cells failed to exhibit such suppressor function after concanavalin A activation. Coculture experiments between autorosetting and nonrosetting cells further demonstrated that the nonrosetting T cells were able to potentiate the proliferation of the autorosetting T cells with concomitant expression of the suppressor properties.This work was presented in part at the 65th Annual Meeting of the Federation of American Societies for Experimental Biology, April 16, 1981.     

Noise characteristic design of CMOS source follower and voltage amplifier for active semiconductor microelectrodes for neural signal recording

A noise performance design method for the pre-amplifiers of an active neural probe is given. The on-chip circuitry of the active neural probe consists of CMOS devices that show high-/ low-frequency noise, so that the device noise can become dominant. Analysis of the signal-to-device-noise ratio (SDNR) for the CMOS source follower buffer and two-stage differential voltage amplifier is given. Closed-form expressions for the output noise power are derived and exploited to tailor the parameters that are controllable during circuit design. The output SDNR is calculated considering the real extracellular action potentials, the electrode-electrolyte interface and the noise spectrum of CMOS devices from typical foundries. It is shown that the output device noise power can be much higher than the output signal power if the devices at the input stage of the pre-amplifier are made as small as given fabrication technology permits. Quantitative information of the circuit parameters to achieve an SDNR higher than 5 for neural spikes with 60μV amplitude are provided for both preamplifier types.     

A low noise isolated amplifier system for electrophysiological measurements: basic considerations and design

An instrumentation amplifier for medical and biological research applications is described. It consists of an isolated preamplifier with a high signal/ noise ratio and a computer or microprocessor controlled main amplifier that incorporates variable highpass and lowpass filtering. The preamplifier includes an input stage, a compensation circuit for electrode offset voltage and an isolation amplifier. Recently introduced ultra low noise operational amplifiers used in the input stage ensure good noise behaviour. Isolation is obtained with an inductive isolation amplifier, which also delivers the supply voltages for the input stage. Accordingly, battery power is not needed, in contrast with optically isolated amplifiers. The main amplifier has computer control for gain, lowpass cut-off frequency and highpass cut-off frequency settings. This features dynamic changes in signal conditioning and data acquisition by the same computer that collects the data. Data acquisition and noise behaviour are discussed. The filter configuration is designed in such a way that several user-defined options can be implemented on the same circuit board. The trade-off between the order of the lowpass filters, their roll-off, and the sampling rate which is used in the subsequent computing system, are of major importance and will be discussed. The amplifier system is at present in sue in laboratories of neurology (BEP, EEG), opthalmology (VEP, EOG, ERG) and cardiology (noninvasive His bundle recordings) from which some results will be presented. The amplifiers form a part of a microprocessor-controlled data acquisition system.     

单电源液压伺服放大器的研制

研制了一种驱动直动式电液阀的单电源伺服放大器,该放大器具有限幅、调零、增益可调功能,同时具有可以实时监控阀芯位置的特点;根据技术指标设计了伺服放大电路,并采用Multisim软件对电路模型进行了仿真分析;制成印刷电路板,对其性能进行了测试,并与仿真结果作对比。结果表明：研制的放大器输出电流线性度好,有效幅值可调范围宽,满足技术要求。     

The significance of the calcium signal in the outer hair cells and its possible role in tinnitus of cochlear origin

Finely tuned changes in intracellular Ca²⁺ concentration modulate a variety of cellular functions in eukaryotic cells. The cytosolic Ca²⁺ concentration is also tightly controlled in the outer hair cells (OHCs), the highly specialized receptor and effector cells in the mammalian auditory epithelium, which are responsible for high sensitivity and sharp frequency discrimination in hearing. OHCs possess a complex system of transporters, pumps, exchangers, channels and binding proteins to develop and to halt the regulatory Ca²⁺ signal. The crucial role of elevated intracellular Ca²⁺ concentration in OHCs is to increase the efficacy of the electromechanical (electromotile) feedback via remodeling of the cortical cytoskeleton. Anomalies in the Ca²⁺ signaling pathway may lead to hypersensitivity of the cochlear amplifier and subsequently trigger tinnitus of cochlear origin. This review describes the dynamics of Ca²⁺ signaling in the OHCs and a model that may convey a putative mechanism of development of subjective idiopathic cochlear tinnitus.