Current-to-voltage convertor for measurement of oxygen

A highly sensitive, miniature, inexpensive circuit for the measurement of PO2 in vivo has been described. The circuit is constructed from a current-to-voltage convertor, clamping circuit, differential amplifier, and reverse voltage and overvoltage protector. The design of the circuit allows us to apply voltage bias to the measuring electrode while grounding the preparation. The clamping circuit holds the selected bias voltage constant while the differential amplifier subtracts this bias potential from the PO2 signal yielding an output voltage that is proportional to the current sensed by the oxygen electrode. The circuit is protected from reverse voltage and overvoltage.     

Non-contacting electrode system for the measurement of strain generated potentials in bone

Current methods employing contact electrodes for the measurement of the electromechanical properties of bone produce errors in the measurement due to the effects of polarization at the bone-electrode interface, and the flow of electric charges in the bone measuring circuit. In addition, signal artefacts may result from the movement of an electrode in contact with a specimen undergoing mechanical deformation. The principles for a non-contacting method, based on charge induction on a conductive plate placed in the field of a charged body (bone), and the resulting non-contacting electrode system are presented in this paper. The new electrode enabled measurement of strain generated potentials (SGP) in bone with minimal effect from the measuring circuit and provided new results previously masked by contacting measurement methods. Furthermore, the new electrode is a potential tool for further investigation of the in vitro electromechanical behaviour of bone, particularly in partially hydrated specimens and in vivo, thereby avoiding invasive methods or use of ionizing radiation.     

A Porometer for Laboratory and Field Operation

A porometer is described which is easily and rapidly attachedto plant leaves and appears to be a versatile and sensitiveinstrument for laboratory or field measurement of leaf resistanceto air flow. In the laboratory it can be connected to a normalresistance porometer circuit, and in the field to a sphygrnomanometer.A theoretical relationship has been developed and tested whichenables the conversion of leaf resistance obtained with a sphygmomanometerto that obtained with a normal porometer circuit.     

Newly explored electrical properties of normal skin and special skin sites.

Skin impedance measurements at various skin sites yield different impedance loci for normal skin and special skin sites. The results of skin impedance measurements taken at such sites with a two-electrode measurement system are presented herein. Some of these sites can be identified as acupuncture points. Data from 4 volunteers were acquired by means of a data acquisition board and a measuring system consisting of the measurement circuit, including several electrode types, and a power supply. The Cole model is a model for an equivalent electrical circuit of the skin-electrode system. The system was used to derive skin-typical parameters from the Bode plot of the whole system. These parameters are the fractional power a, the pseudo-capacity K, the parallel resistance Rp, and the serial resistance Rs of the equivalent electrical circuit. The results show that the measured parameters differ between normal skin and special skin sites. These effects have not previously been discovered by other authors, since there has been no systematic investigation of many acupuncture points to date, and there has been no apparent need for such an investigation. A number of necessary criteria for acupuncture point detection can be derived from the results obtained.     

A new infra-red gas analyser and portable photosynthesis meter

The new infra-red gas analyser for measurement of CO₂ concentration described uses a focussed, dual optical path. The 2W radiation source is a heated alumina bead and a cooled lead selenide photoconductive detector measures the difference in radiation absorption at 4.26 m by the gas in sample and reference tubes. Radiation is chopped alternately between these tubes at 120 Hz. The signal from the detector is processed through an a.c. coupled amplifier, phase sensitive detector and low pass filter. Incorporated into the photosynthesis meter, the sample tube of the analyser is connected to a leaf chamber and circulating pump forming a closed gas circuit. As a leaf in the chamber removes carbon dioxide from the air in the closed circuit, the decrease in its concentration is sensed by the analyser. The time taken for the concentration to decrease by a predetermined amount (typically 30 ppm) is displayed and rate of net photosynthesis can be calculated from this and the volume of the closed circuit. A measurement of the light-saturated rate of net photosynthesis of a healthy flag leaf of wheat can be made in 10–15 seconds. The system is fully portable and has been used intensively in the field for two summers.     

Polarographic measurement of H2 in aqueous solutions

An inexpensive circuit designed for polarographic measurement of dissolved H₂ over a wide concentration range is described. Examples of its application to measurements of hydrogenase and nitrogenase activities are presented.     

近红外生物组织光谱特性测量仪器中半导体激光器驱动方案的研究

近红外生物组织光谱测量仪器中光源采用小功率半导体激光器,本文讨论了两种驱动方法,一种是基于分立器件的设计,另一种采用集成Laser Diode驱动芯片MAX3766,设计的主要目的是保证光源光功率稳定,还讨论了波长随温度变化对测量结果的影响。     

Automatic gas meter for laboratory fermenters

Summary A versatile, cheap and automated system is designed for the measurement of small gas flows produced in laboratory-scale fermentation processes. An automatic sampling device for programmed times is linked to the flow meter. The displacement of a liquid by the gas being measured is the principle on which both the meter and the sampling device are based. The operation of the system is controlled by a simple electronic circuit.     

A thermal method for the determination of tissue blood flow.

An isothermal flowmeter for the determination of local tissue blood flow is described. Flow is determined by the measurement of the thermal conductivity of the tissue in the vicinity of a heated thermistor maintained at a fixed temperature difference above a reference thermistor. Direct heating of the thermistor is utilized to eliminate the need for specially constructed indirectly heated thermistors. This design results in a device with a voltage output directly proportional to tissue thermal conductivity and to tissue blood flow. The device is shown to be adequate for the qualitative measurement of myocardial blood flow under various situations. Construction is simplified and the size of the circuit reduced by the use of readily available integrated circuits.     

Measurement of branchial vascular space of trout,Oncorhynchus mykiss: effects of adrenaline

Summary Using the isolated-perfused head preparation at a constant flow rate, hemodynamic effects of adrenaline were studied in trout gills. The calculation of the vascular spaces was performed with the isotopic pulse technique allowing measurement of the distribution space of the tracer.The results show that the branchial arterial circuit was cleared more quickly than the branchial venous and cephalic circuits. Adrenaline addition significantly increased the volume of the branchial arterial circuit at the expense of the venous circuit, illustrating the closing of arterio-venous sphincters under catecholamine control. The increase of the arterial volume could be explained by a vasodilation of the arterial circuit, rather than resulting from lamellar recruitment. Furthermore, the flow rate of the cephalic circuit represented 5% of the total branchial flow rate.Abbreviations dpm radioactive decay per minute - F flow rate - HSA human serum albumin - T _1/2 half-time clearance - V distribution space     

In-situ root extent measurements by electrical capacitance methods

A conceptual model is presented that provides a rational basis for using plant root capacitance as an in-situ measurement for assessing plant root development. This method is based on measuring the electricla capacitance of an equivalent parallel resistance-capacitance circuit formed by the interface between soil-water and the plant root surface. Nutrient solution studies using tomato (Lycopersicon esculentum Mill.) showed a good correlation between plant root capacitance and root mass. Stage of development studies showed plant root capacitance measurements capable of detecting root development rate and suggested the method to be sensitive to root function. Soil water content was shown to have a significant effect on plant root capacitance measurement. The possibility of using this technique to assess relative root function is discussed. Positioning of the plant shoot electrode was shown to also have a significant effect on measurement of plant root capacitance, demonstrating the need for using consistent measurement techniques. The electrical capacitance method shows considerable promise. More research is needed before it can be used routinely.     

A new chromatographic instrument for measuring trace concentrations of breath-hydrogen

A new instrument has been developed which offers many advantages over instruments presently utilized for the measurement of breath-hydrogen used to evaluate the intestinal absorption of sugars. The gas analyzer has a solid-state sensor which is more specific for hydrogen than most conventional chromatographic detectors. Air can be used as the carrier gas and can be circulated with a small internal pump, thereby eliminating large carrier gas tanks and pressure regulators. The intersample time is approximately 2 min, allowing rapid serial analysis of breath samples. A unique feature allows a short-term memory circuit to recall the signal and present it on a digital panel meter in parts per million. Recorder terminals on the back permit the generation of a permanent record, if desired. The gas analyzer is small, lightweight and simple to operate. Its application to the serial measurement of hydrogen in alveolar air after ingestion of sugars is demonstrated.     

An autonomous CMOS hysteretic sensor for the detection of desorption-free DNA hybridization

This paper describes a sensor for label-free, fully electrical detection of DNA hybridization based on capacitive changes in the electrode-electrolyte interface. The sensor measures capacitive changes in real time according to a charging-discharging principle that is limited by the hysteresis window. In addition, a novel autonomous searching technique, which exclusively monitors desorption-free hybridized electrodes among electrode arrays, enhances the performance of the sensor compared with conventional capacitive measurement. The sensor system achieves a detection range of 80 dB. The integrated circuit sensor is fabricated with a 0.35 μm CMOS process. The proposed sensor offers rapid, robust and inexpensive measurement of capacitance with highly integrated detection circuitry. It also facilitates quantitative evaluations of molecular densities on a chip with distinctive impedance variations by monitoring desorption-free hybridized electrodes. Our electrical biosensor has great potential for use with bio analytical tools and point-of-care diagnosis.     

Biomedical Implementation of Liquid Metal Ink as Drawable ECG Electrode and Skin Circuit

Background

Conventional ways of making bio-electrodes are generally complicated, expensive and unconformable. Here we describe for the first time the method of applying Ga-based liquid metal ink as drawable electrocardiogram (ECG) electrodes. Such material owns unique merits in both liquid phase conformability and high electrical conductivity, which provides flexible ways for making electrical circuits on skin surface and a prospective substitution of conventional rigid printed circuit boards (PCBs).

Methods

Fundamental measurements of impedance and polarization voltage of the liquid metal ink were carried out to evaluate its basic electrical properties. Conceptual experiments were performed to draw the alloy as bio-electrodes to acquire ECG signals from both rabbit and human via a wireless module developed on the mobile phone. Further, a typical electrical circuit was drawn in the palm with the ink to demonstrate its potential of implementing more sophisticated skin circuits.

Results

With an oxide concentration of 0.34%, the resistivity of the liquid metal ink was measured as 44.1 µΩ·cm with quite low reactance in the form of straight line. Its peak polarization voltage with the physiological saline was detected as −0.73 V. The quality of ECG wave detected from the liquid metal electrodes was found as good as that of conventional electrodes, from both rabbit and human experiments. In addition, the circuit drawn with the liquid metal ink in the palm also runs efficiently. When the loop was switched on, all the light emitting diodes (LEDs) were lit and emitted colorful lights.

Conclusions

The liquid metal ink promises unique printable electrical properties as both bio-electrodes and electrical wires. The implemented ECG measurement on biological surface and the successfully run skin circuit demonstrated the conformability and attachment of the liquid metal. The present method is expected to innovate future physiological measurement and biological circuit manufacturing technique in a large extent.     

实验动物用机械测痛仪的研制

目的研制一种疼痛研究中实验动物用的电子式机械测痛仪器。方法通过分析传统机械测痛仪在疼痛神经胜利测量实验中存在的缺陷和不足,本设计选用高精度触力传感器,设计信号采集与处理电路,并配备自行研发编制的基于VC的应用软件,最终完成对疼痛阈值的测量、存储和显示。结果研制出适用于机械痛测量的电子测痛仪,可方便快速实现测量疼痛阈值。结论实验测试表明,本文研制研制的测痛仪稳定性好、测量准确性高;测量结果不受测量环境湿度、温度的影响,从而克服了传统测痛方法的缺陷,为研究分析神经性疼痛的发病机理、评估镇痛药物的治疗效果提供可靠的技术支持。     

An Automated Potometer

An automated potometer is described whose output voltage providesa continuous record of plant water uptake. The measurement systemis based on the capacitive transduction of meniscus positionin a potometer sensing tube, such that a change in output voltageof the capacitance-measuring circuit is proportional to watervolume uptake by the plant. Advantages of the continuous high resolution record of wateruptake made with the potometer are demonstrated by measurementsusing cut plants (a) which show the dependence of calculatedtranspiration flux density and stomatal conductance on climaticvariables and (b) to calibrate a sap flowmeter. A design fora whole plant potometer is presented.     

DNA detection by integrable electronics

This paper presents a new electronic methodology to detect DNA hybridization for rapid identification of diseases, as well as food and environmental monitoring on a genetic base. The proposed solution exploits a new (electrical) capacitive measurement circuit, not requiring any prior labeling of the DNA (as it is often the case with the commonly employed optical detection). The sensitivity, the reliability, and the reproducibility of this device have been evaluated by experiments performed with a (non-integrated) prototype implementation, easily integrable in IC and/or micro-fabricated lab-on-a-chip.     

Photoelectric properties of a detector based on dried bacteriorhodopsin film

The photoelectric response of a detector using dried bacteriorhodopsin (bR) film as the light sensing material is mathematically modeled and experimentally verified in this paper. The photocycle and proton transfer kinetics of dried bR film differ dramatically from the more commonly studied aqueous bR material because of the dehydration process. The photoelectric response of the dried film is generated by charge displacement and recombination instead of transferring a proton from the cytoplasmic side to the extracellular side of the cell membrane. In this work, the wild-type bR samples are electrophoretically deposited onto an indium tin oxide (ITO) electrode to construct a simple multiple layered photo-detector with high sensitivity to small changes in incident illumination. The light absorption characteristics of the thin bR film are mathematically represented using the kinetics of the bR photocycle and the charge displacement theorem. An electrically equivalent RC circuit is used to describe the intrinsic photoelectric properties of the film and external measurement circuitry to analyze the detector's response characteristics. Simulated studies and experimental results show that the resistance of the dried bR film is in the order of 10(11) Omega. When the input impedance of the measurement circuitry is one order of magnitude smaller than the dried film, the detector exhibits a strong differential response to the original time-varying light signal. An analytical solution of the equivalent circuit also reveals that the resistance and capacitance values exhibited by the dried bR film, in the absence of incident light, are almost twice as large as the values obtained while the material is under direct illumination. Experimental observations and a predictive model both support the notion that dried bR film can be used in simple highly sensitive photo-detector designs.     

Phenazine methosulfate system-induced membrane hyperpolarization in the human erythrocytes

Erythrocyte membrane potential was recorded via measurement of pH of the incubation medium in presence ofprothonophore. The increase of intracellular calcium concentration in presence of calcium ionophore A23187 and addition of the artificial redox-system ascorbate-phenazine methosulfate led to membrane hyperpolarization due to opening of Ca(2+)-activated potassium channels that are regulated by multiple signaling pathways. The opening of the Ca(2+)-activated potassium channels in presence of artificial redox-system ascorbate-phenazine methosulfate is mediated at least by two mechanisms including an increase in affinity of channels to calcium ions and involvement of the protein SH-groups and the components of the respiratory circuit which have beer found in erythrocyte membrane.