Glass microneedles for force measurements: a finite-element analysis model

Changes in developed force (0.1–3.0 μN) observed during contraction of single myofibrils in response to rapidly changing calcium concentrations can be measured using glass microneedles. These microneedles are calibrated for stiffness and deflect on response to developed myofibril force. The precision and accuracy of kinetic measurements are highly dependent on the structural and mechanical characteristics of the microneedles, which are generally assumed to have a linear force–deflection relationship. We present a finite-element analysis (FEA) model used to simulate the effects of measurable geometry on stiffness as a function of applied force and validate our model with actual measured needle properties. In addition, we developed a simple heuristic constitutive equation that best describes the stiffness of our range of microneedles used and define limits of geometry parameters within which our predictions hold true. Our model also maps a relation between the geometry parameters and natural frequencies in air, enabling optimum parametric combinations for microneedle fabrication that would reflect more reliable force measurement in fluids and physiological environments. We propose a use for this model to aid in the design of microneedles to improve calibration time, reproducibility, and precision for measuring myofibrillar, cellular, and supramolecular kinetic forces.     

Control of scintigram presentations by means of a digital computer

A digital computer operates on-line in connection with a colour scanner. All information obtained by the latter in scanning the radionuclide distribution in a patient's organ is passed via an interface into a core memory which serves as a data memory. The main memory of the computer contains an operating system which controls the reproduction programs in addition to accepting data from the scanner and teletype. By this means the scintigrams contained in the data memory can be manipulated in various ways and presented on a storage oscilloscope. There are also additional programs to produce high-speed-printer outputs of a scan, as well as an optimal reproduction, calculated and controlled by the computer, of one or more colour scintigrams.     

Detection of needle puncture to blood vessel using puncture force measurement

Although blood sampling is frequently performed, a system to take blood samples automatically has not yet been developed. In the paper, as a first step towards automatic blood sampling, an examination of an automatic method for puncturing blood vessels is described. The force waveforms produced by puncturing rabbit ear veins were measured. A characteristic peak, possibly associated with the needle piercing the vessel wall, was observed in each waveform of ten successful cases of 14 trials. An algorithm that allowed the detection of this peak was developed, and parameters of a filter to improve the accuracy of the algorithm were determined. Using this algorithm, automatic needle punctures were performed in a rabbit ear vein and then were simulated using the data derived from manual needle puncture on four other rabbits. The results gave 30 fully successful cases of 33 trials of needle puncture and showed that measurement of the puncture force may be important for automatic needle puncture of blood vessels.     

Simulation of the complex countermovement jumping by means of a simple four-degrees-of-freedom model

By means of a four-degrees-of-freedom model the vertical movements of an athlete and the time course of the ground reaction force were simulated during a countermovement jump on a concrete and a wooden surface. The model masses were connected to each other and to the surface by springs and dampers. At first the stiffness of the springs decreased in order to initiate the countermovement. Afterwards the stiffness increased like the muscle activity so that the flexion of the model ‘legs’ were decelerated before the extension starts. The best result was attained when the stiffness of the spring between the model masses ‘thighs’ and ‘trunk’ increased before the other three springs. Compared with the muscle activity this means that for a successful jump the upper body segments have to be accelerated before the segments near to the ground are accelerated. The model ‘athlete’ was connected to a model of the surface. It could be shown that the jump on a concrete surface results in a better jump height than the jump on an elastic wooden surface if the muscle activation is not adapted to the surface properties.     

Portable EGG recording system based on a digital voice recorder

Cutaneous electrogastrogram (EGG) recording offers the benefit of non-invasive gastrointestinal diagnosis. With long-term ambulatory recording of signals, researchers and clinicians could have more opportunities to investigate and analyse paroxysmal or acute symptoms. A portable EGG system based on a digital voice recorder (DVR) is designed for long-term recording of cutaneous EGG signals. The system consists of electrodes, an EGG amplifier, a modulator, and a DVR. Online monitoring and off-line acquisition of EGG are handled by software. A special design employing an integrated timer circuit is used to modulate the EGG frequency to meet the input requirements of the DVR. This approach involves low supply voltage and low power consumption. Software demodulation is used to simplify the complexity of the system, and is helpful in reducing the size of the portable device. By using surface-mount devices (SMD) and a low-power design, the system is robust, compact, and suitable for long-term portable recording. As a result, researchers can record an ambulatory EGG signal by means of the proposed circuits in conjunction with an up-to-date voice-recording device.     

A method for the continuous recording of the concentration of sweat by means of the electrical conductivity

Summary A method is described to measure the total osmolar concentration of sweat by means of measuring the electrical conductivity. The method allows a continuous recording, so that the error, introduced by sampling the sweat, will be reduced. For calculations of the total osmolar concentration we have made the assumption that all the solute in sweat was NaCl. Experiments with a synthetic sweat proved the validity of this assumption, the error is about 5%.With 5 Figures in the Text     

Determination of specific hepatitis A markers by a radioimmunological method with autoradiographic recording of the results

The possibility of determining specific markers of hepatitis A by a simple variant of radioimmunoassay on a polyethylene film with autoradiographic recording of the results was demonstrated. The high sensitivity of the method, an extremely simple procedure, no necessity of special radiometric apparatuses, visual demonstration and reliability of the results recommend it for hepatitis A diagnosis.