Development of a Current Injection-Type Impedance Measurement System for Monitoring Soil Water Content and Ion Concentration.

This study was conducted with the aim of developing a circuit system that enables the measurement of the moisture content and ion concentration with a simple circuit configuration. Our previous studies have shown that soil can be represented by an equivalent circuit of a parallel circuit of resistors and capacitors. We designed a circuit that can convert the voltage transient characteristics of the soil when a current is applied to it into a square wave and output frequency information and developed an algorithm to analyze the two types of square waves and calculate R and C. Normal operation was confirmed in the range of 10 kΩ-1 MΩ for the designed circuit, and the calculation algorithm matched within a maximum error of 5%, thus confirming the validity of the program. These successfully confirmed the changes in the water content and ionic concentration. The soil moisture content measurement succeeded in measuring a maximum error of about 10%, except at one point, and the soil ion concentration measurement succeeded in measuring a maximum error of 6.6%. A new, simple, noise-resistant moisture content and ion concentration measurement circuit system with square wave output has been realized.

Characterization of Microscopic Structures in Living Tumor by In Vivo Measurement of Magnetic Relaxation Time Distribution of Intratumor Magnetic Nanoparticles.

Tumor microscopic structure is crucial for determining properties such as cancer type, disease state (key for early diagnosis), and novel therapeutic strategies. Magnetic particle imaging is an early cancer diagnostic tool using magnetic nanoparticles as a tracer, which actualizes cancer theranostics in combination with hyperthermia treatment using the abilities of magnetic nanoparticles as a heat source. This study focuses on the microscopic structures associated with cancer cell distribution, the stromal compartment, and vascularization in different kinds of living tumors by analyzing the intratumor magnetic relaxation response of magnetic nanoparticles injected into the tumors. Furthermore, this study describes a sequential system for the measurement of magnetic relaxation time and analysis of the intratumor structure using nonbiological samples such as viscous fluids and solidified magnetic nanoparticles. Particularly, the fine discriminability achieved by reconstructing a distribution map representing the relationship between magnetic relaxation time and viscosity of medium is demonstrated, based on experimental data with a limited condition number. Observing tumor microscopic structure through the dynamic magnetization response of intratumor magnetic nanoparticles is a low-invasive tool for analyzing tumor tissue without dissection. It holds promise for the advancement of biomedical applications, such as early cancer theranostics, using magnetic nanoparticles.

A miniature integrated multimodal sensor for measuring pH, EC and temperature for precision agriculture.

Making several simultaneous measurements with different kinds of sensors at the same location in a solution is difficult because of crosstalk between the sensors. In addition, because the conditions at different locations in plant beds differ, in situ measurements in agriculture need to be done in small localized areas. We have fabricated a multimodal sensor on a small Si chip in which a pH sensor was integrated with electrical conductivity (EC) and temperature sensors. An ISFET with a Si(3)N(4) membrane was used for the pH sensor. For the EC sensor, the electrical conductivity between platinum electrodes was measured, and the temperature sensor was a p-n junction diode. These are some of the most important measurements required for controlling the conditions in plant beds. The multimodal sensor can be inserted into a plant bed for in situ monitoring. To confirm the absence of crosstalk between the sensors, we made simultaneous measurements of pH, EC, and temperature of a pH buffer solution in a plant bed. When the solution was diluted with hot or cold water, the real time measurements showed changes to the EC and temperature, but no change in pH. We also demonstrated that our sensor was capable of simultaneous in situ measurements in rock wool without being affected by crosstalk.

Development of an earlobe crease identification system to support diagnosis of arteriosclerosis.

It is well known that an earlobe crease (ELC) is related with cardiovascular disease. However evaluation of ELC has been carried out subjectively. We propose a novel system for objective and quantitative evaluation of ELC characteristics. The outline of earlobe was detected using the Canny edge detector. The number of ELCs and the ratio of the ELC length for the lobule from photographs of bilateral earlobes were calculated from the extracted outline of earlobes. Our system's validity for ELCs detection was compared with doctors' diagnosis using sensitivity and specificity analysis. The result showed that the validity of our system was equal to the diagnosis of the medical doctors (kappa coefficient: 0.93). It was thus concluded that the proposed system is useful to predict atherosclerotic disease.