Theoretical Analysis of Terahertz Detection of Resonant Tunneling Diodes

We analyze the terahertz detection characteristics of resonant tunneling diodes (RTDs) using a set of simple equations that covers three detection modes; (i) direct detection, (ii) amplified detection, and (iii) self-homodyne (coherent) detection. (i) and (ii) are based on the square-law detection, and (iii) is on the homodyne detection with the RTD used as an injection-locked local oscillator. The calculated results exhibit small- and large-signal areas depending on irradiation power. In the small-signal area, the detection current is proportional to irradiated power for (i) and (ii), and to square root of irradiated power for (iii). The detection current has a peak at the bias voltage at the boundary between (ii) and (iii). Effect of frequency fluctuation of irradiated wave is analyzed for (iii), and it is shown that the detection current is proportional to irradiated power if the fluctuation becomes wider than injection-locking range. The analytical results in this paper reasonably explain the reported experiments.Comment: 6 pages, 5 figure

Simple model for frequency response of a resonant tunneling diode caused by potential change of quantum well due to electron charge

The frequency dependence of negative differential conductance (NDC) is an important property for the resonant-tunneling-diode terahertz source. Among several phenomena determining the frequency dependence, this paper shows that the effect of potential change of the quantum well due to electron charge can be analyzed with a simple and tractable model based on the tunneling admittance and capacitance. The result is identical to that of Feiginov's analysis based on more fundamental equations, showing a one-to-one correspondence between the parameters of the two analyses. Similar to Feiginov's analysis, our analysis also shows that NDC remains finite even at infinitely high frequency. It is shown in our model that this result is attributed to neglecting the tunneling time at the emitter barrier. Comprehensive analysis of the frequency dependence of NDC will be possible by incorporating the tunneling time into the present model.Comment: 5 pages, 2 figure

Biologically active fibroblast growth factor 1 tagged with various epitopes

<p>Abstract</p> <p>Background</p> <p>Fibroblast growth factor (FGF) family members are involved in the regulation of a variety of biological phenomena. Because most of their activity is exerted via a signaling complex composed of FGF, heparin/heparan sulfate and FGF receptor tyrosine kinase, it is important to study the dynamic behavior of all the molecules in the complex without disturbing their interaction or activity.</p> <p>Findings</p> <p>We used <it>E. coli </it>to express biologically active human FGF1 tagged at its C-terminus with myc-(His)₆, V5-(His)₆or 3xFLAG-(His)₆. We found that the tagged FGF1s had affinities for heparin that were similar to that of the native form. The tagged FGF1s also exhibited mitogenic activity similar to that of the native form. Apparently, the tags do not interfere with the formation of the three-member complex involving FGF1, FGF receptor and heparan sulfate/heparin.</p> <p>Conclusion</p> <p>Tagged FGF1s should be useful for investigating the dynamic behavior of FGF1 in the context of its three-member signaling complex and other molecular complexes.</p

A Simple Optical Method for the Measurement of Glass Wool Fiber Diameter

An optical method for measuring glass wool fiber diameter has been proposed and discussed from the viewpoint of practical use. The method is based on both light scattering and light reflection on the glass wool. The method can measure the mean fiber diameter, d, in the area illuminated by laser light in realtime. The accuracy of the method, i.e., the dimensional resolution, was found to be about 0.7μm within the diameter range of d≤7.0μm

An optical system for monitoring torsion in a power transmission shaft in realtime

An optical system has been proposed and verified experimentally for monitoring the torsion of a power transmission shaft in realtime. The system consists of a pair of lasers, mirrors and light receivers as a sensor head, and logic circuit, high-frequency oscillator, and computer as a data processing system. The smallest measurable angle of torsion can be expressed by ω/ƒ, where ω is the rotational frequency of the power transmission shaft and ƒ is the frequency of the oscillator. The experimental error was found to be a few percentage points

Cloth Weft Densitometer Using a CCD Camera

A cloth weft densitometer has been proposed and its propriety verified by a preliminary experiment. The method is based on the counting of cloth wefts by a CCD camera with a shutter speed of 1 ms. The experiment shows that the densitometer can be used perfectly for many types of cloth if the cloth speed of less than approximately 10 m/min. The accuracy of the cloth-weft counting is above 99%, provided that the image contrast of the weft on the CCD camera is sufficiently high. Only 2-step digitations by the A/D converter is needed for 99% accuracy

各種環境条件に曝されたコンクリート構造物の複合劣化の実態調査とその対策に関する研究

13301甲第4328号博士（工学）金沢大学博士論文要旨Abstrac

各種環境条件に曝されたコンクリート構造物の複合劣化の実態調査とその対策に関する研究

13301甲第4328号博士（工学）金沢大学博士論文本文Ful