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To evaluate 1.5 T magnetic resonance imaging (MRI) brain images with denoising procedures using deep learning-based reconstruction (dDLR) relative to the original 1.5 and 3 T images.Eleven volunteers underwent MRI at 3 and 1.5 T. Two-dimensional fast spin-echo T2-weighted imaging (T2WI), fluid-attenuated inversion recovery (FLAIR) imaging and diffusion-weighted imaging (DWI) sequences were performed. The dDLR method was applied to the 1.5 T data (dDLR-1.5 T), then the image quality of the dDLR-1.5 T data relative to the original 1.5 T and 3 T data was qualitatively and quantitatively assessed based on the structure similarity (SSIM) index; the signal-to-noise ratios (SNRs) of the grey matter (GM) and white matter (WM); and the contrast-to-noise ratios (CNRs) between the GM and WM (CNRgm-wm) and between the striatum (ST) and WM (CNRst-wm).The perceived image quality, and SNRs and CNRs were significantly higher for the dDLR-1.5 T images versus the 1.5 T images for all sequences and almost comparable or even superior to those of the 3 T images. For DWI, the SNRs and CNRst-wm were significantly higher for the dDLR-1.5 T images versus the 3 T images.The dDLR technique improved the image quality of 1.5 T brain MRI images. With respect to qualitative and quantitative measurements, the denoised 1.5 T brain images were almost equivalent or even superior to the 3 T brain images.

The National Metrology Institute of Japan has developed a resistive voltage divider (RVD), which is constructed from a series array of quantized Hall resistance (QHR) bars named “QHR voltage divider” fabricated on one chip. In principle, the QHR voltage divider does not need time-consuming bootstrap self-calibration and is not affected by measurement conditions such as ambient temperature and measurement current Therefore the QHR voltage divider is suitable for use as a reference standard for characteristic evaluation of conventional RVDs. In this paper, the evaluation of RVD current dependence based on the QHR voltage is demonstrated.

At the National Metrology Institute of Japan, we are developing a transformer bridge circuit that can precisely compare the $i = 2$ plateau resistance in an ac quantized Hall resistance with a 100-k $\Omega $ resistance. In this paper, we propose a practical transformer voltage ratio of 7.75:1, which is the most important parameter for developing a transformer bridge circuit. Further, we describe the design of an inductive voltage divider (IVD) to realize the 7.75:1 ratio. We intend to use the proposed IVD as a reference standard for calibrating the voltage ratio of the transformer. The reference IVD was fabricated with the two-stage technique and calibrated by Thompson’s method. The deviation from the nominal ratio of 7.75 was estimated to be $-5.92 \times 10^{\mathrm {-6}}$ for in-phase and $-22.75\times 10^{\mathrm {-6 }}$ for quadrature. The standard uncertainty of this calibration was estimated to be $0.63\times 10^{\mathrm {-6}}$ for in-phase and $6.28\times 10^{\mathrm {-6 }}$ for quadrature.

Among various methodologies of thermodynamic temperature measurements, Johnson noise thermometry (JNT) has an advantage that the structure and size of the temperature sensing probe are similar to conventional probes for contact thermometry. Another distinguishing feature is that the measurements are all electronic. Furthermore, the application of a quantum voltage noise source (QVNS), first introduced by the National Institute of Standards and Technology (NIST), has improved the accuracy of JNT during the past ten years. These developments have been driven under the rationale to determine the Boltzmann constant $$k$$ , in support of the proposed redefinition of the kelvin, and later to provide practical realization of the kelvin. At NMIJ, AIST, we have been developing a QVNS-based JNT system to first measure the Boltzmann constant and then aim to extend the temperature range to higher temperatures where $$T-T_{90}$$ data are lacking. An impact feature of our system is that most of our key elements have been built independently from NIST and the National Institute of Metrology, China (NIM); in particular that the Josephson junction array has been built in house at NeRI, AIST, and its driving method differs from that of either NIST or NIM. In this paper, the unique elements of the system as well as our initial results on the Boltzmann constant measurements are reported.

The National Metrology Institute of Japan has developed a resistive voltage divider (RVD), which is constructed from a series array of quantized Hall resistance (QHR) bars named “QHR voltage divider (QHR-VD).” In principle, the QHR-VD doesn't need time-consuming bootstrap self-calibration and isn't affected by measurement conditions such as measurement current. Therefore, the QHR-VD is suitable for use as a reference standard for the characteristic evaluation of conventional RVDs. In this paper, evaluation of RVD current dependence based on the QHR-VD is presented. From the measurement results of the RVD current dependence, no current dependence was observed within standard uncertainties.

All the contact pads of a quantized Hall resistance (QHR) device should have a low contact resistance (∼1 Ω) for the application of DC resistance standard devices at cryogenic temperatures. Corrosion of a GaAs/AlGaAs substrate occurs along the edge of the photoresist before the deposition of Ni/AuGe, and we assume that this corrosion degrades the contact resistance. A SiO2 protective layer is effective in preventing the corrosion of and protecting the surface of GaAs/AlGaAs substrate. With the use of this SiO2 protective layer, the yield ratio of the contact resistance to the twodimensional electron gas (2DEG) layer at low temperature (∼0.5 K) and high magnetic field (∼9 T) improves to nearly 100%. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A quantum Hall array resistance standard (QHARS) device with a nominal value close to 10 kΩ on the i = 2 plateau has been developed on a GaAs/AlGaAs heterosubstrate. This QHARS device consists of 266 Hall bar elements, and its nominal value has only 0.0342 × 10-6 difference based on RK-90 ( = 25 812.807 Ω) from an integer value of 104. As a result of comparison measurements with the conventional Quantized Hall Resistance Standard via the 100- Ω standard resistor, the value of the QHARS device agrees with its nominal value within 3.5 × 10-8.

A cryogenic current comparator (CCC) is an instrument of great importance in electrical metrology, which provides a ratio of two currents with ultimate accuracy based on superconductivity. It is used for dc resistance calibration in many national metrology institutes. Conventional CCCs consist of multi-turn coils of wire windings, a multi-layered shield of superconductor foils and a separate SQUID sensor. This implementation results in a bulky device too massive to cool with a mechanical cryocooler, making a system inconvenient. A new implementation of CCC, an integrated CCC (ICCC) consisting of thin-film spiral coils, a thin-film superconducting shield and a SQUID sensor integrated on a single chip, enables a user-friendly system operated with a compact cryocooler. Prototype ICCC chips were designed and fabricated by using a superconducting Nb integrated circuit technology with chemical-mechanical polishing. The basic operation of the prototype ICCCs was confirmed by monitoring periodic flux-voltage characteristics of the SQUIDs.

We observed constant voltage steps for an overdamped Josephson array driven by current pulse trains generated by triggering a photo detector located in a cryostat with a mode locked fiber laser. We measured the voltages of the Josephson array as a function of an optical power. Quantized voltage steps were verified at multiples of about 10 μV which corresponds to the repetition frequency of 50 MHz and the number of junctions of 100. A quantitative analysis was done on the current pulse shape which generated by the MSM detector.

We report the experimental results on a Josephson junction array (JJA) driven by current pulse trains generated by triggering a photo detector located in a cryostat with an optical comb. The key components in the experimental system are a mode locked fiber laser, a metal-semiconductor-metal (MSM) photoconductive switch, and an overdamped JJA. Optical pulse trains generated at room temperature are transmitted via an optical fiber to the MSM-photo detector installed at 4.2 K, and then converted into electric current pulse trains to drive the overdamped JJA. Quantized voltage steps have been verified at multiples of 10 muV, which agrees with the repetition rate of the pulse laser and the number of Josephson junctions in the JJA.

In this paper, quantized voltage steps were observed by driving an overdamped Josephson junction array (JJA) with current pulse trains. The current pulse trains were generated by triggering a metal-semiconductor-metal photodetector installed close to JJA at 4.2 K with a mode-locked fiber laser. The intervals of the constant voltage steps were 10 muV, which agrees with the repetition frequency of the light source (49.7 MHz) and the number of Josephson junctions (100) in the JJA. This is the first step toward establishing an ac voltage standard at the National Institute of Advanced Industrial Science and Technology

Radiation from a linear array oscillator with a spiral antenna has been coupled out of the dewar through a Teflon window. Both its linewidth and its power have been measured after coupling the radiation through free space into a second dewar. The linewidth has been determined using a SIS mixer with a spiral antenna which was pumped with an 88 GHz phase-locked Gunn oscillator, and also by Josephson mixing of the array itself. The array oscillator has a distributed array structure of 300 resistively shunted junctions which are placed in groups of 6 junctions. It was fabricated on a silicon wafer and has a two-arm spiral antenna. The chip was attached to a silicon lens with an anti-reflection coating. The linewidth of the array oscillator was determined between 158 GHz and 194 GHz, far below its design frequency of 400 GHz. The measured linewidth and power data of the oscillator reveal interesting information about its phaselocking behavior in the operating range far below its design frequency.

For broadband data communication between Josephson and CMOS digital systems, amplification of small Josephson-output signals and synchronization between the systems are important issues. We present an interface circuit for a Josephson-CMOS hybrid digital system. The interface circuit consists of a parallel-in-parallel-out (PIPO) circuit and built-in Josephson-MOS amplifiers. The PIPO circuit, implemented based on 4JL latching logic technology, performs synchronized data transfer between the Josephson and CMOS circuits. The Josephson-MOS amplifiers consists of stacked Josephson junctions (Suzuki stacks) and MOS inverters which are monolithically integrated on a chip. The circuits have been designed, fabricated and tested. We have successfully confirmed correct operation of the circuits.

Radiation from a linear array oscillator with a spiral antenna has been measured using an off-chip coupled bolometer. The array oscillator has a distributed array structure with 300 resistively shunted junctions which are placed in the groups of 6 junctions. The array oscillator was fabricated on a Si wafer with a two-arm spiral antenna. The chip was attached to a Si lens with an anti-reflection coating. Rather large power (>100 nW) was detected at a number of array bias voltages V/sub bias/ from 115 mV to 196 mV, which correspond from 185 GHz to 315 GHz. The maximum measured power was 550 nW at V/sub bias/=125 mV (200 GHz).

National Metrology Institute of Japan have been proposed and fabricated the quantized Hall resistance (QHR) array devices, and confirmed the performance with uncertainty of as low as 10−8. The new combinations of Hall bars have been designed ranging from 100 Ω to 1 MΩ. This new combinations realize the quantized resistance values more closely to decade values with fewer numbers of Hall bars. In the new design, 10-kΩ QHR array device consists of only 16 Hall bars, and this number is about 16 times lower than that in the previous design however the nominal value is same to previous one. This fact might allow us to evaluate each Hall bar in the array device.

A one-chip quantized voltage divider device based on integrated quantized Hall resistance (QHR) technology has been developed. A QHR voltage divider device that consists of a series of thirty-two quantized Hall bars has been fabricated. The dependence of the Hall resistance R H on the magnetic flux density showed that the device will function as a voltage divider. From the preliminary test of the 1∶1 voltage ratio evaluation, the deviation from the nominal voltage ratio of 1∶1 was estimated to be less than ± 10 × 10−6.

A reliable and compact bonding method for superconductively connecting input coils to pickup coils has been developed using a low-temperature flip-chip bonding technique which does not cause the deterioration of Josephson junctions. Axial first-order gradient pickup coils made of a flexible sheet were fabricated and tested to investigate their mass producibility. The system noise of a single-channel system with a flexible pickup coil, with 17-mm coil diameter and 60-mm baseline, connected by a superconductive flip-chip bonding technique, was about 20 fT/ square root Hz using a large beta L DC-SQUID (superconducting quantum interference device). >

A Nb/AlO/sub x//Nb Josephson process has been developed to fabricate DC superconducting quantum interference devices (SQUIDs) for biomagnetic measurements on 4-in silicon wafers. The purpose of the process is to fabricate high-quality junctions and to keep the quality uniform over a silicon wafer. All the films were deposited using magnetron sputtering. The components of the SQUID, except the junctions, were formed by taper etching to improve the step coverage. The uniformity of the SQUID characteristics (critical current, modulation depth, and mutual inductance between SQUID and modulation coil) was measured, and an excellent value of less than +or-5% was obtained. Three different configurations of SQUIDs, single washer (SW), double washer series (DWS), double washer parallel (DWP) have been fabricated with the same characteristics. The SW (single washer) had a white noise level of 6.3*10/sup -6/ Phi /sub 0// square root Hz, lower than those of DWS and DWP. 1/f crossover frequencies were below 1 Hz. >

The effects of RF interference on the characteristics of DC superconducting quantum interference devices (SQUIDs) are investigated. The noise of a DC SQUID gradiometer radiating an RF field with a frequency between 100 kHz and 80 MHz was measured. As the RF field strength intensified, the white noise level increased and the cut-off frequency was lowered. The flux-voltage transfer function (dV/d Phi ) of the DC SQUID was influenced strongly by the RF field. dV/d Phi decreased as the RF field intensified. Based on these results, the level of the electromagnetic environment at which the operation of the SQUID system would not be affected was found. The effect of high-frequency magnetic field on the flux to voltage transfer function was investigated by computer simulation using a simple resistively shunted junction (RSJ) model. >

The thermal magnetic noise of three Dewars with different structures was measured using a d.c. SQUID magnetometer and the contributions from the metallic conductors in the bottom and in the side vacuum spaces were estimated. It is concluded that the axial component of the thermal magnetic noise of a Dewar is mainly caused by the conductors in the bottom space and the magnitude of thermal noise is determined by the total amount of conductor.

Effects of parasitic capacitance in a magnetically-coupled voltage multiplier (VM) are described. We found that parasitic capacitance between SQUIDs and JTLs in a VM decreases its operating margin. We also found that separation of electric grounds for the output terminal of a VM from those for the JTLs is effective to improve the operating margin. Using this method, a 64-stage VM was fabricated and well-defined output voltage was obtained.

An experimental device of quantum Hall array resistance standards (QHARS) with a nominal value close to 10 kΩ on the i = 2 plateau have been developed on a GaAs/AlGaAs hetero-substrate. This device consists of just 266 Hall bar elements that are connected by triple connection technique. Its nominal value has only 0.034 2 ppm differences from the integer value of 104. This array device clearly shows the well-quantized 10 kΩ plateau (i=2).

We have developed a on-chip double-shielded quantum Hall device and a double-shielded chip-carrier. The device in conjunction with the carrier will realize impedance standard based on the quantum Hall effect. In this configuration, the Hall bar is covered by separated on-chip shields and shields of the chip carrier to retrieve the leakage current. In this paper, we show detail of the QHR device fabrication and the structure of the chip carrier.

High-T/sub c/ DC-SQUID magnetometers made of Bi-Sr-Ca-Cu oxide films were designed and fabricated. A directly coupled scheme where a SQUID loop and a pick-up loop are connected directly in parallel was chosen to avoid fabricating the multilayered structure. The flux noise, which was measured in FLL (flux locked loop) operation at 4.2 K, increased in a form of 1/f as the frequency decreased below 20 Hz. The level of white noise at the frequency range above 20 Hz was about 1*10/sup -4/ Phi /sub 0// square root Hz, corresponding to the field resolution of 1.5 pT/ square root Hz at the pickup loop.

We have performed an experiment to drive an over-damped Josephson junction array (JJA) with modulated current pulse trains, which are generated by a modulated optical comb (an ultra-short pulse laser). The intensities of optical pulse trains are modulated using a pulse pattern generator. We quantitatively verified that the output voltages of the JJA were consistent with the modulation signals.

A one-chip quantized voltage divider device based on the technology of integration of quantized Hall resistance (QHR) bars on a GaAs/AlGaAs Heterostructure Substrate has been developed. The first experimental QHR voltage divider device, which consists of a series of 20 QHR bars, has been fabricated. A preliminary test in our evaluation study of the device clearly shows that it functions as a voltage multiplier/divider.

A 200 mW, 800 MHz class E DC-DC converter is designed using a 0.6 /spl mu/m CMOS process and then simulated. A 22 nH spiral inductor is used in the resonant circuit. An integrated feedback controller with a VCO is used for the output voltage regulation. It is shown that the class E inverter is an excellent candidate for on-chip switching converters because of very high efficiency, and the inductor can be minimized at high operating frequencies. The simulated converter efficiency was 72% at 4.5 V output voltage, 200 mW output power, and 800 MHz switching frequency.

A new method for imaging the random media by analyzing power spectrum shapes using fractal dimensions is presented. It may be possible to estimate the structural characteristics from the spectrum, because the ultrasonic power spectrum shapes may be affected by the statistical distributions of the point scatterers in the random media. Fractal theory is adapted to estimate the power spectrum shapes. The fractal dimension is used for characterization of the complexities of the power spectrum shape because it indicates the complexity or roughness of figures. The relations of mean spacing vs. fractal dimension and irregularity vs. fractal dimension obtained by numerical calculations are given. An experiment for ultrasonic imaging by mapping the fractal dimension is described. >

Digital-to-analog (D/A) converters based on the Josephson effect are promising for ac voltage standards because they produce voltage steps with ultimate precision and stability. We are currently developing a single-flux-quantum (SFQ)-based D/A converter, designed for synthesizing sinusoidal waveforms for metrological applications. In this paper, we examine feasibility of an ac-dc transfer difference measurement for a thermal converter using the SFQ-based D/A converter.

As part of a project to identify genes up-regulated by injury of the motor neuron, a clone encoding dimethylarginine dimethylaminohydrolase (DDAH) was isolated. This enzyme is known to metabolize methylarginines, which are endogenous inhibitors of NOS activity. DDAH may therefore contribute to the control of NO synthesis. The present study demonstrated that both DDAH and nNOS mRNAs are up-regulated after axotomy in injured hypoglossal motor neurons. The profile of DDAH mRNA up-regulation in the injured hypoglossal motor neurons paralleled that of NADPH diaphorase staining. While the expression of both DDAH and nNOS was upregulated in motor neurons following nerve injury, the normal distribution of DDAH and nNOS mRNAs in the noninjured central nervous system were distinctly different. We speculate that both genes are involved in the upregulation of NO production following nerve transection, although the role of NO in the process of nerve regeneration is so far unknown.

Increasing flower’s longevity by blockage of the onset of senescence has economical importance. Currently, STS (silver thiosulfate complex anion), is being used as an anti-senescence preservative in the cut-flower industry. But, STS contains a heavy metal ion (Ag+) and has a potential environmental hazard. Therefore, it is desired to have alternatives to STS, which are safe for organisms and have a less risk for environmental pollution. DPSS is a novel preservative for cut carnation flowers, which were developed recently [1] and has just come to the market in Japan. Its activity to retard carnation flower senescence is compatible to or more than that of STS. DPSS is safe for organisms including mammals, because its oral and dermal administration causes no acute toxicity in mice and exerts no mutagenic effects by Ames test.

A resistive voltage divider, which is constructed from a binary segmented series array of quantized Hall resistance (QHR) bars fabricated on one chip, named the ?QHR voltage divider?, has been developed. The QHR voltage divider does not, in principle, require time-consuming bootstrap self-calibration and will provide voltage ratios that are defined by fundamental physical constants with small uncertainties. To evaluate the performance of the QHR voltage divider, the dependence of the Hall resistances RH?of all serial segments on the magnetic flux density was measured. The results of the RH?measurement showed large and well-defined plateaus, and it was confirmed that the fabricated QHR divider in conjunction with a suitable voltage source would function as a voltage divider. From a preliminary test of the voltage ratios of the QHR voltage divider, deviations from nominal ratios were measured to be less than 1.4???10?6, and the expanded uncertainty of the measurement was estimated to be less than 4.1???10?6.

We demonstrated the operation of pulse-driven Josephson junction arrays (JJAs) for AC voltage standard using a wideband cryo-prober system with a 4-K Gifford-MacMahon (GM) cooler. This unique system was originally developed for high-speed network switch applications of rapid-single-flux-quantum (RSFQ) circuits and enables wideband data transmission at bit rates of higher than 10 Gbps between room-temperature and cryogenic environments. JJA chips were fabricated using NbN-based superconductor-normal metal-superconductor (SNS) junctions. A 5-mm chip was mounted on a 16-mm chip carrier using flip-chip bonding technology for probe contact. To obtain bipolar output voltages, we tried two types of testing based on the AC coupling technique proposed by the National Institute of Standards and Technology (NIST). A pulse pattern generator (PPG) with a large memory of 134 Mbit was used for covering a wide frequency range of output signals. As a result, we succeeded in bipolar operation of the JJA, generating waveforms at frequencies from 60 Hz to several tens of kilo hertz. The maximum rms voltage obtained for a single array was 12.7 mV. The observed spurious level was lower than -93 dBc at 16 kHz.

We have developed a coding technique to drive an overdamped Josephson junction array (JJA) using modulated optical pulses for voltage standard applications. Our system is composed of a multi-channel pulse pattern generator (PPG), a LiNbO3 (LN) modulator with an electrical multiplexer (MUX), a photodiode (PD), and an over-damped JJA cooled with 4 K GM cryocooler. The modulated optical pulses are transmitted via an optical fiber to a PD that is installed close to the JJA on a cold stage, and they are then converted into an electrical current pulse train in order to drive the JJA. To avoid a problem in our LN modulator system, i.e., the duty-ratio dependence of the output pulse waveform, pseudo signals that maintain the duty ratio at approximately 50% are inserted in the original bit stream. We demonstraited that this technique is applicable for arbitrary return-to-zero (RZ) binary bit streams.

We have performed an experiment to drive an overdamped superconductor-insulator-normal-insulator-superconductor (SINIS) Josephson junction array (JJA) with modulated current pulse trains, which are generated by modulated ultra short optical pulses. Averaged voltage outputs of the JJA have been systematically measured for various modulation patterns as a function of the bias voltage of an optical modulator. Quantized voltage steps has been clearly observed in accordance with modulation patterns under certain condition of the bias voltage of the optical modulator.

Total cholesterol level was measured in 8,303 children and youth in Tokyo. Age ranged from 6 to 18 years. The change of total cholesterol level relates to sex and age, and girls showed higher level than boys. Not a small number of children revealed elevated total cholesterol level but some children showed very low level. HDL-cholesterol was determined and prevalence of ischemic coronary heart disease risk factors was studied. The elevation of total cholesterol level in senior high school students was caused by either increase of HDL-cholesterol or increased total minus HDL-cholesterol fraction. High school boys with obesity were found to have higher serum total cholesterol level accompanied by low HDL-cholesterol level. High school boys of parents with myocardial infarction were found to have higher total cholesterol level. Majority of Japanese senior high school students were found to have one or more coronary heart disease risk factors. The necessity of prevention for ischemic coronary heart disease starting from childhood in Japan is emphasized.

The crystal structure of 1,10-dithia-[2.2]metacyclophane, C14H12S2, has been determined by x-ray diffraction methods. The crystals are monoelinic with space group P21/n and cell dimensions a = 7.868, b = 27.269, c = 5.600 Å and β = 98.17°; Z = 4. The structure was solved by direct methods and refined by block-diagonal least-squares methods; R = 0.036 for the 1425 observed reflections. The molecule was found to be highly strained and the boat-shape deformation of both phenyl rings was observed.