Optical frequency domain ranging by a frequency-shifted feedbacklaser

This paper describes the theoretical and experimental study of a new technique for optical frequency domain ranging (OFDR) by a frequency-shifted feedback (FSF) laser. In conventional OFDR, a frequency chirped single-mode laser is used as a light source to convert a distance into a beat frequency, and a tradeoff exists between measurement range and resolution. The FSF laser output consists of periodically generated chirped frequency components whose chirp rate is faster than 100 PHz/s (P=10¹⁵), By use of the FSF laser, the tradeoff is removed and long-distance high-resolution OFDR is realized In the experiment, a distance of 18.5 km was measured with a resolution of 20 mm     

Finding module-based gene networks with state-space models - Mining high-dimensional and short time-course gene expression data

This study explores some problems to analyze time-course gene expression data by state-space models (SSMs). One problem is regarding the methods of parameter estimation and determination of the dimension of the internal state variable. Although several methods have been applied, there are few literature studies which with to compare them. Thus, this paper gives a brief review of the existing literature that use the SSM to analyze the gene expression time-course data. Another problem is the identifiability of the model. If the parameters of SSMs are simply estimated without any constraints for parameter space, they lack identifiability. To identify a system uniquely, it requires a specific algorithm to estimate the parameters with some constraints. For that purpose, an identifiable form of SSMs and an algorithm for estimating parameters are derived. The last problem is the extraction of biological information by interpreting the estimated parameters, such as mechanism of gene regulations at the module level. For that one, this paper explores methods to extract further information using the estimated parameters, that is, reconstruction of a module network from time-course gene expression data     

Extraction of a plasma time-activity curve from dynamic brain PET images based on independent component analysis

A compartment model has been used for kinetic analysis of dynamic positron emission tomography (PET) data [e.g., 2-deoxy-2-18F-fluoro-D-glucose (FDG)]. The input function of the model [the plasma time-activity curve (pTAC)] was obtained by serial arterial blood sampling. It is of clinical interest to develop a method for PET studies that estimates the pTAC without needing serial arterial blood sampling. For this purpose, we propose a new method to extract the pTAC from the dynamic brain PET images using a modified independent component analysis [extraction of the pTAC using independent component analysis (EPICA). Source codes of EPICA are freely available at http://www5f.biglobe.ne.jp/?kimura/Software/top.html]. EPICA performs the appropriate preprocessing and independent component analysis (ICA) using an objective function that takes the various properties of the pTAC into account. After validation of EPICA by computer simulation, EPICA was applied to human brain FDG-PET studies. The results imply that the EPICA-estimated pTAC was similar to the actual measured pTAC, and that the estimated blood volume image was highly correlated with the blood volume image measured using 15O-CO inhalation. These results demonstrated that EPICA is useful for extracting the pTAC from dynamic PET images without the necessity of serial arterial blood sampling.     

Sub-50-nm physical gate length CMOS technology and beyond usingsteep halo

Sub-50-nm CMOS devices are investigated using steep halo and shallow source/drain extensions. By using a high-ramp-rate spike annealing (HRR-SA) process and high-dose halo, 45-nm CMOS devices are fabricated with drive currents of 650 and 300 μA/μm for an off current of less than 10 nA/μm at 1.2 V with T_ox^inv =2.5 nm. For an off current less than 300 nA/μm, 33-nm pMOSFETs have a high drive current of 400 uA/μm. Short-channel effect and reverse short-channel effect are suppressed simultaneously by using the HRR-SA process to activate a source/drain extension (SDE) after forming a deep source/drain (S/D). This process sequence is defined as a reverse-order S/D (R-S/D) formation. By using this formation, 24-nm nMOSFETs are achieved with a high drive current of 800 μA/μm for an off current of less than 300 μA/μm at 1.2 V. This high drive current might be a result of a steep halo structure reducing the spreading resistance of source/drain extensions     

High-speed demonstration of an output interface driver forsingle-flux quantum systems

The high-speed operation of a one-channel output interface for a single-flux quantum (SFQ) system has been demonstrated. The interface consisted of a Josephson latching driver, a room-temperature semiconductor amplifier, and a decision circuit module. The Josephson latching driver was fabricated by using a 2.5-kA/cm² standard Nb junction process and used to amplify an SFQ pulse into a 5.5-mV level signal at 10 Gb/s. The interface converted the SFQ pulse signal into a nonreturn-to-zero signal having an amplitude of 1 V at 10 Gb/s     

Electrical properties of nickel in silicon

Electrical activity and energy levels as well as diffusion properties of nickel in silicon have not yet been reliably established. In this paper, we investigated the diffusion and the electrical properties of nickel in silicon to confirm that nickel is electrically active and introduces one acceptor and one donor level by combined measurements of Hall coefficient and DLTS, and measurements of the distribution of electrically active nickel in various silicon diodes by DLTS. The former experiments show that bothn- andp- type silicon are compensated by nickel and that nickel introduces an acceptor level ofE _c-0.47 ± 0.04 eV and a donor level ofE _v +0.18 ± 0.02 eV. The concentrations of these two levels are almost identical over the diffusion temperatures from about 800 to 1100° C, indicating that these donor and acceptor levels are due to different charge states of the same nickel center. In the distribution measurements of electrically active nickel in silicon diodes, we inspected how nickel can be observed by DLTS. It was found that the nickel diffusion intop- n junction is rather complicated, the distribution profiles of nickel in the vicinity of thep- n junction being markedly influenced by an additional heating at elevated temperatures after the nickel diffusion. This gives evidence that the difference in silicon devices used in various studies could give rise to different results.     

Liver phosphatidylcholine hydroperoxidation provoked by ethionine-containing choline-deficient diet in mice

It is shown that peroxidation of phosphatidylcholine (PC) is enhanced in liver of mice fed a hepatocarcinogenic choline-deficient diet containing 0.1% w/w ethionine. Mice were divided into 4 groups and fed for 3 weeks one of the following diets: choline-supplemented; choline-supplemented containing ethionine; choline-deficient; and choline-deficient containing ethionine. Phosphatidylcholine hydroperoxide (PCOOH) of liver lipids was measured by high performance liquid chromatography using a chemiluminescence detector. Mice fed a choline-deficient diet containing ethionine showed 6-fold higher PCOOH levels than the choline-supplemented control mice: the PCOOH/PC molar ratios of liver lipids were 32.3×10⁻⁵ and 5.6×10⁻⁵, respectively. In addition to this remarkable degree of lipid peroxidation in liver of mice fed the choline-deficient diet containing ethionine, we also observed a significant liver fatty infiltration, a decrease in plasma and liver α-tocopherol, and an increase in liver injury-indicative enzyme activities. Also, marker enzymes for hepatocarcinogenesis, glucose-6-phosphatase and γ-glutamyl transpeptidase were affected. These data suggest that enhanced hydroperoxidation of phosphatidylcholine may participate in hepatocarcinogenesis provoked by choline deficiency in the presence of ethionine.     

Electronically controlled high-speed wavelength-tunable femtosecondsoliton pulse generation using acoustooptic modulator

The compact system of electronically controlled high-speed wavelength-tunable femtosecond (fs) soliton pulse generation is realized for the first time using a passively mode-locked fs fiber laser, a polarization maintaining optical fiber, and an acoustooptic (A-O) modulator. The wavelength of the output pulses can be continuously tuned simply by controlling the input voltage into the A-O modulator. The wavelength of the soliton pulses can be changed at 2.5-μs intervals. Wavelength stabilization, time division wavelength multiplexed soliton pulse generation, and a wavelength scanner have been demonstrated     

256-QAM (64 Gb/s) Coherent Optical Transmission Over 160 km With an Optical Bandwidth of 5.4 GHz

We report a polarization-multiplexed (Pol-Mux) 4-Gsymbol/s 256 quadrature amplitude modulation (QAM) coherent optical transmission over 160 km. A 64-Gb/s data signal was successfully transmitted with an optical bandwidth of 5.4 GHz. We also describe a Pol-Mux, 10-Gsymbol/s, 128- and 64-QAM (140 and 120 Gb/s) transmission over 150 km.      

A 950-MHz rectifier circuit for sensor network tags with 10-m distance

This paper presents a 950-MHz wireless power transmission system and a high-sensitivity rectifier circuit for ubiquitous sensor network tags. The wireless power transmission offers a battery-life-free sensor tag by recharging the output power of a base station into a secondary battery implemented with the tag. For realizing the system, a high-sensitivity rectifier with dynamic gate-drain biasing has been developed in a 0.3-/spl mu/m CMOS process. The measurement results show that the proposed rectifier can recharge a 1.2-V secondary battery over -14-dBm input RF power at a power conversion efficiency of 1.2%. In the proposed wireless system, this sensitivity corresponds to 10-m distance communication at 4-W output power from a base station.