A 60-ns 16-Mbit CMOS DRAM with a transposed data-line structure

Low-noise, high-speed circuit techniques for high-density DRAMs (dynamic random-access memories), as well as their application to a single 5-V 16-Mb CMOS DRAM with a 3.3-V internal operating voltage for a memory array, are described. It was found that data-line interference noise becomes unacceptably high (more than 25% of the signal) and causes a serious problem in 16-Mb DRAM memory arrays. A transposed data-line structure is proposed to eliminate the noise. Noise suppression below 5% is confirmed using this transposed data-line structure. A current sense amplifier is also proposed to maintain the data-transmission speed in common I/O lines, in spite of a reduced operating voltage and increased parasitic capacitance loading in the memory array. A speed improvement of 10 ns is achieved. Using these circuit techniques, a 16-Mb CMOS DRAM with a typical RAS access time of 60 ns was realized     

8 Gb/s 8:1 multiplexer and 1:8 demultiplexer IC's using GaAs DCFLcircuit

High-speed 8:1 multiplexer and 1:8 demultiplexer ICs composed of GaAs direct-coupled FET logic (DCFL) have been designed and fabricated. The ICs were designed with a tree-type architecture and using memory-cell-type flip-flops (MCFFs). Self-aligned GaAs MESFETs with a gate length of 0.5 μm were used in these ICs. The propagation delay time of the DCFL inverter was 19.0 ps/gate. Both ICs operated up to 8 Gb/s with power dissipations of 1.5 W for the multiplexer and 1.9 W for the demultiplexer at a single power supply voltage of 2.0 V. These ICs are applicable for multigigabit lightwave communication systems     

The effect of oxygen in Ru gate electrode on effective work function of Ru/HfO2 stack structure

Effective work function (φ_m,eff) values of Ru gate electrode on SiO₂ and HfO₂ MOS capacitors were carefully examined and discussed from the viewpoint of an effect of oxygen incorporation in Ru gate electrode on φ_m,eff. Annealing at 400 °C in the reduction (3%H₂) and the oxidation (1%O₂) ambient resulted in similar changes in the φ_m,eff of Ru/HfO₂/SiO₂ and Ru/SiO₂ MOS capacitors. Furthermore, the Ru gate MOS capacitor after annealing in the oxidation condition have shown almost the same φ_m,eff value to that of RuO₂ gate MOS capacitors. The oxygen concentration in the Ru/HfO₂ interface after annealing in oxidizing atmosphere is approximately one order of magnitude higher than that after annealing in reducing atmosphere as confirmed by secondary ion mass spectroscopy analysis. Furthermore, the higher oxygen concentration at the Ru/dielectric interface leads to the higher φ_m,eff value, regardless of SiO₂ or HfO₂ dielectrics. This indicates that φ_m,eff of Ru gate MOS capacitor is dominantly determined by the oxygen concentration at the Ru/dielectric layer interface rather than the dipoles originated from the oxygen vacancy in HfO₂.     

Effect of heavy metals on the growth of a methanogen in pure culture and coculture with a sulfate-reducing bacterium

The sensitivity of a methanogen and sulfate-reducing bacterium isolated from a sea-based landfill site to Cd2+ and Cu2+ was studied. Methanogens and sulfate-reducing bacteria in leachates of the waste disposal site were enumerated using the MPN method. Methanobacterium thermoautotrophicum KHT-2, isolated from the leachate, could not grow at 0.5 mM Cd2+ or 1.0 mM Cu2+. Desulfotomaculum sp. RHT-3, isolated from the same leachate, was able to insolubilize 3.0 mM Cd2+ or 2.0 mM Cu2+ by production of hydrogen sulfide. When strains KHT-2 and RHT-3 were cultured together in the presence of the heavy metals, strain KHT-2 could grow at high heavy metal concentrations after insolubilization of the metals by strain RHT-3.     

Mechanism involved in the evolution of physically irreversible fouling in microfiltration and ultrafiltration membranes used for drinking water treatment

Control of membrane fouling is important for more efficient use of membranes in water treatment. Control of physically irreversible fouling, which is defined as fouling that requires chemical cleaning to be cancelled, is particularly important for reduction of operation cost in a membrane process. In this study, a long-term filtration experiment using three different types of MF and UF membranes was carried out at an existing water purification plant, and the evolution of physically irreversible fouling was investigated. The experimental results demonstrated that the extent of physically irreversible fouling differed significantly depending on the membrane type. Cleaning of the fouled membranes with various chemical reagents demonstrated that organic matter was mainly responsible for physically irreversible fouling. Organic matter that had caused physically irreversible fouling in the long-term operation was desorbed from the fouled membranes and was subjected to Fourier transform infrared and 13C nuclear magnetic resonance analyses. These analyses revealed that carbohydrates were dominant in the membrane foulant regardless of the type of membrane. Based on measurements of molecular weight distribution of organic matter in the feedwater and the permeates from the membranes, a two-step fouling mechanism is proposed to explain the dominance of carbohydrates in the foulant: hydrophobic (humic-like) components with small molecular weight are first adsorbed on the membrane and, consequently, narrow the size of micro-pores of membranes, and then hydrophilic (carbohydrate-like) compounds with larger molecular weight plug the narrowed pores or the hydrophilic compounds are adsorbed onto the membrane surface conditioned by the hydrophobic components.     

Development of a genetic transfer system in selenate-respiring bacterium Citrobacter sp. strain JSA which was isolated from natural freshwater sediment

Conjugative mating between the selenate-reducing bacterium Citrobacter sp. strain JSA and Escherichia coli S17-1 harboring the broad-host-range plasmid pKT230 or pKT240 (IncQ) allowed genetic transfer to strain JSA at a maximum frequency of 2.5×10(-5) (pKT230) and 5.1×10(-6) (pKT240) per recipient JSA cell. Kanamycin-resistant (selection marker of pKT230 and pKT240) transconjugants were routinely obtained with this method, and we confirmed that both vectors were also successfully transferred and replicated in strain JSA without alteration of the replicon. Furthermore, an electroporation method has also allowed transformation of JSA at a frequency of 10(-7) to 10(-6) transformants per μg vector DNA (per recipient cell), and PCR and hybridization analyses revealed that pKT230 and pKT240 are stably maintained in transformed JSA cells. These results indicated that both InQ plasmids can be used as vectors for gene transfer to selenate-reducing strain JSA. This is the first study to demonstrate an effective method for genetic transfer in a selenate-reducing Citrobacter bacterium and will aid in the elucidation of the selenium oxyanion reduction mechanism in this genus of environmental selenate-respiring isolates.     

Bi-based electrochromic cell with mediator for white/black imaging

We studied electrochemical properties of bismuth deposit, which showed reversible color change from colorless clear to black by electrochemical reaction, toward paper-like electronic imaging device. Bismuth salt in an electrolyte solution is colorless clear, but turned to black by the electrodeposition on an electrode. Namely, bismuth ion (Bi³⁺) dissolved in the electrolyte solution (colorless clear) is electrochemically reduced on the electrode to deposit the Bi metal showing black color. The Bi deposit on the electrode is electrochemically oxidized to dissolve the deposit into the solution. These processes enable the color change between colorless clear and black. However, the stability of the switching between colorless and black state is not sufficient due to less electroactivity of bismuth deposit. To improve the switching stability of the present electrochromic cell, various mediators were employed to add into the electrolyte solution. Reversible white/black display cell has been successfully demonstrated.     

Wettability of liquid caesium iodine and boron oxide on yttria-stabilized zirconia

During the Fukushima Daiichi Nuclear Power Plant accident occurred in 2011, volatile fission products (FPs) such as Cs and I had released and caused environmental contamination and public exposure, respectively. However, the release mechanism of these FPs from fuels under the accident is still not completely understood. In recent years, we have focused on the wettability of liquid FPs against solid fuels, because the interface between the fuel surface and the FPs becomes the migration pathway, which might have large influences on the release behaviour of the FPs. Here, we studied the wettability of liquid CsI and B₂O₃ on yttria-stabilized zirconia (YSZ) solid surface by the sessile drop test, where YSZ is a simulated material of the fuel. It was revealed that liquid CsI exhibited extremely high wettability against the YSZ surface with the contact angle of nearly zero. This high wettability may act to suppress the FPs release. Furthermore, it was confirmed that the crystal orientation and surface roughness of the YSZ solids have large influences on the wettability of liquid B₂O₃. The present results contribute for deep understanding of the release behaviour of the volatile FPs from fuels.     

Design of 1.28-GB/s high bandwidth 2-Mb SRAM for integrated memoryarray processor applications

We have fabricated a high yield integrated memory array processor (IMAP) LSI, which features a high memory bandwidth (1.28-GB/s) and low power consumption (4-W max.) and which contains a 2-Mb SRAM with 1.28-I/O's and 64 processor elements (PE's) in one chip. A high-bandwidth and low-power memory circuit design is the key technology to realize the IMAP-LSI. We adopted following new designs for memory circuit. (1) Memory access time is designed to be twice as fast as PE execution time (2) Employment of dynamic power control mode, which reduces the memory power consumption down to 30% of maximum power without a loss in access-speed (3) Simplified synchronization with PE's (4) 4-way block redundancy. These design techniques are suitable for future system integrated ULSI's     

Clinical and morphological predictors of renal outcome in adult patients with focal and segmental glomerulosclerosis (FSGS)

In this retrospective study, we examined 35 adult patients with biopsy-proven, primary focal and segmental glomerulosclerosis (FSGS) and nephrotic syndrome to determine whether any of the clinical and morphological features of FSGS were associated with a higher risk of a poor renal outcome. Clinical factors assessed were the age, sex, amount of urinary protein, and presence of microscopic hematuria, hypertension and renal dysfunction at onset in each patient. Morphological parameters included the number of segmental sclerosis and global sclerosis, sclerosis score, location of segmental sclerosis, mean glomerular diameter, grade of tubulo-interstitial changes, and presence of vascular lesions. Twenty-three patients (66%) were in complete or incomplete (partial) remission, and 12 (34%) were non-responders at the end of follow-up. On univariate analysis, the age at onset, sclerosis score, mean glomerular diameter, and grade of tubulo-interstitial changes in no response were significantly greater than those parameters in remission. Multivariate logistic regression analysis revealed that the degree of tubulo-interstitial changes and mean glomerular diameter were independent risk factors for a poor renal outcome. These findings suggest that the estimation of these latter two parameters allows the nephrologist to predict the probable course and prognosis of an adult with FSGS. Intensive and prolonged therapy is recommended for patients without these two morphological features.