Measurements of leakage currents and the capacitance of the storagecapacitor in a single DRAM cell

Methods of measuring leakage currents and the capacitance of the storage capacitor in a single DRAM cell have been developed for correlation with the electrode shape of the capacitor. In the circuit used for these measurements, the plate electrode of the storage capacitor is connected to the gate of the MOSFET which amplifies the voltage variations of the storage capacitor during the measurements. Here, only a conventional transistor parameter analyzer and a capacitance meter are required for the measurements. For the capacitance measurement, the linear region characteristics of the MOSFET are used to simplify the analysis. For the leakage current measurement, however, the subthreshold region characteristics of the MOSFET are used to enhance the accuracy of the measurement. The results show that the very low leakage currents (down to below 0.1 fA) and the capacitance (37.5 fF) of the storage capacitor can be measured accurately. Further, the leakage current-voltage characteristics of the storage capacitor are discussed by comparing with those of a large area planar capacitor whose structure is the same as the storage capacitor     

1.6 Gbit/s optical receiver at 1.3 ?m with SAW timing retrieval circuit

The performance of a 1.6 Gbit/s optical receiver employing a s.a.w. filter as a timing tank is reported. The error-rate characteristics in a p.c.m. transmission system using a 1.3 ?m In-GaAsP laser and single-mode fibres were studied. The average received optical power at a 10?9 error rate was ?28 dBm. In a 15 km transmission experiment, the receiving level was degraded by 2 dB owing to fibre dispersion. Timing phase margin of 75 degrees after 12 km transmission was confined with the self-timed receiver.     

Successes in the all-union socialist competition for collectives in the enterprises and organizations,brigades and workers in key professions,to raise the efficiency ofproduction and improve the quality of the products in the second quarter and the first half of 1976

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Successes in the all-union socialist competition for collectives in the enterprises and organizations, brigades and workers in key professions, to raise the efficiency ofproduction and improve the quality of the products in the second quarter and the first half of 1976     

Changes in stable isotopes, lignin-derived phenols, and fossil pigments in sediments of Lake Biwa, Japan: implications for anthropogenic effects over the last 100 years

We measured stable nitrogen (N) and carbon (C) isotope ratios, lignin-derived phenols, and fossil pigments in sediments of known ages to elucidate the historical changes in the ecosystem status of Lake Biwa, Japan, over the last 100 years. Stable N isotope ratios and algal pigments in the sediments increased rapidly from the early 1960s to the 1980s, and then remained relatively constant, indicating that eutrophication occurred in the early 1960s but ceased in the 1980s. Stable C isotope ratios of the sediment increased from the 1960s, but decreased after the 1980s to the present. This decrease in stable C isotope ratios after the 1980s could not be explained by annual changes in either terrestrial input or algal production. However, when the C isotope ratios were corrected for the Suess effect, the shift to more negative isotopic value in atmospheric CO(2) by fossil fuel burning, the isotopic value showed a trend, which is consistent with the other biomarkers and the monitoring data. The trend was also mirrored by the relative abundance of lignin-derived phenols, a unique organic tracer of material that originated from terrestrial plants, which decreased in the early 1960s and recovered to some degree in the 1980s. We detected no notable difference in the composition of lignin phenols, suggesting that the terrestrial plant composition did not change markedly. However, we found that lignin accumulation rate increased around the 1980s. These results suggest that although eutrophication has stabilized since the 1980s, allochthonous organic matter input has changed in Lake Biwa over the past 25 years.     

Electron emission from PZT ceramic thin plate by pulsed electric field

Abstract

Electron emission into vacuum from a thin plate of ferroelectric lead-zirconatetitanate (PZT) ceramic has been observed under the impression of electric field of pulse consisting of a pair of positive and negative voltages. The emission was observed at pressure lower than about 10^?1 Torr. The emitted charge increases with increasing the positive and the absolute negative voltages of the pulse and the collector voltage. The minimum absolute value of the negative pulse for electron emission is 30V when the positive voltage is larger than 150V. The maximum peak current density is 70A/cm². It is considered from the electrode area and thickness dependences of the charge that electrons are emitted not only from the ceramic surface near the electrode edge but also through the thin metal electrode. The emitted charge per one pulse little depends on pulse frequency when it is less than 2kHz, and so the total current density can be enhanced by increasing the frequency. The emission is observed even at temperatures above Curie temperature. It is considered that the emission is induced by abrupt change of dielectric flux as well as the polarization reversal. Cathodoluminescence from phosphors excited by the emitted electrons has been observed.     

Computer simulation of a porous positive electrode for lithium batteries

The discharge characteristics of a Li/Li_yCoO₂ cell were simulated by numerical calculations. Based on the program proposed by Newman's group, the change in entropy due to lithium-ion insertion into the active materials was introduced into the open-circuit potential (OCP) for more practical applications. The OCP of LiCoO₂ (y = 1) at a full-discharge state was 3.82 V, which was determined from the original program. However, it should show a rapid decrease to minus infinity when discharge is complete (y = 1), which is due to the introduced entropy term. In addition, the local use of active materials across the Li_yCoO₂ electrode was not uniform, whereas the original program showed a constant value throughout the electrode. Based on the present results, the introduction of an entropy term to the OCP of Li_yCoO₂ works reasonably well for more practical applications.     

Effective cell harvesting of the halotolerant microalga Dunaliella tertiolecta with pH control

An effective method for cell harvesting of the halotolerant microalga, Dunaliella tertiolecta ATCC30929, was investigated. By increasing the pH of the culture broth using NaOH solution, suspended D. terfolecta cells rapidly coagulated and settled within a few minutes, which allowed simple harvesting of the concentrated cells from the culture broth. The pHs for successful coagulation were between 8.6 and 10.5 and more than 90% of cells was recovered from the culture broth. Clarified culture broth could be reused for the successive cultivation of D. tertiolecta simply by supplying fresh medium and neutralizing alkali with HCl without the requirement for an additional inoculum.     

Biological oxidation of arsenite in synthetic groundwater using immobilised bacteria

Biological oxidation of arsenite (As(III)) in synthetic groundwater was examined by using arsenite oxidising bacteria (AOB) isolated from an activated sludge. The phylogenetic analysis indicated that the isolated AOB was closely related to Ensifer adhaerens. Batch experiments showed that for an As(III) oxidation with the isolated AOB the optimum ratio of nitrogen source (NH₄-N) concentration to As(III) concentration was 0.5 (52 mg/L-110 mg/L) and the isolated AOB preferred pH values ranging from 6 to 8, and water temperatures greater than 20 °C. Further continuous experiments were conducted using a bioreactor with immobilised AOB. With an initial As(III) concentration of 1 mg/L at a hydraulic retention time (HRT) of 1 h, an As(III) oxidation rate was around 1 × 10⁻⁹ μg/cell/min and an As(III) oxidation efficiency of 92% was achieved. Although the maximum oxidation rate measured at an HRT of 0.5 h was 2.1 × 10⁻⁹ μg/cell/min, the oxidation efficiency decreased to 87%.These results advocate that a biological process involving immobilised AOB may be useful as an economical and environmentally friendly pre-treatment step for As removal from groundwater.     

STM spectroscopy in superconducting phase of (BEDT-TTF)2Cu(NCS)2

The superconducting phase of (BEDT-TTF)₂Cu(NCS)₂ was investigated with use of the scanning tunneling microscope (STM).The tunneling conductance was measured at the b-c surface of a single crystal. The differential conductance shows a clear superconducting gap structure below the transition temperature and its value is reduced to almost zero around zero bias voltage at 1.9 K. The conductance curve is not well fitted to the BCS one but suggests the gap anisotropy. However, the gap with line nodes, expected from the simple d-wave symmetry, is excluded. Possible models for the superconducting gap are as follows; (1) the gap with point nodes or (2) the anisotropic gap with a minimum value Δ_min1 mev. It is understood that the superconducting gap is highly anisotropic in k-space.