Process and design tradeoffs between minimum RC signal propagation delay and interconnect current density and resistance for deep submicrometer ICs

The demand for higher current density in metal interconnects continues to increase to meet the challenges of higher operation frequency and the more complex design requirement of deep submicrometer integrated circuits. However, improvement in the allowable interconnect current density is typically accompanied by higher wire resistance. The tradeoff between wire resistance and allowable current density must be managed to realize the most efficient interconnect system because both wire resistance and allowable current density affect signal propagation delay. This paper studies the impact of allowable current density on signal propagation delay, and demonstrates an approach to balance wire resistance and allowable current density from the perspective of minimizing signal propagation delay.     

Internal Hollows in Cooked Rice Grains (Oryza sativa cv. Koshihikari) Observed by NMR Micro Imaging

Nondestructive analysis of water distribution and structural changes in cooked rice grains, Oryza sativa cv Koshihikari, was performed with Nuclear Magnetic Resonance (NMR) Micro imaging of protons (¹H). Using a specially designed holder, high quality images of cooked rice grains were obtained, even when up to 10 grains were studied simultaneously. Internal hollows were observed in all examined cooked rice grains, and we propose a mechanism to explain their formation. The origin of these hollows was hypothesized to be cracks or fissures, and hollows resulted from sealing of such lacerations by gelatinized starch in the peripheral layer in combination with expansion of the grain during cooking.     

A 16-Mb 400-MHz loadless CMOS four-transistor SRAM macro

We have used a 5-metal 0.18-μm CMOS logic process to develop a 16-Mb 400-MHz loadless CMOS four-transistor SRAM macro. The macro contains: (1) end-point dual-pulse drivers for accurate timing control; (2) a wordline-voltage-level compensation circuit for stable data retention; and (3) an all-adjoining twisted bitline scheme for reduced bitline coupling capacitance. The macro is capable of 400-MHz high-speed access at 1.8-V supply voltage and is 66% the size of a conventional six-transistor SRAM macro. We have also developed a higher-performance 500-MHz loadless four-transistor SRAM macro in a CMOS process using 0.13-μm gate length     

A 15-ns 1-Mbit CMOS SRAM

A 1-Mb CMOS static RAM with a 256 K word×4-bit configuration has been developed. The RAM was fabricated using 0.8-μm double-poly and double-aluminum twin-well CMOS technology. A small cell size of 5.2 μm×8.5 μm and a chip size of 6.15 mm×15.21 mm have been achieved. A fast address access time of 15 ns was achieved using novel circuit techniques: a PMOS-load decoder and a three-stage dynamic gain control sense amplifier combined with an equalization technique and feedback capacitances. A low active current of 50 mA at 20 MHz and low standby currents of 15 mA (TTL) and 2 μA (CMOS) were also attained     

A voltage down converter with submicroampere standby current forlow-power static RAMs

A submicroampere standby current voltage downconverter (VDC) for high-density, low-power static RAMs is described. The current consumption of the VDC in standby mode can be decreased by using a novel low-current and temperature-independent current source circuit. The total current is less than 0.5 μA at external voltage ranging from 3 to 5 V and at temperatures ranging from -20 to 80°C. The voltage-follower circuits for standby and operation modes are stable despite the low current consumption in the standby mode. The phase margin of the voltage follower for standby mode is 50°, and that for operation mode is 90°. This indicates that the VDC is a promising circuit for battery-backup and high-density static RAMs     

Delayed and stage specific phosphorylation of H2AX during preimplantation development of gamma-irradiated mouse embryos

Within minutes of the induction of DNA double-strand breaks in somatic cells, histone H2AX becomes phosphorylated in the serine 139 residue at the damage site. The phosphorylated H2AX, designated as gamma-H2AX, is visible as nuclear foci in the irradiated cells which are thought to serve as a platform for the assembly of proteins involved in checkpoint response and DNA repair. It is known that early stage mammalian embryos are highly sensitive to radiation but the mechanism of radiosensitivity is not well understood. Thus, we investigated the damage response of the preimplantation stage development by analyzing focus formation of gamma-H2AX in mouse embryos gamma-irradiated in utero. Our analysis revealed that although H2AX is present in early preimplantation embryos, its phosphorylation after 3 Gy gamma-irradiation is hindered up to the two cell stage of development. When left in utero for another 24-64 h, however, these irradiated embryos showed delayed phosphorylation of H2AX. In contrast, phosphorylation of H2AX was readily induced by radiation in post-compaction stage embryos. It is possible that phosphorylation of H2AX is inefficient in early stage embryos. It is also possible that the phosphorylated H2AX exists in the dispersed chromatin structure of early stage embryonic pronuclei, so that it cannot readily be detected by conventional immunostaining method. In either case, this phenomenon is likely to correlate with the lack of cell cycle arrest, apoptosis and high radiosensitivity of these developmental stages.     

Targeted proteome analysis of microalgae under high-light conditions by optimized protein extraction of photosynthetic organisms

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