Static-state feedback control of discrete-event systems underpartial observation

Studies static-state feedback control of discrete-event systems under partial observation. The authors present a necessary and sufficient condition for the existence of a static-state feedback controller. A static controller is a special case of a dynamic controller studied by Kumar et al. The authors' condition, however, has computational advantage in contrast to those obtained by Kumar et al. The authors also present a necessary and sufficient condition under which the modular feedback synthesis is possible     

Synthesis of maximally permissive and robust supervisors forprefix-closed language specifications

J.E.R. Cury and B.H. Krogh (1999) have formulated a robust supervisory control problem to synthesize a supervisor for the nominal plant which maximizes robustness. They have solved the problem by unnecessarily restricting the upper bound of the legal behavior. We show that the problem can be solved without restricting the upper bound of the legal behavior when the specification is described by prefix-closed languages. We synthesize a maximally permissive supervisor for the nominal plant which maximizes not only robustness, but also permissiveness for the maximal set of admissible plant variations     

Development of enhanced depth-resolution technique for shallow dopant profiles

A rapid shrinkage in the minimum feature size of integrated circuits requires analysis of dopants in their shallow source–drain and their extensions with an enhanced depth resolution. Rutherford backscattering spectroscopy (RBS) combining a medium-energy He ion beam with a detector of improved energy resolution should meet the requirement of a depth resolution better than 5 nm at a depth of 10–20 nm in the next 10 years. A toroidal electrostatic analyzer of 4×10⁻³ energy resolution has been used to detect the scattered ions of a medium-energy He ion beam. Five keV As⁺ implanted Si or SiO₂ samples were measured. Depth profiling results using the above technique are compared with those of glancing-angle RBS by MeV energy He ions. Limitations in the energy resolution due to various energy-spread contributions have been clarified.     

High Mechanical Strength Double‐Network Hydrogel with Bacterial Cellulose

Double‐network (DN) hydrogels with high mechanical strength have been synthesized using the natural polymers bacterial cellulose (BC) and gelatin. As‐prepared BC contains 90 % water that can easily be squeezed out, with no more recovery in its swelling property. Gelatin gel is brittle and is easily broken into fragments under a modest compression. In contrast, the fracture strength and elastic modulus of a BC–gelatin DN gel under compressive stress are on the order of megapascals, which are several orders of magnitude higher than those of gelatin gel, and almost equivalent to those of articular cartilage. A similar enhancement in the mechanical strength was also observed for the combination of BC with polysaccharides, such as sodium alginate, gellan gum, and ι‐carrageenan.     

A 1-Gb/s/pin 512-Mb DDRII SDRAM using a digital DLL and a slew-rate-controlled output buffer

A 1-Gb/s/pin 512-Mb DDRII SDRAM has been developed using a digital delay-locked loop (DLL) and a slew-rate-controlled output buffer. The digital DLL has a frequency divider for DLL input, performs at an operating frequency of up to 500 MHz at 1.6 V, and provides internal clocking with 50% duty-cycle correction. The DLL has a current-mirror-type interpolator, which enables a resolution as high as 14 ps, needs no standby current, and can operate at voltages as low as 0.8 V. The slew-rate impedance-controlled output buffer circuit reduces the output skew from 107 to 10 ps. This SDRAM was tested using a 0.13-/spl mu/m 126.5-mm/sup 2/ 512-Mb chip.     

Prediction of the biologically active sites in eclosion hormone from the silkworm, Bombyx mori

The structure-activity relationship of eclosion hormone from the silkworm, Bombyx mori, was analyzed. First, the probable active residues in silkworm eclosion hormone and also tobacco hornworm eclosion hormone were predicted by the average distance map method. To examine the contributions of those residues to the activity of silkworm eclosion hormone, Gly-substituted mutants for those predicted residues were produced by site-directed mutagenesis and their activities were evaluated by a bioassay. Finally, Glu12, Met24 and Phe25 were estimated to be the crucial residues for the eclosion hormone activity. The possibility of the development of a blocker of an eclosion hormone receptor on the basis of the present work is also discussed.      

Roles of cell adhesion molecules nectin and nectin-like molecule-5 in the regulation of cell movement and proliferation

In response to chemoattractants, migrating cells form protrusions, such as lamellipodia and filopodia, and structures, such as ruffles over lamellipodia, focal complexes and focal adhesions at leading edges. The formation of these leading edge structures is essential for directional cell movement. Nectin-like molecule-5 (Necl-5) interacts in cis with PDGF receptor and integrin alpha(v)beta(3), and enhances the activation of signalling molecules associated with these transmembrane proteins, which results in the formation of leading edge structures and enhancement of directional cell movement. When migrating cells come into contact with each other, cell-cell adhesion is initiated, resulting in reduced cell velocity. Necl-5 first interacts in trans with nectin-3. This interaction is transient and induces down-regulation of Necl-5 expression at the cell surface, resulting in reduced cell movement. Cell proliferation is also suppressed by the down-regulation of Necl-5, because the inhibitory effect of Necl-5 on Sprouty2, a negative regulator of the Ras signalling, is diminished. PDGF receptor and integrin alpha(v)beta(3), which have interacted with Necl-5, then form a complex with nectin, which initiates cell-cell adhesion and recruits cadherin to the nectin-based cell-cell adhesion sites to form stable adherens junctions. The formation of adherens junctions stops cell movement, in part through inactivation of integrin alpha(v)beta(3) caused by the trans-interaction of nectin. Thus, nectin and Necl-5 play key roles in the regulation of cell movement and proliferation.     

Phosphorylation-dependent control of structures of intermediate filaments: a novel approach using site- and phosphorylation state-specific antibodies

The synovitis of rheumatoid arthritis (RA) is one of few pathological lesions in which B lymphocyte accumulation progresses to the extent of germinal centre formation. The present study was designed to assess the ability of synovial fibroblasts to express molecules implicated in B lymphocyte survival and differentiation, both in vivo, and in response to cytokines in vitro. Normal and diseased synovia were examined by indirect immunofluorescence. In all tissues synovial intimal fibroblasts showed co-expression of vascular cell adhesion molecule-1 (VCAM-1) and complement decay-accelerating factor (DAF) comparable to that of follicular dendritic cells (FDC), but not complement receptor 2 (CR2). In rheumatoid synovia, subintimal cells showed variable expression of VCAM-1 and DAF, with bright co-expression of VCAM-1, DAF and CR2 in lymphoid follicle centres. B lymphocytes, some of which were proliferating cell nuclear antigen-positive, were present in contact with subintimal cells expressing VCAM-1 with or without DAF or CR2. B lymphocytes were rarely present in the intimal layer, and, where present, showed fragmentation. In vitro, synovial fibroblasts exposed to tumour necrosis factor-alpha (TNF-alpha) in combination with interferon-gamma (IFN-gamma) showed enhanced expression of VCAM-1, in comparison with fibroblasts from skin and lung and, unlike skin and lung fibroblasts, also expressed DAF and CR2. These findings support the hypothesis that synovial targeting in RA involves an enhanced ability of synovial fibroblasts to support B lymphocyte survival. This appears to be dependent, not on the constitutive expression of VCAM-1 and DAF on intimal cells, but on the increased ability of subintimal cells to respond to proinflammatory cytokines, perhaps critically in the expression of VCAM-1.