Relationship between segment structures and elastic properties of segmented poly(urethane‐urea) elastic fibers

Studies on segmented poly(urethane‐urea) (SPUU) elastic fibers having various segment structures were done in terms of elastic recovery and stress‐strain relationship (S‐S). Three kinds of segment structures were used: 1) the same composition having different sequences of segment units, 2) the same length of soft segments having different molecular weights of polyol, and 3) different segment structures having almost the same stress at 350% elongation. The SPUU elastic fibers having higher sequence numbers of both soft and hard segment units, that is, greater block structures, show better elastic recovery properties, especially delayed elastic recovery. The SPUU elastic fibers showing better elastic recovery take an optimum value for the number‐average molecular weight (M_n) of soft segments jointed with urethane bonds. Here the optimum M_n depends on the molecular weight of polytetramethyleneglycol (PTMG) as a starting material. The hysteresis loss in S‐S for the pre‐elongation decreases with an increase of M_n of PTMG. The SPUU elastic fibers having greater block structures show lower stress with lower 2C₁ and 2C₁ + 2C₂ of Mooney‐Rivilin plot constants for elastic fibers having the same composition. This indicates a lower density of crosslinks for finite deformation. An increase of the urea bonds or the molar ratio of urea bond to urethane bond raises the stress. It is found that the polymerization process, as well as composition, is important for design structures of SPUU elastic fibers.     

Endoscopic treatment of submucosal invasive colorectal carcinoma with special reference to risk factors for lymph node metastasis

A clinicopathological analysis of the risk factors for lymph node metastasis was performed in 177 patients with submucosal invasive colorectal carcinoma (CRC). The submucosal deepest invasive portion was histologically subclassified as well (W), moderately (M), or poorly (Por) differentiated. M type was further subdivided into moderately-well (Mw) and moderately-poorly (Mp) differentiated. The pattern of tumor growth was classified as polypoid growth (PG) and non-polypoid growth (NPG). Lymph node metastasis was detected in 21 (12%) of the 177 patients. Macroscopically, type IIc and IIa + IIc lesions showed a significantly higher incidence of lymph node metastasis (44% and 30%) than type IIa and I (4% and 8%). Regarding the histologic subclassification, Por and Mp lesions showed a significantly higher incidence of lymph node metastasis (67% and 37%) than W and Mw lesions (4% and 14%). NPG tumors showed a significantly higher incidence of lymph node metastasis (29%) than PG tumors (7%). The depth of submucosal invasion and lymphatic invasion (ly) were also significantly correlated with the incidence of lymph node metastasis (submucosal scanty (sm-s) invasion 4%, massive invasion 20%; ly(+) 23%, ly(-) 5%). None of the lesions with both sm-s invasion and of W or Mw type showed lymph node metastasis. These results indicate that submucosal invasive CRC with both sm-s invasion and of W or Mw type, which shows no ly, is the appropriate indication for endoscopic curative treatment.     

Analysis of coupling noise between adjacent bit lines in megabitDRAMs

Different bit-line structures, bit-line materials, widths, spacings, and passivation materials were fabricated to analyze the effect of the coupling noise between adjacent bit lines in megabit DRAMs. Each component of total bit-line capacitance was measured to obtain the bit-line-to-bit-line capacitance and the other contributions to the total bit-line capacitance. Accelerated soft error tests were performed on each sample. The results suggest the existence of two types of noise effects. One is the READ-signal degradation just after the work-line rises. The other is the disturbance in sensing operation. The larger the ratio of the bit-line coupling capacitance to the other bit-line capacitance contributions the more serious both the noise effects are. These noise mechanisms can be explained by the charge conservation model and the simulation of sensing operation. A polycide bit-line structure is less susceptible to these noises than an Al bit line because its thickness and layer position     

120-ns 128 K*8-bit/64 K*16-bit CMOS EEPROMs

A 1-Mbit CMOS full-featured EEPROM using a 1.0- mu m triple-polysilicon and double-metal process is described. The design is aimed at developing a manufacturable 120-ns 1-Mbit EEPROM with small chip size. Therefore, an advanced memory cell with high read current, an improved differential sensing technique, and an efficient ECC scheme are developed. The differential sensing amplifier utilizes the output of a current sensing amplifier connected to unselected memory as a reference level. The cell size is 3.8*8 mu m/sup 2/ and the chip size is 7.73*11.83 mm/sup 2/. The device is organized as either 128 K*8 or 64 K*16 by via-hole mask options. A 256-byte/128-word page-mode programming is implemented.<>     

Absence of nonpercutaneous transmission of hepatitis C virus in a colony of chimpanzees

Transmission of hepatitis C virus (HCV) was studied in a colony of 85 chimpanzees using assays for anti-HCV and HCV-RNA. Thirteen of the 85 sera were positive for anti-HCV, and 12 of the 13 were also positive for HCV-RNA. All of the anti-HCV positive sera except one were obtained from chimpanzees which had been inoculated with non-A, non-B hepatitis virus. On the other hand, only one of 63 sera of chimpanzees without history of experimental infection of the virus was positive for anti-HCV. Transmission to this chimpanzee was thought to be a needle contaminated with HCV. All 39 samples of chimpanzees born in the center were negative for both anti-HCV and HCV-RNA. Sixteen of their mothers had undergone experimental infection, and 6 of them were positive for both anti-HCV and HCV-RNA. These results suggest that nonpercutaneous transmission, including sexual and mother-to-infant transmissions, is not an important mode of transmission. If these findings apply to humans, definition of inapparent sources of the infection is needed.     

Structure and Function of Retinochrome

Retinochrome is a photo-isomerase of all-trans-retinal to the 11-cis-isomer for rhodopsin synthesis. This protein is probably folded into seven α-helices spanning the membranes. Upon irradiation, it is converted to metaretinochrome, via pre-lumi- and lumiretinochrome, which are stable under 50 and 250 K, respectively. A series of analogue studies revealed that the cyclohexene ring and 6-s-cis-twisted conformation are important for binding. Modification of the 14-position suggests close location of the 14-H to the counterion.     

Mechanical and biological properties of two types of bioactive bone cements containing MgO-CaO-SiO2-P2O5-CaF2 glass and glass-ceramic powder

The electrostatic steering of charged ligands toward the active site of Torpedo californica acetylcholinesterase is investigated by Brownian dynamics simulations of wild type enzyme and several mutated forms, in which some normally charged residues are neutralized. The simulations reveal that the total ligand influx through a surface of 42 A radius centered in the enzyme monomer and separated from the protein surface by 1-14 A is not significantly influenced by electrostatic interactions. Electrostatic effects are visible for encounters with a surface of 32 A radius, which is partially hidden inside the protein, but mostly within the solvent. A clear accumulation of encounter events for that sphere is observed in the area directly above the entrance to the active site gorge. In this area, the encounter events are increased by 40% compared to the case of a neutral ligand. However, the differences among the encounter rates for the various mutants considered here are not pronounced, all rate constants being within +/- 10% of the average value. The enzyme charge distribution becomes more important as the charged ligand moves toward the bottom of the gorge, where the active site is located. We show that neither the enzyme's total charge, nor its dipole moment, fully account for the electrostatic steering of ligand to the active site. Higher moments of the enzyme's charge distribution are also important. However, for a series of mutations for which the direction of the enzyme dipole moment is constant within a few degrees, one observes a gradual decrease in the diffusional encounter rate constant with the number of neutralized residues. On the other hand, for other mutants that change the direction of the dipole moment from that of the wild type, the calculated encounter rate constants can be very close to that of the wild type. The present work yields two new insights to the kinetics of acetylcholinesterase. First, evolution appears to have built a redundant electrostatic steering capability into this important enzyme through the overall distribution of its thousands of partially charged atoms. And second, roughly half of the rate enhancement due to electrostatics arises from steering of the substrate outside the enzyme; the other half of the rate enhancement arises from improved trapping of the substrate after it has entered the gorge. The computational results reproduce qualitatively, and help to rationalize, many surprising experimental results obtained recently for human acetylcholinesterase.     

An evolutionary design methodology of printed circuit boards for high-speed VLSIs

As operation frequencies of the printed circuit boards (PCBs) increase in keeping with VLSI frequencies in the GHz domain, two independent serious problems occur in the PCB design. One is waveform distortion problem, or signal integrity (SI) degradation problem, in PCB traces. And the other is power-supply drop problem, or power integrity (PI) degradation problem, in PCB power planes. Those problems are barely able to be overcome on case-by-case empirical designs conventionally. In this paper we newly propose a design approach for each problem, both of which are based on the genetic algorithm. And we obtained improvement ratios of more than double compared with the both conventional designs for SI and PI degradations, respectively.