Glass-Forming Ability and Crystallization Tendency Evaluated by the DTA Method in the Na2O–B2O3–Al2O3 System

In order to evaluate the crystallization tendency of glasses, the ratio of the crystallization temperature to the liquidus temperature ( T _c/ T _L) was obtained by DTA measurement for the Na₂O–B₂O₃ and Na₂O–B₂O₃–Al₂O₃ systems. The critical cooling rate for glass formation ( Q *) was also measured. The measurements were performed in the composition range of (100 − x )Na₂O–( x )B₂O₃, ( x = 25–35 and 60–100 mol%), and (100 − y )0.5Na₂O·0.5B₂O₃−( y )Al₂O₃, ( y = 6–34 mol%). The relationship between T _c/ T _L and Q * was discussed. A linear relationship between T _c/ T _L and log Q * for these systems was found. Furthermore, the relationship between T _c/ T _L and Q * was verified by computer simulation based on the crystallization kinetics of glass or supercooled liquid.     

Studies on the Dehydrogenative Polymerizations of Monolignol β‐Glycosides. Part 1. Syntheses of Monolignol β‐glycosides, (E)‐Isoconiferin, (E)‐Isosyringin,and (E)‐Triandrin

Abstract

(E)‐4‐O‐Acetyl coniferyl alcohol was synthesized by the reduction of (E)‐4‐O‐acetyl ferulic acid with sodium borohydride and N,N‐dimethylchloromethylenium chloride in 80.2% yield. The glycosylation of (E)‐4‐O‐acetyl coniferyl alcohol with trichloroacetimidoyl 2,3,4,6‐tetra‐O‐pivaloyl‐α‐D‐glucopyranoside in the presence of BF₃-Et₂O in anhydrous CH₂Cl₂, followed by deacylation gave (E)‐isoconiferin in high yield. This synthetic method could be applied to the syntheses of other monolignol β‐glycosides. As a result, (E)‐isoconiferin, (E)‐isosyringin, and (E)‐triandrin were synthesized from vanillin, syringaldehyde, and p‐hydroxybenzaldehyde, respectively, by five reaction steps in high overall yield.     

Tryptophan H33 plays an important role in pyrimidine (6-4) pyrimidone photoproduct binding by a high-affinity antibody

The importance of Trp H33 in antibody recognition of DNA containinga central pyrimidine (6–4) pyrimidone photoproduct wasinvestigated. This residue was replaced by Tyr, Phe and Alaand the binding abilities of these mutants were determined bysurface plasmon resonance and fluorescence spectroscopy. Conservativesubstitution of Trp H33 by Tyr or Phe resulted in moderate lossesof binding affinity; however, replacement by Ala had a significantlylarger impact. The fluorescence properties of DNA containinga (6–4) photoproduct were strongly affected by the identityof the H33 residue. DNA binding by both the wild-type and theW-H33-Y mutant was accompanied by a small degree of fluorescencequenching; by contrast, binding by the W-H33-F and W-H33-A mutantsproduced large fluorescence increases. Taken together, thesevariations in binding and fluorescence properties with the identityof the H33 residue are consistent with a role in photoproductrecognition by Trp H33 in the high-affinity antibody 64M5.     

Positive charge generation due to species of hydrogen during NBTI phenomenon in pMOSFETs with ultra-thin SiON gate dielectrics

Negative bias temperature instability (NBTI) of pMOSFETs with ultra-thin SiON gate dielectrics was investigated. We focused our attention on the behavior of hydrogen atoms released from the interface under NBT stress. From the transient characteristics of pMOSFETs after NBT stresses were stopped, it was found that a portion (60%, in our case) of hydrogen atoms released by the NBT stress remain in a 1.85-nm-thick NO-oxynitride gate dielectric. The existence of the hydrogen in the gate dielectric was shown to lead to the generation of positive charges.     

Spatial ordering of self-organized InGaAs/AlGaAs quantum disks on GaAs (311)B substrates

We report the control of self-organization of In_xGa_1−xAs/AlGaAs quantum disks on GaAs (311)B surfaces using a novel technique based upon lithography-defined SiN dot arrays. A strained InGaAs island array selectively grown using the SiN dots provides periodic strain field. When the pitch of lateral ordering corresponds with the period of the strain field, self-organized quantum disks stacked on the InGaAs islands are precisely arranged just as the buried SiN dot array. The spacing of the array element is 250–300 nm (x = 0.3) and around 150 nm (x = 0.4). Vertical alignment by strain is achieved at a very thick (95 nm) separating layer. Characterization using atomic force microscopy reveals the size-fluctuation of disk is dramatically improved with spatial ordering.     

纺丝及纤维成形的机理(Ⅵ)

本文依据前报阐述的数学模拟法的基础方程式和解析方法,系统地讨论了在不同泵供量和纺丝速度的情况下,沿纺丝线的丝条温度和固化点的变化,以及沿纺丝线聚合物的纵向运动速度梯度、纤维的细化过程、纺丝张力和纺丝应力的分布,并对与以上有关的主要参数进行了列表归纳。     

Stable detonation wave propagation in rectangular-cross-section curved channels

The detonation propagation phenomena in curved channels were experimentally studied in order to determine the stable propagation condition. A stoichiometric ethylene–oxygen mixture gas and five types of rectangular-cross-section curved channels with different inner radii of curvature were employed. The detonation waves propagating through the curved channels were visualized using a high-speed video camera. Multi-frame short-time open-shutter photography (MSOP) was developed in the present study to simultaneously observe the front shock shape of the detonation wave and the trajectories of triple points on the detonation wave. The detonation wave became more stable under the conditions of a higher filling pressure of the mixture gas and/or a larger inner radius of curvature of the curved channel. The critical condition under which the propagation mode of the detonation wave transitioned from unstable to stable was having an inner radius of curvature of the curved channel (r_i) equivalent to 21–32 times the normal detonation cell width (λ). In the stable propagation mode, the normal detonation velocity (D_n) increased with the distance from the inner wall of the curved channel and approached the velocity of the planar detonation propagating through the straight section of the curved channel (D_str). The smallest D_n was observed on the inner wall and decreased with decreasing r_i/λ. The distribution of D_n on the detonation wave in the stable mode was approximately formulated. The approximated D_n given by the formula agreed well with the experimental results. The front shock shape of the detonation wave could be reconstructed accurately using the formula. The local curvature of the detonation wave (κ) nondimensionalized by λ decreased with increasing distance from the inner wall. The largest λκ was observed on the inner wall and increased with increasing r_i/λ. D_n/D_str decreased with increasing λκ. This nondimensionalized D_n–κ relation was nearly independent of r_i/λ.     

Lantibiotics: insight and foresight for new paradigm

Lantibiotics are a unique type of antimicrobial peptide produced by a large number of gram-positive bacteria that contain unusual amino acids, such as lanthionine and dehydrated amino acids. Ribosomally synthesized lantibiotic prepeptide consists of an N-terminal leader peptide followed by a C-terminal propeptide moiety that undergoes several post-translational modification events to yield a biologically active lantibiotic. Research on lantibiotics has drawn much attention in recent years and has undergone extensive progress as a step forward to the next paradigm. Unusual amino acids in lantibiotics solely contribute to their biological activity and also enhance their structural stability. Thus, enzymes involved in lantibiotic biosynthesis would have a high potential for peptide engineering by introducing unusual amino acids into desired peptides, which may establish a universal approach to advance the structural design of novel peptides, termed lantibiotic engineering. In this review, we focus on recent development with contemporary innovations and perspective of lantibiotic research.