Total synthesis and determination of the stereochemistry of 2-amino-3-cyclopropylbutanoic acid,a novel plant growth regulator isolated from the mushroom Amanita castanopsidis Hongo

The unknown stereostructure of 2-amino-3-cyclopropylbutanoic acid 1, a novel plant growth regulator isolated from the mushroom Amanita castanopsidis Hongo, was determined to be (2S,3S)-2 through its racemic and enantioselective syntheses employing the chelate-enolate Claisen rearrangement as a key step.     

Revised structure of cercidinin A, a novel ellagitannin having (R)-hexahydroxydiphenoyl esters at the 3,4-positions of glucopyranose

The structure of cercidinin A, an ellagitannin isolated from the bark of Cercidiphyllum japonicum, was revised to 1,2,6-tri-O-galloyl-3,4-(R)-hexahydroxydiphenoyl-beta-D-glucose by two-dimensional NMR spectral analysis. Cercidinin A represents the first ellagitannin possessing a hexahydroxydiphenoyl group at the 3,4-positions of a modified 4C1-glucopyranose core.     

Synthesis of thermosensitive hydrogels from acryloyloxyethyl trialkyl phosphonium chloride–N‐isopropylacrylamide–N,N′‐methylenebisacrylamide terpolymers and their temperature dependence of water absorption

Thermosensitive polymer hydrogels were prepared by the copolymerization of three kinds of acryloyloxyethyl trialkyl phosphonium chlorides (AETRs) with alkyl chains of different lengths, with N‐isopropyl acrylamide (NIPAAm) and N,N′‐methylenebisacrylamide (MBAAm). The water content of the AETR–NIPAAm–MBAAm terpolymers obtained at molar ratios of the crosslinking agent greater than 2 decreased with increasing temperature and decreased sharply around 35 °C. However, the water contents of the AETR–NIPAAm–MBAAm (X/100/1) terpolymers obtained at a molar ratio of 1 of the crosslinking agent increased once with increasing temperature and then decreased from 3 to around 40 °C. The water contents of the AETR–NIPAAm–MBAAm (3/100/1 or 2) terpolymers decreased with the increasing length of alkyl chains in phosphonium groups in the terpolymers. The water contents of the AETR–NIPAAm–MBAAm terpolymers increased by the addition of a small amount of urea and then decreased with increasing urea concentration. However, the water contents decreased abruptly with the addition of NaCl. The AETR–NIPAAm–MBAAm terpolymers exhibited high adsorption for sodium dodecylbenzene sulfonate but no adsorption for sodium benzene sulfonate. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1505–1514, 2001     

Phase Transition Behaviors of Self‐Oscillating Polymer and Nano‐Gel Particles

Summary: Self‐oscillating polymers and nano‐gel particles consisting of N‐isopropylacrylamide and the ruthenium catalyst of the Belousov‐Zhabotinsky reaction have been prepared. In order to clarify the crosslinking effect on the self‐oscillating behavior, the phase transition behaviors were investigated by measuring the transmittance and the fluorescence intensity of the polymer solution and the gel bead suspension. Cooperative effects due to crosslinking will play an important role for the design of nanoactuators.

Chemical structure of poly(NIPAAm‐co‐Ru(bpy)₃).     

自抽运相位共轭镜的反射率特性用于图像变化的检测

自抽运相位共轭镜的入射光有一个空间均匀的相位变化时,变化后瞬间相位共轭镜的反射率减小。利用此特性检测了液晶显示片像的变化。     

Segmentation of expiratory and inspiratory sounds in baby cry audio recordings using hidden Markov models

The paper describes an application of machine learning techniques to identify expiratory and inspiration phases from the audio recording of human baby cries. Crying episodes were recorded from 14 infants, spanning four vocalization contexts in their first 12 months of age; recordings from three individuals were annotated manually to identify expiratory and inspiratory sounds and used as training examples to segment automatically the recordings of the other 11 individuals. The proposed algorithm uses a hidden Markov model architecture, in which state likelihoods are estimated either with Gaussian mixture models or by converting the classification decisions of a support vector machine. The algorithm yields up to 95% classification precision (86% average), and its ability generalizes over different babies, different ages, and vocalization contexts. The technique offers an opportunity to quantify expiration duration, count the crying rate, and other time-related characteristics of baby crying for screening, diagnosis, and research purposes over large populations of infants.     

Refractive index measurements of solid parahydrogen

Solid para-H2 is a promising gain medium for stimulated Raman scattering, due to its high number density and narrow Raman linewidth. In preparation for the design of a cw solid hydrogen Raman laser, we have made the first measurements, to our knowledge, of the index of refraction of a solid para-H2 crystal, in the wavelength range of 430-1100?nm. For a crystal stabilized at 4.4?K, this refractive index is measured to be n(p-H2)=1.130±0.001 at 514?nm. A slight, but significant, dependence on the final crystal-growth temperature is observed, with higher n(p-H2) at higher crystal-growth temperatures. Once a crystal is grown, it can be heated up to 10?K with no change in n(p-H2). The refractive index varies only slightly over the observed wavelength range, and no significant birefringence was observed.