A novel polyaddition of bifunctional acetylenes containing electron-withdrawing groups. III. Synthesis of polymers having β-alkoxyenoate moieties by the reaction of internal diynes with diols

Tri-n-butylphosphine-catalyzed polyadditions of activated internal diynes (bifunctional β-substituted propiolate, 1B and 1C ) with diols are described. Although a terminal bispropiolate ( 1A ) could not produce soluble polymers, with secondary diols, the polyaddition of 1B or 1C with primary as well as secondary diols gave corresponding polymers ( 3 , only composed of E isomeric units) in high yield. The rate of the present polyaddition was estimated by a model reaction of benzyl alcohol with methyl 2-heptynoate ( 4 ), from which the introduction of alkyl groups at the β-position of propiolate moieties was found to decrease the rate of the reaction by 80 times. Furthermore, the rate-determining step on this polymerization system was speculated to be a protonation step of zwitterionic intermediates with protons from diols. © 1996 John Wiley & Sons, Inc.     

Chemical and genetic diversity of Ligularia virgaurea collected in northern Sichuan and adjacent areas of China. Isolation of 13 new compounds

Root chemicals and DNA sequences were analyzed for Ligularia virgaurea collected in the northern Sichuan Province and adjacent areas of China. Thirty-eight samples were found to contain five chemotypes, two known and three new ones. From samples of the new chemotypes, 13 new compounds were isolated, including 3 sesquiterpene dimers and some rearranged eremophilanes. The DNA sequences suggested that the chemotype differentiation had a genetic origin.     

Thermodynamically Induced Conformational Changes of the Cyanobacterial Circadian Clock Protein KaiB

Site-directed spin labeling electron spin resonance (ESR) was applied to investigate the local environment of the cyanobacterial circadian clock protein KaiB. We prepared five cysteine residue-substituted mutants of KaiB labeled with maleimide spin label (MSL). By comparing the ESR spectra of KaiBs carrying MSL at different positions (Thr64, Lys67, Tyr94, Gly98, and Ala101), local conformational changes were identified. The ESR spectra of MSL-T64C and MSL-K67C showed the relatively slow motion of MSL characterized by τ?=?79 and 59?ns at 4°C, respectively. The spectra of MSL-Y94C, MSL-G98C and MSL-A101C showed relatively fast motion characterized by τ?=?8.0, 4.1 and 3.1?ns at 4°C, respectively. These differences were explained by the local environments of the position in KaiB. On incubation at 40°C for 24?h, all ESR spectra of the labeled KaiBs changed, which can be explained by the structural relaxation of KaiB.     

Depth-adaptive regularized reconstruction for reflection diffuse optical tomography

We study reflection diffuse optical tomography using two-dimensional (2D) continuous-wave source-detector arrays on the surface of semi-infinite medium, aiming at imaging the perfusion and the hemoglobin oxygen saturation variation of human cerebral cortex with brain activation. We had previously formulated the inverse problem with Moore-Penrose inversion. When we use simple regularization in this inverse problem, the reconstruction sensitivity decreases markedly with the depth so that the signal in the deep range may be masked by an unwanted signal in the shallow range. In this paper, we propose a depth-adaptive regularized reconstruction, in which we assign a smaller regularization parameter with the depth. We demonstrate improvement of the three-dimensional (3D) reconstruction uniformity using the proposed scheme.     

Analysis of reaction products of cocaine and hydrogen peroxide by high-performance liquid chromatography/mass spectrometry

The change of chemical structure of cocaine in the presence of hydrogen peroxide, a main component of hair dye and decolorant treatments, was studied. High-performance liquid chromatography/mass spectrometry (LC/MS) was used for the separation and identification of cocaine derivatives. After a mixture of cocaine and hydrogen peroxide solutions was incubated at 39 degrees C (this temperature is commonly used when the hair is treated with hair dye or decolorant) for 24 h, six reaction products were detected by LC/MS. Two of them were ecgonine methyl ester and benzoylecgonine, which are metabolites of cocaine. The other reaction products were assumed to be ortho-, meta- and para-hydroxycocaines and dihydroxycocaine, in each of which the benzene ring was hydroxylated by the reaction. These five reaction products (except for dihydroxycocaine) were found immediately after mixing cocaine and hydrogen peroxide. Therefore, the above reaction products might be present in the hair of cocaine users that had treated their hair with hair dye or decolorant.     

Extremely low vertical-emittance beam in the accelerator test facility at KEK

Electron beams with the lowest, normalized transverse emittance recorded so far were produced and confirmed in single-bunch-mode operation of the Accelerator Test Facility at KEK. We established a tuning method of the damping ring which achieves a small vertical dispersion and small x-y orbit coupling. The vertical emittance was less than 1% of the horizontal emittance. At the zero-intensity limit, the vertical normalized emittance was less than 2.8 x 10(-8) rad m at beam energy 1.3 GeV. At high intensity, strong effects of intrabeam scattering were observed, which had been expected in view of the extremely high particle density due to the small transverse emittance.     

Science and technology: A radiochemist's view

A historical perspective is presented from a radiochemist's point of view.     

Polyaddition reaction of pseudoxazolones with dimercaptans

Polymers having thioether, thiolester, and amide linkages in each repeating unit of a polymer main chain were prepared by the polyaddition reaction of pseudoxazolones (2-isopropylidene-4-alkyl-3-oxazolin-5-ones) and dimercaptans. The polymers had inherent viscosities in a range of 0.08–0.22 and gave transparent films by solution casting.