Observation of optical activity in polythiourethane obtained by the controlled cationic ring‐opening polymerization of chiral cyclic thiourethane derived from serine

The secondary structure of an optically active polythiourethane [(? CH₂C*H(CO₂Me)NHCOS? )_n] was evaluated with ¹H NMR, IR, and circular dichroism (CD) spectroscopy. Hydrogen bonds between the carbonyl and NH groups in the thiourethane group constrained the main chain of the chiral polythiourethane precisely under the direction of chirality in the main chain, whereas the racemic polymer was also constrained but randomly. The secondary structure of the polythiourethane in CHCl₃ changed noticeably in the presence or absence of trifluoroacetic acid, which eliminated constraining intramolecular hydrogen bonds. IR spectroscopy suggested that the secondary structure was almost identical in solid and solution states. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1554–1561, 2005     

Salt effect on polyaddition of bifunctional cyclic carbonate and diamine

The effect of various additives was examined for polyaddition of bifunctional cyclic carbonate and diamine giving poly(hydroxyurethane). Lithium chloride and lithium fluoride especially proved to be effective for the acceleration that resulted in giving polymers with higher molecular weights without coloration. The IR spectroscopic analysis of the mixtures of the additives and the carbonate monomer suggested that the acceleration with the lithium salts depends on the activation of the carbonyl group to enhance its electrophilicity. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6282–6286, 2005     

Quasi nambu-goldstone fermions

We explore in detail the hypothesis that quarks and leptons are the approximately massless quasi Goldstone fermions of a supersymmetric preon theory. In particular, we discuss the possible patterns of states emerging from the spontaneous breakdown of global symmetries in supersymmetric theories and construct the low-energy effective lagrangians describing the interaction of these states. In contrast to what happens in the Goldstone sector, the interactions of the quasi Goldstone fermions contain arbitrary parameters which directly reflect the preon dynamics. Various models are explored, including both models in which the weak interactions are residual and models where these interactions are fundamental. A variety of issues are addressed, from the universality and approximate SU(2)_L nature of the weak interactions, for the former class of models, to the generation of states beyond the quarks and leptons and the nature of the dynamical breaking of SU(2)_L×U(1), for the latter class of models. Open questions and speculations connected with the origin of families and the nature of fermion mass generation, including supersymmetry breaking, are also discussed.     

Rheo-optical studies on the deformation mechanism of semicrystalline polymers. IV. On the nature of alpha mechanical dispersion of low density polyethylene in relation to the mechanism of spherulite deformation

The dynamic mechanical and birefringence behavior of three kinds of test specimens, prepared from a low-density polyethylene by different heat treatments, was investigated over the frequency range 0.008 to 4.3 Hz at various temperatures from 20 to 80°C. Reduction of both kinds of data to the common reference temperature of 50°C revealed rather broad frequency dispersions, corresponding to the α dispersion, with activation energies for the mechanical and optical relaxation processes of around 25 kcal/mole for all specimens. An annealed specimen was further investigated by dynamic x-ray diffraction to determine the dispersions of crystal orientation and of lattice deformation. The mechanical and birefringence dispersions are associated with the dispersion of crystal orientation and with the relatively elastic nature of the lattice deformation. Thus, the mechanical dispersion could be assigned to an α₁ mechanism arising from rotation of crystallites within the spherulites, i.e., a type of grain-boundary phenomena, but not to an α₂ mechanism resulting from a crystal disordering transition or premelting. Combining dynamic birefringence with dynamic crystal orientation, the mechanical α dispersion is further discussed in terms of dynamic orientation behavior of noncrystalline chain segments in order to elucidate the nature of the grain-boundary phenomena in detail in relation to the dynamic deformation mechanism of the spherulitic crystalline texture, i.e., reorientation of “crystal grains” within orienting lamellae due to intralamellar shearing resulting from the paracrystalline nature of the lamellae. A mechanical model characterizing the grain-boundary relaxation in association with the reorientation of the crystal grain is also proposed.     

Radiofrequency spectroscopy inside a laser cavity: Nuclear quadrupole resonance and A1-A2 splitting of CH3Br

The highly sensitive method of infrared-radiofrequency double resonance inside a CO₂N₂O laser cavity has been applied to the observation of “pure” nuclear quadrupole resonance and direct A₁-A₂ transitions of CH₃Br. More than 150 quadrupole resonances have been observed for ¹²CH₃⁷⁹Br, ¹²CH₃⁸¹Br, ¹³CH₃⁷⁹Br, and ¹³CH₃⁸¹Br using direct double resonance as well as collision-induced satellites. Accurate hyperfine constants, i.e., the quadrupole coupling constant eqQ and its rotational dependence χ_J and χ_K, Hougen's coefficient χ_d, and the spin-rotation constants C_N and C_K have been determined for the ground state. The eqQ in the excited states ν₃, ν₆, ν₃ + ν₆, and 2ν₆ have also been determined. About 60 direct l-doubling transitions have been observed, which has enabled us to determine the l-doubling constant q_v(1,1), its rotational dependence δq_v^J(1,1) and the asymmetry parameter for the quadrupole coupling constant eqQη for the ν₆ and ν₃ + ν₆ states. A set of direct A₁-A₂ transitions in the 2ν₆ state with K = 1 and l₆ = ?2 and that in the ν₆ state with K = 2 and l₆ = ?1 have been observed. The rovibrational and isotope assignments of the observed A₁-A₂ are helped by the existence of quadrupole hyperfine structure and many collision-induced satellites. The rovibrational assignments of CH₃Br transitions which are coincident with laser lines are summarized.     

Rapid determination of trace quantities of thallium in heat-resisting cobalt and nickel alloys by graphite furnace atomic absorption spectrometry

Summary A simple and rapid analytical method has been developed for the direct determination of trace quantities of thallium in nickel and cobalt-base heatresisting alloys by graphite furnace atomic absorption spectrometry. Hydrofluoric acid, sulphuric acid, and hydrogen peroxide were used for the dissolution of a wide variety of these alloys. The interferences of matrix elements and acids were eliminated. The absorbance of thallium is constant over a wide range of ashing temperatures. Synthetic standard solutions composed of nickel or cobalt matrix and thallium were used for calibration. The detection limit for thallium by this method is 0.2 ppm in the sample. Mechanisms of the interferences are discussed.

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Schnelle Bestimmung von Thalliumspuren in hitzebeständigen Cobalt- und Nickellegierungen durch Atomabsorptions-Spektralphotometrie mit dem Graphitofen

Zusammenfassung Ein Verfahren zur AAS-Bestimmung von Thallium in verschiedenartigen Cobalt- und Nickellegierungen wird beschrieben. Zur Auflösung der Probe werden Flußsäure, Schwefelsäure und Wasserstoffperoxid verwendet. Störungen durch Matrixelemente und durch die Säuren konnten beseitigt werden. Die Thalliumabsorption ist über einen weiten Temperaturbereich bei der Veraschung konstant. Zur Eichung dienen synthetische Lösungen von Cobalt- bzw. Nikkelmatrix und Thallium. Die Nachweisgrenze für Thallium beträgt 0,2 ppm. Die Mechanismen der Störungen werden diskutiert.

     

Determination of electric dipole moment for the ν2 vibrational state of 15NH3 by infrared-infrared double resonances

An infrared-infrared double-resonance technique, employing the sidebands produced by electro-optic amplitude modulation of a single-frequency CO₂ laser, is used to observe the second-order Stark effect of the ν₂asR(2, 0) transition of ¹⁵NH₃. The technique enables the Stark shifts in ground and vibrationally excited states to be observed separately and yields the electric dipole moments: μ(v₂ = 1) = 1.253 ± 0.003 D, μ(v = 0) = 1.469 ± 0.004 D. The relative intensity distribution, linewidths, and line shapes of features in the double-resonance Stark spectra are also examined.     

Mass spectral aspects of 7-phenacylxanthopterins

7-Phenacylxanthopterin and its para-substituted derivatives, which exist in the chelate rign form initially lose CO from pyrazine rings followed by a hydrogen atom. This ion can also be formed in the reverse order, but not for the 4-amino analogues. Fragmentation of the intramolecularly hydrogen bonded sidechain also occurs involving loss of a benzoyl or phenyl radical. Linear plots at 40 eV for the loss of the benzoyl radical were obtained for log (Z/Z₀) against the Hammet σ constants not only for the fragmentation of the xanthopterins but also for that of the amino analogues.     

Morphology of polytetrafluoroethylene prepared by radiation-induced emulsion polymerization

The original morphology of polytetrafluoroethylene prepared by radiation-induced emulsion polymerization was studied by electron microscopy. The morphology depends on molecular weight, which in turn depends on polymerization conditions, especially the emulsifier concentration. The molecular weight decreases with increasing emulsifier concentration. The morphology changes with molecular weight roughly as follows: fibrils below 10⁵, rods between 10⁵ and 5 × 10⁵, and granular particle above 10⁶. The crystallinity is high for all morphologies.     

Co-doped Y2O3:Tb3+/Tm3+ multicolor emitting phosphors for thermometry

In this study, the new temperature-dependent phosphor, Y2O3:Tb3+/Tm3+, was investigated for high-temperature thermometry. The photoluminescence intensity at 456?nm emitted from Tm3+ was strong at temperatures higher than 1100?K, whereas the peak intensities emitted from Tb3+ decreased due to the thermal quenching effect. Thus, the intensity ratio between those emissions showed an appropriate variation for thermometry over a wide temperature range. In addition, the phosphors showed a distinct change of visible emission colors from green to blue with increasing temperature. These findings suggest the applicability of these phosphors in visual thermo-sensors.