Elastic modulus of poly(isobutylene oxide) crystals parallel to the chain axis

The elastic tensile modulus of the crystalline regions parallel to the chain axis E₁ for poly(isobutylene oxide) (PIBO) was determined by an x-ray diffraction method. The stress-strain (σ—ε) curve calculated from the meridional reflection of (002) shows an inflection point at about 75 MN/m² or an extension of 0.25%. The observed moduli below and above this point are 29 and 47 GN/m², respectively, at room temperature. The initial lower modulus agrees well with the value, 29.7 GN/m², calculated on the basis of the double zigzag structure of PIBO chain determined by Kaji and Sakurada. The higher modulus may be due to an intrachain steric hindrance between the hydrogen atoms of the methylenic group in the main chain and those of the two side methyl groups.     

Achievement of ultralow emittance beam in the accelerator test facility damping ring

For high luminosity in electron-positron linear colliders, it is essential to generate low vertical emittance beams. We report on the smallest vertical emittance achieved in single-bunch-mode operation of the Accelerator Test Facility, which satisfies the requirement of the x-band linear collider. The emittances were measured with a laser-wire beam-profile monitor installed in the damping ring. The bunch length and the momentum spread of the beam were also recorded under the same conditions. The smallest vertical rms emittance measured at low intensity is 4 pm at a beam energy of 1.3 GeV, which corresponds to the normalized emittance of 1.0x1.0(-8) m. It increases by a factor of 1.5 for a bunch intensity of 10(10) electrons. The measured data agreed to the calculation of intrabeam scattering within much better than a factor of 2.     

Quantum beat between two excitonic levels split by spin--orbit interactions in the oxychalcogenide LaCuOS

Degenerate four-wave mixing signals excited by femtosecond laser pulses were measured in LaCuOCh (Ch = S and Se) at 4 K. The signals for LaCuOS exhibit a beat structure with a period of 480 fs just at the exciton peak energy, indicating that the lowest exciton states are split by 9 meV, but no beat structure was observed in LaCuOSe, regardless of the laser's energy. The spin--orbit interaction of the Ch ion accompanied by the hybridization of Cu 3d orbitals causes splitting of the exciton levels. Furthermore, the contribution of Ch p orbitals in the valence band maximum is larger in LaCuOSe owing to increased covalency in the Cu--Ch bond when S is replaced with Se.     

Chemo- and regioselective intermolecular cyclotrimerization of terminal alkynes catalyzed by cationic rhodium(I)/modified BINAP complexes: application to one-step synthesis of paracyclophanes

A highly regioselective intermolecular cyclotrimerization of terminal alkynes has been developed based on the use of the cationic rhodium(I)/DTBM-Segphos complex. This method can be applied to a variety of terminal alkynes to provide 1,2,4-trisubstituted benzenes in high yield and with high regioselectivity. A chemo- and regioselective intermolecular crossed-cyclotrimerization of dialkyl acetylenedicarboxylates with a variety of terminal alkynes has also been developed based on the use of the cationic rhodium(I)/H8-BINAP complex, furnishing 3,6-disubstituted phthalates in high yields. It constitutes a highly efficient new method for intermolecular crossed-cyclotrimerization of two different monoynes in terms of catalytic activity, chemo- and regioselectivity, scope of substrates, and ease of operation. The versatility of this new crossed-alkyne cyclotrimerization procedure is demonstrated through its application to one-step synthesis of a [6]metacyclophane and [7]-[12]paracyclophanes from the corresponding terminal alpha,omega-diynes. Mechanistic studies have revealed that the chemo- and regioselectivity of this crossed-alkyne cyclotrimerization are determined by the preferential formation of a specific rhodium metallacycle derived from a terminal alkyne and a dialkyl acetylenedicarboxylate.     

Piezoluminescence at the air-water interface through dynamic molecular recognition driven by lateral pressure application

The steroid cyclophanes with a cyclic core consisting of a 1,6,20,25-tetraaza[6.1.6.1]paracyclophane connected to four steroid moieties (cholic acid or cholanic acid) through a flexible l-lysine spacer were spread on water as Langmuir monolayers. The pi-A isotherm of the cholic-type steroid cyclophane includes a transition to the condensed phase with a limiting area of approximately 2 nm(2). This value is close to the cross-sectional area of the steroid cyclophane with a standing-up conformation of the cholic acid moieties, strongly suggesting that the cavity converts from a two-dimensional cavity to a three-dimensional cavity upon compressing the monolayer. Surface-reflective fluorescence spectroscopy of the monolayer using an aqueous fluorescent probe (6-(p-toluidino)naphthalene-2-sulfonate (TNS)) showed an abrupt increase in the TNS fluorescence intensity at a molecular area of 2 nm(2). Efficient binding of the guest probe would occur upon the completion of the three-dimensional cavity. Repeated compression and expansion induces periodic changes in the fluorescence intensity. This indicates a piezoluminescence effect through the catch and release of the TNS guest upon dynamic cavity formation. Analyses of the binding behavior of TNS to the steroid cyclophane resulted in binding constants in the range of approximately (5-9) x 10(4) M(-1) which are similar to that observed in lipid bilayer media (K = 5.1 x 10(4) M(-1)). The fluorescence intensity within the condensed phase was significantly increased with increasing pressure, suggesting that suppression of the molecular motion of the bound TNS may retard the nonemission process. Similar monolayer experiments were carried out with the monolayer of the cholanic-type steroid cyclophane that cannot form an open conformation on water. Both the phase transition in the pi-A isotherm and the change in the fluorescence intensity were negligible, confirming that the dynamic characteristic of the cavity is indispensable for the efficient pressure-induced binding of the guest and the consequent luminescence.     

Effect of ionic surfactants on the oscillation frequency of one-electrode-separated piezoelectric quartz crystals modified with chitosan and its derivative

From the pH dependence of oscillation frequencies of one-electrode-separated piezoelectric quartz crystals (ESPQCs) modified with chitosan and N-(1,3-dicarboxypropyl) chitosan (DCPC) in buffer solutions, it was deduced that the chitosan and DCPC films on an ESPQC contained water and that the water content depended on pH. Contrary to the expectation based on the Sauerbrey equation, the binding of ionic surfactants to chitosan and DCPC films increased the frequencies. This apparently abnormal phenomenon was explained by the release of water in swollen films. The frequency of the DCPC-modified ESPQC increased on addition of sodium dodecyl sulfate and hexadecyltrimethylammonium chloride at pH lower and higher, respectively, than 7.8. A linear relationship between surfactant concentration and frequency shift, whose slope depended on only the chain length of the surfactant alkyl group, was obtained in the range 5–50 µmol dm^–3 hexadecyltrimethylammonium chloride. The DCPC-modified ESPQC can be used for a quantitative determination of cationic surfactants in this concentration range.     

Isolation of axial conformers of chloro- and bromocyclohexane in a pure state as inclusion complexes with 9,9'-bianthryl, and the discovery of a novel 1,3 diaxial Cl...H weak interaction

The axial conformers of chloro- and bromocyclohexane were isolated in a pure state as inclusion complexes with 9,9'-bianthryl, and a 1,3 diaxial Cl...H weak interaction was discovered by X-ray analysis of the axial conformer of chlorocyclohexane.     

Spin configurations and spin reorientations in pure and impurity doped Fe3BO6

The spin configurations of Fe₃BO₆ above and below the spin reorientation temperature are analysed by magnetic measurements and a symmetry consideration. The effects of dopants on the magnetic properties are investigated. The dopants induces a different spin configuration and spin reorientation from the pure Fe₃BO₆.     

Poly(S)-iso-propy?thylenoxidel: Synthese und ORD- und NMR-eingenschaften in L?sung

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