Relationship between the furan ring and six and seven-membered lactone rings in obacunone

The presence of a ,β-epoxy-(β-furyl)-δ-lactone group in obacunone was suggested, from the catalytic reduction and conversion to desoxy compound of the dilactone (V), one of the oxidation products of obacunone with potassium permanganate. The stability of saturated, seven-membered lactone ring in obacunone derivatives was discussed. Degradation of the masked hydroxyl group is tertiary and is bonded to isopropyl group. Formula Ie was proposed for the partial structure of obacunone.     

Measurement of the lifetime of the first 2+ state in 124Ba

The lifetime of the first 2⁺ state in the nucleus ¹²⁴Ba has been measured by γ-γ coincidence recoil-distance Doppler shift method. The ¹⁰⁹Ag(¹⁹F, 4n)¹²⁴Ba reaction at a beam energy of 75 MeV was employed to populate excited states in ¹²⁴Ba. The mean lifetime was determined to be 275(12) ps using the differential decay curve method. The value of B(E2;0₁ ⁺→ 2₁ ⁺) for ¹²⁴Ba deduced from the lifetime is in reasonable agreement with the prediction of the proton-neutron interacting boson model(IBM-2) without Pauli blocking effect. Received: 23 February 1998     

Surface hydrogen detection by low energy He ion scattering spectroscopy

Hydrogen adsorbed on a Si(100) surface can be detected by angle-resolved LEIS (low-energy ion scattering spectroscopy) which uses a ⁴He⁺ ion beam with incident energies around 1 keV. The scattering peaks from the surface hydrogen are restricted to narrow scattering angles from 0° to 15°, which is in agreement with those expected by the binary elastic collision model.     

Activation effects of a platinum electrode by laser pulse irradiation on the electro-oxidation of glucose in alkaline solution.

In order to demonstrate the activation effects of a Pt electrode by laser pulse irradiation, the electro-oxidation of glucose was tested at an activated Pt electrode by cyclic voltammetry. A fixed potential was applied to the electrode, and then the electrode was irradiated with laser pulses from a Nd:YAG laser at 20 Hz for 20 s. Activation by the laser pulse irradiation gave two remarkable effects on cyclic voltammograms from the electro-oxidation of glucose in a 0.1 mol dm(-3) NaOH solution, i.e., surface modulation and cleaning effects. Significant differences were found in the cyclic voltammograms at the activated and at the simply polished electrodes. Such differences in the oxidation waves are attributed to a crystallographic change of the electrode surface induced by a laser ablation, accompanied by laser pulse irradiation. Due to the cleaning effect, the activated Pt electrode gave a sharp oxidation wave at -0.3 V even in real samples containing various organic compounds that could foul the electrode, though the activated Pt electrode lacked selectivity to the electro-oxidation of glucose.     

Iterative Multikinoform Method for Improving the Reconstruction of Kinoform

The authors proposed an interlacing technique (IT) approach for the synthesis of kinoform which uses a number of subkinoforms interlaced together into a multikinoform. Using the IT approach, the reconstructed image can be improved by optimizing each subkinoform with the general error-reduction algorithm. In this paper, they show a new iterative algorithm based on the IT, namely an iterative multikinoform method (IMM). After each of the subkinoforms is generated by the IT, the error image, which is the difference between the desired image and the sum of the images reconstructed from all subkinoforms, is circulated into an individual subkinoform to optimize each subkinoform so that the reconstruction error can be reduced further. This process can be performed on all subkinoforms iteratively. Simulation results show that the reconstruction error can be reduced further for kinoforms with larger quantization levels (larger than 2⁴) and its convergence is very rapid when the IMM is used.     

SPECTRAL FORMS AND ORIENTATION OF BACTERIOCHLOROPHYLLS c AND α IN CHLOROSOMES OF THE GREEN PHOTOSYNTHETIC BACTERIUM Chloroflexus aurantiacus

Spectral forms of bacteriochlorophyll (Bchl) in chlorosomes were analyzed by linear dichroism, circular dichroism (CD), and deconvolution of these spectra. Isolated chlorosomes were embedded in polyacrylamide gels and compressed unidirectionally (along the x-axis) while allowing the gel to stretch in another direction (along the z-axis). The chlorosomes were aligned three-dimensionally due to their flat oblong shape; the longest axis was presumed to parallel the z-axis, its shortest axis was presumed to parallel the x-axis, and the intermediate-length axis was presumed to parallel the y-axis. Degrees of polarization (A_I? A₁)/(A_I+ A₁) of Bchl c and a measured from the y-axis with linearly polarized light were significantly different from those measured from the x-axis. Deconvolution of spectra into components revealed the presence of two major forms of Bchl c with peaks at 744 nm and 727 nm. The degrees of polarization of the 744 and 727 nm spectral forms were 0.76 and 0.59 from the y-axis and 0.48 and 0.39 from the x-axis, respectively. The degrees of polarization of Bchl a794 were –0.21 from the y-axis and 0.12 from the x-axis. These values indicate that the direction of the Q_y transition moment of Bchl c744 is almost completely parallel to the longest axis of chlorosomes and that of Bchl c727 is also nearly, but slightly less so, parallel to the longest axis of the chlorosomes. The Q_y transition moment of the baseplate Bchl a peak at 794 nm is nearly perpendicular to the longest axis and parallel to the shortest axis: that is, it is perpendicular to the associated membrane plane in the cell. These alignments of Bchl transition moments in chlorosomes were lost after suspending the chlorosomes in a solution saturated with 1-hexanol accompanying a shift in the peak position from 742 nm to 670 nm. The alignment recovered after the hexanol concentration was decreased. The presence of two major spectral forms of Bchl c was supported by the deconvolution of CD spectra and absorption spectra.     

In-beam gamma-ray spectroscopy of 116Te

High-spin states of the even-even ¹¹⁶Te were studied by in-beam g-ray spectroscopy using the ¹⁰³Rh (¹⁶O, p2n) fusion-evaporation reaction at a beam energy of 80 MeV. γ-γ coincidence and γ-γ angular correlation analyses were employed for determining the level scheme of ¹¹⁶Te. Levels up to I^π = 27^? and several new states were established. We identified two rotational bands with negative parity, one of which was newly established in the present work. We suggest that such two bands be associated with two proton [(g_7/2) ? (h_11/2)] and two neutron [(d_5/2) ? (h_11/2)] configurations, respectively.     

Log-T dependence in the low-temperature resistivity of Sb doped Si

We have studied temperature dependence of the resistivity of Sb doped Si at low temperature down to 10mK. In the vicinity of metal-nonmetal transition in Sb doped Si, the low-temperature resistivity in a just metallic side shows a logarithmic increase with lowering temperature. After thermal annealing the log-T dependence disappears and $\text{T}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ dependence is observed in the same temperature region. We find that the log-T dependence in the low-temperature resistivity comes from a surface-related conduction.