Planarity of ethylene/linear polyene analogues focused on π-electron holding ability of the components

Ethylene/polyene analogues composed of heavier group 14 elements, such as silicon and germanium, do not prefer a planar structure. In the repulsion dominant (RD) model of our previous study mainly focusing on the planarity of hexasilabenzene, it was demonstrated that electron repulsion promotes nonplanarization of heavy benzene analogues. In this study, we have investigated a correlation between intramolecular π-electron transfers (polarization effect) and planarity in various linear unsaturated compounds in order to deepen the RD model. Herein, it was revealed that the ability to hold π-electrons in the planar molecular structure is characteristic of each element. For example, carbon can hold more than one π-electron, whereas silicon and germanium cannot tolerate even one π-electron to keep the planar structure. Thus, π-accepting substituents on the heavy atom were found to make the heavy ethylenes and linear polyenes planar by controlling the number of π-electrons on each skeletal atom.     

Halichonic acid,a new rearranged bisabolene-type sesquiterpene from a marine sponge Halichondria sp.

A new compound, halichonic acid (1), was isolated from a marine sponge Halichondria sp., together with (6R,7S)-7-amino-7,8-dihydro-α-bisabolene (2). The structure of 1 was elucidated by spectroscopic analysis and ECD spectrum calculation to be a rearranged bisabolene-type sesquiterpene having a 3-azabicyclo[3.3.1]nonene moiety. Compound 2 was cytotoxic against HeLa cells with an IC₅₀ value of 50?μM, whereas 1 did not show cytotoxicity even at 50?μM. It is possible that 1 is biosynthesized from farnesyl pyrophosphate and glycine, with rearrangement.     

Helical foldamer-catalyzed enantioselective 1,4-addition reaction of dialkyl malonates to cyclic enones

The introduction of a five-membered ring α,α-disubstituted α-amino acid into l-Leu-based heptapeptides preferentially induced right-handed (P) helical structures. Using 5 ～ 20 mol% of a single helical foldamers-catalyst, enantioselective 1,4-addition reactions of dialkyl malonates to cycloalk-2-enones (5 ～ 7 rings) proceeded to give chiral 3-substituted cycloalkanones with 94 ～ 99% ee in moderate chemical yields, regardless of the ring size of substrates.     

XPS study of silicon spheres as a density standard

As density is one of the basic physical properties of materials, an accurate density standard is absolutely essential. To determine density with high accuracy and precision, two 1-kg single-crystal silicon spheres (NMIJ-S4 and NMIJ-S5) are used as the primary standard at the National Metrology Institute of Japan. For the accurate measurement of the mass and volume of the silicon spheres, the effects of the surface layer must be carefully considered. In this work, a surface layer model of NMIJ-S4 and NMIJ-S5 was proposed and the thicknesses of each surface layer were determined using X-ray photoelectron spectroscopy. A detailed uncertainty budget is presented to aid use of the density standard.     

Storage and retrieval of a squeezed vacuum

Storage and retrieval of a squeezed vacuum was successfully demonstrated using electromagnetically induced transparency. The squeezed vacuum pulse having a temporal width of 930 ns was incident on the laser cooled 87Rb atoms with an intense control light in a coherent state. When the squeezed vacuum pulse was slowed and spatially compressed in the cold atoms, the control light was switched off. After 3 mus of storage, the control light was switched on again, and the squeezed vacuum was retrieved, as was confirmed using the time-domain homodyne method.     

Diode-pumped 65 fs Kerr-lens mode-locked Yb(3+):Lu(2)O(3) and nondoped Y(2)O(3) combined ceramic laser

Diode-pumped Kerr-lens mode-locked laser operation of Yb(3+):Lu(2)O(3) and nondoped Y(2)O(3) combined ceramics has been achieved; 65 fs pulses with an average power of 320 mW under 5 W of pump power were obtained at the center wavelength of 1032 nm. The spectral bandwidth and the time bandwidth product were 18.9 and 0.345 nm, respectively. To our knowledge, this is the first demonstration of a Kerr-lens mode-locked laser operation based on Yb(3+):Lu(2)O(3) ceramic.     

Scanning tunneling microscopy observation of initial growth of Sn and Ge1−xSnx layers on Ge(0 0 1) substrates

We have investigated the initial growth of Sn and Ge_1−xSn_x layers on Ge(0 0 1) surface by using scanning tunneling microscopy. After the growth of a 0.035 ML-thick Sn layer at room temperature, Sn clusters lining vertically to a dimer row was observed. In the case of the 0.035-0.018 ML-thick Sn growth at 250 °C, the characteristic surface reconstruction with the step-edge undulation like a comb was observed. In the growth of a Ge_0.994Sn_0.006 layer at 250 °C, the multilayer polynuclear growth with a lot of two-dimensional small domain was observed. These surface reconstructions should be accounted for by the large compressive stress induced in the surface layer due to the incorporation of Sn atoms.     

TOF-SIMS analysis of magnetic materials in chum salmon head

A piece of tissue extracted from a chum salmon Oncorhynchus keta head was measured with time-of-flight secondary ion mass spectrometry (TOF-SIMS) in order to evaluate the distribution and composition of magnetic materials in the tissue, which may concern with geomagnetic navigation of long-distance migrating salmon. Several depositions of iron compounds were detected in the tissue by TOF-SIMS analysis. Comparing with total ion images providing a topological tissue structure, specific distribution of iron ion in the tissue was clearly shown. Higher magnification TOF-SIMS analysis revealed the existence of the aggregations of iron particles. Iron oxide clusters comprising many submicron particles were also detected in the tissue using scanning electron microscopy and X-ray analysis, suggesting the common existence of submicron-scale iron oxides in salmon heads. These results suggest that TOF-SIMS analysis is a valid method to clarify detailed structures and chemical properties of candidate magnetoreceptors in fish heads.     

Damping constant of Co/Pt multilayer thin-film media

Gilbert's damping constants, α, of Co(t_Co)/Pt (1.4 nm) multilayer thin films are investigated by Q-band FMR analysis. α is calculated from the resonance width of the FMR spectrum. With decreasing t_Co, the α value decreases from 0.034 (t_Co=8.7 nm) to 0.023 (t_Co=1.8 nm), and then increases to 0.037 (t_Co=1.0 nm). The decrease of α with t_Co>1.8 nm is probably due to the eddy current loss effects. The increase of α with t_Co<1.8 nm would be caused by the increase of the distortion between the Co and the Pt layers at the interface. When the magnetic field direction was changed from θ=90° (parallel to the specimen) to θ=0° (perpendicular to the specimen), the α of all the specimens increased, and a sharp step in α was observed around θ=40°, where the α has the maximum value.     

Photoabsorption spectra of CF3I and thermally dissociated CF3I near the C 1s, I 3d and F 1s ionisation thresholds

We report soft X-ray total ion yield and angular-resolved ion yield spectra of CF₃I in the C 1s, I 3d and F 1s ionisation regions, and tentatively assign the observed electronic states. Anisotropy in ion yield is observed only for the C transition, indicating that the dipole moment for this transition is parallel to the C_3v. The effusive source of CF₃I is heated to 800 K to produce a mixture of CF₃ and I, and the resulting spectra are compared to those recorded at room temperature.