Soft X-ray spectral analysis of laser produced molybdenum plasmas using the fundamental and second harmonics of a Nd:YAG laser.

Our measurement of the soft X-ray emission of Mo plasmas produced by picosecond Nd:YAG lasers emitting on the fundamental (1064 nm, 150 ps) and second (532 nm, 130 ps) harmonics is presented. The contrast in intensity between spectral peaks and the intensity outside them is lower for the second harmonic produced plasmas probably due to the presence more intense satellite emission and higher optical thickness. The measured spectra are absolutely calibrated and the observed output photon flux was (7 - 9) × 1013 photons/sr in the water-window (2.3 - 4.4 nm) spectral range for a laser energy of 160 mJ independent of laser wavelength. However, in the short wavelength range 1.5 - 2 nm, the emission using the second harmonic is strongly enhanced and is even higher than for the maximum energy of 220 mJ of the fundamental wavelength, so despite inevitable energy losses, laser wavelength conversion may lead to emission enhancement in certain spectral ranges. This enhancement is attributed to higher absorption of short wavelength laser light and higher charge state generation in denser plasmas.

Effect of Vapor Pressure During the Steam Coating Treatment on Structure and Corrosion Resistance of the Mg(OH)2/Mg-Al LDH Composite Film Formed on Mg Alloy AZ61.

Corrosion resistant films with almost the same film thickness were prepared on the magnesium alloy AZ61 by steam coating at different vapor pressure and treatment times. The effect of the vapor pressure on the structures and the corrosion resistance of the films was investigated by using FE-SEM, SEM-EDX, GAXRD, and potentiodynamic polarization curve measurements in a 3.5 mass percentage NaCl aqueous solution. These studies clarified that the interlayers of Mg-Al Layered Double Hydroxide (LDHs) increased and its structure became non-uniform with an increase in the vapor pressure. The corrosion current density slightly increased with an increase in the vapor pressure during the treatment, but pitting corrosion occurred at both low and high vapor pressures. These results indicate that water molecules were pushed into an interlayer of Mg-Al LDHs by high vapor pressure. Consequently, the interlayer distance of Mg-Al LDH was widened and the cracks were generated in the anti-corrosive film. On the other hand, the Mg-Al LDH with an insufficiently large interlayer distance could not fill the cracks in the Mg(OH)2 crystallites and caused pitting corrosion when the vapor pressure was low.

Two polymorphs of 2,5-dichloro-3,6-bis(dibenzylamino)-p-hydroquinone with flexible dibenzylamino groups.

We obtained two conformational polymorphs of 2,5-dichloro-3,6-bis(dibenzylamino)-p-hydroquinone, C34H30Cl2N2O2. Both polymorphs have an inversion centre at the centre of the hydroquinone ring (Z' = 1/2), and there are no significant differences between their bond lengths and angles. The most significant structural difference in the molecular conformations was found in the rotation of the phenyl rings of the two crystallographically independent benzyl groups. The crystal structures of the polymorphs were distinguishable with respect to the arrangement of the hydroquinone rings and the packing motif of the phenyl rings that form part of the benzyl groups. The phenyl groups of one polymorph are arranged in a face-to-edge motif between adjacent molecules, with intermolecular C-H...π interactions, whereas the phenyl rings in the other polymorph form a lamellar stacking pattern with no significant intermolecular interactions. We suggest that this partial conformational difference in the molecular structures leads to the significant structural differences observed in their molecular arrangements.

Rapid Fabrication of a Crystalline Myristic Acid-Based Superhydrophobic Film with Corrosion Resistance on Magnesium Alloys by the Facile One-Step Immersion Process.

A simple, easy, and rapid process of fabricating superhydrophobic surfaces on magnesium alloy AZ31 by a one-step immersion at room temperature was developed. The myristic acid-modified micro-/nanostructured surfaces showed static water contact angles over 150° and water contact angle hysteresis below 10°, thus illustrating superhydrophobic property. The shortest treatment time for obtaining the superhydrophobic surfaces was 30 s. In addition, we demonstrated for the first time that crystalline solid myristic acid could be formed on a Mg alloy using a suitable molar ratio of Ce ions and myristic acid. The contact angle hysteresis was lowered with an increase in the immersion time. Potentiodynamic polarization curve measurements revealed that the corrosion resistance of AZ31 treated by the immersion process improved considerably by the formation of superhydrophobic surfaces. The chemical durability of the superhydrophobic surfaces fabricated on AZ31 was also examined. The static water contact angle values for the superhydrophobic surfaces after immersion in aqueous solutions at pHs 4, 7, and 10 for 12 h were estimated to be 90 ± 2°, 119 ± 2°, and 138 ± 2°, respectively, demonstrating that their chemical durability in a basic solution was high.

Characteristic Aroma Features of Tencha and Sencha Green Tea Leaves Manufactured by Different Processes.

There are many varieties of tea (Camellia sinensis) obtained by different processing methods. In Japan, sencha tea has been used to brew beverages f6r centuries, and tencha leaves are used to make powdered green tea, matcha, which is used as an important food additive to impart the odor of green tea. We investigated the differences between the odors of sencha and tencha and their aroma profiles. We used our new technique to evaluate the odor of green tea, based on the theory that the aroma characteristics of materials arise from the interactions of groups of compounds with similar structures. Hexane extracts from sencha and tencha leaves were analyzed by gas chromatography-olfactometry. We detected several important compounds for tencha. The hexane extracts were separated by distillation, and groups of compounds with different boiling points were obtained. We investigated the group of high-boiling point constituents, which had a matcha-like odor and consisted of a group of odor constituents common to sencha and tencha. Tencha had a characteristic seaweed-like odor, and the low-boiling point constituents caused the differences in the tencha and sencha odors.

Alternating 2,6-/3,5-substituted pyridine-acetylene macrocycles: π-stacking self-assemblies enhanced by intermolecular dipole-dipole interaction.

Macrocyclic compounds consisting of three 2,6-pyridylene and three 3,5-pyridylene units linked by acetylene bonds were synthesized by a Sonogashira reaction. The X-ray structures showed π-stacked pairs of two macrocycles, in which a 2,6-pyridylene unit of the one molecule overlaps a 3,5-pyridylene of the other molecule because of dipole-dipole interaction. Atomic force microscope (AFM) measurements revealed fibril structures indicating the stacking of the rigid planar macrocycles. Hydrogen-bonding ability of the macrocyclic inside was demonstrated by the addition of octyl ß-D-glucopyranoside.