We develop a simplified light source at 461 nm for laser cooling of Sr without frequency-doubling crystals but with blue laser diodes. An anti-reflection coated blue laser diode in an external cavity (Littrow) configuration provides an output power of 40 mW at 461 nm. Another blue laser diode is used to amplify the laser power up to 110 mW by injection locking. For frequency stabilization, we demonstrate modulation-free polarization spectroscopy of Sr in a hollow cathode lamp. The simplification of the laser system achieved in this work is of great importance for the construction of transportable optical lattice clocks.
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 β-D-glucopyranoside.
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.
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