Flattened chromatic dispersion in square photonic crystal fibers with low confinement losses

This research presents a simple index-guiding square photonic crystal fibers (SPCFs) that has a silica core surrounded by air hole with two different diameters. It is demonstrated that the designed two-different-size hole-arrayed index-guiding SPCFs has a ultra-flattened chromatic dispersion of 0 ± 0.9 ps/(nm·km) in a wavelength range of 1.34 to 1.61 μm and low confinement loss of less than 10⁻⁷ dB/m in a wavelength range of 1.2 to 1.7 μm. It has also been shown that the proposed SPCFs show reasonable dispersion tolerance.     

A practical synthesis of L-ribose

L-Ribose was synthesized by a simple four-step method with overall yield of 76.3% from a protected L-arabinose derivative, which is a compatible intermediate for the synthesis of L-deoxyribose. The key step of this strategy is the Swern oxidation and subsequent stereoselective reduction accompanied by inversion of the 2-hydroxy group of protected L-arabinose.     

Catalytic and highly regiospecific carbon-carbon bond formation at alpha-position of Michael acceptor by palladium complex

Activated olefins react with allyl acetates and Bu3SnH in the presence of a catalytic amount of a palladium catalyst to afford the corresponding products which construct a new C-C bond selectively at the alpha-position of Michael acceptors.     

Novel synthesis of L-ribose from D-mannono-1,4-lactone

[reaction: see text] D-Mannono-1,4-lactone was efficiently converted into L-ribose in eight steps. A key step of this synthesis is the cyclization of a gamma-hydroxyalkoxamate under Mitsunobu conditions. It is noteworthy that the O-alkylation product was obtained in 94% yield and that none of the N-alkylation product was detected in this cyclization.     

Large four-wave mixing of spatially extended excitonic states in thin GaAs layers

We study the size dependence of the nonlinear response of weakly confined excitons for the size region beyond the long wavelength approximation regime. The observed degenerate-four-wave mixing signal of GaAs thin layers exhibits an anomalous size dependence, where the signal is resonantly enhanced at a particular thickness region. The theoretical analysis elucidates that this enhancement is due to the size-resonant enhancement of the internal field with a spatial structure relevant to the nondipole-type excitonic state. These results establish the formerly proposed new type of size dependence of nonlinear response due to the nonlocality induced double resonance.     

Lewis acid mediated claisen-type rearrangement of aryl dienyl ethers

In the presence of BF₃·.OEt₂, aryl dienyl ethers were rearranged under mild conditions to afford dienyl phenols in good yields.     

Polyaddition reaction of pseudoxazolones with dimercaptans

Polymers having thioether, thiolester, and amide linkages in each repeating unit of a polymer main chain were prepared by the polyaddition reaction of pseudoxazolones (2-isopropylidene-4-alkyl-3-oxazolin-5-ones) and dimercaptans. The polymers had inherent viscosities in a range of 0.08–0.22 and gave transparent films by solution casting.