Mechanically switchable photonic crystal filter with either all-pass transmission or flat-top reflection characteristics

We theoretically introduce a new type of optical all-pass filter based on guided resonance in coupled photonic crystal slabs. The filter exhibits near-complete transmission for both on- and off-resonant frequencies and yet generates large resonant group delay. We further show that such a filter can be mechanically switched into a flat-top band rejection filter.     

High-yield synthesis of multi-walled carbon nanotubes by arc discharge in liquid nitrogen

Synthesis of multi-walled carbon nanotubes (MWNTs) by arc discharge in liquid nitrogen is reported. As liquid nitrogen substituted both vacuum and cooling systems, high-quality MWNTs were produced at a low cost. The content of the MWNTs can be as high as 70% of the reaction product. Auger-spectroscopy analysis revealed that no nitrogen is incorporated in the MWNTs. This method can be an economical route for the mass production of highly crystalline MWNTs. Received: 5 July 2002 / Accepted: 8 July 2002 / Published online: 10 September 2002 RID="*" ID="*"Corresponding author. Fax: +82-54/279-8298, E-mail: ce20047@postech.ac.kr     

Acceleration of acid-catalyzed transesterification of 2-hydroxypropyl-p-nitrophenyl phosphate by organic solvents

[structure: see text] Transesterification of 2-hydroxypropyl-p-nitrophenyl phosphate in the presence of 0.092 M HClO4 is 50-5000 times faster in acetonitrile, 1,4-dioxane, methanol, ethanol, N,N-dimethylformamide, or dimethyl sulfoxide than in water. This demonstrates the importance of tuning the microenvironments in designing synthetic nucleases.     

Inhomogeneous low frequency spin dynamics in La(1.65)Eu(0.2)Sr(0.15)CuO(4)

We report Cu and La nuclear magnetic resonance measurements in the title compound that reveal an inhomogeneous glassy behavior of the spin dynamics. A low temperature peak in the La spin lattice relaxation rate and the "wipeout" of Cu intensity both arise from these slow electronic spin fluctuations that reveal a distribution of activation energies. Inhomogeneous slowing of spin fluctuations appears to be a general feature of doped lanthanum cuprate.     

Synthesis, properties, and X-ray structure of [Cu(dpa)Cl2] (dpa = di-(2-picolyl)amine)

The mono(dpa)copper(II) complex [Cu(dpa)Cl₂] (1) (dpa = di-(2-picolyl)amine) has been synthesized and structurally characterized. It crystallizes in the monoclinic system P2₁/n with a = 8.155(1), b = 12.560(1), c = 12.817(2) Å, = 91.64(2)°, V = 1312.3(2) ų, Z = 4. The copper atom is coordinated by three nitrogen atoms from the dpa ligand and two chlorides in a distorted square-pyramidal environment. Cyclic voltammetric data show that 1 undergoes the reversible one-electron oxidation to the Cu(III) and the reversible one-electron reduction to the Cu(I) state.     

Color-image generation by use of binary-phase holograms

A novel, simple scheme for producing full-color images by use of binary-phase holograms and red (632.8-nm), green (543.5-nm), and blue (488-nm), lasers is reported. The theory and experimental results of the system are also presented.