The Enriched Xenon Observatory (EXO) will search for double beta decays of 136 Xe. We report the results of a systematic study of trace concentrations of radioactive impurities in a wide range of raw materials and finished parts considered for use in the construction of EXO-200, the first stage of the EXO experimental program. Analysis techniques employed, and described here, include direct gamma counting, alpha counting, neutron activation analysis, and high-sensitivity mass spectrometry. r

This letter reports that adding nanoparticles in the negative dielectric anisotropic liquid crystal (LC) cell can exhibit the properties of vertical alignment without using alignment layers. The electro-optical properties of this nanoparticles-induced vertical alignment in the LC cell are very similar to the conventional homeotropic LC cell with alignment layers. This technique can be used to fabricate a flexible LC display requiring a low temperature process.

We have found that nanoparticles of polyhedral oligomeric silsesquioxane (POSS) can induce vertical alignment in nematic liquid crystal (LC) cells as long as the doped weight percentage of POSS in the LC cells is higher than ∼1%. Such nanoparticle-induced vertical alignment (NIVA) is a very suitable technique for application in the low-temperature fabrication of plastic LC displays. The dynamic process of LC orientation from randomly parallel alignment to vertical alignment was recorded, and it is posited that the POSS NIVA is due to the adsorption of POSS on the inner surfaces of the LC cells. The influence of the POSS concentration on the electro-optical properties and dielectric constant of LC cells was also investigated and the results indicate that LC cells doped with ∼1 wt% POSS provide the best electro-optical performance.

The pretilt angles of liquid crystal molecules can be controlled by using conventional polyimide (PI) alignment material doped with different concentrations of Polyhedral Oligomeric Silsequioxanes (POSS) nanoparticles, which have been observed to spontaneously induce vertical alignment. The addition of POSS in the homogenous PI changes the surface energy of the alignment layer and generates a variable pretilt angle. Experimental results demonstrate that the pretilt angle thetap is a function of the POSS concentration, and can be tuned continuously over the range of 0 degrees

A polarizer-free flexible and reflective electro-optical switch using dye-doped liquid crystal (LC) gels is demonstrated. The electro-optical performances of both scattering and absorption based dye-doped LC gels depend on curing temperatures due to domain sizes of polymer networks. Such flexible electro-optical switch is bendable and trim-able because of the vertical polymer networks and gel-like materials. The dye-doped LC gel shows good reflectance ~55%, good contrast ratio~450:1 and fast response~6.4 ms at curing temperature 10 degrees C. The bending curvature is 21 mm. The dye-doped LC gels open a new window for trim-able electronic papers, decorative displays, electrically switchable curtains, and electrically switchable sun control film for the automobiles, homes or commercial buildings.