Three-dimensional display by use of integral photography with dynamically variable image planes

A computer-generated integral photography system operating with a variable image plane is proposed. In this scheme, the gap between a lens array and a display panel is adjusted in real time. A synchronized elemental image array for real or virtual mode is integrated in front of or behind the lens array. This integration gives an observer an enhanced perception of depth. The proposed method can be applied to animated three-dimensional imaging.     

Arrays of silicon microdischarge devices with multicomponent dielectrics

Arrays as large as 15x15 of microdischarge devices having inverted pyramidal silicon cathodes (50mumx50mum) and SiO(2)- Si(3)N(4)- polymer composite dielectrics have been fabricated and characterized with Ne gas. The lifetimes, reliability, and ignition characteristics of the arrays are superior to those of earlier designs having a single polymer dielectric. Operating voltages as low as 150 V for a 10x10 pixel array and 1000 Torr of Ne have been measured. Single (50mumx50mum) pyramidal cathode devices operate at voltages as low as 113 V when the Ne pressure is 900 Torr.     

Quantum confinement in amorphous silicon quantum dots embedded in silicon nitride

Amorphous silicon quantum dots (a-Si QDs) were grown in a silicon nitride film by plasma enhanced chemical vapor deposition. Transmission electron micrographs clearly demonstrated that a-Si QDs were formed in the silicon nitride. Photoluminescence and optical absorption energy measurement of a-Si QDs with various sizes revealed that tuning of the photoluminescence emission from 2.0 to 2.76 eV is possible by controlling the size of the a-Si QD. Analysis also showed that the photoluminescence peak energy E was related to the size of the a-Si QD, a (nm) by E(eV) = 1.56+2.40/a(2), which is a clear evidence for the quantum confinement effect in a-Si QDs.     

Dimer to monomer phase transition in alkali-metal fullerides: magnetic susceptibility changes

Ab initio calculations have been employed to investigate the peculiar change in magnetic property (from diamagnetic to paramagnetic) of the dianionic C60-dimer phase in a rapidly cooled AC60 samples ( A: alkali metal). We first note that the triplet state of (C60)-22 which was never considered previously is nearly degenerate with the singlet state, and the transition barrier between the two states is reasonably small. This explains the susceptibility increase with an increase in temperature and the magnetic phase transition in the process of the dimer to monomer phase transition.     

Resolution enhancement in a reflection mode near-field optical microscope by second-harmonic modulation signals

The motion of the probe tip in a near-field scanning optical microscope, dithered by vibration of a tuning fork, can modulate the reflection signal from the sample surface not only at the fundamental dithering frequency but also at its second harmonic. By lock-in amplification of these modulated signals, enhanced optical images are obtained, even with an uncoated fiber probe. In particular, accurate optical images with higher resolution are obtained when the second-harmonic signal is detected, which results from the parametric modulation of the tip-sample separation at the double frequency of the horizontal dithering motion of the tip. Using a DVD ROM with a track pitch of 0.74 mum as a test sample, we observed that the sharp edges around the pits are clearly resolved with the second-harmonic signals and obtained enhanced resolution of ~70 nm full width at half-maximum.     

Origin of the high piezoelectric response in PbZr1-xTixO3

High resolution x-ray powder diffraction measurements on poled PbZr1-xTixO3 (PZT) ceramic samples close to the rhombohedral-tetragonal phase boundary (the so-called morphotropic phase boundary) have shown that for both rhombohedral and tetragonal compositions the piezoelectric elongation of the unit cell does not occur along the polar directions but along those directions associated with the monoclinic distortion. This work provides the first direct evidence for the origin of the very high piezoelectricity in PZT.     

Pep-1 Peptide-modified liposomal carriers for intracellular delivery of gold nanoparticles

A Pep-1 peptide-modified liposomal (Pep1-Lipo) carrier system was investigated to increase the intracellular delivery of gold nanoparticles (Au NPs). Au NPs with a mean diameter of 13 nm were successfully encapsulated into the inner aqueous compartment of the novel carrier using an ethanol injection technique, reserving the distinctive optical characteristics of the surface plasmon resonance peak around 530 nm. The Au NP-loaded liposomal carrier was physically characterized as 150-170 nm in size and 45 mV in zeta potential. Dark field microscopic observation demonstrated that in vitro cellular association and/or translocation of the nanoprobes into the cells was increased by Pep1-Lipo carriers compared to bare Au NPs. In conclusion, this novel liposomal formulation is a promising platform for the intracellular delivery of metallic nanoprobes including Au NPs.     

Synthesis and characterization of poly(1,4-phenylenevinylene-alt-2,5-thienylenevinylene) derivatives for organic light-emitting diodes

A new series of alternating copolymers composed of 1,4-phenylenevinylene and 2,5-thienylenylvinylene repeating units with various side chain substituents were synthesized via the Heck coupling reaction for use in light-emitting diodes (LEDs). The resulting copolymers were characterized using ¹H- and ¹³C-NMR, DSC, and TGA. These polymers were found to be soluble in common organic solvents and are easily spin-coated onto glass substrates, producing high optical quality thin films without defects. The electro-optical properties of ITO/PEDOT/Polymer/Al devices were investigated using UV-VIS, PL and EL spectroscopy. The turn-on voltages of these devices were found to be in the range 4-16 V, with a maximum brightness of about 2900 cd/m² at 12 V.     

Waveform preservation of the backscattered stimulated Brillouin scattering wave by using a prepulse injection

We have found that it is possible to preserve the temporal waveform of the reflected wave generated from stimulated Brillouin scattering (SBS) by using a prepulse technique. The waveform of the SBS wave usually shows a steep rising edge in the ordinary SBS process. It has been found that the waveform of the reflected wave depends on both the prepulse energy and the time delay between the main pulse and the prepulses. A prepulse energy of 5 mJ and a time delay of 5 ns have been measured to be the optimum values under the experimental conditions. This prepulse method is useful in developing a multistage system employing several SBS cells in series for high-power laser applications.     

Color tunability of nanophosphors by changing cations for solid-state lighting

X₃MgSi₂O₈: Eu²⁺, Mn²⁺ (X=Ba, Sr, Ca) phosphors with the mean particle size of 200 nm and the spherical shape are synthesized through combustion method. They show three emission colors under near-ultraviolet light: the blue and green colors from Eu²⁺ ions and the red color from Mn²⁺ ions. Three emission bands show the different emission colors with changing X²⁺ cations. These color shifts are discussed in terms of two competing factors of the crystal field strength and the covalency. These phosphors with maximum excitation of around 375 nm can be applied as color-tunable phosphors for white-light-emitting diode based on ultraviolet/phosphor technology.