Synthesis and Characterization of Al- and SnO2-Doped ZnO Thermoelectric Thin Films.

The effect of SnO2 addition (0, 1, 2, 4 wt.%) on thermoelectric properties of c-axis oriented Al-doped ZnO thin films (AZO) fabricated by pulsed laser deposition on silica and Al2O3 substrates was investigated. The best thermoelectric performance was obtained on the AZO + 2% SnO2 thin film grown on silica, with a power factor (PF) of 211.8 µW/m·K2 at 573 K and a room-temperature (300 K) thermal conductivity of 8.56 W/m·K. PF was of the same order of magnitude as the value reported for typical AZO bulk material at the same measurement conditions (340 µW/m·K2) while thermal conductivity κ was reduced about four times.

Optical gain in capillary light guides filled with NaYF4: Yb3+, Er3+ nanocolloids.

A capillary light guide optical amplifier using nanocolloids of Yb3+-Er3+ co-doped NaYF4 as a filler was successfully demonstrated. A 7-cm-long and 150-micron-inner-diameter capillary light guide was capable to amplify a pulsed optical signal at 1550 nm with a gain coefficient of 0.15 cm-1 at a pump power of 4 mW (980-nm wavelength). The nanocolloid gain medium was prepared by pulverizing the phosphor powder with a high-speed planetary ball mill. Ball milling of the powder in water produced nanoparticles with a size of approximately 130 nm that after drying were transferred to a liquid with high refractive index (1.551 at 1550 nm) required to maintain light confinement within the fused silica capillary light guide. The results show that RE-doped colloids of nanocrystals can be potentially used as liquid gain media fillers in capillary light guide lasers and amplifiers with high photostability and low toxicity.

Milliwatt-level mid-infrared (10.5-16.5 µm) difference frequency generation with a femtosecond dual-signal-wavelength optical parametric oscillator.

We demonstrate the generation of mid-infrared radiation using a femtosecond dual-signal-wavelength optical parametric oscillator and difference frequency generation in an extracavity gallium selenide or silver gallium diselenide crystal. This system generates up to 4.3 mW of average mid-infrared power. Its spectra can be tuned to between 10.5 µm and 16.5 µm wavelength (952 cm(-1)-606 cm(-1)) with more than 50 cm(-1) spectral bandwidth. We demonstrate that the power and spectra of this system are temporally very stable.

1-Benzyl-3,5-bis-(4-chloro-benzyl-idene)piperidin-4-one.

The title compound, C(26)H(21)Cl(2)NO, crystallizes with two symmetry-independent mol-ecules (A and B) in the asymmetric unit. In both mol-ecules, the central heterocyclic ring adopts a sofa conformation. The dihedral angles between the planar part of this central heterocyclic ring [maximum deviations of 0.011 (1) and 0.036 (1) Šin mol-ecules A and B, respectively] and the two almost planar [maximum deviations of 0.020 (1) and 0.008 (1) Šin A and 0.007 (1) and 0.011 (1) in B] side-chain fragments that include the aromatic ring and bridging atoms are 20.1 (1) and 31.2 (1)° in mol-ecule A, and 26.4 (1) and 19.6 (1)° in mol-ecule B. The dihedral angles between the planar part of the heterocyclic ring and the benzyl substituent are 79.7 (1) and 53.2 (1)° in mol-ecules A and B, respectively. In the crystal, weak inter-molecular C-H⋯O hydrogen bonds link the two independent mol-ecules into dimers.

3,5-Bis(4-chloro-benzyl-idene)-1-methyl-piperidin-4-one.

In the title mol-ecule, C(20)H(17)Cl(2)NO, the central heterocyclic ring adopts a flattened boat conformation. The dihedral angles between the planar part of this central heterocyclic ring [maximum deviation = 0.004 (1) Å] and the two almost planar side-chain fragments [maximum deviations = 0.015 (1) and 0.019 (1) Å], that include the aromatic ring and bridging atoms, are 18.1 (1) and 18.0 (1)°. In the crystal, pairs of weak inter-molecular C-H⋯O hydrogen bonds link mol-ecules into inversion dimers that form stacks along the a axis. The structure is further stabilized by weak inter-molecular C-H⋯π inter-actions involving the benzene rings.

3,5-Bis{3-[4-(dimethylamino)phenyl]prop-2-enylidene}-1-methyl-4-piperidone and 3,5-bis[3-(4-methoxyphenyl)prop-2-enylidene]-1-methyl-4-piperidone: potential biophotonic materials.

The structures of the title compounds, C(28)H(33)N(3)O, (I), and C(26)H(27)NO(3), (II), together with their two-photon absorption properties and fluorescence activities are reported. Molecules of (II) reside on crystallographic mirror planes containing the piperidone C=O group and N-methyl H atoms. Because of the conjugation between the donor and acceptor parts, the central heterocycle in both (I) and (II) exhibits a flattened boat conformation, with deviations of the N atom and the opposite C atom from the planar fragment. The dihedral angles between the coplanar heterocyclic atoms and terminal C(6) rings are less than 20 degrees in both (I) and (II). In (I), the N-methyl group of the ring occupies an equatorial position, but in (II) it is positioned in an axial site. In the crystal structure of (I), weak intermolecular C-H...pi(arene) and C-H...O steric contacts link the molecules along the a axis. In the crystal structure of (II), molecules form stacks along the b axis.

Statistical analysis of cloud-cover mitigation of optical turbulence in the boundary layer.

One atmospheric phenomenon that adversely affects laser propagation is optical turbulence. From ten months of observation, the refractive index structure constant in the atmospheric boundary layer was found to be significantly reduced under widespread cloudy conditions. The refractive index structure constant (C(n) (2)) depends upon the turbulent flux of momentum, sensible and latent heat. The intensity of a propagating laser beam will not be degraded nearly as much as would be expected under clear or lightly scattered cloud conditions. New experimental data are presented that support this hypothesis. The refractive index structure constant was measured for various cloud-cover conditions.

3,5-bis[4-(diethylamino)benzylidene]-1-methyl-4-piperidone and 3,5-bis[4-(diethylamino)cinnamylidene]-1-methyl-4-piperidone: prospective biophotonic materials.

The structures of 3,5-bis[4-(diethylamino)benzylidene]-1-methyl-4-piperidone, C(28)H(37)N(3)O, (I), and 3,5-bis[4-(diethylamino)cinnamylidene]-1-methyl-4-piperidone, C(32)H(41)N(3)O, (II), have been characterized. Because of conjugation between donor and acceptor parts, the central heterocycles (including the carbonyl group) in (I) and (II) are flattened and exhibit a 'sofa' conformation, with a deviation of the N atom from the planar fragment. The dihedral angles between the planar part of the heterocycle and the two almost flat fragments that include a phenyl ring and bridging atoms are 23.2 (1) and 11.2 (1) degrees in (I), and 11.8 (1) and 8.7 (2) degrees in (II). One- and two-photon absorption of light and the fluorescence of (I) and (II) have also been characterized.