Structural and electrical characterization of lead metaniobate thin films deposited by pulsed laser ablation

Lead niobate thin films have been prepared by laser ablation, at different substrate temperatures (Tdep) and with different oxygen pressures (pO2). For low deposition temperatures the films presented a rhombohedric-PbNb2O6 structural phase, with hysteresis cycles characteristic of a paraelectric. As Tdep increased the films started to develop an orthorhombic- PbNb2O6 structure that appeared at 400ºC and remained up to 600ºC. For low pO2, a mixture of this phase and a lead deficient phase was present in the films. Increasing the oxygen pressure the lead deficient phase was strongly reduced and the films presented only the ferroelectric orthorhombic- PbNb2O6 structural phase.(undefined

Circadian Consequence of Socio-Sexual Interactions in Fruit Flies Drosophila melanogaster

In fruit flies Drosophila melanogaster, courtship is an elaborate ritual comprising chasing, dancing and singing by males to lure females for mating. Courtship interactions peak in the night and heterosexual couples display enhanced nighttime activity. What we do not know is if such socio-sexual interactions (SSI) leave long-lasting after-effects on circadian clock(s). Here we report the results of our study aimed at examining the after-effects of SSI (as a result of co-habitation of males and females in groups) between males and females on their circadian locomotor activity rhythm. Males undergo reduction in the evening activity peak and lengthening of circadian period, while females show a decrease in overall activity. Such after-effects, at least in males, require functional circadian clocks during SSI as loss-of-function clock mutants and wild type flies interacting under continuous light (LL), do not display them. Interestingly, males with electrically silenced Pigment Dispersing Factor (PDF)-positive ventral lateral (LNv) clock neurons continue to show SSI mediated reduction in evening activity peak, suggesting that the LNv clock neurons are dispensable for SSI mediated after-effects on locomotor activity rhythm. Such after-effects in females may not be clock-dependent because clock manipulated females with prior exposure to males show decrease in overall activity, more or less similar to rhythmic wild type females. The expression of SSI mediated after-effects requires a functional olfactory system in males because males with compromised olfactory ability do not display them. These results suggest that SSI causes male-specific, long-lasting changes in the circadian clocks of Drosophila, which requires the presence of functional clocks and intact olfactory ability in males

Circadian Clock Gene Expression in the Coral Favia fragum over Diel and Lunar Reproductive Cycles

Natural light cycles synchronize behavioral and physiological cycles over varying time periods in both plants and animals. Many scleractinian corals exhibit diel cycles of polyp expansion and contraction entrained by diel sunlight patterns, and monthly cycles of spawning or planulation that correspond to lunar moonlight cycles. The molecular mechanisms for regulating such cycles are poorly understood. In this study, we identified four molecular clock genes (cry1, cry2, clock and cycle) in the scleractinian coral, Favia fragum, and investigated patterns of gene expression hypothesized to be involved in the corals' diel polyp behavior and lunar reproductive cycles. Using quantitative PCR, we measured fluctuations in expression of these clock genes over both diel and monthly spawning timeframes. Additionally, we assayed gene expression and polyp expansion-contraction behavior in experimental corals in normal light:dark (control) or constant dark treatments. Well-defined and reproducible diel patterns in cry1, cry2, and clock expression were observed in both field-collected and the experimental colonies maintained under control light:dark conditions, but no pattern was observed for cycle. Colonies in the control light:dark treatment also displayed diel rhythms of tentacle expansion and contraction. Experimental colonies in the constant dark treatment lost diel patterns in cry1, cry2, and clock expression and displayed a diminished and less synchronous pattern of tentacle expansion and contraction. We observed no pattern in cry1, cry2, clock, or cycle expression correlated with monthly spawning events suggesting these genes are not involved in the entrainment of reproductive cycles to lunar light cycles in F. fragum. Our results suggest a molecular clock mechanism, potentially similar to that in described in fruit flies, exists within F. fragum

Nanomaterials for subsurface application: study of particles retention in porous media

The ability to transport nanoparticles through porous media has interesting engineering applications, notably in reservoir capacity exploration and soil remediation. A series of core-flooding experiments were conducted for quantitative analysis of functionalized TiO2 nanoparticles transport through various porous media including calcite, dolomite, silica, and limestone rocks. The adsorption of surfactants on the rock surface and nanoparticle retention in pore walls were evaluated by chemical oxygen demand (COD) and UV–Vis spectroscopy. By applying TiO2 nanoparticles, 49.3 and 68.0 wt.% of surfactant adsorption reduction were observed in pore walls of dolomite and silica rock, respectively. Not surprisingly, the value of nanoparticle deposition for dolomite and silica rocks was near zero, implying that surfactant adsorption is proportional to nanoparticle deposition. On the other hand, surfactant adsorption was increased for other types of rock in presence of nanoparticles. 5.5, 13.5, and 22.4 wt.% of nanoparticle deposition was estimated for calcite, black and red limestone, respectively. By making a connection between physicochemical rock properties and nanoparticle deposition rates, we concluded that the surface roughness of rock has a significant influence on mechanical trapping and deposition of nanoparticles in pore-throats

Determination of infrared optical parameters of SrTiO3 thin films from the reflectivity spectrum

Strontium titanate thin films have been prepared at different oxygen pressures and subjected to different post-deposition annealing treatments. The films were deposited on Si substrates with a silica buffer layer. Infrared reflectance measurements were performed to determine the optical parameters, and the spectra were fitted using adequate dielectric function forms for the layers and the substrate. The as-deposited films were found to be amorphous. Their infrared spectra presented bands corresponding to highly damped vibrational modes. As the annealing time and temperature were increased, the strontium titanate layer optical parameters became closer to those corresponding to bulk SrTiO3 and a strong increase of the silica layer thickness was observed. The silica layer growth was attributed to the gradual oxidation of the Si substrate during the annealing that induced also a blueshift of the silica Si–O asymmetric stretching frequency. This frequency shift was associated to a decrease in the silicon oxide density as the progressive layer oxidation originated a variation of its stoichiometry from SiO1.5 towards amorphous SiO2

Structural and optical properties of Ge nanocrystals embedded in Al2O3

The authors are grateful to Prof. R. Correia (Univ. de Aveiro) for help in performing the Raman experimental work. Accepted version (9 January 2007)Ge nanocrystals (NCs) embedded in aluminum oxide were grown by RF-magnetron sputtering. Raman, high resolution transmission electron microscopy (HRTEM), selected area diffraction (SAD), and X-ray diffraction (XRD) techniques confirmed good cristallinity of the NCs from samples annealed at 800 °C. The average NC size was estimated to be around 7 nm. Photoluminescence (PL) measurements show an emission related to the NCs. The temperature dependence of the PL confirms the confinement phenomenon in the Ge NCs.Project number POCTI/FIS/56930/2004 and STRP 505285-1 SEMINANO.FCT grant SFRH/BPD/11650/2002