Brillouin scattering self-cancellation.

The interaction between light and acoustic phonons is strongly modified in sub-wavelength confinement, and has led to the demonstration and control of Brillouin scattering in photonic structures such as nano-scale optical waveguides and cavities. Besides the small optical mode volume, two physical mechanisms come into play simultaneously: a volume effect caused by the strain-induced refractive index perturbation (known as photo-elasticity), and a surface effect caused by the shift of the optical boundaries due to mechanical vibrations. As a result, proper material and structure engineering allows one to control each contribution individually. Here, we experimentally demonstrate the perfect cancellation of Brillouin scattering arising from Rayleigh acoustic waves by engineering a silica nanowire with exactly opposing photo-elastic and moving-boundary effects. This demonstration provides clear experimental evidence that the interplay between the two mechanisms is a promising tool to precisely control the photon-phonon interaction, enhancing or suppressing it.

Over 4000 nm bandwidth of mid-IR supercontinuum generation in sub-centimeter segments of highly nonlinear tellurite PCFs.

We report broad bandwidth, mid-IR supercontinuum generation using a sub-cm (8 mm) length of highly nonlinear tellurite microstructured photonic crystal fiber (PCF). We pump the fiber at telecommunication wavelengths by using 1550 nm, 100 fs pulses of energy E=1.9 nJ. When coupled in the PCF, these pulses result in a supercontinuum (SC) bandwidth of 4080 nm extending from 789 to 4870 nm measured at 20 dBm below the peak spectral power. This bandwidth is comparable or in excess of previously reported spectra for other nonlinear glass fiber formulations despite the significantly shorter fiber length. In addition, besides offering a convenient pump wavelength, short fiber lengths enable smoother SC spectra, lower dispersion, and reduced material absorption at longer wavelengths making the use of this PCF particularly interesting.

Hybrid photonic crystal fiber.

We present a hybrid photonic crystal fiber in which a guided mode is confined simultaneously by modified total internal reflection from an array of air holes and antiresonant reflection from a line of high-index inclusions. Experimental results demonstrate that this fiber shares properties of both index-guided and photonic bandgap structures.

Engineering the dispersion of tapered fibers for supercontinuum generation with a 1064 nm pump laser.

We experimentally demonstrate dispersion tailoring of tapered fibers by immersing them in fluids. We obtain a 1200 nm wide supercontinuum in a train of two tapered fibers pumped by a low-cost diode-pumped Nd:YAG laser with a pulse width of 0.6 ns and an output power of 40 mW, where one tapered fiber is immersed in heavy water. To our knowledge, this is the widest spectrum ever generated with a system of such simplicity.

Photonic bandgap with an index step of one percent.

Early work suggested that very large refractive index contrasts would be needed to create photonic bandgaps in two or three dimensionally periodic photonic crystals. It was then shown that in two-dimensionally periodic structures (such as photonic crystal fibres) a non-zero wavevector component in the axial direction permits photonic bandgaps for much smaller index contrasts. Here we experimentally demonstrate a photonic bandgap fibre made from two glasses with a relative index step of only 1%.

Guidance properties of low-contrast photonic bandgap fibres.

We investigate the guidance properties of low-contrast photonic band gap fibres. As predicted by the antiresonant reflecting optical waveguide (ARROW) picture, band gaps were observed between wavelengths where modes of the high-index rods in the cladding are cutoff. At these wavelengths, leakage from the core by coupling to higher-order modes of the rods was observed directly. The low index contrast allowed for bend loss to be investigated; unlike in index-guiding fibres, anomalous "centripetal" light leakage through the inside of the bend can occur.

Power of microsatellite markers for fingerprinting and parentage analysis in Eucalyptus grandis breeding populations.

We report the genetic analysis of 192 unrelated individuals of an elite breeding population of Eucalyptus grandis (Hill ex Maiden) with a selected set of six highly polymorphic microsatellite markers developed for species of the genus Eucalyptus. A full characterization of this set of six loci was carried out generating allele frequency distributions that were used to estimate parameters of genetic information content of these loci, including expected heterozygosity, polymorphism information content (PIC), power of exclusion, and probability of identity. The number of detected alleles per locus ranged from 6 to 33, with an average of 19.8 +/- 9.2. The average expected heterozygosity was 0.86 +/- 0.11 and the average PIC was 0.83 +/- 0.16. Using only three loci, it was possible to discriminate all 192 individuals. The overall probability of identity considering all six EMBRA microsatellite markers combined was lower than 1 in 2 billion. An analysis of the sample size necessary to estimate expected heterozygosity with minimum variance indicated that at least 64 individuals have to be genotyped to characterize this parameter with adequate accuracy for most microsatellites in Eucalyptus. The high degree of multiallelism and the clear and simple codominant Mendelian inheritance of the set of microsatellites used provide an extremely powerful system for the unique identification of Eucalyptus individuals for fingerprinting purposes and parentage testing.

Measurement of phase differences between the diffracted orders of deep relief gratings.

Measurement of the phase difference between the 0th and the 1st transmitted diffraction orders of a symmetrical surface-relief grating recorded on a photoresist film is carried out by replacement of the grating in the same setup with which it was recorded. The measurement does not depend on lateral shifts of thereplaced grating relative to the interference pattern, on environmental phase perturbations or on the wave-front quality of the interfering beams. The experimental data agree rather well with theoretical results calculated for sinusoidal profiled gratings.

Beauveria bassiana (Hyphomycetes) as a possible agent for biological control of Chagas disease vectors.

Beauveria bassiana (Balsamo) Vuillemin (isolate CG306) was tested on 3rd instars of 9 Triatoma spp., 4 Rhodnius spp., 2 Panstrongylus spp. and Dipetalogaster maxima (Uhler) at 25 degrees C and 50% RH. Quantitative sporulation of the fungus on cadavers was studied at 25 degrees C and 97% RH. Mortality, estimates of survival time, and conidial production on cadavers differed significantly among the genera and species tested. Panstrongylus herreri Wygodzinsky, Dipetalogaster maxima, Triatoma picturata Usinger, Rhodnius robustus Larrousse, Rhodnius prolixus Stål, Triatoma infestans (Klug), and Triatoma brasiliensis Neiva were most susceptible to fungal infection. Most conidia per cadaver were produced on Triatoma williami Galvão, Souza & Lima and Triatoma lecticularia (Stål). Results indicate that B. bassiana (CG306) might be a candidate for control of important or potential vectors of Trypanosoma cruzi using the fungus as a bioinsecticide.

Selection of Beauveria bassiana and Metarhizium anisopliae isolates to control Triatoma infestans.

Twenty three isolates of Beauveria bassiana and 13 isolates of Metarhizium anisopliae were tested on third instar nymphs of Triatoma infestans, a serious vector of Chagas disease. Pathogenicity tests at saturated humidity showed that this insect is very susceptible to fungal infection. At lower relative humidity (50%), conditions expected in the vector microhabitat, virulence was significantly different among isolates. Cumulative mortality 15 days after treatment varied from 17.5 to 97.5%, and estimates of 50% survival time varied from 6 to 11 days. Maintaining lower relative humidity, four B. bassiana and two M. anisopliae isolates were selected for analysis of virulence at different conidial concentrations and temperatures. Lethal concentrations sufficient to kill 50% of insects (LC50) varied from 7.1 x 10(5) to 4.3 x 10(6) conidia/ml, for a B. bassiana isolate (CG 14) and a M. anisopliae isolate (CG 491) respectively. Most isolates, particularly B. bassiana isolates CG 24 and CG 306, proved to be more virulent at 25 and 30 degrees C, compared to 15 and 20 degrees C. The differential virulence at 50% humidity observed among some B. bassiana isolates was not correlated to phenetic groups in cluster analysis of RAPD markers. In fact, the B. bassiana isolates analyzed presented a high homogeneity (> 73% similarity).