Third-order nonlinear optical properties of bismuth-borate glasses measured by conventional and thermally managed eclipse Z scan

Third-order nonlinearity one order of magnitude larger than silica is measured in bismuth-borate glasses presenting a fast response (<200 fs). The results for the sign and magnitude of the nonlinearity were obtained using a combination of the eclipse Z scan with thermal nonlinearity managed Z scan, whereas the Kerr shutter technique was employed to obtain the electronic time response of the nonlinearity, all performed with 76 MHz repetition rate 150 fs pulses at 800 nm. Conventional Z scans in the picosecond regime at 532 and 1064 nm were also independently performed, yielding the values of the third-order nonlinear susceptibilities at those wavelengths. The results obtained for the femtosecond response, enhanced third-order nonlinearity of this glass (with respect to silica), place this glass system as an important tool in the development of photonics devices. Electro-optical modulators, optical switches, and frequency converters are some of the applications using second-order nonlinear properties of the Bi-glass based on the rectification model

O meteorito Itapuranga, Goiás, e os sideritos brasileiros

The Itapurunga, Goiás State, Brazil (50º9' longitude W and 15º35' latitude S), meteorite was found at the farm of Curral de Pedra, located 18 km West from the city of Itapuranga. This iron, measuring 75x65x43 cm, exhibits shallow depressions and a dusty appearance on the surface. It weighs 628 kg and has an apparent density of 7.5. Kamacite and taenite are the major minerals, being tiny and irregular fragments of schreibersite (also rhabdite) less abundant. On the structural basis, Itapuranga is classified as a typical coarse octaedrite (bandwidth, 1.5 mm), which shows characteristic Widmanstatten plus Neumann lines when etched by acid. Chemical data (Ni, 6.6%; Ga, 96.9 ppm; Ge, 478 ppm; Ir, 2.8 ppm) allow to place it into the Group IA of the metal-rich meteorites. The main mass is on display at the Museum of the Institute of Geosciences, University of São Paulo, Brazil.O meteorito Itapuranga (longitude 50º9' W, latitude 15º35' S), Estado de Goiás, Brasil, foi encontrado na Fazenda Curral de Pedra, distante 18 km a oeste da cidade de Itapuranga. O meteorito, medindo 75x65x43 cm, apresenta superfície externa oxidada, com abundância de depressões côncavas. O peso é de 628 quilos e sua densidade aparente de 7,5. Mineralógicamente, kamacita e taenita, ocorrendo interpenetrados de forma irregular, numa textura em mosaico, são os principais constituintes. Pequenos e irregulares fragmentos de schreibersita, também sob a forma de rhabdita, aparecem subordinadamente. Do ponto de vista estrutural, o siderito é um típico octaedrito grosseiro (largura da lamela de kamacita, 1,5 mm), exibindo, uma vez atacado por ácido, as características linhas de Widmanstatten e Neumann. Dados químicos (Ni, 6,6%; Ga, 96,9 ppm; Ge, 478 ppm; Ir, 2,8 ppm) permitem enquadrá-lo dentro do Grupo IA dos sideritos. O Itapurunga pertence ao acervo do Museu do Instituto de Geociências da Universidade de São Paulo

Techniques for nonlinear optical characterization of materials: a review

Various techniques to characterize the nonlinear (NL) optical response of centro-symmetric materials are presented and evaluated with emphasis on the relationship between the macroscopic measurable quantities and the microscopic properties of photonic materials. NL refraction and NL absorption of the materials are the phenomena of major interest. The dependence of the NL refraction and NL absorption coefficients on the nature of the materials was studied as well as on the laser excitation characteristics of wavelength, intensity, spatial profile, pulse duration and pulses repetition rate. Selected experimental results are discussed and illustrated. The various techniques currently available were compared and their relative advantages and drawbacks were evaluated. Critical comparisons among established techniques provided elements to evaluate their accuracies and sensitivities with respect to novel methods that present improvements with respect to the conventional techniques

Femtosecond laser-written waveguides in thulium-doped fluoroindate glass for S-band amplification

Channel waveguides were written in a fluoroindate bulk glass containing thulium, with a femtosecond laser operating at 800 nm, 100 fs pulses and repetition rate 1 kHz. Formation of waveguides occurred for average powers from 1 to 8 mW (corresponding to energies of 1 to 8 microJ) and scan velocities in the range 0.1 to 4 mm/s. Passive optical characterization included visual inspection by optical microscope, insertion loss and mode profile. Active characterization was performed by co-propagating pumping in a dual-pump scheme that included a 808 nm and a 1054 nm laser diode for an efficient inversion of the $^3$H$_4$ level which is responsible for stimulated emission in the 1460-1530 nm spectral range. Preliminary tests show a net gain of 2.5 dB at 1487 nm, for straight waveguides 1 cm long. Applications include the fabrication of lossless components working in the S-band region of the optical communication spectrum

Antioxidant properties of different dietary supplements based on Agaricus blazei Murrill

In 2012, the market for nutraceuticals earned $90 billion worldwide and it is predicted to reach$33.6 billion in the next four years. Agaricus blazei Murrill mushroom is native to Brazil and widely cultivated due to nutritional and medicinal value [I ,2]. Its beneficial effects have long been recognized, becoming popular as ordinary food, increasing also its production and marketing as dietary supplements (3]. A. blazei is traditionally used to combat a variety of diseases such as cancer, diabetes, hepatitis and hypercholesterolemia [2]. The use of dietary supplements based on A. blazei has grown significantly, due to pharmacological studies reporting antioxidant, antitumor, anti-inflammatory, antimicrobial, immunostimulant, apoptotic and chemopreventive effects [2,3], attributed to ®-glucans and other bioactive compounds, such as steroids, tocopherols and phenolic compounds [4]. Herein, the antioxidant activity of A. blazei capsules enriched with fmits of Malpighia glabra L. (acerola), Solanum melongena L. (eggplant) and Euterpe oleracea Mart. (açai), calcium and chitosan, were evaluated though in vitro assays: DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity, reducing power, inhibition of G-carotene bleaching and inhibition of lipid peroxidation in brain homogenates by thiobarbituric acid reactive substances (TSARS) assay. Two capsules (daily recommended dose) were dissolved in 100 mL of distilled water in order to prepare a stock solution. Several dilutions were tested until determination of EC50 values (concentration responsible for 50% of antioxidant activity or 0.5 of absorbance in reducing power assay). Globally, all the tested formulations showed high antioxidant activity. A. blazei with acerola gave the highest DPPH scavenging activity (EC50=0.81±0.0 1 mg/mL) and reducing power (EC50=0.53±0.0 1 mg/mL). Nevertheless, A. blazei with ayai showed the highest activity in the lipophilic assays: f3 - carotene bleaching inhibition (EC50=0.55±0.02 mg/mL) and lipid peroxidation inhibition by TSARS assay (EC50=O. 14±0.01 mg/mL). The studied formulations might be useful as antioxidants-enriched supplements to prevent some of the diseases related to oxidative stress

Da Indústria ao Ensino

info:eu-repo/semantics/publishedVersio

Challenges of dehydration result in a behavioral shift in invasive toads

The adaptive nature of invasive species facilitates their survival in conditions that differ markedly from their native range. Behavioral changes in invasive populations are poorly explored but offer a wide potential when combined with physiological traits. For amphibians invading xeric habitats, finding water is important to function optimally and avoid dehydration. The water-finding hypothesis postulates that survival can be enhanced through the increased behavioral ability to find water. We tested the water-finding hypothesis in guttural toads (Sclerophrys gutturalis) from their native range and an invasive population. Additionally, we tested if artificially elevated corticosterone levels, which increase during dehydration, affect behavioral traits linked to water balance. In a labyrinth experiment, we observed the toads’ ability to find water in different hydration states (100%, 90%, and 80%). We found that individuals from the invasive population took longer to engage in water-searching behavior and spent more time close to the water source after finding it. Toads from the invasive population were also more active, and at 90% hydration, their attempts to find water increased. Moreover, artificially increasing corticosterone in fully hydrated invasive toads increased water-finding success. Our experiments demonstrated that invasive toads show water-conservation behaviors that can optimize water balance and might facilitate survival in an invaded xeric environment. Additionally, we suggest a link between elevated corticosterone levels and water-finding success. Our results lend support to the importance of behavior in successful invasions and the modulation of water-finding behavior by corticosterone