Long-Term Stability at High Temperatures for Birefringence in PAZO/PAH Layer-by-Layer Films

Optical memories with long-term stability at high temperatures have long been pursued in azopolymers with photoinduced birefringence. In this study, we show that the residual birefringence in layer-by-layer (LbL) films made with poly[1-[4-(3-carboxy-4 hydroxyphenylazo)benzene sulfonamido]-1,2-ethanediyl, sodium salt] (PAZO) alternated with poly(allylamine hydrochloride) (PAH) can be tuned by varying the extent of electrostatic interactions with film fabrication at different pHs for PAH. The dynamics of both writing and relaxation processes could be explained with a two-stage mechanism involving the orientation of the chromophores per se and the chain movement. Upon calculating the activation energies for these processes, we demonstrate semiquantitatively that reduced electrostatic interactions in films prepared at higher pH, for which PAH is less charged, are responsible for the longer stability at high temperatures. This is attributed to orientation of PAZO chromophores via cooperative aggregation, where the presence of counterions hindered relaxation.

Synthesis and Characterization of Gold/Alanine Nanocomposites with Potential Properties for Medical Application as Radiation Sensors

Radiation dose assessment is essential for several medical treatments and diagnostic procedures. In this context, nanotechnology has been used in the development of improved radiation sensors, with higher sensitivity as well as smaller sizes and energy dependence. This paper deals with the synthesis and characterization of gold/alanine nanocomposites with varying mass percentage of gold, for application as radiation sensors. Alanine is an excellent stabilizing agent for gold nanoparticles because the size of the nanoparticles does not augment with increasing mass percentage of gold, as evidenced by UV-vis spectroscopy, dynamic light scattering, and transmission electron microscopy. X-ray diffraction patterns suggest that the alanine crystalline orientation undergoes alterations upon the addition of gold nanoparticles. Fourier transform infrared spectroscopy indicates that there is interaction between the gold nanoparticles and the amine group of the alanine molecules, which may be the reason for the enhanced stability of the nanocomposite. The application of the nanocomposites as radiation detectors was evaluated by the electron spin resonance technique. The sensitivity is improved almost 3 times in the case of the nanocomposite containing 3% (w/w) gold, so it can be easily tuned by changing the amount of gold nanoparticles in the nanocomposites, without the size of the nanoparticles influencing the radiation absorption. In conclusion, the featured properties, such as homogeneity, nanoparticle size stability, and enhanced sensitivity, make these nanocomposites potential candidates for the construction of small-sized radiation sensors with tunable sensitivity for application in several medical procedures.

Variability of rainfall and temperature (1912-2008) parameters measured from Santa Maria (29 degrees 41 ' S, 53 degrees 48 ' W) and their connections with ENSO and solar activity

In this work, we analyze the long term variability of rainfall and temperature (1912-2008) of Santa Maria (29 degrees S, 53 degrees W) and its possible connection with natural influences such as solar activity and ENSO. Temperature and rainfall present similar frequencies as revealed by spectral analyses. This analysis shows a large number of short periods between 2-8 years and periods of 11.8-12.3, 19.1-21.0, and 64.3-82.5 years. The cross correlation for rainfall and temperature versus Southern Oscillation Index (SOI) have higher cross-power around 2-8 yr. Rainfall and temperature versus sunspot number (Rz) showed higher cross-power around the 11-yr solar cycle period. A high and continuous cross correlation was observed for Rz-22 yr versus rainfall and temperature. Furthermore, the power between 22-yr solar cycle and meteorological parameters was higher than that obtained with the 11-yr solar cycle, suggesting that the effect of Hale cycle on climate may be stronger than the Schwabe cycle effect. These results indicate that the variability of rainfall and temperature is closely related to the variation of the Southern Oscillation Index and solar activity, and that the El Nino Southern Oscillation and solar activity probably play an important role in the climate system over Southern Brazil. (C) 2011 Elsevier Ltd. All rights reserved.

Taxonomical study on a sample of pulmonates from Santa Maria da Vitória, Bahia, Brazil, with description of a new genus and four new species (Mollusca: Orthalicidae and Megalobulimidae)

A sample of Pulmonata collected in Santa Maria da Vitória, interior of Bahia, Brazil, in Caatinga semi-arid environment, is studied taxonomically. From the five species, four are revealed as new, including a new genus. The new taxa are the Bulimulidae (1) Kora corallina gen. et sp. n. characterized by the elongated shell with aperture somewhat dislocated from the shell axis, and an oblique tooth in middle level of inner lip; (2) Spixia coltrorum, mainly characterized by an uneven spire, delicate sculpture and peristome with 4 equidistant teeth; (3) Anostoma tessa, mainly characterized by a broad spire and well-developed anal canal; and the Megalobulimidae (4) Megalobulimus amandus, mainly characterized by pointed protoconch sculptured by dense quantity of axial cords. Rhinus suturalis is the only previously known species, but its geographic distribution is expanded southwards to Bahia state. A discussion with respect to necessity for improving the study on the malacofauna from the interior region of the Brazilian Northeast and the importance for preservation of the Caatinga biome is also provided.

Tentativa de balanço: entrevista com Iumna Maria Simon

Narrando a sua formação intelectual, Iumna Maria Simon analisa a situação da crítica literária na universidade e fora dela, a poesia contemporânea e as condições da leitura da obra literária hoje. A entrevista expõe o modo como desenvolveu sua compreensão da literatura brasileira mais recente e como organiza seu foco crítico e suas referências teóricas, enquanto professora e crítica.

Cirrus clouds observation in Santa Maria, Rio Grande do Sul during the experiment Chuva - Sul.

Cirrus clouds are an interesting point in the research of the atmosphere due their behavior and the effect on the earth radiation budget. They can affect the atmospheric radiation budget by reflecting the incoming solar radiation and absorbing the outgoing terrestrial radiation. Also, this cloud type is involved in the dehydration of the upper troposphere and lower stratosphere. So, it is interesting to increment the measurements of this type of clouds from the ground. During November and December 2012, through the CHUVA-SUL campaign, measurements with lidar in Santa Maria, Rio Grande do Sul were conducted. The system installed in Santa Maria site (29.8 °S; 53.7 °W, 100 m asl) was a single elastic-backscatter lidar using the wavelength of 532 nm. Some days with cirrus clouds lidar measurements were detected. Four days with presence of cirrus cloud are showed in the present study. These days, 7, 8, 19 and 28 November 2012, was selected due the persistence of cirrus clouds over many hours. The raw retrieval lidar signals and inverted backscatter coefficient profiles were analyzed for the selected days. Base and top height was obtained by analysis of raw signal and backscatter coefficient. Extinction coefficient profiles were obtained by the assumption of the lidar ratio. Cirrus cloud optical depth (COD) values were calculated, from the integration of the extinction coefficient between the base and top altitudes of the cirrus clouds.