Federal University of São Carlos

About: Federal University of São Carlos is a education organization based out in São Carlos, Brazil. It is known for research contribution in the topics: Population & Microstructure. The organization has 16471 authors who have published 34057 publications receiving 456654 citations. The organization is also known as: UFSCar & Federal University of São Carlos.

UV-assisted chemiresistors made with gold-modified ZnO nanorods to detect ozone gas at room temperature

Abstract: Two kinds of flexible ozone (O3) sensors were obtained by placing pristine ZnO nanorods and gold-modified ZnO nanorods (NRs) on a bi-axially oriented poly(ethylene terephthalate) substrate. The chemiresistive sensor is operated at typically 1 V at room temperature under the UV-light illumination. The ZnO nanorods were prepared via a hydrothermal route and have a highly crystalline wurtzite structure, with diameters ranging between 70 and 300 nm and a length varying from 1 to 3 μm. The ZnO NRs were then coated with a ca. 10 nm gold layer whose presence was confirmed with microscopy analysis. This sensor is found to be superior to detect ozone at a room temperature. Typical figures of merit include (a) a sensor response of 108 at 30 ppb ozone for gold-modified ZnO NRs, and (b) a linear range that extends from 30 to 570 ppb. The sensor is stable, reproducible and selective for O3 compared to other oxidizing and reducing gases. The enhanced performance induced by the modification of ZnO nanorods with thin layer of gold is attributed to the increased reaction kinetics compared to pristine ZnO NRs. The sensing mechanism is assumed to be based on the formation of a nano-Schottky type barrier junction at the interface between gold and ZnO.

Danos em trigo causados pela infecção de Pyricularia grisea

Abstract: This work was carried out in order to quantify the damages in wheat yield due to natural infection by Pyricularia grisea, (causal agent of wheat blast), in different wheat cultivars and breeding lines, during 2004 crop season, at Dourados county, Mato Grosso do Sul State in the absence of other diseases. The experiments were developed under natural conditions and without fungicide spraying, in experimental plots located at Embrapa Agropecuaria Oeste and Indapolis. After heading stage, all spikes that showed the characteristic blast symptoms (black point infection in the rachis), had been identified and marked in an area of the 1m2. The blast and healthy spikes were harvested, counted and threshed separately. The damages were calculated based on the difference between the actual yield and the estimated yield potential. The results showed that the damages and the blast incidence had been varied according to cultivars/breeding lines and region. The least incidence of blast were observed on cv. BR 18-Terena, with 27% and 42% of infected spikes, from the Embrapa Agropecuaria Oeste and Indapolis experiments, respectively. The average damage due to blast, in 20 tested materials, was 387kg/ha or 10.5% of the yield, in the Embrapa Agropecuaria Oeste experiment. In Indapolis, the damages were greater, reaching, in average 609kg/ha or 13% of yield. The head weight loss was greater (63.4%) with early infection than with late infection (46.0%). It was observed that grains below the infection point in the rachis were larger than the normal ones, thus compensating to some extent the presence of the empty spikelets. Because the white heads were more visible, the yield losses can be overestimated.