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.

Evaluation of Cation Exchange Capacity (CEC) in Tropical Soils Using Four Different Analytical Methods

Abstract: Four analytical methods for determination of cation exchange capacity (CEC) in tropical soils were tested, aiming to define what the most appropriate based on the requirements: analysis time, degree of reliability and cost of operation. A total of 444 soil samples from the Amazon rainforest and Atlantic rainforest were analyzed in eleven soils types. Organic matter, pH and ions Na + , K + , Ca 2+ , Mg 2+ and H + +Al 3+ were also analyzed. The influence of the action of fire on the release of ions to the soil was also tested. The results indicated that there was a momentary increase in CEC in the soil after a fire. Tropical soils have a high humidity and acidity, contributing to an overall increase of CEC. Adverse climatic conditions in the tropics affect soil properties, so that practical methods and low cost have the advantage that they can be applied periodically to analyze the quality of the soil.

Surface Behavior of Alumina-Supported Pt Catalysts Modified with Cerium as Revealed by X-ray Diffraction, X-ray Photoelectron Spectroscopy, and Fourier Transform Infrared Spectroscopy of CO Adsorption

Abstract: The effects of the carrier and pretreatment temperature on the oxidation state of Ce and Pt were evaluated in Pt/Al2O3, Pt/CeO2, and Pt/CeO2−Al2O3 catalyst samples with various CeO2 loadings by applying the following spectroscopic techniques to the samples: X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy of CO adsorption. XRD showed that ceria agglomerates at high CeO2 loadings (>3 wt %) and at a high temperature of calcination. XPS spectra showed that Ce(III) is formed more easily in the presence of Pt caused by the electron transfer between Pt and CeO2. A variation in the intensity and a shift in the IR bands from CO adsorbed on reduced Pt were observed, as a function of the temperature of reduction and type of the support. A heterogeneous distribution of linearly adsorbed CO on Pt at terraces and defect sites was proposed for Pt/Al2O3 reduced at the lower temperature (623 K), while at the higher temperature of reduction (773 K) a comp...

A microfluidic electrochemiluminescent device for detecting cancer biomarker proteins

Abstract: We describe an electrochemiluminescence (ECL) immunoarray incorporated into a prototype microfluidic device for highly sensitive protein detection and apply this system to accurate, sensitive measurements of prostate-specific antigen (PSA) and interleukin-6 (IL-6) in serum. The microfluidic system employed three molded polydimethylsiloxane (PDMS) channels on a conductive pyrolytic graphite chip (2.5 × 2.5 cm) inserted into a machined chamber and interfaced with a pump, switching valve, and sample injector. Each of the three PDMS channels encompasses three 3 μL analytical wells. Capture-antibody-decorated single-wall carbon nanotube forests are fabricated in the bottom of the wells. The antigen is captured by these antibodies on the well bottoms. Then, a RuBPY-silica-secondary antibody (Ab2) label is injected to bind to antigen on the array, followed by injection of sacrificial reductant tripropylamine (TPrA) to produce ECL. For detection, the chip is placed into an open-top ECL measuring cell, and the channels are in contact with electrolyte in the chamber. Potential applied at 0.95 V versus Ag/AgCl oxidizes TPrA to produce ECL by redox cycling the RuBPY species in the particles, and ECL light is measured by a charge-coupled device camera. This approach achieved ultralow detection limits of 100 fg mL(-1) for PSA (9 zeptomole) and 10 fg mL(-1) (1 zeptomole) for IL-6 in calf serum, a 10-25-fold improvement of a similar non-microfluidic array. PSA and IL-6 in synthetic cancer patient serum samples were detected in 1.1 h and results correlated well with single-protein enzyme-linked immunosorbent assays.