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Molin J.P.,University of Sao Paulo | Rabello L.M.,Embrapa Instrumentacao
Engenharia Agricola

The electric conductivity is the capacity of a material in driving electric current and one of its usefulness in the agriculture comes from the fact that the soil electrical conductivity (EC) varies with its intrinsic physicochemical variability. The objective of this work was to study the EC behavior and advance on the factors understanding that affects its variability, and develops systems for measuring and mapping EC. We built a system with several measurement configurations, and on the field tests the results were partially satisfactory. In a detailed study using only a commercial EC measuring equipment the results clearly indicated that EC relates with soil texture and moisture, and may represent an important and low price tool for collecting data and characterizing soil physical properties. Source

Venancio T.,Federal University of Sao Carlos | Colnago L.A.,Embrapa Instrumentacao
Magnetic Resonance in Chemistry

Continuous wave-free precession (CWFP) pulse sequence employing time domain nuclear magnetic resonance spectroscopy (TD-NMR) was used to measure longitudinal (T1) and transverse relaxation times (T2), during the cure of a commercial epoxy resin (AralditeTM) with a 10-min solidification time. The intensity of the NMR signal after the first pulse and in the CWFP regime were used to monitor the concentration of the monomers, and the relaxation times were used to monitor the chain mobility. The main advantage of CWFP over the standard methods to measure relaxation times, inversion recovery (inv-rec) for T1 and Carr-Purcell-Meiboom-Gill (CPMG) for T2, is that the measurement of both relaxation times can be performed in a fast and single NMR experiment and, therefore, using a single reaction batch. CWFP is also as fast as the CPMG measurement but at least fivefold faster than the method to obtain T1 using null point approximation in the inv-rec method. Therefore, the CWFP sequence can be used as a fast and general method to measure relaxation times in polymerization reactions, even with fast solidification time. As a TD-NMR technique, CWFP can be employed in any low-cost bench top TD-NMR equipment commonly used in an academic or industrial laboratory. Copyright © 2012 John Wiley & Sons, Ltd. Source

Kock F.V.C.,University of Sao Paulo | Colnago L.A.,Embrapa Instrumentacao
Carbohydrate Polymers

Time-domain NMR relaxometry was proposed as a simple, rapid method to monitor chitosan (CS) coagulation as a function of pH. The longitudinal (T1) and transverse (T2) relaxation times of three CS concentrations (0.022, 0.22, and 2.2 g L-1) were simultaneously measured by CP-CWFPx-x pulse sequences in a 0.47 T spectrometer. T1 and T2 were shown to be independent of pH as well as to assume values similar to the relaxation time of water (2.7 s) at the lowest tested CS concentration. At the highest concentration, T1 increased whereas T2 decreased as pH varied from 6.0 to 7.0. This indicates a remarkable effect of CS on water relaxation at pH values higher than the pKa of CS amino groups (6.5). Therefore, CS reduced the water mobility at the highest CS concentration and greatest pH values, suggesting a CS supramolecular structure (gel) that entraps the solvent in confined regions. The method proposed here can be further used to study the coagulation of other polysaccharides. © 2016 Elsevier Ltd. All rights reserved. Source

Kock F.V.C.,University of Sao Paulo | Colnago L.A.,Embrapa Instrumentacao
Microchemical Journal

T1 and T2 relaxation times, measured with rapid and simultaneous continuous wave free precession (CWFP) and Carr-Purcell-continuous wave free precession (CP-CWFP) pulse sequences were used to study complexes of EDTA with paramagnetic ions in solution. The relaxation times of Cu(II)-EDTA and [CuEDTA.NH3]-2 complexes, from pH1 to 13, measured in a 0.47T time-domain nuclear magnetic resonance (TD-NMR) spectrometer show good agreement with the absorbance at approximately 730nm. These methods were also used to study colorless complexes containing paramagnetic ions, not accessible by electronic spectroscopy, such as Mn(II)-EDTA. Therefore, these sequences can be used in any bench top TD-NMR spectrometers as faster alternative to spectrophotometry in analytical routine analyses. © 2015 Elsevier B.V. All rights reserved. Source

Delabona P.D.S.,Federal University of Sao Carlos | Pirota R.D.P.B.,Federal University of Sao Carlos | Codima C.A.,Federal University of Sao Carlos | Tremacoldi C.R.,Embrapa Amazonia Oriental | And 2 more authors.
Biomass and Bioenergy

The successful strategy to produce cellulolytic enzymes includes both microorganism selection and improved fermentation process conditions. This work describes the isolation, screening and selection of biomass-degrading fungi species from the Amazon forest and analyzes the enzymatic complex produced by a selected strain of Aspergillus fumigatus cultivated using different agro-industrial residues (wheat bran, sugarcane bagasse, soybean bran, and orange peel) as substrate in solid state fermentation (SSF). The profile of endoglucanase (CMCase), FPase, β-glucosidase and xylanase enzymatic activities obtained during 120h of cultivation is presented. Enzyme activities up 160.1IUg-1 for CMCase, 5.0FPUg-1 for FPAse, 105.82IUg-1 for β-glucosidase and 1055.62IUg-1 for xylanase were achieved. The enzymatic extract with higher CMCase activity was used to run a zymogram analysis that showed 3 bands of endoglucanase activity. Characterization studies of this extract showed that the CMCase was most active at either 65°C or pH 3-3.5, indicating that this microorganism produces a thermophilic and acid endoglucanase. These data demonstrate that the fungal isolates from the Amazon forest are a potential source of cellulases and xylanases, providing support to further studies related to the use of these microorganisms to obtain the enzymes needed for biomass conversion. © 2011 Elsevier Ltd. Source

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