Aqueous solution behavior of thermosensitive (N-isopropylacrylamide-acrylic acid-ethyl methacrylate) terpolymers

A series of N-isopropylacrylamide (NIPAM)-acrylic acid-ethyl methacrylate terpolymers with varied monomer compositions was prepared by radical polymerization. The solution behavior of these polymers was studied in dilute aqueous solution using spectrophotometry, fluorescence spectroscopy and high-sensitivity differential scanning calorimetry. The results obtained revealed that the lower critical solution temperatures depend strongly on the copolymer composition, solution pH and ionic strength. At a high pH, the ionization of acrylic acid (AA) units leads to an increase in solution cloud points (T-c). Solutions of polymers containing 10% or less of AA display a constant T-c for pH above 5.5, with 15% there is a continuous increase in T-c with pH and, for higher AA contents, no clouding was observed within the studied temperature range. Fluorescence probe studies were conducted by following the I (1)/I (3) ratio of pyrene vibronic bands and the emission of anilinonaphtalene sulfonic acid, sodium salt (ANS), both approaches revealing the existence of hydrophobic domains for polymers with higher ethyl methacrylate content at temperatures lower than T-c, suggesting some extent of aggregation and/or a coil-to-globule transition. Scanning calorimetry measurements showed an endothermic transition at temperatures agreeing with the previously detected cloud points. Moreover, the transition curves became broader and with a smaller transition enthalpy, as both the AA content and the solution pH were increased. These broader transitions were interpreted to be the result of a wider molecular distribution upon polymer ionization, hence, displaying varied solution properties. The decrease in transition enthalpy was rationalized as a consequence of reminiscent hydration of NIPAM units, even after phase separation, owing to the presence of electric charges along the polymer chain.

Identification and Analyses of Candidate Genes for Rpp4-Mediated Resistance to Asian Soybean Rust in Soybean

Asian soybean rust is a formidable threat to soybean (Glycine max) production in many areas of the world, including the United States. Only five sources of resistance have been identified (Resistance to Phakopsora pachyrhizi1 [Rpp1], Rpp2, Rpp3, Rpp4, and Rpp5). Rpp4 was previously identified in the resistant genotype PI459025B and mapped within 2 centimorgans of Satt288 on soybean chromosome 18 (linkage group G). Using simple sequence repeat markers, we developed a bacterial artificial chromosome contig for the Rpp4 locus in the susceptible cv Williams82 (Wm82). Sequencing within this region identified three Rpp4 candidate disease resistance genes (Rpp4C1-Rpp4C3 [Wm82]) with greatest similarity to the lettuce (Lactuca sativa) RGC2 family of coiled coil-nucleotide binding site-leucine rich repeat disease resistance genes. Constructs containing regions of the Wm82 Rpp4 candidate genes were used for virus-induced gene silencing experiments to silence resistance in PI459025B, confirming that orthologous genes confer resistance. Using primers developed from conserved sequences in the Wm82 Rpp4 candidate genes, we identified five Rpp4 candidate genes (Rpp4C1-Rpp4C5 [PI459025B]) from the resistant genotype. Additional markers developed from the Wm82 Rpp4 bacterial artificial chromosome contig further defined the region containing Rpp4 and eliminated Rpp4C1 (PI459025B) and Rpp4C3 (PI459025B) as candidate genes. Sequencing of reverse transcription-polymerase chain reaction products revealed that Rpp4C4 (PI459025B) was highly expressed in the resistant genotype, while expression of the other candidate genes was nearly undetectable. These data support Rpp4C4 (PI459025B) as the single candidate gene for Rpp4-mediated resistance to Asian soybean rust.

A Semi-Continuous Analyzer for the Fluorimetric Determination of Atmospheric Formaldehyde

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Expression, purification and spectroscopic analysis of an HdrC: An iron-sulfur cluster-containing protein from Acidithiobacillus ferrooxidans

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Interaction of the nonionic surfactant C12E8 with high molar mass poly(ethylene oxide) studied by dynamic light scattering and fluorescence quenching methods

Dynamic light scattering has been used to investigate ternary aqueous solutions of n-dodecyl octaoxyethylene glycol monoetber (C12E8) with high molar mass poly(ethylene oxide) (PEO). The measurements were made at 20 °C, always below the cloud point temperature (Tc) of the mixed solutions. The relaxation time distributions are bimodal at higher PEO and surfactant concentrations, owing to the preacute of free surfactant micelles, which coexist with the slower component, representing the polymer coil/micellar cluster comptex. As the surfactant concentration is increased, the apparent hydrodynamic radius (RH) of the coil becomes progressively larger. It is suggested that the complex structure consists of clusters of micelles sited within the polymer coil, as previously concluded for the PEO-C12E8-water system. However. C12E8 interacts less strongly than C12E8 with PEO; at low concentrations of surfactant the complex does not contribute significantly to the total scattered intensity. The perturbation of the PEO coil radius with C12E8 is also smaller than that in the C12E8 system. The addition of PEO strongly decreases the clouding temperature of the system, as previously observed for C12E8/PEO mixtures in solution Addition of PEO up to 0.2% to C12E8 (10 wt %) solutions doss not alter the aggregation number (Nagg) of the micelles probably because the surfactant monomers are equally partitioned as bound and unbound micelles. The critical micelle concentration (cmc), obtained from the I1/I3 ratio (a measure of the dependence of the vibronic band intensities on the pyrene probe environment), does not change when PEO is added, suggesting that for neutral polymer/surfactant systems the trends in Nagg and the cmc do not unambiguously reflect the strength of interaction.

Design studies of the magnetic properties of structural materials affecting the magnetic field of high-homogeneity superconducting magnets

Austenitic stainless steel presents phase changes caused by heat treatment and welding processes. Because it represents a problem in the design of high-homogeneity magnets, we have been studying the magnetic properties of Ti alloys for their use instead of stainless steel as structural material for superconducting magnet construction. In this work, we present the comparative study of the influence of magnetic properties of steel and Ti alloys on the magnetic-field homogeneity of a superconducting coil through numerical calculation using the measured magnetic properties. © 2001 Elsevier Science B.V. All rights reserved.

Avaliação de desempenho do microaspersor amanco em bancada de testes

The need for a rational use of water and supply of food for a growing world population have led to the development of research in the area of irrigation systems. Thus, some irrigation systems which join efficiency with low cost of material have been developed. Although some technical characteristics are provided by the manufacturers, tests are required to verify functioning of the system and uniformity of water distribution. Continuous research on uniformity, characteristics of the materials and design of water distribution systems is essential for system improvement. Therefore, the objective of this work was to evaluate the CV (manufacturer's coefficient of variation) of Amanco microsprinkler (1.0 mm light green nipple) using bench testing in the laboratory of Irrigation at UNESP - FCA campus of Botucatu-SP. Twenty-five microsprinklers in a sequential design were used in the tests. Three flow systems were tested as follows: a Coil system based on serial connected pipes; a Lateral system, the most common system in which secondary lines are fed by a main line; and a Mesh system used in the urban water supply. The results showed that 4.17% CVf met the production standards and the Lateral and Mesh systems were similar regarding outflow using bench testing. The Mesh system presented the highest mean value of outflow and the lowest range of variation.

Rational use of residential digesters for sewage treatment with Carbon Credits

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

On the Chaotic Suppression of Both Ideal and Non-ideal Duffing Based Vibrating Systems, Using a Magnetorheological Damper

In this paper the dynamics of the ideal and non-ideal Duffing oscillator with chaotic behavior is considered. In order to suppress the chaotic behavior and to control the system, a control signal is introduced in the system dynamics. The control strategy involves the application of two control signals, a nonlinear feedforward control to maintain the controlled system in a periodic orbit, obtained by the harmonic balance method, and a state feedback control, obtained by the state dependent Riccati equation, to bring the system trajectory into the desired periodic orbit. Additionally, the control strategy includes an active magnetorheological damper to actuate on the system. The control force of the damper is a function of the electric current applied in the coil of the damper, that is based on the force given by the controller and on the velocity of the damper piston displacement. Numerical simulations demonstrate the effectiveness of the control strategy in leading the system from any initial condition to a desired orbit, and considering the mathematical model of the damper (MR), it was possible to control the force of the shock absorber (MR), by controlling the applied electric current in the coils of the damper. © 2012 Foundation for Scientific Research and Technological Innovation.

Estimation of spontaneous blinking main sequence in normal subjects and patients with Graves' upper eyelid retraction

Purpose. We quantified the main sequence of spontaneous blinks in normal subjects and Graves' disease patients with upper eyelid retraction using a nonlinear and two linear models, and examined the variability of the main sequence estimated with standard linear regression for 10-minute periods of time. Methods. A total of 20 normal subjects and 12 patients had their spontaneous blinking measured with the magnetic search coil technique when watching a video during one hour. The main sequence was estimated with a power-law function, and with standard and trough the origin linear regressions. Repeated measurements ANOVA was used to test the mean sequence stability of 10-minute bins measured with standard linear regression. Results. In 95% of the sample the correlation coefficients of the main sequence ranged from 0.60 to 0.94. Homoscedasticity of the peak velocity was not verified in 20% of the subjects and 25% of the patients. The power-law function provided the best main sequence fitting for subjects and patients. The mean sequence of 10-minute bins measured with standard linear regression did not differ from the one-hour period value. For the entire period of observation and the slope obtained by standard linear regression, the main sequence of the patients was reduced significantly compared to the normal subjects. Conclusions. Standard linear regression is a valid and stable approximation for estimating the main sequence of spontaneous blinking. However, the basic assumptions of the linear regression model should be examined on an individual basis. The maximum velocity of large blinks is slower in Graves' disease patients than in normal subjects. © 2013 The Association for Research in Vision and Ophthalmology, Inc.

Dimerization of aurein 1.2: Effects in structure, antimicrobial activity and aggregation of Cândida albicans cells

Antimicrobial peptides (AMPs) are a promising solution to face the antibiotic-resistant problem because they display little or no resistance effects. Dimeric analogues of select AMPs have shown pharmacotechnical advantages, making these molecules promising candidates for the development of novel antibiotic agents. Here, we evaluate the effects of dimerization on the structure and biological activity of the AMP aurein 1.2 (AU). AU and the C- and N-terminal dimers, (AU)2K and E(AU)2, respectively, were synthesized by solid-phase peptide synthesis. Circular dichroism spectra indicated that E(AU)2 has a coiled coil structure in water while (AU)2K has an α-helix structure. In contrast, AU displayed typical spectra for disordered structures. In LPC micelles, all peptides acquired a high amount of α-helix structure. Hemolytic and vesicle permeabilization assays showed that AU has a concentration dependence activity, while this effect was less pronounced for dimeric versions, suggesting that dimerization may change the mechanism of action of AU. Notably, the antimicrobial activity against bacteria and yeast decreased with dimerization. However, dimeric peptides promoted the aggregation of C. albicans. The ability to aggregate yeast cells makes dimeric versions of AU attractive candidates to inhibit the adhesion of C. albicans to biological targets and medical devices, preventing disease caused by this fungus. © 2013 Springer-Verlag Wien.

Estruturação do Eumenine Mastroparano por dinâmica molecular em misturas de TFE-água

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Análise conformacional dos petídeos protonectina e protonectina (1-6), isolados e em associação, em mistura TFE-água

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Contribuição eletrostática e não eletrostática na interação de peptídeos líticos com membranas modelo

Pós-graduação em Biofísica Molecular - IBILCE

Síntese e estudos estrutura/função de um peptídeo extraído da rã Hypsiboas albopunctatus e análogos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)