Study of nanofiber scaffolds of PAA,PAA/CS,and PAA/ALG for its potential use in biotechnological applications

In recent times, electrospun nanofibers have been widely studied from several biotechnological approaches; in this work, poly(acrylic acid) (PAA) solutions mixed with chitosan and alginate were electrospun and characterized to determine the behavior of these fibers when used in combination with bacteria, different samples were incubated with the bacterial strains: Streptomyces spp., Micromonospora spp., and Escherichia coli and a OD600 test was performed. The formation of nanofibers via electrospinning and the physicochemical properties of the obtained fibers were evaluated. Results showed that the presence of chitosan enhanced the thermal stability of PAA, since PAA/alginate fibers lost 5% of their mass at 41°C, whereas PAA/chitosan lost this amount at around 125°C. The fibers demonstrated suitable characteristics to be used as a bacteria bioreactor.     

Energy storage in symmetric and asymmetric supercapacitors based in carbon cloth/polyaniline–carbon black nanocomposites

In this work, the construction of electrochemical capacitors using polyaniline–carbon black nanocomposites as electrode material is described. Symmetric and asymmetric cells were assembled. The active material was supported on carbon cloth acting as current collector as well. The electrolyte was H₂SO₄ 0.5 M, and the selected potential range was 1 V. The electrochemical behavior of the arrayed supercapacitors was studied by cyclic voltammetry and galvanostatic charge/discharge runs. At a constant current density of 0.3 A/g, a specific capacitance value of 1039 F/g was obtained for a symmetric assembly using both electrodes prepared with polyaniline and carbon black nanocomposites. When the set is asymmetric, being the positive electrode made of polyaniline and carbon black nanocomposites, the specific capacitance value is 1534 F/g. For the latter array, the specific power and energy density values are 300 W/kg and 426 Wh/kg at 0.3 A/g, and 13 700 W/kg and 28 Wh/kg at 13.7 A/g. These results suggest a good capacity of fast energy transfer. Moreover, this asymmetric supercapacitor demonstrated a high stability over 1000 cycles being the loss of only 5%. Copyright © 2015 John Wiley & Sons, Ltd.     

Constituents of Amomum tsao-ko and their radical scavenging and antioxidant activities

Constituents of the fruit of Amomum tsao-ko were investigated following a preliminary screening of the antioxidant activity of several extracts of the fruit of this plant that showed that the dichloromethane extract and the ethyl acetatesoluble and water-soluble fractions of the 70% aqueous acetone extract had higher activity than α-tocopherol and butylated hydroxytoluene (BHT). Eleven compounds were isolated from the ethyl acetate-soluble fraction, and their structures were elucidated as (+)-hannokinol (1), meso-hannokinol (2), (+)-epicatechin (3), (−)-catechin (4), β-sitosterol (5), β-sitosterol 3-O-glucoside (6), 2,6-dimethoxyphenol (7), protocatechualdehyde (8), protocatechuic acid (9), vanillic acid (10), and p-hydroxybenzoic acid (11) based on mass and various nuclear magnetic resonance (NMR) spectroscopic techniques. This is the first isolation of epicatechin and catechin from the genus Amomum. The radical scavenging activity of the isolated compounds was evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and colorimetric and electron spin resonance (ESR) analyses. The antioxidant activity of the compounds was also determined based on the oxidative stability index (OSI). The catechins and catechol derivatives showed strong activities in both the DPPH radical scavenging activity and antioxidant activity assays.     

Study by thermal analysis of composites prepared from silica gel,furfuryl alcohol and acetaldehyde

Composites from furfuryl alcohol, acetaldehyde and silica gel were prepared with trifluoracetic acid as a catalyst. The composites were studied by TGA and DSC. The TGA results showed three main losses of weight, the first of which was ascribed to water. The percentage of polymer in the composites reached a limit value, independently of the ratio of furfuryl alcohol/acetaldehyde used. The layer of polymer that covers the silica was not completely cross‐linked. The composites contain soluble oligomers with 97: M _n < 580 g mol^?1, that could be extracted with THF. The soluble fraction of composites prepared from mixtures of furfurylic alcohol and acetaldehyde decreased as the proportion of the acetaldehyde increased. The DSC of the samples indicated a T_g between ?8 and ?15 °C that disappeared after an extraction with THF. The DSC of the oligomers removed showed a possible T_g at 13 °C and an exothermic peak between 70 and 170 °C which corresponded to an enthalpy of 326.1 J g^?1. © 2003 Society of Chemical Industry     

Deep Oxidation of Benzene on Pt/V2O5–TiO2 Catalysts

The combustion of benzene was studied on Pt supported on V₂O₅–TiO₂ samples containing different amounts of V₂O₅. Vanadium was highly dispersed as V⁴⁺ for low V₂O₅ loadings, forming a vanadia monolayer on titanium dioxide for a V₂O₅ concentration of about 5%wt. V₂O₅–TiO₂ samples were more active than V₂O₅ and TiO₂ single oxides, and the activity increased with the vanadia content. The platinum dispersion in Pt/V₂O₅–TiO₂ catalysts increased with the V₂O₅ loading but the activity for the deep oxidation of benzene exhibited an opposite trend. Benzene combustion was a structure sensitivity reaction promoted on larger metallic Pt crystallites which were preferentially formed when the V₂O₅ content in the sample was decreased.     

Construction of a Systemic Quality Model for Evaluating a Software Product

Quality is currently considered one of the main assets with which a firm can enhance its competitive global position. This is one reason why quality has become essential for ensuring that a company's products and processes meet customers' needs. A recent innovation in the systems area is the development of a set of mechanisms and models for evaluating quality. This article describes the design of a Quality Model with a systemic approach to software products that assesses a product's efficiency and effectiveness. Different quality models were studied: McCall, Boehm, FURPS, ISO 9126, Dromey, ISO 15504 in an attempt to identify the aspects present in these models that are deemed important in a Systemic Quality model. We designed a model prototype that reflects the essential attributes of quality. This model was evaluated using a method so it can be validated and also enhanced. The evaluation method consisted of: designing a survey, formulating, validating and applying the measurement instruments; defining an algorithm to obtain the quality estimate and analyzing the results. The model prototype enabled the strengths and weaknesses of the software products studied to be identified. When evaluating a software product using the model prototype, it was possible to ascertain its compliance with the standards and use the results to improve it. Since the evaluation was systemic, processes that affect certain characteristics of the product could be identified. Companies can benefit from the model proposed because it serves as a benchmark that allows their products to evolve and be competitive.     

Mechanical and Fracture Behaviour Evaluation of Commercial Acrylic Bone Cements

The deformation and fracture behaviour of some commercial acrylic bone cements have been investigated. Cements were characterized by gel permeation chromatography, dynamic mechanical analysis and scanning electron microscopy. The influence of liquid to powder ratio, curing temperature, strain rate and non-reacted monomer was analysed for one radiolucent cement. Results showed that the β transition activation process influences both deformation and fracture behaviour. Fracture surface stress whiteness revealed the presence of crazes as the main plastic deformation mechanism. Non-reacted monomer acted as a plasticizer leading to materials with lower yield strength, σ_y, that induces crack tip blunting and improves toughness. It appears that the presence of radiopacifier fillers also improves fracture toughness by promoting interactions between the crack and the second phase dispersion. © 1997 SCI.     

Survival to different acid challenges and outer membrane protein profiles of pathogenic Escherichia coli strains isolated from pozol, a Mexican typical maize fermented food

In this study, the acid resistance and the changes in outer membrane protein (Omps) profiles of Escherichia coli strains isolated from pozol, an acid-fermented maize beverage consumed in Southeastern Mexico, were determined. Results showed that adaptation to acid by these E. coli strains significantly enhances their survival in acid conditions. Changes in Omp profiles were found in non-adapted acid challenged cells compared with non-challenged cells that had not been adapted to acid. Challenged adapted cells showed no significant changes in these profiles when compared with the acid adapted non-challenged strains. N-terminal sequences of some of the Omps were determined. The intensity of the main porins OmpC and OmpA was lower in the acid challenged strains, than in the non-challenged ones. The OmpF porin was identified in non-challenged K12 strain, but did not appear in adapted or non-adapted pozol strains nor in E. coli O157:H7. A protein band with an approximate molecular mass of 22 kDa corresponds to OmpW and its expression decreased in pozol strains challenged with HCl and lactic acid. OmpX was one of the main proteins expressed when strains were acid challenged with organic acids. Seventy out of seventy-three E. coli strains isolated from pozol in a previous work [Sainz, T., Wacher, C., Espinoza, J., Centurion, D., Navarro, A., Molina, J., Cravioto, A., Eslava, C., 2001. Survival and characterization of Escherichia coli strains in a typical Mexican acid-fermented food. International Journal of Food Microbiology 71, 169-176] carry this gene and belong to a reported pathogenic class of E. coli strains, or have virulence factors or survived at pH values less than 4.8. We suggest this protein could be involved in survival to stress conditions.     

Switchgrass pretreatment and hydrolysis using low concentrations of formic acid

BACKGROUND: Acid hydrolysis using organic acids is a promising approach for liquefying biomass without introducing any additional inorganic salt species into the reaction media. Formic acid may be a very useful acid catalyst for biomass pre‐treatment because (i) it is an effective, strong acid catalyst, (ii) it is no more corrosive than sulfuric acid, (iii) it is an organic acid, so it adds noinorganic salt species that might negatively impact downstream catalysis, and (iv) it can be produced from biomass, making ita green reagent. RESULTS: At pH_{25 °C} = 1.65, formic acid yielded high dissolution of switchgrass (52 wt%) at a high temperature (200 °C), comparable with the dissolution yield achieved using sulfuric acid. When treated 9/1 wt/wt with an 8 wt% aqueous solution of formic acid at 150 °C for 1 h, 44 wt% of switchgrass was dissolved, yielding 63 wt% of the carbohydrates from switchgrass. CONCLUSIONS: The efficiency of formic acid for the hydrolysis and dissolution of the carbohydrate fraction of switchgrass was proved and compared with other organic and mineral acids. The liquid product of pretreatment of switchgrass using formic acid at both 150 °C and 200 °C showed that 24 wt% and 28 wt%, respectively, of soluble monosaccharides after enzymatic hydrolysis consisted of glucose. Copyright © 2011 Society of Chemical Industry     

Effect of soluble fiber on the physicochemical properties of cactus pear (Opuntia ficus indica) encapsulated using spray drying

The effects of red cactus pear encapsulation using spray drying with soluble fiber were evaluated. Cactus pear juice was mixed with 15, 22.5, or 30% soluble fiber and dried at 160, 180, or 200°C. Juice showed high levels of polyphenols, quercetin, kaempferol, isoharmetin, betacyanins, betaxanthins, and a high antioxidant activity. Increased soluble fiber amounts significantly (p<0.05) increased the pH, aw, water solubility index (WSI), L*, and b* values. Levels of polyphenols and betacyanins decreased significantly (p<0.05) as the soluble fiber content and the drying temperature increased, respectively. Encapsulation at 160°C and 22.5% of soluble fiber yielded good physical properties and high bioactive compounds. Microscopic analysis showed spherically shaped capsules, the shape was affected by the concentration of added soluble fiber. Low soluble fiber concentrations were associated with more collapsed capsules. Soluble fiber for encapsulating cactus pear resulted in a powder with good properties that can be used as a food ingredient.