Comparative Kinetic Study and Microwaves Non-Thermal Effects on the Formation of Poly(amic acid) 4,4'-(Hexafluoroisopropylidene)diphthalic Anhydride (6FDA) and 4,4'-(Hexafluoroisopropylidene)bis(p-phenyleneoxy)dianiline (BAPHF). Reaction Activated by Microwave, Ultrasound and Conventional Heating

Green chemistry is the design of chemical processes that reduce or eliminate negative environmental impacts. The use and production of chemicals involve the reduction of waste products, non-toxic components, and improved efficiency. Green chemistry applies innovative scientific solutions in the use of new reagents, catalysts and non-classical modes of activation such as ultrasounds or microwaves. Kinetic behavior and non-thermal effect of poly(amic acid) synthesized from (6FDA) dianhydride and (BAPHF) diamine in a low microwave absorbing p-dioxane solvent at low temperature of 30, 50, 70 °C were studied, under conventional heating (CH), microwave (MW) and ultrasound irradiation (US). Results show that the polycondensation rate decreases (MW > US > CH) and that the increased rates observed with US and MW are due to decreased activation energies of the Arrhenius equation. Rate constant for a chemical process activated by conventional heating declines proportionally as the induction time increases, however, this behavior is not observed under microwave and ultrasound activation. We can say that in addition to the thermal microwave effect, a non-thermal microwave effect is present in the system.     

Nanomaterials and the environment: a review for the biennium 2008-2010

Applications of nanotechnology are touching almost every aspect of modern life. The increased use of engineered nanomaterials (ENMs) in consumer products, chemical and medical equipment, information technology, and energy, among others, has increased the number of publications (informative and scientific) on ENMs. By the 1950s, very few papers were committed to nanomaterials (NMs), but in 2009, more than 80,000 journal articles included the concept nanotechnology. The objective of this review is to compile and analyze publications on NMs in the biennium 2008-2010. This review includes the most recent publications in risk assessment/toxicity, characterization and stability, toxicity, fate and transport of NMs in terrestrial ecosystems, and new ENMs. Carbon nanotubes, metallic, metal oxides and hydroxides nanoparticles, quantum dots, and polystyrene NPs are included.     

Comparison of Antimutagenic Activity of Phenolic Compounds in Newly Harvested and Stored Common Beans Phaseolus vulgaris against Aflatoxin B1

ABSTRACT: Phenolic compounds were extracted from recently harvested or stored black Jamapa beans ( Phaseolus vulgaris ) that were subjected or not to thermal treatment. The beans studied were cropped in the same area and were from the same lot. The highest amount of condensed tannins (CT) was found in the seed coat of recently harvested beans [222.41 ± 16mg of (+)-catechin equivalents per gram of seed coat]. After 2 yof storage, the amount of CT dropped significantly [35.8 ± 3.4 mg of (+) -catechin equivalents per gram of seed coat]. Thermal treatment significantly reduced the amount of CT in whole beans by approximately 70%. The raw seeds contained 13.76 ±1.2 mg of (+)-cat-echin equivalents per gram of seeds and a portion of CT appeared in the broth [9.4 ± 0.1 mg of (+) -catechin equivalents per gram of lyophilized broth]. The antimutagenic activity of these extracted phenolic compounds was tested against aflatoxin B₁ (AFB₁) in the Kado microsuspension assay. Newly harvested beans showed higher antimutagenic activity against AFB₁ mutagenicity than stored beans. The results suggest that to take the maximum advantage of components with biological activity present in beans, they must be used fresh.     

Frozen Foods Treated by Pressure Shift Freezing: Proteins and Enzymes

ABSTRACT: This work was focused on the changes that potatoes undergo after pressure shift freezing (PSF) treatment on protein content, peroxidase (POD), and polyphenoloxidase (PPO) enzymes. The samples were subjected to different conditions of P/T (210 MPa at −20°C; 180 MPa at −16°C; 150 MPa at −12°C; and 120 MPa at −8°C). Results showed that none of these conditions were enough to inactivate the POD and PPO enzymes. The POD was more resistant than PPO. Three isoenzymes of POD (61, 51, and 46 kDa) were detected. The protein content decreased about 50% after the PSF treatment at 210 MPa, −20°C; however, sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed 2 bands of about 21 kDa quite resistant to the treatment. On the contrary, mass spectrometry revealed among the resistant proteins, 2 fragments of pH 8.5 and about 20 kDa were more sensitive to 150 MPa, −12°C. The 2 fragments matched to a Solanum tuberosum proteinase inhibitor II protein     

Classification of unaltered and altered dry-cured ham by impedance spectroscopy: A preliminary study

The aims of this work were characterized by the physicochemical and microbiological features of dried-cured hams classified by the manufacturer as altered (deep spoilage and swollen) and unaltered, as well as, correlated these results with the electronic measurements of impedance spectroscopy, in order to lay the groundwork to design a suitable electrode to be used for checking in line all dry-cured ham elaborated. Double electrode and coaxial needle electrode were used in a frequency range of 100 Hz to 1 MHz. The electronic measurements of the two electrodes were able undoubtedly to discriminate between altered and unaltered dry-cured hams; moreover a tendency to classify between deep spoilage and swollen hams was shown. The values into the range of frequencies between 100 Hz–1000 Hz, for both electrodes, showed the best clustering results. More studies are needed to select the best electrode which can be transformed in a robust and versatile electrode which could be used for checking in line all dry-cured ham elaborated.     

Relation of total cholesterol in serum tocopherols, probabilistic study in Mexican children

Epidemiological studies have shown the effect of nutritional status of tocopherols and development of cardiovascular diseases that now are more frequent during early years of life. In this work we evaluated the association between the total cholesterol and serum levels of tocopherols in a population of Mexican children in whom we measured the oxidant status and antioxidant capacity (December 2003). In 1155 children (12-59 months) residents of urban and rural locations we quantified in serum alpha-tocopherol, gamma-tocopherol and total cholesterol; the antioxidant capacity and oxidative status were evaluated with the production of TBARS. Children with serum cholesterol < 170 mg/dL had an average of 472.5 +/- 179.6 microg/dL tocopherol in serum and > or = 240 mg/dL cholesterol recorded an average of 577.3 +/- 200.8 microg/dL. However, when tocopherols were expressed in relation to total cholesterol (micromol/mmol) found that children with < 170 mg/dL had the highest ratios (3.06 +/-1.19) which places them in an adequate nutritional status of tocopherol, unlike the group with > or = 240 mg/dL of cholesterol in whom the relationship was low (1.93 +/- 0.69). There were no differences in serum antioxidant capacity, but if in the production of TBARS for children with > or = 200 mg/dL cholesterol. In preschools the increases in total cholesterol limits the availability of serum tocopherol for circulating lipids, this condition over time could determine the early development of vascular injury mediated by oxidative stress.     

Synthesis and characterization of hydrophilic copolymers of maleimide derivatives with 2‐hydroxyethyl methacrylate: electrochemical and thermal behavior

BACKGROUND: The high‐technology industries have been the driving force in the development of new synthetic polymers that combine thermal stability with specific functional properties. In this study p‐chlorophenylmaleimide, p‐hydroxyphenylmaleimide and p‐nitrophenylmaleimide (R‐PhMI) with 2‐hydroxyethyl methacrylate (HEMA) were synthesized by free radical polymerization to obtain hydrophilic polymers, in order to study the effect of the p‐chloroaryl, p‐hydroxyaryl or p‐nitroaryl group on the copolymer composition, electrochemical behavior and thermal properties. RESULTS: The thermal behavior was correlated with the copolymer composition and functional groups, maleimide derivatives, on the copolymers. Thermal decomposition temperature (TDT) and glass transition temperature (T_g) were influenced by the functional groups of R‐PhMI moiety on the copolymer. The polymers showed an electrochemically irreversible reduction process under the conditions tested. CONCLUSION: Poly[(p‐chloromaleimide)‐co‐(2‐hydroxyethyl methacrylate)] copolymer shows a higher TDT than poly[(p‐hydroxymaleimide)‐co‐(2‐hydroxyethyl methacrylate)] or poly[(p‐nitromaleimide)‐co‐(2‐hydroxyethyl methacrylate)] (NPHE). T_g decreases in going from nitro to hydroxyl to chloro groups. The NPHE copolymer shows a lower stability, losing weight at 200 °C. The NPHE copolymer shows a well‐defined reduction wave which is similar to those of the other copolymers and it also shows an additional quasi‐reversible reduction wave corresponding to the nitrobenzene group. Copyright © 2009 Society of Chemical Industry     

Total Energy Balance Method for Venting Electric Clothes Dryers

A total energy balance method for venting electric tumbler dryers was developed and the experimental methodology and calculation details are provided in this article. The energy to evaporate the water in the load; the energy to heat the water, textile, and dryer; energy losses by convection and radiation; and the energy not used in the process were considered to calculate the total output energy. This method was applied to a domestic venting electric tumble dryer. The results of the method suggested areas of improvement. The maximum difference between the measured total input and the calculated total output energies was 2.6%, indicating the accuracy of the method.     

State of the art in silico tools for the study of signaling pathways in cancer

In the last several years, researchers have exhibited an intense interest in the evolutionarily conserved signaling pathways that have crucial roles during embryonic development. Interestingly, the malfunctioning of these signaling pathways leads to several human diseases, including cancer. The chemical and biophysical events that occur during cellular signaling, as well as the number of interactions within a signaling pathway, make these systems complex to study. In silico resources are tools used to aid the understanding of cellular signaling pathways. Systems approaches have provided a deeper knowledge of diverse biochemical processes, including individual metabolic pathways, signaling networks and genome-scale metabolic networks. In the future, these tools will be enormously valuable, if they continue to be developed in parallel with growing biological knowledge. In this study, an overview of the bioinformatics resources that are currently available for the analysis of biological networks is provided.     

Multivariate analysis for the differentiation of sparkling wines elaborated from autochthonous Spanish grape varieties: volatile compounds, amino acids and biogenic amines

The aim of this work was to focus on the study of the volatile composition of white and rosé base wines elaborated from different autochthonous grape varieties in Spain (Verdejo, Viura, Malvasía, Albarín, Godello, Prieto Picudo and Garnacha) and the evolution of the sparkling wines elaborated from them following the “champenoise” method. The amino acids and biogenic amines were also studied. Multivariate analyses (factorial and stepwise discriminant) were carried out to study the influence of these compounds all together. Base and sparkling wines from Albarín, Verdejo, Godello and Prieto Picudo were the richest in most of the volatile compounds analyzed, especially of ethyl esters and alcohol acetates, compounds that contribute to the fruity aroma of wines. During the aging on lees in the bottle of sparkling wines, an increase in branched ethyl esters, ethyl lactate and γ-butyrolactone, and a decrease in terpenes (mainly citronellol and geraniol) were observed. In general, the levels of biogenic amines in all the sparkling wines studied were very low, which does not represent a negative effect on their quality and safety.