Luminescent polydibenzothiophene thin film obtained by glow discharge method

This work presents the synthesis by plasma and characterization of luminescent polymer thin films of dibenzothiophene (DBT) by plasma polymerization. The DBT is solid at room conditions and was sublimated and introduced to the plasma reactor to produce the chemical reactions with the vapors. The results indicated the production of polymers with benzene and thiophene rings in the structure as well as methylene groups. The polymer structure was studied by Fourier transform infrared spectroscopy and ¹³C‐CPMAS. The thermal analysis showed a residual mass of 60% at 800°C, which suggests a great thermal resilience in the polymer. The critical superficial tension was calculated with a Zisman plot and was 25 mN/m. The polymer has a fluorescent green emission between 400 and 660 nm and an orange emission between 660 and 850 nm. This effect can be a consequence of the electronic distribution along the structure in aliphatic and aromatic segments with benzene and thiophene rings. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Electrical,mechanical, and piezoresistive properties of carbon nanotube–polyaniline hybrid filled polydimethylsiloxane composites

The electrical, mechanical, and piezoresistive properties of ternary composites based on elastomeric polydimethylsiloxane (PDMS), carbon nanotubes (CNTs), and polyaniline (PANI) were studied and compared with those of binary PDMS–CNT composites. The presence of PANI affected the percolating network of the CNTs. At lower PANI concentrations (2.5 and 5%), the conductive network of the CNTs was constructively modified; this led to an enhancement in the conductivity in the sample containing 2% CNTs. A higher PANI content (7.5%) hindered the flow of main charge carriers through the composite. The piezoresistive response of the binary and ternary composites was studied by cyclic experiments under compression loads. In all of the samples, the electrical resistance increased monotonically up to a 10% strain. The reproducibility of the piezoresistive behavior in the binary and ternary composites provided evidence that the fillers could reversibly recover their initial position together with the PDMS chains without a significant displacement with respect to their original positions. The reduction of the piezoresistive sensibility by PANI addition was attributed to the displacement restrictions of the CNTs within the composite under pressure because of the volume exclusion of PANI particles; this maintained the probability of CNT contact and increased the possibility of the formation of new CNT conductive channels. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44780.     

Genetic variants in SLC22A1 are related to serum lipid levels in Mexican women

Dyslipidemia is the main risk factor for coronary artery disease and is characterized by alterations in concentrations of lipids, including low-density lipoprotein cholesterol (LDL-c), high-density lipoprotein cholesterol (HDL-c), and triacylglycerols. The participation of several genes in the development of dyslipidemia has been evidenced. Genetic variants in SLC22A1 have been associated with elevated cholesterol and LDL-c levels. The aim of this study was to evaluate the association between single-nucleotide polymorphisms (SNPs) in the SLC22A1 gene with atherogenic risk lipid levels in Mexican women. Anthropometric and biochemical measurements were performed, and four SNPs in SLC22A1 were genotyped by real-time polymerase chain reaction. The Hardy–Weinberg equilibrium was verified, and haplotype frequencies were calculated. We found significant differences between the allele frequencies of the SNPs analyzed with those reported in Mexico and in the world, which could be due to differences in the historical admixture of the women studied. Generalized linear models were evaluated to determine the association between genotypes and haplotypes with lipids levels. We identified a significant increase in total cholesterol and LDL-c levels in women who were carriers of the GA and AG genotypes of the polymorphisms rs628031 and rs594709, respectively, significant effect that is also shown in a dominant inheritance model. Interestingly, we identified an important relationship of the AGC-GAT haplotype with the elevation in LDL-c levels and AGA-GAT haplotype with the elevation in HDL-c levels. On the other hand, we found a strong linkage disequilibrium between the polymorphisms studied. Our results show that variants in the SLC22A1 gene influence serum levels of atherogenic risk lipids, suggesting that these variants probably affect the function of organic cation transporter-1 and therefore, on the regulation of lipid metabolism.     

Synthesis of Li4SiO4 by a Modified Combustion Method

We report for the first time the synthesis of Li₄SiO₄ by the modified combustion method, a rapid chemical process that takes 5 min for completion. This method uses nonoxidizer compounds instead of nitrate mixtures, which are not always commercially available.
The effects of the following parameters on the production of Li₄SiO₄ were studied: (1) different lithium hydroxide:silicic acid:urea (LiOH:H₂SiO₃:CH₄N₂O) molar ratios; (2) the presence of air flow in the furnace chamber; and (3) the furnace heating temperature. It was found that LiOH:H₂SiO₃:CH₄N₂O molar ratios 6:1:3 heated at 1100°C in the presence of additional air in the muffle chamber formed the best precursors to produce Li₄SiO₄.     

Modification of clarified polypropylene by oxygen plasma to improve the adhesion of thin amorphous hydrogenated carbon films deposited by plasma enhanced chemical vapor deposition

Despite having many potential applications, polypropylene (PP) has limitations that may make its application difficult when there is a requirement for high transparency and low‐gas permeability. In this context, studies have been reported about the usage of amorphous hydrogenated carbon thin films to act as a functional barrier in polymer packaging. Therefore, this current work evaluated the modification on the surface‐clarified polypropylene (cPP) by oxygen plasma to improve the adhesion of amorphous hydrogenated carbon films (a‐C:H) deposited by plasma‐enhanced chemical vapor deposition. However, some applications of these films are limited by the presence of microdefects and low adhesion when applied onto polymeric substrates. So, the surface of cPP was treated with oxygen plasma, and the adhesion between the a‐C:H films and cPP was evaluated. Contact angle goniometry, infrared spectroscopy, and atomic force microscopy were used to analyze chemical and morphological changes, respectively. Tape test and scanning electron microscopy were used to evaluate the adhesion of a‐C:H films deposited on a cPP surface. The results showed that the pretreatment increased the adhesion between the cPP and amorphous hydrogenated carbon, which is crucial for the application of these films in packaging with high‐barrier properties. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Improvement of the Molar Tube Bond Durability with Preheated Orthodontic Adhesive

This study aimed to evaluate the effect of preheated orthodontic adhesives and thermal cycling on the bond strength of molar tubes. One hundred sixty molar tubes were bonded to acid-etched bovine incisors using a conventional orthodontic adhesive (Transbond XT), two microhybrid (Wave and Permaflo), and a nanofilled (Filtek Z350) flowable composite resins, at room temperature or preheated at 60°C. Transbond XT primer and Single Bond 2 adhesive system were used in association with Transbond XT and the flowable composites, respectively. The specimens were stored in water (37°C) for 24 h, and half of the sample was subjected to thermal cycling for 6000 cycles. Ashear bond strength (SBS) test was performed, followed by the appraisal of the adhesive Remnant Index (ARI). Three-way analysis of variance (ANOVA) and the Tukey test were performed at a significance level of 95% (P < .05). Samples bonded with preheated adhesives showed higher SBS regardless of the aging method. Only samples bonded with preheated conventional orthodontic adhesive maintained their bond strength after thermal cycling for 6000 cycles. Preheating orthodontic adhesives improved the bond strength of molar tubes, but only the preheated conventional orthodontic adhesive was capable of maintaining bond strength after thermal cycling.     

Final Drying of Whole Milk Powder in Vibrated-Fluidized Beds

Abstract

Vibro-fluidized beds are widely used in drying sticky powders and agglomerated materials as milk powder. Using a vibro-fluidized laboratory scale dryer, this work is aiming at analyzing preliminarily the effect of its operational variables on the drying kinetics and characteristics of whole milk powder. The full-factorial design technique with three replications at the central point has been employed to generate data and correlations to quantify the effect of inlet air temperature, air flow rate, and vibration bed amplitude on the drying curves and the milk powder properties related to its faster reconstitution in water (as tapped density, Hausner cohesion ratio, agglomerate size distribution, and internal pore concentration). Results obtained are analyzed and discussed to identify the adequate operation condition for final drying whole milk powder in vibro-fluidized beds, assuring a high product quality.     

Grape Drying in a Pilot Plant With a Heat Pump

ABSTRACT

We describe a pilot-scale drying plant comprising a closed-circuit, hot-air convection chamber with a heat pump. In this plant, food and forest products can be drled with lower energy consumption and over a wider range of air, speeds, temperatures and relative humidities than in conventional driers. Also the dryinq conditions can be controlled independently of external conditions. Under several different sets of drying conditions, we determined the kinetics of dryinq of grapes that had been variously pretreated. The effects of drying conditions and the pretreatment on the drying time and the appearance of the dried product were evaluated. The drying kinetics can be described by a diffusion model.     

Epifluorescence studies and secondary relaxation processes in immiscible blends of polybutadiene‐poly(2‐vinyl naphthalene) by fluorescence spectroscopy

The development of the morphology of polybutadiene/poly(2‐vinyl naphthalene) blends in five proportions by mass (5, 10, 50, 90, and 95%, w/w) is studied by epifluorescence and scanning electron microscopy (SEM) techniques. The phase separation process of these immiscible polymers produces a primary morphology that is formed by dispersed droplets in a continuous matrix. In the sequence a secondary phase separation inside the primary domains is detected by epifluorescence microscopy of the intrinsically fluorescent domains. Secondary phase separation is confirmed by SEM fracture surface analysis. The relative size of the droplets and the matrix composition depend on the proportion of the components of the blends. The mechanism of the phase separation process is preferentially by nucleation growth for either primary or secondary phase separation processes. Secondary relaxation processes involving the poly(2‐vinyl naphthalene) phase are studied by fluorescence spectroscopy. The profile of the steady‐state excimer fluorescence of poly(2‐vinyl naphthalene) with the temperature in the blend differs from that of the isolated homopolymer and is explained by the contribution from the interface to the radiationless deactivation. The Arrhenius plot for the temperature dependence exhibits slope changes that are related to the polymer relaxation processes. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1637–1649, 2002; DOI 10.1002/app.10389     

School feeding program in Guatemala: technology transfer to artisan bakers, producers of the nutritionally improved cookie

The Ministry of Education of Guatemala requested from the Institute of Nutrition of Central America and Panama (INCAP), the development of a solid food for delivery to school children who attend the official schools throughout the country. INCAP developed and transferred the processing technology to produce a nutritionally improved cookie to artisan bakers from the different regions of the country. The present paper describes the technological process, focusing on the training, supervision and quality control actions executed with approximately 100 micro baking enterprises, in 1988 and 1989. These actions have had a positive impact on the bakeries, a fact evidenced by the significant improvement of the conditions and processes of the nutritionally improved cookie production. The performance of the above-mentioned activities has allowed us to detect necessities, for the solution of which research and development of technologies are most important for their immediate transference to artisan bakers. Nevertheless, it is necessary to monitor and control the transferred technology, and efforts must continue to increase the effectiveness of the whole system which involves technology transference model, created for this project.