Stabilized Conversion Efficiency and Dye-Sensitized Solar Cells from Beta vulgaris Pigment

Dye-Sensitized Solar Cells (DSSCs), based on TiO₂ and assembled using a dye from Beta vulgaris extract (BVE) with Tetraethylorthosilicate (TEOS), are reported. The dye BVE/TEOS increased its UV resistance, rendering an increase in the cell lifetime; the performance of these solar cells was compared to those prepared with BVE without TEOS. The efficiency η for the solar energy conversion was, for BVE and BVE/TEOS, of 0.89% ± 0.006% and 0.68% ± 0.006% with a current density Jsc of 2.71 ± 0.003 mA/cm² and 2.08 ± 0.003 mA/cm², respectively, using in both cases an irradiation of 100 mW/cm² at 25 °C. The efficiency of the BVE solar cell dropped from 0.9 ± 0.006 to 0.85 ± 0.006 after 72 h of operation, whereas for the BVE/TEOS, the efficiency remained practically constant in the same period of time.     

Global optimization in property‐based interplant water integration

This article presents a new global optimization method for the interplant water integration based on properties to characterize streams with numerous components. The problem is formulated as an mixed‐integer non‐linear programming (MINLP) model based on a superstructure that involves all possible options of interest (i.e., reuse and recycle in the same and to other plants and a set of shared treatment units). This formulation exhibits multiple local minima, and to overcome this problem, this article proposes effective branching rules in addition to two new reformulations for the upper bound (integer feasible solution) and the lower limit (relaxed solution), which are incorporated into a spatial branch and bound procedure to handle the bilinear terms in the model. The objective consists in finding the configuration with the minimum total annual cost. Results show that the global optimal solution (involving significant reductions in the fresh water consumption) is reached in few iterations and short central processing unit (CPU) time. © 2012 American Institute of Chemical Engineers AIChE J, 59: 813–833, 2013     

Effect of zirconia tape porosity on fluorapatite surface film formation by dip coating

Thin fluorapatite (FA) layers on porous 3 mol% yttria-partially stabilized zirconia (Y-PSZ) substrates have been fabricated by dipping porous zirconia tapes into aqueous 27.4 vol% fluorapatite slurries. Two porous Y-PSZ tapes with different volume fraction of porosity were developed using an acrylic latex binder: tapes with 31.4 vol% porosity were prepared using 16.6 vol% starch as fugitive additive and those with 12.7 vol% porosity were fabricated without starch. The influence of the porous structure of the tape surfaces, top and bottom, on the casting rate and consequently on the layer thickness formed on each surface was studied. Layers formed on the top and bottom surfaces of the tapes with 12.7 and 31.4 vol% porosity were compared. The formation of a thin layer on the surface of the tape was governed by both liquid entrainment and slip casting mechanisms. The data for the FA layer formation were in good agreement with the slip casting model for immersion times>0. The casting rate at the top surface of both tapes was greater than that at the bottom surface. This difference was attributed to a greater porosity of the top surface with respect to that of the bottom one and was more pronounced for the tapes prepared with starch. Layers formed on the top surface were found to be about 55 and 32% thicker than those formed on the bottom surface for the tapes fabricated with and without starch, respectively. For the tapes prepared with starch, the greater porosity and number of smaller pores in the matrix of the top surface increased the casting rate and produced the thickest dip coated layers     

Total content and dialyzable iron and zinc in foods from northern and Southern Mexico

Developing countries diets are based on a variety of plant foods that often are the main suppliers of important amounts of iron (Fe) and zinc (Zn). The objectives of this study were 1) to measure the total and dialyzable amounts of Fe and Zn in foods from Northern Mexico (Sonora) and from Southern Mexico (Oaxaca) and 2) to evaluate the effect of meat content of diets on the dialyzable amount of Fe and Zn. Methods to calculate the total dialyzable amount of Fe and Zn, were those of the AOAC and of Shen et al. Total Fe in e northern Mexican foods went from 0.78 +/- 0.0 to 11.59 +/- to 0.03 mg/ 100g (dry weight, DW); in southern Mexican foods the same micronutrient amounts were 0.86 +/- 0.18 to 8.8 +/- 0.57 mg/100 g (BS). Total Zn values were 0.91 +/- 0.00 to 13.58 +/- 0.05 mg/100 g (DW) in Sonora, and 0.64 +/- 0.18 to 20.80 +/- 0.33 mg/100 g (DW) in Oaxaca. In northern Mexico, foods dialyzable Fe had values from 0.1 +/- 0.04% to 10.6 +/- 0.36% and for Zn from 4.0 +/- 0.21% to 55.32 +/- 0.14%. Meanwhile, the range of values of dialyzable Fe for foods from Oaxaca were from 0.22 +/- 0.06% to 9.40 +/- 0.14% for and from 2.41 +/- 0.26% to 54.27 +/- 1.49% for dialyzable Zn. The average value for dialyzable Fe was higher in the foods that contained meat or meat products (p= 0.001).     

Evaluation of the antimicrobial action of honey against Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Escherichia coli, Salmonella enteritidis, Listeria monocytogenes and Aspergillus niger. Evaluation of its microbiological charge

The evaluation of the microbiological charge present in Costa Rican samples as the evaluation of its antimicrobial activity over different microorganisms, including those associated to wound infections, will allow to emit criteria referred to its use in therapeutic treatments, specially as alternative therapy for cases involving antibiotic resistant bacteria. The microbiological charge of 25 honey samples, acquired in Costa Rican markets was evaluated through several indicators including total plate aerobic count, total plate anaerobic count, total aerobic spore count, total anaerobic spore count and molds and yeast count. Also, samples were inoculated in tubes with chopped meat media and plated in egg yolk agar in order to determine the presence of Clostridium botulinum. For the antimicrobial activity evaluation, the diffusion method in Muller Hinton agar was performed, testing different honey concentrations (100, 75, 50, 25, 12,5 and 6,25 % v/v) against Staphylococcus aureus (ATCC 25923), Staphylococcus epidermidis (UCR 2902), Pseudomonas aeruginosa (ATCC 9027), Escherichia coli (ATCC25922), Salmonella enteritidis (ATCC 13076), Listeria monocytogenes (ATCC 19116) and Aspergillus niger. The results obtained for the microbiological characterization of honey show that 91% of samples had counts equal or lower than 1,0 x 10(1) CFU/g. No positive result was obtained for the isolation of C. botulinum. 24 of the samples analyzed inhibited the growth of S. aureus even in a 25% v/v concentration, nevertheless, A. niger was no inhibited by any of the samples tested.     

Bioactive peptides derived from milk proteins

Milk proteins are known for having a wide range of nutritional, functional and biological properties that make them important ingredients in functional or health promoting foods. These properties are partly attributed to bioactive peptides coded in the different milk proteins. Bioactive peptides are inactive within the protein sequence but may be released by the action of native proteolitic enzymes from milk, enzymes from lactic acid bacteria or from exogenous sources or may be produced during gastrointestinal digestion or processing of foods. Peptides derived from caseins and whey proteins were shown to present several bioactive properties such as opioid, antihypertensive, antimicrobial, immunodulatory, mineral carrier and antithrombotic. This overview presents a perspective of the importance of dairy proteins in the production of bioactive peptides and their biological activities, as well as the main analytical tecniques that have been used for the isolation and identification of these peptides.     

Lipidic membranes are potential "catalysts" in the ligand activity of the multifunctional pentapeptide neokyotorphin

Neokyotorphin (NKT) is a multifunctional pentapeptide that is involved in biological functions as diverse as analgesia, antihibernatic regulation and proliferation stimulus of tumour cells. The interaction of neokyotorphin with cell membranes is potentially important to all these multiple biological processes since receptor-mediated processes are thought to be involved in neokyotorphin action. Sargent and Schwyzer proposed in their "membrane catalysis" model that ligands interact with membrane lipids in order to adopt the necessary conformation for cell receptors. We have used fluorescence techniques to study the depth, orientation and extent of incorporation of NKT with model membrane systems (lipidic vesicles). The roles of lipid charge, membrane phase and sterol presence were investigated. The phenolic ring of tyrosine is located in a shallow position in membranes. The extent of partition is less in gel crystalline membranes than in liquid crystalline membranes. Addition of cholesterol causes a reorientation of the tyrosine ring at the interface of lipidic bilayers. Lipidic membranes meet all the conditions required for acting as potential "catalysts" in the ligand activity of the multifunctional pentapeptide NKT, because they modulate the exposure and orientation of the phenolic ring, which is most likely involved in docking to receptors.     

Synthesis of Titanium Carbonitride Phases by Reactive Milling of the Elemental Mixed Powders

Titanium carbonitride (TiC _x N_{1− x} ) powders were obtained by high-energy ball milling of elemental titanium and carbon (activated carbon or graphite) in a nitrogen atmosphere. The formation of the carbonitride phase was controlled by adequately choosing the experimental conditions of the milling process. The stoichiometry of TiC _x N_{1− x} powders was modified by adjusting the titanium-to-carbon molar ratio. The composition and cell parameters of the carbonitride phases were determined. Microstructural characterization of these phases showed a nanocrystalline nature.     

H2S retention with Ca-based sorbents in a pressurized fixed-bed reactor: application to moving-bed design

The H₂S retention with Ca-based sorbents in a pressurized fixed-bed reactor (1 MPa) has been analyzed, obtaining the breakthrough curves with a dolomite and two different limestones, different particle size (+0.8-1.0, +1.25-1.6, and +1.6-2.0 mm), and both at calcining (1173 K) and non-calcining conditions (1123 K). The effect of the stoichiometric time in the breakthrough curves has been analyzed varying the bed length, the gas velocity and the sorbent fraction in the bed. From these results, the conversion and H₂S concentration profiles in the transition zone and the length of unused bed (LUB) have been determined. H₂S retention in fixed-bed until concentration close to the given by the thermodynamic equilibrium was obtained using dolomite or limestone at calcining conditions, and dolomite at non-calcining conditions. The results of H₂S retention in a fixed-bed reactor has been applied to the calculus of the minimum height of a countercurrent moving-bed reactor to obtain the maximum H₂S retention with the minimum amount of sorbent. A mathematical model was developed to predict the experimental results obtained in the fixed-bed reactor, which was also valid for the design of countercurrent moving-bed reactors for gas desulphurization.