Electrical resistivity of a titanium powder mass

In this paper, the variation with the porosity of the electrical resistivity of a compressed powder mass of commercially pure titanium has been studied. The study has been carried out via the direct measurement of the electrical resistance of a powder column subjected to uniaxial compression. The obtained experimental data have been fit to a theoretical model, proposed by the authors in a previous work, which allowed calculation of the effective electrical resistivity of the metallic powder aggregate as a function of its porosity level. This model considers not only the two obvious parameters (the porosity of the powder aggregate and the electrical resistivity of the material that constitutes the powder particles), but also the morphometry of the powder (represented by its mean particle radius and its tap porosity) and the electrical and mechanical characteristics of the oxide layer that surrounds all metallic powder particles. The results obtained from the present study allow determination of the electrical resistivity of a Ti powder aggregate, regardless of the porosity level of the powder. This knowledge is of great importance for the modeling of increasingly complicated electrical consolidation methods.     

The spectral response of the open-circuit voltage: a new characterization tool for solar cells

This paper explores the possibility of measuring the open-circuit voltage of a solar cell as a function of wavelength as a tool for device characterization. Theoretical calculations and computer simulations show that the spectral response of the open-circuit voltage exhibits a similar dependence to the spectral response of the short-circuit current. Experimental studies on silicon solar cells confirmed the strong spectral dependence of the open-circuit voltage. The spectral measurements have been performed using a quasi-steady-state open-circuit voltage method, which also allows to determine the spectral response of the maximum power voltage. The advantages of this new technique over conventional spectral response measurements include its applicability directly after junction formation and the simplicity of the experimental apparatus.     

Degradation of polycyclic aromatic hydrocarbons by the Chilean white-rot fungus Anthracophyllum discolor

The degradation of three- and four-ring polycyclic aromatic hydrocarbons (PAHs) in Kirk medium by Anthracophyllum discolor, a white-rot fungus isolated from the forest of southern Chile, was evaluated. In addition, the removal efficiency of three-, four- and five-ring PAHs in contaminated soil bioaugmented with A. discolor in the absence and presence of indigenous soil microorganisms was investigated. Production of lignin-degrading enzymes and PAH mineralization in the soil were also determined. A. discolor was able to degrade PAHs in Kirk medium with the highest removal occurring in a PAH mixture, suggesting synergistic effects between PAHs or possible cometabolism. A high removal capability for phenanthrene (62%), anthracene (73%), fluoranthene (54%), pyrene (60%) and benzo(a)pyrene (75%) was observed in autoclaved soil inoculated with A. discolor in the absence of indigenous microorganisms, associated with the production of manganese peroxidase (MnP). The metabolites found in the PAH degradation were anthraquinone, phthalic acid, 4-hydroxy-9-fluorenone, 9-fluorenone and 4,5-dihydropyrene. A. discolor was able to mineralize 9% of the phenanthrene. In non-autoclaved soil, the inoculation with A. discolor did not improve the removal efficiency of PAHs. Suitable conditions must be found to promote a successful fungal bioaugmentation in non-autoclaved soils.     

Impact of imidacloprid residues on the development of Eisenia fetida during vermicomposting of greenhouse plant waste

Pesticide application in agriculture causes residues in post-harvest plant waste at different concentrations. Knowledge concerning how pesticide concentrations in such waste affect earthworms is essential for recycling greenhouse plant debris through vermicomposting. Here, we have evaluated the effects of imidacloprid (IMD) residues on earthworms (Eisenia fetida) during the vermicomposting of plant waste from greenhouse crops in Spain. Before, the effect of different IMD concentrations on earthworms was tested using cattle manure as an optimum waste for worm development. The results after using cattle manure indicate that IMD dose ≥ 5 mg kg(-1) hinders worm growth and even causes death, whereas IMD dose ≤ 2 mg IMD kg(-1) allows worm growth similar to control but impedes reproduction. The results from the vermicomposting of plant waste reveal that IMD inhibits adequate worm growth and increases mortality. Although 89% worms became sexually mature in substrate containing 2 mg IMD kg(-1), they did not produce cocoons. IMD also affected microorganisms harboured in the substrates for vermicomposting, as indicated by the reduction in their dehydrogenase activity. This enzyme activity was restored after vermicomposting. This study provides a sound basis for the vermicomposting of pesticide-contaminated plant waste.     

Testing and modelling of an automotive wobble plate compressor

Wobble plate compressors are well used in air conditioning for high-class automobiles. They allow continuous control by automatic adjustment of the piston stroke, to keep the low pressure above a certain limit. Here an externally controlled wobble plate compressor is analyzed experimentally through its isentropic and volumetric effectivenesses and control characteristics. Compressor effectivenesses depend mainly on the compressor speed and pressure ratio: there is obtained, for example, isentropic and volumetric effectivenesses of 0.65 and 0.8 for a pressure ratio of 4 at 1000 rpm and 0.4 and 0.35 for the same pressure ratio at 4000 rpm. This degradation is attributed to the increasing of the supply pressure drop. The “lubricant” (oil + dissolved refrigerant) mass flow rate is obtained by minimization of the residuals of the thermal balances on the compressor, condenser and evaporator. Here an important oil-flow circulation is obtained: between 9.5% and 12.5% of the refrigerant flow rate. A special displacement sensor is used to measure instantaneous piston stroke and to relate it to overall compressor performance. This measurement is then compared with the results obtained with a semi-empirical model, which is able to predict, in part load, the compressor displacement. The model predicts the displacement ratio with deviations that vary between −14.5% and +8.1%.     

Cu (II) removal from tequila using an ion-exchange resin

An ion-exchange resin was employed to remove copper from tequila. Elemental analysis, batch and column copper uptake measurements were performed to assess the extent of metal removal; FTIR and XPS were employed to elucidate the copper complexes formed on the surface of resin; GC was used to investigate resin fouling and the extent of methanol removal. A modified Langmuir isotherm was used to explain adsorption equilibrium data. A ligand density of 2.21 mmol/g as sulphonic group, was measured. Maximum copper uptake by resin was 0.59 mmol/g. GC results from column experiments revealed methanol changes from 311 mg/100 ml anhydrous alcohol (AA) to 212 mg/100 ml AA, complying with Mexican regulations. Tequila solution with copper (5.3 l, 7.3 mg/l) was treated to breakthrough point in column experiments reaching 0.5 mg/l of copper at effluent. These results comply with the Mexican regulation for copper concentration (?2 mg/l) showing the promise of resin for industrial applications in removal of copper and methanol from tequila.     

Isolation of Saccharomyces cerevisiae strains producing higher levels of flavoring compounds for production of "cachaça" the Brazilian sugarcane spirit

In Brazil, spontaneous fermentation and open vessels are still used to produce cacha?a (the Brazilian sugarcane spirit) and this fermentation is characterized by mixed cultures with continuous succession of yeast species. This work shows the development of a methodology for isolation of yeasts, particularly Saccharomyces cerevisiae, used in the production of cacha?a. According to the proposed strategy, the strains were selected for their ability to adapt to stress conditions encountered during fermentation of the sugarcane juice such as high sucrose concentration; high temperatures and high alcohol concentration; for their capacity to flocculate; and for their higher fermentative ability. For strains with such characteristics, specific procedures were employed to select for 5,5,5-trifluoro-DL-leucine (TFL) and cerulenin-resistant strains, since these characteristics are related to a higher capacity of production of the flavoring compounds isoamyl alcohol and caproic acid, respectively. The effectiveness of such a selection strategy was documented. Taken together, the results obtained present the development of a new strategy to isolate yeast strains with appropriated characteristics to be used in the cacha?a industry. Moreover, the results obtained offer an explanation for the great variability in terms of chemical composition found in products obtained even in a single distillery.     

Factors that enable the formation of porous strut morphology in “Swiss Cheese” viscoelastic polyurethane foam technology

Several factors were investigated that affect porous strut morphology in the Highly Porous Supersoft Viscoelastic Foam. Porous strut morphology and high air permeability of the Swiss‐Cheese TDI VE technology were found to be enabled by the combination of immiscible polyether polyols mixed with a third, highly hydrophobic polyol of high equivalent weight that is immiscible with either of the first two polyether polyols. Completely “punctured through” pores in struts were observed more frequently in foam samples where an isocyanate index of 90 versus 100 was employed. When isocyanate index is fixed to 90, it was found that a poly(1,2‐butylene oxide) (“PBO”) monol level of ≥3.0 parts per hundred polyol (pphp) was needed to see the first signs of a “punctured” pore strut morphology. Studies show that a “high‐Eq.Wt.‐hydrophobic‐polyol‐leaving‐voids” model is consistent with observed results. Hydrophobic polyols that allowed the formation of porous strut morphology included BO‐4000 monol (Eq.Wt. ～ 4000) and PBD‐10000 diol (Eq.Wt. ～ 5000). The use of these hydrophobic polyols also yielded air flows that were significantly higher than those obtained with the “standard” viscoelastic foam formulations that were prepared at the same isocyanate index. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44449.     

Fe supported on ceria as effective catalyst for the heterogeneous photo-oxidation of basic orange 2 in aqueous solution with sunlight

Fe^III supported on ceria as an effective catalyst for oxidation was prepared and used for the degradation of basic orange 2 azo textile dye (BO2). BO2 was chosen as a model pollutant and the catalytic oxidation was carried out in a batch reactor using hydrogen peroxide as the oxidant at pH 3. The influent factors on BO2 oxidation, such as catalyst dosage, H₂O₂ concentration, and BO2 concentration were studied by considering the BO2 conversion and chemical oxygen demand (COD) removal. The Fe^III-ceria catalyst showed a high catalytic activity for the oxidation of BO2 in aqueous solution. It was observed that the solution became colorless after 5 h of oxidation and over 90% COD removal was achieved with all the Fe^III-ceria catalysts used under dark conditions in the catalytic oxidation system. The catalytic removal of BO2 during BO2 oxidation was improved under solar radiation, which notably increased the BO2 degradation rate. Consecutive BO2 oxidation cycles carried out with the same Fe^III-ceria catalyst and untreated fresh dyestuff solution showed that the catalyst had good stability and good degradation performance, thus evidencing the possibility of being used in continuous processes. This study showed that the Fe^III-ceria catalytic oxidation process is an efficient method for the treatment of BO2 aqueous solutions.