Age Variation of Douglas-Fir Bark Chemical Composition

The chemical composition of Douglas-fir bark was analyzed at three stem height levels of trees with different ages from two geographical locations. Cork and phloem in the bark’s rhytidome were analyzed separately at stem bottom: extractives (49.8% and 17.0%, respectively), suberin (30.1% in cork) and hemicelluloses, namely arabinose content (25.3% and. 4.8% of all monomers, respectively). Suberin composition includes α,ω-alkanoic diacids (38.6%), ω-hydroxyalkanoic acids (25.6%), alkanoic acids (18.2%), alkanols (2.2%), and aromatics (8.8%). Bark’s chemical composition is age-related, namely regarding suberin content: at 45, 30 and, 17?years of age, bark contained respectively 25.4%, 2.6%, and 0.9% of suberin; 24.5%, 33.9%, and 29.8% of lignin; and 29.4%, 20.6%, and 25.7% of extractives. This difference is due to the small number of periderms and low cork content in barks with 30 or less years. When aiming at a cork-targeted valorization, the lower stem parts of mature Douglas-fir trees should be considered while the high content of polar extractives at all stem heights allows an overall potential valorization.     

Fish Oil Supplementation Decreases Oxidative Stress but Does Not Affect Platelet-Activating Factor Bioactivity in Lungs of Asthmatic Rats

Dietary fish oil supplementation increases the content of n-3 polyunsaturated fatty acids (PUFA) in cellular membranes. The highly unsaturated nature of n-3 PUFA could result in an enhanced lipid peroxidation in the oxidative environment characteristic of asthma. The oxidative reaction cascade culminates in an increased production of components associated to oxidative stress and of an important proinflammatory mediator platelet-activating factor (PAF)-like lipid. We evaluated the effect of fish oil supplementation in asthmatic rats upon the PAF bioactivity and parameters related to oxidative stress in the lung. Fish oil supplementation of asthmatic rats resulted in lower concentrations of nitrite (1.719 ± 0.137 vs. 2.454 ± 0.163 nmol/mL) and lipid hydroperoxide (72.190 ± 7.327 vs. 120.200 ± 11.270 nmol/mg protein). In asthmatic animals, fish oil increased the activities of superoxide dismutase (EC 1.15.1.1) (33.910 ± 2.325 vs. 24.110 ± 0.618 U/mg protein) and glutathione peroxidase (EC 1.11.1.9) (164.100 ± 31.250 vs. 12.590 ± 5.234 U/mg protein). However, fish oil did not affect PAF bioactivity in lung tissue of asthmatic rats (0.545 ± 0.098 340/380 vs. 0.669 ± 0.101 340/380 nm ratio). Considering the two-step process—oxidative stress and PAF bioactivity—fish oil exhibited a divergent action on these aspects of asthmatic inflammation, since the supplement lowered oxidative stress in the lungs of asthmatic rats, presenting an antioxidant effect, but did not affect PAF bioactivity. This suggests a dual effect of fish oil on oxidative stress and inflammation in asthma.     

An extension of the Curie-von Schweidler law for the leakage current decay in MIS structures including progressive breakdown

The leakage current decay and progressive breakdown in Al/HfYO_x/GaAs and Al/Y₂O₃/GaAs structures during constant voltage stress are investigated. It is shown that the Curie-von Schweidler law in combination with series and parallel resistances can describe the observed current decrease in these structures accurately. The circuit model incorporates an additional parallel leakage current path associated with the local degradation of the oxide layer as well. Even though the evolution of the current is remarkably different in HfYO_x than in Y₂O₃ because of the applied stress voltage range and current magnitudes, the proposed model is able to capture the main features exhibited by the current–time characteristic in both cases. Experimental data from other authors are analyzed within the same framework.     

Changes of quality characteristics of pepino fruit (Solanum muricatum Ait) during convective drying

Quality assessment of pepino fruit preserved through convective dehydration was investigated in this work. The effect of process temperature (50, 60, 70, 80 and 90 °C) on physicochemical properties, colour, non‐enzymatic browning, vitamin C, total phenolic content, antioxidant activity and firmness of the fruit were considered. When comparing the fresh with the corresponding dehydrated pepino samples, it was shown that the drying conditions resulted in important reductions of proteins and crude fibres. Discoloration of fruit was noticeable for all treatments due to effects of non‐enzymatic browning and changes in chromatic coordinates leading to a modification of the original colour. Regarding vitamin C and total phenolic content, an increase of drying temperature resulted in a considerable reduction of both initial compounds contents. Antioxidant activity showed an important decrease especially at low temperatures (e.g. 50 °C). Softening of the dried product was observed for all the treatments indicating structural modifications of the fruit due to thermal process.     

Chemical and physical methods for the control of the mite Acarus farris on Cabrales cheese

The astigmatid mite Acarus farris is the main species of mite infesting Cabrales cheese, a traditional Spanish product. This species may reach population density levels of 260 mobile mites/cm², resulting in high economic losses. Different chemical and physical methods that were able to control this pest without affecting the organoleptic quality of Cabrales cheese were tested. The efficacy of four short-chain fatty acids (caproic, caprylic, pelargonic and capric) and two sugar alcohols (ribitol and xylitol) were tested under laboratory conditions against mobile stages of A. farris. Only pelargonic acid significantly increased mortality in comparison with controls (63.4 vs. 26.1%, respectively). Additionally, the contact effect of the monoterpene eucalyptol was assessed in cheese maturing rooms at doses of 2.5 and 1.25 μl/cm². The first dose effectively controlled A. farris, but its application negatively affected the organoleptic values of the treated cheeses. Finally, the application of the waxy food coating READOM CBR to Cabrales cheeses in maturing rooms, kept the mite population low but negatively modified the external appearance of the cheese, an important quality parameter.The physical approach was based on lowering the usual cheese maturing temperature (15 °C) to 6, 4 or 2 °C. As temperature decreased, A. farris density was drastically reduced from 174 ± 33 mites/cm² at the control temperature (15 °C) to 14, 11 and 1 mites/cm² for 6, 4 and 2 °C, respectively, though the maturing time was considerably extended. The feasibility of both chemical and physical methods for the control of A. farris is discussed.     

Metal coordination and selectivity with oxine ligands bound to silica polyamine composites

A series of oxine ligands, 5‐X, 8? OH? C₉H₆N (X = H, Cl, SO₃H) have been covalently bound to a silica gel polyamine composite made from a silanized amorphous silica xerogel and poly(allylamine) (BP‐1) by the Mannich reaction. The resulting modified composites WP‐4(X = H), CB‐1(X = Cl), and SB‐1(X = SO₃H) were characterized by elemental analysis, FTIR, and solid state CPMAS‐¹³C‐NMR. Using the analytical data before and after the ligand modification, the ligand loading could be estimated and in combination with metal ion capacities a metal to ligand ratio could be obtained. The composites WP‐4 and CB‐1 both showed ratios of approximately 1 : 1 while the sulfonate modified composite, SB‐1, showed a metal to ligand ratio of 1 : 2. This is tentatively interpreted in terms of a zwitterionic oxine as the dominant species at pH = 2 where the sulfonic acid group is ionized, the quinoline nitrogen is protonated and where two sulfonate groups on adjacent oxines bind a trivalent or divalent ion. All the modified composites show a clear selectivity for trivalent over divalent ions and a good selectivity for gallium over aluminum. The substituent groups on the oxine ligand have only a minor influence on these selectivity trends but SB‐1 shows slightly better capture kinetics. The selectivity for gallium over aluminum is applied to the separation of gallium from aluminum, ferrous, and zinc in an acid ore leach of solid tailings obtained from a zinc mine using WP‐4. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Comparison of activity coefficient models for electrolyte systems

Three activity coefficient models for electrolyte solutions were evaluated and compared. The activity coefficient models are: The electrolyte NRTL model (ElecNRTL) by Aspentech, the mixed solvent electrolyte model (MSE) by OLI Systems, and the Extended UNIQUAC model from the Technical University of Denmark (DTU). Test systems containing a single salt (NaCl), multiple salts, and mixed solvent aqueous electrolyte solutions were chosen. The performance of the activity coefficient models were compared regarding the accuracy of solid–liquid and vapor–liquid equilibrium calculations for the test systems. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Are soft breakdown and hard breakdown of ultrathin gate oxidesactually different failure mechanisms?

By means of a statistical analysis, the soft breakdown and hard breakdown of thin gate SiO₂ films in MOS devices are shown to have a common physical origin. Being triggered by identical microscopic defects, these breakdown modes can be actually considered to be the same failure mechanism. In particular, it is shown that the soft breakdown conduction path is not precursor of the final hard breakdown event, which generally appears at a different spatial location. The huge differences between the soft and hard post-breakdown current-voltage (I-V) characteristics are attributed to differences in the breakdown spot area and to point contact energy funneling effects     

Effect of Cu on Ni nanoparticles used for the generation of carbon nanotubes by catalytic cracking of methane

In this study, a simple method for the addition of Cu to unsupported nickel nanoparticles is employed to investigate the promotion effect of copper during the nickel-catalyzed decomposition of methane into carbon nanotubes. Bulk nickel and copper acetates were mixed by grinding the parent salts in a mortar, to obtain samples with selected Ni/Cu atomic ratios (NiCu_0.03, NiCu_0.07 and NiCu_0.16) that were decomposed in situ on methane streams using a thermogravimetric analyzer (TGA). Weight increase was related quantitatively to the production of carbon nanotubes by catalytic cracking of methane, and the materials were complementary characterized ex situ by electron microscopy. The results suggest that copper most likely induces the disaggregation of nickel particles during the course of the catalytic cracking, but copper by itself was not effective to improve quantitatively the production of carbon nanotubes. In spite of very low methane conversions, good quality multiwalled carbon nanotubes are obtained and characterized by HRTEM.