Tribological Performance of Aligned Silicon Nitride Ceramics under Isooctane‐Lubricated Oscillating Sliding Conditions

Silicon nitride (Si₃N₄) materials with preferentially aligned β‐Si₃N₄ grains were tribologically characterized with respect to their possible application in a high‐pressure gasoline pump. Tribological tests were performed under oscillating sliding conditions lubricated with isooctane as a substitute for gasoline using Si₃N₄ counterbodies. Performance in terms of wear of the aligned materials surpassed that of nonaligned reference Si₃N₄, as well as that of self‐mated silicon carbide, zirconia, alumina, and a steel sliding pair. The plane perpendicular to the extruding direction and parallel to the hot‐pressing axis was the most wear resistant.     

Class AB amplifier with enhanced slew rate and GBW

The design of a micropower class AB operational transconductance amplifier with large dynamic current to quiescent current ratio is addressed. It is based on a compact and power-efficient adaptive biasing circuit and a class AB current follower using the quasi-floating gate (QFG) technique. The amplifier has been designed and fabricated in a 0.5-μm CMOS process. Simulation and measurement results show a slew rate (SR) improvement factor versus the class A version larger than 4 for the same supply voltage and bias currents, as well as enhanced small-signal performance.     

Selective Furfural Hydrogenation to Furfuryl Alcohol Using Cu-Based Catalysts Supported on Clay Minerals

Copper supported on clay minerals (bentonite and sepiolite) catalysts, with copper loading between 15 and 60 wt%, have been synthesized by precipitation-deposition, calcination and subsequent reduction. The catalysts were characterized by X-ray diffraction, H₂ temperature programmed reduction (H₂-TPR), N₂ adsorption–desorption at ?196?°C and X-ray photoelectron spectroscopy, being detected spherical metal Cu-particles with variable size, mainly located on the surface of clays. The evaluation of their catalytic performance in the furfural (FUR) hydrogenation in gas phase has demonstrated that the use of bentonite as support allows attaining conversion values of 83% for 45Cu-Bent, whereas only a 52% is reached by the 45Cu-Sep catalyst. All catalysts were highly selective towards furfuryl alcohol (FOL), reaching yields of 72% for 45Cu-Bent and 45% for 45Cu-Sep after 5 h of time-on-stream (TOS) at 210?°C, by using a H₂:FUR molar ratio of 11.5 and a WHSV of 1.5 h^?1. However, all catalysts suffer a progressive deactivation with TOS, by deposition of reactants and product (FOL and FUR), as well as the oxidation of the active phase.     

Clay‐Graphene Nanoplatelets Functional Conducting Composites

An approach to functionalize graphene‐based materials has been developed by assembling graphene nanoplatelets (GNP) with clay minerals. Under convenient sonomechanical treatment, clay–GNP mixtures may produce very stable water dispersions in particular using sepiolite fibrous clay. While in the absence of clay a rapid decantation of GNP in water is observed, in the presence of sepiolite the resulting dispersions remain stable during months without syneresis effects. Rigid but flexible self‐supported films are easily obtained by filtering of these dispersions. As the electrical percolation threshold corresponds to sepiolite/GNP composites of 0.5:1 in weight, doping these systems with multiwalled carbon nanotubes (MWCNTs) significantly enhances their electrical conductivity. The particular microporosity of the sepiolite component allows interactions with molecules, such as organic dyes, as well as polymers, such as biopolymers, opening the way to functional materials for advanced applications due to their inherent conductivity afforded by the GNP and MWCNTs carbonaceous components. In fact, using very small amount of MWCNT together with GNP can obtain composites with significant electrical conductivity, maintaining the enhanced mechanical properties, at a lower cost.     

Mechanism involved in the dyeing of wool with an oil‐in‐water microemulsion system

This article investigates the influence of oil‐in‐water (o/w) microemulsions, used as media for both dye solubilization and dye baths, on the dye uptake on fiber surfaces. An acetic acid solution/Synperonic L7/benzyl alcohol microemulsion system was used to solubilize a water‐insoluble antimicrobial natural dye (C.I. Natural Orange 2) and to dye wool fabric at an acidic pH. The results clearly show that the dye exhaustion on the fabric took place mainly when the temperature of the dye bath promoted a change in the molecular organization of the microemulsions with the liberation of the dye solubilized in the oil droplets of the microemulsions. Although uniformly and evenly dyed fabrics were obtained, they showed very low wash fastness. To confirm the mechanism involved and to achieve dyed fabrics with good wash‐fastness properties, two different dyeing methods were also studied. The first method was dyeing at a constant low temperature, at which the o/w microemulsion remained a monophase system; the second one was dyeing at a high temperature, at which it was transformed into a multiphase system. Both the dye exhaustion and wash fastness improved considerably for the fabrics dyed at a high temperature. Moreover, uniform and even dyeing was achieved. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Multivariate Characterization of Milk Fat Fractions by Gas Chromatography

A high-speed gas chromatography method has been developed to separate the fatty acids in different milk fat fractions obtained via the dry fractionation deodorization process (TIRTIAUX method). Exploratory data techniques, namely cluster analysis and principal component analysis (PCA), were applied to gas chromatographic data for fatty acids composition in these milk fractions. Cluster analysis allowed the authors to visualize natural groupings corresponding to milk fat cracking achieved via the TIRTIAUX method. Principal component plots showed that six fractions are grouped in different classes, each group being clearly distinguished. Furthermore, a relationship was established between these classes and fatty acids through PCA analysis. A discriminant linear model for predicting milk fat classes from fatty acid composition was computed; 99 % of the criterion variable (milk fat class) variance was explained by the constructed model. Enrichment in unsaturated cis-fatty acids in the olein fractions and in the saturated and unsaturated trans-fatty acids in the stearin fractions was visualized from chemometric analysis. This differentiation of the milk fat fractions on the basis of fatty acids composition will enable food industries to use these fractions in both an efficient and safe way to enrich dairy products, or other foods, for healthy consumption.     

Effect of prior cold work on the degree of sensitisation of welded joints of AISI 316L austenitic stainless steel studied by using an electrochemical minicell

This work aims to assess the effect of prior cold work on the degree of sensitisation of each of the four welding zones of welded joints of AISI 316L subjected to post-welding sensitisation. Electrochemical potentiokinetic reactivation and double loop electrochemical potentiokinetic reactivation tests are performed on each of the four zones by using a small-scale electrochemical cell (minicell). The results show that the degree of sensitisation of heat affected zone, which achieves its maximum at a prior cold work level of 10%, is significantly lower than that of base material for a prior cold work of 20%.     

Influence of ripening and astringency on carotenoid content of high-pressure treated persimmon fruit (Diospyros kaki L.)

Rojo Brillante is an astringent variety of persimmon fruit that needs a de-astringency treatment (95% CO₂/20 °C/24 h) before commercialisation to improve its sensorial quality. This fruit is a good source of bioactive compounds, such as carotenoids. Effects of high-pressure processing (HPP) (200–400 MPa/25 °C/1–6 min) on carotenoid content of astringent and non-astringent persimmon fruits at two maturity stages (III and V) were studied. With regard to control samples, non-astringent fruits at maturity stage V, showed the highest carotenoid content and vitamin A value. In general, HPP at 200 MPa produced a statistically significant increase in extracted carotenoid content for astringent samples (up to 86% and 45% at maturity stages III and V, respectively), whereas no significant differences or even a decrease was observed for non-astringent ones or those treated at 400 MPa. HPP of astringent persimmon fruit at 200 MPa/25 °C/6 min showed the best result in terms of carotenoid extractability. Therefore, HPP could be a useful tool to produce an improvement on the extraction of potentially health-related compounds and, in consequence, to modify their bioaccessibility.     

Indigenous lactic acid bacteria communities in alcoholic and malolactic fermentations of Tempranillo wines elaborated in ten wineries of La Rioja (Spain)

Indigenous lactic acid bacteria (LAB) communities have been analyzed for three years (2006, 2007 and 2008) during alcoholic (AF) and malolactic (MLF) fermentations of Tempranillo wines in ten wineries of La Rioja. The results showed that analytical composition of wines and physical–chemical conditions of elaboration influenced the LAB populations, the MLF duration and the percentage of each isolated species and strains. The highest diversity of LAB species was observed during AF in all the wineries. Oenococcus oeni was present in all studied stages of the fermentation process, being the predominant species at final AF stage. The study of 925 isolates of O. oeni by Pulsed Field Gel Electrophoresis (PFGE) allowed the detection of a total of 112 distinct genotypes. Most fermentation stages of both AF and MLF showed mixed O. oeni strain populations, so that there were different genotypes able to share their ecological niche or tank in spontaneous MLF. The frequency of participation of each genotype varied either from year to year or from winery to winery. Otherwise, seven genotypes were detected in the three studied years and in at least three out of the ten studied wineries, being four of them also present in the three studied subzones of this region. These results suggest the existence of an endemic microbiota in this region, the adaptation of indigenous O. oeni strains to the winery conditions every year and the interest of selecting predominant genotypes in order to preserve the biodiversity and peculiarity of these wines.     

Control of the Basicity in Ni–MgO Systems: Influence in the Hydrogenation of Styrene Oxide

The addition of basic solutions to the reaction medium in the catalytic hydrogenation of styrene oxide improves the selectivity to 2-phenylethanol (used in perfumery) but also can favour condensation reactions. To study the influence of different basic sites on the reaction products, we prepared several catalysts by mixing a commercial magnesia (MgO), and other previously rehydrated (MgOr), with different amounts of NiO followed by reduction (NiMgO, 4NiMgO, NiMgOr, 4NiMgOr), and by mixing directly MgO with Ni (NiMgOa, 4NiMgOa). Ni–MgO catalysts showed the best conversion and selectivity to 2-phenylethanol values, arriving to 100% when increasing the MgO content. Interestingly, CO₂-TPD study of catalyst NiMgO indicates that metallic nickel covers the weakest basic sites of magnesia. On the other hand, CO₂-TPD profiles of Ni–MgOr and Ni–MgOa catalysts, which present low catalytic activity, showed an important amount of available basic sites that favour the formation of higher amounts of condensation products, which are responsible for the catalyst deactivation.