The pile driver problem via a fixed point argument

In this paper we study, via fixed point and subdifferential arguments, the existence of solutions for a variational inequality which models the dynamics of a pile penetrating into the ground through the action of a pile hammer. This line of reasoning reduces the variational inequality we considered to a nonlinear evolution equation involving a monotone operator.     

Wine Aroma Improvement Using a β-Glucosidase Preparation from Aureobasidium pullulans

Microbial β-glucosidases have been used for the enhancement of wine aroma. Nevertheless, few enzymes are active in the conditions of winemaking. In this work, the production of a β-glucosidase by an Aureobasidium pullulans strain (Ap-β-gl) isolated from grape ecosystems was evaluated. The maximum enzymatic synthesis using submerged fermentation was after 96 h of growth in complex media containing 20 g/L of cellobiose as the sole carbon source. The crude enzyme (Ap-β-gl) showed optimal pH at 5.5 and two peaks of optimum temperature (at 45 and 70 °C). It showed a wide range of pH stability, stability at low temperatures, and tolerance to ethanol, showing suitable characteristics for winemaking conditions. The hydrolysis of glycosidic terpenes by Ap-β-gl was studied, and its ability to efficiently release free terpenols was demonstrated by gas chromatography/mass spectrometry. The enzymatic treatment notably increased the amount of monoterpenes, showing good prospects for its potential application for the development of aroma in wines.     

Band gap engineering approaches to increase InGaN/GaN LED efficiency

Nitride-based quantum well (QW) LEDs for lighting applications suffer from efficiency issues related to the strong built-in fields due to the difference in electric polarization of the constituent materials. In this paper we present a study based on device simulation showing the beneficial impact of band gap engineering approaches on device performance in particular for green LEDs.     

Fast Determination of Phenolic Compounds in Brazilian Wines from Vale do São Francisco Region by CE

Six phenolic compounds were separated and determined by capillary zone electrophoresis in red wine from Brazil’s region Vale do São Francisco with total analysis time of 12 min. The limit of detections varied from 1.59 to 2.24 mg L^?1. The relative standard deviations (for n = 6) varied from 0.28 to 3.50 %. The red wine samples analyzed were bought in the local market and the phenolic compound recoveries were in the range of 98–101 %. The concentrations of gallic acid in the samples of wines varied from 16.0 to 42.0 mg L^?1, caffeic acid (3.16–5.18 mg L^?1), syringic acid (5.73–13.0 mg L^?1), kaempferol (2.32–4.33 mg L^?1), quercetin (1.68–4.03 mg L^?1), myricetin (7.52–25.1 mg L^?1). The concentrations found agree with data reported in the literature.     

Development and validation of a liquid chromatographic/tandem mass spectrometric method for determination of tetracycline in human plasma: application to bioequivalence study

A fast, sensitive, and specific liquid chromatographic/tandem mass spectrometric method was developed and validated for determination of tetracycline in human plasma. Tetracycline and oxytetracycline [internal standard (IS)] were extracted from the plasma by protein precipitation. The mobile phase consisted of acetonitrile-formic acid 0.1% (48 + 52, v/v), run at a flow rate of 1 ml/min (split 1:5). Detection was performed by positive electrospray ionization in multiple reaction monitoring mode, monitoring the transitions 444.8 > 410.0 and 461.0 > 426.0 for tetracycline and IS, respectively. The analysis was performed in 3.5 min and the method was linear in the plasma concentration range of 50-6000 ng/mL. The mean extraction recoveries for tetracycline and IS from plasma were 92.14 and 94.04%, respectively. Method validation investigated parameters such as the linearity, precision, accuracy, specificity, and stability, giving results within the acceptable range. The proposed method was successfully applied for determination of tetracycline in human plasma samples to support bioequivalence studies.     

Density functional theory study of the adsorption of formaldehyde on Pd4 and on Pd4/gamma-Al2O3 clusters

B3LYP/LANL2DZ and B3LYP/6-31G(d)-restricted and -unrestricted calculations are employed to calculate energies and adsorption forms of formaldehyde adsorbed on planar and on tetrahedral Pd4 clusters and on a Pd4 cluster supported on Al10O15. Formaldehyde adsorbs on planar Pd4 in the eta(2)(C,O)-di-sigma adsorption mode, while on tetrahedral Pd4, it adsorbs in the eta(2)(C,O)-pi adsorption mode. The adsorption energy on planar Pd4 is -21.4 kcal x mol(-1), whereas for the tetrahedral Pd4 cluster, the adsorption energy is -13.2 kcal x mol(-1). The latter value is close to experimental findings (-12 to -14 kcal x mol(-1)). Adsorption of formaldehyde on Pd4 supported on an Al10O15 cluster leads essentially to the same result as that found for adsorption on the tetrahedral Pd4 cluster. Charge density analysis for the interaction between formaldehyde and the Pd4 clusters indicates strong backdonation in the eta(2) adsorption mode, leading to positive charge on the Pd4 cluster. NBO analysis shows that the highly coordinated octahedral aluminum atoms of Al10O15 donate electron density to the supported Pd4 cluster, while tetrahedral aluminum atoms with lower coordination number have acidic nature and therefore act as electron acceptors.