Detailed analysis of petroleum hydrocarbon attenuation in biopiles by high-performance liquid chromatography followed by comprehensive two-dimensional gas chromatography

Enhanced bioremediation of petroleum hydrocarbons in two biopiles was quantified by high-performance liquid chromatography (HPLC) followed by comprehensive two-dimensional gas chromatography (GCXGC). The attenuation of 34 defined hydrocarbon classes was calculated by HPLC–GCXGC analysis of representative biopile samples at start-up and after 18 weeks of biopile operation. In general, a-cyclic alkanes were most efficiently removed from the biopiles, followed by monoaromatic hydrocarbons. Cycloalkanes and polycyclic aromatic hydrocarbons (PAHs) were more resistant to degradation. A-cyclic biomarkers farnesane, trimethyl-C13, norpristane, pristane and phytane dropped to only about 10% of their initial concentrations. On the other hand, C29–C31 hopane concentrations remained almost unaltered after 18 weeks of biopile operation, confirming their resistance to biodegradation. They are thus reliable indicators to estimate attenuation potential of petroleum hydrocarbons in biopile processed soils.     

An Improved Pinchoff Equivalent Circuit Model for Determining PHEMT Model Parameters for Millimeterwave Application

An improved equivalent circuit model under pinchoff condition for extracting parasitic model parameters for Double Heterojunction -doped PHEMTs is presented. Good prediction for S parameters and noise performance are obtained up to 40GHz. A modified parameter extraction technique based on this new model was use to determine a PHEMT equivalent circuit model. Signification improvements of the accuracy of S parameters are obtained by using the new pinchoff model.     

Pyrazoles. XVIII. Synthesis of a novel tripyrazolyl by two consecutive cine substitution reactions

Preparation of the C-N coupled tripyrazolyl VII, by two consecutive cine substitution reactions starting from 1,4-dinitropyrazole and using pyrazole as a nucleophile, is described. Solvent dependent nitrations of 4-nitro-3(5)-(1′-pyrazolyl)pyrazole I are reported.     

Unusual electrical properties of hydrothermally grown ZnO

Bulk ZnO of high structural and optical quality can be grown by the hydrothermal method. An X-ray rocking-curve linewidth of 18 arcsec has been measured for the (002) reflection, and a photoluminescence linewidth of 0.3 meV has been found for one of the donor–bound exciton lines. However, the electrical properties are unusual in that shallow donors are not dominant, as is the case for vapor-phase-grown and melt-grown bulk crystals. This situation can be greatly modified by annealing in forming gas (5% H₂ in N₂) at , with bulk shallow donors then becoming completely dominant for , and near-surface donors at lower temperatures. As T_A is varied from 100–650 C, both the mobility and carrier concentration vary in nonmonotonic fashion, due to changes in the relative strengths of the bulk and surface components of conduction.     

Novel Bio-Functional Aloe vera Beverages Fermented by Probiotic Enterococcus faecium and Lactobacillus lactis

Aloe vera has been medicinally used for centuries. Its bioactive compounds have been shown to be very effective in the treatment of numerous diseases. In this work, a novel functional beverage was developed and characterized to combine the health benefits of probiotic bacteria with the Aloe vera plant itself. Two Aloe vera juices were obtained by fermentation either by a novel isolated Enterococcus faecium or a commercial Lactococcus lactis. The extraction of Aloe vera biocompounds for further fermentation was optimized. Extraction with water plus cellulase enhanced the carbohydrates and phenolic compounds in the obtained extracts. The biotransformation of the bioactive compounds from the extracts during fermentation was assessed. Both probiotic bacteria were able to grow on the Aloe vera extract. Lactic acid and short-chain fatty acids (SCFA) together with fourteen individual phenolic compounds were quantified in the produced Aloe vera juice, mainly epicatechin, aloin, ellagic acid, and hesperidin. The amount of total phenolic compounds was maintained through fermentation. The antioxidant activity was significantly increased in the produced juice by the ABTS method. The novel produced Aloe vera juice showed great potential as a functional beverage containing probiotics, prebiotics, SCFA, and phenolic compounds in its final composition.     

Ditopic Chelators of Dicopper Centers for Enhanced Tyrosinases Inhibition

Tyrosinase enzymes (Tys) are involved in the key steps of melanin (protective pigments) biosynthesis and molecules targeting the binuclear copper active site on tyrosinases represent a relevant strategy to regulate enzyme activities. In this work, the possible synergic effect generated by a combination of known inhibitors is studied. For this, derivatives containing kojic acid (KA) and 2-hydroxypyridine-N-oxide (HOPNO) combined with a thiosemicarbazone (TSC) moiety were synthetized. Their inhibition activities were evaluated on purified tyrosinases from different sources (mushroom, bacterial, and human) as well as on melanin production by lysates from the human melanoma MNT-1 cell line. Results showed significant enhancement of the inhibitory effects compared with the parent compounds, in particular for HOPNO-TSC. To elucidate the interaction mode with the dicopper(II) active site, binding studies with a tyrosinase bio-inspired model of the dicopper(II) center were investigated. The structure of the isolated adduct between one ditopic inhibitor (KA-TSC) and the model complex reveals that the binding to a dicopper center can occur with both chelating sites. Computational studies on model complexes and docking studies on enzymes led to the identification of KA and HOPNO moieties as interacting groups with the dicopper active site.     

Linear perturbation amplification in self-similar ablation flows of inertial confinement fusion

Exact similarity solutions for inviscid compressible ablative flows in slab symmetry with nonlinear heat conduction are proposed for studying unsteadiness and compressibility effects on the hydrodynamic stability of ablation fronts relevant to inertial confinement fusion. Both the similarity solutions and their linear perturbations are numerically computed with a dynamical multidomain Chebyshev pseudospectral method. Herewith the first analysis of laser-imprinting based on a dynamic solution is presented, showing that maximum perturbation amplification occurs for a laser-intensity modulation of zero transverse wave number, with growth dominated by the mean flow stretching.