Polychlorinated biphenyls and hydroxylated polychlorinated biphenyls in plasma of bottlenose dolphins (Tursiops truncatus) from the Western Atlantic and the Gulf of Mexico

Polychlorinated biphenyls (PCBs) and hydroxylated metabolic products (OH-PCBs) were measured in plasma collected from live-captured and released bottlenose dolphins (Tursiops truncatus) from five different locations in the Western Atlantic and the Gulf of Mexico in 2003 and 2004. In 2004, the sum (sigma) of concentration of PCBs in plasma of dolphins sampled off Charleston, SC [geometric mean: 223 ng/g of wet weight (w.w.)] was significantly higher (p<0.05) than concentrations detected in animals from the Indian River Lagoon, FL (sigmaPCBs: 122 ng/g w.w.) and the Sarasota Bay, FL (sigmaPCBs: 111 ng/g w.w.). The PCB homolog profiles were similar among locations. Concentrations of OH-PCBs were significantly higher (p<0.05) in plasma of dolphins from Charleston, SC (sigmaOH-PCBs for 2003: 126 ng/g w.w.; 2004: 138 ng/g w.w.) than animals from Florida (sigmaOH-PCBs ranged from 6 to 47 ng/g w.w.) and Bermuda (8.3 ng/g w.w.); however, concentrations in the Charleston samples did not differ from animals captured in Delaware Bay, NJ (57 ng/g w.w.). The sigmaOH-PCBs constituted 2-68% of the total PCB concentrations in plasma. Dichloro- to nonachloro-OH-PCBs were quantified using high-resolution gas chromatography mass spectrometry, but only around 20% of OH-PCBs could be identified by comparison to authentic standards. Results from this study show that OH-PCB are important environmental contaminants in dolphins and suggest that PCBs, decades after their ban, may still constitute a threat to wildlife.     

A GC–FID Method to Determine Styrene in Polystyrene Glasses

The styrene levels of polystyrene (PS) glasses from the most consumed brands of disposable glasses intended for water and coffee in Brazil were determined. A GC–FID method was developed and validated, showing good precision and accuracy. The method was successfully used to determine styrene in 11 PS glass brands. The styrene levels ranged from 1.68 to 43.69 mg/100 g glass, depending on the kind of polymer, thickness, and glass brand. It could be used to control the content of styrene in the polymer. The migration of styrene from the glasses into water and 20 % ethanol was not detected.     

Optimisation of High Hydrostatic Pressure Processing of Pêra Rio Orange Juice

The influence of high hydrostatic pressure (HHP) on Pêra Rio orange juice was investigated using response surface methodology. A central composite design was used to evaluate the effects of three processing conditions (independent variables), namely pressure (100–600 MPa), temperature (30–60 °C) and time (30–360 s), on the native microflora and pectin methylesterase (PME) activity of orange juice. Analysis of variance showed that second-order polynomial models fitted well with the experimental data for PME residual activity (R ²?=?0.9586, p?<?0.001) and aerobic microorganism count (R ²?=?0.9879, p?<?0.001). The optimum HHP processing conditions to produce orange juice with PME residual activity of less than 20 % and low microorganism count (<2 log cycles CFU/mL) were 550 to 600 MPa, 55 to 60 °C and 330 to 360 s.     

Characterization of ZrO2 thin films deposited by MOCVD for high-density 3D capacitors

This work deals with high-density integrated capacitors for output filters in future micro DC–DC converters. To reach high capacitance density, 3D structures were created in silicon with DRIE followed by MOCVD of ZrO₂ (100 nm thick). The step coverage revealed two deposition regimes: a surface reaction controlled regime for cavities aspect ratio lower than 2 and a diffusion-controlled regime for higher aspect ratios. The ZrO₂ films present mostly a cubic/tetragonal structure. The permittivity extracted from the measurement is 26.4. These results are discussed with static dielectric responses calculated in literature.     

Control of Lipase Enantioselectivity by Engineering the Substrate Binding Site and Access Channel

Lipase from Burkholderia cepacia (BCL) has proven to be a very useful biocatalyst for the resolution of 2‐substituted racemic acid derivatives, which are important chiral building blocks. Our previous work showed that enantioselectivity of the wild‐type BCL could be improved by chemical engineering of the substrate's molecular structure. From this earlier study, three amino acids (L17, V266 and L287) were proposed as targets for mutagenesis aimed at tailoring enzyme enantioselectivity. In the present work, a small library of 57 BCL single mutants targeted on these three residues was constructed and screened for enantioselectivity towards (R,S)‐2‐chloro ethyl 2‐bromophenylacetate. This led to the fast isolation of three single mutants with a remarkable tenfold enhanced or reversed enantioselectivity. Analysis of substrate docking and access trajectories in the active site was then performed. From this analysis, the construction of 13 double mutants was proposed. Among them, an outstanding improved mutant of BCL was isolated that showed an E value of 178 and a 15‐fold enhanced specific activity compared to the parental enzyme; thus, this study demonstrates the efficiency of the semirational engineering strategy.     

Modelling and back-analysing failures in steep limestone cliffs

The observation of 12 rock fall scars in steep limestone cliffs has shown that the fallen masses were stable as a result of relatively small rock bridges. These results demonstrate that consideration of rock bridges is necessary for a realistic evaluation of stability. Limit equilibrium methods of analysis are presented for sliding and toppling, for both isostatic and hyperstatic conditions. These methods are illustrated with four case histories. The results of nine back-analyses of rock falls with volumes between 24 and 3500 m³ are presented. The rock cohesion obtained from back-analysis appears to be significantly lower than the cohesion obtained from classical laboratory tests. This discrepancy can be attributed to several factors including: a spatial and temporal scale effect, the oversimplified modelling (two-dimensional limit equilibrium) and some uncertainties affecting the geometrical data. When analysing the stability of a cliff with a limit equilibrium method, the authors suggest dividing the cohesion by a “scale and method” factor of 3.     

Caractérisation d'une pratique d'enseignement des mathématiques : Le cours dialogué

Résumé

L'objet de cet article est de caractériser une pratique d'enseignement des mathématiques que nous nommons cours dialogué, observée dans des classes ordinaires à la fin du collège en France (élèves de 13 à 15 ans) et que nous pensons plus largement utilisée. Pour cela, différentes composantes du contrat didactique sont utilisées en association avec une étude des interactions didactiques observées dans la classe. La méthode d'étude et les composantes du contrat didactique ainsi que les variables des interactions utilisées sont présentées dans les paragraphes 2 et 3 de l'article. Ensuite, ces outils sont utilisés pour analyser une séquence sur la proportionnalité, ce qui permet de dégager les caractéristiques du cours dialogué, notamment en termes de contrat didactique et de fonctions des interactions, par comparaison avec d'autres types d'enseignement mieux connus, la transmission directe du savoir et la transmission du savoir par des situations.     

Analyzing and identifying multiword expressions in spoken language

The present paper investigates multiword expressions (MWEs) in spoken language and possible ways of identifying MWEs automatically in speech corpora. Two MWEs that emerged from previous studies and that occur frequently in Dutch are analyzed to study their pronunciation characteristics and compare them to those of other utterances in a large speech corpus. The analyses reveal that these MWEs display extreme pronunciation variation and reduction, i.e., many phonemes and even syllables are deleted. Several measures of pronunciation reduction are calculated for these two MWEs and for all other utterances in the corpus. Five of these measures are more than twice as high for the MWEs, thus indicating considerable reduction. One overall measure of pronunciation deviation is then calculated and used to automatically identify MWEs in a large speech corpus. The results show that neither this overall measure, nor frequency of co-occurrence alone are suitable for identifying MWEs. The best results are obtained by using a metric that combines overall pronunciation reduction with weighted frequency. In this way, recurring “islands of pronunciation reduction” that contain (potential) MWEs can be identified in a large speech corpus.     

A geoscience perspective on immersive 3D gridded data visualization

We describe visualization software, Visualizer, that was developed specifically for interactive, visual exploration in immersive virtual reality (VR) environments. Visualizer uses carefully optimized algorithms and data structures to support the high frame rates required for immersion and the real-time feedback required for interactivity. As an application developed for VR from the ground up, Visualizer realizes benefits that usually cannot be achieved by software initially developed for the desktop and later ported to VR. However, Visualizer can also be used on desktop systems (unix/linux-based operating systems including Mac OS X) with a similar level of real-time interactivity, bridging the “software gap” between desktop and VR that has been an obstacle for the adoption of VR methods in the Geosciences. While many of the capabilities of Visualizer are already available in other software packages used in a desktop environment, the features that distinguish Visualizer are: (1) Visualizer can be used in any VR environment including the desktop, GeoWall, or CAVE, (2) in non-desktop environments the user interacts with the data set directly using a wand or other input devices instead of working indirectly via dialog boxes or text input, (3) on the desktop, Visualizer provides real-time interaction with very large data sets that cannot easily be viewed or manipulated in other software packages. Three case studies are presented that illustrate the direct scientific benefits realized by analyzing data or simulation results with Visualizer in a VR environment. We also address some of the main obstacles to widespread use of VR environments in scientific research with a user study that shows Visualizer is easy to learn and to use in a VR environment and can be as effective on desktop systems as native desktop applications.     

Behavioral Effects of Basal Forebrain Cholinergic Lesions in Young Adult and Aging Rats.

The interactive effects of age and cholinergic damage were assessed behaviorally in young and middle-aged rats. Rats were lesioned at either 3 or 17 months of age by injection of 192 IgG-saporin immunotoxin into the medial septum and the nucleus basalis magnocellularis, and they were then tested on a range of behavioral tasks: a nonmatching-to-position task in a T-maze, an object-recognition task, an object-location task, and an open-field activity test. Depending on the task used, only an age or a lesion effect was observed, but there was no Age X Lesion interaction. Middle-aged and young rats responded to the cholinergic lesions in the same manner. These results show that in the middle-aged rats in which cholinergic transmission was affected, additional injury to the system was not always accompanied by major cognitive dysfunctions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)