Effect of GABA,a Bacterial Metabolite,on Pseudomonas fluorescens Surface Properties and Cytotoxicity

Different bacterial species and, particularly Pseudomonas fluorescens, can produce gamma-aminobutyric acid (GABA) and express GABA-binding proteins. In this study, we investigated the effect of GABA on the virulence and biofilm formation activity of different strains of P. fluorescens. Exposure of a psychotropic strain of P. fluorescens (MF37) to GABA (10⁻⁵ M) increased its necrotic-like activity on eukaryotic (glial) cells, but reduced its apoptotic effect. Conversely, muscimol and bicuculline, the selective agonist and antagonist of eukaryote GABA_A receptors, respectively, were ineffective. P. fluorescens MF37 did not produce biosurfactants, and its caseinase, esterase, amylase, hemolytic activity or pyoverdine productions were unchanged. In contrast, the effect of GABA was associated to rearrangements of the lipopolysaccharide (LPS) structure, particularly in the lipid A region. The surface hydrophobicity of MF37 was marginally modified, and GABA reduced its biofilm formation activity on PVC, but not on glass, although the initial adhesion was increased. Five other P. fluorescens strains were studied, and only one, MFP05, a strain isolated from human skin, showed structural differences of biofilm maturation after exposure to GABA. These results reveal that GABA can regulate the LPS structure and cytotoxicity of P. fluorescens, but that this property is specific to some strains.     

Interactions of diuron with dissolved organic matter from organic amendments

Diuron is frequently detected in some drinking water reservoirs under the Burgundy vineyards, where organic amendments are applied. The environmental effect of these amendments on pesticide transport is ambiguous: on the one hand it could enhance their retention by increasing soil organic carbon content; on the other hand, dissolved organic matter (DOM) could facilitate their transport. Elutions were performed using columns packed with glass beads in order to investigate DOM-diuron interactions, and the possible co-transport of diuron and DOM. Four organic amendments (A, B, C and D) were tested; C and D were sampled at fresh (F) and mature (M) stages. An increase in diuron leaching was observed only for A and D_F amendments (up to 16% compared to the DOM-free blank samples), suggesting a DOM effect on diuron transport. These results could be explained by the higher DOM leaching for A and D_F compared to B, C_F, C_M and D_M increasing diuron-DOM interactions. These interactions seem to be related to the aromatic and aliphatic content of the DOM, determining formation of hydrogen and non-covalent bonds. The degree of organic matter maturity does not seem to have any effect with amendment C, while a reduction in diuron leaching is observed between D_F and D_M. After equilibrium dialysis measurement of diuron-DOM complexes, it appeared that less than 3% of the diuron applied corresponded to complexes with a molecular weight > 1000 Da. Complexes < 1000 Da could also take part in this facilitated transport.     

Agglomeration for heap leaching: Equipment design, agglomerate quality control, and impact on the heap leach process

In preparation for demonstration heaps, the optimum conditions for agglomeration were determined through testwork. Producing a narrow size distribution of agglomerates in which few agglomerates were smaller than a rice grain, controlling the moisture content to 8–10%, and adding 0.3 kg/t of a commercial polymeric binder were the most important conditions for creating a porous packed bed, as determined from column tests.In a continuous operation, these conditions could be controlled effectively via the ore and solution feed rates to achieve a residence time of 2 min. This ensured that very large, poorly-shaped agglomerates formed before 1.5 min were fragmented into mid-size, well-shaped agglomerates, as well as allowed consolidation of small agglomerates into mid-size ones. Although the residence time of 2 min may not be the optimum for other ores, this study proved that the residence time was the same in a batch or continuous operation regardless of ore type or size distribution.Under the same conditions of agglomeration, the demonstration heaps did not validate the results of the column tests. The heaps were more compact because of the absence of structural support otherwise present in columns through the wall effect. These results highlight the value of demonstration heaps in the scale-up process.     

Empirical Study on Collaborative Writing: What Do Co-authors Do, Use, and Like?

How do people work when they are collaborating to write a document? What kind of tools do they use and, in particular, do they resort to groupware for this task? Forty-one people filled out a questionnaire placed on the World Wide Web. In spite of the existence of specialized collaborative writing tools, most respondents reported using individual word processors and email as their main tools for writing joint documents. Respondents noted the importance of functions such as change tracking, version control, and synchronous work for collaborative writing tools. This study also confirmed the great variability that exists between collaborative writing projects, whether it be group membership, management, writing strategy, or scheduling issues.     

Electrochemical Chromium(III) Oxide Coatings on Non-oxide Ceramic Substrates

SiC and TiB₂ were electrochemically coated with Cr₂O₃ from a 0.1 M aqueous solution of chromium nitrate hydrate with ethanol additives. On both substrate materials poly-crystalline Cr₂O₃ was formed at current densities from 5 to 50 mA/cm² and deposition durations of 5 to 30 min. The coating weight increased with current density and with deposition time. The as-deposited coatings contained microcracks due to drying shrinkage. Microstructural observations indicate that sintering of the Cr₂O₃ coatings on TiB₂ at 1100°C for 1 n in a reducing atmosphere in a closed graphite crucible causes the densification of the coating via a liquid phase, which forms by oxidation of TiB₂. Under similar conditions, the Cr₂O₃ coatings on SiC may be sintered via an evaporation–condensation mechanism.     

Medial prefrontal lesions in the rat and spatial navigation: Evidence for impaired planning.

Rats with medial prefrontal cortical lesions were tested in a modified water maze navigation task. In Stage 1, the rats were trained to locate a hidden platform from a single start location. They were then subjected to a series of trials during which a second start position was used (Stage 2). In Stage 3, the rats had to navigate to a new goal location from the 2 experienced start positions. Stage 4 required the rats to navigate to the same goal as in Stage 3, starting from 4 distinct positions. Finally, a single probe trial with no platform was conducted. Rats with prefrontal lesions were impaired only during Stage 4. This deficit was specific to the 2 start positions newly introduced during this stage, suggesting a dysfunction of planning processes. This impairment might result from a working memory deficit, precluding the animal from forming an adequate representation of the whole course of movements required to reach the platform. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Anionic polymerization and copolymerization of cyclosiloxanes initiated by trimethylsilylmethyllithium

Summary A novel initiator, i.e. trimethylsilylmethyllithium has been successfully used for the ring opening polymerization of cyclosiloxanes, in toluene or in the bulk, in the presence of the cryptand [211] or DMSO. Suitable conditions have been found in which monomodal distributions of molecular weights are observed for homopolymers of 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane (V₄) as well as for copolymers of V₄ with D₃ or D₄. Laboratoire de Chimie Macromoléculaire associé au CNRS, URA 24     

Dissociations entre musique et langage après atteinte cérébrale: Un nouveau cas d'amusie sans aphasie.

Presents the case of a 40-yr-old female, I.R., who sustained bilateral damage to the temporal lobes and to the right frontal lobe as a result of successive brain surgeries. Her performance is compared to that of 4 neurologically intact Ss who were matched in terms of education, sex and age. I.R.'s performance on various tests aiming at assessing her general cognitive functioning is reported with a particular focus on auditory aspects. Results show that I.R.'s speech abilities are essentially intact. The only language impairments are related to a short-term memory deficit, to some abnormal sensitivity to retroactive interference in long-term memory and to articulation. These difficulties do not, however, affect linguistic communication, which is obviously undisturbed. I.R. does not experience and difficulty in the recognition and memorization of familiar sounds such as animal cries, traffic noises and the like. I.R. is severely impaired in most musical abilities: She can no longer discriminate nor identify melodies that were once highly familiar to her; she can no longer discriminate nor memorize novel melodies. Her pattern of musical losses is compatible with a basic and severe perceptual deficit that compromises access to and registration in memory systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social ecological model of illness management in high-risk youths with type 1 diabetes.

In this study, the authors tested a social ecological model of illness management in high-risk, urban adolescents with Type 1 diabetes. It was hypothesized that management behaviors would be associated with individual adolescent characteristics as well as family, peer, and provider relationships. Questionnaires were collected from 96 adolescents in poor metabolic control and their primary caregivers. Variables in each system were correlated with illness management. Multiple regression demonstrated that higher externalizing symptoms, poorer family relationships, lower satisfaction with providers, and greater age contributed to the variance in illness management. Internalizing symptoms and peer relationships were no longer significant in the model. Results support a social ecological model of illness management in high-risk youths. Interventions grounded in social ecological theory are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Gas chromatography/mass spectrometry as a suitable tool for the Li-ion battery electrolyte degradation mechanisms study

To allow electric vehicles to be powered by Li-ion batteries, scientists must understand further their aging processes in view to extend their cycle life and safety. For this purpose, we focused on the development of analytical techniques aiming at identifying organic species resulting from the degradation of carbonate-based electrolytes (EC-DMC/LiPF(6)) at low potential. As ESI-HRMS provided insightful information to the mechanism and chronological formation of ethylene oxide oligomers, we implemented "gas" GC/MS experiments to explore the lower mass range corresponding to highly volatile compounds. With the help of chemical simulation tests, we were able to discriminate their formation pathways (thermal and/or electrochemical) and found that most of the degradation compounds originate from the electrochemically driven linear alkyl carbonate reduction upon cycling and to a lesser extent from a two-step EC reduction. Deduced from these results, we propose an overall electrolyte degradation scheme spanning the entire mass range and the chemical or electrochemical type of processes.