Analysis of poly(oxyethylene) and poly(oxypropylene) triblock copolymers by MALDI-TOF mass spectrometry

Triblock copolymers of ethylene oxide (EO) and propylene oxide (PO) are widely used in the chemical industry as nonionic surfactants. Triblock copolymers can be arranged in a EO-PO-EO or PO-EO-PO sequence. This arrangement results in an amphiphilic copolymer, in which the block sequence and block length determine the properties of the copolymer. MALDI-TOF MS was used to analyze various triblock copolyethers: EO-PO-EO (Mn =2000 g.mol(-1)), PO-EO-PO (Mn = 2000 g.mol(-1)), and a random copolymer EO/PO (Mn = 2500 g.mol(-1)). Data treatment was assisted by using a homemade software allowing a picture of monomer composition of oligomers from the mass spectra. MALDI-TOF mass spectra of EO/PO copolymers were shown to depend strongly on the number of laser shots, relative proportions of polymer/salt, and the nature of the matrix. An unsaturated byproduct was detected. Its presence was demonstrated by prefractionation of copolymers by SEC before MALDI-TOF analysis, and its content was estimated by 1H NMR. The formation of layers inside the MALDI deposit was evidenced by varying the number of laser shots. Lighter oligomers of the copolymer, unsaturated byproduct, or both would be in the core of the deposit, coated with heavier oligomer. The layer formation depends on the nature of the matrix and the quantity of added salt. DHB matrix with a relative high sodium salt content induces layer formation inside the deposit, whereas dithranol matrix or low salt content does not. Consequently, an optimization of experimental parameters in order to estimate the lighter oligomers or unsaturated byproduct content or to obtain the actual representation of the monomer contribution in the copolymers from the MS data only seems obviously critical. MALDI-TOF mass spectrometry is obviously a powerful technique to analyze copolymers, but a careful survey of the experimental parameters is required. The combination of MALDI-TOF MS with separations techniques and NMR brings precious complementary information.     

Postprandial Bowel Sounds

Bowel sounds were recorded under standard conditions for 30 minutes before, and for 90 minutes after a standard meal in 12 healthy human volunteers. The sounds were analyzed with the aid of a computer, and the evolution in time of specific parameters obtained as a quantitative printout. The number, total duration, and mean energy of sounds totaled for ten minute periods were found to be markedly influenced by the ingestion of the meal. A peak of activity occurred immediately after the meal; the activity then decreased to 85% of premeal value 60 minutes later, and a second peak followed after a further 60 minutes. An excellent correlation (correlation coefficient better than 0.9) was found at two recording sites between the three analyzed parameters, taken in pairs. For any given parameter, a correlation was also found between its value at the two sites (k better than 0.9),but the actual value were significantly different (p <0.001). When bowel sounds are interpreted, therefore, food ingestion should be taken into consideration.     

Phosphorylation of yeast plasma membrane H+-ATPase by casein kinase I

The plasma membrane H+-ATPase of Saccharomyces cerevisiae is subject to phosphorylation by a casein kinase I activity in vitro. We show this casein kinase I activity to result from the combined function of YCK1 and YCK2, two highly similar and plasma membrane-associated casein kinase I homologues. First, H+-ATPase phosphorylation is severely impaired in the plasma membrane of YCK-deficient yeast strains. Furthermore, the wild-type level of the phosphoprotein is restored by the addition of purified mammalian casein kinase I to the mutant membranes. We used the H+-ATPase as well as a synthetic peptide substrate that contains a phosphorylation site for casein kinase I to compare kinase activity in membranes prepared from yeast cells grown in the presence or absence of glucose. The addition of glucose results in increased H+-ATPase activity which is associated with a decline in the phosphorylation level of the enzyme. Mutations in both YCK1 and YCK2 affect this regulation, suggesting that H+-ATPase activity is modulated by glucose via a combination of a "down-regulating" casein kinase I activity and another, yet uncharacterized, "up-regulating" kinase activity. Biochemical mapping of phosphorylated H+-ATPase identifies a major phosphopeptide that contains a consensus phosphorylation site (Ser-507) for casein kinase I. Site-directed mutagenesis of this consensus sequence indicates that Glu-504 is important for glucose-induced decrease in the apparent Km for ATP.     

Model-Based Expert System for Design and Simulation of APS Coatings

This article aims at presenting an expert system to assist the design and the simulation of 2-D shapes of alumina-titania (i.e., Al₂O₃-13 wt.% TiO₂) Atmospherically Plasma Sprayed (APS) coatings. Indeed, the expert system derives from a spray deposition mathematic model resulting from experiments. The varied processing parameters were the geometric and the kinematics parameters, mainly, such as: the relative speed gun-substrate, the spray distance, the spray angle, the relative positioning powder injector-spray gun trajectory, the number of passes and the powder feed rate. The variations of the geometry and some of the structural parameters were analyzed relatively to the aforementioned varied parameters. Thus, a large set of spray pattern parameters was designed. This set considers mostly the spray pattern geometry. All the relationships between the processing parameters and the spray pattern parameters were hence grouped in a spray deposition model. The second step of this work consisted in optimizing the robotic (i.e., spray gun) trajectory using a robotic code, which permits a realistic simulation of the spray gun speed and its inertia. Using this simulation software, a trajectory file was built. In the third step of the work, an expert system was developed by combining the spray deposition model with the trajectory. The tasks of the expert system are: (1) to assist the user in designing the coatings by selecting the processing parameters and (2) to simulate the coating shapes by integrating the gun trajectory.

Suspension Plasma-Sprayed Alumina Coating Structures: Operating Parameters Versus Coating Architecture

Suspension plasma spraying (SPS) is able to process sub-micrometric-sized feedstock particles and permits the deposition of layers thinner (from 5 to 50 μm) than those resulting from conventional atmospheric plasma spraying (APS). SPS consists in mechanically injecting within the plasma flow a liquid suspension of particles of average diameter varying between 0.02 and 1 μm, average values. Upon penetration within the DC plasma jet, two phenomena occur sequentially: droplet fragmentation and evaporation. Particles are then processed by the plasma flow prior their impact, spreading and solidification upon the surface to be covered. Depending upon the selection of operating parameters, among which plasma power parameters (operating mode, enthalpy, spray distance, etc.), suspension properties (particle size distribution, powder mass percentage, viscosity, etc.), and substrate characteristics (topology, temperature, etc.), different coating architectures can be manufactured, from dense to porous layers. Nevertheless, the coupling between the parameters controlling the coating microstructure and properties are not yet fully identified. The aim of this study is to further understand the influence of parameters controlling the manufacturing mechanisms of SPS alumina coatings, particularly the spray beads influence.     

Low temperature oxidation of a coking plant soil organic matter and its major constituents: an experimental approach to simulate a long term evolution

In contaminated soils, several natural processes (biodegradation, oxidation, etc.) can induce degradation of organic pollutants. The aim of this work was to evaluate the impact of an abiotic low-temperature oxidation on a coking plant soil and its main organic constituents (coal, coke, coal tar and road asphalts) in order to understand its long term evolution. This natural process was experimentally reproduced by oxidizing the soil and isolated organic matrices at 100 °C during 180 days. The samples were analyzed by total organic carbon measurements and elemental analyses, and the solvent-extractable organic matter was quantified by GC-MS (gas chromatography-mass spectrometry). Oxidation experiments on coal, coal tar and coking plant soil samples lead to the decrease in polycyclic aromatic hydrocarbon (PAH) concentrations correlated to an incorporation of oxygen evidenced by the production of oxygenated PAHs. The increasing amount of polar macromolecules and the decrease in solvent-extractable organic matter suggest a molecular growth through ether/ester cross-linking. The chemical environment of organic compounds and the presence of a reactive mineral fraction are important parameters that improve the efficiency of oxidation. This work reveals that abiotic low temperature oxidation, can strongly contribute to pollutant removal especially by a stabilization process and should be considered in the long term evolution of a soil.     

Architecture and phases composition of suspension plasma sprayed alumina-titania sub-micrometer-sized coatings

Sub-micrometer-sized Al₂O₃-TiO₂ plasma-sprayed coatings exhibit superior performances compared to micrometer-sized ones. Two routes can be implemented to manufacture such finely structured coatings: i) spraying micrometer-sized agglomerates of nanometer-sized particles which results in a two-scale coating architecture and ii) spraying a suspension of sub-micrometer-sized particles (suspension plasma spraying, SPS). SPS was implemented in this study and Al₂O₃-base coatings with 13 and 60 wt.% of titania, respectively, were manufactured by spraying a suspension made of a mixture of Al₂O₃ and TiO₂ particles both of 300 nm, average diameter. Coating structural features and phase contents were studied. Results show that the coatings exhibit a very fine lamellar structure with a homogeneous repartition of Al and Ti. Complex phases, made of intermediate Al, Ti, and O oxides, have been also identified. Indeed, coatings formation results from rapid solidification rates and high transient thermal fluxes imparted by the plasma flow to the substrate due to the short spray distance encountered in SPS (in the order of 30 mm) requested by the small kinetics and thermal inertia of sub-micrometer-sized particles.     

Outcomes and contextual aspects of strategic environmental assessment in a non-mandatory context: the case of Brazil

Within the ample body of literature devoted to strategic environmental assessment (SEA) outcomes and the assessment of its effectiveness, it is accepted that the performance of SEA systems is influenced by contextual aspects. Procedural aspects, objectives, guidance, approach, timing, amongst others, are reported as key components of the different dimensions of SEA effectiveness but their linkage to SEA outcomes is yet to be adequately investigated. In this paper, contextual aspects and related outcomes of a non-mandatory SEA system were identified through systematic literature review and personal interviews with key actors of SEA, aiming at the identification of the influence of contextual factors on SEA effectiveness. The findings indicate three main aspects that may explain the lengthy process of introduction of SEA in plan- and policy-making in the country: (i) lack of proper SEA legislation, (ii) the influence of Environmental Impact Assessment practice and (iii) the influence of the environmental licensing culture. Nevertheless, SEA contributes to improving communication between stakeholders along the planning process and to providing a better level of information for lower tiers of decision-making. In spite of the minor influences on the nature of the strategic action, valuable lessons credited to SEA have been learnt.     

Modeling of Ethylene Glycol Production from Glucose in a Semi-Continuous Reactor

A numerical study describes the catalytic conversion of glucose into ethylene glycol (EG) in a semi-batch reactor. This analysis couples a set of power law models (homogeneous reactions) and Langmuir-Hinshelwood-Hougen-Watson (LHHW) equations (hydrogenations). For this purpose, the kinetic parameters of the LHHW expressions are estimated for the reaction conditions. Then, the kinetic model evaluates the influence of the H₂ pressure and the catalyst concentrations on the selectivity. The results indicate that the EG yield is increased by setting the temperature and the H₂ pressure. In this manner, the process reduces the hexitols and methane production and increases the EG yield. The originality of the work is based on the influence of the H₂ pressure and the catalyst concentrations in the model.