Measurement of enthalpies of mixing in gaseous phase for the binary system carbon dioxide – hydrogen sulphide by an isothermal flow calorimeter

Enthalpies of mixing for the binary system carbon dioxide – hydrogen sulphide were measured by means of an isothermal flow calorimeter at temperatures of 293.15. 305.15 and 313.15 K. For the first isotherm, excess enthalpy measurements were made at pressures of 0.507, 1.013 and 1.419 MPa. For the last two isotherms, these measurements were performed at pressures of 0.507, 1.013 and 1.520 MPa. The experimental data were treated by the same techniques described for the systems previously studied (Barry et al., 1982a, 1982b, 1982c). Two types of binary interaction coefficients k_ij have been utilized for the prediction of experimental data from equations of state: coefficients k_ij independent of temperature and pressure, and k_ij's adjusted as function of temperature and pressure. A better prediction of the excess enthalpy experimental data was obtained from the latter series of binary interaction coefficients.     

Nouvelle méthode de traitement de séries de données tronquées dans l'étude de la pollution atmosphérique

The statistical treatment of sets of data including some values that are below the detection limit is frequently used in air pollution studies. These values are usually, and conventionally, set at one half of the detection limit. The present paper discusses the validity of this convention and shows on both theoretical and empirical grounds that it is better to set these values at two thirds rather than one half of the detection limit.     

On the volume change on non covalent gels in solvent-non solvent mixtures

Summary In this paper, the volume change on polysaccharide gels in non solvent mixtures is investigated. No phase transition is observed. A reversible decrease of the swelling volume is obtained directly related to the mechanical properties of the gels and to the charge parameters of the polymers. The effect of deswelling in presence of acetone or alcohol is increasing from agarose, k-carrageenan and i-carrageenan.     

Application de l'analyse expérimentale du comportement à une situation de remotivation.

In an experiment with 2 groups of 4 schizophrenics, the efficiency of a group discussion run according to the principles of the experimental analysis of behavior was compared with the traditional approach to remotivation. 2 target behaviors were chosen for study: speaking (intervention) and S-to-S interaction (social interaction). The number and length of interventions as well as the number of social interactions were used as the basic measurements. The experiment was divided into 2 parts with 2 Es. Group 1 held the usual group discussion in Part 1 and Part 2 after the leader was instructed. Group 2 used the behavioral approach in both parts of the experiment. Results show that the behavioral approach increased both the length of interventions and the number of social interactions, even though the leaders themselves actually spoke less. The principles of experimental analysis are discussed in relation to their application in a remotivation situation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Formation pratique à la conception d’un circuit intégré spécifique

We present an example of practical works in design methodology for realizing digitalASIC circuit, at the graduate level in the microelectronics engineering program (ISIM) of the University of Montpellier II. This training program is illustrated by the design of a small project from specification to silicon manufacturing files, using a CMOS standard cell approach with theCAD softwares system Hilo (Genrad) and Solo 1400(ES2).     

Stereochemistry of the N-glycosylation sites in glycoproteins

The stereochemical features displayed by the N-glycosidic linkagein crystalline N-linked glycoproteins are analyzed. From thestatistical analysis of 44 different glycosylation sites belongingto 26 glycoproteins of the Brookhaven Protein Data Bank, a meanstandard geometry for the GlcNAc moiety, along with a rationalizationof its confornia-tional behavior, can be proposed. As for theglycopeptide linkage, the distribution of observed conformationshas been analyzed on the basis of molecular mechanics calculations.The rotamer distribution of the Asn side chains conforms tothat observed on non-glycosylated structures, and it agreeswith the pattern of flexible conformations gathered from NMRmeasurements. In characterizing the protein-glycan interactions,some hydrogen bonds occur. Stacking between the amphiphilicmoiety of the glycan and some surrounding aromatic, or at leasthydrophobic, amino acid residues is also found. When lookingat the secondary structure of the glycosylated peptide, only25% of the glycosylation sites correspond to situations whereAsn is located at the top of a ß-turn. Other typesof secondary structure exist which fulfil the spatial requirementof having the glycan exposed at the surface of the protein.These data can be compared with the most recent studies on thepeptide conformation which would be required for glycosylation.     

Solid state and solution features of amylose and amylosic fragments

An understanding of the molecular changes occurring during polymorphic transformations of amylose is sought through the use of energy calculations. Four stable families of low energy conformers are found; three of these correspond to conformations observed in linear and cyclic maltodextrins in the crystalline state. Upon change of solvent, significant variations have been shown to occur in the relative abundance of amylose conformers. This, in turn, influences properties such as chain extension. The relevance of the stable conformers with respect to helical structures of amylose is analyzed. Whereas one of the conformers would generate a V type shallow helix, another one would give rise to a 6 fold left-handed strand having a 3.6 A advance per residue. This would generate a double helical stranded structure.     

Etude cinétique de la déshydrtation du sulfate de cuivre par thermogravimétrie et thermogradientimétrie

A new type of thermobalance has been built, Sample temperatures have been determined by a new technique called “thermogradientimetry”. A special crucible assembly allows control of the atmosphere surrounding the sample. Kinetic results for the three successive stages in the dehydration of copper sulphate indicate that the reactions involved are of zero order. The apparent activation energy for each stage of the dehydration has been avaluated under isobaric conditions for different water vapor pressures.     

Lithographically fabricated nanopore-based electrodes for electrochemistry

We report a new technique for fabricating electrodes for electrochemical applications with lateral dimensions in the range 15-200 nm and a reproducible, well-defined geometry. This technique allows determining the electrode size by electron microscopy prior to electrochemical measurements and without contamination of the metal electrode. We measured the diffusion-limited current with stepped-current voltammetry and showed that its dependence on electrode size can be quantitatively understood if the known geometry of the electrodes is explicitly taken into account.     

Predicting phase noise in crystal oscillators

In order to predict the phase noise in crystal oscillators an enhanced phase-noise model has been built. With this model, the power spectral densities of phase fluctuations can be computed in different points of the oscillator loop. They are calculated from their correlation functions. The resonator-caused noise as well as the amplifier-caused noise are taken into account and distinguished. To validate this enhanced model, the behavior of a batch of 10 MHz quartz crystal oscillators is observed and analyzed. The tested batch has been chosen in a facility production. Their associated resonators have been selected according to the value of their resonant frequency and their motional resistance. Open-loop and closed-loop measurements are given. The phase noise of the overall oscillator working in closed loop is provided by the usual active method. Theoretical and experimental results are compared and discussed.