OH concentration and temperature measurements by use of near-resonant holographic interferometry

Near-resonant holographic interferometry is demonstrated to measure temperature and species concentration in a two-dimensional steady premixed air-acetylene flame. A peak temperature of (2600 +/- 100) K and a peak OH number density of (9.6 +/- 0.3) x 10(22) m(-3) are obtained, consistent with the expected values for such a flame. These values are determined by recording interferograms with a laser assumed sufficiently detuned from line center so that pressure and temperature broadening can be ignored. The results are thus obtained without making prior assumptions on the temperature or pressure of the flame beyond the existence of thermal equilibrium.     

Characterization of the surface charge of oxide particles of PWR primary water circuits from 5 to 320 °C

The point of zero charge of three typical oxides found as colloids in PWR primary circuits has been measured by mass titration in a large range of temperature: from 5 to 320 °C for magnetite and cobalt ferrite, from 5 to 125 °C for nickel ferrite. Comparisons with zetametry were performed near room temperature. The protonation thermodynamic constants have been calculated. The standard protonation enthalpy at 298 K is −27 ± 5, −31 ± 6 and −32 ± 7 kJ mol⁻¹, for the three oxides respectively. The sign of the surface charge of these colloidal particles in the temperature conditions of the primary circuit indicates that their adhesion onto the materials of the circuit is favored.     

Formation of pyroglutamic acid from N-terminal glutamic acid in immunoglobulin gamma antibodies

The status of the N-terminus of proteins is important for amino acid sequencing by Edman degradation, protein identification by shotgun and top-down techniques, and to uncover biological functions, which may be associated with modifications. In this study, we investigated the pyroglutamic acid formation from N-terminal glutamic acid residues in recombinant monoclonal antibodies. Almost half the antibodies reported in the literature contain a glutamic acid residue at the N-terminus of the light or the heavy chain. Our reversed-phase high-performance liquid chromatography-mass spectrometry method could separate the pyroglutamic acid-containing light chains from the native light chains of reduced and alkylated recombinant monoclonal antibodies. Tryptic peptide mapping and tandem mass spectrometry of the reduced and alkylated proteins was used for the identification of the pyroglutamic acid. We identified the formation of pyroglutamic acid from N-terminal glutamic acid in the heavy chains and light chains of several antibodies, indicating that this nonenzymatic reaction does occur very commonly and can be detected after a few weeks of incubation at 37 and 45 degrees C. The rate of this reaction was measured in several aqueous buffers with different pH values, showing minimal formation of pyroglutamic acid at pH 6.2 and increased formation of pyroglutamic acid at pH 4 and pH 8. The half-life of the N-terminal glutamic acid was approximately 9 months in a pH 4.1 buffer at 45 degrees C. To our knowledge, we showed for the first time that glutamic acid residues located at the N-terminus of proteins undergo pyroglutamic acid formation in vitro.     

Alternating projection method applied to indefinite correlation matrices for generation of synthetic MIMO channels

Complex correlation multiple-input multiple-output (MIMO) matrices estimated from measurements under realistic propagation conditions occasionally have positive, zero and negative eigenvalues, converting them to indefinite matrices. In this framework, this paper presents a novel correction procedure (CP) based on the alternating projection (AP) method to find the Hermitian and positive definite matrix closest to an estimated indefinite full spatial correlation (FSC) MIMO matrix. This corrected matrix allows the Cholesky factorisation usually used for generation of synthetic MIMO channel samples. The applicability of the CP has been analysed using real data from non-line-of-sight (NLOS) indoor measurements. The results reported in this paper show that a proper selection of the CP parameters has not a sensitive impact on the cumulative distribution function (CDF) of the eigenvalues of the estimated FSC MIMO matrices. This characteristic makes the CP useful for channel characterisation, allowing to assess the performance of a MIMO system. As an example of the CP application, a study of ergodic and outage MIMO capacities for different array configurations is presented .     

Structural analysis of fMRI data revisited: improving the sensitivity and reliability of fMRI group studies

Group studies of functional magnetic resonance imaging datasets are usually based on the computation of the mean signal across subjects at each voxel (random effects analyses), assuming that all subjects have been set in the same anatomical space (normalization). Although this approach allows for a correct specificity (rate of false detections), it is not very efficient for three reasons: i) its underlying hypotheses, perfect coregistration of the individual datasets and normality of the measured signal at the group level are frequently violated; ii) the group size is small in general, so that asymptotic approximations on the parameters distributions do not hold; iii) the large size of the images requires some conservative strategies to control the false detection rate, at the risk of increasing the number of false negatives. Given that it is still very challenging to build generative or parametric models of intersubject variability, we rely on a rule based, bottom-up approach: we present a set of procedures that detect structures of interest from each subject's data, then search for correspondences across subjects and outline the most reproducible activation regions in the group studied. This framework enables a strict control on the number of false detections. It is shown here that this analysis demonstrates increased validity and improves both the sensitivity and reliability of group analyses compared with standard methods. Moreover, it directly provides information on the spatial position correspondence or variability of the activated regions across subjects, which is difficult to obtain in standard voxel-based analyses.