Nondipolar electron angular distributions from fixed-in-space molecules

The first indication of nondipole effects in the azimuthal dependence of photoelectron angular distributions emitted from fixed-in-space molecules is demonstrated in N (2). Comparison of the results with angular distributions observed for randomly oriented molecules and theoretical derivations for the nondipole correction first order in photon momentum suggests that higher orders will be needed to describe distributions measured in the molecular frame.     

Brain MRI lesion load quantification in multiple sclerosis: a comparison between automated multispectral and semi-automated thresholding computer-assisted techniques

Brain magnetic resonance imaging (MRI) lesion volume measurement is an advantageous tool for assessing disease burden in multiple sclerosis (MS). We have evaluated two computer-assisted techniques: MSA multispectral automatic technique that is based on bayesian classification of brain tissue and NIH image analysis technique that is based on local (lesion by lesion) thresholding, to establish reliability and repeatability values for each technique. Brain MRIs were obtained for 30 clinically definite relapsing-remitting MS patients using a 2.0 Tesla MR scanner with contiguous, 3 mm thick axial, T1, T2 and PD weighted modalities. Digital (Dicom 3) images were analyzed independently by three observers; each analyzed the images twice, using the two different techniques (Total 360 analyses). Accuracy of lesion load measurements using phantom images of known volumes showed significantly better results for the MSA multispectral technique (p < 0.001). The mean intra-and inter-observer variances were, respectively, 0.04 ± 0.4 (range 0.04–0.13), and 0.09 ± 0.6 (range 0.01–0.26) for the multispectral MSA analysis technique, 0.24 ± 2.27 (range 0.23–0.72) and 0.33 ± 3.8 (range 0.47–1.36) for the NIH threshold technique. These data show that the MSA multispectral technique is significantly more accurate in lesion volume measurements, with better results of within and between observers’ assessments, and the lesion load measurements are not influenced by increased disease burden. Measurements by the MSA multispectral technique were also faster and decreased analysis time by 43%. The MSA multispectral technique is a promising tool for evaluating MS patients. Non-biased recognition and delineation algorithms enable high accuracy, low intra-and inter-observer variances and fast assessment of MS related lesion load.     

A charge-transfer-induced spin transition in the discrete cyanide-bridged complex [[Co(tmphen)2]3[Fe(CN)6]2

A charge-transfer-induced spin transition (CTIST) is observed in the discrete cyanide-bridged complex, {[Co(tmphen)2]3[Fe(CN)6]2}. Single-crystal X-ray diffraction, 57Fe M?ssbauer spectroscopy, and magnetic susceptibility were used collectively to describe the oxidation states of the Co and Fe ions in this cluster as a function of temperature. This pentanuclear complex represents the first example of a CTIST at the discrete molecular level.     

Observation of a continuum-continuum interference hole in ultrafast dissociating core-excited molecules

The femtosecond dissociation of HCl after core excitation has been studied through the resonant Auger decay. The spectra contain contributions from decay occurring at both "molecular" and "atomic" internuclear distances. We have observed a new interference mechanism in these spectra: An atomic spectral line develops into a negative spectral contribution, a "hole," when detuning the excitation energy from the maximum of the Cl2p(-1)sigma(*) resonance. Resonant x-ray scattering theory quantitatively explains this behavior as due to a novel destructive continuum-continuum interference between molecular and atomic contributions to the Auger decay.     

Doppler splitting of In-flight auger decay of dissociating oxygen molecules: the localization of delocalized core holes

By exploiting the core-excitation-induced dissociation of O2, we find that the Auger emission exhibits a Doppler-like energy shift. We show this to be a manifestation of localization of the core hole and propose that the problem of core-hole localization versus delocalization in core-hole spectroscopies may be resolved by considering the nature of the measurement.     

Thermogravimetric analysis of layered double hydroxides with chloramphenicol and salicylate in the interlayer space

The thermal behavior of the new inorganic-organic nanohybrid materials obtained by intercalation of chloramphenicol and salicylate into layered double hydroxides (LDHs) by direct synthesis method, anion exchange reaction and the reconstruction method was evaluated by dynamic thermogravimetric analysis in air, at heating rates of 5°C min⁻¹. The XRD patterns of the samples are characteristic for those of well crystallized solids with layered double hydroxide structures. The FTIR spectroscopy results show the presence of the organic compound within the network structure of the synthesized LDHs. The kinetic parameters (reaction order (n) apparent activation energy (E _a) and pre-exponential factor (lnA) were calculated by the Coats-Redfern method. The compensation effects were determined.     

An experimental and kinetic modeling study on the oxidation of 1,3-dioxolane

The modern catalytic or enzymatic advances allow the production of novel biofuel. Among them, 1,3-dioxolane can be produced from formaldehyde and ethylene glycol, both can be obtained from biomass. In this study, the oxidation of 1,3-dioxolane is studied at stoichiometric conditions. The ignition delay times of 1,3-dioxolane/O₂/inert mixtures were measured in a shock tube and in a rapid compression machine at pressures of 20 to 40 bar and temperatures ranging from 630 to 1300 K. The pressure profiles recorded in the rapid compression machine show a first stage of ignition enlightening the influence of the low temperature chemistry of combustion. Furthermore, mole fraction profiles of the stable intermediates produced during the oxidation of 1,3-dioxolane were measured in a jet-stirred reactor at 10 bar. Following these observations, a detailed kinetic model was developed with reaction rate coefficients and thermochemical data calculated by theoretical calculations or estimated by analogies to suitable molecules. In order to get an insight into the most important reaction pathways brute force sensitivity analysis and reaction pathway analysis were performed with the proposed model and discussed. It became clear that in the fuel-in-air case for the alkylhydroperoxide of 1,3-dioxolane the ring opening beta-scission pathway is favored against the further alkane-like second addition to molecular oxygen, which leads to a limited negative temperature coefficient.