Topotactic desolvation and condensation reactions of 3D Zn3TiF7(H2O)2(taz)3·S (S = 3H2O or C2H5OH).

Crystals of two new 3D hybrid compounds, trans-Zn3TiF7(H2O)2(taz)3·3H2O and cis-Zn3TiF7(H2O)2(taz)3·C2H5OH, have been obtained by solvothermal synthesis ((taz)- = 1,2,4-triazolate C2H2N3 ligand). Their structures, determined from X-ray single crystal diffraction data in Cm and Pnma space groups, respectively, are based on Zn3N9(H2O)2F3 trimers linked by TiF6 octahedra that build trans- or cis-chains ∞[Zn3TiN9(H2O)2F7]. Water or ethanol in the structure cavities is released below 110 °C to give trans- or cis-Zn3TiF7(H2O)2(taz)3 and, on further heating, these intermediate phases dehydrate and lead to anhydrous trans- or cis-Zn3TiF7(taz)3. At 110 °C, the loss of ethanol concerns only ≈1/3 of the weight of cis-Zn3TiF7(H2O)2(taz)3·C2H5OH while the remaining part subsists up to 180 °C. This behaviour is attributed to a core-shell type configuration. Rehydration in humid air occurs at room temperature for the anhydrous cis-phase. All desolvated, dehydrated or rehydrated phase structures have been determined by X-ray powder diffraction and ab initio Rietveld refinements. All transformations from solvated or hydrated to anhydrous phases are realised without any symmetry change and the trans or cis connection of the TiF6 octahedra is maintained together with the overall features of the 3D networks. The final loss of water molecules induces a condensation reaction that implies the connection of the trimers by fluorine atoms; the structures of the anhydrous phases Zn3TiF7(taz)3 are then described by Zn3N9F4 trimers. 1H and 19F MAS NMR studies, coupled with DFT calculations of NMR parameters, confirm the water loss and support the strutural models while evidencing both the positional disorders, more likely of the organic parts, and the F motions within TiF6 octahedra.

Foot and mouth disease virus serological study of dromedary camels in Oman.

The potential role of camels in the epidemiology of foot and mouth disease in Oman was investigated. Sera from local dromedaries (n = 151) that graze with animals (cattle and small ruminants) positive for foot and mouth disease virus (FMDV) non-structural protein antibody (NSP-Ab) were tested for the detection of FMDV NSP-Ab. The samples were tested using a commercial competitive enzyme-linked immunosorbent assay (cELISA) , a rapid immunochromatographic assay and a solid-phase cELISA for the detection of antibodies specific to FMDV serotype O. The results from all three assays were negative when tested with dromedary sera. This indicates that FMDV was not transmitted to dromedary camels kept with FMDV NSP-Ab-positive ruminants.

Une étude a été entreprise dans le but de déterminer le rôle potentiel joué par les camélidés dans l'épidémiologie de la fièvre aphteuse à Oman. À cette fin, des échantillons ont été prélevés à partir de dromadaires autochtones (n = 151) qui pâturaient sur les mêmes prairies que des bovins et des petits ruminants possédant des anticorps contre la protéine non structurale du virus de la fièvre aphteuse en vue de rechercher la présence de ces anticorps. Les sérums ont été soumis à trois tests sérologiques : une épreuve immuno-enzymatique de compétition (cELISA), un essai immunochromatographique rapide et une cELISA en phase solide pour la détection spécifique d'anticorps dirigés contre le sérotype O du virus de la fièvre aphteuse. Les sérums des dromadaires ont tous donné des résultats négatifs aux trois tests. Ces résultats indiquent qu'il n'y a pas eu transmission du virus de la fièvre aphteuse entre les ruminants possédant des anticorps contre la protéine non structurale du virus et les dromadaires.

Los autores describen un estudio encaminado a estudiar la posible función del dromedario en la epidemiología de la fiebre aftosa en Omán. Tras extraer suero de dromedarios locales (n = 151) que pastaban junto con animales (ganado vacuno y pequeños rumiantes) positivos para el anticuerpo contra la proteína no estructural del virus de la fiebre aftosa, se sometieron las muestras de suero a técnicas de detección de ese anticuerpo, empleando para ello: un ensayo inmunoenzimático (ELISA) de competición comercial; una prueba rápida de inmunocromatografía; y un ELISA de competición en fase sólida para la detección de anticuerpos específicos contra el serotipo O del virus. Las tres técnicas arrojaron resultado negativo ante los sueros de dromedario, hecho indicativo de que los rumiantes con anticuerpos contra la proteína no estructural del virus de la fiebre aftosa no habían transmitido el virus a los dromedarios con los que convivían.

Seasonal selection and resource dynamics in a seasonally polyphenic butterfly.

Seasonal polyphenisms are widespread in nature, yet the selective pressures responsible for their evolution remain poorly understood. Previous work has largely focussed either on the developmental regulation of seasonal polyphenisms or putative 'top-down' selective pressures such as predation that may have acted to drive phenotypic divergence. Much less is known about the influence of seasonal variation in resource availability or seasonal selection on optimal resource allocation. We studied seasonal variation in resource availability, uptake and allocation in Araschnia levana L., a butterfly species that exhibits a striking seasonal colour polyphenism consisting of predominantly orange 'spring form' adults and black-and-white 'summer form' adults. 'Spring form' individuals develop as larvae in the late summer, enter a pupal diapause in the fall and emerge in the spring, whereas 'summer form' individuals develop directly during the summer months. We find evidence for seasonal declines in host plant quality, and we identify similar reductions in resource uptake in late summer, 'spring form' larvae. Further, we report shifts in the body composition of diapausing 'spring form' pupae consistent with a physiological cost to overwintering. However, these differences do not translate into detectable differences in adult body composition. Instead, we find minor seasonal differences in adult body composition consistent with augmented flight capacity in 'summer form' adults. In comparison, we find much stronger signatures of sex-specific selection on patterns of resource uptake and allocation. Our results indicate that resource dynamics in A. levana are shaped by seasonal fluctuations in host plant nutrition, climatic conditions and intraspecific interactions.

Advances in structural analysis of fluoroaluminates using DFT calculations of 27Al electric field gradients.

Based on the analysis of 23 aluminum sites from 16 fluoroaluminates, the present work demonstrates the strong potential of combining accurate NMR quadrupolar parameter measurements, density functional theory (DFT)-based calculations of electric field gradients (EFG), and structure optimizations as implemented in the WIEN2k package for the structural and electronic characterizations of crystalline inorganic materials. Structure optimizations are essential for compounds whose structure was refined from usually less accurate powder diffraction data and provide a reliable assignment of the 27Al quadrupolar parameters to the aluminum sites in the studied compounds. The correlation between experimental and calculated EFG tensor elements leads to the proposition of a new value of the 27Al nuclear quadrupole moment Q(27Al) = 1.616 (+/-0.024) x 10(-29) m2. The DFT calculations provide the orientation of the 27Al EFG tensors in the crystal frame. Electron density maps support that the magnitude and orientation of the 27Al EFG tensors in fluoroaluminates mainly result from the asymmetric distribution of the Al 3p orbital valence electrons. In most cases, the definition of relevant radial and angular distortion indices, relying on EFG orientation, allows correlations between these distortions and magnitude and sign of the Vii.

19F high magnetic field NMR study of beta-ZrF4 and CeF4: from spectra reconstruction to correlation between fluorine sites and 19F isotropic chemical shifts.

High magnetic field and high spinning frequency one- and two-dimensional one-pulse MAS 19F NMR spectra of beta-ZrF4 and CeF4 were recorded and reconstructed allowing the accurate determination of the 19F chemical shift tensor parameters for the seven different crystallographic fluorine sites of each compound. The attributions of the NMR resonances are performed using the superposition model for 19F isotropic chemical shift calculation initially proposed by Bureau et al. (Bureau, B.; Silly, G.; Emery, J.; Buzaré, J.-Y. Chem. Phys. 1999, 249, 85-104). A satisfactory reliability is reached with a root-mean-square (rms) deviation between calculated and measured isotropic chemical shift values equal to 1.5 and 3.5 ppm for beta-ZrF4 and CeF4, respectively.

Multinuclear high-resolution NMR study of compounds from the ternary system NaF-CaF2-AlF3: from determination to modeling of NMR parameters.

27Al and 23Na NMR satellite transition spectroscopy and 3Q magic-angle-spinning spectra are recorded for three compounds from the ternary NaF-CaF2-AlF3 system. The quadrupolar frequency nuQ, asymmetry parameter etaQ, and isotropic chemical shift deltaiso are extracted from the spectrum reconstructions for five aluminum and four sodium sites. The quadrupolar parameters are calculated using the LAPW-based ab initio code WIEN2k. It is necessary to perform a structure optimization of all compounds to ensure a fine agreement between experimental and calculated parameters. By a comparison of experimental and calculated values, an attribution of all of the 27Al and 23Na NMR lines to the crystallographic sites is achieved. High-speed 19F NMR MAS spectra are recorded and reconstructed for the same compounds, leading to the determination of 18 isotropic chemical shifts. The superposition model developed by Bureau et al. is used, allowing a bijective assignment of the 19F NMR lines to the crystallographic sites.

Correlation between 19F environment and isotropic chemical shift in barium and calcium fluoroaluminates.

High-speed MAS (19)F NMR spectra are recorded and reconstructed for 10 compounds from BaF(2)-AlF(3) and CaF(2)-AlF(3) binary systems which leads to the determination of 77 isotropic (19)F chemical shifts in various environments. A first attribution of NMR lines is performed for 8 compounds using a superposition model as initially proposed by B. Bureau et al. The phenomenological parameters of this model are then refined to improve the NMR line assignment. A satisfactory reliability is reached with a root-mean-square (RMS) deviation between calculated and measured values equal to 6 ppm. The refined parameters are then successfully tested on alpha-BaCaAlF(7) whose structure was recently determined. Finally, the isotropic chemical shift ranges are defined for shared, unshared, and "free" fluorine atoms encountered in the investigated binary systems. So, the fluorine surroundings can be deduced from the NMR line positions in compounds whose structure is unknown. Such an approach can also be applied to fluoride glasses.

High concentrations of glutathione in glandular stomach: possible implications for carcinogenesis.

In laboratory rodents, concentrations of reduced glutathione (GSH) are exceedingly high (up to 7 to 8 millimolar) in the glandular gastric tissue compared to concentrations in other portions of the gastrointestinal tract or to those of most other organs. Gastric GSH varies diurnally, with the highest levels occurring in the late afternoon or early evening. Starvation, treatment with diethyl maleate, or cold-restraint stress all caused marked decreases in stomach GSH, whereas treatment with cobaltous chloride caused an increase in the GSH concentrations. The physiological significance of the high gastric GSH is unknown, but because this endogenous compound may strongly modulate (decrease or increase) the macromolecular binding of certain chemicals capable of inducing stomach tumors, the possible role of glutathione in the pathogenesis of chemically induced gastric cancer should be considered.