•Y0.9Gd0.1Fe2Hx (3 < x < 4) are ferrimagnetic with TC near 310 K.•Y0.9Gd0.1Fe2H4.2 displays a FM-AFM transition around 144 K.•Y0.9Gd0.1Fe2Hx (x > 4.2) are weak ferrimagnets with Gd order below ...15 K.•Magnetovolumic effects are observed for the two monoclinic phases M1 and M2.•Magnetic entropy variations are observed near Tc, TFM-AFM and TO-D.
At 300 K, Y0.9Gd0.1Fe2Hx hydrides crystallize sequentially with increasing H concentration in various structures related to a lowering of the cubic MgCu2 type structure of the parent alloy: cubic C1, monoclinic M1, cubic C2, monoclinic M2, cubic C3, orthorhombic O. Above 300 K, they undergo a first-order transition at a TO-D temperature driven by order-disorder of hydrogen atoms into interstitial sites. Their magnetic, structural and magnetocaloric properties have been investigated through magnetic measurements, and high-resolution synchrotron diffraction experiments. The magnetization at 5 K decreases slightly from 4 to 3.8 µB for x = 3–3.9 H/f.u., then with a larger slope for higher H content. A discontinuous decrease of the magnetic transition temperature is observed: M1 and C2 hydrides are ferrimagnetic with TC near 300 K, M2 hydride displays a sharp ferromagnetic-antiferromagnetic transition at TFM-AFM = 144 K, whereas C3 and O hydrides present only a sharp increase of the magnetization below 15 K and a weak magnetization up to room temperature. Negative magnetic entropy variations (ΔSM) are measured near TC for the M1 and C2 phases, near TFM-AFM for the M2 phase, whereas positive ΔSM peaks due to inverse MCE effect are found near TO-D. A structural and magnetic phase diagram is proposed.
•Y0.9Gd0.1Fe2-H2 system displays a multiplateau Pressure-Composition Isotherm.•Y0.9Gd0.1Fe2Hx (x = 2.9–5) hydrides crystallize in six different structures at RT.•They form three cubic, two monoclinic ...and one orthorhombic phases.•One intermediate cubic phase (C2) presents superstructures indexed in a double cell.•The two monoclinic and the C2 phases undergo order-disorder structural transitions.
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Y0.9Gd0.1Fe2, which crystallize in a C15 cubic structure, can absorb up to 5 H/f.u. and its pressure-composition isotherm displays a multiplateau behavior related to the existence of several hydrides with different crystal structures. At room temperature Y0.9Gd0.1Fe2Hx hydrides (2.9 ≤ x ≤ 5) crystallize in three phases with cubic structure (C1, C2 and C3), two phases with monoclinic structures (M1 and M2), and one phase with orthorhombic structure (O), with the following sequence for increasing H concentration: C1, M1, C2, M2, C3, O. Each phase exists as single phase within a H homogeneity range, and they are separated from each other by two-phase domains. The reductions of crystal symmetry are related to various hydrogen orders into interstitial sites. Weak superstructure peaks were indexed by doubling the cubic cell parameter of the cubic C2 phase. Upon heating, the monoclinic M1 and M2 and the cubic C2 phases undergo order-disorder (O-D) transitions toward a disordered cubic structure CDis. These O-D transitions are reversible with thermal hysteresis effects. The cubic C3 and orthorhombic O phases transform into a disordered cubic phase accompanied by H desorption.
Vitellogenesis is one of the most well‐studied physiological processes in mosquitoes. Expression of mosquito vitellogenin genes is classically described as being restricted to female adult ...reproduction. We report premature vitellogenin transcript expression in three vector mosquitoes: Culex tarsalis, Aedes aegypti and Anopheles gambiae. Vitellogenins expressed during non‐reproductive stages are alternatively spliced to retain their first intron and encode premature termination codons. We show that intron retention results in transcript degradation by translation‐dependent nonsense‐mediated mRNA decay. This is probably an example of regulated unproductive splicing and translation (RUST), a mechanism known to regulate gene expression in numerous organisms but which has never been described in mosquitoes. We demonstrate that the hormone 20‐hydroxyecdysone (20E) is responsible for regulating post‐transcriptional splicing of vitellogenin. After exposure of previtellogenic fat bodies to 20E, vitellogenin expression switches from a non‐productive intron‐retaining transcript to a spliced protein‐coding transcript. This effect is independent of factors classically known to influence transcription, such as juvenile hormone‐mediated competence and amino acid signalling through the target of rapamycin pathway. Non‐canonical regulation of vitellogenesis through RUST is a novel role for the multifunctional hormone 20E, and may have important implications for general patterns of gene regulation in mosquitoes.
MAX is a complete suite of XAFS data analysis computer programs, written with the cross-platform object scripting langage Livecode 1 working on Windows, MacOSX and Linux systems, freely available on ...our web site since 2007 2. The 2009 version presentation is available in the XAFS14 conference proceedings 3 and regularly updated on the www.xafs.org web site 4.
Autogeny, the ability of a mosquito to mature an initial batch of eggs without blood feeding, is an alternative reproductive strategy with important implications for vector-borne disease ...transmission. Regulation of the major yolk protein (vitellogenin; Vg) genes during bloodmeal-induced oogenesis is well studied, but little is known about regulation of vitellogenesis in autogenous mosquitoes. We characterized the expression of four vitellogenin genes (Vg1a, Vg1b, Vg2a and Vg2b) in an autogenous strain of the West Nile Virus vector, Culex tarsalis. All vitellogenin genes were expressed during autogenous reproduction and following a bloodmeal, although the intensity and duration of expression varied amongst genes. Quantitative PCR analysis of vitellogenin transcription during autogeny revealed a similar temporal pattern to known vitellogenin expression profiles in anautogenous Aedes aegypti. Vitellogenin transcript, primarily produced from the Vg1b gene, was also detected in the larval and pupal stages of development, but no detectable vitellogenin protein was produced during this time period.
•Structural characterization of Pb1−xLaxZr0.40Ti0.60O3 (PLZT) ferroelectric ceramic.•X-ray absorption and Raman spectroscopies were used to probe the structure of PLZT.•Dissymmetry of Zr and Pb sites ...was observed in samples long-range cubic symmetry.•Local disorder in all PLZT samples through the observation of Raman active modes.
This paper reports on the structural characterization of Pb1−xLaxZr0.40Ti0.60O3 (PLZT) ferroelectric ceramic compositions prepared by the conventional solid state reaction method. X-ray absorption spectroscopy (XAS) and Raman spectroscopy were used to probe the local structure of PLZT samples that exhibits a normal and relaxor ferroelectric behavior. From the Zr K-edge and Pb LIII-edge EXAFS spectra, a considerable dissymmetry of Zr and Pb sites was observed in all samples, including those showing a long-range order cubic symmetry and a relaxor behavior. The Raman spectroscopy results confirmed the existence of a local disorder in all PLZT samples through the observation of Raman active vibrational modes. The variation in the intensity of the E(TO3) mode in the PLZT relaxor samples indicates that the process of correlation between nanodomains stabilizes at temperatures lower than Tm.
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