THz Magneto-electric atomic rotations in the chiral compound Ba3_3NbFe3_3Si2_2O14_{14}

We have determined the terahertz spectrum of the chiral langasite Ba$_3$NbFe$_3$Si$_2$O$_{14}$ by means of synchrotron-radiation measurements. Two excitations are revealed that are shown to have a different nature. The first one, purely magnetic, is observed at low temperature in the magnetically ordered phase and is assigned to a magnon. The second one persits far into the paramagnetic phase and exhibits both an electric and a magnetic activity at slightly different energies. This magnetoelectric excitation is interpreted in terms of atomic rotations and requires a helical electric polarization

Terminal NK cell maturation is controlled by concerted actions of T-bet and Zeb2 and is essential for melanoma rejection

Natural killer (NK) cell maturation is a tightly controlled process that endows NK cells with functional competence and the capacity to recognize target cells. Here, we found that the transcription factor (TF) Zeb2 was the most highly induced TF during NK cell maturation. Zeb2 is known to control epithelial to mesenchymal transition, but its role in immune cells is mostly undefined. Targeted deletion of Zeb2 resulted in impaired NK cell maturation, survival, and exit from the bone marrow. NK cell function was preserved, but mice lacking Zeb2 in NK cells were more susceptible to B16 melanoma lung metastases. Reciprocally, ectopic expression of Zeb2 resulted in a higher frequency of mature NK cells in all organs. Moreover, the immature phenotype of Zeb2(-/-) NK cells closely resembled that of Tbx21(-/-) NK cells. This was caused by both a dependence of Zeb2 expression on T-bet and a probable cooperation of these factors in gene regulation. Transgenic expression of Zeb2 in Tbx21(-/-) NK cells partially restored a normal maturation, establishing that timely induction of Zeb2 by T-bet is an essential event during NK cell differentiation. Finally, this novel transcriptional cascade could also operate in human as T-bet and Zeb2 are similarly regulated in mouse and human NK cells

Maladie de Hodgkin et maladie des griffes du chat (étude épidémiologique à partir d'un cas clinique )

LE KREMLIN-B.- PARIS 11-BU Méd (940432101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

The XEmTeX Project

International audienceWe are presenting the XEmTeX project which is funded by the French government under the RNTL program (National Network on Software Technologies). The purpose of the project is to provide a high-quality, user-friendly, free integrated typesetting platform to typeset scientific or technical documents.Nous présentons ici le projet XEmTeX qui a été retenu pour être financé par le gouvernement français dans le cadre du Réseau National des Technologies Logicielles. Ce projet a pour objectif de fournir une plateforme typographique intégrée, libre, facile d'accès et de haute qualité pour la mise en page de documents scientifiques et techniques

Design, synthesis and electrochemical properties of a thiophene derivative functionalized with a siderophore-like chelator

International audienceA hybrid 3,4-ethylenedioxythiophene (EDOT)-thiophene precursor functionalized with an hydroxypyridinone group has been synthesized and electropolymerized into the corresponding polymer. The analysis of the dependence of the open circuit potential (OCP) of the modified electrode on the concentration of Fe3+ in aqueous solution shows that metal binding to the hydroxypyridinone groups prevents the oxidation of the conjugated polymer backbone until a threshold determined by the occupancy of the available complexation sites of the functionalized polymer is reached

Design, synthesis and redox properties of two ferrocene-containing iron chelators.

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Engineering nitrogen-and hydrogen-related defects in ZnO nanowires using thermal annealing

International audienceThe chemical bath deposition (CBD) of ZnO nanowires (NWs) is of high interest, but their formation occurs in a growth medium containing many impurities including carbon, nitrogen, and hydrogen, rendering the accurate determination of predominant crystal defects as highly debated. In addition to the typical interstitial hydrogen in bond-centered sites (HBC) and zinc vacancy-hydrogen (VZn−nH) complexes, we reveal that nitrogen-related defects play a significant role on the physical properties of unintentionally doped ZnO NWs. We show by density functional theory that the VZn−NO−H defect complex acts as a deep acceptor with a relatively low formation energy and exhibits a prominent Raman line at 3078cm–1 along with a red-orange emission energy of ∼1.82 eV in cathodoluminescence spectroscopy. The nature and concentration of the nitrogen- and hydrogen-related defects are found to be tunable using thermal annealing under oxygen atmosphere, but a rather complex, fine evolution including successive formation and dissociation processes is highlighted as a function of annealing temperature. ZnO NWs annealed at the moderate temperature of 300 °C specifically exhibit one of the smallest free charge carrier densities of 5.6×1017cm–3 along with a high mobility of ∼60 cm2/Vs following the analysis of longitudinal optical phonon-plasmon coupling. These findings report a comprehensive diagram showing the complex interplay of each nitrogen- and hydrogen-related defect during thermal annealing and its dependence on annealing temperature. They further reveal that the engineering of the nitrogen- and hydrogen-related defects as the major source of crystal defects in ZnO NWs grown by CBD is capital to precisely control their electronic structure properties governing their electrical and optical properties in any devices

Zinc Vacancy-Hydrogen Complexes as Major Defects in ZnO Nanowires Grown by Chemical Bath Deposition

International audienceCrystal defects in unintentionally doped ZnO nanowires grown by chemical bath deposition (CBD) play a capital role in their optical and electrical properties, governing the performances of many nanoscale engineering devices. However, the nature of these crystal defects is still highly debated. In particular, the hydrogen-related defects have not been explored in detail yet although the growth medium operates in an aqueous solution. Using four-point probe resistivity measurements, we show that ZnO nanowires grown by CBD using zinc nitrate and hexamethylenetetramine exhibit a high electrical conductivity with electron densities ranging from 2.7 × 1018 to 3.1 × 1019 cm−3. Most of them have metallic electrical conduction. By combining density-functional theory calculations with cathodoluminescence and Raman spectroscopy, we reveal that the high electrical conductivity mostly originates from the formation of interstitial hydrogen in bond-centered sites (HBC) and of zinc vacancy−hydrogen (VZn-nH) complexes. In particular, the HBC and (VZn-3H) complex are found to act as two shallow donors with very low formation energy, for which the most stable configurations are reported. Additionally, this combined theoretical and experimental approach allows us to revisit the highly debated origin of the visible and ultraviolet emission bands in the luminescence spectra. They are found to be mostly related to VZn and (VZn-nH) complexes located in the bulk and on the surfaces of ZnO nanowires. These findings represent an important step forward in the identification of the predominant native and extrinsic defects driving the electronic structure properties of ZnO nanowires grown by CBD. They further reveal the significance of hydrogen engineering to tune the source of crystal defects for optimizing the physical properties of ZnO nanowires

Modulating the growth of chemically deposited ZnO nanowires and the formation of nitrogen- and hydrogen-related defects using the pH adjustment

International audienceZnO nanowires (NWs) grown by chemical bath deposition (CBD) have received great interest for nanoscale engineering devices, but their formation in aqueous solution containing many impurities needs to be carefully addressed. In particular, the pH of the CBD solution and its effect on the formation mechanisms of ZnO NWs and of nitrogen-and hydrogen-related defects in their center are still unexplored. By adjusting its value in a low-and high-pH region, we show the latent evolution of the morphological and optical properties of ZnO NWs, as well as the modulated incorporation of nitrogenand hydrogen-related defects in their center using Raman and cathodoluminescence spectroscopy. The increase in pH is related to the increase in the oxygen chemical potential (µO), for which the formation energy of hydrogen in bond-centered sites (HBC) and VZn-NO-H defect complexes is found to be unchanged, whereas the formation energy of zinc vacancy (VZn) and zinc vacancy-hydrogen (VZn-nH) complexes steadily decreases as shown from density-functional theory calculations. Revealing that these VZn-related defects are energetically favorable to form as µO is increased, ZnO NWs grown in the high-pH region are found to exhibit a higher density of VZn-nH defect complexes than ZnO NWs grown in the low-pH region. Annealing at 450 °C under an oxygen atmosphere helps tuning the optical properties of ZnO NWs by reducing the density of HBC and VZn-related defects, while activating the formation of VZn-NO-H defect complexes. These findings show the influence of pH on the nature of Zn(II) species, the electrostatic interactions between these species and ZnO NW surfaces, and the formation energy of the involved defects. They emphasize the crucial role of the pH of the CBD solution and open new possibilities for simultaneously engineering the morphology of ZnO NWs and the formation of nitrogenand hydrogen-related defects