Otkriće radio-valova i neki pravni aspekti radio-saobraćaja

International audienceA series of triazole fluoride weberites (M1−x2+Mx3+)M3+F5(Htaz)1−x(taz)x is obtained by hydrothermal synthesis. All phases are found to be isostructural to ZnAlF5(Htaz) by powder X-ray diffraction. Weberite structures are prone to induce the magnetic frustration of antiferromagnetic interactions originating from the cationic topology of HTB layers. The (nD) magnetic properties of (0D) Co–Ga, (1D) Zn–Fe, (3D) Fe–Ga, Mn–Fe, Co–Fe and Co–V couples are thus reported. Co2+ or Fe2+ magnetic anisotropy induces a negative magnetisation below TN and compensation temperatures for Mn–Fe and Co–Fe couples. All iron 3D magnetic phases exhibit high Néel temperatures, between 81 K and 102 K, and large |θP/TN| ratios, signalling strong magnetic frustration. Their cation site occupancies and the deduced (de)protonation states of the amine are accurately determined by 57Fe Mössbauer spectrometry. In addition, this spectroscopy evidences a subtle effect of the atmosphere that surrounds the samples: the magnetic ordering temperatures TN decrease significantly when the samples are cooled under vacuum with respect to samples that are cooled at ambient pressure. This novel phenomenon, which is highlighted for all studied (3D) triazole iron weberites, is reversible, and thus provides promising perspectives for understanding the underlying mechanism

Strong magnetic exchange and frustrated ferrimagnetic order in a weberite-type inorganic-organic hybrid fluoride

LC acknowledges the University of Liverpool for start-up funding and support. Work at the University of St Andrews was supported by a Leverhulme Research Project Grant. Access to beam time at the ISIS Neutron and Muon Facility was supported by the Science and Technology Facilities Council. The authors also gratefully acknowledge Delphine Toulemon, ITODYS, UMR7086 CNRS, Université Paris VII, for assistance with magnetisation measurements.We combine powder neutron diffraction, magnetometry and 57Fe Mössbauer spectrometry to determine the nuclear and magnetic structures of a strongly interacting weberite-type inorganic-organic hybrid fluoride, Fe2F5(Htaz). In this structure, Fe2+ and Fe3+ cations form magnetically frustrated hexagonal tungsten bronze (HTB) layers of corner sharing octahedra. Our powder neutron diffraction data reveal that, unlike its purely inorganic fluoride weberite counterparts which adopt a centrosymmetric Imma structure, the room- temperature nuclear structure of Fe2F5(Htaz) is best described by a non centrosymmetric Ima2 model with refined lattice parameters a = 9.1467(2) Å, b = 9.4641(2) Å and c = 7.4829(2) Å. Magnetic susceptibility and magnetisation measurements reveal that strong antiferromagnetic exchange interactions prevail in Fe2F5(Htaz) leading to a magnetic ordering transition at TN = 93 K. Analysis of low-temperature powder neutron diffraction data indicates that below TN, the Fe2+ sublattice is ferromagnetic, with a moment of 4.1(1) μB per Fe2+ at 2 K, but that an antiferromagnetic component of 0.6(3) μB cants the main ferromagnetic component of Fe3+, which aligns antiferromagnetically to the Fe2+ sublattice. The zero-field and in-field Mössbauer spectra give clear evidence of an excess of high-spin Fe3+ species within the structure and a non collinear magnetic structure.PostprintPeer reviewe

Ocupational hazards in a mobile emergency care

Objetivo: Identificar os riscos ocupacionais peculiares às atividades desenvolvidas em um Serviço de Atendimento Móvel de Urgência. Métodos: Pesquisa descritiva, com abordagem quantitativa realizada com 162 profissionais mediante instrumento constituído por: caracterização pessoal, caracterização profissional e percepção dos profissionais sobre os fatores de risco ocupacionais. O projeto de pesquisa foi apreciado pelo Comitê de Ética da Universidade Federal do Rio Grande do Norte (CAAE: 0165.0.051.000-10). Resultados: Foi constatado que, dentre os riscos físicos, 34,6% consideram os ruídos como os mais importantes; 78,4% valorizaram os gases/fumaças como principal risco químico; 48,8% informaram ser o contato com o sangue o principal risco biológico; 80,9% afirmaram que o principal risco mecânico é o de acidentes de transporte; 40,1% afirmaram que o principal risco ergonômico é a tensão/estresse. Conclusão: Compreender os ambientes de trabalho favorece ações preventivas e corretivas para os riscos ocupacionais

Ocupational hazards in a mobile emergency care

Objectives: To identify occupational risks peculiar to the activities developed in a Service Mobile Emergency. Methods: Descriptive research with quantitative approach conducted with 162 professionals by an instrument consisting of: personal characterization, characterization professional and professionals' perception of the occupational risk factors. The Ethics Committee of the Federal University of Rio Grande do Norte appreciated the research project (CAAE: 0165.0.051.000-10). Results: It was found that among the physical risks, 34.6% consider the noise as the most important; appreciated 78.4% gas / fumes main chemical risk, 48.8% reported to be contact with blood the major biological risk , 80.9% said that the main risk is the mechanic of motor vehicle accidents, 40.1% said that the main ergonomic risk is the tension / stress. Conclusion: Understanding the workplace favors preventive and corrective actions for occupational hazards. Descriptors: Health professional, Occupational risks, Pre-hospital care.Objetivo: Identificar os riscos ocupacionais peculiares às atividades desenvolvidas em um Serviço de Atendimento Móvel de Urgência. Métodos: Pesquisa descritiva, com abordagem quantitativa realizada com 162 profissionais mediante instrumento constituído por: caracterização pessoal, caracterização profissional e percepção dos profissionais sobre os fatores de risco ocupacionais. O projeto de pesquisa foi apreciado pelo Comitê de Ética da Universidade Federal do Rio Grande do Norte (CAAE: 0165.0.051.000-10). Resultados: Foi constatado que, dentre os riscos físicos, 34,6% consideram os ruídos como os mais importantes; 78,4% valorizaram os gases/fumaças como principal risco químico; 48,8% informaram ser o contato com o sangue o principal risco biológico; 80,9% afirmaram que o principal risco mecânico é o de acidentes de transporte; 40,1% afirmaram que o principal risco ergonômico é a tensão/estresse. Conclusão: Compreender os ambientes de trabalho favorece ações preventivas e corretivas para os riscos ocupacionais

Synthèse et caractérisation structurale et diélectrique de céramiques et de monocristaux relaxeurs de structure TTB

Tetragonal Tungsten Bronze structure, thanks to its compositional flexibility, is a legitimate candidate for the development of functional materials. Study of dielectric, pyroelectric, and ferroelectric properties of Ba2NdFeNb4-xTaxO15 ceramics reveals a relaxor-ferroelectric-paraelectric crossover, with thermal hysteresis of the ferroelectric transition. Structural analysis of Ba2LnFeNb4O15 (Ln=La Pr, Nd, Sm, Eu), relaxor single crystals obtained by flux method, highlighted a modulated structure. Refinement of the basic structure proves the existence of a dipolar moment in the ab plane (induced by a distortion of [NbO6] octahedra). In order to establish a correlation between the crystal structure and the properties of a compound derived from multiferroic MnWO4, the crystal growth in image furnace of Mn0,85Mg0,15WO4 was successfully undertaken.La structure bronze quadratique de tungstène, grâce à sa flexibilité cristallochimique, est une candidate légitime pour le développement de matériaux fonctionnels. L’étude des propriétés diélectriques, pyroélectriques, et ferroélectriques de céramiques de formulation Ba2NdFeNb4-xTaxO15 montre un crossover relaxeur-ferroélectrique-paraélectrique, avec une hystérèse thermique de la transition ferroélectrique. L’étude structurale des monocristaux relaxeurs Ba2LnFeNb4O15 (Ln=La, Pr, Nd, Sm, Eu), obtenus par la méthode du flux, a mis en évidence une structure modulée. L’affinement de la structure de base prouve l’existence de moments dipolaires dans le plan ab (dus à une distorsion des octaèdres [NbO6]). Afin d’établir un lien entre la structure cristalline et les propriétés d’un composé dérivé du multiferroïque MnWO4, la croissance en four à image de Mn0,85Mg0,15WO4 a été entreprise avec succès

Synthesis, structural and dielectric characterization of relaxor ceramics and single-crystals with TTB structure

La structure bronze quadratique de tungstène, grâce à sa flexibilité cristallochimique, est une candidate légitime pour le développement de matériaux fonctionnels. L’étude des propriétés diélectriques, pyroélectriques, et ferroélectriques de céramiques de formulation Ba2NdFeNb4-xTaxO15 montre un crossover relaxeur-ferroélectrique-paraélectrique, avec une hystérèse thermique de la transition ferroélectrique. L’étude structurale des monocristaux relaxeurs Ba2LnFeNb4O15 (Ln=La, Pr, Nd, Sm, Eu), obtenus par la méthode du flux, a mis en évidence une structure modulée. L’affinement de la structure de base prouve l’existence de moments dipolaires dans le plan ab (dus à une distorsion des octaèdres [NbO6]). Afin d’établir un lien entre la structure cristalline et les propriétés d’un composé dérivé du multiferroïque MnWO4, la croissance en four à image de Mn0,85Mg0,15WO4 a été entreprise avec succès.Tetragonal Tungsten Bronze structure, thanks to its compositional flexibility, is a legitimate candidate for the development of functional materials. Study of dielectric, pyroelectric, and ferroelectric properties of Ba2NdFeNb4-xTaxO15 ceramics reveals a relaxor-ferroelectric-paraelectric crossover, with thermal hysteresis of the ferroelectric transition. Structural analysis of Ba2LnFeNb4O15 (Ln=La Pr, Nd, Sm, Eu), relaxor single crystals obtained by flux method, highlighted a modulated structure. Refinement of the basic structure proves the existence of a dipolar moment in the ab plane (induced by a distortion of [NbO6] octahedra). In order to establish a correlation between the crystal structure and the properties of a compound derived from multiferroic MnWO4, the crystal growth in image furnace of Mn0,85Mg0,15WO4 was successfully undertaken

Synthesis, structural and dielectric characterization of relaxor ceramics and single-crystals with TTB structure

La structure bronze quadratique de tungstène, grâce à sa flexibilité cristallochimique, est une candidate légitime pour le développement de matériaux fonctionnels. L’étude des propriétés diélectriques, pyroélectriques, et ferroélectriques de céramiques de formulation Ba2NdFeNb4-xTaxO15 montre un crossover relaxeur-ferroélectrique-paraélectrique, avec une hystérèse thermique de la transition ferroélectrique. L’étude structurale des monocristaux relaxeurs Ba2LnFeNb4O15 (Ln=La, Pr, Nd, Sm, Eu), obtenus par la méthode du flux, a mis en évidence une structure modulée. L’affinement de la structure de base prouve l’existence de moments dipolaires dans le plan ab (dus à une distorsion des octaèdres [NbO6]). Afin d’établir un lien entre la structure cristalline et les propriétés d’un composé dérivé du multiferroïque MnWO4, la croissance en four à image de Mn0,85Mg0,15WO4 a été entreprise avec succès.Tetragonal Tungsten Bronze structure, thanks to its compositional flexibility, is a legitimate candidate for the development of functional materials. Study of dielectric, pyroelectric, and ferroelectric properties of Ba2NdFeNb4-xTaxO15 ceramics reveals a relaxor-ferroelectric-paraelectric crossover, with thermal hysteresis of the ferroelectric transition. Structural analysis of Ba2LnFeNb4O15 (Ln=La Pr, Nd, Sm, Eu), relaxor single crystals obtained by flux method, highlighted a modulated structure. Refinement of the basic structure proves the existence of a dipolar moment in the ab plane (induced by a distortion of [NbO6] octahedra). In order to establish a correlation between the crystal structure and the properties of a compound derived from multiferroic MnWO4, the crystal growth in image furnace of Mn0,85Mg0,15WO4 was successfully undertaken

Synthesis, structural and dielectric characterization of relaxor ceramics and single-crystals with TTB structure

La structure bronze quadratique de tungstène, grâce à sa flexibilité cristallochimique, est une candidate légitime pour le développement de matériaux fonctionnels. L’étude des propriétés diélectriques, pyroélectriques, et ferroélectriques de céramiques de formulation Ba2NdFeNb4-xTaxO15 montre un crossover relaxeur-ferroélectrique-paraélectrique, avec une hystérèse thermique de la transition ferroélectrique. L’étude structurale des monocristaux relaxeurs Ba2LnFeNb4O15 (Ln=La, Pr, Nd, Sm, Eu), obtenus par la méthode du flux, a mis en évidence une structure modulée. L’affinement de la structure de base prouve l’existence de moments dipolaires dans le plan ab (dus à une distorsion des octaèdres [NbO6]). Afin d’établir un lien entre la structure cristalline et les propriétés d’un composé dérivé du multiferroïque MnWO4, la croissance en four à image de Mn0,85Mg0,15WO4 a été entreprise avec succès.Tetragonal Tungsten Bronze structure, thanks to its compositional flexibility, is a legitimate candidate for the development of functional materials. Study of dielectric, pyroelectric, and ferroelectric properties of Ba2NdFeNb4-xTaxO15 ceramics reveals a relaxor-ferroelectric-paraelectric crossover, with thermal hysteresis of the ferroelectric transition. Structural analysis of Ba2LnFeNb4O15 (Ln=La Pr, Nd, Sm, Eu), relaxor single crystals obtained by flux method, highlighted a modulated structure. Refinement of the basic structure proves the existence of a dipolar moment in the ab plane (induced by a distortion of [NbO6] octahedra). In order to establish a correlation between the crystal structure and the properties of a compound derived from multiferroic MnWO4, the crystal growth in image furnace of Mn0,85Mg0,15WO4 was successfully undertaken

Synthèse et caractérisation structurale et diélectrique de céramiques et de monocristaux relaxeurs de structure TTB

La structure bronze quadratique de tungstène, grâce à sa flexibilité cristallochimique, est une candidate légitime pour le développement de matériaux fonctionnels. L étude des propriétés diélectriques, pyroélectriques, et ferroélectriques de céramiques de formulation Ba2NdFeNb4-xTaxO15 montre un crossover relaxeur-ferroélectrique-paraélectrique, avec une hystérèse thermique de la transition ferroélectrique. L étude structurale des monocristaux relaxeurs Ba2LnFeNb4O15 (Ln=La, Pr, Nd, Sm, Eu), obtenus par la méthode du flux, a mis en évidence une structure modulée. L affinement de la structure de base prouve l existence de moments dipolaires dans le plan ab (dus à une distorsion des octaèdres [NbO6]). Afin d établir un lien entre la structure cristalline et les propriétés d un composé dérivé du multiferroïque MnWO4, la croissance en four à image de Mn0,85Mg0,15WO4 a été entreprise avec succès.Tetragonal Tungsten Bronze structure, thanks to its compositional flexibility, is a legitimate candidate for the development of functional materials. Study of dielectric, pyroelectric, and ferroelectric properties of Ba2NdFeNb4-xTaxO15 ceramics reveals a relaxor-ferroelectric-paraelectric crossover, with thermal hysteresis of the ferroelectric transition. Structural analysis of Ba2LnFeNb4O15 (Ln=La Pr, Nd, Sm, Eu), relaxor single crystals obtained by flux method, highlighted a modulated structure. Refinement of the basic structure proves the existence of a dipolar moment in the ab plane (induced by a distortion of [NbO6] octahedra). In order to establish a correlation between the crystal structure and the properties of a compound derived from multiferroic MnWO4, the crystal growth in image furnace of Mn0,85Mg0,15WO4 was successfully undertaken.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

Cation ordering in the double tungstate LiFe(WO4)2

Single crystals of lithium iron tungstate, LiFe(WO4)2, were obtained using a high-temperature solution growth method. The analysis was conducted using the monoclinic space group C2/c, with [beta] = 90.597 (2)°, giving R1 = 0.0177. The Li and Fe atoms lie on twofold axes. The structure can also be refined using the orthorhombic space group Cmcm, giving slightly higher residuals. The experimental value of [beta] and the residuals mitigate in favour of the monoclinic description of the structure. Calculated bond-valence sums for the present results are closer to expected values than those obtained using the results of a previously reported analysis of this structure