Determination of the Local Environment of Mn³⁺ and In³⁺ in the YInO₃–YMnO₃ Solid Solution, Which Exhibits an Intense Blue Color

Determination of the Local Environment of Mn³⁺ and In³⁺ in the YInO₃–YMnO₃ Solid Solution, Which Exhibits an Intense Blue Colo

Immunopathologie de la leptospirose humaine : exploration de la réponse immunitaire innée.

Leptospirosis is a bacterial zoonosis caused by Leptospira and affecting 1 million people each year worldwide and mainly in tropical areas such as Reunion Island. Usual presentations encompass flu-like syndrome to multiorgan failure with mortality rate between 5 to 10%. To date, pathophysiology in humans is poorly understood, notably the capacity of innateimmunity to mount a robust response to clear pathogen or to induce tissue damages and contributing to disease severity. Our study aimed at assessing the role of innate immune cells and molecules within the first days of leptospiral infection.Using blood samples, we performed quantitative and qualitative assessment of circulating innate immune cells from leptospirosis cases and healthy controls. The first study explored the levels of gamma-delta T-cells (γδT-cells), a subset of unconventional T cells with innate immune functions. Gamma-delta T cells were found deeply decreased and levels wereinversely correlated to bacterial burden and liver damage. The second study focused on membrane bound receptors indicative of activation and tissue migration ability of neutrophil polymorphonuclear cells: CD15, CD11b, and CD182. Although neutrophil rates were high in leptospirosis cases, the levels of studied receptors were either lower (CD15) or identical to healthy controls (CD11b, CD182). In addition, only low levels of interleukin-8, a key chemokine for neutrophils, was detected in patients. Lastly, we ascertained the plasmatic levels of several shed cell adhesion molecules notably expressed by endothelial cells. The levels of soluble E-selectin and ICAM-1 were significantly increased compared to controls, while P-selectin level was lower. We did not find any correlation with disease severity or organ failure. This finding indicates that endothelial cell may be activated but further experiments are warranted to explain the functional impact of our findings. Altogether, our results add to the field of knowledge of leptospirosis pathophysiology, and in particular the implication of key innate immune cells at the stage of plasmatic bacterial dissemination. Our findings will support the view that there is an inappropriate immune response to Leptospira.La leptospirose est une zoonose causée par les bactéries du genre Leptospira. Elle touche près de 1 million d'individus par an dans le monde entier et sévit à l'état endémique dans les pays au climat tropical tel que La Réunion. Les manifestations habituelles sont variables d'un individu à l'autre et englobent une simple fièvre jusqu'aux défaillances poly-viscérales avec mortalité dans 5 à 10% des cas. Sa physiopathologie est encore mal comprise, en particulier la part que joue une réponse immunitaire inappropriée dans la genèse des manifestations graves qui surviennent en quelques heures, et avant la mise en place d'une réponse immunitaire adaptative propre à éliminer le microorganisme. Si l'échappement de la bactérie au système du complément est bien documenté, le rôle des acteurs cellulaires du système immunitaire inné reste à étayer. Notre étude avait donc pour objectif d'explorer l'immunopathologie de la leptospirose humaine dans la phase initiale de l’infection. Notre méthodologie s'est appuyée principalement sur des analyses quantitatives et qualitatives des acteurs cellulaires du système immunitaire inné à partir de prélèvements sanguins en phase précoce de la maladie, et comparaison avec la phase de convalescence et des sujets contrôles. Dans un premier temps nous avons montré qu'une population particulière de lymphocytes T impliquée dans la réponse immune innée, les lymphocytes Tγδ, avaient un taux abaissé et que cette baisse était corrélée à la charge bactérienne ainsi qu'à l’intensité de l'atteinte hépatique classiquement retrouvée lors de la leptospirose. Dans un deuxième temps, nous avons analysé les polynucléaires neutrophiles circulants dont le taux augmente d’autant plus que la maladie est sévère, mais sans pour autant présenter de modification de certains marqueurs d’activation ou de recrutement tissulaire (CD15, CD11b, CD182). Une des principales chimiokines des neutrophiles, l'interleukine 8, était à taux peu élevés. Les derniers travaux concernent les principales formes solubles issues des molécules membranaires impliquées dans le processus de recrutement/diapédèse leucocytaire. Nous retrouvons de manière isolée une forte élévation des formes solubles d'E-sélectine et ICAM-1 qui sont notamment exprimées par les cellules endothéliales. Ces augmentations n'étaient pas corrélées aux marqueurs de gravité de la maladie. La signification biologique de cette élévation n’est pas encore connue lors de la leptospirose. L'ensemble de nos données permet d’apporter des informations nouvelles sur des acteurs du système immunitaire inné présents dans le compartiment vasculaire lors de la leptospirose humaine. Cette réponse immunitaire semble inadaptée pour permettre une clairance du pathogène au stade de dissémination hématogène

Magnetic Properties and Electronic Structure of Manganese-Based Blue Pigments: A High-Frequency and -Field EPR Study

A variety of new oxide-based materials based on hexagonal phase of YInO₃ have been recently described. In some of these materials, the In­(III) ions are substituted by Mn­(III), which finds itself in a trigonal-bipyramidal (TBP) coordination environment. While YInO₃ is colorless and YMnO₃ is black, mixed systems YIn_1–<i>x</i>Mn_<i>x</i>O₃ (0.02 < <i>x</i> < 0.25) display intense blue color and have been proposed as novel blue pigments. Since the Mn­(III) ion is paramagnetic, its presence imparts distinct magnetic properties to the whole class of materials. These properties were investigated by electron paramagnetic resonance (EPR) in its high-frequency and -field version (HFEPR), a technique ideally suited for transition metal ions such as Mn­(III) that, in contrast to, for example, Mn­(II), are difficult to study by EPR at (conventional) low frequency and field. YIn_1–<i>x</i>Mn_<i>x</i>O₃ with 0.02 < <i>x</i> < 0.2 exhibited high-quality HFEPR spectra up to room temperature that could be interpreted as arising from isolated <i>S</i> = 2 paramagnets. A simple ligand-field model, based on the structure and optical spectra, explains the spin Hamiltonian parameters provided by HFEPR, which were <i>D</i> = +3.0 cm^–1, <i>E</i> = 0; <i>g</i>_⊥ = 1.99, <i>g</i>_∥ = 2.0. This study demonstrates the general applicability of a combined spectroscopic and classical theoretical approach to understanding the electronic structure of novel materials containing paramagnetic dopants. Moreover, HFEPR complements optical and other experimental methods as being a sensitive probe of dopant level

Enhanced Thermoelectric Performance of Synthetic Tetrahedrites

Electrical and thermal transport properties of synthetic tetrahedrites Cu₁₀TM₂Sb₄S₁₃ (TM = Mn, Fe, Co, Ni, Zn) and the solid solution Cu_{12–<i>x</i>}Mn_<i>x</i>Sb₄S₁₃ (0 ≤ <i>x</i> ≤ 2) have been studied in the context of thermoelectric performance. Among these materials, the parent compound Cu₁₂Sb₄S₁₃ exhibits the highest power factor, which is primarily derived from a high electrical conductivity. All substituted derivatives display a significant and uniform reduction in thermal conductivity. Within the TM series, the Mn-substituted sample displays the highest ZT (0.8 at 575 K). Changing the Mn concentration to Cu₁₁MnSb₄S₁₃ produces the highest ZT, i.e., 1.13 at 575 K. The relatively high value derives from a favorable balance of low thermal conductivity and a relatively high power factor

Intense Turquoise and Green Colors in Brownmillerite-Type Oxides Based on Mn⁵⁺ in Ba₂In_2–<i>x</i>Mn_<i>x</i>O_5+<i>x</i>

Brownmillerite-type oxides Ba₂In_2–<i>x</i>Mn_<i>x</i>O_5+<i>x</i> (<i>x</i> = 0.1–0.7) have been prepared and characterized. Magnetic measurements indicate that manganese in as-prepared samples is substituting predominantly as Mn⁵⁺ for all values of <i>x</i> with observed paramagnetic spin-only moments close to values expected for two unpaired electrons. Electron paramagnetic resonance measurements indicate that this Mn⁵⁺ is present in a highly distorted tetrahedral environment. Neutron diffraction structure refinements show that Mn⁵⁺ occupies tetrahedral sites for orthorhombic (<i>x</i> = 0.1) and tetragonal (<i>x</i> = 0.2) phases. For Mn ≥ 0.3 samples, neutron refinements show that the phases are cubic with disordered cations and oxygen vacancies. The colors of the phases change from light yellow (<i>x</i> = 0) to intense turquoise (<i>x</i> = 0.1) to green (<i>x</i> = 0.2, 0.3) or to dark green (<i>x</i> ≥ 0.4). Under reducing conditions, Mn⁵⁺ is reduced to Mn³⁺, and Ba₂In_2–<i>x</i>Mn_<i>x</i>O_5+<i>x</i> phases become black Ba₂In_2–<i>x</i>Mn_<i>x</i>O₅ phases still with the brownmillerite structure

Intense Turquoise and Green Colors in Brownmillerite-Type Oxides Based on Mn⁵⁺ in Ba₂In_2–<i>x</i>Mn_<i>x</i>O_5+<i>x</i>

Brownmillerite-type oxides Ba₂In_2–<i>x</i>Mn_<i>x</i>O_5+<i>x</i> (<i>x</i> = 0.1–0.7) have been prepared and characterized. Magnetic measurements indicate that manganese in as-prepared samples is substituting predominantly as Mn⁵⁺ for all values of <i>x</i> with observed paramagnetic spin-only moments close to values expected for two unpaired electrons. Electron paramagnetic resonance measurements indicate that this Mn⁵⁺ is present in a highly distorted tetrahedral environment. Neutron diffraction structure refinements show that Mn⁵⁺ occupies tetrahedral sites for orthorhombic (<i>x</i> = 0.1) and tetragonal (<i>x</i> = 0.2) phases. For Mn ≥ 0.3 samples, neutron refinements show that the phases are cubic with disordered cations and oxygen vacancies. The colors of the phases change from light yellow (<i>x</i> = 0) to intense turquoise (<i>x</i> = 0.1) to green (<i>x</i> = 0.2, 0.3) or to dark green (<i>x</i> ≥ 0.4). Under reducing conditions, Mn⁵⁺ is reduced to Mn³⁺, and Ba₂In_2–<i>x</i>Mn_<i>x</i>O_5+<i>x</i> phases become black Ba₂In_2–<i>x</i>Mn_<i>x</i>O₅ phases still with the brownmillerite structure

Structure and Properties of Ir-Containing Oxides with Large Spin–Orbit Coupling: Ba₂In_2–<i>x</i>Ir_<i>x</i>O_5+δ

In this work, the solid solution series Ba₂In_2–<i>x</i>Ir_<i>x</i>O_5+δ (<i>x</i> = 0–1.4, 2) was synthesized, and its structural, magnetic, and charge-transport properties were measured. With increasing Ir content, three transitions in the room-temperature structure were observed: orthorhombic to tetragonal to cubic to a monoclinic distortion of a hexagonal BaTiO₃ structure. Neutron diffraction shows Ba₂In_1.6­Ir_0.4O_5.4 to be cubic and Ba₂InIrO₆ to be monoclinic, the latter contrary to previously published X-ray diffraction refinements. Magnetization measurements show Curie–Weiss behavior for <i>x</i> = 0.2–0.6, which arises from nearly 50:50 ratio of Ir­(V) and Ir­(VI). To our knowledge, this is the first time Ir­(VI) has been stabilized with standard solid-state methods under ambient conditions. The electrical resistivity measurements show all the compounds studied are semiconducting and that resistivity decreases with increasing Ir content, suggesting the proximity to a metal–insulator transition. A sign reversal in the high-temperature Seebeck coefficient is observed indicating both electron and hole charge transport

From Serendipity to Rational Design: Tuning the Blue Trigonal Bipyramidal Mn³⁺ Chromophore to Violet and Purple through Application of Chemical Pressure

We recently reported that an allowed d–d transition of trigonal bipyramidal (TBP) Mn³⁺ is responsible for the bright blue color in the YIn_1–<i>x</i>Mn_<i>x</i>O₃ solid solution. The crystal field splitting between a′(d_<i>z</i>²) and e′(d_<i>x</i>²_{–<i>y</i>²}, d_<i>xy</i>) energy levels is very sensitive to the apical Mn–O distance. We therefore applied chemical pressure to compress the apical Mn–O distance in YIn_1–<i>x</i>Mn_<i>x</i>O₃, move the allowed d–d transition to higher energy, and thereby tune the color from blue to violet/purple. This was accomplished by substituting smaller cations such as Ti⁴⁺/Zn²⁺ and Al³⁺ onto the TBP In/Mn site, which yielded novel violet/purple phases. The general formula is YIn_{1–<i>x</i>–2<i>y</i>–<i>z</i>}Mn_<i>x</i>­Ti_<i>y</i>Zn_<i>y</i>Al_<i>z</i>O₃ (<i>x</i> = 0.005–0.2, <i>y</i> = 0.1–0.4, and <i>z</i> ≤ 0.1), where the color darkens with the increasing amount of Mn. Higher <i>y</i> or small additions of Al provide a more reddish hue to the resulting purple colors. Substituting other rare earth cations for Y has little impact on color. Crystal structure analysis by neutron powder diffraction confirms a shorter apical Mn–O distance compared with that in the blue YIn_1–<i>x</i>Mn_<i>x</i>O₃. Magnetic susceptibility measurements verify the 3+ oxidation state for Mn. Diffuse reflection spectra were obtained over the wavelength region 200–2500 nm. All samples show excellent near-infrared reflectance comparable to that of commercial TiO₂, making them ideal for cool pigment applications such as energy efficient roofs of buildings and cars where reducing solar heat to save energy is desired. In a comparison with commercial purple pigments, such as Co₃(PO₄)₂, our pigments are much more thermally stable and chemically inert, and are neither toxic nor carcinogenic

Influence of Structural Disorder on Hollandites A_<i>x</i>Ru₄O₈ (A⁺ = K, Rb, Rb_1–<i>x</i>Na_<i>x</i>)

Structural disorder can play an important role in the electrical properties of correlated materials. In this work we examine the average and local disorder in hollandites A_<i>x</i>Ru₄O₈ (A⁺ = K, Rb, Rb_1–<i>x</i>Na_<i>x</i>) through neutron total scattering techniques. Samples with A⁺ = Rb, Rb_1–<i>x</i>Na_<i>x</i> exhibit the largest amount of local disorder as evidenced by higher atomic displacement parameters, and as a result, a weakened temperature dependence of the resistivity is observed upon cooling as compared to K_<i>x</i>Ru₄O₈. All samples exhibit anisotropic resistivity that is dominated by metallic conductivity at lower temperatures, and this is corroborated by Pauli paramagnetic behavior throughout the measured temperature regime