Mixed Valence Europium Nitridosilicate Eu2SiN3

The mixed valence europium nitridosilicate Eu2SiN3 has been synthesized at 900°C in welded tantalum ampules starting from europium and silicon diimide Si(NH)2 in a lithium flux. The structure of the black material has been determined by single-crystal X-ray diffraction analysis (Cmca (no. 64), a=542.3(11) pm, b=1061.0(2) pm, c=1162.9(2) pm, Z=8, 767 independent reflections, 37 parameters, R1=0.017, wR2=0.032). Eu2SiN3 is a chain-type silicate comprising one-dimensional infinite nonbranched zweier chains of corner-sharing SiN4 tetrahedra running parallel [100] with a maximum stretching factor fs=1.0. The compound is isostructural with Ca2PN3 and Rb2TiO3, and it represents the first example of a nonbranched chain silicate in the class of nitridosilicates. There are two crystallographically distinct europium sites (at two different Wyckoff positions 8f) being occupied with Eu2+ and Eu3+, respectively. 151Eu Mössbauer spectroscopy of Eu2SiN3 differentiates unequivocally these two europium atoms and confirms their equiatomic multiplicity, showing static mixed valence with a constant ratio of the Eu2+ and Eu3+ signals over the whole temperature range. The Eu2+ site shows magnetic hyperfine field splitting at 4.2 K. Magnetic susceptibility measurements exhibit Curie-Weiss behavior above 24 K with an effective magnetic moment of 7.5 μB/f.u. and a small contribution of Eu3+, in accordance with Eu2+ and Eu3+ in equiatomic ratio. Ferromagnetic ordering at unusually high temperature is detected at TC=24 K. DFT calculations of Eu2SiN3 reveal a band gap of ∼0.2 eV, which is in agreement with the black color of the compound. Both DFT calculations and lattice energetic calculations (MAPLE) corroborate the assignment of two crystallographically independent Eu sites to Eu2+ and Eu3+

Improved NOx Storage/Release Properties of Ceria-Based Lean NOx Trap Compositions with MnOx Modification

Ceria/spinel-based lean NOx trap compositions with and without barium were modified with MnOx via incipient wetness impregnation. The effect of the MnOx layer on the aged materials (850 °C) as to the NOx storage and release properties was investigated via NOx adsorption (500 ppm NO/5% O2/balance N2) carried out at 300 °C in a dual-bed with a 1% Pt/Al2O3 catalyst placed upstream of the samples to generate sufficient amounts of NO2 required for efficient NOx storage. Subsequent temperature programmed desorption (TPD) experiments were carried out under N2 from 300 °C to 700 °C. The addition of MnOx to the barium free composition led to a slightly reduced NOx storage capacity but all of the ad-NOx species were released from this material at significantly lower temperatures (ΔT ≈ 100 °C). The formation of a MnOx layer between ceria/spinel and barium had a remarkable effect on ageing stability as the formation of BaAl2O4 was suppressed in favour of BaMnO3. The presence of this phase resulted in an increased NOx storage capacity and lower desorption temperatures. Furthermore, NOx adsorption experiments carried out in absence of the Pt-catalyst also revealed an unexpected high NOx storage ability at low NO2/NO ratios, which could make this composition suitable for various lean NOx trap catalysts (LNT) related applications.A.G.-G. gratefully acknowledges the general financial support of Generalitat Valenciana (PROMETEO/2018/076), MINECO (CTQ2015-64801-R) and the UE (FEDER funding). J.C.M.-M. also acknowledges Spanish Ministry of Science, Innovation and Universities for the financial support through a FPU grant (FPU17/00603)

Cytokine-associated neutrophil extracellular traps and antinuclear antibodies in Plasmodium falciparum infected children under six years of age

<p>Abstract</p> <p>Background</p> <p>In <it>Plasmodium falciparum</it>-infected children, the relationships between blood cell histopathology, blood plasma components, development of immunocompetence and disease severity remain poorly understood. Blood from Nigerian children with uncomplicated malaria was analysed to gain insight into these relationships. This investigation presents evidence for circulating neutrophil extracellular traps (NETs) and antinuclear IgG antibodies (ANA). The presence of NETs and ANA to double-stranded DNA along with the cytokine profiles found suggests autoimmune mechanisms that could produce pathogenesis in children, but immunoprotection in adults.</p> <p>Methods</p> <p>Peripheral blood smear slides and blood samples obtained from 21 Nigerian children under six years of age, presenting with uncomplicated malaria before and seven days after initiation of sulphadoxine-pyrimethamine (SP) treatment were analysed. The slides were stained with Giemsa and with DAPI. Levels of the pro-inflammatory cytokines IFN-γ, IL-2, TNF, CRP, and IL-6, select anti-inflammatory cytokines TGF-β and IL-10, and ANA were determined by immunoassay.</p> <p>Results</p> <p>The children exhibited circulating NETs with adherent parasites and erythrocytes, elevated ANA levels, a Th2 dominated cytokine profile, and left-shifted leukocyte differential counts. Nonspecific ANA levels were significant in 86% of the children pretreatment and in 100% of the children seven days after SP treatment, but in only 33% of age-matched control samples collected during the season of low parasite transmission. Levels of ANA specific for dsDNA were significant in 81% of the children both pre-treatment and post treatment.</p> <p>Conclusion</p> <p>The results of this investigation suggest that NET formation and ANA to dsDNA may induce pathology in falciparum-infected children, but activate a protective mechanism against falciparum malaria in adults. The significance of in vivo circulating chromatin in NETs and dsDNA ANA as a causative factor in the hyporesponsiveness of CpG oligonucleotide-based malaria vaccines is discussed.</p

Anatomical Specializations for Nocturnality in a Critically Endangered Parrot, the Kakapo (Strigops habroptilus)

The shift from a diurnal to nocturnal lifestyle in vertebrates is generally associated with either enhanced visual sensitivity or a decreased reliance on vision. Within birds, most studies have focused on differences in the visual system across all birds with respect to nocturnality-diurnality. The critically endangered Kakapo (Strigops habroptilus), a parrot endemic to New Zealand, is an example of a species that has evolved a nocturnal lifestyle in an otherwise diurnal lineage, but nothing is known about its' visual system. Here, we provide a detailed morphological analysis of the orbits, brain, eye, and retina of the Kakapo and comparisons with other birds. Morphometric analyses revealed that the Kakapo's orbits are significantly more convergent than other parrots, suggesting an increased binocular overlap in the visual field. The Kakapo exhibits an eye shape that is consistent with other nocturnal birds, including owls and nightjars, but is also within the range of the diurnal parrots. With respect to the brain, the Kakapo has a significantly smaller optic nerve and tectofugal visual pathway. Specifically, the optic tectum, nucleus rotundus and entopallium were significantly reduced in relative size compared to other parrots. There was no apparent reduction to the thalamofugal visual pathway. Finally, the retinal morphology of the Kakapo is similar to that of both diurnal and nocturnal birds, suggesting a retina that is specialised for a crepuscular niche. Overall, this suggests that the Kakapo has enhanced light sensitivity, poor visual acuity and a larger binocular field than other parrots. We conclude that the Kakapo possesses a visual system unlike that of either strictly nocturnal or diurnal birds and therefore does not adhere to the traditional view of the evolution of nocturnality in birds

Structure, chemical bonding, and ⁴⁵Sc solid state NMR of Sc₂RuSi₂

The silicide Sc2RuSi2 was synthesized from the elements by arc-melting. The structure was refined on the basis of single crystal X-ray diffractometer data: Zr2CoSi2 type, C2/m, a = 1004.7 (2), b = 406.8 (1), c = 946.6 (2) pm, β = 117.95 (2), wR2 = 0.0230, 743 F2 values, and 32 variables. The structure consists of a rigid three-dimensional [RuSi2] network in which the two crystallographically independent scandium atoms fill larger cages of coordination numbers 16 and 15, respectively. The [RuSi2] network shows short Ru–Si distances (234–247 pm) and two different Si2 pairs: Si1–Si1 at 247 and Si2–Si2 at 243 pm. Each silicon atom has trigonal prismatic Sc6 (for Si2) or Sc4Ru2 (for Si1) coordination. These building units are condensed via common edges and faces. The various Sc–Sc distances between the prisms range from 327 to 361 pm. From electronic structure investigation within DFT, chemical bonding shows a major role of Ru–Si bonding and the presence of strong electron localization around Si–Si pairs pointing to a polyanionic silicide network [RuSi2]δ−. The 45Sc MAS-NMR spectra recorded at 11.7 and 9.4 T clearly resolve the two distinct scandium sites. The large electric field gradients present at both scandium sites result in typical line shapes arising from second-order quadrupole perturbation effects

Ferromagnetic Ordering in CeZnSn

The stannide CeZnSn was obtained in X-ray-pure form by induction-melting of the elements in a sealed tantalum ampoule. CeZnSn crystallizes with the YPtAs-type structure, space group P63/mmc, ..

Ternary Silicides Sc₃<em>T</em>Si₃ (<em>T</em> = Ru, Rh, Ir, Pt) – Structure, Chemical Bonding, and Solid State NMR

New complex silicides Sc3TSi3 (T = Ru, Rh, Ir, Pt) were prepared by arc-melting of the elements. They crystallize with a new orthorhombic structure type, space group Pnma. The four structures were refined from single crystal diffractometer data: a = 1167.6(3), b = 398.20(9), c = 1026.9(2) pm, wR2 = 0.0559, 923 F2 values for Sc3RuSi3, a = 1166.8(1), b = 401.85(5), c = 1019.7(1) pm, wR2 = 0.0355, 819 F2 values for Sc3RhSi3, a = 1160.7(2), b = 402.84(6), c = 1015.1(2) pm, wR2 = 0.0352, 905 F2 values for Sc3IrSi3, and a = 1166.3(1), b = 403.18(5), c = 1019.3(2) pm, wR2 = 0.0465, 917 F2 values for Sc3PtSi3 with 44 variables per refinement. The Sc3TSi3 structures contain complex three-dimensional [TSi3] polyanionic networks with slightly distorted tetrahedral silicon coordination of the transition metal atoms, e.g. 237–254 pm Ru–Si in Sc3RuSi3. The RuSi4 tetrahedra share common corners along the short unit cell axis and these rows are connected by Si–Si bonds, leading to Si3 units (243–244 pm Si–Si) within the [RuSi3] polyanion. Ab initio electronic structure investigations point to dominating Ru–Si interactions and show strong electron localization around the Si3 units, underlining the polyanionic character. Significant differences in the 45Sc quadrupolar interaction strengths between the three distinct scandium sites in the Sc3TSi3 silicide were detected by lineshape analyses of field dependent 45Sc MAS as well as 2D TQMAS NMR spectroscopic data. By comparing the experimentally obtained quadrupole interaction parameters with theoretically calculated ones a site assignment of the equal intense signals is possible

Sc2(MoO4)3 and Sc2(WO4)3: halide flux growth of single crystals and 45Sc solid-state NMR

Single crystals of Sc2(TO4)3 with T = Mo and W were synthesized from Sc2O3, MoO3, and WO3 at 1223 K in NaCl / KCl as solvent. Both structures were refined from X-ray diffractometer data: Pbcn, a = 1325.1(1), b = 954.9(1), c = 964.4(1) pm, wR2 = 0.0425, 2097 F2, 79 variables for Sc2(MoO4)3 and a = 1332.9(9), b = 959.4(7), c = 967.9(2) pm, wR2 = 0.0384, 1971 F2, 79 variables for Sc2(WO4)3. The structures consist of a three-dimensional network of corner-sharing ScO6/2 octahedra and two crystallographically independent TO4/2 tetrahedra. 45Sc MAS NMR spectra show sharp single resonances in accordance with the crystallographic data. The quadrupolar interaction parameters obtained from a simulation of the full 45Sc MAS NMR spectra are found to be in good agreement with those obtained from DFT calculations of the electric field gradient</jats:p