Heterogeneously doped nanocrystalline ceria films by grain boundary diffusion: Impact on transport properties

Heterogeneous doping of nanocrystalline ceria films, by controlled in-diffusion along grain boundaries, is explored as a means for modifying the space charge potential and the inhomogeneous distribution of defects in the space charge layer known to control the electrical properties of nanocrystalline electroceramics. Nanocrystalline cerium oxide thin films were grown by pulsed laser deposition and modified by a novel doping technique. Thin diffusion sources were deposited and cations such as Ni²⁺ and Gd³⁺ were in-diffused at temperatures of 700–800 °C along columnar grain boundaries normal to the surface; the resulting diffusion profiles were examined by Time-of-Flight SIMS. The properties of these modified films were compared with as-deposited samples, with in-diffusion resulting in decreased electrical conductivity. It is proposed that the variation in conductivity results from a redistribution of charge carriers in the space charge layers due to a change in the space charge potential.     

Quantification of increased MUC5AC expression in airway mucus of smoker using an automated image-based approach

Microscopic analysis of mucus quantity and composition is crucial in research and diagnostics on muco-obstructive diseases. Currently used image-based methods are unable to extract concrete numeric values of mucosal proteins, especially on the expression of the key mucosal proteins MUC5AC and MUC5B. Since their levels increase under pathologic conditions such as extensive exposure to cigarette smoke, it is imperative to quantify them to improve treatment strategies of pulmonary diseases. This study presents a simple, image-based, and high-processing computational method that allows determining the ratio of MUC5AC and MUC5B within the overall airway mucus while providing information on their spatial distribution. The presented pipeline was optimized for automated downstream analysis using a combination of bright field and immunofluorescence imaging suitable for tracheal and bronchial tissue samples, and air–liquid interface (ALI) cell cultures. To validate our approach, we compared tracheal tissue and ALI cell cultures of isolated primary normal human bronchial epithelial cells derived from smokers and nonsmokers. Our data indicated 18-fold higher levels of MUC5AC in submucosal glands of smokers covering about 8% of mucosal areas compared to <1% in nonsmoking individuals, confirming results of previous studies. We further identified a subpopulation of nonsmokers with slightly elevated glandular MUC5AC levels suggesting moderate exposure to second-hand smoke or fine particulate air pollution. Overall, this study demonstrates a novel, user-friendly and freely available tool for digital pathology and the analysis of therapeutic interventions tested in ALI cell cultures.     

Structure–Property Relationships in Lanthanide‐Doped Upconverting Nanocrystals: Recent Advances in Understanding Core–Shell Structures

The production of upconverting nanostructures with tailored optical properties is of major technological interest, and rapid progress toward the realization of such production has been made in recent years. Ultimately, accurate understanding of nanostructure organization will lead to design rules for accurately tailoring optical properties. Here, the context of open questions still of general importance to the upconversion and nanocrystal communities is presented, with a particular emphasis on the structure–property relationships of core–shell upconverting nanocrystals. Although the optical properties of the latter have been thoroughly investigated, little is known regarding their atomic‐scale organization. Indeed, solving the atomic‐scale structure of such nanomaterials is challenging because of their intrinsic nonperiodic nature. Familiar concepts of crystallography are no longer appropriate; chemical and structural modulation waves must be introduced. To reveal the exact core–shell structures, innovative characterization techniques need to be applied and developed, as discussed herein. The continued development and application of structural characterization techniques will be vital to consolidate the currently incomplete link between atomic‐scale structure and upconversion properties. This will ultimately provide a valuable contribution to the emerging detailed guidelines on how to better design upconverting nanostructures to achieve given optical properties in terms of efficiency, absorption, spectral emission, and dynamics.     

The effect of B-site Y substitution on cubic phase stabilization in (Ba0.5Sr0.5)(Co0.8Fe0.2)O3−δ

The cubic phase mixed ionic-electronic conductor (Ba_0.5Sr_0.5)(Co_0.8Fe_0.2)O_3−δ (BSCF) is well-known for its excellent oxygen ion conductivity and high catalytic activity. However, formation of secondary phases impedes oxygen ion transport and consequentially a widespread application of BSCF as oxygen transport membrane. B-cation substitution by 1, 3 and 10 at.% Y was employed in this work for stabilization of the cubic BSCF phase. Secondary phase formation was quantified on bulk and powder samples exposed to temperatures between 640 and 1100°C with annealing time up to 44 days. The phase composition, cation valence states, and chemical composition of all samples were analyzed by high-resolution analytical electron microscopic techniques. Y doping effectively suppresses the formation of Ba_n+1Co_nO_3n+3(Co₈O₈) (n ≥ 2) and Co_xO_y phases which would otherwise act as nucleation centers for the highly undesirable hexagonal BSCF phase. This work validates for 10 at.% Y cation substitution perfect stabilization of the cubic BSCF phase at temperatures ≥800°C, while a negligible small volume fraction of the hexagonal BSCF phase was found at lower temperatures. A newly developed model describes the effect of Y doping on the formation of secondary phases and their effective suppression with increasing Y concentration.     

The structural basis for the altered substrate specificity of the R292D active site mutant of aspartate aminotransferase from E.coli

Two refined crystal structures of aspartate aminotransferasefrom E.coli are reported. The wild type enzyme is in the pyridoxalphosphate (PLP) form and its structure has been determined to2.4 Å resolution, refined to an R-factor of 23.2%. Thestructure of the Arg292Asp mutant has been determined at 2.8Å resolution, refined to an R–factor of 20.3%. Thewild type and mutant crystals are isomorphous and the two structuresare very similar, with only minor changes in positions of importantactive site residues. As residue Arg292 is primarily responsiblefor the substrate charge specificity in the wild type enzyme,the mutant containing a charge reversal at this position mightbe expected to catalyze transamination of arginine as efficientlyas the wild type enzyme effects transamination of aspartate[Cronin,C.N. and Kirsch,J.F. (1988) Biochemistry, 27, 4572–4579].This mutant does in fact prefer arginine over aspartate as asubstrate, however, the rate of catalysis is much slower thanthat of the wild type enzyme with its physiological substrate,aspartate. A comparison of these two structures indicates thatthe poorer catalytic efficiency of R292D, when presented witharginine, is not due to a gross conformational difference, butis rather a consequence of both small side chain and main chainreorientations and the pre–existing active site polarenvironment, which greatly favors the wild type ion pair interaction.     

Effects of peroxidative stress and age on the concentration of a deoxyguanosine-malondialdehyde adduct in rat DNA

The effect of age and peroxidative stress on the concentration of a deoxyguanosine malondialdehyde adduct (dG-MDA) in rat tissues was investigated. Vitamin E deficiency had not effect on the dG-MDA content of liver DNA in rats fed a diet containing 10% corn oil. When 2% cod liver oil was added to this diet, the dG-MDA content of liver DNA doubled in the positive controls fed a high level of vitamin E (100 ppm dl-α-tocopherol), and there was a further increase when vitamin E was deleted. Neither iron nitrilotriacetate administration nor choline deficiency had any effect on the dG-MDA content of liver DNA. Carbon tetrachloride had a lowering effect. The failure of iron or carbon tetrachloride administration and of vitamin E deficiency to increase liver dG-MDA is consistent with their failure in previous experiments to affect the urinary excretion of dG-MDA. In contrast, these forms of peroxidative stress produce large increments in the urinary excretion of MDA adducts with lysine, reflecting increased formation and degradation of MDA-modified proteins. DNA appears to be protected from modification by MDA produced at extranuclear sites. The frequency of dG-MDA in different tissues of 4-month-old rats varied markedly: brain ≫ liver > kidneys and testes. Higher concentrations of dG-MDA were found in the liver and kidneys, but not the testes, of 25-month-old rats. The determinants of the concentration of dG-MDA in DNA merit further investigation.     

Polyethylene/Ethylene Vinyl Acetate and Ethylene Octene Copolymer/Clay Nanocomposite Films: Different Processing Conditions and Their Effect on Properties

Polymer nanocomposites based on a layered clay used as nanofiller and copolymers ethylene and vinyl acetate matrix (EVA, the content of vinyl acetate (VA) component 19 wt% and 5 wt%) and ethylene octene copolymer (EOC, 17% and 45% of octene) were prepared. KO Buss kneader and double screw extruder were used. The MMT Na+ and four types of commercial products such as Nanofil N5 and N3000, Cloisite 93A and 30B were used as nanofillers—5 wt% in relation to the content of montmorillonite. The aim was to evaluate the influence of copolymer composition and processing on prepared nanocomposite properties. The morphology of samples was examined by means of X‐ray diffraction (XRD) and transmission electronic microscopy TEM. Furthermore, mechanical and especially barrier properties were observed. Despite the fact that the XRD and microscopy results have revealed that complete exfoliation did not take place in any case, mechanical properties as well as the permeability showed that used 5 wt% of clay was enough to achieve the improvement of properties. Cloisite 30B might be the most suitable for the polyethylene/EVA matrix. In case of EOC copolymer the nanofiller Nanofil N3000 and mainly Cloisite 93A seems to be more suitable. The better properties were achieved for the version of EVA with lower VA content and also for EOC 17, but not for each evaluated property. POLYM. ENG. SCI., 59:2514–2521, 2019. © 2019 Society of Plastics Engineers     

Mouse Liver Compensates Loss of Sgpl1 by Secretion of Sphingolipids into Blood and Bile

Sphingosine 1 phosphate (S1P) lyase (Sgpl1) catalyses the irreversible cleavage of S1P and thereby the last step of sphingolipid degradation. Loss of Sgpl1 in humans and mice leads to accumulation of sphingolipids and multiple organ injuries. Here, we addressed the role of hepatocyte Sgpl1 for regulation of sphingolipid homoeostasis by generating mice with hepatocyte-specific deletion of Sgpl1 (Sgpl1^HepKO mice). Sgpl1^HepKO mice had normal body weight, liver weight, liver structure and liver enzymes both at the age of 8 weeks and 8 months. S1P, sphingosine and ceramides, but not glucosylceramides or sphingomyelin, were elevated by ~1.5–2-fold in liver, and this phenotype did not progress with age. Several ceramides were elevated in plasma, while plasma S1P was normal. Interestingly, S1P and glucosylceramides, but not ceramides, were elevated in bile of Sgpl1^HepKO mice. Furthermore, liver cholesterol was elevated, while LDL cholesterol decreased in 8-month-old mice. In agreement, the LDL receptor was upregulated, suggesting enhanced uptake of LDL cholesterol. Expression of peroxisome proliferator-activated receptor-γ, liver X receptor and fatty acid synthase was unaltered. These data show that mouse hepatocytes largely compensate the loss of Sgpl1 by secretion of accumulating sphingolipids in a specific manner into blood and bile, so that they can be excreted or degraded elsewhere.     

Ambience-sensitive optical refraction in ferroelectric nanofilms of NaNbO3

Optical index of refraction n is studied by spectroscopic ellipsometry in epitaxial nanofilms of NaNbO₃ with thickness ～10 nm grown on different single-crystal substrates. The index n in the transparency spectral range (n ≈ 2.1 – 2.2) exhibits a strong sensitivity to atmospheric-pressure gas ambience. The index n in air exceeds that in an oxygen ambience by δn ≈ 0.05 – 0.2. The thermo-optical behaviour n(T) indicates ferroelectric state in the nanofilms. The ambience-sensitive optical refraction is discussed in terms of fundamental connection between refraction and ferroelectric polarization in perovskites, screening of depolarizing field on surfaces of the nanofilms, and thermodynamically stable surface reconstructions of NaNbO₃.