Microstructure of (Hf-Ta-Zr-Nb)C high-entropy carbide at micro and nano/atomic level

Support from the projects APVV-15-0469, APVV-15-0621, VEGA 2/0163/16, and VEGA 2/0082/17 is acknowledged. MJR and EGC acknowledge the support of EPSRC grant XMAT (EP/K008749/2)

Ce-modified zeolite BEA catalysts for the trichloroethylene oxidation. The role of the different and necessary active sites

[EN] This paper reports the activity of different Ce-BEA zeolites for the catalytic oxidation of trichloroethylene and it is focused on determining the nature of the catalyst active sites. The study was made by using a microporous zeolite BEA, two types of desilicated BEA zeolites and mildly steamed desilicated BEA zeolites. The catalysts were prepared by introducing Ce to the zeolites with incipient wetness impregnation and their structural, textural, and acidic properties were established. The evolution of TCE conversion was correlated with the physicochemical properties of the zeolites. It is shown that highly developed mesopore surface area, well-dispersed cerium species and a high number of Bronsted sites results in the highest activity. The activity and selectivity of the Ce-loaded zeolites were found to be dependent on the number of high strength Bronsted acid centres. The hierarchical materials with a higher density of hydroxyls showed higher yields to HCl while the formation of chlorine was prevented.The work was financed by the Grant No. 2015/18/E/ST4/00191 from the National Science Centre, Poland. J.M-T. and A.E.P thank Spanish Governmentthrough "Severo Ochoa" SEV-2016-0683, RTI2018-099668-B-C21, RTI2018-101784-B-I00 and the Fundacion Ramon Arecesthrough a research contract of the "Life and Materials Science" program.Golabek, K.; Palomares Gimeno, AE.; Martínez-Triguero, J.; Tarach, KA.; Kruczala, K.; Girman, V.; Góra-Marek, K. (2019). Ce-modified zeolite BEA catalysts for the trichloroethylene oxidation. The role of the different and necessary active sites. Applied Catalysis B Environmental. 259:1-12. https://doi.org/10.1016/j.apcatb.2019.11802211225

A simple and straightforward mechanochemical synthesis of the far-from-equilibrium zinc aluminate, ZnAl₂O₄, and its response to thermal treatment

Zinc aluminate (ZnAl2O4) nanoparticles with an average size of about 10 nm are synthesized via one-step mechanochemical processing of the ZnO : g-Al2O3 stoichiometric mixture at ambient temperature. The mechanochemically induced formation of the phase is followed by XRD and 27Al MAS NMR. Highresolution TEM studies reveal a non-uniform nanostructure of mechanosynthesized aluminate consisting of ordered grains surrounded or separated by disordered surface and interfacial regions. Due to the capability of 27Al MAS NMR to probe the local environment of the Al cations, valuable insights into the short-range structure of ZnAl2O4 on the °Angstr¨om length scale are provided. It is demonstrated that the as-prepared aluminate possesses a partly inverse spinel structure with a far-from equilibrium arrangement of cations and distorted polyhedra, which are spatially confined to the surface and interfacial regions with a volume fraction of ca. 50% and a thickness of ca. 1 nm. The response of the nanostructured ZnAl2O4 to subsequent thermal treatment is further investigated. It turned out that the thermally induced grain growth is accompanied by a release of microstrain, by a shrinkage of the lattice parameter, as well as by a variation in the oxygen parameter and metal–oxygen bond lengths. Evidence is given of the thermally induced redistribution of cations approaching their equilibrium positions. Upon heating above 1100 K, mechanosynthesized ZnAl2O4 relaxes towards a structural state that is similar to the bulk one

A Unique Mechanochemical Redox Reaction Yielding Nanostructured Double Perovskite Sr2_{2}FeMoO6_{6} With an Extraordinarily High Degree of Anti-Site Disorder

Strontium ferromolybdate, Sr(2)FeMoO(6), is an important member of the family of double perovskites with the possible technological applications in the field of spintronics and solid oxide fuel cells. Its preparation via a multi-step ceramic route or various wet chemistry-based routes is notoriously difficult. The present work demonstrates that Sr(2)FeMoO(6) can be mechanosynthesized at ambient temperature in air directly from its precursors (SrO, α-Fe, MoO(3)) in the form of nanostructured powders, without the need for solvents and/or calcination under controlled oxygen fugacity. The mechanically induced evolution of the Sr(2)FeMoO(6) phase and the far-from-equilibrium structural state of the reaction product are systematically monitored with XRD and a variety of spectroscopic techniques including Raman spectroscopy, (57)Fe Mössbauer spectroscopy, and X-ray photoelectron spectroscopy. The unique extensive oxidation of iron species (Fe(0) → Fe(3+)) with simultaneous reduction of Mo cations (Mo(6+) → Mo(5+)), occuring during the mechanosynthesis of Sr(2)FeMoO(6), is attributed to the mechanically triggered formation of tiny metallic iron nanoparticles in superparamagnetic state with a large reaction surface and a high oxidation affinity, whose steady presence in the reaction mixture of the milled educts initiates/promotes the swift redox reaction. High-resolution transmission electron microscopy observations reveal that the mechanosynthesized Sr(2)FeMoO(6), even after its moderate thermal treatment at 923 K for 30 min in air, exhibits the nanostructured nature with the average particle size of 21(4) nm. At the short-range scale, the nanostructure of the as-prepared Sr(2)FeMoO(6) is characterized by both, the strongly distorted geometry of the constituent FeO(6) octahedra and the extraordinarily high degree of anti-site disorder. The degree of anti-site disorder ASD = 0.5, derived independently from the present experimental XRD, Mössbauer, and SQUID magnetization data, corresponds to the completely random distribution of Fe(3+) and Mo(5+) cations over the sites of octahedral coordination provided by the double perovskite structure. Moreover, the fully anti-site disordered Sr(2)FeMoO(6) nanoparticles exhibit superparamagnetism with the blocking temperature T (B) = 240 K and the deteriorated effective magnetic moment μ = 0.055 μ (B) per formula unit

Protection of Visual Functions by Human Neural Progenitors in a Rat Model of Retinal Disease

BACKGROUND: A promising clinical application for stem and progenitor cell transplantation is in rescue therapy for degenerative diseases. This strategy seeks to preserve rather than restore host tissue function by taking advantage of unique properties often displayed by these versatile cells. In studies using different neurodegenerative disease models, transplanted human neural progenitor cells (hNPC) protected dying host neurons within both the brain and spinal cord. Based on these reports, we explored the potential of hNPC transplantation to rescue visual function in an animal model of retinal degeneration, the Royal College of Surgeons rat. METHODOLOGY/PRINCIPAL FINDINGS: Animals received unilateral subretinal injections of hNPC or medium alone at an age preceding major photoreceptor loss. Principal outcomes were quantified using electroretinography, visual acuity measurements and luminance threshold recordings from the superior colliculus. At 90–100 days postnatal, a time point when untreated rats exhibit little or no retinal or visual function, hNPC-treated eyes retained substantial retinal electrical activity and visual field with near-normal visual acuity. Functional efficacy was further enhanced when hNPC were genetically engineered to secrete glial cell line-derived neurotrophic factor. Histological examination at 150 days postnatal showed hNPC had formed a nearly continuous pigmented layer between the neural retina and retinal pigment epithelium, as well as distributed within the inner retina. A concomitant preservation of host cone photoreceptors was also observed. CONCLUSIONS/SIGNIFICANCE: Wild type and genetically modified human neural progenitor cells survive for prolonged periods, migrate extensively, secrete growth factors and rescue visual functions following subretinal transplantation in the Royal College of Surgeons rat. These results underscore the potential therapeutic utility of hNPC in the treatment of retinal degenerative diseases and suggest potential mechanisms underlying their effect in vivo

Responsiveness of the Acne-Specific Quality of Life Questionnaire (Acne-QoL) to treatment for acne vulgaris in placebo-controlled clinical trials

The Acne-Specific Quality of Life Questionnaire (Acne-QoL) was developed to measure the impact of facial acne across four dimensions of patient quality of life. The main objective of the current study was to evaluate the responsiveness of this instrument. Secondarily, this study provided an opportunity to extend the developer's psychometric validation. The Acne-QoL was utilized in two randomized, double-blind, placebo-controlled studies of the efficacy of Estrostep ® (norethindrone acetate/ethinyl estradiol) in the treatment of facial acne; a total of 296 Estrostep ® and 295 placebo patients were evaluated. The Acne-QoL was completed at the beginning, middle (cycle 3), and end (cycle 6) of the 6-month treatment period. The responsiveness of the Acne-QoL was demonstrated through its ability to detect both small (baseline to mid-study) and moderate (baseline to study end) treatment advantages for Estrostep ® patients. Confirmatory factor analysis supported the subscale structure, and internal consistency estimates were excellent. Convergent and discriminant validity were supported by correlations between Acne-QoL scores and clinical measures that were both in the direction and relative magnitude hypothesized. Finally, item response theory analyses confirmed that each item is highly related to its subscale's latent construct and that each subscale is sensitive across a broad range of the underlying continuum. The results of this evaluation confirm that the Acne-QoL is responsive, internally consistent, and valid.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43563/1/11136_2004_Article_5089801.pd