Polyethylene-based composites were prepared using keratin fibers obtained from chicken feathers. Fibers of similar diameter but varying aspect ratio were mixed into low-density polyethylene (LDPE) ...using a Brabender mixing head. From uniaxial tensile testing, an elastic modulus and yield stress increase of the composite over the virgin polymer was observed over a wide range of fiber loading. Scanning electron microscopy revealed some interaction between the polymer and keratin feather fiber. In addition, the keratin fiber had a density lower than the LDPE used in this study resulting in composite materials of reduced density. The results obtained from mechanical testing are compared to theoretical predictions based on a simple composite material micromechanical model.
Lyman-break galaxy (LBG) samples observed during reionization (z > or ~ 6) with the Hubble Space Telescope's Wide Field Camera 3 are reaching sizes sufficient to characterize their clustering ...properties. Using a combined catalog from the Hubble eXtreme Deep Field and CANDELS surveys, containing N = 743 LBG candidates at z > or = 6.5 at a mean redshift of z = 7.2, we detect a clear clustering signal in the angular correlation function (ACF) at 4sigma, corresponding to a real-space correlation length (ProQuest: Formulae and/or non-USASCII text omitted) cMpc. Finally, our bias measurements allow us to investigate the fraction of dark matter halos hosting UV-bright galaxies. At z = 7.2 values near unity are preferred, which may be explained by the shortened halo assembly time at high redshift.
We outline a method to synthesize (ATiO3)nAO Ruddlesden–Popper phases with high-n, where the A-site is a mixture of barium and strontium, by molecular-beam epitaxy. The precision and consistency of ...the method described is demonstrated by the growth of an unprecedented (SrTiO3)50SrO epitaxial film. We proceed to investigate barium incorporation into the Ruddlesden–Popper structure, which is limited to a few percent in bulk, and we find that the amount of barium that can be incorporated depends on both the substrate temperature and the strain state of the film. At the optimal growth temperature, we demonstrate that as much as 33% barium can homogeneously populate the A-site when films are grown on SrTiO3 (001) substrates, whereas up to 60% barium can be accommodated in films grown on TbScO3 (110) substrates, which we attribute to the difference in strain. This detailed synthetic study of high n, metastable Ruddlesden–Popper phases is pertinent to a variety of fields from quantum materials to tunable dielectrics.
Fiumara A, Barone R, Arena A, Filocamo M, Lissens W, Pavone L, Sorge G. Krabbe leukodystrophy in a selected population with high rate of late onset forms: longer survival linked to c.121G>A ...(p.Gly41Ser) mutation.
Krabbe leukodystrophy (KD) is a neurodegenerative lysosomal disorder caused by mutations in the galactocerebrosidase (GALC) gene. Different clinical forms are described based on the age at onset. In reported series, the early infantile form (EIKD) accounts for more than 90% of the cases. The rarer late onset forms (LOKD) become manifest later than 6 months up to the adult age. We report clinical, imaging, mutational analysis and geographic data in a large cohort of individuals with Krabbe disease examined over a 30‐year period.
Retrospective analyses of disease onset and long‐term follow‐up were conducted in 26 KD patients. Molecular analysis was performed in 12 patients and their families. Nine cases had EIKD, and 17 LOKD, accounting for two thirds of our series. No correlation was found between enzymatic activity, onset age and disease progression. Despite common geographical origin, only in a few cases could parental consanguinity be proven. The p.Gly41Ser mutation was associated with longer survival. A wide spectrum of LOKD is found despite similar genotype. Although current knowledge about onset age, residual enzyme activity and molecular analysis still fail to allow the identification of patient candidates for treatment, this information is valuable for long‐term outcome prediction and could lead to reconsideration of inclusion criteria for bone marrow transplant (BMT) or other future therapeutic approaches.
Homologous series are layered phases that can have a range of stoichiometries depending on an index n. Examples of perovskite-related homologous series include (ABO3)nAO Ruddlesden–Popper phases and ...(Bi2O2) (An−1BnO3n+1) Aurivillius phases. It is challenging to precisely control n because other members of the homologous series have similar stoichiometry and a phase with the desired n is degenerate in energy with syntactic intergrowths among similar n values; this challenge is amplified as n increases. To improve the ability to synthesize a targeted phase with precise control of the atomic layering, we apply the x-ray diffraction (XRD) approach developed for superlattices of III–V semiconductors to measure minute deviations from the ideal structure so that they can be quantitatively eradicated in subsequent films. We demonstrate the precision of this approach by improving the growth of known Ruddlesden–Popper phases and ultimately, by synthesizing an unprecedented n = 20 Ruddlesden–Popper phase, (ATiO3)20AO where the A-site occupancy is Ba0.6Sr0.4. We demonstrate the generality of this method by applying it to Aurivillius phases and the Bi2Sr2Can–1CunO2n+4 series of high-temperature superconducting phases.
Ferroelectric nanomaterials offer the promise of switchable electronic properties at the surface, with implications for photo- and electrocatalysis. Studies to date on the effect of ferroelectric ...surfaces in electrocatalysis have been primarily limited to nanoparticle systems where complex interfaces arise. Here, we use MBE-grown epitaxial BaTiO
thin films with atomically sharp interfaces as model surfaces to demonstrate the effect of ferroelectric polarization on the electronic structure, intermediate binding energy, and electrochemical activity toward the hydrogen evolution reaction (HER). Surface spectroscopy and
DFT+U calculations of the well-defined (001) surfaces indicate that an upward polarized surface reduces the work function relative to downward polarization and leads to a smaller HER barrier, in agreement with the higher activity observed experimentally. Employing ferroelectric polarization to create multiple adsorbate interactions over a single electrocatalytic surface, as demonstrated in this work, may offer new opportunities for nanoscale catalysis design beyond traditional descriptors.
The Ruddlesden–Popper (A n+1B n O3n+1) compounds are highly tunable materials whose functional properties can be dramatically impacted by their structural phase n. The negligible differences in ...formation energies for different n can produce local structural variations arising from small stoichiometric deviations. Here, we present a Python analysis platform to detect, measure, and quantify the presence of different n-phases based on atomic-resolution scanning transmission electron microscopy (STEM) images. We employ image phase analysis to identify horizontal Ruddlesden–Popper faults within the lattice images and quantify the local structure. Our semiautomated technique considers effects of finite projection thickness, limited fields of view, and lateral sampling rates. This method retains real-space distribution of layer variations allowing for spatial mapping of local n-phases to enable quantification of intergrowth occurrence and qualitative description of their distribution suitable for a wide range of layered materials.
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