Characterisation of Phase Separation in Drop-Tube-Processed Rapidly Solidified CoCrCuFeNi0.8 High-Entropy Alloy

We investigate the impact of cooling rate on a CoCrCuFeNi0.8 high-entropy alloy with a predicted metastable miscibility gap. Rapid solidification via drop-tube processing simulates a containerless, low-gravity solidification environment. Droplets were produced with diameters ranging from 850+ µm to 38 µm, with calculated liquid phase cooling rates of between 600 and 60,000 K s−1. Contrary to studies on similar alloys with a reported metastable miscibility gap and similar investigations on binary alloys known to undergo metastable liquid phase separation, almost no core–shell microstructures were observed in the droplets, likely due to a heavily unbalanced volume fraction ratio between the two phases formed from the parent liquid. Instead, drop-tube processing yielded myriad structures, the occurrences of which vary heavily with cooling rate. At cooling rates of 600 K s−1, a solid-state decomposition reaction begins to become noticeable, populating dendrites with copper-rich dispersions after solidification. The prevalence of these structures increases with increasing cooling rate, occurring in above 95% of droplets once cooling rate exceeds 20,000 K s−1. Occurrence rate of dispersions attributed to liquid phase separation peaks at 8% of droplets at intermediate cooling rates between 5000 and 12,000 K s−1. Spontaneous grain refinement has a maximum prevalence between 1000 and 5000 K s−1. This study begins to show how cooling rate and undercooling can be used to tailor microstructures in HEAs and highlights drastic differences in obtainable microstructures compared to those found in binary and ternary immiscible alloys

Microstructural characterisation and compound formation in rapidly solidified SiGe alloy

Severe Ge segregation to grain boundaries was observed in a Si–14.2 at% Ge thermoelectric alloy rapidly solidified using a drop-tube facility, manifesting itself as a series of regions with uniform stoichiometric compositions. The step change in composition at the interface between adjacent regions was ascribed to the formation of different SiGe pseudocompounds and contradicted the accepted thermodynamic description of the SiGe system as a continuous random solid solution. Rapid solidification increased, rather than decreased, the inhomogeneity degree of the solid product, and the Ge content of the most Ge-rich regions was positively correlated with the cooling rate, which suggested the absence of solute trapping. The transmission electron microscopy/selected area electron diffraction analysis of the most Ge-rich regions revealed superlattice spots indicative of chemical ordering. However, simple chemical ordering within a single diamond cubic unit cell could not explain the fact that most stoichiometries had compositions that were multiples of 5 at% Ge, which indicated the presence of superstructural ordering

Disease-specific, neurosphere-derived cells as models for brain disorders

There is a pressing need for patient-derived cell models of brain diseases that are relevant and robust enough to produce the large quantities of cells required for molecular and functional analyses. We describe here a new cell model based on patient-derived cells from the human olfactory mucosa, the organ of smell, which regenerates throughout life from neural stem cells. Olfactory mucosa biopsies were obtained from healthy controls and patients with either schizophrenia, a neurodevelopmental psychiatric disorder, or Parkinson's disease, a neurodegenerative disease. Biopsies were dissociated and grown as neurospheres in defined medium. Neurosphere-derived cell lines were grown in serum-containing medium as adherent monolayers and stored frozen. By comparing 42 patient and control cell lines we demonstrated significant disease-specific alterations in gene expression, protein expression and cell function, including dysregulated neurodevelopmental pathways in schizophrenia and dysregulated mitochondrial function, oxidative stress and xenobiotic metabolism in Parkinson's disease. The study has identified new candidate genes and cell pathways for future investigation. Fibroblasts from schizophrenia patients did not show these differences. Olfactory neurosphere-derived cells have many advantages over embryonic stem cells and induced pluripotent stem cells as models for brain diseases. They do not require genetic reprogramming and they can be obtained from adults with complex genetic diseases. They will be useful for understanding disease aetiology, for diagnostics and for drug discovery

Resolving a dusty, star-forming SHiZELS galaxy at z = 2.2 with HST, ALMA, and SINFONI on kiloparsec scales

We present ∼0.15 arcsec spatial resolution imaging of SHiZELS-14, a massive (⁠M∗∼1011M⊙⁠), dusty, star-forming galaxy at z = 2.24. Our rest-frame ∼1kpc-scale, matched-resolution data comprise four different widely used tracers of star formation: the Hα emission line (from SINFONI/VLT), rest-frame UV continuum (from HST F606W imaging), the rest-frame far-infrared (from ALMA), and the radio continuum (from JVLA). Although originally identified by its modest Hα emission line flux, SHiZELS-14 appears to be a vigorously star-forming (⁠SFR∼1000M⊙yr−1⁠) example of a submillimetre galaxy, probably undergoing a merger. SHiZELS-14 displays a compact, dusty central starburst, as well as extended emission in Hα and the rest-frame optical and FIR. The UV emission is spatially offset from the peak of the dust continuum emission, and appears to trace holes in the dust distribution. We find that the dust attenuation varies across the spatial extent of the galaxy, reaching a peak of at least AH α ∼ 5 in the most dusty regions, although the extinction in the central starburst is likely to be much higher. Global star-formation rates inferred using standard calibrations for the different tracers vary from ∼10−1000M⊙yr−1⁠, and are particularly discrepant in the galaxy’s dusty centre. This galaxy highlights the biased view of the evolution of star-forming galaxies provided by shorter wavelength data

Increased BDNF levels and NTRK2 gene association suggest a disruption of BDNF/TrkB signaling in autism

The brain-derived neurotrophic factor (BDNF), a neurotrophin fundamental for brain development and function, has previously been implicated in autism. In this study, the levels of BDNF in platelet-rich plasma were compared between autistic and control children, and the role of two genetic factors that might regulate this neurotrophin and contribute to autism etiology, BDNF and NTRK2, was examined. We found that BDNF levels in autistic children (n = 146) were significantly higher (t = 6.82; P < 0.0001) than in control children (n = 50) and were positively correlated with platelet serotonin distribution (r = 0.22; P = 0.004). Heritability of BDNF was estimated at 30% and therefore candidate genes BDNF and NTRK2 were tested for association with BDNF level distribution in this sample, and with autism in 469 trio families. Genetic association analysis provided no evidence for BDNF or NTRK2 as major determinants of the abnormally increased BDNF levels in autistic children. A significant association with autism was uncovered for six single nucleotide polymorphisms (SNPs) [0.004 (Z((1df)) = 2.85) < P < 0.039 (Z((1df)) = 2.06)] and multiple haplotypes [5 × 10(-4) (χ((3df)) = 17.77) < P < 0.042 (χ((9df)) = 17.450)] in the NTRK2 gene. These results do not withstand correction for multiple comparisons, however, reflect a trend toward association that supports a role of NTRK2 as a susceptibility factor for the disorder. Genetic variation in the BDNF gene had no impact on autism risk. By substantiating the previously observed increase in BDNF levels in autistic children in a larger patient set, and suggesting a genetic association between NTRK2 and autism, this study integrates evidence from multiple levels supporting the hypothesis that alterations in BDNF/tyrosine kinase B (TrkB) signaling contribute to an increased vulnerability to autism

Quantum Characterization of a Werner-like Mixture

We introduce a Werner-like mixture [R. F. Werner, Phys. Rev. A {\bf 40}, 4277 (1989)] by considering two correlated but different degrees of freedom, one with discrete variables and the other with continuous variables. We evaluate the mixedness of this state, and its degree of entanglement establishing its usefulness for quantum information processing like quantum teleportation. Then, we provide its tomographic characterization. Finally, we show how such a mixture can be generated and measured in a trapped system like one electron in a Penning trap.Comment: 8 pages ReVTeX, 8 eps figure

Estimation of cooling rates during close-coupled gas atomization using secondary dendrite arm spacing measurement

Al-4 wt pct Cu alloy has been gas atomized using a commercial close-coupled gas-atomization system. The resulting metal powders have been sieved into six size fractions, and the SDAS has been determined using electron microscopy. Cooling rates for the powders have been estimated using a range of published conversion factors for Al-Cu alloy, with reasonable agreement being found between sources. We find that cooling rates are very low relative to those often quoted for gas-atomized powders, of the order of 10 K s for sub-38 μm powders. We believe that a number of numerical studies of gas atomization have overestimated the cooling rate during solidification, probably as a consequence of overestimating the differential velocity between the gas and the particles. From the cooling rates measured in the current study, we estimate that such velocities are unlikely to exceed 20 m s

Can forest management based on natural disturbances maintain ecological resilience?

Given the increasingly global stresses on forests, many ecologists argue that managers must maintain ecological resilience: the capacity of ecosystems to absorb disturbances without undergoing fundamental change. In this review we ask: Can the emerging paradigm of natural-disturbance-based management (NDBM) maintain ecological resilience in managed forests? Applying resilience theory requires careful articulation of the ecosystem state under consideration, the disturbances and stresses that affect the persistence of possible alternative states, and the spatial and temporal scales of management relevance. Implementing NDBM while maintaining resilience means recognizing that (i) biodiversity is important for long-term ecosystem persistence, (ii) natural disturbances play a critical role as a generator of structural and compositional heterogeneity at multiple scales, and (iii) traditional management tends to produce forests more homogeneous than those disturbed naturally and increases the likelihood of unexpected catastrophic change by constraining variation of key environmental processes. NDBM may maintain resilience if silvicultural strategies retain the structures and processes that perpetuate desired states while reducing those that enhance resilience of undesirable states. Such strategies require an understanding of harvesting impacts on slow ecosystem processes, such as seed-bank or nutrient dynamics, which in the long term can lead to ecological surprises by altering the forest's capacity to reorganize after disturbance

The origin of anomalous eutectic structures in undercooled Ag-Cu alloy

A melt encasement (fluxing) method was used to undercool Ag-Cu alloy at its eutectic composition. The recalescence of the undercooled alloy was filmed at a high frame rate. For undercoolings <60 K, a microstructure consisting of mixed anomalous and lamellar eutectic is observed. Analysis of eutectic spacing in the lamellar eutectic reveals little dependence upon the undercooling of the bulk melt and is consistent with growth at an undercooling of 1.5 K. Depending upon undercooling, the progress of the recalescence front may be either continuous or spasmodic, wherein periods of rapid growth are separated by significant interludes in which growth totally arrests. Analysis of spot brightness profiles reveals that, during continuous growth, the recalescence is characteristic of the advancement of a planar, space-filling front, while a double recalescence occurs during spasmodic growth, the first of which is characteristic of the propagation of a dendritic, or non-space-filling, front. It is concluded that, during spasmodic growth, the propagation of two-phase, or eutectic, dendrites is observed, which subsequently remelt to form the anomalous eutectic, while the lamellar eutectic grows during post-recalescence cooling