Mechanically driven alloying and grain size changes in nanocrystalline Fe-Cu powders

Highly supersaturated nanocrystalline FexCu100-x alloys (10 less-than-or-equal-to x less-than-or-equal-to 95) have been prepared by mechanical alloying of elemental crystalline powders. The development of the microstructure is investigated by x-ray diffraction, differential scanning calorimetry, and transmission electron microscopy. The results are compared with data for ball-milled elemental Fe and Cu powders, samples prepared by inert gas condensation, and sputtered films. The deformation during milling reduces the grain size of the alloys to 6-20 nm. The final grain size of the powders depends on the composition of the material. Single-phase fcc alloys with x less-than-or-equal-to 60 and single-phase bcc alloys with x greater-than-or-equal-to 80 are formed even though the Fe-Cu system exhibits vanishingly small solid solubilities under equilibrium conditions. For 60 less-than-or-equal-to x less-than-or-equal-to 80, fcc and bcc solid solutions coexist. The alloy formation is discussed with respect to the thermodynamic conditions of the material. The role of the large volume fraction of grain boundaries between the nanometer-sized crystals, as well as the influence of internal strains and stored enthalpies introduced by ball milling, is critically assessed

Search for instability-induced amorphization in deuterated ErFe2

Experimental evidence–in the form of a specific-heat anomaly–for instability-induced amorphization of ErFe2 by hydrogenation was recently reported by Fecht, Fu, and Johnson [Phys. Rev. Lett. 64, 1753 (1990)]. We have attempted to study this anomaly by in situ elastic neutron diffraction and differential-scanning-calorimetry (DSC) measurements of deuterated ErFe2 below and above the reversible, endothermic, λ-shaped enthalpy signal that they found at ∼200 °C. Our combined diffraction and DSC results reveal that the amorphization transition is irreversible, strongly exothermic and occurs only at a significantly higher temperature than that of the specific-heat anomaly. Rather than resulting from an underlying instability of the crystalline phase, amorphization occurs as a by-product of short-range clustering of the Er and Fe atoms, which is driven by the creation of energetically more favorable sites for the deuterium atoms

Prospects for Improving Alfalfa Yield Using Genomic- and Phenomic-Based Breeding

Alfalfa (Medicago sativa L.) is a perennial outcrossing legume that is cultivated as an important forage crop in many parts of the world. Yield is the most important trait for profitable alfalfa production, yet over the last 30 years yield improvement in California has stagnated. Current breeding methods focus on recurrent phenotypic selection; however, alternatives incorporating genomic- and phenomic-based information may enhance genetic gain and help to address the lack of yield improvement. Here we attempt to increase the yield potential of alfalfa using genomic selection (GS) in combination with high throughput phenotyping (HTP). A total of 193 families from two closely related elite populations were sown in the greenhouse and transplanted into mini sward plots at two locations near Davis, CA in May 2020. The trial was managed as a high-input system under full irrigation. Families were genotyped and phenotyped for biomass yield by mechanical harvest and a combination of drone and tower-based remote sensors across 12 harvests, 3 in the establishment year (2020), 7 in the first full year of production (2021) and 2 in 2022. Alfalfa yields ranged from 13-27 tonnes DM/hectare/year with a number of half-sib families outperforming popular cultivars in the first 2 years of production. Biomass volume predicted from the drone-based cameras had a moderate prediction accuracy with an overall R2 of 0.55. Some individual harvests reached accuracies as high as 0.85. Genotyping resulted in a dataset with 6,838 SNPs. Allele frequencies were used to generate a relationship matrix for GS. Narrow-sense heritability for dry matter yield was 0.31 and the predictive ability of the GS model was 0.15

Direct Evidence of the Role of Hybridization in the X-Ray Magnetic Circular Dichroism of a-Ce

We present an x-ray magnetic circular dichroism (XMCD) study of a [Ce(10 Å)/Fe(30 Å)] multilayer performed at the Ce-M4,5 absorption edges. In this system the Ce-4f electrons are strongly hybridized with the valence band. XMCD experiments show that they carry an ordered magnetic moment. The differences of the shape of the XMCD signals of a typical g-like compound (CeCuSi) and of the Ce/ Fe multilayer highlight the role of hybridization in determining the ground state of cerium atoms in the multilayer, which results in a mixing of J = 5/2 and J = 7/2 coupled states

Working Together May Be Better: Activation of Reward Centers during a Cooperative Maze Task

Humans use theory of mind when predicting the thoughts and feelings and actions of others. There is accumulating evidence that cooperation with a computerized game correlates with a unique pattern of brain activation. To investigate the neural correlates of cooperation in real-time we conducted an fMRI hyperscanning study. We hypothesized that real-time cooperation to complete a maze task, using a blind-driving paradigm, would activate substrates implicated in theory of mind. We also hypothesized that cooperation would activate neural reward centers more than when participants completed the maze themselves. Of interest and in support of our hypothesis we found left caudate and putamen activation when participants worked together to complete the maze. This suggests that cooperation during task completion is inherently rewarding. This finding represents one of the first discoveries of a proximate neural mechanism for group based interactions in real-time, which indirectly supports the social brain hypothesis

Restoration of the external Scandinavian Caledonides

Three models are evaluated for restoring basement rocks coring tectonic windows (Window-Basement) in the Scandinavian Caledonides; parautochthonous (Model I) and allochthonous (models II/III), with initial imbrication of the Window-Basement post-dating or pre-dating, respectively, that in the external imbricate zone (Lower Allochthon). In Model I, the Window-Basement comes from the eastern margin of the basin now imbricated into the Lower Allochthon, while in models II/III it comes from the western margin. In Model II, the Window-Basement formed a basement-high between Tonian and Cryogenian sediments imbricated into the Middle and Lower allochthons; in Model III deposition of the Lower Allochthon sediments commenced in Ediacaran times. Balanced cross-sections and branch-line restorations of four transects (Finnmark–Troms, Västerbotten–Nordland, Jämtland–Trøndelag, Telemark–Møre og Romsdal) show similar restored lengths for the models in two transects and longer restorations for models II/III in the other transects. Model I can result in c. 280 km wide gaps in the restored Lower Allochthon, evidence for which is not seen in the sedimentology. The presence of <3 km thick alluvial-fan deposits at the base of the Middle Allochthon indicates proximal, rapidly uplifting basement during Tonian–Cryogenian periods, taken as the origin of the Window-Basement during thrusting in models II/III. Model I requires multiple changes in thrusting-direction and predicts major thrusts or back-thrusts, currently unrecognized, separating parts of the Lower Allochthon; neither are required in models II/III. Metamorphic data are consistent with models II/III. Despite considerable along-strike structural variability in the external Scandinavian Caledonides, models II/III are preferred for the restoration of the Window-Basement