264 research outputs found
Spiral Growth and Step Edge Barriers
The growth of spiral mounds containing a screw dislocation is compared to the
growth of wedding cakes by two-dimensional nucleation. Using phase field
simulations and homoepitaxial growth experiments on the Pt(111) surface we show
that both structures attain the same characteristic large scale shape when a
significant step edge barrier suppresses interlayer transport. The higher
vertical growth rate observed for the spiral mounds on Pt(111) reflects the
different incorporation mechanisms for atoms in the top region and can be
formally represented by an enhanced apparent step edge barrier.Comment: 11 pages, 4 figures, partly in colo
Strain and structure driven complex magnetic ordering of a CoO overlayer on Ir(100)
We have investigated the magnetic ordering in the ultrathin c(102)
CoO(111) film supported on Ir(100) on the basis of ab-initio calculations. We
find a close relationship between the local structural properties of the oxide
film and the induced magnetic order, leading to alternating ferromagnetically
and anti-ferromagnetically ordered segments. While the local magnetic order is
directly related to the geometric position of the Co atoms, the mismatch
between the CoO film and the Ir substrate leads to a complex long-range order
of the oxide.Comment: 5 pages, 4 figure
Ethical Allocation of Remdesivir
As the federal government distributed remdesivir to some of the states COVID-19 hit hardest, policymakers scrambled to develop criteria to allocate the drug to their hospitals. Our state, Michigan, was among those states to receive an initial quantity of the drug from the U.S. government. The disparities in burden of disease in Michigan are striking. Detroit has a death rate more than three times the state average. Our recommendation to the state was that it should prioritize the communities that bear a disproportionate burden of suffering in the allocation of the new potential treatment. This recommendation is justified not only for new drugs with uncertain effects, but also for drugs of certain benefit or vaccines. For states with significant health disparities, such as Michigan, this allocation priority may help to repair them. In fact, any other allocation strategy may make them wors
Chemical ordering and composition fluctuations at the (001) surface of the Fe-Ni Invar alloy
We report on a study of (001) oriented fcc Fe-Ni alloy surfaces which
combines first-principles calculations and low-temperature STM experiments.
Density functional theory calculations show that Fe-Ni alloy surfaces are
buckled with the Fe atoms slightly shifted outwards and the Ni atoms inwards.
This is consistent with the observation that the atoms in the surface layer can
be chemically distinguished in the STM image: brighter spots (corrugation
maxima with increased apparent height) indicate iron atoms, darker ones nickel
atoms. This chemical contrast reveals a c2x2 chemical order (50% Fe) with
frequent Fe-rich defects on Invar alloy surface. The calculations also indicate
that subsurface composition fluctuations may additionally modulate the apparent
height of the surface atoms. The STM images show that this effect is pronounced
compared to the surfaces of other disordered alloys, which suggests that some
chemical order and corresponding concentration fluctuations exist also in the
subsurface layers of Invar alloy. In addition, detailed electronic structure
calculations allow us to identify the nature of a distinct peak below the Fermi
level observed in the tunneling spectra. This peak corresponds to a surface
resonance band which is particularly pronounced in iron-rich surface regions
and provides a second type of chemical contrast with less spatial resolution
but one that is essentially independent of the subsurface composition.Comment: 7 pages, 5 figure
Evaluation of an Occupational Health and Safety Management System Performance Measurement Tool-III: Measurement of Initiation Elements
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91920/1/Redinger4.pd
An Artificially Lattice Mismatched Graphene/Metal Interface: Graphene/Ni/Ir(111)
We report the structural and electronic properties of an artificial
graphene/Ni(111) system obtained by the intercalation of a monoatomic layer of
Ni in graphene/Ir(111). Upon intercalation, Ni grows epitaxially on Ir(111),
resulting in a lattice mismatched graphene/Ni system. By performing Scanning
Tunneling Microscopy (STM) measurements and Density Functional Theory (DFT)
calculations, we show that the intercalated Ni layer leads to a pronounced
buckling of the graphene film. At the same time an enhanced interaction is
measured by Angle-Resolved Photo-Emission Spectroscopy (ARPES), showing a clear
transition from a nearly-undisturbed to a strongly-hybridized graphene
-band. A comparison of the intercalation-like graphene system with flat
graphene on bulk Ni(111), and mildly corrugated graphene on Ir(111), allows to
disentangle the two key properties which lead to the observed increased
interaction, namely lattice matching and electronic interaction. Although the
latter determines the strength of the hybridization, we find an important
influence of the local carbon configuration resulting from the lattice
mismatch.Comment: 9 pages, 3 figures, Accepted for publication in Phys. Rev.
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