425 research outputs found
Local formation of nitrogen-vacancy centers in diamond by swift heavy ions
We exposed nitrogen-implanted diamonds to beams of swift uranium and gold
ions (~1 GeV) and find that these irradiations lead directly to the formation
of nitrogen vacancy (NV) centers, without thermal annealing. We compare the
photoluminescence intensities of swift heavy ion activated NV- centers to those
formed by irradiation with low-energy electrons and by thermal annealing. NV-
yields from irradiations with swift heavy ions are 0.1 of yields from low
energy electrons and 0.02 of yields from thermal annealing. We discuss possible
mechanisms of NV-center formation by swift heavy ions such as electronic
excitations and thermal spikes. While forming NV centers with low efficiency,
swift heavy ions enable the formation of three dimensional NV- assemblies over
relatively large distances of tens of micrometers. Further, our results show
that NV-center formation is a local probe of (partial) lattice damage
relaxation induced by electronic excitations from swift heavy ions in diamond.Comment: to be published in Journal of Applied Physic
Atomic Force Microscopy Study of an Ideally Hard Contact: The Diamond(111)/Tungsten Carbide Interface
A comprehensive nanotribological study of a hydrogen-terminated diamond(111)/tungsten carbide interface has been performed using ultrahigh vacuum atomic force microscopy. Both contact conductance, which is proportional to contact area, and friction have been measured as a function of applied load. We demonstrate for the first time that the load dependence of the contact area in UHV for this extremely hard single asperity contact is described by the Derjaguin-Müller-Toporov continuum mechanics model. Furthermore, the frictional force is found to be directly proportional to the contact area
Gray space \u3ci\u3eand\u3c/i\u3e green space proximity associated with higher anxiety in youth with autism
This study used ZIP code level data on children\u27s health (National Survey of Children\u27s Health, 2012) and land cover (National Land Cover Database, 2011) from across the United States to investigate connections between proximity to green space (tree canopy), gray space (impervious surfaces), and expression of a critical co-morbid condition, anxiety, in three groups of youth: children diagnosed with autism spectrum disorder (ASD, n=1501), non-ASD children with special healthcare needs (CSHCN, n=15,776), and typically developing children (n=53,650). Both impervious surface coverage and tree canopy coverage increased the risk of severe anxiety in youth with autism, but not CSHCN or typical children. Children with ASD might experience the stress-reducing benefits of nature differently than their typically developing peers. More research using objective diagnostic metrics at finer spatial scales would help to illuminate complex relationships between green space, anxiety, and other co-morbid conditions in youth with ASD
Longitudinal associations between neighborhood child opportunity and physical fitness for New York City public school youth
Communication Services and Supports for Individuals With Severe Disabilities: Guidance for Assessment and Intervention
The National Joint Committee for the Communication Needs of People with Severe Disabilities (NJC) reviewed literature regarding practices for people with severe disabilities in order to update guidance provided in documents originally published in 1992. Changes in laws, definitions, and policies that affect communication attainments by persons with severe disabilities are presented, along with guidance regarding assessment and intervention practices. A revised version of the Communication Bill of Rights, a powerful document that describes the communication rights of all individuals, including those with severe disabilities is included in this article. The information contained within this article is intended to be used by professionals, family members, and individuals with severe disabilities to inform and advocate for effective communication services and opportunities
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Reactivity of Ozone with Solid Potassium Iodide Investigated by Atomic Force Microscopy
The reaction of ozone with the (100) plane of solid potassium iodide (KI) was investigated using atomic force microscopy (AFM). The reaction forming potassium iodate (KIO{sub 3}) initiates at step edges prior to reacting on the flat terraces. Small domains of KIO{sub 3}, initially 3.8 {angstrom} in height are formed on the top of step edges. Following reaction at the step edge, domains of KIO{sub 3} are formed across the terraces. With prolonged exposure to ozone, KIO{sub 3} domains nucleate further growth until the surface is evenly covered with KIO{sub 3} particles that are 4-6 nm in height, at which point the surface is passivated and the reaction terminates
Fabrication of Nanostructured GaAs/AlGaAs Waveguide for Low-Density Polariton Condensation from a Bound State in the Continuum
Exciton-polaritons are hybrid light-matter states that arise from strong
coupling between an exciton resonance and a photonic cavity mode. As bosonic
excitations, they can undergo a phase transition to a condensed state that can
emit coherent light without a population inversion. This aspect makes them good
candidates for thresholdless lasers, yet short exciton-polariton lifetime has
made it difficult to achieve condensation at very low power densities. In this
sense, long-lived symmetry-protected states are excellent candidates to
overcome the limitations that arise from the finite mirror reflectivity of
monolithic microcavities. In this work we use a photonic symmetry protected
bound state in the continuum coupled to an excitonic resonance to achieve
state-of-the-art polariton condensation threshold in GaAs/AlGaAs waveguide.
Most important, we show the influence of fabrication control and how surface
passivation via atomic layer deposition provides a way to reduce exciton
quenching at the grating sidewalls
Strain engineering and one-dimensional organization of metal-insulator domains in single-crystal VO2 beams
Spatial phase inhomogeneity at the nano- to microscale is widely observed in
strongly-correlated electron materials. The underlying mechanism and
possibility of artificially controlling the phase inhomogeneity are still open
questions of critical importance for both the phase transition physics and
device applications. Lattice strain has been shown to cause the coexistence of
metallic and insulating phases in the Mott insulator VO2. By continuously
tuning strain over a wide range in single-crystal VO2 micro- and nanobeams,
here we demonstrate the nucleation and manipulation of one-dimensionally
ordered metal-insulator domain arrays along the beams. Mott transition is
achieved in these beams at room temperature by active control of strain. The
ability to engineer phase inhomogeneity with strain lends insight into
correlated electron materials in general, and opens opportunities for designing
and controlling the phase inhomogeneity of correlated electron materials for
micro- and nanoscale device applications.Comment: 14 pages, 4 figures, with supplementary informatio
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