Community Driven Technology Innovation and Investment: Early Reflections on Efforts to Cultivate a Culture of Engaged Engineering Scholarship at Oregon State University

The engineering curriculum does not often consider social aspects of engineering design and practice. This is problematic because the Organisation for Economic Co-operation and Development (OECD), lists science- and technology-based innovation as central to sustained economic development. Although land-grant Extension services translate benefits of research in agriculture, biology, and related sciences to communities, there is little emphasis on translating outcomes from engineering and technology research and innovation to communities. There is also little recognition of research of this nature in traditional promotion and tenure cases, or among traditional grant-making agencies. The Community Driven Technology Innovation and Investment (CDTII) program introduced in this paper could provide a first step to address this disconnect by developing an engagement process to help engineers forge trust-based partnerships while converting community demands into engineering design solutions and economically viable businesses. To this end, the paper contains two preliminary case studies of engineering engagement on community projects using the CDTII approach. We conclude with lessons learned and plans for future work

Interactions Between Baclofen and DC-induced Plasticity of Afferent Fibers within the Spinal Cord

The aims of the study were to compare effects of baclofen, a GABA B receptor agonist commonly used as an antispastic drug, on direct current (DC) evoked long-lasting changes in the excitability of afferent fibers traversing the dorsal columns and their terminal branches in the spinal cord, and to examine whether baclofen interferes with the development and expression of these changes. The experiments were performed on deeply anesthetized rats by analyzing the effects of DC before, during and following baclofen administration. Muscle and skin afferent fibers within the dorsal columns were stimulated epidurally and changes in their excitability were investigated following epidural polarization by 1.0\u20131.1 \u3bcA subsequent to i.v. administration of baclofen. Epidural polarization increased the excitability of these fibers during post-polarization periods of at least 1 h. The facilitation was as potent as in preparations that were not pretreated with baclofen, indicating that the advantages of combining epidural polarization with epidural stimulation would not be endangered by pharmacological antispastic treatment with baclofen. In contrast, baclofen-reduced effects of intraspinal stimulation combined with intraspinal polarization (0.3 \u3bcA) of terminal axonal branches of the afferents within the dorsal horn or in motor nuclei, whether administered ionophoretically or intravenously. Effects of DC on monosynaptically evoked synaptic actions of these fibers (extracellular field potentials) were likewise reduced by baclofen. The study thus provides further evidence for differential effects of DC on afferent fibers in the dorsal columns and the preterminal branches of these fibers and their involvement in spinal plasticity

High-Quality Si-Doped β-Ga2O3 Films on Sapphire Fabricated by Pulsed Laser Deposition

The EU Horizon 2020 project CAMART2 is acknowledged for partly supporting the project, and the Ion Technology Centre, ITC, in Sweden is acknowledged for ion beam analysis (ERDA).Pulsed laser ablation is used to form high-quality silicon-doped β-Ga2O3 films on sapphire by alternatively depositing Ga2O3 and Si from two separate sources. X-ray analysis reveals a single crystallinity with a full width at half maximum for the rocking curve around the (−201) reflection peak of 1.6°. Silicon doping concentration is determined by elastic recoil detection analysis (ERDA), and the best electrical performance is reached at a Si concentration of about 1 × 1020 cm−3, using optimized deposition parameters. It is found that a high crystalline quality and a mobility of about 2.9 cm2 (V s)−1 can be achieved by depositing Si and Ga2O3 from two separate sources. Two types of Schottky contacts are fabricated: one with a pure Pt and one with a PtOx composition. Electrical results from these structures are also presented.Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

High-Quality Si-Doped β-Ga2O3 Films on Sapphire Fabricated by Pulsed Laser Deposition

The EU Horizon 2020 project CAMART2 is acknowledged for partly supporting the project, and the Ion Technology Centre, ITC, in Sweden is acknowledged for ion beam analysis (ERDA).Pulsed laser ablation is used to form high-quality silicon-doped β-Ga2O3 films on sapphire by alternatively depositing Ga2O3 and Si from two separate sources. X-ray analysis reveals a single crystallinity with a full width at half maximum for the rocking curve around the (−201) reflection peak of 1.6°. Silicon doping concentration is determined by elastic recoil detection analysis (ERDA), and the best electrical performance is reached at a Si concentration of about 1 × 1020 cm−3, using optimized deposition parameters. It is found that a high crystalline quality and a mobility of about 2.9 cm2 (V s)−1 can be achieved by depositing Si and Ga2O3 from two separate sources. Two types of Schottky contacts are fabricated: one with a pure Pt and one with a PtOx composition. Electrical results from these structures are also presented.Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Diffuse transport and spin accumulation in a Rashba two-dimensional electron gas

The Rashba Hamiltonian describes the splitting of the conduction band as a result of spin-orbit coupling in the presence of an asymmetric confinement potential and is commonly used to model the electronic structure of confined narrow-gap semiconductors. Due to the mixing of spin states some care has to be exercised in the calculation of transport properties. We derive the diffusive conductance tensor for a disordered two-dimensional electron gas with spin-orbit interaction and show that the applied bias induces a spin accumulation, but that the electric current is not spin-polarized.Comment: REVTeX4 format, 5 page

Critical properties of S=1/2 Heisenberg ladders in magnetic fields

The critical properties of the $S=1/2$ Heisenberg two-leg ladders are investigated in a magnetic field. Combining the exact diagonalization method and the finite-size-scaling analysis based on conformal field theory, we calculate the critical exponents of spin correlation functions numerically. For a strong interchain coupling, magnetization dependence of the critical exponents shows characteristic behavior depending on the sign of the interchain coupling. We also calculate the critical exponents for the $S=1/2$ Heisenberg two-leg ladder with a diagonal interaction, which is thought as a model Hamiltonian of the organic spin ladder compound ${Cu}_2({1,4-diazacycloheptane})_2{Cl}_4$. Numerical results are compared with experimental results of temperature dependence of the NMR relaxation rate $1/T_1$.Comment: REVTeX, 10 pages, 8 figures, accepted for Phys. Rev.

Ballistic spin-polarized transport and Rashba spin precession in semiconductor nanowires

We present numerical calculations of the ballistic spin-transport properties of quasi-one-dimensional wires in the presence of the spin-orbit (Rashba) interaction. A tight-binding analog of the Rashba Hamiltonian which models the Rashba effect is used. By varying the robustness of the Rashba coupling and the width of the wire, weak and strong coupling regimes are identified. Perfect electron spin-modulation is found for the former regime, regardless of the incident Fermi energy and mode number. In the latter however, the spin-conductance has a strong energy dependence due to a nontrivial subband intermixing induced by the strong Rashba coupling. This would imply a strong suppression of the spin-modulation at higher temperatures and source-drain voltages. The results may be of relevance for the implementation of quasi-one-dimensional spin transistor devices.Comment: 19 pages (incl. 9 figures). To be published in PR

Spin-polarized transport in inhomogeneous magnetic semiconductors: theory of magnetic/nonmagnetic p-n junctions

A theory of spin-polarized transport in inhomogeneous magnetic semiconductors is developed and applied to magnetic/nonmagnetic p-n junctions. Several phenomena with possible spintronic applications are predicted, including spinvoltaic effect, spin valve effect, and giant magnetoresistance. It is demonstrated that only nonequilibrium spin can be injected across the space-charge region of a p-n junction, so that there is no spin injection (or extraction) at low bias.Comment: Minor Revisions. To appear in Phys. Rev. Let

On the Field-Induced Gap in Cu Benzoate and Other S=1/2 Antiferromagnets

Recent experiments on the S=1/2 antiferromagnetic chain compound, Cu benzoate, discovered an unexpected gap scaling as approximately the 2/3 power of an applied magnetic field. A theory of this gap, based on an effective staggered field, orthogonal to the applied uniform field, resulting from a staggered gyromagnetic tensor and a Dzyaloshinskii-Moriya interaction, leading to a sine-Gordon quantum field theory, has been developed. Here we discuss many aspects of this subject in considerable detail, including a review of the S=1/2 chain in a uniform field, a spin-wave theory analysis of the uniform plus staggered field problem, exact amplitudes for the scaling of gap, staggered susceptibility and staggered magnetization with field or temperature, intensities of soliton and breather peaks in the structure function and field and temperature dependence of the total susceptibility.Comment: 34 pages, 13 postscript figures, Rev Tex. Phys. Rev. B, to appea

Developmental, cellular, and biochemical basis of transparency in the glasswing butterfly Greta oto

Numerous species of Lepidoptera have transparent wings, which often possess scales of altered morphology and reduced size, and the presence of membrane surface nanostructures that dramatically reduce reflection. Optical properties and anti-reflective nanostructures have been characterized for several ‘clearwing’ Lepidoptera, but the developmental basis of wing transparency is unknown. We apply confocal and electron microscopy to create a developmental time-series in the glasswing butterfly, Greta oto, comparing transparent and non-transparent wing regions. We find that scale precursor cell density is reduced in transparent regions, and cytoskeletal organization differs between flat scales in opaque regions, and thin, bristle-like scales in transparent regions. We also reveal that sub-wavelength nanopillars on the wing membrane are wax-based, derive from wing epithelial cells and their associated microvillar projections, and demonstrate their role in enhancing-anti-reflective properties. These findings provide insight into morphogenesis of naturally organized micro- and nanostructures and may provide bioinspiration for new anti-reflective materials