311 research outputs found

    Quantum Coherence of Image-Potential States

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    The quantum dynamics of the two-dimensional image-potential states in front of the Cu(100) surface is measured by scanning tunneling microscopy (STM) and spectroscopy (STS). The dispersion relation and the momentum resolved phase-relaxation time of the first image-potential state are determined from the quantum interference patterns in the local density of states (LDOS) at step edges. It is demonstrated that the tip-induced Stark shift does not affect the motion of the electrons parallel to the surface.Comment: Submitted to Phys. Rev. Lett., 4 pages, 4 figures; corrected typos, minor change

    The Role of Authentic Leadership and Cultural Intelligence in Cross-Cultural Contexts: An Objectivist Perspective

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    Cultural adaptation in cross-cultural situations is an integral part of international management and leadership literature. However, there has been little theory or empirical research that takes into account the objectivist perspective of the necessity of leaders remaining true to their moral standards when operating in different host-cultures. We draw upon the authentic leadership and cultural intelligence literatures to explicate a model by which authentic leaders in a cross-cultural context can find a balance in the tension between their own deeply held values and those of the host-country’s culture

    Developing the Psychological Capital of Resiliency

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    In these turbulent times, we propose the importance of developing the psychological capital dimension of resiliency. After providing the theoretical background and meaning of psychological capital in general and resiliency in particular, the authors present proactive and reactive human resource development (HRD) strategies for its development. The proactive HRD includes increasing psychological assets, decreasing risk factors, and facilitating processes that allow human resources to enhance their resilience. The reactive HRD largely draws from a broaden-and-build model of positive emotions and self-enhancement, external attribution, and hardiness. The article includes specific guidelines for HRD applications and an agenda for future needed research

    Giant Spin-splitting in the Bi/Ag(111) Surface Alloy

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    Surface alloying is shown to produce electronic states with a very large spin-splitting. We discuss the long range ordered bismuth/silver(111) surface alloy where an energy bands separation of up to one eV is achieved. Such strong spin-splitting enables angular resolved photoemission spectroscopy to directly observe the region close to the band edge, where the density of states shows quasi-one dimensional behavior. The associated singularity in the local density of states has been measured by low temperature scanning tunneling spectroscopy. The implications of this new class of materials for potential spintronics applications as well as fundamental issues are discussed.Comment: 4 pages, 4 figure

    Studying the Transistor Using Wireless Epistemologies

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    The refinement of 802.11b is an essential prob- lem. Given the current status of autonomous theory, experts dubiously desire the simulation of the producer-consumer problem. We propose an approach for the visualization of sensor networks, which we call BREWIS

    Mentoring Impact on Leader Efficacy Development: A Field Experiment

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    While practitioners and scholars tout the importance of mentorship in leader development, few studies have empirically determined whether mentoring actually positively impacts a leader’s development, and if so, in what ways. In a longitudinal field experiment, we examined how a targeted mentorship program that unfolded over 6 months enhanced the development of protĂ©gĂ©s’ leader efficacy and performance. Results showed that the targeted mentorship intervention increased protĂ©gĂ©s’ level of leader efficacy more than a comparison intervention that was based on a more eclectic leadership education program delivered in a group setting. Leader efficacy then predicted rated leader performance. Both protĂ©gĂ©s’ preferences for feedback and trust in the mentor served as important moderators in contributing to the development of leader efficacy. Findings from this longitudinal field experiment could be used by educational institutions and other organizations to enhance their mentorship programs in content, focus, and evaluation of impact

    Potential for Geologic Sequestration of CO2 in Iowa

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    Photoluminescence of short-period GaAs/AlAs superlattices: A hydrostatic pressure and temperature study

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    URL:http://link.aps.org/doi/10.1103/PhysRevB.58.7222 DOI:10.1103/PhysRevB.58.7222The temperature and pressure dependence of type-I and -II transitions from photoluminescence (PL) spectra in a series of (GaAs)m/(AlAs)m superlattices show that the temperature dependence of energy bands can be described very well with a Bose-Einstein-type equation. From these measurements the parameters that describe the temperature dependence of excitonic transition energies and the corresponding broadening of the PL line are deduced. The pressure dependence of the PL linewidths of the type-I exciton as a function of pressure and temperature yield the intervalley deformation potential. Beyond the type-I-type-II crossover, the PL linewidth increases as a function of both pressure and temperature. The electron-phonon deformation potential for Γ-X scattering is found to be temperature dependent.We thank S. Satpathy and S. Zollner for valuable discussions. One of us ~H.R.C.! acknowledges support by the NSF under Grant No. DMR-9633107. M.C. thanks the U.S. Army for support through Grant No. DAAL03-92-0381. The work at Purdue University was supported by the National Science Foundation: Materials Research Science and Engineering Center Grant Nos. DMR 94-00415 and DMR 93-03186

    Disorder-induced phonon self-energy of semiconductors with binary isotopic composition

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    Self-energy effects of Raman phonons in isotopically disordered semiconductors are deduced by perturbation theory and compared to experimental data. In contrast to the acoustic frequency region, higher-order terms contribute significantly to the self-energy at optical phonon frequencies. The asymmetric dependence of the self-energy of a binary isotope system m1−xMxm_{1-x} M_x on the concentration of the heavier isotope mass x can be explained by taking into account second- and third-order perturbation terms. For elemental semiconductors, the maximum of the self-energy occurs at concentrations with 0.5<x<0.70.5<x<0.7, depending on the strength of the third-order term. Reasonable approximations are imposed that allow us to derive explicit expressions for the ratio of successive perturbation terms of the real and the imaginary part of the self-energy. This basic theoretical approach is compatible with Raman spectroscopic results on diamond and silicon, with calculations based on the coherent potential approximation, and with theoretical results obtained using {\it ab initio} electronic theory. The extension of the formalism to binary compounds, by taking into account the eigenvectors at the individual sublattices, is straightforward. In this manner, we interpret recent experimental results on the disorder-induced broadening of the TO (folded) modes of SiC with a 13C^{13}{\rm C}-enriched carbon sublattice. \cite{Rohmfeld00,Rohmfeld01}Comment: 29 pages, 9 figures, 2 tables, submitted to PR