50,237 research outputs found

    Governance Challenges and the Financial Crisis: Seven Key Questions

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    In the midst of a global economic crisis, the federal government responded on an unprecedented scale and scope, with injections of trillions of dollars into financial markets, infusions of cash to troubled industries, state and local governments, and people in need. Government is employing tools in ways never before considered and inventing new tools, in the hope of stabilizing the economy and spurring economic recovery.Under the leadership of National Academy Fellow Don Kettl and National Academy President Jennifer Dorn, the National Academy of Public Administration convened a roundtable of government leaders, business leaders, researchers and other experts to discuss governance issues related to the government's response to the financial crisis. Seven strategic questions related to governance emerged from the discussion, held earlier this year, which was moderated by Don Kettl. The National Academy and the IBM Center for the Business of Government are pleased to offer this summary of the roundtable in an effort to stimulate a national discussion of these questions.Key Findings Government investments have the potential to transform the role the federal government plays in the private economy. While largely intended to be temporary, many fear that these investments will create long-term, almost "permanent" expectations -- particularly with regard to education, unemployment insurance, infrastructure and tax breaks.One challenge confronting the government is to devise exit strategies that balance policy objectives, such as minimizing economic disruption and securing a return on taxpayer dollars, while not undermining the viability of companies or their market competitors, as well as governments and other groups. Another challenge is to determine the appropriate scope of ongoing federal regulatory authority in light of both practical demands and the appropriate role of the federal government in managing the economy

    Interacting Dirac fermions under spatially alternating pseudo-magnetic field: Realization of spontaneous quantum Hall effect

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    Both topological crystalline insulators surfaces and graphene host multi-valley massless Dirac fermions which are not pinned to a high-symmetry point of the Brillouin zone. Strain couples to the low-energy electrons as a time-reversal invariant gauge field, leading to the formation of pseudo-Landau levels (PLL). Here we study periodic pseudo-magnetic fields originating from strain superlattices. We study the low-energy Dirac PLL spectrum induced by the strain superlattice and analyze the effect of various polarized states. Through self-consistent Hartree-Fock calculations we establish that, due to the strain superlattice and PLL electronic structure, a valley-ordered state spontaneously breaking time-reversal and realizing a quantum Hall phase is favored, while others are suppressed.Comment: 13 pages + 2 appendices, 9 figure

    Zeeman-Induced Gapless Superconductivity with Partial Fermi Surface

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    We show that an in-plane magnetic field can drive two-dimensional spin-orbit-coupled systems under superconducting proximity effect into a gapless phase where parts of the normal state Fermi surface are gapped, and the ungapped parts are reconstructed into a small Fermi surface of Bogoliubov quasiparticles at zero energy. Charge distribution, spin texture, and density of states of such "partial Fermi surface" are discussed. Material platforms for its physical realization are proposed.Comment: 5 pages, 2 figure

    Effect of chain stiffness on ion distributions around a polyelectrolyte in multivalent salt solutions

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    Ion distributions in dilute polyelectrolyte solutions are studied by means of Langevin dynamics simulations. We show that the distributions depend on the conformation of a chain while the conformation is determined by the chain stiffness and the salt concentration. We observe that the monovalent counterions originally condensed on a chain can be replaced by the multivalent ones dissociated from the added salt due to strong electrostatic interaction. These newly condensed ions give an important impact on the chain structure. At low and at high salt concentrations, the conformation of a semiflexible chain is rodlike. The ion distributions show similarity to those for a rigid chain, but difference to those for a flexible chain whose conformation is a coil. In the mid-salt region, the flexible chain and the semiflexible chain collapse but the collapsed chain structures are, respectively, disordered and ordered structures. The ion distributions hence show different profiles for these three chain stiffness with the curves for the semiflexible chain lying between those for the flexible and the rigid chains. The number of the condensed multivalent counterions, as well as the effective chain charge, also shows similar behavior, demonstrating a direct connection with the chain morphology. Moreover, we find that the condensed multivalent counterions form triplets with two adjacent monomers and are localized on the chain axis at intermediate salt concentration when the chain stiffness is semiflexible or rigid. The microscopic information obtained here provides valuable insight to the phenomena of DNA condensation and is very useful for researchers to develop new models.Comment: 28 pages, 10 figures, accepted for publication in JC

    Comparative study of Steel-FRP, FRP and steel reinforced coral concrete beams in their flexural performance

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    In this paper, a comparative study of Carbon Fiber Reinforced Polymer (CFRP) Bar and Steel-Carbon Fiber Composite Bar (SCFCB) reinforced coral concrete beams are made through a series experimental tests and theoretical analysis. The flexural capacity, crack development and failure modes of CFRP and SCFCB reinforced coral concrete were investigated in detail. They are also compared to ordinary steel reinforced coral concrete beams. The results show that under the same condition of reinforcement ratio, the SCFCB reinforced beam exhibits better performance than those of the CFRP reinforced beams, and its stiffness is slightly lower than that of the steel reinforced beam. Under the same load condition, the crack width of the SCFCB beam is between the steel reinforced beam and the CFRP bar reinforced beam. Before the steel core yields, the crack growth rate of SCFCB beam is similar to the steel reinforced beam. SCFCB has a higher strength utilization rate, about 70% -85% of its ultimate strength. The current design guidance was also examined based on the test results. It was found that the existing design specifications for FRP reinforced normal concrete is not suitable for SCFCB reinforced coral concrete structures