9,445 research outputs found
Optimal Drug Policy in Low-Income Neighborhoods
Part of the debate over the control of drug activity in cities is concerned with the effectiveness of implementing demand- versus supply-side drug policies. This paper is motivated by the relative lack of research providing formal economic underpinning for the implementation of either policy. We construct a simple model of drug activity, in which the drug price and the distribution of population in a community are determined according to a career choice rule and a predetermined drug demand. Three potential government objectives are considered. We find that both demand- and supply-side policies have theoretical support under different community conditions. While the demand-side policy discourages active drug sellers, the supply-side policy has an additional drug-dealing replacement effect on inducing potential entry of drug dealers. In low-income neighborhoods, demand-side policy is more effective if the drug problem is more sever or if the government objective is to deter dealer entry or to promote community's aggregate income rather than minimizing active drug selling.
Strong Electron-Phonon Interaction and Colossal Magnetoresistance in EuTiO
At low temperatures, EuTiO system has very large resistivities and
exhibits colossal magnetoresistance. Based on a first principle calculation and
the dynamical mean-field theory for small polaron we have calculated the
transport properties of EuTiO. It is found that due to electron-phonon
interaction the conduction band may form a tiny subband which is close to the
Fermi level. The tiny subband is responsible for the large resistivity.
Besides, EuTiO is a weak antiferromagnetic material and its magnetization
would slightly shift the subband via exchange interaction between conduction
electrons and magnetic atoms. Since the subband is close to the Fermi level, a
slight shift of its position gives colossal magnetoresistance.Comment: 6 pages, 5 figure
Reversal of Thermal Rectification in Quantum Systems
We study thermal transport in anisotropic Heisenberg spin chains using the
quantum master equation. It is found that thermal rectification changes sign
when the external homogeneous magnetic field is varied. This reversal also
occurs when the magnetic field becomes inhomogeneous. Moreover, we can tune the
reversal of rectification by temperatures of the heat baths, the anisotropy and
size of the spin chains.Comment: 4 pages, 7 figure
The Application of Genomic Approaches in Studying a Bacterial Blight-Resistant Mutant in Rice
Rice bacterial blight disease (BBD), caused by Xanthomonas oryzae pv. oryzae (Xoo), is one of the serious diseases in most rice production regions. In this report, we screened for resistance mutants from the mutation pool of TNG67 variety derived by sodium azide (SA) mutagenesis with phenotype investigation and assisted with fluorescent detection. SA0423 is a mutant of broad range resistance against Xoo for many years; the resistance was studied following the concept of central dogma. The inheritance of resistance was characterized, and three QTLs were mapped onto the genome of SA0423 using simple sequence repeat (SSR) markers and R/qtl by genomic approach. In transcriptomic approach, only one differential expression QTLs (eQTLs) were identified; two differentially expressed proteins (pQTLs) were identified and genetically characterized by proteomics after Xoo challenged in SA0423 mutant. To improve the bacterial blight resistance, makers are developed from QTLs, eQTLs and pQTLs to pyramid the resistance genes through marker-assisted breeding in our rice breeding programs
Fractional Quantum Hall Effect in Topological Flat Bands with Chern Number Two
Recent theoretical works have demonstrated various robust Abelian and
non-Abelian fractional topological phases in lattice models with topological
flat bands carrying Chern number C=1. Here we study hard-core bosons and
interacting fermions in a three-band triangular-lattice model with the lowest
topological flat band of Chern number C=2. We find convincing numerical
evidence of bosonic fractional quantum Hall effect at the filling
characterized by three-fold quasi-degeneracy of ground states on a torus, a
fractional Chern number for each ground state, a robust spectrum gap, and a gap
in quasihole excitation spectrum. We also observe numerical evidence of a
robust fermionic fractional quantum Hall effect for spinless fermions at the
filling with short-range interactions.Comment: 5 pages, 7 figures, with Supplementary Materia
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