Time-Reversal Symmetry-Breaking Nematic Insulators near Quantum Spin Hall Phase Transitions

We study the phase diagram of a model quantum spin Hall system as a function of band inversion and band-coupling strength, demonstrating that when band hybridization is weak, an interaction-induced nematic insulator state emerges over a wide range of band inversion. This property is a consequence of the long-range Coulomb interaction, which favors interband phase coherence that is weakly dependent on momentum and therefore frustrated by the single-particle Hamiltonian at the band inversion point. For weak band hybridization, interactions convert the continuous gap closing topological phase transition at inversion into a pair of continuous phase transitions bounding a state with broken time-reversal and rotational symmetries. At intermediate band hybridization, the topological phase transition proceeds instead via a quantum anomalous Hall insulator state, whereas at strong hybridization interactions play no role. We comment on the implications of our findings for InAs/GaSb and HgTe/CdTe quantum spin Hall systems.Comment: 5 pages, 3 figures plus 4 pages supplemental material, accepted for publication in Physical Review Letter

Isonicotinic acid

This is the publisher's version, also available electronically from http://scripts.iucr.org/cgi-bin/paper?S0567740876006754.See article for abstract

Does Migration Encourage Human Capital Formation in Labor-Sending Country?

This study investigates the effects of migration possibilities on the demand for education and human capital formation in the labour-sending country. The paper assumes that workers have to pay a pecuniary cost privately to receive education under budget constraints. It was found that higher migration possibilities result in an increase in the number of workers who demand education due to increases in its return. However, these workers lower the individual demand for education due to price increases. When the education supply is insufficient, higher migration possibilities may lower average human capital; that is, a brain drain may occur. This contrasts with the usual argument that emphasises the positive effect of migration possibilities. Restrictive immigration policies were found not to be completely detrimental to labour-sending countries since such policies may enhance the human capital formation

Illegal Immigration, Immigration Quotas, and Employer Sanctions

We investigate the effects of changes in the quota for skilled immigrants on the welfare of native workers, legal immigrants, and illegal immigrants under different levels of employer sanctions, assuming a small open economy with dual labor markets and efficiency wages. We demonstrate that if fines are large（small），increases in the quota are likely to increase（decrease）the welfare of native workers and legal immigrants. Our results suggest that the policy authority has to manipulate the immigration quota and employer sanctions simultaneously in order to increase the welfare of native workers and legal immigrants

The role of the omega subunit of RNA polymerase in expression of the relA gene in Escherichia coli

The rpoZ gene for the omega subunit of Escherichia coli RNA polymerase constitutes single operon with the spoT gene, which is responsible for the maintenance of stringent response under nutrient starvation conditions. To identify the physiological role of the omega subunit, we compared the gene expression profile of wild-type Escherichia coli with that of an rpoZ deleted strain by microarray analysis using an E. coli DNA chip. Here we report on a set of genes which show changes in expression profile following the removal of rpoZ. We have seen that relA, which is responsible for the synthesis of the stringent factor ppGpp and many ribosomal proteins, exhibited noticeable changes in mRNA levels and were therefore further analyzed for their expression using a GFP/RFP two-fluorescent protein promoter assay vector. In the absence of rpoZ, the promoter for the relA gene was severely impaired, but the promoters from the ribosomal protein genes were not affected as much. Taking these results together we propose that the omega subunit is involved in regulation of the relA gene, but induction of the stringently controlled genes in the absence of rpoZ is, at least in part, attributable to a decrease in ppGpp level