Lifshitz phase transitions in a one-dimensional Gamma model.

In this paper, we study quantum phase transitions and magnetic properties of a one-dimensional spin-1/2 Gamma model, which describes the off-diagonal exchange interactions between edge-shared octahedra with strong spin-orbit couplings along the sawtooth chain. The competing exchange interactions between the nearest neighbors and the second neighbors stabilize the semimetallic ground state in terms of spinless fermions, and give rise to a rich phase diagram, which consists of three gapless phases. We find distinct phases are characterized by the number of Weyl nodes in the momentum space, and such changes in the topology of the Fermi surface without symmetry breaking produce a variety of Lifshitz transitions, in which the Weyl nodes situating at k=π change from type I to type II. A coexistence of type-I and type-II Weyl nodes is found in phase II. The information measures including concurrence, entanglement entropy, and relative entropy can effectively signal the second-order transitions. The results indicate that the Gamma model can act as an exactly solvable model to describe Lifshitz phase transitions in correlated electron systems.

Numerical and analytical results for geometric measure of coherence and geometric measure of entanglement.

Quantifying coherence and entanglement is extremely important in quantum information processing. Here, we present numerical and analytical results for the geometric measure of coherence, and also present numerical results for the geometric measure of entanglement. On the one hand, we first provide a semidefinite algorithm to numerically calculate geometric measure of coherence for arbitrary finite-dimensional mixed states. Based on this semidefinite algorithm, we test randomly generated single-qubit states, single-qutrit states, and a special kind of d-dimensional mixed states. Moreover, we also obtain an analytical solution of geometric measure of coherence for a special kind of mixed states. On the other hand, another algorithm is proposed to calculate the geometric measure of entanglement for arbitrary two-qubit and qubit-qutrit states, and some special kinds of higher dimensional mixed states. For other states, the algorithm can get a lower bound of the geometric measure of entanglement. Randomly generated two-qubit states, the isotropic states and the Werner states are tested. Furthermore, we compare our numerical results with some analytical results, which coincide with each other.

Polarization-dependent photon switch in a one-dimensional coupled-resonator waveguide.

Polarization-dependent photon switch is one of the most important ingredients in building future large-scale all-optical quantum network. We present a scheme for a single-photon switch in a one-dimensional coupled-resonator waveguide, where N(a) Λ-type three-level atoms are individually embedded in each of the resonator. By tuning the interaction between atom and field, we show that an initial incident photon with a certain polarization can be transformed into its orthogonal polarization state. Finally, we use the fidelity as a figure of merit and numerically evaluate the performance of our photon switch scheme in varieties of system parameters, such as number of atoms, energy detuning and dipole couplings.

[Epidemiological survey of HBsAg carriers in the Uighur and Han populations in the Khotan Area of Xinjiang autonomous region].

OBJECTIVE: To survey nonsymptomatic HBsAg carriers in the Uighur and Han populations in Khotan Area of Xinjiang Autonomous region. METHOD: HBsAg was detected using colloidal gold-labeled double antibody sandwich method. RESULTS: These investigations included 2 597 subjects consisting of 2 022 Uighur and 575 Han subjects. The total HBsAg carrier rate in the Uighur population was 1.48% (30/2 022), specifically 1.078% in male and 1.59% in female subjects. No significant differences were observed in the age between male and female HBsAg carriers, who had an average age of 35 years. In the Han population, the total HBsAg carrier rate was 6.09% (30/575), and was 5.6% in male and 4.4% in female subjects. The average age of the male carriers was 36.3 years and 27.6 years in the female carriers, which showed significant difference in respect to HBsAg carrier rate. The HBsAg carrier rate showed significant difference between Uighur and Han populations in Khotan Area (P<0.01). CONCLUSIONS: The HBsAg carrier rate in Uighur population in Khotan Area is consistent with that in areas with low HBV infection, whereas the Han population exhibit features similar to those in areas with moderately HBV prevalence in the inland regions. The low HBsAg carrier rate in Uighurs might be attributed to the their customs in diet, eating habit, local living environment and the difference in HLA gene distribution. The authors suppose that such antigens as HLA-Bw41 might be protective against HBV infection.

[Surgical management of hypopharyngeal cancer].

OBJECTIVE: To investigate the preservation of laryngeal function for the patients with hypopharyngeal cancer. METHODS: Two hundred and ninety-three cases of hypopharyngeal cancer with surgical management were reviewed retrospectively, and 222 cases were originated from pyriform sinus, 13 from post-cricoid, and 21 from posterior pharyngeal wall. Radiotherapy (37 cases), operation only (56 cases) and the combined treatment (operation plus radiation or chemotherapy, 200 cases) were adopted. 159 cases were treated with function preserved laryngectomy and 97 with total laryngectomy. RESULTS: The 5 year survival rates of patient with laryngeal function preserved and no laryngeal function preserved were 51.3%, 47.6% (for stage III); 40.4%, 43.3% (for stage IV), respectively. There were no significant differences in 5-year survival between the functionally preserved group and no functioned group (P > 0.05). The analysis of survival rates revealed a significant difference between combined therapy and radiotherapy. CONCLUSION: There is no significant difference between the survive rates of function preserved and non-preserved groups. Conservation laryngectomy improves the quality of patient's life, and combined therapy is the best choice for hypopharyngeal cancer.