A honeycomb lattice model simulating the surface states of topological insulators.

A honeycomb lattice model exhibiting the quantum spin-Hall effect is proposed, where the low-energy properties of the electrons are mainly determined by the energy spectrum in the vicinity of the Γ point, for suitable parameters. The nontrivial topology of the energy bands is revealed by calculating the Chern numbers, Berry curvature distribution, and edge state spectrum. We further show that in the continuum limit, the model Hamiltonian is equivalent to the effective model for the surface states in thin films of three-dimensional topological insulators. As a consequence, this lattice model provides a useful tool for numerical simulation of the physical properties of the surface states.

Time-reversal-symmetry-broken quantum spin Hall effect.

The quantum spin Hall (QSH) state of matter is usually considered to be protected by time-reversal (TR) symmetry. We investigate the fate of the QSH effect in the presence of the Rashba spin-orbit coupling and an exchange field, which break both inversion and TR symmetries. It is found that the QSH state characterized by nonzero spin Chern numbers C(±) = ±1 persists when the TR symmetry is broken. A topological phase transition from the TR-symmetry-broken QSH phase to a quantum anomalous Hall phase occurs at a critical exchange field, where the bulk band gap just closes. It is also shown that the transition from the TR-symmetry-broken QSH phase to an ordinary insulator state cannot happen without closing the band gap.

[Bronchial sleeve resection and reconstruction of pulmonary artery by video-assisted thoracic small incision surgery for lung cancer].

BACKGROUND: The mini-invasive surgery is now performed widely and these operations have been used in complete resection of lung cancer. The aim of this study is to summarize the results and to explore practicability of bronchial sleeve resection and reconstruction of pulmonary artery by video-assisted thoracic small incision surgery for lung neoplasms. METHODS: A total of 109 patients were retrospectively reviewed, who underwent sleeve lobectomy and bronchoplasty by video-assisted thoracic small incision surgery for lung neoplasms from January 1995 to December 2005. RESULTS: Operations were performed successfully for all the patients. The small incisions' length ranged from 3 to 15 cm and the mean length was 10 cm. The surgical time was 125-180 min and the mean was 150 min; blood loss was 210-450 mL and the mean was 320 mL. There was no operative mortality, occurrence of anastomosis stenosis and fistula. Follow-up results showed that there was no sign of re-perfusion hurt and no edema in remaining lobes. There was no blood transfusion in 80.7% of cases (88/109), no shoulder hurt in 94.5% of cases (103/109). The stay in hospital was 7-15 days, and the average was 9 days. CONCLUSIONS: The bronchial sleeve resection and reconstruction of pulmonary artery by video-assisted thoracic small incision surgery for lung cancer could finish the same work as traditional thoracic lateral incision, with less trauma, less bleeding and blood transfusion, less time in opening and closing thorax.

[Bronchial sleeve resection and reconstruction of pulmonary artery by video-assisted thoracic small incision surgery for central lung cancer: a report of 139 cases].

OBJECTIVE: To evaluate the efficacy and practicability between bronchial sleeve resection or reconstruction of the pulmonary artery by video-assisted thoracic small incision and routine posterolateral incision for lung cancer. METHODS: The clinic data was analyzed retrospectively, including 139 cases in our hospital underwent sleeve lobectomy and bronchoplasty by video-assisted thoracic small incision surgery for lung cancer from January 1995 to July 2007 and 99 cases in the HUAXI Hospital of SICHUAN University underwent routine posterolateral incision from April 2000 to December 2005. All patients whose bronchus and/or pulmonary artery were involved underwent the operation and experienced the bronchial sleeve resection or reconstruction of the pulmonary artery. RESULTS: All patients were done operation successfully with no perioperative mortality and no occurrence of anastomosis stenosis as well as fistula. The median survival period of video-assisted thoracic small incision patients and the posterolateral incision patients were 63.17 months and 42.00 months, respectively (P > 0.05). There was no sign of reperfusion injury in the reconstruction of the pulmonary artery patients. The small incisions' length was from 8 to 13 cm and the mean length was 10 cm. The routine posterolateral incisions' mean length was 30 cm. Compared to the patients underwent the routine posterolateral incision, patients underwent the operation of video assisted thoracic small incision had less operation time, less chest tube time, less hospitalization time and less postoperative shoulder joint dysfunction. CONCLUSIONS: The bronchial sleeve resection and reconstruction of the pulmonary artery by video-assisted thoracic small incision surgery for lung cancer can finish the same work as the traditional thoracic lateral incision with less trauma and recovery time.