Homo-Site Nucleation Growth of Twisted Bilayer MoS2 with Commensurate Angles.

Moiré superlattices, composed of two layers of transition metal dichalcogenides with a relative twist angle, provide a novel platform for exploring the correlated electronic phases and excitonic physics. Here, a gas-flow perturbation chemical vapor deposition (CVD) approach is demonstrated to directly grow MoS2 bilayer with versatile twist angles. It is found that the formation of twisted bilayer MoS2 homostructures sensitively depends on the gas-flow perturbation modes, correspondingly featuring the nucleation sites of the second layer at the same (homo-site) as or at the different (hetero-site) from that of the first layer. The commensurate twist angle of ≈22° in homo-site nucleation strategy accounts for ≈16% among the broad range of twist angles due to its low formation energy, which is in consistence with the theoretical calculation. More importantly, moiré interlayer excitons with the enhanced photoluminescence (PL) intensity and the prolonged lifetime are evidenced in the twisted bilayer MoS2 with a commensurate angle of 22°, which is owing to the reason that the strong moiré potential facilitates the interlayer excitons to be trapped in the moiré superlattices. The work provides a feasible route to controllably built twisted MoS2 homostructures with strong moiré potential to investigate the correlated physics in twistronics systems.

A natural indirect-to-direct band gap transition in artificially fabricated MoS2 and MoSe2 flowers.

Twisted bilayer (tB) transition metal dichalcogenide (TMD) structures formed from two pieces of a periodic pattern overlaid with a relative twist manifest novel electronic and optical properties and correlated electronic phenomena. Here, twisted flower-like MoS2 and MoSe2 bilayers were artificially fabricated by the chemical vapor deposition (CVD) method. Photoluminescence (PL) studies demonstrated that an energy band structural transition from the indirect gap to the direct gap happened in the region away from the flower center in tB MoS2 (MoSe2) flower patterns, accompanied by an enhanced PL intensity. The indirect-to-direct-gap transition in the tB-MoS2 (MoSe2) flower dominantly originated from a gradually enlarged interlayer spacing and thus, interlayer decoupling during the spiral growth of tB flower patterns. Meanwhile, the expanded interlayer spacing resulted in a decreased effective mass of the electrons. This means that the charged exciton (trion) population was reduced and the neutral exciton density was increased to obtain the upgraded PL intensity in the off-center region. Our experimental results were further evidenced by the density functional theory (DFT) calculations of the energy band structures and the effective masses of electrons and holes for the artificial tB-MoS2 flower with different interlayer spacings. The single-layer behavior of tB flower-like homobilayers provided a viable route to finely manipulate the energy band gap and the corresponding exotic optical properties by locally tuning the stacked structures and to satisfy the real requirement in TMD-based optoelectronic devices.

Postoperative chemotherapy on placental site trophoblastic tumor in early stage: analysis of 60 cases.

PURPOSE OF INVESTIGATION: To review the literature of placental site trophoblastic tumor (PSTT) and explore the effect of postoperative chemotherapy in patients with Stage I. MATERIALS AND METHODS: The authors searched literature on Medline, Excerpta Medica Database (EMBASE), and other resources using the keywords "placental site trophoblastic tumor" and "PSTT" from 1981 ito 2014. RESULTS: A total number of 60 patients with Stage I disease were identified, and the presentation, treatment, tumor response, disease status, and follow-up were retrieved and reviewed. According to the authors' knowledge, 725 cases associated with PSTT have been reported in 29 nations/areas since 1981. In this series, the probability of overall survival at ten years in the group of surgery alone and postoperative chemotherapy were 96.7% and 79.1% (p = 0.199), and recurrence-free survival rates were 91.8% and 63.3%, respectively. CONCLUSION: The benefit from postoperative chemotherapy is still equivocal. There is a need for scrupulousness before adding postoperative chemotherapy.

Placental site trophoblastic tumor in early stage: a case report.

Here, the authors present a case of a placental site trophoblastic tumor (PSTT) in a 28-year-old gravida 1 para 1 living 1 woman three months after vaginal delivery of a female infant at diagnosis in 2014. The patient was FIGO Stage I and finally underwent a total laparoscopic hysterectomy with ovarian conservation. Subsequently, the patient received two cycles of EMA/CO chemotherapy. Patient is on regular follow-up (clinical exam, ß-hCG tests, pelvic and abdominal sonography) and has shown no signs of local or systemic recurrence for 24 months.

[Effects of expression of calpain mRNA in rabbits exposed to vibration by hind legs].

OBJECTIVE: To study the effects of expression of calpain mRNA in rabbits exposed to vibration by hind legs. METHODS: 32 New Zealand rabbits were randomly divided into a control group and 3 experimental groups according to 4-hour energy-equivalent frequency-weighted acceleration[ahw (4)]: low (4.33 m/s(2)) , moderate (8.67 m/s(2)) and high (17.34 m/s(2)) intensity group to accepted the vibration by hind legs. 45 ds later, brain and skeletal muscle tissue of rabbits were taken to detect the expression of calpain-1 and calpain-2 mRNA by RT-qPCR technique. RESULTS: The relative content of calpain-1 mRNA in the brain tissues in rabbits of low, medium and high intensity group were 8.35±3.75,9.64±4.54,5.10±5.26. While the relative content of calpain-2 mRNA in the brain tissues in rabbits of low, medium and high intensity group were 7.34±4.97,8.50±5.66, 8.16±5.59. Compared with the control group (1.10±0.29, 0.56±0.43) , the expression of calpain-1 and calpain-2 mRNA of the intensity groups showed an significantly increasing trend (P<0.01). In skeletal muscle tissue, the relative content of calpain-1 mRNA were 4.36±2.05, 7.37±4.06, 12.46±6.21.Compared with the control group (0.98±0.59) , the expression of calpain-1 mRNA of experiment groups were significantly higher (P<0.05) .The expression of calpain-2 mRNA of the intensity groups had no significantly difference with the control group (P>0.05). CONCLUSION: The expression of calpain-1 and calpain-2 mRNA can be promoted by the vibration by the hind legs.

Gate dependence of upper critical field in superconducting (110) LaAlO3/SrTiO3 interface.

The fundamental parameters of the superconducting state such as coherence length and pairing strength are essential for understanding the nature of superconductivity. These parameters can be estimated by measuring critical parameters such as upper critical field, Hc2. In this work, Hc2 of a superconducting (110) LaAlO3/SrTiO3 interface is determined through magnetoresistive measurements as a function of the gate voltage, VG. When VG increases, the critical temperature has a dome-like shape, while Hc2 monotonically decreases. This relationship of independence between the variation of Tc and of Hc2 suggests that the Cooper pairing potential is stronger in the underdoped region and the coherence length increases with the increase of VG. The result is as for high temperature superconducting cuprates and it is different than for conventional low temperature superconductors.

[Repair of lower nasal defect with compound skin flap from forehead with trochlear artery and subcutaneous tissue pedicle].

This article reports the repair of lower nasal defect with forehead compound skin flap consisting of the trochlear artery and subcutaneous tissue pedicle in one stage in 11 patients. The repaired area ranged from 2 x 2 to 4 x 3 cm and the frontal bone area 1.5 x 1 cm. This operation had achieved good results, and the frontal bones were not absorbed, except 1 case, after 1 year follow-up. The methods of this flap design and operation were described. The merits, demerits and points for attention were discussed.

Esophageal perforation during surgery on the cervical spine.

Esophageal perforation during surgery for cervical disc herniation is a rare complication. Differences in the time of diagnosis of this complication in three patients--no delay and delays of 6 hours and 4 days, respectively--resulted in different symptoms and outcomes. Early detection of the perforation allows prompt treatment. In the early stage, primary suture and, if necessary, interposition of vital tissue are sufficient to complete healing. In later stages, only drainage procedures, sometimes with a diversion of the salivary leakage, are indicated. In the reported patients, the outcome was favorable. On the other hand as an ongoing infection may cause mediastinitis, awareness of this complication and urgent surgical treatment may be lifesaving.