519 research outputs found

    Spin-valley qubit in nanostructures of monolayer semiconductors: Optical control and hyperfine interaction

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    We investigate the optical control possibilities of spin-valley qubit carried by single electrons localized in nanostructures of monolayer TMDs, including small quantum dots formed by lateral heterojunction and charged impurities. The quantum controls are discussed when the confinement induces valley hybridization and when the valley hybridization is absent. We show that the bulk valley and spin optical selection rules can be inherited in different forms in the two scenarios, both of which allow the definition of spin-valley qubit with desired optical controllability. We also investigate nuclear spin induced decoherence and quantum control of electron-nuclear spin entanglement via intervalley terms of the hyperfine interaction. Optically controlled two-qubit operations in a single quantum dot are discussed.Comment: 17pages, 10 figure

    Lepton-Flavor Violating Processes li→ljγl_{i}\to l_{j}\gamma in Topcolor Assisted Technicolor Models

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    We consider the lepton-flavor violating(LFV) processes li→ljγl_{i}\to l_{j}\gamma in the framework of topcolor assisted technicolor(TC2) models. We find that the new gauge boson Z′Z^{\prime} predicted by TC2 models can give significantly contributions to these processes via the flavor changing couplings. The present experimental bound on the LFV process μ→eγ\mu \to e\gamma gives severe constraints on the TC2 models. In the case that the Z′Z^{\prime} mass MZM_{Z} is consistent with other experimental constraints, we obtain constraints on the lepton mixing factors KτμK_{\tau\mu} and KτeK_{\tau e}. The future LFV experiments will be probe of the TC2 models.Comment: some mistakes corrected and several references adde

    Surgical Treatment for Unstable Distal Clavicle Fracture with Micromovable and Anatomical Acromioclavicular Plate

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    Between 2006 and 2009, 18 patients of distal clavicle fracture were treated with micro-movable and anatomical acromioclavicular plate (MAAP) in our department. According to the Neer's classification, all cases were unstable with type IIA (12 cases) and type IIB (6 cases). Functional outcome was evaluated using the Karlsson's criteria. The mean follow-up was 18 months (range, 12-36months). No postoperative plate screws complication was observed. Osseous union could be achieved at a mean time of 12 weeks after operation in 18 patients (range, 8 -16 weeks). According to Karlsson's criteria, radiographic appearances and postoperative shoulder functional recovery revealed a good and excellent rate in these cases. We conclude that surgical treatment using MAAP seems to be a good option for unstable type II fractures of the distal clavicle. This technique allows for reliable fixation with early functional exercises and functional recovery

    Shapes of distal tibiofibular syndesmosis are associated with risk of recurrent lateral ankle sprains

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    Distal tibiofibular syndesmosis (DTS) has wide anatomic variability in depth of incisura fibularis and shape of tibial tubercles. We designed a 3-year prospective cohort study of 300 young physical training soldiers in an Army Physical Fitness School. Ankle computed tomography (CT) scans showed that 56% of the incisura fibularis were a "C" shape, 25% were a "1" shape, and 19% were a "Gamma"shape. Furthermore, we invited a randomly selected subcohort of 6 participants in each shape of DTS to undergo a three-dimensional (3D) laser scanning. The "1" shape group showed widest displacement range of the DTS in the y-axis, along with the range of motion (ROM) on the position more than 20 degrees of the ankle dorsiflexion, inversion and eversion. During the 3-year study period, 23 participants experienced recurrent lateral ankle sprains. 7 cases of the incisura fibularis were "C" shape, 13 cases were "1" shape, and 3 cases were "Gamma"shape. The "1" shape showed highest risk among the three shapes in incident recurrent lateral ankle sprains. We propose that it is possible to classify shapes of DTS according to the shapes of incisura fibularis, and people with "1" shape may have more risk of recurrent lateral ankle sprains
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