702 research outputs found

    Clinical report and literature review of female idiopathic hypogonadism with diabetes mellitus

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    通过报道1例女性特发性低促性腺激素性性腺功能减退症合并糖尿病患者,结合现代医学临床循证的方法和查阅相关文献,以期为特发性低促性腺激素性性腺功能减退症合并糖尿病的诊断和治疗提供思路。1 cases of female idiopathic hypogonadotropic hypogonadism in patients with diabetes mellitus was reported in the paper in order to provide ideas for idiopathic hypogonadotropic hypogonadism with diabetes diagnosis and treatment, based on modern clinical medicine and evidence-based literatures

    Crossover between Weak Antilocalization and Weak Localization of Bulk States in Ultrathin Bi2Se3 Films

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    We report transport studies on the 5 nm thick Bi2Se3 topological insulator films which are grown via molecular beam epitaxy technique. The angle-resolved photoemission spectroscopy data show that the Fermi level of the system lies in the bulk conduction band above the Dirac point, suggesting important contribution of bulk states to the transport results. In particular, the crossover from weak antilocalization to weak localization in the bulk states is observed in the parallel magnetic field measurements up to 50 Tesla. The measured magneto-resistance exhibits interesting anisotropy with respect to the orientation of B// and I, signifying intrinsic spin-orbit coupling in the Bi2Se3 films. Our work directly shows the crossover of quantum interference effect in the bulk states from weak antilocalization to weak localization. It presents an important step toward a better understanding of the existing three-dimensional topological insulators and the potential applications of nano-scale topological insulator devices

    SKA sensitivity for possible radio emission from dark matter in Omega Centauri

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    Omega Centauri, the largest known globular cluster in the Milky Way, is believed to be the remains of a dwarf galaxy's core. Giving its potential abundance of dark matter (DM), it is an attractive target for investigating the nature of this elusive substance in our local environment. Our study demonstrates that by observing Omega Centauri with the SKA for 1000 hours, we can detect synchrotron radio or Inverse Compton (IC) emissions from the DM annihilation products. It enables us to constrain the cross-section of DM annihilation down to 1030 cm3 s1\sim {\rm 10^{-30}~cm^3~s^{-1}} for DM mass from several GeV\rm{GeV} to 100 GeV\rm{100~GeV}, which is much stronger compared with other observations. Additionally, we explore the axion, another well-motivated DM candidate, and provide stimulated decay calculations. It turns out that the sensitivity can reach gaγγ1010 GeV1g_{\rm{a\gamma\gamma}} \sim 10^{-10} ~\rm{GeV^{-1}} for 2×107 eV<ma<2×104 eV2\times 10^{-7} ~\rm{eV} < m_a < 2\times 10^{-4} ~\rm{eV}.Comment: 19 pages, 8 figure

    Electron interaction-driven insulating ground state in Bi2Se3 topological insulators in the two dimensional limit

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    We report a transport study of ultrathin Bi2Se3 topological insulators with thickness from one quintuple layer to six quintuple layers grown by molecular beam epitaxy. At low temperatures, the film resistance increases logarithmically with decreasing temperature, revealing an insulating ground state. The sharp increase of resistance with magnetic field, however, indicates the existence of weak antilocalization, which should reduce the resistance as temperature decreases. We show that these apparently contradictory behaviors can be understood by considering the electron interaction effect, which plays a crucial role in determining the electronic ground state of topological insulators in the two dimensional limit.Comment: 4 figure

    Quantum phase transition of light in a 1-D photon-hopping-controllable resonator array

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    We give a concrete experimental scheme for engineering the insulator-superfluid transition of light in a one-dimensional (1-D) array of coupled superconducting stripline resonators. In our proposed architecture, the on-site interaction and the photon hopping rate can be tuned independently by adjusting the transition frequencies of the charge qubits inside the resonators and at the resonator junctions, respectively, which permits us to systematically study the quantum phase transition of light in a complete parameter space. By combining the techniques of photon-number-dependent qubit transition and fast read-out of the qubit state using a separate low-Q resonator mode, the statistical property of the excitations in each resonator can be obtained with a high efficiency. An analysis of the various decoherence sources and disorders shows that our scheme can serve as a guide to coming experiments involving a small number of coupled resonators.Comment: 7 pages, 4 figure

    Room-temperature ammonia sensor based on ZnO nanorods deposited on ST-cut quartz surface acoustic wave devices

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    Using a seed layer-free hydrothermal method, ZnO nanorods (NRs) were deposited on ST-cut quartz surface acoustic wave (SAW) devices of ammonia sensing at room-temperature. For a comparison, a ZnO film layer of 30 nm thick was also coated onto ST-cut quartz SAW device using a sol–gel and spin-coating technique. The ammonia sensing results showed that the sensitivity, repeatability and stability of the ZnO NRs coated SAW device were superior to those of the ZnO film coated SAW device due to the large surface-to-volume ratio of the ZnO NRs

    Even-Odd Layer-Dependent Anomalous Hall Effect in Topological Magnet MnBi2Te4 Thin Films

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    A central theme in condensed matter physics is to create and understand the exotic states of matter by incorporating magnetism into topological materials. One prime example is the quantum anomalous Hall (QAH) state. Recently, MnBi2Te4 has been demonstrated to be an intrinsic magnetic topological insulator and the QAH effect was observed in exfoliated MnBi2Te4 flakes. Here, we used molecular beam epitaxy (MBE) to grow MnBi2Te4 films with thickness down to 1 septuple layer (SL) and performed thickness-dependent transport measurements. We observed a non-square hysteresis loop in the antiferromagnetic state for films with thickness greater than 2 SL. The hysteresis loop can be separated into two AH components. Through careful analysis, we demonstrated that one AH component with the larger coercive field is from the dominant MnBi2Te4 phase, while the other AH component with the smaller coercive field is from the minor Mn-doped Bi2Te3 phase in the samples. The extracted AH component of the MnBi2Te4 phase shows a clear even-odd layer-dependent behavior, a signature of antiferromagnetic thin films. Our studies reveal insights on how to optimize the MBE growth conditions to improve the quality of MnBi2Te4 films, in which the QAH and other exotic states are predicted.Comment: 23 pages, 4 figures, comments are welcom
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