24,769 research outputs found
Exceptional and Anisotropic Transport Properties of Photocarriers in Black Phosphorus
We show that black phosphorus has room-temperature charge mobilities on the
order of 10 cmVs, which are about one order of magnitude
larger than silicon. We also demonstrate strong anisotropic transport in black
phosphorus, where the mobilities along the armchair direction are about one
order of magnitude larger than zigzag direction. A photocarrier lifetime as
long as 100 ps is also determined. These results illustrate that black
phosphorus is a promising candidate for future electronic and optoelectronic
applications.Comment: 5 pages, 4 figure
GeV Scale Asymmetric Dark Matter from Mirror Universe: Direct Detection and LHC Signatures
Mirror universe is a fundamental way to restore parity symmetry in weak
interactions. It naturally provides the lightest mirror nucleon as a unique
GeV-scale asymmetric dark matter particle candidate. We conjecture that the
mirror parity is respected by the fundamental interaction Lagrangian, and its
possible soft breaking arises only from non-interaction terms in the
gauge-singlet sector. We realize the spontaneous mirror parity violation by
minimizing the vacuum Higgs potential, and derive the corresponding Higgs
spectrum. We demonstrate that the common origin of CP violation in the visible
and mirror neutrino seesaws can generate the right amount of matter and mirror
dark matter via leptogenesis. We analyze the direct detections of GeV-scale
mirror dark matter by TEXONO and CDEX experiments. We further study the
predicted distinctive Higgs signatures at the LHC.Comment: 16pp. Plenary talk presented by HJH at the International Symposium on
Cosmology and Particle Astrophysics (CosPA2011). To appear in the conference
proceedings of IJMP. Minor refinement
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Coil combination using linear deconvolution in k-space for phase imaging
Background: The combination of multi-channel data is a critical step for the imaging of phase and susceptibility contrast in magnetic resonance imaging (MRI). Magnitude-weighted phase combination methods often produce noise and aliasing artifacts in the magnitude images at accelerated imaging sceneries. To address this issue, an optimal coil combination method through deconvolution in k-space is proposed in this paper.
Methods: The proposed method firstly employs the sum-of-squares and phase aligning method to yield a complex reference coil image which is then used to calculate the coil sensitivity and its Fourier transform. Then, the coil k-space combining weights is computed, taking into account the truncated frequency data of coil sensitivity and the acquired k-space data. Finally, combining the coil k-space data with the acquired weights generates the k-space data of proton distribution, with which both phase and magnitude information can be obtained straightforwardly. Both phantom and in vivo imaging experiments were conducted to evaluate the performance of the proposed method.
Results: Compared with magnitude-weighted method and MCPC-C, the proposed method can alleviate the phase cancellation in coil combination, resulting in a less wrapped phase.
Conclusions: The proposed method provides an effective and efficient approach to combine multiple coil image in parallel MRI reconstruction, and has potential to benefit routine clinical practice in the future
Exciton-exciton annihilation in MoSe2 monolayers
We investigate the excitonic dynamics in MoSe2 monolayer and bulk samples by
femtosecond transient absorption microscopy. Excitons are resonantly injected
by a 750-nm and 100-fs laser pulse, and are detected by a probe pulse tuned in
the range of 790 - 820 nm. We observe a strong density-dependent initial decay
of the exciton population in monolayers, which can be well described by the
exciton-exciton annihilation. Such a feature is not observed in the bulk under
comparable conditions. We also observe the saturated absorption induced by
exciton phase-space filling in both monolayers and the bulk, which indicates
their potential applications as saturable absorbers.Comment: 5 pages, 4 figure
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