Development of chemical tools for imaging RNA and studying RNA and protein interactions

Tools for study of RNA are divided into two groups: RNA imaging and RNA crosslinking (Chapter 1). RNA imaging denotes visualization of target RNA by labelling it with fluorophores. RNA crosslinking refers to investigating the function of target RNA by capturing bio-macromolecules the RNA interacts with. In consideration of low abundance of some RNAs in living cells, in chapter 2, we have synthesized a new RNA probe based on previously reported aptamers. which reduces background signal to a large extent. We realized imaging of the RNA aptamer in mammalian cells, and the fluorescence obtained from newly constructed probe was apparently brighter.In chapter 3, we developed two psoralen based length tunable crosslinkers (AMT-NHS and AMT dimer) for studying RNA-RNA interactions or RNA-protein interactions. We have synthesized the crosslinkers and verified in vitro experiment that RNA-RNA interactions could be effectively captured by the AMT dimer, and RNA-protein interactions could be effectively tracked by AMT-NHS. In chapter 4, we proved that AMT-NHS could be applied to study RNA-protein interactions in living cells. We also proved that AMT-NHS CLIP is a stable and efficient method for studying RNA-protein interactions, it captured a large portion of interactions that traditional CLIP method may miss.In chapter 5, we have synthesized and incorporated an unnatural photoactivatable amino acid into a protein on a specific site by expanding genetic code, which paves the way to develop a novel and powerful CLIP method to capture more comprehensively RNA-protein interactions

Observation of sub-Doppler absorption in the /Lambda-type three-level Doppler-broadened cesium system

Thanks to the atomic coherence in coupling laser driven atomic system, sub-Doppler absorption has been observed in Doppler-broadened cesium vapor cell via the /Lambda-type three-level scheme. The linewidth of the sub-Doppler absorption peak become narrower while the frequency detuning of coupling laser increases. The results are in agreement with the theoretical prediction by G. Vemuri et al.[PRA,Vol.53(1996) p.2842].Comment: 12 pages, 5 figures, to appear on Applied Physics

MOTRv2: Bootstrapping End-to-End Multi-Object Tracking by Pretrained Object Detectors

In this paper, we propose MOTRv2, a simple yet effective pipeline to bootstrap end-to-end multi-object tracking with a pretrained object detector. Existing end-to-end methods, MOTR and TrackFormer are inferior to their tracking-by-detection counterparts mainly due to their poor detection performance. We aim to improve MOTR by elegantly incorporating an extra object detector. We first adopt the anchor formulation of queries and then use an extra object detector to generate proposals as anchors, providing detection prior to MOTR. The simple modification greatly eases the conflict between joint learning detection and association tasks in MOTR. MOTRv2 keeps the query propogation feature and scales well on large-scale benchmarks. MOTRv2 ranks the 1st place (73.4% HOTA on DanceTrack) in the 1st Multiple People Tracking in Group Dance Challenge. Moreover, MOTRv2 reaches state-of-the-art performance on the BDD100K dataset. We hope this simple and effective pipeline can provide some new insights to the end-to-end MOT community. Code is available at \url{https://github.com/megvii-research/MOTRv2}.Comment: Accepted by CVPR 202

Quantum-dot gain without inversion:Effects of dark plasmon-exciton hybridization

We propose an initial-state-dependent quantum-dot gain without population inversion in the vicinity of a resonant metallic nanoparticle. The gain originates from the hybridization of a dark plasmon-exciton and is accompanied by efficient energy transfer from the nanoparticle to the quantum dot. This hybridization of the dark plasmon-exciton, attached to the hybridization of the bright plasmon-exciton, strengthens nonlinear light-quantum emitter interactions at the nanoscale, thus the spectral overlap between the dark and the bright plasmons enhances the gain effect. This hybrid system has potential applications in ultracompact tunable quantum devices.Physics, Condensed MatterSCI(E)[email protected]

Hexapartite steering based on a four-wave-mixing process with a spatially structured pump

Multipartite Einstein-Podolsky-Rosen (EPR) steering has been widely studied, for realizing safer quantum communication. The steering properties of six spatially separated beams from the four-wave-mixing process with a spatially structured pump are investigated. Behaviors of all (1+i)/(i+1)-mode (i=1,2,3) steerings are understandable, if the role of the corresponding relative interaction strengths are taken into account. Moreover, stronger collective multipartite steerings including five modes also can be obtained in our scheme, which has potential applications in ultra-secure multiuser quantum networks when the issue of trust is critical. By further discussing about all monogamy relations, it is noticed that the type-IV monogamy relations, which are naturally included in our model, are conditionally satisfied. Matrix representation is used to express the steerings for the first time, which is very useful to understand the monogomy relations intuitively. Different steering properties obtained in this compact phase-insensitive scheme have potential applications for different kinds of quantum communication tasks