Mammalian Argonaute 2 (Ago2) protein associates with microRNAs (miRNAs) or small interfering RNAs (siRNAs) forming RNA-induced silencing complexes (RISCs/miRNPs). In the present work, we characterize ...the RNA-binding and nucleolytic activity of recombinant mouse Ago2. Our studies show that recombinant mouse Ago2 binds efficiently to miRNAs forming active RISC. Surprisingly, we find that recombinant mouse Ago2 forms active RISC using pre-miRNAs or long unstructured single stranded RNAs as guides. Furthermore, we demonstrate that, in vivo, endogenous human Ago2 binds directly to pre-miRNAs independently of Dicer, and that Ago2:pre-miRNA complexes are found both in the cytoplasm and in the nucleus of human cells.
The assembly of microRNA Ribonucleoproteins (miRNPs) or RNA-Induced Silencing Complexes (RISC) is essential for the function of miRNAs and initiates from processing of precursor miRNAs (pre-miRNAs) ...by Dicer or by the ribonucleolytic activity of Ago2. Here, we report the generation of a novel in-vitro miRNP/RISC assembly assay programmed by pre-miRNAs from mammalian cell lysates. Parallel studies in cells lacking Dicer that were reconstituted with wild type or catalytically inactive Dicer, confirm the operation of the reported pathways operate in vivo. We find that the miRNA Loading Complex (miRLC) is the primary machinery linking pre-miRNA processing to miRNP/RISC assembly in mammals. We show that a miRNA Precursor Deposit Complex (miPDC) plays a crucial role for the Ago2-dependent miRNA biogenesis and promotes miRNP assembly of certain Dicer-dependent miRNAs. Furthermore, we find that 5’-uridine, 3’-mid base pairing and 5’-mid mismatches within pre-miRNAs promote their assembly into miPDC. Our studies provide a comprehensive view of miRNP/RISC assembly pathways in mammals and our assay provides a versatile platform for further mechanistic dissection of such pathways in mammals. Post-transcriptional regulation of gene expression by the miRNA requires its binding to the Ago protein to form the miRNP or the RISC, whose assembly requires the association of the pre-miRNA with Ago and the processing of the pre-miRNA within the miRLC or the miPDC. The miRNP/RISC assembly is a tightly regulated process and one emerging regulatory paradigm is through tailing of pre-miRNAs. Here, we report the full-length sequence of authentic pre-miRNAs through high-throughput sequencing of Ago-interacting pre-miRNAs. We observe widespread tailing of pre-miRNAs at their 3’ ends, which may suppress the miRNP/RISC assembly through inhibition of Dicer processing. We also find that a group of Ago2-cleaved pre-miRNAs (ac-pre-miRNAs) are tailed at the Ago2-cleavage site. Our findings suggest that tailing of pre-miRNAs and ac-pre-miRNAs may play an important regulatory role in the miRNP/RISC assembly in mammals.
Dark image enhancement aims at converting dark images to normal-light images. Existing dark image enhancement methods take uncompressed dark images as inputs and achieve great performance. However, ...in practice, dark images are often compressed before storage or transmission over the Internet. Current methods get poor performance when processing compressed dark images. Artifacts hidden in the dark regions are amplified by current methods, which results in uncomfortable visual effects for observers. Based on this observation, this study aims at enhancing compressed dark images while avoiding compression artifacts amplification. Since texture details intertwine with compression artifacts in compressed dark images, detail enhancement and blocking artifacts suppression contradict each other in image space. Therefore, we handle the task in latent space. To this end, we propose a novel latent mapping network based on variational auto-encoder (VAE). Firstly, different from previous VAE-based methods with single-resolution features only, we exploit multiple latent spaces with multi-resolution features, to reduce the detail blur and improve image fidelity. Specifically, we train two multi-level VAEs to project compressed dark images and normal-light images into their latent spaces respectively. Secondly, we leverage a latent mapping network to transform features from compressed dark space to normal-light space. Specifically, since the degradation models of darkness and compression are different from each other, the latent mapping process is divided mapping into enlightening branch and deblocking branch. Comprehensive experiments demonstrate that the proposed method achieves state-of-the-art performance in compressed dark image enhancement.
Considering the collision-prone problem near the initial point, goal non-reachable with obstacle nearby (GNWON) and the chattering problem of the traditional artificial potential field ...algorithm(TAPF), the attractive potential field function and the repulsive potential field function are improved respectively, and an improved adaptive artificial potential field algorithm(AAPF) is proposed. The algorithm can calculate the different potential field of each path point on-line in real time. On this basis, a 2D improved adaptive artificial potential field algorithm is extended to 3D space for autonomous obstacle avoidance planning of quadrotor UAV. A 3D obstacle model is established, and the principle of obstacle avoidance at the nearest contact point is designed to calculate the repulsive potential field. Then the obstacle avoidance planning strategy of Four-rotor UAV based on 3D adaptive potential field algorithm is designed. The simulation results show that the improved adaptive algorithm effectively compensates for the shortcomings of the traditional artificial potential field method and can be applied in 3D.
To solve the problem of autonomous position and navigation for UAV(Unmanned aerial vehicle) in complex environment, this paper has proposed a Multi-level variable dimension extended Kalman filter ...fusion algorithm(ML-VDEKF). The motion and observation equations of the filter system have been established, and some low-cost sensors such as IMU(Inertial measurement unit), magnetometer, GPS and barometer have been combined to estimate state information during the flight. The actual experimental data shows that the proposed algorithm can provide accurate attitude, velocity and position. At the same time, the algorithm greatly reduces the computation when running in real-time operation of embedded devices, and can meet the flight requirement.
In the UAV (Unmanned Aerial Vehicle) integrated navigation system, considering the poor fault tolerance, inaccurate system model and robustness of the classic GPS/INS (Inertial Navigation System) ...integrated navigation algorithm, an improved Federated Filter navigation algorithm is put forward in this paper. Firstly, the GPS/INS/MAG (magnetometer) Federated Filter algorithm based on the theory of federated filter was designed. Secondly, the Adaptive Fading Kalman Filter algorithm and Robust Kalman Filter algorithm are introduced into the two sub-filters of the federated filter algorithm to suppress the interference of inaccurate system model and sensor errors on the filter results. The simulation results show that the Federated Filter model is effective and the improved Federated Filter algorithm can effectively enhance the attitude angle accuracy and suppress the influence of sensor error on the filter result.
A
bstract
We take the first step in generalizing the so-called “Schubert analysis”, originally proposed in twistor space for four-dimensional kinematics, to the study of symbol letters and more ...detailed information on canonical differential equations for Feynman integral families in general dimensions with general masses. The basic idea is to work in embedding space and compute possible cross-ratios built from (Lorentz products of) maximal cut solutions for all integrals in the family. We demonstrate the power of the method using the most general one-loop integrals, as well as various two-loop planar integral families (such as sunrise, double-triangle and double-box) in general dimensions. Not only can we obtain all symbol letters as cross-ratios from maximal-cut solutions, but we also reproduce entries in the canonical differential equations satisfied by a basis of d log integrals.
PDF
