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Aptamers, nucleic acid ligands against specific targets, have emerged as drug candidates, sensors, imaging tools, and nanotechnology building blocks. The most successful method for their development has been SELEX (Systematic Evolution of Ligands by EXponential Enrichment), an iterative procedure that is labor- and time-intensive and often enriches candidates for criteria other than those desired. Here we present UltraSelex, a non-iterative method that combines biochemical partitioning, high-throughput sequencing, and computational background minimization through statistical rank modeling. This approach avoids the common bias for abundant sequences and selects high-affinity ligands, even if they are extremely scarce. In six independent UltraSelex experiments (three towards each target), we discovered high-affinity aptamers for a fluorogenic silicon rhodamine dye, and a protein target, the SARS-CoV-2 RNA-dependent RNA polymerase. These aptamers enabled live-cell RNA imaging and efficient enzyme inhibition, respectively. The wet-lab partitioning part of UltraSelex can be completed in a few hours, and including sequencing and rank modeling via a public web server, the identification of lead candidates can be accomplished in about one day. UltraSelex provides a rapid route to novel drug candidates and diagnostic tools with greatly improved performance.

Value function decomposition (VFD) methods under the popular paradigm of centralized training and decentralized execution (CTDE) have promoted multi-agent reinforcement learning progress. However, existing VFD methods proceed from a group's value function decomposition to only solve cooperative tasks. With the individual value function decomposition, we propose MFVFD, a novel multi-agent Q-learning approach for solving cooperative and non-cooperative tasks based on mean-field theory. Our analysis on the Hawk-Dove and Nonmonotonic Cooperation matrix games evaluate MFVFD's convergent solution. Empirical studies on the challenging mixed cooperative-competitive tasks where hundreds of agents coexist demonstrate that MFVFD significantly outperforms existing baselines.

In this paper, the circle formation control problem is addressed for a group of cooperative underactuated fish-like robots involving unknown nonlinear dynamics and disturbances. Based on the reinforcement learning and cognitive consistency theory, we propose a decentralized controller without the knowledge of the dynamics of the fish-like robots. The proposed controller can be transferred from simulation to reality. It is only trained in our established simulation environment, and the trained controller can be deployed to real robots without any manual tuning. Simulation results confirm that the proposed model-free robust formation control method is scalable with respect to the group size of the robots and outperforms other representative RL algorithms. Several experiments in the real world verify the effectiveness of our RL-based approach for circle formation control., Comment: to be published in ICRA2021

In order to ensure the safe transmission of the brine pipeline, this paper designs a leakage detection terminal based on STM32F7. This terminal uses GPS to added time stamps to the collected data. And each distributed terminal uses second pulse signal of GPS to realize the function of synchronously collecting signals. Finally, the data is transmitted to the cloud computing platform through the 4G wireless transmission module system. This paper uses the S transform algorithm to analyze the characteristics of these transmitted data. S transform algorithm fully extracts the characteristics of the data in the time-frequency-mode domain. The simulation results show that the data generates high-frequency signals at default point. Through the whole system, it can effectively realize real-time monitoring.

In some of the adjustable speed drive (ASD) common-mode (CM) prediction models, the high-frequency (HF) motor model needs additional features, for instance, the mutual inductance between phases and the symmetry of single-phase concerning the beginning and ending points. In this paper, a universal HF delta- and star-connected three-phase motor model is presented. The three-phase HF motor model is acquired from CM and differential mode (DM) equivalent circuits, which are extracted from CM and DM measurements of the motor. The obtained three-phase HF induction motor model can be connected as a star and delta configuration in the simulation. The proposed model allows identification with good accuracy up to 200MHz. The method is verified with two induction machines, which have 3kW and 11kW rated powers.

This paper presents a multi-band metamaterial absorber comprising three multi-gap split-ring resonators (SRRs) with different radii and ring widths, designed in combinatorial approach. Experiments demonstrate that it can perform absorption peaks at three resonant frequencies 7.10 GHz, 10.04 GHz, and 17.44 GHz with the absorption of 99.90%, 99.91%, and 99.68%, respectively. The physical mechanism of metamaterial absorber was explained through numerical calculation and simulation, which showed that three absorption peaks were caused respectively by the three four-gap SRRs. The absorber is insensitive to incident angles and polarization states, so it has broad prospect of application.

Silver-dispersed carbon aerogels (CAs) were obtained by direct immersion of organic aerogels prepared by ambient pressure drying technique in AgNO3 aqueous solution and then carbonization. The effect of preparation conditions such as the resorcinol/catalyst ratio, the feed AgNO3 concentration, the ratio of aerogel mass/solution volume, immersion time and carbonization temperature on the bulk density and silver content as well as the BET surface area of the dispersed CAs was studied. The dispersion and structure of silver nanoparticles in obtained materials were investigated by means of scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The Ag-dispersed CAs prepared exhibit strong and long-term antibacterial activity.

This paper presents a research in tunable metamaterial (MM) absorber. We design an original split ring resonator (SRR) absorber, in first. Then through adding different group micro-gaps and increasing the number of micro-gaps, we investigate the change of different structures. We find the micro-gaps with a larger a, which is the position angle on the SRR, have a greater impact to the absorption characteristics, and the affect of the micro-gaps in low position can be ignored. It can be controlled by MEMS switches in theory. In addition, we also design a dual-band MM absorber combined by two micro-gaps structures, which has 96.04% and 96.68% absorptivity at 8.14GHz and 12.72GHz, respectively. The research is an exploration in tunable MM absorber direction and gives us an effective way to design the multi-band MM absorber.

In this paper, a broadband metamaterial absorber (MA) based on a multi-layer structure is presented. The advantages of this MA are the small periodic unit size, they are thin, have excellent polarization characteristics and are adaptive for wide angles of oblique incident electromagnetic waves. The unit cell of the broadband MA is composed of three dual-band sub-cells; each presents two resonant frequencies so as to form a wide absorptive spectrum when stacked. The sandwiched dual-band sub-cell is composed of one metallic annular patch and one metallic circular patch each etched on a lossy substrate. The radii of the metallic patches forming each sub-cell are different so as to appear to have different resonant frequencies. In the design of the unit cell there are metallic circular patches and an air layer at the bottom of each sub-cell to form magnetic coupling and avoid coupling between sub-cells. The broadband MA presents good absorptivity above 80% between 8.8 and 10.8 GHz, with a full width at half maximum (FWHM) absorption bandwidth of 2.3 GHz and a relative FWHM absorption bandwidth of 23%.

The design, fabrication, and measurement of a triple-band metamaterial absorber are presented. The proposed absorber consists of a metallic planar spiral layer and a metallic ground plane separated by a dielectric layer. Experimental results show that the proposed absorber can perform absorption peaks at three resonant frequencies 9.86 GHz, 12.24 GHz, and 15.34 GHz with the absorption of 99.4%, 96.7%, and 99.1%, respectively. In addition, the absorber with the thickness of λ/35 at the lowest fundamental resonant frequency can operate at a wide range of incident angles under both transverse electric and transverse magnetic polarizations.