Since the concept of aptamer emerged, many scientists have launched a rich field of research around it. However, few nucleic acids aptamer which use cell as target can be put into practical applications. We believe that a great deal of this lies in the complexity and irreproducibility of aptamer screening experiments themselves. The complexity is due to the cumbersome processes and the technical requirements for laboratory personnel, whereas irreproducibility arises from the fact that the starting point of such screens is nucleic acid libraries with random fragments, and that different libraries directly determine the differences or even the success or failure of screening results. The complexity and irreproducibility mentioned above, in turn, lead to the inability of this experiment to unfold on a large scale, which naturally cannot lead to excellent results for practical applications. In response to this problem, our group has developed an instrument for automated screening of tumor cell nucleic acid aptamers and characterized the properties of nucleic acid aptamers obtained using this instrument in a comprehensive manner. 相似文献
In this work, the static tensile and free vibration of nanorods are studied via both the strain-driven (StrainD) and stress-driven (StressD) two-phase nonlocal models with a bi-Helmholtz averaging kernel. Merely adjusting the limits of integration, the integral constitutive equation of the Fredholm type is converted to that of the Volterra type and then solved directly via the Laplace transform technique. The unknown constants can be uniquely determined through the standard boundary conditions and two constrained conditions accompanying the Laplace transform process. In the numerical examples, the bi-Helmholtz kernel-based StrainD (or StressD) two-phase model shows consistently softening (or stiffening) effects on both the tension and the free vibration of nanorods with different boundary edges. The effects of the two nonlocal parameters of the bi-Helmholtz kernel-based two-phase nonlocal models are studied and compared with those of the Helmholtz kernel-based models.
Recently,the negative differential thermal resistance effect was discovered in a homojunction made of a negative thermal expansion material,which is very promising for realizing macroscopic thermal transistors.Similar to the Monte Carlo phonon simulation to deal with grain boundaries,we introduce positive temperature-dependent interface thermal resistance in the modified Lorentz gas model and find negative differential thermal resistance effect.In the homojunction,we reproduce a pair of equivalent negative differential thermal resistance effects in different temperature gradient directions.In the heterojunction,we realize the unidirectional negative differential thermal resistance effect,and it is accompanied by the super thermal rectification effect.Using this new way to achieve high-performance thermal devices is a new direction,and will provide extensive reference and guidance for designing thermal devices. 相似文献
Considering the random impulses of mechanical noise and the limitations involved while identifying mechanical fault impulse signals via traditional measurement indices of signal-to-noise ratio, which require the characteristic frequency to be known in advance, this study proposes an adaptive unsaturated stochastic resonance method employing maximum cross-correlated kurtosis as the signal detection index. The proposed method combines the features of a cross-correlated coefficient to indicate periodic fault transients and those of spectrum kurtosis to locate these transients in the frequency domain. Actual vibration signals collected from motor and gear bearings subjected to heavy noise are used to demonstrate the effectiveness of the proposed method. Through a coarse tree-based machine learning method, the proposed method is verified to be more suitable for explaining the periodic impulse components of bearing signals, as compared to the ensemble empirical mode decomposition denoising method and unsaturated stochastic resonance using the kurtosis-intercorrelation index. 相似文献
This paper studies the coordinated aggregation problem of a multi-agent system. Particularly, all the agents reach a consensus within a pre-specified target region. However, only a subset of agents have access to this target region, and each agent merely interacts with its neighbors by communication. Moreover, there exist unknown heterogeneous delays in communication channels. The underlying communication topology is characterized by a digraph. To accommodate the practical digital disposal, a sampled-data distributed protocol is proposed, where the sampling is asynchronous in the sense that the sampling periods of distinct agents are heterogeneous. The resulting closed-loop system from the proposed sampled-data distributed protocol is in a hybrid fashion that the continuous system is fed-back by using discrete states at sampling instants. The convergence performance of this hybrid closed-loop system is analyzed based on the contraction theory. More specifically, it is first shown that all the states are coordinated to aggregate within the target region, i.e., coordinated aggregation. With this result, it is next shown that all the states are coordinated towards a consensus, i.e., state agreement. These together guarantee the fulfillment of the concerned coordinated aggregation objective. Finally, a simulation example is given to validate the theoretical results. 相似文献