Charge Neutralization Drives the Shape Reconfiguration of DNA Nanotubes

Reconfiguration of membrane protein channels for gated transport is highly regulated under physiological conditions. However, a mechanistic understanding of such channels remains challenging owing to the difficulty in probing subtle gating‐associated structural changes. Herein, we show that charge neutralization can drive the shape reconfiguration of a biomimetic 6‐helix bundle DNA nanotube (6HB). Specifically, 6HB adopts a compact state when its charge is neutralized by Mg²⁺; whereas Na⁺ switches it to the expanded state, as revealed by MD simulations, small‐angle X‐ray scattering (SAXS), and FRET characterization. Furthermore, partial neutralization of the DNA backbone charges by chemical modification renders 6HB compact and insensitive to ions, suggesting an interplay between electrostatic and hydrophobic forces in the channels. This system provides a platform for understanding the structure–function relationship of biological channels and designing rules for the shape control of DNA nanostructures in biomedical applications.     

A New Strategy of Discretionarily Reconfigurable Actuators Based on Self-Healing Elastomers for Diverse Soft Robots

Actuators have shown great promise in many fields including soft robotics. Since reconfiguration allows actuators to change their actuation mode, it is considered a key characteristic for new-generation adaptive actuators. However, it remains a challenge to design simple and universal methods to fabricate actuators that can be reconfigured to allow diverse actuation modes. Here, a macroscopically discretionary healing-assembly strategy to fabricate reconfigurable soft actuators based on intrinsic self-healing poly(dimethylglyoxime-urethane) (PDOU) elastomers is developed. The PDOU elastomers with different degrees of crosslinking show different responsiveness to solvents, and are seamlessly healed. Crosslinked and non-crosslinked PDOU elastomers as building units are healing-assembled into actuators/robots with diverse actuation behaviors. Notably, the assembled actuators/robots are readily reprogrammed to exhibit multiple actuation modes by simply tailoring and reassembling without any external stimuli. This work paves a new, simple, powerful, and universal method to construct sophisticated soft robots.     

NIR Light-Triggered Shape Memory Polymers Based on Mussel-Inspired Iron–Catechol Complexes

Shape memory polymers (SMPs) with the permanent shape reconfiguration capability have received much research interest because they are capable of diversified tasks and the ability to work in conditions that required complex geometry. However, most of such SMPs are thermally triggered, which limits their applications. Inspired by reversible mussel adhesive protein chemistry, NIR light-triggered SMPs with the permanent shape reconfiguration capability are prepared. The polymer networks are constructed using biocompatible polyethylene glycol, which is crosslinked based on catechol–Fe³⁺ coordination. The polymer networks have a uniform network structure and exhibit a considerable one-way shape memory effect (1W-SME) as well as a good two-way shape memory effect (2W-SME) under stress conditions. Taking advantage of the dynamic nature of the catechol–Fe³⁺ coordination, the permanent shape of the polymers could be reconfigured. Moreover, the catechol–Fe³⁺ complexes have a broad absorption in the NIR window, which bestows the polymers with excellent NIR light-triggered SME. Further, the great potential of the obtained polymers in biomedical and electronic applications is presented. Owing to the NIR-triggered 1W-SME and the permanent shape reconfiguration capability, the polymer could be used as a personalizing vascular stent. Additionally, the polymer could be applied in light-driven switches based on the NIR light-triggered 2W-SME.     

Embedding and reconfiguration algorithms for service aggregation in network virtualization

Network virtualization and transmission quality optimization are promising techniques for future Internet. Previous researches on virtual network embedding focused on efficient utilization of network resources. In this paper, we present a virtual network embedding scheme that aims at improving the effect of transmission quality optimization. In order to enable more service benefit from optimization, the embedding algorithm presented in this paper follows the service aggregation embedding principle. We also develop a reconfiguration algorithm based on service aggregation and load balance. Simulation experiments demonstrate that the proposed algorithms can achieve good performance on service aggregation as well as efficient resource utilization. Copyright © 2014 John Wiley & Sons, Ltd.     

A Shared Buffer‐Constrained Topology Reconfiguration Scheme in Wavelength Routed Networks

The reconfiguration management scheme changes a logical topology in response to changing traffic patterns in the higher layer of a network or the congestion level on the logical topology. In this paper, we formulate a reconfiguration scheme with a shared buffer‐constrained cost model based on required quality‐of‐service (QoS) constraints, reconfiguration penalty cost, and buffer gain cost through traffic aggregation. The proposed scheme maximizes the derived expected reward‐cost function as well as guarantees the required flow's QoS. Simulation results show that our reconfiguration scheme significantly outperforms the conventional one, while the required physical resources are limited.     

基于国产SoPC平台的外部总线的设计与实现

可重构的SoC(system-on-a-chip)是嵌入式系统发展的一个重要方向,它不仅可以达到较高的性能而且更加的灵活.介绍了一种国产的SoPC(System on a Programmable Chip)平台,并基于此平台提出了一种用于重构计算的外部总线结构.通过该总线,可以通过改变不同的IP(intellectual property)核来组成新的系统.同时回顾总结了部分动态可重构的步骤并完成了一个完整的系统,最后给出了可重构系统的测试结果.     

异构无线网络中支持端到端重配置的资源管理技术

可重配置的异构网络是无线领域研究的一个热点问题。通过有效的资源管理,重配置技术可以实现对异构环境的灵活适应和对异构无线资源的有效利用。作为一种适变能力很强的技术,重配置可以使异构无线系统从目前的隔离状态走向互通与协同,真正实现网络融合。本文描述了异构网络重配置技术的产生背景和基本概念,对重配置研究中的一系列资源管理关键技术,包括动态网络规划与管理、联合无线资源管理和先进频谱管理,进行了系统的总结。     

A Fault Tolerant Technique for FPGAs

In this paper we present a fault tolerant (FT) technique for field programmable gate arrays (FPGAs) that is based on incrementally reconfiguring circuits and applications that have been previously placed and routed. Our technique targets both logic faults and interconnect faults, and our algorithms can be applied to either static or run-time reconfigurable FPGAs. The algorithm for reconfiguring designs in the presence of logic faults uses a matching technique. The matching technique requires no preplaced, spare logic resources and is capable of handling groups of faults. Experimental results indicate there is little or no impact on circuit performance for low numbers of reconfigured logic blocks. For interconnect faults, we present a rip-up and reroute strategy. Our strategy is based on reading back the FPGA configuration memory, so no netlist is required for rerouting around faulty resources. Experimental results indicate high incremental routability for low numbers of interconnect faults. We also lay the foundation for applying our approach to yield enhancement.     

The Erdős–Nagy theorem and its ramifications

Given a simple polygon in the plane, a flip is defined as follows: consider the convex hull of the polygon. If there are no pockets do not perform a flip. If there are pockets then reflect one pocket across its line of support of the polygon to obtain a new simple polygon. In 1934 Paul Erdős introduced the problem of repeatedly flipping all the pockets of a simple polygon simultaneously and he conjectured that the polygon would become convex after a finite number of flips. In 1939 Béla Nagy proved that if at each step only one pocket is flipped the polygon will become convex after a finite number of flips. The history of this problem is reviewed, and a simple elementary proof is given of a stronger version of the theorem. Variants, generalizations, and applications of the theorem of interest in computational knot theory, polymer physics and molecular biology are discussed. Several results in the literature are improved with the application of the theorem. For example, Grünbaum and Zaks recently showed that even non-simple (self-crossing) polygons may be convexified in a finite number of suitable flips. Their flips each take Θ(n²) time to determine. A simpler proof of this result is given that yields an algorithm that takes O(n) time to determine each flip. In the context of knot theory Millet proposed an algorithm for convexifying equilateral polygons in 3-dimensions with a generalization of a flip called a pivot. Here Millet's algorithm is generalized so that it works also in dimensions higher than three and for polygons containing edges with arbitrary lengths. A list of open problems is included.