Base‐Pairing Behavior of a Carbocyclic Janus‐AT Nucleoside Analogue Capable of Recognizing A and T within a DNA Duplex

Janus‐type nucleosides are heterocycles with two faces, each of which is designed to complement the H‐bonding interactions of natural nucleosides comprising a canonical Watson–Crick base pair. By intercepting all of the hydrogen bonds contained within the base pair, oligomeric Janus nucleosides are expected to achieve sequence‐specific DNA recognition through the formation of J‐loops that will be more stable than D‐loops, which simply replaces one base‐pair with another. Herein, we report the synthesis of a novel Janus‐AT nucleoside analogue, J_AT, affixed on a carbocyclic analogue of deoxyribose that was converted to the corresponding phosphoramidite. A single J_AT was successfully incorporated into a DNA strand by solid phase for targeting both A and T bases, and characterized through biophysical and computational methods. Experimental UV‐melting and circular dichroism data demonstrated that within the context of a standard duplex, J_AT associates preferentially with T over A, and much more poorly with C and G. Density functional theory calculations confirm that the J_AT structure is well suited to associate only with A and T thereby highlighting the importance of the electronic structure in terms of H‐bonding. Finally, molecular dynamics simulations validated the observation that J_AT can substitute more effectively as an A‐analogue than as a T‐analogue without substantial distortion of the B‐helix. Overall, this new Janus nucleotide is a promising tool for the targeting of A–T base pairs in DNA, and will lead to the development of oligo‐Janus‐nucleotide strands for sequence‐specific DNA recognition.     

Oblique Vortex Lattice Implies Unconventional Pairing Symmetry in High Temperature Superconductors

The symmetry of order parameters of YBa₂Cu₃O_{7 –} high temperature superconductor was studied with the Ginzburg–Landau theory. The vortex lattice of a YBa₂Cu₃O₇ superconductor is oblique at a temperature well below the transition temperature T _c, where the mixed s– state is expected to have the lowest energy, whereas very close to T _c, the -wave is slightly lower in energy, and a triangular vortex lattice recovers. The coexistence and the coupling between the s- and d-waves would account for the unusual behaviors such as the upward curvature of the upper critical field curve H _C2(T).     

A Novel Approach to the Polaronic Metallic State of Cuprate Superconductors and the d-Wave Pairing Mechanism

The present novel approach consists of two stages: in the first stage the many-electron states of a CuO₆ octahedron or a CuO₅ pyramid are calculated by the first-principles variational method, by taking into account the local distortions of a CuO₆ octahedron or a CuO₅ pyramid. In the second stage a metallic state is constructed in the presence of the local AF ordering constructed by the localized spins. In this metallic state the local distortions are treated in the mean field approximation, so that a pseudopolaronic effect is taken into account. Based on this approach, the hole-concentration dependence of T _c and the isotope effect are calculated for LSCO, and compared with experimental results. This approach leads to d-wave pairing mechanism.     

基于Tate对的指定多接收者签密方案

借鉴身份签密理论，利用超奇异椭圆曲线上Tate对的特性，提出一种高效指定多接收者签密方案，为具有多名合法接收者的签名问题提供了解决途径，此方案不仅保持了基于身份加密的优点，具有签名多向性，而且其抗攻击性好，执行效率高，整个签密过程只需1次Tate对计算，随着指定接收者人数的增多，方案的效率优势会更加明显。     

Hardware architectures for the Tate pairing over GF(2)

In this paper two different approaches to the design of a reconfigurable Tate pairing hardware accelerator are presented. The first uses macro components based on a large, fixed number of underlying Galois Field arithmetic units in parallel to minimise the computation time. The second is an area efficient approach based on a small, variable number of underlying components. Both architectures are prototyped on an FPGA. Timing results for each architecture with various different design parameters are presented.     

基于身份的代理盲签名方案

盲签名和代理签名在密码学中有各自的特殊用途。结合二者的优点，利用椭圆曲线上的Weil配对的双线性性质，在基于身份的签名基础上构造了一种新型基于身份的代理盲签名方案。该方案以身份为基础的公钥取代数字证书形式的公钥，省略了验证签名时从系统中获得公钥的步骤．减少了交互次数和运算量并有效的阻止了签名人伪造代理人签名从而保护了代理人的权益。最后对该方案的安全性进行了全面分析．从而证明了该方案是可行的。     

基于双线性映射的多重签名方案

双线性映射作为一种构建密码体制的新工具,在密码学领域中引起了普遍的关注.基于双线性映射提出两种新的多重签名方案,由于多重签名方案是以双线性对为工具构造的,所以密钥长度和签名长度比用其它方法构造的签名要短,该方案的实现是高效的.在CDH和DLP问题的安全假设下,这两种方案是安全的.     

Impact of continuous versus intermittent CS-UCS pairing on human brain activation during Pavlovian fear conditioning.

During Pavlovian fear conditioning a conditioned stimulus (CS) is repeatedly paired with an aversive unconditioned stimulus (UCS). In many studies the CS and UCS are paired on every trial, whereas in others the CS and UCS are paired intermittently. To better understand the influence of the CS-UCS pairing rate on brain activity, the experimenters presented continuously, intermittently, and non-paired CSs during fear conditioning. Amygdala, anterior cingulate, and fusiform gyrus activity increased linearly with the CS-UCS pairing rate. In contrast, insula and left dorsolateral prefrontal cortex responses were larger during intermittently paired CS presentations relative to continuously and non-paired CSs. These results demonstrate two distinct patterns of activity in disparate brain regions. Amygdala, anterior cingulate, and fusiform gyrus activity paralleled the CS-UCS pairing rate, whereas the insula and dorsolateral prefrontal cortex appeared to respond to the uncertainty inherent in intermittent CS-UCS pairing procedures. These findings may further clarify the role of these brain regions in Pavlovian fear conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Group-based user pairing for virtual MIMO in LTE

A user pairing method is proposed to improve the throughput gain of virtual multiple input multiple output (virtual MIMO) in 3G long-term evolution (LTE).The approach taken in this study separated the user pairing into four steps 1) the users are divided into two groups according to their signal-to-noise ratio (SNR), and different user pairing metrics are proposed for each group; 2) the scheduler chooses a user for transmitting by a given rule; 3) the scheduler searches the pairing candidate for the selected user in each group; 4) the scheduler chooses the final pairing user from the co-group and crossover-group candidates by using a marginal utility function, to balance fairness and efficiency.The method can improve the throughput of users with high SNR, and guarantee fairness for users with low SNR, so it can be used in 3G LTE systems.The article provides both theoretical analysis and simulation results to support the idea.     

基于身份的安全组播密钥协商

如何有效地进行密钥管理是安全组播的难点。在Wang等人所做工作的基础上，提出了一个新的基于身份的密钥协商方案，分析了子组之间的通信过程，以及组成员动态变化时密钥的更新过程，结果表明该方案满足密钥协商安全性要求，且在降低计算和通信代价方面取得了较好的效果。