The Dynamics of the Neuropeptide Y Receptor Type 1 Investigated by Solid-State NMR and Molecular Dynamics Simulation

We report data on the structural dynamics of the neuropeptide Y (NPY) G-protein-coupled receptor (GPCR) type 1 (Y1R), a typical representative of class A peptide ligand GPCRs, using a combination of solid-state NMR and molecular dynamics (MD) simulation. First, the equilibrium dynamics of Y1R were studied using ¹⁵N-NMR and quantitative determination of ¹H-¹³C order parameters through the measurement of dipolar couplings in separated-local-field NMR experiments. Order parameters reporting the amplitudes of the molecular motions of the C-H bond vectors of Y1R in DMPC membranes are 0.57 for the Cα sites and lower in the side chains (0.37 for the CH₂ and 0.18 for the CH₃ groups). Different NMR excitation schemes identify relatively rigid and also dynamic segments of the molecule. In monounsaturated membranes composed of longer lipid chains, Y1R is more rigid, attributed to a higher hydrophobic thickness of the lipid membrane. The presence of an antagonist or NPY has little influence on the amplitude of motions, whereas the addition of agonist and arrestin led to a pronounced rigidization. To investigate Y1R dynamics with site resolution, we conducted extensive all-atom MD simulations of the apo and antagonist-bound state. In each state, three replicas with a length of 20 μs (with one exception, where the trajectory length was 10 μs) were conducted. In these simulations, order parameters of each residue were determined and showed high values in the transmembrane helices, whereas the loops and termini exhibit much lower order. The extracellular helix segments undergo larger amplitude motions than their intracellular counterparts, whereas the opposite is observed for the loops, Helix 8, and termini. Only minor differences in order were observed between the apo and antagonist-bound state, whereas the time scale of the motions is shorter for the apo state. Although these relatively fast motions occurring with correlation times of ns up to a few µs have no direct relevance for receptor activation, it is believed that they represent the prerequisite for larger conformational transitions in proteins.     

Switchable Polymerization Triggered by Fast and Quantitative Insertion of Carbon Monoxide into Cobalt–Oxygen Bonds

A strategy that uses carbon monoxide (CO) as a molecular trigger to switch the polymerization mechanism of a cobalt Salen complex [salen=(R,R)‐N,N′‐bis(3,5‐di‐tert‐butylsalicylidene)‐1,2‐cyclohexanediamine] from ring‐opening copolymerization (ROCOP) of epoxides/anhydrides to organometallic mediated controlled radical polymerization (OMRP) of acrylates is described. The key phenomenon is a rapid and quantitative insertion of CO into the Co?O bond, allowing for in situ transformation of the ROCOP active species (Salen)Co^III‐OR into the OMRP photoinitiator (Salen)Co^III‐CO₂R. The proposed mechanism, which involves CO coordination to (Salen)Co^III‐OR and subsequent intramolecular rearrangement via migratory insertion has been rationalized by DFT calculations. Regulated by both CO and visible light, on‐demand sequence control can be achieved for the one‐pot synthesis of polyester‐b‐polyacrylate diblock copolymers (?<1.15).     

Photochromic Free MOF‐Based Near‐Infrared Optical Switch

We demonstrate herein an all‐optical switch based on stimuli‐responsive and photochromic‐free metal–organic framework (HKUST‐1). Ultrafast near‐infrared laser pulses stimulate a reversible 0.4 eV blue shift of the absorption band with up to 200 s^?1 rate due to dehydration and concomitant shrinking of the structure‐forming [Cu₂C₄O₈] cages of HKUST‐1. Such light‐induced switching enables the remote modulation of intensities of photoluminescence of single crystals of HKUST‐1 as well visible radiation passing through the crystal by 2 order of magnitude. This opens up the possibility of utilyzing stimuli‐responsive MOFs for all‐optical data processing devices.     

A Photochemical/Thermal Switch Based on 4,4′-Bis(benzimidazolio)stilbene: Synthesis and Supramolecular Properties.

Stilbene derivatives are well-recognised substructures of molecular switches based on photochemically and/or thermally induced (E)/(Z) isomerisation. We combined a stilbene motif with two benzimidazolium arms to prepare new sorts of supramolecular building blocks and examined their binding properties towards cucurbit[n]urils (n=7, 8) and cyclodextrins (β-CD, γ-CD) in water. Based on the ¹H NMR data and molecular dynamics simulations, we found that two distinct complexes with different stoichiometry, i. e., guest@β-CD and guest@β-CD₂, coexist in equilibrium in a water solution of the (Z)-stilbene-based guests. We also demonstrated that the bis(benzimidazolio)stilbene guests can be transformed from the (E) into the (Z) form via UV irradiation and back via thermal treatment in DMSO.     

SEROS – A SELF-ROUTING OPTICAL ATM SWITCH

A fault-tolerant high-performance SElf-Routing 2 × 2 Optical ATM Switch (SEROS) is proposed. The switch is designed using all-optical components which allows the exploitation of spatial parallelism. SEROS can be used with any multistage interconnection network such as Omega, Banyan, Shuffle or Benes. For the purpose of this study, SEROS has been incorporated into a generic self-routing multistage interconnection network that uses 2 × 2 switches and is not fault tolerant. Reliability analysis is carried out and the results are compared with two major fault-tolerant networks. They show that without redundant switches, better network survivability is achieved. All the switches in the network are 2 × 2, making it easier to mass produce.     

FAULT-TOLERANT DESIGN OF BATCHER–BANYAN CLASS ATM SWITCHES

Many proposed packet switching systems for high-speed networks have employed the Batcher–banyan fabric due to its modular structure, self-routeing functionality, and distributed conflict-resolving mechanism. In this paper, we present a systematic fault-tolerant design for the Batcher–banyan class of switches. Our first concern is the development of an on-line error detection mechanism which is the prerequisite of any effective fault tolerant operation. Based on the technique developed by Davis, we propose a general fault-testing technique and verify it for a variety of unique-path self-routeing networks. Furthermore, we extend this method to Batcher sorting networks and construct a fault-tolerant Batcher sorter. Lastly, after contemplating the technique constraints and system performance, we deploy the above techniques into different levels of the Batcher–banyan networks and achieve a fault-tolerant version of the StarBurst switch, a member of the Batcher–banyan class of switches.     

PERFORMANCE ANALYSIS OF THE N × N NON-BLOCKING PACKET SWITCH WITH M/M/C PATH AT HEAD-OF-LINE

This paper focuses on a general model M/M/C queue for the switch path application, solving the case when packets at the head-of-line position have the same destination. These packets can pass through C paths to the same output port simultaneously. There are two types of service: the first in first out (FIFO) and the random order of service (ROS). Research concludes that among three switching paths, the response time of the FIFO type, under 70 per cent load condition, is better than that of the ROS type by 10 per cent. The theory of the binary hypercube is also used as a model for finding the steady-state probability (P₀₀₀) in the case of zero packets in the system. Using P₀₀₀ to determine performance, the authors’ proposed approach is shown to be superior to previously suggested methods.     

基于开关信号理论的电流型CMOS多值施密特电路设计

以开关信号理论为指导,建立了描述电流型CMOS多值施密特电路中阈值控制电路的电流传输开关运算.在此基础上,提出了新的电流型CMOS三值和四值施密特触发器设计.所设计的电路可提供多值电流和电压输出信号,回差电流的大小只需通过改变MOS管的尺寸比来调节.所提出的电路较之以往设计具有结构简单,回差值调整容易以及可在较低电压下工作等特点.采用TSMC 0.25 μ m CMOS工艺参数和1.5V电压的HSPICE模拟结果验证了所提出设计方案的有效性和电路所具有的理想回差特性.     

吉林移动核心网组网方案

本文简要描述了软交换设备在移动网中的应用,并就吉林移动采用软交换设备组网方案给出应用分析.同时简单介绍了上海贝尔阿尔卡特软交换设备的体系、硬件组成及特点.     

转换开关不完全可靠的热贮备系统可靠性模型

针对n台可靠度负指数分布的设备组成的热贮备系统,其中转换开关的可靠度或者是常数或者是负指数分布的情况,建立了转换开关不完全可靠的热贮备系统可靠性模型。并通过对系统平均寿命的分析,提出n≤4为宜的结论。