Prefix synchronised RLL sequences: variable-length graph model

The generation of the prefix synchronised RLL sequence is described by the variable-length graph model. This model leads to a regular structure of adjacency matrix, leading to simple calculations for the channel capacity and the channel sequence power spectral density.<>     

Performance analysis of SSC diversity receiver over correlated Ricean fading channels in presence of co-channel interference

A novel infinite-series-based approach for the performance analysis of a dual-branch switched-and-stay combining (SSC) diversity receiver operating over Ricean correlated fading channels in the presence of correlated Nakagami-m distributed co-channel interference (CCI) is presented. The performance analysis is based on outage probability (P_out) and average bit error probability (ABEP) criteria.     

Fluorescent Isoindole Crosslink (FlICk) Chemistry: A Rapid,User‐friendly Stapling Reaction

The stabilization of peptide secondary structure via stapling is a ubiquitous goal for creating new probes, imaging agents, and drugs. Inspired by indole‐derived crosslinks found in natural peptide toxins, we employed ortho‐phthalaldehydes to create isoindole staples, thus transforming inactive linear and monocyclic precursors into bioactive monocyclic and bicyclic products. Mild, metal‐free conditions give an array of macrocyclic α‐melanocyte‐stimulating hormone (α‐MSH) derivatives, of which several isoindole‐stapled α‐MSH analogues (K_i≈1 nm ) are found to be as potent as α‐MSH. Analogously, late‐stage intra‐annular isoindole stapling furnished a bicyclic peptide mimic of α‐amanitin that is cytotoxic to CHO cells (IC₅₀=70 μm ). Given its user‐friendliness, we have termed this approach FlICk (fluorescent isoindole crosslink) chemistry.     

Elucidating Solvent Effects on Strong Intramolecular Hydrogen Bond: DFT-MD Study of Dibenzoylmethane in Methanol Solution

The dynamic aspect of solvation plays a crucial role in determining properties of strong intramolecular hydrogen bonds since solvent fluctuations modify instantaneous hydrogen-bonded proton transfer barriers. Previous studies pointed out that solvent-solute interactions in the first solvation shell govern the position of the proton but the ability of the electric field due to other solvent molecules to localize the proton remains an important issue. In this work, we examine the structure of the O−H⋅⋅⋅O intramolecular hydrogen bond of dibenzoylmethane in methanol solution by employing density functional theory-based molecular dynamics and quantum chemical calculations. Our computations showed that homogeneous electric fields with intensities corresponding to those found in polar solvents are able to considerably alter the proton transfer barrier height in the gas phase. In methanol solution, the proton position is correlated with the difference in electrostatic potentials on the oxygen atoms of dibenzoylmethane even when dibenzoylmethane-methanol hydrogen bonding is lacking. On a timescale of our simulation, the hydrogen bonding and solvent electrostatics tend to localize the proton on different oxygen atoms. These findings provide an insight into the importance of the solvent electric field on the structure of a strong intramolecular hydrogen bond.     

C.P.S.K. receiver performances in presence of carrier-frequency offset

Error probability in a binary c.p.s.k. receiver with a carrier-frequency offset is studied. The error probability has been evaluated as a function of the p.l.l. bandwidth. The optimum value of the p.l.l. bandwidth for a given frequency offset is determined with and without the slow Rice fading.     

Elementary events of electron transfer in a voltage-driven quantum point contact

We find that the statistics of electron transfer in a coherent quantum point contact driven by an arbitrary time-dependent voltage is composed of elementary events of two kinds: unidirectional one-electron transfers determining the average current and bidirectional two-electron processes contributing to the noise only. This result pertains at vanishing temperature while the extended Keldysh-Green's function formalism in use also enables the systematic calculation of the higher-order current correlators at finite temperatures.     

A Lyapunov-Krasovskii stability analysis for game-theoretic based power control in optical links

We analyze the stability of a game-theoretic based power control algorithm for optical links in the presence of time-delays. The control objective is to achieve optimal optical signal to noise ratio (OSNR) values for the signal channels. The control algorithms regularly adjust the signal powers entering the link based on a game-theoretic model. Each signal power is modeled as a player, whose goal is to maximize its own utility function. The utility function increases with an increasing OSNR value, and hence requires an increasing signal power. The trade-off is that if one player increases its OSNR value, this adversely affects the OSNR values of all of the other players. In addition to the signal powers, a dynamic price parameter is fed back to the power control algorithms. Time-delay is present for both the channel pricing parameter and the OSNR feedbacks in the link. We study the stability of the closed-loop, time-delay system. The work utilizes singular perturbation theory modified to handle Lyapunov-Krasovskii techniques.     

Performance analysis of dual switched diversity over correlated Weibull fading channels with co‐channel interference

This paper studies the performance of switch and stay combining (SSC) diversity in the presence of co‐channel interference over correlated Weibull fading channels. SSC diversity based on signal‐to‐interference ratio (SIR) is a low‐complexity and a very efficient technique that reduces fading and co‐channel interference influence. New closed‐form expressions for the probability density function and cumulative distribution function of the output SIR's are derived. These formulas are used in a detailed analysis of the average output SIR and outage probability. The influence of fading severity and correlation coefficient on the optimum switching threshold and system performance is investigated. Monte Carlo simulations are performed to verify obtained theoretical results and determine average bit error rate in detecting binary phase‐shift keying (BPSK), differential BPSK and quadrature amplitude modulation signals. Copyright © 2011 John Wiley & Sons, Ltd.