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.     

Performance analysis of selection diversity over exponentially correlated α– µ fading environment

An approach to the performance analysis of multibranch selection combiner (SC) receiver operating over fading channels is presented. High level of generality for the proposed analysis is achieved by considering correlated α– µ fading environment. The effect of correlation is studied by assuming exponential correlation model of the signals in each diversity branch. The whole analysis is observed in the interference‐limited fading environments (SIR‐based diversity system is assumed). The important performance measures are considered. Closed form of formulae for the output SIR's probability density function and cumulative distribution function are derived. In order to check the accuracy of the complete proposed formulation, some numerical results are presented. Copyright © 2011 John Wiley & Sons, Ltd.     

Performance analysis of system with L‐branch selection combining over correlated Weibull fading channels in the presence of cochannel interference

In this paper, the performance of L‐branch selection combining receiver over correlated Weibull fading channels in the presence of correlated Weibull‐distributed cochannel interference is analyzed. Closed‐form expressions for probability density function and cumulative distribution function of the signal‐to‐interference ratio at the output of the selection combining receiver present main contribution of this paper. Numerical results are also presented to show the effects of various parameters as the fading severity, correlation and number of branches on outage probability. Copyright © 2009 John Wiley & Sons, Ltd.     

Performance of Dual Branch SSC Receiver in Correlated <Emphasis Type="Italic">α</Emphasis>-<Emphasis Type="Italic">μ</Emphasis> Fading Channels

In this paper, the performance analysis of dual branch switch and stay combining (SSC) receivers operating over correlated and identically distributed (i.d.) α-μ fading channels is presented. Assuming this diversity technique, infinite series expressions with fast converging properties are derived for the probability density function (pdf), cumulative distribution function (cdf) and the moments of the output envelope. The proposed analysis is used for evaluating the important performance criteria, such as the outage probability, the mean square output envelope, the amount of fading and the average bit error probability (ABEP). The effects of fading severity, branch correlation and optimum choice of switching threshold are considered and numerically presented. Monte Carlo simulations confirm the validity and accuracy of the derived analytical expressions.     

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.     

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.     

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.