Fault-tolerant analysis of TMR design with noise-aware logic

Due to the effect of thermal noise, ground bounce and process variations in nanometer process, the behavior of any logical circuit becomes increasingly probabilistic. In this paper, based on the noise model [5] on the input and output nodes of a probabilistic CMOS (PCMOS) gate, the correctness probabilities of four PCMOS primitive gates, NOT, NAND, NOR and XOR, can be firstly computed. Based on the concept of the probabilistic transfer matrices (PTMs) and the corresponding operations on PTMs for the serial and parallel compositions of the components in a well-formed circuit, the correctness probability of the output in a 3-input PCMOS majority circuit in a triple modular redundancy (TMR) design can be further computed. For a given circuit with smaller error, it is well known that a TMR design has good fault-tolerant characterization and the correctness probability of the original output is converged to 1. Under the use of noise-aware logic in a TMR design, it is obvious that the fault-tolerant characterization of a TMR design is degraded and the correctness probability of the original output is not converged to 1. The experimental results show that the improvement region of the correctness probability of the original output will be narrowed due to the noise effect on the gates in a 3-input PCMOS majority circuit.     

Stoichiometric aryl nitrile formation from amides and aroyl isocyanates using high-valent early transition metal complexes and a catalytic process from the aroyl isocyanates

Reaction of PhCONH₂ with [WCl₆] under reflux in benzene gives a near quantitative yield of [WOCl₄(NCPh)] (1) which can be prepared directly by the reaction of PhCN and [WOCl₄]. PhCONH₂ reacts with [WOCl₄] under reflux in benzene to give [WO₂Cl₂(NCPh)] (2) and with [NbCl₅] under similar conditions to give [NbOCl₃(NCPh)] (3). PhCONH₂ and TiCl₄ give [TiCl₄(NH₂COPh)₂] (4). Reaction of the aroyl isocyanate PhCONCO with [WOCl₄] gave [WOCl₄(NCPh)] (1) and 4-Me₃CPhCONCO and [WOCl₄] gave [WOCl₄(NCPhCMe₃-4)] (5). PhCONCO reacts catalytically with [WOCl₄] or [WOCl₄(NCPh)] to give quantitative yields of PhCN. Similarly, 4-Me₃CPhCONCO and 2-ClCPhCONCO react catalytically with [WOCl₄] to give complete conversion to 4-Me₃CPhCN and 2-ClCPhCN. DFT studies show structures and intermediates in support of a possible catalytic mechanism. This involves initial complexation followed by formation of a metallocycle from the WO bond and the CN bond of the isocyanate. Rearrangement and elimination of CO₂ leads to an amidate complex that undergoes C-O bond scission and O migration to the W atom to give PhCN bound to the WOCl₄ moiety in a cis arrangement. This complex is unstable with respect to dissociation which completes the catalytic cycle. The overall reaction WOCl₄ + PhC(O)NCO → WOCl₄·PhCN + CO₂ is exothermic (ΔH = −20.7 kJ mol⁻¹) and is favoured from free energy considerations (ΔG = −69.3 kJ mol⁻¹).     

Recent developments in polymer dynamics investigations of architecturally complex systems

The tube model for linear and branched architectures is nowadays able to predict in high precision the linear viscoelastic relaxation time spectrum. For linear chains, the involved time scales fit to the commonly accessible dynamic scattering techniques. This makes it possible to microscopically investigate the correlation between structures and relaxation processes. In branched systems, however, the hierarchical nature of relaxations limits direct investigation via these microscopic methods as the dynamic processes are prolongated to much longer relaxation times that are no more accessible to usual dynamic scattering methods. A way to overcome this difficulty is offered by the use of static small angle neutron scattering. Here, the combination of annealing and quenching steps after a step deformation provides unique information of the structure at particular times along the relaxation spectrum. This, however, necessitates the availability of architecturally clean and specifically deuterium labelled model polymers due to the sensitivity of the scattering method. Therefore, we outline in this contribution first the current status on the synthesis and analysis of such compounds with relation to neutron scattering. Secondly, we present exemplary neutron scattering results from in situ stress relaxation studies inside the neutron beam on linear and H-shaped branched polymers which were molecularly designed to highlight specific relaxation processes. We discuss the relevance of the tube model parameters in linear and non-linear studies.     

Polyzwitterionic brushes: Extreme lubrication by design

Polymers offer the advantage that they may independently combine desirable supramolecular structure with useful local monomeric properties to yield optimal performance of different tasks. Here we utilise the remarkable lubricating properties both of dense polymer brushes, and of hydration sheaths about charges via the emerging paradigm of hydration lubrication, to design a grafted-from polyzwitterionic brush system, where each of the monomers has a structure similar to the highly-hydrated phosphorylcholine headgroups of phosphatidylcholine lipids. Such polyzwitterions are grown from a macroinitiator coating the substrate (mica) surface using atom transfer radical polymerisation (ATRP) of 2-(methacryloyloxy)ethyl phosphorylcholine (MPC) to form exceptionally robust poly(MPC) brushes. We have characterized these brush layers via X-ray reflectometry, X-ray photoelectron spectroscopy, surface forces measurements and atomic force microscopy. Such brushes, designed to optimise their lubrication properties, are indeed found to provide state of the art boundary lubrication, achieving friction coefficients as low as 0.0004 at pressures up to 75 atmospheres over a wide range of sliding velocities. Such low friction is comparable with that of articular cartilage in healthy mammalian joints, which represents nature’s benchmark for boundary lubrication in living organisms, and suggests that hydration lubrication plays a major role in reducing friction in biological systems.     

Cucurbit[7]uril: Surfactant Host–Guest Complexes in Equilibrium with Micellar Aggregates

In order to compare the formation of host–guest complexes between β‐cyclodextrin (β‐CD) or cucurbit[7]uril (CB7) and cationic surfactants we studied the hydrolysis of 4‐methoxybenzenesulfonyl chloride (MBSC). The selected surfactants allowed the length of the hydrocarbon chain to be varied between 6 and 18 carbon atoms. Contrary to the expected behaviour, the values of the binding constants between CB7 and surfactants are independent of the alkyl chain length of the surfactant. In the case of β‐CD, however, a clear dependence of the binding constant on the hydrophobic character of the surfactant was observed. The values obtained with CB7 are significantly higher than those obtained with β‐CD and these differences are explained to be a consequence of electrostatic interactions of the surfactants with the portals of CB7. It was found that a small percentage of uncomplexed CB7 was in equilibrium with the cationic micelles and this percentage increased on increasing the hydrophobic character of the surfactant.     

Iodocyclization versus diiodination in the reaction of 3-alkynyl-4-methoxycoumarins with iodine: synthesis of 3-iodofuro[2,3-b]chromones

The reaction of 3-alkynyl-4-methoxycoumarins with molecular iodine in chlorinated solvents allows access to 3-iodofurochromones in good to excellent yields as the result of a iodocyclization-demethylation process. Competitive diiodination of the coumarin acetylene moiety could be eliminated by simply performing the reactions in refluxing 1,2-dichloroethane, owing to the thermal instability of the resulting (E)-1,2-diiodoethenylcoumarins.     

Indenyl ring slippage in crown thioether complexes [IndMo(CO)2L]+ and C-S activation of trithiacyclononane: experimental and theoretical studies

The macrocycle 1,4,7-trithiacyclononane (ttcn) reacts with [(η(5)-Ind)Mo(CO)(2)(NCMe)(2)](+) (or [(η(5)-Ind)Mo(CO)(2)(κ(2)-dme)](+)) to give [(η(3)-Ind)Mo(CO)(2)(κ(3)-ttcn)](+) as the BF(4)(-) salt (1), but its reaction with [(η(5)-Ind)Mo(CO)(2)(C(3)H(6))(FBF(3))] affords the C-S bond cleavage product [(η(5)-Ind)Mo(CO)(κ(3)-1,4,7-trithiaheptanate)]BF(4) (6), which has been characterised by X-ray crystallography (Ind = C(9)H(7), indenyl). In contrast to ttcn, the macrocycles 1,3,5-trithiane (tt) and 1,4,7,10-tetrathiacyclododecane (ttcd) fail to induce changes in the coordination mode of indenyl: tt and ttcd react with [(η(5)-Ind)Mo(CO)(2)(NCMe)(2)](+) (or [(η(5)-Ind)Mo(CO)(2)(κ(2)-dme)](+)) to give [(η(5)-Ind)Mo(CO)(2)(κ(2)-tt)](+) (2), characterised by X-ray crystallography, and [(η(5)-Ind)Mo(CO)(2)(κ(2)-ttcd)](+) (3), respectively. The cyclopentadienyl (Cp = C(5)H(5)) analogues [(η(5)-CpMo(CO)(2)(κ(2)-tt)](+) (4) and [(η(5)-CpMo(CO)(2)(κ(2)-ttcn)](+) (5) have also been synthesised and 5 characterised by X-ray crystallography. DFT calculations showed that the η(5)-Ind/Cp coordination mode is always the most stable. However, a molecular dynamics study of the macrocycles conformations revealed that the major conformer of ttcn was a chair, which favoured κ(3) coordination. As indenyl complexes undergo slippage with a small barrier (<10 kcal mol(-1)), the kinetically preferred species [(η(3)-Ind)Mo(CO)(2)(κ(3)-ttcn)](+) (1) is the observed one. The conversion to 6 proceeds stepwise, with loss of ethylene followed by loss of CO, as calculated by DFT, with a barrier of 38.7 kcal mol(-1), consistent with the slow uncatalysed reaction.     

Electrochemistry of P(CH2Fc)3 and derivatives

The oxidative electrochemistry of P(CH₂Fc)₃ and three of its derivatives was examined. The electrochemistry of these compounds is sensitive to the functionality added to the phosphorus lone pair and the supporting electrolyte used.