Aqueous Oxidative Heck Reaction as a Protein‐Labeling Strategy

An increasing number of chemical reactions are being employed for bio‐orthogonal ligation of detection labels to protein‐bound functional groups. Several of these strategies, however, are limited in their application to pure proteins and are ineffective in complex biological samples such as cell lysates. Here we present the palladium‐catalyzed oxidative Heck reaction as a new and robust bio‐orthogonal strategy for linking functionalized arylboronic acids to protein‐bound alkenes in high yields and with excellent chemoselectivity even in the presence of complex protein mixtures from living cells. Advantageously, this reaction proceeds under aerobic conditions, whereas most other metal‐catalyzed reactions require inert atmosphere.     

Improved Exciton Dissociation at Semiconducting Polymer:ZnO Donor:Acceptor Interfaces via Nitrogen Doping of ZnO

Exciton dissociation at the zinc oxide/poly(3‐hexylthiophene) (ZnO/P3HT) interface as a function of nitrogen doping of the zinc oxide, which decreases the electron concentration from approximately 10¹⁹ cm^?3 to 10¹⁷ cm^?3, is reported. Exciton dissociation and device photocurrent are strongly improved with nitrogen doping. This improved dissociation of excitons in the conjugated polymer is found to result from enhanced light‐induced de‐trapping of electrons from the surface of the nitrogen‐doped ZnO. The ability to improve the surface properties of ZnO by introducing a simple nitrogen dopant has general applicability.     

Microfluidic Thermally Activated Materials for Rapid Control of Macroscopic Compliance

Macroscopic structures that can undergo rapid and reversible stiffness transitions can serve as functional polymeric materials for many applications in robotics and medical devices. Thermomechanical phase transitions can provide a suitable mechanism for transient control of mechanical properties. However, the characteristic time scale for actuation is large and dictated by the dimensions of the structure. Embedding vascular networks within bulk polymers can reduce the characteristic length scale of the material and permit rapid and reversible thermomechanical transitions. Here, perfusable bulk materials with embedded microvascular networks are reported that can undergo rapid and reversible stiffness transitions. Acrylate‐based thermoplastic structures exhibit storage moduli with a dynamic range between E′ = 1.02 ± 0.07 GPa and E′ = 13.5 ± 0.7 MPa over time scales as small as 2.4 ± 0.5 s using an aqueous thermal perfusate. The spatiotemporal evolutions of temperature profiles are accurately predicted using finite element simulations and compared to experimental values. Rigid‐compliant transitions are leveraged in a demonstration in which a microvascularized device is used to grasp an external object without the aid of moving parts.     

Performance and Stability Enhancement of Dye‐Sensitized and Perovskite Solar Cells by Al Doping of TiO2

Reversible photo‐induced performance deterioration is observed in mesoporous TiO₂‐containing devices in an inert environment. This phenomenon is correlated with the activation of deep trap sites due to astoichiometry of the metal oxide. Interestingly, in air, these defects can be passivated by oxygen adsorption. These results show that the doping of TiO₂ with aluminium has a striking impact upon the density of sub‐gap states and enhances the conductivity by orders of magnitude. Dye‐sensitized and perovskite solar cells employing Al‐doped TiO₂ have increased device efficiencies and significantly enhanced operational device stability in inert atmospheres. This performance and stability enhancement is attributed to the substitutional incorporation of Al in the anatase lattice, “permanently” passivating electronic trap sites in the bulk and at the surface of the TiO₂.     

Generalized analysis of subcarrier multiplexing in dispersive fiber-optic links using Mach-Zehnder external modulator

A new exact analytical model is presented to analyze the dispersive transmission in subcarrier multiplexing (SCM) fiber-optic links using dual-drive Mach-Zehnder external modulator (DD-MZM). The model is very general and can be applied to almost all operating conditions of DD-MZM, such as bias point, drive level, phase shift, and modulation index difference between DD-MZM drives. The model results in simple, new, and closed-form expressions for output power spectrum, permitting an accurate and fast analysis of such links. Two special cases, double sideband (DSB) and single-sideband (SSB) modulation, are studied in detail. Some important system parameters, such as 1-dB compression point, the input third-order intercept point (IIP3), and the system capacity, are derived for the first time. Measured results for system capacity and intermodulation products of different orders match very well with the calculated results.     

Impacts of NBTI and PBTI on SRAM static/dynamic noise margins and cell failure probability

Negative and Positive Bias Temperature Instabilities (NBTI (in PFET) and PBTI (in NFET)) weaken MOSFETs with time. The impact of such device degradation can be severe in Static Random Access Memories (SRAMs) wherein stability is governed by relative strengths of FETs. Degradation in stability with time under ‘worst case condition’ gets more important because of reduced guard-banding due to process induced instability. In this work, circuit insights into worst-case conditions and effect of NBTI and PBTI, individually and in combination, on the stability of an SRAM cell are presented. It is shown that measurable quantities such as static noise-margin are not sufficient to completely understand the combined effect of NBTI and PBTI. Monte-Carlo simulations are performed in a 45 nm PDSOI technology to estimate the increase in cell failure probability with time. In worst case, NBTI and PBTI both degrade read stability (significantly) and writability (marginally). Further, we analyze the choice of optimal power supply considering the trade-off between short-term stability (due to process variations) and long-term stability (due to NBTI/PBTI) to achieve six-sigma confidence in SRAM cell robustness.     

Arsenic redistribution induced by low-temperature Ni silicidation at 450°C on shallow junctions

Redistribution of arsenic (As) during silicidation of a 13-nm Ni film on an n⁺/p junction at 450°C is investigated. NiSi formation is observed by x-ray diffraction, micro-Raman scattering spectroscopy, and Rutherford backscattering spectroscopy (RBS). Both secondary ion mass spectroscopy and RBS data indicate the redistribution and accumulation of As into two layers after the low-temperature annealing. The deeper accumulation peak, located just near the silicide/silicon interface, is attributed to As segregation from silicide into Si substrate. The shallower accumulation peak is located in a vacancy-cluster layer several nanometers below the silicide film surface. The vacancy-cluster layer, characterized by cross-sectional transmission electron microscopy, separates the silicide film into two layers, and is attributed to the well-known Kirkendall effect.     

Reliability Analysis for Degradation of Locomotive Wheels using Parametric Bayesian Approach

This paper undertakes a reliability study using a Bayesian survival analysis framework to explore the impact of a locomotive wheel's installed position on its service lifetime and to predict its reliability characteristics. The Bayesian Exponential Regression Model, Bayesian Weibull Regression Model and Bayesian Log‐normal Regression Model are used to analyze the lifetime of locomotive wheels using degradation data and taking into account the position of the wheel. This position is described by three different discrete covariates: the bogie, the axle and the side of the locomotive where the wheel is mounted. The goal is to determine reliability, failure distribution and optimal maintenance strategies for the wheel. The results show that: (i) under specified assumptions and a given topography, the position of the locomotive wheel could influence its reliability and lifetime; (ii) the Bayesian Log‐normal Regression Model is a useful tool. Copyright © 2013 John Wiley & Sons, Ltd.     

Tunable photonic microwave filter with Hi-Bi chirped grating free from chromatic dispersion

A tunable, stable, photonic microwave filter, using a linearly chirped grating in a double-pass configuration, is demonstrated to have a 45 dB notch rejection. This novel configuration overcomes chromatic dispersion and optical coherence interference.