Chiral pyridin-3-ones and pyridines: syntheses of enantiopure 2,4-disubstituted 6-hydroxy-1,6-dihydro-2H-pyridin-3-ones, 2,3-disubstituted 4-iodopyridines, and enantiopure 2,3-disubstituted 4-pyridinemethanols

The development of an innovative method to access enantiopure 2,4-disubstituted 6-hydroxy-1,6-dihydro-2H-pyridin-3-ones starting from D-glucal via the aza-Achmatowicz transformation has been described. These highly functionalized pyridin-3-ones have been utilized for the synthesis of contiguously substituted pyridines through a rapid and efficient Et(3)N/Ac(2)O promoted cyclo-elimination, aromatization cascade, allowing the facile assembly of important pyridine-based building blocks like 2-substituted 3-acetoxy-4-iodopyridines and enantiopure 2-substituted 3-acetoxy-4-pyridinemethanols possessing benzylic stereogenic centers, whose synthesis otherwise would be tedious. The utilization of commercially available sugars as starting materials, mild reaction conditions, catalytic transfer hydrogen (CTH) of α-furfuryl azide derivatives, transfer of chiral aryl/alkyl methanols from enulosides to pyridin-3-ones and pyridines, high yields, and short reaction times are key features of this method. The utility of the method has been further exemplified by demonstrating the usage of the 2-substituted 3-acetoxy-4-iodopyridine for the construction of biologically significant molecules like 2,7-disubstituted furo[2,3-c]pyridines and 7,7'-disubstituted 2,2'-bifuro[2,3-c]pyridines.     

Comparative study of two CPU router time management algorithms in cellular IP networks

Providing good quality of service (QoS) in cellular IP networks is an important requirement for performance improvement of the cellular IP network. Resource reservation is one of the methods used in achieving this goal and is proven to be effective. The main resources to be reserved in a cellular IP network are bandwidth, buffer and central processing unit (CPU) cycles. Router CPU cycle is the time taken by the router to process the packet of the flow before forwarding it to the next router (hop). This paper proposes a model for CPU cycle optimization of routers for real‐time flows in a cellular IP network. The model applies both genetic algorithm (GA) and particle swarm optimization (PSO) as soft computing tools to optimize the CPU cycles and reduces the flow processing time at each router in the route taken by a flow. Simulation experiments illustrate a comparative study of the model.     

A Weighted Feature Voting Approach for Robust and Real‐Time Voice Activity Detection

This paper concerns a robust real‐time voice activity detection (VAD) approach which is easy to understand and implement. The proposed approach employs several short‐term speech/nonspeech discriminating features in a voting paradigm to achieve a reliable performance in different environments. This paper mainly focuses on the performance improvement of a recently proposed approach which uses spectral peak valley difference (SPVD) as a feature for silence detection. The main issue of this paper is to apply a set of features with SPVD to improve the VAD robustness. The proposed approach uses a weighted voting scheme in order to take the discriminative power of the employed feature set into account. The experiments show that the proposed approach is more robust than the baseline approach from different points of view, including channel distortion and threshold selection. The proposed approach is also compared with some other VAD techniques for better confirmation of its achievements. Using the proposed weighted voting approach, the average VAD performance is increased to 89.29% for 5 different noise types and 8 SNR levels. The resulting performance is 13.79% higher than the approach based only on SPVD and even 2.25% higher than the not‐weighted voting scheme.     

Transient electroluminescence determination of carrier mobility and charge trapping effects in heavily doped phosphorescent organic light-emitting diodes

Transient electroluminescence (EL) was used to measure the delay between the excitation pulse and onset of emission in OLEDs based on phosphorescent bis[3,5-bis(2-pyridyl)-1,2,4-triazolato] platinum(ΙΙ) doped into 4,4′-bis(carbazol-9-yl) triphenylamine (CBP), from which an electron mobility of 3.2 × 10⁻⁶ cm²/V s was approximated. Delayed recombination was observed after the drive pulse had been removed and based on its dependence on frequency and duty cycle, ascribed to trapping and de-trapping processes associated with disorder-induced carrier localization at the interface between the emissive layer and electron blocker. The data suggests that the exciton recombination zone is at, or close to the interface between the emissive layer and electron blocker. Despite the charge trapping effects, a peak power efficiency of 24 lm/W and peak external quantum efficiency of 10.64% were obtained. Mechanisms for the electroluminescence and delayed recombination are proposed.     

Raman active jagged-shaped gold-coated magnetic particles as a novel multimodal nanoprobe

The creation of novel engineered multimodal nanoparticles (NPs) is a key focus in bionanotechnology and can lead to deep understanding of biological processes at the molecular level. Here, we present a multi-component system made of gold-coupled core-shell SPIONs, as a new nanoprobe with signal enhancement in surface Raman spectroscopy, due to its jagged-shaped gold shell coating.     

Efficient and stable panchromatic squaraine dyes for dye-sensitized solar cells

A new series of stable, unsymmetrical squaraine near-IR sensitizers (JK-216 and JK-217), which are assembled using both thiophenyl pyrrolyl and indolium groups, exhibit a panchromatic light harvesting up to 780 nm. The JK-216 based cell exhibited a record efficiency of 6.29% for near-IR DSSCs. In addition, the JK-217 device showed an excellent stability under a light soaking test at 60 °C for 1000 h.     

A novel single source precursor: [bis(N,N-diethyl-N'-naphthoyl-selenoureato)palladium(II)] for palladium selenide thin films and nanoparticles

We describe for the first time the use of a single source precursor to deposit thin films and nanocrystals of palladium selenide.     

New biocompatible thermo-reversible hydrogels from PNiPAM-decorated amyloid fibrils

New biocompatible temperature-responsive hydrogels have been obtained by using unprecedented low concentration of amyloid fibril-PNiPAM hybrids. The viscoelasticity of the hydrogels can be finely controlled by tuning the PNiPAM layers without changing the structure or concentration of the amyloid fibrils.     

Photoreactive gold(I) macrocycles with diphosphine and trans,trans-muconate ligands

A pair of trans,trans-muconate ligands have been successfully aligned in two novel Au(I) macrocycles by design from phosphino metal precursors that undergo photochemical cycloaddition reactions quantitatively, resulting in the formation of cyclooctadiene derivatives.     

The two spin states of an end-on copper(II)-superoxide mimic

The reaction of nitrosobenzene with copper(I) complexes of a tetradentate ligand led to two novel species that are best described as copper(II) complexes of an O-bonded nitrosobenzyl radical anion, in either the singlet or the triplet spin-state. Both states were characterized by crystal structures, magnetic measurements and DFT calculations.