Reversible Speed Regulation of Self-Propelled Janus Micromotors via Thermoresponsive Bottle-Brush Polymers

This work reports a reversible braking system for micromotors that can be controlled by small temperature changes (≈5 °C). To achieve this, gated-mesoporous organosilica microparticles are internally loaded with metal catalysts (to form the motor) and the exterior (partially) grafted with thermosensitive bottle-brush polyphosphazenes to form Janus particles. When placed in an aqueous solution of H₂O₂ (the fuel), rapid forward propulsion of the motors ensues due to decomposition of the fuel. Conformational changes of the polymers at defined temperatures regulate the bubble formation rate and thus act as brakes with considerable deceleration/acceleration observed. As the components can be easily varied, this represents a versatile, modular platform for the exogenous velocity control of micromotors.     

Conformational Space and Stability of ETD Charge Reduction Products of Ubiquitin

Owing to its versatility, electron transfer dissociation (ETD) has become one of the most commonly utilized fragmentation techniques in both native and non-native top-down mass spectrometry. However, several competing reactions—primarily different forms of charge reduction—occur under ETD conditions, as evidenced by the distorted isotope patterns usually observed. In this work, we analyze these isotope patterns to compare the stability of nondissociative electron transfer (ETnoD) products, specifically noncovalent c/z fragment complexes, across a range of ubiquitin conformational states. Using ion mobility, we find that more extended states are more prone to fragment release. We obtain evidence that for a given charge state, populations of ubiquitin ions formed either directly by electrospray ionization or through collapse of more extended states upon charge reduction, span a similar range of collision cross-sections. Products of gas-phase collapse are, however, less stabilized towards unfolding than the native conformation, indicating that the ions retain a memory of previous conformational states. Furthermore, this collapse of charge-reduced ions is promoted if the ions are ‘preheated’ using collisional activation, with possible implications for the kinetics of gas-phase compaction.

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Oxatriphyrins(2.1.1) Incorporating an ortho‐Phenylene Motif

An understanding of fundamental aspects of archetypal organic structural motifs remains a key issue faced by the experimental and theoretical chemists. Two possible bonding modes for a disubstituted benzene ring, that is a meta and para, determines the π delocalization for oligomeric structures. When the less abundant ortho‐substituted variant is introduced into a triphyrin(2.1.1) skeleton an aromatic molecule is obtained and the carbocyclic ring participates in the conjugation of the macrocycle. The two‐electron reduction and introduction of boron(III) changes the aromatic character and results in an anti‐aromatic structure which has been confirmed by single‐crystal analysis and supported by theoretical calculations.     

Stress control by micropits density variation in strained AlGaN/GaN/SiN/AlN/Si(111) heterostructures

AlGaN/GaN heterostructures were deposited on Si utilizing in‐situ SiN masking layer as a mean to decrease stress present in the final heterostructures. Structures were grown under different V/III ratio using metalorganic vapour phase epitaxy (MOVPE). Additional approach was applied to obtain crack‐free heterostructures which was deposition of 15 nm low temperature AlN interlayer. Each of the heterostructure contained GaN layer of 2.4 μm total thickness. In‐situ SiN masking layer were obtained via introduction of SiH4 precursor into reactor under high temperature growth conditions for 100 s. In that manner, few monolayers of SixNx masking layer were deposited, which due to the partial coverage of AlN, played role of a mask leading to initial 3D growth mode enhancing longer coalescence of GaN buffer layer. To study surface morphology AFM images were observed. Three methods were used in order to obtain basal plane stress present in multilayer structures ‐ MicroRaman spectroscopy, XRD studies and optical profilometry. It was found that varying V/III precursors ratio during GaN layer growth characteristic for structures with the SiN mask approach formation of triangular micropits can be minimized. Outcomes for three different methods turned out to be coherent. It was found that certain amount of micropits on the surface can be advantageous lowering stress introduced during cooling after process to the AlGaN/GaN/SiN/AlN/Si(111) structure.     

The impact of cigarette/e‐cigarette vapour on simulated pulmonary surfactant monolayers under physiologically relevant conditions

Deviation in pulmonary surfactant structure–function activity can impair airway patency and lead to respiratory disorders. This novel study aims to evaluate the influence cigarette/e‐cigarette vapour has on model surfactant films located within a simulated pulmonary environment using a lung biosimulator. Chromatographic analysis confirmed that nicotine levels were consistent with the sampling regimen employed. On exposure to smoke vapour, Langmuir isotherms exhibited condensed character and a significant reduction in maximum surface pressure was noted in all cases. Langmuir isocycles, reflective of the human breathing cycle, demonstrated condensed character on smoke vapour delivery. A reduction in the maximum surface pressure was clear only in the case of cigarette vapour application. The components of cigarette vapour can cause oxidative damage to pulmonary surfactant and impair recycling. Neutral nicotine molecules can weaken the structure of the monolayer and cause destabilisation. A protective effect was evident in the case of repeated surfactant compression – relaxation cycles (i.e. the ability to reduce the surface tension term was impaired less), demonstrating a likely innate biological defensive mechanism of the lung. E‐cigarette vapour appeared to have a reduced impact on surfactant performance, which may hold value in harm reduction over the longer term. Copyright © 2017 John Wiley & Sons, Ltd.     

Entropy-Based Combined Metric for Automatic Objective Quality Assessment of Stitched Panoramic Images

Quality assessment of stitched images is an important element of many virtual reality and remote sensing applications where the panoramic images may be used as a background as well as for navigation purposes. The quality of stitched images may be decreased by several factors, including geometric distortions, ghosting, blurring, and color distortions. Nevertheless, the specificity of such distortions is different than those typical for general-purpose image quality assessment. Therefore, the necessity of the development of new objective image quality metrics for such type of emerging applications becomes obvious. The method proposed in the paper is based on the combination of features used in some recently proposed metrics with the results of the local and global image entropy analysis. The results obtained applying the proposed combined metric have been verified using the ISIQA database, containing 264 stitched images of 26 scenes together with the respective subjective Mean Opinion Scores, leading to a significant increase of its correlation with subjective evaluation results.     

New Screening Protocol for Effective Green Solvents Selection of Benzamide,Salicylamide and Ethenzamide

New protocol for screening efficient and environmentally friendly solvents was proposed and experimentally verified. The guidance for solvent selection comes from computed solubility via COSMO-RS approach. Furthermore, solute-solvent affinities computed using advanced quantum chemistry level were used as a rationale for observed solvents ranking. The screening protocol pointed out that 4-formylomorpholine (4FM) is an attractive solubilizer compared to commonly used aprotic solvents such as DMSO and DMF. This was tested experimentally by measuring the solubility of the title compounds in aqueous binary mixtures in the temperature range between 298.15 K and 313.15 K. Additional measurements were also performed for aqueous binary mixtures of DMSO and DMF. It has been found that the solubility of studied aromatic amides is very high and quite similar in all three aprotic solvents. For most aqueous binary mixtures, a significant decrease in solubility with a decrease in the organic fraction is observed, indicating that all systems can be regarded as efficient solvent-anti-solvent pairs. In the case of salicylamide dissolved in aqueous-4FM binary mixtures, a strong synergistic effect has been found leading to the highest solubility for 0.6 mole fraction of 4-FM.     

Effect of graphite and common rubber plasticizers on properties and performance of ceramizable styrene–butadiene rubber-based composites

Journal of Thermal Analysis and Calorimetry - Ceramizable composites are highly filled polymer dispersion composites which create stiff porous and durable ceramic structure when exposed to fire or...