Supersonic COIL with angular jet singlet oxygen generator

Supersonic Chemical Oxy-iodine Laser has been developed using a Singlet Oxygen Generator (SOG) with a novel approach. Generated singlet oxygen is taken out of the SOG at an angle of 40° to avoid the problem of carry over of droplets, which is one of the major drawbacks of horizontal system. The system has been operated up to 22 mmol/s chlorine flow rates. Chlorine utilization and singlet oxygen observed have been more than 90% and 60%, respectively. The observed maximum output power was 350 W, thus yielding a chemical efficiency of 17.5%.     

Stiffness measurement of nanosized liposomes using solid‐state nanopore sensor with automated recapturing platform

This paper describes a method to gauge the stiffness of nanosized liposomes – a nanoscale vesicle – using a custom‐made recapture platform coupled to a solid‐state nanopore sensor. The recapture platform electrically profiles a given liposome vesicle multiple times through automated reversal of the voltage polarity immediately following a translocation instance to re‐translocate the same analyte through the nanopore – provides better statistical insight at the molecular level by analyzing the same particle multiple times compared to conventional nanopore platforms. The capture frequency depends on the applied voltage with lower voltages (i.e., 100 mV) permitting higher recapture instances than at higher voltages (>200 mV) since the probability of particles exiting the nanopore capture radius increases with voltage. The shape deformation was inferred by comparing the normalized relative current blockade ( at the two voltage polarities to that of a rigid particle, i.e., polystyrene beads. We found that liposomes deform to adopt a prolate shape at higher voltages. This platform can be further applied to investigate the stiffness of other types of soft matters, e.g., virus, exosomes, endosomes, and accelerate the potential studies in pharmaceutics for increasing the drug packing and unpacking mechanism by controlling the stiffness of the drug vesicles.     

Air separation by single wall carbon nanotubes: thermodynamics and adsorptive selectivity

Separation of a nitrogen-oxygen mixture (air) by single wall carbon nanotubes has been studied using grand canonical Monte Carlo simulations at a range of nanotube diameters, temperatures, and pressures. It is demonstrated that depending on these operating parameters, the extent of adsorptive selectivity can vary significantly. Detailed calculations are also presented for the adsorption isotherms, energies, and isosteric heats of pure nitrogen, oxygen, and their mixture at 100 K in a carbon nanotube of 12.53-A diameter. In single-component simulations, it is found that near saturation loading nitrogen forms only an annular layer close to the nanotube wall, while smaller-sized oxygen also occupies the region near the center of the nanotube. In mixture adsorption, the energetically favored nitrogen is preferentially adsorbed at low loadings. However, at high loadings oxygen replaces nitrogen due to the dominant entropic effects, and therefore a high selectivity towards oxygen is observed close to the saturation loading. The effect of the entropic change on mixture adsorption is evident from the calculated isosteric heats of adsorption. The mixture isotherms obtained from simulations are found to be in good agreement with the predictions based only on the pure component simulation results.     

Biodegradability of polylactide bottles in real and simulated composting conditions

As new biodegradable polymers and their packaging applications are emerging, there is a need to address their environmental performance. In particular, there is a need to understand the time required for their complete disintegration, before these materials are deployed in commercial composting processes. Standards developed by ASTM and ISO evaluate the biodegradation of biodegradable plastic materials in simulated controlled composting conditions. However, a more detailed understanding of the biodegradation of complete packages is needed in order to have a successful composting operation. This paper investigates the biodegradation performance of polylactide (PLA) bottles under simulated composting conditions according to ASTM and ISO standards, and these results are compared with a novel method of evaluating package biodegradation in real composting conditions. Two simulated composting methods were used in this study to assess biodegradability of PLA bottles: (a) a cumulative measurement respirometric (CMR) system and (b) a gravimetric measurement respirometric (GMR) system. Both CMR and GMR systems showed similar trends of biodegradation for PLA bottles and at the end of the 58th day the mineralization was 84.2±0.9% and 77.8±10.4%, respectively. PLA bottle biodegradation in real composting conditions was correlated to their breakdown and variation in molecular weight. Molecular weight of 4100 Da was obtained for PLA bottles in real composting conditions on the 30th day. The biodegradation observed for PLA bottles in both conditions explored in this study matches well with theoretical degradation and biodegradation mechanisms; however, biodegradation variability exists in both conditions and is discussed in this paper.     

Nanoporous carbon membranes for separation of nitrogen and oxygen: Insight from molecular simulations

Here we summarize some of our recent work on using molecular simulations to understand the key mechanism that result in large differences in the reported permeation rates of O₂ and N₂ in nanoporous carbon membranes. Two different representation of the amorphous nanoporous membrane structure are used; the hypothetical C₁₆₈ Schwarzite and a single wall carbon nanotube with a constriction. By comparing the results obtained from empirical planar graphite potential and an ab initio-based potential, the effect of carbon curvature and the presence of non-hexagonal carbon rings in C₁₆₈ Schwarzite is also investigated. It is found using either force field, that the energetic effect alone cannot explain the experimental observations. However, simulations performed using carbon nanotube with a constriction show that the size or entropic effect can be dominant. In particular, it is shown that an appropriate size constriction can result in large transport resistance to nitrogen while letting oxygen to pass through at a much higher rate, even though these gases have very similar molecular sizes and interaction energetics.     

Recent development in transition metal-catalysed C–H olefination

Transition metal-catalysed functionalizations of inert C–H bonds to construct C–C bonds represent an ideal route in the synthesis of valuable organic molecules. Fine tuning of directing groups, catalysts and ligands has played a crucial role in selective C–H bond (sp² or sp³) activation. Recent developments in these areas have assured a high level of regioselectivity in C–H olefination reactions. In this review, we have summarized the recent progress in the oxidative olefination of sp² and sp³ C–H bonds with special emphasis on distal, atroposelective, non-directed sp² and directed sp³ C–H olefination. The scope, limitation, and mechanism of various transition metal-catalysed olefination reactions have been described briefly.

Transition metal-catalysed functionalizations of inert C–H bonds to construct C–C bonds represent an ideal route in the synthesis of valuable organic molecules.     

Picone’s identity for biharmonic operators on Heisenberg group and its applications

In this paper, we establish a nonlinear analogue of Picone’s identity for biharmonic operators on Heisenberg group. As an applications of Picone’s identity, we obtain Hardy-Rellich type inequality, Morse index, Caccioppoli inequality, Picone inequality for biharmonic operators on Heisenberg group.     

Dry sliding wear behavior of Al-SiO2 composites

Abstract

Al-base composites with different amount of silica (5, 10, 15 and 20 wt.%) were developed using powder metallurgy route and compacts were sintered at 550 °C for 2 h. XRD analysis of all compositions was conducted for phases and amount of the second phase present. Morphology of the composites shows quite uniform distribution of the SiO₂ particles but at higher percentage of SiO₂ particles the clustering starts. Mechanical properties such as uniaxial compressive strength (UCS) and hardness were evaluated and it is seen that among all compositions, composite with 10 wt.% SiO₂ has maximum UCS and hardness. Wear behavior of all composites was studied with sliding distance, applied loads, sliding velocity and composition. All composites show a linear increase in cumulative wear with distance and load. Wear rate with load increases continuously for all compositions, however, composite with 10 wt.% SiO₂ revealed minimum wear rate with distance, sliding velocity and loads. Wear rate with sliding velocity increases sharply after attaining minima at 3 m/s sliding velocity. SEM analysis of wear tracks is in agreement with wear results. Al-10 wt.%SiO₂ also shows minimum wear coefficient values for all loads, however, wear coefficient decreases with load for all compositions.     

Guest Binding with Sulfated Cyclodextrins: Does the Size of Cavity Matter?

Sulfated cyclodextrins have recently emerged as potential candidates for producing host–induced guest aggregation with properties better than p-sulfonatocalixarenes that have previously shown numerous applications involving the phenomena of host-induced guest aggregation. In the class of sulfated cyclodextrins (SCD), sulfated β-cyclodextrin (β-SCD) remains the most extensively investigated host molecule. Although it is assumed that the host-induced guest aggregation is predominantly an outcome of interaction of the guest molecule with the charges on the exterior of SCD cavity, it has not been deciphered whether the variation in the cavity size will make a difference in the efficiency of host-induced guest-aggregation process. In this investigation, we present a systematic study of host–induced guest aggregation of a cationic molecular rotor dye, Thioflavin T (ThT) with three different sulfated cyclodextrin molecules, α-SCD, β-SCD and γ-SCD, which differ in their cavity size, using steady-state emission, ground-state absorption and time-resolved emission measurements. The obtained photophysical properties of ThT, upon interaction with different SCD molecules, indicate that the binding strength of ThT with different SCD molecules correlate with the cavity size of the host molecule, giving rise to the strongest complexation of ThT with the largest host molecule (γ-SCD). The binding affinity of ThT towards different host molecules has been supported by molecular docking calculations. The results obtained are further supported with the temperature and ionic strength dependent studies performed on the host-guest complex. Our results indicate that for host–induced guest aggregation, involving oppositely charged molecules, the size of the cavity also plays a crucial role beside the charge density on the exterior of host cavity.     

Attractions, water structure, and thermodynamics of hydrophobic polymer collapse

We explore the prospects of a perturbation approach for predicting how weak attractive interactions affect collapse thermodynamics of hydrophobic polymers in water. Specifically, using molecular dynamics simulations of model polymers in explicit water, we show that the hydration structure is sensitive to the strength of the van der Waals attractions but that the hydration contribution to the potential of mean force for collapse is not. We discuss how perturbation theory ideas developed for small spherical apolar solutes need to be modified in order to account for the effect of attractions on the conformational equilibria of polymers.