Estimation of zeta potentials of titania nanoparticles by molecular simulation

Non-equilibrium molecular dynamics (NEMD) simulations have been performed for static electric fields for a range of positively charged spherical rutile-titania nanoparticles with radii of 1.5 to 2.9 nm for two different salt concentrations in water, in order to simulate electrophoresis directly. Using the observed limiting drag velocities, Helmholtz-Smoluchowski (HS) theory was used to estimate their ζ potentials. These estimates were compared to values from numerical solution of the non-linear Poisson-Boltzmann (PB) equation for representative configurations of the nanoparticles, in addition to idealised analytic and Debye-Hückel (DH) solutions about spherical particles of the same geometry and charge state, for the given salt concentrations. It was found that reasonable agreement was obtained between the various approaches, with the NEMD-HS results some 15%-15% smaller than the numerical PB results for more highly charged nanoparticles.     

Analysis of charged device model (CDM) ESD in MEMS

The effect of charge injection due to CDM ESD in capacitive MEMS structures is analyzed. The results show that as feature size is reduced, ESD injected charge produces a change for the stiction effect which is inversely proportional to the square of the plate area and a change in the dielectric layer breakdown which is inversely proportional to the plate area. An electric field model is developed to examine charge and voltage modes in MEMS. A charge injection test method is proposed to determine the susceptibility of MEMS to CDM ESD.     

Low molecular weight organogelators derived from threefold symmetric tricarbamates

A group of new low molecular weight organogelators based on threefold symmetric tricarbamate were synthesized and characterized. The tricarbamates with long alkyl chains were able to gelate a wide range of polar and nonpolar organic solvents such as acetonitrile and cyclohexane, generally at concentrations lower than 20 g/L. The best organogel formation was obtained using a threefold symmetric tricarbamate in n-dodecane, in which a sufficiently transparent gel was formed at the critical gelation concentration 1 g/L. Intermolecular hydrogen bonding by the tricarbamate in a nonpolar solvent benzene-d₆ was indicated by ¹H NMR spectra. Its maximum UV absorption was 11 nm higher in chloroform than in n-dodecane, and this red shift indicated increased conjugation between the benzene core and the carbamate substituents, which confirmed a change in its conformation from nonpolar to polar solvent. The self-assembling behavior of the tricarbamate in dilute solutions was investigated by TEM. Fiber-like networks were observed in a large range of solution concentrations.     

Hydrogen bonding in brucinium dihydrogen citrate trihydrate at 130 K

The structure of brucinium dihydrogen citrate trihydrate (systematic name: 2,3‐dimeth­oxy‐10‐oxostrychnidinium dihydrogen citrate trihydrate), C₂₃H₂₇N₂O₄⁺·C₆H₇O₇⁻·3H₂O, has been determined at 130 K. The crystallographic asymmetric unit comprises two brucinium cations, two dihydrogen citrate anions and six water mol­ecules of solvation. The two citrate anions, which are conformationally dissimilar, associate through extensive hydrogen‐bonding inter­actions with the common undulating brucinium cation layer substructures and the water mol­ecules, forming a three‐dimensional framework polymer.     

Creeping flow analysis of an integrated microfluidic device for rheometry

This paper analyzes flow of a power-law fluid in a microfluidic device for the purpose of discovering an algorithm for rheometry. Previous investigations have shown that measurement of the velocity field or the pressure field and the inlet flow rate in a microfluidic T-junction allow determination of rheological parameters uniquely. However, the range of shear induced within the flow domain was limited by the constant pressure drop applied across the micro-device. To avoid this control restriction and further develop our inverse technique, a constant flow rate system was investigated. With this configuration, the flow rate can be set appropriately to achieve a desired shear range and the rheological parameters can be inferred from the measurement of mean pressure at the inlet and at the junction. By assuming creeping flow conditions and the existence of a Hagen-Poiseuille-like law for the relationship between the pressure drop and the volumetric flow rate, the analysis produces an algorithm that is self-consistent (demonstrates the Hagen-Poiseuille law) and permits the inference of the power-law parameters from the ratio of any two field variables measured over a region (averaged), the pressure drop, and the volumetric flow rate.     

Comprehensive software suite for the operation, maintenance, and evaluation of an ion mobility spectrometer

Scientific applications of Ion Mobility Spectrometry require the ability to easily compare data between different laboratories. Reduced mobility values attempt to provide this functionality, but no standard exists for the collection and manipulation of the raw data obtained during an IMS experiment. We have created a comprehensive software suite based on the LabVIEW programming language that can be used to collect and interpret IMS data. The software may be used to collect data from a stand-alone IMS cell, a voltage sweep IMS cell, or a coupled chromatography-IMS system, and this framework may be adapted to incorporate mass spectral data analysis as well. This software is provided under an open source license for the benefit of the IMS community.     

Synthesis of triazole analogues of the nanaomycin antibiotics using ‘click chemistry’

A series of triazole analogues of the nanaomycin family of antibiotics have been prepared using a ‘click’ dipolar cycloaddition of a naphthalene azide to various alkynes, followed by oxidation to the desired pyranonaphthoquinones.