Antimicrobial hydrogels formed by crosslinking polyallylamine with aldaric acid derivatives

Aqueous dispersions (0.1 wt %) of hydrogels 1 and 5 —formed by crosslinking polyallylamine hydrochloride (MW 60,000) with aldaric acid derivatives, diethyl L ‐tartrate and N,N′‐bis(methoxycarbonylmethyl)‐D ‐glucaramide, respectively—exhibited complete (log 5) kill within 4 h of Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans suspended in culture medium. This antimicrobial activity was much higher than that of uncrosslinked polyallylamine (1 wt % killed only 75% of E. coli in 24 h). When dispersed at 10 and 100 ppm, hydrogel 5 displayed complete (log 5) kill of E. coli within 30–60 and 15 min, respectively. Hydrogels 1 and 5 were active against S. aureus and Salmonella choleraesuis dried on hard stainless steel surfaces and accelerated the deaths of E. coli, P. aeruginosa, S. aureus, and C. albicans in a model skin cream formulation. A 0.8% aqueous dispersion of hydrogel 5 was also effective as a hand sanitizer, killing 99.7% of Serratia marcescens on human hands within 5 min. Hydrogels 1 and 5 caused no dermal irritation or allergic contact sensitization under the conditions of a human repeat insult patch test. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Oxygen reduction activity of Pt and Pt-Mn-Co electrocatalysts sputtered on nano-structured thin film support

We report on extensive measurements of oxygen reduction activity of Pt and Pt-Co-Mn electrocatalysts using the rotating ring-disk electrode (RRDE) method. The electrocatalysts were prepared by sputtering from Pt or Pt, Co and Mn targets onto 3M's nano-structured thin film support (NSTF) structures. The area specific activity of Pt/NSTF, measured in 0.1 M HClO₄ and at room temperature, is similar to that of bulk Pt. The area specific measurements show a 20 mV reduction in the Pt-Co-Mn/NSTF overpotential compared to Pt/NSTF. The corresponding kinetic gain in the area specific activity of the ternary alloy is about a factor of two. This ORR enhancement factor observed in the ternary Pt-Co-Mn/NSTF by RRDE measurements is similar to the results obtained in 50 cm² H₂/air fuel cells.     

Direct patterning of vertically aligned carbon nanotube arrays to 20 μm pitch using focused laser beam micromachining

We present a scalable approach for the fabrication of large-area arrays of carbon nanotube (CNT) structures using focused laser beams in the 0.05–10 W range. We show that CNT films can easily be micromachined into arrays of columns using a wide variety of commercially available pulsed lasers – Excimer, diode-pumped solid-state (DPSS), and CO₂ – operating at wavelengths from 248 nm to 9300 nm. We demonstrate that vertically aligned carbon nanotube (VACNT) arrays with pitches from 20 to 500 μm can be produced with aspect ratios greater than 20:1. Machining speeds up to 425 mm/s were demonstrated and trenches were produced from 10 to 200 μm wide depending on the laser method and beam size. The CO₂ laser had the largest beam diameter of 175 μm and produced the widest columns with the most taper. The remaining lasers, having beam diameters between 10 and 100 μm, produced smaller columns and finer pitch arrays. The VACNT arrays were shown to have high surface quality with no observable residue left behind, demonstrating focused laser micromachining as a readily available soft tooling means for direct manufacturing of VACNT devices. Laser micromachining methods are compared to evaluate the tradeoffs between quality and manufacturing costs.     

Protective Effect of Caffeic Acid on Paclitaxel Induced Anti-Proliferation and Apoptosis of Lung Cancer Cells Involves NF-κB Pathway

Caffeic acid (CA), a natural phenolic compound, is abundant in medicinal plants. CA possesses multiple biological effects such as anti-bacterial and anti-cancer growth. CA was also reported to induce fore stomach and kidney tumors in a mouse model. Here we used two human lung cancer cell lines, A549 and H1299, to clarify the role of CA in cancer cell proliferation. The growth assay showed that CA moderately promoted the proliferation of the lung cancer cells. Furthermore, pre-treatment of CA rescues the proliferation inhibition induced by a sub-IC(50) dose of paclitaxel (PTX), an anticancer drug. Western blot showed that CA up-regulated the pro-survival proteins survivin and Bcl-2, the down-stream targets of NF-κB. This is consistent with the observation that CA induced nuclear translocation of NF-κB p65. Our study suggested that the pro-survival effect of CA on PTX-treated lung cancer cells is mediated through a NF-κB signaling pathway. This may provide mechanistic insights into the chemoresistance of cancer calls.     

Computational analysis of citric acid pertraction in emulsion liquid membranes

Citric acid is one of the most widely used acids in industry, and its recovery from waste streams is critical. Emulsion liquid membrane (ELM) is one of the most effective recovery methods that has been investigated in recent years. Numerous transport phenomena parameters affect the efficiency of this process. From the process equipment design point of view, optimization based on overall cost is of great importance, and important equipment sizing decisions/constraints must be considered. A physics-based model for a full-scale simulation of ELM systems is very useful. This work is focused on developing and verifying such a model. A coupled particle/mixture simulation was carried out in this work, and the modelling results were fitted on the experimental data. The novelty of this modelling work is physics-based results based on the system's geometry and its effects on the mass transfer resistances. Since the model is physics-based, the model is capable of simulating similar systems with any geometry or experimental conditions.     

Automated Spore Measurements Using Microscopy,Image Analysis,and Peak Recognition of Near-Monodisperse Aerosols

Rapid detection of airborne fungal and bacterial spores would enable public agencies to respond quickly and appropriately to intentional releases of hazardous aerosols. Automated analysis of microscope images and automated detection of near-monodisperse peaks in aerosol size distribution data offer complementary approaches to traditional methods for the identification and counting of fungal and bacterial spores. First, spores of the fungus Scopulariopsis brevicaulis were aerosolized in a chamber and then collected with a slit impactor; later, digital microscope images were analyzed manually to determine spore cluster distributions. The images also were analyzed with ImageJ, a program that automatically outlined objects and measured Feret's diameter, area, perimeter, and circularity. These characteristics were used to identify spore clusters automatically using two data analysis methods. Second, a computer program was developed to discriminate near-monodisperse bioaerosol peaks from those for polydisperse ambient particulate matter (PM) and was successfully tested using simulated and real aerosol mixtures. The observed agreement between manual and automated spore counts and the ability to detect spore peaks suggest that it may be possible to develop a system to recognize intentional releases rapidly through examination of particle morphology and size distributions. The peak detection procedure is potentially the fastest technique when used with real-time instrument data, but assumes that intentional releases would consist of large numbers of uniformly sized particles in the respirable size range.

Copyright 2012 American Association for Aerosol Research     

Passive Aerosol Sampler. Part I: Principle of Operation

A method has been developed to estimate average concentrations and size distributions with a miniature passive aerosol sampler. To use the passive sampler, one exposes it to an environment for a period of hours to weeks. The passive sampler is intended to monitor ambient, indoor, or occupational aerosols and has potential utility as a personal sampler. The sampler is inexpensive and easy to operate and is capable of taking long-term samples to investigate chronic exposures. After sampling, the passive sampler is covered and brought to the lab. Scanning electron microscopy (SEM) and automated image analysis are used to count and size collected particles with d_p     

Evaluation of Elemental and Black Carbon Measurements from the GAViM and IMPROVE Networks

The GAViM program provides fine particulate and visibility data for several remote locations in Canada. Two long-term intercomparison studies between the GAViM and a major U.S. aerosol monitoring network, IMPROVE, were used to evaluate the uncertainty in the analytical data produced by proton induced x-ray emission (PIXE), proton elastic scattering analysis (PESA), and gravimetric analysis. GAViM and IMPROVE agreed well for elements from Fe to Zn where PIXE is the most sensitive; the relative difference between the 2 networks for Fe and Zn was <2%. Some lighter elements, e.g., sodium or sulphur, revealed a difference of 10-20%. Furthermore, an empiric conversion scheme for the GAViM absorption data produced by the laser integrated plate method (LIPM) was derived from the comparison to the IMPROVE thermal/optical reflectance (TOR) data. This conversion depends on the aerosol composition and is therefore site specific. It allows estimation of the elemental carbon concentrations from the historic raw light absorption values obtained by LIPM. If the mass attenuation coefficient of the fine aerosol collected at the 2 remote GAViM sites is assumed to be equal to 10 m 2 /g, then the results imply that the light absorption coefficient measured by LIPM is generally higher than the true value by up to a factor of 1.3 or 1.8, respectively. In both cases, LIPM overestimated the black carbon content, mostly for the lightly loaded samples.     

An improved accelerated weathering protocol to anticipate Florida exposure behavior of coatings

A new accelerated weathering protocol has been developed which closely replicates the performance of automotive and aerospace coating systems exposed in South Florida. IR spectroscopy was used to verify that the chemical composition changes that occurred during accelerated weathering in devices with a glass filter that produced a high fidelity reproduction of sunlight’s UV spectrum matched those that occurred during natural weathering. Gravimetric water absorption measurements were used to tune the volume of water absorption during accelerated weathering to match that which occurred during natural weathering in South Florida. The frequency of water exposure was then scaled to the appropriate UV dose. A variety of coating systems were used to verify the correlation between the physical failures observed in the accelerated weathering protocol and natural weathering in South Florida. The new accelerated weathering protocol correctly reproduced gloss loss, delamination, cracking, blistering, and good performance in a variety of diverse coating systems. For automotive basecoat/clearcoat paint systems, the new weathering protocol shows significant acceleration over both Florida and previous accelerated weathering tests. For monocoat aerospace systems, the new weathering protocol showed less acceleration than for automotive coatings, but was still an improvement over previous accelerated tests and was faster than Florida exposure.