Miscibility of poly(styrene-co-acrylonitrile) and poly(α-methyl styrene-co-acrylonitrile) with polymethacrylates containing sterically hindered amine groups

Sterically hindered amine groups were incorporated into poly(methy1 methacrylate) and poly(ethy1 methacrylate) by copolymerizing 2,2,6,6 tetramethylpiperidinyl methacrylate (TPMA) with MMA and EMA. The replacement of the pendant alkyl groups of the polymethacrylates by SHA groups reduced their miscibility with poly(styrene-co-acrylonitrile) (SAN) and with poly(α-methyl styrene-co-acrylonitrile) (MSAN). The cloud points of the miscible blends indicated that the effective interaction parameter B of a blend became less negative with increasing TPMA content in the copolymer, and B was more negative for SAN blend than for a corresponding MSAN blend.     

Assessment of distributions for fitting lag times of individual cells in bacterial populations

To develop mathematical models describing lag times of individual bacterial cells (tau), experimental tau data were fitted to a variety of continuous distributions using BestFit. Six strains of Escherichia coli O157:H7 were used, and serial dilutions were made in Bioscreen multi-well plates to get single cells per well. Detection times (td) for individual wells were converted to tau using the maximum specific growth rate (mu) for each strain. All strains were subject to 25 trials, with up to 100 replicate wells per trial. Some strains had significantly longer t(d), and lower mu, but the tau values were not significantly different. Distributions were best fit in the order Pearson V>Pearson VI>Extreme Value>Lognormal>Lognormal2>Inverse Gaussian based on the Anderson-Darling statistic. The Lognormal distribution was selected because there was less variability in the parameter values, and parameters have specific biological meanings. Distributions could be fit to sample populations as low as six, with fittings and parameter values comparable to those obtained with larger samples (up to 89). Extreme Value, Pearson V, and Pearson VI distributions were more suitable for fitting tau values generated from a Lognormal distribution when the numbers of sample points were few, which suggested that there are similarities between the distributions. The results suggest that a Lognormal distribution can be used successfully to characterize tau.     

The effects of nucleus basalis magnocellularis lesions in Long-Evans hooded rats on two learning set formation tasks, delayed matching-to-sample learning, and open-field activity.

Rats with quisqualic acid lesions of the nucleus basalis magnocellularis (nBM) and control rats were compared in discrimination reversal learning set (DRLS) and olfactory discrimination learning set (ODLS) tasks, a delayed matching-to-sample task (DMTS), and open-field activity. Evidence of learning set formation was seen to control rats but not in nBM-lesioned rats in the DRLS and ODLS tasks. Better-than-chance performances were seen for both groups in open-field activity. These findings suggest that the nBM is important for higher cognitive processing such as "learning to learn" and thus is important for a complex form of reference memory. In addition, perseverational, working memory, and attentional deficits could not explain learning set impariment after nBM lesions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visible-Light Removable Photocaging Groups Accepted by MjMAT Variant: Structural Basis and Compatibility with DNA and RNA Methyltransferases

Methylation and demethylation of DNA, RNA and proteins constitutes a major regulatory mechanism in epigenetic processes. Investigations would benefit from the ability to install photo-cleavable groups at methyltransferase target sites that block interactions with reader proteins until removed by non-damaging light in the visible spectrum. Engineered methionine adenosyltransferases (MATs) have been exploited in cascade reactions with methyltransferases (MTases) to modify biomolecules with non-natural groups, including first evidence for accepting photo-cleavable groups. We show that an engineered MAT from Methanocaldococcus jannaschii (PC-MjMAT) is 308-fold more efficient at converting ortho-nitrobenzyl-(ONB)-homocysteine than the wildtype enzyme. PC-MjMAT is active over a broad range of temperatures and compatible with MTases from mesophilic organisms. We solved the crystal structures of wildtype and PC-MjMAT in complex with AdoONB and a red-shifted derivative thereof. These structures reveal that aromatic stacking interactions within the ligands are key to accommodating the photocaging groups in PC-MjMAT. The enlargement of the binding pocket eliminates steric clashes to enable AdoMet analogue binding. Importantly, PC-MjMAT exhibits remarkable activity on methionine analogues with red-shifted ONB-derivatives enabling photo-deprotection of modified DNA by visible light.     

Photonic Devices Out of Equilibrium: Transient Memory,Signal Propagation,and Sensing

Soft photonic materials are important for sensors, displays, or energy management and have become switchable under static equilibrium conditions by integration of responsive polymer features. The next step is to equip such materials with the ability for autonomously dynamic and self‐regulating behavior, which would advance their functionality and application possibilities to new levels. Here, this study shows the system integration of a nonlinear, biocatalytic pH‐feedback system with a pH‐responsive block copolymer photonic gel, and demonstrates autonomous transient memories, remotely controlled signal propagation, and sensing. This study utilizes an enzymatic switch to program the lifetime of the reflective state of a photonic gel, and induces propagation of pH‐waves extinguishable by illumination with UV‐light. The described combination of nonlinear chemistry and responsive photonic gels opens pathways toward out‐of‐equilibrium photonic devices with active and autonomous behavior useful for sensing, computation, and communication.     

Education for Sustainable Development and Civil Engineering for Children: Interactive Model Case Study

This paper describes the further development of a previously reported interactive model developed to enhance the understanding of the concept of sustainable development (SD) and the role of civil engineers among school children. The earlier model and associated teaching materials for a lesson based around a river valley flooding problem for small groups of 6th grade pupils were modified and trialed with a larger group of 8th grade pupils. Subsequently a further lesson using the same model framework was developed based around groundwater contamination from landfill leachate. This was trialed with small groups of both 6th and 8th grade pupils. A competitive element in landfill liner design was introduced into the lessons. The model and lessons received praise and were shown to achieve their aims of teaching SD in a memorable and practical context and explaining something of civil engineering, though the smaller group lessons were found to be much more successful than the larger group lesson.     

Bactericidal and Anticorrosion Properties in PVK/MWNT Nanocomposite Coatings on Stainless Steel

A PVK/MWNT nanocomposite coating on stainless steel is developed and tested for antimicrobial and anticorrosion properties. The coating is prepared via electrochemical deposition onto SS surfaces and is monitored using cyclic voltammetry. High‐resolution XPS measurements of the C 1s and N 1s regions are used to estimate the film composition. AFM shows a homogeneous thin film of several µm thickness with well‐defined globular domains. The bactericidal functionality of the electrodeposited film is demonstrated by its antibacterial activity against Escherichia coli, even with low MWNT loading (≈6%). The excellent anticorrosion property of the coating is demonstrated after 7 d of exposure to NaCl (0.5 M ) solution.

     

Direct airborne acoustic wave modulation of Fabry-Perot fiber laser (FPFL) over 100 kHz of operating bandwidth

The idea of applying a simple Fabry-Perot fiber laser (FPFL) set-up in a free-running condition as an acoustic sensing medium is proposed. Conventional optical microphone requires a stringently aligned diaphragm to mediate the acoustic impedance mismatch between air and silica fiber. Motivated by the difficulty of optical sensing of airborne acoustic waves, a new sensing method is proposed to sense acoustic waves without the assistance of a diaphragm as transducer. By studying the output power fluctuation of the FPFL, the operating bandwidth and sensitivity of the proposed sensing method are determined. The tunability of the resonant frequency from 5 kHz to 85 kHz allows sensing of acoustic waves in the range of 100 Hz to 100 kHz. Tuning of the resonant frequency can be performed by changing the optical pumping power from as low as 10 mW to 68.5 mW or higher.