Crosslinkable micelles from diblock amphiphilic copolymers based on vinylbenzyl thymine and vinylbenzyl triethylammonium chloride

Polymeric micelles (PMs) composed of self‐assembled amphiphilic block copolymers were synthesized from vinylbenzyl thymine (VBT) and vinylbenzyl triethylammonium chloride (VBA) exhibiting improved physical stability. Three diblock copolymers of different chemical compositions and similar molecular weights (polydispersities below 1.5) were obtained via nitroxide mediated radical polymerization. Critical micelle concentration (CMC) was determined by dye micellization method, the shift of the absorption peak of the anionic (EY) due to the interactions with non‐assembled chains and auto‐assembled copolymers was followed. Polymeric systems exhibited good stability revealing that a higher proportion of cationic monomers in the diblock reduce the CMC. Furthermore, after the core of PMs was photocrosslinked by UV irradiation, the CMC decreases notably. Kinetic release studies using EY dye as probe demonstrated that both, higher VBA ratios in the polymer and higher UV‐irradiation, slow down the dye release. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41947.     

Investigating the Role of Conformational Effects on Laccase Stability and Hyperactivation under Stress Conditions

Fungal laccase from Steccherinum ochraceum 1833 displays remarkable stability under different harsh conditions: organic/buffer mixtures, thermal treatment, and microwave radiation. The behavior is particularly significant in the light of the sharp inactivation observed for two different fungal laccases. Laccase from S. ochraceum 1833 also displays hyperactivation under mild thermal treatment (60 °C). Molecular dynamics simulations at 80 °C explained how this laccase retains the geometry of the electron transfer pathway, thereby assuring electron transfer through the copper ions and thus maintaining its catalytic activity at high temperature. Spectroscopic studies revealed that the thermal activation corresponds to specific conformational changes in the protein. The results indicate that this laccase is potentially applicable under denaturing conditions that might be beneficial for the biotransformation of recalcitrant substrates.     

A cluster-based trust-aware routing protocol for mobile ad hoc networks

Routing protocols are the binding force in mobile ad hoc network (MANETs) since they facilitate communication beyond the wireless transmission range of the nodes. However, the infrastructure-less, pervasive, and distributed nature of MANETs renders them vulnerable to security threats. In this paper, we propose a novel cluster-based trust-aware routing protocol (CBTRP) for MANETs to protect forwarded packets from intermediary malicious nodes. The proposed protocol organizes the network into one-hop disjoint clusters then elects the most qualified and trustworthy nodes to play the role of cluster-heads that are responsible for handling all the routing activities. The proposed CBTRP continuously ensures the trustworthiness of cluster-heads by replacing them as soon as they become malicious and can dynamically update the packet path to avoid malicious routes. We have implemented and simulated the proposed protocol then evaluated its performance compared to the clustered based routing protocol (CBRP) as well as the 2ACK approach. Comparisons and analysis have shown the effectiveness of our proposed scheme.     

Transparent Polysilsesquioxane Films Obtained from Bridged Ureasil Precursors: Tunable Photoluminescence Emission in the Visible Region and Filtering of UV‐Radiation

Bridged ureasil precursors were synthesized by the reaction of either ethylenediamine (1 mol) or m‐xylylenediamine (1 mol) with isocyanatepropyltriethoxysilane (2 mol). Transparent polysilsesquioxane films were obtained by the hydrolytic condensation of the pure precursors or their co‐condensation in a 50:50 molar ratio. Films based on pure ureasil precursors showed a blue photoluminescent emission band assigned to the photoinduced proton‐transfer among H‐bonded urea groups and the subsequent radiative recombination of ionized groups. Films synthesized by the co‐condensation of both precursors exhibited a significant red‐shift of their absorption, excitation, and emission spectra, associated to de‐localization of H‐bonds, and a high absorption of UV‐radiation.

     

Visualization of Large Experimental Space Using Holographic Mapping and Artificial Neural Networks. Benchmark Analysis of Multicomponent Catalysts for the Water Gas Shift Reaction

This paper reports the combination of Holographic Mapping (HM) and Artificial Neural Networks (ANNs) in order to provide a benchmark visualization of a multi-dimensional space in two-dimensional forms. In this approach each matrix point in HM represents virtual catalytic data generated by means of ANNs in order to visualize the given multi-dimensional experimental space. A 12-dimensional experimental space related to the composition of catalysts designed for the water gas shift reaction (WGSR) from 12 possible components supported on ZrO₂ is visualized. Catalytic data obtained in an earlier combinatorial screening process at 300 °C were used for training of the ANNs. The results show that the visualization of large experimental spaces having more than half a million virtual experimental points can be accomplished. The analysis of synergistic effects between different components revealed that the key components of water gas shift catalysts at 300 °C were Pt, Fe, Eu and V, while Co, Ru, Sb, Ge and Mo had a pronounced negative effect on the activity.     

Sourcing faecal pollution: a combination of library-dependent and library-independent methods to identify human faecal pollution in non-sewered catchments

Library-dependent (LD) (biochemical fingerprinting of Escherichia coli and enterococci) and library-independent (LI) (PCR detection of human-specific biomarkers) methods were used to detect human faecal pollution in three non-sewered catchments. In all, 550 E. coli isolates and 700 enterococci isolates were biochemically fingerprinted from 18 water samples and compared with metabolic fingerprint libraries of 4508 E. coli and 4833 enterococci isolates. E. coli fingerprints identified human unique biochemical phenotypes (BPTs) in nine out of 18 water samples; similarly, enterococci fingerprints identified human faecal pollution in 10 water samples. Seven samples were tested by PCR for the detection of biomarkers. Human-specific HF134 Bacteroides and enterococci surface protein (esp) biomarkers were detected in five samples. Four samples were also positive for HF183 Bacteroides biomarker. The combination of biomarkers detected human faecal pollution in six out of seven water samples. Of the seven samples analysed for both the indicators/markers, at least one indicator/marker was detected in every sample. Four of the seven PCR-positive samples were also positive for one of the human-specific E. coli or enterococci BPTs. The results indicated human faecal pollution in the studied sub-catchments after storm events. LD and LI methods used in this study complimented each other and provided additional information regarding the polluting sources when one method failed to detect human faecal pollution. Therefore, it is recommended that a combination of methods should be used to identify the source(s) of faecal pollution where possible.     

Use of fecal steroids to infer the sources of fecal indicator bacteria in the Lower Santa Ana River Watershed, California: sewage is unlikely a significant source

The Santa Ana River (SAR), CA and adjacent wetlands have been identified as potential sources of fecal indicator bacteria (FIB) to the surf zone at Huntington Beach, CA. A suite of fecal steroids, including coprostanol (COP), epicoprostanol (eCOP), cholesterol (CHOE), cholestanol (CHOA), alpha-cholestanone (aONE), beta-cholestanone (bONE), beta-sitosterol (bSIT), stigmasterol (STIG), stigmastanol (STAN), and campesterol (CAM), were used as chemical markers to examine whether sewage was a significant source of FIB within the lower Santa Ana River watershed. A total of 54 water samples were collected from three locations in the intertidal zone near the mouth of the Santa Ana River at different tidal stages. Steroid ratios in SAR samples were different from those found in raw and treated sewage from a local wastewater treatment plant or in nearby effluent plume and did not appear to be influenced by the sampling location, daily tides, and spring/neap tidal cycle. The characteristics of steroid ratios suggested a diagenetic ratherthan a biogenic source forthe COP content of the samples. The log-based concentrations of COP and FIB in the SAR samples were not significantly correlated, inconsistent with sewage being the source of FIB in the study area. In addition, multivariate statistical analysis showed that the concentrations of FIB were better correlated with bird fecal steroids than with the typical sewage sterols. The results implied that sewage was not a significant source of fecal steroids, and therefore perhaps FIB to the study area. Instead, birds may be one possible source of the intermittently high levels of FIB observed in the lower Santa Ana River watershed and the nearby surf zone.     

Direct application to dairy foods of a Listeria-specific oligonucleotide probe to 16S rRNA.

A potentially Listeria-specific 28 base oligonucleotide probe was designed from 16S rRNA sequence data. Using either 32P or non-radioactive (alkaline phosphatase) labels, the probe was shown to be highly specific as it hybridised to RNA extracted from all of the species of Listeria but not to any of the other bacteria tested. Both probe methods were highly sensitive and ca 10(2) cfu/ml Listeria could be detected in pure cultures. A rapid procedure for extracting RNA from milk, Camembert and cottage cheese was developed. This allowed the direct application of the probe to these foods and gave a rapid and specific method of detecting > 10(2) cfu/g or ml Listeria in these foods.