A facile spin-cast route for cation exchange of multilayer perpendicularly-aligned nanorod assemblies

A facile spin cast route was developed to convert perpendicularly aligned nanorod assemblies of cadmium chalcogenides into their silver and copper analogues. The assemblies are rapidly cation exchanged without affecting either the individual rod dimensions or collective superlattice order extending over several multilayers.     

Complex Interactions among Sheep,Insects, Grass,and Fungi in a Simple New Zealand Grazing System

Epichloë fungi (Ascomycota) live within aboveground tissues of grasses and can have important implications for natural and managed ecosystems through production of alkaloids. Nonetheless, vertebrate herbivores may possess traits, like oral secretions, that mitigate effects of alkaloids. We tested if sheep saliva mitigates effects of Epichloë alkaloids on a beetle pest of perennial ryegrass (Lolium perenne L.) in a New Zealand pasture setting. Plants with one of several fungal isolates were clipped with scissors, grazed by sheep, or clipped with sheep saliva applied to cut ends of stems. We then assessed feeding damage by Argentine stem weevils on blade segments collected from experimental plants. We found that clipping plants induced synthesis of an alkaloid that reduces feeding by beetles and that sheep saliva mitigates this effect. Unexpectedly, the alkaloid (perloline) that explains variation in beetle feeding is one produced not by the endophyte, but rather by the plant. Yet, these effects depended upon fungal isolate. Such indirect, complex interactions may be much more common in both managed and natural grassland systems than typically thought and could have implications for managing grazing systems.     

Investigation of the temperature homogeneity of die melt flows in polymer extrusion

Polymer extrusion is fundamental to the processing of polymeric materials and melt flow temperature homogeneity is a major factor which influences product quality. Undesirable thermal conditions can cause problems such as melt degradation, dimensional instability, weaknesses in mechanical/optical/geometrical properties, and so forth. It has been revealed that melt temperature varies with time and with radial position across the die. However, the majority of polymer processes use only single‐point techniques whose thermal measurements are limited to the single point at which they are fixed. Therefore, it is impossible for such techniques to determine thermal homogeneity across the melt flow. In this work, an extensive investigation was carried out into melt flow thermal behavior of the output of a single extruder with different polymers and screw geometries over a wide range of processing conditions. Melt temperature profiles of the process output were observed using a thermocouple mesh placed in the flow and results confirmed that the melt flow thermal behavior is different at different radial positions. The uniformity of temperature across the melt flow deteriorated considerably with increase in screw rotational speed while it was also shown to be dependent on process settings, screw geometry, and material properties. Moreover, it appears that the effects of the material, machine, and process settings on the quantity and quality of the process output are heavily coupled with each other and this may cause the process to be difficult to predict and variable in nature. POLYM. ENG. SCI., 54:2430–2440, 2014. © 2013 Society of Plastics Engineers     

Improved zein films using polyethylenemaleic anhydride

The effect on the physical properties and solubility of corn protein (zein) films was studied after reaction of zein with polyethylenemaleic anhydride (PEMA). Reactions were carried out in dimethylformamide (DMF) solution where the concentration of PEMA was varied between 0 and 6%. After reaction at room temperature, cast films were prepared, and the physical and solubility properties were determined. Incorporating more than 2% PEMA provided films with increased tensile strength and elongation. Incorporating 6% PEMA provided films with higher tensile strength (32–42 MPa) and improved solvent resistance (100–21% solubility) relative to control. If the films were heated in an oven, the film's solubility decreased further. Solution rheology experiments demonstrated that the zein and PEMA formed a cross‐linked gel with time in DMF. Dynamic mechanical analysis experiments have shown that the PEMA‐modified zein films undergo a dramatic loss in modulus on reaching 116°C, whereas the control experiences this loss at 98°C. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40122.     

Intravital FRET: Probing Cellular and Tissue Function in Vivo

The development of intravital Förster Resonance Energy Transfer (FRET) is required to probe cellular and tissue function in the natural context: the living organism. Only in this way can biomedicine truly comprehend pathogenesis and develop effective therapeutic strategies. Here we demonstrate and discuss the advantages and pitfalls of two strategies to quantify FRET in vivo—ratiometrically and time-resolved by fluorescence lifetime imaging—and show their concrete application in the context of neuroinflammation in adult mice.     

Assessing the Antimicrobial Activity of Polyisoprene Based Surfaces

There has been an intense research effort in the last decades in the field of biofouling prevention as it concerns many aspects of everyday life and causes problems to devices, the environment, and human health. Many different antifouling and antimicrobial materials have been developed to struggle against bacteria and other micro- and macro-organism attachment to different surfaces. However the “miracle solution” has still to be found. The research presented here concerns the synthesis of bio-based polymeric materials and the biological tests that showed their antifouling and, at the same time, antibacterial activity. The raw material used for the coating synthesis was natural rubber. The polyisoprene chains were fragmented to obtain oligomers, which had reactive chemical groups at their chain ends, therefore they could be modified to insert polymerizable and biocidal groups. Films were obtained by radical photopolymerization of the natural rubber derived oligomers and their structure was altered, in order to understand the mechanism of attachment inhibition and to increase the efficiency of the anti-biofouling action. The adhesion of three species of pathogenic bacteria and six strains of marine bacteria was studied. The coatings were able to inhibit bacterial attachment by contact, as it was verified that no detectable leaching of toxic molecules occurred.     

Modelling a circulating fluidized bed riser reactor with gas—solids downflow at the wall

A predictive model was developed for the fully developed zone of a circulating fluidized bed (CFB) riser reactor operating in the fast fluidization regime that overcomes limitations of existing models. The model accounts for the upward flow of gas and solids in the core and downward flow of the two phases in the annulus. Additionally, a numerical solution methodology for the simulation of a riser reactor employing the hydrodynamic model was devised. A simulation was performed using the fast, main Claus reaction to demonstrate the effects of backmixing in the fast fluidization regime. It was found that the molar flow rates of the reactants leaving a fast fluidized CFB riser reactor were significantly higher than those leaving an identical reactor operating in the pneumatic transport regime.     

Tailoring Encodable Lanthanide‐Binding Tags as MRI Contrast Agents

Lanthanide‐binding tags (LBTs), peptide‐based coexpression tags with high affinity for lanthanide ions, have previously been applied as luminescent probes to provide phasing for structure determination in X‐ray crystallography and to provide restraints for structural refinement and distance information in NMR. The native affinity of LBTs for Gd³⁺ indicates their potential as the basis for engineering of peptide‐based MRI agents. However, the lanthanide coordination state that enhances luminescence and affords tightest binding would not be ideal for applications of LBTs as contrast agents, due to the exclusion of water from the inner coordination sphere. Herein, we use structurally defined LBTs as the starting point for re‐engineering the first coordination shell of the lanthanide ion to provide for high contrast through direct coordination of water to Gd³⁺ (resulting in the single LBT peptide, m‐sLBT). The effectiveness of LBTs as MRI contrast agents was examined in vitro through measurement of binding affinity and proton relaxivity. For imaging applications that require targeted observation, fusion to specific protein partners is desirable. However, a fusion protein comprising a concatenated double LBT (dLBT) as an N‐terminal tag for the model protein ubiquitin had reduced relaxivity compared with the free dLBT peptide. This limitation was overcome by the use of a construct based on the m‐sLBT sequence (q‐dLBT–ubiquitin). The structural basis for the enhanced contrast was examined by comparison of the X‐ray crystal structure of xq‐dLBT–ubiquitin (wherein two tryptophan residues are replaced with serine), to that of dLBT‐ubiquitin. The structure shows that the backbone conformational dynamics of the MRI variant may allow enhanced water exchange. This engineered LBT represents a first step in expanding the current base of specificity‐targeted agents available.     

Measurement of intrinsic rates for homogeneous gas‐phase reactions at high temperatures

A coiled quartz tubular reactor has been designed to measure the intrinsic reaction kinetics for homogeneous reactions at high temperatures up to 1100°C. Actual gas residence times were less than 100 ms. A simple and well‐studied test reaction (i.e., the decomposition of nitrous oxide, N₂O), with published intrinsic kinetics, was used to verify the operation of the experimental reactor. For this system, Peclet numbers (Pe = uL/DL) computed from experimental conversion data were greater than 1000, indicating that the plug flow assumption could be used with this reactor system to determine intrinsic rate expressions with errors of less than 5% for the conditions studied.