Biomolecular conjugation inside synthetic polymer nanopores via glycoprotein-lectin interactions

We demonstrate the supramolecular bioconjugation of concanavalin A (Con A) protein with glycoenzyme horseradish peroxidase (HRP) inside single nanopores, fabricated in heavy ion tracked polymer membranes. Firstly, the HRP-enzyme was covalently immobilized on the inner wall of the pores using carbodiimide coupling chemistry. The immobilized HRP-enzyme molecules bear sugar (mannose) groups available for the binding of Con A protein. Secondly, the bioconjugation of Con A on the pore wall was achieved through its biospecific interactions with the mannose residues of the HRP enzyme. The immobilization of biomolecules inside the nanopore leads to the reduction of the available area for ionic transport, and this blocking effect can be exploited to tune the conductance and selectivity of the nanopore in aqueous solution. Both cylindrical and conical nanopores were used in the experiments. The possibility of obtaining two or more conductance states (output), dictated by the degree of nanopore blocking resulted from the different biomolecules in solution (input), as well as the current rectification properties obtained with the conical nanopore, could also allow implementing information processing at the nanometre scale. Model simulations based on the transport equations further verify the feasibility of the sensing procedure that involves concepts from supramolecular chemistry, molecular imprinting, recognition, and nanotechnology.     

Morphological impact of zinc oxide layers on the device performance in thin-film transistors

Zinc oxide thin-films are prepared either by spin coating of an ethanolic dispersion of nanoparticles (NP, diameter 5 nm) or by spray pyrolysis of a zinc acetate dihydrate precursor. High-resolution electron microscopy studies reveal a monolayer of particles for the low temperature spin coating approach and larger crystalline domains of more than 30 nm for the spray pyrolysis technique. Thin-film transistor devices (TFTs) based on spray pyrolysis films exhibit higher electron mobilities of up to 24 cm2 V(-1) s(-1) compared to 0.6 cm2 V(-1) s(-1) for NP based TFTs. These observations were dedicated to a reduced number of grain boundaries within the transistor channel.     

Toughness optimization of elastomer‐modified glass–fiber reinforced PA6 materials

To investigate the influence of moisture and EPR‐g‐MA content on the fracture behavior of glass–fiber reinforced PA6 materials, brittle‐to‐tough transition temperatures (T_btt) were determined. Water absorption was taken into account by conditioning the analyzed materials. Tensile tests could reveal the temperature range of the largest moisture dependence of mechanical properties between 10 and 50°C. J‐integral values were used to describe the fracture behavior under conditions of impact load as a function of temperature. The brittle‐to‐tough transition of reinforced polyamides was found to be less approximate than in unreinforced materials. Two different characteristic temperature points T_s and T_e were identified, which were the intercept between elastic and elastic–plastic deformation on the one hand and the starting point of dominating stable crack propagation with strong plastic deformation on the other hand. Characteristic brittle‐to‐tough transition temperatures T_btt could be calculated as the arithmetic average of these two points. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Dielectric relaxation studies of low thermal expansion polymer composites

The results of temperature‐dependent dielectric and rheological measurements are reported on polymer‐ceramic composite films, poly(methyl methacrylate) (PMMA) : lead titanate (PbTiO₃). Analyses of relaxational processes of the PMMA host matrix have been investigated using temperature‐dependent dielectric and rheological measurements. It is found that the α‐relaxation is more significantly affected by the addition of filler in comparison to β‐relaxation. The composite films are found to have much lower dielectric constants in comparison to the pure ceramic material. Suitable models have been used to explain the observed dielectric constant of the composite films. Using rheological measurements, occurrence of reinforcement in these composite films due to the addition of ceramic filler has also been observed and the results are discussed in the article. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Modulation of Aphid Alarm Pheromone Emission of Pea Aphid Prey by Predators

Recent studies on animal alarm signaling have shown that alarm calls generally are not uniform, but may vary depending on the type and intensity of threat. While alarm call variability has been studied intensively in birds and mammals, little is known about such variation in insects. We investigated variability in alarm signaling in aphids, group-living insect herbivores. Under attack, aphids release droplets containing a volatile alarm pheromone, (E)-β-farnesene (EBF), that induces specific escape behavior in conspecifics. We used a handheld gas chromatograph (zNose?), which allows real-time volatile analysis, to measure EBF emission by pea aphids, Acyrthosiphon pisum, under attack from different predators, lacewing or ladybird larvae. We demonstrate that aphid alarm signaling is affected by the predator species attacking. Ladybirds generally elicited smaller EBF emission peaks and consumed aphids more quickly, resulting in lower total EBF emission compared to lacewing attacks. In 52 % of the replicates with lacewings and 23 % with ladybirds, no EBF was detectable in the headspace, although aphids secreted cornicle droplets after attack. We, therefore, examined EBF amounts contained in these droplets and the aphid body. While all aphid bodies always contained EBF, many secreted droplets did not. Our experiments show that alarm signaling in insects can be variable, and both the attacker as well as the attacked may affect alarm signal variation. While underlying mechanisms of such variation in aphid-predator interactions need to be investigated in more detail, we argue that at least part of this variation may be adaptive for the predator and the aphid.     

Process Engineering Considerations of Electrochemical Storage

Thermodynamically, electric storages can be generally characterized as a type of regenerative machines able to operate in a work and a power machine mode. A consideration of the concentration term of the Nernst equation already shows a first principal difference between batch and flow processes, because the reaction coordinate depends on time for batch processes and on the flow coordinate for flow processes. Ionic substances may be stored within a volume surrounding the electrodes or on the surface of the electrodes itself. The volume concentrations of the reactants are thus a determining parameter of electrochemical storage beside voltage and the ratio of released electrons per reacting reference substance. Surface storage allows only batch processes while volume storage allows batch and flow processes. This characterization identifies the benefits of certain reactions regarding mass and volume related energy density in a simple way at a very early stage of development. It also allows a simple calculation of possible discharging times.