Dielectric properties of polyethylene terephthalate/polyphenylene sulfide/barium titanate nanocomposite for application in electronic industry

Polymer/ceramic nanocomposites designed for application as electronic packaging were prepared using corotating twin‐screw extruder. The dielectric properties of the composites made from polyethylene terephthalate (PET), polyphenylene sulfide, and barium titanate were studied as a function of BaTiO₃ fraction in the range between 0.75 and 1.5 wt%. Processing parameters were optimized in order to obtain the nanocomposites with appropriate dielectric properties like dielectric permittivity ε′, dielectric losses ε″, and their temperature stability in a wide frequency range. The measurements showed the increase of the dielectric permittivity value ε′ in the composites in comparison to both pure polymers. The dielectric loss factor tgδ of the composites was found to be much smaller than that of the pure PET. The weak influence of the ceramics on the temperature stability of the dielectric properties of the composites was stated. POLYM. ENG. SCI., 50:1613–1619, 2010. © 2010 Society of Plastics Engineers     

The Herbivore-Induced Plant Volatile Methyl Salicylate Negatively Affects Attraction of the Parasitoid <Emphasis Type="Italic">Diadegma semiclausum</Emphasis>

The indirect defense mechanisms of plants comprise the production of herbivore-induced plant volatiles that can attract natural enemies of plant attackers. One of the often emitted compounds after herbivory is methyl salicylate (MeSA). Here, we studied the importance of this caterpillar-induced compound in the attraction of the parasitoid wasp Diadegma semiclausum by using a mutant Arabidopsis line. Pieris rapae infested AtBSMT1-KO mutant Arabidopsis plants, compromised in the biosynthesis of MeSA, were more attractive to parasitoids than infested wild-type plants. This suggests that the presence of MeSA has negative effects on parasitoid host-finding behavior when exposed to wild-type production of herbivore-induced Arabidopsis volatiles. Furthermore, in line with this, we recorded a positive correlation between MeSA dose and repellence of D. semiclausum when supplementing the headspace of caterpillar-infested AtBSMT1-KO plants with synthetic MeSA.     

Self-assembly of iron oxide-poly(ethylene glycol) core-shell nanoparticles at liquid-liquid interfaces

Nanoparticles (NPs) play an increasingly important role in the fabrication of functional advanced materials. Two major steps need to be carried out in order to achieve control of the material properties. First of all, the properties of the single NPs have to be under control, especially in relation to colloidal stability; aggregation and corrosion negate all the benefits associated to the nanoscopic dimensions. Secondly, the assembly process has to be controlled to achieve a material with the desired properties. We propose here to use stabilized ceramic NPs consisting of a magnetite core, coated by a poly(ethylene glycol) (PEG) shell and study their assembly at polar/ non-polar liquid interfaces, en route to fabricating functional NP membranes. These NPs show extraordinary stability in aqueous solutions achieved by anchoring linear PEG chains through an end-terminating nitroDOPA group to their surface. Furthermore, the core and shell sizes of these NPs can be independently varied with ease. We first describe the details of the NP synthesis and stabilization in bulk solutions, discussing the PEG molecular weight needed to achieve bulk stability. Subsequently, we demonstrate self-assembly of these particles at liquid-liquid interfaces (SALI) into monolayers of stable properties. SALI has been chosen as path for the assembly given its suitability for fabricating two-dimensional materials. We report here results from pendant drop tensiometry which illustrate the kinetics of NP adsorption at the liquid-liquid interface and highlight the role played by the molecular weight of the PEG shell in the interfacial assembly. In particular we show that the requisites to ensure particle stability at a liquid interface are more stringent compared to the bulk case.     

Measuring the External Quantum Efficiency of Two‐Terminal Polymer Tandem Solar Cells

Tandem configurations, in which two cells are stacked and connected in series, offer a viable approach to further increase the power conversion efficiency (PCE) of organic solar cells. To enable the future rational design of new materials it is important to accurately assess the contributions of individual subcells. Such accurate measurement of the external quantum efficiency (EQE) of the subcells of two‐terminal organic or polymer tandem solar cells poses specific challenges, caused by two characteristics of these cells, i.e. a sub‐linear light intensity dependence of the current and a field‐assisted charge collection. These properties necessitate that EQE experiments are carried out under representative illumination conditions and electrical bias to maintain short‐circuit conditions for the addressed subcell. We describe a method to determine the magnitudes of the bias illumination and bias voltage during EQE measurements, based on the behavior of single junction cells and optical modeling. The short‐circuit current densities of the subcells obtained by convolution of the EQE with the AM1.5G solar spectrum are consistent with those obtained from optical modeling and correctly predict the current density–voltage characteristics of the tandem cell under AM1.5G conditions.     

Low‐Temperature Superionic Conductivity in Strained Yttria‐Stabilized Zirconia

Very high lateral ionic conductivities in epitaxial cubic yttria‐stabilized zirconia (YSZ) synthesized on single‐crystal SrTiO₃ and MgO substrates by reactive direct current magnetron sputtering are reported. Superionic conductivities (i.e., ionic conductivities of the order ～1 Ω^?1cm^?1) are observed at 500 °C for 58‐nm‐thick films on MgO. The results indicate a superposition of two parallel contributions – one due to bulk conductivity and one attributable to conduction along the film–substrate interface. Interfacial effects dominate the conductivity at low temperatures (<350 °C), showing more than three orders of magnitude enhancement compared to bulk YSZ. At higher temperatures, a more bulk‐like conductivity is observed. The films have a negligible grain‐boundary network, thus ruling out grain boundaries as a pathway for ionic conduction. The observed enhancement in lateral ionic conductivity is caused by a combination of misfit dislocation density and elastic strain in the interface. These very high ionic conductivities in the temperature range 150–500 °C are of great fundamental importance but may also be technologically relevant for low‐temperature applications.     

Trans octadecenoic fatty acid (TFA) isomers in German foods and bakery goods

In the present study, 122 food samples from the German food market were analysed for their C18:1 trans fatty acid (TFA) content and profile. A particular focus of the survey were baked and fried foods. TFA analysis was performed by means of silver ion SPE (Ag⁺‐SPE) in combination with high‐resolution GC (HRGC‐FID). Overall, 51 bakery product samples were analysed of which 25 samples were prepacked bakery products purchased from local retail stores and 26 samples of unpacked bakery products purchased from local bakery shops. In addition, 14 French fries samples obtained from small local fast food restaurants as well as from internationally operating fast food chains, 27 potato and tortillas chips, 15 instant soups as well as 15 dry culinary sauces were analysed. The highest amounts of C18:1 TFA isomers were found in deep‐fried bakery products. Prepacked branded cookies and biscuits on the other hand contained only negligible C18:1 TFA amounts. Regarding their C18:1 trans isomer profile most deep‐fried bakery products exhibited a Gaussian‐distributed isomer profile. The analysed prepacked croissants, cookies and biscuits contained predominantly ruminant TFA (TFA) as suggested by the presence of vaccenic acid (C18:1 trans 11), which was the major C18:1 TFA isomer in these products. All non‐bakery samples (n = 71) contained less than 3 g C18:1 TFA per 100 g fat. In conclusion, TFA still occur in considerable amounts in a few German food products, especially in some deep‐fried bakery products (‘Berliner’ type of doughnuts). Practical applications: Trans fatty acids, in particular the trans octadecenoic fatty acid isomers (C18:1), are generally considered from the nutritional point of view as undesirable food components due to their negative health effects. Tremendous efforts have been made by major food processors in order to decrease or even eliminate the presence of TFA in some foodstuffs (e.g. in margarines in European countries). However, some food processors of other food sectors are still applying oils and fats containing partially hydrogenated vegetable oils, whereas others within the same food category have already switched their processing conditions and/or raw materials towards TFA alternatives. Therefore, actual TFA data of foodstuffs determined by means of state‐of‐the‐art analytical procedures (Ag⁺‐SPE in combination with GC‐FID) is necessary to detect areas of further improvement in the food supply chain and to provide data for an update of dietary TFA intake.     

A molecular-structure hypothesis

The self-similar symmetry that occurs between atomic nuclei, biological growth structures, the solar system, globular clusters and spiral galaxies suggests that a similar pattern should characterize atomic and molecular structures. This possibility is explored in terms of the current molecular structure-hypothesis and its extension into four-dimensional space-time. It is concluded that a quantum molecule only has structure in four dimensions and that classical (Newtonian) structure, which occurs in three dimensions, cannot be simulated by quantum-chemical computation.     

An adsorptive transfer technique coupled with brdicka reaction to reveal the importance of metallothionein in chemotherapy with platinum based cytostatics

The drugs based on platinum metals represent one of the oldest, but also one of the most effective groups of chemotherapeutic agents. Thanks to many clinical studies it is known that resistance of tumor cells to drugs is a frequent cause of chemotherapy failure. With regard to platinum based drugs, multidrug resistance can also be connected with increased expression of low-molecular weight protein metallothionein (MT). This study aimed at investigating the interactions of MT with cisplatin or carboplatin, using the adsorptive transfer technique coupled with differential pulse voltammetry Brdicka reaction (AdTS DPV Brdicka reaction), and a comparison of in vitro results with results obtained in vivo. The results obtained from the in vitro study show a strong affinity between platinum based drugs and MT. Further, we analyzed extracts of neuroblastoma cell lines treated with cisplatin or carboplatin. It is clear that neuroblastoma UKF-NB-4 cisplatin-resistant and cisplatin-sensitive cell lines unlikely respond to the presence of the platinum-based cytostatics cisplatin and carboplatin. Finally, we determined the level of MT in samples from rabbits treated with carboplatin and patients with retinoblastoma treated with the same drug.     

A novel hexagonal honeycomb K–Cr-oxalate anionic network with layers separated by a five-coordinated Cu(II)–pypn complex (pypn = N,N′-bis(2-pyridylmethyl)-1,3-propanediamine). Synthesis,characterisation, spectroscopy and crystal structure of {[KCr(C2O4)3][Cu(pypn)(H2O)](H2O)4}

A novel hexagonal-based honeycomb compound with overall formula {[KCr(C₂O₄)₃][Cu(pypn)(H₂O)](H₂O)₄} is reported in which pypn is with the tetradentate ligand (N,N′-bis(2-pyridylmethyl)-1,3-propanediamine). The [KCr(C₂O₄)₃]^2? moiety forms a hexagonal honeycomb structure, while the five-coordinated [Cu(pypn)(H₂O)]²⁺ moiety is located in between the layers, partly filling the holes in the cavities. The synthesis, X-ray crystal structure and some spectroscopic properties are presented. The coordination of Cr(III) is octahedral, with a CrO₆ chromophore, and the K⁺ ion is in a KO₆ environment (K–O distances vary from 2.36 to 2.48 ?). The [KCr(C₂O₄)₃]^2? layers have the K⁺ ions in a Λ conformation, while the Cr(III) ions in the Δ conformation. The geometry around the Cu(II) is five-coordinated with four nitrogens from the chelating pypn ligand in a plane and the apical position being occupied by the oxygen atom of the coordinating water molecule. The packing of the cationic and the anionic layers appears to be of special interest.