Sintering and densification mechanisms of Y2BaCuO5 pellets

The sintering and densification of Y2BaCuO5 (Y-211) pellets made from powders with different characteristics have been investigated in the temperature range 1000-1140°C. A pellet made from powder containing Ba-rich secondary phases shows very early liquid-assisted sintering and densification and clear evidence of exaggerated grain growth. The melting of BaCuO2 and YBa2Cu3O7-δ (Y-123) secondary phases increases the rate of densification of Y-211 pellets made from other powders at temperatures above 1025-1030°C. All the liquid produced by the melting of the latter phases recrystallizes as intergranular layers of Y-123. These intergranular layers account for the darker appearance and for measurable electrical conductivities at room temperature of the pellets sintered at the higher temperatures. The development of exaggerated grain growth within a uniform fine-grained matrix opens the possibility of using controlled secondary recrystallization to obtain large single domains of Y-211, provided that the trapping of porosity can be avoided or minimized. © 1999 Elsevier Science S.A.

Plasmonic effect of gold nanoparticles in organic solar cells

Light trapping, due to the embedding of metallic nanoparticles, has been shown to be beneficial for a better photoabsorption in organic solar cells. Researchers in plasmonics and in the organic photovoltaics fields are working together to improve the absorption of sunlight and the photon–electron coupling to boost the performance of the devices. Recent advances in the field of plasmonics for organic solar cells focus on the incorporation of gold nanoparticles. This article reviews the different methods to produce and embed gold nanoparticles into organic solar cells. In particular, concentration, size and geometry of gold nanoparticles are key factors that directly influence the light absorption in the devices. It is shown that a careful choice of size, concentration and location of gold nanoparticles in the device result in an enhancement of the power conversion efficiencies when compared to standard organic solar cell devices. Our latest results on gold nanoparticles embedded in on organic solar cell devices are included. We demonstrate that embedded gold nanoparticles, created by depositing and annealing a gold film on transparent electrode, generate a plasmonic effect which can be exploited to increase the power conversion efficiency of a bulk heterojunction solar cell up to 10%.

Provisional matrix deposition in hemostasis and venous insufficiency: Tissue preconditioning for nonhealing venous ulcers

Significance: Chronic wounds represent a major burden on global healthcare systems and reduce the quality of life of those affected. Significant advances have been made in our understanding of the biochemistry of wound healing progression. However, knowledge regarding the specific molecular processes influencing chronic wound formation and persistence remains limited. Recent Advances: Generally, healing of acute wounds begins with hemostasis and the deposition of a plasma-derived provisional matrix into the wound. The deposition of plasma matrix proteins is known to occur around the microvasculature of the lower limb as a result of venous insufficiency. This appears to alter limb cutaneous tissue physiology and consequently drives the tissue into a ‘preconditioned’ state that negatively influences the response to wounding. Critical Issues: Processes, such as oxygen and nutrient suppression, edema, inflammatory cell trapping/extravasation, diffuse inflammation, and tissue necrosis are thought to contribute to the advent of a chronic wound. Healing of the wound then becomes difficult in the context of an internally injured limb. Thus, interventions and therapies for promoting healing of the limb is a growing area of interest. For venous ulcers, treatment using compression bandaging encourages venous return and improves healing processes within the limb, critically however, once treatment concludes ulcers often reoccur. Future Directions: Improved understanding of the composition and role of pericapillary matrix deposits in facilitating internal limb injury and subsequent development of chronic wounds will be critical for informing and enhancing current best practice therapies and preventative action in the wound care field.

A comparison study on hydrogen sensing performance of MoO3 nanoplatelets coated with a thin layer of Ta2O5 or La2O3

There has been significant interest in developing metal oxide films with high surface area-to-volume ratio nanostructures particularly in substantially increasing the performance of Pt/oxide/semiconductor Schottky-diode gas sensors. While retaining the surface morphology of these devices, they can be further improved by modifying their nanostructured surface with a thin metal oxide layer. In this work, we analyse and compare the electrical and hydrogen-sensing properties of MoO3 nanoplatelets coated with a 4 nm layer of tantalum oxide (Ta2O5) or lanthanum oxide (La2O3). We explain in our study, that the presence of numerous defect traps at the surface (and the bulk) of the thin high-� layer causes a substantial trapping of charge during hydrogen adsorption. As a result, the interface between the Pt electrode and the thin oxide layer becomes highly polarised. Measurement results also show that the nanoplatelets coated with Ta2O5 can enable the device to be more sensitive (a larger voltage shift under hydrogen exposure) than those coated with La2O3.

UV Photodissociation Action Spectroscopy of Haloanilinium Ions in a Linear Quadrupole Ion Trap Mass Spectrometer

UV-vis photodissociation action spectroscopy is becoming increasingly prevalent because of advances in, and commercial availability of, ion trapping technologies and tunable laser sources. This study outlines in detail an instrumental arrangement, combining a commercial ion-trap mass spectrometer and tunable nanosecond pulsed laser source, for performing fully automated photodissociation action spectroscopy on gas-phase ions. The components of the instrumentation are outlined, including the optical and electronic interfacing, in addition to the control software for automating the experiment and performing online analysis of the spectra. To demonstrate the utility of this ensemble, the photodissociation action spectra of 4-chloroanilinium, 4-bromoanilinium, and 4-iodoanilinium cations are presented and discussed. Multiple photoproducts are detected in each case and the photoproduct yields are followed as a function of laser wavelength. It is shown that the wavelength-dependent partitioning of the halide loss, H loss, and NH3 loss channels can be broadly rationalized in terms of the relative carbon-halide bond dissociation energies and processes of energy redistribution. The photodissociation action spectrum of (phenyl)Ag-2 (+) is compared with a literature spectrum as a further benchmark.

Ozone-induced dissociation of conjugated lipids reveals significant reaction rate enhancements and characteristic odd-electron product ions

Ozone-induced dissociation (OzID) is an alternative ion activation method that relies on the gas phase ion-molecule reaction between a mass-selected target ion and ozone in an ion trap mass spectrometer. Herein, we evaluated the performance of OzID for both the structural elucidation and selective detection of conjugated carbon-carbon double bond motifs within lipids. The relative reactivity trends for \[M + X](+) ions (where X = Li, Na, K) formed via electrospray ionization (ESI) of conjugated versus nonconjugated fatty acid methyl esters (FAMEs) were examined using two different OzID-enabled linear ion-trap mass spectrometers. Compared with nonconjugated analogues, FAMEs derived from conjugated linoleic acids were found to react up to 200 times faster and to yield characteristic radical cations. The significantly enhanced reactivity of conjugated isomers means that OzID product ions can be observed without invoking a reaction delay in the experimental sequence (i.e., trapping of ions in the presence of ozone is not required). This possibility has been exploited to undertake neutral-loss scans on a triple quadrupole mass spectrometer targeting characteristic OzID transitions. Such analyses reveal the presence of conjugated double bonds in lipids extracted from selected foodstuffs. Finally, by benchmarking of the absolute ozone concentration inside the ion trap, second order rate constants for the gas phase reactions between unsaturated organic ions and ozone were obtained. These results demonstrate a significant influence of the adducting metal on reaction rate constants in the fashion Li > Na > K.

A new dasyurid marsupial from Kroombit Tops, south-east Queensland, Australia : the Silver-headed Antechinus, Antechinus argentus sp. nov. (Marsupialia: Dasyuridae)

Antechinus argentus sp. nov. is currently only known from the plateau at the eastern escarpment of Kroombit Tops National Park, about 400km NNW of Brisbane and 60km SSW of Gladstone, south-east Queensland, Australia. Antechinus flavipes (Waterhouse) is also known from Kroombit Tops NP, 4.5km W of the nearest known population of A. argentus; A. mysticus Baker, Mutton and Van Dyck has yet to be found within Kroombit Tops, but is known from museum specimens taken at Bulburin NP, just 40km ESE, as well as extant populations about 400km to both the south-east and north-west of Kroombit NP. A. argentus can be easily distinguished in the field, having an overall silvery/grey appearance with much paler silver feet and drabber deep greyish-olive rump than A. flavipes, which has distinctive yellow-orange toned feet, rump and tail-base; A. argentus fur is also less coarse than that of A. flavipes. A. argentus has a striking silver-grey head, neck and shoulders, with pale, slightly broken eye-rings, which distinguish it from A. mysticus which has a more subtle greyish-brown head, pale buff dabs of eyeliner and more colourful brownish-yellow rump. Features of the dentary can also be used for identification: A. argentus differs from A. flavipes in having smaller molar teeth, as well as a narrower and smaller skull and from A. mysticus in having on average a narrower snout, smaller skull and dentary lengths and smaller posterior palatal vacuities in the skull. A. argentus is strongly divergent genetically (at mtDNA) from both A. flavipes (9.0–11.2%) and A. mysticus (7.2–7.5%), and forms a very strongly supported clade to the exclusion of all other antechinus species, in both mtDNA and combined (mtDNA and nDNA) phylogenies inferred here. We are yet to make detailed surveys in search of A. argentus from forested areas to the immediate east and north of Kroombit Tops. However, A. mysticus has only been found at these sites in low densities in decades past and not at all in several recent trapping expeditions conducted by the authors. With similar habitat types in close geographic proximity, it is plausible that A. argentus may be found outside Kroombit. Nevertheless, it is striking that from a range of surveys conducted at Kroombit Tops in the last 15 years and intensive surveys by the authors in the last 3 years, totalling more than 5 080 trap nights, just 13 A. argentus have been captured from two sites less than 6 km apart. If this is even close to the true geographic extent of the species, it would possess one of the smallest distributions of an Australian mammal species. With several threats identified, we tentatively recommend that A. argentus be listed as Endangered, pending an exhaustive trapping survey of Kroombit and surrounds.

Foil-based atom chip for Bose-Einstein condensates

We describe a novel method of fabricating atom chips that are well suited to the production and manipulation of atomic Bose–Einstein condensates. Our chip was created using a silver foil and simple micro-cutting techniques without the need for photolithography. It can sustain larger currents than conventional chips, and is compatible with the patterning of complex trapping potentials. A near pure Bose–Einstein condensate of 4 × 104 87Rb atoms has been created in a magnetic microtrap formed by currents through wires on the chip. We have observed the fragmentation of atom clouds in close proximity to the silver conductors. The fragmentation has different characteristic features to those seen with copper conductors.

Desorption electrospray ionisation mass spectrometry reveals in situ modification of a hindered amine light stabiliser resulting from direct N–OR bond cleavage

Detection and characterisation of structural modifications of a hindered amine light stabiliser (HALS) directly from a polyester-based coil coating have been achieved by desorption electrospray ionisation mass spectrometry (DESI-MS) for the first time. In situ detection is made possible by exposing the coating to an acetone vapour atmosphere prior to analysis. This is a gentle and non-destructive treatment that allows diffusion of analyte to the surface without promoting lateral migration. Using this approach a major structural modification of the HALS TINUVIN®123 (bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate) was discovered where one N-ether piperidine moiety (N-OC8H17) is converted to a secondary piperidine (N–H). With the use of 2-dimensional DESI-MS imaging the modification was observed to arise during high curing temperatures (ca. 260 °C) and under simulated physiological conditions (80 °C, full solar spectrum). It is proposed that the secondary piperidine derivative is a result of a highly reactive aminyl radical intermediate produced by N–O homolytic bond cleavage. The nature of the bond cleavage is also suggested by ESR spin-trapping experiments employing α-phenyl-N-tert-butyl nitrone (PBN) in toluene at 80 °C. The presence of a secondary piperidine derivative in situ and the implication of N–OR competing with NO–R bond cleavage suggest an alternative pathway for generation of the nitroxyl radical—an essential requirement in anti-oxidant activity that has not previously been described for the N-ether sub-class of HALS.

Control of ion density distribution by magnetic traps for plasma electrons

The effect of a magnetic field of two magnetic coils on the ion current density distribution in the setup for low-temperature plasma deposition is investigated. The substrate of 400 mm diameter is placed at a distance of 325 mm from the plasma duct exit, with the two magnetic coils mounted symmetrically under the substrate at a distance of 140 mm relative to the substrate centre. A planar probe is used to measure the ion current density distribution along the plasma flux cross-sections at distances of 150, 230, and 325 mm from the plasma duct exit. It is shown that the magnetic field strongly affects the ion current density distribution. Transparent plastic films are used to investigate qualitatively the ion density distribution profiles and the effect of the magnetic field. A theoretical model is developed to describe the interaction of the ion fluxes with the negative space charge regions associated with the magnetic trapping of the plasmaelectrons. Theoretical results are compared with the experimental measurements, and a reasonable agreement is demonstrated.

Enhancement of optical absorption in thin-film solar cells through the excitation of higher-order nanoparticle plasmon modes

Recent research in the rapidly emerging field of plasmonics has shown the potential to significantly enhance light trapping inside thin-film solar cells by using metallic nanoparticles. In this article it is demonstrated the plasmon enhancement of optical absorption in amorphous silicon solar cells by using silver nanoparticles. Based on the analysis of the higher-order surface plasmon modes, it is shown how spectral positions of the surface plasmons affect the plasmonic enhancement of thin-film solar cells. By using the predictive 3D modeling, we investigate the effect of the higher-order modes on that enhancement. Finally, we suggest how to maximize the light trapping and optical absorption in the thin-film cell by optimizing the nanoparticle array parameters, which in turn can be used to fine tune the corresponding surface plasmon modes.

A study of the effects metal residues in poly(9,9-dioctylfluorene) have on field-effect transistor device characteristics

The amount of metal residues from organometallic reagents used in preparation of poly(9,9-dioctylfluorene) by palladium catalysed Suzuki and nickel-induced Yamamoto polycondensations have been determined, and their effect upon the behaviour of the polymer in field-effect transistors (FETs) has been measured. The metal levels from material polymerised by Suzuki method were found to be much higher than from that made by the Yamamoto procedure. Simple treatment of the polymers with suitable metal trapping reagents lowered the metal levels significantly, with EDTA giving best results for nickel and triphenylphosphine for palladium. Comparison of the behaviour of FETs using polyfluorenes with varying levels of metal contamination, showed that the metal residues have little effect upon the mobility values, but often affect the degree of hysteresis, possibly acting as charge traps. Satisfactory device performances were obtained from polymer with palladium levels of 2000 μg/g suggesting that complete removal of metal residues may not be necessary for satisfactory device performance.

Recommendations for the categorization of germ cell mutagens

Germ cell mutagens are currently classified into three categories in the German List of MAK- and BAT-Values. These categories have been revised and extended in analogy to the new categories for carcinogenic chemicals. Germ cell mutagens produce heritable gene mutations, and heritable structural and numerical chromosome aberrations in germ cells. The original categories 1 and 2 for germ cell mutagens remained unchanged. Two new categories 3 A and 3 B are proposed for chemicals which are suspected to be germ cell mutagens. A new category 5 is proposed for germ cell mutagens with low potency which contribute negligibly to human genetic risk provided the MAK value is observed. The following categories are presented for further discussion. 1. Germ cell mutagens which have been shown to increase the mutant frequency among the progeny of exposed humans. 2. Germ cell mutagens which have been shown to increase the mutant frequency among the progeny of exposed animals. 3 A. Substances which have been shown to induce genetic damage in germ cells of humans or animals, or which are mutagenic in somatic cells and have been shown to reach the germ cells in their active forms. 3 B. Substances which are suspected of being germ cell mutagens because of their genotoxic effects in mammalian somatic cells in vivo or, in exceptional cases in the absence of in vivo data, if they are clearly mutagenic in vitro and structurally related to in vivo mutagens. 4. not applicable (Category 4 was introduced for carcinogenic substances with nongenotoxic modes of action. By definition, germ cell mutagens are genotoxic. Therefore, a Category 4 for germ cell mutagens cannot exist.) 5. Germ cell mutagens, the potency of which is considered to be so low that, provided the MAK value is observed, their contribution to genetic risk is expected not to be significant.

Non-destructive DNA extraction from Chironomidae, including of fragile pupal exuviae, extends analysable collections and enhances vouchering

It is well established that the traditional taxonomy and nomenclature of Chironomidae relies on adult males whose usually characteristic genitalia provide evidence of species distinction. In the early days some names were based on female adults of variable distinctiveness – but females are difficult to identify (Ekrem et al. 2010) and many of these names remain dubious. In Russia especially, a system based on larval morphology grew in parallel to the conventional adult-based system. The systems became reconciled with the studies that underlay the production of the Holarctic generic keys to Chironomidae, commencing notably with the larval volume (Wiederholm, 1983). Ever since Thienemann’s pioneering studies, it has been evident that the pupa, notably the cast skins (exuviae) provide a wealth of features that can aid in identification (e.g. Wiederholm, 1986). Furthermore, the pupae can be readily associated with name-bearing adults when a pharate (‘cloaked’) adult stage is visible within the pupa. Association of larvae with the name-bearing later stages has been much more difficult, time-consuming and fraught with risk of failure. Yet it is identification of the larval stage that is needed by most applied researchers due to the value of the immature stages of the family in aquatic monitoring for water quality, although the pupal stage also has advocates (reviewed by Sinclair & Gresens, 2008). Few use the adult stage for such purposes as their provenance and association with the water body can be verified only by emergence trapping, and sampling of adults lies outside regular aquatic monitoring protocols.

Temporal and spatial distribution and habitat associations of an urban population of New Zealand long-tailed bats (Chalinolobus tuberculatus)

Two ultrasound survey methods were used to determine the presence and activity patterns of New Zealand long-tailed bats (Chalinolobus tuberculatus) in the city of Hamilton. First, 13 monthly surveys conducted at 18 green spaces found C. tuberculatus in only one urban forest reserve, Hammond Bush, where they were found consistently throughout the year. Bat activity was strongly related to temperature. Second, twice-yearly citywide surveys conducted over 2 years determined the distribution and habitat associations of C. tuberculatus. Bats were found only in the southern part of the city and were strongly associated with the Waikato River. Bat activity was negatively correlated with housing and street light density and positively correlated with topographical complexity. In Hamilton, topographical complexity indicates the presence of gullies. Gullies probably provide foraging and roosting opportunities and connect the river to distant forest patches. These results suggest that urban habitats can be useful for bats if gullies can link these to distant habitat fragments.