Enhanced efficiency of tri-layered dye solar cells with hydrothermally synthesized titania nanotubes as light scattering outer layer

In the present study dye sensitized solar cells (DSSCs) have been fabricated with a tri-layer photo anode consisting of hydrothermally prepared titania nano tubes (TNT) having a diameter of 9-10 nm and length of several micrometers as outer layer, P25 TiO2 powder as transparent light absorbing middle layer and a compact TiO2 inner layer to improve the adhesion of different layers on a transparent conducting oxide coated substrate. In comparison to cells fabricated using TNTs or P25 alone, the tri-layer DSSCs exhibit an enhanced efficiency of 7.15% with a current density of 17.12 mA cm(-2) under AM 1.5 illumination. The enhancement is attributed to the light scattering generated by TNTs aggregates, reduction in electron transport resistance at the TiO2/dye/electrolyte interface and an improvement in electron life-time. (c) 2012 Elsevier B.V. All rights reserved.

Enhanced efficiency of near-UV emitting LEDs for solid-state lighting applications

The performance of a series of near-UV (∼385 nm) emitting LEDs, consisting of high efficiency InGaN/AlInGaN QWs in the active region, was investigated. Significantly reduced roll-over of efficiency at high current density was found compared to InGaN/GaN LEDs emitting at a similar wavelength. The importance of optical cavity effects in flip-chip geometry devices has also been investigated. The light output was enhanced by more than a factor of 2 when the lightemitting region was located at an anti-node position with respect to a high reflectivity current injection mirror. A power of 0.49 mW into a numerical aperture of 0.5 was obtained for a junction area of 50μm in diameter and a current of 30 mA, corresponding to a radiance of 30 W/cm2/str.

White electroluminescence from a single polymer system: Improved performance by means of enhanced efficiency and red-shifted luminescence of the blue-light-emitting species

High-efficiency white electrolurninescence from a single polymer is achieved by enhancing the electroluminescence efficiency and effecting a red-shift in the emission spectrum of the blue emissive species. A single-layer device of the resultant polymer exhibits a higher luminous efficiency than the nonmodified species (12.8 cd A(-1), see figure) and an external quantum efficiency of 5.4 % with CIE coordinates of (0.31,0.36), exemplifying the success of the reported methodology.

Enhanced efficiency of light-emitting polymers through intra-molecular energy transfer

To enhance the photoluminescence and electroluminescence efficiency, light-emitting polymers with energy transferring chromophores including N,N,N'N'-phenylene-diamine, naphthalene-imide, oxadiazole, meta-phenylene vinylene are designed and synthesized.

Enhanced efficiency of envelope-tracking based broadband inverse class-E power amplifier

In this paper, the envelope-tracking technique is exploited to boost average efficiency of the newly introduced broadband Inverse Class-E power amplifier. A 2.26 GHz - 20.5 dBm - 3 V power amplifier was designed, constructed, and measured. For a multi-carrier input signal with 10 dB peak-to-average ratio, the average PAE was increased from 5.7% to 54.5%. © 2008 IEEE.

Delivering enhanced efficiency in the synthesis of α-diazosulfoxides by exploiting the process control enabled in flow

Continuous-flow generation of α-diazosulfoxides results in a two- to three-fold increase in yields and decreased reaction times compared to standard batch synthesis methods. These high yielding reactions are enabled by flowing through a bed of polystyrene-supported base (PS-DBU or PS-NMe2) with highly controlled residence times. This engineered solution allows the α-diazosulfoxides to be rapidly synthesized while limiting exposure of the products to basic reaction conditions, which have been found to cause rapid decomposition. In addition to improved yields, this work has the added advantage of ease of processing, increased safety profile, and scale-up potential.

Annual nitrogen dynamics and urea fertilizer recoveries from a dairy pasture using 15N; effect of nitrification inhibitor DMPP and reduced application rates

Direct nitrogen (N) losses from pastures contribute to the poor nitrogen use efficiency of the dairy industry, though the exact fate of applied N and the processes involved are largely unknown. Nitrification inhibitors such as DMPP can potentially increase fertilizer N use efficiency (NUE), though few studies globally have examined the effectiveness of DMPP coated urea in pastures. This study quantified the NUE of DMPP combined with reduced application rates, and the effect on N dynamics and plant–soil interactions over an annual ryegrass/kikuyu rotation in Queensland, Australia. Labeled 15N urea and DMPP was applied over 7 winter applications at standard farmer (45 kg N ha−1) and half (23 kg N ha−1) rates. Fertilizer recoveries and NUE were calculated over 13 harvests, and the contribution of fertilizer and soil N estimated. Up to 85% of the annual N harvested was from soil organic matter. DMPP at the lower rate increased annual yields by 31% compared to the equivalent urea treatment with no difference to the high N rates. Almost 40% of the N added at the conventional fertilizer application rate as urea was lost to the environment; 80 kg N ha−1 higher than the low DMPP. Combining the nitrification inhibitor DMPP with reduced fertilizer application rates shows substantial potential to reduce N losses to the environment while sustaining productivity in subtropical dairy pastures.

Nitrification (DMPP) and urease (NBPT) inhibitors had no effect on pasture yield, nitrous oxide emissions nor nitrate leaching under irrigation in a hot-dry climate

Modern dairy farming in Australia relies on substantial inputs of fertiliser nitrogen (N) to underpin economic production. However, N lost from dairy systems represents an opportunity cost and can pose a number of environmental risks. Nitrogen cycle inhibitors can be co-applied with N fertilisers to slow the conversion of urea to NH4+ to reduce losses via volatilisation, and slow the conversion of NH4+ to NO3- to minimize leaching of NO3- and gaseous losses via nitrification and denitrification. In a field campaign in a high input ryegrass-kikuyu pasture system we compared the soil N pools, losses and pasture production between a) urea coated with the nitrification inhibitor (3,4-dimethyl pyrazole phosphate - DMPP) b) urea coated with the urease inhibitor (N-(n-butyl) thiophosphoric triamide - NBPT) and c) standard urea. There was no treatment effect (P>0.05) on soil mineral N, pasture yield, N2O flux nor leaching of NO3- cf. standard urea. We hypothesise that at our site, because gaseous losses were highly episodic (rainfall was erratic and displayed no seasonal rainfall nor soil wetting pattern) that there was a lack of coincidence of N application and conditions conducive to gaseous losses, thus the effectiveness of the inhibitor products was minimal and did not result in an increase in pasture yield. There remains a paucity of knowledge on N cycle inhibitors in relation to their effective use in field system to increase N use efficiency. Further research is required to define under what field conditions inhibitor products are effective in order to be able to provide accurate advice to managers of nitrogen in production systems.

Improved efficiency of PPV due to bulky tetraphenylmethane pendants

A PPV derivative containing bulky tetraphenylmethane side chains was synthesised. Its optical properties were examined. Compared to its parent PPV polymer, its UV-Vis absorption and PL showed less red-shift from solution to film, its PL showed much less concentration quenching effect and higher efficiency, its EL device showed 9-fold enhanced efficiency. These improvements were attributed to weakened inter-chain interaction caused by the tetraphenylmethane group.

The influence of substrate on the properties of Er2O3 films grown by magnetron sputtering

The structural properties and the room temperature luminescence of Er2O3 thin films deposited by RF magnetron sputtering have been studied. Films characterized by good morphological properties have been obtained by using a SiO2 interlayer between the film and the Si substrate. The evolution of the properties of the Er2O3 films due to rapid thermal annealing processes in O2 ambient performed at temperatures in the range 800-1200 °C has been investigated in details. The existence of well-defined annealing conditions (temperature of 1100 °C or higher) allowing to avoid the occurrence of extensive chemical reactions with the oxidized substrate has been demonstrated and an increase of the photoluminescence (PL) intensity by about a factor of 40 with respect to the as deposited material has been observed. The enhanced efficiency of the photon emission process has been correlated with the longer lifetime of the PL signal. The same annealing processes are less effective when Er2O3 is deposited on Si. In this latter case interfacial reactions and pit formation occur, leading to a material characterized by stronger non-radiative phenomena that limit the PL efficiency. © 2006 Elsevier B.V. All rights reserved.

Optical and structural properties of Er2O3 films grown by magnetron sputtering

The structural properties and the room temperature luminescence of Er 2O3 thin films deposited by magnetron sputtering have been studied. In spite of the well-known high reactivity of rare earth oxides towards silicon, films characterized by good morphological properties have been obtained by using a SiO2 interlayer between the film and the silicon substrate. The evolution of the properties of the Er2O3 films due to thermal annealing processes in oxygen ambient performed at temperatures in the range of 800-1200°C has been investigated in detail. The existence of well defined annealing conditions (rapid treatments at a temperature of 1100°C or higher) allowing to avoid the occurrence of extensive chemical reactions with the oxidized substrate has been demonstrated; under these conditions, the thermal process has a beneficial effect on both structural and optical properties of the film, and an increase of the photoluminescence (PL) intensity by about a factor of 40 with respect to the as-deposited material has been observed. The enhanced efficiency of the photon emission process has been correlated with the longer lifetime of the PL signal. Finally, the conditions leading to a reaction of Er2O3 with the substrate have been also identified, and evidences about the formation of silicate-like phases have been collected. © 2006 American Institute of Physics.

Towards more sustainable and environmentally-friendly concretes: The use of silica fume

Concrete is the most widely used construction material. At the same time, however, the concrete industry is a major CO2 emitter thus contributing towards global warming. While enhanced efficiency in the production of concrete is not likely to dramatically reduce the CO2 emissions, cement replacement by a supplementary material or mineral additive, such as silica fume, which is not associated with CO2 emission, can substantially reduce the aforementioned problem. The present work discusses the benefits of incorporating mineral additives in concrete and shows that these additives can improve both the mechanical and physical properties of the end-product, and hence its durability, albeit with a reduction in cement content. © 2009 WIT Press.

Expression of the SEPT9_i4 isoform confers resistance to microtubule-interacting drugs

BACKGROUND: The evolutionarily conserved septin family of genes encode GTP binding proteins involved in a variety of cellular functions including cytokinesis, apoptosis, membrane dynamics and vesicle trafficking. Septin proteins can form hetero-oligomeric complexes and interact with other proteins including actin and tubulin. The human SEPT9 gene on chromosome 17q25.3 has a complex genomic architecture with 18 different transcripts that can encode 15 distinct polypeptides. Two distinct transcripts with unique 5' ends (SEPT9_v4 and SEPT9_v4*) encode the same protein. In tumours the ratio of these transcripts changes with elevated levels of SEPT9_v4* mRNA, a transcript that is translated with enhanced efficiency leading to increased SEPT9_i4 protein.

METHODS: We have examined the effect of over-expression of SEPT9_i4 on the dynamics of microtubule polymer mass in cultured cells.

RESULTS: We show that the microtubule network in SEPT9_i4 over-expressing cells resists disruption by paclitaxel or cold incubation but also repolymerises tubulin more slowly after microtubule depolymerisation. Finally we show that SEPT9_i4 over-expressing cells have enhanced survival in the presence of clinically relevant microtubule acting drugs but not after treatment with DNAinteracting agents.

CONCLUSIONS: Given that SEPT9 over-expression is seen in diverse tumours and in particular ovarian and breast cancer, such data indicate that SEPT9_v4 expression may be clinically relevant and contribute to some forms of drug resistance.

Nonlinear scattering by anisotropic dielectric periodic structures

The combinatorial frequency generation by the periodic stacks of binary layers of anisotropic nonlinear dielectrics is examined. The products of nonlinear scattering are characterised in terms of the three-wave mixing processes. It is shown that the intensity of the scattered waves of combinatorial frequencies is strongly influenced by the constitutive and geometrical parameters of the anisotropic layers, and the frequency ratio and angles of incidence of pump waves. The enhanced efficiency of the frequency conversion at Wolf-Bragg resonances has been demonstrated for the lossless and lossy-layered structures. © 2012 O. V. Shramkova and A. G. Schuchinsky.