Impact of a change in tillage and crop residue management practice on soil chemical and microbiological properties in a cereal-producing red duplex soil in NSW, Australia

The effect of a change of tillage and crop residue management practice on the chemical and micro-biological properties of a cereal-producing red duplex soil was investigated by superimposing each of three management practices (CC: conventional cultivation, stubble burnt, crop conventionally sown; DD: direct-drilling, stubble retained, no cultivation, crop direct-drilled; SI: stubble incorporated with a single cultivation, crop conventionally sown), for a 3-year period on plots previously managed with each of the same three practices for 14 years. A change from DD to CC or SI practice resulted in a significant decline, in the top 0-5 cm of soil, in organic C, total N, electrical conductivity, NH4-N, NO3-N, soil moisture holding capacity, microbial biomass and CO2 respiration as well as a decline in the microbial quotient (the ratio of microbial biomass C to organic C; P <0.05). In contrast, a change from SI to DD or CC practice or a change from CC to DD or SI practice had only negligible impact on soil chemical properties (P >0.05). However, there was a significant increase in microbial biomass and the microbial quotient in the top 0-5 cm of soil following the change from CC to DD or SI practice and with the change from SI to DD practice (P <0.05). Analysis of ester-linked fatty acid methyl esters (EL-FAMEs) extracted from the 0- to 5-cm and 5- to 10-cm layers of the soils of the various treatments detected changes in the FAME profiles following a change in tillage practice. A change from DD practice to SI or CC practice was associated with a significant decline in the ratio of fungal to bacterial fatty acids in the 0- to 5-cm soil (P <0.05). The results show that a change in tillage practice, particularly the cultivation of a previously minimum-tilled (direct-drilled) soil, will result in significant changes in soil chemical and microbiological properties within a 3-year period. They also show that soil microbiological properties are sensitive indicators of a change in tillage practice.

Capacity of fatty acid profiles and substrate utilization patterns to describe differences in soil microbial communities associated with increased salinity or alkalinity at three locations in South Australia

Fatty acid methyl ester (FAME) profiles, together with Biolog substrate utilization patterns, were used in conjunction with measurements of other soil chemical and microbiological properties to describe differences in soil microbial communities induced by increased salinity and alkalinity in grass/legume pastures at three sites in SE South Australia. Total ester-linked FAMEs (EL-FAMEs) and phospholipid-linked FAMEs (PL-FAMEs), were also compared for their ability to detect differences between the soil microbial communities. The level of salinity and alkalinity in affected areas of the pastures showed seasonal variation, being greater in summer than in winter. At the time of sampling for the chemical and microbiological measurements (winter) only the affected soil at site 1 was significantly saline. The affected soils at all three sites had lower organic C and total N concentrations than the corresponding non-affected soils. At site 1 microbial biomass, CO 2-C respiration and the rate of cellulose decomposition was also lower in the affected soil compared to the non-affected soil. Biomarker fatty acids present in both the EL- and PL-FAME profiles indicated a lower ratio of fungal to bacterial fatty acids in the saline affected soil at site 1. Analysis of Biolog substrate utilization patterns indicated that the bacterial community in the affected soil at site 1 utilized fewer carbon substrates and had lower functional diversity than the corresponding community in the non-affected soil. In contrast, increased alkalinity, of major importance at sites 2 and 3, had no effect on microbial biomass, the rate of cellulose decomposition or functional diversity but was associated with significant differences in the relative amounts of several fatty acids in the PL-FAME profiles indicative of a shift towards a bacterial dominated community. Despite differences in the number and relative amounts of fatty acids detected, principal component analysis of the EL- and PL-FAME profiles were equally capable of separating the affected and non-affected soils at all three sites. Redundancy analysis of the FAME data showed that organic C, microbial biomass, electrical conductivity and bicarbonate-extractable P were significantly correlated with variation in the EL-FAME profiles, whereas pH, electrical conductivity, NH 4-N, CO 2-C respiration and the microbial quotient were significantly correlated with variation in the PL-FAME profiles. Redundancy analysis of the Biolog data indicated that cation exchange capacity and bicarbonate-extractable K were significantly correlated with the variation in Biolog substrate utilization patterns.

Electron-accepting conjugated materials based on 2-Vinyl-4,5- dicyanoimidazoles for application in organic electronics

We report the Heck coupling of 2-vinyl-4,5-dicyanoimidazole (vinazene) with selected di- and trihalo aromatics in an effort to prepare linear and branched electron-accepting conjugated materials for application in organic electronics. By selecting the suitable halo-aromatic moiety, it is possible to tune the HOMO - LUMO energy levels, absorption, and emission properties for a specific application. In this regard, materials with strong photoluminescence from blue → green → red are reported that may have potential application in organic light-emitting diodes (OLEDs). Furthermore, derivatives with strong absorption in the visible spectrum, coupled with favorable HOMO-LUMO levels, have been used to prepare promising organic photovoltaic devices (OPVs) when combined with commercially available semiconducting donor polymers.

Water-based nanoparticulate solar cells using a diketopyrrolopyrrole donor polymer

Organic photovoltaic devices with either bulk heterojunction (BHJ) or nanoparticulate (NP) active layers have been prepared from a 1:2 blend of (poly{3,6-dithiophene-2-yl-2,5-di(2-octyldodecyl)-pyrrolo[3,4-c]pyrrole-1, 4-dione-alt-naphthalene}) (PDPP-TNT) and the fullerene acceptor, ([6,6]-phenyl C71-butyric acid methyl ester) (PC70BM). Atomic force microscopy (AFM) and scanning electron microscopy (SEM) have been used to investigate the morphology of the active layers of the two approaches. Mild thermal treatment of the NP film is required to promote initial joining of the NPs in order for the devices to function, however the NP structure is retained. Consequently, whereas gross phase segregation of the active layer occurs in the BHJ device spin cast from chloroform, the nanoparticulate approach retains control of the material domain sizes on the length scale of exciton diffusion in the materials. As a result, NP devices are found to generate more than twice the current density of BHJ devices and have a substantially greater overall efficiency. The use of aqueous nanoparticulate dispersions offers a promising approach to control the donor acceptor morphology on the nanoscale with the benefit of environmentally- friendly, solution-based fabrication. © 2014 the Owner Societies.

Nanoscale phase domain structure and associated device performance of organic solar cells based on a diketopyrrolopyrrole polymer

We investigate the blend morphology and performance of bulk heterojunction organic photovoltaic devices comprising the donor polymer, pDPP-TNT (poly{3,6-dithiophene-2-yl-2,5-di(2-octyldodecyl)-pyrrolo[3,4-c]pyrrole-1, 4-dione-alt-naphthalene}) and the fullerene acceptor, [70]PCBM ([6,6]-phenyl C71-butyric acid methyl ester). The blend morphology is heavily dependent upon the solvent system used in the fabrication of thin films. Thin films spin-coated from chloroform possess a cobblestone-like morphology, consisting of thick, round-shaped [70]PCBM-rich mounds separated by thin polymer-rich valleys. The size of the [70]PCBM domains is found to depend on the overall film thickness. Thin films spin-coated from a chloroform:dichlorobenzene mixed solvent system are smooth and consist of a network of pDPP-TNT nanofibers embedded in a [70]PCBM-rich matrix. Rinsing the films in hexane selectively removes [70]PCBM and allows for analysis of domain size and purity. It also provides a means for investigating exciton dissociation efficiency through relative photoluminescence yield measurements. Devices fabricated from chloroform solutions show much poorer performance than the devices fabricated from the mixed solvent system; this disparity in performance is seen to be more pronounced with increasing film thickness. The primary cause for the improved performance of devices fabricated from mixed solvents is attributed to the greater donor-acceptor interfacial area and resulting greater capacity for charge carrier generation.

Measurement of contact voltage drop and resistance in organic solar cells

Bulk heterojunction organic solar cells based on poly[4,7-bis(3- dodecylthiophene-2-yl) benzothiadiazole-co-benzothiadiazole] and [6,6]-phenyl C71-butyric acid methyl ester are investigated. A prominent kink is observed in the fourth quadrant of the current density-voltage (J-V) response. Annealing the active layer prior to cathode deposition eliminates the kink. The kink is attributed to an extraction barrier. The J-V response in these devices is well described by a power law. This behavior is attributed to an imbalance in charge carrier mobility. An expected photocurrent for the device displaying a kink in the J-V response is determined by fitting to a power law. The difference between the expected and measured photocurrent allows for the determination of a voltage drop within the device. Under simulated 1 sun irradiance, the peak voltage drop and contact resistance at short circuit are 0.14 V and 90 Ω, respectively. © 2012 American Institute of Physics.

Biodiesel production from non-edible beauty leaf (Calophyllum Inophyllum) oil : process optimization using response surface methodology (RSM)

In recent years, the beauty leaf plant (Calophyllum Inophyllum) is being considered as a potential 2nd generation biodiesel source due to high seed oil content, high fruit production rate, simple cultivation and ability to grow in a wide range of climate conditions. However, however, due to the high free fatty acid (FFA) content in this oil, the potential of this biodiesel feedstock is still unrealized, and little research has been undertaken on it. In this study, transesterification of beauty leaf oil to produce biodiesel has been investigated. A two-step biodiesel conversion method consisting of acid catalysed pre-esterification and alkali catalysed transesterification has been utilized. The three main factors that drive the biodiesel (fatty acid methyl ester (FAME)) conversion from vegetable oil (triglycerides) were studied using response surface methodology (RSM) based on a Box-Behnken experimental design. The factors considered in this study were catalyst concentration, methanol to oil molar ratio and reaction temperature. Linear and full quadratic regression models were developed to predict FFA and FAME concentration and to optimize the reaction conditions. The significance of these factors and their interaction in both stages was determined using analysis of variance (ANOVA). The reaction conditions for the largest reduction in FFA concentration for acid catalysed pre-esterification was 30:1 methanol to oil molar ratio, 10% (w/w) sulfuric acid catalyst loading and 75 °C reaction temperature. In the alkali catalysed transesterification process 7.5:1 methanol to oil molar ratio, 1% (w/w) sodium methoxide catalyst loading and 55 °C reaction temperature were found to result in the highest FAME conversion. The good agreement between model outputs and experimental results demonstrated that this methodology may be useful for industrial process optimization for biodiesel production from beauty leaf oil and possibly other industrial processes as well.

Experimental evidence for competitive N–O and O–C bond homolysis in gasphase alkoxyamines

The extensive use of alkoxyamines in controlled radical polymerisation and polymer stabilisation is based on rapid cycling between the alkoxyamine (R1R2NO–R3) and a stable nitroxyl radical (R1R2NO•) via homolysis of the labile O–C bond. Competing homolysis of the alkoxyamine N–O bond has been predicted to occur for some substituents leading to production of aminyl and alkoxyl radicals. This intrinsic competition between the O–C and N–O bond homolysis processes has to this point been difficult to probe experimentally. Herein we examine the effect of local molecular structure on the competition between N–O and O–C bond cleavage in the gas phase by variable energy tandem mass spectrometry in a triple quadrupole mass spectrometer. A suite of cyclic alkoxyamines with remote carboxylic acid moieties (HOOC–R1R2NO–R3) were synthesised and subjected to negative ion electrospray ionisation to yield [M – H]− anions where the charge is remote from the alkoxyamine moiety. Collision-induced dissociation of these anions yield product ions resulting, almost exclusively, from homolysis of O–C and/or N–O bonds. The relative efficacy of N–O and O–C bond homolysis was examined for alkoxyamines incorporating different R3 substituents by varying the potential difference applied to the collision cell, and comparing dissociation thresholds of each product ion channel. For most R3 substituents, product ions from homolysis of the O–C bond are observed and product ions resulting from cleavage of the N–O bond are minor or absent. A limited number of examples were encountered however, where N–O homolysis is a competitive dissociation pathway because the O–C bond is stabilised by adjacent heteroatom(s) (e.g., R3 = CH2F). The dissociation threshold energies were compared for different alkoxyamine substituents (R3) and the relative ordering of these experimentally determined energies is shown to correlate with the bond dissociation free energies, calculated by ab initio methods. Understanding the structure-dependent relationship between these rival processes will assist in the design and selection of alkoxyamine motifs that selectively promote the desirable O–C homolysis pathway.

Transcriptional pathway signatures predict MEK addiction and response to selumetinib (AZD6244)

Selumetinib (AZD6244, ARRY-142886) is a selective, non-ATP-competitive inhibitor of mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK)-1/2. The range of antitumor activity seen preclinically and in patients highlights the importance of identifying determinants of response to this drug. In large tumor cell panels of diverse lineage, we show that MEK inhibitor response does not have an absolute correlation with mutational or phospho-protein markers of BRAF/MEK, RAS, or phosphoinositide 3-kinase (PI3K) activity. We aimed to enhance predictivity by measuring pathway output through coregulated gene networks displaying differential mRNA expression exclusive to resistant cell subsets and correlated to mutational or dynamic pathway activity. We discovered an 18-gene signature enabling measurement of MEK functional output independent of tumor genotype. Where the MEK pathway is activated but the cells remain resistant to selumetinib, we identified a 13-gene signature that implicates the existence of compensatory signaling from RAS effectors other than PI3K. The ability of these signatures to stratify samples according to functional activation of MEK and/or selumetinib sensitivity was shown in multiple independent melanoma, colon, breast, and lung tumor cell lines and in xenograft models. Furthermore, we were able to measure these signatures in fixed archival melanoma tumor samples using a single RT-qPCR-based test and found intergene correlations and associations with genetic markers of pathway activity to be preserved. These signatures offer useful tools for the study of MEK biology and clinical application of MEK inhibitors, and the novel approaches taken may benefit other targeted therapies.

Self-reflection as an intervention to influence achievement goal orientations and intrinsic motivation

In the context of physical activity, intrinsic motivation refers to the inherent satisfaction associated with participation in the activity. Interest-enjoyment, perceived competence, and effort have been identified as three underlying components of intrinsic motivation. Achievement goal theory stipulates that achievement goals guide our beliefs and behavior. The two main achievement goal orientations identified in the sport and physical activity literature are task and ego orientations. A person with a strong task orientation defines success in self-referenced terms, as improving one’s own performance or mastering new skills. Someone with a strong ego orientation defines success normatively, as being better than others. The majority of research suggests that having a strong task orientation is a good thing, whether with regard to motivationally adaptive responses, sources of sport confidence, students’ satisfaction with learning, or the use of cognitive and self-regulatory strategies. Although the literature supporting the potential benefits of having a strong task orientation is vast, considerably less research has tested interventions designed to strengthen task orientations and intrinsic motivation. A climate that emphasises individual mastery has resulted in increased interest-enjoyment and perceived competence, whereas an emphasis on competition and comparison with others has resulted in a decrease in interest-enjoyment and an increase in tension-pressure. One possible intervention is the use of structured self-reflection. Using self-reflection sheets that cause respondents to focus on specific elements of technique or skills, and rate one’s own performance, should theoretically promote a task focus. Hanrahan suggested that engaging in self-reflection may enhance intrinsic motivation. Perceived competence could be positively affected, as self-analysis and self-monitoring have been found to positively influence the acquisition of physical skills. The purpose of this study was to determine if the use of structured self-reflection in community dance classes would influence achievement goal orientations or levels of intrinsic motivation.

Time-independent charge carrier mobility in a model polymer:fullerene organic solar cell

The technique of photo-CELIV (charge extraction by linearly increasing voltage) is one of the more straightforward and popular approaches to measure the faster carrier mobility in measurement geometries that are relevant for operational solar cells and other optoelectronic devices. It has been used to demonstrate a time-dependent photocarrier mobility in pristine polymers, attributed to energetic relaxation within the density of states. Conversely, in solar cell blends, the presence or absence of such energetic relaxation on transport timescales remains under debate. We developed a complete numerical model and performed photo-CELIV experiments on the model high efficiency organic solar cell blend poly[3,6-dithiophene-2-yl-2,5-di(2-octyldodecyl)-pyrrolo[3,4-c]pyrrole-1,4-dione-alt-naphthalene] (PDPP-TNT):[6,6]-phenyl-C71-butyric-acid-methyl-ester (PC70BM). In the studied solar cells a constant, time-independent mobility on the scale relevant to charge extraction was observed, where thermalisation of photocarriers occurs on time scales much shorter than the transit time. Therefore, photocarrier relaxation effects are insignificant for charge transport in these efficient photovoltaic devices.

Crystal structures and hydrogen-bonding in the co-crystalline adducts of 3,5-dinitrobenzoic acid with 4-aminosalicylic acid and 2-hydroxy-3-(1H-indol-3-yl)propenoic acid

The structures of the cocrystalline adducts of 3,5-dinitrobenzoic acid (3,5-DNBA) with 4-aminosalicylic acid (PASA), the 1:1 partial hydrate, C7H4N2O6 .C7H7NO3 . 2H2O, (I) and 2-hydroxy-3-(1H-indol-3-yl)propenoic acid (HIPA) and the 1:1:1 d6-dimethylsulfoxide solvate, C7H4N2O6 . C11H9NO3 . C2D6OS, (II) are reported. The crystal substructure of (I) comprises two centrosymmetric hydrogen-bonded R2/2(8) homodimers, one with 3,5-DNBA, the other with PASA, and an R2/2(8) 3,5-DNBA-PASA heterodimer. In the crystal, inter-unit amine N-H...O and water O-H...O hydrogen bonds generate a three-dimensional supramolecular structure. In (II), the asymmetric unit consists of the three constituent molecules which form an essentially planar cyclic hydrogen-bonded heterotrimer unit [graph set R2/3(17)] through carboxyl, hydroxy and amino groups. These units associate across a crystallographic inversion centre through the HIPA carboxylic acid group in an R2/2~(8) hydrogen-bonding association, giving a zero-dimensional structure lying parallel to (100). In both structures, pi--pi interactions are present [minimum ring centroid separations: 3.6471(18)A in (I) and 3.5819(10)A in (II)].

Crystal structures and hydrogen bonding in the proton transfer salts of nicotine with 3,5-dinitrosalicylic acid and 5-sulfosalicylic acid

The structures of the 1:1 anhydrous salts of nicotine (NIC) with 3,5-dinitrosalicylic acid (DNSA) and 5-sulfosalicylic acid (5-SSA), namely (1R,2S)-1-methyl-2-(3-pyridyl)-1H-pyrrolidin-1-ium 2-carboxy-4,6-dinitrophenolate, C10H15N2+ C7H3N2O7-, (I) and (1R,2S)-1-methyl-2-(3-pyridyl)-1H-pyrrolidin-1-ium 3-carboxy-4-hydroxybenzenesulfonate, C10H15N2+ C7H5O6S-, (II) are reported. The asymmetric units of both (I) and (II) comprise two independent nicotinium cations (C and D) and either two DNSA or two 5-SSA anions (A and B), respectively. One of the DNSA anions shows a 25% rotational disorder in the benzene ring system. In the crystal of (I), inter-unit pyrrolidinium N-H...N(pyridine) hydrogen bonds generate zigzag NIC cation chains which extend along a while the DNSA anions are not involved in any formal inter-species hydrogen bonding but instead form pi--pi associated stacks which parallel the NIC chains along a [ring centroid separation, 3.857(2)A]. Weak C-H...O interactions between chain substructures give an overall three-dimensional structure. With (II), A and B anions form independent zigzag chains with C and D cations, respectively, through carboxylic acid O-H...N(pyridine) hydrogen bonds. These chains, which extend along b are pseudo-centrosymmetrically related and give pi--pi interactions between the benzene rings of anions A and B and the pyridine rings of the NIC cations C and D, respectively [ring centroid separations, 3.6422(19) and 3.7117(19)A]. Present also are weak intermolecular C-H...O hydrogen-bonding interactions between the chains, giving an overall three-dimensional structure.