Two dicot-infecting mastreviruses (family Geminiviridae) occur in Pakistan

Most mastreviruses (family Geminiviridae) infect monocotyledonous hosts and are transmitted by leafhopper vectors. Only two mastrevirus species, Tobacco yellow dwarf virus from Australia and Bean yellow dwarf virus (BeYDV) from South Africa, have been identified whose members infect dicotyledonous plants. We have identified two distinct mastreviruses in chickpea stunt disease (CSD)-affected chickpea originating from Pakistan. The first is an isolate of BeYDV, previously only known to occur in South Africa. The second is a member of a new species with the BeYDV isolates as its closest relatives. A PCR-based diagnostic test was developed to differentiate these two virus species. Our results show that BeYDV plays no role in the etiology of CSD in Pakistan, while the second virus occurs widely in chickpea across Pakistan. A genomic clone of the new virus was infectious to chickpea (Cicer arietinum L.) and induced symptoms typical of CSD. We propose the use of the name Chickpea chlorotic dwarf Pakistan virus for the new species. The significance of these findings with respect to our understanding of the evolution, origin and geographic spread of dicot-infecting mastreviruses is discussed. © 2008 Springer-Verlag.

Soil N2O emissions under N2-fixing legumes and N-fertilised canola: A reappraisal of emissions factor calculations

Introducing nitrogen (N)-fixing legumes into cereal-based crop rotations reduces synthetic fertiliser-N use and may mitigate soil emissions of nitrous oxide (N2O). Current IPCC calculations assume 100% of legume biomass N as the anthropogenic N input and use 1% of this as an emission factor (EF)—the percentage of input N emitted as N2O. However, legumes also utilise soil inorganic N, so legume-fixed N is typically less than 100% of legume biomass N. In two field experiments, we measured soil N2O emissions from a black Vertosol in sub-tropical Australia for 12 months after sowing of chickpea (Cicer arietinum L.), canola (Brassica napus L.), faba bean (Vicia faba L.), and field pea (Pisum sativum L.). Cumulative N2O emissions from N-fertilised canola (624 g N2O-N ha−1) greatly exceeded those from chickpea (127 g N2O-N ha−1) in Experiment 1. Similarly, N2O emitted from canola (385 g N2O-N ha−1) in Experiment 2 was significantly greater than chickpea (166 g N2O-N ha−1), faba bean (166 g N2O-N ha−1) or field pea (135 g N2O-N ha−1). Highest losses from canola were recorded during the growing season, whereas 75% of the annual N2O losses from the legumes occurred post-harvest. Legume N2-fixation provided 37–43% (chickpea), 54% (field pea) and 64% (faba bean) of total plant biomass N. Using only fixed-N inputs, we calculated EFs for chickpea (0.13–0.31%), field pea (0.18%) and faba bean (0.04%) that were significantly less than N-fertilised canola (0.48–0.78%) (P < 0.05), suggesting legume-fixed N is a less emissive form of N input to the soil than fertiliser N. Inputs of legume-fixed N should be more accurately quantified to properly gauge the potential for legumes to mitigate soil N2O emissions. EF’s from legume crops need to be revised and should include a factor for the proportion of the legume’s N derived from the atmosphere.

Towards executable specification : combining i* and AgentSpeak(L).

Agent-oriented conceptual modelling (AoCM) approaches in Requirements Engineering (RE) have received considerable attention recently. Semi-formal modeling frameworks such as i* assist analysts in requirements elicitation and reasoning of early-phase RE. AgentSpeak(L) is a widely accepted agent programming language. The Strategic Rationale (SR) model of the i* framework naturally lends itself to AgentSpeak(L) programs. Furthermore, the Strategic Dependency (SD) component of the i* framework prescribes the interaction between the agents in a multi-agent environment. This paper proposes a formal methodology for transforming a SR model to an AgentS- peak(L) agent. The constructed AgentSpeak(L) agents will then form the essential components of a multi-agent system, MAS.

Enhanced human bone marrow stromal cell affinity for modified poly(L-lactide) surfaces by the upregulation of adhesion molecular genes

To enhance and regulate cell affinity for poly (l-lactic acid) (PLLA) based materials, two hydrophilic ligands, poly (ethylene glycol) (PEG) and poly (l-lysine) (PLL), were used to develop triblock copolymers: methoxy-terminated poly (ethylene glycol)-block-poly (l-lactide)-block-poly (l-lysine) (MPEG-b-PLLA-b-PLL) in order to regulate protein absorption and cell adhesion. Bone marrow stromal cells (BMSCs) were cultured on different composition of MPEG-b-PLLA-b-PLL copolymer films to determine the effect of modified polymer surfaces on BMSC attachment. To understand the molecular mechanism governing the initial cell adhesion on difference polymer surfaces, the mRNA expression of 84 human extracellular matrix (ECM) and adhesion molecules was analysed using quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). It was found that down regulation of adhesion molecules was responsible for the impaired BMSC attachment on PLLA surface. MPEG-b-PLLA-b-PLL copolymer films improved significantly the cell adhesion and cytoskeleton expression by upregulation of relevant molecule genes significantly. Six adhesion genes (CDH1, ITGL, NCAM1, SGCE, COL16A1, and LAMA3) were most significantly influenced by the modified PLLA surfaces. In summary, polymer surfaces altered adhesion molecule gene expression of BMSCs, which consequently regulated cell initial attachment on modified PLLA surfaces.

Synthesis of 4-arm star poly(L-Lactide) oligomers using an in situ-generated calcium-based initiator

Using an in situ-generated calcium-based initiating species derived from pentaerythritol, the bulk synthesis of well-defined 4-arm star poly(L-lactide) oligomers has been studied in detail. The substitution of the traditional initiator, stannous octoate with calcium hydride allowed the synthesis of oligomers that had both low PDIs and a comparable number of polymeric arms (3.7 – 3.9) to oligomers of similar molecular weight. Investigations into the degree of control observed during the course of the polymerization found that the insolubility of pentaerythritol in molten L-lactide resulted in an uncontrolled polymerization only when the feed mole ratio of L-lactide to pentaerythritol was 13. At feed ratios of 40 and greater, a pseudo-living polymerization was observed. As part of this study, in situ FT-Raman spectroscopy was demonstrated to be a suitable method to monitor the kinetics of the ring-opening polymerization (ROP) of lactide. The advantages of using this technique rather than FT-IR-ATR and 1H NMR for monitoring L-lactide consumption during polymerization are discussed.

L'étendue internationale des nouvelles firmes de hautes technologies: le rôle du capital humain et de l'intention stratégique des fondateurs

De récentes recherches ont mis l’accent sur l’importance pour les nouvelles entreprises internationales de l’existence de ressources et de compétences spécifiques. La présente recherche, qui s’inscrit dans ce courant, montre en particulier l’importance du capital humain acquis par les entrepreneurs sur base de leur expérience internationale passée. Mais nous montrons en même temps que ces organisations sont soutenues par une intention délibérée d’internationalisation dès l’origine. Notre recherche empirique est basée sur l’analyse d’un échantillon de 466 nouvelles entreprises de hautes technologies anglaises et allemandes. Nous montrons que ce capital humain est un actif qui facilite la pénétration rapide des marchés étrangers, et plus encore quand l’entreprise nouvelle est accompagnée d’une intention stratégique délibérée d’internationalisation. Des conclusions similaires peuvent être étendues au niveau des ressources que l’entrepreneur consacre à la start-up : plus ces ressources sont importantes, plus le processus d’internationalisation tend à se faire à grande échelle ; et là aussi, l’influence de ces ressources est augmenté par l’intention stratégique d’internationalisation. Dans le cadre des études empiriques sur les born-globals (entreprises qui démarrent sur un marché globalisé), cette recherche fournit une des premières études empiriques reliant l’influence des conditions initiales de création aux probabilités de croissance internationale rapide.

Three-dimensional hydrogen-bonded structures in the 1:1 proton-transfer compounds of L-tartaric acid with the associative-group monosubstituted pyridines 3-minopyridine, 3-carboxypyridine (nicotinic acid) and 2-carboxypyridine (picolinic acid).

The 1:1 proton-transfer compounds of L-tartaric acid with 3-aminopyridine [3-aminopyridinium hydrogen (2R,3R)-tartrate dihydrate, C5H7N2+·C4H5O6-·2H2O, (I)], pyridine-3-carboxylic acid (nicotinic acid) [anhydrous 3-carboxypyridinium hydrogen (2R,3R)-tartrate, C6H6NO2+·C4H5O6-, (II)] and pyridine-2-carboxylic acid [2-carboxypyridinium hydrogen (2R,3R)-tartrate monohydrate, C6H6NO2+·C4H5O6-·H2O, (III)] have been determined. In (I) and (II), there is a direct pyridinium-carboxyl N+-HO hydrogen-bonding interaction, four-centred in (II), giving conjoint cyclic R12(5) associations. In contrast, the N-HO association in (III) is with a water O-atom acceptor, which provides links to separate tartrate anions through Ohydroxy acceptors. All three compounds have the head-to-tail C(7) hydrogen-bonded chain substructures commonly associated with 1:1 proton-transfer hydrogen tartrate salts. These chains are extended into two-dimensional sheets which, in hydrates (I) and (III) additionally involve the solvent water molecules. Three-dimensional hydrogen-bonded structures are generated via crosslinking through the associative functional groups of the substituted pyridinium cations. In the sheet struture of (I), both water molecules act as donors and acceptors in interactions with separate carboxyl and hydroxy O-atom acceptors of the primary tartrate chains, closing conjoint cyclic R44(8), R34(11) and R33(12) associations. Also, in (II) and (III) there are strong cation carboxyl-carboxyl O-HO hydrogen bonds [OO = 2.5387 (17) Å in (II) and 2.441 (3) Å in (III)], which in (II) form part of a cyclic R22(6) inter-sheet association. This series of heteroaromatic Lewis base-hydrogen L-tartrate salts provides further examples of molecular assembly facilitated by the presence of the classical two-dimensional hydrogen-bonded hydrogen tartrate or hydrogen tartrate-water sheet substructures which are expanded into three-dimensional frameworks via peripheral cation bifunctional substituent-group crosslinking interactions.

Carbodiimide-mediated synthesis of poly(L-lactide)-based networks

Poly(L-lactide-co-succinic anhydride) networks were synthesised via the carbodiimide-mediated coupling of poly(L-lactide) (PLLA) star polymers. When 4-(dimethylamino)pyridine (DMAP) alone was used as the catalyst gelation did not occur. However, when 4-(dimethylamino)pyridinium p-toluenesulfonate (DPTS), the salt of DMAP and p-toluenesulfonic acid (PTSA), was the catalyst, the networks obtained had gel fractions comparable to those which were reported for networks synthesised by conventional methods. Greater gel fractions and conversion of the prepolymer terminal hydroxyl groups were observed when the hydroxyl-terminated star prepolymers reacted with succinic anhydride in a one-pot procedure than when the hydroxyl-terminated star prepolymers reacted with presynthesised succinic-terminated star prepolymers. The thermal properties of the networks, glass transition temperature (Tg), melting temperature (Tm) and crystallinity (Xc) were all strongly influenced by the average molecular weights between the crosslinks ((M_c). The network with the smallest (M_c )(1400 g/mol) was amorphous and had a Tg of 59 °C while the network with the largest (M_c ) (7800 g/mol) was 15 % crystalline and had a Tg of 56 °C.

Phenyl-ring disorder in the two-dimensional hydrogen-bonded structure of the 1:1 proton-transfer salt of the diazo-dye precursor 4-(phenyldiazenyl)aniline (aniline yellow) with L-tartaric acid

The structure of the 1:1 proton-transfer compound from the reaction of L-tartaric acid with the azo-dye precursor aniline yellow [4-(phenylazo)aniline], 4-(phenyldiazenyl)anilinium hydrogen 2R,3R-tartrate C12H12N3+ . C4H6O6- has been determined at 200 K. The asymmetric unit of the compound contains two independent phenylazoanilinium cations and two hydrogen L-tartrate anions. The structure is unusual in that all four phenyl rings of both cations have identical 50% rotational disorder. The two hydrogen L-tartrate anions form independent but similar chains through head-to-tail carboxylic O--H...O~carboxyl~ hydrogen bonds [graph set C7] which are then extended into a two-dimensional hydrogen-bonded sheet structure through hydroxyl O--H...O hydrogen-bonding links. The anilinium groups of the phenyldiazenyl cations are incorporated into the sheets and also provide internal hydrogen-bonding extensions while their aromatic tails layer in the structure without significant interaction except for weak \p--\p interactions [minimum ring centroid separation, 3.844(3) \%A]. The hydrogen L-tartrate residues of both anions have the common short intramolecular hydroxyl O--H...O~carboxyl~ hydogen bonds. This work has provided a solution to the unusual disorder problem inherent in the structure of this salt as well as giving another example of the utility of the hydrogen tartrate in the generation of sheet substructures in molecular assembly processes.