Profiling glucosinolates in vegetative and reproductive tissues of four Brassica species of the U‐triangle for their biofumigation potential

Glucosinolates are amino acid derived allelochemicals present in all plants of the order Capparales. These compounds are degraded by myrosinase isoenzymes, releasing a series of biologically active products defined by the parent glucosinolate and the reaction conditions. Species within the Brassicaceae are found to differ in their glucosinolate profile and glucosinolate concentrations. Different tissues within a single plant also show such variations, which are further influenced by the growth stage and environmental conditions. In the experiments described in this paper, four Brassica species of the U‐triangle (B. carinata, B. nigra, B. juncea and B. rapa) were compared with respect to their glucosinolate profiles in roots, stems, leaves and reproductive organs at different developmental stages. The glucosinolate profile of corresponding ripe seeds was also determined. Prop‐2‐enylglucosinolate was identified as the major glucosinolate in the three mustards, where it represented over 90% of the total glucosinolate concentration of ripe seeds and over 50% of green tissues. The relative concentration of this glucosinolate increased in all tissues during plant growth. Brassica rapa showed a different glucosinolate profile than the three mustards, with higher concentrations of but‐3‐enylglucosinolate, 2‐hydroxybut‐3‐enylglucosinolate and 2‐hydroxypent‐4‐enylglucosinolate. The concentration of indol‐3‐ylmethylglucosinolates was also higher in B. rapa than in the mustard plants, with 4‐hydroxyglucobrassicin representing 30% of the total glucosinolate concentration in ripe seeds. The total glucosinolate concentration of the species studied varied with growth stage and the mustards achieved a maximum towards the end of the period monitored. Glucosinolate concentration decreased in roots and leaves but increased in reproductive tissues. The determined glucosinolate profiles are an initial step in assessing the biofumigation potential of these species of the Brassicaceae family. Copyright © 2007 Society of Chemical Industry     

The complexity of checking consistency of pedigree information and related problems

Consistency checking is a fundamental computational problem in genetics. Given a pedigree and information on the genotypes (of some) of the individuals in it, the aim of consistency checking is to determine whether these data are consistent with the classic Mendelian laws of inheritance. This problem arose originally from the geneticists‘ need to filter their input data from erroneous information, and is well motivated from both a biological and a sociological viewpoint. This paper shows that consistency checking is NP-complete, even with focus on a single gene and in the presence of three alleles. Several other results on the computational complexity of problems from genetics that are related to consistency checking are also offered. In particular, it is shown that checking the consistency of pedigrees over two alleles, and of pedigrees without loops, can be done in polynomial time.     

Newly Isolated Animal Pathogen Corynebacterium silvaticum Is Cytotoxic to Human Epithelial Cells

Corynebacterium silvaticum is a newly identified animal pathogen of forest animals such as roe deer and wild boars. The species is closely related to the emerging human pathogen Corynebacterium ulcerans and the widely distributed animal pathogen Corynebacterium pseudotuberculosis. In this study, Corynebacterium silvaticum strain W25 was characterized with respect to its interaction with human cell lines. Microscopy, measurement of transepithelial electric resistance and cytotoxicity assays revealed detrimental effects of C. silvaticum to different human epithelial cell lines and to an invertebrate animal model, Galleria mellonella larvae, comparable to diphtheria toxin-secreting C. ulcerans. Furthermore, the results obtained may indicate a considerable zoonotic potential of this newly identified species.     

Effects of cropping history and phosphorus source on yield and nitrogen fixation in sole and intercropped cowpea–maize systems

Symbiotic N₂-fixation, N uptake efficiency, biomass- and crop production of cowpea and maize as affected by P source, sole- and intercropped, and introduction of break crops were studied on a farmer’s fields in semi-arid Tanzania. Cowpea fixed around 60% of its N from the atmosphere amounting to 70 kg N ha⁻¹ under sole and 36 kg N ha⁻¹ under intercropping as estimated by the ¹⁵N isotope dilution method around peak biomass production. The amount of N₂-fixed was 30–40% higher when P was applied as either TSP or MRP whereas cowpea yield were unaffected. Intercropped maize with 19,000 plant ha⁻¹ accumulated the same amount of N as 38,000 sole cropped maize plants although intercropping reduced the dry matter accumulation by 25%. The N uptake efficiency of the applied ¹⁵N labelled fertiliser was 26%, which equal a total pool of early available plant N of 158 kg N ha⁻¹. Under the N deficient conditions, P application did not increase the grain yield of maize. The LER indicate that sole cropping required 18% more area than intercropping in order to produce the same grain yield, and 35% more land when LER was based on N uptakes. Introduction of break crops in the maize systems, more than doubled accumulation of dry matter and N in the grain compared to continuous maize cropping. During maturation sole crop cowpea shedded leaves containing 41 kg N ha⁻¹. The current findings underline the importance of crop diversity in Sub Saharan Africa agriculture and emphasise the need for including all residues, including shedded leaves, in nutrient balance studies.     

From hygroscopic single particle to batch fluidized bed drying kinetics

A new normalization concept for convective drying of hygroscopic particulates is introduced. Both, intraparticle drying kinetics and sorption equilibrium are considered separately, and integrated into a new heterogeneous fluid bed model for coupled heat and mass transfer. Experiments were carried out using spherical γ-Al₂O₃ particles. Sorption isotherms, as well as drying curves, for single particles and fluidized beds have been measured. Batch fluid bed drying curves appear to be predictable on the basis of single particle and material equilibrium data and with the help of the model. All model parameters are directly taken, or estimated from fluidization literature, without any fitting.     

Nonparametric Autoregression with Multiplicative Volatility and Additive mean

For over a decade, nonparametric modelling has been successfully applied to studying nonlinear structures in financial time series. It is well known that the usual nonparametric models often have less than satisfactory performance when dealing with more than one lag. When the mean has an additive structure, however, better estimation methods are available which fully exploit such a structure. Although in the past such nonparametric applications had been focused more on the estimation of the conditional mean, it is equally if not more important to measure the future risk of the series along with the mean. For the volatility function, i.e. the conditional variance given the past, a multiplicative structure is more appropriate than an additive structure, as the volatility is a positive scale function and a multiplicative model provides a better interpretation of each lagged value's influence on such a function. In this paper we consider the joint estimation of both the additive mean and the multiplicative volatility. The technique used is marginally integrated local polynomial estimation. The procedure is applied to the deutschmark/US dollar daily exchange returns.     

Growth and characterization of gold catalyzed SiGe nanowires and alternative metal-catalyzed Si nanowires

The growth of semiconductor (SC) nanowires (NW) by CVD using Au-catalyzed VLS process has been widely studied over the past few years. Among others SC, it is possible to grow pure Si or SiGe NW thanks to these techniques. Nevertheless, Au could deteriorate the electric properties of SC and the use of other metal catalysts will be mandatory if NW are to be designed for innovating electronic. First, this article's focus will be on SiGe NW's growth using Au catalyst. The authors managed to grow SiGe NW between 350 and 400°C. Ge concentration (x) in Si1-xGex NW has been successfully varied by modifying the gas flow ratio: R = GeH4/(SiH4 + GeH4). Characterization (by Raman spectroscopy and XRD) revealed concentrations varying from 0.2 to 0.46 on NW grown at 375°C, with R varying from 0.05 to 0.15. Second, the results of Si NW growths by CVD using alternatives catalysts such as platinum-, palladium- and nickel-silicides are presented. This study, carried out on a LPCVD furnace, aimed at defining Si NW growth conditions when using such catalysts. Since the growth temperatures investigated are lower than the eutectic temperatures of these Si-metal alloys, VSS growth is expected and observed. Different temperatures and HCl flow rates have been tested with the aim of minimizing 2D growth which induces an important tapering of the NW. Finally, mechanical characterization of single NW has been carried out using an AFM method developed at the LTM. It consists in measuring the deflection of an AFM tip while performing approach-retract curves at various positions along the length of a cantilevered NW. This approach allows the measurement of as-grown single NW's Young modulus and spring constant, and alleviates uncertainties inherent in single point measurement.     

Extraction of heavy metals from soils using biodegradable chelating agents

Metal pollution of soils is widespread across the globe, and the clean up of these soils is a difficulttask. One possible remediation technique is ex-situ soil washing using chelating agents. Ethylenediaminetetraacetic acid (EDTA) is a very effective chelating agent for this purpose but has the disadvantage that it is quite persistent in the environment due to its low biodegradability. The aim of our work was to investigate the biodegradable chelating agents [S,S]-ethylenediaminedisuccinic acid (EDDS), iminodisuccinic acid (IDSA), methylglycine diacetic acid (MGDA), and nitrilotriacetic acid (NTA) as potential alternatives and compare them with EDTA for effectiveness. Kinetic experiments showed for all metals and soils that 24 h was the optimum extraction time. Longer times only gave minor additional benefits for heavy metal extraction but an unwanted increase in iron mobilization. For Cu at pH 7, the order of the extraction efficiency for equimolar ratios of chelating agent to metal was EDDS > NTA> IDSA > MGDA > EDTA and for Zn it was NTA > EDDS > EDTA >MGDA > IDSA. The comparatively low efficiency of EDTA resulted from competition between the heavy metals and co-extracted Ca. For Pb the order of extraction was EDTA > NTA >EDDS due to the much stronger complexation of Pb by EDTA compared to EDDS. At higher concentration of complexing agent, less difference between the agents was found and less pH dependence. There was an increase in heavy metal extraction with decreasing pH, but this was offset by an increase in Ca and Fe extraction. In sequential extractions EDDS extracted metals almost exclusively from the exchangeable, mobile, and Mn-oxide fractions. We conclude that the extraction with EDDS at pH 7 showed the best compromise between extraction efficiency for Cu, Zn, and Pb and loss of Ca and Fe from the soil.