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[en] Highlights: → The thickness of the compound layer increases with increasing in temperature and groove width. → Surface layer at the remote regions from the edge is thinner than that of closer regions. → The hardness and the case depth of the nitrided layer increase with increasing the width of the groove. → Intensity of ε phase increases with increasing the width of the groove in both methods. → The ASPN specimens are covered by hexagonal particles and for the CPN by cauliflower shape nitrides. -- Abstract: The main aim of this work was to investigate the effect of the sample geometry on properties of the conventional plasma nitrided (CPN) and active screen plasma nitrided (ASPN) steel. Sample assemblies consisting of rectangular grooved steel blocks with different groove dimensions of 2, 4, 6, 8 and 10 (W) x 40 (H) x 20 (L) mm3 and AISI 4340 steel plates (substrates) with dimensions of 10 x 40 x 60 mm3, to serve as groove cover, were prepared. The sample assemblies were conventional and active screen plasma nitrided under the gas mixture of 75%N2 + 25%H2, at temperatures of 500 oC and 540 oC, pressure of 4 torr, for 5 h. Properties of the nitrided substrates were investigated by evaluating compound layer thickness, case depth, phase composition and hardness profile. Results of the experiments showed that the thickness of the compound layer, hardness and nitrided case depth increased with increasing the width of the groove for both methods. Also, in each sample, nitrogen atoms penetrated more deeply in the regions of the groove closer to the edge. Hallow cathode effect occurred at the sample with 2 mm width groove, in the CPN method, leading to the overheating of the sample. In ASPN, the hardness and the nitrided case depth are lower in comparison with CPN. The surface morphology of the CPN treated samples consists of cauliflower shape surface nitrides while the surface of the AS plasma nitrided samples are covered by the hexagonal particles with uniform distribution.
[en] Electrochemical characteristics of nitrite ion were investigated at a poly(methylene blue)-modified glassy carbon electrode by cyclic voltammetry and differential pulse voltammetry. The poly(methylene blue)- modified glassy carbon electrode exhibited enhanced anodic signals for nitrite. The effects of key parameters on the detection of nitrite were evaluated at the modified electrode, such as pH, accumulation time, and scan rate. Under optimum condition, the chemically modified electrode can detect nitrite in the concentration range 2.0 x 10-6 to 5.0 x 10-4 M with the detection limit of 2.0 x 10-6 M and a correlation coefficient of 0.999. The detection of nitrite using the chemically modified electrode was not affected by common ions such as Na+, K+, Ca2+, Cl-, HPO42- and H2PO4-. The modified electrode showed good stability and reproducibility. The practical application of the present method was successfully applied to the determination of nitrite ion in cabbage samples
[en] Lipases (Triacylglycerol acyl hydrolass EC 220.127.116.11) defined as enzymes that catalyse the hydrolysis of triacylglycerols, releasing long-chain fatty acids. Germinating oilseeds have been explored as a possible source of lipases for biotechnological processing of oils and fats. However, purification and sensitive assays to be able to detect a true lipase activity in plant cellular homogenates and culture media. The aim of this study was to evaluate the advantage of a new lipase activity assay using natural long-chain triacyiglycerois (TAGs). Oil was extracted from Parnari glabernimunm seed kernels and the purified TAGs were used as a substrate for detecting low levels of lipase activities. The purified TAGs are naturally fluorescent because more than half of the fatty acids from Parinari oil are known to contain 9,11,13,1 5- octadecatetraenoic acid (parinaric acid) in its esterified form. We tested the rapeseed lipase activity using two different substrates, the naturally fluorescent TAGs and the radiolabeled TAGs. A significant level of lipase activity was detected by the used methods. Results obtained by the naturally fluorescent TAGs are identical of the obtained ones using the radiolabeled method. The specific activity obtained by the two methods was about 92 nkat.mg-1 using the naturally fluorescent TAGs and about 94 nkat.mg-1 using the radioactive method. Our results prove that this new method, performed under non-oxidative conditions, was applied successfully to detect low lipase levels in crude protein extracts form plant seeds and it can be used as a continuous and a specific lipase activity assay
[en] Variations in cadmium accumulation and translocation among 40 Chinese cabbage cultivars were studied to identify and screen out Cd-safe cultivars (CSCs), i.e. cultivars with low enough accumulation of Cd in their edible parts even when grown in contaminated soils. It was observed in the pot-culture experiment that there was a significant difference (p < 0.05) in shoot Cd concentrations under three Cd treatments (1.0, 2.5 and 5.0 mg/kg), with corresponding average values 0.88, 4.45 and 7.76 mg/kg, respectively. Shoot Cd concentrations in 16 cabbage cultivars were lower than 0.50 mg/kg. The translocation factors (TFs) and the extraction factors (EFs) in five cabbage cultivars were lower than 1.0 in the pot-culture experiment. The field-culture experiment further validated that New Beijing 3 and Fengyuanxin 3 could be considered as CSCs. In particular, the two cultivars can be cultivated in low to moderate Cd-contaminated soils (Cd concentration <1.25 mg/kg) to minimize the Cd accumulation in the food.
[en] In field O3-enrichment experiments increased herbivore densities have been reported, which could be due to negatively affected host location behavior of natural enemies. We addressed the impact of doubling background O3 on the host location of the parasitoid Cotesia plutellae by conducting 24-h trials in an open-air O3-fumigation system during two consecutive years. Two circles (radii 1.40 and 4.00 m) of Plutella xylostella-infested potted cabbage plants were placed in the O3 and ambient plots. Female wasps were released into each plot from the center, and observed 5 times over a 24-h period to assess their host location capability. Thereafter, plants were kept in laboratory conditions until larvae pupation to determine parasitism rates. No significant differences were detected between ambient and O3-enriched environments either in the number of wasps found in the field, or in the percentages of parasitized larvae. This suggests that moderately elevated O3 will not affect the behavior of this parasitoid. - Atmospheric ozone increases do not directly affect the biological control of the cabbage pest, Plutella xylostella
[en] The sites of Nitrogen assimilation of Fl hybrid cauliflower (Brassica oleracea L.) grown in vermiculite: pearlite on either NO3 or NH4 nutrition was investigated using 15 N techniques. Labelling studies using 15NO3 Or 15NH4 alone to follow a time course of 15 NO3 or 15NH4 incorporated into amino compounds in Fl hybrid cauliflower was conducted over periods of up to 24 hours. The 15N enrichment of amino compounds in various plant parts was measured using GC-MS and isotopic abundance mass spectrometry techniques. In roots of 15NH4-N fed plant, the 15N label rapidly appears in glutamate at high enrichment within 30 minutes and increased substantially up to 6 hours after feeding. The labelled glutamate appears to decrease slowly after 6 hours. In leaves, the glutamate shows much lower labelling within 30 minutes than in the roots and became slowly enriched 6 hours after feeding. Labelled glutamate was only detected in the curd 6 hours later. This may indicate that in NH4-N fed plants, most NH4 is assimilated in the roots and translocated as amino acids to the leaves and curd. In contrast to 15NO3-N fed plant, both the roots and leaves showed significant label in glutamate within 30 minutes and subsequently increased in labelled enrichment over the time period of 6 hours. The leaves contained higher labelled glutamate than the roots. The labelled glutamate in the leaves decreased significantly at 24 hours after feeding. Label was incorporated in glutamate at low level in the curd after 2 hours and became highly enriched at 6 and 24 hours after feeding. Thus in NO3-N fed plants, NO3 reduction and assimilation occurred both in root and leaf which mainly occur in the leaf. Therefore differences in the response of plant growth to NO3- and NH4+ nutrition observed in other studies could be due to the fact that NO3 is primarily assimilated in the leaf whereas NH4 is root based. No significant labelling was found in serine in both roots of 15NH4-N and 15NO3 -fed plants after 30 minutes with low level of label detected in serine after 2 hours feeding. This could be related to the serine metabolism with photo assimilation, which cannot occur in the roots. In the leaves of 15NO3-N high enrichment of label in serine was detected at 6 hours after feeding and decreased at 24 hours, possibly due to translocation to the root and curd. Mixture of N as 15NH4NO3 or NH415NO3 were used in short and long term experiments to see whether Fl cauliflower plants had a preference for one or the other. Short terms labelling experiments using 15NH4NO3 or NH415NO3 have shown that the label glutamate from 15NO3 was significantly higher than from 15NH4. The enrichment in labelled glutamate subsequently increased after 6 hours feeding and decreased after 24 hours. Long term labelling experiments using 15NH4NO3 or NH415NO3 have shown that the leaves had higher 15N enrichment from 15NO3 than from 15NH4. The 15N enrichment in the leaves from 15NO3 showed apparent steady state 3 days after feeding. In contrast, 15N enrichment from 15NH4 has shown an increased in 15N enrichment in the leaves up to 14 days after feeding. Thus, both the results from short and long term labelling using labelled mixture of N as 15NH4NO3 or NH415NO3 suggest that the NO3 was preferred over NH4. (Author)
[en] In this study we tested and compared a multiplicative stomatal model and a coupled semi-empirical stomatal-photosynthesis model in their ability to predict stomatal conductance to ozone (gst) using leaf-level data from oilseed rape (Brassica napus L.) and broccoli (Brassica oleracea L. var. italica Plenck). For oilseed rape, the multiplicative model and the coupled model were able to explain 72% and 73% of the observed gst variance, respectively. For broccoli, the models were able to explain 53% and 51% of the observed gst variance, respectively. These results support the coupled semi-empirical stomatal-photosynthesis model as a valid alternative to the multiplicative stomatal model for O3 flux modelling, in terms of predictive performance. - A multiplicative stomatal model and a coupled semi-empirical stomatal-photosynthesis model performed equally well when tested against leaf-level data for oilseed rape and broccoli.
[en] Field evaluation of twenty three Brassica campestris L. genotypes was conducted for aphid (Homoptera: Aphididae) resistance during 2008 crop season. The parameters used to assess tolerance of germplasm lines included pest population during growth season and grain yield at crop maturity. Aphids showed obvious preferences for all of the germplasm investigated; however, the evaluation for resistance to pest identified several genotypes with variable potential for tolerance and sensitivity. Estimated grain yield also varied significantly due to variable pest intensity noted, and seemed to be more appropriately dependent on the pest population conditions at the experimental site. Among the germplasm, the estimation obtained regarding both the parameters sorted out MM-II/02-3 and MM-I285 genotypes as most tolerant due to less pest infestation and damage. Peak infestations by aphid caused severe crop fatalities on S-9-S-97-0.75+75/55 and S-9-1006/95 genotypes, affecting the seed weight and resulting an immense reduction in grain Brassica genotypes appeared to be governed by means of varietals characteristics of diverse germplasms. The result of resistance test conducted under field environment is an effective and consistent approach in the practical selection of crop lines resistant or partially resistant to pests for use in future breeding programs. (author)
[en] Cowpea mottle virus (CPMoV) is a T = 3 virus that belongs to Carmovirus genus of the Tombusviridae family. Here, we report the crystal structure of CPMoV determined to a resolution of 7.0 A. The structures and sequences of three Carmoviruses, CPMoV, Turnip crinkle virus (TCV), and Carnation mottle virus (CarMV) have been compared to TBSV from the Tombusvirus genus. CPMoV, TCV, and CarMV all have a deletion in βC strand in the S domain relative to TBSV that may be distinctive to the genus. Although CPMoV has an elongated C-terminus like TBSV, it does not interact with the icosahedrally related P domain as observed in TBSV. In CPMoV, the termini of A and B interact with the icosahedrally related shell domains of A and C, respectively, to form a chain of interactions around the 5-fold axes. The C subunit terminus does not, however, interact with the B subunit because of quasi-equivalent differences in the P domain orientations