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51.
Migratory ability of second-stage juveniles (J2) of two Meloidogyne chitwoodi races and a M. hapla population were compared in soil-filled columns at 12, 18, and 24 C. J2 of all populations migrated farthest at 18 C and least at 12 C. Nematode survival was significantly reduced (P = 0.05) at 24 C.M. chitwoodi J2 migrated further and in greater numbers than M. hapla J2 at all temperatures. A comparison with and without a host plant demonstrated no preferential migration toward the plant. Water percolation through the migration columns stimulated upward migration. 相似文献
52.
The application of porous graphitic carbon as adsorbing phase for direct separation of enantiomeric acids and amines using chiral ion-pair chromatography is described. The enantiomeric amines were separated as diastereomeric ion pairs with N-benzyloxycarbonylglycyl-L -proline, N-benzyloxycarbonylglycylglycyl-L -proline, or captopril as the chiral counterion. High enantioselectivities were obtained for amines having a hydrogen bonding function in the vicinity of the asymmetrical carbon atom. Quinine was the chiral counterion used to separate the enantiomeric acids. The strongly UV-absorbing quinine improved detection of solutes having low UV-absorbing properties, e.g., (R,S)-2-chloropropionic acid, by “indirect detection.” Retention and stereoselectivity of enanticmeric acids were regulated by the quinine concentration and by the addition of carboxylic acids as well as polar modifiers, e.g., methanol and 2-propanol, to the mobile phase. © 1992 Wiley-Liss, Inc. 相似文献
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L.S. Panchakarla Author VitaeAuthor Vitae C.N.R. Rao Author Vitae 《Inorganica chimica acta》2010,363(15):4163-4174
Multi-walled, single-walled and double-walled carbon nanotubes as well as graphene can be doped with boron and nitrogen. B2H6 has been generally used as the boron source while NH3 or pyridine is employed as the nitrogen source. Doping carbon nanotubes and graphene with boron and nitrogen brings about significant changes in the electronic structure and properties. Such doping not only results in desirable properties but also allows manipulation of properties for specific purposes. Doping with boron- and nitrogen-causes marked changes in the Raman spectra of the carbon nanostructures. In this article, we present the synthesis, characterization and properties of boron- and nitrogen-doped carbon nanotubes and graphene. 相似文献
55.
There was little release of extractable SO4-S during four weeks from CS2 applied by injecting into two S-deficient soils. In this incubation experiment, the rate of CS2 was 30 μg S g−, placement was injection at 9 cm depth, soil temperature was 20°C, and soil moisture tension was 33 kPa. The yield of barley
forage after seven weeks in the greenhouse showed only small increases from 10 or 30 μg S g−1 of CS2 as compared to Na2SO4, on the two soils.
While CS2 supplied little plant available S in the short term, it was an effective inhibitor of nitrification. In the laboratory, or
in the field, the injection of CS2 (with N fertilizers) at a point 9 cm into the soils either stopped or reduced nitrification. In one laboratory experiment,
35 μg of CS2 g−1 of soil with urea reduced nitrification for at least four weeks; and in another experiment 20 μg of CS2 g−1 of soil with aqua NH3 nearly or completely inhibited nitrification at 20 days. In two field experiments, 3 and 12 μg of CS2 g−1 of soil (or 6 and 24 kg ha−1) with aqua NH3 inhibited nitrification from October to the subsequent May. In addition, CS2 reduced the amount of ammonium produced from the soil N, both in these two field experiments and in the laboratory experiments.
That is to say, CS2 injected at a point, inhibited both nitrification and ammonification.
In other field experiments, CS2 at a rate of 10 kg ha−1 was injected in bands 9 cm deep with urea in October, and by May there was still reduced nitrification. Less than half of
the fall-applied urea alone was recovered as mineral N, but with the application of CS2 the recovery was increased to three-quarters.
The yield and N uptake of barley grain was increased where fall-applied banded urea or aqua NH3 received banded CS2, (NH4)2CS3, or K2CS3. The average increase in yield from fall-applied fertilizer, from inhibitor with fall-applied fertilizer, and from spring-applied
fertilizer was 800, 1370, and 1900 kg ha−1, respectively. In the same order, the apparent % recovery of fertilizer N in grain was 24, 42, and 60. 相似文献
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S. A. Frank 《Journal of evolutionary biology》2010,23(6):1245-1250
An individually costly act that benefits all group members is a public good. Natural selection favours individual contribution to public goods only when some benefit to the individual offsets the cost of contribution. Problems of sex ratio, parasite virulence, microbial metabolism, punishment of noncooperators, and nearly all aspects of sociality have been analysed as public goods shaped by kin and group selection. Here, I develop two general aspects of the public goods problem that have received relatively little attention. First, variation in individual resources favours selfish individuals to vary their allocation to public goods. Those individuals better endowed contribute their excess resources to public benefit, whereas those individuals with fewer resources contribute less to the public good. Thus, purely selfish behaviour causes individuals to stratify into upper classes that contribute greatly to public benefit and social cohesion and to lower classes that contribute little to the public good. Second, if group success absolutely requires production of the public good, then the pressure favouring production is relatively high. By contrast, if group success depends weakly on the public good, then the pressure favouring production is relatively weak. Stated in this way, it is obvious that the role of baseline success is important. However, discussions of public goods problems sometimes fail to emphasize this point sufficiently. The models here suggest simple tests for the roles of resource variation and baseline success. Given the widespread importance of public goods, better models and tests would greatly deepen our understanding of many processes in biology and sociality. 相似文献
60.
Ainara Pealver‐Cruz Elisa Garzo Ins Prieto‐Ruiz Miguel Díaz‐Carro Ana Winters Arnzazu Moreno Alberto Fereres 《Insect Science》2020,27(3):558-570
The continuous rise of CO2 concentrations in the atmosphere is reducing plant nutritional quality for herbivores and indirectly affects their performance. The whitefly (Bemisia tabaci, Gennadius) is a major worldwide pest of agricultural crops causing significant yield losses. This study investigated the plant‐mediated indirect effects of elevated CO2 on the feeding behavior and life history of B. tabaci Mediterranean species. Eggplants were grown under elevated and ambient CO2 concentrations for 3 weeks after which plants were either used to monitor the feeding behavior of whiteflies using the Electrical Penetration Graph technique or to examine fecundity and fertility of whiteflies. Plant leaf carbon, nitrogen, phenols and protein contents were also analyzed for each treatment. Bemisia tabaci feeding on plants exposed to elevated CO2 showed a longer phloem ingestion and greater fertility compared to those exposed to ambient CO2 suggesting that B. tabaci is capable of compensating for the plant nutritional deficit. Additionally, this study looked at the transmission of the virus Tomato yellow leaf curl virus (Begomovirus) by B. tabaci exposing source and receptor tomato plants to ambient or elevated CO2 levels before or after virus transmission tests. Results indicate that B. tabaci transmitted the virus at the same rate independent of the CO2 levels and plant treatment. Therefore, we conclude that B. tabaci Mediterranean species prevails over the difficulties that changes in CO2 concentrations may cause and it is predicted that under future climate change conditions, B. tabaci would continue to be considered a serious threat for agriculture worldwide. 相似文献