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381.
Jana Wäldchen Ingo Schöning Martina Mund Marion Schrumpf Susanne Bock Nadine Herold Kai Uwe Totsche Ernst Detlef Schulze 《植物养料与土壤学杂志》2012,175(3):367-376
Soil texture is one of the main factors controlling soil organic carbon (SOC) storage. Accurate soil‐texture analysis is costly and time‐consuming. Therefore, the clay content is frequently not determined within the scope of regional and plot‐scale studies with high sample numbers. Yet it is well known that the clay content strongly affects soil water content. The objective of our study was to evaluate if the clay content can be estimated by a simple and fast measure like the water content of air‐dried soil. The soil samples used for this study originated from four different European regions (Hainich‐Dün, Germany; Schwäbische Alb, Germany; Hesse, France; Bugac, Hungary) and were collected from topsoils and subsoils in forests, grasslands, and croplands. Clay content, water content of air‐dried soil, and SOC content were measured. Clay content was determined either by the Pipette method or by the Sedigraph method. The water content of air‐dried soil samples ranged from 2.8 g kg–1 to 63.3 g kg–1 and the corresponding clay contents from 60.0 g kg–1 to 815.7 g kg–1. A significant linear relationship was found between clay content and water content. The scaled mean absolute error (SMAE) of the clay estimation from the water content of air‐dried soil was 20% for the dataset using the Pipette method and 28% for the Sedigraph method. The estimation of the clay content was more accurate in fine‐textured than in coarse‐textured soils. In this study, organic‐C content played a subordinate role next to the clay content in explaining the variance of the water content. The water retention of coarse‐textured soils was more sensitive to the amount of organic C than that of fine‐textured soils. The results indicate that in our study the water content of air‐dried soil samples was a good quantitative proxy of clay contents, especially useful for fine‐textured soils. 相似文献
382.
Purpose
The purpose of this study was to investigate relationships between chemical and thermal stabilities of Cu–humic complexes. The study of the chemical stability was based on pedological methods used for the determination of the bond strength of metal ions in soils by chemical leaching agents. The samples with various contents of the Cu(II) ions and their bond strength were put to the thermal analysis in order to correlate their thermo-oxidative behavior with their stability determined by leaching.Materials and methods
The humic acid was extracted from the South-Moravian lignite by standard alkaline extraction. The humic sample was used in two different forms: as the solid powder and as the hydrogel prepared by the acidic precipitation of humate. Six various concentrations of copper(II) solutions were used for the complexation of the humic powder and the hydrogel, in order to study the influence of their initial concentration on both the determined stabilities of the prepared complexes. Their chemical stability was assessed in terms of the Cu(II) ions release from the humic acid structure into two different extraction agents (MgCl2 and HCl solutions). Their thermo-oxidative behavior was investigated employing the thermogravimetry.Results and discussion
The complexation capacity of the humic hydrogel was higher in comparison with the humic powder. The amounts extractable from the Cu–humic complexes by the used leaching agents are higher for the humic powder, which shows on the lower chemical stability. The thermal degradation of the prepared complexes proceeds in several steps and this character remains also after the removal of the mobile and the ion-exchangeable fractions by the MgCl2. The elimination of these fractions as well as the extraction of the strongly bound Cu(II) ions shift the thermal degradation to higher temperatures. The incombustible residue increases with the Cu(II) content in the complexes except for the samples extracted by the HCl.Conclusions
The form of humic sample used for the preparation of the Cu–humic complexes influences both the chemical stability and the thermal one. The main reason is probably a better accessibility of the functional groups in the humic gel, which enables forming stronger binding copper(II) ions. The results showed that the thermal and chemical stabilities are closely related, which corresponds with the shift of the thermal degradation to higher temperatures after removing the less stable fractions from the humic complexes. 相似文献383.
Hvorup RN Goetz BA Niederer M Hollenstein K Perozo E Locher KP 《Science (New York, N.Y.)》2007,317(5843):1387-1390
BtuCD is an adenosine triphosphate-binding cassette (ABC) transporter that translocates vitamin B12 from the periplasmic binding protein BtuF into the cytoplasm of Escherichia coli. The 2.6 angstrom crystal structure of a complex BtuCD-F reveals substantial conformational changes as compared with the previously reported structures of BtuCD and BtuF. The lobes of BtuF are spread apart, and B12 is displaced from the binding pocket. The transmembrane BtuC subunits reveal two distinct conformations, and the translocation pathway is closed to both sides of the membrane. Electron paramagnetic resonance spectra of spin-labeled cysteine mutants reconstituted in proteoliposomes are consistent with the conformation of BtuCD-F that was observed in the crystal structure. A comparison with BtuCD and the homologous HI1470/71 protein suggests that the structure of BtuCD-F may reflect a posttranslocation intermediate. 相似文献
384.
Osterhaus AD Rimmelzwaan GF Martina BE Bestebroer TM Fouchier RA 《Science (New York, N.Y.)》2000,288(5468):1051-1053
Influenza B virus is a human pathogen whose origin and possible reservoir in nature are not known. An influenza B virus was isolated from a naturally infected harbor seal (Phoca vitulina) and was found to be infectious to seal kidney cells in vitro. Sequence analyses and serology indicated that influenza virus B/Seal/Netherlands/1/99 is closely related to strains that circulated in humans 4 to 5 years earlier. Retrospective analyses of sera collected from 971 seals showed a prevalence of antibodies to influenza B virus in 2% of the animals after 1995 and in none before 1995. This animal reservoir, harboring influenza B viruses that have circulated in the past, may pose a direct threat to humans. 相似文献
385.
Snégaroff J Branlard G Bouchez-Mahiout I Laudet B Tylichova M Chardot T Pecquet C Choudat D Raison-Peyron N Vigan M Kerre S Laurière M 《Journal of agricultural and food chemistry》2007,55(24):9837-9845
Two genes of wheat low-molecular-weight glutenin subunits (LMW-GS), B16 and P73, were cloned and expressed in E. coli. They were homologous to proteins encoded respectively at Glu-B3 and Glu-D3 loci. The N-terminal and C-terminal halves of B16 (NB16 and B16C) and the two chimeras combining the halves of the two genes (B16-P73 and P73- B16) were also expressed. All these constructs were compared for their reactivity with IgE from 24 patients suffering from different forms of wheat allergies. The results confirmed that LMW-GSs bound IgE in all adult allergies tested. Strong differences in reactivity between all the constructs were observed. They were disease-dependent. In wheat-dependent exercise-induced anaphylaxis (WDEIA), the reactivity of the constructs depended partly on common epitopes with omega-5 gliadins but also on differences in molecule conformation. The presence of NB16 in the constructs greatly influenced their IgE reactivity. 相似文献
386.
Solanum spegazzinii Bitt., a wild diploid potato species endemic to Argentina, possesses resistance to adverse biotic and
abiotic agents. Northwestern Argentinean populations grouped according to their morphological variability (G1 = localities
East of the Calchaquí Valley, G2 = Calchaquí Valley and G3 = locality Belén) presented problems in seed set following controlled
crosses. Thus, to evaluate if the morphological variability previously reported was sustained on a genetic basis, three introductions
per group and five plants per introduction were used in controlled crosses (genotypic combinations). These were classified
according to the number of seeds produced per fruit. Pollen-style compatibility relations were studied in those crosses that
did not set seeds or that produced less than 30 seeds each. Within groups, G1 produced seeds normally, whereas hybridization
barriers were found in 71.4% and 50.0% of the combinations within G2 and G3, respectively; on the other hand, from 46.7% to
73.3% of the combinations among groups exhibited similar barriers. Variability in the expression of the sites of pollen tube
inhibition in the style was observed both within and among groups. Speculations are made on the possible hybrid origin of
the populations.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
387.