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  • 1
    Electronic Resource
    Electronic Resource
    Transformation and binding of 13C and 14C-labelled atrazine in relation to straw decomposition in soil (2000)
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 51 (2000), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: As a source of organic matter, crop residues affect the behaviour of pesticides in agricultural soils. The fate of [U-ring-13C] and [U-ring-14C] atrazine (6-chloro-N-ethyl-N-isopropyl-1,3,5-triazine-2,4-diamine) was investigated during laboratory incubation under controlled conditions in a loamy soil amended with wheat straw at two different states of decomposition: no preliminary decomposition or 6 months’ preliminary decomposition. After 3 months, non-extractable, so-called ‘bound’, 13C-atrazine residues were recovered in three particle-size fractions (〉 200, 50–200 and 〈 50 μm), and investigated with solid-state 13C-NMR spectroscopy. Parallel incubations with [U-ring-14C] atrazine were carried out to quantify the bound residues as well as the extractable and mineralized fractions. The effect of straw residues on atrazine behaviour depended on whether they had been previously decomposed or not. When straw was decomposed for 6 months prior to incubation, atrazine mineralization was enhanced to 50% of the initial 14C in contrast to 15% of the initial 14C in soil alone and soil amended with fresh straw. In parallel, atrazine bound residues were formed in greater amount representing up to 20% of the initial 14C. CP/MAS 13C-NMR on soil size fractions of soil–straw mixtures after incubation with 13C-atrazine showed that bound residues contained mostly triazinic C, corresponding to atrazine or primary metabolites. Non-humified organic materials recovered in size fractions 〉 200 and 50–200 μm contained significant amounts of bound residues, especially when straw was added to the soil. CP/MAS 13C-NMR analysis of humic acids obtained from 〈 50-μm fractions was difficult due to overlapping of the native carboxyl 13C signal with the 13C-atrazine signal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2389.2000.00288.x
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  • 2
    Electronic Resource
    Electronic Resource
    Litter quality and its potential effect on decay rates of materials from Canadian forests (1995)
    Springer
    Water, air & soil pollution 82 (1995), S. 215-226 
    Details
    ISSN: 1573-2932
    Keywords: NMR ; principal components ; proximate analysis ; decay models ; CIDET
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Decomposition is influenced by a wide array of factors including macroclimate, microclimate, soil biota, soil nutrients, substrate piece size and substrate quality. To separate the influence of some of these factors a 10-year study, the Canadian Intersite Decomposition Experiment, was established in 1992 to measure the decay of 11 standard litter types on a range of forest types at 21 sites across Canada. As part of the study we analysed the initial elemental contents (N, P, S, K, Ca, Mg) and carbon (C) fractions (extractables, cellulose, hemicellulose, lignin) by13C NMR and wet chemical proximate analysis in a total of 37 primarily foliar litter types representative of the range of species found at the different CIDET sites. Litter types especially non-conifer species varied greatly in their qualities. Principal component analyses showed that the litter types could be distinguished by the elemental macronutrient contents through the ratio of N+P+K:S, by proximate chemical analyses through the ratio of water soluble:acid fractions, and by NMR through the ratio of O-alkyl:alkyl C. Litter quality data was used in three simple models of litter decay to predict how the mass loss of the different litter types could vary. Two models using a linear or single exponential decay equation and litter lignin and N content predicted a 2–5 fold difference in total mass loss for the different litter types. A third model using a summed exponential decay equation for three chemical fractions and a ligno-cellulose index predicted that for all but one litter type, variation in mass loss between types would be less than a 20%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01182835
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  • 3
    Electronic Resource
    Electronic Resource
    A bioassay of the availability of residual 15N fertilizer eight years after application to a forest soil in interior British Columbia (1994)
    Springer
    Plant and soil 160 (1994), S. 281-285 
    Details
    ISSN: 1573-5036
    Keywords: 15N availability ; bioassay ; immobilization ; nitrification ; organic N ; Pinus contorta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Although a high proportion of fertilizer N may be immobilized in organic forms in the soil, no studies have examined the long-term availability of residual fertilizer 15N in forestry situations. We investigated this by growing lodgepole pine (Pinus contorta) seedlings in surface (0–10 cm) soil sample eight years after application of 15N-urea, 15NH4NO3 and NH4 15NO3 to lodgepole pine in interior British Columbia. After nine months of growth in the greenhouse, seedlings took up an average of 8.5% of the 15N and 4.6% of the native N per pot. Most of the mineral N in the pots without seedlings was in the form of nitrate, while pots with seedlings had very low levels of mineral N. In contrast to the greenhouse study, there was no significantuptake of 15N by trees in the field study after the first growing season, although half of the soil organic 15N was lost between one and eight years after fertilization. This indicates the need to understand the mechanisms which limit the uptake of mineral N by trees in the field, and the possible mismatch of tree demand and mineral N availability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010154
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of acid hydrolysis on the13C NMR spectra of humic substances (1983)
    Springer
    Plant and soil 75 (1983), S. 201-211 
    Details
    ISSN: 1573-5036
    Keywords: Amino acids ; Carbohydrates ; Aromaticity ; Aliphatic carbon ; Carboxyl groups
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Two humic and one fulvic acid were hydrolyzed with hot 6M HCl and a combination of 12M and 0.5M H2SO4. Effects of acid hydrolysis on the chemical structures of the humic materials were assessed by comparing liquid-state13C NMR spectra of hydrolyzed with those of unhydrolyzed humic substances. Hydrolysis with 6M HCl was found to be more efficient for removing ptoteinaceous materials and carbohydrates than was hydrolysis with 12M-0.5M H2SO4. The latter appeared to better preserve the structural integrity of the humic materials, especially in the lower aliphatic region (0–50 ppm). Hydrolysis with the two acids increased the aromaticity of the humic materials, in part by removing proteinaceous components and carbohydrates. It also lowered the CO2H content of two out of three humic preparations, probably because of acid decarboxylation. The data presented demonstrate the great potential of13C NMR spectroscopy for structural research on humic materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02375565
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  • 5
    Electronic Resource
    Electronic Resource
    Characterization of organic matter in a forest soil of coastal British Columbia by NMR and pyrolysis-field ionization mass spectrometry (1994)
    Springer
    Plant and soil 158 (1994), S. 69-82 
    Details
    ISSN: 1573-5036
    Keywords: Douglas-fir ; forest soil ; fulvic acid ; humic acid ; humin ; litterfall ; NMR ; pyrolysis-mass ; spectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Organic matter in the soil profile under a young Douglas-fir stand in coastal British Columbia was characterized by examining intact samples of fresh litterfall and organic horizons (LF, H), and fractions (floatables, humic acid [HA], fulvic acid [FA], humin [HU]) from the three mineral horizons (Ae, Bm, BC). Some 30–40% of the carbon in the mineral horizons was found in poorly-decomposed plant material floatable in water, a fraction whose characteristics changed little with depth, and which contained over 1% Fe. The proportion of soil C in HA plus FA was approximately 8%, but the ratio of C in FA/HA increased with depth. Solid-state 13C NMR spectra of litterfall, LH and H samples showed effects of decomposition, in particular a decrease in 0-alkyl C from litterfall to LH to H, and degradation of resolution from LF to H. For the mineral soil fractions, both floatables and de-ashed HU (‘HUd’ prepared by HCl/HF treatment) indicated high levels of the original plant biopolymers, including a large alkyl component. Solution 13C spectra of the HAs from mineral horizons showed little difference with depth, except that peaks due to lignin were more pronounced for the Bm HA. The NMR spectra of FAs were high in 0-alkyl and carboxyl C. Pyrolysis-field ionization mass spectrometry confirmed and extended the results from NMR and chemical analyses, in particular demonstrating the accumulation of suberin in some fractions and the leaching and decomposition of lignin components with increasing depth in the mineral horizons. The general features of the HA, FA and HUd from this forest soil, and the effects of decomposition and pedogenesis were similar to those widely found for agricultural and forest soils. However, the accumulation of suberin, and the leaching and decomposition of lignin are particularly associated with forest soils. The low proportion of soil C in HA and FA, and the high proportion in poorly decomposed, iron-rich plant fragments suggest that decomposition is somewhat limited at this site, which is classified as having low fertility. The high accumulations of alkyl C from suberin may also indicate, or contribute to inhibition of decomposition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00007919
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  • 6
    Electronic Resource
    Electronic Resource
    The effect of copper applications on the movement of copper and other elements in organic soils (1984)
    Springer
    Water, air & soil pollution 22 (1984), S. 277-288 
    Details
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Copper concentrations should be maintained at 100 ppm (gg Cu g−1 dry soil) in the surface layers of undecomposed peat soils, and 400 ppm in humified muck soils. The Cu supports plant nutrition, and inhibits enzymes that degrade the organic soils (Histosols). The required or extravagant applications of Cu may threaten groundwater quality if the Cu, or elements displaced by the Cu, moves downwards in the soils. To test this, powdered CUSO4.5H2O was applied to the top 15 cm of replicated microplots of organic soils to increase their Cu concentrations by 0, 150, 500, and 1500 ppm at field sites A (peat) and B (muck) in May 1978 and by 0, 100, 300, and 800 ppm at field site C (mucky peat) in 1979. Duplicate cores of up to 50 cm depth were taken in the spring of 1981 from each of the 56 microplots and analyzed. At all sites, none of the Cu additions caused significant displacement and downward movement of Ca, Mg, K, Fe, Mn, or Zn. There was a leaching of small fractions of the applied Cu down to 40 cm depth only when 1500 ppm of Cu was added to the humus-poor, acidic peat at site A. Some of the Cu applied at the 500 ppm rate at site A and 1500 ppm rate at site B was found in the 20 to 30 cm zone. At site C, none of the applied Cu moved from the top 20 cm (plow layer).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00159349
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  • 7
    Electronic Resource
    Electronic Resource
    Trichuris muris: Structure and formation of the egg polar plugs (1985)
    Springer
    Parasitology research 71 (1985), S. 373-381 
    Details
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The structure and development of the polar plugs ofTrichuris muris eggs were observed by light and electron microscopy. Initial stages in plug formation commenced in the spermatheca of the adult female where two polar papillae became delimited from the remainder of the oocyte cytoplasm. These papillae exhibited a discrete PAS positive reaction and were regarded as prospective plug regions from which cytoplasmic granules were absent. Glycogen rosettes, initially concentrated in these prospective areas, were later transformed into an irregular fine network of chitin-protein microfibrils. This arrangement of microfibrils was in contrast to that of the surrounding collar region which displayed a distinct lamellate organization. The fully developed polar plug was of lower electron density than the shell. Each plug was covered externally by the vitelline layer and lined internally by the lipid layer of the eggshell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00928339
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  • 8
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    Expression of Herpes Simplex Virus 1 MicroRNAs in Cell Culture Models of Quiescent and Latent Infection [Genome Replication and Regulation of Viral Gene Expression] (2014)
    The American Society for Microbiology (ASM)
    Details
    Publication Date: 2014-02-01
    Description: To facilitate studies of herpes simplex virus 1 latency, cell culture models of quiescent or latent infection have been developed. Using deep sequencing, we analyzed the expression of viral microRNAs (miRNAs) in two models employing human fibroblasts and one using rat neurons. In all cases, the expression patterns differed from that in productively infected cells, with the rat neuron pattern most closely resembling that found in latently infected human or mouse ganglia in vivo .
    Print ISSN: 0022-538X
    Electronic ISSN: 1098-5514
    Topics: Medicine
    Published by The American Society for Microbiology (ASM)
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  • 9
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    Breast cancer risk and protracted low-to-moderate dose occupational radiation exposure in the US Radiologic Technologists Cohort, 1983–2008 (2016)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2016-10-27
    Description: Breast cancer risk and protracted low-to-moderate dose occupational radiation exposure in the US Radiologic Technologists Cohort, 1983–2008 British Journal of Cancer 115, 1105 (25 October 2016). doi:10.1038/bjc.2016.292 Authors: D L Preston, C M Kitahara, D M Freedman, A J Sigurdson, S L Simon, M P Little, E K Cahoon, P Rajaraman, J S Miller, B H Alexander, M M Doody & M S Linet
    Keywords: radiationbreast canceroccupational exposurecohort study
    Print ISSN: 0007-0920
    Electronic ISSN: 1532-1827
    Topics: Medicine
    Published by Nature Publishing Group (NPG)
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