The onset of planet formation in brown dwarf disks     

Apai D  Pascucci I  Bouwman J  Natta A  Henning T  Dullemond CP 《Science (New York, N.Y.)》2005,310(5749):834-836

The onset of planet formation in protoplanetary disks is marked by the growth and crystallization of sub-micrometer-sized dust grains accompanied by dust settling toward the disk mid-plane. Here, we present infrared spectra of disks around brown dwarfs and brown dwarf candidates. We show that all three processes occur in such cool disks in a way similar or identical to that in disks around low- and intermediate-mass stars. These results indicate that the onset of planet formation extends to disks around brown dwarfs, suggesting that planet formation is a robust process occurring in most young circumstellar disks.  相似文献   

Adhesion of Salmonella enterica serotype Enteritidis isolates to chicken isthmal glandular secretions     

De Buck J  Van Immerseel F  Meulemans G  Haesebrouck F  Ducatelle R 《Veterinary microbiology》2003,93(3):223-233

The ability of Salmonella enterica serotype Enteritidis isolates to adhere to immobilized secretions of the isthmus of the laying hen was determined in an ELISA-type assay. One-third of the 56 isolates tested in the logarithmic growth phase, adhered to the isthmal secretions. Using a binding assay of the isolates to thin paraffin sections of the oviduct, we demonstrated that the receptor of the adhesion was localized inside the tubular gland cells of the isthmus. The adhesion to immobilized isthmal secretions as well as to the paraffin sections was blocked by the addition of mannose. A fimD mutant of S. Enteritidis, lacking type 1 fimbriae, did not adhere, confirming that the adhesion was mediated by type 1 fimbriae. Mannosylated glycoproteins were demonstrated in the isthmus glandular cells using confocal laser scanning microscopy by FITC-labelled Lens culinaris lectins. It is hypothesized that the binding of S. Enteritidis to isthmal secretions could play a role in the contamination of eggs through incorporation of the bacteria in the shell membranes.  相似文献   

Aggregation and organic matter in subarctic Andosols under different grassland management     

Taru Lehtinen  Guðrún Gísladóttir  Georg J. Lair  Jeroen P. van Leeuwen  Winfried E.H. Blum  Jaap Bloem 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(3):246-263

Quantity and quality of soil organic matter (SOM) affect physical, chemical, and biological soil properties, and are pivotal to productive and healthy grasslands. Thus, we analyzed the distribution of soil aggregates and assessed quality, quantity, and distribution of SOM in two unimproved and improved (two organic and two conventional) grasslands in subarctic Iceland, in Haplic and Histic Andosols. We also evaluated principal physicochemical and biological soil properties, which influence soil aggregation and SOM dynamics. Macroaggregates (>250 µm) in topsoils were most prominent in unimproved (62–77%) and organically (58–69%) managed sites, whereas 20–250 µm aggregates were the most prominent in conventionally managed sites (51–53%). Macroaggregate stability in topsoils, measured as mean weight diameter, was approximately twice as high in organically managed (12–20 mm) compared with the conventionally managed (5–8 mm) sites, possibly due to higher organic inputs (e.g., manure, compost, and cattle urine). In unimproved grasslands and one organic site, macroaggregates contributed between 40% and 70% of soil organic carbon (SOC) and nitrogen to bulk soil, whereas in high SOM concentration sites free particulate organic matter contributed up to 70% of the SOC and nitrogen to bulk soil. Aggregate hierarchy in Haplic Andosols was confirmed by different stabilizing mechanisms of micro- and macroaggregates, however, somewhat diminished by oxides (pyrophosphate-, oxalate-, and dithionite-extractable Fe, Al, and Mn) acting as binding agents for macroaggregates. In Histic Andosols, no aggregate hierarchy was observed. The higher macroaggregate stability in organic farming practice compared with conventional farming is of interest due to the importance of macroaggregates in protecting SOM and soils from erosion, which is a prerequisite for soil functions in grasslands that are envisaged for food production in the future.  相似文献   

Biological activity of volatiles from marine and terrestrial bacteria     

Schulz S  Dickschat JS  Kunze B  Wagner-Dobler I  Diestel R  Sasse F 《Marine drugs》2010,8(12):2976-2987

The antiproliferative activity of 52 volatile compounds released from bacteria was investigated in agar diffusion assays against medically important microorganisms and mouse fibroblasts. Furthermore, the activity of these compounds to interfere with the quorum-sensing-systems was tested with two different reporter strains. While some of the compounds specific to certain bacteria showed some activity in the antiproliferative assay, the compounds common to many bacteria were mostly inactive. In contrast, some of these compounds were active in the quorum-sensing-tests. γ-Lactones showed a broad reactivity, while pyrazines seem to have only low intrinsic activity. A general discussion on the ecological importance of these findings is given.  相似文献   

Temperature related instability of a naturally induced cytoplasmic male sterility in industrial chicory (Cichorium intybus L.)          下载免费PDF全文

Jeroen Van der Veken  Stany Vandermoere  Olivier Maudoux  Christine Notté  Tom Eeckhaut  Joost Baert  Stefaan Werbrouck  Johan Van Huylenbroeck 《Plant Breeding》2018,137(3):423-432

Natural alloplasmic cytoplasmic male sterile (CMS) clones of industrial chicory were obtained after crossing wild chicory with selected breeding lines. We investigated the CMS stability of 10 clones in various environmental growing conditions. CMS was stable under cool growing conditions in most of them. Fertility restoration, based on pollen production scores, was observed in all clones after a period of hot temperatures. The early flower bud stage was sensitive, resulting in fertile flowers 12–17 days after exposure to high temperatures. Experiments under controlled growing conditions at 15°C demonstrated that a heat shock of 2 days at 25 or 30°C was sufficient to restore fertility. Sterile flowers were formed when plants were again grown at lower temperatures. Significant differences between individual clones were observed, indicating the potential of genetic selection to obtain stable CMS parent lines.  相似文献   

Calculating Dry Deposition and Canopy Exchange with the Canopy Budget Model: Review of Assumptions and Application to Two Deciduous Forests     

Jeroen Staelens  Daniel Houle  An De Schrijver  Johan Neirynck  Kris Verheyen 《Water, air, and soil pollution》2008,191(1-4):149-169

The canopy budget model simulates the interaction of major ions within forest canopies based on throughfall and precipitation measurements. The model has been used for estimating dry deposition and canopy exchange fluxes in a wide range of forest ecosystems, but different approaches have been reported. We give an overview of model variations with respect to the time step, type of open-field precipitation data, and tracer ion, and discuss the strengths and weaknesses of different assumptions on ion exchange within forest canopies. To examine the effect of model assumptions on the calculated fluxes, nine approaches were applied to data from two deciduous forest plots located in regions with contrasting atmospheric deposition, i.e. a beech (Fagus sylvatica L.) plot in Belgium and a mixed sugar maple (Acer saccharum Marsh.) plot in Quebec. For both forest plots, a semi-annual time step in the model gave similar results as an annual time step. Na⁺ was found to be more suitable as a tracer ion in the filtering approach than Cl^? or ${\text{SO}}_4^{2 - } $ . Using bulk instead of wet-only precipitation underestimated the potentially acidifying deposition. To compute canopy uptake of ${\text{NH}}_4^ + $ and H⁺, ion exchange with K⁺, Ca²⁺, and Mg²⁺ as well as simultaneous cation and anion leaching should be considered. Different equations to allocate ${\text{NH}}_4^ + $ vs H⁺ uptake had most effect on the estimated fluxes of the cation that was less important at a plot. More research is needed on the relative uptake efficiency of H⁺, ${\text{NH}}_4^ + $ , and ${\text{NO}}_{_3 }^{\text{ - }} $ for varying tree species and environmental conditions.  相似文献   

Moisture movement and thickness swelling in oriented strandboard,part 1. Analysis using nuclear magnetic resonance microimaging     

Jeroen?H.?van?HoutsEmail author  Siqun?Wang  Huiping?Shi  Hongjun?Pan  George?W.?Kabalka 《Wood Science and Technology》2004,38(8):617-628

A procedure was developed to observe the water absorption characteristics of small specimens of oriented strandboard (OSB) and solid wood in a nuclear magnetic resonance (NMR) microimaging facility. The procedure allowed a specimen to be surrounded in water while remaining in a fixed position within the imaging coil, after which the water could be removed and the specimen immediately imaged. This technique permitted images of the specimen to be taken after a number of different periods of water soak without having to remove and replace the specimen, thus easily maintaining the same image location. Both the distribution of free water and its movement as a function of time were observed using this technique. Inter-strand voids within OSB were shown to be the main route for moisture movement through a specimen of this type. The influence of the inherent anisotropy of OSB on moisture movement was investigated by sealing selected surfaces of a specimen with silicone to observe moisture absorption in predetermined directions.  相似文献   

A high-morbidity outbreak of Johne’s disease in game-ranched elk     

Taya Forde  Mathieu Pruvot  Jeroen De Buck  Karin Orsel 《The Canadian veterinary journal. La revue veterinaire canadienne》2015,56(5):479-483

Following an outbreak of Johne’s disease on an elk farm in northern Alberta, Canada, fecal culture, fecal polymerase chain reaction (PCR), and serum enzyme-linked immunosorbent assay (ELISA) tests were performed on individual animals. The magnitude of the outbreak is described and the challenges associated with poor test agreement, as well as herd management options, are discussed.  相似文献   

Recovery of Moraxella ovis from the bovine respiratory tract and differentiation of Moraxella species by tDNA-intergenic spacer PCR     

Catry B  Boyen F  Baele M  Dewulf J  de Kruif A  Vaneechoutte M  Haesebrouck F  Decostere A 《Veterinary microbiology》2007,120(3-4):375-380

The purpose of the present study was to identify Moraxella (M.)—like organisms recovered from calves suffering from respiratory disease down to species level by means of tDNA-intergenic spacer length polymorphism analysis (tDNA-PCR), and to perform antimicrobial susceptibility testing of these isolates using an agar dilution technique. A total of 16 isolates originating from 12 unrelated occasions were identified as Moraxella ovis, and tDNA fingerprinting showed clear delineation from other Moraxella species. The minimal inhibitory concentrations (in μg/mL) for 90% of the investigated isolates were ≤0.03 for ampicillin; 0.25 for ceftiofur; 0.5 for oxytetracycline; 8 for gentamicin; 64 for spectinomycin; 0.5/9.5 for the combination trimethoprim-sulfonamides; 4 for erythromycin; 8 for tilmicosin; 1 for florfenicol and 0.125 for enrofloxacin.  相似文献   

Determination of lactate concentrations in blood plasma and peritoneal fluid in horses with colic by an Accusport analyzer     

Delesalle C  Dewulf J  Lefebvre RA  Schuurkes JA  Proot J  Lefere L  Deprez P 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2007,21(2):293-301

BACKGROUND: Intestinal hypoperfusion can lead to increased lactate concentrations in plasma and peritoneal fluid of horses with colic. HYPOTHESIS: The purposes of this study were to (1) evaluate the reliability of the Accusport analyzer to assess peritoneal fluid lactate (PFL) concentrations in healthy horses and those with colic, (2) identify clinical features associated with abnormal blood plasma lactate (BPL) and PFL concentrations, and (3) evaluate the prognostic value of BPL and PFL. ANIMALS: BPL and PFL were determined in 20 healthy horses and in 106 horses with colic. RESULTS: The Accusport was reliable for determining BPL concentrations < 13 mM and PFL concentrations < 20 mM. Multivariate analysis indicated that PCV and the need for intestinal resection were independently associated with the BPL; pulse, PCV, venous pO2, the presence of necrotic intestine, an increased amount of peritoneal fluid, and fluid total protein content were independently associated with PFL. With a 1 mM increase in BPL or PFL, the respective odds ratios for required abdominal surgery increase to 1.23 (BPL) and 1.58 (PFL), odds ratios for a required intestinal resection increase to 1.20 (BPL) and 1.41 (PFL), and odds ratios for developing ileus increase by 1.33 (BPL) and 1.36 (PFL). PFL concentrations of 1, 6, 12, and 16 mM correspond to a probability of death of 11, 29, 63, and 82%, respectively, in horses without strangulating obstruction and of 25, 52, 82, and 92%, respectively, in horses with strangulating obstruction. CONCLUSION: PFL is more useful and sensitive than BPL for prognostic purposes in horses with colic.  相似文献