Changes in landscape naturalness derived from a historical land register—a case study from NE Germany     

Florian Jansen  Stefan Zerbe  Michael Succow 《Landscape Ecology》2009,24(2):185-198

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Pilot project to investigate over-wintering of free-living gastrointestinal nematode larvae of sheep in Ontario,Canada     

Laura C. Falzon  Paula I. Menzies  John VanLeeuwen  Krishna P. Shakya  Andria Jones-Bitton  Jacob Avula  Jocelyn T. Jansen  Andrew S. Peregrine 《The Canadian veterinary journal. La revue veterinaire canadienne》2014,55(8):749-756

This study investigated the overwintering survival and infectivity of free-living gastrointestinal nematode (GIN) stages on pasture. The presence of GIN larvae was assessed on 3 sheep farms in Ontario with a reported history of clinical haemonchosis, by collecting monthly pasture samples over the winter months of 2009/2010. The infectivity of GIN larvae on spring pastures was evaluated using 16 tracer lambs. Air and soil temperature and moisture were recorded hourly. Free-living stages of Trichostrongylus spp. and Nematodirus spp. were isolated from herbage samples. Gastrointestinal nematodes were recovered from all tracer lambs on all farms; Teladorsagia sp. was the predominant species. Very low levels of Haemonchus contortus were recovered from 1 animal on 1 farm. The results suggest that Haemonchus larvae do not survive well on pasture, while Teladorsagia sp., Trichostrongylus spp. and Nematodirus spp. are able to overwinter on pasture in Ontario and are still infective for sheep in the spring.  相似文献   

Confirmation of spatial patterns and temperature effects in Bluetongue virus serotype-8 transmission in NW-Europe from the 2007 reported case data     

Gert Jan Boender  Thomas J Hagenaars  Armin RW Elbers  J?rn M Gethmann  Estelle Meroc  Helene Guis  Aline A de Koeijer 《Veterinary research》2014,45(1)

Two separate analyses were carried out to understand the epidemiology of Bluetongue virus serotype 8 (BTV-8) in 2007 in North West Europe: First, the temporal change in transmission rates was compared to the evolution of temperature during that season. Second, we evaluated the spatio-temporal dynamics of newly reported outbreaks, to estimate a spatial transmission kernel. For both analyses, the approach as used before in analysing the 2006 BTV-8 epidemic had to be adapted in order to take into account the fact that the 2007 epidemic was not a newly arising epidemic, but one advancing from whereto it had already spread in 2006. We found that within the area already affected by the 2006 outbreak, the pattern of newly infected farms in 2007 cannot be explained by between-farm transmission, but rather by local re-emergence of the virus throughout that region. This indicates that persistence through winter was ubiquitous for BTV-8. Just like in 2006, we also found that the temperature at which the infection starts to spread lies close to 15 °C. Finally, we found that the shape of the transmission kernel is in line with the one from the 2006 epidemic. In conclusion, despite the substantial differences between 2006 and 2007 in temperature patterns (2006 featured a heat wave in July, whereas 2007 was more regular) and spatial epidemic extent, both the minimum temperature required for transmission and the transmission kernel were similar to those estimated for the 2006 outbreak, indicating that they are robust properties, suitable for extrapolation to other years and similar regions.  相似文献   

Ticks and tick borne pathogens in domestic animals in the Netherlands     

Bodaan C  Nihof AM  Postigo M  Nieuwenhuijs H  Opsteegh M  Franssen L  Jebbink F  Jansen S  Jongejan F 《Tijdschrift voor diergeneeskunde》2007,132(13):517-523

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Major genes for resistance to beet necrotic yellow vein virus (BNYVV) in Beta vulgaris     

Olga E. Scholten  Ritsert C. Jansen  L. C. Paul Keizer  Theo S. M. De Bock  Wouter Lange 《Euphytica》1996,91(3):331-339

Summary Inheritance of resistance to beet necrotic yellow vein virus (BNYVV) was studied in segregating F2 and backcross families obtained from crosses between resistant plants of the sugar beet selection Holly-1-4 or the wild beet accession Beta vulgaris subsp. maritima WB42 and susceptible parents. Greenhouse tests were carried out, in which seedlings were grown in a mixture of sand and infested soil. Virus concentrations of BNYVV in the rootlets were estimated by ELISA. To discriminate resistant and susceptible plants, mixtures of normal distributions were fitted to log₁₀ virus concentrations, estimated for segregating F1, F2 and BC populations of both accessions. The hypothesis that Holly-1-4 contained one single dominant major gene was accepted. For WB42, results fitted with the hypotheses that resistance was based on either one (or more) dominant major gene(s) showing distorted segregation, or two complementary dominant genes, which are both required for resistance. Resistance from WB42 appeared to be more effective against BNYVV than resistance from Holly-1-4.This research was carried out as part of a PhD study at the Graduate School Experimental Plant Sciences (EPS), Department of Virology, Wageningen, The Netherlands  相似文献   

Interactions between plant and aphid genotypes in resistance of lettuce to Myzus persicae and Macrosiphum euphorbiae     

K. Reinink  F. L. Dieleman  J. Jansen  A. M. Montenarie 《Euphytica》1989,43(3):215-222

Summary Six lettuce lines, representing two types of resistance to the green peach aphid, Myzus persicae, and a control line with high susceptibility to M. persicae were tested for resistance to six different clones of Myzus persicae and two clones of the potato aphid, Macrosiphum euphorbiae.The clones of M. persicae showed very different levels of aggressiveness on lettuce: two had a high level of reproduction, two had an intermediate level and two were poorly adapted to lettuce as a host. Differences between lettuce lines in aphid reproduction increased with increasing aggressiveness of the aphid clone, which means that aggressive clones are most effective for selection purposes. No evidence was found for clone-specific plant genotype reactions, meaning that lines resistant to one clone will also be resistant to other clones of M. persicae, allthough not neccessarily at the same level. The lettuce lines selected for partial resistance to the aggressive clone WMp1 were completely or almost completely resistant to less aggresive clones.No differences in level of reproduction were found between the two clones of M. euphorbiae and no relation was observed between resistance to M. persicae and M. euphorbiae, indicating the species-specific character of resistance to leaf aphids in lettuce.  相似文献   

Dorsal spinocerebellar tract: response pattern of nerve fibers to muscle stretch   总被引：1，自引：0，他引：1  

J K Jansen  T Rudjord 《Science (New York, N.Y.)》1965,149(688):1109-1111

The response to muscle stretch of second-order neurons of the dorsal spinocerebellar tract was studied in anesthetized cats. Three different types of neurons are defined; the response of each type is remarkably similar to that of the corresponding stretch-receptors of the muscle. Accordingly, the cerebellum receives information on the mechanical situation in muscle from three qualitatively different channels: one has a high degree of sensitivity to dynamic stretch (Ia units) and provides a mixed signal of muscle length and speed of movement; another provides information mainly on muscle length (group-Il units); and the third signals information on the degree of contraction of the muscle (Ib units).  相似文献   

Normal metallic point contacts     

Jansen AG  Mueller FM  Wyder P 《Science (New York, N.Y.)》1978,199(4333):1037-1040

The measured voltage derivative of the nonlinear resistance of tiny point contacts can be separated into a phonon-emission effect (alpha(2)F) and an analytic functional form (background effect). The alpha(2)F's show structure coincident with bulk phonon densities of states. Values of the integral of 2 alpha(2)F/omega are closely related to literature values. The background effect is related to the impurity concentration of the materials.  相似文献   

Spatial Variability of Turbulent Mixing in the Abyssal Ocean   总被引：3，自引：0，他引：3  

KL Polzin  JM Toole  JR Ledwell  RW Schmitt 《Science (New York, N.Y.)》1997,276(5309):93-96

Ocean microstructure data show that turbulent mixing in the deep Brazil Basin of the South Atlantic Ocean is weak at all depths above smooth abyssal plains and the South American Continental Rise. The diapycnal diffusivity there was estimated to be less than or approximately equal to 0.1 x 10(-4) meters squared per second. In contrast, mixing rates are large throughout the water column above the rough Mid-Atlantic Ridge, and the diffusivity deduced for the bottom-most 150 meters exceeds 5 x 10(-4) meters squared per second. Such patterns in vertical mixing imply that abyssal circulations have complex spatial structures that are linked to the underlying bathymetry.  相似文献   

Frog communities and wetland condition: relationships with grazing by domestic livestock along an Australian floodplain river     

Amy Jansen  Michael Healey 《Biological conservation》2003,109(2):207-219

Frogs are in decline worldwide, and are known to be sensitive indicators of environmental change. Floodplains of the Murray-Darling Basin in southeastern Australia have been altered in many ways by livestock grazing, by the introduction of exotic fish, and by changes to flooding regimes. These changes have led to declines in wetland condition and hence to the availability of habitat for wetland frogs. This study examined relationships between frogs, wetland condition and livestock grazing intensity at 26 wetlands on the floodplain of the Murrumbidgee River. Frog communities, species richness, and some individual species of frogs declined with increased grazing intensity. Wetland condition also declined with increased grazing intensity, particularly the aquatic vegetation and water quality components. There were clear relationships between frog communities and wetland condition, with several taxa responding to aquatic and fringing vegetation components of wetland condition. Thus, grazing intensity appeared to influence frog communities through changes in wetland habitat quality, particularly the vegetation. Reduced stocking rates may result in improved wetland condition and more diverse frog communities. River management to provide natural seasonal inundation of floodplain wetlands may also enhance wetland condition, frog activity and reproductive success.  相似文献