Testing the spatial significance of weed patterns in arable land using Mead's test   总被引：1，自引：0，他引：1  

S HEIJTING  W VAN DER WERF  W KRUIJER†  & A STEIN‡ 《Weed Research》2007,47(5):396-405

There is a need in weed science for statistical tests for patchiness and spatial pattern. The objective of this study was to investigate the performance of Mead’s test for detecting patterns in synthetic data and in real weed counts made in maize, and making a first assessment of its applicability in ecological studies on weeds. In an extension to Mead’s test, made here for the first time, we merge original quadrat count data into rectangular cells of m by n quadrats. Care was taken to rule out the effect of starting point on the test result. Using the synthetic data, we demonstrate the ability of the test to detect both patchiness and homogeneity as deviations from randomness. The first deviation results in right‐sided significance, and the second in left‐sided significance of the test. Analysis of the real weed patterns demonstrated patchiness at many scales for five of the six investigated species and lack of any deviation from randomness in the sixth: Taraxacum officinale. The latter was the only wind dispersing species in the dataset. No deviation towards homogeneity was found in any of the real weed species at any scale. All patchy patterns showed anisotropy, being elongated in the direction of field traffic. As it turns out, Mead’s test is well suited to detect departures from randomness in observed weed patterns and enhances the suite of diagnostic tools that can be employed by weed ecologists.  相似文献   

Oral treatment with ketoconazole of plantar candidosis in a mute swan     

A-D. DEGRYSE  J. VAN  CUTSEM J. FRANSEN 《The Journal of small animal practice》1985,26(10):619-623

Candida albicans infection of the plantar region of the digit was diagnosed in a mute swan (Cygnus olor). Diagnosis was based on histological examination and on cultures. The pathogenicity of the C. albicans isolate was proven by inoculation in laboratory animals. Oral treatment with ketoconazole resulted in complete clinical recovery; no relapse occurred during a sixteen-month follow-up period.  相似文献   

THE MOVEMENT OF LABELLED 2,4-D IN YOUNG BARLEY PLANTS     

W. VAN DER  ZWEEP 《Weed Research》1961,1(4):258-266

Summary. After the 4- or 5-leaf stage in young barley plants, there is a decrease in the translocation of 2,4-D from the leaves to the root system. It is shown that there is no relation between this phenomenon and ear initiation, which occurs at this stage of development. Movement of 2,4-D out of leaves of the tiller in the axils of the 1st and 2nd leaves was also shown to be very small. There is some evidence for a'block'in the movement of 2,4-D in established grass plants.
La migration du 2,4-D marqué dans l'orge  相似文献   

Disease resistance of carp, Cyprinus carpio L.: identification of individual genetic differences by bath challenge with atypical Aeromonas salmonicida     

G. F. WIEGERTJES  J. G. DALY  W. B. VAN  MUISWINKEL 《Journal of fish diseases》1993,16(6):569-576

Abstract. The present study was undertaken to identify female breeders, resistant or susceptible to disease, which might be used to obtain gynogenetically cloned carp lines differing in disease resistance. Experimentally induced erythrodermatitis was used as the disease model. Firstly, the effect of age on the resistance to bath challenge with atypical Aeromonas salmonicida was examined. These challenges indicated a shift from subacute to chronic infection with increasing age, as shown by a lower survival at 3 and 5 months (both 15%) compared to 10 months of age (60%). Then, to conserve and characterize breeder females, offspring of two females (nos 21 and 38), including F1, F2 and backcross (B1 and B2) progenies, were bath challenged at the age of 3 months. Comparison of the survival data showed a segregation into two groups of progenies: one resistant with nearly 100% survivors (W, F1 and B2), and one relatively susceptible group with 25% (R8 and F2) or 50% (B1) mortality. Analysis of inheritance indicated dominance of the resistant phenotype. Thus, the results identified two breeder females whose (gynogenetic) progeny might be expected to differ in resistance to bath challenge with atypical A. salmonicida.  相似文献   

Assessment of impact of the introduction of exotic fish species in north-east Thailand     

H. H. DE  IONGH J. C. J. VAN  ZON 《Aquaculture Research》1993,24(3):279-289

Abstract. Within the framework of a fisheries project in north-east Thailand, project MK/FSPC/069 entitled ‘The Fish Seed Production Centre, North East Thailand’, an assessment was carried out of the ecological impact of introducing exotic fish species (common carp, Cyprinus carpio L., Nile tilapia, Oreochromis niloticus (L.), and Chinese and Indian carps). For the assessment, the protocol of Kohler & Stanley (1984) was followed, covering feasibility of introduction, acclimatization potential, potential impact, and control potentials. Regarding the (ongoing) use of the proposed exotic species in aquaculture, it was concluded that so far no clear ecological impact has been reported from escapes to open water; the use of the exotic species has shown to be highly beneficial from a 9 socio-economic point of view. Regarding the proposed introduction of the exotic species into public waters (natural lakes and man-made reservoirs), it was concluded that earlier releases of these species in north-east Thailand did not provoke severe ecological impact in terms of deterioration of aquatic ecosystems. Incidental cases of minor ecological impact were reported for common carp and nile tilapia. Indications were obtained for niche competition between Chinese and Indian carps and indigenous carps, while similar niche competition was concluded for bighead carp, Aristichthys nobilis (Richardson), and indigenous pelagic zooplankton feeders. Observing the prolific development of the Nile tilapia in a number of reported cases, it was recommended not to include this species in stocking programmes for public water bodies, until more risk assessments are available.  相似文献   

A conceptual framework and an empirical test of complementarity and facilitation with respect to phosphorous uptake by plant species mixtures     

Chunjie LI  Thomas W. KUYPER  Wopke VAN DER WERF  Junling ZHANG  Haigang LI  Fusuo ZHANG  Ellis HOFLLAND 《土壤圈》2022,32(2):317-329

Plant species have different traits for mobilizing sparingly soluble phosphorus (P) resources, which could potentially lead to overyielding in P uptake by plant species mixtures compared to monocultures due to higher P uptake as a result of resource (P) partitioning and facilitation. However, there is circumstantial evidence at best for overyielding as a result of these mechanisms. Overyielding (the outcome) is easily confused with underlying mechanisms because of unclear definitions. We aimed to define a conceptual framework to separate outcome from underlying mechanisms and test it for facilitation and complementarity with respect to P acquisition by three plant species combinations grown on four soils. Our conceptual framework describes both mechanisms of complementarity and facilitation and outcomes (overyielding of mixtures or no overyielding) depending on the competitive ability of the species to uptake the mobilized P. Millet/chickpea mixtures were grown in pots on two calcareous soils mixed with calcium-bound P (CaP) and phytate P (PhyP). Cabbage/faba bean mixtures were grown on both acid and neutral soils mixed with P-coated iron (hydr)oxide (FeP) and PhyP. Wheat/maize mixtures were grown on all four soils. Rhizosphere carboxylate concentration and acid phosphatase activity (mechanisms) as well as plant P uptake and biomass (outcome) were determined for monocultures rhizosphere and species mixtures. Facilitation of P uptake occurred in millet/chickpea mixtures on one calcareous soil. We found no indications for P acquisition from different P sources, neither in millet/chickpea, nor in cabbage/faba bean mixtures. Cabbage and faba bean on the neutral soil differed in rhizosphere acid phosphatase activity and carboxylate concentration, but showed no overyielding. Wheat and maize, with similar root exudates, showed overyielding (the observed P uptake being 22% higher than the expected P uptake) on one calcareous soil. We concluded that although differences in plant physiological traits (root exudates) provide necessary conditions for complementarity and facilitation with respect to P uptake from different P sources, they do not necessarily result in increased P uptake by species mixtures, because of the relative competitive ability of the mixed species.  相似文献   

Photosynthetic inhibition in Phaseolus vulgaris II. The influence of light on herbicidal action     

J. L. P. VAN  OORSCHOT P. H. VAN  Leeuwen 《Weed Research》1974,14(2):81-86

The influence of pre-treatment and post-treatment illumination upon the herbicidal effect produced in Phaseolus vulgaris L. cv. Berna by simeton, diuron, diquat and ioxynil was examined. The increased effect noted at lower pre-treatment and higher post-treatment levels of illumination was correlated with increased inhibition of net photosynthesis. This increased effect was ascribed to enhanced photo-oxidation.  相似文献   

VASCULAR ANOMALY CAUSING SUBCLAVIAN STEAL AND CERVICAL MYELOPATHY IN A DOG: DIAGNOSIS AND ENDOVASCULAR MANAGEMENT     

DICCON R. WESTWORTH  KAREN M. VERNAU  SEAN P. CULLEN  CRAIG D. LONG  VAN V. HALBACH  RICHARD A. LECOUTEUR 《Veterinary radiology & ultrasound》2006,47(3):265-269

A 3-year-old dog with cervical myelopathy resulting from a vascular anomaly is described. Marked intradural-extramedullary spinal cord compression was observed, in association with multilevel ectatic anastomotic radicular arterial branches connecting the left and right vertebral arteries. A nonpatent proximal segment of the right subclavian artery had resulted in compensatory enlargement of the left vertebral artery. Flow within the right vertebral artery was retrograde and fed into the patent distal segment of the right subclavian artery. Multiple imaging techniques including myelography, computed tomography, magnetic resonance imaging, and selective digital angiography were used to document this anomaly. To reduce spinal cord compression the largest collateral vessel was embolized without complication. Good clinical response was observed within 6 weeks and improved clinical neurologic function was maintained at the time of a 12-month re-evaluation.  相似文献   

Lidocaine decay and hepatic extraction in the Pig     

B. METS  R. ALLIN  J. VAN DYKE  R. HICKMAN† 《Journal of veterinary pharmacology and therapeutics》1993,16(1):8-14

Plasma lidocaine decay after injection was studied in five anaesthetized pigs and fitted to a two compartment open model. Derived pharniacokinetic paranieter-s were eniployed to rapidly achieve plateau concentrations within 60 min of starting a two stage infusion of lidocaine hydrochloride. Hepatic extraction and clearance of lidocaine at steady state were determined in 10 pigs by transhep;ttic: sampling and nieasurenient of hepatic arterial and portal venous blood flow using perivascular ultrasonic flow probes placed at laparotomy. These data were compared with siniilar studies performed in man as well as the sheep, (log, monkey and cat. The lidocaine extraction ratio of 0.60 in the pig was found t o be similar to that determined by others in man.  相似文献   

Sulphadimidine metabolism in vitro: I. sex differences in acetylation and hydroxylation in cultured rat hepatocytes     

G. A. E. VAN T KLOOSTER  F. M. A. WOUTERSEN-VAN NIJNANTEN  B.J. BLAAUBOER†  J. NOORDHOEK†  A. S.J. P. A. M. VAN MIERT 《Journal of veterinary pharmacology and therapeutics》1993,16(3):343-349

The hydroxylation and acetylation of 0.5 mM sulphadimidine (SDD) was studied in primary cultures of hepatocytes from male and female rats, and from castrated male and sham operated male rats. In addition, SDD metabolism was investigated in hepatocytes from castrated male rats treated with testosterone, prior to liver cell isolation. In male rat hepatocytes a significantly higher hydroxylation activity was observed than in hepatocytes from female and castrated male rats. Acetylation activity was higher in females. Testosterone induced hydroxylation but did not affect acetylation. These results correlate well with data from previous in vivo studies, showing the relevance of this in vitro model.  相似文献