Automated crop plant counting from very high-resolution aerial imagery     

Valente  João  Sari  Bilal  Kooistra  Lammert  Kramer  Henk  Mücher  Sander 《Precision Agriculture》2020,21(6):1366-1384

Precision Agriculture - Knowing before harvesting how many plants have emerged and how they are growing is key in optimizing labour and efficient use of resources. Unmanned aerial vehicles (UAV)...  相似文献   

The synergistic effect of combining woodlands and green veining for biodiversity     

Carla J. Grashof-Bokdam  J. Paul Chardon  Claire C. Vos  Ruud P. B. Foppen  Michiel WallisDeVries  Marja van der Veen  Henk A. M. Meeuwsen 《Landscape Ecology》2009,24(8):1105-1121

Combining nature reserves with small semi-natural elements (green veining) may improve the persistence of plant and animal species in fragmented landscapes. A better understanding of this synergy is essential to improve species diversity in the European Natura 2000 sites and in green veining elements. To test this hypothesis, we investigated the relationship between the occurrence of 40 forest plant and animal species in 1,000 km grid cells in the Netherlands and the spatial cohesion of the surrounding large woodlands and small woody elements. Two types of synergy were found. First, nine species were more often present if there was more cohesion of large elements; small elements enhanced this effect. Second, 11 other species were more often present when there was more cohesion of small elements; large elements enhanced this effect. Eight species showed both effects, indicating two-way synergy. The remaining 12 species preferred landscapes dominated by either large or small elements, or displayed no positive relationship whatsoever to woody elements. Species showing synergy often had a low dispersal capacity; the type of synergy seemed to be related to their habitat preference. These results imply that species diversity could be improved by integrating different policy instruments used for nature reserves and green veining. Using a zoning principle where green veins surround and connect nature reserves, the different spatial and habitat preferences of species can be secured. In this way a coherent network could become reality.  相似文献   

Testicular responsiveness to gonadotropic hormonein vitro and Leydig and Sertoli cell ultrastructure during pubertal development of male African catfish (Clarias gariepinus)     

Rüdiger W. Schulz  Karlien Lubberink  Matthijs A. Zandbergen  Coby Janssen-Dommerholt  Jan Peute  Henk J. Th. Goos 《Fish physiology and biochemistry》1996,15(3):243-254

The gonadotropin (GTH)-stimulated testicular androgen secretionin vitro and the ultrastructure of Leydig and Sertoli cells was studied during the pubertal development in male African catfish. Testicular weight increased from less than 1 mg in the ninth week of age to nearly 600 mg in the 28th week. Immature testes (stage I: spermatogonia) were highly sensitive to GTH and secreted very high amounts of androgens per mg of tissue. The secretion per mg tissue decreased gradually in stages II (spermatogonia and spermatocytes) and III (spermatogonia, spermatocytes, and spermatids), but precipitously in stage IV (all germ cell stages, including spermatozoa). However, due to the testicular weight gain, the total androgen output per pair of testes increased slightly in stage III and strongly in stage IV. The sensitivity to GTH decreased with the appearance of haploid germ cells in stage III. Leydig cells but not Sertoli cells showed the ultrastructural characteristics of steroid producing cells. Leydig cell morphology did not change in stages I–III, while in stage IV, more smooth endoplasmic reticulum was present. The ultrastructural characteristics of Sertoli cells did not change prominently. Thus, spermatogonial multiplication and spermatocyte formation takes place when the testicular steroidogenic system is highly active and responsive to GTH; whereas the differentiation of haploid germ cells is accompanied by a reduced responsiveness to GTH and by the secretion of several-fold lower androgen amounts per mg of tissue.  相似文献   

Arabinogalactan proteins are incorporated in negatively charged coffee brew melanoidins     

Bekedam EK  De Laat MP  Schols HA  Van Boekel MA  Smit G 《Journal of agricultural and food chemistry》2007,55(3):761-768

The charge properties of melanoidins in high molecular weight (HMw) coffee brew fractions, isolated by diafiltration and membrane dialysis, were studied. Ion exchange chromatography experiments with the HMw fractions showed that coffee brew melanoidins were negatively charged whereas these molecules did not expose any positive charge at the pH of coffee brew. Fractions with different ionic charges were isolated and subsequently characterized by means of the specific extinction coefficient (K(mix 405nm)), sugar composition, phenolic group content, nitrogen content, and the arabinogalactan protein (AGP) specific Yariv gel-diffusion assay. The isolated fractions were different in composition and AGP was found to be present in one of the HMw fractions. The AGP accounted for 6% of the coffee brew dry matter and had a moderate negative charge, probably caused by the presence of uronic acids. As the fraction that precipitated with Yariv was brown (K(mix 405nm) = 1.2), compared to a white color in the green bean, it was concluded that these AGPs had undergone Maillard reaction resulting in an AGP-melanoidin complex. The presence of mannose (presumably from galactomannan) indicates the incorporation of galactomannans in the AGP-melanoidin complex. As the uronic acid content in the more negatively charged melanoidin-rich, AGP-poor HMw fractions decreased, it was hypothesized that acidic groups are formed or incorporated during melanoidin formation.  相似文献   

Screaming like a......     

Boissevain I  Vrieselaar H 《Tijdschrift voor diergeneeskunde》2006,131(24):925

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The genus phytophthora anno 2012     

Kroon LP  Brouwer H  de Cock AW  Govers F 《Phytopathology》2012,102(4):348-364

Plant diseases caused by Phytophthora species will remain an ever increasing threat to agriculture and natural ecosystems. Phytophthora literally means plant destroyer, a name coined in the 19th century by Anton de Bary when he investigated the potato disease that set the stage for the Great Irish Famine. Phytophthora infestans, the causal agent of potato late blight, was the first species in a genus that at present has over 100 recognized members. In the last decade, the number of recognized Phytophthora species has nearly doubled and new species are added almost on a monthly basis. Here we present an overview of the 10 clades that are currently distinguished within the genus Phytophthora with special emphasis on new species that have been described since 1996 when Erwin and Ribeiro published the valuable monograph 'Phytophthora diseases worldwide' (35).  相似文献   

ParaCalc®--a novel tool to evaluate the economic importance of worm infections on the dairy farm     

Charlier J  Van der Voort M  Hogeveen H  Vercruysse J 《Veterinary parasitology》2012,184(2-4):204-211

Subclinical infections with gastrointestinal nematodes and liver fluke are important causes of production losses in grazing cattle. Although there is an extensive compilation of literature describing the effect of these infections on animal performance, only a few attempts have been made to convert these production losses to an economic cost. Here, we propose a novel tool (ParaCalc(?)), available as a web-application, to provide herd-specific estimates of the costs of these infections on dairy farms. ParaCalc(?) is a deterministic spread-sheet model where results from diagnostic methods to monitor the helminth infection status on a herd and anthelmintic usage are used as input parameters. Default values are provided to describe the effects of the infections on production and the cost of these production losses, but the latter can be adapted to improve the herd-specificity of the cost estimate. After development, ParaCalc(?) was applied on input parameters that were available for 93 Belgian dairy herds. In addition, the tool was provided to 6 veterinarians and their user experiences were evaluated. The estimated median [25th-75th percentile] cost per year per cow was € 46 [29-58] and € 6 [0-19] for gastrointestinal nematode and liver fluke infection, respectively. For both infections, the major components in the total costs were those associated with milk production losses in the adult cows. The veterinarians evaluated ParaCalc(?) as a useful tool to raise the farmers' awareness on the costs of worm infections, providing added value for their services. However, the score given for user-friendliness was diverse among users. Although the model behind ParaCalc(?) is a strong simplification of the real herd processes inducing economic losses, the tool may be used in the future to support economic decisions on helminth control.  相似文献   

Actinobacillus pleuropneumoniae is impaired by the garlic volatile allyl methyl sulfide (AMS) in vitro and in-feed garlic alleviates pleuropneumonia in a pig model     

Becker PM  van Wikselaar PG  Mul MF  Pol A  Engel B  Wijdenes JW  van der Peet-Schwering CM  Wisselink HJ  Stockhofe-Zurwieden N 《Veterinary microbiology》2012,154(3-4):316-324

Decomposition products of ingested garlic are to a certain extent excreted via the lungs. If the supposed health-supporting capacities associated with garlic extend to these exhaled sulfurous compounds, they could have an effect on the course of pneumonia. In this study, the garlic-derived volatile allyl methyl sulfide (AMS) as a lead compound of volatile garlic metabolites was shown to exhibit an antibacterial effect against the pig pathogen Actinobacillus pleuropneumoniae serotype 9. AMS caused a delay in the appearance of the optical density-monitored growth of A. pleuropneumoniae in medium when compared to unaffected growth curves, yet without lowering the stationary phase yield at the concentration range tested. At 1.1mM, AMS impaired the in vitro growth rate of A. pleuropneumoniae serotype 9 by 8% compared to unimpeded growth. In an animal trial, a garlic-fed group of 15 pigs that received a diet with 5% garlic feed component and a control group of 15 pigs that received a diet without garlic were infected with A. pleuropneumoniae serotype 2 via an aerosol and subsequently followed for 4 days. At the day of the challenge, blood AMS in the garlic-fed group amounted to 0.32 ± 0.13 μM. A beneficial, alleviating effect of garlic on the course and severity of an A. pleuropneumoniae infection in pigs was indicated by the reduced occurrence of characteristic pleuropneumonia lesions (27% of the lungs affected in the garlic-fed group vs. 47% in the control group) and a near to significant (p=0.06) lower relative lung weight post mortem in the garlic-fed group.  相似文献   

A functional dosage compensation complex required for male killing in Drosophila     

Veneti Z  Bentley JK  Koana T  Braig HR  Hurst GD 《Science (New York, N.Y.)》2005,307(5714):1461-1463

Bacteria that selectively kill males ("male-killers") were first characterized more than 50 years ago in Drosophila and have proved to be common in insects. However, the mechanism by which sex specificity of virulence is achieved has remained unknown. We tested the ability of Spiroplasma poulsonii to kill Drosophila melanogaster males carrying mutations in genes that encode the dosage compensation complex. The bacterium failed to kill males lacking any of the five protein components of the complex.  相似文献   

Elucidation of pectin methylester distributions by capillary electrophoresis     

Williams MA  Foster TJ  Schols HA 《Journal of agricultural and food chemistry》2003,51(7):1777-1781

Evidence is presented that the electrophoretic mobility of the polysaccharide pectin in typical capillary electrophoresis (CE) experiments is determined largely by its chain-averaged charge density, irrespective of how that charge is distributed. This was found to be the case for both high and low calcium sensitive sister fractions separated from a mother sample on the grounds of calcium affinity and for blocky methylester distributions generated by a processive demethylating enzyme. The blockiness of the generated intramolecular methylester distribution was substantiated experimentally, also by CE, by observing the oligomeric digest fragments produced by incubation with endo-polygalacturonase II from Aspergillus niger. The conclusion that the CE migration time is largely invariant to the intramolecular methylester distribution supports the idea that the CE peak shapes can be used to give a useful indication of the intermolecular methylester distribution.  相似文献