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141.
F.?Rodriguez-MorenoEmail author J.?Kren F.?Zemek J.?Novak V.?Lukas M.?Pikl 《Precision Agriculture》2017,18(4):615-634
Nowadays it is known how to resolve many questions through satellite imagery such as Landsat 8 and the like, both from the theoretical point of view, i.e. research, as well as from the practical standpoint, e.g. commercial applications. This study evaluated the possibility of generalizing the training for supervised classification of multispectral images with sub-centimeter resolution. Images were taken under uncontrolled conditions of lighting and sun-target-sensor geometry and in the presence of normal interference in the agricultural environment. The images were obtained by the DuncanTech MS3100 camera (Auburn, CA, USA), a multispectral camera (green, red and near infra-red) mounted on a mobile ground platform and transformed into reflectance. For each element present (leaves, stems, spikes, soil, shadows, spectral references and sampling implements), a representative area was delimited in each image. These regions of interest were used, first, to quantify the separability of the classes. The next step was to define groups for cross-validation within these regions of interest; ten-folds were defined randomly with the constraint of a uniform distribution of classes. These folds were used in training and evaluation of the supervised classification using spectral angle mapper, maximum likelihood and decision trees. Spectral angle mapper correctly classified 49.2 % of cases, the maximum likelihood achieved a success rate of 86.8 % and the decision tree correctly classified 99.5 % of the spectral signatures. These results prove that multispectral images taken under uncontrolled conditions can be successfully classified by a generalized model that takes advantage of the higher spatial resolution. This opens a new line in which those pixels that do not correspond to vegetation, which bias the estimates of the crop parameters and complicate the recognition of objects, could be automatically masked. 相似文献
142.
Effects of short-term thermomechanical densification on the structure and properties of wood veneers
Pavlo Bekhta Stanisław Proszyk Tomasz Krystofiak Jan Sedliacik Igor Novak Miroslava Mamonova 《Wood material science & engineering》2017,12(1):40-54
The effects of short-term thermomechanical (STTM) densification temperature and pressure on the changes in surface roughness, wettability, mass loss (ML), thickness and density of alder, beech, birch, and pine wood veneer with low moisture content (~5%) were investigated. The anatomical structure of veneers was also observed. Veneer sheets were densified using pressure levels of 4, 8 and 12 MPa at three temperatures: 100°C, 150°C and 200°C for 4 min. The results were compared with those of the non-densified veneers. The obtained results show that STTM densification of veneers similarly to long-term densification of solid wood causes irreversible changes in their properties. The STTM-densified veneer surfaces became smoother and more hydrophobic, ML increased slightly while roughness and thickness values decreased significantly, the cell lumens collapsed and a certain amount of fractures in cell walls developed with increasing densification temperature and pressure. All of the investigated wood species showed higher density values after densification. It was found that an even STTM densification of veneers provides stable properties under normal atmosphere conditions; in particular, the thickness and contact angle values were stable for 24 hours after densification, which is an important consideration for industrial applications. 相似文献
143.
Successful vaccination of sheep against footrot and attempts to eradicate the disease depend on there being a limit to the antigenic diversity of the causative bacterium, Bacteroides nodosus. Fimbrial antigenic variation was therefore investigated in vivo, both under conditions of chronic infection and under the pressure of a vaccine-induced immune response, to ascertain whether this represented an obstacle to such goals. Material was available from 5 experiments and although B. nodosus appeared to have undergone changes in its fimbrial antigens in one of these, the possibility that superinfection was responsible for the variation detected could not be ruled out because all sheep in this case were maintained at pasture. Overall, the results provided no evidence of fimbrial antigenic shift in B. nodosus in vivo and in conclusion, the survival of the organism in the sheep's foot, both in long-term natural infection and following vaccination, must therefore be related to factors other than the ability to undergo antigenic variation in order to evade the host's immune response. 相似文献
144.
145.
The objectives of the present study were 1) to study potential effects of previous nutritional treatment on developmental competence of early fertilized oocytes in vitro; 2) to study responses to insulin treatment during the period of feed restriction in the late luteal phase which has deleterious effects on subsequent fertility; and 3) to establish the metabolic and endocrine status of gilts during treatment and the subsequent periestrous period. Nineteen trios of littermate gilts were subjected to feed restriction during the first (RH) or second (HR) week of the estrous cycle. A second group of HR gilts received injections of long-acting insulin during their period of feed restriction (HR+I). Intensive sampling was performed in a subgroup of 23 animals on d 15 and 16 of the cycle for analyses of endocrine (gonadotropins and steroid hormones) and metabolic (insulin, IGF-I, leptin, total triiodothyronine [T3], and free T3) variables. Gilts were checked for estrus every 6 h, and time of ovulation was monitored by transcutaneous ultrasonography. Surgeries were performed 12 to 20 h after ovulation, and the early-fertilized oocytes recovered were cultured in vitro under standardized conditions. There was no treatment effect on the developmental competence of fertilized oocytes in vitro; however, ovulation rate was increased in HR+I gilts. No effect of treatment was observed on plasma leptin and IGF-I concentrations on d 15 and 16. However, HR+I gilts had higher (P < 0.05) postprandial insulin and lower (P < 0.05) postprandial total and free T3 on d 15. Plasma concentrations of LH, FSH, and progesterone on d 15 and 16 and plasma estradiol concentrations on d 16 were not affected by previous nutritional or insulin treatment. In the periestrous period, plasma concentrations of LH, FSH, and estradiol were higher (P < 0.05) in RH and HR+I, and the rise in plasma progesterone after the LH surge was lower (P < 0.05), than in HR gilts. No effect of treatment was observed on plasma concentrations of metabolic hormones, except on plasma leptin concentrations, which were higher (P < 0.05) at the time of the LH surge in RH gilts. These results suggest that feed restriction during the late luteal phase may have deleterious effects on ovarian function in the periestrous period, which may be counteracted by insulin. 相似文献
146.
Metka Novak Andreja Urbanek Krajnc Ljerka Lah Neja Zupanec Nada Kraševec Mitja Križman Joerg Bohlmann Radovan Komel 《European Journal of Forest Research》2014,133(4):573-583
Among the most devastating pests of Norway spruce (Picea abies) are the European spruce bark beetle (Ips typographus) and the associated pathogenic blue-stain fungus Ceratocystis polonica. Following attack and colonization, the beetle and the fungus must cope with induced host chemical defenses, such as monoterpenes that are generally thought to be toxic to both symbionts. The goal of this study was to better understand the response of Norway spruce following C. polonica inoculation at low density that does not overwhelm the tree and to identify monoterpenes mobilized toward the fungus. We inoculated healthy mature trees and monitored monoterpene profiles 2, 3, and 5 months post-inoculation. We also exposed three different C. polonica strains to the most abundant or significantly up-regulated monoterpenes to determine differences in monoterpene toxicity and resistance among strains. Total monoterpene levels, including limonene, were increased at 2 and 3 months after inoculation and had dropped after 5 months. In in vitro assays, all monoterpenes were inhibitory to C. polonica. Limonene and β-pinene were the most potent inhibitors of fungal growth. The extent of inhibition varied between the three strains tested. These results showed a defense response of Norway spruce to C. polonica, in which limonene may play a critical role in inhibiting the spread of the fungus. We also showed that differences between strains of C. polonica must be taken into account when assessing the role of the fungus in this bark beetle–symbiont system. 相似文献
147.
148.
Mumma MJ Dello Russo N DiSanti MA Magee-Sauer K Novak RE Brittain S Rettig T McLean IS Reuter DC Xu LH 《Science (New York, N.Y.)》2001,292(5520):1334-1339
In the current paradigm, Oort cloud comets formed in the giant planets' region of the solar nebula, where temperatures and other conditions varied greatly. The measured compositions of four such comets (Halley, Hyakutake, Hale-Bopp, and Lee) are consistent with formation from interstellar ices in the cold nebular region beyond Uranus. The composition of comet C/1999 S4 (LINEAR) differs greatly, which suggests that its ices condensed from processed nebular gas, probably in the Jupiter-Saturn region. Its unusual organic composition may require reevaluation of the prebiotic organic material delivered to the young Earth by comets. 相似文献