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Literatura académica sobre el tema "Effect of light on weeds"

Autor: Grafiati

Publicado: 4 de junio de 2021

Última modificación: 21 de febrero de 2023

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Artículos de revistas sobre el tema "Effect of light on weeds"

Maynard, Elizabeth T. "Effect of Light during Cultivation on Weed Emergence". HortScience 32, n.º 3 (junio de 1997): 428F—429. http://dx.doi.org/10.21273/hortsci.32.3.428f.

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This experiment was conducted to determine whether light conditions during cultivation affect the number or species composition of emerging weeds. Plots were cultivated on 31 May 1996 under the following light conditions: 1) Ambient nighttime light (full moon) plus tractor headlights, 2) ambient nighttime light plus tractor headlights covered by transparent green film (green tractor lights), 3) ambient nighttime light with no tractor headlights, 4) ambient mid-day light. A fifth treatment was not cultivated at all, but was treated with glyphosate on 31 May to kill emerged plants. Results discussed below are based on weed densities determined 3 weeks after cultivation. Cultivated plots had more broadleaf weeds than uncultivated plots (119/m2 vs. 40/m2). Annual grass populations were the same in cultivated and uncultivated plots (20/m2). Common lambsquarters (Chenopodium album) and carpetweed (Mollugo verticillata) were the most common annual broadleaf weeds, representing more than 80% of the annual broadleaf population in cultivated plots. Light conditions during cultivation did not influence the total number of broadleaves, number of annual grasses, or total number of weeds emerging. Lambsquarters emerged in greater numbers after daytime or night cultivation using green tractor lights (48/m2) than after night cultivation using standard tractor headlights (32/m2). These results suggest no practical benefit to night cultivation for reducing overall weed density. A similar study in 1995 led to a similar conclusion. Although measurable effects of light conditions on weed emergence were observed in both years, the magnitude and consistency of the effects were not enough to suggest changes in cultivation practices without further research.

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Yasin, Muhammad, Eva Rosenqvist y Christian Andreasen. "The Effect of Reduced Light Intensity on Grass Weeds". Weed Science 65, n.º 5 (14 de agosto de 2017): 603–13. http://dx.doi.org/10.1017/wsc.2017.17.

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The effect of reduced light intensity on the growth and development of three common grass weeds, blackgrass, silky windgrass, and annual bluegrass, was studied. Two identical greenhouse experiments displaced in time were performed with six light levels aiming at 0%, 20%, 50%, 80%, 90%, and 95% shade corresponding to a mean daily light integral (DLI) of 12.4, 9.63, 7.13, 2.74, 0.95, and 0.69 mol m−2d−1in experiment 1 and 21.2, 18.0, 10.7, 3.71, 1.64, 1.20 mol m−2d−1in experiment 2. Climate screens of acrylic fabric were used to create the light levels. A DLI of 0.69 to 3.71 mol m−2d−1substantially reduced the plant height, the number of leaves, leaf chlorophyll content index, stomatal conductance, maximum photochemical efficiency of photosystem II, and dry matter of blackgrass. It also reduced plant height, the number of leaves, and dry matter and delayed flowering of windgrass and annual bluegrass. Annual bluegrass reacted most rapidly when light levels increased from the lowest levels by producing more leaves. DLI thresholds for blooming were estimated to be about 7.13 mol m−2d−1for windgrass and 1.64 mol m−2d−1for annual bluegrass. Annual bluegrass was able to bloom and sustain biomass even at a DLI of 1.64 mol m−2d−1. This ability may contribute to an explanation of why annual bluegrass is among the most common weed species in highly competitive and well-fertilized crops even though it is much smaller than the two other grass species.

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MONDANI, Farzad, Farid GOLZARDI, Godarz AHMADVAND, Reza GHORBANI y Rooholla MORADI. "Influence of Weed Competition on Potato Growth, Production and Radiation Use Efficiency". Notulae Scientia Biologicae 3, n.º 3 (25 de agosto de 2011): 42–52. http://dx.doi.org/10.15835/nsb336125.

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Weed management in potato production is one of the main cost and time consuming practices. Understanding the most effective time of weed control could reduce the costs and increase potato yield. Field study was conducted in the west region of Iran during 2006 to evaluate the effect of weeds damage in potato fields. Twelve treatments used consisted of six initial weed-free periods in which plots were kept free of weeds for 0, 10, 20, 30, 40 and 50 days after crop emergence (DAE), and then weeds were allowed to grow until harvest, and six initial weed-infested periods in which, weeds were allowed to grow for 0, 10, 20, 30, 40 and 50 DAE, then the plots were kept free of weeds until harvest. Experiment was arranged as a randomized complete block design with three replications. The results showed effect of weed competition on crop dry matter started about 40 DAE and about 90 DAE reached its maximum. The weeds competition decreased dry matter accumulation, leaf area index, crop growth rate, leaf area index duration, light absorption, light extinction coefficient and radiation use efficiency (RUE) of potato. Weeds reduced the potato yield 54.8 percent. The beginning and the end of the critical period of weed control in potato (CPWC) was based on 5% and 10% tuber yield loss. The onset of the CPWC ranged from 486 to 572 GDD, at 5% and 10% yield loss level corresponding to 11 and 19 days after crop emergence, respectively. The end of the CPWC varied from 1372 to 1164 GDD, at 5% and 10% yield loss level corresponding to 65 and 51 days after crop emergence, respectively. RUE in the weed infestation treatment in comparison to the weed free treatment, reduced 11.8 percent.

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Nordby, Dawn E., Dustin L. Alderks y Emerson D. Nafziger. "Competitiveness with Weeds of Soybean Cultivars with Different Maturity and Canopy Width Characteristics". Weed Technology 21, n.º 4 (diciembre de 2007): 1082–88. http://dx.doi.org/10.1614/wt-06-190.1.

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Field studies were conducted in 2005 at five locations throughout Illinois to determine the effect of maturity date and canopy width characteristics of selected glyphosate-resistant soybean cultivars on competitive ability against weeds. Natural weed populations at all sites were allowed to compete with the soybean cultivars until the V1, V3, V5, or V7 growth stage and then removed with an application of glyphosate. Light-interception readings, weed control ratings, and soybean yield were all measured to compare cultivars. Cultivars of later maturities tended to withstand early season weed competition better and attained higher yields when weeds were removed at later timings than those of earlier maturity. Although canopy width differed moderately among cultivars in some cases, canopy width had no effect on the ability of soybeans to compete with weeds. Thus, choosing soybean cultivars of later maturity might provide more flexibility in weed management and might reduce losses due to weeds, but that benefit needs to be balanced with yield potential.

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Lotz, L. A. P., M. J. Kropff y M. W. Groeneveld. "Modelling weed competition and yield losses to study the effect of omission of herbicides in winter wheat." Netherlands Journal of Agricultural Science 38, n.º 4 (1 de diciembre de 1990): 711–18. http://dx.doi.org/10.18174/njas.v38i4.16559.

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Omission of application of various herbicides to winter wheat cv. Arminda, cv. Citadel, cv. Okapi, cv. Granada, cv. Sarino and cv. Tombola on clay and sandy soil in 1982-86 caused a significantly lower crop yield only when the densities of certain weed species were extremely high in spring. A dynamic model simulating the competition for light and water between broadleaved weeds and winter wheat was used to assess the observed small effects of weeds on yield in terms of the relative emergence time, physiological and morphological characteristics of weeds. Like the experiments, the simulations indicated that in the Netherlands weeds emerging in spring hardly affect crop yield. Weeds emerging in autumn, however, reduced crop yield considerably if they grew as tall as winter wheat (20% loss at a density of 100 plants/msuperscript 2). The results are discussed in relation to characteristics of crop rotation systems that include root and tuber crops. (Abstract retrieved from CAB Abstracts by CABI’s permission)

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Gallagher, Robert S. y John Cardina. "The effect of light environment during tillage on the recruitment of various summer annuals". Weed Science 46, n.º 2 (abril de 1998): 214–16. http://dx.doi.org/10.1017/s0043174500090445.

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Weed seeds can require an exposure to light for induction of germination. Conducting tillage operations at night and thus preventing the photoinduction of germination has been proposed as a means to reduce weed emergence in agricultural systems. This research was conducted to evaluate night tillage as a weed management option and to determine which tillage operations have the greatest effect on light-mediated recruitment. Weed emergence was evaluated after conducting factorial combinations of day and night moldboard plowing and disking in the springtime from 1992 through 1995. The light environment during disking generally had a slightly greater effect on emergence than the light environment during plowing. Emergence of pigweed species and giant foxtail was, at most, 30 to 55% higher following day vs. night disking. Emergence of other weeds was not affected by the light environment during tillage. We conclude that night tillage may not be a viable approach to weed management due to insufficient reductions in weed emergence associated with night tillage and the high degree of variability in the recruitment response to light conditions during tillage.

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Buhler, Douglas D. "Effects of Tillage and Light Environment on Emergence of 13 Annual Weeds". Weed Technology 11, n.º 3 (septiembre de 1997): 496–501. http://dx.doi.org/10.1017/s0890037x00045310.

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Seeds of many plant species require a brief exposure to light to induce germination. Modifying the light environment during soil tillage may alter weed emergence in agricultural systems. The objective of this research was to evaluate the effect of secondary tillage conducted during daylight and at night on the emergence of 13 summer annual weed species under the same soil and environmental conditions. Annual grass and large-seeded broadleaf species showed little response to light environment during tillage. However, emergence was often less when no tillage was conducted than with any tillage by light environment combination. Emergence of small-seeded broadleaf species often was lower when tillage was conducted during darkness than with tillage during the light. Reductions varied by experiment and species and ranged from 70% for common lambsquarters to less than 30% for Pennsylvania smartweed. Large variations in response also occurred within species.

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Chen, Zhengqiang y Zhaomin Ma. "A Review: The Survey of the Effects of Light on Weed Recognition". MATEC Web of Conferences 228 (2018): 04008. http://dx.doi.org/10.1051/matecconf/201822804008.

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Weeding is one of the important tasks in agricultural field management. With the development of society and information technology, automatic weeding has become a developing trend. The automatic recognition of weeds based visual is the important step. In this paper, the effects of lighting on green identification and weed identification algorithms are summarized. In order to improve the accuracy and stability of the identification of crops and weeds, some further worth problems in the study are also put forward. This will help further research on automatic weeding.

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Everaarts, A. P. "Effects of competition with weeds on growth, development and yield of soyabeans." Netherlands Journal of Agricultural Science 40, n.º 1 (1 de marzo de 1992): 91–107. http://dx.doi.org/10.18174/njas.v40i1.16531.

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Two field experiments were carried out in the inland Zanderij area of Suriname to study competition between soyabeans and weeds. The crop was kept weed-free or without weed control for increasing periods of time after sowing. An analysis of the growth and development of a crop with weed control and of a crop without weed control was obtained by making observations at the end of each period of time with or without weed control. Uncontrolled weed growth concentrated mainly between the rows. Competition with weeds reduced ground cover and LAI of the crop, leading to a lower weight and yield. Plant density was not affected, but weed competition reduced the number of branches, inflorescences, and pods per plant. Timing of flowering was not influenced. Competition for water was inferred and competition for light seemed likely. Competition for nutrients was weak. Weeding in the period of pod initiation, i.e. around 45-70 days after sowing, appeared to be essential to avoid competition with weeds. A period of around 4 weed-free weeks after sowing was necessary to avoid yield reduction or too much weed growth at harvest. (Abstract retrieved from CAB Abstracts by CABI’s permission)

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Johnson, Mark S. y Steven A. Fennimore. "Weed and Crop Response to Colored Plastic Mulches in Strawberry Production". HortScience 40, n.º 5 (agosto de 2005): 1371–75. http://dx.doi.org/10.21273/hortsci.40.5.1371.

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The phase out of methyl bromide has forced strawberry (Fragaria ×ananassa Duchesne) growers to consider the use of cultural methods such as colored mulches to enhance weed control. Black plastic mulch controls most weeds; however, black mulch often does not warm the soil as well as clear mulch. Soil warming with clear mulch is desirable for early season markets, but clear mulch does not control weeds. Neither black nor clear mulches combine the ideal weed control and soil warming characteristics required. Seven colored mulches, as well as clear, black and no mulch were evaluated in California organic and conventional strawberries to identify mulch factors associated with weed control and soil warming. Laboratory and greenhouse experiments were also conducted to isolate the effects of light transmittance through mulch on weed germination and growth. The effect of mulch color on transmittance of photosynthetically active light (400 to 700 nm) through mulches was the key weed control factor, and was more important than the effect of mulch color effect on weed germination. Satisfactory weed control was provided by all mulches except clear, blue and red-brown laminated. Clear and black mulches provided the greatest soil warming in sunny and cloudy climatic conditions, respectively, although plants in clear mulched conventional production system plots produced the highest yield of marketable berries. Green and brown plastic mulches provided the best combinations of soil warming and weed control benefits at all trial locations.

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Tesis sobre el tema "Effect of light on weeds"

Omami, Elizabeth Nabwile, of Western Sydney Hawkesbury University, of Agriculture Horticulture and Social Ecology Faculty y School of Horticulture. "Amaranthus retroflexus seed dormancy and germination responses to environmental factors and chemical stimulants". THESIS_FAHSE_HOR_Omami_E.xml, 1993. http://handle.uws.edu.au:8081/1959.7/66.

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A large number of weed seeds in the soil persist because of seed dormancy, and depletion of the seed bank through manipulation of seed dormancy has been suggested as one of the goals in weed control. This study was designed to investigate some of the factors which control dormancy and germination in Amaranthus retroflexus seeds. Germination studies were conducted at different temperatures, and either in continuous white light or in the dark. Higher temperatures increased germination and, although light interacted with temperature, its effect on germination varied with the temperature. In an attempt to determine changes in dormancy during dry storage, two lots of seeds were stored dry at different temperatures. Loss in dormancy increased with an increase in storage temperature and duration, but the time required for maximum germination varied according to the seedlot. Seeds germinated to higher percentages at high temperatures, but storage at higher temperatures and for prolonged duration resulted in seeds gaining the ability to germinate at lower temperatures. Changes in dormancy under field conditions were also examined. Seeds were buried at different depths and for different durations and they all lost viability with time, but this loss was greater in surface-sown and shallowly buried seeds. Dormancy was broken during cold periods and induced as warmer periods progressed. The effects of chemical stimulants on dormancy and germination were investigated. The response of seeds to ethephon and nitrate were assessed at different temperatures either at continuous white light or in the dark. Germination increased with the concentration of the chemicals, and a greater response was observed at lower temperatures. The response to light varied depending on temperature
Master of Science (Hons)

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Omami, Elizabeth Nabwile. "Amaranthus retroflexus seed dormancy and germination responses to environmental factors and chemical stimulants". Thesis, [S.l. : s.n.], 1993. http://handle.uws.edu.au:8081/1959.7/66.

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Bigley, Richard Ernest. "Ecological physiology of conifer seedling and sapling suppression by, and release from, competing vegetation". Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28625.

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The overall objective of this thesis was to improve our understanding of the light environment associated with two of the major deciduous competitors of commercial conifer seedlings in low elevation coastal British Columbia, and the physiological response of young conifers to specific environments and changes in the environment. Studies were conducted to investigate: 1) seasonal and herbicide-induced changes in the light regimes beneath the canopies of two brush species, 2) growth and physiology of seedlings of three conifer species in several different deciduous brush environments throughout the year, and 3) changes in the physiology and growth of suppressed conifer saplings when different methods and schedules were used to reduce shading from an overtopping red alder canopy. Seasonal changes in the light quantity and quality were documented within salmonberry (Rubus spectabilis Pursch) and below red alder (Alnus rubra Bong.) canopies. The prediction of light attenuation within salmonberry canopies using the Beer-Lambert law was good for foliated canopies using leaf area index, and defoliated canopies using stem area index. As salmonberry leaf area increased, the ratio of red to far-red light declined exponentially. Growth of grand fir (Abies qrandis (Dougl.) Forbes), western hemlock (Tsuga heterophylla (Raf.) Sarg.) and Douglas-fir (Pseudetsuga menziesii (Mirbel) Franco) seedlings decreased with increases in the canopy density of overtopping deciduous species. Physiological differences between conifer species and differences between overtopping canopy treatments declined in the autumn and winter. Based on the physiological measurements, suppression of the shade intolerant Douglas-fir seedlings was greatly reduced during the period that overtopping deciduous canopies were leafless. Animal damage reduces growth and probably increases the duration seedlings are under overtopping canopies. Suppressed Douglas-fir saplings released from overtopping by red alder canopies showed the greatest growth response when the alder canopies were removed in the spring; complete removal of the alder canopy during the summer had a predictably deleterious effect on the sapling physiology and growth. Herbicide injections resulted in a slower but predictable increase in conifer growth.
Forestry, Faculty of
Graduate

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Ma, Li. "Ecophysiology of the effect of red to far-red light ratio on selected weed and crop species". Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/63174.

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Plants growing in canopies are exposed to reduced light intensity as well as low red/far-red light ratios, a signal of impending competition. In order to advance our understanding of the eco-physiological role of red/far-red ratio in agroecosystems, growth chamber and greenhouse studies were conducted to investigate 1. the growth and morphological responses of common lamb’s-quarters (Chenopodium album L.), redroot pigweed (Amaranthus retroflexus L.) and tomato (Solanum lycopersicum L.) to different red/far-red ratios, 2. how leaf optical properties at red (660 nm) and far-red (730 nm) wavelengths change with leaf position and plant development, and 3. if red/far-red ratio influences response of corn (Zea mays L.), lettuce (Lactuca sativa L.), and pigweed plants to UV-B radiation. Three red/far-red ratios were achieved by using supplemental far-red lamps in growth chambers, while maintaining the photosynthetically active radiation. Results showed that red/far-red ratio treatment influenced several growth and allometric parameters and tomato, lamb’s-quarters, and pigweed differed in this regard. This differential response among species suggests that fluctuations in the red/far-red ratio in canopies could impact inter-plant interactions among these species. Red/far-red ratio in a plant canopy is affected by leaf optical properties. A study of leaf optical properties of lamb’s-quarters, pigweed and tomato using a CI-710 Miniature Leaf Spectrometer showed that leaf optical properties changed with leaf position and plant development, which could modify the light environment in canopies comprising populations of these species. Interestingly, these species differed in this regard, suggesting differences in their ability to signal potential competition. Leaf optical properties, as well as leaf position and plant development effects, therefore, should be taken into consideration in assessing the eco-physiological functions of a vegetation cover. Effect of pre-exposure to low red/far-red ratio on plant susceptibility to UV-B radiation could impact plant interaction. However, my research showed that red/far-red ratio pre-treatment and the associated change in anthocyanin concentration did not alter the response of corn, lettuce and pigweed seedlings to enhanced UV-B radiation. This improves our understanding of the eco-physiological role of these environmental stressors in agro-ecosystems, where both red/far-red ratio and UV-B levels fluctuate.
Land and Food Systems, Faculty of
Graduate

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Röhrig, Manfred. "Modelling the light competition between crops and weeds". [S.l. : s.n.], 1999. http://deposit.ddb.de/cgi-bin/dokserv?idn=956719619.

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Umeda, Kai. "Effect of Halosulfuron on Rotational Crops". College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2002. http://hdl.handle.net/10150/214957.

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A field test was conducted to evaluate and determine the safety of halosulfuron on typical rotational crops such as lettuce, broccoli, spinach, onion, alfalfa, barley, field corn, and melons after an initial application on cantaloupes. Halosulfuron at 0.05 or 0.1 lb AI/A applied on cantaloupes did not detrimentally affect crop stand establishment, height, or whole plant fresh weights when alfalfa, barley, spinach, lettuce, onion, and broccoli were planted at approximately 4 to 5 MAT. Cantaloupes and field corn planted at 1 YAT were not affected in establishing a stand and in growing during the early season as height or vine lengths were measured. At 15 to 16 MAT, lettuce, onion, and broccoli were not affected in establishing a stand. Watermelon planted at 1 YAT exhibited slight stand reduction and crop injury with halosulfuron applied PREE. Alfalfa planted after PREE applications indicated slightly depressed height and yield compared to POST treatments and the untreated check. Spinach planted where POST applications were made on cantaloupes tended to show a slight reduction in fresh weight at 15 to 16 MAT. Halosulfuron does not appear to be a major deterrent to typical crop rotational schemes in the diverse desert agricultural systems.

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Umeda, K. y N. Lund. "Effect of Prowl and Prefar Herbicides on Onions". College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001. http://hdl.handle.net/10150/214935.

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Significant onion height reduction was observed when Prowl (pendimethalin) and Prefar (bensulide) herbicide combinations were applied preemergence (PREE). The onions resumed growth but the height was still slightly reduced later in the growing season compared to the handweeded check and the standard herbicide treatment, Dacthal (DCPA). The onion crop stand emerged initially but later in the season, a significant crop stand reduction was observed for the higher rate of Prowl at 0.5 lb AI/A plus Prefar. A lower rate of Prowl at 0.25 lb AI/A plus Prefar also caused a reduction of the onion stand compared to the handweeded check or Dacthal.

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Fillmore, Andrew Nathan. "Droplet Size Effect on Herbicide Used in Cereals to Control Dicotyledonous Weeds". Thesis, North Dakota State University, 2014. https://hdl.handle.net/10365/27419.

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Experiments were conducted to evaluate the effect of droplet size on the efficacy of translocated and non-translocated herbicides. Translocated and non-translocated herbicides provided similar control when comparing droplet size effect on efficacy. Medium and very coarse droplet sizes gave the greatest visible injury whereas coarse-sized gave the lowest visible injury assessments for most species. However, droplet size generally did not affect contact herbicide efficacy. Overall, droplet size was not a strong factor contributing to herbicide efficacy and often, differences were only between herbicides. Non-ionic surfactant solutions measured by a Sympatec droplet analysis system gave the highest percent of volume in droplets <150?m compared to other adjuvants. The lowest percent of volume in droplets <150?m was a 0.5x rate. A liquid herbicide formulation gave the largest percent of volume in droplets <150?m whereas an emulsifiable concentrate formulation was lowest. Percent volume in droplets <150?m was often related to the solution VMD.

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Harati, Ebrahim. "Fatigue strength of welds in 800 MPa yield strength steels : Effects of weld toe geometry and residual stress". Licentiate thesis, Högskolan Väst, Avd för tillverkningsprocesser, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-8009.

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Nowadays there is a strong demand for lighter vehicles in order to increase the pay load. Through this the specific fuel consumption is decreased, the amount of greenhouse gases is lowered and the transport economy improved. One possibility to optimize the weight is to make the components from high strength steels and join them by welding. Welding is the main joining method for fabrication of a large proportion of all engineering structures. Many components experience fatigue loading during all or part of their life time and welded connections are often the prime location of fatigue failure.Fatigue fracture in welded structures often initiates at the weld toe as aconsequence of large residual stresses and changes in geometry acting as stress concentrators. The objective of this research is to increase the understanding of the factors that control fatigue life in welded components made from very high strength steels with a yield strength of more than 800 MPa. In particular the influences of the local weld toe geometry (weld toe radius and angle) and residual stress on fatigue life have been studied. Residual stresses have been varied by welding with conventional as well as Low Transformation Temperature (LTT) filler materials. The three non-destructive techniques Weld Impression Analysis (WIA), Laser Scanning Profiling (LSP) and Structured Light Projection (SLP) have been applied to evaluate the weld toe geometry.Results suggest that all three methods could be used successfully to measure the weld toe radius and angle, but the obtained data are dependent on the evaluation procedure. WIA seems to be a suitable and economical choice when the aim is just finding the radius. However, SLP is a good method to fast obtain a threedimensional image of the weld profile, which also makes it more suitable for quality control in production. It was also found that the use of LTTconsumables increased fatigue life and that residual stress has a relatively larger influence than the weld toe geometry on fatigue strength of welded parts.

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Hewitt, Cade Alan. "Effect of row spacing and seeding rate on grain sorghum tolerance of weeds". Thesis, Kansas State University, 2015. http://hdl.handle.net/2097/19784.

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Master of Science
Department of Agronomy
J. A. Dille
Weed control in grain sorghum has always presented a challenge to producers in the semi-arid Great Plains. Cultural control tactics such as narrowing of row spacings and increasing seeding rates can be effective control methods. The objective of this research was to determine the row spacing and seeding rates that maximizes yield while suppressing weeds. Grain sorghum row spacings of 25, 51, and 76-cm and seeding rates of 75,000, 100,000, 125,000, and 150,000 seeds ha[superscript]-1 were evaluated in Kansas at Beloit and Manhattan in 2013 and Beloit, Manhattan, and Hays in 2014. Grain sorghum growth and yield response were measured in response to natural weed communities. After evaluation, Beloit was considered a low weed pressure site while Manhattan and Hays were considered to be moderate and high weed pressure sites, respectively. Grain sorghum biomass was different while weed biomass was consistent across row spacings. Yield loss equations and profit functions were derived to determine the amount of grain yield and $ ha[superscript]-1 loss from each of the three locations. Yield and profit lost was greatest amongst weedy observations. Results indicated that grain sorghum grown on wide row spacings and seeding rates of 125,000 seeds ha[superscript]-1 out yielded all other treatments under a low weed pressure site (Beloit) and narrow row spacings out yielded wider spacings in moderate and high weed pressure sites (Manhattan and Hays). These results imply that a Kansas grain sorghum producer should evaluate potential weed pressure before determining a final row spacing and seeding rate.

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Libros sobre el tema "Effect of light on weeds"

Mallory-Smith, Carol. Herbicide-resistant weeds and their management. [Moscow, Idaho]: University of Idaho Cooperativae Extension System, 1993.

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Mallory-Smith, Carol. Herbicide-resistant weeds and their management. [Moscow, Idaho]: University of Idaho Cooperativae Extension System, 1993.

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Mallory-Smith, Carol. Herbicide-resistant weeds and their management. [Moscow, Idaho]: University of Idaho Cooperativae Extension System, 1993.

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Mallory-Smith, Carol. Herbicide-resistant weeds and their management. [Moscow, Idaho]: University of Idaho Cooperativae Extension System, 1999.

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Mallory-Smith, Carol. Herbicide-resistant weeds and their management. [Moscow, Idaho]: University of Idaho Cooperativae Extension System, 1999.

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Ritter, Ronald Lloyd. Understanding herbicide resistance in weeds. Des Plaines, Ill: Sandoz Crop Protection Corp., 1989.

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Introduction to light: The physics of light, vision, and color. Mineola, N.Y: Dover Publications, 2002.

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1940-, Barber J., ed. The Light reactions. Amsterdam: Elsevier, 1987.

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Hart, J. W. Light and plant growth. London: Unwin Hyman, 1988.

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Hart, J. W. Light and plant growth. London: Unwin Hyman, 1987.

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Capítulos de libros sobre el tema "Effect of light on weeds"

Fajkus, Matt y Dason Whitsett. "Light and Effect". En Architectural Science and the Sun, 207–14. New York : Routledge, 2018.: Routledge, 2018. http://dx.doi.org/10.4324/9781315708041-10.

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Cohen-Tannoudji, Claude N. "The Autler-Townes Effect Revisited". En Amazing Light, 109–23. New York, NY: Springer New York, 1996. http://dx.doi.org/10.1007/978-1-4612-2378-8_11.

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Dodd, John N. "The Photoelectric Effect". En Atoms and Light: Interactions, 141–60. Boston, MA: Springer US, 1991. http://dx.doi.org/10.1007/978-1-4757-9331-4_12.

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Haghighipour, Nader. "Light Travel Time Effect". En Encyclopedia of Astrobiology, 1385–86. Berlin, Heidelberg: Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-662-44185-5_5301.

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Haghighipour, Nader. "Light Travel Time Effect". En Encyclopedia of Astrobiology, 1–2. Berlin, Heidelberg: Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-27833-4_5301-4.

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Saha, Biswanath, Heena Kauser, Meena Khwairakpam y Ajay S. Kalamdhad. "Effect and Management of Various Terrestrial Weeds—Review". En Lecture Notes in Civil Engineering, 231–38. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-0990-2_17.

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Rana, Neha, Aruna V. Varanasi y Brent A. Sellers. "Effect of Environmental Factors on Weed Germination and Management". En Biology, Physiology and Molecular Biology of Weeds, 27–44. Boca Raton, FL: CRC Press, 2017. | “A science publishers book.”: CRC Press, 2017. http://dx.doi.org/10.1201/9781315121031-3.

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Thorhallsson, Andri I. "Anode Effect Reduction at Nordural - Practical Points". En Light Metals 2015, 539–43. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2015. http://dx.doi.org/10.1002/9781119093435.ch90.

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Thorhallsson, Andri I. "Anode Effect Reduction at Nordural — Practical Points". En Light Metals 2015, 539–43. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-48248-4_90.

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Dando, Neal R., Lise Sylvain, Janice Fleckenstein, Ciro Kato, Vince Van Son y Laura Coleman. "Sustainable Anode Effect Based Perfluorocarbon Emission Reduction". En Light Metals 2011, 325–28. Cham: Springer International Publishing, 2011. http://dx.doi.org/10.1007/978-3-319-48160-9_58.

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Actas de conferencias sobre el tema "Effect of light on weeds"

Bush, Ronald A. y Theodore P. Williams. "Effect of optic nerve section on retinal light damage". En OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1985. http://dx.doi.org/10.1364/oam.1985.wj45.

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Sprague-Dawley rats, age 20-24 weeks, were obtained from Zivic-Miller Laboratories with unilateral intracranial optic nerve sections which did not interrupt the blood flow or any other innervation to the eye. They were then kept in uniform illumination of 1000 lx continuously for 24 h. The outer nuclear layer (ONL) areas of the two eyes in the same animal were compared five days postexposure. Light of this intensity causes damage primarily to the photoreceptors in the retina of the albino rat. Since the ONL of the retina contains photoreceptor cell bodies, reduction in the area of this layer is proportional to the number of cells lost due to the bright light exposure. Although the ONL area was reduced in both eyes, the retina with the intact optic nerve had an ONL area which averaged ~25 % less than that in the other eye with the optic nerve cut. Controls with unilateral optic nerve sections performed in the same manner but not exposed to damaging light showed no difference in ONL area between the two eyes. A second experiment using pigmented rats gave similar results. These results suggest a role for the brain in retinal light damage.

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de Barbadillo, John J., Brian A. Baker y Xishan Xie. "Microstructure Stability of Alloy 740H and its Effect on Material Properties". En ASME 2014 Symposium on Elevated Temperature Application of Materials for Fossil, Nuclear, and Petrochemical Industries. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/etam2014-1000.

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Alloy 740H was developed specifically for boiler tube and steam transfer pipe for the Advanced-Ultrasupercritical steam boiler application. The composition was formulated to provide creep strength, weldability and oxidation and coal ash corrosion resistance. It is the first nickel-base age-hardened alloy to be approved under Section 1 of the ASME Boiler and Pressure Vessel Code. Although a significant amount of microstructure and creep data was submitted to support the code case, it was largely collected on tube and light plate, much of this from pilot-scale material. The data package did not cover other product forms, sizes, hot working methods and weld joint configurations that may be required to construct a power plant. These include large diameter pipe, bends, fittings, heavy section welds, dissimilar metal welds, etc. that have complex thermal cycles and composition gradients. An ongoing effort is underway to characterize the microstructure and properties of alloy 740H under a range of manufacturing processes and to project these results through the potential life cycle of a plant. This paper describes the current status of this work. Paper published with permission.

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Joly, Pierre, François Roch y Christophe Primault. "Effect of Thermal Ageing on Properties of Pressure Vessel Low Alloy Steel". En ASME 2013 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/pvp2013-97643.

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The shells of the PWR heavy components are made of quenched and tempered low alloy steel (type A508 cl.3). Slow thermal ageing of the steel may occur by inter-granular segregation of impurities, depending on the service temperature and the concentration of residual elements (mainly phosphorus) in the steel. This phenomenon may generate embrittlement (i.e. a shift of ductile to brittle transition temperature). The pressurizer service temperature is the highest of the primary loop (345°C), and this component may be affected by more important ageing effects than others. In order to support rules for embrittlement predictions and to anticipate the potential embrittlement of the pressure boundary of this component, AREVA launched a research program, on different materials (base materials, weld metals, and heat affected zones of welds) based on accelerated ageing (400°C up to 30,000 hours and 450°C up to 20,000 hours), and Charpy impact toughness measurements. The aim of this paper is to present available results and to analyze them in the light of the literature and the available models.

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Trevisan, R. E., N. F. Santos, H. C. Fals y A. A. Santos. "Effect of Interpass Temperature on Morphology, Microstructure and Microhardness of Welded API 5L X65 Steel". En 2002 4th International Pipeline Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/ipc2002-27112.

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The overwhelming bulk of oil and gas in pipeline construction is done by welding the individual joints of pipe together. In a broad sense, welding is a metal-joining process wherein coalescence is produced by heating to a suitable temperature. In pipeline construction, this temperature has to be sufficient to render fusion of the joint. The mechanical and metallurgical properties and distortions usually present in weld structures are strongly influenced by preheating and interpass temperatures that are applied during the welding process. Basically, interpass temperatures depend on two factors: composition of the material and cooling rate. It is very important to choose the correct interpass temperatures, however, this is not a completely dominating matter. The objective of this paper is to present a study on the effect of different interpass temperatures on morphology, microstructure and consequently on microhardness of welded API 5L X65 steel. The welds were deposited by a Flux Cored Arc Welding Process and the heat input was held constant during all welding production. The interpass temperatures were calculated by different methods. Such temperatures were later verified experimentally. Temperature data were collected via a data acquisition system. The geometry and microstructure characterizations were performed via light optical microscopy and image analysis. These data were related to the different thermal cycles obtained. The results showed that the morphology, the microstructure and the microhardness of welded API 5L X65 steel were strongly influenced by the interpass temperature, revealing how important it is to choose the appropriate value.

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Shi, Lei, Hua Liu, Yumei Wei, Ming Ma y Rui Jiang. "The Persistence of Invasion and Diffusion Model of Poisonous Weeds with Allee Effect". En 2017 International Conference on Applied Mathematics, Modeling and Simulation (AMMS 2017). Paris, France: Atlantis Press, 2017. http://dx.doi.org/10.2991/amms-17.2017.36.

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Bingham, Carl, Gary Jorgensen y Amy Wylie. "Exposure of Polymeric Glazing Materials Using NREL’s Ultra-Accelerated Weathering System (UAWs)". En ASME 2010 4th International Conference on Energy Sustainability. ASMEDC, 2010. http://dx.doi.org/10.1115/es2010-90489.

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NREL’s Ultra-Accelerated Weathering System (UAWS) selectively reflects and concentrates natural sunlight ultraviolet irradiance below 475 nm onto exposed samples to provide accelerated weathering of materials while keeping samples within realistic temperature limits. This paper will explain the design and implementation of the UAWS which allow it to simulate the effect of years of weathering in weeks of exposure. Exposure chamber design and instrumentation will be discussed for both a prototype UAWS used to test glazing samples as well as a commercial version of UAWS. Candidate polymeric glazing materials have been subjected to accelerated exposure testing at a light intensity level of up to 50 UV suns for an equivalent outdoor exposure in Miami, FL exceeding 15 years. Samples include an impact modified acrylic, fiberglass, and polycarbonate having several thin UV-screening coatings. Concurrent exposure is carried out for identical sample sets at two different temperatures to allow thermal effects to be quantified along with resistance to UV.

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Roth, Armin, Matthias Herbst, Jürgen Rudolph, Paul Wilhelm, Xaver Schuler, Karl-Heinz Herter, Matthias Kammerer y Thomas Weissenberg. "Environmental Influences on the Fatigue Assessment of Austenitic and Ferritic Steel Components Including Welds". En ASME 2014 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/pvp2014-28728.

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The fatigue assessment of safety relevant components is of importance for ageing management with regard to safety and reliability. For cyclic stress evaluation, different country specific design codes and standards provide fatigue analysis procedures to be performed considering the various mechanical and thermal loading histories and geometric complexities of the components. For the fatigue design curves used as limiting criteria, the influence of different factors like e.g. environment, surface, temperature and data scatter must be taken into consideration in an appropriate way. In this context there is a need of consolidating and increasing the current knowledge. In the framework of an ongoing three years German cooperative project performed by Materials Testing Institute MPA Stuttgart and AREVA GmbH (Erlangen) it is the aim to both improve the state of the art based on an experimental program on the factors mentioned above including hold-times at transient free static load and on the derivation of a practicable engineering fatigue assessment concept. Emanating from a review of the current state of the art the cooperative project is split up into three major parts: 1) Experimental investigations concerning the influence of loading parameters and environmentally assisted fatigue (EAF) effects (light water reactor environment) on the fatigue strength of ferritic steels including weldments. 2) Experimental investigations concerning the influence of long hold times and the EAF effects on the fatigue strength of austenitic and ferritic steels. 3) The results of the outlined experimental program and published results will constitute the input for the proposal of an engineering fatigue assessment concept. This concept includes the differentiation between numerous factors of influence as an essential feature. In this context the margins between mean data curves and design curves are to be discussed in detail considering the factors of influence in general and EAF in particular. Based on a comprehensive consolidation of the state of the art and previous investigations in air and in light water reactor environment an experimental program is set up with the following key aspects: - Strain controlled fatigue tests on welded (microstructure of the weldment excluding microscopic and macroscopic weld notch effects) and unwelded smooth laboratory specimens subjected to constant and variable strain amplitude loading in air and light water reactor environment. - Strain controlled fatigue tests on notched specimens for the consideration of multi-axiality effects in air and light water reactor environment. - Strain controlled fatigue tests on smooth round laboratory specimens in air and in light water reactor environment focusing on long (power plant relevant) hold time effects.

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Burden, Dane, Nic Roniger y Matt Romney. "Puddling Puddle Welds". En 2020 13th International Pipeline Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/ipc2020-9476.

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Abstract Unique characteristics of individual pipelines come from over a century of evolving design, construction, maintenance, regulation and operation. These characteristics are especially true for legacy, pre-regulated pipelines. Due to the unique nature of the threats present on these assets, there is a need for unique inspection technologies and techniques that can increase pipeline integrity. Reconditioned and repaired pipe utilizing puddle weld repairs is one such threat. An advanced analysis was completed on a 10-inch, 68-mile light products pipeline. The pipeline was constructed with reconditioned pipe that was estimated to contain tens of thousands of puddle welds. Historical in-line inspection (ILI) data generally underperformed in classifying and discriminating puddle welds versus metal loss features. The primary objective of this project was to assess the probability of identification (POI) of a multiple dataset ILI tool utilizing multiple magnetic flux leakage (MFL) magnetization directions and residual (RES) magnetization measurements. A secondary objective was to scrutinize data for signs of coincident features. Hydrostatic testing failures showed that puddle welds with porosity and cracking were susceptible to failure and that the identification of these features would be beneficial. Analysis of historical puddle weld investigations and newly completed multiple dataset ILI data revealed strong identification capabilities in the RES dataset. The high-field magnetizations offered secondary confirmation but often saturated out thermal effects or material differences. The final report included over 40,000 identified puddle welds and five classifications for further investigation. Field investigations for 212 features were completed and the results compared to the ILI data to assess performance. A confusion matrix was created for true positive (TP), true negative (TN), false positive (FP) and false negative (FN) conditions. The smallest TP puddle weld dimension was 0.7″ × 0.7″, and the population had a statistical sensitivity value of 98% (132 TP and 3 FP). Three additional anomalies denoted as atypical were also investigated. The ILI signatures at these locations were consistent with previous repairs in which puddle welds with cracking were found and repaired. Two of the three features investigated were found to have cracking. Crack propagation was found to be both axial and non-axial in orientation. The results show that puddle welds can be detected and identified with extremely high accuracy. In addition, the preliminary classification results for atypical puddle welds show a high potential for identifying secondary coincident features. This paper details the stages, deliverables and results from an ILI advanced analysis focused on puddle welds.

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Zheng, Youfei, Wei Gao, Chuanhai Wang, Wei Xiao y Ronggang Zhang. "Effect of increased UV-B on weeds and big worms in a farmland ecological system". En Optical Science and Technology, SPIE's 48th Annual Meeting, editado por James R. Slusser, Jay R. Herman y Wei Gao. SPIE, 2003. http://dx.doi.org/10.1117/12.509662.

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Rudolph, Jürgen, Matthias Herbst, Armin Roth, Christian Swacek y Tim Schopf. "Important Effects in Environmentally Assisted Fatigue (EAF) of Austenitic and Ferritic Steel Components Including Welds and Their Consideration in a Fatigue Assessment Concept". En ASME 2019 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/pvp2019-93913.

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Abstract The fatigue assessment of pressure boundary components is of importance for the aging management regarding safety and reliability in nuclear power plants with light water reactors. For the evaluation of cyclic loading conditions, different country specific design codes and standards are applied to consider various mechanical and thermal loadings as well as geometrical and material effects. Those different influencing factors have also to be taken into account in the fatigue design curves. Current state of the art methods account for life time influencing factors such as temperature, surface finish, stress multi-axiality and loading history by the application of reduction factors for fatigue lives (penalty respectively margin factors) determined from fatigue design curves which are derived from laboratory test data. Other effects, such as environmental effects or hold times, are often considered with high levels of conservatism or are not taken into account at all. On the one hand, this may lead to non-conservative predictions of the materials fatigue behavior, while on the other hand, there are often large discrepancies between calculated fatigue life and practical experience from power plant operation, where the operating experience reveals much higher fatigue lifetimes as their predictions based on laboratory tests and conservative consideration of major influencing factors (plastification by Ke-factors, Environmentally Assisted Fatigue (EAF) by FEN-factors) in the calculation approach. Therefore, Framatome GmbH, Erlangen, and the Material Testing Institute MPA Stuttgart currently conducting a cooperative research program which aims to improve the understanding of environmental and loading effects as well as of welds on fatigue life time and to improve fatigue lifetime assessment methods in the framework of the well established engineering approach. Based on the results of a previous research project of the same project partners, an experimental program is performed to investigate the effect of loading parameters and hold times on environmentally assisted fatigue (EAF). Experiments on specimens of ferritic and austenitic stainless steels and austenitic stainless steel welds as well as component tests are performed under laboratory and operating conditions to improve fatigue assessment and serve to bridge the gap between specimen behavior and component fatigue in operation. Emanating from previous and ongoing cooperative research projects, the experimental results will contribute to the proposal of an engineering fatigue assessment concept, allowing more specific differentiation in the influencing factors for component fatigue life prediction. Furthermore, hold time effects are simulated based on further developed material models.

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Informes sobre el tema "Effect of light on weeds"

Olsen, D. K. Effect of wettability on light oil steamflooding. Office of Scientific and Technical Information (OSTI), diciembre de 1991. http://dx.doi.org/10.2172/5921887.

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Olsen, D. K. Effect of wettability on light oil steamflooding. Office of Scientific and Technical Information (OSTI), diciembre de 1991. http://dx.doi.org/10.2172/10112474.

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Aly, Radi y John I. Yoder. Development of resistant crop plants to parasitic weeds based on trans-specific gene silencing. United States Department of Agriculture, enero de 2013. http://dx.doi.org/10.32747/2013.7598146.bard.

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Broomrapes (Orobanche/Phelipanchespp.) are holo parasitic plants that subsist on the roots of a variety of agricultural crops and cause severe losses to the yield quality and quantity. Effective methods for controlling parasitic weeds are scarce, with only a few known cases of genetic resistance. In the current study, we proposed an improved strategy for the control of parasitic weeds based on trans-specific gene-silencing of three parasite genes at once. We used two strategies to express dsRNA containing selected sequences of three Phelipancheaegyptiacagenes PaACS, PaM6PR and PaPrx1 (pma): transient expression using Tobacco rattle virus (TRV:pma) as a virus-induced gene-silencing (VIGS) vector and stable expression in transgenic tomato Solanumlycopersicum(Mill.) plants harboring a hairpin construct (pBINPLUS35:pma). siRNA-mediated transgene-silencing (20–24 nt) was detected in the host plants. Our results demonstrate that the quantities of PaACSand PaM6PR transcripts from P. aegyptiacatubercles grown on transgenic tomato or on Tobacco rattle virus-infected Nicotianabenthamianaplants were significantly reduced. However, only partial reductions in the quantity of PaPrx1 transcripts were observed in the parasite tubercles grown on tomato and on N. benthamianaplants. Concomitant with the suppression of the target genes, there were significant decreases in the number and weight of the parasite tubercles that grew on the host plants, in both the transient and the stable experimental systems. The results of the work carried out using both strategies point to the movement of mobile exogenous siRNA from the host to the parasite, leading to the impaired expression of essential parasite target genes. In light of the importance of parasitic weeds to world agriculture and the difficulty of obtaining resistance by conventional methods, we assume that genetic resistance based on the silencing of key metabolic genes in the parasite is now feasible. BARD Report - Project4622 Page 2 of 60

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Ewing, Reid. Effect of Light-Rail Transit on Traffic in a Travel Corridor. Portland State University Library, junio de 2014. http://dx.doi.org/10.15760/trec.56.

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Sonder, E., A. B. Ahmed, K. L. McMahan, D. S. Colwell y P. R. Smith. The effect of visible light on Harshaw Model 8801 thermoluminescent dosimeters. Office of Scientific and Technical Information (OSTI), septiembre de 1990. http://dx.doi.org/10.2172/6240515.

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Ruden, P. P. y Darryl L. Smith. Device Model for Light-Emitting Field-Effect Transistors with Organic Semiconductor Channel. Office of Scientific and Technical Information (OSTI), abril de 2007. http://dx.doi.org/10.2172/1304691.

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Van Cauter, Eve. Phase-Shifting Effect of Light and Exercise on the Human Circadian Clock. Fort Belvoir, VA: Defense Technical Information Center, febrero de 1992. http://dx.doi.org/10.21236/ada253012.

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Van Cauter, Eve, Jeppe Sturis, Maria M. Byrne, John D. Blackman, Neal H. Scherberg, Rachel Leproult, Samuel Refetoff y Olivier Van Reeth. Phase-Shifting Effect of Light and Exercise on the Human Circadian Clock. Fort Belvoir, VA: Defense Technical Information Center, mayo de 1993. http://dx.doi.org/10.21236/ada265732.

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Marasco, Peter L. y H. L. Task. The Effect on Vision of Light Scatter From HMD Visors and Aircraft Windscreens. Fort Belvoir, VA: Defense Technical Information Center, enero de 1999. http://dx.doi.org/10.21236/ada430274.

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Chen, Yujia, Li Peng, Jiarun Wang, Jing Zhao, Zhijie Zou y Xiaoli Chen. Effect of bright light therapy on perinatal depression: Systematic review and meta-analysis. INPLASY - International Platform of Registered Systematic Review and Meta-analysis Protocols, noviembre de 2022. http://dx.doi.org/10.37766/inplasy2022.11.0007.

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