Literatura académica sobre el tema "Effect of temperature on weeds"
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Artículos de revistas sobre el tema "Effect of temperature on weeds"
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Monks, C. Dale, David W. Monks, Tom Basden, Arthur Selders, Suzanne Poland y Edward Rayburn. "Soil Temperature, Soil Moisture, Weed Control, and Tomato (Lycopersicon esculentum) Response to Mulching". Weed Technology 11, n.º 3 (septiembre de 1997): 561–66. http://dx.doi.org/10.1017/s0890037x00045425.
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Shredded newspaper (2.5, 7.6, 12.7, and 17.8 cm depth), chopped newspaper (2.5 and 7.6 cm), wheat straw (15.2 cm), black plastic, and plastic landscape fabric were evaluated during 1993 and 1994 in West Virginia for their effect on soil temperature, soil moisture, weed control, and yield in tomato. Shredded newspaper and wheat straw applied at 0, 2, 4, or 6 weeks after transplanting (WAT) and napropamide (2.1 kg ai/ha) plus metribuzin (0.28 kg ai/ha) applied at transplanting were evaluated during 1992 and 1993 in North Carolina for effect on weed control and tomato yield. Results from West Virginia indicated that shredded (7.6 cm) and chopped (7.6 cm) newspaper conserved moisture similar to higher application rates of the shredded material. Higher newspaper mulching rates reduced soil temperature compared to black plastic and bare ground. Chopped newspaper controlled weeds more consistently than other treatments. At least 7.6 cm of chopped newspaper mulch was required to control weeds at least 90%. Wheat straw was not as effective in controlling weeds as 7.6 cm or greater of newspaper mulch. Chopped newspaper provided higher tomato yields than shredded newspaper applied at the same rates. Mulches applied at 0, 2, or 4 WAT resulted in weed control similar to the chemical treatment. In North Carolina, mulches applied 2 or 4 WAT resulted in tomato yields similar to the chemical treatment. Shredded and chopped newspaper have potential as a mulching material but may vary in effect in different environments and vegetable crops.
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Aziz, Fahrurrozi y Katrine A. Stewart. "EFFECT OF SPECTRAL QUALITIES OF PLASTIC MULCH ON WEED DEVELOPMENT AND GROWTH". HortScience 29, n.º 4 (abril de 1994): 251c—251. http://dx.doi.org/10.21273/hortsci.29.4.251c.
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The types of plastic mulch used in horticultural production often fulfill only a few of the grower's needs. Black plastic mulch controls weeds, but can burn young plants. Clear mulch, while warming the soil and enhancing early crop growth, allows prolific weed growth and development. Accordingly, an experiment using a randomized complete-block design with-four replications was set up to compare the effects of black, microperforated black, silver, and wavelength-selective (IRT-76) green mulches, and bare soil on weed growth and development, and on soil temperature and moisture. Each mulch was evaluated for its optical properties. All mulches significantly reduced final stands of seeded weeds compared with bare soil. IRT-76 green had the warmest mean soil temperatures, followed by silver, black, and microperforated black mulches, and bare soil. Soil moisture content was generally higher under plastic mulches than bare soil.
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Kumar, Vipin, Annu Kumari, Andrew J. Price, Ram Swaroop Bana, Vijay Singh y Shanti Devi Bamboriya. "Impact of Futuristic Climate Variables on Weed Biology and Herbicidal Efficacy: A Review". Agronomy 13, n.º 2 (15 de febrero de 2023): 559. http://dx.doi.org/10.3390/agronomy13020559.
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Our changing climate will likely have serious implications on agriculture production through its effects on food and feed crop yield and quality, forage and livestock production, and pest dynamics, including troublesome weed control. With regards to weeds, climatic variables control many plant physiology functions that impact flowering, fruiting, and seed dormancy; therefore, an altered climate can result in a weed species composition shift within agro-ecosystems. Weed species will likely adapt to a changing climate due to their high phenotypic plasticity and vast genetic diversity. Higher temperatures and CO2 concentrations, and altered moisture conditions, not only affect the growth of weeds, but also impact the effectiveness of herbicides in controlling weeds. Therefore, weed biology, growth characteristics, and their management are predicted to be affected greatly by changing climatic conditions. This manuscript attempted to compile the available information on general principles of weed response to changing climatic conditions, including elevated CO2 and temperature under diverse rainfall patterns and drought. Likewise, we have also attempted to highlight the effect of soil moisture dynamics on the efficacy of various herbicides under diverse agro-ecosystems.
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Wright, Shawn R., Harold D. Coble, C. David Raper y Thomas W. Rufty. "Comparative responses of soybean (Glycine max), sicklepod (Senna obtusifolia), and Palmer amaranth (Amaranthus palmeri) to root zone and aerial temperatures". Weed Science 47, n.º 2 (abril de 1999): 167–74. http://dx.doi.org/10.1017/s004317450009158x.
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Experiments were conducted to compare germination efficiencies and vegetative growth of soybean and the competing weed species, sicklepod and Palmer amaranth, over a range of temperatures in the root zone and aerial environments. From genetic origins we hypothesized that the weeds would have a higher temperature optimum, which would help explain competitive interactions seen in the southeastern U.S. Germination experiments indicated that germination efficiency of the weeds was much more sensitive to low temperature than soybean, being markedly inhibited below 18 C. Similarly, experiments in an automated, temperature-controlled hydroponic system revealed that the weed species were less tolerant of low root zone temperature but more tolerant of high root zone temperature than soybean. At 16 C, dry weight of soybean was 74% of the control dry weight at 24 C, whereas dry weights of sicklepod and Palmer amaranth were 5 and 20% of the control, respectively. At 32 C, soybean root dry weight was only 80% of the 24 C treatment, whereas root dry weight of the weed species was not significantly different. When plants were grown at a low aerial temperature, growth of all plants was strongly inhibited] but the negative effects were somewhat more severe in the weed species than with soybean. An increase in aerial temperature from 26/22 C to 34/30 C (day/night) had a positive influence on dry matter accumulation of the weed species, stimulating sicklepod 150 to 200% and Palmer amaranth 150 to 1,600% compared to their respective controls, whereas soybean remained at about 80 to 90% of the control. All species grew taller with increasing temperature. Leaf area of the weeds increased but leaf area of soybean did not increase. Consistent with our original hypothesis, the results clearly show that the weeds, which originate from warm geographical regions, respond more negatively than soybean to low temperatures in the growth environment but more positively to high temperatures. The temperature characteristics help to explain why the intensity of weed pressure increases as the soybean growing season progresses, even after canopy closure.
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Park, Hyun-Hwa, Do-Jin Lee y Yong-In Kuk. "Effects of Various Environmental Conditions on the Growth of Amaranthus patulus Bertol. and Changes of Herbicide Efficacy Caused by Increasing Temperatures". Agronomy 11, n.º 9 (3 de septiembre de 2021): 1773. http://dx.doi.org/10.3390/agronomy11091773.
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Understanding the effects of climate change on weed growth and herbicide activity is important for optimizing herbicide applications for effective weed control in the future. Therefore, this study examined how climate change affects the growth of Amaranthus patulus and the efficacy of soil and foliar herbicides at different temperatures. Although the control values for A. patulus differed between herbicides and temperature, the control values increased with increasing time after the herbicide treatments. Under growth conditions in which the temperature remained constant, the efficacy of soil-applied herbicides, ethalfluralin, metolachlor, linuron, and alachlor, on A. patulus was highest when the weeds were grown at high temperature. In particular, 100% control values of A. patulus were achieved in response to metolachlor treatments at the total recommended dosage in growth chambers at 35 °C. The efficacy of foliar herbicides, glufosinate-ammonium, bentazone, and mecoprop, on A. patulus was also highest when the plant was grown at high temperature, except for glyphosate isopropylamine, which had similar efficacy rates regardless of the temperature. A. patulus was 100% controlled in response to glufosinate-ammonium, bentazone, and mecoprop at the recommended dosages in growth chambers at 30 and 35 °C. Under growth conditions in which the temperature changed from day to night, the efficacy of soil-applied herbicides, alachlor and linuron, on A. patulus was highest when the weeds were grown at high temperature. On the other hand, the efficacy of the soil-applied herbicides metolachlor and linuron on A. patulus was similar regardless of the temperature. The efficacy of foliar herbicides, glyphosate isopropylamine, glufosinate-ammonium, bentazone, and mecoprop, on A. patulus was highest when the weeds were grown at high temperature. Although herbicide efficacy varied depending on whether the weeds were grown at constant or alternating temperatures, herbicide efficacy was generally highest when the temperature was high.
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Kirigiah, Richard, Masinde Peter y Mworia G. Erick. "Effect of Plastic Mulch Color and Transplanting Stage on Baby Corn Plant Performance". European Journal of Agriculture and Food Sciences 4, n.º 5 (20 de octubre de 2022): 103–11. http://dx.doi.org/10.24018/ejfood.2022.4.5.567.
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Different colored plastic mulches have been developed and used in various crop production methods. The main goals of using colored plastic mulches are to modify the radiation budget and reduce soil water loss. In addition, it aids in controlling weed and insect infestation as well as soil temperature, water use effectiveness, plant development, yield, and quality. The growth and development of baby corn depend on several geographical and climatic conditions in its surrounding (air and soil). This study determined the effect of different colored plastic mulches on soil temperature and the performance of two baby corn varieties (Pan 14 and Thai Gold). Black plastic mulches showed significantly higher soil temperatures, followed by transparent films, yellow films, and non-mulched, respectively. However, there were no significant changes in soil temperatures over the 17 weeks for specific plastic mulches. Pan 14 produced a higher yield and displayed improved vegetative growth compared to Thai Gold under similar conditions. Transparent plastic mulches showed the best yield and vegetative growth for both varieties but could not effectively control weeds. Black plastic mulches produced significantly higher yield and vegetative performance than non-mulched but were lower than the transparent film performance. Additionally, black plastic mulches showed better performance on weed minimization. The combined results indicated that the effect of colored plastic mulches is highly significant on soil temperature, moisture, and water-holding capacity. While black plastics increase soil temperature, transparent and yellow decrease it.
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Tremmel, D. C. y D. T. Patterson. "Effects of elevated CO2 and temperature on development in soybean and five weeds". Canadian Journal of Plant Science 74, n.º 1 (1 de enero de 1994): 43–50. http://dx.doi.org/10.4141/cjps94-009.
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Developmental rates of soybean [Glycine max (L.) Merr. 'Braxton'], johnsongrass [Sorghum halepense (L.) Pers.], quackgrass [Elytrigia repens (L.) Nevski], redroot pigweed (Amaranthus retroflexus L.), sicklepod (Cassia obtusifolia L.), and velvetleaf (Abutilon theophrasti Medic.) were compared among plants grown in all combinations of two temperature levels (avg. day/night of 26/19 °C and 30/23 °C) and two CO2 levels (350 and 700 ppm). Neither temperature nor CO2 affected johnsongrass tillering rate, but plants began tillering earlier at higher temperatures. Adverse effects of higher temperatures on quackgrass development were alleviated by elevated CO2 conditions. Plastochron rate was higher at higher temperatures in all dicot species (soybean, redroot pigweed, sicklepod, and velvetleaf), and was higher at elevated CO2 in all dicots except velvetleaf. Calculating plastochron rates on a degree day basis removed differences between temperature treatments, but did not affect responses to CO2. Responses of dicot branch and branch leaf production to treatments varied among species. Branch production per day increased with higher temperatures in redroot pigweed, decreased with higher temperatures in sicklepod, and was unaffected by temperature in soybean. The relationship between main axis and branch developmental rates was altered by temperature in soybean, and by both temperature and CO2 in sicklepod, but was unaffected by either treatment in redroot pigweed. These results indicate that developmental responses to temperature and CO2 depend on both the species and the aspect of development being considered. Key words: Plastochron index, CO2 by temperature interaction, johnsongrass, quackgrass, redroot pigweed, sicklepod, velvetleaf
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Martinez-Ghersa, Maria A., Emilio H. Satorre y Claudio M. Ghersa. "Effect of soil water content and temperature on dormancy breaking and germination of three weeds". Weed Science 45, n.º 6 (diciembre de 1997): 791–97. http://dx.doi.org/10.1017/s0043174500088986.
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In laboratory experiments, we studied barnyardgrass, common lambsquarters, and redroot pigweed seed dormancy release by alternating temperatures under different soil water regimes, to determine whether that response serves as a mechanism for assuring seedling establishment. Alternating temperatures were important in breaking seed dormancy in the three weeds, but the species' response to alternating temperatures differed with soil water content. For redroot pigweed and newly dispersed seeds of barnyardgrass, dormancy breaking by alternating temperatures occurred only when soil water content was high enough for germination. Moreover, adverse incubation conditions (constant temperature and low water content) induced secondary dormancy in these seeds. Seventy percent of seeds incubated in open boxes emerged before the soil reached wilting point, when seeds were incubated at temperatures high enough for a high germination rate. A dormancy breaking mechanism that triggers a high rate of germination may be important in assuring success of seedling establishment where rainfall patterns result in wetting and drying cycles of the soil, especially in soil types that lose water rapidly from the surface layers.
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Swanton, Clarence J., Jian Zhong Huang, William Deen, Matthijs Tollenaar, Anil Shrestha y Hamid Rahimian. "Effects of temperature and photoperiod onSetaria viridis". Weed Science 47, n.º 4 (agosto de 1999): 446–53. http://dx.doi.org/10.1017/s0043174500092067.
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Understanding the environmental variables influencing the phenological development of weeds is essential for simulation model development. Temperature and photoperiod are important variables governing the phenological development of weeds. Growth cabinet studies were conducted to characterize the phenological development ofSetaria viridisin response to variations in temperature and photoperiod and to determine the duration of the juvenile phase and the effect of temperature and photoperiod on reproductive development.Setaria viridiswas adapted to a temperature range from 6.5 to 47 C. Phenological development ofS. viridiswas described accurately in terms of thermal days (cumulative day degrees above a base temperature) and biological days (Bd: chronological days at the optimum temperature and photoperiod). Four developmental phases ofS. viridiswere described: (1) a juvenile (photoperiod insensitive) phase of 2.6 Bd; (2) a photoperiod-sensitive inductive phase of 2.2 Bd; (3) a photoperiod-sensitive postinductive phase of 6.0 Bd; and (4) a photoperiod-insensitive inductive phase of 10.9 Bd. Photoperiod sensitivity ofS. viridisdid not differ with stage of development when expressed as a rate. Interpretation of constant sensitivity to photoperiod will simplify simulation of weed phenology in mechanistic models.
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WEAVER, S. E., C. S. TAN y P. BRAIN. "EFFECT OF TEMPERATURE AND SOIL MOISTURE ON TIME OF EMERGENCE OF TOMATOES AND FOUR WEED SPECIES". Canadian Journal of Plant Science 68, n.º 3 (1 de julio de 1988): 877–86. http://dx.doi.org/10.4141/cjps88-105.
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The relative times to emergence of seedlings of tomato (Lycopersicon esculentum L.) and four weed species were compared at five alternating temperatures and five levels of available soil moisture in a growth chamber. Weed seeds were sown either on the soil surface or 1.5 cm below it. A cumulative distribution function was used to describe the time required for emergence under a given set of conditions. Time to 50% emergence, base temperatures and accumulated degree days required for 50% emergence were calculated for each species. In general, total emergence decreased as soil moisture decreased, but the species differed in the optimum temperature for emergence. Time to 50% emergence decreased with increasing temperature and increased slightly with decreasing soil moisture. Base temperatures and thermal times required for 50% emergence varied among species, but were relatively insensitive to soil moisture above a critical level. Differences in relative times to emergence of crop and weeds in response to temperature can be used to suggest optimal crop sowing dates and to estimate potential crop yield losses.Key words: Germination, Solanum ptycanthum, Amaranthus powellii, Setaria viridis, Chenopodium album, Lycopersicon esculentum
Tesis sobre el tema "Effect of temperature on weeds"
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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 temperatureMaster 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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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
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Suryani, Titik. "The effects of temperature, hours of leaf wetness, age of giant foxtail (setaria faberi herrm.), and host specificity of phoma sp. as a biological herbicide". Virtual Press, 1995. http://liblink.bsu.edu/uhtbin/catkey/941362.
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Inoculation studies were conducted in controlled environments with isolates of a Phoma sue. collected from leaf spot lesions on the weed giant foxtail. Limited host specificity studies resulted in this potential bioherbicide fungus killing all three foxtail species tested including Setaria faberi (giant), a. viridis (green) and S. lutescens (yellow). Several agronomically important plant species tested exhibited a hypersensitive-type response to infection, but these plants soon grew out of this symptom and appeared healthy. This bioherbicide preferred cool temperatures, exhibiting optimal biomass loss (100%) or death against foxtail seedlings following 120 hours leaf wetness with plants incubated at 20°C. At more conducive growth temperatures for the weed (25'C-300C), optimum biomass loss achieved was only 70% following 50 hours leaf wetness. Susceptibility to this Phoma sue. greatly decreased as foxtail seedlings attained 4 or more leaves per plant. To kill this weed, the author recommends inoculation of foxtail seedlings in early evening to take advantage of cooler temperatures and to inoculate plants between cotyledon to 3-leaf stages of growth.Department of Biology
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Antill, Marc. "The effect of repair welds on the high temperature low cycle fatigue behaviour of nickel base superalloy turbine blades". Thesis, University of Bristol, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297923.
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Pline, Wendy Ann. "Effect of Temperature and Chemical Additives on the Efficacy of the Herbicides Glufosinate and Glyphosate in Weed Management of Liberty-Link and Roundup-Ready Soybeans". Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/31699.
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The introduction of herbicide resistant crops offers producers many more options for weed control systems. These crops allow environmentally safe, non-selective herbicides to be used as selective herbicides, broadening the spectrum of weeds controlled, while not harming the crop. As these crops are very new on the market, investigation of their performance under various environmental conditions as well as in various weed control programs is needed. Liberty-link ® soybeans are resistant to the herbicide glufosinate, because of the incorporation of a gene encoding phosphinothricin acetyl-transferase (pat), which is able to detoxify glufosinate. Roundup-Ready ® soybeans are transformed with an altered, non-sensitive form of 5-enolpyruvylshikimate- 3-phosphate synthase (EPSPS), which confers glyphosate resistance. Field and greenhouse studies were conducted to determine the efficacy of glufosinate and glyphosate on annual and perennial weeds. Also to determine whether the use of ammonium sulfate (AMS) or pelargonic acid (PA), a 9-carbon fatty acid, as additives of glufosinate or glyphosate would increase their efficacy, while maintaining their safety on the transgenic soybeans. Three annual weeds: common lambsquarters, giant foxtail, sicklepod, as well as two perennial weeds: common milkweed and horsenettle were included in studies. Uptake, translocation, and metabolism of 14C-glufosinate + AMS or PA, were studied in the five weeds in order to determine the basis for their differential weed sensitivity to glufosinate, and the effect of the two additives. The effect of temperature on Liberty-Link ® and Roundup-Ready ® soybeans after application of glufosinate or glyphosate was investigated. Injury was quantified by measuring chlorophyll content of herbicide treated soybean trifoliolates. Uptake, translocation, and metabolism studies of 14C-glufosinate and 14C-glyphosate in transgenic soybeans were conducted to determine the potential cause for the observed temperature-dependent sensitivity. Since glufosinate is a synthetic analog of a naturally occurring bacterial toxin, it was tested for possible bactericidal activity on the soybean pathogen Pseudomonas syringae. Greenhouse and field-studies showed that the 5 weeds responded differently to glufosinate and glyphosate. Common milkweed was the most tolerant to glufosinate and common lambsquarters to glyphosate while giant foxtail was the most sensitive species to both herbicides. Some interactions between AMS or PA and glufosinate or glyphosate were also observed. Uptake and translocation studies showed that AMS increased the uptake of 14C-glufosinate in some weeds, whereas PA had only minimal effects on absorption and translocation of glufosinate. Metabolism of glufosinate was detected only in common lambsquarters. A rate dependent loss of chlorophyll in Liberty-Link ® soybeans treated with glufosinate was observed that was greater at 15° C than at 25° or 35° C. Metabolism studies showed a decrease in the rate of glufosinate metabolism 3 hours after treatment in Liberty-Link ® soybeans grown at 15° C versus 25° C. Conversely, chlorophyll loss in glyphosate-treated Roundup-Ready soybeans was greater at 35° C than at 15° or 25° C. Translocation studies showed a significantly greater percentage of absorbed 14C-glyphosate translocated to developing meristems at 35° C than at 15° C in Roundup-Ready® soybeans. Glufosinate concentrations of 1 mM and higher significantly inhibited the growth of Pseudomonas syringae (L-529) in liquid media cultures. Typical field use rates of glufosinate also reduced the number of live P. syringae on Liberty-Link® soybean leaves. Overall, the results of this research show that annual and perennial weeds differ in their sensitivity to glufosinate and glyphosate. Additives such as AMS and PA may enhance the efficacy of glufosinate on perennial weed species, and glyphosate in most weeds. Differences in weed sensitivity to herbicides and effects of additives can in most cases be explained by differences in absorption or metabolism. Variable temperatures may affect the engineered resistance of transgenic soybeans to the herbicides glufosinate and glyphosate. The herbicide glufosinate has some bacteriocidal activity on P. syringae. Nomenclature: Glufosinate, 2-amino-4-(hydroxymethylphosphinyl) butanoic acid; Glyphosate, N-(phosphonomethyl)glycine; PA, pelargonic acid (nanoic acid); AMS, ammonium sulfate; giant foxtail, Setaria faberi Herrm.; common lambsquarters,
Chenopodium album L.; sicklepod, Cassia obtusifolia L.; horsenettle, Solanum carolinense L.; common milkweed, Ascleipias syriaca L. pat, phosphinothricin acetyl transferase; EPSPS, 5-enolpyruvylshikimate-3-phosphate synthase.Master of Science
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Virbickait-Staniulienė, Rasa. "The impact of high-temperature environment on weeds highly resistant to thermal killing". Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2010. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2010~D_20101214_140738-85437.
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The dissertation has set the aim to determine the influence of a high-temperature environment on highly resistant to thermal killing. Not all weeds equally respond to the thermal effect when wet water vapour is applied for thermal weed control. After thermal destruction of the above-ground part some varieties of weeds spring up again. Analysis of the morphological structure of weeds and their responsiveness to wet water vapour allows weed classification into three groups: weeds of low resistance to thermal killing, those of high resistance to thermal killing (meadow-grass and rosette weeds) and of very high resistance to thermal killing. If the thermal control of these weeds is carried out too late, weeds overgrow cultivated plants, which results in harvest losses. In order to improve the technology of thermal weed control it was necessary evaluate the parameters of a high-temperature environment, the morphological structure of weeds highly resistant to thermal killing, stages of weed growth and development, the influence of air inter-layers in weed leaves on the spread of a high-temperature field to deeper tissues, and the influence of the angle of tilt of weed leaves on thermal control. This paper analyses the influence of the aforementioned factors on the control of weeds highly resistant to thermal destruction and proposes measures for the formation of a high-temperature environment intended for a more efficient thermal control of weeds using wet water vapour.Darbo tikslas – nustatyti aukštatemperatūrės aplinkos poveikį sunkiai termiškai sunaikinamoms piktžolėms. Terminei piktžolių kontrolei naudojant drėgną vandens garą, ne visos piktžolės vienodai reaguoja į terminį poveikį. Termiškai sunaikinus antžeminę dalį, atskiros piktžolių rūšys po kurio laiko atželia. Išnagrinėjus piktžolių morfologinę sandarą ir piktžolių jautrumą drėgnam vandens garui, galima piktžoles suskirstyti į tris grupes: lengvai termiškai sunaikinamos, sunkiai termiškai sunaikinamos (miglinės ir skrotelinės piktžolės) ir labai sunkiai termiškai sunaikinamos piktžolės. Terminėje piktžolių kontrolėje didelę problemą kelia sunkiai termiškai sunaikinamos piktžolės. Suvėlinus šių piktžolių terminę kontrolę, piktžolės stelbia žemės ūkio augalus, patiriami derliaus nuostoliai. Norint tobulinti piktžolių terminės kontrolės technologiją teko įvertinti aukštatemperatūrės aplinkos parametrus, sunkiai termiškai sunaikinamų piktžolių morfologinę sandarą, piktžolių augimo ir vystymosi tarpsnius, piktžolių lapų oro tarpsluoksnių įtaką aukštatemperatūrio lauko plitimui į gilesnius audinius, piktžolių lapų posvyrio kampo įtaką terminei kontrolei. Šiame darbe yra nagrinėjama minėtų veiksnių įtaka sunkiai termiškai sunaikinamų piktžolių kontrolei, bei siūlomos sprendimo priemonės formuojant aukštatemperatūrę aplinką efektyvesnei terminei piktžolių kontrolei drėgnuoju vandens garu.
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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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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 ScienceDepartment 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.
Libros sobre el tema "Effect of temperature on weeds"
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Hansson, David. Hot water weed control on hard surface areas. Alnarp: Swedish University of Agricultural Sciences, 2002.
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Hamada, Azhari Abdelazim. Investigations on the germination requirements and competitive effects of weeds: A case study of the Rahad Scheme in the Sudan. Weikersheim [Germany]: Josef Margraf, 1992.
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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, 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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Harań, Grzegorz. Impurity effect in high temperature superconductors. Wrocław: Oficyna Wydawnicza Politechniki Wrocławskiej, 2001.
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Franklin, Keara A. y Philip A. Wigge. Temperature and plant development. Ames, Iowa USA: Wiley Blackwell, 2014.
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Ritter, Ronald Lloyd. Understanding herbicide resistance in weeds. Des Plaines, Ill: Sandoz Crop Protection Corp., 1989.
Buscar texto completoCapítulos de libros sobre el tema "Effect of temperature on weeds"
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Marques, Severino P. C. y Guillermo J. Creus. "Temperature Effect". En Computational Viscoelasticity, 51–58. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-25311-9_6.
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Zhang, Guigen. "Temperature Effect". En Bulk and Surface Acoustic Waves, 257–71. New York: Jenny Stanford Publishing, 2021. http://dx.doi.org/10.1201/9781003256625-7.
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Alderliesten, René. "Effect of Temperature". En Fatigue and Fracture of Fibre Metal Laminates, 253–70. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-56227-8_11.
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Brown, R. P. "Effect of temperature". En Physical Testing of Rubber, 235–58. Dordrecht: Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-011-0529-3_15.
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Brown, Roger. "Effect of Temperature". En Physical Test Methods for Elastomers, 305–31. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-66727-0_21.
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Ferrell, Richard A. "The Josephson Effect". En High Temperature Superconductivity, 60–83. New York, NY: Springer New York, 1990. http://dx.doi.org/10.1007/978-1-4612-3222-3_3.
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Oka, Yoshiaki. "Temperature Effect of Reactivity". En Nuclear Reactor Kinetics and Plant Control, 23–33. Tokyo: Springer Japan, 2012. http://dx.doi.org/10.1007/978-4-431-54195-0_3.
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Wen, Shengmin. "Temperature Effect on Fatigue". En Encyclopedia of Tribology, 3538–40. Boston, MA: Springer US, 2013. http://dx.doi.org/10.1007/978-0-387-92897-5_281.
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Shur, M. y M. A. Khan. "GaN-based field effect transistors". En High Temperature Electronics, 297–320. Boston, MA: Springer US, 1997. http://dx.doi.org/10.1007/978-1-4613-1197-3_10.
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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.
Texto completoActas de conferencias sobre el tema "Effect of temperature on weeds"
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Dai, H., R. J. Moat y P. J. Withers. "Modelling the Interpass Temperature Effect on Residual Stress in Low Transformation Temperature Stainless Steel Welds". En ASME 2011 Pressure Vessels and Piping Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/pvp2011-57329.
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Weld residual stresses often have serious implications for the integrity of engineering structures (distortion, stress-corrosion cracking, hydrogen-induced cracking). Previously, it has been demonstrated by the authors that the use of a stainless steel welding consumable with a low martensite start temperature in single-pass welding can lead to lower (potentially harmful) tensile residual stresses or even compressive stress within the fusion zone and heat affected zones compared to non-transforming austenitic fillers. However, such effects may not carry over to multi-pass welding if the filler transforms fully on cooling from the first pass. In this paper finite element modelling is used to examine the use of interpass hold temperatures on the residual stresses introduced using such weld fillers in multi-pass welding of 304L stainless steel plate. Four levels of interpass temperature have been studied. The model has also been verified against experimental data obtained using the contour method for two welded plates having two different inter-pass temperatures. It is demonstrated that interpass hold temperatures above, or around, the transformation temperature can have very significant effects, allowing residual stress management of the resulting welded joint.
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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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Bandara, R. M. U. S., T. K. Ilangakoon, H. M. M. K. K. H. Dissanayaka, Y. M. S. H. I. U. De Silva, C. H. Piyasiri y D. M. C. B. Dissanayaka. "EFFECT OF ELEVATED TEMPERATURE ON WEED SEED GERMINATION IN PADDY SOIL SEED BANK". En International Conference on Agriculture and Forestry. The International Institute of Knowledge Management (TIIKM), 2018. http://dx.doi.org/10.17501/icoaf.2017.3103.
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Ronevich, Joseph A., Chris San Marchi y Dorian K. Balch. "Temperature Effects on Fracture Thresholds of Hydrogen Precharged Stainless Steel Welds". En ASME 2017 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/pvp2017-65603.
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Austenitic stainless steels are typically used in hydrogen environments due to their resistance to hydrogen embrittlement; however, the behavior of welds is not as well understood and can vary from wrought base materials due to chemical composition differences and the presence of ferrite in the fusion zone of the weld. Applications of welded austenitic stainless steels exposed to hydrogen are not limited to room temperature but also include sub-ambient environments, which can have an additional effect on the degradation. In this study, fracture thresholds were measured of three different austenitic stainless steel welds in the hydrogen-precharged condition. Forged 304L, 316L, and 21Cr-6Ni-9Mn stainless steels were gas tungsten arc welded with 308L filler metal and machined into 3-pt bend bars for fracture testing. Crack growth resistance (J-R) curves were measured of the three welds in the hydrogen-precharged condition at ambient (293 K) and sub-ambient (223 K) temperatures to determine the effects of temperature on fracture threshold. Fracture thresholds were determined using elastic-plastic fracture mechanics through development of J-R curves to determine the stress intensity factor following standard practice for determination of fracture toughness. Fracture threshold tests for the welds revealed significant susceptibility to subcritical cracking when tested in the hydrogen-precharged condition. The 21-6-9/308L and 304L/308L welds exhibited some variability in fracture thresholds that did not appear to trend with temperature, while the 316L/308L weld exhibited a reduction of over 50% in fracture threshold at the lower temperature compared to room temperature. In addition to fracture testing, mini-tensile specimens were extracted from the weld region and tested at 293 K and 223 K in the hydrogen-precharged condition. Hydrogen-precharging slightly increased the yield strength relative to the as-welded condition for all three welds at both temperatures. For all three welds, hydrogen reduced the total elongation by 3–11% at 293 K, whereas reductions in total elongation from 50–64% were observed at 223 K (relative to room temperature without hydrogen). The role of slip planarity on hydrogen-induced degradation of ductility and fracture resistance is discussed as a function of temperature, nickel content, and hydrogen. The fracture surfaces were examined to elucidate the observed differences and similarities in mechanical properties.
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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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Dodge, Michael, Lars Magne Haldorsen, Mike Gittos y Kasra Sotoudeh. "Effect of Temperature on Resistance to Hydrogen Embrittlement of Dissimilar Metal Welds Subjected to SENB and SENT Testing". En ASME 2022 41st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/omae2022-79852.
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Abstract Dissimilar metal welds (DMWs), as manifested by low alloy steels welded with nickel alloys, are commonly used in subsea production systems. In such applications, there is a risk of hydrogen embrittlement, due to the use of cathodic protection. Historically, one of the most reliable means of establishing the resistance of DMWs to hydrogen embrittlement has been to conduct fracture mechanics-based tests, under representative service conditions. These tests have proved valuable in ranking the performance of various DMWs and, also, emulating the fracture morphologies observed in many subsea failures. Much of the established data from these tests has been generated using single edge notched bend (SENB) specimens, tested at the seabed temperature, to produce ‘tearing resistance’ J R-curves. However, whilst it is recognized that most failures have occurred after equipment has been shut down, there has been little exploration of how parameters, such as temperature and loading mode, influence the resistance to hydrogen-assisted cracking. This paper uses the results of SENB and single edge notched tension (SENT) tests on DMWs, consisting of 2.25Cr-1Mo Grade F22 welded with ERNiCrMo-3 (Alloy 625), to understand how temperature and level of constraint affect fracture resistance, at a range of temperatures (4 to 80°C). The merits and drawbacks of both techniques are summarized, alongside the practical implications for subsea components currently in operation.
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Andresen, Peter L. y Martin M. Morra. "Effect of Rising and Falling K Profiles on SCC Growth Rates in High Temperature Water". En ASME 2005 Pressure Vessels and Piping Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/pvp2005-71643.
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Effects of rising and falling stress intensity factor (K) profiles on the SCC growth rates of stainless steel and nickel alloys has been studied in high temperature water. Sophisticated test control software was used that changes loading (P) based on crack length (a) to achieve a specific K trajectory by controlling dK/da, not simply dP/dt. The majority of SCC problems develop adjacent to welds, which have a complex residual stress profile vs. wall thickness. This, coupled with the dependence of K on crack length, causes K to change as the crack grows, not per se with time (t). The effect of “K-dot” on crack tip strain rate and the associated crack growth rate is discussed, along with the repercussions to understanding and dispositioning SCC response.
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Tanaka, Tomohiro, Masamitsu Abe, Mitsuyoshi Nakatani y Hidenori Terasaki. "Effect of Postweld Heat Treatment Conditions on Mechanical Properties of 9Cr-1Mo-V Steel Welds for Pressure Vessel". En ASME 2017 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/pvp2017-65320.
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2¼Cr-1Mo steel and 2¼Cr-1Mo-V steel which have high performance in high-temperature and high-hydrogen service are widely used in fabricating process equipment for the oil refining industry. With the demand for plants using low-grade crude oil expected to increase in the future, equipment will after to operate at higher temperatures and higher pressures to meet such demand. In addition, the demand for gasification process equipment for coal using high-temperature strength material, which is to be used as an alternative of oil, is expected to grow also. Although 2¼Cr-1Mo steel and 2¼Cr-1Mo-V steel are adopted for high-temperature and high-pressure equipment used at temperatures up to 450°C, 9Cr-1Mo-V steel is suited for operation at even higher temperatures and pressures. It is used as structural material for boilers of power plants and elsewhere. The application of 9Cr-1Mo-V steel is anticipated for oil refineries. However, it is necessary for the welds to consider the hardness and the low-temperature toughness in addition to the high-temperature strength. In this paper, the effect of postweld heat treatment (PWHT) conditions on mechanical properties of 9Cr-1Mo-V steel welds was investigated. The PWHT conditions are organized with reference to the tempering parameter (Larson-Miller Parameter), with the heat treatment conducted in an LMP range of 20.46 to 22.42 × 103. As LMP increased, the hardness and high-temperature strength decreased. In the hardness distribution of the welds subjected to PWHT, the hardness tended to maximize near the bond of the heat affected zone (HAZ); however, applying heat treatment to materials with an LMP equal to or higher than 21.15 × 103 allowed a hardness of 260HV or less to be obtained. In terms of the high-temperature strength, the welds met the specified value as the 0.2 proof stress of ASME SA387-91-2, the base metal, under the PWHT conditions of an LMP equal to 22.42 × 103; the tensile strength was 0.9 times or more of the specified value. The Charpy absorbed energy increased with the LMP, and, when an LMP of 21.99 × 103 or more was used as the PWHT conditions, an absorbed energy of 60 J or more could be obtained at 0°C, as well. From the above results, the effect of PWHT conditions on mechanical properties of the welds is clarified, and it is suggested that 9Cr-1Mo-V steel can be used for the equipment in oil refining plants.
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Siefert, J., J. Parker y J. Foulds. "Effect of PWHT on the Fracture Toughness and Burst Test Response of Grade 91 Tube Weldments". En ASME 2018 Symposium on Elevated Temperature Application of Materials for Fossil, Nuclear, and Petrochemical Industries. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/etam2018-6714.
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Requirements for post-weld heat treatment (PWHT) of steels for pressure boundary component applications have been defined in terms of exceeding a minimum Charpy impact energy in an attempt to overcome the risk of brittle cracking. This approach can be excessively conservative since it does not properly assess resistance to cracking under the relatively static conditions encountered in pressure service. It is well established that under these conditions, cracking resistance, brittle or ductile, is more properly characterized using fracture toughness (KIc/JIc) type tests. The current paper describes room temperature fracture testing conducted via Charpy testing, fracture toughness testing, and tube (burst) pressurization of Grade 91 weldments after different PWHT conditions. The results obtained highlight (a) the excessive conservatism associated with use of Charpy data for assessing burst, (b) the value of fracture toughness testing to measure the sensitivity of fracture resistance to changes in PWHT (not seen in the Charpy data), and (c) the response of tube weldments with known flaws to pressurization. The observed burst pressure results are consistent with predictions made by analysis using the fracture toughness test results. Detailed analysis, including information from post-test examination of tube weldments and a fracture mechanics-based interpretation of test data for component flaw tolerance, provide a quantitative basis for specifying repair procedures and quality assurance methods for such welds. The findings illustrate the need to utilize long-established material fracture toughness testing methods and related properties to establish rules for construction and for post-construction repair. This is particularly true for the creep strength enhanced ferritic (CSEF) steels where the elevated temperature behavior may be compromised by potentially over-tempering weldments to meet requirements based simply on the results from inexpensive but inappropriate tests such as the Charpy test.
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Narayanan, Badri K. y Jon Ogborn. "Effect of Strain Ageing on Mechanical Properties of Pipeline Girth Welds". En ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-49818.
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Pipeline girth welds for on-shore and off-shore pipelines use a variety of arc welding processes. The trend towards strain based designs for line pipe installation and the effect of coatings for off-shore pipelines have resulted in evaluation and testing of pipe material subjected to strain ageing. However, very little work has been done to systematically study the effect on ferritic weld metal. This work details some initial work done on evaluating the effect of strain ageing on ferritic weld metal deposited with a 1.2 mm diameter flux cored wire under 75% Ar −25% CO2 shielding gas. Pipeline girth welds were welded on API Grade X-70 pipe and tested to get all weld metal tensile and Charpy V-Notch properties. The weld metal strength overmatched the base material by 7–9%. The ductile to brittle transition temperature for the weld metal was −40°C. The effect of strain ageing on weld metal properties was evaluated. All weld metal tensile samples were subjected to varying levels of pre-strain and ageing treatments to evaluate the effect on yield strength and post-yield behavior. An increase in yield strength after straining and ageing as well as the re-appearance of yield point is observed. Increase in pre-strain decreases elongation. Increase in ageing temperature delays the appearance of dynamic strain ageing. The activation energy for the increase in strength after strain ageing has been measured by assuming a diffusion controlled mechanism. Charpy V-Notch samples were taken to generate transition curves of weld metal after strain ageing and compared to the as-welded condition.
Informes sobre el tema "Effect of temperature on weeds"
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VanderGheynst, Jean, Michael Raviv, Jim Stapleton y Dror Minz. Effect of Combined Solarization and in Solum Compost Decomposition on Soil Health. United States Department of Agriculture, octubre de 2013. http://dx.doi.org/10.32747/2013.7594388.bard.
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In soil solarization, moist soil is covered with a transparent plastic film, resulting in passive solar heating which inactivates soil-borne pathogen/weed propagules. Although solarization is an effective alternative to soil fumigation and chemical pesticide application, it is not widely used due to its long duration, which coincides with the growing season of some crops, thereby causing a loss of income. The basis of this project was that solarization of amended soil would be utilized more widely if growers could adopt the practice without losing production. In this research we examined three factors expected to contribute to greater utilization of solarization: 1) investigation of techniques that increase soil temperature, thereby reducing the time required for solarization; 2) development and validation of predictive soil heating models to enable informed decisions regarding soil and solarization management that accommodate the crop production cycle, and 3) elucidation of the contributions of microbial activity and microbial community structure to soil heating during solarization. Laboratory studies and a field trial were performed to determine heat generation in soil amended with compost during solarization. Respiration was measured in amended soil samples prior to and following solarization as a function of soil depth. Additionally, phytotoxicity was estimated through measurement of germination and early growth of lettuce seedlings in greenhouse assays, and samples were subjected to 16S ribosomal RNA gene sequencing to characterize microbial communities. Amendment of soil with 10% (g/g) compost containing 16.9 mg CO2/g dry weight organic carbon resulted in soil temperatures that were 2oC to 4oC higher than soil alone. Approximately 85% of total organic carbon within the amended soil was exhausted during 22 days of solarization. There was no significant difference in residual respiration with soil depth down to 17.4 cm. Although freshly amended soil proved highly inhibitory to lettuce seed germination and seedling growth, phytotoxicity was not detected in solarized amended soil after 22 days of field solarization. The sequencing data obtained from field samples revealed similar microbial species richness and evenness in both solarized amended and non-amended soil. However, amendment led to enrichment of a community different from that of non-amended soil after solarization. Moreover, community structure varied by soil depth in solarized soil. Coupled with temperature data from soil during solarization, community data highlighted how thermal gradients in soil influence community structure and indicated microorganisms that may contribute to increased soil heating during solarization. Reliable predictive tools are necessary to characterize the solarization process and to minimize the opportunity cost incurred by farmers due to growing season abbreviation, however, current models do not accurately predict temperatures for soils with internal heat generation associated with the microbial breakdown of the soil amendment. To address the need for a more robust model, a first-order source term was developed to model the internal heat source during amended soil solarization. This source term was then incorporated into an existing “soil only” model and validated against data collected from amended soil field trials. The expanded model outperformed both the existing stable-soil model and a constant source term model, predicting daily peak temperatures to within 0.1°C during the critical first week of solarization. Overall the results suggest that amendment of soil with compost prior to solarization may be of value in agricultural soil disinfestations operations, however additional work is needed to determine the effects of soil type and organic matter source on efficacy. Furthermore, models can be developed to predict soil temperature during solarization, however, additional work is needed to couple heat transfer models with pathogen and weed inactivation models to better estimate solarization duration necessary for disinfestation.
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Samach, Alon, Douglas Cook y Jaime Kigel. Molecular mechanisms of plant reproductive adaptation to aridity gradients. United States Department of Agriculture, enero de 2008. http://dx.doi.org/10.32747/2008.7696513.bard.
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Annual plants have developed a range of different mechanisms to avoid flowering (exposure of reproductive organs to the environment) under adverse environmental conditions. Seasonal environmental events such as gradual changes in day length and temperature affect the timing of transition to flowering in many annual and perennial plants. Research in Arabidopsis and additional species suggest that some environmental signals converge on transcriptional regulation of common floral integrators such as FLOWERING LOCUS T (FT). Here we studied environmental induction of flowering in the model legume Medicago truncatula. Similarly to Arabidopsis, the transition to flowering in M. truncatula is hastened by long photoperiods and long periods of vernalization (4°C for 2-3 weeks). Ecotypes collected in Israel retain a vernalization response even though winter temperatures are way above 4°C. Here we show that this species is also highly responsive (flowers earlier) to mild ambient temperatures up to 19°C simulating winter conditions in its natural habitat. Physiological experiments allowed us to time the transition to flowering due to low temperatures, and to compare it to vernalization. We have made use of natural variation, and induced mutants to identify key genes involved in this process, and we provide here data suggesting that an FT gene in M.truncatula is transcriptionally regulated by different environmental cues. Flowering time was found to be correlated with MtFTA and MtFTB expression levels. Mutation in the MtFTA gene showed a late flowering phenotype, while over-expressing MtFTA in Arabidopsis complemented the ft- phenotype. We found that combination of 4°C and 12°C resulted in a synergistic increase in MtFTB expression, while combining 4°C and long photoperiods caused a synergistic increase in MtFTA expression. These results suggest that the two vernalization temperatures work through distinct mechanisms. The early flowering kalil mutant expressed higher levels of MtFTA and not MtFTB suggesting that the KALIL protein represses MtFTA specifically. The desert ecotype Sde Boker flowers earlier in response to short treatments of 8-12oc vernalization and expresses higher levels of MtFTA. This suggests a possible mechanism this desert ecotype developed to flower as fast as possible and finish its growth cycle before the dry period. MtFTA and FT expression are induced by common environmental cues in each species, and expression is repressed under short days. Replacing FT with the MtFTA gene (including regulatory elements) caused high MtFTA expression and early flowering under short days suggesting that the mechanism used to repress flowering under short days has diversified between the two species.The circadian regulated gene, GIGANTEA (GI) encodes a unique protein in Arabidopsis that is involved in flowering mechanism. In this research we characterized how the expression of the M.truncatula GI ortholog is regulated by light and temperature in comparison to its regulation in Arabidopsis. In Arabidopsis GI was found to be involved in temperature compensation to the clock. In addition, GI was found to be involved in mediating the effect of temperature on flowering time. We tested the influence of cold temperature on the MtGI gene in M.truncatula and found correlation between MtGI levels and extended periods of 12°C treatment. MtGI elevation that was found mostly after plants were removed from the cold influence preceded the induction of MtFT expression. This data suggests that MtGI might be involved in 12°C cold perception with respect to flowering in M.truncatula. GI seems to integrate diverse environmental inputs and translates them to the proper physiological and developmental outputs, acting through several different pathways. These research enabled to correlate between temperature and circadian clock in M.truncatula and achieved a better understanding of the flowering mechanism of this species.
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Nathan, Harms y Cronin James. Variability in weed biological control : effects of foliar nitrogen on larval development and dispersal of the alligatorweed flea beetle, Agasicles hygrophila. Engineer Research and Development Center (U.S.), septiembre de 2021. http://dx.doi.org/10.21079/11681/41886.
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Host quality can have dramatic effects on performance of biological control agents but its importance is understudied. We used a combination of field measurements and laboratory experiments to determine the range of foliar nitrogen (FN) that larvae of the alligatorweed flea beetle (Agasicles hygrophila) are exposed to in the field and its importance to larval development and dispersal. Seasonal variability in FN was assessed at field sites spanning southern to northern Louisiana every 2–3 weeks during the growing season for four years. In a series of laboratory experiments, alligatorweed FN was manipulated to examine its influence on larval development and survival (under different temperature regimes), adult biomass, and dispersal of the biological control agent, A. hygrophila. Foliar nitrogen and rearing temperature had strong independent effects on larval development rate. We demonstrated that increasing nitrogen in leaf tissues shortens larval A. hygrophila developmental time and increases survival to adulthood, regardless of exposure temperature during development. It also suggests that foliar nitrogen may have important effects on biological control of alligatorweed, particularly as a result of seasonal variation in temperature and plant nutrition at field sites and could contribute to observed variation in A. hygrophila efficacy in the field.
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Yahav, Shlomo, John Brake y Orna Halevy. Pre-natal Epigenetic Adaptation to Improve Thermotolerance Acquisition and Performance of Fast-growing Meat-type Chickens. United States Department of Agriculture, septiembre de 2009. http://dx.doi.org/10.32747/2009.7592120.bard.
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: The necessity to improve broiler thermotolerance and performance led to the following hypothesis: (a) thethermoregulatory-response threshold for heat production can be altered by thermal manipulation (TM) during incubation so as to improve the acquisition of thermotolerance in the post-hatch broiler;and (b) TM during embryogenesis will improve myoblast proliferation during the embryonic and post-hatch periods with subsequent enhanced muscle growth and meat production. The original objectives of this study were as follow: 1. to assess the timing, temperature, duration, and turning frequency required for optimal TM during embryogenesis; 2. to evaluate the effect of TM during embryogenesis on thermoregulation (heat production and heat dissipation) during four phases: (1) embryogenesis, (2) at hatch, (3) during growth, and (4) during heat challenge near marketing age; 3. to investigate the stimulatory effect of thermotolerance on hormones that regulate thermogenesis and stress (T₄, T₃, corticosterone, glucagon); 4. to determine the effect of TM on performance (BW gain, feed intake, feed efficiency, carcass yield, breast muscle yield) of broiler chickens; and 5. to study the effect of TM during embryogenesis on skeletal muscle growth, including myoblast proliferation and fiber development, in the embryo and post-hatch chicks.This study has achieved all the original objectives. Only the plasma glucagon concentration (objective 3) was not measured as a result of technical obstacles. Background to the topic: Rapid growth rate has presented broiler chickens with seriousdifficulties when called upon to efficiently thermoregulate in hot environmental conditions. Being homeotherms, birds are able to maintain their body temperature (Tb) within a narrow range. An increase in Tb above the regulated range, as a result of exposure to environmental conditions and/or excessive metabolic heat production that often characterize broiler chickens, may lead to a potentially lethal cascade of irreversible thermoregulatory events. Exposure to temperature fluctuations during the perinatal period has been shown to lead to epigenetic temperature adaptation. The mechanism for this adaptation was based on the assumption that environmental factors, especially ambient temperature, have a strong influence on the determination of the “set-point” for physiological control systems during “critical developmental phases.” In order to sustain or even improve broiler performance, TM during the period of embryogenesis when satellite cell population normally expand should increase absolute pectoralis muscle weight in broilers post-hatch. Major conclusions: Intermittent TM (39.5°C for 12 h/day) during embryogenesis when the thyroid and adrenal axis was developing and maturing (E7 to E16 inclusive) had a long lasting thermoregulatory effect that improved thermotolerance of broiler chickens exposed to acute thermal stress at market age by lowering their functional Tb set point, thus lowering metabolic rate at hatch, improving sensible heat loss, and significantly decreasing the level of stress. Increased machine ventilation rate was required during TM so as to supply the oxygen required for the periods of increased embryonic development. Enhancing embryonic development was found to be accomplished by a combination of pre-incubation heating of embryos for 12 h at 30°C, followed by increasing incubation temperature to 38°C during the first 3 days of incubation. It was further facilitated by increasing turning frequency of the eggs to 48 or 96 times daily. TM during critical phases of muscle development in the late-term chick embryo (E16 to E18) for 3 or 6 hours (39.5°C) had an immediate stimulatory effect on myoblast proliferation that lasted for up to two weeks post-hatch; this was followed by increased hypertrophy at later ages. The various incubation temperatures and TM durations focused on the fine-tuning of muscle development and growth processes during late-term embryogenesis as well as in post-hatch chickens.
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Nanstad, R. K., G. M. Goodwin y M. J. Swindeman. Effects of nonstandard heat treatment temperatures on tensile and Charpy impact properties of carbon-steel casting repair welds. Office of Scientific and Technical Information (OSTI), abril de 1993. http://dx.doi.org/10.2172/10144288.
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Sawatzky, H., I. Clelland y J. Houde. Effect of topping temperature on Cold Lake asphalt's susceptibility to temperature. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 1991. http://dx.doi.org/10.4095/304486.
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Cheng, Juei-Teng y Lowell E. Wenger. Josephson Effect Research in High-Temperature Superconductors. Fort Belvoir, VA: Defense Technical Information Center, agosto de 1988. http://dx.doi.org/10.21236/ada201483.
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Korinko, P. EFFECT OF FILTER TEMPERATURE ON TRAPPING ZINC VAPOR. Office of Scientific and Technical Information (OSTI), marzo de 2011. http://dx.doi.org/10.2172/1025512.
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Sun, W. D., Fred H. Pollak, Patrick A. Folkes y Godfrey A. Gumbs. Band-Bending Effect of Low-Temperature GaAs on a Pseudomorphic Modulation-Doped Field-Effect Transistor. Fort Belvoir, VA: Defense Technical Information Center, marzo de 1999. http://dx.doi.org/10.21236/ada361412.
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Price, J. T., J. F. Gransden, M. A. Khan y B. D. Ryan. Effect of selected minerals on high temperature properties of coke. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 1992. http://dx.doi.org/10.4095/304533.
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