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Matteo Smerlak - One of the best experts on this subject based on the ideXlab platform.
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Thermal Time and TolmanEhrenfest effect: temperature as the speed of Time
Classical and Quantum Gravity, 2011Co-Authors: Carlo Rovelli, Matteo SmerlakAbstract:The notion of Thermal Time has been introduced as a possible basis for a fully general-relativistic thermodynamics. Here we study this notion in the restricted context of stationary spaceTimes. We show that the Tolman-Ehrenfest effect (in a stationary gravitational field, temperature is not constant in space at Thermal equilibrium) can be derived very simply by applying the equivalence principle to a key property of Thermal Time at equilibrium: temperature is the rate of Thermal Time with respect to proper Time - the 'speed of (Thermal) Time '. Unlike other published derivations of the Tolman-Ehrenfest law, this one is free from any further dynamical assumption, thereby illustrating the physical import of the notion of Thermal Time.
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Thermal Time and Tolman-Ehrenfest effect: 'temperature as the speed of Time'
Classical and Quantum Gravity, 2011Co-Authors: Carlo Rovelli, Matteo SmerlakAbstract:The notion of Thermal Time has been introduced as a possible basis for a fully general-relativistic thermodynamics. Here we study this notion in the restricted context of stationary spaceTimes. We show that the Tolman–Ehrenfest effect (in a stationary gravitational field, temperature is not constant in space at Thermal equilibrium) can be derived very simply by applying the equivalence principle to a key property of Thermal Time; at equilibrium, temperature is the rate of Thermal Time with respect to proper Time—the 'speed of (Thermal) Time'. Unlike other published derivations of the Tolman–Ehrenfest relation, this one is free from any further dynamical assumption, thereby illustrating the physical import of the notion of Thermal Time.
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Thermal Time and the Tolman-Ehrenfest effect: temperature as the "speed of Time
Classical and Quantum Gravity, 2011Co-Authors: Carlo Rovelli, Matteo SmerlakAbstract:The Thermal Time hypothesis has been introduced as a possible basis for a fully general-relativistic thermodynamics. Here we use the notion of Thermal Time to study Thermal equilibrium on stationary spaceTimes. Notably, we show that the Tolman-Ehrenfest effect (the variation of temperature in space so that T\sqrt{g_{00}} remains constant) can be reappraised as a manifestation of this fact: at Thermal equilibrium, temperature is locally the rate of flow of Thermal Time with respect to proper Time - pictorially, "the speed of (Thermal) Time". Our derivation of the Tolman-Ehrenfest effect makes no reference to the physical mechanisms underlying Thermalization, thus illustrating the import of the notion of Thermal Time.
Carlo Rovelli - One of the best experts on this subject based on the ideXlab platform.
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Thermal Time and TolmanEhrenfest effect: temperature as the speed of Time
Classical and Quantum Gravity, 2011Co-Authors: Carlo Rovelli, Matteo SmerlakAbstract:The notion of Thermal Time has been introduced as a possible basis for a fully general-relativistic thermodynamics. Here we study this notion in the restricted context of stationary spaceTimes. We show that the Tolman-Ehrenfest effect (in a stationary gravitational field, temperature is not constant in space at Thermal equilibrium) can be derived very simply by applying the equivalence principle to a key property of Thermal Time at equilibrium: temperature is the rate of Thermal Time with respect to proper Time - the 'speed of (Thermal) Time '. Unlike other published derivations of the Tolman-Ehrenfest law, this one is free from any further dynamical assumption, thereby illustrating the physical import of the notion of Thermal Time.
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Thermal Time and Tolman-Ehrenfest effect: 'temperature as the speed of Time'
Classical and Quantum Gravity, 2011Co-Authors: Carlo Rovelli, Matteo SmerlakAbstract:The notion of Thermal Time has been introduced as a possible basis for a fully general-relativistic thermodynamics. Here we study this notion in the restricted context of stationary spaceTimes. We show that the Tolman–Ehrenfest effect (in a stationary gravitational field, temperature is not constant in space at Thermal equilibrium) can be derived very simply by applying the equivalence principle to a key property of Thermal Time; at equilibrium, temperature is the rate of Thermal Time with respect to proper Time—the 'speed of (Thermal) Time'. Unlike other published derivations of the Tolman–Ehrenfest relation, this one is free from any further dynamical assumption, thereby illustrating the physical import of the notion of Thermal Time.
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Thermal Time and the Tolman-Ehrenfest effect: temperature as the "speed of Time
Classical and Quantum Gravity, 2011Co-Authors: Carlo Rovelli, Matteo SmerlakAbstract:The Thermal Time hypothesis has been introduced as a possible basis for a fully general-relativistic thermodynamics. Here we use the notion of Thermal Time to study Thermal equilibrium on stationary spaceTimes. Notably, we show that the Tolman-Ehrenfest effect (the variation of temperature in space so that T\sqrt{g_{00}} remains constant) can be reappraised as a manifestation of this fact: at Thermal equilibrium, temperature is locally the rate of flow of Thermal Time with respect to proper Time - pictorially, "the speed of (Thermal) Time". Our derivation of the Tolman-Ehrenfest effect makes no reference to the physical mechanisms underlying Thermalization, thus illustrating the import of the notion of Thermal Time.
Nathan L. Cline - One of the best experts on this subject based on the ideXlab platform.
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Wet‑Thermal Time and Plant Available Water in the Seedbeds and Root Zones Across the Sagebrush Steppe Ecosystem of the Great Basin
2014Co-Authors: Nathan L. ClineAbstract:Wet‐Thermal Time and Plant Available Water in the Seedbeds and Root Zones Across the Sagebrush Steppe Ecosystem of the Great Basin Nathan L. Cline Department of Plant and Wildlife Sciences, BYU Doctor of Philosophy Following wildfires, plant materials are direct-seeded to limit erosion and annual weed invasion. Seedlings often fail to establish because selected plant materials are not always well adapted to local soil moisture and temperature conditions. In an effort to help improve plant materials selection and to evaluate sites potential revegetation, we have worked toward developing methodology to predict germination and root growth based on site specific soil moisture and temperature conditions. First, we characterized the seedbed environment of 24 sagebrush (Artemisia spp.) steppe sites throughout the Intermountain West to determine the wetThermal Time of five temperature ranges relevant to germination response and Thermal-Time model accuracy (Chapter 1). Second, we predicted potential germination for 31 plant materials at those same sites (Chapter 2). Third, in preparation to predict root growth at multiple sites, we characterized the drying patterns and the associated plant-available water for in the seedling root zone across nine woodland (Juniperus spp. and Pinus spp.) sites (Chapter 3). For all of these studies, we determined the effects of tree reduction and tree infilling phase at Time of tree reduction. Our key findings are that seedbeds generally sum most wet-Thermal Time at temperature ranges where the germination rates fit Thermal accumulation models quite well (R2 ≥ 0.7). The majority of plant materials summed enough wet-Thermal Time for a potential germination at most sites during the fall, early spring, and late spring. Soil drying primarily occurs from the soil surface downward. Drying rates and Plant available water associated with the first drying event increase with increasing soil depth. Root zone (1-30 cm) plant-available water increases before and decreases after the first spring drying event with increasing soil depth. Tree removal with increasing pretreatment tree infilling phase generally added progress toward germination, plant available water, and wet-Thermal Time in the seedbed and root zones of the sagebrush steppe in the Great Basin. Because soil moisture and temperature does not appear to be limiting for potential germination, combining germination and root growth models to create a more comprehensive model may allow for a more robust prediction for seedling survival. For either root growth or combined germination and root growth models, plant available water and wet-Thermal Time before the first spring drying period hold the most potential for successfully predicting seedling survival.
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wet Thermal Time and plant available water in the seedbeds and root zones across the sagebrush steppe ecosystem of the great basin
2014Co-Authors: Nathan L. ClineAbstract:Wet‐Thermal Time and Plant Available Water in the Seedbeds and Root Zones Across the Sagebrush Steppe Ecosystem of the Great Basin Nathan L. Cline Department of Plant and Wildlife Sciences, BYU Doctor of Philosophy Following wildfires, plant materials are direct-seeded to limit erosion and annual weed invasion. Seedlings often fail to establish because selected plant materials are not always well adapted to local soil moisture and temperature conditions. In an effort to help improve plant materials selection and to evaluate sites potential revegetation, we have worked toward developing methodology to predict germination and root growth based on site specific soil moisture and temperature conditions. First, we characterized the seedbed environment of 24 sagebrush (Artemisia spp.) steppe sites throughout the Intermountain West to determine the wetThermal Time of five temperature ranges relevant to germination response and Thermal-Time model accuracy (Chapter 1). Second, we predicted potential germination for 31 plant materials at those same sites (Chapter 2). Third, in preparation to predict root growth at multiple sites, we characterized the drying patterns and the associated plant-available water for in the seedling root zone across nine woodland (Juniperus spp. and Pinus spp.) sites (Chapter 3). For all of these studies, we determined the effects of tree reduction and tree infilling phase at Time of tree reduction. Our key findings are that seedbeds generally sum most wet-Thermal Time at temperature ranges where the germination rates fit Thermal accumulation models quite well (R2 ≥ 0.7). The majority of plant materials summed enough wet-Thermal Time for a potential germination at most sites during the fall, early spring, and late spring. Soil drying primarily occurs from the soil surface downward. Drying rates and Plant available water associated with the first drying event increase with increasing soil depth. Root zone (1-30 cm) plant-available water increases before and decreases after the first spring drying event with increasing soil depth. Tree removal with increasing pretreatment tree infilling phase generally added progress toward germination, plant available water, and wet-Thermal Time in the seedbed and root zones of the sagebrush steppe in the Great Basin. Because soil moisture and temperature does not appear to be limiting for potential germination, combining germination and root growth models to create a more comprehensive model may allow for a more robust prediction for seedling survival. For either root growth or combined germination and root growth models, plant available water and wet-Thermal Time before the first spring drying period hold the most potential for successfully predicting seedling survival.
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predicting germination in semi arid wildland seedbeds ii field validation of wet Thermal Time models
Environmental and Experimental Botany, 2012Co-Authors: Jennifer K Rawlins, Bruce A Roundy, Dennis Egget, Nathan L. ClineAbstract:Abstract Accurate prediction of germination for species used for semi-arid land revegetation would support selection of plant materials for specific climatic conditions and sites. Wet Thermal-Time models predict germination Time by summing progress toward germination subpopulation percentages as a function of temperature across intermittent wet periods or within singular wet periods. Wet periods may be defined by any reasonable seedbed water potential above which seeds are expected to imbibe sufficiently to germinate. These models may be especially applicable to the Artemisia steppe of the western U.S.A. where water availability limits germination in summer and early fall while cool temperatures limit germination in late fall, winter, and spring when soil water is available. To test accuracy of wet Thermal-Time models we placed seedbags with seeds of five species commonly used in wildland revegetation, as well as two collections of the invasive annual grass, Bromus tectorum L. into Artemisia tridentata Nutt. ssp. wyomingensis Beetle and Young zone seedbeds for 19 field incubation periods over four seasons. Hourly surface (1–3 cm) soil temperatures and soil water potentials were measured near the seedbags. These data were input into Thermal-Time models which predicted Time to germination for each seedbag retrieval date. Binomial data representing agreement (1) or lack of agreement (0) of predicted and actual germination for each retrieval date were analyzed using logistic regression. Thermal summation method, season, water potential threshold, and species most affected accuracy of predictions ( P
Jean Roger-estrade - One of the best experts on this subject based on the ideXlab platform.
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Integration of Thermal Time and hydroTime models to describe the development and growth of temperate earthworms
Soil Biology and Biochemistry, 2013Co-Authors: Pascaline Moreau-valancogne, Michel Bertrand, Martin Holmstrup, Jean Roger-estradeAbstract:Thermal Time and hydroTime models have been developed to predict the development of various organisms with life traits regulated by temperature and humidity. They consider development rate to increase linearly with temperature or water availability above a base temperature or water potential. The objective of this work was to integrate concepts from Thermal Time and hydroTime models to describe the combined effects of temperature and water potential on development and growth of temperate earthworms. The model was calibrated with experimental data from the scientific literature. When water potential conditions were favourable for earthworms, the Thermal Time model suggested a linear increase in cocoon development and growth with increasing temperature between the base temperature (T-b) and the optimal temperature (T-o) followed by a linear decline in these parameters between T-o and the ceiling temperature (T-c). The model predicted T-b values of 4.3 degrees C and 2.5 degrees C, T-o values of 21.2 degrees C and 17.6 degrees C, and T-c values of 38.1 degrees C and 25.8 degrees C for cocoon development and growth, respectively. Development and growth rates were maximal at optimal temperatures T-o of 21.2 and 17.6 degrees C, respectively. Cocoon development rate and growth rate increased linearly between T-b and T-o. Above T-o, development and growth rates decreased linearly until T-c, at which both rates are null. For anecic species, T-c was found to be 38.1 and 25.8 degrees C for cocoon development and growth, respectively. At constant temperature, cocoon development and growth decreased linearly with water potential, as described by the hydroTime model. Base water potential (the water potential at which life history parameter values are zero) was found to be close to very wet conditions for growth (-23 and -10 kPa for juveniles and adults, respectively) and cocoon production (-32 kPa). The integrated model incorporated the effect of water potential into the Thermal Time model. Water potential modified the three cardinal temperatures (T-b, T-o and T-c) for growth and the growth rate at T-o, but not the slopes of the relationships between growth rate and temperature. Thus, increasing water potential reduced the temperature range at which earthworm growth was possible and the maximum growth at the optimal temperature. No data was available to validate this model for cocoon development. (c) 2013 Elsevier Ltd. All rights reserved.
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Integration of Thermal Time and hydroTime models to describe the development and growth of temperate earthworms
Soil Biology and Biochemistry, 2013Co-Authors: Pascaline Moreau-valancogne, Michel Bertrand, Martin Holmstrup, Jean Roger-estradeAbstract:Abstract Thermal Time and hydroTime models have been developed to predict the development of various organisms with life traits regulated by temperature and humidity. They consider development rate to increase linearly with temperature or water availability above a base temperature or water potential. The objective of this work was to integrate concepts from Thermal Time and hydroTime models to describe the combined effects of temperature and water potential on development and growth of temperate earthworms. The model was calibrated with experimental data from the scientific literature. When water potential conditions were favourable for earthworms, the Thermal Time model suggested a linear increase in cocoon development and growth with increasing temperature between the base temperature ( T b ) and the optimal temperature ( T o ) followed by a linear decline in these parameters between T o and the ceiling temperature ( T c ). The model predicted T b values of 4.3 °C and 2.5 °C, T o values of 21.2 °C and 17.6 °C, and T c values of 38.1 °C and 25.8 °C for cocoon development and growth, respectively. Development and growth rates were maximal at optimal temperatures T o of 21.2 and 17.6 °C, respectively. Cocoon development rate and growth rate increased linearly between T b and T o . Above T o , development and growth rates decreased linearly until T c , at which both rates are null. For anecic species, T c was found to be 38.1 and 25.8 °C for cocoon development and growth, respectively. At constant temperature, cocoon development and growth decreased linearly with water potential, as described by the hydroTime model. Base water potential (the water potential at which life history parameter values are zero) was found to be close to very wet conditions for growth (−23 and −10 kPa for juveniles and adults, respectively) and cocoon production (−32 kPa). The integrated model incorporated the effect of water potential into the Thermal Time model. Water potential modified the three cardinal temperatures ( T b , T o and T c ) for growth and the growth rate at T o , but not the slopes of the relationships between growth rate and temperature. Thus, increasing water potential reduced the temperature range at which earthworm growth was possible and the maximum growth at the optimal temperature. No data was available to validate this model for cocoon development.
Jhonathan E Ephrath - One of the best experts on this subject based on the ideXlab platform.
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a Thermal Time model for predicting parasitism of orobanche cumana in irrigated sunflower field validation
Field Crops Research, 2012Co-Authors: Hanan Eizenberg, J Hershenhorn, Guy Achdari, Jhonathan E EphrathAbstract:Abstract A major part of its life cycle, the root parasitic weed broomrapes ( Orobanche and Phelipanche species) grow underground. Predicting their developmental stages underground is a challenge that can be met by using a modeling approach, as reported for Phelipanche aegyptiaca and Orobanche cumana , in sunflower grown under temperature-controlled conditions. In those studies the relation between parasitism dynamics and Thermal Time was described by Sigmoid functions. To confirm these relations and calibrate the parameters under field conditions, a 5-year field study was conducted in nine fields in Israel, in various locations under different climatic conditions. As a result, a robust Thermal Time model that allows precisely estimating the parasitism dynamics was developed. Development of O. cumana in the subsurface was detected, monitored and recorded non-destructively in situ by the use of a minirhizotron. The data from field experiments, conducted in 2006, 2007, 2008 and 2009, were used for model calibration. For model validation, five field experiments were independently performed in 2009 and 2010. To relate the number of attachments and shoot emergence to Thermal Time, the following equations were tested: Sigmoid, Gompertz (both three-parameter) and Weibull (four parameters with lag phase). In the calibration studies, the number of attachments was best fitted to Thermal Time using the Weibull equation, which further resulted in very good fit in the validation studies for number of attachments (RMSE = 0.066; R 2 = 0.99) and O. cumana shoot emergence (RMSE = 0.0096; R 2 = 0.97). The Weibull equation thus adds a biological dimension (lag phase) to the model that the other equations lack, as the lag phase allows estimating the precise timing of parasite attachment to host roots and shoot emergence. This information is crucial in any attempt to develop control strategies for these parasitic weeds.
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A Thermal Time model for predicting parasitism of Orobanche cumana in irrigated sunflower—Field validation
Field Crops Research, 2012Co-Authors: Hanan Eizenberg, J Hershenhorn, Guy Achdari, Jhonathan E EphrathAbstract:Abstract A major part of its life cycle, the root parasitic weed broomrapes ( Orobanche and Phelipanche species) grow underground. Predicting their developmental stages underground is a challenge that can be met by using a modeling approach, as reported for Phelipanche aegyptiaca and Orobanche cumana , in sunflower grown under temperature-controlled conditions. In those studies the relation between parasitism dynamics and Thermal Time was described by Sigmoid functions. To confirm these relations and calibrate the parameters under field conditions, a 5-year field study was conducted in nine fields in Israel, in various locations under different climatic conditions. As a result, a robust Thermal Time model that allows precisely estimating the parasitism dynamics was developed. Development of O. cumana in the subsurface was detected, monitored and recorded non-destructively in situ by the use of a minirhizotron. The data from field experiments, conducted in 2006, 2007, 2008 and 2009, were used for model calibration. For model validation, five field experiments were independently performed in 2009 and 2010. To relate the number of attachments and shoot emergence to Thermal Time, the following equations were tested: Sigmoid, Gompertz (both three-parameter) and Weibull (four parameters with lag phase). In the calibration studies, the number of attachments was best fitted to Thermal Time using the Weibull equation, which further resulted in very good fit in the validation studies for number of attachments (RMSE = 0.066; R 2 = 0.99) and O. cumana shoot emergence (RMSE = 0.0096; R 2 = 0.97). The Weibull equation thus adds a biological dimension (lag phase) to the model that the other equations lack, as the lag phase allows estimating the precise timing of parasite attachment to host roots and shoot emergence. This information is crucial in any attempt to develop control strategies for these parasitic weeds.
