Higher Base Temperature Research Articles

Seed Fatty Acid Changes Germination Response to Temperature and Water Potentials in Six Sesame (Sesamum indicum L.) Cultivars: Estimating the Cardinal Temperatures

Seed fatty acid composition can influence seed quality, followed by seed germination and optimal seedling establishment. Therefore, to find out the role of seed fatty acids in changing the cardinal temperatures of six sesame cultivars germinated at different temperatures (10, 15, 20, 25, 30, 35, 40, and 45 °C) and water potentials (0, −0.2, −0.4, −0.6, −0.8, −1, and −1.2 MPa), an experiment was conducted. The dent-like, beta, and segmented models were used to analyze the data. The results showed that different cultivars at optimal temperatures show different reactions to environmental conditions; for example, the germination rate in Halil and Dashtestan2 cultivars followed the dent-like model, Darab1, Oltan, and Yellow-White followed the beta model, and Naz followed the segmented model. Based on the results, the average temperature in all water potentials of the base, sub-optimal, supra-optimum, and ceiling was determined as 12.6, 33.3, 38, and 43.9 °C, respectively, once the superior dent-like model was used. Using the superior beta model, the average temperatures in the base, optimum, and ceiling were 8.5, 31.2, and 50.5 °C. In contrast, when the segmented superior model was used, they were determined to be 7.6, 34, and 44.1 °C, respectively. According to the results, it can be stated that the Halil cultivar with more oleic acid and less linoleic acid has a higher base temperature and is more adapted to high temperatures for later cultivations. The Naz cultivar with a long biological clock is suitable for earlier cultivations. The ceiling temperature of these cultivars was also affected by the osmotic potential and decreased significantly with the increase in osmotic levels. Dashtestan2 cultivar with a high germination rate could be chosen for cultivation in water and high-temperature stress areas.

Comparison of the effect of temperature and water potential on the seed germination of five Pedicularis kansuensis populations from the Qinghai-Tibet plateau.

Temperature and water potentials are considered the most critical environmental factors in seed germinability and subsequent seedling establishment. The thermal and water requirements for germination are species-specific and vary with the environment in which seeds mature from the maternal plants. Pedicularis kansuensis is a root hemiparasitic weed that grows extensively in the Qinghai-Tibet Plateau's degraded grasslands and has seriously harmed the grasslands ecosystem and its utilization. Information about temperatures and water thresholds in P. kansuensis seed germination among different populations is useful to predicting and managing the weed's distribution in degraded grasslands. The present study evaluated the effects of temperature and water potentials on P. kansuensis seed germination in cool and warm habitats, based on thermal time and hydrotime models. The results indicate that seeds from cool habitats have a higher base temperature than those from warm habitats, while there is no detectable difference in optimum and ceiling temperatures between habitats. Seed germination in response to water potential differed among the five studied populations. There was a negative correlation between the seed populations' base water potential for 50% (Ψ b(50)) germination and their hydrotime constant (θ H). The thermal time and hydrotime models were good predictors of five populations' germination time in response to temperature and water potentials. Consequently, future studies should consider the effects of maternal environmental conditions on seed germination when seeking effective strategies for controlling hemiparasitic weeds in alpine regions.

Experimental investigation of a topology-optimized phase change heat sink optimized for natural convection

In this study, a topology-optimized heat sink is developed and applied to electronics cooling by utilizing a phase change material interspersed through a finned structure. The topology optimization is performed by the minimization of the global thermal compliance in the solution of the modified momentum equation with the Boussinesq approximation to account for natural convection. The optimized heat sink, namely the natural convection topology-optimized heat sink, was fabricated by Selective Laser Melting, a metal additive manufacturing technique. The natural convection topology-optimized heat sink was experimentally characterized based on its base temporal temperature and its operation time. The performance of our newly developed heat sink was then evaluated by comparing against a conventional heat sink design, a baseline design with no surface enhancements, and a second topology-optimized heat sink based on heat conduction. The results show that the natural convection topology-optimized heat sink has a lower base temperature compared to the conventional heat sink, but higher base temperature than the second topology-optimized heat sink during the PCM melting phase. However, the natural convection topology-optimized heat sink has an operation time which is 31.0% longer than all the other heat sinks with enhanced structures. Through visualization of the melting process, we can deduce that the longer operation time of the natural convection topology-optimized heat sink is primarily due to the movement of the melt front which results in a slower melting, while optimizing natural convection of the melted material. These mechanisms maintain a reasonably low heat sink base temperature.

Germination response of black nightshade (Solanum nigrum) to temperature and the establishment of a thermal time model

AbstractBlack nightshade (Solanum nigrum L.) is one of the worst weeds in crop fields, and it spreads mainly by the dispersal of seeds. Temperature is one of the key environmental factors affecting seed germination. We investigated the seed germination response to temperature in six populations of S. nigrum from mid- to northern China and derived mathematical models from germination data. The results showed that S. nigrum seeds exhibit distinct germination responses to temperature within the range of 15 to 35 C. The optimum temperature for populations XJ1600, JL1697, and HLJ2134 was 30 C, and those for populations NMG1704, HN2160, and LN2209 were 25, 20, and 15 C, respectively. Based on the nonlinear fitting and thermal time models, the predicted base temperatures of the six populations ranged from 2.3 to 6.4 C, and the required accumulated growing degree days (GDD) ranged from 50.3 to 106.0 C·d. The base temperatures and the accumulated GDD for germination differed among populations, and there was a significant negative correlation. HLJ2134 population required a high base temperature and accumulated GDD for germination, indicating that it might be highly adapted to a warmer and moister environment. Based on the different germination responses of S. nigrum populations to temperature, the thermal time model reflects an innate relationship between base temperature and accumulated GDD required for initiation of seed germination, which provides a better basis for predicting seedling emergence and the timing for optimal control of S. nigrum under field conditions.

Maximal steady-state entanglement and perfect thermal rectification in non-equilibrium interacting XXZ chains

We propose a scheme for dissipative preparation of maximal entanglement in a two-qubit Heisenberg XXZ model interacting asymmetrically with two independent boson thermal reservoirs with different temperature. One reservoir is common to both qubits, while the other is connected with just one qubit. We analytically and numerically investigate the steady-state entanglement of the qubits, based on the Markovian quantum master equation. We study the influence of the inherent asymmetry induced by the asymmetrically couplings of qubits to the reservoirs, on the steady-state entanglement of the qubits. While the temperature gradient of reservoirs generally deteriorate quantum correlations, we show that in the presence of the inherent asymmetry, the maximal entanglement can revive by increasing temperature gradient, at high base temperature of the reservoirs. We find that by turning on the asymmetry, perfect rectification can be achieved without introducing any additional asymmetry to the system. We also discover that the obtained perfect rectification is associated with maximizing of the steady-state entanglement.

Modeling the Adhesion Bonding Strength in Injection Overmolding of Polypropylene Parts.

In this work, the bonding strength of overmolded polypropylene is investigated and modeled. A T-joint specimen was designed to replicate the bonding between a base and an overmolded stem made of the same polymer: a previously molded plaque was used for the base, and the stem was directly overmolded. The effect of melt temperature, holding pressure, and localized heating was investigated following the design of experiments approach. Both the melt and base temperature positively affect the welding strength. On the contrary, the holding pressure negatively contributed, as the crystallization temperature significantly increases with pressure. Then, the bonding strength of the specimens was predicted using a non-isothermal healing model. Moreover, the quadratic distance of diffusion (based on the self-diffusion model) was calculated and correlated with the bonding strength prediction. The non-isothermal healing model well predicts the bonding strength when the reptation time is calculated within the first 0.09 s of the interface temperature evolution. The prediction error ranges from 1% to 35% for the specimens overmolded at high and low melt and base temperatures, respectively.

Modeling Temperature Variations Using Monte Carlo Simulation: Implications for Estimation of the Postmortem Interval Based on Insect Development Times*, †.

The association between insect development and temperature is well established. Thermal summation using accumulated degree-day measures is commonly used. However, the time at which evidence is collected is important in these estimates. The aim of this study was to provide a simulated model of the effect of temperatures on six dipteran species commonly associated with cadavers, from the death scene to the refrigerator, and finally at the time of autopsy. Temperatures measurements were sampled over a 16-month period from the external environment (external to the mortuary), within the mortuary refrigerator, and within the mortuary autopsy suite. Monte Carlo simulation using accumulated degree-days (ADD) was used to estimate the variations based on the mean and standard deviation of the temperature measurements. It was found that there was a negative correlation between the base temperature of the fly species (lowest temperature at which the flies will survive) and developmental likelihood. Species with high base temperatures (Chrysomya albiceps, Chrysomya chloropyga, and Musca domestica) were less likely to continue development in refrigerators than species with lower base temperatures (Lucilia sericata and Piophila casei). The findings of this study highlight the importance of recording temperature measurements and the period of refrigeration on PMI estimation especially when continued development occurs in spite of a period of cooling of the insect evidence.

Steady-state entanglement and coherence of two coupled qubits in equilibrium and nonequilibrium environments

We investigate analytically and numerically the steady-state entanglement and coherence of two coupled qubits each interacting with a local boson or fermion reservoir, based on the Bloch-Redfield master equation beyond the secular approximation. We find that there is non-vanishing steady-state coherence in the nonequilibrium scenario, which grows monotonically with the nonequilibrium condition quantified by the temperature difference or chemical potential difference of the two baths. The steady-state entanglement in general is a non-monotonic function of the nonequilibrium condition as well as the bath parameters in the equilibrium setting. We also find that weak inter-qubit coupling and high base temperature or chemical potential of the baths can strongly suppress the steady-state entanglement and coherence, regardless of the strength of the nonequilibrium condition. On the other hand, the energy detuning of the two qubits, when used in a compensatory way with the nonequilibrium condition, can lead to significant enhancement of the steady-state entanglement in some parameter regimes. In addition, the qubits typically have a stronger steady-state entanglement when coupled to fermion baths exchanging particle with the system than boson baths exchanging energy with the system under similar conditions. We also discussed the possible experimental realization of measuring the steady state entanglement and coherence for coupled qubits systems in nonequilibrium environments. These results offer some general guidelines for optimizing the steady-state entanglement and coherence in the coupled qubit system and may find potential applications in quantum information technology.

Upholding labour productivity under climate change: an assessment of adaptation options

ABSTRACTChanges in labour productivity feed through directly to national income. An external shock, like climate change, which may substantially reduce the productivity of workers is therefore a macroeconomic concern. The biophysical impact of higher temperatures on human performance is well documented. Less well understood are the wider effects of higher temperatures on the aggregate productivity of modern, diversified economies, where economic output is produced in contexts ranging from outdoor agriculture to work in air-conditioned buildings. Working conditions are at least to some extent the result of societal choices, which means that the labour productivity effects of heat can be alleviated through careful adaptation. A range of technical, regulatory/infrastructural and behavioural options are available to individuals, businesses and governments. The importance of local contexts prevents a general ranking of the available measures, but many appear cost-effective. Promising options include the optimization of working hours and passive cooling mechanisms. Climate-smart urban planning and adjustments to building design are most suitable to respond to high base temperature, while air conditioning can respond flexibly to short temperature peaks if there is sufficient cheap, reliable and clean electricity.Key policy insightsThe effect of heat stress on labour productivity is a key economic impact of climate change, which could affect national output and workers’ income.Effective adaptation options exist, such as shifting working hours and cool roofs, but they require policy intervention and forward planning.Strategic interventions, such as climate-smart municipal design, are as important as reactive or project-level adaptations.Adaptation solutions to heat stress are highly context specific and need to be assessed accordingly. For example, shifting working hours could be an effective way of reducing the effect of peak temperatures, but only if there is sufficient flexibility in working patterns.

How do seed and seedling traits influence germination and emergence parameters in crop species? A comparative analysis

AbstractEarly plant establishment through seed germination and seedling emergence is a crucial process that determines seedling number, emergence time distribution and the early growth of seedlings, all of which are affected by soil climate and soil structure. In the current context of climate change, in which increasing the diversity of cultivated species is considered desirable, and new tillage practices are considerably modifying top-soil surface characteristics, we need to improve our ability to model the effects of the environment on plant establishment. Using a trait-based and model-based framework, we aimed to identify general relationships between seed and seedling traits (e.g. seed mass and lipid content, seedling diameter, base temperature) and germination and emergence model parameters (e.g. time to mid-germination, shoot elongation rate) measured for 18 genotypes belonging to 14 species. Relationships were also investigated among model parameters or traits. Germination rates were faster for species with a high base temperature and for species with seed reserves located principally in the embryo (rather than the endosperm or perisperm). During heterotrophic growth, maximal shoot length and elongation rate increased with seed dry mass. The sensitivity of seedlings to soil obstacles was negatively related to shoot diameter. Thus apart from the known effects of seed mass on seedling establishment, we found that seed reserve location, seedling shoot diameter and shape affected germination rate and emergence success. Such generic rules linking plant traits to germination and emergence parameters enhance our understanding of the determinants of environmental effects on plant establishment success.

Homotopy Perturbation Method for the Analysis of Heat Transfer in an Annular Fin With Temperature-Dependent Thermal Conductivity

A recent mathematical technique of homotopy perturbation method (HPM) for solving nonlinear differential equations has been applied in this paper for the analysis of steady-state heat transfer in an annular fin with temperature-dependent thermal conductivity and with the variation of thermogeometric fin parameters. Excellent benchmark agreement indicates that this method is a very simple but powerful technique and practical for solving nonlinear heat transfer equations and does not require large memory space that arises out of discretization of equations in numerical computations, particularly for multidimensional problems. Three conditions of heat transfer, namely, convection, radiation, and combined convection and radiation, are considered. Dimensionless parameters pertinent to design optimization are identified and their effects on fin heat transfer and efficiency are studied. Results indicate that the heat dissipation under combined mode from the fin surface is a convection-dominant phenomenon. However, it is also found that, at relatively high base temperature, radiation heat transfer becomes comparable to pure convection. It is worth noting that, for pure radiation condition, the dimensionless parameter of aspect ratio (AR) of a fin is a more desirable controlling parameter compared to other parameters in augmenting heat transfer rate without much compromise on fin efficiency.

Nanoscale Measurement of Laser-Induced Temperature Rise and Field Evaporation Effects in CdTe and GaN

The measurement of laser-induced temperature change and its influence on the field evaporation behavior in nanoscale CdTe and GaN specimens was assessed through systematic studies using laser pulsed atom probe tomography. For CdTe, the laser was shown to induce a linear thermal response in the material. Using the determined relationships, a phase map of the field evaporation behavior was created. This shows that at high base temperatures, high laser energies, or low fields, significant Cd sublimation occurs, leading to apparently Te-rich measured compositions. In contrast, the highest fields result in simultaneous evaporation of multiple Te species, leading to apparently Cd-rich measured compositions. For GaN, increasing laser energy reduced the applied bias necessary for a given detection rate, whereas base temperature changes produced no significant effect on the evaporation behavior, indicative of a largely athermal evaporation mechanism. Similarly, the laser energy and bias affected the measured compo...

ITER-W monoblocks under high pulse number transient heat loads at high temperature

In the context of using a full-tungsten (W) divertor for ITER, thermal shock resistance has become even more important as an issue that may potentially influence the long term performance. To address this issue a unique series of experiments has been performed on ITER-W monoblock mock ups in three EU high heat flux facilities: GLADIS (neutral beam), JUDITH 2 (electron beam) and Magnum-PSI (plasma beam). This paper discusses the JUDITH 2 experiments. Two different base temperatures, 1200°C and 1500°C, were chosen superimposed by ∼18,000/100,000 transient events (Δt=0.48ms) of 0.2 and 0.6GW/m2.Results showed a stronger surface deterioration at higher base temperature, quantified by an increase in roughening. This is intensified if the same test is done after preloading (exposure to high temperature without transients), especially at higher base temperature when the material recrystallizes.

Base temperature determination of tropical Panicum spp. grasses and its effects on degree-day-based models

Development of management tools is essential to explore the potential of grassland systems and such tools include simulation models used for management, planning and research purposes. The simulation models account for temperature effects on forage growth in various ways, and most of them use degree-day-based sub-models to simulate plant growth. Little or no growth is expected for tropical grasses when temperatures are between 10 and 15°C; thus, the assumption of 15°C as the base temperature for growth of these plants is not uncommon. The objective of this paper is to test an approach, commonly used for row crops, for determination of pasture grasses base temperature using a Panicum spp. dataset, and to compare different methods of calculation. Data was collected from well-established plots (4m×10m) of five Panicum spp. cultivars (Atlas, Massai, Mombaça, Tanzânia and Tobiatã), arranged in four randomized complete blocks, sampled from December 2002 to April 2004 in Piracicaba, SP, Brazil. Light interception measurements from three summer and one winter growth cycles were used to determine thermal time to reach 95% canopy light interception. Base-temperature was calculated using iteration method, the b-coefficient method, minimum coefficient of variation of accumulated degree-days, and minimum standard deviation in degree-days and in days. The order of best methods was iteration, coefficient of variation of accumulated degree-days and b-coefficient method, respectively. The standard deviation method in degree-days and in days resulted in high base temperatures and was not able to detect differences among cultivars. Overall base temperatures were different among cultivars: Massai: 16°C, Atlas: 15°C, Mombaça: 11°C, Tobiatã: 10°C and Tanzânia: 7°C.

Prediction of germination rates of weed species: Relationships between germination speed parameters and species traits

In fields, the timing of weed emergence flushes is mostly related to the timing and rate of seed germination, which depend on seed dormancy level, soil temperature and water potential conditions as well as soil tillage and crop sowing date. Seed germination parameters are essential in weed dynamics models to account for the effects of soil conditions on weed demography. Since these parameters are difficult to measure, our objective was to test the possibility of estimating them from easily accessible information. Seed germination parameters (germination lag-time, time to mid-germination and mid-germination rate) were measured or collected from the literature for 25 weed species with contrasted seed characteristics. Correlations were then searched for between these parameters and morphological, chemical and physiological seed traits as well as seed dormancy level. The dormancy level was positively correlated with speed of germination parameters. Earliness of germination was positively correlated with seed lipid content and the seed area to mass ratio. Germination was also earlier and faster in species with a high base temperature for germination. These relationships explained about half the observed variability in germination speed parameters but should be further tested before being used to predict the germination behaviour of weed species in the field in different seasons.

Effects of thermal model and base temperature on estimates of thermal time to bud break in white spruce seedlings

To improve the predictability of bud burst and growth of boreal trees under varying climate, the thermal time for bud break in white spruce ( Picea glauca (Moench) Voss) seedlings was evaluated under a range of temperature conditions in controlled environment chambers. Thermal time requirements were calculated as the sum of growing degree days or growing degree hours above base temperatures ranging from –1 to 5 °C. The results indicated that the common modeling approach, which uses a high base temperature of 5 °C and growing degree days, may not be appropriate for future climatic conditions. Estimates of thermal time requirements using a base temperature of 5 °C varied considerably among temperature treatments and thus would reduce the predictability of bud burst under changing climate. In contrast, estimates of thermal time requirements with lower temperatures closer to 1 °C were relatively consistent among treatments. Growing degree hour models were less sensitive to base temperature than degree day models. These results should help in the selection of appropriate base temperatures and thermal time models in quantification of thermal time for bud burst modeling in other boreal trees.

SOMA TÉRMICA PARA O SUBPERÍODO SEMEADURA-MATURAÇÃO DE FEIJÃO CV. CARIOCA EM COLORADO DO OESTE, RONDÔNIA

Heat unit (degrees-day) was determined for the bean (Phaseolus vulgaris L.) cv. ‘Carioca’ sowing-maturation sub-period. Tests were based on phenological data from field experiments carried out during break crop period with irrigation, in 2006, and regular harvest period with and without irrigation, in 2007. Experiments were conducted at the Instituto Federal de Rondônia (IFRO), in Colorado do Oeste, Rondônia State, Brazil. The degrees-day sum (DD) was determined by using two methods. The first method consisted of three different lower base-temperatures (Bt), 10°C, 12°C, and 15°C, and the second one consisted of three different lower base-temperatures (Bt), 10°C, 12°C, and 15°C, and a higher base-temperature (BT), 35°C. Daily air temperature values were obtained at the IFRO weather station, located near the experiments field. There were no significant differences between methods, averaging from 686 to 1,261.9 degrees-day, with Bt of 15°C for the regular harvest period with irrigation and 10°C for the break crop period, respectively. The results show that the accumulated heat unit conditions for bean cultivation are favorable, especially in the regular harvest period with irrigation. KEY-WORDS: Phaseolus vulgaris L.; bean plant; degrees-day; base-temperature; physicochemical conditions.

Fabrication and characterization of Pd/Nb 40Ti 30Ni 30/Pd/porous nickel support composite membrane for hydrogen separation and purification

A porous nickel support was successfully prepared by uniaxial compression of nickel powders. Microstructures and mechanical properties of Nb 40Ti 30Ni 30 membranes fabricated by magnetron sputtering were investigated. Deposited and annealed Nb 40Ti 30Ni 30 membranes consisted of amorphous and crystalline phases, respectively. Higher base temperature was shown to increase the hardness and elastic modulus of the Nb 40Ti 30Ni 30 membrane. Pd/Nb 40Ti 30Ni 30/Pd/porous nickel support composite membranes were then fabricated using a multilayer magnetron sputtering method. The hydrogen permeability of the composite membranes with amorphous and crystallized Nb 40Ti 30Ni 30 metal layer was measured and compared with that of self-supported Nb 40Ti 30Ni 30 and Pd alloys. Solid-state diffusion was shown to be the rate-controlling factor when the thickness of the Nb 40Ti 30Ni 30 layer was about 12 μm or greater, while other factors were in effect for thinner layers (such as 6 μm). The Pd/Nb 40Ti 30Ni 30/Pd/porous nickel support composite membrane exhibited excellent permeation capability and satisfactory mechanical properties. It is a promising new permeation membrane that could replace Pd and PdAg alloys for hydrogen separation and purification.

Estimation of key parameters for weed population dynamics models: Base temperature and base water potential for germination

Abstract In fields, the timing of weed emergence flushes is mostly related to the timing and rate of seed germination, which depend on soil temperature and water potential as well as soil tillage and crop sowing date. Base temperature and base water potential for seed germination are parameters required in weed dynamics models to take into account the effects of soil conditions on weed demography. Since these parameters are difficult to measure, our objective was to develop a method for estimating them from easily accessible information. Data on base temperature and base water potential for germination were collected from the literature for 28 weed species. Correlations were then searched for between these parameters and (i) the species ecological indicator values of Landolt and Ellenberg for temperature and moisture and (ii) dates of the onset and end of weed emergence based on experts’ knowledge. Both base temperature and base water potential for germination were partially correlated with the species indicator values found in the literature. These correlations explained however only a small proportion of the variance of base temperature and water potential. In contrast, the base temperature of spring-emerging species was highly correlated with the mean soil temperature at the mean onset date of each species’ spring emergence flush. Water potential for germination was higher for species requiring high base temperature. The date of spring emergence onset of a species, which can be easily assessed from experts’ knowledge, can thus be used to estimate their base temperature and then their base water potential for germination.

Using Capsulated Liquid Metal Fins for Heat Transfer Enhancement

This work introduces a novel method that enhances the heat transfer from a given surface by using a capsulated liquid metal fin. The thermal performance of this fin is estimated and compared with that of a conventional solid fin. It is found that using the capsulated fin may enhance the performance of an equal size conventional solid fin significantly. The effect of different design and operating parameters on the capsulated fin thermal performance is investigated. Two equal-size geometries for the capsulated fins longitudinal sectional area are investigated: the rectangular and the half-circular fins. It is found that the rectangular fins show better performance than that of the half-circular fins. Also, it is found that using the capsulated fin is justified in applications that involve a high base temperature, high height-to-width aspect ratio, and high external convective heat transfer coefficient.