The evolutionary processes and genetics underlying local adaptation at a specieswide level are largely unknown. Recent work has indicated that a frameshift mutation in a member of a family of ...transcription factors, C‐repeat binding factors or CBFs, underlies local adaptation and freezing tolerance divergence between two European populations of Arabidopsis thaliana. To ask whether the specieswide evolution of CBF genes in Arabidopsis is consistent with local adaptation, we surveyed CBF variation from 477 wild accessions collected across the species’ range. We found that CBF sequence variation is strongly associated with winter temperature variables. Looking specifically at the minimum temperature experienced during the coldest month, we found that Arabidopsis from warmer climates exhibit a significant excess of nonsynonymous polymorphisms in CBF genes and revealed a CBF haplotype network whose structure points to multiple independent transitions to warmer climates. We also identified a number of newly described mutations of significant functional effect in CBF genes, similar to the frameshift mutation previously indicated to be locally adaptive in Italy, and find that they are significantly associated with warm winters. Lastly, we uncover relationships between climate and the position of significant functional effect mutations between and within CBF paralogs, suggesting variation in adaptive function of different mutations. Cumulatively, these findings support the hypothesis that disruption of CBF gene function is adaptive in warmer climates, and illustrate how parallel evolution in a transcription factor can underlie adaptation to climate.
Negative obstacles have long been a challenging aspect of autonomous navigation for ground vehicles. However, as terrestrial lidar sensors have become lighter and less costly, they have increasingly ...been deployed on small, low-flying UAV, affording an opportunity to use these sensors to aid in autonomous navigation. In this work, we develop an analytical model for predicting the ability of UAV or UGV mounted lidar sensors to detect negative obstacles. This analytical model improves upon past work in this area because it takes the sensor rotation rate and vehicle speed into account, as well as being valid for both large and small view angles. This analytical model is used to predict the influence of velocity on detection range for a negative obstacle and determine a limiting speed when accounting for vehicle stopping distance. Finally, the analytical model is validated with a physics-based simulator in realistic terrain. The results indicate that the analytical model is valid for altitudes above 10 m and show that there are drastic improvements in negative obstacle detection when using a UAV-mounted lidar. It is shown that negative obstacle detection ranges for various UAV-mounted lidar are 60–110 m, depending on the speed of the UAV and the type of lidar used. In contrast, detection ranges for UGV mounted lidar are found to be less than 10 m.
•A ferro-nanofluid oscillating heat pipe (OHP) was used to generate voltage.•Marked improvement in OHP heat transfer occurred (∼70%) when using ferro-nanofluid.•A bias magnetic field is needed to ...locally magnetize suspended ferro-nanoparticles.•Energy harvesting via ferrofluidic induction can decrease OHP heat transfer.
A unique thermal-to-mechanical-to-electrical energy conversion process is demonstrated via thermally-excited, pulsating ferro-nanofluid within a solenoid-equipped oscillating heat pipe (i.e., ferrofluid-OHP or FF-OHP). The FF-OHP was charged with an aqueous cobalt ferrite ferro-nanofluid, comprised of custom-synthesized CoFe2O4 nanoparticles surface-modified with citric acid for increased suspensibility. Annular bias magnets were placed directly above and below the FF-OHP solenoid to temporarily magnetize the internal, oscillating ferrofluid. During FF-OHP operation, a measured peak-to-peak voltage of ∼2 mV was measured across the solenoid due to electromagnetic induction. When filled with ferro-nanofluid, the OHP heat transfer was enhanced (relative to pure water) by ∼58% with bias magnets and ∼71% without bias magnets. A maximum effective thermal conductivity of 12.9 kW/m·K was achieved in the FF-OHP at ∼470 W of heat input. With the bias magnets installed (i.e., harvesting configuration), the FF-OHP effective thermal conductivity was ∼11% lower than when the bias magnets were not present, and this is attributed to an increase in ferrofluid viscosity due to particle magnetization in the bias field. The FF-OHP/solenoid harvesting process is a novel means for accomplishing thermal-to-electrical energy conversion while maintaining high heat transfer capabilities and extreme temperature functionality.
•Oscillating heat pipes (OHPs) can be used for thermal energy conversion.•Fluid motion within an OHP can agitate a suspended magnet for induction.•Thermal performance of OHP harvester increases at ...cost of power generation.•Suspending larger magnets within OHP tube can increase power generation.•OHP harvester is a portable means for electric power generation.
An ‘oscillating magnet’ energy harvesting module was developed and integrated into a 4-turn, tubular oscillating heat pipe (OHP) filled with water. The harvesting module consisted of a 1000-turn solenoid wrapped around a polycarbonate tube and two transverse posts, which were placed through the tube above and below the solenoid. Electromagnetic induction was accomplished via the thermally-driven, fluidic agitation of a suspended neodymium magnet placed between the transverse posts. The thermal performance and energy harvesting ability of this ‘oscillating-magnet OHP’ (OMHP) was experimentally investigated over a range of heat inputs with either 1.59 mm or 3.17 mm diameter neodymium magnets. Results demonstrate that the OMHP heat transfer performance decreased as the magnet diameter approached that of the OHP tube due to increased local pressure drops across the magnet, which disrupted advection between the evaporator and condenser. At 400 W of heat input, the OMHP equipped with a smaller oscillating magnet (i.e. 1.59 mm diameter) produced a maximum peak electrical power of 21.9 µW and provided an effective thermal conductivity of ∼7000 W/m K. In contrast, the OMHP equipped with a larger oscillating magnet (i.e. 3.17 mm diameter) produced a maximum peak electrical power of 428 µW and an effective thermal conductivity of ∼2600 W/m K at 200 W of heat input. Since the confined magnet motion is coupled with the heat transfer and internal fluid motion of the OHP, the design of the OMHP is driven by the importance of energy harvesting relative to thermal performance. This technology is unique in that it can be used for thermal management and in situ electric power production.
Modern agriculture is facing multiple challenges including the necessity for a substantial increase in production to meet the needs of a burgeoning human population. Water shortage is a deleterious ...consequence of both population growth and climate change and is one of the most severe factors limiting global crop productivity. Brassica species, particularly canola varieties, are cultivated worldwide for edible oil, animal feed, and biodiesel, and suffer dramatic yield loss upon drought stress. The recent release of the Brassica napus genome supplies essential genetic information to facilitate identification of drought-related genes and provides new information for agricultural improvement in this species. Here we summarize current knowledge regarding drought responses of canola, including physiological and -omics effects of drought. We further discuss knowledge gained through translational biology based on discoveries in the closely related reference species Arabidopsis thaliana and through genetic strategies such as genomewide association studies and analysis of natural variation. Knowledge of drought tolerance/resistance responses in canola together with research outcomes arising from new technologies and methodologies will inform novel strategies for improvement of drought tolerance and yield in this and other important crop species.
Climate change is altering natural selection globally, which could shift the evolutionary trajectories of traits central to the carbon (C) cycle. Here, we examine the components necessary for the ...evolution of C cycling traits to substantially drive changes in global C cycling and integrate these components into a framework of ecoevolutionary dynamics. Recent evidence points to the evolution of C cycling traits during the Anthropocene and the potential to significantly affect atmospheric CO2. We identify directions for further collaboration between evolutionary, ecosystem, and climate scientists to study these ecoevolutionary feedback dynamics and determine whether this evolution will ultimately accelerate or decelerate the current trend in rising atmospheric CO2.
Global climate change is altering natural selection and shifting the evolutionary trajectories of organism traits.
C cycling and other ecosystem functions are mediated by organism traits, which are subject to evolutionary processes; however, evolution is not yet explicitly included in current global C cycling models.
Rapid evolution of C cycling traits has been recently observed in several organisms, indicating that evolutionary responses to climate change could alter the C cycle and ultimately impact atmospheric CO2.
The evolution of C cycling traits could generate particularly important ecoevolutionary feedbacks, the understanding of which will require greater integration of evolutionary, ecosystem, and climate science.
Current approaches to tailoring the thermal expansion coefficient of materials or finding materials with negative thermal expansion rely on careful manipulation of either the material's composition ...and/or the complex fabrication of composites. Here, by contrast, we report a new principle that enables the precise control of macroscopic thermal expansion response of bulk materials via crystallographic texture manipulation and by taking advantage of anisotropic Coefficients of Thermal Expansion (CTE) in a large class of martensitically transforming materials. Through simple thermo-mechanical processing, it is possible to tailor the thermal expansion response of a single material––without manipulating its composition––over a wide range of positive and negative values. We demonstrate this principle by gradually tuning the macroscopic CTE in a model NiTiPd alloy between a positive (+14.90 × 10−6 K−1) and a negative (−3.06 × 10−6 K−1) value, simply by incrementally increasing tensile plastic deformation in the martensite phase. This surprising response is linked to the large positive, +51.33 × 10−6 K−1, and negative, −34.51 × 10−6 K−1, CTE anisotropy, at the lattice level, along the different crystal directions in martensite. Similar CTE anisotropy is also shown experimentally in CoNiGa and TiNb alloys. In a model TiNb alloy, giant macroscopic CTEs of +181 × 10−6 K−1 and −142 × 10−6 K−1 are measured. A connection between the CTE anisotropy and the martensitic transformation in these and other materials systems such as NiTi, pure uranium, and PbTiO3 is later made. It is shown that negative or positive thermal expansion crystallographic directions are connected to the crystallographic relationship between the austenite and martensite lattices, and can easily be predicted using the lattice parameters of austenite and martensite phases. Our current observations and analyses suggest that the tunability of the macroscopic CTE through thermo-mechanical processing is universal in materials––both ceramic and metals––that undergo martensitic transformations.
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