Heat transfer, evaporation and carbon dioxide transfer in soil

Latent heat flux associated with soil water evaporation connects the surface water balance with the surface energy balance. Soil water evaporation and soil carbon dioxide (CO2) fluxes both involve soil gas transport processes and properties, and both impact the soil environment and physical, chemical, and biological processes occurring in the soil. Accurate and dynamic measurements of soil water evaporation and soil CO2 fluxes enhance the understanding of water, energy, and carbon partitioning at the soil-atmosphere interface and the mechanisms of mass and energy movement in the soil. Most previous work focused on measurements made above the soil surface, and quantitative determinations of in situ water evaporation and carbon dioxide fluxes within soil profile were absent. The objectives of this dissertation were to accurately determine transient soil water evaporation and soil CO2 fluxes with depth in bare soil and in different management zones of a corn field and to evaluate in situ measurement techniques. Three-needle heat pulse sensors were used to measure subsurface soil water evaporation at depths of 3 mm and below in a bare field. The daily evaporation estimated from the heat pulse method agreed well with the daily evaporation estimated from Bowen ratio and micro-lysimeter methods. The results showed that heat pulse sensors alone could accurately determine subsurface soil water evaporation with time and depth, and surface and subsurface evaporation could be accurately determined with heat pulse measurements combined with Bowen ratio measurements in a bare field. Newly designed 11-needle heat pulse sensors were used at the following locations within a corn field: within-row (ROW), between-rows with roots (BR), and between-rows without roots (BRNR). The findings showed that heat pulse sensors measured the dynamic soil water evaporation at the three locations. The daily heat pulse evaporation estimates agreed well with micro-lysimeter measurements of daily soil water evaporation at ROW and BR in the corn field. In addition to heat pulse measurements for soil water evaporation, plant transpiration and evapotranspiration (ET) were measured using stem flow gauges and an eddy covariance system in the corn field. The evapotranspiration estimated from the sum of heat pulse evaporation and stem flow transpiration (E+T), eddy covariance ET, and potential evapotranspiration, ET0, estimated from the Penman-Monteith equation had similar trends. ET0 was larger than the individually measured E+T and eddy covariance ET. The individually measured E+T and ET0 had similar values but eddy covariance measurements underestimated ET. Bare soil CO2 fluxes were determined using a concentration gradient method with in situ measured soil CO2 concentrations and model estimated gas coefficients during natural wetting and drying periods. Results showed that CO2 fluxes decreased with depth and most of the CO2 was produced at shallow soil depths. CO2 fluxes decreased with depth from 0 to 90 mm, and kept stable at depths of 90 to 200 mm. The gradient method determined CO2 fluxes agreed well with surface closed-chamber measured CO2 fluxes. For 10 out of 12 days the daily mean gradient CO2 flux values were within the ranges of the closed-chamber CO2 fluxes values during a soil drying period. The conclusions of the dissertation were that the heat pulse sensors were able to accurately determine soil water evaporation with time and depth in a bare field and in different soil management zones in a corn field. Soil CO2 fluxes and soil CO2 production rates with depth in a bare field were accurately determined using a concentration gradient method with in situ CO2 concentration profiles. These simultaneous soil water evaporation and soil CO2 flux measurements could serve as a foundation for testing the numerical models of coupled heat, water, and gas transfer in soil, and could enhance further understanding of the complex soil system, and could guide the management of soil properties and processes

Quantification of the influence of drugs on zebrafish larvae swimming kinematics and energetics

The use of zebrafish larvae has aroused wide interest in the medical field for its potential role in the development of new therapies. The larvae grow extremely quickly and the embryos are nearly transparent which allows easy examination of its internal structures using fluorescent imaging techniques. Medical treatment of zebrafish larvae can directly influence its swimming behaviours. These behaviour changes are related to functional changes of central nervous system and transformations of the zebrafish body such as muscle mechanical power and force variation, which cannot be measured directly by pure experiment observation. To quantify the influence of drugs on zebrafish larvae swimming behaviours and energetics, we have developed a novel methodology to exploit intravital changes based on observed zebrafish locomotion. Specifically, by using an in-house MATLAB code to process the recorded live zebrafish swimming video, the kinematic locomotion equation of a 3D zebrafish larvae was obtained, and a customised Computational Fluid Dynamics tool was used to solve the fluid flow around the fish model which was geometrically the same as experimentally tested zebrafish. The developed methodology was firstly verified against experiment, and further applied to quantify the fish internal body force, torque and power consumption associated with a group of normal zebrafish larvae vs. those immersed in acetic acid and two neuroactive drugs. As indicated by our results, zebrafish larvae immersed in 0.01% acetic acid display approximately 30% higher hydrodynamic power and 10% higher cost of transport than control group. In addition, 500 μM diphenylhydantoin significantly decreases the locomotion activity for approximately 50% lower hydrodynamic power, whereas 100 mg/L yohimbine has not caused any significant influences on 5 dpf zebrafish larvae locomotion. The approach has potential to evaluate the influence of drugs on the aquatic animal’s behaviour changes and thus support the development of new analgesic and neuroactive drugs

A colour preference technique to evaluate acrylamide-induced toxicity in zebrafish

The zebrafish has become a commonly used vertebrate model for toxicity assessment, of particular relevance to the study of toxic effects on the visual system because of the structural similarities shared by zebrafish and human retinae. In this article we present a colour preference-based technique that, by assessing the functionality of photoreceptors, can be used to evaluate the effects of toxicity on behaviour. A digital camera was used to record the locomotor behaviour of individual zebrafish swimming in a water tank consisting of two compartments separated by an opaque perforated wall through which the fish could pass. The colour of the lighting in each compartment could be altered independently (producing distinct but connected environments of white, red or blue) to allow association of the zebrafish's swimming behaviour with its colour preference. The functionality of the photoreceptors was evaluated based on the ability of the zebrafish to sense the different colours and to swim between the compartments. The zebrafish tracking was carried out using our algorithm developed with MATLAB. We found that zebrafish preferred blue illumination to white, and white illumination to red. Acute treatment with acrylamide (2 mM for 36 h) resulted in a marked reduction in locomotion and a concomitant loss of colour-preferential swimming behaviour. Histopathological examination of acrylamide-treated zebrafish eyes showed that acrylamide exposure had caused retinal damage. The colour preference tracking technique has applications in the assessment of neurodegenerative disorders, as a method for preclinical appraisal of drug efficacy and for behavioural evaluation of toxicity

Spatial and Temporal Dynamics of Soil-Surface Carbon Dioxide Emissions in Bioenergy Corn Rotations and Reconstructed Prairies

The interest in bioenergy crops has raised questions as to the potential of management strategies to preserve soil C pools and soil quality. Since soil-surface CO2 effluxes are a major fate of soil C, knowledge of CO2 efflux’s spatial and temporal trends among bioenergy crops will facilitate advances in research on improving terrestrial C-cycle models as well as decision support tools for policy and land-management. Our objective was to evaluate spatial and temporal dynamics of soil-surface CO2 effluxes in bioenergy-based corn (Zea mays L.) and reconstructed prairie systems. Systems evaluated included continuous corn (harvested for grain and 50% of the corn stover) with and without a cover crop, mixed prairies (harvested for aboveground biomass) with and without N fertilization, and corn–soybean [Glycine max (L.) Merr.] rotations harvested for grain. Soil-surface CO2 effluxes, soil temperature, and soil water contents were monitored weekly from July 2008 to September 2011 and hourly during portions of 2010 and 2011. Annual soil-surface CO2 effluxes were greater in prairies than row crops and are attributed to greater plant root respiration. Soil-surface CO2 effluxes spatially varied among intra-crop management zones only for continuous corn with stover removal. However, the cover crop reduced CO2 efflux spatial variability 70% of the time as compared to stover removal without a cover crop. Spatial variability of effluxes was not explained by soil physical properties or conditions. Temperature-induced diurnal fluctuations of CO2 effluxes were not evident during apparent soil–water redistribution. Further research on the mechanisms behind this process is needed followed by incorporation of mechanisms into CO2efflux models

Cellular Phenotype Plasticity in Cancer Dormancy and Metastasis

Cancer dormancy is a period of cancer progression in which residual tumor cells exist, but clinically remain asymptomatic for a long time, as well as resistant to conventional chemo- and radiotherapies. Cellular phenotype plasticity represents that cellular phenotype could convert between epithelial cells and cells with mesenchymal traits. Recently, this process has been shown to closely associate with tumor cell proliferation, cancer dormancy and metastasis. In this review, we have described different scenarios of how the transition from epithelial to mesenchymal morphology (EMT) and backwards (MET) are connected with the initiation of dormancy and reactivation of proliferation. These processes are fundamental for cancer cells to invade tissues and metastasize. Recognizing the mechanisms underlying the cellular phenotype plasticity as well as dormancy and targeting them is likely to increase the efficiency of traditional tumor treatment inhibiting tumor metastasis

Improving Soil Heat Flux Accuracy with the Philip Correction Technique

Soil heat flux Gs is an important component of the surface energy balance. Soil heat flux plates (SHFPs) are widely used to measure Gs, although several errors are known to occur. The Philip correction has been applied to minimize errors in Gs measured by SHFPs (Gp) if the soil thermal conductivity λs, SHFP thermal conductivity λp, and plate geometry function H are known. The objective of this study is to evaluate the effectiveness of the Philip correction for a variety of SHFPs. The λp were determined without thermal contact resistance and differed from the manufacturer-specified λp. A simplified H formulation was similar to or less than the full H equation for different SHFP shapes. The G ratio (Gp/Gs) was sensitive to λs/λp and H when they were relatively small. Compared with the Gs determined by a gradient method (Gs_grad), the Gpmeasured under a full corn (Zea mays, L.) canopy in the field underestimated Gs by 38%–62%. After applying the Philip correction, almost all Gp agreed better with Gs_grad. Generally, the Gp corrected with measured plate parameters agreed better with Gs_grad than those corrected with manufacturer-specified values. The Gp corrected with the simplified and full H expression differed for different SHFPs. These results indicate that SHFPs always underestimate Gs and that the performance of the Philip correction is affected by λp, plate dimensions, and H. An alternative method to measure Gs by a three-needle heat-pulse sensor or a gradient method, in which soil temperature and water content are measured at several depths, is recommended

Research on interface slippage of fiber reinforced composite ceramics

Based on the microscopic characteristics of fiber reinforced composite ceramics, the slippage stress at the interface of composite ceramics under external loading is analyzed. The relation between the applied strain of the triangular symmetrical eutectic and the load of composite ceramics is confirmed. And the maximum shear stress that the triangular symmetrical eutectic can endure is computed. The yield shear stress was calculated by the hardness and fracture toughness of composite ceramics. When the maximum shear stress which the triangular symmetrical eutectic can bear is equal to the yield shear stress, the slipping stress of micro-mechanical interface in composite ceramics is obtained. The results showed that fiber inclusions in the eutectic having smaller dimension and larger volume content would provide larger partial plastic deformation of composite ceramics