Transport of E. coli D21g with runoff water under different solution chemistry conditions and surface slopes

Tracer and indicator microbe runoff experiments were conducted to investigate the influence of solution chemistry on the transport, retention, and release of Escherichia coli D21g. Experiments were conducted in a chamber (2.25 m long, 0.15 m wide, and 0.16 m high) packed with ultrapure quartz sand (to a depth of 0.10 m) that was placed on a metal frame at slopes of 5.6%, 8.6%, or 11.8%. Runoff studies were initiated by adding a step pulse of salt tracer or D21g suspension at a steady flow rate to the top side of the chamber and then monitoring the runoff effluent concentrations. The runoff breakthrough curves (BTCs) were asymmetric and exhibited significant amounts of concentration tailing. The peak concentration levels were lower and the concentration tailing was higher with increasing chamber slope because of greater amounts of exchange with the sand and/or extents of physical nonequilibrium (e.g., water flow in rills and incomplete mixing) in the runoff layer. Lower amounts of tailing in the runoff BTC and enhanced D21g retention in the sand occurred when the solution ionic strength (IS) was 100 mM NaCl compared with 1 mM NaCl, due to compression of the double layer thickness which eliminated the energy barrier to attachment. Retained cells were slowly released to the runoff water when the IS of the runoff water was reduced to deionized water. The amount and rate of cell release was greatest at the highest chamber slope, which controlled the amount of exchange with the sand and/or the extent of physical nonequilibrium in the runoff layer, and the amount of retained cells. The observed runoff BTCs were well described using a transient storage model, but fitted parameters were not always physically realistic. A model that accounted for the full coupling between flow and transport in the runoff and sand layers provided useful information on exchange processes at the sand surface, but did not accurately describe the runoff BTCs which were influenced by physical nonequilibrium in the runoff layer

Water and Nitrogen Productivity of Potato Growth in Desert Areas under Low-Discharge Drip Irrigation

Narrow profit margins, resource conservation issues and environmental concerns are the main driving forces to improve fertilizer uptake, especially for potatoes. Potatoes are a high value crop with a shallow, inefficient root system and high fertilizer rate requirements. Of all essential nutrients, nitrogen (N) is often limiting to potato production. A major concern in potato production is to minimize N leaching from the root zone. Therefore, the main objective of this study was to examine the potato crop characteristics under drip irrigation with low-discharge (0.6 L h−1) and to determine the optimal combination of irrigation (40, 60, 80, and 100%) and fertigation (0, 50, and 100%) doses. In this study, the 80% (438.6 mm) irrigation dose and a 50% (50 mg N L−1) fertigation dose (W80%F50%) showed that these doses are sufficient for optimal potato yield (about 40 ton ha−1) in conjunction with water and fertilizer savings. Moreover, this treatment did not exhibit any qualitative changes in the potato tuber compared to the 100% treatments. When considering water productivity and yield, one may select a harsher irrigation regime if the available agricultural soils are not a limiting factor. Thus, higher yields can be obtained with lower irrigation and fertigation doses and a larger area

Greywater irrigation and soil quality: An assessment framework adjustment and application

The on-site use of greywater is increasingly popular for alleviating water stress in various parts of the world, particularly as a water source for irrigation. However, greywater can contain a range of pathogenic bacteria that may compromise public health as well as substances with the potential to induce environmental consequences, such as soil hydrophobicity, accumulation of salts, and damage to plants. While the health issues are being addressed by greywater legislation, its environmental risks are largely ignored. Therefore, the main objective of the current study was to quantify the impacts of greywater irrigation on soils by developing a soil quality index (SQI) using a 14-month planter experiment. The sum of the absolute value of all indicator scores represents the final score of the integrated SQI, which ranges from 0 to 100. Three threshold values were used: 70 represents optimal quality. The results based on the planter experiment revealed that, after 14 months, the SQI of all raw greywater-irrigated soils was lower than 70, indicating soil functions and plant health might be compromised. The use of scoring functions was a useful tool for quantifying and comparing the effects of greywater irrigation on different soil quality indicators. Integration of all indicator scores into a single SQI quantifies and summarizes the overall beneficial and detrimental effects of greywater irrigation. However, for better understanding and management decisions, SQI scores should be used and interpreted in conjunction with the scores of the single indicators constituting the index. In our experiment, treated ​greywater ​did ​not compromise ​soil quality even after 14 months of irrigation. As such, based on the fact that irrigation with raw greywater might compromise soil quality, treatinggreywater prior to its use is recommended

Wetting properties of poultry litter and derived hydrochar.

Detailed assessment of hydrochar wetting properties, which could provide an essential understanding of underlying mechanisms during its application to soils, is lacking. We characterized hydrochar produced from hydrothermal carbonization (HTC) performed on poultry litter at various temperatures and for different times in terms of hydrophobicity and surface free energy properties. Hydrochar was more hydrophobic than untreated poultry litter, and its hydrophobicity increased with increasing HTC temperature (contact angle > 130°). These changes were correlated with degradation of hemicellulose and cellulose. Hydrochar produced at 250°C contained mostly lignin and displayed high hydrophobicity over both prolonged wetting periods and repeated wetting cycles. Surface free energy was calculated using the Owens-Wendt-Rabel-Kaelble and Wu models, with the latter resulting in lower standard errors. The surface free energy decreased as HTC treatment severity increased from 26 mJ/m2 in the poultry litter to 8 mJ/m2 after treatment at 250°C for 60 min. The dispersive component fraction of the surface free energy increased with increasing treatment severity. This study demonstrated that changes in the physical composition of hydrochar due to increased treatment severity increase its hydrophobicity and decrease its surface free energy. Moreover, due to non-persistent hydrophobicity, hydrochar produced at temperatures lower than 250°C will likely not show adverse effects on soils

Estimating electrical conductivity tensors of biological tissues using microelectrode arrays

Finding the electrical conductivity of tissue is important for understanding the tissue's structure and functioning. However, the inverse problem of inferring spatial conductivity from data is highly ill-posed and computationally intensive. In this paper, we propose a novel method to solve the inverse problem of inferring tissue conductivity from a set of transmembrane potential and stimuli measurements made by microelectrode arrays (MEA). We propose a parallel optimization algorithm based on a single-step approximation with a parallel alternating optimization routine. This algorithm simplifies the joint tensor field estimation problem into a set of computationally tractable subproblems, allowing the use of efficient standard optimization tools

Image interpolation and denoising for division of focal plane sensors using Gaussian processes

Image interpolation and denoising are important techniques in image processing. These methods are inherent to digital image acquisition as most digital cameras are composed of a 2D grid of heterogeneous imaging sensors. Current polarization imaging employ four different pixelated polarization filters, commonly referred to as division of focal plane polarization sensors. The sensors capture only partial information of the true scene, leading to a loss of spatial resolution as well as inaccuracy of the captured polarization information. Interpolation is a standard technique to recover the missing information and increase the accuracy of the captured polarization information. Here we focus specifically on Gaussian process regression as a way to perform a statistical image interpolation, where estimates of sensor noise are used to improve the accuracy of the estimated pixel information. We further exploit the inherent grid structure of this data to create a fast exact algorithm that operates in O (N-3/2) (vs. the naive O (N-3)), thus making the Gaussian process method computationally tractable for image data. This modeling advance and the enabling computational advance combine to produce significant improvements over previously published interpolation methods for polarimeters, which is most pronounced in cases of low signal-to-noise ratio (SNR). We provide the comprehensive mathematical model as well as experimental results of the GP interpolation performance for division of focal plane polarimeter. (C) 2014 Optical Society of Americ

Adaptive smoothing based on Gaussian processes regression increases the sensitivity and specificity of fMRI data

Temporal and spatial filtering of fMRI data is often used to improve statistical power. However, conventional methods, such as smoothing with fixed‐width Gaussian filters, remove fine‐scale structure in the data, necessitating a tradeoff between sensitivity and specificity. Specifically, smoothing may increase sensitivity (reduce noise and increase statistical power) but at the cost loss of specificity in that fine‐scale structure in neural activity patterns is lost. Here, we propose an alternative smoothing method based on Gaussian processes (GP) regression for single subjects fMRI experiments. This method adapts the level of smoothing on a voxel by voxel basis according to the characteristics of the local neural activity patterns. GP‐based fMRI analysis has been heretofore impractical owing to computational demands. Here, we demonstrate a new implementation of GP that makes it possible to handle the massive data dimensionality of the typical fMRI experiment. We demonstrate how GP can be used as a drop‐in replacement to conventional preprocessing steps for temporal and spatial smoothing in a standard fMRI pipeline. We present simulated and experimental results that show the increased sensitivity and specificity compared to conventional smoothing strategies. Hum Brain Mapp 38:1438–1459, 2017. © 2016 Wiley Periodicals, Inc

Bioremediation of Petroleum-Contaminated Soils with Biosurfactant-Producing Degraders Isolated from the Native Desert Soils

A crude oil spill in 2014 resulted in extensive soil contamination of the hyper arid Evrona Nature Reserve in Israel’s Negev Desert. The contaminated soils became highly hydrophobic, threatening the existence of plants in the habitat. We hypothesized that bioaugmenting the soil with indigenous biosurfactant-producing, hydrocarbon-degrading bacteria (HDB) would accelerate the reduction in the soil’s hydrophobicity. We aimed to isolate and characterize biosurfactant-producing HDBs from the desert-contaminated soil and test if they can be used for augmenting the soil. Twelve hydrocarbon-degrading strains were isolated, identified as Pseudomonas, and classified as biosurfactants “producing” and “nonproducing”. Inoculating 109 CFU/g of “producing” strains into the polluted soil resulted in a 99.2% reduction in soil hydrophobicity within seven days. At the same time, nonproducing strains reduced hydrophobicity by only 17%, while no change was observed in the untreated control. The microbial community in the inoculated soil was dominated by the introduced strains over 28 days, pointing to their persistence. Rhamnolipid biosynthesis gene rhlAB remained persistent in soil inoculated with biosurfactants, indicating in situ production. We propose that the success of the treatment is due to the use of inoculum enriched from the polluted soil