Soil water potential (SWP) is a key parameter for characterizing water stress. Typically, a tensiometer is used to measure SWP. However, the measurement range for commercially available tensiometers ...is limited to −90 kPa and a tensiometer can only provide estimate of SWP at a single location. In this study, a new approach was developed for estimating SWP from spectral reflectance data of a standing rice crop over the visible to shortwave‐infrared region (wavelength: 350–2,500 nm). Five water stress treatments corresponding to targeted SWP of −30, −50, −70, −120, and −140 kPa were examined by withholding irrigation during the vegetative growth stage of three rice varieties. Tensiometers and mechanistic water flow model were used for monitoring SWP. Spectral models for SWP were developed using partial‐least‐squares regression (PLSR), support vector regression (SVR), and coupled PLSR and feature selection (PLSRFS) approaches. Results showed that the SVR approach was the best model for estimating SWP from spectral reflectance data with the coefficient of determination values of 0.71 and 0.55 for the calibration and validation data sets, respectively. Observed root‐mean‐squared residuals for the predicted SWPs were in the range of −7 to −19 kPa. A new spectral water stress index was also developed using the reflectance values at 745 and 2,002 nm, which showed strong correlation with relative water contents and electrolyte leakage. This new approach is rapid and noninvasive and may be used for estimating SWP over large areas.
Key Points
A new noninvasive approach is developed and tested for estimating soil water potential based on canopy spectral reflectance
New spectral vegetation indices (SVI) are developed for characterizing water stress
New water stress SVIs showed high correlation with physiological stress parameters
Toeplitz Operators on the Symmetrized Bidisc Bhattacharyya, Tirthankar; Das, B Krishna; Sau, Haripada
International mathematics research notices,
06/2021, Letnik:
2021, Številka:
11
Journal Article
Recenzirano
Odprti dostop
Abstract
The symmetrized bidisc has been a rich field of holomorphic function theory and operator theory. A certain well-known reproducing kernel Hilbert space of holomorphic functions on the ...symmetrized bidisc resembles the Hardy space of the unit disc in several aspects. This space is known as the Hardy space of the symmetrized bidisc. We introduce the study of those operators on the Hardy space of the symmetrized bidisc that are analogous to Toeplitz operators on the Hardy space of the unit disc. More explicitly, we first study multiplication operators on a bigger space (an $L^2$-space) and then study compressions of these multiplication operators to the Hardy space of the symmetrized bidisc and prove the following major results.
(1) Theorem I analyzes the Hardy space of the symmetrized bidisc, not just as a Hilbert space, but as a Hilbert module over the polynomial ring and finds three isomorphic copies of it as $\mathbb D^2$-contractive Hilbert modules.
(2) Theorem II provides an algebraic, Brown and Halmos-type characterization of Toeplitz operators.
(3) Theorem III gives several characterizations of an analytic Toeplitz operator.
(4) Theorem IV characterizes asymptotic Toeplitz operators.
(5) Theorem V is a commutant lifting theorem.
(6) Theorem VI yields an algebraic characterization of dual Toeplitz operators.
Every section from Section 2 to Section 7 contains a theorem each, the main result of that section.
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•We explored irrigation strategies for mitigating GHGs emission from paddy fields.•Irrigation at −30kPa can save water, maintain rice yield and mitigate CH4 emission.•Soil ...temperature, Eh, pH and EC contribute to the variance in GHGs fluxes.•Vegetative growth stage accounted for about 50% seasonal cumulative GHGs emission.•Trade-offs among CH4, CO2 and N2O were studied.
In the anticipated water scarcity and global warming scenario; it is imperative to identify suitable irrigation scheduling strategy in paddy fields for increasing water productivity and mitigating greenhouse gas (GHG) emissions. We conducted a two year (dry season of 2014 and 2015) field experiment for irrigation scheduling based on tensiometric measurement of soil water potential (SWP) in order to quantify temporal and seasonal variations in GHGs emissions and their trade off relationship at five levels of SWPs viz. SWP 1 (−20kPa), SWP 2 (−30kPa), SWP 3 (−40kPa), SWP 4 (−50kPa) and SWP 5 (−60kPa), in addition to the traditional practice of growing flooded rice (CF). Fluxes of methane (CH4) and nitrous oxide (N2O) during the growing period were measured using manual closed chamber-gas chromatograph and the carbon dioxide (CO2) flux was measured using an infrared CO2 analyzer. A significant decrease in seasonal cumulative CH4 emission (30–60.2%) was recorded at different SWPs as compared to CF. In contrast, emission of CO2 and N2O increased by 12.9–26.6% and 16.3–22.1% respectively at SWPs 1 and 2; conversely, a significant decrease in emissions of these gases were observed at higher SWPs (SWPs 3–5). Among different SWP treatments, irrigation scheduling at SWP 2 maintained yield at par with CF with water saving of 32.9–41.1% and reduced CH4 emission (43–44.1%). However, due to increase in CO2 and N2O emission at SWP 2, there was no significant reduction in global warming potential (GWP) as compared with CF. Among different rice growth stages GHGs emission were predominant during vegetative growth stage. Regression relationship of GHGs emission with key soil parameters was employed to predict seasonal emissions of GHGs from paddy field. The results of this study suggest that scheduling irrigation at SWP 2 can be an effective strategy in order to save water, maintain rice yield and mitigate CH4 emission from direct seeded paddy fields in eastern India, however further research is needed to identify suitable management strategy for reducing CO2 and N2O emissions at SWP 2 in order to reduce the GWP.
This work illustrates the reduction roasting and magnetic separation studies of a complex Indian iron ore with 57% Fe that could not be upgraded to >61% Fe using a flow sheet comprising of the ...conventional unit operations like scrubbing, jigging, magnetic separation or flotation. The sole reason of the poor response to physical beneficiation was mainly attributed to the inadequate liberation of iron as visualized under the reflected light microscope, which revealed the fine dispersion of silica particles within the hematite grains and vice versa. In order to overcome this problem, the ore was subjected to reduction roasting using conventional as well as microwave heating followed by magnetic separation. The effects of different process variables such as reductant concentration, time, and temperature during the process of roasting were studied and subsequently optimized using the Taguchi statistical design. Optical microscopy and X-ray diffraction (XRD) studies of the roasted mass confirmed the formation of magnetite with simultaneous disappearance of the hematite and goethite phases. In the microwave roasting process, the reduction could be achieved in a considerably shorter time as compared to the conventional roasting, and the formation of undesired non-magnetic iron minerals like fayalite was limited as well. In both the processes, it was possible to achieve an iron ore concentrate having 63–65% Fe accompanied by ~85–90% weight recovery.
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•Reduction roasting using conventional & microwave (MW) heating was attempted.•Both routes yield iron concentrates with ~63–64% Fe at ~85% weight recovery.•MW route is promising considering the requirement of less roasting time.•Lesser formation of fayalite in case of microwave roasting is an advantage.
In recent history, local scour around the bridge piers has been a major cause of bridge failure; therefore, it is important to precisely predict the equilibrium scour depth. When the flow of water ...interacts with the bridge pier in the mobile bed, it usually results in local scour. In this paper, a total of 442 clear-water scouring (CWS) data and 300 live-bed scouring (LBS) data are collected from literature to model scour depth using a support vector machine. A sensitivity study was also carried out to assess the reliability of the model, and the strength of the proposed model is tested via an error analysis. The coefficient of determination (R.sup.2) value was found to be greater than 0.90 for both CWS and LBS. The present model is compared with more than 10 popular existing models and it has been discovered to be more reliable and efficient in estimating scour depth around bridge piers.
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•Nickel doped Graphitic carbon nitride (GCN) was synthesized chemically.•Mott-Schottky was done to calculate the flat band potentials and donor densities of pure and doped ...samples.•Toxic Methyl Orange dye was degraded efficiently by doped samples in the presence of NaBH4 accompanied by hydrogen evolution.•Enhancement of catalytic activity with increasing doping concentration was studied in presence of varying amount of NaBH4.•A plausible mechanism for catalytic degradation was discussed in details.
A facile synthesis of transition metal-nickel doped graphitic carbon nitride (NiGCN) nanosheets with varying doping concentrations has been reported. X-Ray diffraction and Fourier transformed infrared spectroscopic study were performed to analyse the structural phase formation and different bonds present in the samples, whereas, field emission and transmission electron microscopic study provided the morphological information. The thermal stability of the samples was measured from the TG-DTA analysis. Photoluminescence spectroscopy was performed to elucidate the emissive property of the samples. The flat band potential of the samples was measured by Mott-Schottky analysis. First principle study was carried out to delineate the probable doping site of the Ni atom along with the effect of doping on the pure material. The samples were effectively utilized to degrade toxic methyl orange (MO) dye from water in the presence of sodium borohydride (NaBH4) without exploiting any visible light source. The plausible catalysis mechanism following a series of several chemical reactions has been discussed in details.
Recent developments in unmanned aerial platforms (UAP) have provided research opportunities in assessing land allocation and crop physiological traits, including response to abiotic and biotic ...stresses. UAP-based remote sensing can be used to rapidly and cost-effectively phenotype large numbers of plots and field trials in a dynamic way using time series. This is anticipated to have tremendous implications for progress in crop genetic improvement.
We present the use of a UAP equipped with sensors for multispectral imaging in spatial field variability assessment and phenotyping for low-nitrogen (low-N) stress tolerance in maize. Multispectral aerial images were used to (1) characterize experimental fields for spatial soil-nitrogen variability and (2) derive indices for crop performance under low-N stress. Overall, results showed that the aerial platform enables to effectively characterize spatial field variation and assess crop performance under low-N stress. The Normalized Difference Vegetation Index (NDVI) data derived from spectral imaging presented a strong correlation with ground-measured NDVI, crop senescence index and grain yield.
This work suggests that the aerial sensing platform designed for phenotyping studies has the potential to effectively assist in crop genetic improvement against abiotic stresses like low-N provided that sensors have enough resolution for plot level data collection. Limitations and future potential uses are also discussed.
CXCR1 is one of two high-affinity receptors for the CXC chemokine interleukin-8 (IL-8), a major mediator of immune and inflammatory responses implicated in many disorders, including tumour growth. ...IL-8, released in response to inflammatory stimuli, binds to the extracellular side of CXCR1. The ligand-activated intracellular signalling pathways result in neutrophil migration to the site of inflammation. CXCR1 is a class A, rhodopsin-like G-protein-coupled receptor (GPCR), the largest class of integral membrane proteins responsible for cellular signal transduction and targeted as drug receptors. Despite its importance, the molecular mechanism of CXCR1 signal transduction is poorly understood owing to the limited structural information available. Recent structural determination of GPCRs has advanced by modifying the receptors with stabilizing mutations, insertion of the protein T4 lysozyme and truncations of their amino acid sequences, as well as addition of stabilizing antibodies and small molecules that facilitate crystallization in cubic phase monoolein mixtures. The intracellular loops of GPCRs are crucial for G-protein interactions, and activation of CXCR1 involves both amino-terminal residues and extracellular loops. Our previous nuclear magnetic resonance studies indicate that IL-8 binding to the N-terminal residues is mediated by the membrane, underscoring the importance of the phospholipid bilayer for physiological activity. Here we report the three-dimensional structure of human CXCR1 determined by NMR spectroscopy. The receptor is in liquid crystalline phospholipid bilayers, without modification of its amino acid sequence and under physiological conditions. Features important for intracellular G-protein activation and signal transduction are revealed. The structure of human CXCR1 in a lipid bilayer should help to facilitate the discovery of new compounds that interact with GPCRs and combat diseases such as breast cancer.
The structural and magnetic properties of nanostructured Co-rich transition-metal alloys, Co(100-x)TMx (TM = Hf, Zr and 10 ≤ x ≤ 18), were investigated. The alloys were prepared under non-equilibrium ...conditions using cluster-deposition and/or melt-spinning methods. The high-anisotropy HfCo7 and Zr2Co11 structures were formed for a rather broad composition region as compared to the equilibrium bulk phase diagrams, and exhibit high Curie temperatures of above 750 K. The composition, crystal structure, particle size, and easy-axis distribution were precisely controlled to achieve a substantial coercivity and magnetization in the nanostructured alloys. This translates into high energy products in the range of about 4.3-12.6 MGOe, which are comparable to those of alnico.
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