Oilseed Rape (Brassica napus L.) Phenology Estimation by Averaged Stokes-Related Parameters

Accurate and timely knowledge of crop phenology assists in planning and/or triggering appropriate farming activities. The multiple Polarimetric Synthetic Aperture Radar (PolSAR) technique shows great potential in crop phenology retrieval for its characterizations, such as short revisit time, all-weather monitoring and sensitivity to vegetation structure. This study aims to explore the potential of averaged Stokes-related parameters derived from multiple PolSAR data in oilseed rape phenology identification. In this study, the averaged Stokes-related parameters were first computed by two different wave polarimetric states. Then, the two groups of averaged Stokes-related parameters were generated and applied for analyzing averaged Stokes-related parameter sensitivity to oilseed rape phenology changes. At last, decision tree (DT) algorithms trained using 60% of the data were used for oilseed rape phenological stage classification. Four Stokes parameters (g0, g1, g2 and g3) and eight sub parameters (degree of polarization m, entropy H, ellipticity angle χ, orientation angle φ, degree of linear polarization Dolp, degree of circular polarization Docp, linear polarization ratio Lpr and circular polarization ratio Cpr) were extracted from a multi-temporal RADARSAT-2 dataset acquired during the whole oilseed rape growth cycle in 2013. Their sensitivities to oilseed rape phenology were analyzed versus five main rape phenology stages. In two groups (two different wave polarimetric states) of this study, g0, g1, g2, g3, m, H, Dolp and Lpr showed high sensitivity to oilseed rape growth stages while χ, φ, Docp and Cpr showed good performance for phenology classification in previous studies, which were quite noisy during the whole oilseed rape growth circle and showed unobvious sensitivity to the crop’s phenology change. The DT algorithms performed well in oilseed rape phenological stage identification. The results were verified at the parcel level with left 40% of the point dataset. Five phenology intervals of oilseed rape were identified with no more than three parameters by simple but robust decision tree algorithm groups. The identified phenology stages agree well with the ground measurements; the overall identification accuracies were 71.18% and 79.71%, respectively. For each growth stage, the best performance occurred at stage S1 with the accuracy of 95.65% for Group 1 and 94.23% for Group 2, and the worst performance occurred at stage S3 and S5 with the values around 60%. Most of the classification errors may resulted from the indistinguishability of S3 and S5 using Stokes-related parameters.

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Low optical polarization at the core of the optically thin jet of M87

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1566 ◽

2020 ◽

Vol 496 (2) ◽

pp. 2204-2212

Author(s):

A Y Fresco ◽

J A Fernández-Ontiveros ◽

M A Prieto ◽

J A Acosta-Pulido ◽

A Merloni

Keyword(s):

Circular Polarization ◽

Linear Polarization ◽

Position Angle ◽

Field Configuration ◽

Stokes Parameters ◽

No Emission ◽

The Core ◽

Level Of Activity ◽

High Degree ◽

Disordered Magnetic

ABSTRACT We study the optical linear and circular polarization in the optically thin regime of the core and jet of M87. Observations were acquired two days before the Event Horizon Telescope (EHT) campaign in early 2017 April. A high degree (∼20 per cent) of linear polarization (Plin) is detected in the bright jet knots resolved at $\sim 10\,\mathrm{ to}\,23\, \rm {arcsec}$ ($0.8{-}1.8\, \rm {kpc}$) from the centre, whereas the nucleus and inner jet show Plin ≲ 5 per cent. The position angle of the linear polarization shifts by ∼90° from each knot to the adjacent ones, with the core angle perpendicular to the first knot. The nucleus was in a low level of activity (Plin ∼ 2–3 per cent), and no emission was detected from HST-1. No circular polarization was detected either in the nucleus or the jet above a 3 σ level of Pcirc ≤ 1.5 per cent, discarding the conversion of Plin into Pcirc. A disordered magnetic field configuration or a mix of unresolved knots polarized along axes with different orientations could explain the low Plin. The latter implies a smaller size of the core knots, in line with current interferometric observations. Polarimetry with EHT can probe this scenario in the future. A steep increase of both Plin and Pcirc with increasing frequency is expected for the optically thin domain, above the turnover point. This work describes the methodology to recover the four Stokes parameters using a λ/4 waveplate polarimeter.

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Strong variable linear polarization in the cool active star II Peg

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314002518 ◽

2013 ◽

Vol 9 (S302) ◽

pp. 369-372

Author(s):

Lisa Rosén ◽

Oleg Kochukhov ◽

Gregg A. Wade

Keyword(s):

Magnetic Field ◽

Circular Polarization ◽

Linear Polarization ◽

Transverse Component ◽

Doppler Imaging ◽

Stokes Parameters ◽

Limited Information ◽

Magnetic Imaging ◽

Field Geometry ◽

The Magnetic Field

AbstractMagnetic fields of cool active stars are currently studied polarimetrically using only circular polarization observations. This provides limited information about the magnetic field geometry since circular polarization is only sensitive to the line-of-sight component of the magnetic field. Reconstructions of the magnetic field topology will therefore not be completely trustworthy when only circular polarization is used. On the other hand, linear polarization is sensitive to the transverse component of the magnetic field. By including linear polarization in the reconstruction the quality of the reconstructed magnetic map is dramatically improved. For that reason, we wanted to identify cool stars for which linear polarization could be detected at a level sufficient for magnetic imaging. Four active RS CVn binaries, II Peg, HR 1099, IM Peg, and σ Gem were observed with the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope. Mean polarization profiles in all four Stokes parameters were derived using the multi-line technique of least-squares deconvolution (LSD). Not only was linear polarization successfully detected in all four stars in at least one observation, but also, II Peg showed an extraordinarily strong linear polarization signature throughout all observations. This qualifies II Peg as the first promising target for magnetic Doppler imaging in all four Stokes parameters and, at the same time, suggests that other such targets can possibly be identified.

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Full-Stokes polarimetry with circularly polarized feeds

Astronomy and Astrophysics ◽

10.1051/0004-6361/201630301 ◽

2018 ◽

Vol 609 ◽

pp. A68 ◽

Cited By ~ 7

Author(s):

I. Myserlis ◽

E. Angelakis ◽

A. Kraus ◽

C. A. Liontas ◽

N. Marchili ◽

...

Keyword(s):

Circular Polarization ◽

Linear Polarization ◽

Stokes Parameters ◽

Polarization Degree ◽

Polarization Angle ◽

Instrumental Effects ◽

Circularly Polarized ◽

Angle Measurements ◽

Linearly Polarized ◽

Stokes Polarimetry

We present an analysis pipeline that enables the recovery of reliable information for all four Stokes parameters with high accuracy. Its novelty relies on the effective treatment of the instrumental effects even before the computation of the Stokes parameters, contrary to conventionally used methods such as that based on the Müller matrix. For instance, instrumental linear polarization is corrected across the whole telescope beam and significant Stokes Q and U can be recovered even when the recorded signals are severely corrupted by instrumental effects. The accuracy we reach in terms of polarization degree is of the order of 0.1–0.2%. The polarization angles are determined with an accuracy of almost 1°. The presented methodology was applied to recover the linear and circular polarization of around 150 active galactic nuclei, which were monitored between July 2010 and April 2016 with the Effelsberg 100-m telescope at 4.85 GHz and 8.35 GHz with a median cadence of 1.2 months. The polarized emission of the Moon was used to calibrate the polarization angle measurements. Our analysis showed a small system-induced rotation of about 1° at both observing frequencies. Over the examined period, five sources have significant and stable linear polarization; three sources remain constantly linearly unpolarized; and a total of 11 sources have stable circular polarization degree mc, four of them with non-zero mc. We also identify eight sources that maintain a stable polarization angle. All this is provided to the community for future polarization observations reference. We finally show that our analysis method is conceptually different from those traditionally used and performs better than the Müller matrix method. Although it has been developed for a system equipped with circularly polarized feeds, it can easily be generalized to systems with linearly polarized feeds as well.

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Absorption, Distribution, and Translocation of Nitrogen at Growth Stages in Oilseed Rape Plant

ACTA AGRONOMICA SINICA ◽

10.3724/sp.j.1006.2010.00321 ◽

2010 ◽

Vol 36 (2) ◽

pp. 321-326

Author(s):

Zhen-Hua ZHANG ◽

Hai-Xing SONG ◽

Qiang LIU ◽

Xiang-Min RONG ◽

Gui-Xian XIE ◽

...

Keyword(s):

Oilseed Rape ◽

Growth Stages ◽

Rape Plant

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HOW THE MEDIAN S-BAND CIRCULAR POLARIZATION RATIO OF KILOMETER-SCALE CRATERS EVOLVES WITH TIME ON THE LUNAR MARIA

10.1130/abs/2018am-320385 ◽

2018 ◽

Author(s):

Caleb I. Fassett ◽

◽

Isabel R. King ◽

Cole A. Nypaver ◽

Bradley J. Thomson

Keyword(s):

Circular Polarization ◽

Polarization Ratio ◽

Lunar Maria

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RNAi efficacy is enhanced by chronic dsRNA feeding in pollen beetle

Communications Biology ◽

10.1038/s42003-021-01975-9 ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Jonathan Willow ◽

Liina Soonvald ◽

Silva Sulg ◽

Riina Kaasik ◽

Ana Isabel Silva ◽

...

Keyword(s):

Rna Interference ◽

Pest Management ◽

Oilseed Rape ◽

Growth Stages ◽

Short Term ◽

Pollen Beetle ◽

Brassicogethes Aeneus ◽

Crop Growth Stages ◽

Insecticidal Compounds ◽

Significant Mortality

AbstractDouble-stranded RNAs (dsRNAs) represent a promising class of biosafe insecticidal compounds. We examined the ability to induce RNA interference (RNAi) in the pollen beetle Brassicogethes aeneus via anther feeding, and compared short-term (3 d) to chronic (17 d) feeding of various concentrations of dsRNA targeting αCOP (dsαCOP). In short-term dsαCOP feeding, only the highest concentration resulted in significant reductions in B. aeneus survival; whereas in chronic dsαCOP feeding, all three concentrations resulted in significant mortality. Chronic dsαCOP feeding also resulted in significantly greater mortality compared to short-term feeding of equivalent dsαCOP concentrations. Our results have implications for the economics and development of dsRNA spray approaches for managing crop pests, in that multiple lower-concentration dsRNA spray treatments across crop growth stages may result in greater pest management efficacy, compared to single treatments using higher dsRNA concentrations. Furthermore, our results highlight the need for research into the development of RNAi cultivars for oilseed rape protection, given the enhanced RNAi efficacy resulting from chronic, compared to short-term, dsRNA feeding in B. aeneus.

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Broadband Linear Polarization in Ap Stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100020662 ◽

1993 ◽

Vol 138 ◽

pp. 305-309

Author(s):

Marco Landolfi ◽

Egidio Landi Degl’Innocenti ◽

Maurizio Landi Degl’Innocenti ◽

Jean-Louis Leroy ◽

Stefano Bagnulo

Keyword(s):

Magnetic Field ◽

Circular Polarization ◽

Linear Polarization ◽

Rotation Axis ◽

Spectral Lines ◽

Line Of Sight ◽

Long Time ◽

Rotating Star ◽

Ap Stars ◽

The Magnetic Field

AbstractBroadband linear polarization in the spectra of Ap stars is believed to be due to differential saturation between σ and π Zeeman components in spectral lines. This mechanism has been known for a long time to be the main agent of a similar phenomenon observed in sunspots. Since this phenomenon has been carefully calibrated in the solar case, it can be confidently used to deduce the magnetic field of Ap stars.Given the magnetic configuration of a rotating star, it is possible to deduce the broadband polarization at any phase. Calculations performed for the oblique dipole model show that the resulting polarization diagrams are very sensitive to the values of i (the angle between the rotation axis and the line of sight) and β (the angle between the rotation and magnetic axes). The dependence on i and β is such that the four-fold ambiguity typical of the circular polarization observations ((i,β), (β,i), (π-i,π-β), (π-β,π-i)) can be removed.

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Alteration in non-classicality of light on passing through a linear polarization beam splitter

Modern Physics Letters B ◽

10.1142/s0217984916502894 ◽

2016 ◽

Vol 30 (21) ◽

pp. 1650289

Author(s):

Namrata Shukla ◽

Ranjana Prakash

Keyword(s):

Linear Polarization ◽

Beam Splitter ◽

Output Port ◽

Polarization Beam Splitter ◽

Stokes Parameters ◽

Coherent Light ◽

Squeezed Light ◽

Squeezed Vacuum

We observe the polarization squeezing in the mixture of a two mode squeezed vacuum and a simple coherent light through a linear polarization beam splitter. Squeezed vacuum not being squeezed in polarization, generates polarization squeezed light when superposed with coherent light. All the three Stokes parameters of the light produced on the output port of polarization beam splitter are found to be squeezed and squeezing factor also depends upon the parameters of coherent light.

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In-Field Observation of Root Growth and Nitrogen Uptake Efficiency of Winter Oilseed Rape

Agronomy ◽

10.3390/agronomy10010105 ◽

2020 ◽

Vol 10 (1) ◽

pp. 105

Author(s):

Julien Louvieaux ◽

Antoine Leclercq ◽

Loïc Haelterman ◽

Christian Hermans

Keyword(s):

Root Growth ◽

Oilseed Rape ◽

Root Development ◽

Nitrogen Uptake ◽

Root Morphology ◽

Growth Stages ◽

Winter Oilseed Rape ◽

Nitrogen Uptake Efficiency ◽

Uptake Efficiency ◽

N Concentration

Field trials were conducted with two nitrogen applications (0 or 240 kg N ha−1) and three modern cultivars of winter oilseed rape (Brassica napus L.) previously selected from a root morphology screen at a young developmental stage. The purpose is to examine the relationship between root morphology and Nitrogen Uptake Efficiency (NUpE) and to test the predictiveness of some canopy optical indices for seed quality and yield. A tube-rhizotron system was used to incorporate below-ground root growth information. Practically, clear tubes of one meter in length were installed in soil at an angle of 45°. The root development was followed with a camera at key growth stages in autumn (leaf development) and spring (stem elongation and flowering). Autumn was a critical time window to observe the root development, and exploration in deeper horizons (36–48 cm) was faster without any fertilization treatment. Analysis of the rhizotron images was challenging and it was not possible to clearly discriminate between cultivars. Canopy reflectance and leaf optical indices were measured with proximal sensors. The Normalized Difference Vegetation Index (NDVI) was a positive indicator of biomass and seed yield while the Nitrogen Balance Index (NBI) was a positive indicator of above-ground biomass N concentration at flowering and seed N concentration at harvest.

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Simultaneous Five Color (UBVRI) Polarimetry of VV Puppis

International Astronomical Union Colloquium ◽

10.1017/s0252921100104877 ◽

1987 ◽

Vol 93 ◽

pp. 203-203

Author(s):

V. Piirola ◽

A. Reiz ◽

G.V. Coyne

Keyword(s):

Circular Polarization ◽

Linear Polarization ◽

Wavelength Dependence ◽

Position Angle ◽

Orbital Inclination ◽

V Band ◽

Highly Active ◽

Phase Interval ◽

In The Beginning ◽

Bright Phase

AbstractObservations of linear and circular polarization in five colour bands during a highly active state of VV Puppis in January 86 are reported. A strong linear polarization pulse with the maximum in the blue, PB ≈ 22%, is observed at the end of the bright phase when the active pole is at the limb and a weaker secondary pulse, PB ≈ 7%, is seen in the beginning of the bright phase, when the active pole reappears. Strong positive circular polarization is also observed in the blue and the ultraviolet, РU ≈ PB ≈ 18%, PV ≈ 10% during the bright phase. The circular polarization reverses the sign in the B and V bands during the faint phase and a negative polarization hump is seen when the active pole crosses the limb. The circular polarization in the V band reaches the value PV ≈ −10% at the hump, after which it remains near PV ≈ −5% during the faint phase. This is probably due to radiation coming from the second, less active pole and accretion thus takes place onto both poles. The wavelength dependences of the positive and negative parts of the circular polarization curve are different and no polarization reversal is seen in the U band. The position angle of the linear polarization is well determined during a large portion of the cycle, especially in the V band, thanks to the activity from both poles. A best fit to the position angle curve, taking into account also the duration of the positive circular polarization phase interval ΔΦ = 0.40 (in the V band), yields the values of orbital inclination i = 78° ± 2° and the colatitude of the active magnetic pole ß = 146° ± 2°. The relatively good fit to the position angle data indicates that the simple dipole model is nearly correct in the case of VV Puppis. Some wavelength dependence is, however, seen in the position angle curves, especially in the I band where the slope Δθ/ΔΦ at the main pulse is considerably smaller than in the other bands. The shape of the position angle curves changes also in the blue and the ultraviolet around the middle of the bright phase. This is probably due to optical thickness effects as the side of the accretion column which is toward the observer changes near this phase.

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