Average Polarization Research Articles

First-principles-integrated Study of Blazar Synchrotron Radiation and Polarization Signatures from Magnetic Turbulence

Blazar emission is dominated by nonthermal radiation processes that are highly variable across the entire electromagnetic spectrum. Turbulence, which can be a major source of nonthermal particle acceleration, can widely exist in the blazar emission region. The Turbulent Extreme Multi-Zone (TEMZ) model has been used to describe turbulent radiation signatures. Recent particle-in-cell (PIC) simulations have also revealed the stochastic nature of the turbulent emission region and particle acceleration therein. However, radiation signatures have not been systematically studied via first-principles-integrated simulations. In this paper, we perform combined PIC and polarized radiative transfer simulations to study synchrotron emission from magnetic turbulence in the blazar emission region. We find that the multiwavelength flux and polarization are generally characterized by stochastic patterns. Specifically, the variability timescale and average polarization degree (PD) are governed by the correlation length of the turbulence. Interestingly, magnetic turbulence can result in polarization angle swings with arbitrary amplitudes and duration, in either direction, that are not associated with changes in flux or PD. Surprisingly, these swings, which are stochastic in nature, can appear either bumpy or smooth, although large-amplitude swings (>180°) are very rare, as expected. Our radiation and polarization signatures from first-principles-integrated simulations are consistent with the TEMZ model, except that in the latter, there is a weak correlation, with zero lag, between flux and degree of polarization.

Fast decomposed method to devise broadband polarization-conversion metasurface

Designing a broadband, wide-angle, and high-efficient polarization converter with a simple geometry remains challenging. This work proposes a simple and computationally inexpensive method for devising broadband polarization conversion metasurfaces. We focus on a cross-shape configuration consisting of two bars of different lengths connected at the center. To design the metasurface, we decompose the system into two parts with two orthogonally polarized responses and calculate the response of each part separately. By selecting the parameters with a proper phase difference in the response between the two parts, we can determine the dimensions of the system. For designing broadband polarization conversion metasurfaces, we define a fitness function to optimize the bandwidth of the linear polarization conversion. Numerical results demonstrate that the proposed method can be used to design a metasurface that achieves a relative bandwidth of 97% for converting linearly polarized waves into cross-polarized waves. Additionally, the average polarization conversion ratio of the designed metasurface is greater than 91% over the frequency range of 10.9–28.5 GHz. This method significantly reduces the computational expense compared to the traditional method and can be easily extended to other complex structures and configurations.

Emotionalität in der COVID-19-Krisenkommunikation von Behörden und unabhängigen Expert*innen auf Twitter

ZusammenfassungHintergrundZu Beginn der COVID‑19-Pandemie herrschte in Deutschland große Unsicherheit in der Bevölkerung und bei den für die Krisenkommunikation Verantwortlichen. Ein wesentlicher Teil der Kommunikation von Expert*innen und zuständigen Behörden fand in den sozialen Medien statt, insbesondere auf der Plattform Twitter. Die dort mit der Krisenkommunikation transportierten positiven, negativen und neutralen Sentiments (Emotionen) sind für Deutschland bisher nicht vergleichend untersucht worden.Ziel der ArbeitDie Sentiments in Twitter-Meldungen von verschiedenen (Gesundheits‑)Behörden und unabhängigen Expert*innen zu COVID‑19 sollen für das erste Pandemiejahr (01.01.2020–15.01.2021) ausgewertet werden, um eine Wissensgrundlage für die Verbesserung zukünftiger Krisenkommunikation zu schaffen.Material und MethodenVon n = 39 Twitter-Akteur*innen (21 Behörden und 18 Expert*innen) flossen n = 8251 Tweets in die Auswertung ein. Diese erfolgte mit dem sog. Lexikonansatz, einer Methode der Social-Media-Analyse. Es wurden deskriptive Statistiken berechnet u. a. zur Bestimmung der durchschnittlichen Polarität der Sentiments und der Häufigkeiten positiv und negativ besetzter Wörter in 3 Phasen der Pandemie.Ergebnisse und DiskussionDie Entwicklung der Emotionalität in COVID‑19-Tweets und der Anzahl von Neuinfektionen in Deutschland verlaufen in etwa parallel. Die Analyse zeigt, dass die Polarität der Sentiments bei beiden Akteursgruppen im Durchschnitt negativ ist. Expert*innen twittern im Untersuchungszeitraum deutlich negativer über COVID‑19 als Behörden. Behörden kommunizieren in der zweiten Phase nahe der Neutralitätslinie, also weder ausgeprägt positiv noch negativ.

A novel Li3Mg3NbO7 microwave dielectric ceramic with ultra-low loss

Novel ultra-low-loss Li3Mg3NbO7 ceramics were synthesized using solid-state reaction method. The microstructure, bond characteristics, and microwave dielectric properties (MDPs) of the Li3Mg3NbO7 ceramics were explored. Furthermore, the Li3Mg3NbO7 ceramics crystallized in the orthorhombic rock-salt structure and the optimized density (97.7%) was obtained at 1200 °C. Utilizing complex chemical bond theory (P–V-L theory) and Raman spectra, the connection between structure and properties was constructed. εr value was mainly affected by the ρrel and average ionic polarization. The UNb–O and packing fraction were the key internal factors influencing the Q × f value. The τf was intimately relevant to Nb–O bond and τε. Notably, the Li3Mg3NbO7 ceramics sintered at 1200 °C exhibited excellent MDPs (εr = 14.7, Q × f = 121,047 GHz, τf = −24.8 ppm/°C), offering enormous prospects for 5G/6G communication applications.

Chemical constituents and antioxidant capacity of fruit extracts from Vismia cayennensis

The genus Vismia producing exudates of secretory structures present in botanical parts such as stems, fruits and roots, presenting a wide variety of secondary metabolites of both chemical and biological complexity. The objective is evaluate the antioxidant capacity of the species, in addition to isolating substances from fractions of the fruit extract. The antioxidant capacity of crude fruit extracts of Vismia cayennensis was assessed by DPPH and their content of total phenolic compounds was quantified. structures were determined by spectroscopy, including NMR, and compared to literature data. The extracts exhibited antioxidant activity against the radical under investigation, especially the hexane (EHVcFr) and dichloromethane (EDVcFr). The EDVcFr extract also exhibited the highest content of total phenolic compounds. The extract with average polarity EDVcFr, was selected for chromatographic analysis, resulting in the isolation of the triterpene friedelin and three prenylated anthranoids: harunganol B, vismin, and ferruginine A. This is the first account of isolation of harunganol B in the genus Vismia. Therefore, the species V. cayennensis can be another promising source of phytoantioxidants for future to fight free radicals.

Stochastic theory of ferroelectric domain structure formation dominated by quenched disorder

A self-consistent stochastic model of domain structure formation in a uniaxial ferroelectric, quenched from a high-temperature paraelectric phase to a low-temperature ferroelectric phase, is developed with an account of the applied electric field and the feedback effect via local depolarization fields. Both polarization and field components are considered as Gauss random variables. A system of integro-differential equations for correlation functions of all involved variables is derived and solved analytically and numerically. Phase diagram in terms of the average value and dispersion of polarization reveals different possible equilibrium states and available final single-domain and multi-domain states. The time-dependent evolution of the average polarization and dispersion discloses a bifurcation behavior and the temperature-dependent value of the electric field, deciding between the single-domain and multi-domain final states, which can be interpreted as the coercive field. Analytical and numerical results for the time-dependent correlation length and correlation functions exhibit plausible agreement with available experimental data.

Triplet-DNP in magnetically oriented microcrystal arrays

We explore dynamic nuclear polarization using electron spins in the photo-excited triplet state (Triplet-DNP) in magnetically oriented microcrystal arrays (MOMAs) of pentacene-doped p-terphenyl, in which the individual crystallites are magnetically aligned and UV-cured. In contrast to the conventional approach to Triplet-DNP in powder, which suffers from reduced nuclear polarization due to the averaged electron polarization and the broadening of electron-spin resonance, Triplet-DNP of the MOMAs offers as high dynamic polarization as that attainable in single-crystals. In the case of pentacene-doped p-terphenyl, the enhanced 1H polarization in the one-dimensional MOMA, prepared simply by leaving the suspension in a stationary magnetic field before UV curation, can be higher than that attainable in the powder sample by an order of magnitude and comparable to that in single crystals and in the three-dimensional MOMA made using a modulational rotating field. Triplet-DNP of the MOMAs may find potential applications, such as the polarization of the co-doped target molecules and dissolution experiments.

Continuous fabrication of polarization maintaining fibers via an annealing improved infinity additive manufacturing technique for THz communications.

We report the design and fabrication of a polarization-maintaining fiber for applications in fiber-assisted THz communications. The fiber features a subwavelength square core suspended in the middle of a hexagonal over-cladding tube by four bridges. The fiber is designed to have low transmission losses, high birefringence, high flexibility, and near-zero dispersion at the carrier frequency of 128 GHz. An infinity 3D printing technique is used to continuously fabricate a 5 m-long polypropylene fiber of ∼6.8 mm diameter. The fiber transmission losses are furthermore reduced by as high as ∼4.4 dB/m via post-fabrication annealing. Cutback measurements using 3 m-long annealed fibers show ∼6.5-11 dB/m and ∼6.9-13.5 dB/m losses (by power) over a 110-150 GHz window for the two orthogonally polarized modes. Signal transmission with bit error rates of ∼10-11-10-5 is achieved at 128 GHz for 1-6 Gbps data rates using a 1.6 m-long fiber link. The average polarization crosstalk values of ∼14.5 dB and ∼12.7 dB are demonstrated for the two orthogonal polarizations in fiber lengths of 1.6-2 m, which confirms the polarization-maintaining property of the fiber at ∼1-2 meter lengths. Finally, THz imaging of the fiber near-field is performed and shows strong modal confinement of the two orthogonal modes in the suspended-core region well inside of the hexagonal over-cladding. We believe that this work shows a strong potential of the infinity 3D printing technique augmented with post-fabrication annealing to continuously produce high-performance fibers of complex geometries for demanding THz communications applications.

A monolithic composite based on zeolite-like metal-organic framework@divinylbenzene polymer separates azeotropic fluorocarbon mixture efficiently

Organic monolithic columns are mainly used to separate macromolecules; however, many attempts to extend their performance toward small molecules were examined by incorporating micro- and nanoparticles. The incorporation technique enabled utilizing organic monoliths in gas chromatography (GC) for small molecules, which are still scarce. Here, we prepared a composite matrix of capillary monolithic columns of a zeolite-like metal-organic framework with a sodalite topology (sod-ZMOF) and Divinylbenzene polymer (DVB) for GC separations under 0.5 MPa. Relatively short DVB monolithic columns (18 cm long × 0.25 mm i.d.) incorporated with a tiny amount of sod-ZMOF nanoparticles (0.7 and 1.17 wt%) with an average particle size of 225 nm were successfully fabricated and used to separate linear alkanes and polar probes mixtures with increasing resolution up to 3.7 and 5.1 times, respectively, compared to a blank DVB monolithic column. A high-performance separation of linear alkanes series mixture (methane to decane) was exhibited in less than 2 min. McReynolds constants revealed that sod-ZMOF provided the composite monolith with a nonpolar character yielding a negative average polarity value smaller than the standard squalene column. An Excellent retention time of pentane and octane day-to-day reproducibility was achieved during 16 days and over more than 500 runs with RSD% of 2.25% and 3.3% using a composite monolithic column with 5 mg mL−1 sod-ZMOF (5-ZMOF@DVB). In addition, a qualitative determination of the gas mixture content of three commercially available Lighter gas cartridges was performed via the 5-ZMOF@DVB column. Finally, successfully separating an azeotropic freon mixture of difluoromethane (R-32) and pentafluoroethane (R-125) was achieved with a selectivity of up to 4.84. A further thermodynamic study related the preferential adsorption of R-125 to entropic factors rather than enthalpic while trapping inside ZMOF pores. This work sheds light on utilizing the infinite diversity of MOFs and combining their properties with high permeability and easily fabricated organic monoliths for GC separations of light molecules and gasses. Furthermore, the study highlights the role of GC as an easy and fast approach for the preliminary evaluation of the separation efficiency of porous polymers.

Compact Polarized X-Ray Source Based on All-Optical Inverse Compton Scattering

Polarized x-ray source is a useful probe for many fields, such as fluorescence imaging, magnetic microscopy, and nuclear physics research. All-optical inverse Compton scattering source (AOCS) based on a laser wakefield accelerator (LWFA) has drawn great attention in recent years due to its compact scale and high performance, especially its potential to generate polarized x rays. Here, polarization-tunable AOCS x rays are generated by a plasma-mirror-based scheme. The linearly and circularly polarized AOCS x rays are measured to have the mean photon energy of $60(\ifmmode\pm\else\textpm\fi{}5)/64(\ifmmode\pm\else\textpm\fi{}3)$ keV and the single-shot photon yield of approximately $1.1/1.3\ifmmode\times\else\texttimes\fi{}{10}^{7}$. A Compton polarimeter is designed to diagnose the x-ray polarization states, demonstrating the polarization tunability of AOCS, and indicating that the average polarization degree of the linearly polarized AOCS is $75(\ifmmode\pm\else\textpm\fi{}3)\mathrm{%}$ within 18.2 mrad x-ray divergence.

What Determines the Critical Electric Field of AFE-to-FE in Pb(Zr,Sn,Ti)O3-Based Perovskites?

Electric-field-induced antiferroelectric-ferroelectric (AFE-FE) phase transition is a prominent feature of antiferroelectric (AFE) materials. The critical electric field of this phase transition is crucial for the device performance of AEFs in many applications, but the determining factor of the critical electric field is still unclear. Here, we have established the correlation between the underlying structure and the critical electric field by using in situ synchrotron X-ray diffraction and high-resolution neutron diffraction in Pb(Zr,Sn,Ti)O3-based antiferroelectrics. It is found that the critical electric field is determined by the angle between the average polarization vector in the incommensurate AFE state and the [111]P polarization direction in the rhombohedral FE state. A large polarization rotation angle gives rise to a large critical electric field. Further, density functional theory (DFT) calculations corroborate that the lower energy is required for driving a smaller angle polarization rotation. Our discovery will offer guidance to optimize the performance of AFE materials.

Pulsar polarization: a broad-band population view with the Parkes Ultra-Wideband receiver

ABSTRACTThe radio polarization properties of the pulsar population are only superficially captured by the conventional picture of pulsar radio emission. We study the broadband polarization of 271 young radio pulsars, focusing particularly on circular polarization, using high-quality observations made with the Ultra-Wideband Low receiver on Murriyang, the Parkes radio telescope. We seek to encapsulate polarization behaviour on a population scale by defining broad categories for frequency- and phase-dependent polarization evolution, studying the co-occurrences of these categorizations and comparing them with average polarization measurements and spin-down energy ($\dot{E}$). This work shows that deviations of the linear polarization position angle from the rotating vector model are linked to the presence of circular polarization features and to frequency evolution of the polarization. Polarization fraction, circular polarization contribution, and profile complexity all evolve with $\dot{E}$ across the population, with the profiles of high-$\dot{E}$ pulsars being simple and highly linearly polarized. The relationship between polarization fraction and circular contribution is also seen to evolve such that highly polarized profiles show less variation in circular contribution with frequency than less strongly polarized profiles. This evolution is seen both across the population and across frequency for individual sources. Understanding pulsar radio polarization requires detailed study of individual sources and collective understanding of population-level trends. For the former, we provide visualizations of their phase- and frequency-resolved polarization parameters. For the latter, we have highlighted the importance of including the impact of circular polarization and of $\dot{E}$.

The Rapid ASKAP Continuum Survey III: Spectra and Polarisation In Cutouts of Extragalactic Sources (SPICE-RACS) first data release

AbstractThe Australian SKA Pathfinder (ASKAP) radio telescope has carried out a survey of the entire Southern Sky at 887.5 MHz. The wide area, high angular resolution, and broad bandwidth provided by the low-band Rapid ASKAP Continuum Survey (RACS-low) allow the production of a next-generation rotation measure (RM) grid across the entire Southern Sky. Here we introduce this project as Spectral and Polarisation in Cutouts of Extragalactic sources from RACS (SPICE-RACS). In our first data release, we image 30 RACS-low fields in StokesI,Q,Uat 25$^{\prime\prime}$angular resolution, across 744–1032 MHz with 1 MHz spectral resolution. Using a bespoke, highly parallelised, software pipeline we are able to rapidly process wide-area spectro-polarimetric ASKAP observations. Notably, we use ‘postage stamp’ cutouts to assess the polarisation properties of 105912 radio components detected in total intensity. We find that our StokesQandUimages have anrmsnoise of$\sim$80$\unicode{x03BC}$Jy PSF$^{-1}$, and our correction for instrumental polarisation leakage allows us to characterise components with$\gtrsim$1% polarisation fraction over most of the field of view. We produce a broadband polarised radio component catalogue that contains 5818 RM measurements over an area of$\sim$1300 deg$^{2}$with an average error in RM of$1.6^{+1.1}_{-1.0}$rad m$^{-2}$, and an average linear polarisation fraction$3.4^{+3.0}_{-1.6}$%. We determine this subset of components using the conditions that the polarised signal-to-noise ratio is$>$8, the polarisation fraction is above our estimated polarised leakage, and the StokesIspectrum has a reliable model. Our catalogue provides an areal density of$4\pm2$RMs deg$^{-2}$; an increase of$\sim$4 times over the previous state-of-the-art (Taylor, Stil, Sunstrum 2009, ApJ, 702, 1230). Meaning that, having used just 3% of the RACS-low sky area, we have produced the 3rd largest RM catalogue to date. This catalogue has broad applications for studying astrophysical magnetic fields; notably revealing remarkable structure in the Galactic RM sky. We will explore this Galactic structure in a follow-up paper. We will also apply the techniques described here to produce an all-Southern-sky RM catalogue from RACS observations. Finally, we make our catalogue, spectra, images, and processing pipeline publicly available.

RHIC optics and spin dynamics with snakes and rotators

The operation of RHIC collider rings in polarized proton runs includes helical snakes, which allow for preserving polarization during acceleration to store energies. The RHIC lattice also includes spin rotators, operated when nonvertical polarization or corrections to the orientation of polarization at the interaction points are required. Utilization of OPERA field maps of snakes and rotators has been systematized in the past decade, in order to assess in detail the effects of these spin devices on beam polarization, and their perturbative effects on beam optics. The method is also used in ongoing studies regarding the future Electron Ion Collider, to permit increasing average store polarization to at least 70% at 275 GeV and the acceleration of polarized helion with low polarization losses. This paper reviews various applications and outcomes of these field map methods. It is thereby also a review of studies undertaken as part of beam polarization research activities at RHIC in recent years.

Seismic upper mantle anisotropy beneath the Polish Sudetes from SKS splitting — Effect of present-day asthenospheric mantle flow deflected by cratonic keel?

To better characterize the structure and evolution of the upper mantle beneath the Polish Sudetes (NE margin of the Variscan internides), we performed shear-wave splitting analysis using teleseismic data from 23 temporary and 8 permanent broadband seismic stations from a period of about two years. SKS and SKKS phases were analysed using the minimum energy and the rotation-correlation method to determine average splitting parameters (φ, δt), characterizing orientation and strength of mantle anisotropy. The observations were interpreted in terms of one-layer anisotropy with a horizontal symmetry axis. The average fast polarization azimuth for this region is equal to ∼113°, and the delay time to ∼1.1 s. The results document a large-scale trend of the upper mantle fabric with NW-SE to WNW-ESE orientation, coinciding with fast velocity axes obtained from the shallower lithospheric studies of the Pn and Pg phases. At smaller scale, anisotropy parameters seem to vary between the SW and NE regions, suggesting moderate differences in orientation of the mantle fabric. Small-scale variations are likely to reflect anisotropy changes related to differences between lithospheric blocks, while more uniform large-scale trend may be related with fabric induced by asthenospheric flow. Estimated thickness of the anisotropic layer exceeds the thickness of the mantle lithosphere, supporting plausibility of substantial asthenospheric contribution. According to previous studies, the large-scale trend of fast polarizations observed in the Sudetes extends also over broader area located to the SW of the Teisseyre-Tornquist Zone, independently of the orientation of the tectonic sutures and of lithospheric inhomogeneity, suggesting its asthenospheric origin. The trend runs obliquely to the plate motion direction, but is sub-parallel to the NW-SE-striking margin of thick East European Craton lithosphere located to the NE of the study area, supporting the concept of the mantle flow re-oriented to ∼NW-SE direction by a thick cratonic keel.

Constraints on clumps in the representative wind of the WN8 Wolf–Rayet star HD 96548 = WR 40 with simultaneous broad-band light and linear-polarization variability

ABSTRACT We report precision ground-based broad-band optical intensity and linear-polarization light curves for the sky’s brightest WN8 star, WR 40. WN8 stars are notorious for their high level of variability, stemming from stochastic clumps in their strong winds that are slower and less hot than the winds of most other Wolf–Rayet (WR) stars. We confirm previous results that many WR stars display an amplitude of variability that is an order of magnitude higher in photometry than in polarimetry. For the first time, the unique nature of near simultaneity of our photometric and polarimetric observations of WR 40 allows us to check whether the two types of variability show correlated behaviour, of which we find none. Assuming simple temporal functions for the brightness and polarization of individual clumps, a model for simulated light curves is found to reproduce the properties of the observations, specifically the absence of correlation between photometric and polarimetric variations, the ratio of standard deviations for photometric and polarimetric variability, and the ratio of the average intrinsic polarization relative to its standard deviation. Mapping the solution for time variability to a spatial coordinate suggests that the wind clumps of WR 40 are free-free emitting in addition to light scattering.

In-line mode-dependent loss equalizer with femtosecond laser induced refractive index modification.

We demonstrate an in-line all-fiber mode-dependent loss (MDL) equalizer with femtosecond laser induced refractive index (RI) modification. By inscribing an RI-modified structure into the core of a few-mode fiber (FMF), a differential mode attenuation (DMA) can be achieved for LP01 and LP11 modes. The DMA can serve as an in-line MDL equalizer for the long-haul mode-division multiplexing transmission system. Through numerical simulations, we identify that the LP01 mode has a larger attenuation than that of higher-order modes, where the sign of DMA is contrary to that of the conventional FMF links and devices. Finally, a proof-of-concept experiment is implemented by inscribing an RI modified region with a width of 4 µm, a height of 13 µm, and a length of 200 µm into the FMF core. An average additional attenuation of 8.4 dB and 3 dB can be applied to the LP01 and LP11 modes over the C-band, respectively, leading to an MDL equalization range of 5.4 dB. Meanwhile, the average polarization dependent loss (PDL) of the LP01 and LP11 modes induced by the in-line MDL equalizer is approximately 0.3 dB over the C-band. Power matrix measurement indicates that the in-line MDL equalizer has a negligible mode coupling. The proposed in-line MDL equalizer with a wider range and low insertion loss is feasible by precise manipulation of femtosecond laser inscription.

A generalizable TCAD framework for silicon FinFET spin qubit devices with electrical control

We present a TCAD-based simulation framework established for quantum dot spin qubits in a silicon FinFET platform with all-electrical control of the spin state. The framework works down to 1K and consists of a two-step simulation chain, from definition of the quantum dot confinement potential with DC bias voltages, to calculation of microwave response electric field at qubit locations using small-signal AC analysis. An average field polarization vector at each quantum dot is extracted via a post-processing step. We demonstrate functionality of this approach by simulation of a recently reported two-qubit device in the form of a 5-gate silicon FinFET. The impact of the number of holes in each quantum dot on the MW response E-field polarization direction is further investigated for this device. The framework is easily generalizable to study future multi-qubit large-scale systems.

Examining the dust of the tailless Oort-cloud comet C/2020 T2

We report our latest analysis of the Oort-cloud comet C/2020 T2 (also named Palomar or T2) observed at 2.06 au from the Sun (phase angle of 28.°5) roughly two weeks before perihelion. It lacks a significant dust tail in scattered light, showing a strong central condensation of the coma throughout the apparition that is reminiscent of so-called Manx comets. Its spectral slope of polarized light increases and decreases in the J (1.25 μm) and H (1.65 μm) bands, respectively, resulting in an overall negative (blue) slope (−0.31 ±0.14% μm−1 ) in contrast to the red polarimetric color of active comets observed at similar geometries. The average polarization degree of T2 is 2.86±0.17% for the J and 2.75±0.16% for the H bands. Given that near-infrared wavelengths are sensitive to the intermediate-scale structure of cometary dust (i.e., dust aggregates), our light-scattering modeling of ballistic aggregates with different porosities and compositions shows that the polarimetric properties of T2 are compatible with low-porosity (~66%), absorbing dust aggregates with negligible ice contents on a scale of 10–100 μm (density of ~652 kg m−3). This is supported by the coma morphology of T2 which has a viable β (the relative importance of solar radiation pressure on dust particles) range of ≲10−4. The secular evolution of r-band activity of T2 from archival data reveals that the increase in its brightness accelerates around 2.4 au pre-perihelion, with its overall dust production rate that is about 100 times smaller than those of active Oort-cloud comets. We also found an apparent concentration of T2 and Manx comets toward ecliptic orbits. This paper underlines the heterogeneous nature of Oort-cloud comets, which may be investigated in the near future with dedicated studies of their dust characteristics.

Manganese(III) Acetate‐Based Radical Cyclization Reactions for Pyranocoumarin and Pyranoquinoline Compounds: Synthesis, DFT and Molecular Docking Studies

AbstractPyranofuroquinoline and pyranofurocoumarin derivatives are significant class of compounds due to being useful in many diverse applications. The synthesis of the compounds are succeeded in one step by radical cyclization reaction in the presence of manganese(III) acetate. Furoquinoline and furocoumarin reactants were used together with 1,1‐disubstituted‐, 1,2‐disubstituted and cyclic alkenes giving pyranofuroquinoline and pyranofurocoumarin compounds in moderate to high yields. Also, we were able to isolate alkenyl and acetoxy‐ side‐products in minor low yields. The electronic and optical features of furoquinoline and furocoumarin reactants and pyranofuroquinoline products were inquired using theoretical approaches (DFT and TD‐DFT). Their excitation and emission spectrums were computed. The results revealed that the pyranofuroquinoline molecules did not show the energy transfer feature. It was observed that the behavior of nonlinear optic of furoquinoline is higher than the pyranofuroquinoline and furocoumarin molecules. But the average polarization and the anisotropy of the polarizability of pyranofuroquinoline increased and was found to be 262.7 and 141.9 respectively. Also, according to the calculated docking parameters, the investigated pyranofuroquinoline and pyranofurocoumarin compounds were found to have higher activity than the substances with anticancer and antibacterial standards.