Gotowe bibliografie tematyczne / Corona polarization

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Gotowa bibliografia na temat „Corona polarization”

Autor: Grafiati

Data publikacji: 6 września 2023

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Artykuły w czasopismach na temat "Corona polarization"

Ursini, F., G. Matt, S. Bianchi, A. Marinucci, M. Dovčiak, and W. Zhang. "Prospects for differentiating extended coronal geometries in AGNs with the IXPE mission." Monthly Notices of the Royal Astronomical Society 510, no. 3 (2021): 3674–87. http://dx.doi.org/10.1093/mnras/stab3745.

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ABSTRACT X-ray polarimetry can potentially constrain the unknown geometrical shape of active galactic nucleous (AGN) coronae. We present simulations of the X-ray polarization signal expected from AGN coronae, assuming three different geometries, namely slab, spherical, and conical. We use the fully relativistic Monte Carlo Comptonization code monk to compute the X-ray polarization degree and angle. We explore different coronal parameters such as shape, size, location, and optical depth. Different coronal geometries give a significantly different X-ray polarization signal. A slab corona yields a high polarization degree, up to 14 per cent depending on the viewing inclination; a spherical corona yields low values, about 1–3 per cent, while a conical corona yields intermediate values. We also find a difference of 90 degrees in polarization angle between the slab corona and the spherical or conical coronae. Upcoming X-ray polarimetry missions like IXPE will allow us to observationally distinguish among different coronal geometries in AGNs for the first time.

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Liang, Y., Z. Q. Qu, Y. J. Chen, Y. Zhong, Z. M. Song, and S. Y. Li. "Registration and imaging polarimetry of the Fe 6374 Å red coronal line during the 2017 total solar eclipse." Monthly Notices of the Royal Astronomical Society 503, no. 4 (2021): 5715–29. http://dx.doi.org/10.1093/mnras/stab463.

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ABSTRACT Strict registration is critical for imaging polarimetry; a highly accurate registration approach to the coronal image and imaging polarimetry of the Fe 6374 Å red coronal line have been researched in this paper. In order to improve the registration accuracy, this paper proposes the idea of image enhancement based on blind deconvolution combined with noise-adaptive fuzzy equalization algorithms. After image enhancement, the cross-correlation registration algorithm achieves better results. To diagnose a low-temperature corona, the polarization brightness of the red coronal line data and the Mauna Loa Solar Observatory (MLSO)/KCor data are compared to study the structural features and polarization information of the inner corona. We found that the polarization brightness radiation of the red coronal line has overall features similar to that of the MLSO/KCor data, but it has more detailed features, such as the cavity, polar plume, and interplume characteristics. Active regions, polar plumes, and interplumes show similar performance in red coronal line intensity, polarization brightness, degree of linear polarization, K-corona, and electron density along with the radial height. An interesting finding is that the polarization brightness of the red coronal line changes drastically along with the radial height across the cavity above the solar west limb, while neither the K-corona nor the electron density changes obviously. This seems to be a piece of possible evidence indicating that the red coronal line is not unpolarized in the cavity region.

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Merzlyakov, V., Ts Tsvetkov, L. Starkova, and R. Miteva. "Polarization of white-light solar corona and sky polarization effect during total solar eclipse on March 29, 2006." Serbian Astronomical Journal, no. 199 (2019): 83–87. http://dx.doi.org/10.2298/saj190620005m.

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Ground-based total solar eclipse observations are still the key method for coronal investigations. The question about its white-light degree of polarization remains unanswered. There are hypotheses claiming that the degree of polarization in certain regions of the corona may be higher than the maximal theoretically predicted value determined by Thomson scattering. We present polarization of the white-light solar corona observations obtained by three different teams during the March 29, 2006 solar total eclipse. We give an interpretation on how the polarization of the sky impacts brightness of the polarized solar corona, depending on the landscape during the totality. Moreover, it is shown that the singular polarization points of the corona are in linear dependence with the height of the Sun above the horizon.

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Lebedev, A. N., I. A. Belenko, O. I. Bougaenko, et al. "Eclipse Polarimetric Research of Prominences." International Astronomical Union Colloquium 167 (1998): 66–69. http://dx.doi.org/10.1017/s0252921100047308.

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AbstractA polarization analysis of E–limb prominences on November 3, 1994 is presented. Photometry and data reduction of 24 prominence pictures based on IDL software and Stokes–vector presentation and applied to Hα emission resulted in an accuracy of 1–1.5% in determination of the polarization degree and of 1.5–2.0° in the polarization direction. Distributions of polarization degree (polarization images) for prominences and the “white light” corona are presented. A polarization degree of 2–5% for prominences and 10–25% for the nearby white light corona are found. The polarization direction is found to be tangential to the solar limb. It is noted that eclipse observations can provide a powerful method for deriving the magnetic field at high altitudes in the coronal volume.

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Kulidzanishvili, V., A. Mayer, V. Mayer, and S. Danik. "The Corona Electropolarimetry during July 11, 1991 Solar Eclipse." International Astronomical Union Colloquium 144 (1994): 529–33. http://dx.doi.org/10.1017/s0252921100025987.

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AbstractThe electropolarimetry of July 11, 1991 eclipse solar corona using the new photoelectric polarimeter of Abastumani Astrophysical Observatory of the Georgian Academy of Sciences, equipped with the IBM computer, is described in this paper.By means of measurable values the isopolarization lines were constructed, which turned out to be stretched along the coronal streamers. The polarization plane has, entirely, radial direction; however, small but real deviations from radiality were established. The errors of measurements of intensity, polarization degree and polarization plane direction are evaluated.

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Megha, A., M. Sampoorna, K. N. Nagendra, and K. Sankarasubramanian. "Coronal magnetic field measurements using forbidden emission lines." Proceedings of the International Astronomical Union 13, S340 (2018): 61–62. http://dx.doi.org/10.1017/s1743921318001023.

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AbstractThe polarization measurement of coronal forbidden emission lines is the most promising method of determining the direction of magnetic fields in the corona. A classical theory for the forbidden lines was presented in Megha et al. (2017) for the case of arbitrary strength magnetic fields. Here we apply that theoretical formalism to study the effect of density distributions, magnetic field configurations, and velocity fields on the Stokes profiles formed in corona. For illustrations we use the atomic parameters of the [Fe xiii] 10747 Å coronal forbidden line.

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Liu, Yu, Haosheng Lin, and Jeff Kuhn. "Coronal magnetic fields from the inversion of linear polarization measurements." Proceedings of the International Astronomical Union 5, S264 (2009): 96–98. http://dx.doi.org/10.1017/s174392130999247x.

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AbstractReal 3-D coronal magnetic field reconstruction is expected to be made based on the technologies of IR spectrometry and tomography, in which the data from other wavelengths can be used as critical reference. Our recent studies focused on this issue are briefly reviewed in this paper. Liu & Lin (2008) first evaluated the validity of potential field source surface model applied to one of five limb regions in the corona by comparing the theoretical polarization maps with SOLARC observations in the IR Fe XIII 10747 Å forbidden coronal emission line (CEL). The five limb coronal regions were then studied together in order to study the spatial relation between the bright EUV features on the solar disk and the inferred IR emission sources, which were obtained from the inversion of the SOLARC linear polarization (LP) measurements (Liu 2009). The inversion for each fiber data in the field of view was made by finding the best location where the difference between the synthesized and the observed polarizations reaches the minimum in the integration path along the line of sight. We found a close relationship between the inferred IR emission source locations and the EUV strong emission positions.

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Zhang, J. W., F. K. Gao, H. C. Sun, C. Putson, and R. T. Liu. "Electrostrictive energy conversion property of cellular electrets after corona discharge." International Journal of Modern Physics B 32, no. 07 (2018): 1850069. http://dx.doi.org/10.1142/s0217979218500698.

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In this paper, the authors present the electrostrictive energy conversion ability of cellular electrets after the high-voltage corona polarization. Moreover, the electrostrictive effect of such foamed polymer before and after corona polarization has also been compared and discussed. The enhancement of electrostrictive effect of cellular electrets after corona polarization was observed. In particular, the impact on the electrostrictive effect of the macroscopic electric dipoles inside of cellular polymer which are generated by high-voltage corona poling procedure has been investigated. The present research has promoted the development of the application of electret in the field of energy conversion, actuator, transducers, etc.

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Gelfreikh, G. B., V. M. Bogod, V. E. Abramov-Maximov, and S. V. Tsvetkov. "Measurements of Solar Magnetic Fields Using Radio Observations with the RATAN-600." International Astronomical Union Colloquium 141 (1993): 271–74. http://dx.doi.org/10.1017/s0252921100029213.

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AbstractThree ways of measuring magnetic fields in the corona and chromosphere have been developed based on spectral polarization observations with high spatial resolution using the radio telescope RATAN-600. The methods rely on effects from the theory of the generation and propagation of microwaves in the solar atmosphere: thermal bremsstrahlung, thermal cyclotron emission, and inversion of the polarization sign in quasi-transverse field regions. The new radio spectrograph (PAS) at the RATAN-600 resulted in higher accuracy measurements of the strength and structure of coronal magnetic fields. Using observations made with the PAS on 1992 January 10, we show that the magnetic field strength in the lower corona above all large sunspots can be measured with an accuracy ≈ 3%. The correlation with photospheric magnetic fields is good, ‘radio’ magnetic fields being weaker by ≈ 20%.

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Saint-Hilaire, Pascal, Juan Carlos Martínez Oliveros, and Hugh S. Hudson. "Thomson Scattering in the Lower Corona in the Presence of Sunspots." Astrophysical Journal 923, no. 2 (2021): 276. http://dx.doi.org/10.3847/1538-4357/ac2f9b.

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Abstract Polarized scattered light from low (few tens of megameter altitudes) coronal transients has been recently reported in Solar Dynamics Observatory/Helioseismic and Magnetic Image (HMI) observations. In a classic paper, Minnaert (1930) provided an analytic theory of polarization via electron scattering in the corona. His work assumed axisymmetric input from the photosphere with a single-parameter limb-darkening function. This diagnostic has recently been used to estimate the free-electron number and mass of HMI transients near the solar limb, but it applies equally well to any coronal material, at any height. Here we extend his work numerically to incorporate sunspots, which can strongly effect the polarization properties of the scattered light in the low corona. Sunspot effects are explored first for axisymmetric model cases, and then applied to the full description of two sunspot groups as observed by HMI. We find that (1) as previously reported by Minnaert, limb darkening has a strong influence, usually increasing the level of linear polarization tangential to the limb; (2) unsurprisingly, the effects of the sunspot generally increase at the lower scatterer altitudes, and increase the larger the sunspot is and the closer to their center the scatterer subpoint is; (3) assuming the Stokes Q > 0 basis to be tangential to the limb, sunspots typically decrease the Stokes Q/I polarization and the perceived electron densities below the spotless case, sometimes dramatically; and (4) typically, a sizeable non-zero Stokes U/I polarization component will appear when a sunspot’s influence becomes non-negligible. However, that is not true in rare cases of extreme symmetry (e.g., scattering mass at the center of an axisymmetric sunspot). The tools developed here are generally applicable to an arbitrary image input.

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Rozprawy doktorskie na temat "Corona polarization"

Costa, Mauro Miguel. "Estudo dos sistemas poliméricos: poliestireno e poli(metacrilato de metila) dopado com o corante vermelho disperso 1." Universidade de São Paulo, 1999. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-15042014-095801/.

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Neste trabalho foi investigado o comportamento elétrico dos sistemas poliméricos preparados com o poliestireno, PS, e poli(metacri1ato de metila), PMMA, dopados com o corante vermelho disperso 1, DR1. O processo de polarização dos filmes poliméricos foi realizado usando o triodo de corona operando em duas configurações: i) carregamento com corrente de carga constante, ii) com tensão de grade constante. O processo de polarização por corona foi investigado variando-se os parâmetros do processo, tais como: corrente de carga, tempo, temperatura, campo elétrico de saturação e porcentagem de corante das amostras. As medidas da corrente elétrica no estado estacionário em função campo elétrico permitiram mostrar que o processo de condução elétrica nos dois sistemas obedecem o modelo de Poole-Frenkel. O valor da polarização elétrica induzida foi avaliada através de medidas do coeficiente piroelétrico, o qual é diretamente proporcional a polarização na amostra. No caso do PS(DR1) deu-se ênfase a investigação de medidas de corrente termo estimulada para avaliar a polarização elétrica induzida nas amostras por aplicação de uma ddp. Medidas da constante dielétrica complexa para os dois sistemas poliméricos foram realizadas em função da freqüência para diferentes temperaturas. Os resultados obtidos mostraram que a orientação e relaxação dos corantes nas amostras são associados ao movimento das cadeias poliméricas, i.e., relaxação do tipo &#945. Some electrical properties of guest-host polymeric systems made with polystyrene, PS, and poly(methyl methacrylate), PMMA, and the disperse red 1 dye, DR1 were investigated. The poling process of films were performed with the corona triode set up operating in two modes: i) charging with constant current, ii) with a constant grid voltage. The influence of parameters such as the charging current, electric field at the s, time, temperature and the percentage of DR1 was investigated. Measurements of the steady state current versus the electric field allowed us to show that the electric conduction process in both polymeric systems follow the Poole-Frenkel model. The electric polarization induced in samples was evaluated measuring the piroelectric coefficient, which is directly proportional to the polarization value. For PS(DR1) samples thermally stimulated current measurements were performed to investigate the electric polarization obtained by application of a dc voltage. Measurements of the complex dielectric constant with the two polymeric systems as function of the frequency for different temperatures were performed. Results showed that orientation and relaxation of DR1 dye in samples are related to the chain movement, i.e., &#945 relaxation process.

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Ramírez, Ray Fernando Hidalgo. "Atividade solar em comprimentos de onda mm e sub-mm e sua associação com uma ejeção de massa coronal." Universidade Presbiteriana Mackenzie, 2015. http://tede.mackenzie.br/jspui/handle/tede/1304.

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Made available in DSpace on 2016-03-15T19:35:53Z (GMT). No. of bitstreams: 1 Ray Fernando Hidalgo Ramirez.pdf: 3985319 bytes, checksum: 0a36b0e596cb2c3f1eadaccfa8f843ee (MD5) Previous issue date: 2015-06-17 Universidade Presbiteriana Mackenzie Solar flares radio emissions provide detailed information on the energy release, particle acceleration, heating processes and plasma conditions at the sites where the radiation is generated. This study focuses in radio emission from millimeter, sub-millimeter and another complementary wavelengths obtained by recent observations that might improve the understanding of processes from the low chromosphere to the corona. Here we study a GOES class X1.7 flare on January 27, 2012 detected by the Solar Sub-millimeter Telescope (SST) at 212 and 405 GHz, and by the solar radio polarimeters (POEMAS) at 45 and 90 GHz. LASCO C2 coronagraph observed a coronal mass ejection (CME) with possible physical connection with phenomena observed at radio-frequencies, including changes in polarization degree (45 and 90 GHz) and enhancements of scintillation index (212 and 405 GHz). The complementary radio observations were obtained by the Radio Solar Telescopes Network (RSTN) at the single frequencies 0.2, 0.4, 0.6, 1.4, 2.7, 4.9, 8.8 and 15.4 GHz and at the 25 - 180 MHz band, and by the Green Bank Solar Radio Burst Spectrometer (GBSRBS) at the 100 - 300 MHz and 300 - 1200 MHz bands. The solar flare exhibits a complex time structure at microwaves consisting of three major enhancements. Type III-like metric and decametric bursts were accompanied by small polarized burst at 45 and 90 GHz with polarization degrees of 0.09 and 0.12, suggesting changes in the magnetic field strength the order of 700 and 2000 G, respectively. SST detected one impulsive burst and significant 10% enhancements of scintillation index intermittently throughout the event. The CME launch time inferred by back extrapolation of the LASCO coronagraph observations to the solar limb coincides approximately in time to the changes in polarization degree, suggesting that CME might be a result of a magnetic transient causing an instability generating the subsequent impulsive structures. As emissões em rádio das explosões solares provém informações detalhadas dos processos de liberação de energia, aceleração de partículas, aquecimento e condições do plasma na região onde a radiação é gerada. Este estudo concentra-se em rádio emissões nos comprimentos de onda milimétricos, sub-milimétricos e outras frequências complementares obtidas por observações recentes que podem melhorar o entendimento dos processos na baixa cromosfera até a coroa. Foi estudada uma explosão solar classe GOES X1.7 ocorrida no dia 27 de janeiro de 2012, detectada pelo Telescópio Solar Sub-milimétrico (SST) em 212 e 405 GHz e pelos rádio polarímetros solares em 45 e 90 GHz. Uma ejeção de massa coronal (CME) foi observada pelo coronógrafo C2 de LASCO com possível conexão física com os fenômenos observados em rádio frequências, incluindo mudanças no grau de polarização (45 e 90 GHz) e aumentos no índice de cintilação (212 e 405 GHz). As rádio observações complementares foram obtidas em frequências distintas, pela Rede de Rádio Telescópios Solares (RSTN), de 0,2; 0,4; 0,6; 1,4; 2,7; 4,9; 8,8 e 15,4 GHz e nas faixas de 25 - 180 MHz, e pelo Rádio Espectrômetro Solar Green Bank (GBSRBS) nas faixas de 100 - 300 MHz e 300 - 1200 MHz. A explosão solar apresenta uma estrutura temporal complexa em micro-ondas composta por três aumentos característicos. Explosões métricas e decamétricas tipo III foram acompanhadas por pequenas explosões com polarização em 45 e 90 GHz com graus de polarização de 0,09 e 0,12, sugerindo variações de campo magnético da ordem de 700 e 2000 G, respectivamente. O SST detectou uma explosão impulsiva e aumentos significativos de 10% no índice de cintilação de forma intermitente durante todo o evento. O tempo de lançamento da CME inferido por extrapolação das observações do coronógrafo LASCO ao limbo solar coincide aproximadamente com o instante do excesso de emissão e mudança do grau de polarização em 45 e 90 GHz, sugerindo que a CME tenha resultado de um transiente magnético ocasionando uma instabilidade que gerou as estruturas impulsivas subsequentes.

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Schmeltz, Margaux. "Microscopie de second harmonique résolue en polarisations linéaire et circulaire pour caractériser l'organisation 3D du collagène." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLX074.

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Le collagène est un élément majeur de l'architecture des organes chez les mammifères où il forme diverses structures tridimensionnelles (3D) propres à chaque tissu. La visualisation de cette organisation 3D multi-échelle est cruciale pour comprendre la structuration d'organes tels que la cornée ou la peau et guider l'ingénierie de tissus artificiels, qui doivent être structurés de manière appropriée pour être fonctionnels. L’organisation du collagène est de plus affectée dans de nombreuses pathologies. Caractériser ces désordres tissulaires in situ de manière quantitative constitue ainsi un enjeu biomédical majeur.La microscopie SHG est reconnue depuis plusieurs années comme la technique de référence pour imager le collagène fibrillaire in situ dans des tissus sans marquage, et ceci avec un excellent contraste. Cette thèse présente la mise en place et l'application de nouvelles modalités de microscopie SHG fondées sur la polarisation, visant à obtenir des paramètres fiables et quantitatifs pour décrire plus précisément la structure tridimensionnelle du collagène.Tout d’abord, nous présentons une modalité utilisant des polarisations incidentes linéaires (P-SHG) pour analyser l’organisation multi-échelle du collagène dans divers tissus, sains et pathologiques. Ces analyses ont été conduites sur des objets du patrimoine (parchemins, constitués de collagène de peaux animales) ainsi que sur des tissus biologiques (cornées). D’une part, tirant parti du caractère non invasif de cette modalité, nous caractérisons la dégradation du collagène dans des parchemins, précieux objets d’art et d’Histoire, démontrant ainsi l’intérêt de la microscopie SHG dans le domaine du patrimoine, notamment pour des diagnostics de l’état de conservation des objets riches en collagène. D’autre part, une imagerie quantitative de cornées humaines saines est présentée, et comparée à des cornées présentant un kératocône, pathologie courante aujourd’hui. Des modèles murins de kératocônes cornéens sont également étudiés, dans le but de valider leur pertinence.Enfin, une modalité utilisant des polarisations incidentes circulaires pour mesurer des signaux de dichroïsme circulaire (CD-SHG) est exposée. Dans un premier temps, nous présentons la mise en place expérimentale rigoureuse de cette modalité, en identifiant et corrigeant des artefacts typiques de cette technique. Dans un second temps, nous proposons une nouvelle approche théorique pour décrire les signaux de CD-SHG. Les simulations numériques de l’expression analytique obtenue sont comparées aux résultats expérimentaux, dans le but de comprendre l’évolution des signaux de CD-SHG en fonction de l’architecture 3D du collagène Collagen is a major component of organ architecture in mammals where it forms various three-dimensional (3D) structures specific to each tissue. The visualization of this multi-scale 3D organization is crucial to decipher the structure of organs such as the cornea or the skin and to guide the engineering fully functional tissue substitutes. Moreover, the organization of collagen is also affected in many diseases, so that in situ quantitative characterization of such disorders is a major biomedical issue.SHG microscopy has been recognized for several years as the gold-standard technique for imaging fibrillar collagen in situ in unmarked tissues with excellent contrast. This thesis presents the development and the application of new polarization-based SHG microscopy modalities to obtain reliable and quantitative parameters in order to more accurately describe the three-dimensional structure of collagen.First, we present a modality using linear incident polarizations (P-SHG) to analyze the multi-scale organization of collagen in various tissues, healthy and pathological. These analyses were carried out on cultural heritage objects (parchments, made of collagen from animal skins) as well as on biological tissues (corneas). On one hand, taking advantage of the non-invasive nature of this modality, we characterize the degradation of collagen in ancient parchments, precious objects of art and history. This proves the interest of SHG microscopy in the field of cultural heritage, particularly to decipher the state of conservation of objects rich in collagen. On the other hand, quantitative imaging of healthy human corneas is presented, and compared to corneas with keratoconus, a common pathology today. Murine models of corneal keratoconus are also being studied to validate their relevance.Finally, a modality using circular incident polarizations to measure circular dichroism signals (CD-SHG) is exposed. First, we present the rigorous experimental implementation of this modality, by identifying and correcting typical artifacts of this technique. Secondly, we propose a new theoretical approach to describe CD-SHG signals. Numerical simulations of the obtained analytical expression are compared to experimental results in order to understand the evolution of CD-SHG signals with the 3D architecture of collagen

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Mohanakrishna, R. "Hyperspectral and Spectropolarimetric Instrumentation for the Solar Atmosphere." Thesis, 2018. https://etd.iisc.ac.in/handle/2005/5408.

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The Sun is the closest star whose surface can be resolved to great a detail. Understanding the working of Sun helps in understanding a large fraction of stellar system as it falls under the spectral class G2V which is the second most abundant type found in our galaxy. It has been speculated for some time that the layers in the solar atmosphere are coupled to each other and the coupling mechanism would reveal a lot about the dynamics of the Sun and the long standing problem of coronal heating. Thus physical parameters of the solar atmosphere should be obtained simultaneously at different heights. Estimates on the parameters at a particular region in the solar atmosphere is carried out using spectroscopic or polarimetric measurements of the atomic emission or absorption lines in that region. Traditionally there are two types of spectrograph used in solar astronomy to perform spectroscopy. They are the Fabry-Pérot interferometer and Slit-Grating based spectrograph. Both these instruments have their share of advantages and disadvantages. With telescopes getting bigger, the spatial resolution and light gathering power is increasing. Due to increased size in the telescope aperture, the instruments will be able to resolve small scale structures of the sun. But the small scale structures in the Photosphere and Chromosphere are dynamic in nature and have short time scales. Thus fast time cadence spectro-polarimetry is a very important capability for new instruments in solar observation. Coupling between the layers of the solar atmosphere can be studied with simultaneous observation at multiple wavelength regions corresponding to different height in the solar atmosphere. A traditional grating spectrograph is incapable of achieving high time cadence but can operate at multiple wavelength bands simultaneously. A Fabry-Pérot spectrographs is incapable of simultaneous wavelength measurement but has high time cadence of observation. This thesis aims at addressing the disadvantages of both the instruments and coming up with a solution for the same. An instrument for each type (i. e. Fabry-Pérot and Grating) is built and their capabilities are demonstrated through the data obtained from the engineering run. The slit and grating based spectrograph is extended to include polarimetry in order to measure the vector magnetic field of the solar atmosphere. Although the instruments are developed and their capabilities are demonstrated for photospheric and chromospheric observations, they can be modified to observe the corona. But the corona is a million times fainter than the photosphere with weak fields of the order of tenths of Gauss in contrast to the kilo Gauss fields on the photosphere. The polarimeters required to measure such field have to be sensitive. A case study of polarimetric accuracy needed to measure the corona polarization and the possible sources of noise affecting the signal is also under-taken

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Części książek na temat "Corona polarization"

Badalyan, O. G., V. N. Obridko, and J. Sýkora. "Relationship between the Green-Line Corona Polarization and Coronal Magnetic Fields." In Solar Polarization. Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-015-9329-8_32.

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Gnedin, Y. N., and E. D. Lopez. "Magnetic Polarimetric Refraction in the Solar Corona." In Solar Polarization. Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-009-0231-2_8.

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dos Santos Prezas, Pedro Rafael, Manuel Jorge de Araújo Pereira Soares, Mauro Miguel Costa, and Manuel Pedro Fernandes Graça. "The Corona Triode Charging/Polarization System." In NATO Science for Peace and Security Series B: Physics and Biophysics. Springer Netherlands, 2020. http://dx.doi.org/10.1007/978-94-024-2018-0_3.

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Marat-Mendes, J. N., Maria Raposo, and Paulo-António Ribeiro. "Corona Polarization Effects on Polymer Surfaces." In Equilibrium Structure and Properties of Surfaces and Interfaces. Springer US, 1992. http://dx.doi.org/10.1007/978-1-4615-3394-8_21.

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Badalyan, O. G., M. A. Livshits, and J. Sykora. "Results of Polarization Observations of the White-Light Corona." In Theoretical and Observational Problems Related to Solar Eclipses. Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-011-5492-5_3.

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Fang, Y., P. L. Lamy, and A. Llebaria. "Synthetic Maps of the Brightness and Polarization of the F-Corona." In Origin and Evolution of Interplanetary Dust. Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3640-2_40.

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Belenko, I. A., O. I. Bougaenko, I. S. Kim, S. Koutchmy, O. T. Matsuura, and E. Picazzio. "Degree Polarization Distribution in the Solar Corona of 03 November 1994." In Theoretical and Observational Problems Related to Solar Eclipses. Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-011-5492-5_4.

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Horváth, Gábor, and Dezső Varjú. "Polarization of the Sky and the Solar Corona During Total Solar Eclipses." In Polarized Light in Animal Vision. Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-662-09387-0_11.

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Wardana, Rebecca, Beate Klösch, and Markus Hadler. "Umwelt in der Krise. Einstellungen zu Klimawandel und Umweltbesorgnis sowie Bereitschaft zu umweltbewusstem Verhalten in Krisenzeiten." In Die österreichische Gesellschaft während der Corona-Pandemie. Springer Fachmedien Wiesbaden, 2022. http://dx.doi.org/10.1007/978-3-658-34491-7_9.

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ZusammenfassungDieser Beitrag widmet sich der Frage, wie sich die Einstellungen zum Klimawandel, die Umweltbesorgnis und die Bereitschaft zu umweltbewusstem Handeln im Laufe der Corona-Krise in der österreichischen Bevölkerung entwickelt haben. In Anbetracht der unmittelbaren Bedrohung durch die Covid-19-Pandemie und deren direkte Auswirkungen auf die österreichische Bevölkerung (Herunterfahren der Wirtschaft, Einschränkungen des sozialen Lebens usw.) liegt die Vermutung nahe, dass das Thema Umwelt in den Hintergrund rückte. Um dies zu untersuchen, wurden drei voneinander unabhängige Datensätze (OeNB,Values in Crisis und Polarization in Public Opinion) herangezogen. Die drei Datensätze sind in ihrer Erhebungszeit vor, während und nach der ersten Covid-19-Welle einzuordnen. Lineare Modelle zeigen, dass sowohl die Umweltbesorgnis als auch die Bereitschaft zu umweltbewusstem Verhalten in der Krise gesunken sind, wenngleich nur in den Ballungsräumen Wien, Niederösterreich und Steiermark. Andererseits stieg die Wahrnehmung der negativen Auswirkungen des Klimawandels an. Im Verlauf der Krise zeigt sich zudem, dass trotz der sinkenden Umweltbesorgnis diese dennoch der stärkste Prädiktor zu intentionsorientiertem Umweltverhalten bleibt und nach Ende der ersten Welle einen noch stärkeren Erklärungswert liefert als zuvor.

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Cugnon, P., and J. R. Gabryl. "The Solar Corona: White Light Polarization and Modelling of the Large Scale Electron Density Distribution." In Advances in Solar Research at Eclipses from Ground and from Space. Springer Netherlands, 2000. http://dx.doi.org/10.1007/978-94-011-4325-7_4.

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Streszczenia konferencji na temat "Corona polarization"

Smartt, Raymond N., and Domenico Bonaccini. "Fabry-Perot etalons for solar corona spectral measurements." In OSA Annual Meeting. Optica Publishing Group, 1987. http://dx.doi.org/10.1364/oam.1987.mv4.

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Fabry-Perot etalons with birefringent substrates are studied for application to the measurement of the spectral profile of faint solar corona emission lines. The method uses polarization spectral chopping by means of a photoelastic modulator that allows alternate measurements of the radiation within the bandwidth corresponding to the coronal line and orthogonally polarized radiation in a similar adjacent bandwidth. These two bands are isolated from their associated channeled spectra by an interference filter. Electronic subtraction gives the coronal signal. The line profile is obtained by successive sampling through the line. Design parameters of the etalons such as the interorder spectral interval, the spectral interval between orthogonally polarized components, the bandwidth, transmittance, and the angular characteristics are investigated for optimum performance.

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Zhang, J. W., Y. C. Cui, C. Putson, R. T. Liu, and C. L. Liu. "Surface charge accumulation effect of polyimide after temperature controlling corona polarization." In 2016 IEEE International Conference on Dielectrics (ICD). IEEE, 2016. http://dx.doi.org/10.1109/icd.2016.7547821.

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Gasperini, Leonardo, Giacomo Selleri, Davide Pegoraro, and Davide Fabiani. "Corona poling for polarization of nanofibrous mats: advantages and open issues." In 2022 IEEE Conference on Electrical Insulation and Dielectric Phenomena (CEIDP). IEEE, 2022. http://dx.doi.org/10.1109/ceidp55452.2022.9985267.

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Shaw, Joseph A., and Nathan J. Pust. "Dual-polarization lidar identification of ice in a corona-producing wave cloud." In SPIE Optical Engineering + Applications. SPIE, 2011. http://dx.doi.org/10.1117/12.894893.

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Bonaccini, D., and Raymond N. Smartt. "Tunable Fabry-Perot interferometer using liquid crystals." In OSA Annual Meeting. Optica Publishing Group, 1988. http://dx.doi.org/10.1364/oam.1988.mx6.

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A liquid crystal Fabry-Perot etalon (LCFPI), in which tuning is achieved via the electrooptic effect, is described. The design is applicable to measurements of the solar emission corona, which requires precise subtraction of the scattered light component from the faint emission signal of the coronal lines. For this, spectral chopping is used, in which the signal from one polarization Fabry-Perot channel positioned in the continuum of the spectrum is subtracted electronically from the tunable orthogonally polarized channel via a polarization modulator. The particular use that we require from the filter established the class of LC material to be used and requires special care in the preparation of the substrates. Applications in the IR are possible preserving the full tunability of the filter with low voltages and low powers. The basic design properties of the LCFPI are discussed, and analysis is performed of its thermal sensitivity, transmittance, and stability.

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Sassen, Kenneth. "In Situ and Remote Sensing Analysis of a Corona-Producing Cirrus Cloud." In Light and Color in the Open Air. Optica Publishing Group, 1997. http://dx.doi.org/10.1364/lcoa.1997.lwb.2.

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On the night of 19 April 1994 coordinated University of North Dakota Citation aircraft and University of Utah polarization lidar data were collected from a lunar corona-producing high altitude cirrus cloud from the DOE Cloud and Radiation Testbed (CART) site near Lamont, OK. In agreement with earlier lidar studies (Sassen 1991), relatively strong laser depolarization was noted near the frigid (-70°C) cloud top, which was located slightly above the tropopause. Although the two-ringed corona was not successfully photographed, the radius of the first red ring was estimated to be 2.5 moon diameters (~2.5°). The mean in situ ice crystal sizes derived from the FSSP measurements (the particles were too small to be effectively sampled by the 2D-C ice crystal probe) varied from 20-25 μm in diameter, which is consistent with the estimated size of the corona using simplified diffraction theory. Ice crystal concentrations were atypically high for cirrus, ranging between 400-500 cm-3. The habits of these ice crystals are currently being examined photomicrographically using the plastic replicas of the particles captured by impaction during the aircraft mission.

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Fiorini, Céline, Fabrice Charra, Jean-Michel Nunzi, and Joseph Zyss. "Permanent all-optical poling of octupolar molecules." In The European Conference on Lasers and Electro-Optics. Optica Publishing Group, 1994. http://dx.doi.org/10.1364/cleo_europe.1994.cmk2.

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Conjugated intramolecular charge transfer systems such as the paranitroaniline derivatives have remained so far one of the most studied classes of organic molecules with enhanced quadratic optical properties. Nevertheless, under the influence of dipole/dipole interactions such molecules are prone to form light scattering aggregates in dilute media or crystallize in centrosymmetric lattices, that results thus in the material having no macroscopic second-order susceptibility. This approach was recently revised, and a new engineering scheme was proposed: octupolar molecules, that can possess large nonlinear optical properties together with good transparency but that do not possess a permanent dipole moment, may circumvent the problem discussed above.1,2 However, since the absence of dipole moment in such molecules prevents dipolar orientation, no polar order can be expected from standard polarization techniques such as Corona poling.

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Shieh, Jay, Szu-Wei Chen, and Chia-Yu Fang. "Photocurrent Response of Composite Perovskite Oxide Thin Films With Specific Semiconducting and Ferroelectric Properties." In ASME 2013 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/smasis2013-3058.

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The goal of this study is to investigate photocatalytic semiconductor systems which are layered thin film composites built from perovskite oxide materials with characteristics such as small and large band gaps and/or ferroelectricity. In order to improve the efficiency of photocatalysis, semiconductor heterojunctions within the developed composites have been designed to possess electronic band offsets favoring the separation of photo-induced electron and hole (e−/h+) pairs. Furthermore, the remanent polarization of the ferroelectric component within the composites has been utilized to induce favorable band bending at the material interface, lowering the potential barrier for electron transfer. The band offsets and ferroelectric polarization could be considered as built-in electric fields; how they interact with photo-induced e−/h+ would greatly affect the photocatalytic properties of the composites. In this study, various perovskite oxide thin film materials — large band gap strontium titanate (SrTiO3), small band gap silver niobate (AgNbO3) and ferroelectric lead lanthanum titanate (PLT) — were combined to form layered thin film composites. The composites were then adopted as photoanodes in a photoelectrochemical cell and detailed characterization of their photocurrent response was carried out under different light irradiation and ferroelectric polarization conditions. Electronic band offsets at the material interface (i.e., heterojunction) were determined by ultraviolet-visible spectrophotometry and ultraviolet photoelectron spectroscopy. Electric field poling of the ferroelectric component was achieved by non-contact corona charging. Our results have shown that the band offsets at the SrTiO3-AgNbO3 heterojunction were about 1.0 eV in conduction band edge and 0.4 eV in valence band edge, promoting the rapid separation of photo-induced charge carriers; i.e., the flow of e− from SrTiO3 to AgNbO3 and the flow of h+ from AgNbO3 to SrTiO3. It was found that ferroelectric PLT could be used as a seeding layer for the low-temperature (500 °C) growth of SrTiO3/AgNbO3 thin film composites on ITO/glass substrates, forming a layered structure of SrTiO3/AgNbO3/PLT/ITO. In addition, the photocurrent density of the composites could be increased by depositing gold nanoparticles at the PLT-ITO interface. When the polarization of the PLT layer was poled toward the AgNbO3 layer, the potential barrier associated with the flow of e− to the ITO electrode was reduced by favorable band bending created at the AgNbO3-PLT interface. This resulted in a significant increase in photocurrent density.

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Hayden, L. M., G. F. Sauter, C. S. L. Chun, and P. Pasillas. "Electric field sensors using nonlinear optical polymers." In OSA Annual Meeting. Optica Publishing Group, 1989. http://dx.doi.org/10.1364/oam.1989.mw2.

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This work is part of a continuing project that is investigating the use of integrated optical (IO) waveguides and optical fibers coated with nonlinear optical (NLO) polymers as electric field sensing devices. The IO waveguides were fabricated using three different techniques: (1) in the NLO polymer itself (on glass and silicon substrates), (2) in glass microscope slides using thin film silver diffusion and silver ion exchange methods, and (3) in thin film optical epoxies. The Ag+ glass and UV cured optical epoxy waveguides were subsequently coated with NLO polymers; the 3-D patterned waveguides provided lateral confinement of the optical wave that propagated in the polymer. A low index buffer layer of polysiloxane glass resin (Owens Illinois GR650E) was needed on the silicon substrates to decrease the propagation loss. The NLO polymers were dip coated or spun on these substrates and were poled with a corona poling technique with fields of the order of 3 MV/cm. Interferometric and polarization rotation methods were used to measure the effects of applied electric fields on the NLO devices at wavelengths of 633, 780, and 830 nm. Electrooptic coefficients were determined and compared with similar coefficients obtained using second harmonic generation methods on the same NLO polymers.

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Khin, Maung H., Shuichi Kawabata, Kazuo Ishikawa, Toyohiko Hatada, and Hitoshi Ohzu. "Polarization effect of the in-vivo cornea." In International Symposium on Polarization Analysis and Applications to Device Technology, edited by Toru Yoshizawa and Hideshi Yokota. SPIE, 1996. http://dx.doi.org/10.1117/12.246243.

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