113 results on '"R. Casini"'
Search Results
2. Magnetic Fields and Plasma Heating in the Sun’s Atmosphere
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P. Judge, L. Kleint, R. Casini, A. G. de Wijn, T. Schad, and A. Tritschler
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Solar coronal heating ,Solar chromospheric heating ,Solar magnetic fields ,Magnetohydrodynamics ,Astrophysics ,QB460-466 - Abstract
We use the first publicly available data from the Daniel K. Inouye Solar Telescope to track magnetic connections from the solar photosphere into the corona. We scrutinize relationships between chromospheric magnetism and bright chromospheric, transition region, and coronal plasmas. In 2022 June, the Visible Spectro-Polarimeter (ViSP) instrument targeted unipolar network within a decaying active region. ViSP acquired rastered scans with longitudinal Zeeman sensitivities of 0.25 Mx cm ^−2 (Fe i, 630.2 nm) and 0.5 Mx cm ^−2 (Ca ii, 854.2 nm). ViSP was operated in a “low” resolution mode (0.″214 slit width, spectral resolution ${ \mathcal R }\approx {\rm{70,000}}$ ) to produce polarization maps over a common area of 105″ × 50″. Data from the Solar Dynamics Observatory and Interface Region Imaging Spectrograph are combined to ask: Why is only a fraction of emerging flux filled with heated plasma? What is the elemental nature of the plasmas? No correlations were found between heated plasma and the properties of chromospheric magnetic fields derived from the weak field approximation, on scales below supergranules. Processes hidden from our observations control plasma heating. While improved magnetic measurements are needed, these data indicate that “the corona is a self-regulating forced system.” Heating depends on the state of the corona, not simply on boundary conditions. Heating models based upon identifiable bipolar fields, including cool loops, tectonics, and observable magnetic reconnection, are refuted for these regions with unipolar chromospheric magnetic fields.
- Published
- 2024
- Full Text
- View/download PDF
3. Ultraviolet Spectropolarimetry with Polstar: Using Polstar to Test Magnetospheric Mass-Loss Quenching
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M. E. Shultz, R. Casini, M. C. M. Cheung, A. David-Uraz, T. del Pino Alemán, C. Erba, C. P. Folsom, K. Gayley, R. Ignace, Z. Keszthelyi, O. Kochukhov, Y. Nazé, C. Neiner, M. Oksala, V. Petit, P. A. Scowen, N. Sudnik, A. ud-Doula, J. S. Vink, and G. A. Wade
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Astrophysics ,Space Sciences (General) - Abstract
Polstar is a proposed NASA MIDEX space telescope that will provide high-resolution, simultaneous full-Stokes spectropolarimetry in the far ultraviolet, together with low-resolution linear polarimetry in the near ultraviolet. This observatory offers unprecedented capabilities to obtain unique information on the magnetic and plasma properties of the magnetospheres of hot stars. We describe an observing program making use of the known population of magnetic hot stars to test the fundamental hypothesis that magnetospheres should act to rapidly drain angular momentum, thereby spinning the star down, whilst simultaneously reducing the net mass-loss rate. Both effects are expected to lead to dramatic differences in the evolution of magnetic vs. non-magnetic stars.
- Published
- 2022
- Full Text
- View/download PDF
4. The Visible Spectro-Polarimeter of the Daniel K. Inouye Solar Telescope
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A. G. de Wijn, R. Casini, A. Carlile, A. R. Lecinski, S. Sewell, P. Zmarzly, A. D. Eigenbrot, C. Beck, F. Wöger, and M. Knölker
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Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Astrophysics::Instrumentation and Methods for Astrophysics ,Astrophysics::Solar and Stellar Astrophysics ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics - Instrumentation and Methods for Astrophysics ,Instrumentation and Methods for Astrophysics (astro-ph.IM) ,Solar and Stellar Astrophysics (astro-ph.SR) - Abstract
The Daniel K. Inouye Solar Telescope (DKIST) Visible Spectro-Polarimeter (ViSP) is a traditional slit-scanning spectrograph with the ability to observe solar regions up to a $120\times 78~\mbox{arcsec}^{2}$ 120 × 78 arcsec 2 area. The design implements dual-beam polarimetry, a polychromatic polarization modulator, a high-dispersion echelle grating, and three spectral channels that can be automatically positioned. A defining feature of the instrument is its capability to tune anywhere within the 380 – 900 nm range of the solar spectrum, allowing for a virtually infinite number of combinations of three wavelengths to be observed simultaneously. This enables the ViSP user to pursue well-established spectro-polarimetric studies of the magnetic structure and plasma dynamics of the solar atmosphere, as well as completely novel investigations of the solar spectrum. Within the suite of first-generation instruments at the DKIST, ViSP is the only wavelength-versatile spectro-polarimeter available to the scientific community. It was specifically designed as a discovery instrument to explore new spectroscopic and polarimetric diagnostics and test improved models of polarized line formation through high spatial-, spectral-, and temporal-resolution observations of the Sun’s polarized spectrum. In this instrument article, we describe the science requirements and design drivers of ViSP and present preliminary science data collected during the commissioning of the instrument.
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- 2022
- Full Text
- View/download PDF
5. TIC: A Stokes inversion code for scattering polarization with partial frequency redistribution and arbitrary magnetic fields
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H. Li, T. del Pino Alemán, J. Trujillo Bueno, and R. Casini
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Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Astrophysics::Solar and Stellar Astrophysics ,FOS: Physical sciences ,Astronomy and Astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) - Abstract
We present the Tenerife Inversion Code (TIC), which has been developed to infer the magnetic and plasma properties of the solar chromosphere and transition region via full-Stokes inversion of polarized spectral lines. The code is based on the HanleRT forward engine, which takes into account many of the physical mechanisms that are critical for a proper modeling of the Stokes profiles of spectral lines originating in the tenuous and highly dynamic plasmas of the chromosphere and transition region: quantum level population imbalance and interference (atomic polarization), frequency coherence effects in polarized resonance scattering (partial frequency redistribution), and the impact of arbitrary magnetic fields on the atomic polarization and the radiation field. We present first results of atmospheric and magnetic inversions, and discuss future developments for the project., Comment: 17pages, 7 figures. Accepted for publication in The Astrophysical Journal
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- 2022
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6. Erratum: Spectral Lines for Polarization Measurements of the Coronal Magnetic Field. II. Consistent Treatment of the Stokes Vector for Magnetic-dipole Transitions (1999, ApJ, 522, 524)
- Author
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R. Casini and P. G. Judge
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Space and Planetary Science ,Astronomy and Astrophysics - Published
- 2021
7. Magnetic Diagnostics of the Solar Corona: Synthesizing Optical and Radio Techniques
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R. Casini, S. M. White, and P. G. Judge
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- 2017
8. Fabrication of air-bridge sub-micron Schottky junctions on Ge/SOI for THz detection
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R. Bagni 1, E. Giovine 2, S. Carta 2, A. Di Gaspare 2, R. Casini 2, 3, M. Ortolani 3, 4, V. Foglietti 2, F. Evangelisti 1, A. Notargiacomo 2, Bagni, R, Giovine, E, Carta, S, Di Gaspare, A, Casini, R, Ortolani, M, Foglietti, V, Evangelisti, Florestano, and Notargiacomo, A.
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Fabrication ,Materials science ,schottky diode ,Equivalent series resistance ,air bridge technology ,business.industry ,Schottky barrier ,Silicon on insulator ,chemistry.chemical_element ,Schottky diode ,Germanium ,thz detector ,Condensed Matter Physics ,Metal–semiconductor junction ,Atomic and Molecular Physics, and Optics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,germanium ,Resist ,chemistry ,Optoelectronics ,Electrical and Electronic Engineering ,business - Abstract
We report on the fabrication and electrical characterization of Schottky diodes on epitaxial relaxed germanium for THz detection, which implement both a sub-micron junction area and the air-bridge technology. The small footprint necessary for low capacitances and T-shaped contacts are obtained by using a triple layer of electronic resists with different sensitivity. The cross-sectional analyses revealed a clearly suspended air-bridge and the T-shape of the metal contact with footprint width below 400 nm. The electrical characterization at room temperature shows well defined Schottky diode behavior with ideality factor between 1 and 2 and low series resistance suitable for THz detection.
- Published
- 2013
9. Fabrication of Schottky diodes for terahertz imaging
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Ennio Giovine, R. Casini, Andrea Notargiacomo, Vittorio Foglietti, D. Dominijanni, and Michele Ortolani
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EBL ,Materials science ,Fabrication ,Terahertz radiation ,business.industry ,Schottky barrier ,Schottky diode ,Condensed Matter Physics ,Diffusion capacitance ,Atomic and Molecular Physics, and Optics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Resist ,T-gate ,Air-bridge ,Optoelectronics ,Electrical and Electronic Engineering ,business ,Lithography ,THz detector ,Diode - Abstract
In this paper we present design, fabrication and characterization of Schottky terahertz diodes. The diode is based on a Ti/n-GaAs junction with very low junction capacitance. T-gate technology, based on trilayer of electronic resists and electron-beam lithography, and air-bridge technique have been used to obtain Schottky diodes with cutoff frequency in the THz range. The device fabrication process is fully planar and suitable for integration in monolithic arrays for active spectroscopic imaging.
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- 2011
10. First steps towards an innovative compressive sampling based-THz imaging system for early crack detection on aereospace plates
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R. Casini, Antonello Andreone, Domenico Accardo, Francesco Bonavolonta, Gian Paolo Papari, Leopoldo Angrisani, R. Schiano Lo Moriello, Angrisani, Leopoldo, Bonavolonta', Francesco, SCHIANO LO MORIELLO, Rosario, Andreone, Antonello, Casini, Roberto, Papari, Gian Paolo, and Accardo, Domenico
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Pixel ,business.industry ,Computer science ,Terahertz radiation ,compressive sampling ,Collimated light ,Power (physics) ,Optics ,Compressed sensing ,THz imaging ,Continuous wave ,Time domain ,cracks detection ,business ,Raster scan ,nondestructive evaluation - Abstract
The paper deals with the problem of early detecting cracks in composite materials for avionic applications. In particular, the authors present a THz imaging system that exploits compressive sampling (CS) to detect submillimeter cracks with a reduced measurement burden. Traditional methods for THz imaging usually involve raster scan of the issue of interest by means of highly collimated radiations and the corresponding image is achieved by measuring the received THz power in different positions (pixels) of the desired image. As it can be expected, the higher the required resolution, the longer the measurement time. On the contrary, two different approaches for THz imaging (namely, continuous wave and time domain spectroscopy) combined with a proper CS solution are used to assure as good results as those granted by traditional raster scan; a proper set of masks (each of which characterized by a specific random pattern) are defined to the purpose. A number of tests conducted on simulated data highlighted the promising performance of the proposed method thus suggesting its implementation in an actual measurement setup.
- Published
- 2014
11. Hybrid metamaterial based structures for the development of a THz spatial light modulator
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M. Lisitskiy, Volodymyr Tkachenko, R. Casini, Hakan Altan, Antonello Andreone, Gian Paolo Papari, Nassim Chikhi, Chikhi, Nassim, Casini, Roberto, Papari, Gian Paolo, Lisitskiy, M., Tkachenko, V., Altan, H., and Andreone, Antonello
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Fabrication ,Materials science ,Spatial light modulator ,business.industry ,Terahertz radiation ,Bandwidth (signal processing) ,Physics::Optics ,Metamaterial ,Split-ring resonator ,Optics ,Liquid crystal ,Metamaterial absorber ,Optoelectronics ,business - Abstract
We investigate new classes of artificial materials exhibiting unconventional properties in order to build novel devices operating in the Terahertz regime. The design, fabrication and electromagnetic characterization of tunable metamaterials with unit cells based on Split Ring Resonators are presented. By incorporation of a nematic liquid crystal in the structure, we observe a frequency shift in the resonant response over 10% in bandwidth and more than 10 dB change in the signal absorption. We discuss how such a hybrid structure can be exploited for the development of a THz spatial light modulator.
- Published
- 2014
12. Prevalence, awareness, treatment and control of hypertension in the elderly: results from a population survey
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C Ferretti, Nicola Scaldaferri, Manuela Santini, A R Casini, Franco Culasso, and Massimiliano Prencipe
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Male ,medicine.medical_specialty ,medicine.medical_treatment ,Overweight ,Internal medicine ,Diabetes mellitus ,Epidemiology ,Prevalence ,Internal Medicine ,medicine ,Humans ,Stage (cooking) ,Life Style ,Aged ,Population survey ,Aged, 80 and over ,Chemotherapy ,business.industry ,Public health ,Awareness ,medicine.disease ,Surgery ,Blood pressure ,Hypertension ,Female ,medicine.symptom ,business - Abstract
Prevalence, awareness, treatment and control of hypertension were assessed in 1032 (90%) of 1147 elderly (or = 65 years) inhabitants of three Italian villages. Blood pressure (BP) was measured at home on two separate occasions following a standardised protocol. Persons taking antihypertensive drugs or with BP valuesor = 140/90 mm Hg were considered as affected by hypertension. Prevalence of hypertension was 64.8%, with higher rates in women than men, and in those aged 75-84 than in those aged 65-74. Diabetes, strokes and hypercholesterolaemia were more frequent in hypertensive than normotensive people, whereas cardiac diseases, overweight and smoking did not differ significantly between hypertensive and normotensive people. Of the 669 hypertensive patients, 439 (65.6%) were aware of their hypertension, 398 (59.5%) were being treated, and 70 (10.5%) had their hypertension controlled. Of the 230 unaware patients, 201 (87.4%) had had their BP measured in the previous year. Of these, 174 (86.6%) had stage 1 hypertension, while 27 had stage 2 hypertension with SBP values170 mm Hg. Overall, the patients with stage 1 hypertension accounted for 68.3% of the untreated and 50.5% of the treated patients. The use of a single drug was more frequent in patients with controlled (97.1%) or stage 1 (97.0%) than with stages 2-3 (18.9%) hypertension. The drugs prescribed most were angiotensin-converting enzyme (ACE) inhibitors (45%), followed by diuretics (43%). As our findings suggest that BP values can be effectively reduced by treating or increasing drug treatment in stage 1 hypertensive patients, data on safety and effectiveness of this policy are urgently needed. Journal of Human Hypertension (2000) 14, 825-830
- Published
- 2000
13. Theoretical polarization profiles of optically-thick hydrogen lines from slabs in the presence of electric and magnetic fields
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R. Casini and E. Landi Degl'Innocenti
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Source function ,Physics ,Hydrogen ,Physics::Optics ,General Physics and Astronomy ,chemistry.chemical_element ,Plasma ,Polarization (waves) ,Magnetic field ,Magnetization ,chemistry ,Physics::Plasma Physics ,Slab ,Radiative transfer ,Atomic physics - Abstract
The theory of formation of hydrogen lines in the presence of stationary electric and magnetic fields is applied to the calculation of the emerging Stokes profiles from a slab of hydrogen plasma, for different optical thicknesses of the slab. The calculations are performed assuming different analytical dependences of the source function on the optical depth. Typical results for hydrogen lines of interest in solar plasmas investigation are then shown.
- Published
- 1997
14. Responsivity at 0.27 THz of a heterostructure field effect transistor detector in a quasi-optical package
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Hartmut G. Roskos, Michele Ortolani, Alvydas Lisauskas, R. Casini, Valeria Giliberti, and Alessandra Di Gaspare
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Heterostructure field-effect transistors ,Materials science ,Quasi-optical ,Silicon ,business.industry ,Detector ,chemistry.chemical_element ,Heterojunction ,Substrate (electronics) ,On chip antenna ,law.invention ,Gallium arsenide ,Lens (optics) ,Responsivity ,chemistry.chemical_compound ,chemistry ,law ,Optoelectronics ,Field-effect transistor ,business - Abstract
We have fabricated AlGaAs/InGaAs/AlGaAs heterostructure field effect transistors (HFET) with integrated on-chip antennas and we have measured their optical responsivity when mounted in a in-house developed quasi-optical package with a silicon substrate lens.
- Published
- 2013
15. Antenna-coupled heterostructure field effect transistors for integrated terahertz heterodyne mixers
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Sergey Sadofev, Ennio Giovine, Claudio Lanzieri, Alessandra Di Gaspare, Florestanto Evangelisti, Dominique Coquillat, Michele Ortolani, Wojciech Knap, Raffaella Calarco, R. Casini, Valeria Giliberti, M. Dispenza, Laboratoire Charles Coulomb (L2C), and Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)
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Heterodyne ,Materials science ,Terahertz radiation ,mixers ,Physics::Optics ,Electrons ,Integrated circuits ,02 engineering and technology ,Integrated circuit ,terahertz (thz) ,heterodyne detection ,high-electron mobility transistors ,integrated antenna ,gallium nitride ,Field effect transistors ,law.invention ,Computer Science::Hardware Architecture ,Fabrication ,020210 optoelectronics & photonics ,law ,Polarization ,0202 electrical engineering, electronic engineering, information engineering ,Heterodyne detection ,business.industry ,Transistor ,Gallium nitride ,Polarization (waves) ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Cutoff frequency ,[PHYS.PHYS.PHYS-GEN-PH]Physics [physics]/Physics [physics]/General Physics [physics.gen-ph] ,Heterojunctions ,Optoelectronics ,Heterodyning ,Field-effect transistor ,Antennas ,business - Abstract
We present the realization of high electron mobility transistors on GaN-heterostructures usable for mixing and rectification in the THz range. Device fabrication is fully compatible with industrial processes employed for millimetre wave integrated circuits. On-chip, integrated, polarization-sensitive, planar antennas were designed to allow selective coupling of THz radiation to the three terminals of field effect transistors in order to explore different mixing schemes for frequencies well above the cutoff frequency for amplification. The polarization dependence of the spectral response in the 0.18-0.40 THz range clearly demonstrated the possible use as integrated heterodyne mixers.
- Published
- 2013
16. The first and second order moments of the polarization profiles of hydrogen lines
- Author
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E. Landi Degl'Innocenti and R. Casini
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Physics ,Zeeman effect ,Hydrogen ,chemistry.chemical_element ,Astronomy and Astrophysics ,Plasma ,Polarization (waves) ,Second order moments ,Magnetic field ,symbols.namesake ,Stark effect ,chemistry ,Space and Planetary Science ,symbols ,Emission spectrum ,Atomic physics - Abstract
The main properties of the first- and second-order moments of polarized hydro-gen lines, forming in the presence of stationary electric and magnetic fields, are reviewed. The analytical results presented here apply directly to the case of optically-thin emission lines in the LTE regime. Some applications of such results to electric- and magnetic-field diagnostics in (solar) plasmas are then briefly considered.
- Published
- 1996
17. Devic?s neuromyelitis optica and mitochondrial DNA mutation: a case report
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G. Leoni, T. Koudriavtseva, S. Baldini, A. Ghezzi, Massimo Zeviani, A. R. Casini, and M. Zaffaroni
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Adult ,medicine.medical_specialty ,Pathology ,Mitochondrial DNA ,Neurology ,Devic's sneuromyelitis optica ,Leber's optic atrophy ,Mitochondrial DNA mutation ,Multiple sclerosis ,DNA, Mitochondrial ,Female ,Humans ,Magnetic Resonance Imaging ,Neuromyelitis Optica ,Spinal Cord ,Mutation ,genetic structures ,Dermatology ,Atrophy ,medicine ,Neuroradiology ,Neuromyelitis optica ,business.industry ,DNA ,General Medicine ,medicine.disease ,eye diseases ,Mitochondrial ,Psychiatry and Mental health ,Mutation (genetic algorithm) ,sense organs ,Neurology (clinical) ,Neurosurgery ,business - Abstract
Cases are described with Leber's optic atrophy and neurological symptoms and/or MRI lesions suggestive of multiple sclerosis. We describe a case of a young woman with Devic's neuromyelitis optica and 3460 homoplasmic mitochondrial DNA mutation.
- Published
- 2004
18. Asymmetric double grating gate detector fabricated on industrial pseudomorphic AlGaAs/InGaAs/AlGaAs heterostructure
- Author
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Sergey Ganichev, Nina Diakonova, C. Drexler, Wojciech Knap, Valeria Giliberti, Michele Ortolani, A. Di Gaspare, Dominique Coquillat, and R. Casini
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Materials science ,business.industry ,Terahertz radiation ,Physics::Optics ,Heterojunction ,Grating ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Gallium arsenide ,chemistry.chemical_compound ,Optics ,Rectification ,chemistry ,Unequal spacing ,Logic gate ,Drain bias ,Optoelectronics ,Room temperature ,Field-effect transistor ,business ,Diffraction grating - Abstract
Rectification at room temperature by asymmetric double-grating-gate GaAs-based field effect transistors has been observed up to 3.89 THz at zero drain bias, and attributed to the peculiar unequal spacing among the two gratings.
- Published
- 2012
19. Progress in producing terahertz detector arrays
- Author
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Alessandra Di Gaspare, Michele Ortolani, and R. Casini
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Materials science ,business.industry ,Optoelectronics ,Terahertz detector ,business - Published
- 2011
20. Three-dimensional Shaping of Sub-micron GaAs Schottky Junctions for Zero-bias Terahertz Rectification
- Author
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Ennio Giovine, Andrea Notargiacomo, Vittorio Foglietti, Michele Ortolani, R. Casini, and A. Di Gaspare
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Materials science ,Physics and Astronomy (miscellaneous) ,genetic structures ,business.industry ,Terahertz radiation ,Schottky barrier ,Schottky diode ,semiconductors ,Metal–semiconductor junction ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,terahertz ,Responsivity ,Condensed Matter::Superconductivity ,Optoelectronics ,business ,Noise-equivalent power ,Quantum tunnelling ,DC bias - Abstract
We demonstrate a rectification mechanism based on quantum tunneling through the narrow Schottky barrier of a sub-micrometric Au/Ti/n-GaAs junction, which is capable of efficient power detection of free-space terahertz radiation beams even without an applied dc bias. Three-dimensional shaping of the junction geometry provides an enhanced zero-bias tunneling probability due to increased electric fields at the junction, resulting in cutoff frequencies up to 0.55 THz, responsivity up to 200 V/W, and noise equivalent power better than 10^-9 W/sqrt(Hz) without applied dc bias.
- Published
- 2011
- Full Text
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21. Fabrication and quantitative comparison of quasi-optical terahertz rectifiers with integrated antennas
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Michele Ortolani, P. Romanini, Vittorio Foglietti, Ennio Giovine, Florestano Evangelisti, D. Dominijanni, R. Casini, A. Di Gaspare, and Marco Peroni
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Heterostructure field-effect transistors ,Air-bridges ,GaAs ,Materials science ,Silicon ,business.industry ,Terahertz radiation ,Schottky barrier ,Transistor ,Schottky diode ,chemistry.chemical_element ,Metal–semiconductor junction ,law.invention ,Lens (optics) ,Terahertz detectors ,chemistry ,law ,Field-Effect transistors ,Optoelectronics ,Field-effect transistor ,business - Abstract
We fabricated GaAs air-bridge Schottky diodes and pseudomorphic InGaAs/AlGaAs heterostructure field-effect transistors with similar on-chip lithographic antennas. Detectors were packaged with a silicon lens and their rectified signal when exposed to 450-700 GHz radiation was compared. © 2011 IEEE.
- Published
- 2011
22. Quasi-optical terahertz detectors based on compound semiconductor heterostructures
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M. Ortolani (1), R. Casini (1), A. Di Gaspare (1), E. Giovine (1), V. Foglietti (1), F. Evangelisti (1), M. Peroni (2), D. Dominijanni (1), P. Romanini (2), C. Lanzieri (2), and A. Cetronio (2)
- Published
- 2011
23. Towards substrate removal in quasi-optical Schottky detector arrays
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L. Di Gaspare, R. Bagni, Florestano Evangelisti, Michele Ortolani, Vittorio Foglietti, R. Casini, A. Di Gaspare, Andrea Notargiacomo, S. Carta, Giovanni Capellini, Ennio Giovine, Casini, R, Di Gaspare, A, Giovine, E, Notargiacomo, A, Ortolani, M, Bagni, R, Carta, S, DI GASPARE, Luciana, Capellini, Giovanni, Evangelisti, F, and Foglietti, V.
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Materials science ,THz Schottky detectors ,business.industry ,Physics::Instrumentation and Detectors ,Schottky barrier ,Detector ,Schottky diode ,Physics::Optics ,Substrate (electronics) ,Metal–semiconductor junction ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Gallium arsenide ,chemistry.chemical_compound ,Condensed Matter::Materials Science ,Optics ,chemistry ,Optoelectronics ,Wafer ,Free space ,GaAs ,Half-space ,business ,Diode - Abstract
The beam of planar THz Schottky detectors is strongly concentrated in the dielectric half-space. With the goal of illuminating arrays from the free-space side, we started to investigate substrate removal from both GaAs and Ge-on-Si diode wafers. © 2011 IEEE.
- Published
- 2011
24. Arrays of Planar Air-bridge GaAs Schottky Diodes for THz Applications
- Author
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R. Casini, M. Ortolani, A. Di Gaspare, E. Giovine, A. DAmico, and V. Foglietti
- Published
- 2011
25. Fabrication of planar sub-micron Schottky diodes for terahertz imaging applications
- Author
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Arnaldo D'Amico, Michele Ortolani, F. Gatta, Vittorio Foglietti, D. Dominijanni, Ennio Giovine, and R. Casini
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Materials science ,Fabrication ,Terahertz radiation ,business.industry ,Schottky diode ,Schottky diodes ,Dielectric ,High-electron-mobility transistor ,Gallium arsenide ,chemistry.chemical_compound ,chemistry ,THz imaging ,Optoelectronics ,business ,Penetration depth ,Noise-equivalent power - Abstract
Imaging sensors employing sub-millimeter waves and terahertz radiation (frequencies from 100 to 3000 GHz) are needed for security applications requiring stand-off, non-destructive sensing, due to its much larger penetration depth into dielectric materials. © 2011 Springer Science+Business Media B.V.
- Published
- 2011
- Full Text
- View/download PDF
26. Trilayer Electron-beam Lithography and surface preparation for sub-micron Schottky contacts on GaAs heterostructures
- Author
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P. Romanini, Marco Peroni, Ennio Giovine, D. Dominijanni, Vittorio Foglietti, Andrea Notargiacomo, R. Casini, Michele Ortolani, and Claudio Lanzieri
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EBL ,Materials science ,business.industry ,GaAs ,Transistor ,Schottky diode ,Heterojunction ,Gallium arsenide ,law.invention ,chemistry.chemical_compound ,Resist ,chemistry ,law ,Area reduction ,Heterostructures ,Optoelectronics ,Schottky contacts ,business ,Lithography ,Electron-beam lithography ,Diode - Abstract
Foreseen operation at sub-THz frequencies of Schottky contacts for diodes and transistor gates on GaAs based heterostructures requires area reduction down to 0.1×1 microns, and wet chemical processes. We report on the compatibility of Trilayer Electron-beam Lithography with such wet processes. © 2010 IEEE.
- Published
- 2010
27. The effect of puberty on insulin resistance in obese children
- Author
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S. Pilia, Luigi Minerba, P. Civolani, V. Marras, M. C. Musiu, Sandro Loche, M. L. Foschini, and M. R. Casini
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Blood Glucose ,Male ,medicine.medical_specialty ,Adolescent ,Cross-sectional study ,Endocrinology, Diabetes and Metabolism ,medicine.medical_treatment ,Body Mass Index ,Fasting glucose ,Endocrinology ,Insulin resistance ,Internal medicine ,medicine ,Humans ,Insulin ,Obesity ,Child ,business.industry ,Body Weight ,Puberty ,Case-control study ,medicine.disease ,Cross-Sectional Studies ,Case-Control Studies ,Child, Preschool ,Female ,Metabolic syndrome ,Insulin Resistance ,business ,Body mass index - Abstract
Objective: Insulin resistance (IR) increases during puberty in normal children. IR is the first adverse metabolic event of obesity, and the marker of the metabolic syndrome. We aimed to study the effect of puberty on IR in obese and normal-weight children. Design: Cross-sectional evaluation of fasting glucose, insulin concentrations, and homeostasis model assessment of IR (HOMA-IR) in obese and control children throughout puberty. Patients and methods: We recruited 424 obese children (207 pre-pubertal and 217 pubertal divided in Tanner stages 2–3, 4, and 5) and estimated IR using the HOMA-IR index. Data were compared to those obtained in 123 healthy normal-weight children (40 pre-pubertal and 83 pubertal divided in Tanner stages 2–3, 4, and 5). Results: In the obese children mean HOMA-IR increased progressively across Tanner stages, and was significantly higher in all groups (pre-pubertal and Tanner stages 2–3, 4, and 5) of obese than in control children. HOMA-IR was significantly correlated with BMI. Conclusions: HOMA-IR in obese children increases at puberty more than in normal-weight children and does not return to pre-pubertal values at the end of puberty.
- Published
- 2009
28. Astrophysical Plasmas
- Author
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R. Casini and E. Landi Degl'Innocenti
- Published
- 2007
29. Dispersion of carbon nanotubes in melt compounded polypropylene based composites investigated by THz spectroscopy
- Author
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D Marrazzo, R. Casini, Antonella Patti, Pietro Russo, Antonello Andreone, Gian Paolo Papari, Casini, R., Papari, G., Andreone, A., Marrazzo, D., Patti, A., Russo, P., Casini, Roberto, Papari, Gian Paolo, Andreone, Antonello, and Patti, Antonella
- Subjects
Polypropylene ,Nanocomposite ,Materials science ,Polymers ,Terahertz ,Physics::Optics ,Thz Spectroscopy ,Carbon nanotube ,Dielectric ,Dispersion ,Atomic and Molecular Physics, and Optics ,law.invention ,Terahertz spectroscopy and technology ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,chemistry ,law ,Dispersion (optics) ,Carbon Nanotubes ,Composite material ,Spectroscopy ,Refractive index ,Nanomaterials - Abstract
We investigate the use of Terahertz Time Domain Spectroscopy as a tool for the measurement of the index dispersion of multi walled carbon nanotubes in polypropylene based composites. Samples containing 0.5% by volume concentration of not functionalized and functionalized carbon nanotubes are prepared by melt compounding technology. Results indicate that the THz response of the investigated nanocomposites is strongly dependent on the kind of nanotube functionalization, which in turn impacts on the level of dispersion inside the polymer matrix. We show that specific dielectric parameters such as the refractive index and the absorption coefficient measured by THz spectroscopy can be both correlated to the index of dispersion as estimated using a traditional and well established approach based on the analysis of optical microscopy images performed on purpose-prepared nanocomposite slices.
- Published
- 2015
30. Growth hormone treatment in non-growth hormone-deficient short children
- Author
-
Sandro Loche, Graziamaria Ubertini, Marco Cappa, and M. R. Casini
- Subjects
Puberty, Delayed ,medicine.medical_specialty ,Adolescent ,business.industry ,Endocrinology, Diabetes and Metabolism ,medicine.disease ,Growth hormone ,Short stature ,Adult height ,Growth hormone secretion ,Body Height ,Growth hormone treatment ,Endocrinology ,Internal medicine ,Growth Hormone ,Turner syndrome ,Medicine ,Chronic renal failure ,Humans ,medicine.symptom ,business ,Child ,Prolonged treatment ,Growth Disorders - Abstract
The unlimited availability of GH obtained by recombinant DNA technology has allowed optimization of treatment in GH-deficient (GHD) children. At the same time it has prompted a number of studies in conditions not characterized by GHD such as Turner syndrome, intrauterine growth retardation, chronic renal failure and other chromosomal and genetic abnormalities associated with short stature. Several controlled and uncontrolled studies have now reported the adult height of patients with short stature and normal GH secretion. Critical reviewing of the data shows that some short non-GHD children may benefit from a prolonged treatment with GH. However, further studies are needed in order to be able to identify the subjects for whom treatment is really beneficial.
- Published
- 2005
31. Stroke, disability, and dementia: results of a population survey
- Author
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Manuela Santini, C Ferretti, Massimiliano Prencipe, Franco Culasso, Franco Giubilei, and Anna R. Casini
- Subjects
Gerontology ,Male ,Rural Population ,Central nervous system disease ,Disability Evaluation ,Age Distribution ,Risk Factors ,medicine ,Prevalence ,Dementia ,Elderly people ,Humans ,cardiovascular diseases ,Sex Distribution ,Stroke ,Population survey ,Aged ,Advanced and Specialized Nursing ,Aged, 80 and over ,Neurologic Examination ,business.industry ,medicine.disease ,Rural environment ,Cerebrovascular Disorders ,Italy ,Population Surveillance ,Female ,Neurology (clinical) ,Cardiology and Cardiovascular Medicine ,business ,Rural population - Abstract
Background and Purpose Stroke, disability, and dementia often coexist in elderly people. We assessed the prevalence and mutual association of these disorders in an elderly rural population. Methods We carried out a door-to-door survey on all subjects aged 65 years or over (n=1032) living in a rural community. To evaluate the associations between stroke and disability and between stroke and dementia, we compared stroke patients with all stroke-free subjects by means of two multiple logistic regression analyses. Subsequently, we performed a case-control analysis by comparing each stroke patient with two age- and sex-matched population control subjects. Results We identified 80 stroke patients. After the exclusion of five incident cases, the prevalence of stroke was 7.3% (95% confidence interval [CI], 5.7 to 8.9). Sixty-five percent of stroke survivors and 23% of stroke-free subjects were disabled (age- and sex-adjusted odds ratio [OR], 6.3; 95% CI, 3.7 to 10.9). Thirty percent of stroke survivors and 5.7% of stroke-free subjects were demented. The OR for dementia (stroke patients versus all stroke-free subjects) was 5.8 (95% CI, 3.1 to 10.8) and became 3.4 (95% CI, 1.5 to 8.0) in the case-control analysis. Conclusions In our population, the prevalence of stroke was higher than in previous studies. Stroke survivors were more disabled and more at risk for dementia than stroke-free subjects.
- Published
- 1997
32. The GH/IGF-I axis in puberty
- Author
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S, Loche, M R, Casini, and A, Faedda
- Subjects
Insulin-Like Growth Factor Binding Proteins ,Male ,Adolescent ,Growth Hormone ,Puberty ,Humans ,Female ,Growth ,Insulin-Like Growth Factor I ,Gonadal Steroid Hormones ,Growth Substances - Abstract
Puberty, either spontaneous, precocious or pharmacologically induced has profound effects on the physiology of the GH/IGF-I axis. Both spontaneous and stimulated GH secretion increase with puberty. The increase in spontaneous GH secretion is the result of increased GH pulse amplitude rather than frequency, and is probably an oestrogen-dependent effect. Parallel to the increase in GH secretion at puberty, circulating IGF-I and IGF binding protein-3 also increase. The pubertal increase in IGF-I correlates with stages of puberty as well as sex steroid levels. Circulating immunoreactive GHRH also increases with puberty, while circulating GH-binding protein levels are not affected by sexual maturation. Several data suggest an important role for the GH/IGF-I axis in the pubertal growth spurt. More recent data, however, have provided evidence of an important role for gonadal hormones in promoting adolescent growth independent of GH.
- Published
- 1996
33. The First and Second Order Moments of the Polarization Profiles of Hydrogen Lines
- Author
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R. Casini and E. Landi Degl’Innocenti
- Published
- 1996
34. Terahertz current oscillations in a gated two-dimensional electron gas with antenna integrated at the channel ends
- Author
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Ennio Giovine, Vittorio Foglietti, Alessandra Di Gaspare, Michele Ortolani, Valeria Giliberti, and R. Casini
- Subjects
Physics ,Physics and Astronomy (miscellaneous) ,business.industry ,Terahertz radiation ,Physics::Optics ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,MIXER ,Signal ,transistor ,terahertz ,antenna ,Gallium arsenide ,chemistry.chemical_compound ,Responsivity ,chemistry ,Modulation ,FIELD-EFFECT ,TRANSISTORS ,RADIATION ,Optoelectronics ,Field-effect transistor ,Antenna (radio) ,business ,Noise-equivalent power - Abstract
We studied terahertz current oscillations induced by a frequency-tunable radiation source in a AlGaAs/InGaAs/AlGaAs heterostructure field effect transistor channel. A planar antenna was integrated on-chip, and a substrate lens was used for broadband coupling of free-space radiation at 0.18-0.72 THz to the channel ends. Through spectral analysis of the detection signal, we identified two different mixing mechanisms: one related to channel current oscillations and the other to modulation of the gate-to-channel potential. Depending on gate bias and radiation frequency, the two mechanisms either compete or cooperate, leading to responsivity up to 300 V/W and noise equivalent power of 1 nW/Hz(0.5) (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4717464]
- Published
- 2012
35. Scattering polarization of hydrogen lines in the presence of turbulent electric fields.
- Author
-
R Casini and R Manso
- Published
- 2006
36. From multiple views to object recognition
- Author
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R. Casini, C. Raspollini, M. T. Pareschi, and V. Cappellini
- Subjects
Orientation (computer vision) ,business.industry ,3D single-object recognition ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,General Engineering ,Representation (systemics) ,Cognitive neuroscience of visual object recognition ,Pattern recognition ,Iterative reconstruction ,Real image ,Object (computer science) ,Pattern recognition (psychology) ,Computer vision ,Artificial intelligence ,business ,ComputingMethodologies_COMPUTERGRAPHICS ,Mathematics - Abstract
A computational method is presented for recovering 3-D shapes by exploiting multiple views of an object. The method provides a volumetric representation of the object starting from the occluding contours, i.e., the contours which separate the object image from the background. A detailed description of the geometrical transformations applied to build the volumetric representation of objects from multiple occluding contours of real images is reported. The only input parameters necessary are the orientation of the TV cameras used. The volumetric representation obtained is recognized by matching it with a library of models. Object recognition is performed in two steps. In the first step, some 3-D global structure parameters are used. If these are not sufficient to unambiguously recognize the object, in the second step the candidates chosen among the models are projected into the image planes of the TV cameras, and some 2-D features are used to perform the recognition, The models can be built either by means of a CAD technique or via the same method used to reconstruct the volumetric representation of the object.
- Published
- 1987
37. The Magnetic Sensitivity of the Resonance and Subordinate Lines of Mg II in the Solar Chromosphere.
- Author
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T. del Pino Alemán, J. Trujillo Bueno, R. Casini, and R. Manso Sainz
- Subjects
SOLAR chromosphere ,RADIATION trapping ,MAGNETIC resonance ,SOLAR atmosphere ,ZEEMAN effect ,MAGNETIC flux density - Abstract
We carry out a theoretical study of the polarization of the solar Mg ii h–k doublet (including its extended wings) and the subordinate ultraviolet (UV) triplet around 280 nm. These lines are of great diagnostic interest, as they encode information on the physical properties of the solar atmosphere from the upper photosphere to the chromosphere–corona transition region. We base our study on radiative transfer calculations of spectral line polarization in one-dimensional models of quiet and plage regions of the solar atmosphere. Our calculations take into account the combined action of atomic polarization, quantum level interference, frequency redistribution, and magnetic fields of arbitrary strength. In particular, we study the sensitivity of the emergent Stokes profiles to changes in the magnetic field through the Zeeman and Hanle effects. We also study the impact of the chromospheric plasma dynamics on the emergent Stokes profiles, taking into account the angle-dependent frequency redistribution in the h–k resonance transitions. The results presented here are of interest for the interpretation of spectropolarimetric observations in this important region of the solar UV spectrum. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
38. Status epilepticus due to abrupt diazepam withdrawal: a case report
- Author
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F Tozzi, M Bartelli, R Casini, P Innocenti, L Rossi, R Zappoli, and Gaetano Zaccara
- Subjects
medicine.diagnostic_test ,business.industry ,Status epilepticus ,Electroencephalography ,medicine.disease ,Psychiatry and Mental health ,Epilepsy ,Anesthesia ,medicine ,Surgery ,Neurology (clinical) ,Withdrawal syndrome ,medicine.symptom ,business ,Diazepam ,medicine.drug ,Research Article - Published
- 1986
39. [Clinico-critical review on the use of Ethrane in general anesthesia]
- Author
-
F, Tozzi and R, Casini
- Subjects
Acid-Base Equilibrium ,Central Nervous System ,Methyl Ethers ,Hydrocarbons, Halogenated ,Respiration ,Proteins ,Electroencephalography ,Water-Electrolyte Balance ,Kidney ,Lipid Metabolism ,Cardiovascular System ,Body Temperature ,Liver ,Muscle Tonus ,Adrenal Glands ,Carbohydrate Metabolism ,Humans ,Anesthesia, Inhalation ,Blood Coagulation ,Anesthetics - Published
- 1974
40. [Behavior of central venous pressure during intravenous administration of ketamine]
- Author
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F, Tozzi, G F, Rossi, and R, Casini
- Subjects
Adult ,Male ,Anesthesia, Intravenous ,Humans ,Female ,Ketamine ,Middle Aged ,Aged - Published
- 1973
41. Spectropolarimetry of the Solar Mg II h and k Lines.
- Author
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R. Manso Sainz, T. del Pino Alemán, R. Casini, and S. McIntosh
- Published
- 2019
- Full Text
- View/download PDF
42. Removal of Spectro-polarimetric Fringes by Two-dimensional Principal Component Analysis.
- Author
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R. Casini and W. Li
- Subjects
- *
ASTROPHYSICAL spectropolarimetry , *PRINCIPAL components analysis , *OPTICAL polarization , *MATHEMATICAL transformations , *PERFORMANCE evaluation - Abstract
We investigate the application of two-dimensional Principal Component Analysis (2D PCA) to the problem of removal of polarization fringes from spectro-polarimetric data sets. We show how the transformation of the PCA basis through a series of carefully chosen rotations allows us to confine polarization fringes (and other stationary instrumental effects) to a reduced set of basis “vectors,” which at the same time are largely devoid of the spectral signal from the observed target. It is possible to devise algorithms for the determination of the optimal series of rotations of the PCA basis, thus opening the possibility of automating the procedure of defringing of spectro-polarimetric data sets. We compare the performance of the proposed method with the more traditional Fourier filtering of Stokes spectra. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
43. Experimental Testing of Scattering Polarization Models.
- Author
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W. Li, R. Casini, S. Tomczyk, E. Landi Degl’Innocenti, and B. Marsell
- Published
- 2018
- Full Text
- View/download PDF
44. CLASP Constraints on the Magnetization and Geometrical Complexity of the Chromosphere-Corona Transition Region.
- Author
-
J. Trujillo Bueno, J. Štěpán, L. Belluzzi, A. Asensio Ramos, R. Manso Sainz, T. del Pino Alemán, R. Casini, R. Ishikawa, R. Kano, A. Winebarger, F. Auchère, N. Narukage, K. Kobayashi, T. Bando, Y. Katsukawa, M. Kubo, S. Ishikawa, G. Giono, H. Hara, and Y. Suematsu
- Published
- 2018
- Full Text
- View/download PDF
45. A Statistical Inference Method for Interpreting the CLASP Observations.
- Author
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J. Štěpán, J. Trujillo Bueno, L. Belluzzi, A. Asensio Ramos, R. Manso Sainz, T. del Pino Alemán, R. Casini, R. Kano, A. Winebarger, F. Auchère, R. Ishikawa, N. Narukage, K. Kobayashi, T. Bando, Y. Katsukawa, M. Kubo, S. Ishikawa, G. Giono, H. Hara, and Y. Suematsu
- Subjects
SPECTROPOLARIMETERS ,INFERENTIAL statistics ,SOLAR flares ,SOLAR chromosphere ,MAGNETIC fields - Abstract
On 2015 September 3, the Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP) successfully measured the linear polarization produced by scattering processes in the hydrogen Lyα line of the solar disk radiation, revealing conspicuous spatial variations in the Q/I and U/I signals. Via the Hanle effect, the line-center Q/I and U/I amplitudes encode information on the magnetic field of the chromosphere–corona transition region, but they are also sensitive to the three-dimensional structure of this corrugated interface region. With the help of a simple line-formation model, here we propose a statistical inference method for interpreting the Lyα line-center polarization observed by CLASP. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
46. Rayleigh Scattering in Spectral Series with L-term Interference.
- Author
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R. Casini, T. del Pino Alemán, and R. Manso Sainz
- Subjects
- *
RAYLEIGH scattering , *ATOMIC transitions , *POLARIZATION interferometers , *SPECTRAL line formation , *INTERFERENCE spectrometers - Abstract
We derive a formalism to describe the scattering of polarized radiation over the full spectral range encompassed by atomic transitions belonging to the same spectral series (e.g., the H i Lyman and Balmer series, the UV multiplets of Fe i and Fe ii). This allows us to study the role of radiation-induced coherence among the upper terms of the spectral series, and its contribution to Rayleigh scattering and the polarization of the solar continuum. We rely on previous theoretical results for the emissivity of a three-term atom of the Λ-type, taking into account partially coherent scattering, and generalize its expression in order to describe a “multiple Λ” atomic system underlying the formation of a spectral series. Our study shows that important polarization effects must be expected because of the combined action of partial frequency redistribution and radiation-induced coherence among the terms of the series. In particular, our model predicts the correct asymptotic limit of 100% polarization in the far wings of a complete (i.e., ) group of transitions, which must be expected on the basis of the principle of spectroscopic stability. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
47. Explicit Form of the Radiative and Collisional Branching Ratios in Polarized Radiation Transport with Coherent Scattering.
- Author
-
R. Casini, T. del Pino Alemán, and R. Manso Sainz
- Subjects
- *
ATOMIC transitions , *EMISSIVITY , *PHOTONS , *ASTROPHYSICS , *STELLAR spectra - Abstract
We consider the vector emissivity of the polarized radiation transfer in a Λ-type atomic transition, which we recently proposed to account for both complete frequency redistribution (CRD) and partial redistribution (PRD) contributions to the scattered radiation. This expression can concisely be written as ε = ( ε ( 1 ) − ε f . s . ( 2 ) ) + ε ( 2 ) , where and are the emissivity terms describing, respectively, one-photon and two-photon processes in a Λ-type atom, and where “f.s.” means that the corresponding term must be evaluated assuming an appropriate “flat spectrum” average of the incident radiation across the spectral line. In this follow-up study, we explicitly consider the expressions of these various terms for the case of a polarized multi-term atom to derive the algebraic forms of the branching ratios between the CRD and PRD contributions to the emissivity. In the limit of a two-term atom with non-coherent lower term, our results are shown to be in full agreement with those recently derived by Bommier. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
48. Solar Spectral Lines with Special Polarization Properties for the Calibration of Instrument Polarization.
- Author
-
W. Li, R. Casini, T. del Pino Alemán, and P. G. Judge
- Subjects
- *
SOLAR spectra , *POLARIZATION (Nuclear physics) , *MAGNETIC fields , *SOLAR telescopes , *LARGE astronomical telescopes - Abstract
We investigate atomic transitions that have previously been identified as having zero polarization from the Zeeman effect. Our goal is to identify spectral lines that can be used for the calibration of instrumental polarization of large astronomical and solar telescopes, such as the Daniel K. Inouye Solar Telescope, which is currently under construction on Haleakala. We use a numerical model that takes into account the generation of scattering polarization and its modification by the presence of a magnetic field of arbitrary strength. We adopt values for the Landé factors from spectroscopic measurements or semi-empirical results, thus relaxing the common assumption of LS-coupling previously used in the literature. The mechanisms dominating the polarization of particular transitions are identified, and we summarize groups of various spectral lines useful for the calibration of spectropolarimetric instruments, classified according to their polarization properties. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
49. A Note on the Radiative and Collisional Branching Ratios in Polarized Radiation Transport with Coherent Scattering.
- Author
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R. Casini, T. del Pino Alemán, and R. Manso Sainz
- Subjects
- *
SPECTRAL line formation , *RADIATIVE transfer equation , *SCATTERING (Physics) , *POLARIZATION (Nuclear physics) , *COHERENT radiation - Abstract
We discuss the implementation of physically meaningful branching ratios between the CRD and partial redistribution contributions to the emissivity of a polarized multi-term atom in the presence of both inelastic and elastic collisions. Our derivation is based on a recent theoretical formulation of partially coherent scattering, and it relies on a heuristic diagrammatic analysis of the various radiative and collisional processes to determine the proper form of the branching ratios. The expression we obtain for the emissivity is where and are the emissivity terms for the redistributed and partially coherent radiation, respectively, and where “f.s.” implies that the corresponding term must be evaluated assuming a flat-spectrum average of the incident radiation. This result is shown to be in agreement with prior literature on the subject in the limit of the unpolarized multi-level atom. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
50. LABORATORY FREQUENCY REDISTRIBUTION FUNCTION FOR THE POLARIZED Λ-TYPE THREE-TERM ATOM.
- Author
-
R. Casini and R. Manso Sainz
- Subjects
- *
VIBRATIONAL redistribution (Molecular physics) , *POLARIZED targets (Nuclear physics) , *ATOMIC polarization , *METASTABLE states , *COLLISIONAL plasma - Abstract
We present the frequency redistribution function for a polarized three-term atom of the Λ-type in the collisionless regime, and we specialize it to the case where both the initial and final terms of the three-state transition are metastable (i.e., with infinitely sharp levels). This redistribution function represents a generalization of the well-known RII function to the case where the lower terms of the transition can be polarized and carry atomic coherence, and it can be applied to the investigation of polarized line formation in tenuous plasmas, where collisional rates may be low enough that anisotropy-induced atomic polarization survives even in the case of metastable levels. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
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