scholarly journals Investigating the presence of two belts in the HD 15115 system

2019 ◽  
Vol 622 ◽  
pp. A192 ◽  
Author(s):  
N. Engler ◽  
A. Boccaletti ◽  
H. M. Schmid ◽  
J. Milli ◽  
J.-C. Augereau ◽  
...  
Keyword(s):  
Imaging Techniques ◽  
Polarized Light ◽  
Position Angle ◽  
Structural Features ◽  
High Contrast ◽  
Photometric Analysis ◽  
Near Ir ◽  
Average Grain Size ◽  
Gravitational Influence ◽  
Differential Imaging

Context. High-contrast instruments like SPHERE (Spectro- Polarimetric High-contrast Exoplanet REsearch) enable spatial resolution of young planetary systems and allow us to study the connection between planets and the dust contained in debris discs by the gravitational influence a planet can have on its environment. Aims. We present new observations of the edge-on debris disc around HD 15115 (F star at 48.2 pc) obtained in the near-IR. We search for observational evidence for a second inner planetesimal ring in the system. Methods. We obtained total intensity and polarimetric data in the broad bands J and H and processed the data with differential imaging techniques achieving an angular resolution of about 40 mas. A grid of models describing the spatial distribution of the grains in the disc is generated to constrain the geometric parameters of the disc and to explore the presence of a second belt. We perform a photometric analysis of the data and compare disc brightness in two bands in scattered and in polarized light. Results. We observe an axisymmetric planetesimal belt with a radius of ~2′′, an inclination of 85.8° ± 0.7° and position angle of 278.9° ± 0.1°. The photometric analysis shows that the west side is ~2.5 times brighter in total intensity than the east side in both bands, while for polarized light in the J band this ratio is only 1.25. We also find that the J–H colour of the disc appears to be red for the radial separations r ≲ 2′′ and is getting bluer for the larger separations. The maximum polarization fraction is 15–20% at r ~ 2.5′′. The polarized intensity image shows some structural features inside the belt which can be interpreted as an additional inner belt. Conclusions. The apparent change of disc colour from red to blue with an increasing radial separation from the star could be explained by the decreasing average grain size with distance. The presence of an inner belt slightly inclined with respect to the main planetesimal belt is suspected from the data but the analysis and modelling presented here cannot establish a firm conclusion due to the faintness of the disc and its high inclination.

scholarly journals NaCo polarimetric observations of Sz 91 transitional disc: a remarkable case of dust filtering

2019 ◽  
Vol 492 (2) ◽  
pp. 1531-1542 ◽  
Author(s):  
Karina Maucó ◽  
Johan Olofsson ◽  
Hector Canovas ◽  
Matthias R Schreiber ◽  
Valentin Christiaens ◽  
...  
Keyword(s):  
Polarized Light ◽  
Position Angle ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Remarkable Case ◽  
The North ◽  
Near Ir ◽  
Hot Start ◽  
Low Mass ◽  
Rule Out

ABSTRACT We present polarized light observations of the transitional disc around Sz 91 acquired with VLT/NaCo at H (1.7μm) and Ks (2.2μm) bands. We resolve the disc and detect polarized emission up to ∼0.5 arcsec (∼80 au) along with a central cavity at both bands. We computed a radiative transfer model that accounts for the main characteristics of the polarized observations. We found that the emission is best explained by small, porous grains distributed in a disc with a ∼45 au cavity. Previous ALMA observations have revealed a large sub-mm cavity (∼83 au) and extended gas emission from the innermost (<16 au) regions up to almost 400 au from the star. Dynamical clearing by multiple low-mass planets arises as the most probable mechanism for the origin of Sz 91’s peculiar structure. Using new L′-band ADI observations, we can rule out companions more massive than Mp ≥ 8 MJup beyond 45 au assuming hot-start models. The disc is clearly asymmetric in polarized light along the minor axis, with the north side brighter than the south side. Differences in position angle between the disc observed at sub-mm wavelengths with ALMA and our NaCo observations were found. This suggests that the disc around Sz 91 could be highly structured. Higher signal-to-noise near-IR and sub-mm observations are needed to confirm the existence of such structures and to improve the current understanding of the origin of transitional discs.

Reflected polarized darkfield imaging of bone surfaces

1992 ◽  
Vol 50 (2) ◽  
pp. 956-957
Author(s):  
Masahiko Sato ◽  
Janice Herring ◽  
John Kim ◽  
Eli Lilly ◽  
Keyword(s):  
Imaging Techniques ◽  
Polarized Light ◽  
Stray Light ◽  
High Contrast ◽  
Reflected Light ◽  
Darkfield Imaging ◽  
Dual Imaging ◽  
Silver Grains ◽  
Silver Granules

Reflected polarized light microscopy (Fig. 1A) was used previously to generate high contrast images of birefringent and light scattering samples, including bone surfaces and autoradiographic specimens. We now present a modification (Fig. 1B) of the Gullberg system with improved sensitivity for the characterization of bone specimens and quantitation of silver granules on autoradiographic specimens. Reflected imaging techniques were useful to generate high contrast images superior to transmitted light strategies, and both of the strategies presented can be adapted easily to any fluorescence microscope.Reflected light produced images free of refractile noise from materials through the thickness of the specimen which detracts from transmission darkfield imaging of silver grains and brightfield imaging of bone surfaces. The use of crossed polars also eliminated noise from stray light reflected off of internal microscope elements. The rotatable lambda/4 plate mounted on the objective front element (Fig. 1A) allowed considerable manipulation of image contrast, permitting dual imaging of silver granules, birefringent tissues in autoradiographic specimens and the surface topography of bone specimens by rotating the lambda/4 plate to 45°.

Quantitative nano-characterization of heterogeneous catalysts

1995 ◽  
Vol 53 ◽  
pp. 398-399
Author(s):  
P.A. Crozier ◽  
M. Pan
Keyword(s):  
Heterogeneous Catalysts ◽  
Low Dose ◽  
Imaging Techniques ◽  
Structural Features ◽  
Catalyst Characterization ◽  
New Developments ◽  
Double Phase ◽  
Phase Systems ◽  
Dose Imaging

Heterogeneous catalysts can be of varying complexity ranging from single or double phase systems to complicated mixtures of metals and oxides with additives to help promote chemical reactions, extend the life of the catalysts, prevent poisoning etc. Although catalysis occurs on the surface of most systems, detailed descriptions of the microstructure and chemistry of catalysts can be helpful for developing an understanding of the mechanism by which a catalyst facilitates a reaction. Recent years have seen continued development and improvement of various TEM, STEM and AEM techniques for yielding information on the structure and chemistry of catalysts on the nanometer scale. Here we review some quantitative approaches to catalyst characterization that have resulted from new developments in instrumentation.HREM has been used to examine structural features of catalysts often by employing profile imaging techniques to study atomic details on the surface. Digital recording techniques employing slow-scan CCD cameras have facilitated the use of low-dose imaging in zeolite structure analysis and electron crystallography. Fig. la shows a low-dose image from SSZ-33 zeolite revealing the presence of a stacking fault.

scholarly journals A High-Contrast Search for Variability in HR 8799bc with VLT-SPHERE

2021 ◽  
Author(s):  
B A Biller ◽  
D Apai ◽  
M Bonnefoy ◽  
S Desidera ◽  
R Gratton ◽  
...  
Keyword(s):  
Position Angle ◽  
High Contrast ◽  
Rule Out

Abstract The planets HR8799bc display nearly identical colours and spectra as variable young exoplanet analogues such as VHS 1256-1257ABb and PSO J318.5-22, and are likely to be similarly variable. Here we present results from a 5-epoch SPHERE IRDIS broadband-H search for variability in these two planets. HR 8799b aperture photometry and HR 8799bc negative simulated planet photometry share similar trends within uncertainties. Satellite spot lightcurves share the same trends as the planet lightcurves in the August 2018 epochs, but diverge in the October 2017 epochs. We consider Δ(mag)b − Δ(mag)c to trace non-shared variations between the two planets, and rule out non-shared variability in Δ(mag)b − Δ(mag)c to the 10-20% level over 4-5 hours. To quantify our sensitivity to variability, we simulate variable lightcurves by inserting and retrieving a suite of simulated planets at similar radii from the star as HR 8799bc, but offset in position angle. For HR 8799b, for periods <10 hours, we are sensitive to variability with amplitude $>5\%$. For HR 8799c, our sensitivity is limited to variability $>25\%$ for similar periods.

scholarly journals Imaging the disc rim and a moving close-in companion candidate in the pre-transitional disc of V1247 Orionis

2018 ◽  
Vol 621 ◽  
pp. A7 ◽  
Author(s):  
Matthew Willson ◽  
Stefan Kraus ◽  
Jacques Kluska ◽  
John D. Monnier ◽  
Michel Cure ◽  
...  
Keyword(s):  
Dust Emission ◽  
Three Dimensional ◽  
Position Angle ◽  
Asymmetric Structures ◽  
North East ◽  
The North ◽  
Band Emission ◽  
Upper Limits ◽  
Multi Wavelength ◽  
Differential Imaging

Context. V1247 Orionis harbours a pre-transitional disc with a partially cleared gap. Earlier interferometric and polarimetric observations revealed strong asymmetries both in the gap region and in the outer disc. The presence of a companion was inferred to explain these asymmetric structures and the ongoing disc clearing. Aims. Using an extensive set of multi-wavelength and multi-epoch observations we aimed to identify the origin of the previously detected asymmetries. Methods. We have observed V1247 Ori at three epochs spanning ~678 days using sparse aperture masking interferometry with Keck/NIRC2 and VLT/NACO. In addition, we search for signs of accretion through VLT/SPHERE-ZIMPOL spectral differential imaging in Hα and R-band continuum. Our SMA sub-millimetre interferometry in 880 μm continuum and in the CO(3-2) line allows us to constrain the orientation and direction of rotation of the outer disc. Results. We find the L′-band emission to be dominated by static features which trace forward-scattered dust emission from the inner edge of the outer disc located to the north-east. In H- and K-bands, we see evidence for a companion candidate that moved systematically by 45° within the first ~345 days. The separation of the companion candidate is not well constrained, but the observed position angle change is consistent with Keplerian motion of a body located on a 6 au orbit. From the SMA CO moment map, the location of the disc rim, and the detected orbital motion, we deduced the three-dimensional orientation of the disc. We see no indication of accretion in Hα and set upper limits for an accreting companion. Conclusions. The measured contrast of the companion candidate in H and K is consistent with an actively accreting protoplanet. Hence, we identify V1247 Ori as a unique laboratory for studying companion–disc interactions and disc clearing.

scholarly journals Model of colposcopy using polarized light and effective early

2017 ◽  
Vol 20 (K2) ◽  
pp. 96-100
Author(s):  
Cat Ngoc Khuong Phan ◽  
Linh Quang Huynh ◽  
Quynh Ngoc Nguyen ◽  
Duong Cao Ly
Keyword(s):  
Imaging Techniques ◽  
Polarized Light ◽  
Analysis And Evaluation ◽  
Common Features ◽  
Common Diseases ◽  
Cervical Disease ◽  
Examination Methods ◽  
The Common ◽  
Image Processing Algorithms ◽  
Processing Algorithms

Cervical disease is one of the common diseases, it occurs in women and has a growing tendency. In particular, cervical cancer is one of the most common diseases. The disease can be cured if it is detected early and treated under the guidance of a physician. The usual cervical examination methods are biopsies, and colposcopy. Recently, many studies have applied imaging techniques in the analysis and evaluation of cervical pathology characteristics [1-3]. In this study, we improved the traditional colposcopy with a polarized light source, and captured images with high resolution. Based on the image obtained, we developed image processing algorithms, initially analyzed and evaluated some of the common features of cervical disease

scholarly journals New Results on the Binary Companion of T Tauri

1983 ◽  
Vol 71 ◽  
pp. 505-507 ◽  
Author(s):  
Theodore Simon ◽  
P.R. Schwartz ◽  
H.M. Dyck ◽  
B. Zuckerman
Keyword(s):  
Main Sequence ◽  
Position Angle ◽  
Speckle Interferometry ◽  
Main Sequence Star ◽  
Near Ir ◽  
T Tauri ◽  
Optical Star ◽  
T Tau

We have recently reported the discovery of a cool (650–800 K) low-luminosity companion to the pre-main-sequence star, T Tauri (Dyck et al. 1982). We proposed that the optical star and its infrared companion form a physical pair with a N-S separation of 100 a.u. However, there remained in our 2-5 μm speckle interferometry an ambiguity of 180° in the position angle of the secondary. In addition, Cohen et al. (1982) noted an 800 milliarcsec (mas) offset between the visual and 6 cm radio positions at T Tau. Both of these positional discrepancies have now been clarified by accurate visual and radio astrometry of T Tau, and by further near-IR speckle interferometry.

Applications of Dispersion Staining Technique in Image Analysis of Colorless Particles

2001 ◽  
Vol 7 (S2) ◽  
pp. 836-837
Author(s):  
Shu-Chun Su
Keyword(s):  
Image Analysis ◽  
Focal Plane ◽  
Imaging Techniques ◽  
Polarized Light ◽  
Staining Technique ◽  
Visible Range ◽  
Objective Lens ◽  
Conventional Imaging ◽  
Immersion Liquid ◽  
Staining Techniques

particles and their surrounding immersion liquid medium into a color in the When analyzing particle size distribution of colorless, translucent or transparent particles by image analysis, a major challenge is to obtain images of particles that ensure proper object detection, especially if the particles are amorphous or non-crystalline. Conventional imaging techniques, such as brightfield, darkfield, cross-polarized light, etc., might not applicable for these types of materials.Dispersion staining (DS) is a technique that coverts the refractive index (RI) difference between visible range and renders particles optically stained with that particular color. There are two modes of dispersion staining techniques: central stop (CS) and annular Stop (AS). For image analysis, CS is preferred.In the CS mode, the matching wavelength λm, i.e., the wavelength at which the RI of a particle equals that of liquid, is not refracted at the particle/liquid interface and therefore blocked by a 3-4 mm opaque round disk located at the center of the back focal plane of objective lens.

Wood identification of charcoal with 3D-reflected light microscopy

IAWA Journal ◽  
2020 ◽  
Vol 41 (4) ◽  
pp. 478-489 ◽  
Author(s):  
Valentina Zemke ◽  
Volker Haag ◽  
Gerald Koch
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Light Microscopy ◽  
Field Emission ◽  
Polarized Light ◽  
Structural Features ◽  
Light Illumination ◽  
Reflected Light ◽  
Carbonized Wood ◽  
Scanning Electron

Abstract The present study focusses on the application of 3D-reflected light microscopy (3D-RLM) for the wood anatomical identification of charcoal specimens produced from domestic and tropical timbers. This special microscopic technique offers a detailed investigation of anatomical features in charcoal directly compared with the quality of field emission scanning electron microscopy (FESEM). The advantages of using the 3D-RLM technology are that fresh fracture planes of charcoal can be directly observed under the microscope without further preparation or surface treatment. Furthermore, the 3D-technique with integrated polarized light illumination creates high-contrast images of uneven and black charcoal surfaces. Important diagnostic structural features such as septate fibres and intercellular canals can be clearly detected and intervessel pits are directly measured. The comparison of the microscopic analyses reveals that 3D-reflected light microscopy (3D-RLM) provides an effective alternative technique to conventional field emission scanning electron microscopy for the identification of carbonized wood.

scholarly journals Demonstration of polarization control GaN-based micro-cavity lasers using a rigid high-contrast grating reflector

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Tsu-Chi Chang ◽  
Kuo-Bin Hong ◽  
Shuo-Yi Kuo ◽  
Tien-Chang Lu
Keyword(s):  
Semiconductor Lasers ◽  
Optical Pumping ◽  
Polarized Light ◽  
Transverse Magnetic ◽  
Bragg Reflector ◽  
Degree Of Polarization ◽  
High Contrast ◽  
Distributed Bragg Reflector ◽  
Output Mirror ◽  
High Contrast Grating

Abstract We reported on GaN microcavity (MC) lasers combined with one rigid TiO2 high-contrast grating (HCG) structure as the output mirror. The HCG structure was directly fabricated on the GaN structure without an airgap. The entire MC structure comprised a bottom dielectric distributed Bragg reflector; a GaN cavity; and a top HCG reflector, which was designed to yield high reflectance for transverse magnetic (TM)- or transverse electric (TE)-polarized light. The MC device revealed an operation threshold of approximately 0.79 MW/cm2 when pulsed optical pumping was conducted using the HCG structure at room temperature. The laser emission was TM polarized with a degree of polarization of 99.2% and had a small divergence angle of 14° (full width at half maximum). This laser operation demonstration for the GaN-based MC structure employing an HCG exhibited the advantages of HCGs in semiconductor lasers at wavelengths from green to ultraviolet.

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